A growing body of evidence from studies in laboratory animals indicates that green tea protects against cancer development at various organ sites. We have previously shown that green tea, administered as drinking water, inhibits lung tumor development in A/J mice treated with 4-(methylnitrosamino)-1-(3-pyridyl)-l-butanone (NNK), a potent nicotine-derived lung carcinogen found in tobacco. The inhibitory effect of green tea has been attributed to its major polyphenolic compound, epigallocatechin gallate (EGCG), and, to a lesser extent, to caffeine. We have also demonstrated that while levels of O6-methylguanine, a critical lesion in NNK lung tumorigenesis, were not affected in lung DNA. However, the levels of 8-hydroxydeoxyguanosine (8-OH-dG), a marker of oxidative DNA damage, were significantly suppressed in mice treated with green tea or EGCG. These studies underscore the importance of the antioxidant activity of green tea and EGCG for their inhibitory activity against lung tumorigenesis. Unlike green tea, the effect of black tea on carcinogenesis has been scarcely studied, even though the worldwide production and consumption of black tea far exceeds that of green tea. The oxidation products found in black tea, thearubigins and theaflavins, also possess antioxidant activity, suggesting that black tea may also inhibit NNK-induced lung tumorigenesis. Indeed, bioassays in A/J mice have shown that black tea given as drinking water retarded the development of lung cancer caused by NNK. However, data on the relationship of black tea consumption with the lung cancer risk in humans are limited and inconclusive. There is a need for additional tumor bioassays in animal models to better examine the protective role of black tea against lung cancer. The development of adenocarcinomas and adenosquamous carcinomas in F344 rats upon chronic administration of NNK provides an important and relevant model for lung carcinogenesis in smokers. Thus far, no information was previously available regarding the effects of tea on this model. We conducted a 2-year lifetime bioassay in F344 rats to determine whether black tea and caffeine are protective against lung tumorigenesis induced by NNK. Our studies in both mice and rats have generated important new data that support green and black tea and caffeine as potential preventive agents against lung cancer, suggesting that a closer examination of the roles of tea and caffeine on lung cancer in smokers may be warranted.[1]
The effects of caffeine, a naturally occurring stimulant, on the brain and plasma concentrations of neuroactive steroids were examined in the rat. A single intraperitoneal injection of caffeine induced dose- and time-dependent increases in the concentrations of pregnenolone, progesterone, and 3α-hydroxy-5α-pregnan-20-one (allopregnanolone) in the cerebral cortex. The increases were significant at a caffeine dose of 25 mg/kg and greatest (+188, +388, and +71%, respectively) at a dose of 100 mg/kg in rats killed 30 min after caffeine administration. Caffeine also increased the plasma concentrations of pregnenolone and progesterone with a dose-response relation similar to that observed in the brain, whereas the caffeine-induced increase in the plasma concentration of allopregnanolone was maximal at a dose of 50 mg/kg. Caffeine increased the plasma concentration of corticosterone, but it had no effect on the brain or plasma concentrations of 3α,21-dihydroxy-5α-pregnan-20-one and dehydroepiandrosterone. Moreover, the brain and plasma concentrations of pregnenolone, progesterone, and allopregnanolone were not affected by caffeine in adrenalectomized-orchiectomized rats. These results suggest that neuroactive steroids may modulate the stimulant and anxiogenic effects of caffeine.[2]
Here, we examined the effect of black tea and caffeine on lung tumorigenesis in F344 rats induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in a 2-year bioassay. NNK was administered s.c. at a dose of 1.5 mg/kg body weight three times weekly for 20 weeks. Animals were given either black tea as drinking water at concentrations of 2%, 1%, or 0.5%, or caffeine in drinking water at concentrations identical to those in 2% and 0.5% tea infusions for 22 weeks. The treatment period began 1 week before and ended 1 week after the NNK administration. The animals were sacrificed on week 101 for the examination of tumors in target organs, including lung, liver, nasal cavity, and other major organs. The NNK-treated group, given 2% black tea, showed a significant reduction of the total lung tumor (adenomas, adenocarcinomas, and adenosquamous carcinomas) incidence from 47% to 19%, whereas the group given 1% and 0.5% black tea showed no change. The 2% tea also reduced liver tumor incidence induced by NNK from 34% in the group given only deionized water to 12%. The tumor incidence in the nasal cavity, however, was not affected by either black tea or caffeine at any of the concentrations tested. The most unexpected finding was the remarkable reduction of the lung tumor incidence, from 47% to 10%, in the group treated with 680 ppm caffeine, a concentration equivalent to that found in the 2% tea. This incidence is comparable to background levels seen in the control group. This study demonstrated for the first time in a 2-year lifetime bioassay that black tea protects against lung tumorigenesis in F344 rats, and this effect appears to be attributed, to a significant extent, to caffeine as an active ingredient of tea.[3]
The purpose of this study was to determine whether or not caffeine could influence the development of ovarian hormone dependent mammary tumors in GR mice. Virgin female GR mice were treated daily for 24 weeks with 17β-estradiol and progesterone, commencing at 8 – 10 weeks of age. One week after the onset of hormone treatment, caffeine (500 mg/l drinking water) was administered daily until experiment termination to one-half of the hormone-treated mice. Hormone treatment induced mammary tumors in 95–100% of the mice. Caffeine treatment significantly (P < 0.05) reduced the mean number of mammary tumors per mouse and significantly (P < 0.05) increased the mean latency period of mammary tumor appearance.[4]
The purpose of this study was to assess the influence of caffeine on the incidence of benign mammary tumors in carcinogen (DMBA) treated female Sprague-Dawley rats. Four different animal models were used in these studies, i.e., the administration of DMBA to: [1] 55 day old virgin rats; [2] 53 day old ovariectomized, estrogen treated virgin rats; [3] 135 day old virgin rats and [4] 135 day old parous rats. A high incidence of benign mammary fibroadenomas was observed in each of the four animal models. In addition, in the estrogen treated ovariectomized animals, a high incidence of secretory mammary gland cysts was observed. Caffeine (500 mg/L drinking water) was administered daily throughout the study commencing 3–31 days after carcinogen treatment. Caffeine treatment significantly (P<0.05 to P<0.001) reduced the incidence of benign mammary fibroadenomas in the 55 day old virgin rat model (P<0.01), in the 53 day old estrogen treated ovariectomized virgin rat model (P<0.05 to P<0.001) and in the 135 day old virgin rat model (P<0.05). The number of benign mammary fibroadenomas was reduced by caffeine in the 135 day old parous rat model but this reduction was not significant (P<0.10). In addition, in the estrogen treated ovariectomized virgin rat model, caffeine significantly (P<0.05 to P<0.001) reduced the incidence of mammary gland cysts. Caffeine treatment either increased or had no significant effect on body weight gains, depending upon the animal model. Thus, caffeine consumption can influence the development of benign mammary tumors (fibroadenomas and cysts) in carcinogen treated female Sprague-Dawley rats, an influence that was shown to be consistently inhibitory.[5]
Studies have associated coffee and/or caffeine with human fibrocystic breast disease. Two animal studies have implicated caffeine as a promoter in rat mammary cancer. The current investigation examines the effect of two caffeine doses in ACI rats with and without diethylstilbestrol (DES). Without DES, cancer did not develop in any of the rats receiving either of the two caffeine dosages. With DES, increasing caffeine dosage lengthened the time to first cancer, decreased the number of rats that developed cancers, and decreased the number of cancers overall. The presence or amount of caffeine did not cause detectable histologic differences in the breast cancers. The presence or amount of caffeine did not influence animal weight or mortality, although the rats without DES weighed more and survived better into old age. The presence or amount of caffeine did not influence pituitary weights and prolactin levels, although values of the DES groups were three times higher than the values for the group without DES (P less than 0.05). In conclusion, chronic caffeine ingestion inhibits rat breast cancer, neither by interfering with the high prolactin levels--a necessary step in murine tumor development--nor by causing hypocaloric intake.[6]
Caffeine intake has been proposed to influence breast cancer risk. Its effect may be mediated by hormonal changes. The relationships between caffeine-containing beverages (coffee, green tea, black tea, oolong tea, and cola) and serum concentrations of estradiol and sex hormone-binding globulin were evaluated in 50 premenopausal Japanese women. Intakes of caffeine and caffeine-containing beverages were assessed by a semiquantitative food-frequency questionnaire. Blood samples were obtained from each woman on Days 11 and 22 of her menstrual cycle. High intakes of caffeinated coffee, green tea, and total caffeine were commonly correlated with increasing sex hormone-binding globulin on Days 11 and 22 of the cycle after controlling for potential confounders [Spearman correlation coefficients (r) ranged from 0.23 to 0.31]. Green tea but not caffeinated coffee intake was inversely correlated with estradiol on Day 11 of the cycle (r = -0.32, p = 0.04). Although the effect of caffeine cannot be distinguished from effects of coffee and green tea, consumption of caffeine-containing beverages appeared to favorably alter hormone levels associated with the risk of developing breast cancer.[7]
The purpose of this study was to determine the comparative activities of three methylxanthines, i.e., 1,3,7-trimethylxanthine (caffeine), 1,3-dimethylxanthine (theophylline), and 3,7-dimethylxanthine (theobromine) on developmental growth of the mammary gland in ovarian-hormone treated, mature nulliparous female Balb/c mice. When caffeine or theophylline was administered daily (via drinking water, 500 mg/L) for 30 days to 17 beta-estradiol/progesterone-treated intact or ovariectomized mice, a significant (p less than 0.05) enhancement of hormone-induced mammary gland lobulo-alveolar differentiation was observed. Caffeine or theophylline thus accelerated and/or intensified mammae lobulo-alveolar differentiation induced by the ovarian steroids. In contrast, theobromine (500 mg/L drinking water) did not significantly modify this developmental process. The stimulatory effect of caffeine and theophylline on mammae development was comparable quantitatively. In an effort to determine whether or not the stimulatory effect of caffeine or theophylline was directly on the mammary gland, small slow-release Elvax-40P pellets containing these methylxanthines were implanted directly into the mammary gland of mice concurrently treated with estrogen and progesterone. No significant stimulatory effect of caffeine or theophylline (or theobromine) was observed. Furthermore, the addition of methylxanthines (caffeine, 100 microM) to the culture media of whole mouse mammary glands (organ cultures) did not enhance lobulo-alveolar differentiation induced by mammotrophic hormones. Thus, while a consistent significant stimulatory effect of caffeine and theophylline on mammary lobulo/alveolar differentiation was observed when the methylxanthines were consumed orally (drinking water), no direct effect of these methylxanthines, when placed directly into the mammary gland or in culture media, on mammae development was observed. These data demonstrate that certain methylxanthines (e.g., caffeine and theophylline) but not others (e.g., theobromine) can significantly enhance mammotrophic hormone-induced mammary lobulo-alveolar differentiation in female Balb/c mice, an effect that appears not to be manifested via a direct action of the methylxanthines on the mammary gland.[8]
Previously we have reported that the stimulatory effect of caffeine on lobulo-alveolar development in the mammary glands of female Balb/c mice is not due to a direct action of the drug on the mammary gland but appears to be due to a caffeine-induced alteration of a yet to be defined systemic physiological process (VanderPloeg et al., J Environ Pathol Toxicol Oncol 11:177-189, 1992). In the present study, we administered caffeine (via the drinking water, 500 mg/L) to ovariectomized, estrogen- and progesterone-treated Balb/c mice. After 30 days of caffeine treatment, a significant (p < 0.001) enhancement of lobulo-alveolar development in the mammary glands of the hormone-treated mice, compared with hormone treated control mice, was observed. Six blood components, that is, total free fatty acids (FFA), glucose, IGF-1, insulin, prolactin and corticosterone, each known to enhance normal or neoplastic mammary gland growth processes in mice or rats, were quantitatively assessed in the blood of these mice. Of these six blood components, only corticosterone (p < 0.001) increased significantly in the caffeine-treated mice. These results provide evidence that the enhancement of mammary gland lobulo-alveolar development in mice by chronic consumption of caffeine appears to be a result of caffeine-enhanced secretion of corticosterone.[9]
Dietary caffeine intake has been suggested as a risk factor for bone loss in postmenopausal women. We measured the bone density of both hips and the total body in 138 healthy, postmenopausal women aged 55-70 y who had either never used hormone replacement therapy (HRT) or had used HRT for < 1 y. In this cross-sectional study, participants were stratified according to their reported current and long-time caffeinated beverage use into one of three groups: low [0-2 cups (180 mL, or 6 oz per cup) caffeinated coffee per day], moderate (3-4 cups caffeinated coffee per day), or high (> or = 5 cups caffeinated coffee per day). Caffeine intake was measured from diet records and by gas chromatography of each subject's brewed, caffeinated beverages. No association between caffeine intake and any bone measurement was observed. The anthropometric and nutrient intakes of the three groups were similar. Compared with caffeine intake based on chemical analysis of brewed beverages, 3-d prospective food records and computer-assisted analysis overestimated caffeine intake by nearly two-thirds. In conclusion, the habitual dietary caffeine intake of this cohort of 138 postmenopausal women ranged from 0-1400 mg/d and was not associated with total body or hip bone mineral density measurements. This study does not support the notion that caffeine is a risk factor for bone loss in healthy postmenopausal women.[10]
Previously, we found that chronic ingestion of the extract of coffee cherry (CC), the residue after the removal of coffee beans, induced a marked suppression of the development and the growth of spontaneous mammary tumours in a high mammary tumour strain of SHN mice. As a possible step to clarify the mechanism of this effect, the immunomodulating role of CC was examined in this study. CC treatment resulted in significant weight gain in the spleen. CC treated experimental mice showed a significant decrease in the proportion of immature (CD4+8+) thymocytes and an increase in the percentages of mature cells expressing helper/inducer (CD4+8-) or cytotoxic/suppressor (CD4-8+) phenotypes. The proportion of T cells expressing CD25, a lymphocyte activation marker, in the spleen and peripheral blood tended to increase in the CC treated group. The natural killer activity of the spleen cells was not affected by CC ingestion. These results have revealed that CC can enhance the differentiation of thymocytes and the activation of peripheral T lymphocytes. [11]
The antiallergic effects of green tea, oolong tea, and black tea extracts by hot water were examined. These extracts inhibited the passive cutaneous anaphylaxis (PCA) reaction of rat after oral administration. Three tea catechins, (--)-epigallocatechin (EGC), (--)-epicatechin gallate (ECg), and (--)-epigallocatechin gallate (EGCg) isolated from green tea showed stronger inhibitory effects than that of a green tea extract on the PCA reaction. The inhibitory effects of EGC and EGCg on the PCA reaction were greater than that of ECg. Caffeine also showed a inhibitory effect on the PCA reaction. These results indicate that tea could provide a significant protection against the type-I allergic reaction. These findings also suggest that tea catechins and caffeine play an important role in having an inhibitory effect on the type-I allergic reaction. [12]
In a case-control, serially matched study, 70 patients with thyroid cancer, 55 with benign thyroid disease and 71 controls were interviewed in regard to a variety of socioeconomic, social and dietary characteristics. Statistical analysis revealed a strikingly negative (p less than 0.05) association between benign and malignant thyroid disease and consumption of coffee. After adjustment for possible confounding variables, the association remained statistically significant. The mechanism by which coffee consumption may play a protective role against development of benign or malignant thyroid neoplasms may be the stimulatory effect of caffeine on the intracellular cyclic AMP production, which is known to inhibit cell growth. [13]
Consumption of caffeine-rich beverages, which have diuretic properties, may decrease serum uric acid concentrations. We examined cross-sectionally the relationship of coffee and green tea consumption to serum uric acid concentrations in 2240 male self-defence officials who received a pre-retirement health examination at four hospitals of the Self-Defence Forces between 1993 and 1994. The mean levels of coffee and green tea consumption were 2.3 and 3.1 cups/d respectively. There was a clear inverse relationship between coffee consumption and serum uric acid concentration. When adjusted for hospital only, those consuming less than one cup of coffee daily had a mean serum uric acid concentration of 60 mg/l, while that of those drinking five or more cups of coffee daily was 56 mg/l (P < 0.0001). No such relationship was observed for green tea, another major dietary source of caffeine in Japan. The relationship between coffee consumption and serum uric acid concentration was independent of age, rank in the Self-Defence Forces, BMI, systolic blood pressure, serum creatinine, serum total cholesterol and serum HDL-cholesterol concentrations, smoking status, alcohol use, beer consumption and intake of dairy products. These findings suggest that coffee drinking may be associated with lower concentrations of serum uric acid, and further studies are needed to confirm the association. [14]
Oral administration of green or black tea inhibited UVB light-induced complete carcinogenesis in the skin of SKH-1 mice. Green tea was a more effective inhibitor than black tea. Oral administration of decaffeinated green or black tea resulted in substantially less inhibitory activity than did administration of the regular teas, and in one experiment, administration of a high-dose level of the decaffeinated teas enhanced the tumorigenic effect of UVB. Oral administration of caffeine alone had a substantial inhibitory effect on UVB-induced carcinogenesis, and adding caffeine to the decaffeinated teas restored the inhibitory effects of these teas on UVB-induced carcinogenesis. In additional studies, topical application of a green tea polyphenol fraction after each UVB application inhibited UVB-induced tumorigenesis. The results indicate that caffeine contributes in an important way to the inhibitory effects of green and black tea on UVB-induced complete carcinogenesis. [15]
The urine of human coffee drinkers who ingested 12 g of instant coffee per day, during 4 days in a first experiment or 12 g within 2 h in a second experiment, was fractionated by XAD-2 column chromatography.
The non-polar urine fractions so obtained were not mutagenic in the Ames Salmonella tester strains TA98 or TA100 in either experiment, either with or without β-glucuronidase treatment of the urine.
The non-polar urine fraction of smokers, who smoked 20–30 cigarettes per day during 4 days in the first experiment or 7–18 cigarettes during 7 h in the second experiment, was mutagenic when metabolically activated. [16]
Reduced offspring growth was found following introduction of caffeine into the normal diet of rats during pregnancy and lactation. When maternal caffeine (10 mg/kg/day) was consumed together with supplementary sucrose (7 g/kg/day) the expected offspring growth reduction attributed to caffeine did not occur. It is concluded that maternal nutritional status may determine the outcome of caffeine exposure at low concentrations which mimic human usage. [17]
The effects of caffeine on neuronal survival independent of trophic factor support were examined in developing superior cervical ganglion in vitro. We found that caffeine promoted neuronal survival in the absence of nerve growth-factor (NGF) in a dose-dependent manner (EC50 =6 nM). Pulse treatment with caffeine or high K+ (40 mM), which caused only a transient increase in intracellular free Ca2+ levels ([Ca2+]i), did not promote survival. In contrast, caffeine potentiated the saving effect of various phosphodiesterase inhibitors including theophylline (EC50 = 3nM) and 3-isobutyl-1-metylxanthine (EC50 = 0.4 nM). Non-xanthine phosphodiesterase inhibitor Ro 20–1724 potentiated the survival promoting effect of caffeine or IBMX. Indeed, administration of 20 mM caffeine rapidly restored the cAMP level of NGF-deprived neurons to normal (0.34 pmol/well) within 10 min; the level reached a plateau level (0.69 pmol/well) at 10 h. Even after 1 day, the sustained level was maintained in the presence of caffeine. In contrast, noradrenaline and isoproterenol, which cause only a transient increase in cAMP levels, did not support survival. These data, in conjunction with others, suggest that sustained levels of second messengers, including not only the [Ca2+]i but also the cAMP level, would support the survival of superior cervical ganglion cells independent of trophic factor support. [18]
Context The projected expansion in the next several decades of the elderly population at highest risk for Parkinson disease (PD) makes identification of factors that promote or prevent the disease an important goal.
Objective To explore the association of coffee and dietary caffeine intake with risk of PD.
Design, Setting, and Participants Data were analyzed from 30 years of follow-up of 8004 Japanese-American men (aged 45-68 years) enrolled in the prospective longitudinal Honolulu Heart Program between 1965 and 1968.
Main Outcome Measure Incident PD, by amount of coffee intake (measured at study enrollment and 6-year follow-up) and by total dietary caffeine intake (measured at enrollment).
Results During follow-up, 102 men were identified as having PD. Age-adjusted incidence of PD declined consistently with increased amounts of coffee intake, from 10.4 per 10,000 person-years in men who drank no coffee to 1.9 per 10,000 person-years in men who drank at least 28 oz/d (P<.001 for trend). Similar relationships were observed with total caffeine intake (P<.001 for trend) and caffeine from noncoffee sources (P=.03 for trend). Consumption of increasing amounts of coffee was also associated with lower risk of PD in men who were never, past, and current smokers at baseline (P=.049, P=.22, and P=.02, respectively, for trend). Other nutrients in coffee, including niacin, were unrelated to PD incidence. The relationship between caffeine and PD was unaltered by intake of milk and sugar.
Conclusions Our findings indicate that higher coffee and caffeine intake is associated with a significantly lower incidence of PD. This effect appears to be independent of smoking. The data suggest that the mechanism is related to caffeine intake and not to other nutrients contained in coffee.
Parkinson disease (PD) afflicts 3% of the population older than 65 years1 and is a significant source of morbidity and health services use. Based on the projected growth of the US population, this percentage could double in the next 30 to 40 years.2 While rare genetic forms exist, determinants of typical late-onset disease appear to be largely environmental.3,4 No treatment has definitively been shown to prevent disease or slow progression. Identification of risk factors may lead to an understanding of pathogenic mechanisms and to effective strategies for prevention.
Coffee intake has been inversely associated with PD occurrence in some studies, but evidence has been equivocal.5- 8 In an earlier longitudinal study from the Honolulu Heart Program, coffee intake measured prospectively appeared to be protective against PD, but not after adjustment for cigarette smoking.5
This article presents an expanded analysis of the relationship between consumption of coffee and dietary caffeine and risk of PD within the Honolulu Heart Program cohort, based on longer follow-up and nearly twice the number of incident PD cases than were previously available.5 The role of other nutrients contained in coffee are also examined. [19]
Treatment of SKH-1 mice with ultraviolet B light (UV-B, 30 mJ/cm2) twice a week for 22-23 weeks resulted in tumor-free animals with a high risk of developing malignant and nonmalignant tumors during the next several months in the absence of further UV-B treatment (high-risk mice). In three separate experiments, oral administration of green tea or black tea (4-6 mg tea solids/ml) as the sole source of drinking fluid for 18-23 weeks to these high-risk mice inhibited the formation and decreased the size of nonmalignant squamous cell papillomas and keratoacanthomas as well as the formation and size of malignant squamous cell carcinomas. In one experiment all these inhibitory effects of tea were statistically significant, whereas in the two other experiments many but not all of the inhibitory effects of tea were statistically significant. The decaffeinated teas were inactive or less effective inhibitors of tumor formation than the regular teas, and adding caffeine back to the decaffeinated teas restored biological activity. Oral administration of caffeine alone (0.44 mg/ml) as the sole source of drinking fluid for 18-23 weeks inhibited the formation of nonmalignant and malignant tumors, and this treatment also decreased tumor size in these high-risk mice. [20]
The association of coffee consumption with the development of increased serum aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) activities over 4 years was studied in 1221 liver dysfunction-free (serum AST and ALT < or = 39 IU/l and no medical care for or no past history of liver disease) Japanese male office workers aged 35 to 56 years. From the analysis using the Kaplan-Meier method, the estimated incidence of serum AST and/or ALT > or = 40 IU/l, > or = 50 IU/l, and > or = 60 IU/l decreased with an increase in coffee consumption. From the Cox proportional hazards model, coffee drinking was independently inversely associated with the development of serum AST and/or ALT > or = 40 IU/l (p = 0.019 by test for tendency), > or = 50 IU/l (p = 0.002), and > or = 60 IU/l (p = 0.007), controlling for age, body mass index, alcohol intake, and cigarette smoking. These results suggest that coffee may be protectively against the liver dysfunction in middle-aged Japanese men. [21]
BACKGROUND: Attention has long been drawn to the potentially harmful effects of coffee on health, however recent epidemiological studies have suggested unexpected, possibly beneficial effects of coffee against the occurrence of alcoholic liver cirrhosis and upon serum liver enzyme levels. METHODS:
We examined the potential inverse association between coffee drinking and serum concentrations of gamma-glutamyltransferase (GGT) and aminotransferases, with special reference to interaction with alcohol consumption, in a cross-sectional study involving 12687 health examinees (7398 men and 5289 women) aged 40-69 years from over 1000 workplaces in Nagano prefecture in central Japan. Those who had a history of liver disease and/or serum aminotransferases exceeding the normal range were excluded. Possible confounding effects of alcohol consumption, body mass index, cigarette smoking, and green tea consumption were controlled through multivariate analyses.
RESULTS: Increased coffee consumption was strongly and independently associated with decreased GGT activity among males (P trend < 0.0001); the inverse association between coffee and serum GGT was more evident among heavier alcohol consumers (P < 0.0001), and was absent among non-alcohol drinkers. Among females, however, coffee was only weakly related to lower GGT level. Similar inverse associations with coffee and interactions between coffee and alcohol intake were observed for serum aspartate aminotransferase and alanine aminotransferase. Intake of green tea, another popular source of caffeine in Japan, did not materially influence the liver enzyme levels.
CONCLUSIONS: Our results suggest that coffee may inhibit the induction of GGT in the liver by alcohol consumption, and may possibly protect against liver cell damage due to alcohol. [22]
Both carbohydrate (CHO) and caffeine have been used as ergogenic aids during exercise. It has been suggested that caffeine increases intestinal glucose absorption, but there are also suggestions that it may decrease muscle glucose uptake. The purpose of the study was to investigate the effect of caffeine on exogenous CHO oxidation. In a randomized crossover design, eight male cyclists (age 27 +/- 2 yr, body mass 71.2 +/- 2.3 kg, maximal oxygen uptake 65.7 +/- 2.2 ml x kg(-1) x min(-1)) exercised at 64 +/- 3% of maximal oxygen uptake for 120 min on three occasions. During exercise subjects ingested either a 5.8% glucose solution (Glu; 48 g/h), glucose with caffeine (Glu+Caf, 48 g/h + 5 mg x kg(-1) x h(-1)), or plain water (Wat). The glucose solution contained trace amounts of [U-13C]glucose so that exogenous CHO oxidation could be calculated. CHO and fat oxidation were measured by indirect calorimetry, and 13C appearance in the expired gases was measured by continuous-flow IRMS. Average exogenous CHO oxidation over the 90- to 120-min period was 26% higher (P < 0.05) in Glu+Caf (0.72 +/- 0.04 g/min) compared with Glu (0.57 +/- 0.04 g/min). Total CHO oxidation rates were higher (P < 0.05) in the CHO ingestion trials compared with Wat, but they were highest when Glu+Caf was ingested (1.21 +/- 0.37, 1.84 +/- 0.14, and 2.47 +/- 0.23 g/min for Wat, Glu, and Glu+Caf, respectively; P < 0.05). There was also a trend (P = 0.082) toward an increased endogenous CHO oxidation with Glu+Caf (1.81 +/- 0.22 g/min vs. 1.27 +/- 0.13 g/min for Glu and 1.12 +/- 0.37 g/min for Wat). In conclusion, compared with glucose alone, 5 mg x kg(-1) x h(-1) of caffeine coingested with glucose increases exogenous CHO oxidation, possibly as a result of an enhanced intestinal absorption. [23]
Rats consuming Coca-Cola and Purina chow ad libitum increased their total energy intake by 50% without excess weight gain. Their resistance to cold was markedly improved. These phenomena were characterized by significant increases in interscapular brown adipose tissue weight (IBAT) (91%), cellularity (59%), triglyceride content (52%), protein content (94%), and cytochrome oxidase activity (167%). In contrast, Coca-Cola consumption did not significantly affect the cellularity or triglyceride content of parametrial white adipose tissue (PWAT), although it slightly augmented PWAT weight. The effects of Coca-Cola on cold resistance, IBAT cellularity, and composition were entirely reproduced by sucrose, but not caffeine, consumption. Although caffeine also increased IBAT cellularity and composition, it significantly decreased the rate of body weight gain, PWAT weight, and adipocyte size. Moreover, it markedly inhibited adipocyte proliferation in PWAT thereby mimicking the effects of exercise training and food restriction (Bukowiecki et al., Am. J. Physiol. 239 (Endocrinol. Metab. 2): E422-E429, 1980). It is concluded a) that sucrose and Coca-Cola consumption improve the resistance of rats to cold, most probably by increasing brown adipose tissue cellularity, and b) that moderate caffeine intake might be useful for inhibiting proliferative activity in white adipose tissue, thereby preventing obesity. [24]
Our previous study demonstrated that long-term cola consumption reduced body weight and improved insulin sensitivity in healthy male rats. In this study, we investigated the effect and mechanism of caffeine and sucrose, major components of cola, on glucose metabolism in 90% pancreatectomized diabetic rats. After a 12-week administration of 0.01% caffeine solution, the rats exhibited reduced body weight, fats, and insulin resistance, without a change in food intake, regardless of an 11% sucrose solution supplementation. In addition, caffeine enhanced glucose-stimulated first- and second-phase insulin secretion and beta-cell hyperplasia. This insulinotropic action was explained by potentiating an insulin/insulin-like growth factor 1 (IGF-1) signaling cascade via induction of insulin receptor substrate 2 in islets. In contrast, sucrose supplementation deteriorated insulin sensitivity and attenuated insulin/IGF-1 signaling in islets, which reduced the number of beta cells. Caffeine nullified the adverse effect of sucrose on glucose homeostasis. These findings indicate that long-term caffeine consumption can help alleviate diabetic symptoms by enhancing insulin sensitivity and beta-cell function through improved insulin/IGF-1 signaling via induction of insulin receptor substrate 2 in mildly diabetic rats. [25]
BACKGROUND: Caffeine is known to inhibit phosphodiesterases, to mobilise intracellular calcium, and to act as an antagonist at adenosine receptors, all of which can potentially alter nitric oxide (NO) production. It was therefore hypothesised that caffeine may alter exhaled NO (eNO) levels.
METHODS: In a randomised, single blind, crossover manner, 12 normal subjects consumed either (1) coffee and a placebo capsule, (2) decaffeinated coffee and a capsule of 200 mg caffeine, or (3) decaffeinated coffee and a placebo capsule. Serum caffeine levels were measured at baseline and 1 hour later. Exhaled NO levels were also measured at baseline and each hour for 4 hours.
RESULTS: A significant percentage fall in mean (SE) eNO from baseline was seen 1 hour after either caffeinated coffee or a caffeine capsule when compared with placebo (13.5 (4.0)%, p=0.009 and 19.0 (3.8)%, p=0.001, respectively).
CONCLUSION: Caffeine causes a significant decrease in eNO which will need to be considered when designing trials to measure eNO levels. The mechanism may be via adenosine receptor antagonism or by altering levels of cGMP. [26]
The effects of caffeine, a naturally occurring stimulant, on the brain and plasma concentrations of neuroactive steroids were examined in the rat. A single intraperitoneal injection of caffeine induced dose- and time-dependent increases in the concentrations of pregnenolone, progesterone, and 3α-hydroxy-5α-pregnan-20-one (allopregnanolone) in the cerebral cortex. The increases were significant at a caffeine dose of 25 mg/kg and greatest (+188, +388, and +71%, respectively) at a dose of 100 mg/kg in rats killed 30 min after caffeine administration. Caffeine also increased the plasma concentrations of pregnenolone and progesterone with a dose-response relation similar to that observed in the brain, whereas the caffeine-induced increase in the plasma concentration of allopregnanolone was maximal at a dose of 50 mg/kg. Caffeine increased the plasma concentration of corticosterone, but it had no effect on the brain or plasma concentrations of 3α,21-dihydroxy-5α-pregnan-20-one and dehydroepiandrosterone. Moreover, the brain and plasma concentrations of pregnenolone, progesterone, and allopregnanolone were not affected by caffeine in adrenalectomized-orchiectomized rats. These results suggest that neuroactive steroids may modulate the stimulant and anxiogenic effects of caffeine. [27]
Paracetamol has mild analgesic and antipyretic properties and is, along with acetylsalicylic acid, one of the most popular "over the counter" analgesic agents. However, the mechanism underlying its clinical effects is unknown. Another drug whose mechanism of action is unknown is caffeine, which is often used in combination with other analgesics, augmenting their effect. We investigated the inhibitory effect of paracetamol and caffeine on lipopolysaccharide (LPS)-induced cyclooxygenase (COX)- and prostaglandin (PG)E(2)-synthesis in primary rat microglial cells and compared it with the effect of acetylsalicylic acid, salicylic acid, and dipyrone. Furthermore, combinations of these drugs were used to investigate a possible synergistic inhibitory effect on PGE(2)-synthesis. Both paracetamol (IC(50)=7.45 microM) and caffeine (IC(50)=42.5 microM) dose-dependently inhibited microglial PGE(2) synthesis. In combination with acetylsalicylic acid (IC(50)=3.12 microM), both substances augmented the inhibitory effect of acetylsalicylic acid on LPS-induced PGE(2)-synthesis. Whereas paracetamol inhibited only COX enzyme activity, caffeine also inhibited COX-2 protein synthesis. These results are compatible with the view that the clinical activity of paracetamol and caffeine is due to inhibition of COX. Furthermore, these results may help explain the clinical experience of an adjuvant analgesic effect of caffeine and paracetamol when combined with acetylsalicylic acid. [28]
Methylxanthines are widely consumed because of their stimulating effect primarily on the central nervous system. Their diuretic and respiratory stimulant action is used in clinical medicine. L-Arginine metabolism in the brain is very important for normal brain function. In addition to brain protein synthesis, arginine is a substrate for the production of urea, creatine, nitric oxide, agmatine, glutamic acid, ornithine, proline and polyamines. As known, many of these compounds are very important in brain function. There is no information relating to effects of caffeine on arginine metabolism in the brain, however, there is a lot of new information about arginine metabolism and caffeine action on the central nervous system. So, we have hypothesized the existence of a relationship that may be of interest in understanding mechanisms of caffeine effects on the central nervous system that may have utility in the clinical applications.
In our experiment protocol we used male Wistar rats weighing about 200 g. Caffeine was added to the drinking water in gradually increasing amounts, from 2 g/l over the first 3 days, to 4 g/l over the last 7 days. A control group was given drinking water without caffeine. The level of lipid peroxidation, arginase and diamine oxidase (DAO) activity in the brain was measured. The results of our study show that arginase and diamine oxidase were decreased in animals treated with caffeine. The level of lipid peroxidation (MDA) was decreased also.
The inhibitory effect of caffeine on arginase activity indicates that caffeine provides more arginine for consumption in other metabolic pathways. Considering the central stimulant effects of caffeine and the decreased lipid peroxidation level, it can be assumed that moderate short-term consumption of caffeine may be beneficial for brain function. [29]
It was demonstrated that the altered endocrine environment caused by caffeine consumption could be equated with a stress-like pattern of response. A single acute treatment with caffeine (30 or 60 mg/kg) to male rats approximately 85 days old caused plasma concentrations of corticosterone, progesterone, testosterone and Na+ to rise significantly above control values. These changes were evident 3 min after caffeine administration and were maintained for 1–4 h before returning to normal. In animals exposed to daily chronic caffeine treatment for 10 days or more the levels of progesterone fell and Na+ rose significantly compared with control values at 24 h after administration. Following a single treatment of 30 mg/kg, caffeine was detected in blood plasma after 3 min, and reached peak levels by 1 h. After 24 h, less than 2% of the peak levels of caffeine remained. Metabolites of caffeine were detectable within 6 min and reached their peak levels 4 and 12 h later for theophylline and theobromine respectively.
It is suggested that high steroid levels may in the long-term cause an altered hepatic clearance pattern affecting both steroid metabolism and caffeine elimination. A preliminary study of the morphology of livers from males chronically exposed to caffeine revealed that the hepatic cells lost cytoplasmic matrix, and that the sinusoids did not show up as clear spaces, compared with those in the controls. [30]
1. Relationships between ornithine decarboxylase (ODC) and adenosine diphosphate ribosyl transferase (ADPRT) in human mononuclear leukocytes (HML) were tested by statistical comparisons of their values in a group of 46 people, and by use of inhibitors of ADPRT.
2. ODC was assayed following exposure of HML, for 20 hr, to mitogens [phytohemagglutinin (PHA) and pokeweed mitogen]; ADPRT was measured following exposure of HML to H2O2, (100 μM) for 1 hr (activated ADPRT), and in parallel cultures without H2O; (constitutive ADPRT).
3. Significant correlations were found between ODC and ADPRT values; the effects of smoking disturbed the correlations. PHA induction of ODC was negatively influenced by age (standardized β coefficient = −2.95, P = 0.005), while age also influenced ADPRT values negatively in non-smokers (for H2O2, activated ADPRT, standardized β coefficient = −2.74, P < 0.008).
4. Inhibitors of ADPRT, nicotinamide, caffeine and benzamide inhibited the induction of ODC by PHA in a concentration-dependent manner, in the range (0.6–10mM) known to inhibit ADPRT. [31]
Both carbohydrate (CHO) and caffeine have been used as ergogenic aids during exercise. It has been suggested that caffeine increases intestinal glucose absorption, but there are also suggestions that it may decrease muscle glucose uptake. The purpose of the study was to investigate the effect of caffeine on exogenous CHO oxidation. In a randomized crossover design, eight male cyclists (age 27 +/- 2 yr, body mass 71.2 +/- 2.3 kg, maximal oxygen uptake 65.7 +/- 2.2 ml x kg(-1) x min(-1)) exercised at 64 +/- 3% of maximal oxygen uptake for 120 min on three occasions. During exercise subjects ingested either a 5.8% glucose solution (Glu; 48 g/h), glucose with caffeine (Glu+Caf, 48 g/h + 5 mg x kg(-1) x h(-1)), or plain water (Wat). The glucose solution contained trace amounts of [U-13C]glucose so that exogenous CHO oxidation could be calculated. CHO and fat oxidation were measured by indirect calorimetry, and 13C appearance in the expired gases was measured by continuous-flow IRMS. Average exogenous CHO oxidation over the 90- to 120-min period was 26% higher (P < 0.05) in Glu+Caf (0.72 +/- 0.04 g/min) compared with Glu (0.57 +/- 0.04 g/min). Total CHO oxidation rates were higher (P < 0.05) in the CHO ingestion trials compared with Wat, but they were highest when Glu+Caf was ingested (1.21 +/- 0.37, 1.84 +/- 0.14, and 2.47 +/- 0.23 g/min for Wat, Glu, and Glu+Caf, respectively; P < 0.05). There was also a trend (P = 0.082) toward an increased endogenous CHO oxidation with Glu+Caf (1.81 +/- 0.22 g/min vs. 1.27 +/- 0.13 g/min for Glu and 1.12 +/- 0.37 g/min for Wat). In conclusion, compared with glucose alone, 5 mg x kg(-1) x h(-1) of caffeine coingested with glucose increases exogenous CHO oxidation, possibly as a result of an enhanced intestinal absorption. [32]]
Adenosine consists of one ribose and one purine moiety and binds to specific receptors on cell membranes. The receptors are coupled to G-proteins and additionally to various effector-systems. When a mismatch occurs between energy supply and energy demand, adenosine is produced by the catabolism of adenosine triphosphate. The metabolism of an organ is thereby coupled to the local blood supply (metabolic vasodilation). In addition to vasodilation, adenosine has several electrophysiological, cardioprotective, metabolic, and antiinflammatory properties. Adenosine is rapidly metabolized in blood and interstitial fluid, through cell absorption and degradation by adenosine deaminase. The short half-life of adenosine limits its clinical value. However, there are several ways of increasing the interstitial concentration of adenosine. At present, adenosine or adenosine-potentiating substances are used clinically to terminate supraventricular tachycardias, to induce myocardial ischemia in patients who are unable to exercise, and to reduce myocardial ischemia or reperfusion injury. Caffeine and other methylxanthines are adenosine receptor antagonists, and several of the pharmacodynamic properties of these substances are caused by adenosine receptor antagonism. [33]
Summary:
Background Characterization of mechanisms that can reverse residual damage from prior skin exposure to ultraviolet (UV) would be of considerable biological and therapeutic interest. Topical caffeine application to mouse skin that had previously been treated with UV has been shown to inhibit the subsequent development of squamous cell carcinomas.
Objectives We used an established mouse photodamage model to investigate other possible effects of topical caffeine application after UV.
Methods SKH-1 hairless mice were treated with ultraviolet B (UVB) followed immediately by topical application of caffeine or vehicle three times weekly for 11 weeks.
Results Caffeine applied topically after UV treatment resulted in a significant decrease in UV-induced skin roughness/transverse rhytides as assessed by treatment-blinded examiners. Histologically, topical caffeine application after a single dose of UVB more than doubled the number of apoptotic keratinocytes as evaluated by sunburn cell formation, caspase 3 cleavage and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) staining. A trend towards decreased solar elastosis was noted in the caffeine-treated group although this was not statistically significant. Other histological parameters including epidermal hyperplasia, solar elastosis and angiogenesis were increased in mice treated with UV but topical application of caffeine did not alter these particular UV effects.
Conclusions These findings support the concept that topical application of caffeine to mouse skin after UV irradiation promotes the deletion of DNA-damaged keratinocytes and may partially diminish photodamage as well as photocarcinogenesis. [34]
Despite caffeine's wide consumption and well-documented psychoactive effects, little is known regarding the effects of caffeine on neurovascular coupling. In the present study, we evaluated the effects of caffeine, an adenosine receptor antagonist, on intracerebral arterioles in vitro and subsequently, on the pial circulation in vivo during cortical activation induced by contralateral sciatic nerve stimulation (SNS). In our in vitro studies, we utilized isolated intracerebral arterioles to determine the effects of caffeine (10 or 50 micromol/L) on adenosine-induced vasodilatation. At the lower concentration, caffeine was without effect, but at the higher concentration, caffeine produced significant attenuation. In our in vivo studies, we determined the cerebrospinal fluid (CSF) caffeine concentrations at 15, 30, and 60 mins after intravenous administration of 5, 10 and 40 mg/kg. At the latter two concentrations, CSF levels exceeded 10 micromol/L. We then evaluated the pial arteriolar response during cortical activation caused by contralateral SNS after administering caffeine intravenously (0, 5, 10, 20 30, and 40 mg/kg). The pial circulation was observed through a closed cranial window in chloralose-anesthetized Sprague-Dawley rats. The contralateral sciatic nerve was isolated, positioned on silver electrodes and stimulated for 20 secs (0.20 V, 0.5 ms, and 5 Hz). Arteriolar diameter was quantified using an automated video dimension analyzer. Contralateral SNS resulted in a 23.8% +/-3.9% increase in pial arteriolar diameter in the hindlimb sensory cortex under control conditions. Intravenous administration of caffeine at the lowest dose studied (5 mg/kg) had no effect on either resting arteriolar diameter or SNS-induced vasodilatation. However, at higher doses (10, 20, 30, and 40 mg/kg, intravenously), caffeine significantly (P < 0.05; n = 6) attenuated both resting diameter and cerebral blood flow (CBF) responses to somatosensory stimulation. Intravenous administration of theophylline (10, 20, and 40 mg/kg), another adenosine receptor antagonist, also significantly reduced SNS-induced vasodilatation in a dose-dependent manner. Hypercarbic vasodilatation was unaffected by either caffeine or theophylline. The results of the present study show that caffeine significantly reduces cerebrovascular responses to both adenosine and to somatosensory stimulation and supports a role of adenosine in the regulation of CBF during functional neuronal activity. [35]
Frequent coffee consumption has been associated with a reduced risk of colorectal cancer in a number of case-control studies. Coffee is a leading source of methylxanthines, such as caffeine. The induction of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) is an essential feature of tumor angiogenesis, and the hypoxia-inducible factor-1 (HIF-1) transcription factor is known to be a key regulator of this process. In this study, we investigated the effects of caffeine on HIF-1 protein accumulation and on VEGF and IL-8 expression in the human colon cancer cell line HT29 under hypoxic conditions. Our results show that caffeine significantly inhibits adenosine-induced HIF-1alpha protein accumulation in cancer cells. We show that HIF-1alpha and VEGF are increased through A3 adenosine receptor stimulation, whereas the effects on IL-8 are mediated via the A2B subtype. Pretreatment of cells with caffeine significantly reduces adenosine-induced VEGF promoter activity and VEGF and IL-8 expression. The mechanism of caffeine seems to involve the inhibition of the extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and Akt, leading to a marked decrease in adenosine-induced HIF-1alpha accumulation, VEGF transcriptional activation, and VEGF and IL-8 protein accumulation. From a functional perspective, we observe that caffeine also significantly inhibits the A3 receptor-stimulated cell migration of colon cancer cells. Conditioned media prepared from colon cells treated with an adenosine analog increased human umbilical vein endothelial cell migration. These data provide evidence that adenosine could modulate the migration of colon cancer cells by an HIF-1alpha/VEGF/IL-8-dependent mechanism and that caffeine has the potential to inhibit colon cancer cell growth. [36]
Chronic inflammation of rheumatoid arthritis (RA) is promoted by proinflammatory cytokines and closely linked to angiogenesis. In the present study, we investigated the anti-inflammatory effects of emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) isolated from the root of Rheum palmatum L. in interleukin 1 beta (IL-1β) and lipopolysaccharide (LPS)-stimulated RA synoviocytes under hypoxia. Emodin significantly inhibited IL-1β and LPS-stimulated proliferation of RA synoviocytes in a dose-dependent manner under hypoxic condition. Also, enzyme linked immunosorbent assay (ELISA) revealed that emodin significantly reduced the production of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-α), IL-6 and IL-8], mediators [prostagladin E(2) (PGE(2)), matrix metalloproteinase (MMP)-1 and MMP-13] and vascular endothelial growth factor (VEGF) as an angiogenesis biomarker in IL-1β and LPS-treated synoviocytes under hypoxia. Consistently, emodin attenuated the expression of cyclooxygenase 2 (COX-2), VEGF, hypoxia inducible factor 1 alpha (HIF-1α), MMP-1 and MMP-13 at mRNA level in IL-1β and LPS-treated synoviocytes under hypoxia. Furthermore, emodin reduced histone deacetylase (HDAC) activity as well as suppressed the expression of HDAC1, but not HDAC2 in IL-1β and LPS-treated synoviocytes under hypoxia. Overall, these findings suggest that emodin inhibits proinflammatory cytokines and VEGF productions, and HDAC1 activity in hypoxic RA synoviocytes. [37]
Hormone-refractory relapse is an inevitable and lethal event for advanced prostate cancer patients after hormone deprivation. A growing body of evidence indicates that hormone deprivation may promote this aggressive prostate cancer phenotype. Notably, androgen receptor (AR) not only mediates the effect of androgen on the tumor initiation but also plays the major role in the relapse transition. This provides a strong rationale for searching new effective agents targeting the down-regulation of AR to treat or prevent advanced prostate cancer progression. Here, we show that emodin, a natural compound, can directly target AR to suppress prostate cancer cell growth in vitro and prolong the survival of C3(1)/SV40 transgenic mice in vivo. Emodin treatment resulted in repressing androgen-dependent transactivation of AR by inhibiting AR nuclear translocation. Emodin decreased the association of AR and heat shock protein 90 and increased the association of AR and MDM2, which in turn induces AR degradation through proteasome-mediated pathway in a ligand-independent manner. Our work indicates a new mechanism for the emodin-mediated anticancer effect and justifies further investigation of emodin as a therapeutic and preventive agent for prostate cancer. [38]
Effects of emodin (EMD) treatment on mitochondrial ATP generation capacity and antioxidant components as well as susceptibility to ischemia–reperfusion (I–R) injury were examined in male and female rat hearts. Isolated-perfused hearts prepared from female rats were less susceptible to I–R injury than those of male rats. I–R caused significant decreases in ATP generation capacity and reduced glutathione (GSH) and α-tocopherol (α-TOC) levels as well as glutathione reductase, Se-glutathione peroxidase and Mn-superoxide dismutase (SOD) activities. The lower susceptibility of female hearts to myocardial I–R injury was associated with higher levels of GSH and α-TOC as well as activity of SOD than those of male hearts. EMD treatment at 3 daily doses (0.6 or 1.2 mmol/kg) could enhance myocardial mitochondrial ATP generation capacity and antioxidant components in both male and female rat hearts, but it only significantly protected against I–R injury in female hearts. Treatment with a single dose of EMD invariably enhanced mitochondrial antioxidant components and protected against I–R injury in both male and female hearts. The gender-dependent effect of EMD treatment at multiple doses may be related to the differential antioxidant response in the myocardium and/or induction of drug metabolizing enzymes in the liver. [39]
Using an ex vivo rat heart model of ischemia-reperfusion (I-R) injury, we examined the effect of pharmacological preconditioning by chronic treatment with emodin (EMD)/oleanolic acid (OA) at low dose (25 micromol/kg/day x 15) and/or ischemic preconditioning (IPC) (4 cycles of 5 min ischemia followed by 5 min of reperfusion) on myocardial I-R injury. The results indicated that EMD/OA pretreatment, IPC, or their combinations (EMD+IPC and OA+IPC) protected against myocardial I-R injury, as assessed by lactate dehydrogenase leakage and contractile force recovery. The cardioprotection was associated with a differential enhancement in mitochondrial antioxidant components. The combined EMD/OA and IPC pretreatment produced cardioprotective action in a semi-additive manner. This suggested that EMD/OA pretreatment and IPC protected against myocardial I-R injury via a similar but not identical biochemical mechanism. [40]
Rhubarb extracts provide neuroprotection after brain injury, but the mechanism of this protective effect is not known. The present study tests the hypothesis that rhubarb extracts interfere with the release of glutamate by brain neurons and, therefore, reduce glutamate excitotoxicity. To this end, the effects of emodin, an anthraquinone derivative extracted from Rheum tanguticum Maxim. Ex. Balf, on the synaptic transmission of CA1 pyramidal neurons in rat hippocampus were studied in vitro. The excitatory postsynaptic potential (EPSP) was depressed by bath-application of emodin (0.3–30 μM). Paired-pulse facilitation (PPF) of the EPSP was significantly increased by emodin. The monosynaptic inhibitory postsynaptic potential (IPSP) recorded in the presence of glutamate receptor antagonists (DNQX and AP5) was not altered by emodin. Emodin decreased the frequency, but not the amplitude, of the miniature EPSP (mEPSP). The inhibition of the EPSP induced by emodin was blocked by either 8-CPT, an adenosine A1 receptor antagonist, or by adenosine deaminase. These results suggest that emodin inhibits the EPSP by decreasing the release of glutamate from Schaffer collateral/commissural terminals via the activation of adenosine A1 receptors in rat hippocampal CA1 area and that the neuroprotective effects of rhubarb extracts may result from decreased glutamate excitotoxicity. [41]
Using an ex vivo rat heart model of ischemia-reperfusion (I-R) injury, we examined the effect of pharmacological preconditioning by chronic treatment with emodin (EMD)/oleanolic acid (OA) at low dose (25 micromol/kg/day x 15) and/or ischemic preconditioning (IPC) (4 cycles of 5 min ischemia followed by 5 min of reperfusion) on myocardial I-R injury. The results indicated that EMD/OA pretreatment, IPC, or their combinations (EMD+IPC and OA+IPC) protected against myocardial I-R injury, as assessed by lactate dehydrogenase leakage and contractile force recovery. The cardioprotection was associated with a differential enhancement in mitochondrial antioxidant components. The combined EMD/OA and IPC pretreatment produced cardioprotective action in a semi-additive manner. This suggested that EMD/OA pretreatment and IPC protected against myocardial I-R injury via a similar but not identical biochemical mechanism. [42]
Enhanced cell migration is one of the underlying mechanisms in cancer invasion and metastasis. Therefore, inhibition of cell migration is considered to be an effective strategy for prevention of cancer metastasis. We found that emodin (3-methyl-1,6,8-trihydroxyanthraquinone), an active component from the rhizome of Rheum palmatum, significantly inhibited epidermal growth factor (EGF)- induced migration in various human cancer cell lines. In the search for the underlying molecular mechanisms, we demonstrated that phosphatidylinositol 3-kinase (PI3K) serves as the molecular target for emodin. In addition, emodin markedly suppressed EGF-induced activation of Cdc42 and Rac1 and the corresponding cytoskeleton changes. Moreover, emodin, but not LY294002, was able to block cell migration in cells transfected with constitutively active (CA)-Cdc42 and CA-Rac1 by interference with the formation of Cdc42/Rac1 and the p21-activated kinase complex. Taken together, data from this study suggest that emodin inhibits human cancer cell migration by suppressing the PI3K-Cdc42/Rac1 signaling pathway. [43]
An anthraquinone derivative, emodin, suppresses tumor development both in vitro and in vivo. In this study, we examined the anti-angiogenic activity of emodin and its modifying effect on the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. In cell cultures, emodin inhibited endothelial cell proliferation, migration, and tube formation in a dose-dependent manner. In addition, the mouse dorsal air sac assay revealed the vivo anti-angiogenic potential of emodin. Matrix metalloproteinase-9 (MMP-9) expression, which is critical for the angiogenic process, including migration and tube formation, decreased after exposure to emodin, as determined by polymerase chain reaction with reverse transcription (RT-PCR) and gelatin zymography. Moreover, the phosphorylation of ERK 1/2 decreased after exposure to emodin in a dose-dependent manner. These observations suggest that emodin has the potential to inhibit several angiogenic processes and that these effects may be related to suppression of the phosphorylation of ERK 1/2. [44]
Emodin, an inhibitor of protein tyrosine kinase, possesses antiviral, immunosuppressive, anti-inflammatory and anticancer effects. In the present study, we investigated the effect of emodin on the hyaluronic acid (HA)-induced invasion of human glioma cells. Emodin significantly inhibited the HA-induced invasion through a Matrigel coated chamber, secretion of matrix metalloproteinase (MMP)-2, and HA-induced secretion of MMP-9 in glioma cells. To investigate the possible mechanisms involved in these events, we performed Western blot analysis using phospho-specific antibodies, and found that emodin inhibited phosphorylation of focal adhesion kinase (FAK), extracellular regulated protein kinase (ERK) 1/2 and Akt/PKB; emodin also suppressed the transcriptional activity of two transcription factors, activator protein-1 (AP-1) and nuclear factor-κB (NF-κB), in glioma cells. In addition, oral administration of emodin suppressed in vivo MMP secretion by glioma tumors in nude mice. Taken together, our results indicate that emodin can effectively inhibit HA-induced MMP secretion and invasion of glioma through inhibition of FAK, ERK1/2 and Akt/PKB activation and partial inhibition of AP-1 and NF-κB transcriptional activities. Consequently, these results provide important insights into emodin as an anti-invasive agent for the therapy of human glioma. [45]
The herbs Rheum palmatum B and Polygonum cuspidatum S are frequently used as laxatives and anticancer drugs in Chinese medicine. The antimutagenic activity of these herbs as well as their active component emodin was examined in Salmonella typhimurium TA98. The crude extracts and emodin induced a dose-dependent decrease in the mutagenicity of benzo[a]pyrene (B[a]P), 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Furthermore, emodin reduced the mutagenicity of IQ by direct inhibition of the hepatic microsomal activation and not by interaction with proximate metabolites of IQ and/or by modification of DNA repair processes in the bacterial cell. Abbreviations:
B[a]P = benzo[a]pyrene; DMSO = dimethylsulphoxide; IQ = 2-amino-3-methylimidazo[4,5-f]quinoline; Trp-P-2 = 3-amino-1-methyl-5H-pyrido[4,3-b]indole [46]
Emodin, an anthraquinones component of Rheum palmatun, has been used for anti-inflammatory purposes. However, its underlying molecular effect(s) on target cells remain to be well clarified. Thus, our current study was aimed at investigating the regulatory mechanism of emodin on liposaccharide-induced inflammatory responses in RAW 264.7 macrophages by RT-PCR, Western blot analysis, immunocytochemical staining and immunofluorescence analysis. It was found that a treatment of 20 microg/ml emodin inhibited the expression of a panel of inflammatory-associated genes, including TNFalpha, iNOS, IL-10, cytosolic IkappaBalpha, IKK-alpha and IKK-gamma, to different extents as well as the nuclear translocation of NF-kappaB (nuclear factor-kappaB). The promoting effect of emodin on the production and translocation of p105 (the precursor of NF-kappaB p50) was time-dependent and reached a maximum at 5 h. Our data suggest that emodin plays its anti-inflammatory roles by regulating inflammatory cytokines, specifically by suppressing NF-kappaB activation. [47]
A high concentration of glutamate in the eyes not only activates N-methyl-D-aspartate (NMDA) receptors, but also is toxic to the retina ganglion cells (RGCs) in glaucomatous patients. Our previous study had found that aloe-emodin sulfates/glucuronides metabolites, an anthraquinone polyphenol, exerted a neuroprotective activity upon RGCs. In order to understand the mechanisms involved in this neuroprotective effect, this study aimed to determine the expressions of RNAs and proteins in various treatments. The proteins expressed in the control group, NMDA-treated group, and aloe-emodin metabolites-cotreated group were separated by two-dimensional gel electrophoresis (2-DE). Protein spots were excised from 2-DE and analyzed by nano-LC-MS/MS (nano-liquid chromatography with mass spectrometry; tandem MS). Quantitative polymerase chain reaction (Q-PCR) was used to investigate the RNA related to these proteins. There were 84 spots with significant differences in various treatments. Among the 84 spots, we identified 9 spots whose functions were closely related to regulate the apoptosis of cells. The results of Q-PCR were not completely unanimous with those of 2-DE. Our results suggested that aloe-emodin metabolites decreased NMDA-induced apoptosis of RGCs by preserving, and inducing, some proteins related to the antioxidation and regulation of cells' energy. Both the level of RNA and protein of superoxide dismutase (Cu-Zn) were significantly elevated after aloe-emodin metabolites were added. The mechanisms of neuroprotection are complicated, and involve not only the transcription and stability of mRNA, but also post-translation protein modifications, degradation, and protein-protein interaction. [48]
The aim of the present study was intended to investigate the ameliorating effects of emodin on memory consolidation via cholinergic, serotonergic and GABAergic neuronal systems in rats. First, we evaluated the ameliorating effects of emodin on cycloheximide (CXM)-induced impairment of passive avoidance response in rats. Secondly, we clarified the role of cholinergic, serotonergic or GABAergic system on the ameliorating effect of emodin by using 5-HT1A receptor partial agonist, 5-HT2 receptor antagonist, GABAB agonist, GABAA antagonist and muscarinic receptor antagonist. Emodin protected the rat from CXM-induced memory consolidation impairment. The beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by 8-OH-DPAT (5-HT1A receptor partial agonist) and ritanserin (5-HT2 receptor antagonist), but reduced by scopolamine. These results suggested that the beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by serotonergic 5-HT1A-receptor partial agonist and 5-HT2 receptor antagonist but reduced by muscarinic receptor antagonist. [49]
To study the influences of emodin and reconstruction of double blood supplies on liver regeneration of reduced size graft liver in rat model. A total of 45 SD-SD rat reduced size liver transplantation models were randomly divided into three groups (A-C). The conventional reduced size liver transplantation was performed on rats in group A, while the hepatic artery blood supply was restored in groups B and C. The emodin (1.5 mg/kg/d) was given by intraperitoneal route in group C only. The recipients were killed on the seventh day after the operation. The proliferative cell nuclear antigen (PCNA), TBil and ALT of serum were detected, and the pathological changes of liver cell were observed. The numbers of the rats that survived in A, B, and C group on the seventh day after operation were 14, 13, 13, respectively. The levels of TBil (31.5+/-5.2 micromol/L, 23.2+/-3.1 micromol/L vs 38.6+/-6.8 micromol/L), and ALT (5 351+/-1 050 nKat, 1300+/-900 nKat vs 5779+/-1202 nKat) in serum in groups B and C were lower than those in group A (P<0.05), while the expression of PCNA in groups B or C was higher than that in group A (22.0+/-3.5%, 28.2+/-4.2% vs 18.6+/-3.2%, P<0.05). The deeper staining nuclei, double nuclei, multi-nuclei and much glycogen were observed in liver cells of groups B and C, especially in group C, while fewer were found in liver cells of group A.
The reconstruction of arterial blood supply is very important for rat liver regeneration after reduced size liver transplantation. Emodin has the effect of promoting liver regeneration and improving liver function in rats after reduced size transplantation. The possible mechanism is improving proliferation of liver cell and protecting liver cells from injury. [50]
Anthraquinones represent a large family of compounds having diverse biological properties. Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is a naturally occurring anthraquinone present in the roots and barks of numerous plants, molds, and lichens, and an active ingredient of various Chinese herbs. Earlier studies have documented mutagenic/genotoxic effects of emodin, mainly in bacterial system. Emodin, first assigned to be a specific inhibitor of the protein tyrosine kinase p65lck, has now a number of cellular targets interacting with it. Its inhibitory effect on mammalian cell cycle modulation in specific oncogene overexpressed cells formed the basis of using this compound as an anticancer agent. Identification of apoptosis as a mechanism of elimination of cells treated with cytotoxic agents initiated new studies deciphering the mechanism of apoptosis induced by emodin. At present, its role in combination chemotherapy with standard drugs to reduce toxicity and to enhance efficacy is pursued vigorously. Its additional inhibitory effects on angiogenic and metastasis regulatory processes make emodin a sensible candidate as a specific blocker of tumor-associated events. Additionally, because of its quinone structure, emodin may interfere with electron transport process and in altering cellular redox status, which may account for its cytotoxic properties in different systems. However, there is no documentation available which reviews the biological activities of emodin, in particular, its growth inhibitory effects. This review is an attempt to analyze the biological properties of emodin, a molecule offering a broad therapeutic window, which in future may become a member of anticancer armamentarium. [51]
Polygonum cuspidatum S. (PC) is frequently used as a laxative and an anticancer drug in Chinese medicine. The inhibitory effect of this herb and its component, emodin, on the direct-acting mutagenicity of 1-nitropyrene (1-NP) was examined using the Ames/microsomal test with Salmonella typhimurium TA98 and the genotoxicity of 1-NP was evaluated using the SOS chromotest with E. coli PQ37. Emodin and water extracts of PC markedly decreased the mutagenicity of 1-NP in a dose-dependent manner in both assay systems. Furthermore, emodin and the extracts of PC significantly inhibited the formation of 1-NP DNA adducts in S. typhimurium TA98 in the 32P-postlabeling study. The results suggest that PC extracts and emodin act as blocking and/or suppressing agents to reduce the direct-acting mutagenicity of 1-NP. [52]
AIM: To establish the rats model of chronic fibrosing pancreatitis and to prove the anti-fibrotic effect of emodin in chronic pancreatitis with fibrosis.
METHODS: Fifty rats were randomly divided into five groups, 10 rats in each group. Trinitrobenzene sulfonic acid (TNBS) was infused into the pancreatic duct to induce chronic pancreatitis in rats (except for normal group). Emodin-treated rats were fed with different doses of emodin (20, 40 and 80 mg/kg body weight) for 28 d, while normal group and control group received 0.9% sodium chloride solution. Serum levels of hyaluronic acid (HA) and laminin (LN) were determined by radioimmunoassay. Histopathological alterations were studied by optical microscopy. Expression of collagen was also examined while transforming growth factor-beta-1 (TGF-β1) was localized by immunochemistry.
RESULTS: In emodin-treated rats, the serum levels of HA and LN were decreased significantly (HA, 62.2 ± 19.3 μg/L vs 112.7 ± 26.5 µg/L, P < 0.05; LN 44.3 ± 10.4 μg/L vs 86.2 ± 16.5 µg/L, P < 0.05); the degree of fibrosis was ameliorated observably; the expression of collagen in pancreatic tissue was reduced especially in high-dose emodin-treated group (36% ± 5% vs 42% ± 6%, P < 0.05); with the increased doses of emodin, the expression of TGF-β1 was declined, compared with those in control group.
CONCLUSION: Emodin has an anti-fibrotic effect on pancreatic fibrosis in rats. Because of its anti-fibrotic effect, it could be a potential herb for the treatment of chronic pancreatitis. [53]
AIM: To determine the anti-angiogenic activity of emodin.
METHODS: Chick embryo assay and cultured endothelial cells were used.
RESULTS: Emodin at doses of 150 and 300 microg/egg caused 37.6% and 63.2% inhibition of angiogenesis, respectively. Emodin was shown to inhibit the proliferation of primary cultured bovine aortic endothelial cells in the absence or presence of basic-fibroblast growth factor (bFGF) or the presence of vascular endothelial growth factor (VEGF) in a dose-dependent manner. The IC50 values by MTT assay were 5.56, 8.40 or 6.91 mg x L(-1), respectively. Emodin at concentrations from 5.4 to 21.6 mg x L(-1) induced apoptosis of endothelial cells for 37.6% to 72.6%. Emodin caused endothelial cell cycle arrest at G2/M phase. After emodin treatment, there was a down-regulation of Cyclin B1, P34cdc2, and Bcl-2 protein expression while the Bax protein expression was unaffected.
CONCLUSION: Emodin shows anti-angiogenic activity and might be useful for the development of novel anti-cancer therapy. [54]
Acute myocardial infarction (AMI) is associated with inflammation and apoptosis. Emodin plays an anti-inflammatory role in several inflammatory diseases. Recent studies have demonstrated that emodin protects against myocardial ischemia/reperfusion injury. However, its mechanism underlying its effects remains unknown. In a murine model of AMI, based on ligation of the left coronary artery, administration of emodin reduced myocardial infarct size (MIS) in a dose-dependent manner. Emodin significantly suppressed TNF-alpha expression and NF-kappaB activation in the local myocardial infarction area. Treatment with emodin inhibited myocardial cell apoptosis by inhibiting caspase-3 activation. Therefore, these studies demonstrate that emodin protects against myocardial cell injury via suppression of local inflammation and apoptosis. [55]
OBJECTIVE: To investigate effect of emodin on hepatic fibrosis in rats.
METHODS: The rat hepatic fibrosis model was induced by the subcutaneous injection of 40% CCl4 (twice a week for 6 weeks) dissolved in olive oil. The emodin-treated rats were treated with low-dose, mediate-dose and high-dose emodin (20, 40 and 80 mg/kg body weight, once a day for 42 days) dissolved in 0.5% sodium carboxymethylcellulose (CMC), except receiving CCl4. Control group received only olive oil and 0.5% CMC. Liver functions were determined by standard procedure. Serum hyaluronic acid and laminin were determined by radioimmunoassay. Liver hydroxyprolines were determined. Histopathological changes were examined by optical microscopy.
RESULTS: Compared with model group, the emodin-treated rats showed (1) liver functions were improved, alanine transaminase (ALT) and alkaline phosphatase (AKP) were obviously reduced, and total protein (TP) and albumin (ALB) were significantly increased; (2) serum hyaluronic acid and laminin were markedly reduced; (3) liver hydroxyproline was significantly decreased; (4) the degrees of fibrosis were reduced. The changes of parameters mentioned above were significant (P < 0.05 or P < 0.01).
CONCLUSION: Emodin has effect on hepatic fibrosis in rats. The hepatoprotective of emodin may be one of mechanisms for liver fibrosis. [56]
OBJECTIVE: To study the effects of emodin on proliferation and differentiation of 3T3-L1 preadipocyte and the possible mechanism.
METHODS: Cell proliferation was determined by MTT spectrophotometry, cell differentiation was determined by Oil Red O staining,and fatty acid synthase (FAS) activity was determined by spectrophotometry.
RESULTS: Emodin promoted proliferation of 3T3-L1 preadipocyte at low concentration and inhibited the proliferation at high concentration in a dose-related manner. In contrast, it inhibited cell differentiation into adipocyte at low concentration in a dose-related manner. In vitro emodin inhibited the activity of FAS in a dose-related manner.
CONCLUSIONS: The effects of emodin on 3T3-L1 cell's proliferation and differentiation are dose dependent. Emodin inhibits the activity of FAS. Our results suggest that emodin should have a potential to serve as a fat-reducing drug. [57]
The amplification and overexpression of the HER-2/neu proto-oncogene, which encodes the tyrosine kinase receptor p185neu, have been observed frequently in tumors from human breast cancer patients and are correlated with poor prognosis. To explore the potential of chemotherapy directed at the tyrosine kinase of p185neu, we have found that emodin (3-methyl-1,6,8-trihydroxyanthraquinone), a tyrosine kinase inhibitor, suppresses autophosphorylation and transphosphorylation activities of HER-2/neu tyrosine kinase, resulting in tyrosine hypophosphorylation of p185neu in HER-2/neu-overexpressing breast cancer cells. Emodin, at a 40-microM concentration, which repressed tyrosine kinase of p185neu, efficiently inhibited both anchorage-dependent and anchorage-independent growth of HER-2/neu-overexpressing breast cancer cells. However, the inhibition was much less effective for those cells expressing basal levels of p185neu under the same conditions. Emodin also induced differentiation of HER-2/neu-overexpressing breast cancer cells by exhibiting a morphological maturation property of large lacy nuclei surrounded by sizable flat cytoplasm and by showing a measurable production of large lipid droplets, which is a marker of mature breast cells. Therefore, our results indicate that emodin inhibits HER-2/neu tyrosine kinase activity and preferentially suppresses growth and induces differentiation of HER-2/neu-overexpressing cancer cells. These results may have chemotherapeutic implications for using emodin to target HER-2/neu-overexpressing cancer cells. [58]
Overexpression of the HER-2/neu proto-oncogene which encodes tyrosine kinase receptor p185neu, has been observed frequently in many human cancers, including non-small cell lung cancer (NSCLC), and is correlated with poor patient survival in these cancers. In addition, HER-2/neu overexpression in NSCLC is known to induce chemoresistance. Recently, we demonstrated that emodin, a tyrosine kinase inhibitor, suppresses HER-2/neu tyrosine kinase activity in HER-2/neu-overexpressing breast cancer cells and preferentially represses proliferation of these cells. The work described here was carried out to examine (1) whether the tyrosine kinase activity of p185neu is required for resistance to chemotherapeutic drugs of HER-2/neu-overexpressing NSCLC cells and (2) whether the tyrosine kinase inhibitor emodin can sensitize these cells to chemotherapeutic drugs. We found that emodin decreased tyrosine phosphorylation of HER-2/neu and preferentially suppressed proliferation of HER-2/neu-overexpressing NSCLC cells. Furthermore, the combination of emodin with cisplatin, doxorubicin or etoposide (VP16) synergistically inhibited the proliferation of HER-2/neu-overexpressing lung cancer cells, whereas low doses of emodin, cisplatin, doxorubicin, or VP16 alone had only minimal antiproliferative effects on these cells. These results indicate that tyrosine kinase activity is required for the chemoresistant phenotype of HER-2/neu-overexpressing NSCLC cells and that tyrosine kinase inhibitors such as emodin can sensitize these cells to chemotherapeutic drugs. The results may have important implications in chemotherapy for HER-2/neu-overexpressing cancers. [59]
Overexpression of the HER-2/neu proto-oncogene, which encodes the tyrosine kinase receptor p185neu, has been observed in tumors from breast cancer patients. We demonstrated previously that emodin, a tyrosine kinase inhibitor, suppresses tyrosine kinase activity in HER-2/neu-overexpressing breast cancer cells and preferentially represses transformation phenotypes of these cells in vitro. In the present study, we examined whether emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and whether emodin can sensitize these tumors to paclitaxel, a commonly used chemotherapeutic agent for breast cancer patients. We found that emodin significantly inhibited tumor growth and prolonged survival in mice bearing HER-2/neu-overexpressing human breast cancer cells. Furthermore, the combination of emodin and paclitaxel synergistically inhibited the anchorage-dependent and -independent growth of HER-2/neu-overexpressing breast cancer cells in vitro and synergistically inhibited tumor growth and prolonged survival in athymic mice bearing s.c. xenografts of human tumor cells expressing high levels of p185neu. Both immunohistochemical staining and Western blot analysis showed that emodin decreases tyrosine phosphorylation of HER-2/neu in tumor tissue. Taken together, our results suggest that the tyrosine kinase activity of HER-2/neu is required for tumor growth and chemoresistance and that tyrosine kinase inhibitors such as emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and also sensitize these tumors to paclitaxel. The results may have important implications in chemotherapy for HER-2/neu-overexpressing breast tumors. [60]
We have made several reports on the signal transduction mechanism that emodin enhance the calcium concentrations of smooth muscle cells (SMCs) in the physiological condition by inositol [1, 4 and 5]-friphosphate (IP3). The observation that IP3 concentrations in SMCs were decreased in multiple organ dysfunction syndrome (MODS) prompted us to ask whether emodin can activate SMCs to contract by way of elevating [Ca2+] and thus modulating the critical Ca2+ signal transduction pathways involved in the contraction of the SMCs in the pathological setting of MODS. To test this hypothesis, we used the rat model of MODS to explore the potential roles of emodin in Ca2+ signal transduction in the SMCs of colon in rats. ML-7 [an inhibitor of myosin light-chain kinase (MLCK)] and Calphostin C [an inhibitor of protein kinase C (PKC)] were used to observe the influence of emodin on the muscle strips and SMCs in rats after MODS. Nifedipine (an antagonist of voltage-gated Ca2+ channel), EGTA (removal of extracellular Ca2+), heparine (a specific IP3 receptor antagonist), and ryanodine were used to probe the potential mechanisms involved in emodin-mediated elevation of the global cytoplasmic Ca2+ in SMCs of colon in the rats after MODS. Our results show that emodin is capable of contract the smooth muscles of colon in rats after MODS by MLCK increasing [Ca2+] of SMCs, and by PKC enhancing the calcium sensitivity of SMCs. The mechanism by which emodin triggers elevated [Ca2+] of smooth muscles of colon in rats after MODS is likely to operate through IP3 and RyR receptors in the sarcoplasm. It is hoped that deeper insights into how emodin modulates the critical calcium signaling in SMCs might lead to the potential development of emodin in the treatment of MODS. [61]
Increasing evidence indicated that plaque stabilization is attributed to the composition of the atherosclerotic plaque, and inflammation plays an important role in the formation and progress of vulnerable atherosclerotic plaque (VAP), which is prone to rupture. Emodin, an important component of traditional Chinese herb rhubarb, has obvious anti-inflammatory effect, although its effect on atherosclerotic plaque stabilization is unknown. Apolipoprotein E (ApoE) is an important component of plasma lipoprotein with anti-atherosclerosis function, and the plaque in the aorta of ApoE-deficient mice has been demonstrated with characteristics of VAP. Therefore, this study was designed to determine whether emodin can stabilize the VAP in the ApoE-deficient mice and explain the possible mechanism. After fat-fed for 13 weeks, mice were randomized into three groups (11 animals/group) and intragastrically administrated with emodin, simvastatin or distilled water for 13 weeks, respectively. The plaque stability was evaluated by the morphology and composition of atherosclerotic plaques. Additionally, the expression of peroxisomal proliferator-activated receptor-γ (PPAR-γ), granulocyte-macrophage colony-stimulating factor (GM-CSF), and matrix metalloproteinase 9 (MMP-9) in plaques was determined by the immunohistochemistry method. We showed that emodin could decrease the lipid core area and the ratio of lipid to collagen content in plaques. In addition, emodin significantly inhibited the expression of GM-CSF and MMP-9, whereas it induced the expression of PPAR-γ in plaques. In conclusion, these results suggest that emodin can stabilize the VAP in the aortic root of ApoE-knockout mice, which is probably due to its anti-inflammatory effect. [62]
OBJECTIVE: To study the effects of emodin on proliferation and differentiation of 3T3-L1 preadipocyte and the possible mechanism.
METHODS: Cell proliferation was determined by MTT spectrophotometry, cell differentiation was determined by Oil Red O staining,and fatty acid synthase (FAS) activity was determined by spectrophotometry.
RESULTS: Emodin promoted proliferation of 3T3-L1 preadipocyte at low concentration and inhibited the proliferation at high concentration in a dose-related manner. In contrast, it inhibited cell differentiation into adipocyte at low concentration in a dose-related manner. In vitro emodin inhibited the activity of FAS in a dose-related manner.
CONCLUSIONS: The effects of emodin on 3T3-L1 cell's proliferation and differentiation are dose dependent. Emodin inhibits the activity of FAS. Our results suggest that emodin should have a potential to serve as a fat-reducing drug. [63]
1,8-Dihydroxyanthraquinones, present in laxatives, fungi imperfecti, Chinese herbs and possibly vegetables, are in debate as human carcinogens. We screened a variety of vegetables (cabbage lettuce, beans, peas), some herbs and herbal-flavoured liquors for their content of the 'free' anthraquinones emodin, chrysophanol and physcion. For qualitative and quantitative analysis, reversed-phase HPLC (RP-LC), gas chromatography-mass spectrometry (GC-MS) and RP-LC-MS were used. The vegetables showed a large batch-to-batch variability, from 0.04 to 3.6, 5.9 and 36 mg total anthraquinone per kg fresh weight in peas, cabbage lettuce, and beans, respectively. Physcion predominated in all vegetables. In the herbs grape vine leaves, couch grass root and plantain herb, anthraquinones were above the limit of detection. Contents ranged below 1 mg/kg (dry weight). All three anthraquinones were also found in seven of 11 herbal-flavoured liquors, in a range of 0.05 mg/kg to 7.6 mg/kg. The genotoxicity of the analysed anthraquinones was investigated in the comet assay, the micronucleus test and the mutation assay in mouse lymphoma L5178Y tk+/- cells. Emodin was genotoxic, whereas chrysophanol and physcion showed no effects. Complete vegetable extract on its own did not show any effect in the micronucleus test. A lettuce extract completely abolished the induction of micronuclei by the genotoxic anthraquinone danthron. Taking into consideration the measured concentrations of anthraquinones, estimated daily intakes, the genotoxic potency, as well as protective effects of the food matrix, the analysed constituents do not represent a high priority genotoxic risk in a balanced human diet. [64]
A balance study was conducted to assess the effects of consuming low-copper diets, high in fructose or cornstarch. The study involved 19 apparently healthy males, aged 21-57 y. The two experimental diets averaged 0.35 mg Cu/1000 kcal and provided 20% of the calories from fructose or cornstarch. Cu, zinc, calcium, magnesium, and iron balances were determined 1 wk before the study (pretest) when the subjects consumed self-selected diets and after consuming the experimental diets for 6 wk. No major differences in mineral balances were evident between the two groups during the pretest study when the subjects ate self-selected diets. In contrast, when fed the test diets, the group consuming the low-Cu fructose diet had significantly more positive balances for all minerals studied than the group fed the low-Cu cornstarch diet. The results indicate that dietary fructose enhances mineral balance. [65]
The transport of [l25I]T3., and [l25I]T4 through the brain capillary wall, i.e. the blood-brain barrier, was studied in barbiturate-anesthetized rats using a tissue-sampling-carotid injection technique. The percent extraction of unidirectional influx of thyroid hormone during a single pass through the brain was measured relative to a highly diffusible [3H]water reference. The Km of T3 transport was 1.1 μM; T3 transport was inhibited by T4 (Ki = 2.6 μM), rT3;, (Ki = 5.4 μM), and D-T3 but not by 1000 μM concentrations of tyrosine, leucine, or potassium iodide. Bovine albumin also inhibited blood-brain barrier transport of T3). The fractional inhibition of T3 transport by albumin was a measure of the binding of T3 by albumin in vivo, i.e. in the presence of a competing binding system, the BBB T3 carrier. The apparent dissociation constant (Kd) of albumin binding of T3 at the brain capillary level (76 μM) was 16-fold greater than the K3 of albumin binding of T3 in vitro (4.7 μM), as determined by equilibrium dialysis. A model was derived that allowed for the in vivo application of the principles of the competitive ligand-binding assay; given apparent Kd = Kd (1 4- C/Km), the local capillary T3-binding capacity (C) may be calculated from the known values for apparent Kd) Kd, and Km. Based on the relative binding index (C/Km) of BBB binding of T3 vs. the binding index of physiological concentrations of albumin, it may be estimated that about 10% of albumin-bound T3 (which is 10-fold the fraction of dialyzable T3) is transported into the brain on a single pass in the rat. [66]
T4 and reverse T3 (rT3) can inhibit 5′-deiodinase type II activity in rat brain cortex, pituitary, and brown adipose tissue, raising the possibility that T4 may act in vivo after conversion to rT3. The aim of this study was to measure in hypothyroid (Tx) rats the content of brain cortex rT3 during a constant 7-day infusion of either [l25I]T4 alone, corresponding to 12 pmol T4/dayl00 g body weight (BW), or together with 400 pmol T4/day. [125I]T4, rT3, and T3 were extracted from brain cortex, pituitary, kidney, and liver with a combination of adsorption chromatography on Sephadex G-25, HPLC, and immunoprecipitation. [131I]T4, T3, or rT3 were used as internal standards. [125I]rT3 could be detected in brain cortex, liver, and kidney in Tx rats infused with [125I]T4 (12 pmol T4/day 100 g BW) and in those infused with 400 pmol T4/dayl00 g BW. The highest rT3 concentrations were found in brain cortex, where it represented 6% to 10.5% of the local T4 concentration. During an infusion of 400 pmol T4/dayl00 g BW, brain cortex T3 concentration was 6 times higher in the brain cortex than in serum, and even exceeded that of T4. In Tx rats receiving [125I]T4 alone the brain cortex to serum T3 ratio was 3:1, but the total serum T3 concentration, measured by RIA, was much higher than that due to conversion [0.50 ± (SE) 0.1 pmol/ml vs. 0.018 ± 0.002 pmol T3/ml], indicating thyroidal secretion. The effect of the blood-brain barrier on rT3 was measured by infusing [125I]rT3 over 4 days. After killing, rT3 was isolated as above. Approximately 3% of serum rT3 was retrieved from the brain cortex, whereas during the T4 infusion 40–50% of serum rT3 was found demonstrating that brain cortex rT3 is locally produced. [67]
Previous studies have shown that the fraction of hormone or drug that is plasma protein bound is readily available for transport through the brain endothelial wall, i.e., the blood-brain barrier (BBB). To test whether these observations are reconcilable with the free-hormone hypothesis, a tracer-kinetic model is used in the present investigations to analyze in vivo initial extraction data on BBB transport of protein-bound steroid hormones (dihydrotestosterone, testosterone, estradiol, and corticosterone), thyroid hormones (triiodothyronine), and lipophilic amine drugs (propranolol). The plasma proteins used are bovine albumin and human orosomucoid. Transport data was fit to a modification of the Kety-Renkin-Crone equation of capillary physiology; the modified equation incorporates the principles of both capillary physiology and plasma protein-ligand mass action binding relationships. In most cases, the experimental data is best fit to the model equation when the apparent in vivo dissociation constant, KDa, of the ligand protein binding reaction increases to values that are 5- to 50-fold greater than the in vitro dissociation constant, KD. This result indicates that the rate of ligand dissociation from the plasma protein is accelerated in the capillary bed relative to the in vitro situation. It is hypothesized that the major factor leading to the rapid transport in vivo of protein-bound ligands into tissues such as brain is an endothelial-induced decrease in the affinity of the plasma protein for the ligand. Under these conditions, the amount of plasma ligand available for tissue clearance in vivo parallels the protein-bound fraction, not the free hormone. [68]
T3 covalently bound to red blood cells (RBCs), stimulated the uptake rate of 2-deoxy-D-glucose (2-DOG) in cultured chick embryo heart cells. The response, measured 6 h after exposure, was at least the same than that to free T3. An inhibitor of rhodamine-T3 internalization, bacitracin, did not affect the stimulation of sugar uptake by T3 regardless of whether T3 was covalently bound or free. Pretreatment of RBC-T3 with anti-T3 immunoglobulin G completely blocked the effect of T3,whereas normal rabbit immunoglobulin G failed to do so.
Addition of 5% chick serum to the medium stimulated 2-DOG uptake to 144% of the control at 6 h. Adding T3 (10 nM)to the serum-containing medium increased 2-DOG uptake to 171% of the control. The effect of T3 alone or in the presence of serum was not inhibited by cycloheximide, puromycin, or actinomycin D. A T3 dose response curve, in medium containing 10% dehormonized serum, showed enhancement of the T3 effect when compared with the curve obtained in the serum-free medium. The minimal effective concentration of T3 was 10 pM in the presence of serum and 100 pM in its absence. The slope of the linear portion of the dose response curve was greatly increased and the maximal response markedly enhanced by serum. The ED50 was 0.33 nM vs. 0.43 nM in terms of total T3 concentration and 0.16 nM vs. 0.43 nM in terms of free T3 in the presence or absence of serum, respectively.
These data suggest that T3,in physiological concentrations, activates sugar transport through an external contact with the cell surface. [69]
The stereospecificity of T3 transport through the walls of the brain capillary, i.e. the blood-brain barrier (BBB), and the salivary gland capillary and through the hepatocyte plasma membrane was studied with a tissue-sampling single injection technique in rats. In the absence of plasma proteins, the ED50 of inhibition of the saturable transport of [125I]L-T3 through the BBB was 1 μM for unlabeled L-T3 and 9 ftM for unlabeled D-T3. The brain extraction of [125I]D-T3, 5.9 ± 0.1% (±SE), was about one third that of [125I]L-T3. Conversely, no saturable and no stereospecific T3 transport was observed for the salivary gland capillary, which, unlike the brain capillary, is porous. The hepatic extraction of T3 was minimally stereospecific in the absence of plasma proteins. In the presence of 5 g/dl bovine albumin, the fraction of circulating D- or L-T3 that was available for transport into liver (50-100%) was many-fold greater than the fraction that was free in vitro (-2%); therefore, both D-T3 and L-T3 were available for uptake by liver from the circulating albumin-bound pool. This plasma protein-mediated transport of T3 is believed to represent a process of enhanced dissociation of T3 from the albumin-binding site, since the plasma protein per se is not significantly taken up by liver on a single pass. However, in the presence of 5 g/dl bovine albumin, the extravascular hepatic extraction of [125I]D-T3 (50 ± 2%) was nearly half that for [125I]T3 (93 ± 12%), although no significant difference in the in vitro binding of [125I]D-T3 and [126I]L-T3 to 5 g/dl bovine albumin was found with equilibrium dialysis. In addition, the isoelectric point of bovine albumin bound to [125I] L-T3 (5.1) was higher than that of bovine albumin bound to [125I] D-T3 (5.0), as determined by isoelectric focusing, which indicates that the surface of the bovine albumin molecule is slightly more positive when the protein binds L-T3 as opposed to D-T3. The isoelectric focusing and in vivo transport data together suggest that the interaction between the surfaces of the plasma protein and the hepatic microcirculation that is presumed to cause enhanced hormone dissociation from the protein-binding site is electrostatic in nature. These studies (1) show that the BBB thyroid hormone transport system is sharply stereospecific, and this property is probably a major factor underlying the low biological potency of D-T3 in brain; and (2) provide the first evidence for stereospecificity of plasma protein-mediated transport of hormones into tissues in vivo. [70]
1. Steady-state iodothyronine profiles in plasma are composed of thyroid gland-synthesized hormones (mainly thyroxine) and tissue iodothyronine metabolites (mainly triiodothyronine and reverse triiodothyronine) that have entered the bloodstream. The hormones circulate in noncovalently bound complexes with a panoply of carrier proteins. Transthyretin (TTR), the major high-affinity thyroid hormone binding protein in rat plasma, is formed in the liver. It is also actively and independently synthesized in choroid plexus, where its function as a chaperone of thyroid hormones from bloodstream to cerebrospinal fluid (CSF) is undergoing close scrutiny by several groups of investigators. Because TTR has high-affinity binding sites for both thyroxine and retinol binding protein, its potential role as a mediator of combined thyroid hormone and retinoic acid availability in brain is of further interest.
2. While they are in the free state relative to their binding proteins, iodothyronines in the cerebral circulation are putatively subject to transport across both the blood-brain barrier (BBB) and choroid plexus CSF barrier (CSFB) before entering the brain. Previous autoradiographic studies had already indicated that after intravenous administration the transport mechanisms governing thyroxine and triiodothyronine entry into brain were probably similar, whereas those for reverse triiodothyronine were very different, although the basis for the difference was not established at that time. Intense labeling seen over brain ventricles after intravenous administration of all three iodothyronines suggested that all were subject to transport across the CSFB.
3. To evaluate the role of the BBB and CSFB in determining iodothyronine access to brain parenchyma, autoradiograms prepared after intravenous administration of [125I]-labeled hormones (revealing results of transport across both barriers) were compared with those prepared after intrathecal (icv) hormone injection (reflecting only their capacity to penetrate into the brain after successfully navigating the CSFB).
4. Those studies revealed that thyroxine and triiodothyronine were mainly transported across the BBB. They shared with reverse triiodothyronine a generally similar, limited pattern of penetration from CSF into the brain, with circumventricular organs likely to be the main recipients of iodothyronines (with or without retinol) transported across the CSFB.
5. Analysis of all of the images obtained after intravenous and icv hormone administration clarified the basis for the unique distribution of intravenously injected reverse triiodothyronine. The hormone is excluded by the BBB but may be subject to limited penetration into brain parenchyma via the CSF.
6. Overall the observations single out reverse triiodothyronine as the iodothyronine showing the most distinctive as well as the most limited pattern of transport from blood to brain.(ABSTRACT TRUNCATED AT 400 WORDS) [71]
Thyroid hormone entering the brain from the cerebral circulation must first cross barriers at the the blood:brain and choroid plexus:cerebrospinal fluid interfaces. The route taken after entry through those barriers might bring about selective delivery of hormone to different regions of the brain and those differences might be crucial for the ultimate functional effects of the hormone. To determine whether and how distribution of hormone in the brain might vary according to the route of entry, film autoradiograms of serially sectioned brains were prepared after delivery of a pulse of 125I-labeled thyroid hormone into either the right lateral cerebral ventricle or the femoral vein. The results after intrathecal injection, reflecting the penetration of hormone into brain after crossing the choroid plexus:cerebrospinal fluid barrier, revealed a markedly limited, essentially periventricular distribution of radioactivity at both 3 and 48 h after hormone administration. Results after i.v. administration, which allows hormone access across both barriers, revealed an initial distribution pattern (at 3 h) generally similar to that seen after administration of markers of cerebral blood flow; at 48 h there was strong resolution in selected brain regions never noted to be labeled after intrathecal hormone injection. The functional implications of the differences in results produced by the two different routes of hormone entry are not known. However, ready access to circumventricular organs would appear to be favored by hormone crossing the choroid plexus:cerebrospinal fluid barrier whereas access to the panoply of nuclear triiodothyronine receptors would be favored by hormone crossing the blood:brain barrier. Therefore both routes of barrier transport should be taken into account in assessing the kinetics and actions of thyroid hormones in the central nervous system. [72]
An age-related decline in blood-brain barrier transport of thyroid hormones may contribute to the central nervous system changes with aging. To test this hypothesis, the brain uptake index (BUI) of levo (L) and dextro (D) triiodothyronine (T3) was determined in male Fischer 344 rats at 6 months of age (young) and 26 months of age (aged). Young rats pair fed with aged were included to control for reduced food intake in aged rats. The L-T3 BUI of aged rats (22.4 +/- 2.1%) was significantly reduced compared to young rats (29.5 +/- 2.0%) or young rats pair fed with aged rats (28.5 +/- 2.5%) (p less than 0.05). This could not be attributed to age-related changes in BBB permeability or to reduced cerebral blood flow. At steady state conditions, the brain uptake of either L-T3 or D-T3 was not altered with aging. There were no significant changes in plasma or brain binding of T3. These results indicate that the reduced BBB transport of T3 in aged rats is counterbalanced by a reduction in T3 clearance from the brain. [73]
The stereospecificity of T3 transport through the walls of the brain capillary, i.e. the blood-brain barrier (BBB), and the salivary gland capillary and through the hepatocyte plasma membrane was studied with a tissue-sampling single injection technique in rats. In the absence of plasma proteins, the ED50 of inhibition of the saturable transport of [125I]L-T3 through the BBB was 1 μM for unlabeled L-T3 and 9 ftM for unlabeled D-T3. The brain extraction of [125I]D-T3, 5.9 ± 0.1% (±SE), was about one third that of [125I]L-T3. Conversely, no saturable and no stereospecific T3 transport was observed for the salivary gland capillary, which, unlike the brain capillary, is porous. The hepatic extraction of T3 was minimally stereospecific in the absence of plasma proteins. In the presence of 5 g/dl bovine albumin, the fraction of circulating D- or L-T3 that was available for transport into liver (50-100%) was many-fold greater than the fraction that was free in vitro (-2%); therefore, both D-T3 and L-T3 were available for uptake by liver from the circulating albumin-bound pool. This plasma protein-mediated transport of T3 is believed to represent a process of enhanced dissociation of T3 from the albumin-binding site, since the plasma protein per se is not significantly taken up by liver on a single pass. However, in the presence of 5 g/dl bovine albumin, the extravascular hepatic extraction of [125I]D-T3 (50 ± 2%) was nearly half that for [125I]T3 (93 ± 12%), although no significant difference in the in vitro binding of [125I]D-T3 and [126I]L-T3 to 5 g/dl bovine albumin was found with equilibrium dialysis. In addition, the isoelectric point of bovine albumin bound to [125I] L-T3 (5.1) was higher than that of bovine albumin bound to [125I] D-T3 (5.0), as determined by isoelectric focusing, which indicates that the surface of the bovine albumin molecule is slightly more positive when the protein binds L-T3 as opposed to D-T3. The isoelectric focusing and in vivo transport data together suggest that the interaction between the surfaces of the plasma protein and the hepatic microcirculation that is presumed to cause enhanced hormone dissociation from the protein-binding site is electrostatic in nature. These studies (1) show that the BBB thyroid hormone transport system is sharply stereospecific, and this property is probably a major factor underlying the low biological potency of D-T3 in brain; and (2) provide the first evidence for stereospecificity of plasma protein-mediated transport of hormones into tissues in vivo. [74]
The transport of [125I]T3 [125I]T4, [3H]testosterone, and [3H]estradiol through the blood-brain barrier (BBB) of the newborn rabbit was studied with a tissue-sampling, single injection technique. The first pass extractions of T3 and T4 were 22 ± 2%, and 14 ± 1%, respectively, after carotid injection of Ringer's solution (0.025% albumin). Thyronine transport was saturated and cross-competitive, but was not inhibited by a large excess of leucine, a neutral amino acid. The extraction of T3 was reduced to 7 ± 1% after injection of hormone mixed in a 10% T3-specific rabbit antiserum, and this value approximated the extraxction of an extracellular space marker, such as sucrose (6 ± 1%). Therefore, antibody-bound T3 was not available for transport in vivo. Conversely, T3 bound to the plasma proteins in newborn rabbit antiserum, e.g. albumin, was transported into the brain. The concentration of plasma protein required to inhibit T3 transport 50% in vivo was 28-fold greater than the serum concentration that resulted in 50% binding of T3 in vitro. The first pass extractions of testosterone and estradiol after injection of hormone in Ringer's solution were 100 ± 5% and 91 ± 5%, respectively. A 5 g/100 ml concentration of albumin bound abut 95% of steroid in vitro, but resulted in only a 17-20% inhibition of testosterone or estradiol transport in vivo. Similarly, testosterone bound to the progesterone-binding globulin of pregnant guinea pig serum was also transported, although to a lesser extent than albumin-bound hormone. Conversely, testosterone bound to a specific rabbit antiserum, or testosterone or estradiol bound to the sex hormone-binding globulin in human serum was not transported into the brain. These results indicate that the mechanisms of thyroid and steroid hormone transport through the BBB of the newborn rabbit are very similar to those of the adult rat; therefore, the processes mediating BBB transport of protein-bound hormones are firmly established by at least the first 8-24 h of postnatal life. [75]
The transport of [125I]T3 and [125I]T4 through the brain capillary wall, i.e. the blood-brain barrier, was studied in barbiturate-anesthetized rats using a tissue-sampling-carotid injection technique. The percent extraction of undirectional influx of thyroid hormone during a single pass through the brain was measured relative to a highly diffusible [3H]water reference. The K(m) of T3 transport was 1.1 μM; T3 transport was inhibited by T4 (K(i)=2.6 μM), rT3 (K(i)=5.4 μM), and D-T3 but not by 1000 μM concentrations of tyrosine, leucine, or potassium iodide. Bovine albumin also inhibited blood-brain barrier transport of T3. The fractional inhibition of T3 transport by albumin was a measure of the binding of T3 by albumin in vivo, i.e. in the presence of a competing binding system, the BBB T3 carrier. The apparent dissociation constant (K(d)) of albumin binding of T3 at the brain capillary level (76 μM) was 16-fold greater than the K(d) of albumin binding of T3 in vitro (4.7 μM), as determined by equilibrium dialysis. A model was derived that allowed for the in vivo application of the principles of the competitive ligand-binding assay; given apparent K(d)=K(d) (1+C/K(m)), the local capillary T3-binding capacity (C) may be calculated from the known values for apparent K(d), K(d), and K(m). Based on the relative binding index (C/K(m)) of BBB binding of T3 vs. the binding index of physiological concentrations of albumin, it may be estimated that about 10% of albumin-bound T3 (which is 10-fold the fraction of dialyzable T3) is transported into the brain on a single pass in the rat. [76]
In vivo studies of the exchange of tracer [125I]L-triiodothyronine (T3) between plasma (P), and the anterior pituitary (AP), posterior pituitary (PP), median eminence (ME) and the frontal lobes of the brain (B), in the rat show that from 2.5 h onwards the concentration of net [125I]T3 in AP, PP and B were parallel to that of the plasma, with a t½ of 7.4 h; the t½ for ME was 10.3 h.
The extrapolation of these curves to zero time was assumed to indicate the relative concentration of T3 per unit weight in terms of total body T3. T3 content of these tissues was determined by radioimmunoassay. The values obtained validated the steady state parameters derived from the radio-isotopic measurements.
As an indicator of the concentration gradient between tissue and plasma the organ⁄plasma (O⁄P) ratio was calculated; these data indicate that under steady state conditions, the order of T3 concentration is AP > PP > ME > B.
Binding studies have shown that AP and PP contain “specific,” saturable binders while ME and B do not. Evaluation of the binding parameters of the high affinity binders in both AP and PP gave similar association constants. These association constants, when corrected for the binding strength of T3 to plasma proteins, resulted in values similar to those of nuclear T3 binders. [77]
The free hormone hypothesis states that the biological activity of a given hormone is affected by its unbound (free) rather than protein-bound concentration in the plasma. The fundamental mathematical and physiological principles relating to this hypothesis are reviewed, along with experimental data that shed light on its validity. It is shown that whether or not this hypothesis is likely to be valid for any given hormone will depend largely on which step in the tissue uptake process (plasma flow, dissociation from plasma binding proteins, influx, or intracellular elimination) is rate-limiting to the net tissue uptake of that hormone. It is further shown that the free hormone hypothesis could hold even if tissue uptake of hormone occurred by a mechanism that acted directly on one or more circulating protein-bound pools of hormone. Indeed, many of the data previously interpreted as being inconsistent with the free hormone hypothesis are in fact readily consistent with it when its predictions are fully understood. Nevertheless, the free hormone hypothesis is not likely to be valid for all hormones with respect to all tissues. It is likely to be valid with respect to all tissues for the thyroid hormones, for cortisol, and for the hydroxylated metabolites of vitamin D. For many of the other steroid hormones, however, it is likely to be valid with respect to some tissues, but not with respect to others (in particular, the liver). And for some of the steroid hormones (in particular, progesterone) it may not hold at all. [78]
The affinities with steroid hormones (alpha-estradiol, ethynylestradiol, progesterone, androsterone, dehydroisoandrosterone and testosterone) were observed for Cohn's fraction IV-1 and V (albumin). It was estimated from the comparison with the binding coefficient K (protein-bound form/free form of hormone) in a 3.5% (w/v) bovine serum albumin (BSA) solution that 40-80% of bound hormone in bovine serum is the BSA-bound form. It becomes clear in a liquid membrane system consisting of a hexane source phase (I), a water phase and a hexane receiving phase (II) that the transport flux of hormone is governed primarily by the partition coefficients between the water/hexane phases. In the case of a hormone with a lower partition coefficient, the uptake process from the hexane phase (I) to the water phase is a rate-determining step in the transport system and the serum proteins accelerate the transport of hormones, while with an increase in the partition coefficient the rate-determining step changes from the uptake step to the release step from the water phase to the hexane phase (II) and the hormone transport is decelerated owing to the significant decrease of free hormone concentration in the aqueous phase by the associated with serum proteins for the system having the restricted amount of hormone in the hexane source phase. [79]
Experimental and clinical studies have shown the beneficial effects of triiodothyronine (T3) following myocardial revascularization on cardiopulmonary bypass (CPB). In this study, open-label T3 was administered to 68 high-risk patients undergoing open heart surgery. The New Jersey Risk Assessment was used to calculate the preoperative estimated surgical mortality. A loading dose of T3 was administered: (a) at release of the aortic cross-clamp, (b) whenever the patient became CPB dependent, (c) if the patient exhibited low cardiac output after discontinuing CPB and (d) as pretreatment before initiating CPB. All therapeutic modalities were followed by a continuous T3 infusion. Following T3 therapy, CPB was discontinued in all patients. Based upon discriminant analysis, a total of 26 deaths were expected from the entire group, but only 7 patients died, therefore, the observed mortality was reduced by 72% (p < 0.007). The use of T3 had a major impact on reducing surgical mortality, and may be advocated as a new therapeutic modality in patients with high estimated mortality undergoing open heart surgery. [80]
Male sex hormones [dihydrotestosterone (DTS), and testosterone] and progesterone, when added to the isolated rat liver mitochondria before or after some protonophores, lower the respiration rate and increase the delta psi level, i.e., reverse the protonophore-induced uncoupling. Such a recoupling ability shows specific structural requirements correlating with hormonal activity of steroids studied. For instance, epiandrosterone, a DTS isomer of very low hormonal activity, and deoxycorticosterone, differing from progesterone by additional OH-group and possessing quite different hormonal activity, as well as female sex hormones (estron and estradiol) show no recoupling effect. Like 6-ketocholestanol (kCh), male sex hormones and progesterone recouple mitochondria uncoupled by low concentrations of SF6847, FCCP and CCCP, but not by high concentration of these uncouplers or by any concentration of DNP, palmitate and gramicidin. In contrast to recoupling by kCh, hormonal recoupling requires addition of serum albumin and is inhibited by low concentrations of palmitate. Recoupling can also be shown on the heart and skeletal muscle mitochondria, being absent from the heart muscle submitochondrial particles, the bacterial chromatophores and the cytochrome oxidase proteoliposomes. In mitochondria it does not depend upon the oxidation substrate used (succinate or PMS + ascorbate were tested). Pronounced seasonal effect upon the DTS recoupling degree was revealed. The recoupling is maximal in January, February and from June to November, being minimal in the spring months and in December. In spring, the in vivo administration of thyroxine, di- or triiodothyronine improves the recoupling ability of DTS. 2 x 10 - 6 M. Thyroxine, when added in vitro, does not affect energy coupling if SF6847 was absent. In the presence of small amounts of SF6847, thyroxine stimulates the uncoupling in a DTS-sensitive fashion, di- and triiodothyronines being less effective. Addition of thyroxine to azide-inhibited mitochondria (oligomycin is present) stimulates respiration and normalizes the delta psi level. In this system, triiodothyronine is much less effective, whereas diiodothyronine is not effective at all. In the intact cells (thymocytes and the Krebs-II cells were tested), DTS lowers the respiration rate stimulated by low concentrations of SF6846 or FCCP. In this case, serum albumin is not required. It is suggested that recoupling effects of male sex hormones and progesterone are involved in their anabolic action just as uncoupling takes part in the catabolic activity of thyroid hormones. [81]
not found (Thyroid 1996 Oct;6(5):531-6. Novel actions of thyroid hormone: the role of triiodothyronine in cardiac transplantation. Novitzky D.)
not found (Rev Med Chil 1996 Oct;124(10):1248-50. [Severe cardiac failure as complication of primary hypothyroidism]. Novik V, Cardenas IE, Gonzalez R, Pena M, Lopez Moreno JM.)
The thyroid hormone plays a critical role in normal development of the mammalian central nervous system. This study was designed to examine the effect of perinatal hypothyroidism on ontogenic change in cytochrome c oxidase subunit I (COX I) gene expression in the rat cerebellum by using quantitative in situ hybridization histochemistry (ISH). Newborn rats were rendered hypothyroid by continuous administration of methimazole in the mothers' drinking water. The pups were then killed by decapitation on 1, 5, 10, 15, 20, and 30 days after birth (P1, P5, P10, P15, P20, and P30). Their cerebella were removed, and frozen sections were cut and processed for ISH with 35S-labeled RNA probe for COX I messenger RNA. After hybridization, emulsion autoradiography was performed. The numbers of grains within the external granule cell layer, molecular layer, and internal granule cell layer were then counted. A significant decrease in grain density was detected in the hypothyroid animal in all these areas on P5, P10, and P15. On P15, in the molecular layer, a greater hybridization signal was detected in the inner portion than in the outer portion in the euthyroid animal. No such difference was seen in the hypothyroid animal. Daily T4 treatment for 15 days restored the effect of methimazole treatment. The significant effect of perinatal hypothyroidism on COX I gene expression was not detected after P20. These results indicate that altered thyroid states affect the COX I gene expression in the cerebellar cortex during development, suggesting that the COX I gene is one of the key genes regulated by the thyroid hormone and plays an important role in the morphogenetic changes observed in the perinatal hypothyroid cerebellum. [82]