Effects of long-term tea polyphenols consumption on hepatic microsomal drug-metabolizing enzymes and liver function in Wistar rats

Epigallocatechin-3-Gallate Reduces Hepatic Oxidative Stress and Lowers CYP-Mediated Bioactivation and Toxicity of Acetaminophen in Rats

Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol in green tea. To investigate the effects of dietary EGCG on oxidative stress and the metabolism and toxicity of acetaminophen in the liver, rats were fed diets with (0.54%) or without EGCG supplementation for four weeks and were then injected intraperitoneally with acetaminophen (1 g/kg). The results showed that EGCG lowered hepatic oxidative stress and cytochrome P450 (CYP) 1A2, 2E1, and 3A, and UDP-glucurosyltransferase activities prior to acetaminophen injection. After acetaminophen challenge, the elevations in plasma alanine aminotransferase activity and histological changes in the liver were ameliorated by EGCG treatment. EGCG reduced acetaminophen-induced apoptosis by lowering the Bax/Bcl2 ratio in the liver. EGCG mildly increased autophagy by increasing the LC3B II/I ratio. Lower hepatic acetaminophen–glutathione and acetaminophen–protein adducts contents were observed after EGCG treatment. EGCG increased glutathione peroxidase and NAD(P)H quinone 1 oxidoreductase activities and reduced organic anion-transporting polypeptides 1a1 expression in the liver after acetaminophen treatment. Our results indicate that EGCG may reduce oxidative stress and lower the metabolism and toxicity of acetaminophen. The reductions in CYP-mediated acetaminophen bioactivation and uptake transporter, as well as enhanced antioxidant enzyme activity, may limit the accumulation of toxic products in the liver and thus lower hepatotoxicity.

Effects of short-term saffron (Crocus sativus L.) intake on the in vivo activities of xenobiotic metabolizing enzymes in healthy volunteers

Crocus sativus L., a perennial plant grown mainly around the Mediterranean and Iran, has many medicinal properties including anti-inflammatory, anti-depressive and cancer preventing properties. Aqueous herbal extracts may affect the activity of Phase I and II enzymes involved in xenobiotic metabolism. The present study was designed to determine whether C. sativus infusion alters the activity of CYP1A2, CYP2A6, XO and NAT2 enzymes in humans. Thirty-four healthy volunteers consumed infusion prepared from C. sativus stigmata for six days. Enzyme phenotyping was assessed in saliva and urine using caffeine metabolite ratios as follows: CYP1A2: 17X/137Χ (saliva) and CYP1A2: (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X) and NAT2: AFMU/(AFMU+1U+1X) (urine). Following C. sativus intake, CYP1A2 index was reduced by ∼13.7% in saliva (before: 0.51 ± 0.22, after: 0.44 ± 0.14; p = 0.002) and ∼6.0% in urine (before: 3.81 ± 1.20, after: 3.58 ± 0.92; p = 0.054). CYP1A2 index was significantly reduced only in males (saliva, before: 0.65 ± 0.22, after: 0.51 ± 0.16; p = 0.0001; urine, before: 4.53 ± 1.19, after: 4.03 ± 0.87; p = 0.017) suggesting sexual dimorphism in CYP1A2 inhibition. There was no effect of C. sativus intake on CYP2A6, XO or NAT2 indices. Short-term consumption of C. sativus infusion is unlikely to result in significant herb-drug interactions involving the enzymes studied, with the exception of potential herb-CYP1A2 substrate interaction in males.

Advances in the Antagonism of Epigallocatechin-3-gallate in the Treatment of Digestive Tract Tumors

Due to changes in the dietary structure of individuals, the incidence of digestive tract tumors has increased significantly in recent years, causing a serious threat to the life and health of patients. This has in turn led to an increase in cancer prevention research. Many studies have shown that epigallocatechin-3-gallate (EGCG), an active ingredient in green tea, is in direct contact with the digestive tract upon ingestion, which allows it to elicit a significant antagonizing effect on digestive tract tumors. The main results of EGCG treatment include the prevention of tumor development in the digestive tract and the induction of cell cycle arrest and apoptosis. EGCG can be orally administered, is safe, and combats other resistances. The synergistic use of cancer drugs can promote the efficacy and reduce the anti-allergic properties of drugs, and is thus, favored in medical research. EGCG, however, currently possesses several shortcomings such as poor stability and low bioavailability, and its clinical application prospects need further development. In this paper, we have systematically summarized the research progress on the ability of EGCG to antagonize the activity and mechanism of action of digestive tract tumors, to achieve prevention, alleviation, delay, and even treat human gastrointestinal tract tumors via exogenous dietary EGCG supplementation or the development of new drugs containing EGCG.

Dietary effects of Sideritis scardica "mountain tea" on human in vivo activities of xenobiotic metabolizing enzymes in healthy subjects

Sideritis scardica(S. scardica) is an endemic plant of the Balkan Peninsula traditionally used as herbal tea for inflammation and gastric disorders. Aqueous herbal extracts may affect the activity of Phase I and II enzymes involved in xenobiotic metabolism. The purpose of the present study was to determine whether S. scardica decoction alters the activity of CYP1A2, CYP2A6, XO, NAT2 and UGT1A1/1A6 enzymes in humans. Fourteen healthy subjects consumed S. scardica decoction for six days. Enzyme phenotyping was assessed in saliva and urine using caffeine and paracetamol metabolite ratios as follows: CYP1A2: 17X/137X (saliva) and (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X), NAT2: AFMU/(AFMU+1U+1X) and UGT1A1/1A6: glucuronidated/total paracetamol (urine). After S. scardica intake, CYP1A2 index was reduced by ∼16% and ∼8% in saliva (before: 0.54 ± 0.18, after: 0.46 ± 0.09; p = 0.08) and urine (before: 3.59 ± 0.52, after: 3.67 ± 0.78; p = 0.12), respectively. CYP2A6 index was significantly reduced only in males (before: 0.76 ± 0.08, after: 0.67 ± 0.07; p = 0.004), suggesting sexual dimorphism in CYP2A6 inhibition. There was no effect of Sideritis scardica treatment on XO, NAT2 or UGT1A1/1A6 indices. Usual consumption of the aerial parts of S. scardica decoction is unlikely to result in herb-drug interactions involving the enzymes studied, with the exception of potential herb-CYP2A6 substrate interaction in males.

(-)-Epigallocatechin-3-gallate attenuates myocardial injury induced by ischemia/reperfusion in diabetic rats and in H9c2 cells under hyperglycemic conditions

(−)-Epigallocatechin gallate (EGCG) exerts multiple beneficial effects on cardiovascular performance. In this study, we aimed to examine the effects of EGCG on diabetic cardiomyopathy during myocardial ischemia/reperfusion (I/R) injury. EGCG (100 mg/kg/day) was administered at week 6 for 2 weeks to diabetic rats following the induction of type 1 diabetes by streptozotocin (STZ). At the end of week 8, the animals were subjected to myocardial I/R injury. The EGCG-elicited structural and functional effects were analyzed. Additionally, EGCG (20 μM) was administered for 24 h to cultured cardiac H9c2 cells under hyperglycemic conditions (30 mM glucose) prior to hypoxia/reoxygenation (H/R) challenge, and its effects on oxidative stress were compared to H9c2 cells transfecteed with silent information regulator 1 (SIRT1) small interfering RNA (siRNA). In rats with STZ-induced diabetes, EGCG treatment ameliorated post-ischemic cardiac dysfunction, decreased the myocardial infarct size, apoptosis and cardiac fibrosis, and reduced the elevated lactate dehydrogenase (LDH) and malonaldehyde (MDA) levels, and attenuated oxidative stress. Furthermore, EGCG significantly reduced H/R injury in cardiac H9c2 cells exposed to high glucose as evidenced by reduced apoptotic cell death and oxidative stress. The protein expression levels of SIRT1 and manganese superoxide dismutase (MnSOD) were reduced in the diabetic rats and the H9c2 cells under hyperglycemic conditions, compared with the control rats following I/R injury and H9c2 cells under normal glucose conditions. EGCG pre-treatment significantly upregulated the levels of htese proteins in vitro and in vivo. However, treatment with EX527 and SIRT1 siRNA blocked the EGCG-mediated cardioprotective effects. Taken together, our data indicate that SIRT1 plays a critical role in the EGCG-mediated amelioration of I/R injury in diabetic rats, which suggests that EGCG may be a promising dietary supplement for the prevention of diabetic cardiomyopathy.

Dietary Flavonoids, CYP1A1 Genetic Variants, and the Risk of Colorectal Cancer in a Korean population

The role of dietary flavonoid intake in colorectal carcinogenesis might differ according to flavonoid subclasses and individual genetic variants related to carcinogen metabolism. Therefore, we examined whether greater dietary intake of flavonoid subclasses was associated with a lower risk of colorectal cancer and whether CYP1A1 genetic variants altered this association. A semi-quantitative food frequency questionnaire was used to assess the dietary intake of six flavonoid subclasses (flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins, and isoflavones) in 923 patients with colorectal cancer and 1,846 controls; furthermore, CYP1A1 genetic variants (rs4646903 and rs1048943) were genotyped. Among the subclasses of flavonoids, higher intake of flavonols and flavan-3-ols showed a stronger association with a reduced risk of colorectal cancer after adjusting for potential confounding factors. Carriers of the CYP1A1 rs4646903 CC homozygous variant showed a reduced risk of rectal cancer compared with that in TT carriers. The inverse association between dietary flavonol intake and colorectal cancer risk was stronger among carriers of the CC homozygous variant than among T allele carriers (P for interaction = 0.02), particularly for rectal cancer (P for interaction = 0.005). In conclusion, the effect of dietary flavonoid intake on colorectal cancer risk differs according to flavonoid subclasses and CYP1A1 genetic variants.

Protective effects of (-)-epigallocatechin-3-gallate against acetaminophen-induced liver injury in rats)

(-)-Epigallocatechin-3-gallate (EGCG) is the most abundant catechin with various biological activities found in tea. In this study, the effects of EGCG on the metabolism and toxicity of acetaminophen in rat liver were investigated. Male Sprague-Dawley rats were fed a controlled diet without or with EGCG (0.54 %, w/w) for 1 week and were then intraperitoneally injected with acetaminophen (1 g/kg body weight) and killed after 12 h. Concentrations of acetaminophen and its conjugates in plasma and liver were then determined. The cytochrome P450 (CYP) and phase II enzymes activities were also evaluated. Rats fed the EGCG diet had lower plasma alanine aminotransferase and aspartate aminotransferase activities, as indices of hepatotoxicity, after acetaminophen treatment. Morphological damage by acetaminophen was lower in rats fed the EGCG diet. In addition, EGCG significantly reduced hepatic activities of midazolam 1-hydroxylation (CYP3A), nitrophenol 6-hydroxylase (CYP2E1), UDP-glucurosyltransferase, and sulfotransferase. Finally, EGCG feeding reduced acetaminophen-glucuronate and acetaminophen-glutathione contents in plasma and liver. These results indicate that EGCG feeding may reduce the metabolism and toxicity of acetaminophen in rats.

The effects of green tea polyphenols on drug metabolism

INTRODUCTION

Tea, made from the dried leaves of the plant Camellia sinensis Theaceae, is a very popular beverage consumed worldwide. Recently, green tea extract-based dietary supplements have also been widely consumed for the acclaimed beneficial health effects, such as weight reduction. Although tea consumption is considered to be innocuous, the potential interactions between tea polyphenols and drugs have been demonstrated in studies in vitro and in vivo.

AREAS COVERED

This article reviews the current literature on the chemistry and biotransformation of tea constituents, mainly catechins from green tea. The article also provides a review of their effects on the absorption, efflux, metabolism and elimination of different drugs.

EXPERT OPINION

Tea catechins may bind to certain drugs to affect their absorption and bioactivities. Tea catechins may inhibit the activities of drug-metabolizing enzymes and drug transporters or affect the expression of these proteins, either upregulation or downregulation. Although these effects have been demonstrated in studies in vitro and in animal models, such effects have only been observed in limited cases in humans at common doses of human tea consumption. The ingestion of tea catechins from dietary supplements, which could be in large bullet doses, may produce more profound effects on drug metabolism, and such effects with drugs need to be further investigated.

Green tea catechin, epigallocatechin-3-gallate (EGCG): mechanisms, perspectives and clinical applications

An expanding body of preclinical evidence suggests EGCG, the major catechin found in green tea (Camellia sinensis), has the potential to impact a variety of human diseases. Apparently, EGCG functions as a powerful antioxidant, preventing oxidative damage in healthy cells, but also as an antiangiogenic and antitumor agent and as a modulator of tumor cell response to chemotherapy. Much of the cancer chemopreventive properties of green tea are mediated by EGCG that induces apoptosis and promotes cell growth arrest by altering the expression of cell cycle regulatory proteins, activating killer caspases, and suppressing oncogenic transcription factors and pluripotency maintain factors. In vitro studies have demonstrated that EGCG blocks carcinogenesis by affecting a wide array of signal transduction pathways including JAK/STAT, MAPK, PI3K/AKT, Wnt and Notch. EGCG stimulates telomere fragmentation through inhibiting telomerase activity. Various clinical studies have revealed that treatment by EGCG inhibits tumor incidence and multiplicity in different organ sites such as liver, stomach, skin, lung, mammary gland and colon. Recent work demonstrated that EGCG reduced DNMTs, proteases, and DHFR activities, which would affect transcription of TSGs and protein synthesis. EGCG has great potential in cancer prevention because of its safety, low cost and bioavailability. In this review, we discuss its cancer preventive properties and its mechanism of action at numerous points regulating cancer cell growth, survival, angiogenesis and metastasis. Therefore, non-toxic natural agent could be useful either alone or in combination with conventional therapeutics for the prevention of tumor progression and/or treatment of human malignancies.

Green tea and prevention of esophageal and lung cancers

Green tea contains high concentrations of tea polyphenols that have shown inhibitory effects against the development, progress, and growth of carcinogen-induced tumors in animal models at different organ sites, including the esophagus and lung. Green tea polyphenols also have shown to suppress cell proliferation and induce apoptosis. Besides antioxidative property, green tea polyphenols have pro-oxidative activities under certain conditions and modulate phase II metabolic enzymes that can enhance the detoxification pathway of environmental toxicants and carcinogens. Although epidemiological studies have provided inconclusive results on the effect of green tea consumption against the development of esophageal and lung cancers in humans overall, the inverse association between green tea intake and risk of esophageal cancer risk is more consistently observed in studies with adequate control for potential confounders. Epidemiological studies also have demonstrated an inverse, albeit moderate, association between green tea consumption and lung cancer, especially in non-smokers. This article reviews data on the cancer-preventive activities of green tea extract and green tea polyphenols and possible mechanisms against the esophageal and lung carcinogenesis in experimental animals, and summarizes the current knowledge from epidemiological studies on the relationship between green tea consumption and esophageal and lung cancer risk in humans.

Modulation of lead biohazards using a combination of epicatechin and lycopene in rats

The toxicity of many heavy metals is due to their ability to cause oxidative damage to tissues. Lead is one of the most important metals that pollute the natural environment due to man’s impact The aim of this study is to investigate the potential protective effect of epicatechin alone or combined with lycopene against toxicity of lead in male rats. Five groups of rats were involved in this study; the first was control while the other four injected with lead acetate (100 mg/kg BW) subcutaneous for 2 weeks. On the other hand, the third, fourth and fifth groups were injected with epicatechin, lycopene or epicatechin + lycopene, respectively. Results obtained showed that, the combined treatment (epicatechin + lycopene) exert its effects (100%) against toxic effects against lead by lowering the liver enzymes alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and gamma glutamyle transferase (GGT) activities and decrease lipid peroixdation (MDA) and enhances the superoxide dismutase (SOD) activity. The high-density lipoprotein cholesterol (HDL-c) level was significantly decreased and low-density lipoprotein cholesterol (LDL-c) level was statistically significantly increased in lead-injected rats as compared with control group. The combined treatment with epicatechin and lycopene justify these levels to nearly normal values. The erythrocyte level of total glutathione was decreased in lead-injected rats as compared with control group ( p < 0.001). The combined effect is significantly higher than individual treatment lycopene alone or epicatechin. A negative correlation was found between the blood lead and SOD (r = −0.6) and glutathione (r = −0.81) while a positive correlation with MDA level (r = 0.7).

The antioxidant and pro-oxidant activities of green tea polyphenols: a role in cancer prevention

Green tea (Camellia sinensis) is rich in catechins, of which (-)-epigallocatechin-3-gallate (EGCG) is the most abundant. Studies in animal models of carcinogenesis have shown that green tea and EGCG can inhibit tumorigenesis during the initiation, promotion and progression stages. Many potential mechanisms have been proposed including both antioxidant and pro-oxidant effects, but questions remain regarding the relevance of these mechanisms to cancer prevention. In the present review, we will discuss the redox chemistry of the tea catechins and the current literature on the antioxidant and pro-oxidative effects of the green tea polyphenols as they relate to cancer prevention. We report that although the catechins are chemical antioxidants which can quench free radical species and chelate transition metals, there is evidence that some of the effects of these compounds may be related to induction of oxidative stress. Such pro-oxidant effects appear to be responsible for the induction of apoptosis in tumor cells. These pro-oxidant effects may also induce endogenous antioxidant systems in normal tissues that offer protection against carcinogenic insult. This review is meant point out understudied areas and stimulate research on the topic with the hope that insights into the mechanisms of cancer preventive activity of tea polyphenols will result.

Protective effect of tea polyphenols against paracetamol-induced hepatotoxicity in mice is significanly correlated with cytochrome P450 suppression

AIM: To investigate the hepatoprotective activity of tea polyphenols (TP) and its relation with cytochrome P450 (CYP450) expression in mice.

METHODS: Hepatic CYP450 and CYPb₅ levels were measured by UV-spectrophotometry in mice 2 d after intraperitoneal TP (25, 50 and 100 mg/kg per day). Then the mice were intragastricly pre-treated with TP (100, 200 and 400 mg/kg per day) for six days before paracetamol (1000 mg/kg) was given. Their acute mortality was compared with that of control mice. The mice were pre-treated with TP (100, 200, and 400 mg/kg per day) for five days before paracetamol (500 mg/kg) was given. Hepatic CYP2E1 and CYP1A2 protein and mRNA expression levels were evaluated by Western blotting, immunohistochemical staining and transcriptase-polymerase chain reaction.

RESULTS: The hepatic CYP450 and CYPb₅ levels in mice of TP-treated groups (100, 200 and 400 mg/kg per day) were decreased in a dose-dependent manner compared with those in the negative control mice. TP significantly attenuated the paracetamol-induced hepatic injury and dramatically reduced the mortality of paracetamol-treated mice. Furthermore, TP reduced CYP2E1 and CYP1A2 expression at both protein and mRNA levels in a dose-dependent manner.

CONCLUSION: TP possess potential hepatoprotective properties and can suppress CYP450 expression.

Antioxidative and anti-carcinogenic activities of tea polyphenols

Tea (Camellia sinensis, Theaceace), a popular beverage consumed world-wide, has been studied for its preventive effects against cancer as well as cardiovascular, neurodegenerative, and other diseases. Most of the proposed beneficial effects have been attributed to the polyphenolic compounds in tea, but the nature of these activities and the molecular mechanisms of their actions remain unclear. Tea polyphenols are known to be strong antioxidants. Prevention of oxidative stress, modulation of carcinogen metabolism, and prevention of DNA damage have been suggested as possible cancer preventive mechanisms for tea and tea polyphenols. In this chapter, we discuss these topics in the light of biotransformation and bioavailability of tea polyphenols. We also review the preventive effects of tea polyphenols in animal models of carcinogenesis and some of the possible post-initiation mechanisms of action. Finally, we discuss the effects of tea consumption on cancer risk in humans. It is our aim to raise some of the unanswered questions regarding cancer prevention by tea and to stimulate further research in this area.

Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and have activity as cancer preventive agents. Additionally, they are extremely safe and associated with low toxicity, making them excellent candidates for chemopreventive agents. The cancer protective effects of flavonoids have been attributed to a wide variety of mechanisms, including modulating enzyme activities resulting in the decreased carcinogenicity of xenobiotics. This review focuses on the flavonoid effects on cytochrome P450 (CYP) enzymes involved in the activation of procarcinogens and phase II enzymes, largely responsible for the detoxification of carcinogens. A number of naturally occurring flavonoids have been shown to modulate the CYP450 system, including the induction of specific CYP isozymes, and the activation or inhibition of these enzymes. Some flavonoids alter CYPs through binding to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acting as either AhR agonists or antagonists. Inhibition of CYP enzymes, including CYP 1A1, 1A2, 2E1 and 3A4 by competitive or mechanism-based mechanisms also occurs. Flavones (chrysin, baicalein, and galangin), flavanones (naringenin) and isoflavones (genistein, biochanin A) inhibit the activity of aromatase (CYP19), thus decreasing estrogen biosynthesis and producing antiestrogenic effects, important in breast and prostate cancers. Activation of phase II detoxifying enzymes, such as UDP-glucuronyl transferase, glutathione S-transferase, and quinone reductase by flavonoids results in the detoxification of carcinogens and represents one mechanism of their anticarcinogenic effects. A number of flavonoids including fisetin, galangin, quercetin, kaempferol, and genistein represent potent non-competitive inhibitors of sulfotransferase 1A1 (or P-PST); this may represent an important mechanism for the chemoprevention of sulfation-induced carcinogenesis. Importantly, the effects of flavonoids on enzymes are generally dependent on the concentrations of flavonoids present, and the different flavonoids ingested. Due to the low oral bioavailability of many flavonoids, the concentrations achieved in vivo following dietary administration tend to be low, and may not reflect the concentrations tested under in vitro conditions; however, this may not be true following the ingestion of herbal preparations when much higher plasma concentrations may be obtained. Effects will also vary with the tissue distribution of enzymes, and with the species used in testing since differences between species in enzyme activities also can be substantial. Additionally, in humans, marked interindividual variability in drug-metabolizing enzymes occurs as a result of genetic and environmental factors. This variability in xenobiotic metabolizing enzymes and the effect of flavonoid ingestion on enzyme expression and activity can contribute to the varying susceptibility different individuals have to diseases such as cancer. As well, flavonoids may also interact with chemotherapeutic drugs used in cancer treatment through the induction or inhibition of their metabolism.

Effects of frying oil and Houttuynia cordata thunb on xenobiotic-metabolizing enzyme system of rodents

AIM: To evaluate the effects of frying oil and Houttuynia cordata Thunb (H. cordata), a vegetable traditionally consumed in Taiwan, on the xenobiotic-metabolizing enzyme system of rodents.

METHODS: Forty-eight Sprague-Dawley rats were fed with a diet containing 0%, 2% or 5% H. cordata powder and 15% fresh soybean oil or 24-h oxidized frying oil (OFO) for 28 d respectively. The level of microsomal protein, total cytochrome 450 content (CYP450) and enzyme activities including NADPH reductase, ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-dealkylase (PROD), aniline hydroxylase (ANH), aminopyrine demethylase (AMD), and quinone reductase (QR) were determined. QR represented phase II enzymes, the rest of the enzymes tested represented phase I enzymes.

RESULTS: The oxidized frying oil feeding produced a significant increase in phase I and II enzyme systems, including the content of CYP450 and microsomal protein, and the activities of NADPH reductase, EROD, PROD, ANH, AMD and QR in rats (P<0.05). In addition, the activities of EROD, ANH and AMD decreased and QR increased after feeding with H. cordata in OFO-fed group (P<0.05). The feeding with 2% H. cordata diet showed the most significant effect.

CONCLUSION: The OFO diet induces phases I and II enzyme activity, and the 2% H. cordata diet resulted in a better regulation of the xenobiotic-metabolizing enzyme system.