Search

Objective: Tea is the most consumed beverage in the world. (−)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, is effective in the prevention of several chronic diseases, and is marketed as part of many dietary supplements. We have now examined the myocardiotoxic effect of high doses of EGCG in mice. Results: EGCG (500 and 1000 mg/kg·d) induced cardiac collagen synthesis and fibrosis-related protein expression, such as connective tissue growth factor (CTGF) and fibronectin (FN) in mice. Moreover, EGCG decreased the protein expression of p-AMPK and increased the levels of p-p70S6 K and p-S6. Conclusion: This is the first evidence that high oral doses of EGCG could induce cardiac fibrosis, and shed new light on the understanding of EGCG-mediated myocardiotoxicity. [ABSTRACT FROM AUTHOR]

The binding interactions between (−)-epigallocatechin-3-gallate (EGCG) and bovine β-lactoglobulin ( β-LG) during food processing under different temperatures (25-100 °C) and pH levels (3.2-7.4) were investigated using the fluorescence quenching method. The results indicated that temperature and pH had different effects on the structure and EGCG-binding ability of β-LG. At a higher pH (≥6.4) and temperature (≥80 °C), the structure and conformation of β-LG were more open than those of its native state due to the heat-induced denaturation and unfolding of protein, which increased its binding affinity with EGCG through hydrophobic interactions and hydrogen bonds, which in turn promoted its further unfolding. The highest binding constant ( K) and the binding site numbers (n) were 12.50 (±0.60) × 10 M (pH 6.4, 80 °C), and 0.62 (±0.02)~0.97 (±0.16), respectively. However, at 100 °C and a neutral pH, the oxidative loss of EGCG during thermal processing probably led to a decrease in β-LG-EGCG interactions. These results would be helpful to better understand the relevance of the β-LG-EGCG interaction to the bioactivity and bioavailability of EGCG during food processing, and to maintain the health benefits of this type of functional products in the food industry. [ABSTRACT FROM AUTHOR]

Stroke is the second leading cause of death among adults worldwide. (−)-Epigallocatechin-3-gallate (EGCG) has been demonstrated to exhibit neuroprotective functions in cerebral ischemia/reperfusion injury. However, the underlying mechanisms in this process and its contribution to the protection function remain unknown. The current study examined the neuroprotective effects of EGCG after transient middle cerebral artery occlusion (tMCAO) in rats. tMCAO for 120 min was induced in male Sprague-Dawley rats treated with EGCG (50 mg/kg, i.p.) or Vehicle immediately after reperfusion. Neurological score, infarct ratio and inflammation-related molecules (assessed by 2,3,5-triphenyltetrazolium chloride, enzyme-linked immunosorbent assays, quantitative real-time PCR or western blotting) were estimated at 24 h after operation. EGCG prevented the impairment of neurological function and decreased the infarct volume, compared with the Vehicle group. The inflammation-related molecules TNF-α, IL-1β, IL-6 levels usually caused by ischemia/reperfusion were significantly ameliorated by EGCG. EGCG also inhibited the upregulation of nuclear factor-kappa B/p65 (NF-κB/p65), and induction of cyclooxygenase 2 and inducible nitric oxide synthase. The present study indicates that EGCG may be a promising therapeutic agent for cerebral ischemia/reperfusion injury through attenuation of inflammation. [ABSTRACT FROM AUTHOR]

The tea catechin (−)-epigallocatechin-3-gallate (EGCG) inhibits cancer cell proliferation and induces apoptosis. Effects of EGCG on growth of immortalized intestinal and colon cancer cells and involvement of reactive oxygen species (ROS) were studied. Low concentrations of EGCG (<20 μM) stimulated cell growth (up to 60%) and high concentrations were inhibitory and induced apoptosis. H2O2 at concentrations similar to levels generated by low dosage EGCG (<5 μM) stimulated cell growth. Addition of SOD and catalase to EGCG-treated cells reduced these effects, suggesting a role for EGCG-produced ROS. EGCG produced HO in a cell culture medium. Fetal bovine serum and bovine serum albumin reduced cell associated EGCG by 90% and decreased growth inhibitory effects and HO generation from EGCG slightly. EGCG modulated intestinal cell growth either by induction of cell death or by growth stimulation via ROS generation in a culture medium. [ABSTRACT FROM AUTHOR]

Background: Human pancreatic cancer is currently one of the deadliest cancers with high mortality rate. It has been previously shown that (−)-epigallocatechin-3-gallate (EGCG), the most abundant catechin found in green tea, has showed suppressive effects on human pancreatic cancer cells. Bleomycin, (BLM), an anti-cancer chemotherapeutic drug that induces DNA damage, has antitumor effects by induction of apoptosis in several cancer cell lines and also in pancreatic cancer cells. The present study investigated for the first time, the inhibitory effect of EGCG and BLM on pancreatic cancer cell growth. Methods: Using the pancreatic cancer cell lines MIA PaCa-2 cells the efficacy and synergism of EGCG and BLM were evaluated by in vitro tests. Inhibition of cell proliferation was determined by MTT assay. Mitochondrial depolarization was performed with JC-1 probe. Viability and apoptosis were determined by Flow Cytometry with annexin V, propidium iodide staining and DNA fragmentation assay. Results: Cell proliferation assay revealed significant additive inhibitory effects with combination of EGCG and BLM at 72 h in a dose dependent manner. The combination of EGCG and BLM induced cell cycle S-phase arrest and mitochondrial depolarization. Viability, apoptosis and DNA fragmentation assay indicated that the combination of EGCG and bleomycin potentiated apoptosis. Conclusions: Our results indicate that EGCG and BLM have additive anti-proliferative effects in vitro by induction of apoptosis of MIA PaCa-2 cells. This combination could represent a new strategy with potential advantages for treatment of pancreatic cancer. To date, this is the first report published of the inhibitory effect of EGCG and BLM on human pancreatic cancer MIA Paca-2 cell growth. [ABSTRACT FROM AUTHOR]

Epigenetic changes are involved in learning and memory, and histone deacetylase (HDAC) inhibitors are considered potential therapeutic agents for Alzheimer׳s disease (AD). We previously reported that (−)-epigallocatechin-3-gallate (EGCG) acts as an HDAC inhibitor. Here, we demonstrate that EGCG reduced β-amyloid (Aβ) accumulation in vitro and rescued cognitive deterioration in senescence-accelerated mice P8 (SAMP8) via intragastric administration of low- and high-dose EGCG (5 and 15 mg/kg, respectively) for 60 days. The AD brain has decreased levels of the rate-limiting degradation enzyme of Aβ, neprilysin (NEP). We found an association between EGCG-induced reduction in Aβ accumulation and elevated NEP expression. Further, NEP silencing prevented the EGCG-induced Aβ downregulation. Our findings suggest that EGCG might be effective for treating AD. [ABSTRACT FROM AUTHOR]

The aim of this study is to show that protective effects of the main catechin (−)-epigallocatechin-3-gallate (EGCG) against capsaicin (CAP) induced oxidative stress and DNA damage in human blood in vitro. Superoxide dismutase, catalase, glutathione peroxidase and malondialdehyde (MDA) level were studied in erythrocytes and leucocytes with increased concentrations of CAP. DNA damage in leucocytes was measured by the comet assay. Human blood cells have been administered with doses between 0 and 200 μM of CAP and/or EGCG (20 μM) for an hour at 37 °C. Treatment with CAP alone has increased the levels of MDA and decreased antioxidant enzymes in human blood cells. A significant increase in tail DNA%, mean tail length and tail moment indicating DNA damage has been observed at the highest dose of CAP treatment when compared to controls. Treatment of cells with CAP plus EGCG prevented CAP-induced changes in antioxidant enzyme activities and MDA level and mean tail lenght indicating DNA damage. A significant increase in mean tail lenght was observed at high doses of CAP. These data suggest that EGCG can prevent toxicity to human erythrocytes and leucocytes caused by CAP, only at low doses. [ABSTRACT FROM AUTHOR]

(−)-Epigallocatechin-3-gallate (EGCG), a constituent of green tea, has been suggested to have numerous health-promoting effects. On the other hand, high-dose EGCG is able to evoke hepatotoxicity. In the present study, we elucidated the responses of hepatic major antioxidant enzymes and nuclear factor erythroid 2-related factor 2 (Nrf2) rescue pathway to high-dose levels of EGCG in Kunming mice. At a non-lethal toxic dose (75 mg/kg, i.p.), repeated EGCG treatments markedly decreased the levels of superoxide dismutase, catalase, and glutathione peroxidase. As a rescue response, the nuclear distribution of Nrf2 was significantly increased; a battery of Nrf2-target genes, including heme oxygenase 1 (HO1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione S-transferase (GST), and those involved in glutathione and thioredoxin systems, were all up-regulated. At the maximum tolerated dose (45 mg/kg, i.p.), repeated EGCG treatments did not disturb the major antioxidant defense. Among the above-mentioned genes, only HO1, NQO1, and GST genes were significantly but modestly up-regulated, suggesting a comprehensive and extensive activation of Nrf2-target genes principally occurs at toxic levels of EGCG. At a lethal dose (200 mg/kg, i.p.), a single EGCG treatment dramatically decreased not only the major antioxidant defense but also the Nrf2-target genes, demonstrating that toxic levels of EGCG are able to cause a biphasic response of Nrf2. Overall, the mechanism of EGCG-triggered hepatotoxicity involves suppression of major antioxidant enzymes, and the Nrf2 rescue pathway plays a vital role for counteracting EGCG toxicity. [ABSTRACT FROM AUTHOR]

Human case-studies have reported an association between green tea-based dietary supplements and hepatotoxicity. Studies have demonstrated the hepatotoxicity of high-dose oral bolus dosing with the tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) in mice and dogs. We examined the effect of pretreatment with dietary EGCG on the hepatotoxicity and bioavailability of acute oral bolus dosing with EGCG in CF-1 mice. EGCG (750 mg/kg, i.g., once daily for 3 days) increased plasma alanine aminotransferase by 80-fold, decreased both reduced (by 59%) and total (by 33%) hepatic glutathione, and increased hepatic levels of phosphorylated histone 2AX. Pretreatment with dietary EGCG (3.2 mg/g diet) for 2 weeks mitigated hepatotoxicity. Acute oral EGCG also decreased mRNA expression of glutathione reductase. Dietary pretreatment prevented these decreased and increased glutathione peroxidase (Gpx)2, Gpx3, Gpx5, and Gpx7 expression. We found that dietary EGCG reduced the plasma (57% reduction) and hepatic (71% reduction) EGCG exposure following oral bolus dosing compared to mice that were not pre-treated. Overall, it appears that EGCG can modulate its own bioavailability and that dietary treatment may reduce the toxic potential of acute high oral bolus doses of EGCG. These data may partly explain the observed variation in hepatotoxic response to green tea-containing dietary supplements. [ABSTRACT FROM AUTHOR]

Epigallocatechin gallate (EGCG), a major polyphenol in green tea, possesses antioxidant properties and regulates various cell functions. Here, we examined the function of EGCG in inflammatory bone resorption. In calvarial organ cultures, lipopolysaccharide (LPS)-induced bone resorption was clearly suppressed by EGCG. In osteoblasts, EGCG suppressed the LPS-induced expression of COX-2 and mPGES-1 mRNAs, as well as prostaglandin E2 production, and also suppressed RANKL expression, which is essential for osteoclast differentiation. LPS-induced bone resorption of mandibular alveolar bones was attenuated by EGCG in vitro , and the loss of mouse alveolar bone mass was inhibited by the catechin in vivo . [ABSTRACT FROM AUTHOR]

Epigenetic modifications are involved in cancer pathogenesis, and HDACis are considered potential therapeutic agents. We and others have shown the inhibitory activity of EGCG on HDAC1. But little is known about the effect of EGCG as on epigenetic regulation in cancer. Here, we try to demonstrate that EGCG acts as an HDACi downregulated APP expression, which was pathophysiologically upregulated in cancers and exerts a key role in cancer cell growth. We used PC-12 cells, SK-N-SH cells and primary tumor tissues for our analysis. Male 4-week-old athymic nude mice were used for heterotopic tumor growth assay. We employed Western blotting analysis to detect Bcl-2, Bax, APP, caspase-3, caspase-7, HDAC1 and H4Ac. We used AnnexinV-FITC and TUNEL staining for apoptosis detection. Tumor tissues were examined by immunohistochemical staining. We demonstrated that EGCG suppresses the growth of xenografted adrenal pheochromocytoma. Flow cytometry analysis and TUNEL staining showed that EGCG induced the apoptosis. Treatment with EGCG resulted in decrease in Bcl-2 but increase in Bax and activated caspase-3 and caspase-7. HDAC inhibitor EGCG leaded to hyperacetylated histone H4 by immunofluorescence. EGCG decreased APP levels by immunofluorescence staining and Western blot analysis. Silencing specific to HDAC1 leaded to caspase-3 and caspase-7 activation and cleavage. Our results are the first to demonstrate a functional interaction between EGCG and APP in suppression tumor growth, and provide a new epigenetic effects of EGCG on antitumor. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the most common neurodegenerative disease. Many efforts have been directed to prevent AD due to its rising prevalence and the lack of an effective curative treatment. Various epigenetic mechanisms are linked to pathogenesis of AD. Epigenetic alterations may occur through external factors and are known for their reversibility. Dietary factors can influence epigenetic mechanisms. Several neuroprotective nutrients have been shown to enhance cognition, memory and other impaired functions seen in AD. Within recent years neuroprotective nutrients have gained more attention in the field of epigenetic. A growing body of evidence suggest that epigenetic changes triggered by dietary nutrients have an important role in health and in prevention of some diseases, especially neurodegenerative disorders. Several studies have shown that folic acid, vitamin B12, choline, zinc, selenium, dietary polyphenols are capable of interacting with epigenetic mechanisms and ultimately gene expression. Epigenetic mechanisms resulting in neuronal dysfunction may be modified by diet. Therefore manipulation of epigenetic mechanisms via dietary nutrients may affect influence the vulnerability of neurons to degeneration which is seen in AD. The aim of this article is to provide a brief overview about the recent findings related to epigenetic alterations that are linked to AD pathogenesis, and to discuss the bioactive nutrients which can affect these epigenetic mechanisms. [ABSTRACT FROM AUTHOR]

Phytoferritin is a promising resource of non-heme iron supplementation, but it is not stable against degradation by proteases in the gastrointestinal tract. Therefore, how to improve the stability of ferritin in the presence of proteases is a challenge. Since (−)-epigallocatechin-3-gallate (EGCG) is rich in phenolic-hydroxyl groups, it could interact with ferritin through hydrogen bonds, thereby preventing protein from degradation. To confirm this idea, we focus on the interaction between EGCG and phytoferritin, and the consequence of such interaction. Results demonstrated that EGCG did interact with ferritin, and such interaction induced the change in the tertiary/quaternary structure of protein but not in its secondary structure. Furthermore, stopped-flow and dynamic light scattering (DLS) results showed that EGCG could trigger ferritin association. Consequently, such protein association markedly inhibited protein digestion by pepsin at pH 4.0 and by trypsin at pH 7.5. These findings raise the possibility to improve the stability of phytoferritin in the presence of proteases. [ABSTRACT FROM AUTHOR]

EGCG attenuates the neurotoxicity of methylglyoxal by inhibiting advanced glycation end products formation and regulating MAPK and the downstream signaling pathways. [Display omitted] • EGCG attenuated PC12 cells damage induced by MGO and MGO-derived AGEs. • MAPK and downstream pathways were involved in EGCG alleviating the toxicity of MGO. • EGCG suppressed MGO-derived AGEs formation by interacting with protein. Methylglyoxal (MGO), a reactive α-oxoaldehyde formed in many foods and beverages during processing and storage, has neurotoxicity. The purpose of this study was to investigate the inhibition mechanism of (−)-epigallocatechin-3-gallate (EGCG) on MGO-induced PC12 cells damage. Cell apoptosis and reactive oxygen species (ROS) level were measured with fluorescent staining methods. Western blotting was used to detect the signal transduction mechanism. The results indicated that EGCG decreased ROS level, inhibited apoptosis and increased the expression of brain-derived neurotrophic factor. Pathways analysis revealed that the neuroprotective mechanism of EGCG might rely on regulating mitogen-activated protein kinase (MAPK) and downstream pathways. Multi-spectroscopy and molecular docking indicated that EGCG inhibited MGO-derived advanced glycation end products (AGEs) formation. Moreover, the neurotoxicity of AGEs could be alleviated by EGCG. These results suggested that EGCG could attenuate MGO-induced nerve damage via regulating MAPK and downstream pathways and inhibiting AGEs formation. [ABSTRACT FROM AUTHOR]

(−)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, has been reported to inhibit the Wnt/β-catenin pathway, which is aberrantly up-regulated in colorectal cancers, but its precise mechanism of action remains unclear. Here, we used a sensitive cell-based system to demonstrate that EGCG suppresses β-catenin response transcription (CRT), activated by Wnt3a-conditioned medium (Wnt3a-CM), by promoting the degradation of intracellular β-catenin. EGCG induced β-catenin N-terminal phosphorylation at the Ser33/37 residues and subsequently promoted its degradation; however, this effect was not observed for oncogenic forms of β-catenin. Pharmacological inhibition or depletion of glycogen synthase kinase-3β (GSK-3β) did not abrogate the EGCG-mediated β-catenin degradation. EGCG did not affect the activity and expression of protein phosphatase 2A (PP2A). Consistently, the phosphorylation and degradation of β-catenin was found in adenomatous polyposis coli (APC) mutated colon cancer cells after EGCG treatment. EGCG repressed the expression of cyclin D1 and c-myc, which are β-catenin/T-cell factor-dependent genes, and inhibited the proliferation of colon cancer cells. Our findings suggest that EGCG exerts its cancer-preventive or anticancer activity against colon cancer cells by promoting the phosphorylation and proteasomal degradation of β-catenin through a mechanism independent of the GSK-3β and PP2A. © 2014 BioFactors, 40(6):586-595, 2014 [ABSTRACT FROM AUTHOR]

The molecular interaction between bovine lactoferrin (LF) and (−)-epigallocatechin-3-gallate (EGCG) was investigated in an aqueous solution at pH 6.0. The presence of EGCG did not change the size and turbidity of LF–EGCG complex in an aqueous solution until the LF/EGCG molar ratio was over a critical value of 1:25. The fluorescence spectra revealed that both tryptophanyl and tyrosyl groups of LF were associated with the interaction with EGCG. The infrared spectra of freeze-dried LF–EGCG complexes showed that they were different from those of LF and EGCG alone, FTIR and far-UV CD results indicated that EGCG induced a progressive increase in the proportion of α -helix structure at the cost of β -sheet structure of LF. The near-UV CD data testified that LF tertiary conformation was altered in the presence of EGCG. Isothermal titration calorimetry (ITC) analysis implied that EGCG was spontaneously bound to LF by a two-stage mechanism, about 31 EGCG molecules were integrated with 1 molecule LF and hydrogen bonds were always involved in the assembly process. [ABSTRACT FROM AUTHOR]

(−)-Epigallocatechin-3-gallate (EGCG), the most abundant polyphenolic constituent in green tea, is known as a powerful antioxidant but concomitantly possesses a prooxidant property. We investigated the effect of EGCG on phloxine B (PhB)-induced photocytotoxicity in human T lymphocytic leukemia Jurkat cells. EGCG significantly potentiated PhB-induced photocytotoxic effects, including the inhibition of cell proliferation, DNA fragmentation, and caspase-3 activity induction in Jurkat cells. Catalase attenuated the enhanced cytotoxicity by EGCG, suggesting the involvement of extracellularly produced hydrogen peroxide. Indeed, EGCG significantly enhanced extracellular hydrogen peroxide formation induced by photo-irradiated PhB. The EGCG also enhanced intracellular reactive oxygen species accumulation, c-Jun N-terminal kinase (JNK) phosphorylation, and interferon-γ (IFN-γ) gene expression, all of which are involved in PhB-induced apoptosis. Taken together, our data suggest that EGCG is capable of potentiating photodynamic therapy responses, presumably through the intracellular oxidative stress-sensitive JNK/IFN-γ pathway by exogenous hydrogen peroxide formation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Nasal polyps are chronic inflammatory conditions characterized by myofibroblast differentiation and extracelluar matrix accumulation. The major catechin from green tea is (−)-epigallocatechin-3-gallate (EGCG), which has garnered attention for its potential to prevent oxidative stress-related diseases. The purpose of this study was twofold: (i) to determine the effect of EGCG on fibroblast differentiation into myofibroblasts and extracellular matrix accumulation in transforming growth factor (TGF)-β1-induced nasal polyp-derived fibroblasts (NPDFs) and (ii) to determine if the antioxidative effect of EGCG on reactive oxygen species (ROS) production in TGF-β1-induced NPDFs is involved in the aforementioned processes. TGF-β1-induced NPDFs were treated with or without EGCG. α-smooth muscle actin (α-SMA) and collagen type I mRNA were analyzed by reverse transcription-polymerase chain reaction. α-SMA protein was also detected using immunofluorescent staining. The amount of total soluble collagen was analyzed by Sircol collagen assay. ROS activity was measured by the nitroblue tetrazolium reduction assay and visualized by fluorescent microscopy. EGCG significantly inhibited expressions of α-SMA and collagen type I mRNA and reduced α-SMA and collagen protein levels at concentrations of 10-20 µg/mL. EGCG also inhibited TGF-β1-induced ROS production at the same concentrations. These results suggest the possibility that EGCG may be effective at inhibiting the development of nasal polyps through an anti-oxidant effect. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The green tea polyphenol, (−)-epigallocatechin-3-gallate (EGCG), has been shown to have anti-carcinogenic effects in several skin tumor models, and efforts are continued to investigate the molecular targets responsible for its cytotoxic effects to cancer cells. Our recent observation that β-catenin is upregulated in skin tumors suggested the possibility that the anti-skin carcinogenic effects of EGCG are mediated, at least in part, through its effects on β-catenin signaling. We have found that treatment of the A431 and SCC13 human skin cancer cell lines with EGCG resulted in reduced cell viability and increased cell death and that these cytotoxic effects were associated with inactivation of β-catenin signaling. Evidence of EGCG-induced inactivation of β-catenin included: (i) reduced accumulation of nuclear β-catenin; (ii) enhanced levels of casein kinase1α, reduced phosphorylation of glycogen synthase kinase-3β, and increased phosphorylation of β-catenin on critical serine45,33/37 residues; and (iii) reduced levels of matrix metalloproteinase (MMP)-2 and MMP-9, which are down-stream targets of β-catenin. Treatment of cells with prostaglandin E2 (PGE2) enhanced the accumulation of β-catenin and enhanced β-catenin signaling. Treatment with either EGCG or an EP2 antagonist (AH6809) reduced the PGE2-enhanced levels of cAMP, an upstream regulator of β-catenin. Inactivation of β-catenin by EGCG resulted in suppression of cell survival signaling proteins. siRNA knockdown of β-catenin in A431 and SCC13 cells reduced cell viability. Collectively, these data suggest that induction of cytotoxicity in skin cancer cells by EGCG is mediated by targeting of β-catenin signaling and that the β-catenin signaling is upregulated by inflammatory mediators. [Copyright &y& Elsevier]

Abstract: Green tea catechins have been shown to affect the activities of drug transporters in vitro, including P-glycoprotein and organic anion transporting polypeptides. However, it remains unclear whether catechins influence the in vivo disposition of substrate drugs for these transporters. In the present study, we investigated effects of green tea extract (GTE) and (−)-epigallocatechin-3-gallate (EGCG) on pharmacokinetics of a non-selective hydrophilic β-blocker nadolol, which is reported to be a substrate for several drug transporters and is not metabolized by cytochrome P450 enzymes. Male Sprague-Dawley rats received GTE (400mg/kg), EGCG (150mg/kg) or saline (control) by oral gavage, 30min before a single intragastric administration of 10mg/kg nadolol. Plasma and urinary concentrations of nadolol were determined using high performance liquid chromatography. Pharmacokinetic parameters were estimated by a noncompartmental analysis. Pretreatment with GTE resulted in marked reductions in the maximum concentration (C max) and area under the time–plasma concentration curve (AUC) of nadolol by 85% and 74%, respectively, as compared with control. In addition, EGCG alone significantly reduced C max and AUC of nadolol. Amounts of nadolol excreted into the urine were decreased by pretreatments with GTE and EGCG, while the terminal half-life of nadolol was not different among groups. These results suggest that the coadministration with green tea catechins, particularly EGCG, causes a significant alteration in the pharmacokinetics of nadolol, possibly through the inhibition of its intestinal absorption mediated by uptake transporters. [Copyright &y& Elsevier]

Tea polyphenol ( TP) inhibits digestive enzymes and reduces food digestibility. To explore the interaction between TP with digestive enzymes, bindings of -epigallocatechin-3-gallate ( EGCG) to trypsin and α-chymotrypsin were studied in detail using fluorescence, resonance light-scattering, circular dichroism, fourier transform infrared spectroscopy methods and protein-ligand docking. The binding parameters were calculated according to Stern- Volmer equation, and the thermodynamic parameters were determined by the van't Hoff equation. The results indicated that EGCG was capable of binding trypsin and α-chymotrypsin with high affinity, resulting in a change of native conformation of these enzymes. EGCG had a greater influence on the structure of α-chymotrypsin than trypsin. This study can be used to explain the binding interaction mechanism between TP and digestive enzymes. [ABSTRACT FROM AUTHOR]

Highlights: [•] EGCG inhibits the entry of influenza A and B viruses into cells with EC50 values between 5.7 and 17.3μM. [•] EGCG has no inhibitory effects on the viral HA and polymerase activities. [•] EGCG marginally inhibits the NA activity derived from influenza virus as well as from nonviral C. perfringens. [•] Upon EGCG treatment, influenza viral particles became resistant to NA and tightly fixed on the surface of cells. [•] EGCG damages influenza virus particle integrity, rendering viral membranes permeable and resulting in particle shrinkage. [Copyright &y& Elsevier]

Highlights: [•] Vc can enhance the effect of EGCG or TF3 on inducing apoptosis of cancer cells. [•] EGCG or TF3 with Vc significantly increased activity of caspase-3/9 in cancer cells. [•] EGCG or TF3 with Vc induced apoptosis through different MAPK pathways in two cells. [ABSTRACT FROM AUTHOR]

Abstract: (−)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, has been shown to inhibit carcinogenesis of various tumor types. The aim of this study was to elucidate the antiproliferative potential of EGCG and its mechanism in human endometrial cancer cells (Ishikawa cells) and primary endometrial adenocarcinoma cells. The antiproliferative effect of EGCG was evaluated by cell viability assay. Apoptosis was measured by annexin/propidium iodide staining. Reactive oxygen species (ROS) generation was measured by using 2’,7’-dichlorofluorescin diacetate dye. Expression of mitogen-activated protein kinases, proliferation and apoptotic markers were measured by immunoblot analysis. EGCG was found to inhibit proliferation in Ishikawa as well as in primary endometrial adenocarcinoma cells and effectively down-regulated the expression of proliferation markers, i.e., estrogen receptor α, progesterone receptor, proliferating cell nuclear antigen and cyclin D1. EGCG also decreased the activation of ERK and downstream transcription factors fos and jun. EGCG caused apoptotic cell death accompanied by up-regulation of proapoptotic Bax and down-regulation of antiapoptotic protein Bcl2. EGCG induced the cleavage of caspase-3 and poly(ADP-ribose) polymerase, the hallmark of apoptosis. EGCG significantly induced the ROS generation as well as p38 activation in Ishikawa cells, which appeared to be a critical mediator in EGCG-induced apoptosis. The apoptotic effect of EGCG and the p38 activation were blocked by pretreatment of cells with the ROS scavenger N-acetylcysteine. EGCG reduced the glutathione levels, which might be responsible for enhanced ROS generation causing oxidative stress in endometrial cancer cells. Taken together, these results suggest that EGCG inhibits cellular proliferation via inhibiting ERK activation and inducing apoptosis via ROS generation and p38 activation in endometrial carcinoma cells. [Copyright &y& Elsevier]

Abstract: In this study the extraction of (−)-Epigallocatechin-3-gallate (EGCG) from Iranian green tea was investigated by supercritical CO2 with ethanol as co-solvent. Design of experiments and modeling were carried out with response surface methodology by Minitab software. The HPLC analysis of the extracted samples was used in conjunction with response surface design to optimize four operating variables of supercritical CO2 extraction (pressure, temperature, CO2 flow rate and extraction dynamic time). Optimum recovery of EGCG (0.462g/g) was obtained at 19.3MPa, 43.7°C, 106min (dynamic) and 1.5ml/min (CO2 flow rate). Moreover, a three-layer artificial neural network was developed for modeling EGCG extraction from green tea. In this regard, different networks (by changing the number of neurons in the hidden layer and algorithm of network training) were compared with evaluation of networks accuracy in extraction recovery prediction. Finally, the Levenberg–Marquardt algorithm with the six neurons in the hidden layer has been found to be the most suitable network. [Copyright &y& Elsevier]

Neuroblastoma is an extracranial solid tumor that usually occurs in infants and children. Malignant neuroblastomas remain mostly refractory to currently available chemotherapeutic agents. So, new therapeutic agents and their molecular mechanisms for induction of cell death must be explored for successful treatment of human malignant neuroblastomas. Two polyphenolic compounds, which are abundant in green tea, are (−)-epigallocatechin (EGC) and (−)-epigallocatechin-3-gallate (EGCG) that possess impressive anti-cancer properties. It is not known yet whether EGC and EGCG can modulate the levels of expression of specific microRNAs (miRs) for induction of apoptosis in human malignant neuroblastomas. In this investigation, we revealed that treatment with EGC or EGCG caused induction of apoptosis with significant changes in expression of specific oncogenic miRs (OGmiRs) and tumor suppressor miRs (TSmiRs) in human malignant neuroblastoma SH-SY5Y and SK-N-DZ cell lines. Treatment of both cell lines with either 50 μM EGC or 50 μM EGCG decreased expression of the OGmiRs (miR-92, miR-93, and miR-106b) and increased expression of the TSmiRs (miR-7-1, miR-34a, and miR-99a) leading to induction of extrinsic and intrinsic pathways of apoptosis. Our data also demonstrated that overexpression of miR-93 decreased efficacy while overexpression of miR-7-1 increased efficacy of the green tea polyphenols for induction of apoptosis in both cell lines. In conclusion, our current investigation clearly indicates that overexpression of miR-7-1 can highly potentiate efficacy of EGCG for induction of apoptosis in human malignant neuroblastoma cells. [ABSTRACT FROM AUTHOR]

Abstract: (−)-Epigallocatechin-3-gallate (EGCG), the principal constituent of green tea, protects neurons from toxic insults by suppressing the microglial secretion of neurotoxic inflammatory mediators. Voltage-gated proton channels are expressed in microglia, and are required for NADPH oxidase-dependent reactive oxygen species generation. Brain damage after ischemic stroke is dependent on proton channel activity. Accordingly, we examined whether EGCG could inhibit proton channel function in the murine microglial BV2 cells. EGCG potently inhibited proton currents with an IC50 of 3.7μM. Other tea catechins, (−)-epigallocatechin, (−)-epicatechin and (−)-epicatechin-3-gallate, were far less potent than EGCG. EGCG did not change the kinetics of proton currents such as the activation and the deactivation time constants, the reversal potential and the activation voltage, suggesting that the gating process of proton channels were not altered by EGCG. EGCG is known to disturb lipid rafts by sequestering cholesterol. However, neither extraction of cholesterol with methyl-β-cyclodextrin or cholesterol supplementation could reverse the EGCG inhibition of proton currents. In addition, the EGCG effect was preserved in the presence of the cytoskeletal stabilizers paclitaxel and phalloidin, phosphatase inhibitors, the antioxidant Trolox, superoxide dismutase or catalase. The proton channel inhibition can be a substantial mechanism for EGCG to suppress microglial activation and subsequent neurotoxic events. [Copyright &y& Elsevier]

Background: (-)-Epigallocatechin-3-gallate (EGCG) is an active constituent of green tea, whose efficacy on chemoprevention and chemotherapy has been extensively researched. Its anticancer potency with low toxicity and easy administration allows for its widespread use. Bortezomib, a proteasome inhibitor, has a significant influence on multiple myeloma (MM) in chemotherapy. Previous studies about the role of EGCG in the antitumor effect induced by bortezomib remain controversial., Objectives: In our study, the effect of EGCG on the antitumor activity of bortezomib was investigated in myeloma cell lines U266 and RPMI8226, and the underlying mechanism was explored., Material and Methods: The effect of EGCG on the antiproliferative and pro-apoptotic activities of bortezomib were investigated in myeloma cells using MTT assay and cell cycle analysis, respectively. The Wnt/β-catenin signaling pathway and related proteins were involved in this antagonistic effect and measured with western blot assay., Results: Our results showed the inhibitory activity of EGCG on myeloma cells in a timeand dose-dependent manner. The EGCG neutralized the antiproliferative and pro-apoptotic effect induced by bortezomib by activating Wnt/β-catenin signaling pathway with the accumulation of β-catenin. An increase of the downstream target proteins as c-Myc and cyclin D1 was also observed. was also observed. These findings demonstrated the antagonistic role of EGCG in the antitumor effect of bortezomib likely through the activated Wnt/β-catenin signaling pathway and the upregulated target proteins., Conclusions: When bortezomib is involved in the MM chemotherapy, the consumption of green tea should be avoided in order to maintain the biological efficacy of bortezomib.

Our recent study showed that glutamate can inhibit dopamine oxidation via chelating copper. l-Theanine is an amino acid analogue of glutamate, whereas tea (-)-epigallocatechin-3-gallate (EGCG) is similar to dopamine in avidly undergoing oxidation. We thus hypothesized that l-theanine could also restrain EGCG oxidation via chelating copper. The current study scrutinized influences of l-theanine on EGCG oxidation in vitro and in vivo. The in vitro results showed that l-theanine and copper formed an l-theanine-copper complex with impaired redox activity of copper. Accordingly, l-theanine effectively suppressed copper-facilitated EGCG oxidation, hydroxyl radical production, and DNA damage; inhibited EGCG autoxidation which in essence involves catalysis of transition metals such as copper; and reduced EGCG oxidation-associated formation of a quinone adduct with proteins known as quinoproteins. Consistently, l-theanine significantly increased hepatic EGCG levels and reduced hepatic quinoprotein levels and liver injury in mice treated with EGCG. These lines of evidence together suggest that tea l-theanine can protect against tea catechin oxidation.

Abstract: We previously reported that (−)-epigallocatechin-3-gallate (EGCG) increased the level of SHARP-1 mRNA via a phosphoinositide 3-kinase/atypical protein kinase C lambda signaling pathway in rat H4IIE hepatoma cells. In the present study, we investigated other signaling pathway(s). Treating with either compound-C, BAY11-7082, or both, partially blocked the up-regulation of the SHARP-1 gene by EGCG. This suggests that AMP-activated protein kinase (AMPK)- and nuclear factor-kappa B (NF-κB)-signaling pathways were additively involved in the induction mediated by EGCG. Indeed, an AMPK activator induced a level of SHARP-1 mRNA. Although actinomycin D partially blocked the EGCG-induction of that SHARP-1 mRNA level, the nucleotide sequence between −1501 and −1 in the rat SHARP-1 gene did not positively respond to EGCG and NF-κB, respectively. Thus, we conclude that EGCG stimulates multiple signaling pathways in the SHARP-1 gene expression at the transcriptional and post-transcriptional levels and that there is no regulatory region susceptible to EGCG and NF-κB in the examined region. [Copyright &y& Elsevier]

Abstract: Neuroblastoma is a solid tumor that mostly occurs in children. Malignant neuroblastomas have poor prognosis because conventional chemotherapeutic agents are hardly effective. Survivin, which is highly expressed in some malignant neuroblastomas, plays a significant role in inhibiting differentiation and apoptosis and promoting cell proliferation, invasion, and angiogenesis. We examined consequences of survivin knockdown by survivin short hairpin RNA (shRNA) plasmid and then treatment with (−)-epigallocatechin-3-gallate (EGCG), a green tea flavonoid, in malignant neuroblastoma cells. Our Western blotting and laser scanning confocal immunofluorescence microscopy showed that survivin was highly expressed in malignant neuroblastoma SK-N-BE2 and SH-SY5Y cell lines and slightly in SK-N-DZ cell line. Expression of survivin was very faint in malignant neuroblastoma IMR32 cell line. We transfected SK-N-BE2 and SH-SY-5Y cells with survivin shRNA, treated with EGCG, and confirmed knockdown of survivin at mRNA and protein levels. Survivin knockdown induced morphological features of neuronal differentiation, as we observed following in situ methylene blue staining. Combination of survivin shRNA and EGCG promoted neuronal differentiation biochemically by increases in the expression of NFP, NSE, and e-cadherin and also decreases in the expression of Notch-1, ID2, hTERT, and PCNA. Our in situ Wright staining and Annexin V-FITC/PI staining showed that combination therapy was highly effective in inducing, respectively, morphological and biochemical features of apoptosis. Apoptosis occurred with activation of caspase-8 and cleavage of Bid to tBid, increase in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and increases in the expression and activity of calpain and caspase-3. Combination therapy decreased migration of cells through matrigel and inhibited proliferative (p-Akt and NF-κB), invasive (MMP-2 and MMP-9), and angiogenic (VEGF and b-FGF) factors. Also, in vitro network formation ability of cells was significantly inhibited by survivin silencing and completely by combination of survivin silencing and EGCG treatment. Collectively, survivin silencing potentiated anti-cancer effects of EGCG in human malignant neuroblastoma cells having survivin overexpression. [Copyright &y& Elsevier]

Muscle degeneration and impairment following nerve injury could lead to apoptosis as a result of increased levels of reactive oxygen species. This activates the apoptotic cascade through mitochondrial dysfunction and damage to lipids, proteins, and DNA. In considering of the multifactorial protective properties of green tea polyphenols (−)-epigallocatechin-3-gallate (EGCG), this study investigates whether EGCG treatment does improve skeletal muscle function impairments, induced by crushing of the sciatic nerve. Compared to the saline-treated injured group of animals, EGCG treatment of axonotomized animals showed significant motor enhancement in the toe spread and foot positioning analysis and gain in the percentage motor deficit. The proprioceptive function expressed by the hopping response showed significant progression in the EGCG-treated group. Recovery of sensory innervation was followed by a slowly retreating neuropathic pain-like syndrome in the EGCG-treated animals. Muscle tissues from injured limb showed severe histopathological alterations that were significantly attenuated by EGCG treatment at the end of week 3 post-surgery. Semi-quantitative desmin immunohistochemistry revealed intense staining in the saline-treated injured animals, whereas EGCG treatment decreased the desmin immunoreactivity back to sham control levels. Using RT-PCR, EGCG treatment induced a significant anti-apoptotic effect in injured muscle tissues by normalizing the Bax/Bcl-2 ratio back to baseline levels and inhibiting overexpression of the p53 apoptotic gene at days 3 and 7 post-surgery. In conclusion, our results demonstrate that EGCG enhances functional recovery, protects muscle fibers from cellular death by activating anti-apoptotic signaling pathway, and improves morphological recovery in skeletal muscle after nerve injuries. [ABSTRACT FROM AUTHOR]

Abstract: The molecular interactions between EGCG and insulin were investigated to probe the mechanism of EGCG-induced insulin precipitation. The results indicated that 1–5mM EGCG induced insulin into reversible globular precipitates of 185–365nm. The formation of precipitates was facilitated at high salt concentration and pH values close to insulin''s isoelectric point, indicating that hydrophobic interaction was the main driving force. The precipitation was positively related to insulin concentration, but for EGCG, there was a suitable concentration (2mM at 2mg/mL of insulin) at which the precipitate content reached maximum. Mass spectroscopy analysis indicated that EGCG formed clusters in the aqueous solution and the clusters correlate with the insulin precipitation. Based on extensive investigation, a physical model was proposed to explain the molecular interactions between EGCG and insulin. Namely, EGCG monomers and clusters first bound to insulin dimers via hydrophobic interaction, leading to the reduction of the thickness of the hydration layer and the partial denaturation of insulin. Then, EGCG clusters acted as bridges to induce the aggregation and precipitation of insulin. [Copyright &y& Elsevier]

Abstract: Malignant neuroblastomas are childhood tumors that remain mostly incurable. We explored efficacy of N-(4-hydroxyphenyl) retinamide (4-HPR) and (−)-epigallocatechin-3-gallate (EGCG) in altering expression of oncogenic microRNAs (OGmiRs) and tumor suppressor miRs (TSmiRs) for controlling growth of human malignant neuroblastoma SK-N-BE2 and IMR-32 cells. Combination of 4-HPR and EGCG most significantly decreased expression of OGmiRs (miR-92, miR-93, and miR-106b) and increased expression of TSmiRs (miR-7-1, miR-34a, and miR-99a) in both cell lines. Overexpression of miR-93 and miR-7-1, respectively, decreased and increased efficacy of treatments. Thus, alterations in expression of specific OGmiRs and TSmiRs by 4-HPR and EGCG inhibited growth of malignant neuroblastomas. [Copyright &y& Elsevier]

Abstract: Delphinidin-3-O-galactoside (D3G) is a water-soluble anthocyanin with antioxidant activity. (−)-Epigallocatechin-3-gallate (EGCG) is also known as a powerful antioxidant but concomitantly possesses a prooxidative property. We hypothesized that D3G is capable of protecting the EGCG-induced cytotoxicity and endoplasmic reticulum (ER) stress via inducing self-protective proteins and antioxidant enzymes. (−)-Epigallocatechin-3-gallate (200-500 μM) dose dependently decreased the viability of hepa1c1c-7 mouse hepatocytes, whereas D3G (50-500 μM) did not change it. Pretreatment with D3G significantly suppressed EGCG-induced cytotoxicity in a time-dependent manner (0, 6, and 24 hours). (−)-Epigallocatechin-3-gallate drastically decreased heme oxygenase-1 and heat shock protein 70 messenger RNA (mRNA) levels, whereas, pretreatment with D3G markedly attenuated their down-regulations. Delphinidin-3-O-galactoside remarkably decreased EGCG-induced ER stress responses such as C/EBP-homologus protein mRNA expression and X-box–binding protein-1 mRNA splicing. Taken together, our data suggest that D3G is capable of masking the EGCG-induced cytotoxicity and ER stress, presumably through up-regulation of antioxidant enzymes and heat shock proteins. [Copyright &y& Elsevier]

Abstract: (−)-Epigallocatechin-3-gallate (EGCG), a food additive derived from green tea, has been reported to effectively inhibit the fibrillation of many amyloid proteins, but not insulin. So herein, the influences of EGCG on the fibrillation kinetics of human insulin at two conditions (pH 2.0, 60°C and pH 7.4, 37°C) were extensively studied. It was found that at pH 2.0 and 60°C the inhibitory effect increased with increasing EGCG concentration from 0.35 to 3.5mmol/L but kept almost unchanged from 3.5 to 5mmol/L EGCG. The addition of EGCG reduced the length and width of fibrils and kept part of insulin from fibrillation at this condition. At pH 7.4 and 37°C, however, EGCG altered the fibrillation pathway of insulin and redirected it into globular aggregates, and the inhibitory effect of EGCG on the aggregation reached maximum at about 0.1–0.2mmol/L. In this case, part of insulin molecules were prevented from aggregation and existed as a mixture of monomer, dimer, tetramer, and hexamer in the solution. Circular dichroism spectroscopy indicated that EGCG slowed down the changes of the secondary structures of insulin in the aggregation. Finally, two physical models were proposed to explain the molecular interactions between insulin and EGCG at the two conditions. The research has clarified the kinetic mechanism of the inhibitory effect of EGCG on insulin fibrillation/aggregation. [Copyright &y& Elsevier]

Abstract: Isothermal titration calorimetry (ITC), circular dichroism (CD) spectroscopy, fluorescence spectroscopy and dynamic light scattering were utilized to investigate the molecular interactions between human insulin and EGCG. The ITC results suggest that the binding stoichiometry is independent of pH, salt concentration and temperature, but increases with the increase of EGCG concentration. The interactions between insulin and EGCG are always enthalpically favorable, indicating that hydrogen bonding is always involved in the binding process. However, with the increase of EGCG concentration, both ΔH and ΔS increase gradually, indicating an enhanced contribution of hydrophobic interaction at the physiological condition. The binding of EGCG to insulin can be promoted by increasing temperature at about 120mmol/L NaCl and pH values away from insulin''s isoelectric point. The CD results indicate that the binding of EGCG slightly changes the secondary structure of insulin. The fluorescence spectra reveal that EGCG binding gives little effect on the polarity of the environments in which tyrosine residues exist and the solvent-accessible hydrophobic surfaces of insulin. The addition of EGCG decreases the hydrodynamic radius of insulin, indicating that EGCG directly binds to the protein [Copyright &y& Elsevier]

Abstract: Alzheimer’s disease is associated with amyloid-β plaques eliciting neuronal oxidative stress. Many naturally occurring compounds have antioxidant properties, but it is unclear if this alone protects against amyloid-β exposure. This study investigated the protective effects of selected bioactive compounds against amyloid-β and pro-oxidant-evoked neurotoxicity in PC12 cells. Neither resveratrol, (−)-epigallocatechin-3-gallate, cyanidin rutinoside or grape skin extract protected PC12 cells against H2O2 or tert butyl hydroperoxide toxicity. Amyloid-β resulted in a concentration-dependent reduction in PC12 cell viability that was unaffected by resveratrol or cyanidin rutinoside pre-treatment. By contrast, (−)-epigallocatechin-3-gallate and grape skin extract significantly reduced amyloid-β-evoked neurotoxicity (by 40%). Only (−)-epigallocatechin-3-gallate was directly able to inhibit amyloid-β aggregate and fibril formation. These results suggest that (−)-epigallocatechin-3-gallate protects neuronal cells by disrupting amyloid-β fibril formation; bioactive polyphenols which disrupt fibril aggregation may confer additional neuroprotection when compared against antioxidant activity alone. [Copyright &y& Elsevier]

Abstract: The aim of the study was to examine the photostability of the major catechin of green tea, (−)-epigallocatechin-3-gallate (EGCG), which possesses important antioxidant and skin photoprotective properties. In order to simulate realistic conditions of use of topical preparations, the photolysis studies were performed in model creams (oil-in-water emulsions) containing 1% (w/w) EGCG and exposed to a solar simulator at an irradiance corresponding to natural sunlight. The extent of photodegradation was measured by HPLC–UV and HPLC–ESI-MS. EGCG was found to decompose by 68.9±2.3%, after 1h irradiation. Addition of the coantioxidants, vitamin E or butylated hydroxytoluene to the emulsion formulation, significantly enhanced the photolability of the catechin, the EGCG loss reached 85.7±1.3% and 80.5±1.4%, respectively. On the other hand, inclusion of the UVB (290–320nm) filter, ethylhexyl methoxycinnamate in the cream produced a small but significant reduction of EGCG photodegradation to 61.0±2.9%, while the UVA (320–400nm) filter, butyl methoxydibenzoylmethane was ineffective (EGCG degradation, 67.8±1.5%). A more marked decrease in the light-induced decomposition of EGCG to 51.6±2.7% was achieved, under the same conditions, using the water-soluble UVB filter, benzophenone-4 (BP-4). This effect was concentration dependent, maximal EGCG photostabilization (catechin loss, 29.4±2.2%) was attained in the presence of 2.1% (w/w) BP-4. Therefore, BP-4 represents a useful additive to improve the light stability of EGCG in topical formulations for skin photoprotection. [Copyright &y& Elsevier]

Objective: The aim of our study was to investigate the effects of (−)-epigallocatechin-3-gallate (EGCG, the major phytochemistry component in green tea) on the expression of connexin43 (Cx43) gene and detect the intercellular communication of the human bladder cancer cell lines BIU-87, and explore its possible mechanisms of prevention and cure for the bladder tumor. Methods: The methyl thiazolyl tetrazolium and Annexin-V/PI double-labeled flow cytometry methods were used to observe the growth inhibitory rate (IR) and apoptosis rate (AR) of BIU-87 cells treated by EGCG at different concentrations (0, 5, 10 and 20 mg/L), respectively. The reverse transcription-polymerase chain reaction (RT-PCR) and Western Blotting analysis were employed to detect the relative expression levels of the Cx43 mRNA and its protein. The scrape-loading fluorescence dye transfer method was used to assess the gap junction intercellular communication (GJIC) under fluorescence microscope. Results: EGCG at concentrations (10 and 20 mg/L) both could significantly inhibit the proliferation and induce the apoptosis of BIU-87 cells. The IR and AR were (15.67 ± 1.15)%, (18.33 ± 1.53)% and (42.00 ± 4.34)%, (27.33 ± 3.21)%, respectively. And compared with the control groups of 0 mg/L and 5 mg/L ( P<0.05), EGCG could significantly up-regulate the expression of Cx43 mRNA and its protein and enhance the function of BIU-87 cells. The effects had the significant correlation with the dose-dependent of EGCG. Conclusion: EGCG (10, 20 mg/L) could effectively up-regulate Cx43 expression and enhance the GJIC of BIU-87 cells. The results may indicate the effects of EGCG inducing bladder tumor cells apoptosis and inhibiting its growth which provides the experimental evidence for further demonstrating the mechanism of chemical prevention and cure for the bladder tumor by EGCG. [ABSTRACT FROM AUTHOR]

Abstract: Several natural polyphenols with potent inhibitory effects on amyloid fibril formation have been reported. Herein, we studied modulation of transthyretin (TTR) fibrillogenesis by selected polyphenols. We demonstrate that both curcumin and nordihydroguaiaretic acid (NDGA) bind to TTR and stabilize the TTR tetramer. However, while NDGA slightly reduced TTR aggregation, curcumin strongly suppressed TTR amyloid fibril formation by generating small “off-pathway” oligomers and EGCG maintained most of the protein in a non-aggregated soluble form. This indicates alternative mechanisms of action supported by the occurrence of different non-toxic intermediates. Moreover, EGCG and curcumin efficiently disaggregated pre-formed TTR amyloid fibrils. Our studies, together with the safe toxicological profile of these phytochemicals may guide a novel pharmacotherapy for TTR-related amyloidosis targeting different steps in fibrillogenesis. Structured summary of protein interactions: TTR binds to TTR by comigration in gel electrophoresis (View interaction) TTR binds to TTR by dynamic light scattering (View interaction) TTR binds to TTR by electron microscopy (View interaction) [Copyright &y& Elsevier]

Abstract: Green tea (Camellia sinensis, Theaceace) is the second most popular beverage in the world and has been extensively studied for its putative disease preventive effects. Green tea is characterized by the presence of a high concentrations of polyphenolic compounds known as catechins, with (−)-epigallocatechin-3-gallate (EGCG) being the most abundant and most well-studied. Metabolic syndrome (MetS) is a complex condition that is defined by the presence of elevated waist circumference, dysglycemia, elevated blood pressure, decrease serum high-density lipoprotein-associated cholesterol, and increased serum triglycerides. Studies in both in vitro and laboratory animal models have examined the preventive effects of green tea and EGCG against the symptoms of MetS. Overall, the results of these studies have been promising and demonstrate that green tea and EGCG have preventive effects in both genetic and dietary models of obesity, insulin resistance, hypertension, and hypercholesterolemia. Various mechanisms have been proposed based on these studies and include: modulation of dietary fat absorption and metabolism, increased glucose utilization, decreased de novo lipogenesis, enhanced vascular responsiveness, and antioxidative effects. In the present review, we discuss the current state of the science with regard to laboratory studies on green tea and MetS. We attempt to critically evaluate the available data and point out areas for future research. Although there is a considerable amount of data available, questions remain in terms of the primary mechanism(s) of action, the dose–response relationships involved, and the best way to translate the results to human intervention studies. [Copyright &y& Elsevier]

Abstract: (−)-Epigallocatechin-3-gallate (EGCG), the most abundant and biologically active polyphenol in green tea, induces apoptosis and suppresses proliferation of cancer cells by modulating multiple signal transduction pathways. However, the fundamental mechanisms responsible for these cancer-preventive effects have not been clearly elucidated. Recently, we found that EGCG can covalently bind to cysteine residues in proteins through autoxidation and subsequently modulate protein function. In this study, we demonstrate the direct binding of EGCG to cellular proteins in AZ521 human gastric cancer cells by redox-cycle staining. We comprehensively explored the binding targets of EGCG from EGCG-treated AZ521 cells by proteomics techniques combined with the boronate-affinity pull-down method. The DEAD-box RNA helicase p68, which is overexpressed in a variety of tumor cells and plays an important role in cancer development and progression, was identified as a novel EGCG-binding target. Exposure of AZ521 cells to EGCG lowered the p68 level dose dependently. The present findings show that EGCG inhibits AZ521 cell proliferation by preventing β-catenin oncogenic signaling through proteasomal degradation of p68 and provide a new perspective on the molecular mechanism of EGCG action. [Copyright &y& Elsevier]

Abstract: Arsenic trioxide (ATO) treatment is a useful therapy against human acute promyelocytic leukemia (APL), however, it concomitantly brings potential adverse consequences including serious side effect, human carcinogenicity and possible development of resistance. This investigation revealed that those problems might be relaxed by simultaneous application with (−)-epigallocatechin-3-gallate (EGCG), one of the major components from green tea. EGCG significantly lowered down the ATO concentration required for an effective control of APL cells, HL-60. The simultaneous treatment of ATO with EGCG induced a mitochondria-dependent apoptosis in HL-60 cells significantly, which accounted for more than 70% of the cell death in the treatment. The mechanism of apoptosis induction was elucidated. EGCG in HL-60 cells acted as a pro-oxidant enhancing intracellular hydrogen peroxide significantly. ATO, on the other hand, induced heme oxygenase-1 (HO-1) to catalyze heme degradation, thereby provided ferrous iron for EGCG-induced hydrogen peroxide to precede Fenton reaction, which in turn generated deleterious reactive oxygen species to damage cell. In addition, EGCG inhibited expression of ferritin, which supposedly to sequester harmful ferrous iron, thereby augmented the occurrence of Fenton reaction. This investigation also provided evidence that ATO, since mainly acted to induce HO-1 in simultaneous treatment with EGCG, could be replaced by other HO-1 inducer with much less human toxicity. Furthermore, several of our preliminary investigations revealed that the enhanced cytotoxicity induced by combining heme degradation and Fenton reaction is selectively toxic to malignant but not non-malignant cells. [ABSTRACT FROM AUTHOR]

Abstract: Thioredoxin (Trx) and thioredoxin reductase (TrxR) function as antioxidant and anti-apoptotic proteins, which are often up-regulated in drug-resistant cancer cells. (−)-epigallocatechin-3-gallate (EGCG) is a naturally occurring antioxidant in green tea, but also exhibits prooxidant and apoptosis-inducing properties. We have previously showed a linkage between EGCG-induced inactivation of TrxR and decreased cell survival, revealing TrxR as a new target of EGCG. However, the molecular events underlying the importance of Trx/TrxR in EGCG-induced cytotoxicity remain unclear. Here, we show that the crosstalk between EGCG and Trx/TrxR occurred in a redox-dependent manner, and EGCG induced inactivation of Trx/TrxR in parallel with increased ROS levels in HeLa cells. Moreover, EGCG displayed great reactivity with Cys/Sec residues that have low pK a values. The structure of EGCG suggests that its quinone form would readily react with thiolate and selenolate nucleophiles. Using mass spectrometry, we have demonstrated the formation of EGCG-Trx1 (Cys32) and EGCG-TrxR (Cys/Sec) conjugates, confirming that EGCG quinone specifically conjugates with active-site Cys32 in Trx or C-terminal Cys/Selenocysteine (Sec) couple in TrxR under conditions where Trx/TrxR are reduced. Non-reduced form of Trx/TrxR could escape from EGCG inhibition. These data reveal a potential mechanism for enhancing EGCG-induced cancer cell death by the NADPH-dependent reduction of Trx/TrxR. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to investigate the involvement of inducible nitric oxide synthase (iNOS) in the action of (−)-epigallocatechin-3-gallate (EGCG), a potential neuroprotective agent against Parkinson’s disease (PD), and to test for toxicity resulting from high doses of EGCG. EGCG was administered to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice at two different doses (10mg/kg and 50mg/kg). EGCG treatment reduced the neuronal death rate to less than 50%. The level of iNOS expression in the MPTP group was 20% higher than that seen in the control group, but in the EGCG groups, iNOS expression was reduced to the level observed in the negative control group. The two doses of EGCG were equally beneficial for cell rescue, and no toxicity was observed with the higher dose. Inhibition of iNOS may be an important mechanism underlying the prevention of MPTP toxicity, and EGCG may potentially be a neuroprotective agent against PD. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2010) 112, 1415–1430. Alzheimer’s disease (AD) is an age-related neurodegenerative disease increasingly recognized as one of the most important medical problems affecting the elderly. Although a number of drugs, including several cholinesterase inhibitors and an NMDA receptor antagonist, have been approved for use, they have been shown to produce diverse side effects and yield relatively modest benefits. To overcome these limitations of current therapeutics for AD, extensive research and development are underway to identify drugs that are effective and free of undesirable side effects. Certain naturally occurring dietary polyphenolic phytochemicals have received considerable recent attention as alternative candidates for AD therapy. In particular, curcumin, resveratrol, and green tea catechins have been suggested to have the potential to prevent AD because of their anti-amyloidogenic, anti-oxidative, and anti-inflammatory properties. These polyphenolic phytochemicals also activate adaptive cellular stress responses, called ‘neurohormesis’, and suppress disease processes. In this commentary, we describe the amyloid-β-induced pathogenesis of AD, and summarize the intracellular and molecular targets of selected dietary phytochemicals that might slow the progression of AD. [ABSTRACT FROM AUTHOR]

Abstract: The tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) has been studied for chronic disease preventive effects, and is marketed as part of many dietary supplements. However, case-reports have associated the use of green tea-based supplements with liver toxicity. We studied the hepatotoxic effects of high dose EGCG in male CF-1 mice. A single dose of EGCG (1500mg/kg, i.g.) increased plasma alanine aminotransferase (ALT) by 138-fold and reduced survival by 85%. Once-daily dosing with EGCG increased hepatotoxic response. Plasma ALT levels were increased 184-fold following two once-daily doses of 750mg/kg, i.g. EGCG. Moderate to severe hepatic necrosis was observed following treatment with EGCG. EGCG hepatotoxicity was associated with oxidative stress including increased hepatic lipid peroxidation (5-fold increase), plasma 8-isoprostane (9.5-fold increase) and increased hepatic metallothionein and γ-histone 2AX protein expression. EGCG also increased plasma interleukin-6 and monocyte chemoattractant protein-1. Our results indicate that higher bolus doses of EGCG are hepatotoxic to mice. Further studies on the dose-dependent hepatotoxic effects of EGCG and the underlying mechanisms are important given the increasing use of green tea dietary supplements, which may deliver much higher plasma and tissue concentrations of EGCG than tea beverages. [Copyright &y& Elsevier]

Abstract: Patients with paclitaxel-eluting stents are concerned with stent thrombosis caused by premature discontinuation of dual antiplatelet therapy or clopidogrel resistance. This study investigates the effect of (−)-epigallocatechin-3-gallate (EGCG) on the expression of thrombin/paclitaxel-induced endothelial tissue factor (TF) expressions in human aortic endothelial cells (HAECs). EGCG was nontoxic to HAECs at 6h up to a concentration of 25μmol/L. At a concentration of 25μmol/L, EGCG pretreatment potently inhibited both thrombin-stimulated and thrombin/paclitaxel-stimulated endothelial TF protein expression. Thrombin and thrombin/paclitaxel-induced 2.6-fold and 2.9-fold increases in TF activity compared with the control. EGCG pretreatment caused a 29% and 38% decrease in TF activity on thrombin and thrombin/paclitaxel treatment, respectively. Real-time polymerase chain reaction (PCR) showed that thrombin and thrombin/paclitaxel-induced 3.0-fold and 4.6-fold TF mRNA expressions compared with the control. EGCG pretreatment caused an 82% and 72% decrease in TF mRNA expression on thrombin and thrombin/paclitaxel treatment, respectively. The c-Jun terminal NH2 kinase (JNK) inhibitor SP600125 reduced thrombin/paclitaxel-induced TF expression. Furthermore, EGCG significantly inhibited the phosphorylation of JNK to 49% of thrombin/paclitaxel-stimulated HAECs at 60min. Immunofluorescence assay did not show an inhibitory effect of EGCG on P65 NF-κB nuclear translocation in the thrombin/paclitaxel-stimulated endothelial cells. In conclusion, EGCG can inhibit TF expression in thrombin/paclitaxel-stimulated endothelial cells via the inhibition of JNK phosphorylation. The unique property of EGCG may be used to develop a new drug-eluting stent by co-coating EGCG and paclitaxel. [Copyright &y& Elsevier]