Epigallocatechin-3-gallate Pretreatment Research Articles

The green tea polyphenol (−)-epigallocatechin-3-gallate ameliorates experimental immune-mediated glomerulonephritis

The unchecked overproduction of reactive oxygen and nitrogen species by inflammatory cells can cause tissue damage, intensify inflammation, promote apoptosis, and accelerate the progression of immune-mediated glomerulonephritis (GN). Here we tested whether the anti-inflammatory and antioxidant properties of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) favorably affect the development of immune-mediated GN. Pretreatment of 129/svJ mice with EGCG from 2 days before to 2 weeks after the induction of GN led to reduced proteinuria and serum creatinine, and marked improvement in renal histology when compared with vehicle-pretreated diseased mice. This pretreatment reduced oxidative stress, and normalized osteopontin, p65/nuclear factor-κB, inducible nitric oxide synthase, nitric oxide metabolites, p-Akt, phosphorylated extracellular signal-regulated kinases 1 and 2, p47phox, and myeloperoxidase, all of which were elevated in vehicle-pretreated diseased mice. Levels of glutathione peroxidase and peroxisome proliferator-activated receptor-γ (PPARγ), both reduced in the vehicle-pretreated diseased mice, were normalized. This renoprotective effect was reversed by concomitant administration of the PPARγ antagonist GW9662 throughout the EGCG pretreatment period. Importantly, mortality and renal dysfunction were significantly attenuated even when the polyphenol treatment was initiated 1 week after the onset of GN. Thus, EGCG reversed the progression of immune-mediated GN in mice by targeting redox and inflammatory pathways.

Effects of Epigallocatechin-3-Gallate on the Expression of TGF-β1, PKC α/βII, and NF-κB in High-Glucose-Stimulated Glomerular Epithelial Cells

Epigallocatechin-3-gallate (EGCG) is the most potent antioxidant polyphenol in green tea. In the present study, we investigated whether EGCG plays a role in the expression of transforming growth factor-beta1 (TGF-β1), protein kinase C (PKC) α/βII, and nuclear factor-kappaB (NF-κB) in glomerular epithelial cells (GECs) against high-glucose injury. Treatment with high glucose (30 mM) increased reactive oxygen species (ROS)/lipid peroxidation (LPO) and decreased glutathione (GSH) in GECs. Pretreatment with 100 µM EGCG attenuated the increase in ROS/LPO and restored the levels of GSH, whereas ROS, LPO, and GSH levels were not affected by treatment with 30 mM mannitol as an osmotic control. Interestingly, high-glucose treatment affected 3 separate signal transduction pathways in GECs. It increased the expression of TGF-β1, PKC α/βII, and NF-κB in GECs, respectively. EGCG (1, 10, 100 µM) pretreatment significantly decreased the expression of TGF-β1 induced by high glucose in a dose-dependent manner. In addition, EGCG (100 µM) inhibited the phosphorylation of PKC α/βII caused by glucose at 30 mM. Moreover, EGCG (1, 10, 100 µM) pretreatment significantly decreased the transcriptional activity of NF-κB induced by high glucose in a dose-dependent manner. These data suggest that EGCG could be a useful factor in modulating the injury to GECs caused by high glucose.

Cigarette smoke-induced biochemical perturbations in human erythrocytes and attenuation by epigallocatechin-3-gallate – tea catechin

The protective effect of epigallocatechin-3-gallate (EGCG) against cigarette smoke (CS) induced alterations in human erythrocyte was studied using an in vitro model. Hemolysis, carboxyhemoglobin, osmotic fragility, hemin, lipid peroxidation (LPO), protein thiol, protein carbonyl, glutathione, antioxidant enzymes, membrane bound ATPases and erythrocyte ghost protein were assessed to investigate the effect of EGCG. Erythrocytes were incubated with CS and/or 10µM EGCG under physiological conditions of temperature and pH for 2h. CS significantly increased the percentage of hemolysis, carboxyhemoglobin, hemin, LPO and osmotic fragility in human erythrocytes whereas EGCG pretreatment significantly reduced all the above parameters. The levels of protein carbonyls significantly increased whereas the level of protein thiol decreased significantly in erythrocytes incubated with CS. EGCG pretreatment significantly decreased the levels of carbonyls and increased the level of protein thiol. The level of glutathione, antioxidant enzyme and membrane bound ATPases were decreased significantly in erythrocytes incubated with CS. However, EGCG pretreatment significantly increased the activities of GSH, antioxidant enzymes and membrane bound ATPases. CS incubated erythrocytes showed a progressive loss of the cytoskeleton proteins and formation of low molecular weight bands and protein aggregates. EGCG pretreatment of CS incubated erythrocytes showed a near normal protein profile compared to that of control erythrocytes. The present study divulges that EGCG can reduce the abnormalities of cigarette smoking by ameliorating the oxidative stress. This finding raises the possibility that EGCG may provide protection from CS induced toxicity.

Abstract 5610: Epigallocatechin 3-gallate (EGCG) as a natural product (NP) with potent antitumor activity against human ovarian cancer

Abstract A substantial challenge in the practice of integrative cancer treatment is to identify active combinations of natural products (NPs) that can collaborate with conventional treatment modalities to achieve enhanced tumor control. This approach is especially attractive for tumors that are inherently chemoresistant or become chemoresistant as a consequence of multidrug resistance. But it has been difficult to prove efficacy of combining NPs with conventional treatment such as chemotherapy due in large part to the challenges inherent in conducting controlled clinical trials with combination regimens. These challenges provide a rationale for translational research studies to characterize effects of NPs on tumor processes relevant to chemoresistance. The current study investigated the activity of Epigallocatechin 3-gallate (EGCG), the principal polyphenol from green tea extract to modulate tumor proliferation and sensitivity to antitumor immunity in human ovarian cancer cells. Tumor proliferation was assessed with a standard MTS assay using the ATCC cell line, OvCar 3 as well as single cell suspensions prepared from human ovarian cancer surgical specimens. Sensitivity to IL2-activated human lymphocytes was assessed with a standard, 4 hr 51Chromium-release assay. EGCG produced a dose-dependent inhhibition of proliferation of the OvCar 3 cell line ranging from <5% (10 ug/mL) through 33% (30 ug/mL). Notably, these concentrations of EGCG are all achievable pharmacologically with a dose of 8, 200 mg capsules daily. Dose dependent inhibition of proliferation was also observed with cells from human ovarian cancer specimens with inhhibition ranging from 10.5% (5 ug/mL) to as much as 54% (25 ug/mL). The effects of EGCG were found to collaborate with pharmacologically achievable concentrations of both cisplatinum (Pt; 500 ng/mL) and gemcitabine (Gz; 10 ng/mL). Thus, 24%, 21% and 60% inhibition of OvCar 3 cells was observed with Pt, EGCG and Pt+EGCG respectively. The corresponding values were 30%, 34%, and 50% inhibition for Gz, EGCG, and Gz+EGCG. Additional effects of EGCG on OvCar 3 were shown in studies using EGCG pre-treatment of target cells prior to testing sensitivity to lysis by IL2-activated human lymphocytes. The results showed that EGCG pretreatment, in doses that did not reduce cell number or inhibit prolliferation over 72 hrs rendered the cells 53% more sensitive to lysis in the 51Chromium-release assay. These results demonstrate direct effects of the principal polyphenol of green tea extract on both the proliferative and immunologic sensitivitiy of human ovarian cancer cells. That these effects can collaborate with chemotherapeutic agents commonly used in the treatment of ovarian cancer patients suggests that combination regimens of this NP with cancer chemotherapy may be valuable in patients for both adjuvant therapy and for maintenance of remission. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5610.

(−)-Epigallocatechin-3-gallate decreases thrombin/paclitaxel-induced endothelial tissue factor expression via the inhibition of c-Jun terminal NH2 kinase phosphorylation

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.

Neuroprotective effect of epigallocatechin-3-gallate against β-amyloid-induced oxidative and nitrosative cell death via augmentation of antioxidant defense capacity

beta-Amyloid (Abeta) peptide, a major component of senile plaques has been regarded to play a crucial role in the development and neuropathogenesis of Alzheimer's disease (AD). Increasing data from in vitro and in vivo studies indicate that Abeta-induced damages in neurons and glia are mediated via nitrosative as well as oxidative stress. Therefore, recent researches have been focused on searching for dietary and herbal manipulations to protect against the Abeta-induced oxidative and/or nitrosative cell death. Epigallocatechin-3-gallate (EGCG), one of these candidates is a major polyphenolic compound present in green tea and has been reported to exhibit potent antioxidant and anti-inflammatory properties. In the present study, we have investigated the effect of EGCG against Abeta-induced oxidative and/or nitrosative cell death in BV2 microglia. Abeta treatment led to apoptosis in BV2 cells as revealed by DNA fragmentation, perturbation of mitochondrial transmembrane potential, and alterations in the expression of apoptosis-regulator Bcl-2 family proteins. EGCG pretreatment effectively ameliorated Abeta-induced cytotoxicity and manifestation of proapoptotic signals. Furthermore, BV2 cells exposed to Abeta underwent nitrosative stress as shown by the increased expression of inducible nitric oxide synthase (iNOS) and subsequent production of nitric oxide (NO) and peroxynitrite, which were effectively suppressed by EGCG pretreatment. To elucidate a molecular mechanism underlying the neuroprotective effect of EGCG, we have examined the cellular metabolism of reduced glutathione (GSH) with antioxidant properties. EGCG treatment fortified cellular GSH pool through elevated mRNA expression of gamma-glutamylcysteine ligase (GCL), the rate limiting enzyme in the glutathione biosynthesis. These results suggest that EGCG may have preventive and/or therapeutic potential in AD patients by augmenting cellular antioxidant defense capacity and attenuating Abeta-mediated oxidative and/or nitrosative cell death.

Apoptotic and immunomodulatory effects of green tea extracts (GTE) on chemoresistant human tumor cells

e22101 Background: GTE and Epigallocatechin 3-gallate (EGCG), the most abundant polyphenol in GTE, have been shown to exert inhibitory effects on carcinogenesis; modulatory effects on tumor proliferation and differentiation; and immunomodulatory effects on tumor immunity in different pre-clinical models. These pluripotent effects suggest that GTE may have clinical activity that could be exploited for treatment of chemo-insensitive but immunologically responsive tumors. Thus, the present study investigated the effects of EGCG on the proliferation and immunologic sensitivity of human renal cell cancer (RCC) and malignant melanoma (MM) cell lines. Methods: Human RCC (769-P) and MM (A375) cell lines were tested following incubation in media ± 21.8μM EGCG, a pharmacologically-achievable concentration produced by 8, 200mg capsules GTE daily. Tumor proliferation was assessed by MTS assay; lytic sensitivity to IL2-activated human peripheral blood lymphocytes (IL2PBL) by 51Chromium release assay; and gene expression by quantitative RT-PCR assay. Results: EGCG produced significant inhibition of proliferation of both RCC and MM cells (61.5% and 67.3% of media control values respectively; p<0.01 by 2-tailed, paired t test). EGCG also caused significantly increased expression (≥ 2 times (×) media control values) of pro-apoptotic genes in both RCC: BCL2L1 (5.4×); BCL2L10 (7.9×); BIK (2.9×); Caspase 5 (6.3×); and Caspase 14 (6.3×) and MM cells: Caspase8 (2X) and Card6 (2.5X). Unfortunately, EGCG pre-treatment also decreased the sensitivity of RCC (43% of control) and MM (53% of control) to IL2PBL-mediated lysis (p<0.01 respectively). This occured in association with significant upregulation of Fas ligand mRNA in RCC (6.3×) and TRAF2 mRNA in MM (33 ×). Conclusions: The results of this pre-clinical study demonstrate that EGCG exerts significant antiproliferative effects against human RCC and MM cells in vitro in association with increased expression of different pro-apoptotic genes. Unfortunately, EGCG-treated cells also demonstrated reduced sensitivity to lysis by IL2-activated human lymphocytes. Taken together, the results suggest that GTE may have activity in vivo in patients against chemoresistant RCC or MM but should not be used in conjunction with IL2 therapy. No significant financial relationships to disclose.

Epigallocatechin-3-gallate reduces retinal ischemia/reperfusion injury by attenuating neuronal nitric oxide synthase expression and activity

Retinal ischemia/reperfusion (IR) injury causes profound tissue damage, especially retinal ganglion cell death. The aims of the study were twofold: (1) to investigate the benefits of epigallocatechin-3-gallate (EGCG), the major catechin found in tea, after IR challenge, and (2) to elucidate the mechanism of EGCG inhibition of nitric oxide synthase (NOS) expression. Wistar female rats were divided into four groups: normal control, EGCG with sham operation, retinal IR, and EGCG with IR groups. EGCG (50mg/kg) was administered by intraperitoneal injection 30min before the experiment. IR injury to a rat's retina was induced by raising intraocular pressure to 150mmHg for 60min. With EGCG pretreatment, retinal ganglion cell death from IR was reduced by approximately 10% 3days afterward. EGCG significantly downregulated IR-induced glial fibrillary acidic protein expression. EGCG treatment also reduced TUNEL-positive cells after IR in the inner retina as well as IR-induced lipid peroxidation. Histological analyses showed fewer neuronal NOS and nicotinamide adenine dinucleotide phosphate diaphorase-positive cells in the retina after IR with EGCG administration. Therefore, EGCG is effective in protecting retinal ganglion cells from IR challenge by ameliorating retinal nitrosactive stress and by regulating cell death through apoptotic pathways.

Inhibition of intestinal ischemia/repurfusion induced apoptosis and necrosis via down-regulation of the NF-kB, c-Jun and caspace-3 expression by epigallocatechin-3-gallate administration

Intestinal ischemia/reperfusion (I/R) produces reactive oxygen species (ROS) activating signal transduction and apoptosis. The aim of this study was to evaluate the effect of (−)-epigallocatechin-3-gallate (EGCG) administration in inhibition of apoptosis by attenuating the expression of NF-kB, c-Jun and caspace-3 in intestinal I/R. Thirty male wistar rats were used. Group A sham operation, B I/R, C I/R-EGCG 50 mg/kg ip. Intestinal ischemia was induced for 60 min by clamping the superior mesenteric artery. Malondialdehyde (MDA), myeloperoxidase (MPO), light histology, Fragment End Labelling of DNA (TUNEL), immunocytochemistry for NF-kB, c-Jun and caspace-3 analysis in intestinal specimens were performed 120 min after reperfusion. Apoptosis as indicated by TUNEL and Caspace-3, NF-kB and c-Jun was widely expressed in I/R group but only slightly expressed in EGCG treated groups. MDA and MPO showed a marked increase in the I/R group and a significant decrease in the EGCG treated group. Light histology showed preservation of architecture in the EGCG treated group. In conclusion, EGCG pre-treatment is likely to inhibit intestinal I/R-induced apoptosis by down-regulating the expression of NF-kB, c-Jun and caspase-3.

Protective effect of epigallocatechin-3-gallate on inflammatory bowel disease: experiment with rat models of induced colitis

To explore the protective effect of epigallocatechin-3-gallate (EGCG) on ulcerative colitis (UC) and mechanism thereof. Sixty SD rats underwent enema of trinitrobenzene sulfonic acid (TNBS) to cause UC and then randomly divided into 6 groups: model group, undergoing enema of normal saline (NS) once a day for 2 weeks; positive drug control group, undergoing enema of 5-aminosalicylic acid (ASA), an anti-UC drug; high-dose EGCG group, undergoing enema of 100 mg/kg EGCG; low-dose EGCG group, undergoing 5 enema of 50 mg/kg EGCG; and EGCG pretreatment group, undergoing enema of 100 mg/kg once a day 3 days before the model establishment and then once a day for 2 weeks after the model establishment. Another 12 rats were used as normal controls. Two weeks later the rats were killed. The histological score of the colonic mucosa was evaluated. The cyclooxygenase-2 protein expression in the colonic mucosa was detected by immunohistochemistry and the cyclooxygenase-2 mRNA expression was assessed by semiquantitative reverse-transcription polymerase chain reaction. The histological score of the model group was 6.4 +/- 2.7, significantly higher than that of the normal control group (1.0 +/- 0.7, P < 0.01). The histological scores of the 5-ASA, and 100 mg/kg and 50 mg/kg EGCG groups were 3.4 +/- 1.8, 2.6 +/- 1.5, and 4.0 +/- 2.0 respectively, all significantly lower than that of the model group (all P < 0.05). The histological scores of the EGCG pretreatment group was the lowest (1.2 +/- 0.8), especially compared with the model group (P < 0.01). Cyclooxygenase -2 mRNA was not expressed in the normal control group, was highly expressed in the model group, and the expression levels of the 5-ASA and EGCG groups were all significantly lower than that of the model group (chi(2) = 22.017, P < 0.05). Preventing and ameliorating colitis by inhibiting cyclooxygenase-2 activity, EGCG may be a potential medicine in treating inflammatory bowel disease.

Green tea polyphenol EGCG suppresses cigarette smoke condensate-induced NF-κB activation in normal human bronchial epithelial cells

Cigarette smoke is a powerful inducer of inflammatory responses resulting in disruption of major cellular pathways with transcriptional and genomic alterations driving the cells towards carcinogenesis. Cell culture and animal model studies indicate that (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea, possesses potent anti-inflammatory and antiproliferative activity capable of selectively inhibiting cell growth and inducing apoptosis in cancer cells without adversely affecting normal cells. Here, we demonstrate that EGCG pretreatment (20-80 microM) of normal human bronchial epithelial cells (NHBE) resulted in significant inhibition of cigarette smoke condensate (CSC)-induced cell proliferation. Nuclear factor-kappaB (NF-kappaB) controls the transcription of genes involved in immune and inflammatory responses. In most cells, NF-kappaB prevents apoptosis by mediating cell survival signals. Pretreatment of NHBE cells with EGCG suppressed CSC-induced phosphorylation of IkappaBalpha, and activation and nuclear translocation of NF-kappaB/p65. NHBE cells transfected with a luciferase reporter plasmid containing an NF-kappaB-inducible promoter sequence showed an increased reporter activity after CSC exposure that was specifically inhibited by EGCG pretreatment. Immunoblot analysis showed that pretreatment of NHBE cells with EGCG resulted in a significant downregulation of NF-kappaB-regulated proteins cyclin D1, MMP-9, IL-8 and iNOS. EGCG pretreatment further inhibited CSC-induced phosphorylation of ERK1/2, JNK and p38 MAPKs and resulted in a decreased expression of PI3K, AKT and mTOR signaling molecules. Taken together, our data indicate that EGCG can suppress NF-kappaB activation as well as other pro-survival pathways such as PI3K/AKT/mTOR and MAPKs in NHBE cells, which may contribute to its ability to suppress inflammation, proliferation and angiogenesis induced by cigarette smoke.

Green tea polyphenol (–)‐epigallocatechin‐3‐gallate inhibits ethanol‐induced activation of pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a central role in the pathogenesis of pancreatic fibrogenesis and inflammation. Ethanol, a major cause of chronic pancreatitis, directly induces PSC activation and oxidative stress. Inhibition of PSC activation or stimulation to PSC might be an effective therapeutic strategy for the prevention of pancreatic fibrosis, and (-)-epigallocatechin-3-gallate (EGCG), a major component of green tea extracts, is a potent antioxidant of polyphenols. Therefore, we examined the mechanisms through which ethanol induces oxidative stress on PSCs and evaluated the effect of EGCG on activation and cell functions of ethanol-stimulated PSCs. The PSCs were isolated from the pancreas of male Wister rats with Nycodenz gradient methods and cells between passages one and four were used. Isolated PSCs were cultured with ethanol (50 mM) in the absence or presence of EGCG (5 microM or 25 microM). The EGCG pre-treatment abolished ethanol-induced lipid peroxidation of the cell membrane, loss of total superoxide dismutase (SOD) activity and suppressed ethanol-induced gene expressions of Mn- and Cu/Zn-SOD. EGCG also suppressed ethanol-induced p38 mitogen-activated protein (MAP) kinase phosphorylation, alpha-smooth muscle actin production in PSCs and activated transforming growth factor-beta1 secretion into the medium. Furthermore, EGCG inhibited ethanol-induced type-I procollagen production and collagen secretion. In addition, EGCG inhibited transformation of freshly isolated cells to activated myofibroblast-like phenotype. Our results suggest that green tea and polyphenols could prevent pancreatic fibrosis by inhibiting PSC activation through the antioxidative effect.

Protective Mechanism of Epigallocatechin‐3‐Gallate against Helicobacter pylori‐Induced Gastric Epithelial Cytotoxicity via the Blockage of TLR‐4 Signaling

Helicobacter pylori infection leads to gastric mucosal damage by several mechanisms including the direct effect of virulence factors produced by H. pylori, propagation of inflammation, oxidative stress, DNA damage, and induction of apoptosis. (-)-Epigallocatechin-3-gallate (EGCG), one of the green tea catechins, is known to suppress H. pylori-induced gastritis through its antioxidative and antibacterial actions. In this study, we evaluated the protective mechanism of EGCG against H. pylori-induced cytotoxicity in gastric epithelial cells. MTT assays and dye exclusion assays were performed to analyze the effect of EGCG on the viability of gastric epithelial cells. The degree of DNA damage was evaluated by Comet assay and apoptotic DNA fragmentation assay. To investigate the effect of EGCG on H. pylori-induced toll-like receptor 4 (TLR-4) signaling, reverse transcription-polymerase chain reaction and Western blot analysis corresponding to glycosylated TLR-4 were carried out. Lipoxygenase metabolites were measured with reverse-phase, high-performance liquid chromatography. EGCG pretreatment effectively rescued gastric mucosal cells from the H. pylori-induced apoptotic cell death and DNA damage, and administration of this catechin enhanced gastric epithelial cell proliferation. Helicobacter pylori infection stimulated the glycosylation of TLR-4, which initiates intracellular signaling in the infected host cell, but the pretreatment with EGCG completely blocked the TLR-4 glycosylation. The blockage of TLR-4 activation by EGCG resulted in inactivation of extracellular signal response kinase 1/2 and of nuclear factor-kappaB, the downstream molecules of TLR-4 signaling induced by H. pylori. This disturbance of H. pylori-induced host cell signaling by EGCG attenuated the synthesis of the proinflammatory mediator, hydroxyeicosatetraenoic acid. EGCG pretreatment showed significant cytoprotective effects against H. pylori-induced gastric cytotoxicity via interference of the TLR-4 signaling induced by H. pylori. Thus, our result implies that continuous intakes of green tea could prevent the deleterious consequences of H. pylori infection.

Green tea polyphenol (-)-epigallocatechin-3-gallate treatment of human skin inhibits ultraviolet radiation-induced oxidative stress.

The use of naturally occurring botanicals with substantial antioxidant activity to afford protection to human skin against UV damage is receiving increasing attention. The green tea constituent (-)-epigallocatechin-3-gallate (EGCG) is a potent antioxidant and has shown remarkable preventive effects against photocarcinogenesis and phototoxicity in mouse models. In this study we have investigated the effects of topical application of EGCG, the major polyphenol present in green tea, to human skin before UV irradiation on UV-induced markers of oxidative stress and antioxidant enzymes. Using immunohistochemistry and analytical enzyme assays, we found that application of EGCG (mg/cm(2) skin) before a single UV exposure of 4x minimal erythema dose (MED) markedly decreases UV-induced production of hydrogen peroxide (68-90%, P < 0.025-0.005) and nitric oxide (30-100%, P < 0.025-0.005) in both epidermis and dermis in a time-dependent manner. EGCG pretreatment also inhibits UV-induced infiltration of inflammatory leukocytes, particularly CD11b(+) cells (a surface marker of monocytes/macrophages and neutrophils), into the skin, which are considered to be the major producers of reactive oxygen species. EGCG treatment was also found to inhibit UV-induced epidermal lipid peroxidation at each time point studied (41-84%, P < 0.05). A single UV exposure of 4x MED to human skin was found to increase catalase activity (109-145%) and decrease glutathione peroxidase (GPx) activity (36-54%) and total glutathione (GSH) level (13-36%) at different time points studied. Pretreatment with EGCG was found to restore the UV-induced decrease in GSH level and afforded protection to the antioxidant enzyme GPx. Further studies are warranted to study the preventive effects of EGCG against multiple exposures to UV light of human skin.