Epigallocatechin-3-gallate (EGCG) protects against chromate-induced toxicity in vitro |
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Authors: | Wu Fen Sun Hong Kluz Thomas Clancy Hailey A Kiok Kathrin Costa Max |
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Affiliation: | Department of Environmental Medicine, New York University School of Medicine, Tuxedo, NY 10987, USA |
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Abstract: | Hexavalent chromium [Cr(VI)] is a human carcinogen that results in the generation of reactive oxygen species (ROS) and a variety of DNA lesions leading to cell death. Epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea, possesses potent antioxidative activity capable of protecting normal cells from various stimuli-induced oxidative stress and cell death. Here we demonstrated that co-treatment with EGCG protected human normal bronchial epithelial BEAS-2B cells from Cr(VI)-induced cell death in a dose-dependent manner. Cr(VI) induces apoptosis as the primary mode of cell death. Co-treatment of BEAS-2B cells with EGCG dose-dependently suppressed Cr(VI)-induced apoptosis. Fluorescence microscopic analyses and quantitative measurement revealed that EGCG significantly decreased intracellular levels of ROS induced by Cr(VI) exposure. Using a well-established K+/SDS precipitation assay, we further showed that EGCG was able to dose-dependently reduce DNA-protein cross-links (DPC), lesions that could be partially attributed to Cr(VI)-induced oxidative stress. Finally, analyses of Affymetrix microarray containing 28,869 well-annotated genes revealed that, among the 3412 genes changed more than 1.5-fold by Cr(VI) treatment, changes of 2404 genes (70%) were inhibited by pretreatment of EGCG. Real-time PCR confirmed the induction of 3 genes involved in cell death and apoptosis by Cr(VI), which was eliminated by EGCG. In contrast, Cr(VI) reduced the expression of 3 genes related to cellular defense, and this reduction was inhibited by EGCG. Our results indicate that EGCG protects BEAS-2B cells from Cr(VI)-induced cytotoxicity presumably by scavenging ROS and modulating a subset of genes. EGCG, therefore, might serve as a potential chemopreventive agent against Cr(VI) carcinogenesis. |
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Keywords: | EGCG, Epigallocatechin-3-gallate Cr(VI), Hexavalent chromium ROS, Reactive oxygen species H2O2, Hydrogen peroxide O2&minus &bull , Superoxide anion K2CrO4, Potassium chromate MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide H2DCFDA, 6-carboxy-2&prime ,7&prime -dichlorodihydrofluoresce in diacetate,di(acetoxymethyl ester) PARP, Poly (ADP-ribose) polymerase DPC, DNA-protein cross-links EGR1, Early growth response 1 PPP1R15A, Protein phosphatase 1,regulatory (inhibitor) subunit 15 GADD45A, Growth arrest and DNA-damage-inducible,alpha SMUG1, single-strand-selective monofunctional uracil-DNA glycosylase 1 XRCC4, X-ray repair complementing defective repair in Chinese hamster cells 4 ERCC4, Excision repair cross-complementing rodent repair deficiency, and complementation group 4 |
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