title: Hydrogen peroxide mediates EGCG-induced antioxidant protection in human keratinocytes.
abstract: The beneficial health effects of (-)-epigallocatechin-3-gallate (EGCG), the main catechin of green tea, have been attributed to complex interactions with a focus on antioxidative properties. Susceptibility to autoxidation and production of cytotoxic reactive oxygen species (ROS), mostly H(2)O(2), have been suggested to occur in vitro but also in vivo. In this study, we address whether autoxidation-derived H(2)O(2) may be involved in the cytoprotective effects of EGCG. To that end we investigated keratinocyte-derived HaCat and HL-60 promyelocytic leukemia cells with significantly different sensitivities to H(2)O(2) (IC(50) 117.3 versus 58.3 μM, respectively) and EGCG (134.1 versus 84.1 μM). HaCat cells significantly resisted cytotoxicity and DNA damage based on enhanced H(2)O(2) clearance, improved DNA repair, and reduced intracellular ROS generation. Cumulative versus bolus EGCG and H(2)O(2) treatment and H(2)O(2) pretreatment before subsequent high-dose EGCG and vice versa significantly reduced DNA damage and cytotoxicity in HaCat cells only. Addition of catalase abolished the protective activities of low-dose H(2)O(2) and EGCG. In summary, our data suggest that autoxidative generation of low-dose H(2)O(2) is a significant player in the cell-type-specific cytoprotection mediated by EGCG and support the hypothesis that regular green tea consumption can contribute as a pro-oxidant to increased resistance against high-dose oxidative stressors.
authors: Institute of Cancer Research, Department of Medicine I, Medical University of Vienna, 1090 Vienna, Austria. leonilla.elbling@meduniwien.ac.at
authors: Leonilla
authors: L
authors: Elbling
authors: Irene
authors: I
authors: Herbacek
authors: Rosa-Maria
authors: RM
authors: Weiss
authors: Christian
authors: C
authors: Jantschitsch
authors: Michael
authors: M
authors: Micksche
authors: Christopher
authors: C
authors: Gerner
authors: Heinrich
authors: H
authors: Pangratz
authors: Michael
authors: M
authors: Grusch
authors: Siegfried
authors: S
authors: Knasmüller
authors: Walter
authors: W
authors: Berger
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002374:Catalase / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002460:Cell Line; D019610:Cytoprotection; D004249:DNA Damage / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress
chemical_list: D000975:Antioxidants; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D002374:Catalase