Green tea polyphenol epigallocatechin-3-gallate inhibits the expression of nitric oxide synthase and generation of nitric oxide induced by ultraviolet B in HaCaT cells
Song, X-zu.; Bi, Z-gang.; Xu, A-e.
Chinese Medical Journal 119(4): 282-287
2006
ISSN/ISBN: 0366-6999 PMID: 16537022 Document Number: 596662
Background: Nitric oxide (NO) has been implicated in the pathogenesis of various inflammatory diseases, including sunburn and pigmentation induced by ultraviolet radiation. Epigallocatechin-3-gallate (EGCG) is the major effective component in green tea that can protect the skin from ultraviolet radiation-induced damage. The purpose of this study was to investigate the protective mechanisms of EGCG on inducible nitric oxide synthase (iNOS) expression and NO generation by ultraviolet B (UVB) irradiation in human HaCaT cell line. Methods: The HaCaT cells were irradiated with UVB 30 mJ/cm2 and pretreated with EGCG at varying concentrations. The iNOS mRNA was detected using reverse transcriptase polymerase chain reaction (RT-PCR), and NO production was quantified using a spectrophotometric method. The expression of NF- kappa B P65 was measured using immunofluorescence cytochemistry staining. Results: The expression of iNOS mRNA and generation of NO in HaCaT cells were increased by UVB irradiation. EGCG downregulated the UVB-induced iNOS mRNA synthesis and NO generation in a dose-dependent manner. The UVB-induced activation and translocation of NF- kappa B were also downregulated by EGCG treatment in HaCaT cells (P<0.01). Conclusions: The green tea derived-EGCG can inhibit and downregulate the UVB-induced activation and translocation of NF- kappa B, the expression of iNOS mRNA and the generation of NO, indicating that EGCG may have a protective effect against UVB-induced skin damage.