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

Background Nitic oxide (NO) has been implicated in the pathogenesis of various inflammatory diseases, including sunburn and pigmentation induced by ultraviolet irradiation. Epigallocatechin-3-gallate (EGCG) is the major effective component in green tea and can protect skin from ultraviolet-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 HaCaT cells. Methods HaCaT cells were irradiated with UVB 30 mJ/cm(2) and pretreated with EGCG at varying concentrations. The iNOS mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR) and NO production was quantified by spectrophotometric method. The expression of NF-kappa B P65 was measured by immunofluorescence cytochemistry staining. Results The expression of iNOS mRNA and generation of NO in HaCaT cells were increased by UVB irradiation. EGCG down regulated 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 down regulated by EGCG treatment in HaCaT cells (P<0.01). Conclusions Green tea derived-EGCG can inhibit and down regulate the UVB-induced activation and translocation of NF-kappa B, expression of iNOS mRNA and generation of NO respectively, indicating EGCG may play a protective role from UVB-induced skin damage.