Protective Effects Of (-) Epigallocatechin Gallate From Tea Against UVB-induced Damages

Skin is the body' s first protective screen against external stimulate.The ultraviolet(UV)radiation of the sunlight can cause a variety of skin damages.UV radiation can be devided into ultraviolet A(UVA,320-380 nm),Ultraviolet B(UVB,280-320 nm)and ultraviolet C(UVC,220-180 nm).UVB radiation is particularly important as it has higher energy than UVA and its intensity on the earth surface is stronger than UVC.UVB can induce pigmentation and DNA damage,sometimes even cutaneum carcinoma.Epigallocatechin gallate(EGCG)is an abundant active ingredient in tea,which has strong antioxidant effect.Although many researches have been made to reveal the effects of EGCG on UV radiation,the specific mechanisms and exact signaling pathways of EGCG actions remain to be investigated.In the present study,we established a UVB-induced nude mouse model and a UVB-induced L929 cell model to investigate the effect of EGCG on UVB-induced damages in nude mouse skin and L929 cells.The major results are as follows:1.UVB radiation induced serious erythema and decrustation of nude mouse skin.EGCG pretreatment showed protective effect to the skin damage against UVB radiation in a dose-dependant manner.2.EGCG alleviated the thickening of epidermal cuticle induced by UVB-radiationin dose-dependent manner.When the concentration of EGCG was at 10 mg/mL or 50 mg/mL,the thickening of epidermal was significantly inhibited.However,low concentration of EGCG(1 mg/mL)showed little protective effect on the skin damages induced by UVB.3.UVB radiation induced mitochondrial crest and matrix density in of the tested nude mouseskin.When EGCG concentration was 10 mg/ml or above,EGCG pretreatment showed a markedly protective effect on mitochondria.EGCG pretreatment couild also alleviate the UVB-induced increase in melanosomes in nude mouse skin when the concentration of EGCG was at 50 mg/mL.4.UVB irradiation suppressed proliferation L929 cells,accompanying with an increase in the expression of phosphorylated P38MAPK.EGCG pretreatment down-regulated the expression of the phosphorylated P38MAPK,resulting in alleviation of the suppression of L929 cell proliferation,suggesting that EGCG suppressed the UVB-induced cell apoptosis via inhibition of P38MAPK expression.5.Quantitative real-time PCR analysis showed that EGCG pretreatment down-regulated the expression of genes Caspase-3?P53?C-jun?C-fos?NF-?B?Bax,resulting in reduction of apoptosis in L929 cells.