Background It is known that ultraviolet irradiation can affect cellular function through a number of signaling pathways. (-)-epigallocatechin-3-gallate (EGCG) is the major effective component in green tea and can offer protection from ultraviolet-induced damage. In this study, we investigated the protective mechanism of EGCG on human dermal fibroblasts damaged by ultraviolet A (UVA) in vitro.Methods Transcription factor Jun protein levels were measured by Western blot. Matrix metalloproteinase 1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA were studied by reverse transcription-polymerase chain reaction (RT-PCR) analysis in conjunction with computer-assisted image analysis. MMP-1 and TIMP-1 proteins were quantified by enzyme-linked immunosorbent assay (ELISA).Results EGCG decreased transcription activity of Jun protein after induction by UVA. Both the mRNA and protein levels of MMP-1 were increased by UVA irradiation, while no significant changes were observed in TIMP-1 levels. The ratio of MMP-1 to TIMP-1 showed statistically significant differences compared with the control. EGCG decreased the ratio of MMP-1 to TIMP-1 by inhibiting UVA-induced MMP-1 expression ( P <0. 05).Conclusion EGCG can protect human fibroblasts against UVA damage by downregulating the transcription activity of Jun protein and the expression of MMP-I. The ratio of MMP-1 to TIMP-1,rather than the levels of MMP-1 or TIMP-1 alone, may play a significant role in human skin photodamage.

完成机构：DepartmentofDermatology,FirstAffiliatedHospitalofNanjingMedicalUniversity,Nanjing210029,China

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