Abstract: Objective To determine the effects of Tempol,one of the nitroxides,in the presence of ultraviolet-AI (UVA1,340 nm-400 nm) on superoxide enzyme (SOD) activity,lipid peroxidation,and expression of collagen Ⅰ,collagen Ⅲ and matrix metalloproteinases (MMP)-1,MMP-3 in human dermal fi broblasts in vitro.Methods Fibroblasts were irradiated by a single exposure to UVA1 and at the same time incubated with or without Tempol,and detected 24 h later.SOD activity and lipid peroxidation,as shown by accumulation of malondialdehyde (MDA),were detected by biochemical assay.Expression of collagen Ⅰ,collagen Ⅲ (protein levels) and MMP-1,MMP-3 (mRNA level) was examined by ELISA and semi-quantitative RT-PCR,respectively.Results A dose of 15 J/cm² UVA1 significantly inhibited SOD activity and collagen Ⅰ ,collagen Ⅲ protein levels,increased MDA level and stimulated MMP-1,MMP-3 mRNA expression (P<0.05).Tempol could reverse these effects caused by UVA1 to some degree or completely,and with proper concentration,the results were statistically significant (P<0.05).Conclusions Tempol exerts photoprotective activities against UVA1 irradiation in vitro.With antioxidant ability,Tempol may normalize extracellular matrix metabolism in dermis and could be used as an anti-photoageing agent.

Key words: Ultraviolet rays, Reactive oxygen species, Fibroblasts, Superoxide dismutase, Malon dialdehyde