Expressions of cathepsin B in photoaging skin and its significance.

Abstract

Objective To investigate the expression of cathepsin B in photoaging skin and its signifi-cance.Methods Skin specimens were obtained from the right forearm(sun-exposed sites)and buttock (unexposed sites)of 6 healthy volunteers with informed consent and subjected to immunohistochemistry for the detection of cathepsin B expression.Primary human fibroblasts derived from the prepuce of children aged 3 to 6 years were cultured in vitro;after 10 to 15 passages,cells were divided into four groups to be treated with methoxsalen of 50 mg/L for 24 hours followed by ultraviolet A(UVA)exposure(premature senescence group),phosphate buffered saline(PBS)only(control group),UVA exposure only(UVA group),methoxsalen only(methoxsalen group).Then,the protein and mRNA expressions of cathepsin B were detected by Western blot and RT-PCR,respectively,in these fibroblasts 1,2,3 weeks after the treatment.Results Cathepsin B was observed in both exposed and unexposed sites of all volunteers,and the average absorbence of cathepsin B was significantly lower in exposed sites than in unexposed sites(0.2130±0.7997 vs 0.4520±0.5921,t=5.37,P<0.05).Decreased protein expression of cathepsin B was also noted in the premature senescence group compared with the other three groups.Moreover,the gray ratio between cathepsin B protein and glyceraldehyde phosphate dehydrogenase(GAPDH)in premature senescence group reduced from 28.099±O.054 before treatment to 25.1 03±0.102 in week 1 and 17.693±0.099 in week 3 after UVA exposure.RT-PCR revealed that the mRNA expression level of cathepsin B in fibroblasts of premature senescence group decreased by 36 percent compared with that in the control group.Conclusions The expression of cathepsin B decreases in photoaged skin as well as in UVA-exposed fibroblasts in a time-dependent manner,which may be associated with the self-repair of photoaged skin. Key words: Skin aging; Cathepsin B; Fibroblasts