反复紫外线损伤后人体皮肤组织蛋白酶K活性变化

Decreased activity of cathepsin K in human skin after repeated ultraviolet irradiation

目的:在人体光老化皮肤中检测组织蛋白酶K的活性变化,为探讨皮肤光老化机制提供实验依据。方法:日光模拟紫外线反复照射[剂量为最小红斑量(MED),5 d/周,共6周]8例成人臀部皮肤,诱导光老化后,检测照射部位局部组织蛋白酶K活性变化。结果:和对照组皮肤相比,紫外线照射诱导后的皮肤组织蛋白酶K活性明显下降(P<0.001)。结论:组织蛋白酶K在紫外线反复照射诱导的皮肤中活性明显降低,提示其与皮肤光老化密切相关。推测紫外线可能通过降低皮肤组织蛋白酶K活性使弹性纤维降解减少,从而导致其在真皮层堆积。

Objective： To investigate the roles of cathepsin K （catK） in the pathogenesis of photoaging through detecting its activity in human skin after repeated ultraviolet irradiation. Methods： Eight healthy Chinese volunteers （four males and four females, 21 to 26 years old） with Fitzpatrick＇s skin type III or IV were enrolled in this study. One side of the untanned upper buttock was randomly selected to receive solar-simulated UV irradiation（SSR）（spectrum of 290 to 400 nm, 30% UVA＋ 70% UVB） at the dose of 1 MED daily. The SSR exposure was given for 5 successive days each week for a total of 6 weeks. The other side of the upper buttock received no irradiation as a control. Biopsies were performed 72 h after the last UV exposure for histological study and the catK activity detection.. The activity of catK was determined according to the intensity of the fluorescence, with the use of specific catK substrate, z-Leu-Arg-7-amido-4-methyl coumarin. The fluorescence was recorded at 360 nm, at which the cleavage product emitted. Results： The 6-week SSR exposure successfully induced a significant clinical and histological change of chronic photodamage. The catK activity of the SSR-exposure skin was obviously decreased compared to that of the control skin（P〈 0.001）. Conclusions： These data suggests that the decrease of catK activi- ty is related to photoaging, which might lead to a decline of elastin degradation and subsequent accumulation of elastin in the extracellular space of the dermis.