Ultraviolet B‐induced apoptosis of human skin fibroblasts involves activation of caspase‐8 and ‐3 with increased expression of vimentin

Background: After irradiation with a high dose of ultraviolet B (UVB), cells undergo apoptosis. Caspase‐8 and ‐3 are key mediators of apoptosis in many cells. Vimentin, an important cytoskeleton component, can be cleaved by caspase‐3, ‐6, ‐7 and ‐8. Cell apoptosis is promoted via caspase‐triggered proteolysis of vimentin. In this study, we explored the roles of caspase‐8 and ‐3 and the changes in vimentin expression in UVB‐induced apoptosis of human dermal fibroblasts. Methods: Skin fibroblasts were irradiated with 150 mJ/cm² UVB and cell death was monitored by the 3‐(4,5)‐dimethylthiahiazo(‐z‐y1)‐3,5‐diphenytetrazoliumromide assay and Hoechst staining. Caspase‐8 and ‐3 activities were detected by the caspase activity assay. Vimentin expression was assessed by immunofluorescence and Western blot. Results: Caspase‐8 and ‐3 were activated by 150 mJ/cm² UVB irradiation. Caspase‐8 and ‐3 activities changed in a time‐dependent way after UVB irradiation to induce apoptosis of fibroblasts, and caspase‐8 and ‐3 interacted with each other in this process. However, their substrate, vimentin, showed an enhanced expression over time after UVB irradiation. Conclusions: UVB‐triggered apoptosis of fibroblasts was dependent on the activation of caspase‐8 and ‐3 with an increased expression of vimentin.