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.