Caspase-3-induced gelsolin fragmentation contributes to actin cytoskeletalcollapse, nucleolysis, and apoptosis of vascular smooth muscle cells exposed to proinflammatory cytokines

Gelsolin, an 80 kDa actin-severing protein, has been recently identified as a substrate for the cell death-promoting cysteinyl protease caspase-3 (CPP 32/apopain/YAMA). We investigated the role of gelsolin and its cleavage pro duct in apoptosis of vascular smooth muscle cells (SMC) induced by the proi nflammatory cytokines interferon-gamma (IFN-gamma) and tumor necrosis facto r-alpha (TNF-alpha). Treatment with a combination of IFN-gamma and TNF-alph a reduced viability of SMC in a time- and concentration-dependent manner. I mmunoblotting revealed that SMC treated with the cytokines generated a 41 k Da gelsolin fragment, The gelsolin fragmentation required activation of cas pase-3, as the caspase-3 inhibitor diminished cytokine-induced cell death a s well as the fragmentation. Gelsolin cleavage was accompanied by a reducti on in F-actin content and by a marked disruption of cell structure, Adenovi rus-mediated transfection of this N-terminal gelsolin fragment into SMC alt ered cell morphology, reduced cell viability, increased the number of TUNEL -positive cells, and promoted internucleosomal DNA fragmentation, Compared to wild-type cells, gelsolin-deficient SMC showed resistance to apoptosis i nduced by the inflammatory cytokines, These results suggest a mechanistic r ole for gelsolin cleavage during SMC apoptosis, a process implicated in ves sel development as wed as stability of atherosclerotic plaque.