Inhibition of apoptosis and caspase-3 in vascular smooth muscle cells by plasminogen activator inhibitor type-1

✍ Scribed by Yabing Chen; Robert J. Kelm Jr.; Ralph C. Budd; Burton E. Sobel; David J. Schneider

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 253 KB
• Volume: 92
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.20058

✦ Synopsis

Abstract

Increased expression of plasminogen activator inhibitor type 1 (PAI‐1) is associated with decreased apoptosis of neoplastic cells. We sought to determine whether PAI‐1 alters apoptosis in vascular smooth muscle cells (VSMC) and, if so, by what mechanisms. A twofold increase in the expression of PAI‐1 was induced in VSMC from transgenic mice with the use of the SM‐22α gene promoter (SM22‐PAI^+^). Cultured VSMC from SM22‐PAI^+^ mice were more resistant to apoptosis induced by tumor necrosis factor plus phorbol myristate acetate or palmitic acid compared with VSMC from negative control littermates. Both wild type (WT) and a stable active mutant form of PAI‐1 (Active) inhibited caspase‐3 amidolytic activity in cell lysates while a serpin‐defective mutant (Mut) PAI‐1 did not. Similarly, both WT and Active PAI‐1 decreased amidolytic activity of purified caspase‐3, whereas Mut PAI‐1 did not. WT but not Mut PAI‐1 decreased the cleavage of poly‐[ADP‐ribose]‐polymerase (PARP), the physiological substrate of caspase‐3. Noncovalent physical interaction between caspase‐3 and PAI‐1 was demonstrable with the use of both qualitative and quantitative in vitro binding assays. High affinity binding was eliminated by mutations that block PAI‐1 serpin activity. Accordingly, attenuated apoptosis resulting from elevated expression of PAI‐1 by VSMC may be attributable, at least in part, to reversible inhibition of caspase‐3 by active PAI‐1.