A small molecule PAI-1 functional inhibitor attenuates neointimal hyperplasia and vascular smooth muscle cell survival by promoting PAI-1 cleavage

• Published in: Cellular signalling 2015-05, Vol.27 (5), p.923-933
• Main Authors: Simone, Tessa M., Higgins, Stephen P., Archambeault, Jaclyn, Higgins, Craig E., Ginnan, Roman G., Singer, Harold, Higgins, Paul J.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis - drug effects; Biocompatibility; Carotid stenosis; Carotid Stenosis - drug therapy; Carotid Stenosis - metabolism; Carotid Stenosis - pathology; Cell Line; Cell Survival - drug effects; Density; Fibrinolysin - metabolism; Hyperplasia - drug therapy; Hyperplasia - metabolism; Hyperplasia - pathology; Indoleacetic Acids - pharmacology; Inhibitors; Lipoproteins; Male; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - metabolism; Muscles; Neointima - drug therapy; Neointima - metabolism; Neointima - pathology; PAI-1; Plasminogen Activator Inhibitor 1 - metabolism; Protease inhibitors; Proteins; Rats, Sprague-Dawley; SERPIN; Vascular injury
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2015.01.009

Plasminogen activator inhibitor-1 (PAI-1), the primary inhibitor of urokinase-and tissue-type plasminogen activators (uPA and tPA), is an injury-response gene implicated in the development of tissue fibrosis and cardiovascular disease. PAI-1 mRNA and protein levels were elevated in the balloon catheter-injured carotid and in the vascular smooth muscle cell (VSMC)-enriched neointima of ligated arteries. PAI-1/uPA complex formation and PAI-1 antiproteolytic activity can be inhibited, via proteolytic cleavage, by the small molecule antagonist tiplaxtinin which effectively increased the VSMC apoptotic index in vitro and attenuated carotid artery neointimal formation in vivo. In contrast to the active full-length serine protease inhibitor (SERPIN), elastase-cleaved PAI-1 (similar to tiplaxtinin) also promoted VSMC apoptosis in vitro and similarly reduced neointimal formation in vivo. The mechanism through which cleaved PAI-1 (CL-PAI-1) stimulates apoptosis appears to involve the TNF-α family member TWEAK (TNF-α weak inducer of apoptosis) and it's cognate receptor, fibroblast growth factor (FGF)-inducible 14 (FN14). CL-PAI-1 sensitizes cells to TWEAK-stimulated apoptosis while full-length PAI-1 did not, presumably due to its ability to down-regulate FN14 in a low density lipoprotein receptor-related protein 1 (LRP1)-dependent mechanism. It appears that prolonged exposure of VSMCs to CL-PAI-1 induces apoptosis by augmenting TWEAK/FN14 pro-apoptotic signaling. This work identifies a critical, anti-stenotic, role for a functionally-inactive (at least with regard to its protease inhibitory function) cleaved SERPIN. Therapies that promote the conversion of full-length to cleaved PAI-1 may have translational implications. [Display omitted] •PAI-1 expression is increased in the neointima of balloon-catheterized and ligated carotid arteries.•The small molecule PAI-1 inhibitor tiplaxtinin inhibits PAI-1/uPA complex formation and stimulates PAI-1 cleavage.•Tiplaxtinin and cleaved PAI-1, each independently, attenuate the neointimal response in the ligated carotid.•Tiplaxtinin and cleaved PAI-1 both stimulate VSMC apoptosis in vitro.•Prolonged exposure of VSMCs to cleaved PAI-1 induces apoptosis by augmenting TWEAK/FN14 pro-apoptotic signaling.