pai-039 and Neointima

Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that promotes and inhibits cell migration, plays a complex and important role in adverse vascular remodeling. Little is known about the effects of pharmacological PAI-1 inhibitors, an emerging drug class, on migration of vascular smooth muscle cells (SMCs) and endothelial cells (ECs), crucial mediators of vascular remodeling. We investigated the effects of PAI-039 (tiplaxtinin), a specific PAI-1 inhibitor, on SMC and EC migration in vitro and vascular remodeling in vivo.. PAI-039 inhibited SMC migration through collagen gels, including those supplemented with vitronectin and other extracellular matrix proteins, but did not inhibit migration of PAI-1-deficient SMCs, suggesting that its antimigratory effects were PAI-1-specific and physiologically relevant. However, PAI-039 did not inhibit EC migration. PAI-039 inhibited phosphorylation and nuclear translocation of signal transducers and activators of transcription-1 in SMCs, but had no discernable effect on signal transducer and activator of transcription-1 signaling in ECs. Expression of low-density lipoprotein receptor-related protein 1, a motogenic PAI-1 receptor that activates Janus kinase/signal transducers and activators of transcription-1 signaling, was markedly lower in ECs than in SMCs. Notably, PAI-039 significantly inhibited intimal hyperplasia and inflammation in murine models of adverse vascular remodeling, but did not adversely affect re-endothelialization after endothelium-denuding mechanical vascular injury.. PAI-039 inhibits SMC migration and intimal hyperplasia, while having no inhibitory effect on ECs, which seems to be because of differences in PAI-1-dependent low-density lipoprotein receptor-related protein 1/Janus kinase/signal transducer and activator of transcription-1 signaling between SMCs and ECs. These findings suggest that PAI-1 may be an important therapeutic target in obstructive vascular diseases characterized by neointimal hyperplasia.

Topics: Animals; Carotid Artery Injuries; Cell Movement; Cell Proliferation; Cells, Cultured; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelial Cells; Genotype; Humans; Hyperplasia; Indoleacetic Acids; Janus Kinases; Low Density Lipoprotein Receptor-Related Protein-1; Male; Mice, Inbred C57BL; Mice, Knockout; Molecular Targeted Therapy; Muscle, Smooth; Muscle, Smooth, Vascular; Neointima; Phenotype; Phosphorylation; Plasminogen Activator Inhibitor 1; Re-Epithelialization; Receptors, LDL; Serine Proteinase Inhibitors; Signal Transduction; STAT1 Transcription Factor; Tumor Suppressor Proteins; Vascular Remodeling; Vena Cava, Inferior

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.

Topics: Animals; Apoptosis; Carotid Stenosis; Cell Line; Cell Survival; Fibrinolysin; Hyperplasia; Indoleacetic Acids; Male; Muscle, Smooth, Vascular; Neointima; Plasminogen Activator Inhibitor 1; Rats, Sprague-Dawley