Protease nexin-1: A cellular serpin down-regulated by thrombin in rat aortic smooth muscle cells

• Published in: Journal of cellular physiology 2004-10, Vol.201 (1), p.138-145
• Main Authors: Richard, Benjamin, Arocas, Véronique, Guillin, Marie-Claude, Michel, Jean-Baptiste, Jandrot-Perrus, Martine, Bouton, Marie-Christine
• Format: Article
• Language: English
• Subjects: Amyloid beta-Protein Precursor; Animals; Antibodies - pharmacology; Aorta - cytology; Carrier Proteins - genetics; Carrier Proteins - metabolism; Carrier Proteins - secretion; Cell Membrane - enzymology; Cells, Cultured; Culture Media, Conditioned - pharmacology; Cycloheximide - pharmacology; Down-Regulation; Fibroblast Growth Factor 2 - immunology; Fibroblast Growth Factor 2 - metabolism; Gene Expression Regulation, Enzymologic - drug effects; Hemostatics - pharmacology; Male; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - physiology; Protease Nexins; Protein Synthesis Inhibitors - pharmacology; Rats; Rats, Wistar; Receptors, Cell Surface; RNA, Messenger - analysis; Thrombin - pharmacology
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.20103

Protease nexin‐1 (PN‐1), a potent inhibitor of serine proteases, is present in vascular cells and forms complexes with thrombin, plasminogen activators, and plasmin. We examined the effect of thrombin on PN‐1 expression by rat aortic smooth muscle cells (RASMCs). PN‐1 expression was determined by measuring protein and mRNA levels, using respectively immunoblotting and semi‐quantitative reverse transcriptase polymerase chain reaction (PCR). Thrombin down‐regulated PN‐1 expression in a dose‐ and time‐dependent manner. This effect was mediated via the interaction of thrombin with its receptor protease activated receptor (PAR‐1) since the peptide thrombin receptor activating peptide (TRAP) reduced PN‐1 expression. PN‐1 secreted by smooth muscle cells remained essentially associated to cell‐surface glycosaminoglycans and was released from the cell surface by heparin. A lower amount of PN‐1 was released by heparin from TRAP‐stimulated versus unstimulated cells and correlated with a decreased capacity to inhibit thrombin. In addition, the ability to generate peri‐cellular plasmin was increased in cells with a low PN‐1 expression. Pre‐treatment of smooth muscle cells with cycloheximide abolished the reduction of PN‐1 expression by thrombin. Furthermore, conditioned media from thrombin‐treated cells reproduced the effect of thrombin, suggesting that thrombin acted via the induction of auto/paracrine mediator(s). We observed that fibroblast growth factor‐2 (FGF‐2)‐neutralizing antibodies abolished thrombin effect whereas FGF‐2 reproduced it, indicating that FGF‐2 is one of the involved mediator. Together, these results indicate that (i) PN‐1 modulates the activity of endogenous and exogenous serine proteases in RASMCs, (ii) thrombin down‐regulates PN‐1 expression and thus may increase its own activity on cells. J. Cell. Physiol. 201: 138–145, 2004. © 2004 Wiley‐Liss, Inc.