title: Noninhibitory PAI-1 enhances plasmin-mediated matrix degradation both in vitro and in experimental nephritis.
abstract: Plasminogen activator inhibitor-type 1 (PAI-1) is thought to be profibrotic by inhibiting plasmin generation, thereby decreasing turnover of pathological extracellular matrix (ECM). A mutant, noninhibitory PAI-1 (PAI-1R) was recently shown by us to increase glomerular plasmin generation and reduce disease in anti-thy-1 nephritis. Here, in vitro and in vivo studies were performed to determine whether enhanced plasmin-dependent ECM degradation underlies the therapeutic effect of PAI-1R. 3H-labeled ECM was produced by rat mesangial cells (MCs). The effect of wild-type PAI-1 (wt-PAI-1) and PAI-1R on ECM degradation by newly plated MCs was measured by the release of 3H into medium. In vivo, anti-thy-1 nephritis was assessed in normal, untreated diseased and PAI-1R treated rats with or without the plasmin/plasminogen inhibitor, tranexamic acid (TA). wt-PAI-1 totally inhibited plasmin generation and reduced ECM degradation by 76% when exogenous plasminogen was added. Although PAI-1R alone had no effect, PAI-1R in the presence of wt-PAI-1 reversed the wt-PAI-1 inhibition of ECM degradation in a time- and dose-dependent manner (P<0.001). Plasmin activity and zymography were consistent with ECM degradation. Plasmin inhibitors: alpha2-antiplasmin, aprotinin, and TA completely blocked PAI-1R's ability to normalize ECM degradation (P<0.001). Consistent with the in vitro results, TA reversed PAI-1R-induced reductions in glomerular fibrin and ECM accumulation. Other measures of disease severity were either unaltered or partially reversed. PAI-1R reduces pathological ECM accumulation, in large part through effectively competing with native PAI-1 thereby restoring plasmin generation and increasing plasmin-dependent degradation of matrix components.
authors.affiliation: Fibrosis Research Laboratory, Division of Nephrology, University of Utah School of Medicine, Salt Lake City, Utah 84108, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.forename: W A
authors.initials: WA
authors.lastname: Border
authors.forename: D A
authors.initials: DA
authors.lastname: Lawrence
authors.forename: N A
authors.initials: NA
authors.lastname: Noble
mesh_terms: D000818:Animals; D000933:Antifibrinolytic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005341:Fibrinolysin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005921:Glomerulonephritis / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D066298:In Vitro Techniques; D008264:Macrophages / Q000473:pathology; D008297:Male; D050527:Mesangial Cells / Q000378:metabolism* / Q000473:pathology; D009000:Monocytes / Q000473:pathology; D009154:Mutation; D010958:Plasminogen / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000494:pharmacology*; D011507:Proteinuria / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014148:Tranexamic Acid / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D014316:Tritium
chemical_list: D000933:Antifibrinolytic Agents; D024042:Collagen Type I; D005353:Fibronectins; D017395:Plasminogen Activator Inhibitor 1; D053773:Transforming Growth Factor beta1; D014316:Tritium; D014148:Tranexamic Acid; D010958:Plasminogen; D005341:Fibrinolysin