Study Of Plasminogen Activator Inhibitor-1(PAI-1) Regulates Vascular Smooth Muscle Cell Phenotype Modulation

Background:Vascular smooth muscle cell (VSMC)phenotypic modulation is considered to be key event in the developmentof vascular injury disorders， such as atherosclerosis, angioplastyrestenosis．Plasminogen activator inhibitor-1(PAI-1） play a keyrole in the regulation of VSMC function. Several diseases, includingdiabetes mellitus and atherosclerosis, are characterized by increasedPAI-1expression, both within vascular wall. PAI-1over-expression maypromote intimal hyperplasia and adverse vascular remodeling. The goalsof the present studies were to investigate the relationship between activePAI-1, PAI-1mutants and VSMC phenotypic switch and to determine themolecular mechanisms by which PAI-1affects this essential process inVSMC biology.Through our studies to evaluate the role of PAI-1insmooth muscle phenotype modulation process, looking for therapeutictargets and providing the basis of theories and practice for prevention andtreatment of blood vessel related disease.Methods: Cultured humanumbilical vein smooth muscle cells (HUVSMC) were treated by saline ormutant forms of PAI-1for24hours, including an active stable mutant(PAI-1-WT), a mutant lacking anti-PA activity (PAI-1-R), or a mutantdefective in vitronectin (VN) binding (PAI-1-AK), or an active stable mutant with markedly reduced binding affinity for LRP1, but normal VNbinding affinity (PAI-1-E). Real-time PCR was used to determine thedifferent of synthetic and contractile markers from HUVSMC treated byPAI-1mutants. Furthermore, cultured medium MMPs activity weremeasured by Zemography.Results: PAI-1mutants enhanced theexpression of VSMC contractile genes as well by increasing serumresponse factor through binding to vitronectin. Similarly, Usingrecombinant PAI-1mutants with selective loss-of-function mutations wedemonstrated that PAI-1increased the expression of VSMC syntheticgenes through a pathway that involves three separable steps, one entailingbinding to VN, uPAR, and another requiring binding to the low densitylipoprotein receptor related protein-1(LRP-1). The changes of VSMCphenotypes by PAI-1are not associated with MMP2/9activity.Conclusions: Taken together, these results indicate thatPAI-1promotes VSMC contractile phenotype by promoting theassociation of the serum response factor. PAI-1also increases VSMCsynthetic phenotype by involving both vitronectin binding, uPAR, andLRP-1, suggest that the PAI-1play diverse roles in regulating phenotypicswitch of VSMCs.