Induction of apoptosis in vascular cells by plasminogen activator inhibitor-1 and high molecular weight kininogen correlates with their anti-adhesive properties

Plasminogen activator inhibitor-1 (PAI-1) and twochain high molecular weight kininogen (HKa) exert antiadhesive properties in vitronectindependent cell adhesion. Here, the hypothesis was tested that these antiadhesive components promote apoptosis in vascular cells. PAI-1 or HKa induced a 2- to 3-fold increase in apoptosis of human umbilicalvein endothelial cells (HUVEC) and vascular smooth muscle cells (VSMC) adherent to vitronectin, as determined by annexin VFACS assay, similar to [alpha]vintegrin inhibitor cyclo(ArgGlyAspDPheVal)peptide (cRGDfV). Apoptosis occurred after 12 h incubation and was attributable to caspase 3 activation that in turn induced DNA fragmentation. Induction of apoptosis strongly correlated with the antiadhesive effect of PAI-1 and HKa on these cells. In contrast, PAI-1 and HKa did not affect fibronectindependent adhesion or cell survival. uPA did not influence apoptosis in vitronectin or fibronectinadherent cells. In atherosclerotic vessel sections, congruent distribution of vitronectin, PAI-1, HK, and of components of the urokinase plasminogen activator/receptor system with apoptotic cells lining foam cell lesions was demonstrated by immunostaining. These results indicate that inhibition of vitronectindependent cell adhesion through PAI-1 and HKa correlates with apoptosis induction in vascular cells mediated through the caspase 3 pathway. Codistribution of apoptosis with plasminogen activation system components in atherosclerosis exemplifies the significance of antiadhesive mechanisms and apoptosis for tissue remodeling, such as in neointima development.