Plasminogen Activator Inhibitor-1 Promotes Formation of Endothelial Microparticles With Procoagulant Potential

Abstract

Background-Endothelial dysfunction is emerging as a common denominator for diverse and highly prevalent cardiovascular diseases. Increased level of plasminogen activator inhibitor-1 (PAI-1) and procoagulant activity have been recognized as hallmarks of endothelial dysfunction. This study was aimed at investigating cellular actions of PAI-1 and a potential link between PAI-1 and procoagulant state. Methods and Results-Human umbilical vein endothelial cells treated with PAI-1 were subjected to laser confocal fluorescence microscopy, immunoprecipitation and Western blotting, and FACS analysis for isolation and identification of endothelial microparticles. PAI-1 treatment resulted in a reduced expression of uPAR, its colocalization with caveolin, and the concomitant increase of uPAR abundance in the culture medium. FACS analysis revealed that PAI-1 rapidly and dose-dependently increased the number of endothelial microparticles expressing uPAR and ␣ V ␤ 3 integrin. This process was attenuated by pretreatment with neutralizing anti-uPAR antibodies. PAI-1 knockout mice showed a significantly decreased number of circulating endothelial microparticles than wild-type mice; however, PAI-1-deficient animals responded to infusion of PAI-1 with a more pronounced rise in the number of microparticles. PAI-1 treatment increased the number of microparticles stained with Annexin V, evidence for the expression of anionic phospholipids. This was accompanied by the accelerated generation of thrombin. Conclusions-The data disclose a novel effect of PAI-1 to dose-dependently promote formation of endothelial microparticles with the reduced transmembrane asymmetry of phospholipids. This phenomenon may be responsible for the observed increase in in vitro thrombin generation. These findings could potentially link these hallmarks of endothelial dysfunction-elevated levels of PAI-1 and propensity toward thrombosis.

Mast Cell–Derived Exosomes Activate Endothelial Cells to Secrete Plasminogen Activator Inhibitor Type 1

“…Interestingly, the rate of in vitro thrombin generation is accelerated significantly by microparticles obtained from the cultured HUVECs pretreated with PAI-1. 22 However, mast cell-derived exosomes significantly induce PAI-1 expression in endothelial cells and its secretion, providing feedback between the characteristically elevated PAI-1 levels and procoagulant state, both observed in diverse syndromes manifesting as endothelial cell dysfunction. However, because these data were obtained using HMC-1, it remains to be confirmed whether they apply to other human mast cells.…”

“…22 Factor Xa activity and thrombin generation was monitored by continuous measurement of absorbance at 405 nm. The chromogenic assay was standardized with pure human ␣-thrombin (20 nmol/L).…”

The lost correlation between heat shock protein 70 (HSPA1A) and plasminogen activator inhibitor-1 in patients with type 2 diabetes and albuminuria

“…Elevated plasma level of PAI-1 is considered as a non-traditional risk factor for cardiovascular diseases (Brodsky et al 2002). Rucker et al demonstrated that heat shock stress increases the expression of PAI-1 in vascular tissues of rat muscle (Rucker et al 2006).…”

Central Obesity and the Metabolic Syndrome: Implications for Primary Care Providers

“…Investigators have shown that central obesity correlates with elevated plasma levels of plasminogen activator inhibitor 1 (PAI-1), which has been strongly associated with dysfibrinolysis within the fibrinolytic system, meaning that the balance between normal clot lysis and clot formation is disturbed (Alessi et al, 1997;Bastard et al, 1995;Brodsky, Malinowski, Golightly, Jesty, & Goligorsky, 2002;Vague, Vague, & Cloix, 1971). It is this disturbance in clotting that has led investigators to focus on the plasma levels of PAI-1, which, if abnormally high, lead to both ruptured plaque and thrombotic occlusion.…”

“…It is this disturbance in clotting that has led investigators to focus on the plasma levels of PAI-1, which, if abnormally high, lead to both ruptured plaque and thrombotic occlusion. Ruptured plaque is considered an important mechanism in the development of a myocardial infarction (Brodsky et al;Falk, 1992). Further, elevated plasma PAI-1 levels have been shown to predict infarction and stroke (Juhan- Vague & Alessi, 1996;Juhan-Vague, Morange, & Alessi, 1999).…”