Angiotensin-Converting Enzyme Inhibition Suppresses Plasminogen Activator Inhibitor-1 Expression in the Neointima of Balloon-Injured Rat Aorta

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Abstract
Background Plasminogen activator inhibitor-1 (PAI-1), an important regulator of fibrinolysis and extracellular matrix turnover, has been implicated in a number of vascular diseases. Studies demonstrating angiotensin II (Ang II) to be a potent stimulator of PAI-1 expression in cultured vascular cells suggests that the renin-angiotensin system may modulate vascular PAI-1 expression. Methods and Results We examined the effects of the ACE inhibitor captopril on PAI-1 expression in control and balloon-injured rat aorta. Northern blot analysis demonstrated that aortic PAI-1 mRNA expression was 7.6-fold elevated 3 hours ( P <.05) after balloon injury, back to baseline at 2 days, increased again at 4 days, and by 7 days after balloon injury was 3.2-fold elevated ( P <.05) when compared with control. In captopril-treated rats, the induction of PAI-1 expression by balloon injury was significantly suppressed by 44% ( P <.05) in the 7-day group but was not altered in the 3-hour group. Captopril also reduced baseline aortic PAI-1 mRNA. In situ hybridization and immunohistochemistry revealed dense PAI-1 staining of 7-day neointima in untreated rats and a dramatic decrease in PAI-1 in neointima of captopril-treated rats. Conclusions This report demonstrates that balloon injury results in both a rapid ACE inhibitor–independent induction of aortic PAI-1 expression and a later increase in PAI-1 in the neointima that is significantly suppressed by captopril. This provides the first evidence that the renin-angiotensin system regulates neointimal PAI-1 expression and that ACE inhibitors can reduce PAI-1 in the vessel wall in vivo.

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