Plasminogen activator inhibitor-1 and restenosis

Plasma urokinase antigen and C-reactive protein predict angina recurrence after coronary angioplasty

This study evaluates the predictive value of several biochemical indices of the coagulation-fibrinolysis system, platelet function, and inflammatory state for angina recurrence after successful percutaneous transluminal coronary angioplasty (PTCA). We measured preprocedural and follow-up plasma levels of C-reactive protein (CRP), fibrinogen, and urokinase plasminogen activator antigen (uPA), plasminogen activator inhibitor-1 (PAI-1) activity, tissue plasminogen activator activity, and adenosine diphosphate-induced platelet aggregation in 53 patients with chronic stable angina who underwent successful elective PTCA of single hemodynamically significant lesions in coronary arteries. All patients were followed up for 12 months after PTCA. The Cox proportional hazards model was used to assess the association of variables with angina recurrence rate. At the end of the follow-up, 16 patients had angina recurrence. Among 36 clinical, biochemical, and angiographic variables, the duration of stable angina more than 12 months before PTCA (χ (2) = 5.73; P = 0.02, hazard ratio (HR) 3.7, 95 % confidence interval (CI) 1.26-10.6), high baseline levels of CRP (>7 mg/l) (χ (2) = 8.34; P = 0.004, HR 2.9, 95 % CI 1.4-5.9), uPA antigen baseline (>1 ng/ml) (χ (2) = 17.11; P = 0.0001, HR 11.5, 95 % CI 3.6-36.7) and 48 h after PTCA (χ (2) = 15.73; P = 0.0001, HR 8.8, 95 % CI 3.01-25.96), baseline PAI-1 activity (>18 IU/ml) (χ (2) = 9.37; P = 0.002, HR 7.6, 95 % CI 2.07-27.84) were significant predictors of recurrent angina by univariate analyses. According to stepwise multivariate analyses, only the levels of plasma uPA antigen and serum CRP were shown to be significant independent predictors of angina recurrence (multivariate uPA χ (2) = 8.22, P = 0.004, HR 6.2, 95 % CI 1.78-21.67; CRP χ (2) = 4.09, P = 0.04, HR 1.9, 95 % CI 1.02-3.68). High preprocedural plasma uPA and serum CRP levels are indicative of angina recurrence after successful PTCA, and are valuable for the prognosis of restenosis.

Maximal PAI-1 inhibition in vivo requires neutralizing antibodies that recognize and inhibit glycosylated PAI-1

Plasminogen activator inhibitor-1 (PAI-1) regulates the activity of t-PA and u-PA and is an important inhibitor of the plasminogen activator system. Elevated PAI-1 levels have been implicated in the pathogenesis of several diseases. Prior to the evaluation of PAI-1 inhibitors in humans, there is a strong need to study the effect of PAI-1 inhibition in mouse models. In the current study, four monoclonal antibodies previously reported to inhibit recombinant PAI-1 in vitro, were evaluated in an LPS-induced endotoxemia model in mice. Both MA-33H1F7 and MA-MP2D2 exerted a strong PAI-1 inhibitory effect, whereas for MA-H4B3 and MA-124K1 no reduced PAI-1 activity was observed in vivo. Importantly, the lack of PAI-1 inhibition observed for MA-124K1 and MA-H4B3 in vivo corresponded with the absence of inhibition toward glycosylated mouse PAI-1 in vitro. Three potential N-glycosylation sites were predicted for mouse PAI-1 (i.e. N209, N265 and N329). Electrophoretic mobility analysis of glycosylation knock-out mutants before and after deglycosylation indicates the presence of glycan chains at position N265. These data demonstrate that an inhibitory effect toward glycosylated PAI-1 is a prerequisite for efficient PAI-1 inhibition in mice. Our data also suggest that PAI-1 inhibitors for use in humans must preferably be screened on glycosylated PAI-1 and not on recombinant non-glycosylated PAI-1.

Restenosis after PCI. Part 1: pathophysiology and risk factors

Restenosis is a complex disease for which the pathophysiological mechanisms have not yet been fully elucidated, but are thought to include inflammation, proliferation, and matrix remodeling. Over the years, many predictive clinical, biological, (epi)genetic, lesion-related, and procedural risk factors for restenosis have been identified. These factors are not only useful in risk stratification of patients, they also contribute to our understanding of this condition. Furthermore, these factors provide evidence on which to base treatment tailored to the individual and aid in the development of novel therapeutic modalities. In this Review, we will evaluate the available evidence on the pathophysiological mechanisms of restenosis and provide an overview of the various risk factors, together with the possible clinical application of this knowledge.

Plasminogen activator inhibitor-1 (PAI-1) is cardioprotective in mice by maintaining microvascular integrity and cardiac architecture

Although the involvement of plasminogen activator inhibitor-1 (PAI-1) in fibrotic diseases is well documented, its role in cardiac fibrosis remains controversial. The goal of this study was to determine the effect of a PAI-1 deficiency (PAI-1(-/-)) on the spontaneous development of cardiac fibrosis. PAI-1(-/-) mice developed pervasive cardiac fibrosis spontaneously with aging, and these mice displayed progressively distorted cardiac architecture and markedly reduced cardiac function. To mechanistically elucidate the role of PAI-1 in cardiac fibrosis, 12-week-old mice were chosen to study the biologic events leading to fibrosis. Although fibrosis was not observed at this early age, PAI-1(-/-) hearts presented with enhanced inflammation, along with increased microvascular permeability and hemorrhage. A potent fibrogenic cytokine, transforming growth factor-beta (TGF-beta), was markedly enhanced in PAI-1(-/-) heart tissue. Furthermore, the expression levels of several relevant proteases associated with tissue remodeling were significantly enhanced in PAI-1(-/-) hearts. These results suggest that PAI-1 is cardioprotective, and functions in maintaining normal microvasculature integrity. Microvascular leakage in PAI-1(-/-) hearts may provoke inflammation, and predispose these mice to cardiac fibrosis. Therefore, a PAI-1 deficiency contributes to the development of cardiac fibrosis by increasing vascular permeability, exacerbating local inflammation, and increasing extracellular matrix remodeling, an environment conducive to accelerated fibrosis.