PB0627 - Hypofibrinolysis in patients with aortic stenosis is driven by overexpression of plasminogen activator inhibitor type 1 (PAI- 1) associated with elevated oxidized lipoproteins

Background: Aortic stenosis (AS) is associated with hypofibrinolysis, but the mechanism underlying this phenomenon is poorly understood.

Aims: We investigated whether hypofibrinolysis in AS is associated with plasminogen activator inhibitor type 1 (PAI-1) overexpression and if oxidized (ox)LDL-cholesterol affects this process.

Methods: We enrolled 75 patients with isolated severe AS (aged 66±9 years) and 10 healthy well-matched controls. Plasma PAI-1 concentrations and oxLDL levels were assayed using commercially available ELISAs. Primary cultures of valve interstitial cells (VICs) obtained from AS valves were stimulated with oxLDL (300 µg/ml) or TNF-α (50 ng/ml). Inhibitors of PAI-1 (50 µM) or NF-κB (10-6 mol/l) were used to suppress PAI-1 synthesis. After 7 days of culturing VICs were used for immunofluorescence, PCR and ELISAs. Clot lysis time (CLT) was measured in patients’ plasma and PAI-deficient plasma supplemented with VICs supernatants. The Ethical Committee approved the study and all participants provided written informed consent in accordance with the Declaration of Helsinki.

Results: AS patients compared with controls had 51.2% higher oxLDL-cholesterol levels (p=0.027), 67% higher plasma PAI-1 (p=0.003) and 19% prolonged CLT (p=0.000014). The expression of PAI-1 was observed within stenotic but not control valves (24.6% vs. 0%, p=0.00001). Valvular PAI-1 expression strongly correlated with CLT (r2=0.34, p=0.00001). oxLDL-cholesterol was weakly associated with plasma PAI-1 (r2=0.10; p=0.007) and CLT (r2=0.14, p=0.0008). In vitro VICs expressed PAI-1 independently of TNF-α or oxLDL stimulation, which was downregulated by PAI-1 (-33 ±6.3%, p=0.002), and NF-kB (-29 ±4.7%, p=0.0026) inhibitors. Inhibition of PAI-1 significantly downregulated SERPINE1 expression in VICs (all p < 0.001). TNF-α stimulation prolonged CLT by 10.7% compared with VICs cultured in standard medium, while PAI-1 inhibition shortened CLT by 8.9% (both p< 0.01).

Conclusion(s): In severe AS patients hypofibrinolysis is driven by local PAI-1 overexpression associated with increased oxLDL.
This work was supported by the Polish National Science Centre (UMO-2018/29/B/NZ5/02629).