Pleiotropic effects of the protease‐activated receptor 1 (Par1) inhibitor, vorapaxar, on atherosclerosis and vascular inflammation

Abstract

Background: Protease‐activated receptor 1 (PAR1) and toll‐like receptors (TLRs) are inflammatory mediators contributing to atherogenesis and atherothrombosis. Vorapaxar, which selectively antagonizes PAR1‐signaling, is an approved, add‐on antiplatelet therapy for secondary prevention. The non‐hemostatic, platelet‐independent, pleiotropic effects of vorapaxar have not yet been studied. Methods and Results: Cellular targets of PAR1 signaling in the vasculature were identified in three patient cohorts with atherosclerotic disease. Evaluation of plasma biomarkers (n = 190) and gene expression in endomyocardial biopsies (EMBs) (n = 12) revealed that PAR1 expression correlated with endothelial activation and vascular inflammation. PAR1 colocalized with TLR2/4 in human carotid plaques and was associated with TLR2/4 gene transcription in EMBs. In addition, vorapaxar reduced atherosclerotic lesion size in apolipoprotein E–knock out (ApoEko) mice. This reduction was associated with reduced expression of vascular adhesion molecules and TLR2/4 presence, both in isolated murine endothelial cells and the aorta. Thrombin‐induced uptake of oxLDL was augmented by additional TLR2/4 stimulation and abrogated by vorapaxar. Plaque-infiltrating pro‐inflammatory cells were reduced in vorapaxar‐treated ApoEko mice. A shift toward M2 macrophages paralleled a decreased transcription of pro‐inflammatory cytokines and chemokines. Conclusions: PAR1 inhibition with vorapaxar may be effective in reducing residual thrombo‐inflammatory event risk in patients with atherosclerosis independent of its effect on platelets.