Abstract Body: Introduction: Increased dietary intake of omega-3 fatty acids derived from fish oil has long been associated with a reduced risk of major adverse cardiovascular events (MACE). Eicosapentaenoic acid (EPA), a principal omega-3 fatty acid in fish oil supplements, confers cardiovascular benefits. Further, icosapent ethyl (IPE) is an FDA-approved prodrug that is converted to EPA upon digestion and results in a significant reduction in MACE. Despite widespread use, the biological mechanisms underlying EPA-mediated cardiovascular protection remain undefined.
Hypothesis: The cardiovascular benefits of EPA and IPE arise, in part, from inhibition of platelet activation and subsequent reduction in thrombotic risk. We further hypothesized that EPA mediates its antiplatelet effects through conversion to the bioactive oxylipin 12(S)-hydroxyeicosapentaenoic acid (12-HEPE) via platelet 12(S)-lipoxygenase (12-LOX).
Methods & Results: Washed human platelets incubated with EPA or IPE exhibited dose-dependent inhibition of collagen-induced aggregation as measured by light transmission aggregometry. Under arterial shear, incubation of human whole blood with EPA attenuated thrombus formation in the Total Thrombus formation Analysis System. In vivo, daily oral administration of EPA (50 mg/kg) or IPE (50 mg/kg) for six weeks in wild-type mice attenuated platelet accumulation and fibrin formation in the cremaster laser injury thrombosis model. To determine if the antiplatelet and antithrombotic effects of EPA are 12-LOX dependent, platelets were pretreated with the 12-LOX inhibitor ML355, which partially reversed EPA’s inhibition of platelet aggregation. The 12-LOX–derived EPA oxylipin, 12-HEPE, inhibited platelet aggregation with greater potency than EPA and remained effective in the presence of ML355. Oxylipin analysis by mass spectrometry identified 12-HEPE as the predominant metabolite generated in whole blood in the presence of EPA.
Conclusions: These findings demonstrate that supplementation with IPE and EPA exerts similar antiplatelet and antithrombotic effects. Moreover, EPA-mediated platelet inhibition is largely 12-LOX dependent, with platelet-derived 12-HEPE serving as a primary bioactive metabolite. This mechanistic insight provides a biological basis for the clinical efficacy of IPE and supports its therapeutic use in cardiovascular diseases associated with elevated thrombotic risk.