The EPA oxylipin, 12-HEPE, directly regulates human platelet activity.

Arterial thrombosis, driven by platelet hyperactivity, is the underlying pathophysiology of most major cardiovascular events. Dietary fish oil supplementation containing ω-3 polyunsaturated fatty acids (PUFAs) elicits cardiovascular protection in at-risk patients. Studies have attributed the cardiovascular benefits of ω-3 PUFAs to eicosapentaenoic acid (EPA), the primary ω-3 PUFA present in fish oil supplements. However, the role of EPA in platelet activation remains unclear. This study aimed to evaluate whether the cardiovascular protection observed in individuals taking dietary supplements containing EPA is achieved by altering platelet function. Additionally, we investigated whether these effects are mediated through the 12-lipoxygenase (12-LOX)-derived oxidized lipid (oxylipin) metabolite of EPA, 12(S)-hydroxy-5Z,8Z,10E,14Z,17Z-eicosapentaenoic acid (12-HEPE). Human whole blood, platelet-rich plasma, and washed platelets were treated with EPA or 12-HEPE to assess their ability to regulate platelet activity. Both EPA and 12-HEPE inhibited agonist-stimulated platelet aggregation, and 12-HEPE was found to be the primary oxylipin produced by platelets in the presence of EPA. Furthermore, 12-HEPE more potently attenuated dense granule secretion, α-granule secretion, and integrin α_IIbβ₃ activation, in comparison to EPA. Interestingly, while EPA delayed thrombin-induced clot retraction and reduced platelet adhesion under flow, 12-HEPE did not affect these processes. Both EPA and 12-HEPE attenuated ex vivo thrombus formation; however, the same inhibitory concentrations did not alter coagulation parameters in thromboelastography. This study demonstrates that EPA and its 12-LOX metabolite, 12-HEPE, effectively inhibit platelet activation. These findings suggest the antiplatelet effects of EPA are regulated, in part, through 12-HEPE, advancing our understanding of the cardiovascular benefits of EPA.