Attenuation of EPA and DHA‐Mediated Platelet Inhibition Effects Following Heterogeneous Agonist Treatment

Abstract

Agonist‐induced platelet activation following vascular damage is a critical event for the propagation of thrombi formed as a part of either hemostasis or thrombosis. Several studies have indicated this activation can be impaired after platelet membrane enrichment with the polyunsaturated omega‐3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This attenuated platelet function represents a potential mechanism behind the anti‐thrombotic benefits of EPA and DHA observed in many human trials. However, nearly all platelet studies with EPA and DHA examined the alterations to platelet activation in response to a single agonist, rather than with multiple agonists that mimic the more complex heterogeneous environment of a developing arterial clot. We therefore asked if high levels of EPA and DHA could still inhibit platelet activation if platelets were stimulated with a combination of agonists designed to simulate the activating conditions found in the thrombus inner core (using thrombin and collagen) or outer shell (using ADP and thromboxane A2). To test this question, we treated platelets with EPA and DHA concentrations in vitro that raise the membrane content of both fatty acids to levels analogous to subjects taking EPA and DHA supplements. After this modification, the platelets were stimulated with the agonist combinations and measured for an activation response. Surprisingly, inherent measures of platelet activation using these agonist combinations, including adhesion, aggregation, granule release, and integrin activation were either only mildly affected or non‐significantly altered after EPA and DHA membrane enrichment. We also tested the ability of the core agonist combination to stimulate platelet‐derived thrombin generation, a catalytic process thought to be necessary for rapid thrombus core development. Contrary to the other measures of platelet function, thrombin generation was still consistently impaired by elevated EPA and DHA levels. We conclude that elevated levels of EPA and DHA in the developing clot environment do not readily inhibit most events of platelet activation. Instead, the impairment of amplified thrombin generation in the platelet‐rich arterial clot may provide a more likely candidate for how EPA and DHA prevent detrimental cardiovascular events.Support or Funding InformationResearch reported in this abstract was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103443, a South Dakota/National Science Foundation EPSCoR RII Track 1 grant, the Sanford Program for Undergraduate Research, and an American Physiological Society Undergraduate Summer Research Fellowship.