PB0863 - Fatty acid oxidation fuels agonist-induced platelet activation and thrombus formation: Targeting beta-oxidation of fatty acids as an effective anti-platelet strategy

Background: Platelet mitochondria possess remarkable plasticity for oxidation of energy substrates, where metabolic energy dependency on glucose or fatty acids is higher than glutamine. Since platelets metabolize nearly the entire pool of glucose to lactate rather than fluxing through mitochondrial tricarboxylic acid cycle, we posit that majority of mitochondrial ATP, which is essential for platelet granule secretion and thrombus formation, is sourced from oxidation of fatty acids. Hence, we performed a comprehensive analysis of energy metabolism and platelet function responses in the presence of etomoxir, trimetazidine and oxfenicine, three pharmacologically distinct inhibitors of fatty acid oxidation.

Aims: We aim to establish the role of fatty acid oxidation in platelet function and bioenergetics.

Methods: The effect of fatty acid oxidation inhibitors on platelet function and thrombosis was assessed by light transmission aggregometry, flow cytometry and BioFlux microfluidics thrombosis assay in vitro as well as ferric-chloride-induced mesenteric thrombosis, collagen-epinephrine-induced pulmonary embolism and tail bleeding assay in mice. The underlying mechanism was explored by flow cytometry, high-resolution respirometry and biochemical assays.

Results: All three inhibitors significantly impaired OXPHOS in unstimulated as well as thrombin-stimulated platelets leading to a small but consistent drop in ATP level in activated cells due to a lack of compensation from glycolytic ATP. Trimetazidine and oxfenicine attenuated platelet aggregation, ATP release, P-selectin exposure and integrin alpha2b beta3 activation. Both etomoxir and trimetazidine impeded agonist-induced dense granule release and platelet thrombus formation on collagen under arterial shear, but neither of them could protect mice from collagen-epinephrine-induced pulmonary embolism or prolong mouse tail bleeding time. However, mice pre-administered with etomoxir and trimetazidine were protected from ferric-chloride-induced mesenteric thrombosis.

Conclusion(s): Beta-oxidation of fatty acids sustains ATP levels in stimulated platelets and is therefore essential for energy-intensive agonist-induced platelet responses and consequent thrombus formation. Thus, fatty acid oxidation may constitute an attractive therapeutic target for novel antiplatelet therapies.