Activation of metabolite receptor GPR91 promotes platelet aggregation and transcellular biosynthesis of leukotriene C₄

Background: Succinate is a Krebs cycle intermediate whose formation is enhanced under metabolic stress, and for which a selective sensor GPR91 has been identified on various cell types including platelets. Platelet-derived eicosanoids play pivotal roles in platelet activation/aggregation, which is key to thrombus formation and progression of atherothrombosis.

Objectives: This study aims to decipher the molecular mechanism(s) and potential involvement of eicosanoids in succinate enhanced platelet activation/aggregation.

Methods: We used liquid chromatography-mass spectrometry (LC-MS)/MS-based lipid mediator profiling to identify eicosanoids regulated by succinate. We ran light transmittance aggregometry and flow cytometry to assess platelet aggregation, P-selectin expression, and platelet-polymorphonuclear leukocyte (PMN) adherence. Various pharmacological tools were used to assess the contributions of GPR91 signalling and eicosanoids in platelet aggregation.

Results: Succinate and two types of synthetic non-metabolite GPR91 agonists-cis-epoxysuccinate (cES) and Cmpd131-potentiated platelet aggregation, which was partially blocked by a selective GPR91 antagonist XT1. GPR91 activation increased production of 12-hydroxy-eicosatetraenoic acid (12-HETE), thromboxane (TX) A₂ , and 12-hydroxy-heptadecatrienoic acid (12-HHT) in human platelets, associated with phosphorylation of cytosolic phospholipase A₂ (cPLA₂ ), suggesting increased availability of free arachidonic acid. Blocking 12-HETE and TXA₂ synthesis, or antagonism of the TXA₂ receptor, significantly reduced platelet aggregation enhanced by GPR91 signalling. Moreover, platelet-PMN suspensions challenged with succinate exhibited enhanced transcellular biosynthesis of leukotriene C₄ (LTC₄ ), a powerful proinflammatory vascular spasmogen.

Conclusion: Succinate signals through GPR91 to promote biosynthesis of eicosanoids, which contribute to platelet aggregation/activation and potentially vascular inflammation. Hence, GPR91 may be a suitable target for pharmacological intervention in atherothrombotic conditions.