Platelet Lipidomic Profiling: Novel Insight into Cytosolic Phospholipase A2? Activity and Its Role in Human Platelet Activation.

ABSTRACT: With a newer, more selective and efficacious cytosolic phospholipase A2? (cPLA2?) inhibitor available, we revisited the role of cPLA2? activity in platelet activation and discovered that a component of platelet signaling, even larger than previously appreciated, relies on this enzyme. In a whole blood shear-based flow chamber assay, giripladib, a cPLA2? inhibitor, reduced platelet adhesion and accumulation on collagen. Moreover, giripladib differentially affected P-selectin expression and GPIIbIIIa activation depending on the agonist employed. While protease-activated receptor 1 (PAR1)-mediated platelet activation was unaffected by giripladib, the levels of PAR4- and GPVI-mediated platelet activation were significantly reduced. Meanwhile, the thromboxane A2 receptor antagonist SQ29548 had no effect on PAR-, GPVI-, or puriniergic receptor-mediated platelet activation, suggesting that another eicosanoid produced downstream of arachidonic acid liberation by cPLA2? was responsible for this large component of PAR4- and GPVI-mediated platelet activation. In parallel, we profiled PAR-mediated changes in glycerophospholipid (GPL) mass with and without giripladib to better understand cPLA2?-mediated lipid metabolism. Phosphatidylcholine and phosphatidylethanolamine (PE) demonstrated the largest consumption of mass during thrombin stimulation. Additionally, we confirm phosphatidylinositol as a major substrate of cPLA2?. A comparison of PAR1- and PAR4-induced metabolism revealed the consumption of more putative arachidonyl-PE species downstream of PAR1 activation. Instead of enhanced cPLA2? activity and therefore more arachidonic acid liberation downstream of PAR4, these results indicate the major role that cPLA2? activity plays in platelet function and suggest that a novel eicosanoid is produced in response to platelet activation that represents a large component of PAR4- and GPVI-mediated responses.

SUBMITTER: Duvernay MT 

PROVIDER: S-EPMC7748375 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature