Human Platelets Utilize Cycloxygenase-1 to Generate Dioxolane A3, a Neutrophil-activating Eicosanoid

Abstract

Eicosanoids are important mediators of fever, pain, and inflammation that modulate cell signaling during acute and chronic disease. We show by using lipidomics that thrombin-activated human platelets generate a new type of eicosanoid that both stimulates and primes human neutrophil integrin (Mac-1) expression, in response to formylmethionylleucylphenylalanine. Detailed characterization proposes a dioxolane structure, 8-hydroxy-9,11-dioxolane eicosatetraenoic acid (dioxolane A3, DXA3). The lipid is generated in nanogram amounts by platelets from endogenous arachidonate during physiological activation, with inhibition by aspirin in vitro or in vivo, implicating cyclooxygenase-1 (COX). Pharmacological and genetic studies on human/murine platelets revealed that DXA3 formation requires protease-activated receptors 1 and 4, cytosolic phospholipase A2 (cPLA2), Src tyrosine kinases, p38 MAPK, phospholipase C, and intracellular calcium. From data generated by purified COX isoforms and chemical oxidation, we propose that DXA3 is generated by release of an intermediate from the active site followed by oxygenation at C8. In summary, a new neutrophil-activating platelet-derived lipid generated by COX-1 is presented that can activate or prime human neutrophils, suggesting a role in innate immunity and acute inflammation.

Neutrophil Activation and Enhanced Release of Granule Products in HIV-TB Immune Reconstitution Inflammatory Syndrome: Erratum

“…21 Similarly, NLRP12 (Pypaf-7) is crucial for neutrophil recruitment in other models of infection, 22 including to the lungs, 23 whereas (among its other actions) COX-1 generates eicosanoids, which activate neutrophils. 24 We have also shown that neutrophil markers strongly colocalise with IL-10 in human tuberculous granulomas. 20 Our gene expression data, therefore, suggested a role for neutrophils in TB-IRIS pathogenesis and we examined this in another patient cohort, subsequently recruited in Cape Town.…”

Endothelial damage effects of circulating microparticles from patients with stable angina are reduced by aspirin through ERK/p38 MAPKs pathways

“…It was reported that: aspirin can inhibit the formation of prostaglandins and thromboxane A 2 (promote platelet aggregation and vasoconstriction by inhibiting of the COX‐1 enzyme irreversibly). And cox‐1 can activate platelet …”

Platelet lipidome: Dismantling the “Trojan horse” in the bloodstream

“…Platelet eicosanoids (TXA2, 12‐HETE) and prostaglandins (PGE2, PGD2) regulate monocyte and neutrophil functions. Activated platelets also release dioxolane A3 (DXA3) following PAR1‐PAR4 activation or by collagen, ionophore, or collagen‐thrombin combination employing cPLA2 and AA metabolism (Figure A), independent of TxA2 synthesis. DXA3 generation is affected by genetic deficiency of cPLA2, by cPLA2, and COX‐1 inhibitors (aspirin, indomethacin), but is enhanced in 12‐LOX −/− murine platelets .…”

“…Activated platelets also release dioxolane A3 (DXA3) following PAR1‐PAR4 activation or by collagen, ionophore, or collagen‐thrombin combination employing cPLA2 and AA metabolism (Figure A), independent of TxA2 synthesis. DXA3 generation is affected by genetic deficiency of cPLA2, by cPLA2, and COX‐1 inhibitors (aspirin, indomethacin), but is enhanced in 12‐LOX −/− murine platelets . DXA3 is rapidly esterified to 16:0‐, 18:1‐, 18:0‐PE‐plasmalogen, and 18:0‐acyl‐PE by lysophospholipid acyltransferases (Figure A); so mostly remains platelet associated, while free DXA3 adds to serum levels during clotting.…”