Inherited Human gp91phox deficiency is associated with impaired isoprostane formation and platelet dysfunction

Abstract

OBJECT-: Platelet isoprostane 8-ISO-prostaglandin F2α (8-iso-PGF2α), a proaggregating molecule, is believed to derive from nonenzymatic oxidation of arachidonic acid. We hypothesized that NADPH is implicated in isoprostane formation and platelet activation. Methods and results-: We studied 8-iso-PGF2α in platelets from 8 male patients with hereditary deficiency of gp91phox, the catalytic subunit of NADPH oxidase, and 8 male controls. On stimulation, platelets from controls produced 8-iso-PGF2α, which was inhibited -8% by aspirin and -58% by a specific inhibitor of gp91phox. Platelets from patients with gp91 phox hereditary deficiency had normal thromboxane A2 formation but marked 8-iso-PGF2α reduction compared with controls. In normal platelets incubated with a gp91phox inhibitor or with SQ29548, a thromboxane A2/isoprostane receptor inhibitor, platelet recruitment, an in vitro model of thrombus growth, was reduced by 44% and 64%, respectively; a lower effect (-17%) was seen with aspirin. Moreover, thrombus formation under shear stress (blood perfusion at the wall shear rate of 1500 s) was reduced in samples in which isoprostane formation was inhibited by NADPH oxidase inhibitors. In gp91 phox-deficient patients, agonist-induced platelet aggregation was within the normal range, whereas platelet recruitment was reduced compared with controls. Incubation of platelets from gp91-deficient patients with 8-iso-PGF2α dose-dependently (1 to 100 pmol/L) increased platelet recruitment by mobilizing platelet Ca and activating gpIIb/IIIa; a further increase in platelet recruitment was detected by platelet coincubation with l-NAME, an inhibitor of NO synthase. Conclusion-: This study provides the first evidence that platelet 8-iso-PGF2α maximally derives from gp91 phox activation and contributes to platelet recruitment via activation of gpIIb/IIIa. © 2011 American Heart Association, Inc.