Peroxynitrite can affect platelet responses by inhibiting energy production (original) (raw)

Peroxynitrite (ONOO -) strongly inhibits agonist-induced platelet responses. However, the mechanisms involved are not completely defined. Using porcine platelets, we tested the hypothesis that ONOOreduces platelet aggregation and dense granule secretion by inhibiting energy production. It was found that ONOO -(25-300 µM) inhibited collagen-induced dense granule secretion (IC 50 = 55 ± 7 µM) more strongly than aggregation (IC 50 = 124 ± 16 µM). The antiaggregatory and antisecretory effects of ONOOwere only slightly (5-10%) reduced by 1H-[1,2,4]-oxadiazolo-[4,3α]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylate cyclase. In resting platelets ONOO -(50-300 µM) enhanced glycolysis rate and reduced oxygen consumption, in a dose dependent manner. The ONOOeffects on glycolysis rate and oxygen consumption were not abolished by ODQ. The extent of glycolysis stimulation exerted by ONOOwas similar to that produced by respiratory chain inhibitors (cyanide and antimycin A) or an uncoupler (2,4-dinitrophenol). Stimulation of platelets by collagen was associated with a rise in mitochondrial oxygen consumption, accelerated lactate production, and unchanged intracellular ATP content. In contrast to resting cells, in collagen-stimulated platelets, ONOO -(200 µM) distinctly decreased the cellular ATP content. The glycolytic activity and oxygen consumption of resting platelets were not affected by 8-bromoguanosine 3',5'-cyclic monophosphate. Blocking of the mitochondrial ATP production by antimycin A slightly reduced collagen-induced aggregation and strongly inhibited dense granule secretion. Treatment of platelets with ONOO -(50-300 µM) resulted in decreased activities of NADH : ubiquinone oxidoreductase, succinate dehydrogenase and cytochrome oxidase. It is concluded that the inhibitory effect of ONOOon platelet secretion and to a lesser extent on aggregation may be mediated, at least in part, by the reduction of mitochondrial energy production.