Antiplatelet Effect of Carbon Monoxide Is Mediated by NAD⁺ and ATP Depletion

Objectives: Carbon monoxide (CO) produced by haem oxygenases or released by CO-releasing molecules (CORM) affords antiplatelet effects, but the mechanism involved has not been defined. Here, we tested the hypothesis that CO-induced inhibition of human platelet aggregation is mediated by modulation of platelet bioenergetics. Approach and Results: To analyze the effects of CORM-A1 on human platelet aggregation and bioenergetics, a light transmission aggregometry, Seahorse XFe technique and liquid chromatography tandem-mass spectrometry-based metabolomics were used. CORM-A1-induced inhibition of platelet aggregation was accompanied by the inhibition of mitochondrial respiration and glycolysis. Interestingly, specific inhibitors of these processes applied individually, in contrast to combined treatment, did not inhibit platelet aggregation considerably. A CORM-A1-induced delay of tricarboxylic acid cycle was associated with oxidized nicotinamide adenine dinucleotide (NAD⁺) depletion, compatible with the inhibition of oxidative phosphorylation. CORM-A1 provoked an increase in concentrations of proximal (before GAPDH [glyceraldehyde 3-phosphate dehydrogenase]), but not distal glycolysis metabolites, suggesting that CO delayed glycolysis at the level of NAD⁺-dependent GAPDH; however, GAPDH activity was directly not inhibited. In the presence of exogenous pyruvate, CORM-A1-induced inhibition of platelet aggregation and glycolysis were lost, but were restored by the inhibition of lactate dehydrogenase, involved in cytosolic NAD⁺ regeneration, pointing out to the key role of NAD⁺ depletion in the inhibition of platelet bioenergetics by CORM-A1.

Conclusions: The antiplatelet effect of CO is mediated by inhibition of mitochondrial respiration-attributed to the inhibition of cytochrome c oxidase, and inhibition of glycolysis-ascribed to cytosolic NAD⁺ depletion.