Inhibition of platelet aggregation by S-nitroso-cysteine via cGMP-independent mechanisms: evidence of inhibition of thromboxane A 2 synthesis in human blood platelets

Abstract

S-Nitroso-cysteine (SNC), a putative endothelium-derived relaxing factor, potently inhibited collagen- and arachidonic acid-induced platelet aggregation (IC 50=100 nM) and thromboxane A 2 (TxA 2) synthesis of human blood platelets. ODQ, a selective inhibitor of the soluble guanylyl cyclase, inhibited SNC-induced formation of cGMP but did not reverse inhibition by SNC of collagen- and arachidonic acid-induced platelet aggregation. Combination of ODQ with SQ-29548, a specific platelet TxA 2 receptor antagonist, did not modify the antiaggregatory action of SNC. Our study shows that SNC inhibits platelet aggregation by cGMP-independent mechanisms that may involve inhibition of TxA 2 synthesis in human platelets.