S‐Nitrosylation of Prostacyclin Synthase Instigates Nitrate Cross‐Tolerance <i>In Vivo</i>

Abstract

Development of nitrate tolerance is a major drawback to nitrate therapy. Prostacyclin (PGI2) is a powerful vasodilator produced from prostaglandin (PGH2) by prostacyclin synthase (PGIS) in endothelial cells. This study aimed to determine the role of PGIS S‐nitrosylation in nitrate tolerance induced by nitroglycerin (GTN). In endothelial cells, GTN increased PGIS S‐nitrosylation and disturbed PGH2 metabolism, which were normalized by mutants of PGIS cysteine 231/441 to alanine (C231/441A). Clearance of nitric oxide by carboxy‐PTIO or inhibition of S‐nitrosylation by N‐acetyl‐cysteine decreased GTN‐induced PGIS S‐nitrosylation. Enforced expression of mutated PGIS with C231/441A markedly abolished GTN‐induced PGIS S‐nitrosylation and nitrate cross‐tolerance in Apoe ‐/‐ mice. Inhibition of cyclooxygenase 1 by aspirin, supplementation of PGI2 by beraprost, and inhibition of PGIS S‐nitrosylation by N‐acetyl‐cysteine improved GTN‐induced nitrate cross‐tolerance in rats. In patients, increased PGIS S‐nitrosylation was associated with nitrate tolerance. In conclusion, GTN induces nitrate cross‐tolerance through PGIS S‐nitrosylation at cysteine 231/441.