S-Glutathionylation Reshapes Our Understanding of Endothelial Nitric Oxide Synthase Uncoupling and Nitric Oxide/Reactive Oxygen Species-Mediated Signaling

Abstract

Oxidative stress has been shown to convert endothelial nitric oxide synthase (eNOS) from an NO-producing enzyme to an enzyme that generates superoxide, a process termed NOS uncoupling. This uncoupling of eNOS converts it to function as an NADPH oxidase with superoxide and hydrogen peroxide generation. eNOS uncoupling has been associated with many pathophysiologic conditions, such as heart failure, ischemia/reperfusion injury, hypertension, atherosclerosis, and diabetes. The mechanisms implicated in the uncoupling of eNOS include oxidation of the critical NOS cofactor tetrahydrobiopterin, depletion of l-arginine, and accumulation of methylarginines. All of these prior mechanisms of eNOS-derived reactive oxygen species formation occur primarily at the heme of the oxygenase domain and are blocked by heme blockers or the NOS inhibitor N-nitro-larginine methylester. Recently, we have identified another unique mechanism of redox regulation of eNOS through S-glutathionylation that was shown to be important in cell signaling and vascular disease. Herein, we briefly review the mechanisms of eNOS uncoupling as well as their interrelationships and the evidence for their importance in disease. Antioxid. Redox Signal. 14, 1769-1775. Oxidative stress has been shown to be of critical importance in the pathogenesis of a wide variety of disease processes including heart attack, stroke, diabetes, hypertension, cancer, excitotoxic brain injury, neurodegenerative disease, and the broad spectrum of inflammatory disease (35). Oxidative stress occurs in cells and tissues because of overproduction of superoxide (O 2 -) and its secondary oxidants that are formed from several sources, including NADPH oxidase, xanthine oxidase, and the mitochondrial electron transport chain (3,35,48,56). In addition, under some conditions, nitric oxide synthase (NOS) can become a source of O 2 - (15,31,36,43,49,50). Moreover, nitric oxide (NO) produced from NOS can react with O 2 -to generate the potent oxidant, peroxynitrite (ONOO -) (2, 46, 51, 54, 55). Endothelial NOS (eNOS) is responsible for the enzymatic generation of NO within the endothelium. eNOS is a homodimeric heme-containing enzyme that converts l-arginine and oxygen to l-citrulline, NO, and water, using NADPH as a source of reducing equivalents (36). This process involves the calcium/calmodulin-regulated transfer of electrons from NADPH through a flavin adenine dinucleotide (FAD)-and flavin mononucleotide (FMN)-containing reductase domain to the heme of the l-arginine-binding oxygenase domain, which also binds tetrahydrobiopterin (BH 4 ) (6, 30). In the absence of BH 4 , NO synthesis is abrogated, and instead, O 2 -is generated (43,50).NO is involved in a number of roles within the endothelium, regulating vascular tone, vascular growth, platelet aggregation, and modulation of inflammation (23,29,32). As such, endothelial dysfunction produced by a decrease in bioavailable NO is a characteristic feature in many disease states, and one of the mechanisms underlying this dysfunction is th...

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

“…Likely candidates for participation in sulfate synthesis include cys-184, the axial ligand to the heme iron in the oxygenase domain, the cys-94 and cys-99 residues from each chain that form the Zn tetrathiolate group, or cys-689 and cys-908, located near the FAD-and FMN-binding regions. Cys-689 and cys-908 have recently been shown to undergo S-glutathionylation by oxidized glutathione (GSSG), resulting in eNOS uncoupling and superoxide generation in the reductase domain [67,68]. The next proposed step in our mechanistic scheme involves photocatalyzed reaction of the eNOS cys-persulfide intermediate with superoxide and water to generate sulfite and restore the cys residue to the thiol form ( Figure 1).…”

Subcellular Localization of Oxidants and Redox Modulation of Endothelial Nitric Oxide Synthase

“…83 Oxidant stress generated through the S-glutathionylation reaction is not inhibited by competitive inhibitors of the NOS substrate L-arginine. 84 The relevance of this pathway has been studied in Wistar rats, in which S-glutathionylation is associated with impaired endothelium-dependent vasodilation. 85 …”

Endothelial Monocyteactivating Factor Ii Cancels Oxidative Stress, Сonstitutive Nos Uncoupling and Induced Violations of Cardiac Hemodynamics in Hypertension (Part Ii)

“…В умовах окисного стресу відбувається глутатіонування SH-груп цистеїну в молекулі ендотеліальної NOS (еNOS) окисненим глутатіоном, що і спричи-няє її неспряження [1][2][3]. Дані останніх дос-лід жень свідчать, що неспряження еNOS мо же бу ти також результатом впливу активованих при запаленні моноцитів [4].…”