Reduction of cardiomyocyteS-nitrosylation byS-nitrosoglutathione reductase protects against sepsis-induced myocardial depression

Abstract

Myocardial depression is an important contributor to morbidity and mortality in septic patients. Nitric oxide (NO) plays an important role in the development of septic cardiomyopathy, but also has protective effects. Recent evidence has indicated that NO exerts many of its downstream effects on the cardiovascular system via protein S-nitrosylation, which is negatively regulated by S-nitrosoglutathione reductase (GSNOR), an enzyme promoting denitrosylation. We tested the hypothesis that reducing cardiomyocyte S-nitrosylation by increasing GSNOR activity can improve myocardial dysfunction during sepsis. Therefore, we generated mice with a cardiomyocyte-specific overexpression of GSNOR (GSNOR-CMTg mice) and subjected them to endotoxic shock. Measurements of cardiac function in vivo and ex vivo showed that GSNOR-CMTg mice had a significantly improved cardiac function after lipopolysaccharide challenge (LPS, 50 mg/kg) compared with wild-type (WT) mice. Cardiomyocytes isolated from septic GSNOR-CMTg mice showed a corresponding improvement in contractility compared with WT cells. However, systolic Ca(2+) release was similarly depressed in both genotypes after LPS, indicating that GSNOR-CMTg cardiomyocytes have increased Ca(2+) sensitivity during sepsis. Parameters of inflammation were equally increased in LPS-treated hearts of both genotypes, and no compensatory changes in NO synthase expression levels were found in GSNOR-overexpressing hearts before or after LPS challenge. GSNOR overexpression however significantly reduced total cardiac protein S-nitrosylation during sepsis. Taken together, our results indicate that increasing the denitrosylation capacity of cardiomyocytes protects against sepsis-induced myocardial depression. Our findings suggest that specifically reducing protein S-nitrosylation during sepsis improves cardiac function by increasing cardiac myofilament sensitivity to Ca(2+).

Nitrosative Stress, Hypernitrosylation, and Autoimmune Responses to Nitrosylated Proteins: New Pathways in Neuroprogressive Disorders Including Depression and Chronic Fatigue Syndrome

“…Excessive O&NS also leads to the nitrosylation of crucial tyrosine residues on Trx and Trx1 [29,[87][88][89] leading to the inactivation of both enzymes. Excessive O&NS also leads to the depletion of reduced and oxidized glutathione, which also has serious consequences for levels of protein nitrosylation in a cellular environment [90].…”

“…RNS decreases GSH in the cellular pool, stabilizing SNO formation by reducing GSH-mediated transnitrosylation or denitrosylation [91,92]. The Snitrosoglutathione reductase pathway is a major player in maintaining SNO protein homeostasis by negatively regulating levels of protein nitrosylation [73,90]. However, this denitrosylation system is dependent on cellular levels of reduced glutathione, which initially acts as a NO sink.…”

S-Nitrosylation of Sarcomeric Proteins Depresses Myofilament Ca2+ Sensitivity in Intact Cardiomyocytes

“…Furthermore, in this case, low levels of protein S-nitrosylation can be protective against the deleterious effects of irreversible protein oxidation, which can occur during acute events of ischemia-reperfusion (32,55). However, at supraphysiological concentrations, for example, during sepsis (51), NO may cause an overload of protein Snitrosylation that substantially inhibits cardiac contractile properties (Fig. 9C).…”

How widespread is stable protein S-nitrosylation as an end-effector of protein regulation?

“…Cells also contain an S-nitrosoglutathione (GSNO) reductase (GSNOR) system comprising of GSH, GSNOR and GR [13,48]. GSNOR is thought to be the key enzyme in the regulation of plant Snitrosothiols, with some evidence that it plays the same role in mammals.…”

“…Many reviews ascribe S-nitrosothiols as end-effectors of NO signalling that contribute to homeostasis during health [6][7][8], with dysregulation of these processes contributing to disease pathogenesis. For example, hyper-or hypo-S-nitrosylation contributes to a range cardiovascular disease including type 1 and 2 diabetes [9], atherosclerosis [10], cardiac ischemic injury [11], hypertrophy [12] and sepsis [13].…”