Abstract 13167: S-Nitrosoglutathione Reductase Improves Cardiac Dysfunction in a Mouse Model of Sepsis
We tested the hypothesis that protein S-nitrosylation, a downstream signaling event induced by nitric oxide, is involved in the pathogenesis of sepsis-induced cardiac dysfunction. We generated novel transgenic mice overexpressing S-nitrosoglutathione reductase (GSNOR), an enzyme promoting protein denitrosylation, specifically in cardiomyocytes. As a model of sepsis, we used i.p. injection of 50 mg/kg of lipopolysaccharide (LPS). All analyses were performed at 6 h after injection. In vivo cardiac function was measured using echocardiography. Hearts isolated from mice challenged with LPS or vehicle were analyzed in a Langendorff setup to evaluate ex vivo cardiac function. Contractility and Ca2+ handling parameters were measured in cardiomyocytes isolated from mice challenged with LPS or vehicle. Protein S-nitrosylation was assessed using the biotin switch method. We found that GSNOR overexpressing (GSNOR-TG) hearts had a significantly improved ejection fraction in vivo as compared to wild-type (WT) hearts after LPS challenge (65.5±2.5 and 43.1±1.4%, respectively; P<0.001), while no difference was found at baseline (GSNOR-TG: 83.1±0.5, WT: 82.9±0.5%). We also observed that isolated GSNOR-TG hearts had improved contractility compared to WT hearts after LPS. Isolated GSNOR-TG cardiomyocyte showed significantly higher cell shortening than WT cells after LPS (at a 4 Hz pacing frequency: GSNOR-TG: 11.2±0.7%, WT: 8.0±0.7%; P<0.01), with no differences at baseline (GSNOR-TG: 13.6±0.4%, WT: 13.2±0.6%). However, we found that intracellular systolic Ca2+ transients were similarly depressed after LPS challenge in both genotypes (in nM, at 4 Hz after vehicle: GSNOR-TG: 144±15, WT: 131±9; after LPS: GSNOR-TG: 71±9, WT: 77±10), indicating an increase in Ca2+ sensitivity in GSNOR-TG after LPS. Finally, our results suggest a decrease in S-nitrosylation of both the ryanodine receptor and troponin C in GSNOR-TG mice after LPS. Taken together, our results indicate that cardiomyocyte-specific GSNOR overexpression protects against sepsis-induced cardiac dysfunction. This effect appears to be due to improved cardiomyocyte Ca2+ sensitivity during sepsis, associated with decreased levels of protein S-nitrosylation of key regulators of Ca2+ handling.
- © 2012 by American Heart Association, Inc.