Cardiomyocyte Overexpression of Neuronal Nitric Oxide Synthase Delays Transition Toward Heart Failure in Response to Pressure Overload by Preserving Calcium Cycling

Abstract

Background— Defects in cardiomyocyte Ca 2+ cycling are a signature feature of heart failure (HF) that occurs in response to sustained hemodynamic overload, and they largely account for contractile dysfunction. Neuronal nitric oxide synthase (NOS1) influences myocyte excitation-contraction coupling through modulation of Ca 2+ cycling, but the potential relevance of this in HF is unknown. Methods and Results— We generated a transgenic mouse with conditional, cardiomyocyte-specific NOS1 overexpression (double-transgenic [DT]) and studied cardiac remodeling, myocardial Ca 2+ handling, and contractility in DT and control mice subjected to transverse aortic constriction (TAC). After TAC, control mice developed eccentric hypertrophy with evolution toward HF as revealed by a significantly reduced fractional shortening. In contrast, DT mice developed a greater increase in wall thickness ( P <0.0001 versus control+TAC) and less left ventricular dilatation than control+TAC mice ( P <0.0001 for both end-systolic and end-diastolic dimensions). Thus, DT mice displayed concentric hypertrophy with fully preserved fractional shortening (43.7±0.6% versus 30.3±2.6% in control+TAC mice, P <0.05). Isolated cardiomyocytes from DT+TAC mice had greater shortening, intracellular Ca 2+ transients, and sarcoplasmic reticulum Ca 2+ load ( P <0.05 versus control+TAC for all parameters). These effects could be explained, at least in part, through modulation of phospholamban phosphorylation status. Conclusions— Cardiomyocyte NOS1 may be a useful target against cardiac deterioration during chronic pressure-overload–induced HF through modulation of calcium cycling.