Regulation of cardiac remodeling by nitric oxide: focus on cardiac myocyte hypertrophy and apoptosis.

Cardiac hypertrophy occurs in pathological conditions associated with chronic increases in hemodynamic load. Although hypertrophy can initially be viewed as a salutary response, ultimately, it often enters a phase of pathological remodeling that may lead to heart failure and premature death. A prevailing concept predicts that changes in gene expression in hypertrophied cardiac myocytes and cardiac myocyte loss by apoptosis contribute to the transition from hypertrophy to failure. In recent years, nitric oxide (NO) has emerged as an important regulator of cardiac remodeling. Specifically, NO has been recognized as a potent antihypertrophic and proapoptotic mediator in cultured cardiac myocytes. Studies in genetically engineered mice have extended these findings to the in vivo situation. It appears that low levels and transient release of NO by endothelial NO synthase exert beneficial effects on the remodeling process by reducing cardiac myocyte hypertrophy, cavity dilation and mortality. By contrast, high levels and sustained production of NO by inducible NO synthase seem to be maladaptive by reducing ventricular contractile function, and increasing cardiac myocyte apoptosis, and mortality. In the future, these novel insights into the role of NO in cardiac remodeling should allow the development of novel therapeutic strategies to treat cardiac remodeling and failure.