Downregulation of Cytoskeletal Muscle LIM Protein by Nitric Oxide

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Abstract
Background— In chronic heart failure, myocardial expression of the inducible isoform of nitric oxide (NO) synthase (NOS2) is enhanced, leading to a sustained production of NO. We postulated that NO modulates expression of genes in cardiac myocytes that may be functionally important in the context of cardiac hypertrophy and failure. Methods and Results— As revealed by cDNA expression array analyses, the NO donor SNAP, which has been shown previously to inhibit agonist-induced cardiac myocyte hypertrophy, downregulates expression of the cytoskeleton-associated muscle LIM protein (MLP) in endothelin-1 (ET-1)–stimulated neonatal rat cardiac myocytes. Northern blotting and immunoblotting experiments confirmed this finding and established that SNAP negatively controls MLP mRNA (−49%, PPPConclusions— NO negatively controls MLP expression in cardiac myocytes. Because MLP is necessary and sufficient for hypertrophy and sarcomere assembly, MLP downregulation may restrain hypertrophic growth in pathophysiological situations with increased cardiac NO production.