Mechanical Stretch Induces Endothelial Nitric Oxide Synthase Gene Expression in Neonatal Rat Cardiomyocytes

Mechanical stretch leads to cardiac hypertrophy and may ultimately cause heart failure. However, the effect of mechanical stretch on gene induction in cardiomyocytes remains to be determined. In the present study, we compared transcript profiles of mechanically stretched neonatal rat cardiomyocytes with those of unstretched cells using cDNA microarrays. The microarrays contained probes for 480 known genes, including those involved in signal transduction, cell cycle regulation, the cytoskeleton and cell motility. Eighteen genes, including the eNOS gene, were identified as having significantly differential expression in response to mechanical stretch in cardiomyocytes. Northern and western blot analysis further quantified the expression of the eNOS gene. Mechanical stretch increased constitutive NOS activity and nitric oxide (NO) production. The NO donor s-nitroso-N- acetylpenicillamine (SNAP) inhibited mechanical stretch- stimulated protein synthesis, as measured by [H-3]-leucine uptake . In addition, cardiomyocytes were infected with adenoviral vectors encoding cDNA for eNOS (Ad-eNOS) and a phosphoglycerate kinase (PGK) empty vector (Ad-PGK). In contrast with Ad-PGK-infected cells, in cardiomyocytes infected with Ad-eNOS, there was increased calcium- dependent NOS activity and nitrite production. Cardiomyocytes infected with Ad-eNOS exhibited diminished mechanical stretch-stimulated protein synthesis. In contrast, in eNOS- knockdown cells, the increased eNOS protein levels and NOS activity induced by mechanical stretch were abolished, but protein synthesis was enhanced. The results of the present study indicate that eNOS gene expression is induced by mechanical stretch, leading to increased constitutive NOS activity and NO production, which may be a negative regulator in cardiomyocyte hypertrophy.