Neuronal NO synthase mediates plenylephrine induced cardiomyocyte hypertrophy through facilitation of NFAT-dependent transcriptional activity.

Neuronal nitric oxide synthase (NOS1) has been consistently shown to be the predominant isoform of NOS and/or NOS-derived NO that may be involved in the myocardial remodeling including cardiac hypertrophy. However, the direct functional contribution of NOS1 in this process remains to be elucidated. Therefore, in the present study, we attempted to use silent RNA and adenovirus mediated silencing or overexpression to investigate the role of NOS1 and the associated molecular signaling mechanisms during OKphenylephrine (PE)-induced cardiac hypertrophy growth in neonatal rat ventricular cardiomyocytes (NRVMs). We found that the expression of NOS1 was enhanced in PE-induced hypertrophic cardiomyocytes. Moreover, LVNIO treatment, a selective NOS1 inhibitor, significantly decreased PE-induced NRVMs hypertrophy and [H]-leucine incorporation. We demonstrated that NOS1 gene silencing attenuated both the increased size and the transcriptional activity of the hypertrophic marker atrial natriuretic factor (ANF) induced by PE stimulation. Further investigation suggested that deficiency of NOS1-induced diminished NRVMS hypertrophy resulted in decreased calcineurin protein expression and activity (assessed by measuring the transcriptional activity of NFAT) and, an increased activity of the anti-hypertrophic pathway, GSK-3β (estimated by its augmented phosphorylated level). In contrast, exposing the NOS1 overexpressed NRVMs to PE-treatment further increased the hypertrophic growth, ANF transcriptional activity and calcineurin activity. Together, the results of the present study suggest that NOS1 is directly involved in controlling the development of cardiomyocyte hypertrophy.