Role of PKA in the process of neonatal cardiomyocyte hypertrophy induced by urotensin II

Abstract

The model of urotensin II (UII)-induced cardiomyocyte hypertrophy has been widely used in studies on hypertrophy. However, the molecular mechanisms responsible for UII-induced cardiomyocyte hypertrophy have not yet been fully elucidated. It has been demonstrated that cardiomyocyte hypertrophy induced by UII is associated with changes in the intracellular Ca2+ concentration. In the present study, we investigated whether the cAMP-dependent protein kinase A (PKA)-mediated upregulation of the phosphorylation levels of phospholamban (PLN) at Ser16 contributes to UII-induced cardiomyocyte hypertrophy. After primary cultures of neonatal rat cardiomyocytes were exposed to UII for 48 h, cell size, protein/DNA contents and intracellular Ca2+ levels were detected. Western blot analysis was used to quantify the phosphorylated and total forms of PKA, PLN and the total amount of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA)2a. UII increased the cell size, the protein/DNA ratio and the intracellular Ca2+ levels, consistent with the characteristics of hypertrophic response. In addition, exposure to UII upregulated the phosphorylation levels of PKA, and the expression levels of its downstream proteins, PLN and SERCA2a. However, treatment with PKA inhibitor (KT-5720) reversed all these effects of UII. On the whole, our results suggest that UII induces cardiomyocyte hypertrophy through the PKA-mediated upregulation of PLN phosphorylation at Ser16, which provides a new experimental foundation for the prevention and/or treatment of cardiac hypertrophy.