NAKα2 inhibits fibrosis formation and protects against cardiomyocyte hypertrophy by suppressing hypertrophy associated molecules and activating LTCC/NCX signaling pathway.

Abstract

OBJECTIVE\nCardiomyocyte hypertrophy is considered to be a compensatory process of heart suffering from pathological damages. This study aimed to evaluate effects of Na+/K+ APTaseα2 (NAKα2) on isoprenaline (ISO) induced cardiomyocyte hypertrophy.\n\n\nMATERIALS AND METHODS\nMouse atrial cardiomyocytes were cultured and treated with ISO to establish cardiomyocyte hypertrophy model. NAKα2 over-expression and small interfere RNA (siRNA) plasmids were constructed and transfected to cardiomyocytes. Influx Ca2+ ([Ca2+]i) was measured using flow cytometry method. Fibrosis formation was examined with Masson staining. Transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining was used to examine apoptosis. Major histocompatibility complex β (β-MHC), atrial natriuretic peptides (ANP), B-type natriuretic peptides (BNP) were evaluated with quantitative Real-time PCR (qRT-PCR). Western blot was used to detect β-MHC, ANP, BNP, Na+/Ca2+ exchanger (NCX) and L-type calcium channel (LTCC).\n\n\nRESULTS\nNAKα2 significantly inhibited NCX and LTCC expression compared to that in ISO-treated cardiomyocytes (p<0.05). NAKα2 significantly suppressed expression of β-MHC, ANP and BNP compared to that in ISO-treated cardiomyocytes (p<0.05). NAKα2 significantly alleviated fibrosis formation and inhibited apoptosis compared to that in ISO-treated cardiomyocytes (p<0.05). NAKα2 reduced intracellular calcineurin and activated phosphorylation of calcineurin-nuclear factor of activated T cells (NFAT) compared to ISO-treated cardiomyocytes (p<0.05). NAKα2 significantly strengthened effects of Klotho on ISO-induced up-regulation of hypertrophy associated molecules (p<0.05) by activating LTCC and NCX. Comparing to ISO-treated cardiomyocytes, NAKα2 combining Klotho treatment exhibited significantly better improvement of Ca2+ influx, alleviation of fibrosis and reduction of apoptosis by triggering LTCC/NCX signaling pathway.\n\n\nCONCLUSIONS\nOver-expression of NKAα2 suppressed fibrosis formation and protected against cardiomyocyte hypertrophy by inhibiting hypertrophy associated molecules, alleviating apoptosis and activating LTCC/NCX signaling pathway.