Neuronostatin Attenuates Myocardial Contractile Function through Inhibition of Sarcoplasmic Reticulum Ca²⁺-ATPase in Murine Heart

BACKGROUND/AIMS: Neuronostatin, derived from the somatostatin preprohormone, was recently identified to be produced by several tissues exerting a role in cardiovascular regulation and metabolism. Nonetheless, the precise mechanism behind neuronostatin-elicited myocardial responses remains elusive. METHODS: This study was designed to elucidate the impact of neuronostatin on cardiac contractile function and the underlying mechanism of action involved. Adult male C57 BL/6 mice were subjected to a bolus injection of neuronostatin (50 μg/kg, i.p.). Echocardiographic, cardiomyocyte contractile and intracellular Ca2+ handling properties were monitored to evaluate the effect of neuronostatin on cardiac function. Western blot analysis was used to examine potential signaling mechanisms involved. RESULTS: Neuronostatin administration suppressed myocardial and cardiomyocyte contractile function and disturbed intracellular Ca2+ homeostasis. We observed enlarged LVESD (with unchanged LVEDD), reduced fractional shortening, depressed peak shortening, maximal velocity of shortening/relengthening, resting and electrically-stimulated rise in intracellular Ca2+, and prolonged relengthening duration in hearts from neuronostatin-treated mice. These effects were accompanied by downregulation of phosphorylation of sarcoplasmic reticulum Ca2+- ATPase (SERCA) and phospholamban (PLB) and activation of AMPK. CONCLUSION: Our data suggest that the cardiac depressant properties of neuronostatin possibly associated with loss of SERCA phosphorylation and AMPK activation. These findings revealed a potent inhibitory capacity for neuronostatin on cardiac function, the physiological relevance of which deserves further study.