Nicorandil Prevents Gα_q-Induced Progressive Heart Failure and Ventricular Arrhythmias in Transgenic Mice

<div><h3>Background</h3><p>Beneficial effects of nicorandil on the treatment of hypertensive heart failure (HF) and ischemic heart disease have been suggested. However, whether nicorandil has inhibitory effects on HF and ventricular arrhythmias caused by the activation of G protein alpha q (Gα_q) -coupled receptor (GPCR) signaling still remains unknown. We investigated these inhibitory effects of nicorandil in transgenic mice with transient cardiac expression of activated Gα_q (Gα_q-TG).</p> <h3>Methodology/Principal Findings</h3><p>Nicorandil (6 mg/kg/day) or vehicle was chronically administered to Gα_q-TG from 8 to 32 weeks of age, and all experiments were performed in mice at the age of 32 weeks. Chronic nicorandil administration prevented the severe reduction of left ventricular fractional shortening and inhibited ventricular interstitial fibrosis in Gα_q-TG. SUR-2B and SERCA2 gene expression was decreased in vehicle-treated Gα_q-TG but not in nicorandil-treated Gα_q-TG. eNOS gene expression was also increased in nicorandil-treated Gα_q-TG compared with vehicle-treated Gα_q-TG. Electrocardiogram demonstrated that premature ventricular contraction (PVC) was frequently (more than 20 beats/min) observed in 7 of 10 vehicle-treated Gα_q-TG but in none of 10 nicorandil-treated Gα_q-TG. The QT interval was significantly shorter in nicorandil-treated Gα_q-TG than vehicle-treated Gα_q-TG. Acute nicorandil administration shortened ventricular monophasic action potential duration and reduced the number of PVCs in Langendorff-perfused Gα_q-TG mouse hearts. Moreover, HMR1098, a blocker of cardiac sarcolemmal K_ATP channels, significantly attenuated the shortening of MAP duration induced by nicorandil in the Gα_q-TG heart.</p> <h3>Conclusions/Significance</h3><p>These findings suggest that nicorandil can prevent the development of HF and ventricular arrhythmia caused by the activation of GPCR signaling through the shortening of the QT interval, action potential duration, the normalization of SERCA2 gene expression. Nicorandil may also improve the impaired coronary circulation during HF.</p>