NPR-C (Natriuretic Peptide Receptor-C) Modulates the Progression of Angiotensin II–Mediated Atrial Fibrillation and Atrial Remodeling in Mice

Abstract

Background: Atrial fibrillation (AF) commonly occurs in hypertension and in association with elevated Ang II (angiotensin II) levels. The specific mechanisms underlying Ang II–mediated AF are unclear, and interventions to prevent the effects of Ang II are lacking. NPs (natriuretic peptides), which elicit their effects through specific NP receptors, including NPR-C (natriuretic peptide receptor-C), are cardioprotective hormones that affect cardiac structure and function. Methods: This study used wild-type and NPR-C knockout (NPR-C−/−) mice to investigate the effects of Ang II (3 mg/kg per day for 3 weeks) on AF susceptibility and atrial function using in vivo electrophysiology, high-resolution optical mapping, patch clamping, and molecular biology. In some experiments, wild-type mice were cotreated with Ang II and the NPR-C agonist cANF (0.07–0.14 mg/kg per day) for 3 weeks. Results: In wild-type mice, Ang II increased susceptibility to AF in association with a prolongation of P-wave duration, increased atrial refractory period, and slowed atrial conduction. These effects were exacerbated in Ang II–treated NPR-C−/− mice. Ang II prolonged action potential duration and reduced action potential upstroke velocity (Vmax). These effects were greater in left atrial myocytes from Ang II–treated NPR-C−/− mice. Ang II also increased fibrosis in both atria in wild-type mice, whereas Ang II–treated NPR-C−/− mice exhibited substantially higher fibrosis throughout the atria. Fibrotic responses were associated with changes in expression of profibrotic genes, including TGF&bgr; and TIMP1. Cotreating wild-type mice with Ang II and the NPR-C agonist cANF dose dependently reduced AF inducibility by preventing some of the Ang II–induced changes in atrial myocyte electrophysiology and preventing fibrosis throughout the atria. Conclusions: NPR-C may represent a new target for the prevention of Ang II–induced AF via protective effects on atrial electrical and structural remodeling.