Abstract 19478: Endothelial and Cardiomyocyte -derived C-type Natriuretic Peptide Coordinate Heart Structure and Function

Abstract

Background: Endothelium-derived C-type natriuretic peptide (CNP) plays a key vascular homeostatic role governing vascular tone, blood pressure, leukocyte flux, platelet reactivity and the integrity of the vessel wall. However, relatively little is known about physiological role(s) for endogenous CNP in regulating cardiac structure and function. Herein, we have utilised novel mouse strains with endothelium or cardiomyocyte -specific deletion of CNP to determine if the peptide modulates heart function under basal conditions and during cardiac stress. Methods: Blood pressure and ECG were assessed by radiotelemetry. A Langendorff heart model was used to study coronary vascular reactivity and ischemia-reperfusion (I/R) injury ex vivo. Echocardiography was performed to determine cardiac function at baseline and following pressure overload (trans-aortic constriction; 6 weeks) -induced left ventricular hypertrophy/heart failure. Results: Hearts from endothelium-specific CNP knockout (ecCNP KO) mice exhibited smaller reductions in coronary perfusion pressure (CPP) compared to wildtype (WT) littermates in response to the vasodilators bradykinin (ΔCPP: WT=31.7±2.7%, KO=21.1±2.9%, n=8, p<0.05) and acetylcholine (ΔCPP: WT=36.4±4.4%, KO=18.5±3.8%, n=6, p<0.05). Shear-stress induced coronary dilatation (i.e. reactive hyperaemia) was also blunted in ecCNP KO hearts (AUC: WT=2804±280 [a.u.], KO=1493±280 [a.u.], n=8, p<0.05). Under basal conditions the heart rate (BPM: WT=605±5, KO 579±4, n=5, p<0.001) and contractility (QA interval; WT=13.7±0.1ms, KO=14.8±0.1ms, n=5, p<0.001) were significantly reduced in cardiomyocyte-specific CNP (cmCNP) KO mice compared to WT. Myocardial infarct size was larger in cmCNP KO following I/R injury ex vivo (Infarct size: WT=14.1±6.3%, KO=21.8±1.8 %, n=6, p<0.05). Furthermore, cmCNP KO mice exhibited greater cardiac dysfunction following pressure-overload (e.g. fractional shortening: WT=34.4±0.9%, KO=30.5±1.4%, n=8, p<0.05). Conclusion: These data suggest that CNP of endothelial and cardiomyocyte origin preserves cardiac function and morphology via the regulation of coronary vascular tone, heart rate, and myocardial contractility/hypertrophy.