Local Action of Neprilysin Exacerbates Pressure Overload Induced Cardiac Remodeling

NEP (Neprilysin) degrades natriuretic peptides, and its inhibition is a clinically accepted target for heart failure treatment. NEP is widely expressed in various organs, including the heart. However, the pathophysiological significance of local cardiac NEP is not fully understood. To study the local function of NEP in the heart, we generated transgenic mice overexpressing NEP, specifically in cardiomyocytes (CM-NEP Tg). At baseline, CM-NEP Tg mice showed significantly lower levels of plasma ANP (atrial natriuretic peptide), plasma cGMP, and cardiac tissue cGMP versus wild-type (WT) mice. Blood pressure, heart weight, and cardiomyocyte diameter were greater in CM-NEP Tg than WT mice. There were no significant differences in interstitial fibrosis or ejection fraction. Transverse aortic constriction (TAC) surgery significantly increased left ventricular weight in WT and CM-NEP Tg mice 3 weeks post-op versus sham surgery; however, the cardiac hypertrophic response to TAC was higher in CM-NEP Tg than WT mice. Cardiac interstitial fibrosis was induced in TAC CM-NEP Tg mice, whereas TAC WT mice had none. TAC CM-NEP Tg, but not TAC WT, mice developed cardiac dysfunction secondary to TAC with echocardiography. Furthermore, administration of human ANP to raise plasma ANP levels comparable to those in WT mice neither improved the exacerbated cardiac hypertrophy and fibrosis nor recovered impaired cardiac function in CM-NEP Tg mice after TAC. In conclusion, overexpression of NEP in cardiomyocytes promoted degradation of natriuretic peptides in the heart and led to an exaggerated response of hypertrophy and fibrosis to pressure overload.