Inhibition of Angiotensin-Converting Enzyme 2 Exacerbates Cardiac Hypertrophy and Fibrosis in Ren-2 Hypertensive Rats

BACKGROUND: Emerging evidence suggests that cardiac angiotensin-converting enzyme 2 (ACE2) may contribute to the regulation of heart function and hypertension-induced cardiac remodeling. We tested the hypothesis that inhibition of ACE2 in the hearts of (mRen2)27 hypertensive rats may accelerate progression of cardiac hypertrophy and fibrosis by preventing conversion of angiotensin II (Ang II) into the antifibrotic peptide, angiotensin-(1-7) (Ang-(1-7)). METHODS: Fourteen male (mRen2)27 transgenic hypertensive rats (12 weeks old, 401 + or - 7 g) were administered either vehicle (0.9% saline) or the ACE2 inhibitor, MLN-4760 (30 mg/kg/day), subcutaneously via mini-osmotic pumps for 28 days. RESULTS: Although ACE2 inhibition had no effect on average 24-h blood pressures, left ventricular (LV) Ang II content increased 24% in rats chronically treated with the ACE2 inhibitor (P < 0.05). Chronic ACE2 inhibition had no effect on plasma Ang II or Ang-(1-7) levels. Increased cardiac Ang II levels were associated with significant increases in both LV anterior, posterior, and relative wall thicknesses, as well as interstitial collagen fraction area and cardiomyocyte hypertrophy in the transgenic animals chronically treated with the ACE2 inhibitor. Cardiac remodeling was not accompanied by any further alterations in LV function. CONCLUSIONS: These studies demonstrate that chronic inhibition of ACE2 causes an accumulation of cardiac Ang II, which exacerbates cardiac hypertrophy and fibrosis without having any further impact on blood pressure or cardiac function.