The ACE2-Ang (1-7)-Mas receptor axis attenuates cardiac remodeling and fibrosis in post-myocardial infarction

Abstract

Myocardial remodeling serves an important role in the pathophysiology of coronary heart disease. The angiotensin-converting enzyme (ACE)2-angiotensin-(1-7) [Ang (1‑7)]‑Mas receptor (MasR) axis is a key regulator in myocardial remodeling and development of heart failure. To investigate how ACE2‑Ang‑(1‑7)‑MasR axis function on myocardial remodeling and cardiac fibrosis in post‑myocardial infarction (MI), male Sprague‑Dawley rats (weight, 200±20 g) were used to establish the model of myocardial infarction by ligating the left coronary artery. The present study suggests that telmisartan (Tel) and olmesartan (Olm) (5 mg/kg/d) can inhibit myocardial remodeling of post‑myocardial infarction through the ACE2‑Ang (1‑7)‑MasR pathway. Administration of Tel or Olm was demonstrated to significantly inhibit collagen deposition using Masson staining. In addition, telmisartan and olmesartan was indicated to antagonize angiotensin II (Ang II) and upregulate ACE2, MasR, Ang (1‑7) expression in myocardial tissue using immunoassay and ELISA test, and the effect of Olm was more marked than that of Tel at the same dosage. Simultaneously, compared with the MI or Sham group, the mRNA and protein expression of ACE2, Ang II and MasR in myocardial tissue demonstrated a remarkable increase in the Olm group, when compared with the Tel group. Taken together, our data demonstrated that ACE2‑Ang (1‑7)‑MasR axis may present a potential protective role in the development of myocardial remodeling and may provide a new target for drug development of cardiac fibrosis. In conclusion, Olm is superior to Tel in inhibiting myocardial local Ang II level reducing myocardial collagen deposition and improving myocardial remodeling by upregulating the expression of ACE2, Ang (1‑7) and MasR.

Figure 1.

Collagen deposition in post-myocardial infarction. (A) Myocardial Masson staining of each group. Normal myocardium is presented in red, and cellulose is presented in blue (magnification, ×400). (B) CVF in sham, MI, Tel and Olm groups. *P<0.05 vs. sham group; ^&P<0.05 vs. Tel group; ^#P<0.05 vs. MI group. (n=10 each group). CVF, collagen volume fraction; MI, myocardial infarction; Tel, telmisartan (5 mg/kg); Olm, olmesartan (5 mg/kg); CVF, collagen volume fraction.

Figure 2.

Ang (–7) and Ang II level. (A) The plasma level of Ang II. (B) The plasma level of Ang (–7). *P<0.05 vs. sham group; ^#P<0.05 vs. MI group; ^&P<0.05 vs. Tel group. Ang, angiotensin.

Figure 3.

Immunohistochemical determination of myocardial ACE-2, Ang (–7), MasR and Ang II. (A) Light microscopic images of Ang II immunohistochemical labeling (brown staining) of cardiomyocytes in left ventricle. (B) Light microscopic images of ACE2 immunohistochemical labeling (brown staining) of cardiomyocytes in left ventricle. (C) Light microscopic images of Ang (–7) immunohistochemical labeling (brown staining) of cardiomyocytes in left ventricle. (D) Light microscopic images of MasR immunohistochemical labeling (brown staining) of cardiomyocytes in left ventricle. Scale bar = 200 µm; magnification, ×100. Data are expressed as means ± standard error of the mean. *P<0.05 vs. sham group; ^#P<0.05 vs. MI group; ^&P<0.05 vs. Tel group (n=10 each group). ACE2, angiotensin-converting enzyme 2; Ang, angiotensin; MasR, Mas receptor; MI, myocardial infarction; Tel, telmisartan (5 mg/kg); Olm, olmesartan (5 mg/kg).

Figure 4.

The protein expression of ACE2, MasR, Ang II Collagen I and Collagen III in myocardial tissue. Myocardial tissue homogenates from MI group or Tel treatment were subjected to SDS-PAGE. The non-responsive gene β-actin is shown as loading control. (A) Quantitative analysis of Ang II protein expression. (B) Quantitative analysis of ACE2 protein expression. (C) Quantitative analysis of Mas protein expression. (D) Quantitative analysis of Collagen I protein expression. (E) Quantitative analysis of Collagen III protein expression. *P<0.05 vs. sham group. ^#P<0.05 vs. MI group; ^&P<0.05 vs. Tel group (n=10 each group). ACE2, angiotensin-converting enzyme 2; MasR, Mas receptor; Ang, angiotensin; Tel, telmisartan (5 mg/kg); Olm, olmesartan (5 mg/kg).

Figure 5.

The mRNA expression of ACE2, MasR and Ang II in myocardial tissue. (A and C) Cardiac ACE2 mRNA, (A and D) MasR mRNA and (A and B) Ang II mRNA. (A) sham operation group; (B) MI group; (C) Tel group (5 mg/kg); (D) Olm group (5 mg/kg). *P<0.05 vs. sham group; ^#P<0.05 vs. MI group; ^&P<0.05 vs. Tel group (n=10 each group). ACE2, angiotensin-converting enzyme 2; MasR, Mas receptor; Ang, angiotensin; Tel, telmisartan (5 mg/kg); Olm, olmesartan (5 mg/kg).