Exercise Training Attenuates Right Ventricular Remodeling in Rats with Pulmonary Arterial Stenosis

Abstract

Introduction: Pulmonary arterial stenosis (PAS) is a congenital defect that causes outflow tract obstruction of the right ventricle (RV). Currently, negative issues are reported in the PAS management: not all patients may be eligible to surgeries; there is often the need for another surgery during passage to adulthood; patients with mild stenosis may have later cardiac adverse repercussions. Thus, the search for approaches to counteract the long-term PAS effects showed to be a current target. At the study herein, we evaluated the cardioprotective role of exercise training in rats submitted to PAS for 9 weeks. Methods and Results: Exercise resulted in improved physical fitness and systolic RV function. Exercise also blunted concentric cavity changes, diastolic dysfunction, and fibrosis induced by PAS. Exercise additional benefits were also reported in a pro-survival signal, in which there were increased Akt₁ activity and normalized myocardial apoptosis. These findings were accompanied by microRNA-1 downregulation and microRNA-21 upregulation. Moreover, exercise was associated with a higher myocardial abundance of the sarcomeric protein α-MHC and proteins that modulate calcium handling-ryanodine receptor and Serca 2, supporting the potential role of exercise in improving myocardial performance. Conclusion: Our results represent the first demonstration that exercise can attenuate the RV remodeling in an experimental PAS. The cardioprotective effects were associated with positive modulation of RV function, survival signaling pathway, apoptosis, and proteins involved in the regulation of myocardial contractility.

Keywords: artery pulmonary stenosis; cardiac hypertrophy; cardiac remodeling; exercise training; right ventricular hypertrophy.

Figure 1

Experimental design.

Figure 2

Exercise training improves functional fitness in animals with PAS. Data are representative of eight samples from each group in the baseline (filled columns) and at the end of the study (open columns). (A) Body weight. (B) Pressure gradient; (C) maximal oxygen uptake (VO₂max). ^#p < 0.001 vs. SHAM group for the respective time.

Figure 3

Effects of exercise training on right ventricular hypertrophy and fibrosis induced by PAS. (A) Echocardiographic analysis of eight samples from each group in the baseline (filled columns) and at the end of the study (open columns): RVDA, right ventricular diastolic area; RVSA, right ventricular systolic area; FAC, fractional area change; E/A ratio, ratio between the E and A waves. (B) RVMBW, right ventricular mass/body weight (SHAM, n = 5; SS, n = 6; TS, n = 6); CCA, cross-sectional cardiomyocyte area (SHAM, n = 3; SS, n = 4; TS, n = 5); (C) Representative photomicrographs of four samples from each group showing myocardial collagen on magnification ×40 (Scale bar, 250 μm). ^#p < 0.001 vs. SHAM group for the respective time. ^&p < 0.05 vs. SS group.

Figure 4

Exercise training modulates key components of the survival and mitochondrial apoptosis pathway in the RV myocardial on PAS. It is remarkable that activated form of Akt₁ (A: SHAM, n = 8; SS, n = 8; TS, n = 7) and anti-apoptotic Bcl-xL (B: SHAM, n = 8; SS, n = 6; TS, n = 7) were significantly up-regulated in the exercise animals. Moreover, a beneficial effect of exercise was observed for cleaved caspase-3 protein (B), in which indicates a myocardial apoptosis normalization. ^#p < 0.05 vs. SHAM group. ^&p < 0.01 vs. SS group.

Figure 5

Exercise training decreases microRNA-1 (A) and normalizes microRNA-21 (B) myocardial expression in PAS animals (SHAM, n = 4; SS, n = 6; TS, n = 6). All values were normalized for levels of U6 gene. ^#p < 0.001 vs. SHAM group. ^&p < 0.001 vs. SS group.

Figure 6

Exercise training modulates β-MHC and α-MHC isoform expression in myocardial. (A) Gene expression was evaluated by real-time PCR (SHAM, n = 4; SS, n = 6; TS, n = 6). (B) Protein expression was evaluated by Western blot (SHAM, n = 7; SS, n = 6; TS, n = 7). Values were normalized for levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). ^#p < 0.05 vs. SHAM group. ^&p < 0.01 vs. SS group.

Figure 7

Exercise training modulates myocardial calcium handling protein levels in PAS animals (SHAM, n = 8; SS, n = 8; TS, n = 7). Values were normalized for levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). ^#p < 0.05 vs. SHAM group. ^&p < 0.05 vs. SS group.