ACE2 gene combined with exercise training attenuates central AngII/AT1 axis function and oxidative stress in a prehypertensive rat model

Abstract

Angiotensin-converting enzyme 2 (ACE2) or exercise training (ExT) is beneficial to hypertension, but their combined effects remain unknown. In this study, lentivirus containing enhanced green fluorescent protein (eGFP) and ACE2 were microinjected into the paraventricular nucleus (PVN) of young male spontaneous hypertensive rats (SHRs), and SHRs were assigned into five groups: sedentary (SHR), SHR-ExT, SHR-eGFP, ACE2 gene (SHR-ACE2), and ACE2 gene combined with ExT (SHR-ACE2-ExT). Wistar-Kyoto (WKY) rats were used as a control. ACE2 gene or ExT significantly delayed the elevation of blood pressure, and the combined effect prevented the development and progression of prehypertension. Either ACE2 overexpression or ExT improved arterial baroreflex sensitivity (BRS), whereas the combined effect normalized BRS in SHR. Compared with SHR, SHR-ACE2 and SHR-ExT displayed a significantly higher level of ACE2 protein but had lower plasma norepinephrine (NE) and angiotensin II (AngII) as well as angiotensin II type 1 receptor (AT1) protein expression in the PVN. SHR-ACE2-ExT showed the largest decrease in AngII and AT1 protein expression. Reactive oxygen species (ROS) level and NADPH oxidase (NOX2 and NOX4) protein expression in PVN were also decreased in SHR-ACE2-ExT group than in SHR-ACE2 and SHR-ExT groups. It was concluded that the combined effect has effectively prevented prehypertension progression and baroreflex dysfunction in SHR, which is associated with the reduction in AngII/AT1 axis function and oxidative stress in the PVN.NEW & NOTEWORTHY Angiotensin-converting enzyme 2 (ACE2) gene in combination with exercise training (ExT) delayed the progression of hypertension via normalizing the blunted baroreflex sensitivity (BRS) and inhibiting sympathetic nerve activity (SNA). Its underlying mechanism may be related to the inhibition of AngII/AT1 axis function and central oxidative stress in the paraventricular nucleus (PVN) of prehypertensive rats.

Keywords: baroreflex; exercise training; hypertension; paraventricular nucleus; renin-angiotensin system.

Graphical abstract

Figure 1.

Effects of ACE2 gene, exercise training (ExT), and combined intervention on systolic blood pressure (SBP) among groups. SBP was monitored before paraventricular nucleus (PVN) microinjection, 4 wk, and 8 wk after the intervention. The effect of ACE2 gene (A), ExT (B), the combined effects of angiotensin-converting enzyme 2 (ACE2) with ExT (C and D) compared with the Wistar–Kyoto (WKY) rats or spontaneous hypertensive rats (SHRs). Data are represented as means ± SD, n = 8–10/group. *P < 0.01 vs. WKY; #P < 0.01 vs. SHR; &P < 0.05, $P < 0.05 vs. SHR-ExT. Two-way analysis of variance (ANOVA) followed by Student–Newman–Keuls (SNK) post hoc test.

Figure 2.

Effects of ACE2 gene, exercise training (ExT), and combined intervention on baroreflex sensitivity (BRS) and plasma norepinephrine (NE) among groups. A: BRS is calculated by a ratio of the change of heart rate to the change of mean arterial pressure induced by bolus phenylephrine, n = 5 or 6/group. B: plasma NE level is determined by ELISA, n = 4/group. Data are represented as means ± SD, *P < 0.05, **P < 0.01 was considered statistically significant.

Figure 3.

Effects of ACE2 gene, exercise training (ExT), and combined intervention on paraventricular nucleus (PVN) angiotensin II (AngII)/angiotensin II type 1 receptor (AT1) axis function among groups. A: angiotensin II (AngII) level. Western blot analyses (B–D) revealed the protein levels of angiotensin II type 1 receptor (AT1) and angiotensin-converting enzyme 2 (ACE2) protein expression. The bars represent the relative protein quantification of renin-angiotensin system (RAS) (AT1 and ACE2) and were normalized to GAPDH expression and Wistar–Kyoto (WKY) group. Data are represented as means ± SD, n = 3 or 4/group, *P < 0.05, **P < 0.01 was considered statistically significant.

Figure 4.

Effects of ACE2 gene, exercise training (ExT), and combined intervention on paraventricular nucleus (PVN) oxidative stress among groups. A: representative microphotographs of reactive oxygen species (ROS) were detected by dihydroethidium (DHE) staining and displayed red color. Scale bar = 100 μm. B: bar represents the intensities of ROS staining. C and D: protein expression of NADPH oxidase (NOX2 and NOX4) in PVN. The bars represent the relative protein quantification of NADPH and were normalized to GAPDH expression and Wistar–Kyoto (WKY) group. Data are represented as means ± SD, n = 4/group *P < 0.01, **P < 0.001 was considered statistically significant.