Angiotensin-(1-7) inhibits autophagy in the brain of spontaneously hypertensive rats

Abstract

Autophagy is an important cellular process that mediates lysosomal degradation of damaged organelles, which is activated in response to a variety of stress-related diseases, including hypertension. The basal level of autophagy plays an important role in the maintenance of cellular homeostasis, whereas excessive autophagic activity leads to cell death and is considered as a contributing factor to several disorders. Recent works have demonstrated that Angiotensin-(1-7) [Ang-(1-7)] exerted its neuroprotective effects by modulating classic components of renin-angiotensin system associated with reducing oxidative stress and apoptosis in brains of spontaneously hypertensive rats (SHRs). However, the effect of Ang-(1-7) on autophagic activity in brain of hypertensive individual remains unclear. In this study, Wistar-Kyoto rats received intracerebroventricular (I.C.V.) infusion of artificial cerebrospinal fluid (aCSF) while SHRs received I.C.V. infusion of aCSF, Ang-(1-7), Mas receptor antagonist A-779, or angiotensin II type 2 receptor antagonist PD123319 for 4 weeks. Brain tissues were collected and analyzed by western blotting analysis, immunofluorescence assay, and transmission electron microscopic examination. Our study showed that infusion of Ang-(1-7) for 4 weeks inhibited the increase of microtubule-associated protein 1 light chain 3 (LC3)-II and Beclin-1 levels, as well as the autophagosome formation in SHR brain. Meanwhile, the reduction of p62 expression in SHR brain was also reversed by Ang-(1-7). Of note, the anti-autophagic effects of Ang-(1-7) were independent of blood pressure reduction and can be inhibited by A-779 and PD123319. These findings suggest that treatment with Ang-(1-7) may be useful to prevent hypertension-induced excessive autophagic activation in brain.