Activation of the ACE2/Ang-(1–7)/Mas pathway reduces oxygen–glucose deprivation-induced tissue swelling, ROS production, and cell death in mouse brain with angiotensin II overproduction

Abstract

We previously demonstrated that mice which overexpress human renin and angiotensinogen (R+A+) show enhanced cerebral damage in both in vivo and in vitro experimental ischemia models. Angiotensin converting enzyme 2 (ACE2) counteracts the effects of angiotensin (Ang-II) by transforming it into Ang-(1-7), thus reducing the ligand for the AT1 receptor and increasing stimulation of the Mas receptor. Triple transgenic mice, SARA, which specifically overexpress ACE2 in neurons of R+A+ mice were used to study the role of ACE2 in ischemic stroke using oxygen and glucose deprivation (OGD) of brain slices as an in vitro model. We examined tissue swelling, the production of reactive oxygen species (ROS), and cell death in cerebral cortex (CX) and the hippocampal CA1 region during OGD. Expression levels of NADPH oxidase isoforms, Nox2 and Nox4 were measured using western blots. Results show that SARA mice and R+A+ mice treated with the Mas receptor agonist Ang-(1-7) had less swelling, cell death, and ROS production in CX and CA1 areas compared to those in R+A+ animals. Treatment of slices from SARA mice with the Mas antagonist A779 eliminated this protection. Finally, western blots revealed less Nox2 and Nox4 expression in SARA mice compared with R+A+ mice both before and after OGD. We suggest that reduced brain swelling and cell death observed in SARA animals exposed to OGD results from diminished ROS production coupled with lower expression of NADPH oxidases. Thus, the ACE2/Ang-(1-7)/Mas receptor pathway plays a protective role in brain ischemic damage by counteracting the detrimental effects of Ang-II-induced ROS production.

Neuroprotective Mechanisms of the ACE2–Angiotensin-(1-7)–Mas Axis in Stroke

“…This hypothesis is supported by findings from multiple groups that axis activation resulted in upregulation of endothelial NOS (eNOS) and NO production in stroke [28,29, 30•, 54, 55], as well as improved endothelial function in spSHRs [56, 57]. It was very recently demonstrated that application of Ang-(1-7) into the RVLM resulted in complete attenuation of the detrimental stroke-induced pressor response as well as preventing increased heart rate [19].…”

“…Our group first used an ischemic stroke model of endothelin-1 (ET-1)-induced MCAO and found that rats that were infused centrally via the intracerebroventricular (ICV) route with Ang-(1-7) performed better on neurological function testing and had an ~50 % reduction in infarct sizes [24••, 25], which was prevented by co-administration of the Mas antagonist A-779, findings that have subsequently been verified in models of permanent MCAO [26, 27••]. In a study using AngII-overexpressing mice subjected to permanent focal ischemic stroke, neuronal ACE2 overexpression resulted in similar cerebroprotection in vivo [28] and in vitro [29]. Additionally, lentiviral ACE2 priming of endothelial progenitor cells enhanced the ability of these cells to reduce infarct size and improve neurological function [30•].…”

“…These effects may be particularly relevant in the subacute period of stroke to limit excessive inflammatory cell infiltration across the compromised blood-brain barrier. In addition to reducing stroke infarct size, ACE2 overexpression in neurons of mice engineered to overproduce AngII resulted in attenuated levels of reactive oxygen species following stroke in vivo [28], in vitro [29], and in aged mice [31•], likely secondary to the observed reduction in NADPH oxidase levels. While it remains to be more clearly demonstrated, it is possible that the augmented activity of neuronal ACE2 in these mice may be exerting anti-oxidative effects indirectly through alterations in neuron-to-microglia signaling, possibly in a way that limits the activation of inflammatory microglia.…”

Neuroprotection by post‐stroke administration of an oral formulation of angiotensin‐(1–7) in ischaemic stroke

“…Activation of the latter pathway, the ACE2/Ang‐(1–7)/Mas axis, has indeed shown therapeutic promise in both ischaemic and haemorrhagic strokes, according to studies from independent groups of investigators using different models of stroke induction, as recently reviewed (Gironacci, Cerniello, Longo Carbajosa, Goldstein, & Cerrato, ; Regenhardt, Bennion, & Sumners, ). In each of those studies, Ang‐(1–7) was infused directly into the brain via the intracerebroventricular route, to circumvent the blood–brain barrier (Chen et al., ; Jiang et al, ; Jiang et al., ; Lu et al, ; Mecca et al., ; Regenhardt et al., ; Regenhardt & Mecca, et al., ; Zheng, Li, Chen, Bihl et al., ; Zheng, Li, Chen, Wang et al., ). Furthermore, intracerebroventricular infusion of the ACE2 activator diminazine aceturate (DIZE) also elicited significant neuroprotection (Mecca et al., ).…”

ACE2 and vasoactive peptides: novel players in cardiovascular/renal remodeling and hypertension

“…Ang-(1-7) induces regional and systemic vasodilation, diuresis and natriuresis, and also has antiproliferative and antimigratory effects on smooth muscle cells, cardiomyocytes, fibroblasts and glomerular cells. The cardioprotective effects of Ang-(1-7) are mediated by MasR to different signaling pathways involving MAPK, phosphoinositide 3-kinase (PI3K)/Akt and NADPH oxidase [Nemoto et al 2014;Zheng et al 2014]. The interaction Ang-(1-7)/MasR leads to activation of different effectors such as forkhead box protein O1 (FOXO1), COX-2 and vasodilator mediators such as prostanoids and NO.…”