Background:
Recent studies show that pharmacological induction of the angiotensin converting enzyme 2/angiotensin-(1-7)/mas [ACE2-Ang-(1-7)-Mas] axis, a protective pathway of the renin angiotensin system, elicits neuroprotection in ischemic stroke. However, endogenous levels and activity of the components of this axis in the brain and serum following stroke are not well established. Here, we assessed the post-stroke activity and expression of ACE2 in rat cerebral cortex and serum after ischemic stroke in rats, in the absence or presence of an ACE2 activator.
Methods:
Sprague Dawley rats underwent sham surgery or endothelin-1-induced middle cerebral artery occlusion (ET-1 MCAO). Activity of ACE2 was analyzed within serum and cerebral cortical tissue samples using a fluorometric assay, and mRNA levels were assessed by qRT-PCR. In an additional experiment, rats received daily intraperitoneal administration of diminazene aceturate (DIZE), a putative ACE2 activator, or vehicle after ET-1 MCAO. Data are normalized to corresponding control values and expressed as means ± SEM with a significance of p<0.05.
Results:
ACE2 activity levels were significantly increased in ischemic brain cortex at 4, 12, and 24 h after a stroke (4h: 237.1±46.1%; 12h: 212.4±12.8%; 24h: 191.6±19.1%) versus rats with sham strokes. Paradoxically, there was a significant decrease in ACE2 mRNA levels in the ischemic cortex at 24h (0.71±0.1) compared to shams (1.0±0.08). After decreasing in activity at 4h after stroke, serum ACE2 activity was increased at 24h in stroked rats (96.08±9.4%) versus shams (70.80±7.1%). Post-stroke treatment with DIZE (7.5 mg/kg) resulted in significantly increased ACE2 activity in serum (213.7±49.8%) versus controls, two days following stroke.
Conclusions:
Activity of the protective enzyme ACE2 is increased in rat cerebral cortex following stroke, with a rebound increase in serum activity. Post-stroke treatment with an ACE2 activator resulted in significantly increased ACE2 activity in serum. These results suggest that stroke therapeutics designed to target the ACE2/Ang-(1-7)/Mas axis may act in synergy with endogenous changes in the acute post-stroke setting, lending promise to their further study as potential neuroprotective agents.
Decision letter for "Insight into the molecular sex dimorphism of ischemic stroke in rat cerebral cortex: focus on neuroglobin, sex steroids and autophagy"