Neuroprotective effect of an angiotensin receptor type 2 agonist following cerebral ischemia in vitro and in vivo

Primary cortical neurons were cultured from E17 C57Bl6 mouse embryos for 9 d, exposed to glucose deprivation for 24 h alone or with drug treatments, and percent cell survival assessed using trypan blue exclusion. Ischemic stroke was induced in adult male C57Bl6 mice by middle cerebral artery occlusion for 30 min, followed by reperfusion for 23.5 h. Neurological assessment was performed and then mice were euthanized and infarct and edema volume were analysed.During glucose deprivation, CGP42112 (1x10-8 M and 1x10-7 M) reduced cell death by ~30%, an effect that was prevented by the AT2R antagonist, PD123319 (1x10-6 M). Neuroprotection by CGP42112 was lost at a higher concentration (1x10-6 M) but was unmasked by co-application with the AT1R antagonist, candesartan (1x10-7 M). By contrast, Compound 21 (1x10-8 M to 1x10-6 M), a second AT2R agonist, had no effect on neuronal survival. Mice treated with CGP42112 (1 mg/kg i.p.) after cerebral ischemia had improved functional outcomes over vehicle-treated mice as well as reduced total and cortical infarct volumes.These results indicate that CGP42112 can directly protect neurons from ischemia-like injury in vitro via activation of AT2Rs, an effect opposed by AT1R activation at high concentrations. Furthermore, systemic administration of CGP42112 can reduce functional deficits and infarct volume following cerebral ischemia in vivo.Stroke is the world’s second most common cause of death and a leading cause of long-term disability in adults [1]. Currently, there are very few safe and effective treatment options available for patients following stroke [2] and hence there is a great need to develop new therapies that may improve stroke outcome. It is conceivable that targeting elements of the renin-angiotensin system (RAS) may provide neuroprotection prior to and/or following stroke [3-11].The major peptide of the RAS is angiotensin II (Ang II), which acts with equal affinity at two membrane-bound receptors, the angiotensin type 1