Insulin-Regulated Aminopeptidase Deficiency Provides Protection against Ischemic Stroke in Mice

Recent studies have demonstrated that angiotensin IV (Ang IV) provides protection against brain injury caused by cerebral ischemia. Ang IV is a potent inhibitor of insulin-regulated aminopeptidase (IRAP). Therefore, we examined the effect of IRAP gene inactivation on neuroprotection following transient middle cerebral artery occlusion (MCAo) in mice. IRAP knockout mice and wild-type controls were subjected to 2 h of transient MCAo using the intraluminal filament technique. Twenty-four hours after reperfusion, neurological deficits of the stroke-induced mice were assessed and infarct volumes were measured by TTC staining. The cerebral infarct volume was significantly reduced in the IRAP knockout mice compared to wild-type littermates with corresponding improvement in neurological performance at 24 h post-ischemia. An increase in compensatory cerebral blood flow during MCAo was observed in the IRAP knockout animals with no differences in cerebral vascular anatomy detected. The current study demonstrates that deletion of the IRAP gene protects the brain from ischemic damage analogous to the effect of the IRAP inhibitor, Ang IV. This study indicates that IRAP is potentially a new therapeutic target for the development of treatment for ischemic stroke.