Microglial AT1R Conditional Knockout Ameliorates Hypoperfusive Cognitive Impairment by Reducing Microglial Inflammatory Responses

•Hippocampal microglial AT1R may contribute to cognitive impairment caused by CCH.•Microglial AT1R cKO can reduce microglial inflammatory responses and activation.•Candesartan may be a feasible drug for ameliorating cognitive impairments.•Ctss, Fcer1g, Tyrobp play an essential role in cognitive impairment caused by CCH. Chronic cerebral hypoperfusion (CCH) can cause vascular cognitive impairment and dementia. AT1R, angiotensin II type I receptor, plays a vital role in central nervous system pathologies, but its concrete function in vascular dementia is still unclear. Herein, we investigated the effects of AT1R during CCH by conditional knockout of the microglial AT1R and candesartan treatment. Using the bilateral carotid artery stenosis (BCAS) model, we found that the AT1R is crucial in exacerbating CCH-induced cognitive impairment via regulating microglial activation. The levels of AT1R were increased in the hippocampus and the hippocampal microglia after CCH induction. Microglial AT1R conditional knockout ameliorated cognitive impairment by reducing inflammatory responses and microglial activation, and so did candesartan treatment. However, we observed restoration of cerebral blood flow (CBF) but no significant neuronal loss in the hippocampus at 28 days after BCAS. Finally, we screened three hub genes (Ctss, Fcer1g, Tyrobp) associated with CCH. Our findings indicated that microglial expression of AT1R is critical for regulating neuroinflammation in CCH, and AT1R antagonism may be a feasible and promising method for ameliorating CCH-caused cognitive impairment.