Absence in CX3CR1 receptor signaling promotes post-ischemic stroke cognitive function recovery through suppressed microglial pyroptosis in mice

Abstract

Background: Post-stroke cognitive impairment (PSCI) is a major source of morbidity and mortality after stroke, but the pathological mechanisms remain unclear. Previous studies have demonstrated that the CX3CR1 receptor plays a crucial role in maintaining an early protective microenvironment after stroke, but whether it persistently influences cognitive dysfunction in the chronic phase requires further investigation. Methods: Mouse was used to establish a middle cerebral artery occlusion (MCAO)/reperfusion model to study PSCI. Cognitive function was assessed by the Morris water maze (MWM) and the novel object recognition test. Neurogenesis was assessed by immunofluorescence staining with Nestin+/Ki67+ and DCX+/BrdU+ double-positive cells. The cerebral damage was monitored by [18F]-DPA-714 positron emission tomography, Nissel, and TTC staining. The pyroptosis was histologically, biochemically, and electron microscopically examined. Results: Upon MCAO, at 28 to 35 days, CX3CR1 knockout (CX3CR1−/−) mice had better cognitive behavioral performance both in MWM and novel object recognition test than their CX3CR1+/− counterparts. Upon MCAO, at 7 days, CX3CR1−/− mice increased the numbers of Nestin+/Ki67+ and DCX+/BrdU+ cells, and meanwhile it decreased the protein expression of GSDMD, NLRP3 inflammasome subunit, caspase-1, mature IL-1β/IL-18, and p-P65 in the hippocampus as compared with CX3CR1+/− mice. In addition, CX3CR1−/− mice could reverse infarct volume in the hippocampus region post-stroke. Conclusion: Our study demonstrated that CX3CR1 gene deletion was beneficial to PSCI recovery. The mechanism might lie in inhibited pyroptosis and enhanced neurogenesis. CX3CR1 receptor may serve as a therapeutic target for improving the PSCI.