Effect And Mechanism Of Exercise Preconditioning On Cognitive Impairment After Cerebral Ischemia-reperfusion In Mice

Objective:Post-stroke cognitive impairment(PSCI)is one of the negative outcomes of stroke and has become the leading cause of physical disability in adults worldwide.Studies have shown that exercise preconditioning(EP)is an effective means of ameliorating PSCI,but its modulation of cognitive function has not been fully elucidated.This study focuses on the effects of exercise on cognitive function during the promotion of PSCI and the role and mechanisms of the microbiota-gutinflammasome-brain axis in the promotion of PSCI by exercise.Methods:C57BL/6J mice(males)were randomly divided into 4 groups(n=12):sham operation(sham control,Sham)group:only the right common carotid artery,internal and external carotid arteries were separated without ligation.Middle cerebral artery occlusion(MCAO)group:MCAO was performed to render the right brain tissue ischaemic for 90 min,then the plug was removed to allow reperfusion for 24 h.Exercise preconditioning+sham control(EP+Sham)group:mice were autonomously runwheeled for 4 weeks before the sham operation.Exercise preconditioning+middle cerebral artery occlusion(EP+MCAO)group:mice were autonomously run-wheeled for 4 weeks before the MCAO operation.The internationally accepted Longa plug method was used to establish the cerebral ischemia-reperfusion model.After successful modelling,the mice were scored for neurological function according to Longa and those with a score of 1-3 were selected for subsequent experiments.Then using the new object recognition test and the Y-maze test were used to test the non-spatial and spatial recognition memory abilities of the mice respectively.TTC staining and HE staining were used to observe the area of cerebral infarction and the extent of neuronal damage in the hippocampal region in each group of mice.Western blot assay was performed to detect the expression levels of NLRP3,Caspase-1,IL-1β and IL-18 in brain tissue.ELISA assay was performed to detect the levels of serum IL-1β and IL-18.The 16S rRNA high throughput sequencing technique was used to sequence the gut microbiota of mice.Results:The neurological function scores of mice in the Sham and EP+Sham groups were 0 and the neurological function was basically normal;the neurological function scores of the MCAO and EP+MCAO groups were significantly higher(P<0.01),and the scores of the EP+MCAO group were lower compared to the MCAO group(P<0.05).Compared with the MCAO group,object recognition index and spontaneous alternation rate were increased in the EP+MCAO group(P<0.05),and cognitive function was improved in mice with cerebral ischemia-reperfusion pretreated with exercise.The results of TTC staining showed that the brain tissues of both MCAO and EP+MCAO groups showed obvious white infarct areas(P<0.01),and the area of brain infarction was reduced in the EP+MCAO group compared with the MCAO group(P<0.01).The neuronal cells in the hippocampal region of the mice in the MCAO group were disorganized and structurally destroyed as observed by HE staining,while the cell damage in the mice in the EP+MCAO group was improved.Compared with the Sham group,the protein expression of NLRP3 and inflammatory factors Caspase-1,IL-1βand IL-18 were increased in the ischemic side of the brain tissue of mice in the MCAO group(P<0.05);compared with the MCAO group,the protein expression of NLRP3 and inflammatory factors Caspase-1,IL-1β and IL-18 were decreased in the ischemic side of the brain tissue of mice in the EP+MCAO group(P<0.05).The distribution of gut microbiota was significantly altered in the MCAO group,and Chaol and Faith’s PD indexes were increased in the MCAO group compared with the Sham group(P<0.05);exercise preconditioning could reshape the structure of the gut microbiota of mice with cerebral ischemia-reperfusion at the level of β-diversity.The abundance of Helicobacter at the genus level was significantly increased after ischemia-reperfusion,and exercise preconditioning increased the relative abundance of beneficial bacteria Lactobacillus and Alistipes significantly at the genus level.Conclusion:1.Exercise preconditioning reduces neurological function scores in mice with cerebral ischemia reperfusion,attenuates brain damage on the ischemic side,downregulates NLRP3 inflammasome in brain tissue as well as in serum,and improves post-stroke cognitive impairment.2.Exercise preconditioning alters the number and structure of the gut microbiota and restores gut microbiota distribution in mice with cerebral ischemia reperfusion.3.Exercise preconditioning may exert a protective effect on cognitive function after ischemic stroke by modulating microbiota-gut-inflammasome-brain axis,improving the inflammatory response and reshaping the gut microbiota structure.