The Role And Mechanisms Of Lipocalin2 And Astrocyte In Electroacupuncture Protection Against Depression And Cognitive Impairment Following Stroke

Background and Objective: Clinically,acute ischemic stroke(AIS)not only causes neurological sensory and motor dysfunction,it also leads to a series of post-stroke neuropsychological complications.Among them,post-stroke cognitive impairment(PSCI)is the most common type of neurological complications,while post-stroke depression(PSD)is the most common type of psychiatric complications.In most cases,PSCI and PSD occur together,and are extremely detrimental for the survival rate and functional recovery of stroke survivors.Currently,there are limited effective treatments for cognitive impairment and depression following ischemic stroke.Electroacupuncture(EA),as a combination of traditional chinese acupuncture therapy and modern electricity,has shown to be safe and efficacious for the treatment of PSCI and/or PSD in a number of clinical studies and meta-analyses.However,the mechanisms underlying the protective effects of EA on PSCI,PSD and their complications have not been elucidated.According to the previous studies by our group,EA protects against acute cerebral ischemia-reperfusion injury by modulating neuroinflammation in the brain.In addition,neurons,microglia and endothelial cells are involved in the effects of EA.However,as the most abundant glia cell type in the brain,astrocyte(AS)plays an essential role in memory function and emotional response,whether AS is involved in the protection of EA remains largely unknown.Therefore,with the aim of filling a gap in astrocytic involvement in post-stroke neuropsychiatric complications in EA,our present study focused primarily on the role and mechanism of astrocytes in PSCI and PSD with EA treatment.Methods: This study used C57/ B6 male mice,and the global cerebral ischemia-reperfusion(GCI/R)model was established by bilateral common carotid artery occlusion(BCCAO).Chronic spatial restraint(CSR)was used to simulate the post-stroke stress state.Firstly,the effects of EA treatment on post-stroke cognition and depressive-like behaviors were observed in mice with behavioral tests.Secondly,the effects of EA on inflammatory cytokines,Lipocalin2 protein(LCN2),astrocytic activation and polarization in the hippocampus were detected by ELISA,real-time PCR,Western blot and immunofluorescence.To explore the involvement of LCN2 in EA treatment on PSCI,adenovirus LCN2 overexpression were applied.Thirdly,the effects and mechanisms of EA treatment on PSD were studied by detecting neurons,synapse-related proteins,and astrocytic morphology in the prefrontal cortex(PFC)and hippocampus regions.Results: In the PSCI study,the results showed: 1.EA treatment in the early stages of GCI/R was effective in improving cognitive impairment after stroke in mice(P<0.05);2.EA was able to reduce levels of hippocampal neuroinflammation in mice with GCI/R(P<0.05);3.LCN2 in the hippocampus increased significantly after GCI/R,and early-EA treatment effectively reduced the expression of LCN2(P<0.05);4.LCN2 overexpression significantly attenuated the protective effects of EA on cognitive function and astrocyte activation as well as inflammatory-phenotype switch after stroke(P<0.05).The results of PSD research are as follows: 1.Anhedonia tested by the sucrose preference test was significantly improved by both sessions of EA therapy(P<0.05);However,the behavioral desperation detected by the forced swimming test can not be influenced by EA treatment(P>0.05);2.Electroacupuncture can systematically relieve post-stroke depressive-like behaviors(P<0.05);3.EA at the late stage had no significant effect on the number of hippocampal CA1 neurons(P > 0.05),but EA significantly inhibited the decreases in synapse-associated proteins(P<0.05).4.EA improves the morphological atrophy and reduction in the process complexity of astrocytes in PSD mice,and this protective role in maintaining the normal morphology of astrocytes may be closely related to the behavioral improvement.Conclusion: Early-EA treatment protects cognitive function after stroke is time interval-dependent;Modulating LCN2 and neuroinflammation,astrocyte activation and inflammatory phenotype polarization may be important mechanisms for EA treatment in improving cognitive impairments after stroke;Protecting synapse and inhibiting abnormal morphological changes in astrocytes may play essential role in the treatment of PSD by EA treatment.