Role Of Autophagy On Depression And Cognitive Impairment In Rats With Environmental Enrichment

Part I The effects of autophagy on the improvement of depression and cognitive impairment in chronic unpredictable mild stress(CUMS)-induced rats by environmental enrichment(EE)Backgroud and objective: With the increasing pressure,more and more people suffer from depression.Currently,drug treatment for depression is of limited effectiveness,and new drug development for a single target has not been effective.Therefore,it is considered as one of the potential ways to improve depressive symptoms by changing life behavior patterns.Rats exposed to CUMS are prone to depression and cognitive impairment.EE,a behavioral lifestyle intervention,has been shown to improve depression-like behavior and cognitive impairment in CUMS rats by inhibiting inflammation.However,the specific mechanism of how EE inhibits inflammatory response to improve depressive symptoms and cognitive impairment in CUMS rats has not been fully clarified.The purpose of this study was to investigate the effects of EE on depression and cognitive impairment induced by CUMS and its molecular mechanismMethods: The rats were randomly divided into 5 groups as follows :(1)Control +standard environment(SE),(2)CUMS + SE,(3)CUMS + EE,(4)CUMS + EE +3-methyladenine(3-MA),(5)CUMS + SE + 3-MA.CUMS program was performed for 5 weeks in all groups except Control + SE group.After the CUMS program,rats were fed in EE or SE for 3 weeks.Rats were injected daily with normal saline or3-MA during EE or SE treatment.Behavioral tests were used to study depression-like and cognitive-like behavior after EE treatment.Then,Western blot(WB)was used to determine the autophagy-related proteins and inflammation-related molecules,and ELISA was used to measure the contents of pro-inflammatory cytokines.The structure and level of autolysosome were observed by transmission electron microscopy(TEM).At the same time,the expression of IBA-1 and CD68 was observed by single immunofluorescence method,and the expression and co-localization of LC3 and NLRP3 in rat hippocampus were observed by double immunofluorescence technique.Results: We found that CUMS induced depression-like behavior and cognitive impairments,which were reflected in poor behavioral tests,such as reduced sucrose preference,decreased motor and exploration activities,increased immobility,and spatial learning and memory impairments.In addition,CUMS rats showed decreased autophagy flux and increased inflammatory activation.After EE treatment,these changes induced by CUMS were reversed.However,the autophagy inhibitor 3-MA blocked the neuroprotective effects of EE on depression-like behavior and cognitive decline and neutralized the anti-inflammatory effects of EE.Conclusion: This study suggests that EE may play a neuroprotective role in depression and cognitive impairment caused by CUMS by inducing autophagy-mediated inflammation inhibition.Part II The role of autophagy in the improvement of cognitive dysfunction caused by chronic cerebral hypoperfusion(CCH)by environmental enrichment(EE)Backgroud and objective: With the aging of the population,the number of people with dementia is increasing,but effective drugs to treat dementia have not been successfully developed.Previous studies have reported that EE can alleviate CCH-induced cognitive dysfunction by improving blood brain barrier(BBB)damage.However,the mechanism of how EE improves BBB and thus reduces CCH-induced cognitive impairment remains unclear.The purpose of this study was to investigate the effects and molecular mechanisms of EE on cognitive dysfunction induced by CCH.Methods: Bilateral common carotid occlusion(2-vessel occlusion,2VO)was used to establish a CCH rat model.They were randomly divided into 5 groups:(1)Sham operation + SE group;(2)2VO + SE group;3)Sham + EE group;(4)2VO + EE group;(5)2VO + EE + chloroquine(CQ)group.The Morris water maze(MWM)was used to assess cognitive function in rats.Evans blue was determined by chemical colorimetry to evaluate the permeability of BBB.The levels of BBB-related proteins and autophagy-related proteins were detected by WB.The expression and co-localization of LC3 and LAMP1 were detected by immunofluorescence staining.The structure of BBB and autophagy lysosome in hippocampus of rats were observed by TEM.Results: We found that the performance of MWM test in CCH rats was worse,indicating that CCH induced the decline of cognitive function in rats,and the decreased expression of BBB-related molecules in CCH rats was accompanied by lysosomal dysfunction and autophagy accumulation.After EE intervention,the lysosomal function of CCH rats was improved and the expression of BBB-related molecules was increased,thus alleviating the cognitive impairment.However,the lysosomal inhibitor CQ blocked the protective effects of EE on cognitive function and BBB in CCH rats.Conclusion: This study suggests that EE protects BBB structure and function in CCH rats by improving lysosomal dysfunction in the autophagy process,thereby ameliorating cognitive impairment.