| BackgroundPost-stroke depression(PSD)is the most common mood disorder after stroke.The physiological and pathological mechanisms of PSD are complex,and the neuroimmunoinflammatory mechanism is the current research hotspot.The transcription factor NF-E2-related factor 2/antioxidant response element(NF-E2-related factor 2/antioxidant response element,Nrf2/ARE)signaling pathway is one of the body’s important defense mechanisms against oxidative stress and inflammatory damage.Therefore,regulating the Nrf2/ARE pathway may be a powerful target for the treatment of PSD.The synthetic triterpenoid 2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide(CDDO-Im)is a Nrf2 agonist with antiinflammatory,antioxidant and neuroprotective effects.ObjectiveThis study intends to observed whether CDDO-Im has an antidepressant effect in a rat model of post-stroke depression;and to explore the effects of CDDO-Im on oxidative stress,inflammation and Nrf2/ARE signal transduction pathway in hippocampus of PSD rats.MethodsSprague-Dawley rats were randomly divided into four groups: the Control group(Ctrl),Control+CDDO-Im group(Ctrl+CDDO-Im),PSD group(MCAO+CUMS),and PSD+CDDO-Im group(MCAO+CUMS+CDDO-Im).The rats are kept in groups normally without special treatment in the Ctrl group and Ctrl+CDDO-Im.The PSD group and PSD+CDDO-Im group employed the widely used MCAO surgery to build a stroke model.And seven days after MCAO,the CUMS was given in combination with solitary housing for 4 weeks to replicate the PSD model.After successful modeling of PSD,the rats in Control+CDDO-Im group and PSD+CDDO-Im group were injected with CDDO-Im(0.5mg/kg body weight)through the tail vein,once a day for one week.Weight and behavioral tests were performed regularly during modeling.We observed the morphological structure and damage of neurons in hippocampal of model rats by using Nissl staining.The levels of oxidative stress were measured by Malondialdehyde(MDA)content and Superoxide dismutase(SOD)activity in left hippocampus of rats.Western blot method was used to detect the protein levels of nuclear Nrf2,Nuclear Factor Kappa B p65(NF-κB p65),heme oxygenase-1(HOMX1),quinone oxidoreductase-1(NQO1),interleukin-1b(IL-1β)and interleukin-6(IL-6)in the left hippocampus of each group of rats.Real-time fluorescent quantitative PCR(q-PCR)was used to detect the expression levels of Nrf2,IL-1β and IL-6m RNA in hippocampus of each model rats.Observation of Nrf2 protein expression level in rat hippocampal nerve tissue by immunofluorescence.Results1.The body weight of PSD rats increased slowly,and CDDO-Im intervention did not show any significant improvement:The body weight of rats in the PSD group and PSD+CDDO-Im group decreased(both P < 0.01 vs Ctrl)at week 1;The body weight of rats in the PSD group and PSD+CDDO-Im group decreased(both P < 0.001 vs Ctrl)at week5;at week 6 after treatment with CDDO-Im,the body weight of rats in the PSD+CDDO-Im group still decreased(P < 0.001 vs Ctrl).2.CDDO-Im decreased depression-like behavior in PSD rats: the sucrose preference in PSD group and PSD+ CDDO-IM group decreased(both P < 0.05,vs Ctrl)at week 5,and the immobility time of forced swimming increased(both P < 0.05,vs Ctrl)at week 5,indicating that the modeling of PSD rats was successful.Compared with the PSD group,the preference for the sucrose solution was significantly increased(P < 0.05),and the immobility time was also decreased(P < 0.05)in PSD+CDDO-Im group at week 6 after treatment with CDDOIm,indicating that depression-like behavior was improved.3.CDDO-IM improved the morphology of hippocampal tissue in PSD rats: the number of surviving neurons was decreased significantly in the PSD group(CA1:P < 0.01 vs Ctrl;CA3: P < 0.05,vs Ctrl;DG:P < 0.05,vs Ctrl),the number of neurons in the hippocampal CA1(P < 0.01 vs PSD)and CA3(P < 0.01 vs PSD)areas of the PSD+CDDO-Im group is significantly increased compared with the PSD group,and the hippocampal structure is relatively more complete.4.CDDO-Im reduced oxidative stress and inflammation in the hippocampus of PSD rats:the MDA content and SOD activity in the hippocampus of the PSD group were increased(both P < 0.05 vs Ctrl),and the MDA content and SOD activity of the PSD+CDDO-Im group were decreased(both P < 0.05 vs PSD).Wertern Blot detected that the level of NF-κB p65 in the hippocampal nucleoprotein of the PSD group was significantly higher(P <0.05 vs Ctrl),and the downstream inflammatory factors IL-6 and IL-1β were also significantly increased(both P < 0.001 vs Ctrl).In the PSD+CDDO-Im group,CDDO-Im treatment significantly decreased the protein level of NF-κB p65(P <0.05 vs PSD)and reduced the downstream inflammatory factors,IL-6 and IL-1β,NF-κB p65 decreased(both P < 0.001 vs PSD).The m RNA expression of IL-6 and IL-1β in the rat hippocampus of the PSD group increased(P < 0.01 vs PSD),and CDDO-Im treatment reduced the expression of IL-1β(P < 0.01 vs PSD)and IL-6(P < 0.05 vs PSD).5.The Nrf2/ARE signal pathway was activated in PSD rats,and it’s expression decreased in PSD+CDDO-Im rats : wertern Blot detected that the expression of Nrf2 in the hippocampus of rats in the PSD group increased(P < 0.01 vs Ctrl),and the downstream antioxidant enzymes HMOX1 and NQO1 also increased significantly(both P < 0.01 vs Ctrl),while CDDO-Im treatment reduced The expression of nucleoprotein Nrf2(P < 0.01 vs Ctrl)also reduced the expression levels of total protein HMOX1(P < 0.01 vs PSD)and NQO1(P< 0.01 vs PSD).q-PCR detection of hippocampal Nrf2 m RNA in PSD group significantly increased(P < 0.001 vs Ctrl),while CDDO-Im treatment reduced the level of Nrf2 m RNA expression(P < 0.01 vs PSD).Compared with the Ctrl group,the expression of Nrf2 in the DG area of rats in the PSD group was increased significantly,and the fluorescence intensity in the nucleus also was more intense.Compared with the PSD group,the Nrf2 expression decreased,and the fluorescence intensity in the nucleus became weaker in the rats hippocaumpus DG area of the PSD+CDDO-Im group.Conclusion1.CDDO-Im can decrease depression-like behavior in PSD rats.2.CDDO-Im reduces the oxidative stress and inflammatory damage in the hippocampus of PSD rats to exert antidepressant effects maybe through the Nrf2/ARE pathway. |
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