Effects Of Fecal Bacteria Transplantation In Exercise Mice On Depression Behavior And The Mechanism Of MAPK Mediated Neuroplasticity In Stress Mice

Background: Depression is currently a common and high incidence disease worldwide.According to the World Health Organization,the number of patients with depression worldwide exceeds 300 million.Depression is related to changes in neural plasticity,which is accompanied by changes in cell signal transduction.Mitogen activated protein kinase(MAPK)pathway plays a crucial role in the changes in neural plasticity.Research has shown that the MAPK signal pathway in the brain of patients with depression changes.Exercise is an effective method for preventing and treating depression,which can reshape the brain structure.Research has shown that exercise can affect the activation of the MAPK pathway.The gut brain axis is closely related to behavior and emotions,and exercise can change the composition of the intestinal flora.Studies have shown that removing intestinal microflora and colonizing probiotics can both alter the activation of MAPK signaling pathways in mice,and intestinal microflora metabolites can also affect MAPK signaling pathways.However,the role of intestinal flora in the improvement of depression through exercise remains unclear,and whether exercise induced flora plays a role through MAPK signaling remains to be explored.The chronic restraint stress(CRS)model is similar to the pathogenesis of human depression,and is widely used in the study of depressive behavior.Fecal microbiota transplantation(FMT),as an effective means of reconstructing intestinal flora,has been widely used in the treatment of intestinal related diseases.This study used the CRS model and FMT technology as a means to explore the effect and mechanism of exercise induced bacterial flora on depression like behavior in stressed mice.Objective: To explore the changes in depression like behavior and neural plasticity induced by chronic restraint stress(CRS),and to explore the impact of intestinal flora induced by different exercise intensities on CRS induced depression like behavior and its mechanism.Methods: 140 healthy adult male C57BL/6J mice aged 20 weeks were randomly divided into four groups: control group: CON group,CRS group;Donor group: SED group,LE group,ME group,HE group;CON receptor group: SC group,LC group,MC group,HC group;CRS receptor group:SR group,LR group,MR group,HR group.CRS,SR,LR,MR,HR received CRS for 4 weeks,and then the mice in each group received behavioral tests;In the SED group,LE,ME,and HE received low intensity(6 m/min),medium intensity(12 m/min),and high intensity(18 to 20 m/min)exercise training for 6 weeks without exercise intervention,and then received behavioral tests;SC,SR,LC,LR,MC,MR,HC,HR entered the FMT procedure from week 5,where SC,SR received intestinal flora from SED,LC,LR received intestinal flora from LE,MC,MR received intestinal flora from ME,and HC,HR received intestinal flora from HE.After the completion of the FMT procedure,blood was collected from the heart,and the mice were decapitated.Serum,whole brain,prefrontal cortex,and other tissues were taken from the mice.The levels of SYP,PSD-95,BDNF,MAPK3,MAPK1,MAPK14,and MAPK8 in the prefrontal cortex were detected using Real-time PCR;Western blotting was used to detect the levels of GAP-43,SYP,PSD-95,BDNF,ERK1/2,pEKE1/2,p38,p-p38,p-JNK1/2,CREB,and p-CREB in the prefrontal cortex;The number of neurons in the hippocampus of mice was observed by Nissl staining;Golgi staining was used to observe the morphological changes of hippocampal neurons.Result:(1)Compared with CON,CRS mice showed a decrease in sucrose preference in the sugar preference test(SPT)(p<0.05),and a significant increase in immobility time in the forced swim test(FST)and tail suspension test(TST)(p<0.05);In the open field test(OFT),the number of exploratory holes decreased(p<0.05)and the central distance decreased(p<0.05).(2)With the increase of exercise intensity,the immobility time of donor group exercise mice in TST showed a downward trend compared to SED mice,with LE(p<0.05)and HE(p<0.01)significantly decreased;In SPT,sucrose preference gradually decreased,with a significant decrease in HE(p<0.05);In OFT,the central distance gradually increased,and the number of exploratory holes decreased overall,with a significant decrease in LE(p<0.05);In FST,the immobility time tends to decrease.(3)FMT had no significant effect on the sucrose preference of CON type receptors.In FST,CON type receptors have a lower struggle time than CON(p<0.01),and gradually decrease with increasing exercise intensity(p<0.05);The immobility time showed a downward trend,with LC significantly decreasing compared to CON(p<0.05),and MC and HC immobility time gradually increasing compared to LC.In TST,the immobility time of CON type receptors decreased compared to CON type receptors,with SC and LC significantly decreased(p<0.05);The struggling time showed an increasing trend,with SC and LC struggling time significantly increasing(p<0.05).In OFT,with the increase of exercise intensity,the central distance of CON receptors gradually increased compared to CON,with a significant increase in HC(p<0.05).For CRS type receptors,in SPT,the sucrose preference of mice showed an increasing trend compared to CRS,with significant increases in LR and MR(p<0.05).In FST,with the increase of exercise intensity,the struggle time of CRS type receptors gradually decreased compared to CRS(p<0.05),while the immobility time gradually increased(p<0.05).In TST,CRS type receptors showed a trend of increasing struggle time and decreasing immobility time compared to CRS;Compared with CRS,SR and LR significantly decreased immobility time(p<0.05),while struggle time significantly increased(p<0.05);With the increase of exercise intensity,the immobility time of MR and HR significantly increased compared to SR(p<0.05).In OFT,all CRS type receptors significantly increased their central pathway compared to CRS(p<0.01).(4)The number of pyramidal cells in the CA1 region of the hippocampus of CRS mice decreased significantly(p<0.05);The number of dendritic intersections of hippocampal dentate gyrus neurons decreased significantly within the range of 32.5 to 68.5 um from the cell body(p<0.05),and the number of dendritic intersections decreased as a whole from 32.5 um compared to CON;The density of dendritic spines,the number of dendritic branches,and the total length of dendrites decreased significantly(p<0.01).The number of pyramidal cells in the CA1 region of the hippocampus of LR mice was significantly higher than that of CRS mice(p<0.05).Compared with CRS mice,SR and LR mice showed an increase in the intersection of dendrites(p<0.05),the density of dendritic spines(p<0.01),the number of dendritic branches(p<0.05),and the total length of dendrites(p<0.05)at a distance of 32.5 um from the cell body.Compared with CRS,there were no significant changes in the morphology of neurons in the hippocampus of MR and HR.(5)The levels of BDNF(p<0.01),GAP-43(p<0.01),PSD-95(p<0.01),and SYP(p<0.01)in the prefrontal cortex of CRS mice were significantly lower than those of CON mice.Compared with CRS mice,BDNF in the prefrontal cortex of SR mice increased significantly(p<0.05),while GAP-43,PSD-95,and SYP showed an increasing trend.Compared with CRS mice,the levels of BDNF(p<0.05),GAP-43(p<0.05),and PSD-95(p<0.01)in the prefrontal cortex of LR mice were significantly increased,while SYP showed an increasing trend.With the increase of exercise intensity,the contents of BDNF(p<0.05),GAP-43(p<0.05),PSD-95(p<0.05),and SYP(p<0.05)in the prefrontal cortex of CRS type receptors gradually decreased.Compared with CON mice,pERK1/2(p<0.01),CREB(p<0.05),and p-CREB(p<0.05)in the prefrontal cortex of CRS mice were significantly decreased,while p38(p<0.01),p-p38(p<0.05),and p-JNK1/2(p<0.05)were significantly increased.There were no significant changes in all CRS type receptors compared to ERK1/2 and p-ERK1/2 in CRS mice.SR(p<0.01),LR(p<0.01),MR(p<0.05),and HR(decreased but not significantly)were lower than those in the CRS group(p38),and the level of p38 gradually increased as exercise intensity increased.The levels of SR(p<0.05),LR(p<0.05),and HR(p<0.05)were significantly lower than those of CRS mice;The level of p-p38 in MR group was lower than that in CRS,but still significantly higher than that in CON(p<0.05);There was no significant difference in p-p38 levels between SR and LR and CON.The levels of p-JNK1/2 in SR and LR mice were significantly lower than those in CRS mice(p<0.05),and the levels of p-JNK1/2 in CRS type receptors gradually increased with the increase of exercise intensity.The levels of p-CREB in SR and LR groups were significantly higher than those in CRS(p<0.05);However,there was no significant change in p-CREB and CRS in MR and HR;The level of p-CREB in HR group was significantly lower than that in CON group(p<0.01).Conclusion:(1)Exercise can change depression like behavior in mice,and different exercise intensities have different effects.(2)Exercise induced intestinal microflora can partially reverse the depression like behavior caused by CRS,while also affecting the depression like behavior of healthy recipient mice.(3)CRS caused changes in the morphology and structure of neurons in mice.Transplanting healthy flora and low intensity exercise induced flora can reverse the changes brought about by CRS.Transplantation of intestinal flora induced by moderate and high intensity exercise cannot reverse the changes brought about by CRS.(4)CRS causes changes in neural plasticity related proteins and MAPK signaling pathways in mice.The flora induced by low intensity exercise may participate in the regulation of neural plasticity by inhibiting p38MAPK/CREB signaling pathway.