| Objective:Depression has the following characteristics:high incidence,difficult treatment,and serious harm,so its mechanism needs to further study.In addition,the traditional treatment methods have various limitations,and finding new treatment methods has practical clinical significance.Nervous system inflammation is a widely studied cause of depression,and NLRP3-mediated inflammatory response plays a role in regulating the occurrence and development of depression.Mitochondria are the energy factories of cells,and the "mitochondrial theory" is further studied as a new pathogenesis of depression.As a gas signal molecule,hydrogen sulfide has also received further attention in the research of central nervous system diseases.Previous studies have shown that it has a certain effect in the treatment of Alzheimer’s,ischemic stroke,depression,etc.,but the mechanism needs to be further studied.Therefore,this study investigated the mechanism of the effect of hydrogen sulfide on depressive-like behavior in mice at exogenous pharmacological doses.Furthermore,exercise has received more attention as a new noninvasive intervention for relieving depression.Many basic studies have shown that exercise can alleviate depression-like behaviors in various chronic models,mainly by improving mitochondrial function and inhibiting inflammation in the nervous system.At the same time,exercise will also promote the content of hydrogen sulfide in various tissues of the body,including the hippocampus.Then,whether exercise improves depression-like behavior is related to its physiological increase in hydrogen sulfide content remains to be further studied.Methods:1st study:The effect of hydrogen sulfide on LPS-induced depression-like behavior in mice8-week-old ICR male mice were selected and randomly divided into three groups:control group,LPS group,and LPS+NaHS group.After 7 days of adaptive feeding,on the 8th to 14th day,the LPS+NaHS group was injected with NaHS solution twice a day,and the other two groups were injected with the same amount of saline.The model was established on the 14th day.The LPS group and the LPS+NaHS group were injected with LPS solution intraperitoneally,and the control group was injected with the same amount of saline.The behavioral tests were started on the 15th day.After these tests,mice were sacrificed by anesthesia,and the hippocampus was dissected from both sides.Store at-80℃ on one side,and then use WB method to detect NLRP3/ASC/NF-κB/P-NF-κB/GSDMD/GSDMD-N/pro-caspase-1/caspase-1/pro-IL1β/IL-1β/CD45/iNOS expression.At the same time,a part of the hippocampal fixed-embedded section was taken for TUNEL and IF detection.On the other side of the fresh hippocampus,on the one hand,the morphology of mitochondria was detected by electron microscopy,and on the other hand,mitochondria were extracted to detect membrane potential,ATP,ROS and O2K mitochondrial respiration rate.2nd study:The effect of exercise preconditioning on depressive-like behaviors in LPS-induced miceEight-week-old ICR male mice were selected and randomly divided into three groups,namely the control group,the LPS group,and the EX+LPS group.After the 1th week of adaptive feeding and the 2nd week of adaptive exercise,the EX+LPS group underwent treadmill aerobic training in 3th-8th week.At the end of the 8th week,the LPS group and EX+LPS group were injected with LPS solution,and the control group was injected with the same amount of saline.After 24 hours,behavioral tests were performed,and then the mice were anesthetized and sacrificed,and bilateral hippocampi were collected.Results1st study:The effect of hydrogen sulfide on LPS-induced depressive-like behaviors1.Hydrogen sulfide alleviates LPS induced depression like behavior in mice Compared with the LPS group,LPS+NaHS group increased the sugar water preference rate(P<0.05),the immobility time was significantly decreased in the forced swimming test(P<0.05),and the shuttle distance in the open field test was significantly increased(P<0.05),and the number of times entering the central area and the probability of entering the open arm in the elevated O maze experiment did not increase significantly(P>0.05),but the z-score increased significantly(P<0.001).2.Hydrogen sulfide inhibits LPS induced hippocampal inflammatory response in miceCompared with LPS group,the levels of the LPS+NaHS group of P-NF-κB(P<0.001),NLRP3(P<0.05),ASC(P<0.01),caspase-1(P<0.05)and IL-1β(P<0.05)were significantly decreased,while the expressions of NF-κB,caspase-1 and pro-IL-1β remained unchanged(P>0.05).Compared with the LPS group,the Proportion of positive cells in CA1(P<0.01),CA3(P<0.01)and DG(P<0.05)regions in the hippocampus of LPS+NaHS group was significantly decreased.Compared with LPS group,the level of the GSDMD-N(P<0.01)of LPS+NaHS group was significantly decreased3.Hydrogen sulfide inhibits LPS induced M1 polarization of hippocampal microgliaCompared with the LPS group,the Iba-1-labeled microglia in the LPS+NaHS group was decreased.Compared with the LPS group,the expression of iNOS in the hippocampus of the mice in the LPS+NaHS group was increased(P<0.01),and the expression of CD45 was increased(P<0.05).4.Hydrogen sulfide improves LPS induced hippocampal mitochondrial dysfunctionCompared with the LPS group,the mitochondrial swelling in the LPS+NaHS group was relieved and the mitochondrial ridges were clear.Compared with the LPS group,the mitochondrial membrane potential of the LPS+NaHS group was increased(P<0.01),ROS produced by mitochondria was decreased(P<0.05),and mitochondrial ATP content was increased(P<0.01).Compared with the LPS group,CⅠ OXPHOS(P<0.05),CⅠ&Ⅱ OXPHOS(P<0.05),CⅠ&Ⅱ ETS(P<0.05)in the LPS+NaHS group were all increased,and the CⅡ ETS(P>0.05)and CⅣ OXPHOS(P>0.05)were not different.2nd Study:The effect of exercise Preconditioning on depressive-like behaviors in LPS-induced mice1.The sugar water experiment showed that compared with the control group,the sugar water preference of the LPS group was decreased(P<0.05);the sugar water preference rate of the EX+LPS group was no different from that of the LPS group(P>0.05).2.The forced swimming test showed that compared with the control group,the immobility time of the LPS group was increased(P<0.01);the immobility time of the EX+LPS group was not different from that of the LPS group(P>0.05).3.The open field experiment showed that compared with the control group,the shuttle distance of the LPS group was decreased(P<0.05),and the shuttle distance of the EX+LPS group was no different from that of the LPS group(P>0.05).4.The z-score of the integrated behavioral test showed that compared with the control group,the z-score of the LPS group was decreased,and the z-score of the EX+LPS group was not different from that of the LPS group(P>0.05).Conclusions:1.LPS can induce depression-like behavior in mice,and the mechanism may involve hippocampal mitochondrial dysfunction,microglia polarization,NLRP3 inflammasome activation and subsequent inflammatory responses.2.Hydrogen sulfide can alleviate LPS-induced depression-like behaviors in mice,and the mechanisms may involve improving mitochondrial function,inhibiting microglial polarization,and inhibiting NLRP3 inflammasome activation and subsequent inflammatory responses.3.Six consecutive weeks of treadmill aerobic exercise preconditioning had no significant effect on the depression-like behavior of LPS-induced ICR mice. |
