The Role Of Hippocampal TRPV4 In Depression-like Behavior In Mice Induced By LPS

Objective:To explore the role of hippocampal TRPV4 in LPS-induced depression-like behavior in mice and its possible mechanism.Method:1)Animal grouping:8-week-old male C57BL6/J mice(20-25g)were randomly divided into normal saline control group(NS),LPS model group(LPS),vehicle control group(Vehicle),vehicle with LPS model group(Vehicle+LPS),HC067047 treatment with LPS group(HC067047+LPS group),the control lentiviral vector expressing GFP with NS group(GFP+NS),the control lentiviral vector expressing GFP with LPS intervention group(GFP+LPS),the lentiviral vector harboring sh RNA sequence targeting the TRPV4 gene with LPS group(LV-TRPV4-sh RNA+LPS)and the lentiviral vector harboring sh RNA sequence targeting the TRPV4 gene with NS group(LV-TRPV4-sh RNA+NS);2)Model establishment:a single intraperitoneal injection of LPS in mice to establishe the depression model;3)TRPV4 inhibitor HC067047 intervention:the mouse is intraperitoneal injection of TRPV4inhibitor HC067047(10mg/kg),30 minutes later,intraperitoneal injection of LPS;4)Stereotaxic virus injection:inject the control lentiviral vector expressing green fluorescent protein or harboring sh RNA sequence targeting the TRPV4 gene into the hippocampus of mice,to observe the effect of silencing hippocampal TRPV4 on depression-like behavior in LPS model;5)Behavioral testing:the open field experiment was used to detect the locomotive activity of the mice,the sucrose preference test,the forced swimming test and the novelty suppressed feeding test were modified to detect the depression-like behavior of the mice;6)RT-PCR was used to detect the expression of TRPV4,IL-6,IL-1βand TNF-αmRNA in the hippocampus of mice;Immunohistochemistry was used to examine the expression of TRPV4,IBA-1,GFAP,DCX in the hippocampus of mice;Sholl Analysis was used to asses the IBA-1~+cells morphological change;ELISA was used to detect the expression of IL-6,IL-1βand TNF-αin the serum of mice;Western blot was used to examine the expression of TRPV4,GFAP,CD68,CD11B,P2RX7,CamkIIα,p-CamkIIα,NLRP3,ASC,Caspase-1,IL-18,IL-1βin hippocampus of mice.Results:1)Compared to the NS group,the expression of TRPV4protein(P<0.01)and mRNA(P<0.001)in the hippocampus of the LPS mice were significantly up-regulated and the average optical density of positive TRPV4 cells in CA3 of LPS mice was increased(P<0.001);2)Compared to the Vehicle mice,the Vehicle+LPS mice showed significantly decreased percent of sucrose preference in the SPT(P<0.001),increased immobility time in the FST(P<0.01)and longer latency time In the NSFT(P<0.001),with the treatment of HC067047,the depression-like behaviors were reversed(P<0.05);3)Compared to GFP+NS mice,the GFP+LPS mice showed decreased percent of sucrose preference(P<0.001)in the SPT and increased immobility time(P<0.05)in the FST,compared with GFP+LPS mice,the LV-TRPV4-sh RNA+LPS mice showed increased percent of sucrose preference(P<0.05)and decreased immobility time(P<0.05);4)Compared to the Vehicle mice,the Vehicle+LPS mice showed an increased number of IBA-1 and GFAP positive cells in the hippocampus,the complexity of IBA-1~+were decreased and the protein levels of GFAP,CD68,CD11B;P2RX7 were increased(p<0.05),with the treatment of HC067047,the changes above were reversed(P<0.05);5)Compared to the Vehicle group,the expression of CamkIIαand NLRP3 inflammasome associate proteins in the hippocampus of the Vehicle+LPS mice were increased(P<0.05),with the treatment of HC067047,the expression of CamkIIαand NLRP3inflammasome associate proteins were decreased(P<0.05);6)Compared to the Vehicle group,the expression of hippocampal inflammatory factors mRNA and serum inflammatory factors of Vehicle+LPS group were significantly increased(P<0.05),with the treatment of HC067047,the expression of inflammatory factors mRNA and inflammatory factors of mice were decreased(P<0.05);7)Compared to the Vehicle group,the number of DCX positive cells in the hippocampus of LPS mice were significantly decreased(P<0.01),which were reversed by HC067047treatment(P<0.05).Conclusion:TRPV4 may participate in LPS-induced depressive behavior in mice by regulating the CamkIIα/NLRP3 signaling pathway,promote glial cells activation and release of inflammatory factors,inhibit hippocampal neurogenesis.