The Role Of Hippocampal TRPV4 In Diabetic Cognitive Impairment

[Objective] To explore the role and possible mechanism of TRPV4 in cognitive impairment in diabetic mice.[Method](1)Animal grouping: 60 male ICR mice(25-35g)were randomly divided into five groups: Normal saline group(NS group),Streptozotocin group(STZ group),Vehicle control group(NS+DMSO group),Drug intervention control group(STZ+DMSO group),Drug intervention group(STZ+GSK group);(2)Model induction and TRPV4 agonist(GSK1016790A)intervention: The diabetes cognitive impairment model was established by intraperitoneal injection of streptozotocin(STZ,55mg/kg)once a day for 5 days;8 weeks after the last injection of STZ,GSK1016790A(0.125mg/kg)was injected intraperitoneally once a day for 7 days;(3)General conditions observations: 24-hour food and fluid intake was monitored in each group every week and blood glucose was measured once every two weeks;(4)Behavioral testing: 8 weeks after the last injection of STZ,locomotive was recorded among all the groups by open filed test,cognitive function was determined by novel place recognition test and novel object recognition test;(5)Detection and verification of differentially expressed genes in diabetic cognitively impaired mice: mice hippocampus of Gene ontology analysis of NS and STZ group was detected by RNA-Seq technology,RT-PCR,immunoblotting and immunohistochemistry were used to verify the expression of TRPV4 in the hippocampus and cortex;(6)The effect of TRPV4 agonists GSK1016790 A on the expression of hippocampal neurogenesis marker DCX of diabetic cognitive impairment mice were determined by immunoblotting and immunohistochemistry.[Results](1)Compared with the NS group,the blood glucose of STZ group increased significantly(P<0.0001),and the 24-hour food and fluid intake increased weekly(P<0.0001);(2)Compared with the NS group,the STZ group showed obviously decreased in discrimination index of both in novel place recognition test(P<0.0001)and novel objective recognition test(P<0.001),while no difference on locomotive was found between the NS and STZ group(P>0.05).(3)Compared with the NS group,the STZ group showed 595 differentially expressed genes,of which 453 genes were significantly up-regulated and 142 genes were clearly down-regulated in the hippocampus RNA-Seq.These genes with significantly altered expression affect the development of human disease,metabolism or cellular activity by regulating biochemical processes,cellular components or molecular functions.(4)Compared with the NS group,the STZ group showed significantly reduced expression of hippocampal TRPV4 protein(P<0.01)and mRNA(P<0.01)and average IOD(P<0.01);(5)Compared with the NS group,the STZ group showed no difference expression of cortex TRPV4 protein(P>0.05).(6)Compared with the STZ+DMSO group,the STZ+GSK1016790A group had no obviously changes in the blood glucose concentration,food and water intake in 24 hours and activity(P>0.05);however,GSK intervention reversed the discrimination index effectively of new position(P <0.001)and new object(P<0.01);(7)Compared with NS+DMSO group,the STZ+DMSO group showed definitely reduced in the number of DCX-positive cells(P<0.01)and the expression of DCX protein(P<0.001)in mice hippocampus,and GSK1016790 A intervention increased the number of DCX-positive cells(P<0.05)and the expression of DCX protein(P<0.05)in mice hippocampus.[Conclusion] The cognitive impairment induced by diabetes in mice might be associated with the down-regulation of TRPV4 that inhibits neurogenesis in hippocampus.