Effect Of TNF-alpha Expression In Hippocampus On Neuropathic Pain And Associated Depression In Sciatic Nerve Ligation Model

Objectives:In the process of human development,the pain caused by disease and the accompanying psychological depression have always been the two major problems that trouble human beings.However,the depression caused by neuropathic pain has not been clearly understood by humans,and the hippocampus in the nervous system often plays a very important role in the development of learning and memory,anxiety and depression.Therefore,by studying the changes in the content of proinflammatory cytokines in the hippocampus of depressed mice induced by neuropathic pain induced by the sciatic nerve Cuff model(Cuff),this paper discusses the relationship between neuropathic pain and the severity of depression,hoping to provide a basis for the experimental study of chronic pain and depression in the future.Methods:Thirty male Kunming mice(weight 22±2g)were divided into the Sham group(only the sciatic nerve trunk was separated and the cuff was not implanted),and the Cuff+VEL group(sciatic nerve ligation+equivalent saline injection)),Cuff+PTX group(sciatic nerve ligation+TNF-α synthesis inhibitor pentoxifylline(PTX)40mg/kg intraperitoneal injection).Within 14 days after the operation,all mice were intervened with drugs.Next,behavioral tests such as open field test and sucrose preference test were used to evaluate two types of conditions induced by the sciatic nerve ligation model(Cuff).The two types of conditions are depressive behavior conditions and the other is neuropathic pain conditions.Fourteen days later,the mice were sacrificed,and then the hippocampus tissue was extracted,used for paraffin section and staining.After the serum extraction operation is completed,the TNF-α and IL-6 levels in the serum are detected by ELISA;Fresh hippocampal tissue is taken and Western blot technology is used to determine in the hippocampus tissue-Expression of TNF-α、JNK、p-JNK、p38、p-p38.Results:1.Behavioral changes of mice:In the Sham group(only the sciatic nerve trunk was isolated without cuff implantation),no significant behavioral changes were observed.In the mouse Cuff group(after ischial nerve ligation)and the Cuff+VEL group(after ischial nerve ligation+intraperitoneal injection with equal amount of normal saline),dorsal flexion and eversion of the ligated lateral toe were observed.Mice from the Cuff+PTX group(40mg/kg intraperitoneally injected with TNF-leutothepine(PTX))showed significant relief of neuropathic pain symptoms such as plantar valgus and hanging claw on the operative side.2.PWPT test results:Before Cuff surgery and on days 2,5,7,10,and 14 after surgery,the PWPT value of mice in the Cuff+VEL group was significantly lower than that in the Sham group(P<0.01);compared with the Cuff+VEL group,the Cuff+PTX group PWPT values increased significantly on the second,fifth,seventh,tenth,and 14th days after surgery(P<0.05).3.SPT test results:There were significant differences in the ratio of sucrose consumption among the three groups of mice.The ratio of sucrose consumption of mice in the Cuff+VEL group was significantly reduced compared with the Sham group(P<0.01);the ratio of sucrose consumption of the mice in the Cuff+PTX group was significantly increased compared to the Cuff+VEL group(P<0.05)4.OFT test results:Three groups of mice level score(crossing)(P<0.01)and vertical(rearing)score(P<0.05)there were significant differences.Cuff+VEL mice crossing and rearing score relative to Sham group significantly reduced(P<0.05);Cuff+PTX group crossing and rearing score relative to the Cuff+VEL group increased significantly(P<0.05).5.FST test results:The immobility time of the three groups was significantly different.The immobility time of mice in the Cuff+VEL group was significantly longer than that in the Sham group(P<0.01).The time of immobility of Cuff+PTX group was significantly shortened compared with that of Cuff+VEL group(P<0.05).5.Effects of Cuff surgery and intraperitoneal injection of PTX on the morphological structure of the Ca3 region of the hippocampus in mice:The morphology of HE staining in the hippocampal CA3 region of the three groups of mice changed significantly.Compared with the Sham group,the hippocampal pyramidal cells in the Cuff+VEL group solidified and atrophic,showing a loose structure and a large number of inflammatory cells infiltration.Compared with the Cuff+PTX group,the cells in the Cuff+VEL group were neatly arranged,with clear layers,and fewer inflammatory cells.7.Serum levels of TNF-α and il-6 in mice were determined by ELISA:Compared with the Sham group,the serum levels of TNF-α and IL-6 in the Cuff+VEL group were significantly increased(P<0.01),and the serum levels of TNF-α and IL-6 in the Cuff+PTX group were also higher than those in the Sham group,but there was an obvious trend of decline compared with the Cuff+VEL group(P<0.05).8.Effects of Cuff surgery and intraperitoneal injection of PTX on the expression of p-JNK、JNK、p-p38、p38 和 TNF-α in the hippocampus of mice:Compared with the Sham group,the expressions of TNF-α,p-JNK and p-p38 in hippocampus of Cuff+VEL group were significantly increased(P<0.01);Expressions of TNF-α,P-JNK and P-p38 in the Cuff+PTX group were decreased compared with the Cuff+VEL group.Conclusion:Sciatic nerve graft model(Cuff)can induce infiltration of inflammatory cells in thehippocampal CA3 region of mice,increase the expressions of TNF-α and IL-6in the serum of mice,and lead to increased expressions of TNF-α,p-JNK and p-p38 in the hippocampus of mice.Intraperitoneal injection of TNF-α synthesis inhibitor hexantheobroline(PTX)after surgery can inhibit the expression of TNF-α,IL-6,p-JNK and p-p38,thus alleviating the depression-like behaviors in mice induced by Cuff.