The Effects Of Trigeminal Neuralgia On Neurodegeneration In Rats And The Mechanism Of CD95/CD95L Pathway In It

Objective:Researches have shown that patients with chronic pain were in high-risk of suffering neurodegeneration?such as dementia?,but the mechanism remains unclear.Neuropathic pain is a common chronic pain.In recent years,researchers have found that neuropathic pain can cause neuroinflammation and neuronal apoptosis,which played an important role in the occurrence and development of neurodegeneration,while CD95/CD95L pathway was the key factor of neuroinflammation and neuronal apoptosis.Therefore,we hypothesized that neuropathic pain could activate the CD95/CD95L pathway to induce neuroinflammation and neuronal apoptosis,thereby resulting in neurodegeneration.To test this hypothesis,the experiment was designed to observe the effects of trigeminal neuralgia?TN?on neurodegeneration in rats,and to explore whether the mechanism was related to the CD95/CD95L pathway,to provide a theoretical basis for prevention and intervention of neurodegeneration in patients with trigeminal neuralgia.Methods:1.Copy TN animal models:Sixty adult male SD rats were randomly divided into two groups:Infraorbital nerve ligation operation group?ION-CCI group,n=30?and sham group?sham group,n=30?.In ION-CCI group,right infraorbital nerve was exposed and ligated to induce chronic constriction injury of trigeminal nerve to copy TN animal models.In sham group,right infraorbital nerve was only exposed but not ligated.2.Pain threshold detection:Ten rats in each group were randomly selected for pain threshold detection by Von Frey Filament at the preoperative and 1^st,7^th,15^th,30^th day after operation respectively.3.Morris water maze test:Ten rats in each group were randomly selected at 1^st,15^th,30^th day after operation respectively.The results were recorded as Test 1,Test 2,Test 3.The swim speed,the escape latency,the crossing platform number and the time percentage in the target quadrant were observed.4.Detection of proteins related to neurodegeneration:Rats were sacrificed on the 5^th,19^th,34^th day after operation?after water maze test?.Then,the next parameters were detected.The serum concentrations of S100?and the expression of A?1-42 in hippocampus were detected by ELISA,Total-Tau was detected by Western blotting,and the level of phosphorylation at Ser404 siste was detected by immunofluorescence and Western blotting.5.Detection of proteins related to CD95/CD95L pathway:The expression of CD95,CD95L and Cleaved-caspase3 were detected by immunofluorescence and Western blotting on the 5^th,19^th,34^th day after operation.Results:1.Rat models:Three rats died after anesthesia in sham group.Two rats died after anesthesia,one rat died after operation and one rat had no significant pain threshold change in ION-CCI group.Another seven rats were selected and divided into two groups according to the random number method.A total of sixty rats were analyzed in this study.2.Pain threshold change:There was no statistical difference between all time points in sham group?P>0.05?.In ION-CCI group,there was significantly increased on the 1^st day after operation compared to the preoperative?P<0.05?,and significantly decreased on the 7^th,15^th,30^th day after operation compared to the preoperative?P<0.05?.The pain threshold was lowest at the 15^th day after operation,followed by the 30^th day in ION-CCI group?P<0.05?.By the 1^st day after operation,it was significantly increased in ION-CCI group compared to the sham group?P<0.05?.By the 15^th and30^th day after operation,it was significantly decreased in ION-CCI group compared to the sham group?P<0.05?.3.Morris water maze test:There was no statistical difference between three Tests in sham group?P>0.05?.In ION-CCI group,from Test 1 to Test 3,the escape latency prolonged in turn,the crossing platform number and the time percentage in the target quadrant decreased in turn?P<0.05?.There were statistical differences between all Tests in ION-CCI group?P<0.05?.Either within-group or between-group,there was no statistical difference in the swim speed?P>0.05?.There was no statistical difference in the water maze performance between two groups of Test 1?P>0.05?.The escape latency significantly prolonged and the crossing platform number and the time percentage in the target quadrant significantly decreased in Test 2 and Test 3compared to Test 1?P<0.05?.4.The level of proteins related to neurodegeneration:There was no statistical difference in S100?or A?1-42 or ^Ser404P-Tau in all time points in sham group?P>0.05?.There was statistical difference in serum concentrations of S100?in all time points in ION-CCI group?P<0.05?,S100?was the highest at 19^th day after operation,the second at 34^th day,and the lowest at 5^th day,there was statistical difference between 19^thh day and 5^thh day after operation?P<0.05?.A?1-42 and ^Ser404P-Tau showed statistical differences in all time points in ION-CCI group?P<0.05?,they were the highest at 34^th day after operation,the second at 19^th day,and the lowest at 5^thh day.A?1-42 significantly increased on the 34^th day compared to the 5^th day after operation in ION-CCI group?P<0.05?.^Ser404P-Tau significantly increased on the 34^th and 19^th day compared to the 5^th day after operation in ION-CCI group?P<0.05?.There was no statistical difference in the expression of Total-Tau within or between two groups?P>0.05?.By the 19^th and 34^th day after operation,the serum concentrations of S100?and the expression of A?1-42 and ^Ser404P-Tau in hippocampus significantly increased in ION-CCI group compared to the sham group?P<0.05?,without statistical difference between two groups on the 5^th day after operation?P>0.05?.5.The level of proteins related to CD95/CD95L pathway:There was no statistical difference in the expression of CD95,CD95L and Cleaved-caspase3 in hippocampus in all time points in sham group?P>0.05?.CD95,CD95L and Cleaved-caspase3 had statistical differences in all time points in ION-CCI group?P<0.05?.CD95 and CD95L were the highest at 19^th day after operation,the second at 34^th day,the lowest at 5^th day in ION-CCI group.CD95 significantly increased on the 19^th day compared to the 5^th day after operation in ION-CCI group?P<0.05?.CD95L significantly increased on the34^th and 19^th day compared to the 5^th day after operation in ION-CCI group?P<0.05?.Cleaved-caspase3 was the highest at 19^th day after operation,the second at 5^th day,and the lowest at 34^th day in ION-CCI group.Cleaved-caspase3 significantly increased on the 19^th day compared to the 5^thh and 34^th day after operation in ION-CCI group?P<0.05?.CD95 significantly increased in ION-CCI group compared to the sham group in all time points?P<0.05?.By the 19^th and 34^th day after operation,CD95L significantly increased in ION-CCI group compared to the sham group?P<0.05?.By the 5^th and 19^th day after operation,Cleaved-caspase3significantly increased in ION-CCI group compared to the sham group?P<0.05?.In ION-CCI group,the expression of Cleaved-caspase3 and CD95 were positively related?r=0.570,P=0.027?.The expression of Cleaved-caspase3and CD95L were positively related?r=0.650,P=0.009?.Conclusion:1.Trigeminal neuralgia rats could induce neurodegeneration,including decline of learning ability and memory,increase of S100?in serum and A?1-42 and ^Ser404P-Tau in hippocampus.2.Trigeminal neuralgia could increase the expression of CD95,CD95L and Cleaved-caspase3 in hippocampus of rats.Trigeminal neuralgia could activate CD95/CD95L pathway to induce neuroinflammation and neuronal apoptosis,which may be an important mechanism of trigeminal neuralgia to lead neurodegeneration.