Study On The Mechanism Of Emodin On Neuropathic Pain Based On JNK3 Pathway

ObjectiveNeuropathic pain(NP)is a recognized world problem.It is caused by various diseases or injuries.It has a variety of clinical manifestations and affects the patients’ life quality for a long time.The reasons that result in NP can be divided into the peripheral and the central,and also,it can be subdivided into ectopic discharge,inflammation,nerve growth factor and its receptor and ion channel expression,sensory nerve and spinal cord plasticity,sympathetic nerve remodeling maintained pain,glutamatergic regulation,JNK pathway and glial cells etc.We researched the Emodin throught the JNK signaling pathway,in order to find a Chinese medicine preparation for treating neuropathic pain(NP).MethodsTo observe the effects of Emodin on pain behavior in bmSNI rat model:60 150-220g healthy male SD rats were randomly divided into normal group(C),sham operation group(SH),model group(M),Emodin group(D)and SP600125 group(SP)and DMSO group(DS).After cutting bilateral tibial nerve to cause bmSNI model,D group were gave Emodin 40mg/kg/d ig for 14 days,SP group were gave SP600125 20 L/d,0.25g/L intrathecal administration for 7 days,and DS group were gave 0.05%DMSO 20 L/d intrathecal administration for 7 days.And 1 days before the operation,and 1,2,3,5,7,10,14 after the operation,we measured all the rats’ mechanical and thermal hyperalgesia.The telencephalon and lumbar enlargement were taken on the 7 day after modeling.JNK3 blotting was used to detect lumbar enlargement,and JNK3 mRNA real-time fluorescence PCR was used to detect the telencephalon.EXCEL、SPSS 20.0、Photoshop and GraphPadwere used to analyze the behavioral data of each group.Results1.Mechanical pain threshold results:First,bmSNI model rats had a significant decrease in mechanical pain after operation,and decreased to a minimum of 5.62g after 7 days.The duration of pain was long and the stability wasgood.It is a good model for studying neuropathic pain.Second,Emodin has obvious therapeutic effect on bmSNI model rats,and the analgesic effect is greater than that of SP600125.Compared with group M,the lowest threshold of mechanical pain was 5.62g at 7 days after operation,while Emodin group was 9.4133g at 3 days after operation,and then gradually increased,and the mechanical pain threshold value was significantly higher than that in M group.It is proved that Emodin is effective in the treatment of neuropathic pain in the bmSNI model.Third,the analgesic effect of Emodin on bmSNI model rats was greater than that of SP600125.SP600125 had definite therapeutic effect on neuropathic pain,and the threshold of mechanical pain in group D was significantly lower than that in group SP second,third days after operation,and significantly higher than that in group SP after fifth days after operation.The D group was 9.4133g at the third day after the operation,and the group SP was 7.98g at the fifth day after the operation.The minimum value of group D was higher than that of group SP,and the mechanical pain sensitivity was higher than that of group SP after thefifth days.It could prove that the analgesic effect of Emodin was greater than that of SP600125.The former mechanical hyperalgesia of D groud were higer,however,after that were lower than that of the SP group.These can be explained that Emodin can anti inflammation,and has certain protective effect on the uninjured nerve.After that,Emodin can anti inflammation and lead the wound to recovery,therefore,the mechanical hyperalgesia of D group is higher to SP group.It has been proved that the neuropathic pain of the bmSNI model is more effective than the SP600125.2.Thermosensitive pain threshold results:First,the heat sensitivity of bmSNI model rats was general.The thermosensitivity of the model group decreased at 5-7 days after operation,and there was a significant difference between the model group and the normal group.There was statistical difference between the model group and the sham operation group at 1,2,5,7 and 10 days after operation.Second,the heat sensitivity of the Emodin group was higher than that of the model group at 3,5,7 and 10 days after operation,and there was a statistical difference.It was concluded that Emodin had a therapeutic effect on bmSNI model rats.Third,the postoperative thermosensitive effect of Emodin group was higher than that of group SP600125,and there was statistical difference on the 3 day after operation.It was concluded that Emodin had a stronger therapeutic effect on bmSNI rats than SP600125.3.From the behavior,the trend of thermo hypersensitivity analysis is not as good as that of mechanical pain test,which may be related to the bmSNI model.In the model study,it is pointed out that the thermal stimulation of SNI seriesmodel is not obvious.4.Protein immunoblotting and real time fluorescence PCR test,combined with behavioral data analysis,speculated that 1)the experimental operation may not be standardized,and the results were false negative;2)the analgesic effect of Emodin to neuropathic pain may affect the protein expression after JNK;3)the bmSNI model was less injured and didn’ t sensitize to the End brain;4)this model may have little effect on p-JNK3.Conclusion1.The mechanical pain sensitivity of bmSNI model rats decreased significantly,and the heat pain decreased slowly.The mechanical pain sensitivity decreased to the lowest value at 5.62g for 7 days.The duration of pain was long and the stability was good.It may be a good model for studying the neuropathic pain.2.Emodin has a therapeutic effect on neuropathic pain.SP600125,a JNK inhibitor,has a clear therapeutic effect on neuropathic pain.According to the analysis of behavioral data,the effect of Emodin to the model is stronger than that of SP600125.3.Western Blotting analysis showed that there was no significant differencein p-JNK3 protein expression in lumbar enlargement between groups.The mean value of Emodin expression appears to be a certain trend.Emodin group>SP600125 group>sham operation group>model group,but there is no significant difference in P value among each group.The significance of this trend can not be confirmed.This trend may be proved afterincreasingthe sample size.