Studies On The Anti-neuropathic Pain Effects And Its Mechanism Of The Escin

Objective This study aims to investigate potential analgesic effects and its mechanism of the escin on alleviating neuropathic pain(NP)in rat model of CCI.Method 1.The acute pain model induced by formalin and carrageenan was used to record the duration of licking,number of flinches,nociceptive score and the paw edema to verify the analgesic effect of escin.Real-time PCR(RT-PCR)was used to detect the gene expression of c-Fos,μ opoid receptor and Potassium Two-pore domain Channel Subfamily member 1.1(KCNK1)in dorsal root ganglion(DRG).2.Lipopolysaccharide(LPS)was used to induce PC12 cell damage,and the effects of different concentrations of escin on PC12 cell survival and lactate dehydrogenase(LDH)levels were detected,and the cell morphology was observed under an inverted microscope.3.NP was induced by chronic sciatic nerve compression injury(CCI),and behavioral measurements were performed at 3,5,7 and 14 days after surgery.Three days after the operation,the drug was administered by gavage,with gabapentin(60 mg/kg/d),low dose of escin(7 mg/kg/d),medium dose of escin(14 mg/kg/d)and high dose of escin(28 mg/kg/d)for 14 days.After the end of the administration,the rat DRGs tissues was collected and the relevant indicators were detected.RT-PCR was used to detect the expression of Tolllike receptor 4(TLR4)and nuclear factor-κB(NF-κB).Immunohistochemical analysis was used to analyze the expression of GFAP and nerve growth factor(NGF).The levels of tumor necrosis factor-α(TNF-α)and interleukin-1β(IL-1β)were detected by enzyme-linked immunosorbent assay(ELISA).Result 1.In formalin-induced pain test,the duration of licking,number of flinches,nociceptive score in the model group were significantly higher than those in the normal group(phase I and phase II)(P<0.01).Compared with the model group,escin and indomethacin were able to significantly reduce the duration of licking,number of flinches,nociceptive score of mice(phase II)(P<0.01 or P<0.05),but there was no significant difference in the behavior of phase I(P>0.05).RT-PCR results showed that,compared with the model group,escin and indomethacin can significantly reduce the gene expression of c-Fos in DRGs(P<0.01 or P<0.05),and obviously increase the gene expression of KCNK1(P<0.01).In addition,high dose of escin and indomethacin significantly increase the gene expression of μ opoid receptor(P<0.05).In carrageenan-induced rat paw edema test,the paw edema in the model group was significantly increased after injection of carrageenan for 1 to 6 h(P<0.05 or P<0.01).Compared with the model group,indomethacin and high dose of escin significantly decreased the rats paw edema after injection of carrageenan for 1 h and 2 h(P<0.05),and after injection of carrageenan for 2 h,the medium dose of escin significantly reduced the rats paw edema(P<0.05);the escin and indomethacin significantly reduced the paw edema after injection of carrageenan for 3 to 6 h(P<0.05).2.The morphology of PC12 cells pretreated with escin under inverted microscope was improved,and the PC12 cells remained in a normal state with protrusions and not aggregated.Otherwise,compared with the model group,the medium and high-dose of escin significantly increased the cell viability(P<0.05 or P<0.01)and significantly decreased LDH level(P<0.05 or P<0.01).3.The CCI model was successfully established.Compared with the normal group,no significant difference were found in the thermal threshold and biochemical indexes of the sham group(P>0.05),excluding the interference of operation.Compared with the model group,the thermal threshold of the rats in the gabapentin and low-dose,medium-dose of escin were significantly increased(P<0.05),and the high-dose escin significantly increase the thermal threshold of rats(P<0.01).Gabapentin and escin significantly reduced the gene expression of TLR4 and NF-κB(P<0.01),as well as the levels of TNF-α and IL-1β(P<0.01).Furthermore,the medium and high-dose escin significantly decreased the expression of GFAP and NGF(P<0.01 or P<0.05).Conclusion 1.Escin has an analgesic effect on acute inflammatory pain,and its mechanism may be related to down-regulation of c-Fos and up-regulation of MOR and KCNK1.2.Escin has an anti-neuropathic pain effect,and its mechanism may be related to the neuroprotection,inhibition of TLR4 / NF-κB signaling pathway,down-regulation of GFAP and NGF expression,and decrease the contents of TNF-α and IL-1β.