Curcumin Down Regulates P38MAPK Pathway Alleviates Neuropathic Pain In Mice

Objective:The purpose of this study was to explore the possible mechanism of curcumin in relieving neuropathic pain.Methods:Adult male C57BL/6 mice aged 6-8 weeks and weighing 20±2g were selected and the neuropathic pain model was established by the method of spared nerve injury?SNI?.To observe the effect of different doses of cur on behavior of mice.part 1:?1?30 mice were randomly divided into five groups:sham group,SNI 1d,SNI3d,SNI 7d and SNI 14d.Each group consisted of six mice,and the paw withdrawal threshold?PWT?was used to judge whether the model was successful.After the success of the model,After the success of the model,PWT was measured at the present time points?1d,3d,7d,14d?,and then the experimental animals were killed and L_4-6 spinal cord tissues were retained.The expression of inflammatory factors?IL-1?,IL-6,TNF-??and p-p38 in the spinal cord tissues of mice were observed by Western blot and the changes with time were observed by immunofluorescence.?2?Thirty mice were randomly divided into sham group,SNI+DMSO group,SNI+low-dose Cur?50mg/kg?group,SNI+medium-dose Cur?100mg/kg?group,and SNI+high-dose Cur?200mg/kg?group.5 groups?n=6?;no intervention was performed in the sham group,the same volume of DMSO was injected intraperitoneally in the no-load group,and different doses of Cur?50,100,200?mg/kg were injected intraperitoneally daily in the experimental group,and whether the model was judged by PWT The effects of different doses of Cur on the neuropathic pain behavior of mice were successfully observed.The experimental animals were sacrificed on the Third day and L_4-6 segmental spinal cord tissue was extracted.Western blot was used to observe the different levels of Cur on inflammatory factors and Effect of p-p38.The expression and localization of p-p38 in the spinal dorsal horn of mice were observed by immunofluorescence.Part 2:To observe the effect of Cur on neuropathic pain behavior in mice after intrathecal injection of p38 activator?U-46619?,24 mice were randomly divided into sham group,SNI+DMSO group,SNI+Cur 100mg/kg)group,SNI+U-46619+Cur?100mg/kg?group,a total of 4 groups?n=6?,Western blot and immunofluorescence were used to observe the expression of p-p38 in mouse spinal cord and spinal cord tissues.Western blot was used to observe the expression of inflammatory factors in the spinal cord tissue of mice.The expression of inflammatory factors?IL-1?,IL-6,IL-10,TNF-??in the spinal cord and serum of mice was detected by enzyme-linked immunosorbent assay,The expression of p-p38in the dorsal horn of spinal cord of mice after intrathecal injection of p38 activator was observed by immunofluorescence.Result:1.Results of behavioral test:?1?There was no significant difference in PWT between the two groups.?P>0.05?;?2?PWT of mice operated by SNI on the first day after operation was significantly lower than that of sham group?P<0.01?;PWT of mice in curcumin 100mg/kg group was significantly higher than that of SNI group on the third day after operation?P<0.001?;?3?The PWT of mice in the p38activator?U-46619?group was significantly lower than that of the Cur group?100mg/kg?group?P<0.001?.2.Western blotting results:?1?on the third day after operation,compared with sham group,the expression of inflammatory factors?IL-1?,IL-6,TNF-??and p-p38in the spinal dorsal horn of SNI group showed the highest expression levels?P<0.05?;?2?Compared with the SNI group,the expression levels of inflammatory factors?IL-1?,IL-6,TNF-??and p-p38 in the spinal dorsal horn of the Cur group?100mg/kg?were decreased?P<0.01?.?3?Compared with Cur?100mg/kg?group,the expression levels of inflammatory factors?IL-1?,IL-6,TNF-??and p-p38 in the spinal dorsal horn of the group using p38 activator?U-46619?were significantly increased?P<0.01?.3.Immunofluorescence test results:?1?compared with sham group,the expression of p-p38 in spinal dorsal horn of SNI group increased significantly;?2?compared with SNI group,the expression of p-p38 in spinal dorsal horn of cur?100mg/kg?group decreased significantly;?3?compared with cur?100mg/kg?,the expression of p-p38 in spinal dorsal horn of U-46619 group recovered significantly.4.Results of enzyme-linked immunosorbent assay:compared with sham group,the expression of inflammatory factors?IL-1?,IL-6,IL-10,TNF-??in SNI group was significantly higher?P<0.01?;compared with SNI group,the expression of cur?100mg/kg?group was significantly lower?P<0.01?;compared with cur?100mg/kg?,the expression of p38 activator?U-46619?was significantly higher?P<0.01?There was significant difference between the two groups?P<0.05?.Conclusion:1.Spared nerve injury?SNI?can induce neuropathic pain in mice;2.Curcumin at different doses has analgesic effect on neuropathic pain,of which curcumin at the medium dose?100mg/kg?has the best effect;3.Curcumin relieves neuropathic pain in mice by down-regulating p38MAPK pathway.