HSO14 Participated In Neuropathic Pain Through Regulating Inflammatory Cytokines Mediated By ERK1/2 Signaling Pathway In CCI Rats

Object To observe the effect of HS014(MC4R antagonist)and U0126(ERK inhibitor)on the pain threshold of CCI rats,and the effect of p-ERK in spinal dorsal horn and inflammatory factor TNF-alpha and IL-1 beta expression,to discuss the effect of HSO14 plays in neuropathic pain,to explore the mechanism of MC4 R involved in this type of pain.Methods Ninety-six Sprague Dawley(SD)rats were randomly divided into four groups?Sham group :only to expose the sciatic nerve and not get surgical ligation.CCI group:expose the sciatic nerve with 4 loose ligatures on the sciatic nerve by 4-0 silk suture at 1mm intervals.HS014 group: CCI+HSO14(MC4 Rantagonist),10?g/day,for seven days.U0126group: CCI + U0126(ERK1/2 antagonist)5?g/day,for seven days.Thermal hyperalgesia and mechanical allodynia were respectively measured on pre-operative day 1 and postoperative day 3,7 and 14.In addition,DRG linked to the injury sciatic nerve were isolated for analyzing protein and cytokine levels by immunohistochemistry staining.The level of ERK1/2 and MC4 R in the L4-6 spinal cord horn was tested by western blot and immunofluorescence.The protein expressions of TNF-?,IL,-1? were investigated by ELISA kit.Result Our results show that :1)The thermal threshold in CCI group was obviously lower than sham group with operation(p<0.01).thermal hyperalgesia were reduced in the HS014 group and U0126 group as compared to that in the CCI group.2)HS014 not only inhibited the expression of MC4 R,but also reduced the ERK1/2 in DRG.Moreover,HS014 significantly suppressed the release of pro-inflammatory cytokines in CCI-treated DRG,including interleukin 1-?(IL-1?)and so on.3)Intrathecal injection of U0126 prevented the release of pro-inflammatory cytokines unaccompanied by blocking the activaton of ERK1/2but not the expression of M4 CR.Conclusion The mechanisms of neuropathic pain is that HS014 decrease the neuropathic pain related to the inbitition of ERK1/2 activation,and at the same time ERK1/2 may be a downstream of MC4 R in the neuropathic pain induced by CCI.Based on these findings we propose that HS014 participated in this kind of neuropathic pain by the means of ERK1/2.