鞘内注射盐酸羟考酮下调脊髓小胶质细胞中c-JNK/CXCL1信号减弱坐骨神经结扎大鼠的神经病理性痛

Intrathecal injection of oxycodone hydrochloride reduces neuropathic pain in rat model of chronic constriction injury via inhibition of microglial c-JNK/CXCL1 signal

目的 观察鞘内注射盐酸羟考酮对坐骨神经结扎大鼠痛阈、脊髓小胶质细胞中c-JNK/CXCL1信号的影响.方法 SD大鼠按随机数字表法分为5组（每组40只）：假手术组（Sham组）、坐骨神经结扎组（CCI组）、盐酸羟考酮组[Oxy组,结扎前3d鞘内注射盐酸羟考酮（5μg/30μl）]、米诺环素组[Mino组,结扎前3d鞘内注射米诺环素（5μg/30μl）]及c-JNK抑制剂组[SP组,结扎前3d鞘内注射S1P600125（5μg/30μl）].Sham组仅暴露坐骨神经而不结扎.其余各组均行右侧坐骨神经结扎术,于L5-6鞘内置管并连续注射3d.术后1、3、5、7、14 d分别测定各组大鼠的热痛阈及机械性痛阈;取第4～6节腰段脊髓采用免疫荧光法观察小质细胞的活化状态,Weston blot法检测脊髓组织中小胶质细胞特异性标记物Ⅰ ba-1、p-c-JNK以及CXCL1表达.结果 与Sham组相比,CCI组大鼠术后各观察点热痛阈和机械性痛阈明显降低,损伤后7d脊髓组织中Ⅰ ba-1、p-c-JNK和CXCL1的表达增加（P＜0.05）;与CCI组比较,Oxy组、Mino组和SP组大鼠热痛阈和机械性痛阈值明显提高（P＜0.05）,脊髓组织中p-c-JNK、Ⅰ ba-1和CXCL1的表达降低（P＜0.05）.损伤后7d,免疫荧光染色显示CCI组脊髓背角内可见Ⅰ ba-1阳性的细胞明显增加（P＜0.05）,外形由静息多分支样转变成变形虫样,而Oxy组、Mino组、SP组小胶质细胞多呈树枝样,Ⅰ ba-1阳性细胞数目减少.Oxy组、Mino组和SP组三组比较上述指标差异无统计学意义（P＞0.05）.结论 鞘内注射盐酸羟考酮可以通过下调脊髓小胶质细胞中c-JNK/CXCL1信号减轻坐骨神经结扎引起的神经病理性疼痛程度,为临床治疗神经病理性疼痛提供新的治疗靶点.

Objective To observe the effect of intrathecal injection （IT） of oxycodone hydrochloride on neuropathic pain and spinal cord level of microglial c-Jun N-terminal kinase/chemokine （C-X-C motif） ligand 1 （c-JNK/CXCL） 1signal in rat model of chronic constriction injury （CCI）.Methods Male Sprague-Dawley rats were randomly divided into five groups （n =40 per group）：sham group （intrathecal normal saline,IT NS）,CCI group （CCI ＋ IT NS）,oxy group （CCI ＋ IT 5 μg/30 μl oxy）,mino group （CCI ＋ IT 5 μg/30 μl Minocycline）,and c-JNK inhibitor group （SP group,CCI ＋ IT 5 μg/30 μl SP600125）.The lumbar intrathecal catheters were implanted in L5-6 of rats and CCI models were established as previously described.The thermal and mechanical nociceptive thresholds were assessed by paw withdrawal latency （PWL） to radiant heat and von Frey filaments.The oxycodone,minocycline and SP600125 were administered intrathecally for 3 days before surgery.The spinal cord expression of Ⅰ ba-1,p-c-JNK and CXCL1 proteins assessed by Western blot.Immunofluorescence staining was performed to examine microglia morphology and the number of Ⅰ ba-1 positives cells in dorsal horn of injured spinal cord at 7 days post-IR.Results Compared to sham group,rats in CCI group had significantly lower mechanical and thermal pain thresholds,but higher spinal proteins expression of Ⅰ ba-1,and p-c-JNK and CXCL1 （P 〈0.05）.Rats in oxy group,mino group and SP group had significantly higher mechanical and thermal pain thresholds and significantly lower proteins expression of Ⅰ ba-1,p-c-JNK and CXCL1 compared to those in CCI group （at any observed time-point after ligation,but most significantly at 7days,P 〈 0.05）.At the 7days after surgery,microglial cells in CCI group transformed from the ramified shape to amoeboid macrophage-like shape by immunofluorescence staining with the increases of Ⅰ ba-1 positive cells;while the other three groups exhibited hypertrophic morphology with less number Ⅰ ba-1 positive cells （P 〈 0.05）.There were no significant differences between these three groups at any observed time （P 〉 0.05）.Conclusions Intrathecal injection of oxycodone hydrochloride can relieve CCI-induced neuropathic pain by down-regulation microglial c-JNK/CXCL1 signal in spinal cords.Provide new therapeutic targets for clinical treatment of neuropathic pain.