鞘内注射转运蛋白配体对神经病理性疼痛的调节作用及其机制

THE EFFECTS AND UNDERLYING MECHANISMS OF INTRATHECAL INJECTION OF TSPO LIGANDS ON NEUROPATHIC PAIN

目的：探讨鞘内注射18 kDa转运蛋白（18 kDa translocator protein,TSPO）配体对神经病理性疼痛（neuropathic pain,NP）的调节作用及其可能的机制.方法：雄性SD大鼠随机分为4组：假手术组（Vehicle＋Sham组）、对照组（Vehicle＋SNI组）、TSPO激动剂Ro5-4864组（Ro＋SNI组）、TSPO拮抗剂PK11195组（PK＋SNI组）.各组分别于术前、术后第三天（D 3）、第七天（D 7）、第14天（D 14）和第21天（D21）测定大鼠50％的机械刺激缩足阈值（Paw withdrawl threshold,PWT）,第三天行为学测试后,Vehicle＋Sham组和Vehicle＋SNI组鞘内注射溶剂20％ DMSO 4μl,Ro＋SNI组和PK＋SNI组分别注射2 μg激动剂Ro5-4864和2μg拮抗剂PK-11195.应用westernblot检测术后D5、D7、D14、D21天的大鼠L4～6节段同侧脊髓,分别测定胶质纤维酸性蛋白（GFAP）、肿瘤坏死因子-α（TNF-α）的表达水平.结果：（1）各组术前PWT无明显统计学差异（P＞0.05）;术后其余3组较Vehicle＋Sham组相比,PWT值从D3直至D21明显降低,与Vehicle＋Sham组同时间点相比差异具有统计学意义（P＜0.01）;与Ro＋SNI组比较,Ro＋SNI组在鞘内给药后PWT有明显升高,差异有统计学意义（P＜0.01）;而PK＋SNI组在给药后的PWT较Vehicle＋SNI组比较,差异无统计学意义. （2）神经损伤后,Vehicle＋SNI组的GFAP和TNF-α的表达明显增高,与Vehicle＋Sham组同时间点相比差异具有统计学意义（P＜0.01）;与Vehicle＋SNI组比较,Ro＋SNI组在给药后D5的脊髓GFAP表达稍有增高,但在D7、D 14、D21表达明显降低（P＜0.01）,TNF-α的表达在给药后D5直至D 14明显下降,差异有统计学意义（P＜0.0l）.结论：鞘内单次注射TSPO激动剂Ro5-4864可缓解NP大鼠的痛觉超敏,调节星形胶质细胞的活性以及神经免疫反应是其可能的机制之一.

Objective： To investigate the effects and possible mechanisms of intrathecal injection of ligands of 18 kDa translocator protein （TSPO） on neuropathic pain. Methods： All male Sprague-Dawley rats were randomly assigned into 4 groups： sham group （Vehicle＋Sham group）; control group （Vehicle＋SNI group）; TSPO agonist Ro5-4864 group （Ro＋SNI group）; and TSPO antagonist PK11195 group （PK＋SNI group）. The paw withdrawal thresholds （PWT） were measured before surgery and on day 3, 7, 14 and 21 post-operation. On the third day after operation after measuring of PWT, vehicle （20% DMSO 4/μl） were injected intrathecally in Vehicle＋Sham group and Vehicle＋SNI group, and Ro5-4864 and PK1195 （2 μg） were injected intrathecally in Ro＋SNI group and PK＋SNI group. The expression of GFAP and TNF- α in the ipsilateral L4_6 lumbar segments of the spinal cord was analyzed by Western blotting. Results： （1） At baseline, there was no significant difference of PWT among the four groups （P 〉 0.05）. Compared with the Vehicle＋Sham group, rats in the other groups showed significantly lower PWT from Day 3 to 21 （P 〈 0.01）. Compared with the Vehicle＋SNI group, rats in the Ro＋SNI group showed a significant improvement of PWT （P 〈 0.01）. However, TSPO antagonist PK11195 didn＇t show such protective effects in SNI rats. （2） After surgery, the expression of GFAP and TNF- α in the spinal cord were markedly increased （P 〈 0.01）. The expression of GFAP was mildly increased on day 5, but remarkably decreased from day 7 to day 21 in the Ro＋SNI group compared with the control group （P 〈 0.01）. Spinal TNF- α contents were also decreased in the Ro＋SNI group. Conclusions： A single intrathecal injection of TSPO agonist Ro5-4864 attenuated the development of mechanical allodynia in neuropathic pain. TSPO produced these effects via regulation of activities of astrocytes and nerve immune reaction.