脊髓背角ERK/MAPK通路在髓核致炎大鼠神经根炎性痛维持中的作用

ROLE OF ERK/MAPK SIGNALING PATHWAY IN SPINAL DORSAL HORN IN A RAT MODEL WITH RADICULAR PAIN INDUCED BY INFLAMMATORY NUCLEUS PULPOSUS RADICULAR PAIN INDUCED BY INFLAMMATORY NUCLEUS PULPOSUS

目的:观察脊髓背角磷酸化ERK(pERK)在髓核致炎大鼠神经根炎性痛进程中的表达变化,及硬膜外腔注射ERK通路抑制剂U0126对大鼠机械性痛阈的影响。方法:成年雄性SD大鼠56只,随机分为3组:Blank组(13只)、Sham组(13只)、手术模型组(NP组,30只),检测所有大鼠术前1 d,术后1、4、7、14、21 d和28 d的50%机械痛缩足阈值(50%MWT)。Blank组和Sham组于术后7 d及NP组于术后1、4、7、14、21 d取大鼠腰段脊髓背角,应用Western blot方法检测各时点pERK蛋白含量。另一成年雄性SD大鼠80只,随机分为blank组(13只),sham组(13只),NP组(13只),DMSO组(13只)和U0126组(28只),DMSO组、U0126组分别于术后第6天单次硬膜外腔注射10%DMSO 50μl和10μg/50μl U0126。给药前和给药后多个时点均进行疼痛行为学测定。Blank、Sham和NP组于术后第6d取腰段脊髓背角,DMSO组于给药后6 h取材,U0126组于给药后2、4、6、24 h取材,通过免疫组化技术观察脊髓背角pERK阳性产物。结果:与Sham组相比,髓核致炎性神经根痛大鼠腰段脊髓背角pERK在术后1、4、7、14和21 d多个时点表达均增加(P<0.05)。术后第6 d单次硬膜外腔给予U0126后4 h髓核致痛大鼠的50%MWT明显提高(P<0.05),持续至给药后8 h,同时伴有脊髓背角pERK表达减少(P<0.05)。结论:腰段脊髓背角pERK在髓核致炎性神经根痛进程中表达增加,给予ERK通路抑制剂U0126可缓解痛觉过敏,脊髓背角ERK/MAPK通路在髓核致炎大鼠神经根炎性痛维持中起重要作用。

Objective：To investigate the changes of phosphorylation of ERK in spinal dorsal horn and the effect of epidural injection of ERK signaling pathway inhibitor U0126 on the mechanical hyperalgesia in rats with inflammatory radicular pain of nucleus pulposus（NP）. Methods ：The experiment was carried out in two parts. In part I, 56 adult male rats were randomized into three groups： blank（n = 13）, sham（n = 13） and model（NP group,n = 30）. 50% paw withdrawal mechanical threshold（50% MWT） was measured 1 day before surgery and on postoperative days 1, 4, 7, 14, 21, 28 in each group. On day 7 the blank and sham group rats and on days 1, 4, 7, 14, 21 after surgery the NP group rats were killed and the lumbar（L4-6） segment of spinal dorsal horns were removed for the determination of pERK expression by western blot technique. In part II, 80 adult male rats were randomized into five groups： blank（n = 14）, sham（n = 13）, model（n = 13）, U0126（n = 13） and DMSO（n = 28）. A dose of 50 μl of 10 μg Osthole or 10% DMSO was epidurally administrated on postoperative day 6. The L4-6 spinal dorsal horns were harvested on day 6 in the blank and sham group and at 6 hours after drug administration in DMSO group and at 2, 4, 6, 24 hours after drug administration in NP group for the determination of pERK expression in the spinal dorsal horn by immunohistochemical technique. Results：Compared with sham group, the expression of pERK in spinal dorsal horn was enhanced in the rats with inflammatory radicular pain（P〈0.05）. The 50% MWT was elevated significantly from 4 hour to 8 hour after epidural application of ERK signaling pathway inhibitor U0126 on postoperative day 6（P〈0.05）, accompanied by reduced expression of pERK（P〈0.05）. Conclusion ：The expression of pERK in spinal dorsal horn was enhanced in the rats with inflammatory radicular pain and the mechanical hyperalgesia was alleviated by epidural application of ERK signaling pathway inhibitor U0126. Activation of ERK/MAPK signaling pathway in spinal dorsal horn plays an important role in the radicular pain induced by inflammatory nucleus pulposus.