Ito Toshinori, Ohtori Seiji, Inoue Gen, Koshi Takana, Doya Hideo, Ozawa Tomoyuki, Saito Tomoko, Moriya Hideshige, Takahashi Kazuhisa
Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
Spine (Phila Pa 1976). 2007 Jan 15;32(2):159-67. doi: 10.1097/01.brs.0000251437.10545.e9.
Immunohistochemical and behavioral study using rat models of lumbar disc herniation and cauda equina syndrome.
To investigate the expression of activated p38 mitogen-activated protein kinases (p38 MAP kinase; p38) in the spinal cord and to determine the effect of intrathecal administration of a specific p38 inhibitor on pain in a lumbar disc herniation model and on motor function and hypoalgesia in a spinal canal stenosis (SCS) model.
In pathologic lumbar disc herniation-induced neuropathic pain and compression of cauda equina-induced motor dysfunction and hypoalgesia caused by SCS, glia are activated and produce certain cytokines, including tumor necrosis factor-alpha (TNF-alpha) and interleukins, which play a crucial role in the pathogenesis of nerve degeneration. p38 is phosphorylated by these cytokines, suggesting that it may play an important role in pain transmission and nerve degeneration. Here we have examined the role of p38 in rat models of lumbar disc herniation and SCS.
Six-week-old male Sprague-Dawley rats were used. For the disc herniation model, autologous nucleus pulposus was applied to L5 nerve roots, which were then crushed. For the SCS model, a piece of silicon was placed under the lamina of the fourth lumbar vertebra. We assessed mechanical allodynia, hypoalgesia, and motor function using von Frey hairs, treadmill tests, and immunohistochemical localization of phosphorylated p38 (P-p38) in the cauda equina, dorsal root ganglion (DRG), and spinal cord, which were also double-stained with NeuN (neuronal marker), GFAP (astrocyte/Schwann cell marker), or isolectin B4 (IB4; microglia marker). We also examined the effects of intrathecal administration of a specific p38 inhibitor, FR167653, on nucleus pulposus-induced pain, hypoalgesia, and motor dysfunction following SCS.
We demonstrated that activated P-p38-immunoreactive cells in the spinal cord and cauda equina were not observed before nerve injury but appeared in the cauda equina, DRG, and spinal dorsal horn in the disc herniation and SCS models. Double-labeling revealed that most P-p38-immunoreactive cells were isolectin B4-labeled microglia and GFAP-immunoreactive Schwann cells. Intrathecal administration of the p38 inhibitor FR167653 decreased mechanical allodynia in the disc herniation model and improved hypoalgesia and intermittent motor dysfunction in the SCS model.
Our findings suggest that activated p38 may play an important role in the involvement of microglia in the pathophysiology of pain following lumbar disc herniation and mechanical hypoalgesia, and motor nerve dysfunction of cauda equina following SCS.
使用腰椎间盘突出症和马尾综合征大鼠模型进行免疫组织化学和行为学研究。
研究活化的p38丝裂原活化蛋白激酶（p38 MAP激酶；p38）在脊髓中的表达，并确定鞘内注射特异性p38抑制剂对腰椎间盘突出症模型疼痛以及椎管狭窄（SCS）模型运动功能和痛觉减退的影响。
在病理性腰椎间盘突出症引起的神经性疼痛以及SCS导致的马尾受压引起的运动功能障碍和痛觉减退中，胶质细胞被激活并产生某些细胞因子，包括肿瘤坏死因子-α（TNF-α）和白细胞介素，它们在神经变性的发病机制中起关键作用。这些细胞因子使p38磷酸化，提示其可能在疼痛传递和神经变性中起重要作用。在此，我们研究了p38在腰椎间盘突出症和SCS大鼠模型中的作用。
使用6周龄雄性Sprague-Dawley大鼠。对于椎间盘突出症模型，将自体髓核应用于L5神经根，然后进行挤压。对于SCS模型，在第四腰椎椎板下放置一块硅片。我们使用von Frey毛发、跑步机试验评估机械性异常性疼痛、痛觉减退和运动功能，并通过免疫组织化学定位马尾、背根神经节（DRG）和脊髓中磷酸化p38（P-p38），并用NeuN（神经元标记物）、GFAP（星形胶质细胞/雪旺细胞标记物）或异凝集素B4（IB4；小胶质细胞标记物）进行双重染色。我们还研究了鞘内注射特异性p38抑制剂FR167653对髓核诱导的疼痛、痛觉减退以及SCS后运动功能障碍的影响。
我们证明，在神经损伤前未观察到脊髓和马尾中活化的P-p38免疫反应性细胞，但在椎间盘突出症和SCS模型的马尾、DRG和脊髓背角中出现。双重标记显示，大多数P-p38免疫反应性细胞是IB4标记的小胶质细胞和GFAP免疫反应性雪旺细胞。鞘内注射p38抑制剂FR167653可减轻椎间盘突出症模型中的机械性异常性疼痛，并改善SCS模型中的痛觉减退和间歇性运动功能障碍。
我们的研究结果表明，活化的p38可能在小胶质细胞参与腰椎间盘突出症后疼痛的病理生理学以及SCS后马尾的机械性痛觉减退和运动神经功能障碍中起重要作用。
