Sung Chun-Sung, Wen Zhi-Hong, Chang Wen-Kuei, Chan Kwok-Hon, Ho Shung-Tai, Tsai Shen-Kou, Chang Yi-Chen, Wong Chih-Shung
Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan.
J Neurochem. 2005 Aug;94(3):742-52. doi: 10.1111/j.1471-4159.2005.03226.x.
We have reported recently that intrathecal (i.t.) injection of interleukin-1beta (IL-1beta), at a dose of 100 ng, induces inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in the spinal cord and results in thermal hyperalgesia in rats. This study further examines the role of mitogen-activated protein kinase (MAPK) in i.t. IL-1beta-mediated iNOS-NO cascade in spinal nociceptive signal transduction. All rats were implanted with an i.t. catheter either with or without an additional microdialysis probe. Paw withdrawal latency to radiant heat is used to assess thermal hyperalgesia. The iNOS and MAPK protein expression in the spinal cord dorsal horn were examined by western blot. The [NO] in CSF dialysates were also measured. Intrathecal IL-1beta leads to a time-dependent up-regulation of phosphorylated p38 (p-p38) MAPK protein expression in the spinal cord 30-240 min following IL-1beta injection (i.t.). However, neither the phosphorylated extracellular signal-regulated kinase (p-ERK) nor phosphorylated c-Jun NH2-terminal kinase (p-JNK) was affected. The total amount of p38, ERK, and JNK MAPK proteins were not affected following IL-1beta injection. Intrathecal administration of either selective p38 MAPK, or JNK, or ERK inhibitor alone did not affect the thermal nociceptive threshold or iNOS protein expression in the spinal cord. However, pretreatment with a p38 MAPK inhibitor significantly reduced the IL-1beta-induced p-p38 MAPK expression by 38-49%, and nearly completely blocked the subsequent iNOS expression (reduction by 86.6%), NO production, and thermal hyperalgesia. In contrast, both ERK and JNK inhibitor pretreatments only partially (approximately 50%) inhibited the IL-1beta-induced iNOS expression in the spinal cord. Our results suggest that p38 MAPK plays a pivotal role in i.t. IL-1beta-induced spinal sensitization and nociceptive signal transduction.
我们最近报道，鞘内（i.t.）注射剂量为100 ng的白细胞介素-1β（IL-1β）可诱导大鼠脊髓中诱导型一氧化氮合酶（iNOS）表达和一氧化氮（NO）生成，并导致热痛觉过敏。本研究进一步探讨丝裂原活化蛋白激酶（MAPK）在鞘内IL-1β介导的脊髓伤害性信号转导中iNOS-NO级联反应中的作用。所有大鼠均植入了鞘内导管，部分大鼠还额外植入了微透析探针。通过测量对辐射热的爪部退缩潜伏期来评估热痛觉过敏。采用蛋白质印迹法检测脊髓背角中iNOS和MAPK蛋白表达。同时也测量脑脊液透析液中的[NO]。鞘内注射IL-1β后30 - 240分钟，脊髓中磷酸化p38（p-p38）MAPK蛋白表达呈时间依赖性上调。然而，磷酸化细胞外信号调节激酶（p-ERK）和磷酸化c-Jun氨基末端激酶（p-JNK）均未受影响。注射IL-1β后，p38、ERK和JNK MAPK蛋白的总量未受影响。单独鞘内注射选择性p38 MAPK、JNK或ERK抑制剂均不影响热痛觉阈值或脊髓中iNOS蛋白表达。然而，用p38 MAPK抑制剂预处理可使IL-1β诱导的p-p38 MAPK表达显著降低38 - 49%，并几乎完全阻断随后的iNOS表达（降低86.6%）、NO生成和热痛觉过敏。相比之下，ERK和JNK抑制剂预处理仅部分（约50%）抑制IL-1β诱导的脊髓中iNOS表达。我们的结果表明，p38 MAPK在鞘内IL-1β诱导的脊髓敏化和伤害性信号转导中起关键作用。
