Abe Tetsuya, Matsumura Shinji, Katano Tayo, Mabuchi Tamaki, Takagi Kunio, Xu Li, Yamamoto Akitsugu, Hattori Kotaro, Yagi Takeshi, Watanabe Masahiko, Nakazawa Takanobu, Yamamoto Tadashi, Mishina Masayoshi, Nakai Yoshihide, Ito Seiji
Department of Medical Chemistry, Kansai Medical University, Moriguchi 570-8506, Japan.
Eur J Neurosci. 2005 Sep;22(6):1445-54. doi: 10.1111/j.1460-9568.2005.04340.x.
Despite abundant evidence implicating the importance of N-methyl-D-aspartate (NMDA) receptors in the spinal cord for pain transmission, the signal transduction coupled to NMDA receptor activation is largely unknown for the neuropathic pain state that lasts over periods of weeks. To address this, we prepared mice with neuropathic pain by transection of spinal nerve L5. Wild-type, NR2A-deficient, and NR2D-deficient mice developed neuropathic pain; in addition, phosphorylation of NR2B subunits of NMDA receptors at Tyr1472 was observed in the superficial dorsal horn of the spinal cord 1 week after nerve injury. Neuropathic pain and NR2B phosphorylation at Tyr1472 were attenuated by the NR2B-selective antagonist CP-101,606 and disappeared in mice lacking Fyn kinase, a Src-family tyrosine kinase. Concomitant with the NR2B phosphorylation, an increase in neuronal nitric oxide synthase activity was visualized in the superficial dorsal horn of neuropathic pain mice by NADPH diaphorase histochemistry. Electron microscopy showed that the phosphorylated NR2B was localized at the postsynaptic density in the spinal cord of mice with neuropathic pain. Indomethacin, an inhibitor of prostaglandin (PG) synthesis, and PGE receptor subtype EP1-selective antagonist reduced the NR2B phosphorylation in these mice. Conversely, EP1-selective agonist stimulated Fyn kinase-dependent nitric oxide formation in the spinal cord. The present study demonstrates that Tyr1472 phosphorylation of NR2B subunits by Fyn kinase may have dual roles in the retention of NMDA receptors in the postsynaptic density and in activation of nitric oxide synthase, and suggests that PGE2 is involved in the maintenance of neuropathic pain via the EP1 subtype.
尽管有大量证据表明脊髓中的N-甲基-D-天冬氨酸（NMDA）受体在疼痛传递中具有重要作用，但对于持续数周的神经性疼痛状态，与NMDA受体激活相关的信号转导在很大程度上仍不清楚。为了解决这个问题，我们通过切断L5脊髓神经制备了患有神经性疼痛的小鼠。野生型、NR2A缺陷型和NR2D缺陷型小鼠均出现了神经性疼痛；此外，在神经损伤后1周，在脊髓背角浅层观察到NMDA受体NR2B亚基在Tyr1472位点的磷酸化。NR2B选择性拮抗剂CP-101,606可减轻神经性疼痛和Tyr1472位点NR2B的磷酸化，在缺乏Fyn激酶（一种Src家族酪氨酸激酶）的小鼠中则消失。与NR2B磷酸化同时，通过NADPH黄递酶组织化学在神经性疼痛小鼠的脊髓背角浅层观察到神经元型一氧化氮合酶活性增加。电子显微镜显示，磷酸化的NR2B定位于患有神经性疼痛小鼠脊髓的突触后致密区。前列腺素（PG）合成抑制剂吲哚美辛和PGE受体亚型EP1选择性拮抗剂可降低这些小鼠中NR2B的磷酸化。相反，EP1选择性激动剂可刺激脊髓中Fyn激酶依赖性一氧化氮的形成。本研究表明，Fyn激酶介导的NR2B亚基Tyr1472磷酸化可能在NMDA受体在突触后致密区的保留以及一氧化氮合酶的激活中具有双重作用，并提示PGE2通过EP1亚型参与神经性疼痛的维持。
