Choi Sheu-Ran, Beitz Alvin J, Lee Jang-Hern
Department of Veterinary Physiology, BK21 PLUS Program for Creative Veterinary Science Research, Research Institute for Veterinary Science and College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
Exp Neurobiol. 2019 Aug 31;28(4):516-528. doi: 10.5607/en.2019.28.4.516.
We have previously demonstrated that the neurosteroid dehydroepiandrosterone sulfate (DHEAS) induces functional potentiation of -methyl-D-aspartate (NMDA) receptors via increases in phosphorylation of NMDA receptor GluN1 subunit (pGluN1). However, the modulatory mechanisms responsible for the expression of the DHEA-synthesizing enzyme, cytochrome P450c17 following peripheral nerve injury have yet to be examined. Here we determined whether oxidative stress induced by the spinal activation of nitric oxide synthase type II (NOS-II) modulates the expression of P450c17 and whether this process contributes to the development of neuropathic pain in rats. Chronic constriction injury (CCI) of the sciatic nerve induced a significant increase in the expression of NOS-II in microglial cells and NO levels in the lumbar spinal cord dorsal horn at postoperative day 5. Intrathecal administration of the NOS-II inhibitor, L-NIL during the induction phase of neuropathic pain (postoperative days 0~5) significantly reduced the CCI-induced development of mechanical allodynia and thermal hyperalgesia. Sciatic nerve injury increased the expression of PKCand PKA-dependent pGluN1 as well as the mRNA and protein levels of P450c17 in the spinal cord at postoperative day 5, and these increases were suppressed by repeated administration of L-NIL. Co-administration of DHEAS together with L-NIL restored the development of neuropathic pain and pGluN1 that were originally inhibited by L-NIL administration alone. Collectively these results provide strong support for the hypothesis that activation of NOS-II increases the mRNA and protein levels of P450c17 in the spinal cord, ultimately leading to the development of central sensitization and neuropathic pain induced by peripheral nerve injury.
我们之前已经证明，神经甾体硫酸脱氢表雄酮（DHEAS）通过增加N-甲基-D-天冬氨酸（NMDA）受体GluN1亚基的磷酸化（pGluN1）来诱导NMDA受体的功能增强。然而，外周神经损伤后负责DHEA合成酶细胞色素P450c17表达的调节机制尚未得到研究。在这里，我们确定脊髓中II型一氧化氮合酶（NOS-II）激活所诱导的氧化应激是否调节P450c17的表达，以及这一过程是否促成大鼠神经性疼痛的发展。坐骨神经慢性压迫损伤（CCI）在术后第5天导致小胶质细胞中NOS-II的表达以及腰脊髓背角中NO水平显著增加。在神经性疼痛诱导期（术后第0至5天）鞘内注射NOS-II抑制剂L-NIL可显著减轻CCI诱导的机械性异常性疼痛和热痛觉过敏的发展。坐骨神经损伤在术后第5天增加了脊髓中PKC和PKA依赖性pGluN1的表达以及P450c17的mRNA和蛋白水平，而这些增加被反复注射L-NIL所抑制。将DHEAS与L-NIL共同给药可恢复原本单独注射L-NIL所抑制的神经性疼痛和pGluN1的发展。总体而言，这些结果为以下假设提供了有力支持：NOS-II的激活增加了脊髓中P450c17的mRNA和蛋白水平，最终导致外周神经损伤诱导的中枢敏化和神经性疼痛的发展。
