Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, People's Republic of China.
Center for Laboratory Medicine, the First Affiliated Hospital of Nanchang University, Nanchang, China.
Pain. 2020 Apr;161(4):758-772. doi: 10.1097/j.pain.0000000000001761.
High-frequency stimulation (HFS) of the sciatic nerve has been reported to produce long-term potentiation (LTP) and long-lasting pain hypersensitivity in rats. However, the central underlying mechanism remains unclear. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) belongs to a group of electron-transporting transmembrane enzymes that produce reactive oxygen species (ROS). Here, we found that NOX2 was upregulated in the lumbar spinal dorsal horn after HFS of the left sciatic nerve, which induced bilateral pain and spinal LTP in both male and female rats. Blocking NOX2 with blocking peptide or shRNA prevented the development of bilateral mechanical allodynia, the induction of spinal LTP, and the phosphorylation of N-methyl-d-aspartate (NMDA) receptor 2B (GluN2B) and nuclear factor kappa-B (NF-κB) p65 after HFS. Moreover, NOX2 shRNA reduced the frequency and amplitude of both spontaneous excitatory postsynaptic currents and miniature excitatory postsynaptic currents in laminar II neurons. Furthermore, 8-hydroxyguanine (8-OHG), an oxidative stress marker, was increased in the spinal dorsal horn. Spinal application of ROS scavenger, Phenyl-N-tert-butylnitrone (PBN), depressed the already established spinal LTP. Spinal application of H2O2, one ROS, induced LTP and bilateral mechanical allodynia, increased the frequency and amplitude of spontaneous excitatory postsynaptic currents in laminar II neurons, and phosphorylated GluN2B and p65 in the dorsal horn. This study provided electrophysiological and behavioral evidence that NOX2-derived ROS in the spinal cord contributed to persistent mirror-image pain by enhancing the synaptic transmission, which was mediated by increasing presynaptic glutamate release and activation of NMDA receptor and NF-κB in the spinal dorsal horn.
高频刺激（HFS）坐骨神经已被报道在大鼠中产生长时程增强（LTP）和持久的痛觉过敏。然而，中枢潜在机制尚不清楚。烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶（NOX）属于一组产生活性氧（ROS）的电子传递跨膜酶。在这里，我们发现 HFS 左侧坐骨神经后，L4-L6 脊髓背角中 NOX2 上调，导致雌雄大鼠双侧痛觉过敏和脊髓 LTP。用阻断肽或 shRNA 阻断 NOX2 可防止双侧机械性痛觉过敏、脊髓 LTP 的诱导以及 NMDA 受体 2B（GluN2B）和核因子 kappa-B（NF-κB）p65 的磷酸化。此外，NOX2 shRNA 降低了 II 层神经元中自发性兴奋性突触后电流和微小兴奋性突触后电流的频率和幅度。此外，脊髓背角中 8-羟基鸟嘌呤（8-OHG），一种氧化应激标志物增加。ROS 清除剂 Phenyl-N-tert-butylnitrone（PBN）的脊髓应用抑制了已经建立的脊髓 LTP。ROS 之一 H2O2 的脊髓应用诱导 LTP 和双侧机械性痛觉过敏，增加 II 层神经元中自发性兴奋性突触后电流的频率和幅度，并使背角中的 GluN2B 和 p65 磷酸化。本研究提供了电生理学和行为学证据，表明脊髓中 NOX2 衍生的 ROS 通过增强突触传递而导致持续的镜像疼痛，这是通过增加突触前谷氨酸释放和 NMDA 受体和 NF-κB 在脊髓背角中的激活来介导的。
