Azrieli Faculty of Medicine, Bar-Ilan University, Zefat, Israel.
Research Institute of Galilee Medical Center, P.O.B 21, 22100, Nahariya, Israel.
J Transl Med. 2023 Aug 15;21(1):545. doi: 10.1186/s12967-023-04414-x.
Peripheral nerve injury can cause neuroinflammation and neuromodulation that lead to mitochondrial dysfunction and neuronal apoptosis in the dorsal root ganglion (DRG) and spinal cord, contributing to neuropathic pain and motor dysfunction. Hyperbaric oxygen therapy (HBOT) has been suggested as a potential therapeutic tool for neuropathic pain and nerve injury. However, the specific cellular and molecular mechanism by which HBOT modulates the development of neuropathic pain and motor dysfunction through mitochondrial protection is still unclear.
Mechanical and thermal allodynia and motor function were measured in rats following sciatic nerve crush (SNC). The HBO treatment (2.5 ATA) was performed 4 h after SNC and twice daily (12 h intervals) for seven consecutive days. To assess mitochondrial function in the spinal cord (L2-L6), high-resolution respirometry was measured on day 7 using the OROBOROS-O2k. In addition, RT-PCR and Immunohistochemistry were performed at the end of the experiment to assess neuroinflammation, neuromodulation, and apoptosis in the DRG (L3-L6) and spinal cord (L2-L6).
HBOT during the early phase of the SNC alleviates mechanical and thermal hypersensitivity and motor dysfunction. Moreover, HBOT modulates neuroinflammation, neuromodulation, mitochondrial stress, and apoptosis in the DRG and spinal cord. Thus, we found a significant reduction in the presence of macrophages/microglia and MMP-9 expression, as well as the transcription of pro-inflammatory cytokines (TNFa, IL-6, IL-1b) in the DRG and (IL6) in the spinal cord of the SNC group that was treated with HBOT compared to the untreated group. Notable, the overexpression of the TRPV1 channel, which has a high Ca permeability, was reduced along with the apoptosis marker (cleaved-Caspase3) and mitochondrial stress marker (TSPO) in the DRG and spinal cord of the HBOT group. Additionally, HBOT prevents the reduction in mitochondrial respiration, including non-phosphorylation state, ATP-linked respiration, and maximal mitochondrial respiration in the spinal cord after SNC.
Mitochondrial dysfunction in peripheral neuropathic pain was found to be mediated by neuroinflammation and neuromodulation. Strikingly, our findings indicate that HBOT during the critical period of the nerve injury modulates the transition from acute to chronic pain via reducing neuroinflammation and protecting mitochondrial function, consequently preventing neuronal apoptosis in the DRG and spinal cord.
周围神经损伤可引起神经炎症和神经调节，导致背根神经节（DRG）和脊髓中线粒体功能障碍和神经元凋亡，导致神经性疼痛和运动功能障碍。高压氧治疗（HBOT）已被提议作为治疗神经性疼痛和神经损伤的潜在治疗工具。然而，HBOT 通过保护线粒体来调节神经性疼痛和运动功能障碍发展的确切细胞和分子机制尚不清楚。
在坐骨神经挤压（SNC）后测量大鼠的机械和热感觉过敏和运动功能。在 SNC 后 4 小时进行 HBO 治疗（2.5ATA），并连续 7 天每天两次（12 小时间隔）。为了评估脊髓（L2-L6）中的线粒体功能，在第 7 天使用 OROBOROS-O2k 进行高分辨率呼吸测量。此外，在实验结束时进行 RT-PCR 和免疫组织化学，以评估 DRG（L3-L6）和脊髓（L2-L6）中的神经炎症、神经调节和细胞凋亡。
SNC 早期的 HBOT 可减轻机械和热感觉过敏以及运动功能障碍。此外，HBOT 调节 DRG 和脊髓中的神经炎症、神经调节、线粒体应激和细胞凋亡。因此，我们发现与未治疗组相比，SNC 组中巨噬细胞/小胶质细胞的存在以及 MMP-9 表达和促炎细胞因子（TNFa、IL-6、IL-1b）的转录（IL6）在脊髓中的表达明显减少。值得注意的是，TRPV1 通道的过度表达（具有高钙通透性）与 DRG 和 HBOT 组脊髓中的凋亡标志物（cleaved-Caspase3）和线粒体应激标志物（TSPO）一起减少。此外，HBOT 可防止 SNC 后脊髓中线粒体呼吸减少，包括非磷酸化状态、ATP 连接呼吸和最大线粒体呼吸。
周围神经性疼痛中的线粒体功能障碍被发现是由神经炎症和神经调节介导的。令人惊讶的是，我们的研究结果表明，在神经损伤的关键时期进行 HBOT 通过减少神经炎症和保护线粒体功能来调节从急性到慢性疼痛的转变，从而防止 DRG 和脊髓中的神经元凋亡。
