Wan Li, Guo Haiyue, Hu Fan, Pan Yinbing, Yang Shuo, Jiang Chun-Yi, Liu Wentao, Wu Xuefeng, Wu Xudong
State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China.
Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China.
Brain Behav Immun. 2025 Aug;128:234-255. doi: 10.1016/j.bbi.2025.04.007. Epub 2025 Apr 8.
Effective management of neuropathic pain remains a significant challenge due to the limited understanding of its underlying mechanisms. We found that the FDA-approved enhancer of zeste homolog 2 (EZH2) inhibitor, EPZ6438, can prevent the development of neuropathic pain caused by chronic constriction injury (CCI). Therefore, we utilized EPZ6438 as a probe to investigate the molecular events involved in the early stage of neuropathic pain. RNA-seq analysis reveals that EPZ6438 significantly upregulates Timp1 transcription in the spinal cord of mice. As a specific endogenous inhibitor of MMP-9, tissue inhibitor of metalloproteinase 1 (TIMP1) levels significantly decrease in the cerebrospinal fluid of both neuropathic pain patients and the CCI rat models. Importantly, intrathecal administration of mouse recombinant TIMP1 protein (rmTIMP1) reverses CCI-induced mechanical and thermal hyperalgesia. Mechanistically, substance P released from primary sensory neurons suppresses TIMP1 in spinal GABAergic interneurons by elevating EZH2 expression, which enhances H3K27me3 enrichment at the Timp1 promoter. Blocking spinal NK1R effectively prevents the downregulation of TIMP1 and alleviates CCI-induced hyperalgesia. The imbalance between TIMP1 and MMP-9 leads to NLRP3 activation in spinal microglia and increases IL-1β maturation via TLR2/4 pathway. TIMP1 injection eliminates MMP-9-induced NLRP3 activation and blocks hyperalgesia, suggesting that TIMP1 is a critical gatekeeper in preventing neuroinflammation during neuropathic pain development.
由于对神经性疼痛潜在机制的了解有限，其有效管理仍然是一项重大挑战。我们发现，美国食品药品监督管理局（FDA）批准的zeste同源物2（EZH2）抑制剂EPZ6438可预防慢性压迫性损伤（CCI）引起的神经性疼痛的发展。因此，我们利用EPZ6438作为探针来研究神经性疼痛早期涉及的分子事件。RNA测序分析表明，EPZ6438可显著上调小鼠脊髓中Timp1的转录。作为基质金属蛋白酶9（MMP-9）的特异性内源性抑制剂，金属蛋白酶组织抑制剂1（TIMP1）在神经性疼痛患者和CCI大鼠模型的脑脊液中的水平均显著降低。重要的是，鞘内注射小鼠重组TIMP1蛋白（rmTIMP1）可逆转CCI诱导的机械性和热痛觉过敏。从机制上讲，初级感觉神经元释放的P物质通过提高EZH2表达来抑制脊髓GABA能中间神经元中的TIMP1，这增强了Timp1启动子处的H3K27me3富集。阻断脊髓神经激肽1受体（NK1R）可有效防止TIMP1的下调并减轻CCI诱导的痛觉过敏。TIMP1和MMP-9之间的失衡导致脊髓小胶质细胞中NLRP3激活，并通过Toll样受体2/4（TLR2/4）途径增加白细胞介素-1β（IL-1β）的成熟。注射TIMP1可消除MMP-9诱导的NLRP3激活并阻断痛觉过敏，这表明TIMP1是在神经性疼痛发展过程中预防神经炎症的关键守门人。
