BACKGROUND Chronic pain is a debilitating medical condition that lacks effective treatments. Increasing evidence suggests that microglia and neuroinflammation underlie pain pathophysiology, which therefore supports a potential strategy for developing pain therapeutics. Here, our study is testing the hypothesis that the promise of pain amelioration can be achieved using the small-molecule pexidartinib (PLX-3397), a previously food and drug administration (FDA)-approved cancer medicine and a colony-stimulating factor-1 receptor (CSF-1R) inhibitor that display microglia-depleting properties. METHOD We used the previously reported chronic constriction injury (CCI) mouse model, in which PLX-3397 or vehicle was orally administrated to mice daily for 21 days, then applied to the CCI model, followed by PLX-3397 or vehicle administration for an additional 28 days. Additionally, we examined microglia-related neuroinflammation markers using positron emission tomography (PET) neuroimaging and immunofluorescence (IF). RESULTS We showed that PLX-3397 significantly ameliorated pain-related behavioral changes throughout the entire experimental period after CCI (vehicle versus PLX-3397 at day 14, effect size: 2.57, P = .002). Microglia changes were first analyzed by live-animal PET neuroimaging, revealing PLX-3397-associated reduction of microglia by probing receptor-interacting serine/threonine-protein kinase 1 (RIPK1), a protein primarily expressed in microglia, which were further corroborated by postmortem immunohistochemistry (IHC) analysis using antibodies for microglia, including ionized Ca2+ binding adaptor molecule 1 (Iba-1) (somatosensory cortex, hindlimb area; vehicle versus PLX-3397, effect size 3.6, P = .011) and RIPK1 (somatosensory cortex, hindlimb area; vehicle versus PLX-3397, effect size 2.9, P = .023. The expression of both markers decreased in the PLX-3397 group. Furthermore, we found that PLX-3397 led to significant reductions in various proteins, including inducible nitric oxide synthase (iNOS) (somatosensory cortex, hindlimb area; vehicle versus PLX-3397, effect size: 2.3, P = .048), involved in neuroinflammation through IHC. CONCLUSIONS Collectively, our study showed PLX-3397-related efficacy in ameliorating pain linked to the reduction of microglia and neuroinflammation in mice. Furthermore, our research provided new proof-of-concept data supporting the promise of testing PLX-3397 as an analgesic.

中文翻译：

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Pexidartinib 通过影响小鼠的小胶质细胞和神经炎症对神经性疼痛的影响。


背景 慢性疼痛是一种缺乏有效治疗方法的使人衰弱的疾病。越来越多的证据表明，小胶质细胞和神经炎症是疼痛病理生理学的基础，因此支持开发疼痛治疗的潜在策略。在这里，我们的研究正在检验这样一个假设，即可以使用小分子 pexidartinib （PLX-3397） 实现改善疼痛的承诺，pexidartinib 是一种先前获得美国食品和药物管理局 （FDA） 批准的癌症药物和集落刺激因子-1 受体 （CSF-1R） 抑制剂，显示出小胶质细胞耗竭特性。方法 我们使用了先前报道的慢性缩窄性损伤 （CCI） 小鼠模型，其中 PLX-3397 或载体每天口服给小鼠，持续 21 天，然后应用于 CCI 模型，然后是 PLX-3397 或载体给药另外 28 天。此外，我们使用正电子发射断层扫描 （PET） 神经影像学和免疫荧光 （IF） 检查了与小胶质细胞相关的神经炎症标志物。结果我们表明，PLX-3397 在 CCI 后的整个实验期间显着改善了与疼痛相关的行为变化 （第 14 天载体与 PLX-3397，效应量：2.57，P = .002）。首先通过活体动物 PET 神经成像分析小胶质细胞的变化，通过探测受体相互作用的丝氨酸/苏氨酸蛋白激酶 1 （RIPK1） 揭示了 PLX-3397 相关的小胶质细胞减少，这是一种主要在小胶质细胞中表达的蛋白质，这进一步证实了使用小胶质细胞抗体的死后免疫组织化学 （IHC） 分析，包括电离的 Ca2+ 结合接头分子 1 （Iba-1）（体感皮层，后肢区域;载体与 PLX-3397， 效应量 3.6，P = 。011） 和 RIPK1 （体感皮层，后肢区域;载体与 PLX-3397，效应量 2.9，P = .023。PLX-3397 组两种标志物的表达均降低。此外，我们发现 PLX-3397 导致各种蛋白质的显着减少，包括诱导型一氧化氮合酶 （iNOS）（体感皮层，后肢区域;载体与 PLX-3397，效应量：2.3，P = .048），通过 IHC 参与神经炎症。结论总的来说，我们的研究表明 PLX-3397 在改善与减少小鼠小胶质细胞和神经炎症相关的疼痛方面的疗效。此外，我们的研究提供了新的概念验证数据，支持测试 PLX-3397 作为镇痛药的承诺。