Department of Structural and Functional Biology, Institute of Biology. P.O. Box: 6109, University of Campinas - UNICAMP. 13083-970, Campinas, SP, Brazil.
Brain Res Bull. 2020 Jul;160:24-32. doi: 10.1016/j.brainresbull.2020.04.005. Epub 2020 Apr 17.
Traumatic injury to the peripheral nervous system (PNS) often generates sensorimotor deficits that impair the quality of life of the patient. The success of nerve regeneration is related to tissue clearance and the formation of a microenvironment that sustains and stimulates axon growth up to the target. In this sense, macrophages are important for axon and myelin debris removal, neovascularization and the production of neurotrophic factors. Macrophage activation is improved by T helper (Th) lymphocytes, whose role remains few explored upon traumatic nerve injuries. Dimethyl fumarate (DMF) is the first-line drug for the treatment of multiple sclerosis due to its neuroprotective, anti-inflammatory and immunomodulatory properties. DMF improves nerve regeneration via antioxidant and cytoprotective cell signaling pathways. However, the direct activity on the cell immune response following nerve axotomy requires further investigation. In the present study, we evaluated DMF activity on Th cells and macrophage polarization, axonal regeneration and motor recovery following sciatic nerve crush in mice. For this aim, operated animals received DMF or vehicle once a day, starting at 3 days postinjury (dpi). Using an in vivo cell migration assay, we observed reduced lymphocyte infiltration in the nerves of DMF-treated mice at 7 dpi. Flow cytometry revealed DMF-responsive lymphocyte polarization from the pro- (Th1) to anti-inflammatory (Th2) phenotype at 7 dpi but not at 14 dpi. No effect was observed on macrophage polarization (from M1 to M2), although DMF reduced the frequency of the proinflammatory M1 subset from 7 to 14 dpi. Quantification of neurofilament (axon marker) and growth-associated protein 43 (GAP-43) immunolabeling showed improved axonal regeneration under DMF treatment at 14 dpi. Better motor recovery was observed in the DMF-treated group, as verified by an automated walking track test. Overall, our data reinforce the pro-regenerative capacity of DMF after traumatic nerve injury based on downmodulation of the proinflammatory immune response.
周围神经系统（PNS）的创伤性损伤常导致感觉运动功能障碍，从而损害患者的生活质量。神经再生的成功与组织清除以及维持和刺激轴突生长到靶标的微环境的形成有关。在这方面，巨噬细胞对于轴突和髓鞘碎片的清除、新生血管形成和神经营养因子的产生很重要。辅助性 T 淋巴细胞（Th 淋巴细胞）可改善巨噬细胞的激活，但其在创伤性神经损伤后的作用仍鲜有探索。二甲基富马酸（DMF）因其具有神经保护、抗炎和免疫调节特性，是治疗多发性硬化症的一线药物。DMF 通过抗氧化和细胞保护信号通路改善神经再生。然而，神经轴突切断后对细胞免疫反应的直接作用仍需要进一步研究。在本研究中，我们评估了 DMF 对 Th 细胞和巨噬细胞极化、轴突再生和运动功能恢复的作用，方法是在小鼠坐骨神经挤压后每天一次给予 DMF 或载体，从损伤后 3 天开始。通过体内细胞迁移实验，我们观察到损伤后 7 天 DMF 处理小鼠的神经中淋巴细胞浸润减少。流式细胞术显示，损伤后 7 天 DMF 可使淋巴细胞从促炎（Th1）表型向抗炎（Th2）表型极化，但在 14 天无此作用。DMF 对巨噬细胞极化（从 M1 向 M2）没有影响，尽管 DMF 从 7 天到 14 天减少了促炎 M1 亚群的频率。神经丝（轴突标志物）和生长相关蛋白 43（GAP-43）免疫标记的定量分析显示，DMF 处理后 14 天轴突再生得到改善。通过自动行走轨迹试验观察到 DMF 治疗组运动功能恢复更好。总的来说，我们的数据基于促炎免疫反应的下调，强化了 DMF 在创伤性神经损伤后的促再生能力。
