Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China.
Tianjin Neurological Institute, Key Laboratory of Post Neuro-injury Neuro-repair and Regeneration in Central Nervous System, State Key Laboratory of Experimental Hematology, Ministry of Education, Tianjin, China.
CNS Neurosci Ther. 2024 Mar;30(3):e14669. doi: 10.1111/cns.14669.
Diffuse brain injury (DBI) models are characterized by intense global brain inflammation and edema, which characterize the most severe form of TBI. In a previous experiment, we found that fingolimod promoted recovery after controlled cortical impact injury (CCI) by modulating inflammation around brain lesions. However, it remains unclear whether fingolimod can also attenuate DBI because of its different injury mechanisms. Furthermore, whether fingolimod has additional underlying effects on repairing DBI is unknown.
The impact acceleration model of DBI was established in adult Sprague-Dawley rats. Fingolimod (0.5 mg/kg) was administered 0.5, 24, and 48 h after injury for 3 consecutive days. Immunohistochemistry, immunofluorescence analysis, cytokine array, and western blotting were used to evaluate inflammatory cells, inflammatory factors, AQP4 polarization, apoptosis in brain cells, and the accumulation of APP after DBI in rats. To evaluate the function of the glymphatic system (GS), a fluorescent tracer was injected into the cistern. The neural function of rats with DBI was evaluated using various tests, including the modified neurological severity score (mNSS), horizontal ladder-crossing test, beam walking test, and tape sensing and removal test. Brain water content was also measured.
Fingolimod administration for 3 consecutive days could reduce the levels of inflammatory cytokines, neutrophil recruitment, microglia, and astrocyte activation in the brain following DBI. Moreover, fingolimod reduced apoptotic protein expression, brain cell apoptosis, brain edema, and APP accumulation. Additionally, fingolimod inhibited the loss of AQP4 polarization, improved lymphatic system function, and reduced damage to nervous system function. Notably, inhibiting the GS weakened the therapeutic effect of fingolimod on the neurological function of rats with DBI and increased the accumulation of APP in the brain.
In brief, these findings suggest that fingolimod alleviates whole-brain inflammation and GS system damage after DBI and that inhibiting the GS could weaken the positive effect of fingolimod on nerve function in rats with DBI. Thus, inhibiting inflammation and regulating the GS may be critical for the therapeutic effect of fingolimod on DBI.
弥漫性脑损伤（DBI）模型的特点是强烈的全脑炎症和水肿，这是 TBI 最严重的形式。在之前的实验中，我们发现 fingolimod 通过调节脑损伤周围的炎症来促进皮质冲击伤（CCI）后的恢复。然而，由于其不同的损伤机制，目前尚不清楚 fingolimod 是否也能减轻 DBI。此外，fingolimod 是否对修复 DBI 有额外的潜在作用尚不清楚。
在成年 Sprague-Dawley 大鼠中建立 DBI 的冲击加速模型。在损伤后 0.5、24 和 48 小时，连续 3 天给予 fingolimod（0.5mg/kg）。免疫组织化学、免疫荧光分析、细胞因子阵列和 Western blot 用于评估大鼠 DBI 后炎症细胞、炎症因子、AQP4 极化、脑细胞凋亡和 APP 积累。为了评估神经淋巴系统（GS）的功能，向脑池内注射荧光示踪剂。使用各种测试评估 DBI 大鼠的神经功能，包括改良神经严重程度评分（mNSS）、水平梯越测试、束走测试和胶带感知和去除测试。还测量了脑水含量。
连续 3 天给予 fingolimod 可降低 DBI 后大脑中炎症细胞因子、中性粒细胞募集、小胶质细胞和星形胶质细胞激活的水平。此外，fingolimod 降低了凋亡蛋白表达、脑细胞凋亡、脑水肿和 APP 积累。此外，fingolimod 抑制了 AQP4 极化的丧失，改善了淋巴系统功能，并减轻了神经系统功能的损伤。值得注意的是，抑制 GS 减弱了 fingolimod 对 DBI 大鼠神经功能的治疗作用，并增加了大脑中 APP 的积累。
总之，这些发现表明，fingolimod 减轻 DBI 后的全脑炎症和 GS 系统损伤，抑制 GS 可能削弱 fingolimod 对 DBI 大鼠神经功能的积极作用。因此，抑制炎症和调节 GS 可能是 fingolimod 治疗 DBI 的关键。
