BACKGROUND The prognosis of spinal cord injury (SCI) is closely related to secondary injury, which is dominated by neuroinflammation. There is evidence that α-synuclein aggregates after SCI and that inhibition of α-synuclein aggregation can improve the survival of neurons after SCI, but the mechanism is still unclear. This study was designed to investigate the effects of α-synuclein on neuroinflammation after SCI and to determine the underlying mechanisms. METHOD A T3 spinal cord contusion model was established in adult male Sprague-Dawley rats. An SNCA-shRNA-carrying lentivirus (LV-SNCA-shRNA) was injected into the injury site to block the expression of α-synuclein (forming the SCI+KD group), and the SCI and sham groups were injected with an empty vector. Basso-Beattie-Bresnahan (BBB) behavioural scores and footprint analysis were used to detect motor function. Inflammatory infiltration and myelin loss were measured in the spinal cord tissues of each group by haematoxylin-eosin (HE) and Luxol Fast Blue (LFB) staining, respectively. Immunohistochemistry, Western blot analysis, and RT-qPCR were used to analyse protein expression and transcription levels in the tissues. Immunofluorescence was used to determine the morphology and function of glial cells and the expression of matrix metalloproteinase-9 in the central canal of the spinal cord. Finally, peripheral serum cytokine levels were determined by enzyme-linked immunosorbent assay. RESULTS Compared with the SCI group, the SCI+KD group exhibited reduced inflammatory infiltration, preserved myelin, and functional recovery. Specifically, the early arrest of α-synuclein inhibited the pro-inflammatory factors IL-1β, TNF-α, and IL-2 and increased the expression of the anti-inflammatory factors IL-10, TGF-β, and IL-4. The neuroinflammatory response was regulated by reduced proliferation of Iba1+ microglia/macrophages and promotion of the shift of M1-polarized Iba1+/iNOS+ microglia/macrophages to M2-polarized Iba1+/Arg1+ microglia/macrophages after injury. In addition, compared with the SCI group, the SCI+KD group also exhibited a smaller microglia/astrocyte (Iba1/GFAP) immunostaining area in the central canal, lower MMP-9 expression, and improved cerebrospinal barrier function. CONCLUSION Lentivirus-mediated downregulation of α-synuclein reduces neuroinflammation, improves blood-cerebrospinal barrier function, promotes functional recovery, reduces microglial activation, and promotes the polarization of M1 microglia/macrophages to an M2 phenotype to confer a neuroprotective immune microenvironment in rats with SCI.

中文翻译：

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慢病毒介导的α-突触核蛋白下调可减少脊髓损伤大鼠的神经炎症并促进功能恢复。


背景脊髓损伤（SCI）的预后与以神经炎症为主的继发性损伤密切相关。有证据表明 SCI 后 α-突触核蛋白聚集，抑制 α-突触核蛋白聚集可以提高 SCI 后神经元的存活率，但其机制仍不清楚。本研究旨在研究 α-突触核蛋白对 SCI 后神经炎症的影响并确定其潜在机制。方法 成年雄性Sprague-Dawley大鼠建立T3期脊髓挫伤模型。将携带SNCA-shRNA的慢病毒（LV-SNCA-shRNA）注射到损伤部位以阻断α-突触核蛋白的表达（形成SCI+KD组），SCI和假手术组注射空载体。 Basso-Beattie-Bresnahan (BBB) 行为评分和足迹分析用于检测运动功能。分别通过苏木精-伊红（HE）和卢克索固蓝（LFB）染色测量各组脊髓组织中的炎症浸润和髓磷脂丢失。使用免疫组织化学、蛋白质印迹分析和RT-qPCR来分析组织中的蛋白质表达和转录水平。采用免疫荧光法测定脊髓中央管胶质细胞的形态、功能及基质金属蛋白酶9的表达。最后，通过酶联免疫吸附测定测定外周血清细胞因子水平。结果与SCI组相比，SCI+KD组炎症浸润减少，髓磷脂保存，功能恢复。具体来说，α-突触核蛋白的早期抑制抑制促炎因子IL-1β、TNF-α和IL-2，并增加抗炎因子IL-10、TGF-β和IL-4的表达。 神经炎症反应是通过损伤后 Iba1+ 小胶质细胞/巨噬细胞增殖减少和促进 M1 极化 Iba1+/iNOS+ 小胶质细胞/巨噬细胞向 M2 极化 Iba1+/Arg1+ 小胶质细胞/巨噬细胞转变来调节的。此外，与SCI组相比，SCI+KD组还表现出中央管内小胶质细胞/星形胶质细胞（Iba1/GFAP）免疫染色面积更小、MMP-9表达更低、脑脊屏障功能改善。结论 慢病毒介导的α-突触核蛋白下调可减轻神经炎症，改善血脑脊液屏障功能，促进功能恢复，减少小胶质细胞活化，并促进M1小胶质细胞/巨噬细胞极化为M2表型，从而为SCI大鼠提供神经保护性免疫微环境。