Department of Anesthesiology, Affiliated Hospital of Southwest Medical University, Luzhou, P.R. China.
Department of Anesthesiology, The First affiliated Hospital of Chongqing Medical University, Chongqing, P.R. China.
Shock. 2021 Jan 1;55(1):90-99. doi: 10.1097/SHK.0000000000001557.
Sepsis is a kind of maladjustment response to bacterial infection and activation of coagulation, which can induce neuromuscular dysfunction. However, there is scarce of experimental evidence about the relationship between Schwann cells (SCs) and sepsis in neuromuscular dysfunction. We therefore set out to identify the potential role of SCs in sepsis-induced neuromuscular dysfunction and to explore the underlying molecular mechanism.
Primary SCs were isolated from the left hind limb sciatic nerve of sepsis mice, which was constructed by cecal ligation and puncture. Then, the SCs were infected with adenovirus encoding toll-like receptor 4 (TLR4), MyD88, or IL-1R (with lipopolysaccharide stimulation), and the Raw 264.7 macrophages were injected with adenovirus with CCR2 silencing (with mMCP-1 stimulation). Further investigation of the interleukin 1 beta (IL-1β) and macrophage cationic peptide 1 (MCP-1) expressions, we followed reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay techniques, the F4/80 and Ki67 expressions was observed by immunofluorescence staining, while the expressions of CCR2, FAK/p-FAK, nuclear factor-κB (NFκB)/p-NFκB, and ERK1/2/p-ERK1/2 were determined by Western blot analysis. Last, but not the least, the cell migration ability and cell proliferation ability were detected by Transwell assay and Flow cytometry respectively.
Our results showed that in sepsis mice, the TLR4/MyD88/ERK pathway was activated in SCs, which triggered the cells to secrete IL-1β and MCP-1. The secreted IL-1β bound with IL-1β receptor on the surface of SCs, thereby activating the IL-1β/IL-1R/MyD88/ERK pathway and further promoting the secretion of MCP-1 by SCs. MCP-1 was found to bind to CCR2 on the surface of Raw264.7 macrophages to activate the TLR4/MyD88/ERK pathway which caused the inhibition of neuromuscular function.
Sepsis significantly promotes the infiltration of macrophages by activating the TLR4/MyD88 pathway in SCs, thereby impeding neuromuscular function. Consistently, our study provides a novel concept in the area of neuromuscular dysfunction therapeutics following sepsis.
败血症是一种对细菌感染和凝血激活的失调反应，可导致神经肌肉功能障碍。然而，关于施万细胞（SCs）与败血症引起的神经肌肉功能障碍之间的关系，目前还缺乏实验证据。因此，我们着手确定SCs在败血症引起的神经肌肉功能障碍中的潜在作用，并探讨其潜在的分子机制。
从盲肠结扎和穿刺构建的败血症小鼠的左侧后肢坐骨神经中分离原代SCs。然后，用脂多糖刺激感染编码 Toll 样受体 4（TLR4）、MyD88 或 IL-1R 的腺病毒，用单核细胞趋化蛋白 1（MCP-1）刺激沉默 CCR2 的腺病毒注射 Raw 264.7 巨噬细胞。进一步研究白细胞介素 1β（IL-1β）和巨噬细胞阳离子肽 1（MCP-1）的表达，我们采用逆转录定量聚合酶链反应和酶联免疫吸附试验技术，通过免疫荧光染色观察 F4/80 和 Ki67 的表达，通过 Western blot 分析检测 CCR2、FAK/p-FAK、核因子-κB（NFκB）/p-NFκB 和 ERK1/2/p-ERK1/2 的表达。最后，通过 Transwell 测定法和流式细胞术分别检测细胞迁移能力和细胞增殖能力。
我们的结果表明，在败血症小鼠中，SCs 中 TLR4/MyD88/ERK 通路被激活，导致细胞分泌 IL-1β和 MCP-1。分泌的 IL-1β与 SCs 表面的 IL-1β 受体结合，从而激活 IL-1β/IL-1R/MyD88/ERK 通路，并进一步促进 SCs 分泌 MCP-1。MCP-1 被发现与 Raw264.7 巨噬细胞表面的 CCR2 结合，激活 TLR4/MyD88/ERK 通路，从而抑制神经肌肉功能。
败血症通过激活 SCs 中的 TLR4/MyD88 通路显著促进巨噬细胞浸润，从而阻碍神经肌肉功能。我们的研究为败血症后神经肌肉功能障碍治疗提供了一个新的概念。
