Department of Neuroscience and Experimental Therapeutics, Institute for Biomedical Research of Barcelona (IIBB), Spanish National Research Council (CSIC), Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri-IRCCS, 20156 Milan, Italy.
Exp Neurol. 2021 Dec;346:113865. doi: 10.1016/j.expneurol.2021.113865. Epub 2021 Sep 20.
Leukocyte infiltration and blood-brain barrier breakdown contribute to secondary brain damage after traumatic brain injury (TBI). TBI induces neuroimmune responses triggering pathogenic complement activation through different pathways, including the lectin pathway. We investigated mechanisms underlying mannose-binding lectin (MBL)-mediated brain damage focusing on neutrophil infiltration and blood-brain barrier breakdown in a TBI mouse model. Wild type mice and MBL null mice were subjected to controlled cortical impact. We studied neutrophil infiltration and regional localization by confocal microscopy 1, 4 and 15 days post-trauma, and investigated neutrophil extracellular trap (NET) formation. By immunofluorescence and/or Western blotting in various brain regions we studied the presence of fibrin(ogen), pentraxin-3, albumin and immunoglobulin G. Finally, we studied neurofilament proteins, synaptophysin, and αII-spectrin, and assessed white matter content in the injured tissue. TBI triggered an acute wave of neutrophil infiltration at day 1 followed by a more discrete persistence of neutrophils in the injured tissue at least until day 15. We detected the presence of NETs and pentraxin-3 in the injured tissue, as well as accumulation of fibrin(ogen), increased blood-brain barrier permeability, and neurofilament, synaptophysin and white matter loss, and calpain-mediated αII spectrin breakdown. MBL mice showed reduced number of Ly6G neutrophils 4 days after TBI, lower accumulation of pentraxin-3 and fibrin(ogen) in the injured tissue, reduced global plasma protein extravasation, and better preservation of axonal and white matter integrity. These results show that MBL participates in secondary neutrophil accumulation and blood-brain barrier breakdown, and promotes axonal and white matter damage after TBI in mice.
白细胞浸润和血脑屏障破坏导致创伤性脑损伤 (TBI) 后的继发性脑损伤。TBI 通过不同途径诱导神经免疫反应，触发致病补体激活，包括凝集素途径。我们研究了甘露聚糖结合凝集素 (MBL) 介导的脑损伤的机制，重点研究了 TBI 小鼠模型中的中性粒细胞浸润和血脑屏障破坏。野生型小鼠和 MBL 缺失型小鼠接受皮质撞击控制损伤。我们通过共聚焦显微镜研究了创伤后 1、4 和 15 天的中性粒细胞浸润和区域定位，并研究了中性粒细胞细胞外陷阱 (NET) 的形成。通过免疫荧光和/或 Western blot 在不同的脑区研究纤维蛋白（原）、五聚素-3、白蛋白和免疫球蛋白 G 的存在。最后，我们研究了神经丝蛋白、突触小体蛋白和 αII spectrin，并评估了损伤组织中的白质含量。TBI 在第 1 天引发了急性中性粒细胞浸润波，随后在损伤组织中至少持续到第 15 天存在离散的中性粒细胞。我们在损伤组织中检测到 NET 和五聚素-3 的存在，以及纤维蛋白（原）的积累、血脑屏障通透性增加、神经丝、突触小体和白质丢失，以及钙蛋白酶介导的 αII spectrin 断裂。MBL 小鼠在 TBI 后 4 天显示 Ly6G 中性粒细胞数量减少，损伤组织中 pentraxin-3 和纤维蛋白（原）的积累减少，全血浆蛋白外渗减少，轴突和白质完整性更好。这些结果表明，MBL 参与了继发性中性粒细胞聚集和血脑屏障破坏，并促进了 TBI 后小鼠的轴突和白质损伤。
