Istituto Di Ricerche Farmacologiche Mario Negri IRCCS, Via Mario Negri 2, 20156, Milan, Italy.
San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), San Raffaele Hospital, 20132, Milan, Italy.
Sci Rep. 2021 May 5;11(1):9616. doi: 10.1038/s41598-021-89032-7.
Long pentraxin PTX3, a pattern recognition molecule involved in innate immune responses, is upregulated by pro-inflammatory stimuli, contributors to secondary damage in traumatic brain injury (TBI). We analyzed PTX3 involvement in mice subjected to controlled cortical impact, a clinically relevant TBI mouse model. We measured PTX3 mRNA and protein in the brain and its circulating levels at different time point post-injury, and assessed behavioral deficits and brain damage progression in PTX3 KO mice. PTX3 circulating levels significantly increased 1-3 weeks after injury. In the brain, PTX3 mRNA was upregulated in different brain areas starting from 24 h and up to 5 weeks post-injury. PTX3 protein significantly increased in the brain cortex up to 3 weeks post-injury. Immunohistochemical analysis showed that, 48 h after TBI, PTX3 was localized in proximity of neutrophils, likely on neutrophils extracellular traps (NETs), while 1- and 2- weeks post-injury PTX3 co-localized with fibrin deposits. Genetic depletion of PTX3 did not affect sensorimotor deficits up to 5 weeks post-injury. At this time-point lesion volume and neuronal count, axonal damage, collagen deposition, astrogliosis, microglia activation and phagocytosis were not different in KO compared to WT mice. Members of the long pentraxin family, neuronal pentraxin 1 (nPTX1) and pentraxin 4 (PTX4) were also over-expressed in the traumatized brain, but not neuronal pentraxin 2 (nPTX2) or short pentraxins C-reactive protein (CRP) and serum amyloid P-component (SAP). The long-lasting pattern of activation of PTX3 in brain and blood supports its specific involvement in TBI. The lack of a clear-cut phenotype in PTX3 KO mice may depend on the different roles of this protein, possibly involved in inflammation early after injury and in repair processes later on, suggesting distinct functions in acute phases versus sub-acute or chronic phases. Brain long pentraxins, such as PTX4-shown here to be overexpressed in the brain after TBI-may compensate for PTX3 absence.
长型五聚素家族成员 PTX3 是一种参与固有免疫反应的模式识别分子，可被促炎刺激物上调，是创伤性脑损伤 (TBI) 继发性损伤的促成因素。我们分析了 PTX3 在受控皮质撞击模型中，即一种与临床相关的 TBI 小鼠模型中所涉及的作用。我们在损伤后不同时间点测量了脑组织和循环中的 PTX3mRNA 和蛋白水平，并评估了 PTX3 敲除小鼠的行为缺陷和脑损伤进展。损伤后 1-3 周，PTX3 的循环水平显著增加。在大脑中，PTX3mRNA 从损伤后 24 小时开始到 5 周时，在不同的脑区被上调。PTX3 蛋白在脑皮质中的表达在损伤后 3 周内显著增加。免疫组织化学分析显示，TBI 后 48 小时，PTX3 定位于靠近中性粒细胞的位置，可能位于中性粒细胞细胞外陷阱 (NETs) 上，而在损伤后 1 周和 2 周时，PTX3 与纤维蛋白沉积物共定位。PTX3 基因缺失不影响损伤后 5 周内的感觉运动缺陷。在这个时间点，KO 小鼠与 WT 小鼠相比，病变体积和神经元计数、轴突损伤、胶原沉积、星形胶质细胞激活、小胶质细胞吞噬作用无差异。神经元五聚素 1 (nPTX1) 和五聚素 4 (PTX4) 等长型五聚素家族成员也在受损伤的大脑中过度表达，但神经元五聚素 2 (nPTX2) 或短型五聚素 C 反应蛋白 (CRP) 和血清淀粉样蛋白 P 成分 (SAP) 没有。PTX3 在大脑和血液中持久的激活模式支持其在 TBI 中的特定作用。PTX3 KO 小鼠中缺乏明显的表型可能取决于该蛋白的不同作用，其可能在损伤后早期的炎症中发挥作用，而在后期的修复过程中发挥作用，这表明其在急性相和亚急性或慢性相中有不同的功能。大脑长型五聚素，如本文所示在 TBI 后大脑中过度表达的 PTX4，可能弥补了 PTX3 的缺失。
