School of Graduate Studies, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States; Reynolds Family Spine Laboratory, Department of Neurological Surgery, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
Reynolds Family Spine Laboratory, Department of Neurological Surgery, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
Brain Behav Immun. 2019 Aug;80:328-343. doi: 10.1016/j.bbi.2019.04.010. Epub 2019 Apr 3.
Increasing evidence indicates that innate immune receptors play important, yet controversial, roles in traumatic central nervous system (CNS) injury. Despite many advances, the contributions of toll-like receptors (TLRs) to spinal cord injury (SCI) remain inadequately defined. We previously reported that a toll-like receptor 9 (TLR9) antagonist, oligodeoxynucleotide 2088 (ODN 2088), administered intrathecally, improves the functional and histopathological outcomes of SCI. However, the molecular and cellular changes that occur at the injury epicenter following ODN 2088 treatment are not completely understood. Following traumatic SCI, a glial scar, consisting primarily of proliferating reactive astrocytes, forms at the injury epicenter and assumes both beneficial and detrimental roles. Increased production of chondroitin sulfate proteoglycans (CSPGs) by reactive astrocytes inhibits the regeneration of injured axons. Astrocytes express TLR9, which can be activated by endogenous ligands released by damaged cells. It is not yet known how TLR9 antagonism modifies astrocyte function at the glial scar and how this affects axonal preservation or re-growth following SCI. The present studies were undertaken to address these issues. We report that in female mice sustaining a severe mid-thoracic (T8) contusion injury, the number of proliferating astrocytes in regions rostral and caudal to the lesion border increased significantly by 30- and 24-fold, respectively, compared to uninjured controls. Intrathecal ODN 2088 treatment significantly reduced the number of proliferating astrocytes by 60% in both regions. This effect appeared to be, at least partly, mediated through the direct actions of ODN 2088 on astrocytes, since the antagonist decreased proliferation in pure SC astrocyte cultures by preventing the activation of the Erk/MAPK signaling pathway. In addition, CSPG immunoreactivity at the lesion border was more pronounced in vehicle-treated injured mice compared to uninjured controls and was significantly reduced following administration of ODN 2088 to injured mice. Moreover, ODN 2088 significantly decreased astrocyte migration in an in vitro scratch-wound assay. Anterograde tracing and quantification of corticospinal tract (CST) axons in injured mice, indicated that ODN 2088 preserves proximal axons. Taken together, these findings suggest that ODN 2088 modifies the glial scar and creates a milieu that fosters axonal protection at the injury site.
越来越多的证据表明，先天免疫受体在创伤性中枢神经系统 (CNS) 损伤中发挥着重要但有争议的作用。尽管取得了许多进展，但 Toll 样受体 (TLR) 对脊髓损伤 (SCI) 的贡献仍未得到充分定义。我们之前的研究报告称，鞘内给予 Toll 样受体 9 (TLR9) 拮抗剂寡脱氧核苷酸 2088 (ODN 2088) 可改善 SCI 的功能和组织病理学结果。然而，ODN 2088 治疗后损伤中心的分子和细胞变化尚不完全清楚。在创伤性 SCI 后，主要由增殖性反应性星形胶质细胞组成的神经胶质瘢痕在损伤中心形成，并发挥有益和有害的作用。反应性星形胶质细胞中软骨素硫酸盐蛋白聚糖 (CSPG) 的产生增加会抑制损伤轴突的再生。星形胶质细胞表达 TLR9，内源性配体可被受损细胞释放而激活 TLR9。TLR9 拮抗如何改变神经胶质瘢痕中的星形胶质细胞功能以及如何影响 SCI 后轴突的保存或再生长尚不清楚。目前的研究旨在解决这些问题。我们报告说，在雌性小鼠中，严重的中胸 (T8) 挫伤伤后，损伤边界处的星形胶质细胞增殖数量分别增加了 30 倍和 24 倍，与未受伤的对照组相比明显增加。鞘内 ODN 2088 治疗可使两个区域中增殖的星形胶质细胞数量分别减少 60%。这种作用似乎至少部分是通过 ODN 2088 对星形胶质细胞的直接作用介导的，因为拮抗剂通过阻止 Erk/MAPK 信号通路的激活，减少了纯 SC 星形胶质细胞培养物中的增殖。此外，与未受伤的对照组相比，在接受载体治疗的受伤小鼠的损伤边界处的 CSPG 免疫反应性更为明显，并且在向受伤小鼠给予 ODN 2088 后明显减少。此外，ODN 2088 可显著减少体外划痕损伤试验中的星形胶质细胞迁移。受伤小鼠皮质脊髓束 (CST) 轴突的顺行追踪和定量表明，ODN 2088 可保护近端轴突。综上所述，这些发现表明，ODN 2088 可改变神经胶质瘢痕并创造有利于损伤部位轴突保护的环境。
