Glaser Ethan P, Kopper Timothy J, Bailey William M, Kashif Hassan K, Kumari Reena, Stewart Andrew N, Gensel John C
Department of Physiology, Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY, 40536, USA.
Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, 12800 E 19th Ave, Aurora, CO, 80045, USA.
Sci Rep. 2025 Jan 2;15(1):1. doi: 10.1038/s41598-024-84936-6.
Spinal cord injury (SCI) leads to permanent motor and sensory loss that is exacerbated by intraspinal inflammation and persists months to years after injury. After SCI, monocyte-derived macrophages (MDMs) infiltrate the lesion to aid in myelin-rich debris clearance. During debris clearance, MDMs adopt a proinflammatory phenotype that exacerbates neurodegeneration and hinders recovery. The underlying cause of the lipid-mediated MDM phenotype shift is unclear. Our previous work suggests that cytosolic phospholipase A2 (cPLA2) plays a role in the proinflammatory potentiating effect of myelin on macrophages in vitro. Cytosolic phospholipase A2 (cPLA2) frees arachidonic acid from phospholipids, generating eicosanoids that play an important role in inflammation, immunity, and host defense. cPLA2 is expressed in macrophages along with multiple other cell types after SCI, and cPLA2 inhibition has been reported to both reduce and exacerbate secondary injury pathology recovery. The role of cPLA2 in MDMs after SCI is not fully understood. We hypothesize that cPLA2 activation in MDMs after SCI contributes to secondary injury. Here, we report that cPLA2 plays an important role in the myelin-induced inflammatory macrophage phenotype in vitro using macrophages derived from cPLA2 knockout bone marrow. Furthermore, to investigate the role of cPLA2 in MDMs after SCI, we generated female bone marrow chimeras using cPLA2 knock-out donors and assessed locomotor recovery using the Basso Mouse Scale (BMS), CatWalk gait analysis system, and horizontal ladder task over six weeks. We also evaluated tissue sparing and intralesional axon density six weeks after injury. cPLA2 KO chimeras did not display altered locomotor recovery or tissue pathology after SCI compared to WT chimera controls. These data suggest that although cPLA2 plays a critical role in myelin-mediated potentiation of proinflammatory macrophage activation in vitro, it may not contribute to secondary injury pathology in vivo after SCI.
脊髓损伤（SCI）会导致永久性的运动和感觉丧失，脊髓内炎症会加剧这种情况，且损伤后数月至数年这种丧失依然存在。SCI后，单核细胞来源的巨噬细胞（MDMs）会浸润损伤部位，以帮助清除富含髓磷脂的碎片。在碎片清除过程中，MDMs会呈现促炎表型，这会加剧神经退行性变并阻碍恢复。脂质介导的MDM表型转变的根本原因尚不清楚。我们之前的研究表明，胞质磷脂酶A2（cPLA2）在体外髓磷脂对巨噬细胞的促炎增强作用中发挥作用。胞质磷脂酶A2（cPLA2）从磷脂中释放花生四烯酸，生成类花生酸，其在炎症、免疫和宿主防御中起重要作用。SCI后，cPLA2在巨噬细胞以及多种其他细胞类型中表达，据报道，抑制cPLA2既能减轻也能加剧继发性损伤病理恢复。cPLA2在SCI后MDMs中的作用尚未完全明确。我们假设SCI后MDMs中cPLA2的激活会导致继发性损伤。在此，我们报告，使用源自cPLA2基因敲除骨髓的巨噬细胞，cPLA2在体外髓磷脂诱导的炎性巨噬细胞表型中起重要作用。此外，为了研究cPLA2在SCI后MDMs中的作用，我们使用cPLA2基因敲除供体生成雌性骨髓嵌合体，并在六周内使用Basso小鼠评分量表（BMS）、CatWalk步态分析系统和水平阶梯任务评估运动恢复情况。我们还在损伤六周后评估了组织保留情况和损伤部位内的轴突密度。与野生型嵌合体对照组相比，cPLA2基因敲除嵌合体在SCI后未表现出运动恢复或组织病理学改变。这些数据表明，尽管cPLA2在体外髓磷脂介导的促炎性巨噬细胞激活增强中起关键作用，但它可能对SCI后体内的继发性损伤病理没有影响。
