Center for Immunology and Inflammation, The Feinstein Institutes for Medical Research, 350 Community Dr., Manhasset, NY 11030, United States.
Department of Surgery, Zucker School of Medicine at Hofstra/Northwell, 350 Community Dr., Manhasset, NY 11030, United States.
J Leukoc Biol. 2024 Nov 4;116(5):1072-1079. doi: 10.1093/jleuko/qiae132.
Macrophages are essential immune cells for host defense against bacterial pathogens after radiation injury. However, the role of macrophage phagocytosis in infection following radiation injury remains poorly examined. Extracellular cold-inducible RNA-binding protein is a damage-associated molecular pattern that dysregulates host immune system responses such as phagocytosis. We hypothesized that radiation-induced extracellular cold-inducible RNA-binding protein release impairs macrophage phagocytosis of bacteria. Adult healthy mice were exposed to 6.5 Gy total body irradiation. Primary peritoneal macrophages isolated from adult healthy mice were exposed to 6.5 Gy radiation. Extracellular cold-inducible RNA-binding protein-neutralizing monoclonal antibody was added to the cell culture prior to irradiation. Bacterial phagocytosis by peritoneal macrophages was assessed using pHrodo Green-labeled Escherichia coli 7 d after irradiation ex vivo and in vitro. Bacterial phagocytosis was also assessed after treatment with recombinant murine cold-inducible RNA-binding protein. Rac1 and ARP2 protein expression in cell lysates and extracellular cold-inducible RNA-binding protein levels in the peritoneal lavage were assessed by western blotting. Bacterial phagocytosis by peritoneal macrophages was significantly decreased after irradiation compared with controls ex vivo and in vitro. Rac1 and ARP2 expression in the peritoneal macrophages were downregulated after total body irradiation. Total body irradiation significantly increased extracellular cold-inducible RNA-binding protein levels in the peritoneal cavity. Recombinant murine cold-inducible RNA-binding protein significantly decreased bacterial phagocytosis in a dose-dependent manner. Extracellular cold-inducible RNA-binding protein monoclonal antibody restored bacterial phagocytosis by peritoneal macrophages after irradiation. Ionizing radiation exposure impairs bacterial phagocytosis by macrophages after irradiation. Neutralization of extracellular cold-inducible RNA-binding protein restores the phagocytic ability of macrophages after irradiation. Our findings elucidate a novel mechanism of immune dysfunction and provide a potential new therapeutic approach for limiting infection after radiation injury.
巨噬细胞是宿主防御辐射损伤后细菌病原体的重要免疫细胞。然而，巨噬细胞吞噬作用在辐射损伤后感染中的作用仍未得到充分研究。细胞外冷诱导 RNA 结合蛋白是一种损伤相关分子模式，可使宿主免疫系统反应失调，如吞噬作用。我们假设辐射诱导的细胞外冷诱导 RNA 结合蛋白释放会损害巨噬细胞对细菌的吞噬作用。成年健康小鼠接受 6.5 Gy 全身照射。从成年健康小鼠中分离出原代腹腔巨噬细胞，暴露于 6.5 Gy 辐射下。在照射前向细胞培养物中加入细胞外冷诱导 RNA 结合蛋白中和单克隆抗体。用 pHrodo Green 标记的大肠杆菌评估辐射后 7 天离体和体外腹腔巨噬细胞的细菌吞噬作用。还在用重组鼠冷诱导 RNA 结合蛋白处理后评估细菌吞噬作用。通过 Western 印迹法评估细胞裂解物中 Rac1 和 ARP2 蛋白表达以及腹腔灌洗液中细胞外冷诱导 RNA 结合蛋白水平。与对照组相比，离体和体外照射后腹腔巨噬细胞的细菌吞噬作用明显降低。全身照射后，腹腔巨噬细胞中 Rac1 和 ARP2 的表达下调。全身照射显著增加腹腔细胞外冷诱导 RNA 结合蛋白水平。重组鼠冷诱导 RNA 结合蛋白以剂量依赖性方式显著降低细菌吞噬作用。细胞外冷诱导 RNA 结合蛋白单克隆抗体可恢复照射后腹腔巨噬细胞的细菌吞噬作用。电离辐射暴露会损害照射后巨噬细胞的细菌吞噬作用。中和细胞外冷诱导 RNA 结合蛋白可恢复照射后巨噬细胞的吞噬能力。我们的研究结果阐明了免疫功能障碍的一种新机制，并为限制辐射损伤后感染提供了一种潜在的新治疗方法。
