Qi Fangfang, Lennon Vanda A, Zhao Shunyi, Guo Yong, Ding Husheng, Liu Caiyun, Bartley Whitney M, Chen Tingjun, Lucchinetti Claudia F, Wu Long-Jun
bioRxiv. 2025 Aug 28:2025.08.22.671883. doi: 10.1101/2025.08.22.671883.
Neutrophils and neutrophil extracellular traps (NETs) contribute to early neuromyelitis optica (NMO) histopathology initiated by IgG targeting astrocytic aquaporin-4 water (AQP4) channels. Yet, the mechanisms recruiting neutrophils and their pathogenic roles in disease progression remain unclear. To investigate molecular-cellular events preceding classical complement cascade activation in a mouse NMO model, we continuously infused, via spinal subarachnoid route, a non-complement-activating monoclonal AQP4-IgG. Parenchymal infiltration of netting neutrophils containing C5a ensued with microglial activation and motor impairment, but no blood-brain barrier leakage. Motor impairment and neuronal dysfunction both reversed when AQP4-IgG infusion stopped. Two-photon microscopy and electron-microscopy-based reconstructions revealed physical interaction of infiltrating neutrophils with microglia. Ablation of either peripheral neutrophils or microglia attenuated the motor deficit, highlighting their synergistic pathogenic roles. Of note, mice lacking complement receptor C5aR1 exhibited reduction in neutrophil infiltration, microglial lysosomal activation, neuronal lipid-droplet burden and motor impairment. Pharmacological inhibition of C5aR1 recapitulated this protection. Immunohistochemical analysis of an NMO patient's early spinal cord lesions revealed analogous pathological findings. Our study identifies neutrophil-derived C5a signaling through microglial C5aR1 as a key early driver of reversible motor neuron dysfunction in the precytolytic phase of NMO.
Neutrophil-derived C5a coactivates microglia to drive reversible motor paresis initiated by a non-complement-activating aquaporin-4-IgG binding to astrocytes in a mouse model of neuromyelitis optica.
中性粒细胞和中性粒细胞胞外陷阱（NETs）参与了由靶向星形胶质细胞水通道蛋白4（AQP4）通道的IgG引发的早期视神经脊髓炎（NMO）组织病理学过程。然而，招募中性粒细胞的机制及其在疾病进展中的致病作用仍不清楚。为了研究小鼠NMO模型中经典补体级联激活之前的分子细胞事件，我们通过脊髓蛛网膜下腔途径持续注入一种非补体激活的单克隆AQP4-IgG。随后出现了含有C5a的网状中性粒细胞的实质浸润，并伴有小胶质细胞激活和运动障碍，但没有血脑屏障渗漏。当停止注入AQP4-IgG时，运动障碍和神经元功能障碍均得到逆转。双光子显微镜和基于电子显微镜的重建显示浸润的中性粒细胞与小胶质细胞存在物理相互作用。外周中性粒细胞或小胶质细胞的消融减轻了运动缺陷，突出了它们的协同致病作用。值得注意的是，缺乏补体受体C5aR1的小鼠中性粒细胞浸润、小胶质细胞溶酶体激活、神经元脂滴负荷和运动障碍均有所减轻。对C5aR1的药理抑制也产生了类似的保护作用。对一名NMO患者早期脊髓病变的免疫组织化学分析显示出类似的病理结果。我们的研究确定，在NMO的细胞溶解前阶段，中性粒细胞衍生的C5a通过小胶质细胞C5aR1发出的信号是可逆性运动神经元功能障碍的关键早期驱动因素。
在视神经脊髓炎小鼠模型中，中性粒细胞衍生的C5a共同激活小胶质细胞，以驱动由非补体激活的水通道蛋白4-IgG与星形胶质细胞结合引发的可逆性运动性麻痹。
