Pilot Exploration of RGMa-BMP4 Signaling in Neutrophil Activation in NMOSD: Integrating Clinical and Molecular Insights.

Neuromyelitis optica spectrum disorder (NMOSD) is a disabling autoimmune disease. Neutrophil activation plays a crucial role in the neuroinflammatory damage observed during disease exacerbations. This study aims to elucidate the potential role of the repulsive guidance molecule A-bone morphogenetic protein 4 (RGMa-BMP4) signaling pathway in neutrophil activation during NMOSD attacks. We employed transcriptomic sequencing, quantitative PCR, flow cytometry, and Western blot analysis on peripheral blood samples from NMOSD patients in acute and remission phases. Additionally, an NMO rat model was established to investigate in vivo molecular mechanisms, focusing on key signaling molecules, including RGMa, BMP4, and SMADs. Transcriptomic analysis identified five genes associated with NMOSD pathogenesis or neutrophil activation, with RGMA, EGFR, and HLA-DOB showing the most significant differences. RT-qPCR confirmed elevated levels of RGMA, BMP4, and SMADs in the acute phase. Flow cytometry and Western blotting demonstrated an increased nuclear-to-cytoplasmic ratio of SMAD4 protein in neutrophils from acute-phase NMOSD patients. In the NMO rat model, we observed significant upregulation of RGMA, BMP4, and SMAD4 mRNA in brain and spinal cord tissues, along with enhanced nuclear translocation of SMAD4 protein. Furthermore, there was a marked increase in myeloperoxidase (MPO) mRNA expression, a marker of neutrophil activation, in both brain and spinal cord tissues in the model group. Our findings indicate that the RGMa-BMP4 signaling pathway likely plays a key role in neutrophil-mediated neuroinflammation during NMOSD attacks. These results suggest potential therapeutic targets within this pathway, warranting further investigation into their clinical implications.