Systemic Inflammation Triggers Motor Axon Degeneration Via Macrophage IL-1β-Mediated P53/SIRT1/Autophagy Pathway

BACKGROUND: Axonal degeneration of motor neurons is a hallmark pathological feature of neurodegenerative diseases, culminating in motor dysfunction in advanced stages. Systemic inflammation exacerbates motor dysfunction, yet the relationship between systemic inflammation and motor axon degeneration remains poorly understood. We investigated whether macrophages impair motor axon morphology during systemic inflammation and the underlying mechanisms. METHODS: A zebrafish systemic inflammation model was established using CuSO₄ exposure. In vivo confocal imaging examined spatiotemporal relationships between macrophages and motor axon morphology in transgenic zebrafish. Motor function was assessed using behavioral analysis. RAW264.7 macrophage-like cells stimulated with lipopolysaccharide were co-cultured with NSC-34 motor neurons to investigate molecular mechanisms. RESULTS: CuSO₄ treatment induced elevated inflammatory cytokines and motor dysfunction in zebrafish. Histological analysis revealed increased macrophage infiltration around motor axons with concurrent reductions in axon number, length, and diameter. Macrophage depletion or IL-1Ra pretreatment significantly ameliorated motor axon damage and dysfunction. In vitro, LPS activated the NLRP3 inflammasome in RAW264.7 macrophage-like cells, releasing IL-1β, which was accompanied by disruption of the SIRT1-autophagy axis in motor neurons. Increased IL-1β release from macrophages was accompanied by upregulated P53 expression in motor neurons, which paralleled reduced SIRT1 levels, impaired autophagy, and decreased axon-associated protein expression. Pharmacological inhibition of NLRP3 with MCC950, IL-1Ra treatment, or P53 knockdown restored the SIRT1-autophagy axis and axon protein expression. CONCLUSIONS: Systemic inflammation activates macrophage NLRP3 inflammasome and promotes the release of inflammatory mediators including IL-1β, with findings suggestive of a model in which elevated IL-1β paralleled increased motor neuronal P53 expression and disruption of the SIRT1-autophagy balance, potentially contributing to motor axon morphological damage and dysfunction.