La fonction neuronale et microgliale du récepteur P2X4 dans la Sclérose latérale amyotrophique et son potentiel en tant que biomarqueur

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive degeneration of motor neurons (MNs), driven by misfolded protein aggregation and neuroimmune dysregulation. P2X4 receptor, an ATP-gated ion channel expressed in neurons and glial cells, has emerged as a key player in ALS pathogenesis. Under normal conditions, P2X4 is primarily internalized, maintaining low surface expression. However, in pathological states such as ALS, P2X4 is increasingly localized to the cell surface.Using double-transgenic SOD1 G93A (SOD1) mice expressing either an internalization-defective P2X4-mCherryIN knock-in or invalidated for the P2X4 gene, it was reported that both the increase in surface P2X4 and its absence improved disease outcomes. These findings suggest complex cell-specific roles of P2X4 receptor, which remains unexplored.This study aims to investigate the distinct neuronal and microglial roles of the P2X4 receptor in ALS using triple-transgenic mice designed to selectively manipulate P2X4 expression in microglia/macrophages or neurons in the SOD1 mice model. Our results demonstrate that an increase in neuronal surface P2X4 accelerates ALS progression, while its upregulation in microglia/macrophages slows disease progression. In microglia, surface P2X4 mitigates immune overactivation in the spinal cord and reduces immune cell infiltration along MN axons in SOD1 mice. Consistent with this data, cell-specific deletion of P2X4 had opposing effects on ALS progression: the absence of P2X4 in neurons was protective, whereas its deletion in microglia/macrophages worsened disease outcomes. Altogether, we found that neuronal and microglial P2X4 play dual and opposing roles in ALS pathophysiology.In SOD1 mice, elevated surface P2X4 expression was previously observed in peritoneal macrophages even before symptom onset. Translating this finding to humans, we developed a flow cytometry-based method to measure the surface-to-total ratio of P2X4 in monocytes from peripheral blood samples. ALS patients, particularly women, exhibited significantly higher surface P2X4 levels in monocytes compared to patients with other neuromuscular diseases. This aberrant surface P2X4 expression was detected regardless of the disease onset and etiology, underscoring the broad utility of the receptor as a blood-based biomarker for ALS.In conclusion, our data reveal dual and opposing roles of neuronal and microglial P2X4 receptors in ALS progression and highlight its potential as a therapeutic target and biomarker for ALS.