P2X4 Drives Sex-Specific Neuroprotection in Autoimmune Neuroinflammation

Microglia critically influence multiple sclerosis (MS) pathophysiology through debris clearance, myelin repair, and modulation of neuroinflammation. These processes are partly regulated by ATP-gated ion channel P2X4, predominantly expressed in microglia. We previously reported that ivermectin (IVM), a positive allosteric modulator of P2X4, promotes myelin phagocytosis, remyelination, and functional recovery in experimental autoimmune encephalomyelitis (EAE). Here, we dissected the cellular basis of P2X4-mediated effects using P2X4mCherryIN knock-in (P2X4KI) mice, in which P2X4 is replaced by a non-internalized variant (P2X4KI), leading to increased surface localization at the plasma membrane. Constitutive and myeloid-specific P2X4KI (Cd11b-P2X4KI) mice showed significant amelioration of EAE motor deficits, although exclusively in females. Despite equivalent P2X4 expression, function, and IVM responsiveness between sexes, progesterone potentiated P2X4 currents and prolonged channel deactivation, revealing direct hormonal modulation of P2X4 gating. Notably, ovariectomy abolished P2X4-mediated protection in females, confirming the requirement of female hormones. These findings identify microglial P2X4 as a critical modulator of neuroinflammatory outcomes and uncover a previously unrecognized hormone–P2X4 interaction that underlies sex-specific disease modulation. Targeting this pathway may enable precision therapies for MS.