The IL-25–ILC2–IL-13 axis improves traumatic brain injury by mediating CXCL-10-dependent regulation of Blood Brain Barrier integrity

Traumatic brain injury (TBI) induces severe disruption of the blood brain barrier (BBB), a pivotal event that drives secondary neurological damage. Interleukin-25 (IL-25) has emerged as a key modulator of neuroinflammation, but its role and underlying mechanisms in BBB repair after TBI remain unclear. Here, we investigated the protective effects of IL-25 on BBB integrity and neurological function in mice following TBI. Using enzyme-linked immunosorbent assay, we found that IL-25 levels in brain tissue and serum were significantly elevated after TBI, peaking at day 3, with brain microvascular endothelial cells (BMECs) identified as the primary source through immunofluorescence staining. Exogenous IL-25 administration ameliorated BBB dysfunction, as shown by restored expression of tight junction proteins (ZO-1, occludin, claudin-5), reduced Evans Blue extravasation, and decreased cerebral edema on magnetic resonance imaging. Mechanistically, flow cytometry and in vitro oxygen glucose deprivation/reoxygenation models revealed that IL-25 exerted its effects indirectly by activating brain-resident group 2 innate lymphoid cells to secrete interleukin-13 (IL-13), rather than acting directly on BMECs. Cytokine array and Western blot analyses demonstrated that IL-13 preserved BBB integrity by suppressing C-X-C motif chemokine ligand 10 (CXCL-10) expression and inhibiting endothelial cell pyroptosis. Single-cell RNA sequencing further confirmed that IL-25 upregulated BBB-protective genes (e.g., tiam1, hsp90aa1) and activated tight junction and transforming growth factor-beta signaling pathways. Behaviorally, IL-25 treatment improved motor coordination (modified Neurological Severity Score, rotarod test) and cognitive performance (Morris water maze) after TBI. Collectively, our findings indicate that IL-25 promotes BBB repair and neurological recovery after TBI by activating ILC2-derived IL-13, which suppresses CXCL-10 and endothelial pyroptosis. This study highlights IL-25 as a promising therapeutic target for TBI-induced BBB disruption.