Targeting TLR4 alleviates the progression of experimental autoimmune encephalomyelitis by regulating central resident cells and Th1/Th17 cell differentiation

Multiple sclerosis (MS) is an autoimmune demyelinating disease characterized by neuroinflammation. Toll-like receptor 4 (TLR4) is a receptor for damage-associated molecular patterns, such as high-mobility group box 1 (HMGB1) and plays a role in innate immunity. However, its precise role and cellular dynamics in MS pathogenesis are unclear. Using the experimental autoimmune encephalomyelitis (EAE) model, we mapped the expression dynamics of TLR4 and found that in the spinal cords, the cell type associated with the disease shifted from neurons to activated glia. To establish causality, we subjected TLR4 ^-/^- mice to EAE and observed significantly attenuated disease severity, reduced demyelination, and preserved neuronal integrity, alongside suppressed microglial and astrocytic activation. Furthermore, TLR4 deficiency was not merely dampening CNS-localized inflammation but was also associated with suppressed peripheral MOG_35-55-specific Th1/Th17 effector responses, as evidenced by reduced production of IFN-γ and IL-17A in lymphoid organs, together with reduced TNF-α, as well as diminished expression of the Th1/Th17 lineage-defining transcription factors T-bet and RORγt in the spinal cord infiltrates. This suggests that TLR4 plays a key role in EAE pathology by connecting peripheral Th1/Th17 differentiation with central glial inflammatory responses. Critically, to translate these findings, we evaluated the small-molecule TLR4 antagonist TAK-242. While prophylactic administration was effective, therapeutic dosing initiated after disease onset still significantly alleviated clinical scores and delayed progression, highlighting its potential for clinical intervention. Overall, our results demonstrate that targeting TLR4 simultaneously curtails pathogenic T-cell differentiation and local neuroinflammation, establishing TLR4 as a dual-action therapeutic target for MS.