Modulation of the HMGB1/TLR4/NF-κB signaling pathway in the CNS by matrine in experimental autoimmune encephalomyelitis

The inflammatory mediator high-mobility group box 1 (HMGB1)-induced signaling pathway has been shown to play an important role in the pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Matrine (MAT), a quinolizidine alkaloid component derived from the root of Sophorae flavescens, has the capacity to effectively suppress EAE. However, the impact of MAT treatment on HMGB1-induced signaling is not known. In the present study, we show that MAT treatment alleviated disease severity of ongoing EAE, reduced inflammatory infiltration and demyelination, and reduced the production of inflammatory factors including TNF-α, IL-6, and IL-1β in the CNS. Moreover, MAT administration significantly reduced the protein and RNA expression of HMGB1 and TLR4 in the spinal cord, particularly in astrocytes and microglia/infiltrating macrophages. The expression of MyD88 and TRAF6, and the phosphorylation of NF-κB p65, was also down-regulated after MAT treatment. In contrast, the level of IκB-α, an inhibitory molecule for NF-κB activation, was significantly increased. Furthermore, the direct inhibitory effect of MAT on HMGB1/TLR4/NF-κB signaling in macrophages was further confirmed in vitro. Taken together, these findings demonstrate that MAT treatment alleviated CNS inflammatory demyelination and activation of astrocytes and microglia/macrophages in EAE rats, and that the mechanism underlying these effects may be closely related to modulation of HMGB1/TLR4/NF-κB signaling pathway.