MYELOID-DERIVED TLR4-TRIF SIGNALING PATHWAY MEDIATES OXIDATIVE STRESS IN LPS/D-GALN-INDUCED ACUTE LIVER FAILURE.

Background: Acute liver failure (ALF) is a severe clinical syndrome characterized by massive hepatocyte death in a short time due to viruses, drugs, alcohol, or other factors. Oxidative stress is an important pathogenic mechanism of ALF. LPS-induced internalization of toll-like receptor 4 (TLR4) and the subsequent activation of the toll/IL-1R domain-containing adaptor-inducing IFN-beta (TRIF) signaling pathway widely mediate inflammatory responses in a series of diseases. However, whether the TLR4-TRIF signaling pathway contributes to ALF by mediating oxidative stress processes remains unclear. Methods: An ALF mouse model was induced by lipopolysaccharide (LPS)/D-galactosamine (D-GalN). TLR4-TRIF systemic knockout mice and TLR4 conditional knockout mice were used to determine the role of the TLR4-TRIF signaling pathway in ALF. The effects of TLR4 or TRIF deficiency on oxidative stress were investigated. In addition, we examined the protective role of the clodronate liposomes (macrophage scavengers) and the antioxidant N-acetylcysteine (NAC) in ALF. Results: TLR4 or TRIF deficiency significantly alleviated LPS/D-GalN-induced lethality, hepatic dysfunction, and hepatic pathologic injury, which was dependent on myeloid-derived TLR4. Hence, macrophage clearance exhibits a similar protective effect. Mechanically, TLR4 or TRIF deficiency was observed to inhibit oxidative stress by increasing glutathione, while decreasing malondialdehyde, 8-hydroxy-2-deoxyguanosine, and γ-H2AX. Therefore, the pharmacologic antioxidant NAC exhibited significant hepato-protective effects. Conclusions: Targeting myeloid-derived TLR4-TRIF signaling pathway or antioxidant therapy may be a potential therapeutic direction to treat ALF.