Therapeutic approach to regulate innate immune response by Toll-like receptor 4 antagonist E5564 in rats with D-galactosamine-induced acute severe liver injury

Background and Aims:  Toll-like receptor 4 (TLR4) is a transmembrane protein, existing mainly in macrophages, such as Kupffer cells of the liver. It plays an important role in recognizing and mediating macrophage activation and pro-inflammatory cytokine release. Activation of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α is pivotal in the progression of liver injury. Gut-derived endotoxin has been considered to play an important role in the development and progression of a D-galactosamine (GalN)-induced acute severe liver injury (ALI) model. E5564, a synthetic analog of the lipid A component of endotoxin, inhibits endotoxin-stimulated inflammation and is under study for patients with sepsis. In this study, we seek to explore the effect of TLR4 antagonist E5564 on GalN-induced ALI in rats. Methods:  ALI was induced in male Wistar rats by the i.p. injection of 1 g/kg bodyweight of GalN and immediately after GalN injection they were treated with an i.v. injection of 3 mg/kg bodyweight of E5564. At 24 h after GalN injection with or without E5564, serum levels of total bilirubin (T.Bil), alanine aminotransferase (ALT) and TNF-α were analyzed. Expression levels of TNF-α, TLR4 and CD14 mRNA in the whole liver of rats was detected by reverse transcription polymerase chain reaction analysis. Results:  The i.v. injection of E5564 reduced the elevation of serum T.Bil, ALT and TNF-α levels in rats treated with GalN. The expression level of TNF-α mRNA in the whole liver, which was increased at 24 h after GalN injection, was also reduced by i.v. injection of E5564. Conclusion:  TLR4 antagonist E5564 reduced GalN-induced ALI in rats. It may contribute to the treatment of acute liver failure through blocking endotoxin-induced TNF-α overproduction of macrophages.