Expression of Toll‐like receptor 4 in various organs in rats with d‐galactosamine‐induced acute hepatic failure

Abstract

Activation of the pro-inflammatory cytokine cascade, including tumor necrosis factor alpha (TNF-alpha) is considered to play an important role in the pathophysiology and clinical outcome of severe liver injury. Kupffer cells, resident macrophages of the liver, have a transmembrane protein Toll-like receptor 4 (TLR4), which recognizes endotoxin (lipopolysaccharide; LPS) or LPS-CD14 complex and mediates macrophage activation and pro-inflammatory cytokine release. D-Galactosamine (GalN), a hepatocyte-specific inhibitor of RNA synthesis, is known to sensitize animals to the lethal effects of LPS and TNF-alpha. In the present study we seek to address TLR4-signaling in the development of GalN-induced acute hepatic failure (AHF) and explore the expression of TLR4 mRNA as compared to TNF-alpha mRNA and CD14 mRNA in the liver, spleen and lung of rats with GalN-induced hepatitis. AHF was induced in male Wistar rats by the intraperitoneal injection of 1 g/kg bodyweight GalN. Expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole liver, spleen and lung of rats were detected by reverse transcription-polymerase chain reaction analysis. Expression level of TLR4 mRNA in the liver of rats with GalN-induced AHF was increased parallel with that of TNF-alpha and CD14 mRNA as compared to the control rats. However, expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole spleen and lung were not different between rats with AHF and control. There may be a difference of stimulatory effects of endotoxin on the innate immunity between the liver and other organs of rats with GalN-induced AHF.