Z Gastroenterol 2009; 47 - A8
DOI: 10.1055/s-0029-1223987

Non-alcoholic steatohepatitis sensitizes to TLR9-induced liver injury

T Csak 1, A Dolganiuc 1, B Nath 1, J Patrasek 1, K Kodys 1, G Szabo 1
  • 1Dept. of Medicine, UMMS, Worchester, USA

Background/Aims: Inflammatory activation superimposed over non-alcoholic fatty liver disease (NAFLD) results in the clinical syndrome known as non-alcoholic steatohepatitis (NASH). Increased susceptibility of fatty liver to damage induced by ischemia or the TLR4 ligand, lipopolysaccharide, has been previously shown. The effect of other pathogen-derived insults is yet to be delineated. The aim of this study was to evaluate the effect of TLR9 ligand stimulation in a mouse model of NASH.

Methods: C57/Bl6 mice were fed methionine-choline deficient (MCD) or supplemented (MCS) diets for 5 weeks and challenged with the TLR9 ligand, CpG for 2 or 6 hours (5mg/bwk;n=6/group). Liver was evaluate by histology. Serum levels of ALT and inflammatory cytokines, (TNFα and IL-6), Type I interferons (IFN) were measured by ELISA, and/or gene expression in the liver quantified by real-time PCR.

Results: MCD diet induced macrovesicular steatosis and elevated serum ALT indicating liver damage compared to the control, MCS diet. Serum TNFα and IL6 protein and hepatic TNFα and IL6 mRNA levels were increased in MCD compared to MCS diet-fed mice, suggesting liver inflammation. Hepatic TLR9 mRNA expression was significantly higher in MCD compared to MCS diet-fed mice. CpG challenge lead to increased serum ALT, TNFα and IL6 and liver mRNA levels, suggesting liver damage and inflammation. MCD diet-fed mice had higher elevation of TNFα and IL-6 liver mRNA compared to MCS controls after CpG challenge. TLR9 stimulation-triggered mRNA expression of type 1 IFNs (IFNα and IFNß) was comparable between livers of MCD and MCS diet-fed mice but there was an increase in IFN-stimulated gene (ISG56 and IRF7) mRNA levels in steatohepatitis. Further, the extent of TypeI IFN increase was significantly higher in MCD- compared to MCS diet-fed mice.

Conclusions: Steatohepatitis in the MCD diet model is associated with upregulation of TLR9 mRNA and sensitization to TLR9-induced liver injury and typeI IFN production. These findings suggest an increased susceptibility of livers with steatohepatitis to TLR9 ligand-induced liver damage.