title: Modulation of non-alcoholic steatohepatitis by pattern recognition receptors in mice: the role of toll-like receptors 2 and 4.
abstract: Toll-like receptors (TLR) recognize pathogen-derived molecules and induce downstream activation of inflammatory pathways. Fatty liver has been shown to result in increased sensitivity to lipopolysaccharide (LPS), a TLR4 ligand. In this study, we investigated the roles of TLR2 and TLR4 in liver damage and on cytokine induction in a methionine-choline deficient (MCD) diet-induced model of nonalcoholic steatohepatitis. We found that mice with nonalcoholic fatty liver had increased liver injury and inflammatory cytokine induction after challenge with a TLR4 but not with a TLR2 ligand. TLR2 deficient mice were not protected against the development of steatohepatitis after MCD diet feeding. On the contrary, TLR2 mice had significantly higher levels of serum ALT and greater TNF-alpha levels after LPS challenge suggesting increased liver injury. This was associated with reduced production of IL-6, a cytokine with hepatoprotective effects in fatty liver. Increased liver injury in the MCD diet-fed TLR2 mice was associated with reduced baseline and LPS-induced NF-kB and PPRE binding compared to MCS controls. These results demonstrate that TLR2 deficiency results in increased liver injury in association with nonalcoholic steatohepatitis and may suggest a protective role for TLR2-mediated signals in liver injury.
authors.affiliation: Liver Center, Division of Gastroenterology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA. gyongyi.szabo@umassmed.edu
authors.forename: Gyongyi
authors.initials: G
authors.lastname: Szabo
authors.forename: Arumugam
authors.initials: A
authors.lastname: Velayudham
authors.forename: Laszlo
authors.initials: L
authors.lastname: Romics
authors.forename: Pranoti
authors.initials: P
authors.lastname: Mandrekar
mesh_terms: D000818:Animals; D005234:Fatty Liver / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D015850:Interleukin-6 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D051195:Toll-Like Receptor 2 / Q000187:drug effects / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000187:drug effects / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D015850:Interleukin-6; D008070:Lipopolysaccharides; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha