title: Over-activation of TLR5 signaling by high-dose flagellin induces liver injury in mice.
abstract: Flagellin is a potent activator of a broad range of cell types that are involved in innate and adaptive immunity. Therefore, it is a good adjuvant candidate for vaccines, and it might function as a biological protectant against both major acute radiation syndrome during cancer radiotherapy and a mitigator of radiation emergencies. However, accumulating evidence has implicated flagellin in the occurrence of some inflammatory diseases, such as acute lung inflammation, cardiovascular collapse and inflammatory bowel disease. The aim of this study was to elucidate whether only flagellin-TLR5 signaling activation plays a role in the pathophysiology of liver or whether some other flagellin activity also contributes to liver injury either via bacterial infections or during clinical applications. Recombinant flagellin proteins with or without TLR5-stimulating activity were used to evaluate the role of flagellin-TLR5 signaling in liver injury in wild-type and TLR5 KO mice. Gross lesions and large areas of hepatocellular necrosis were observed in liver tissue 12 h after the intraperitoneal administration of 100 or 200 µg flagellin (FliC) in a dose- and time-dependent manner in wild-type mice, but not in TLR5 KO mice. Deletion of the N-terminal or TLR5 binding domain of flagellin inhibited flagellin-induced inflammatory responses and the subsequent acute liver function abnormality and damage. These data confirmed that flagellin is an essential determinant of liver injury and demonstrated that the over-activation of TLR5 signaling by high-dose flagellin caused acute inflammatory responses, neutrophil accumulation and oxidative stress in the liver, which contributes to the progression and severity of flagellin-induced liver injury.
authors.forename: Yang
authors.initials: Y
authors.lastname: Xiao
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Jingyi
authors.initials: J
authors.lastname: Yang
authors.forename: Maohua
authors.initials: M
authors.lastname: Zhong
authors.forename: Ejuan
authors.initials: E
authors.lastname: Zhang
authors.forename: Yaoming
authors.initials: Y
authors.lastname: Li
authors.forename: Dihan
authors.initials: D
authors.lastname: Zhou
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cao
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Yu
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Huimin
authors.initials: H
authors.lastname: Yan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005260:Female; D005408:Flagellin / Q000235:genetics* / Q000276:immunology / Q000494:pharmacology; D005786:Gene Expression Regulation; D008099:Liver / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D020556:Neutrophil Infiltration; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D019779:Salmonella enterica / Q000737:chemistry / Q000472:pathogenicity; D017384:Sequence Deletion; D015398:Signal Transduction; D051198:Toll-Like Receptor 5 / Q000172:deficiency / Q000235:genetics* / Q000276:immunology
chemical_list: D011994:Recombinant Proteins; D051198:Toll-Like Receptor 5; D005408:Flagellin