title: TLR4 signaling induces retinoic acid-inducible gene-I and melanoma differentiation-associated gene 5 in mesangial cells.
abstract: BACKGROUND
  It is known that recognition of bacterial lipopolysaccharide (LPS) and various endogenous ligands by Toll-like receptor 4 (TLR4) induces inflammatory reactions. However, the role of TLR4 activation in mesangial inflammation remains to be elucidated. Retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are putative RNA helicases and are involved in immune and inflammatory reactions. The purpose of the present study was to investigate the implication of RIG-I and MDA5 in TLR4 signaling in mesangial cells.
  
  
  METHODS
  Normal human mesangial cells in culture were treated with LPS. Expression of RIG-I, MDA5, interferon-β (IFN-β), CXCL10 and CXCL8 was examined using real-time RT-PCR, Western blotting and ELISA. The cells were also subjected to RNA interference against TLR4, IFN-β, RIG-I or MDA5.
  
  
  RESULTS
  LPS induced the expression of IFN-β, RIG-I, MDA5, CXCL8 and CXCL10 in human mesangial cells. RNA interference against either TLR4 or IFN-β inhibited LPS-induced RIG-I and MDA5 expression. Knockdown of TLR4, IFN-β, RIG-I or MDA5 resulted in decreased induction of CXCL10, while only TLR4 knockdown inhibited CXCL8 induction.
  
  
  CONCLUSIONS
  TLR4 signaling induces the expression of RIG-I and MDA5 in mesangial cells. RIG-I and MDA5 may be involved in inflammatory reactions by regulating CXCL10 expression in the downstream of TLR4 signaling in human mesangial cells.
authors.affiliation: Department of Vascular Biology, Hirosaki University Graduate School of Medicine, Hirosaki - Japan.
authors.forename: Tadaatsu
authors.initials: T
authors.lastname: Imaizumi
authors.forename: Tomomi
authors.initials: T
authors.lastname: Aizawa-Yashiro
authors.forename: Shojiro
authors.initials: S
authors.lastname: Watanabe
authors.forename: Tomoh
authors.initials: T
authors.lastname: Matsumiya
authors.forename: Hidemi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tatsuta
authors.forename: Fei
authors.initials: F
authors.lastname: Xing
authors.forename: Pengfei
authors.initials: P
authors.lastname: Meng
authors.forename: Ryo
authors.initials: R
authors.lastname: Hayakari
authors.forename: Kazushi
authors.initials: K
authors.lastname: Tsuruga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000378:metabolism; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1; D016899:Interferon-beta / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides; D050527:Mesangial Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011971:Receptors, Immunologic; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection / Q000379:methods
chemical_list: D054357:Chemokine CXCL10; D016209:Interleukin-8; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011971:Receptors, Immunologic; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D016899:Interferon-beta; C452820:RIGI protein, human; C452815:IFIH1 protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1