title: Alpha-lipoic acid inhibits TNF-alpha induced NF-kappa B activation through blocking of MEKK1-MKK4-IKK signaling cascades.
abstract: The therapeutic effects of alpha-lipoic acid (alpha-LA) via NF-kappa B down regulation were demonstrated on joint inflammation and erosion in an animal model. In this study, we investigated how alpha-LA inhibits the pathway of NF-kappa B activation by TNF-alpha via the mitogen-activated protein kinase (MAPK) pathway in rheumatoid arthritis (RA) fibroblast-like synovial cells (FLS). FLS were stimulated with TNF-alpha following pre-treatment with or without alpha-LA. Electrophoretic mobility shift assays (EMSA) revealed that TNF-alpha activates NF-kappa B in FLS. This was inhibited by alpha-LA at concentrations of 1 mM. TNF-alpha induced IKK mediated phosphorylation of GST-I kappa B and pre-treatment with alpha-LA inhibited this pathway. FLS constitutively express MEKK1, MEKK2, MEKK3, and TAK1 and that their levels are unaffected by TNF-alpha or alpha-LA. Immunoprecipitation using anti-MEKK1 antibody phosphorylated GST-I kappa B and pre-treating the cells with alpha-LA could abolish the reaction. FLS were immunoprecipitated using an antibody to MEKK1, and MKK4 was coprecipitated with MEKK1. In addition, immune complexes precipitated with anti-MKK4 antibody phosphorylated GST-I kappa B, and pre-treatment with alpha-LA inhibited the phosphorylation. Immunoprecipitation assay showed that MEKK1, MKK4, IKK-alpha, IKK-beta, I kappa B, and NF-kappa B comprised immunocomplex. It can be concluded that TNF-alpha activates NF-kappa B in FLS through MEKK1-MKK4-IKK signaling complex, and alpha-LA inhibits this signaling at the level of or upstream of IKK-alpha and IKK-beta.
authors.affiliation: Division of Allergy and Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Chang-Keun
authors.initials: CK
authors.lastname: Lee
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Yong Gil
authors.initials: YG
authors.lastname: Kim
authors.forename: Se Hwan
authors.initials: SH
authors.lastname: Mun
authors.forename: Hee-Bom
authors.initials: HB
authors.lastname: Moon
authors.forename: Bin
authors.initials: B
authors.lastname: Yoo
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors*; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors*; D048728:MAP Kinase Kinase Kinase 1 / Q000037:antagonists & inhibitors*; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D008063:Thioctic Acid / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
chemical_list: D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D008063:Thioctic Acid; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human