title: VLA-4 integrin cross-linking on human monocytic THP-1 cells induces tissue factor expression by a mechanism involving mitogen-activated protein kinase.
abstract: Adhesion molecules such as VLA-4 are important not only for monocyte adhesion to extracellular matrix proteins, but also for subsequent cell activation. Monocyte adherence to fibronectin or engagement of VLA-4 has been demonstrated to stimulate production of potent inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1, and the procoagulant tissue factor protein. However, the intracellular signaling cascades leading to gene expression have not been elucidated. Using the human monocytic THP-1 cell line, VLA-4 cross-linking by monoclonal antibodies directed against its alpha4 and beta1 subunits produced a time-dependent increase in tyrosine phosphorylation of a broad range of cellular proteins. Using Western blot analysis directed against the phosphorylated form of the extracellular signal-related kinase (ERK) mitogen-activated protein (MAP) kinase proteins, as well as immunoprecipitation and in vitro kinase assays, we found that VLA-4 cross-linking increased ERK1/ERK2 tyrosine phosphorylation and activity. In conjunction, integrin cross-linking also increased NF-kappaB nuclear translocation and 4-h expression of tissue factor. Inhibition of tyrosine kinase activity with genistein (10 microg/ml) as well as selective MAP kinase inhibition with the MEK-1 inhibitor PD98059 abolished the VLA-4-dependent ERK tyrosine phosphorylation, inhibited NF kappaB nuclear binding, and abrogated tissue factor expression induced by both VLA-4 cross-linking and adhesion to fibronectin in THP-1 cells and human peripheral blood monocytes. These studies point to the involvement of the MAP kinase pathway in the activation of monocytic cells during transmigration to inflammatory sites.
authors.affiliation: Departments of Surgery, Toronto Hospital-General Division and the University of Toronto, Toronto, Ontario M5G 2C4, Canada.
authors.forename: I D
authors.initials: ID
authors.lastname: McGilvray
authors.forename: Z
authors.initials: Z
authors.lastname: Lu
authors.forename: R
authors.initials: R
authors.lastname: Bitar
authors.forename: A P
authors.initials: AP
authors.lastname: Dackiw
authors.forename: C J
authors.initials: CJ
authors.lastname: Davreux
authors.forename: O D
authors.initials: OD
authors.lastname: Rotstein
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D019833:Genistein; D006801:Humans; D039041:Integrin alpha4beta1; D019012:Integrin beta1 / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism*; D007529:Isoflavones / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism*; D016029:Receptors, Very Late Antigen / Q000378:metabolism*; D013925:Thromboplastin / Q000096:biosynthesis*; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D014764:Viral Proteins; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005353:Fibronectins; D005419:Flavonoids; D039041:Integrin alpha4beta1; D019012:Integrin beta1; D016023:Integrins; D007529:Isoflavones; D016328:NF-kappa B; D009687:Nuclear Proteins; D016201:Receptors, Lymphocyte Homing; D016029:Receptors, Very Late Antigen; D015534:Trans-Activators; D014764:Viral Proteins; D014443:Tyrosine; D013925:Thromboplastin; D019833:Genistein; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one