title: Lipopolysaccharide Regulation of Intestinal Tight Junction Permeability Is Mediated by TLR4 Signal Transduction Pathway Activation of FAK and MyD88.
abstract: Gut-derived bacterial LPS plays an essential role in inducing intestinal and systemic inflammatory responses and have been implicated as a pathogenic factor in necrotizing enterocolitis and inflammatory bowel disease. The defective intestinal tight junction barrier was shown to be an important factor contributing to the development of intestinal inflammation. LPS, at physiological concentrations, causes an increase in intestinal tight junction permeability (TJP) via a TLR4-dependent process; however, the intracellular mechanisms that mediate LPS regulation of intestinal TJP remain unclear. The aim of this study was to investigate the adaptor proteins and the signaling interactions that mediate LPS modulation of intestinal tight junction barrier using in vitro and in vivo model systems. LPS caused a TLR4-dependent activation of membrane-associated adaptor protein focal adhesion kinase (FAK) in Caco-2 monolayers. LPS caused an activation of both MyD88-dependent and -independent pathways. Small interfering RNA silencing of MyD88 prevented an LPS-induced increase in TJP. LPS caused MyD88-dependent activation of IL-1R-associated kinase 4. TLR4, FAK, and MyD88 were colocalized. Small interfering silencing of TLR4 inhibited TLR4-associated FAK activation, and FAK knockdown prevented MyD88 activation. In vivo studies also confirmed that the LPS-induced increase in mouse intestinal permeability was associated with FAK and MyD88 activation; knockdown of intestinal epithelial FAK prevented an LPS-induced increase in intestinal permeability. Additionally, high-dose LPS-induced intestinal inflammation was dependent on the TLR4/FAK/MyD88 signal transduction axis. To our knowledge, our data show for the first time that the LPS-induced increases in intestinal TJP and intestinal inflammation were regulated by TLR4-dependent activation of the FAK/MyD88/IL-1R-associated kinase 4 signaling pathway.
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and Albuquerque Veterans Affairs Medical Center, Albuquerque, NM 87108.
authors.forename: Shuhong
authors.initials: S
authors.lastname: Guo
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and.
authors.forename: Meghali
authors.initials: M
authors.lastname: Nighot
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and Albuquerque Veterans Affairs Medical Center, Albuquerque, NM 87108.
authors.forename: Rana
authors.initials: R
authors.lastname: Al-Sadi
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and.
authors.forename: Tarik
authors.initials: T
authors.lastname: Alhmoud
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and.
authors.forename: Prashant
authors.initials: P
authors.lastname: Nighot
authors.affiliation: Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131; and Albuquerque Veterans Affairs Medical Center, Albuquerque, NM 87108 tma@salud.unm.edu.
authors.forename: Thomas Y
authors.initials: TY
authors.lastname: Ma
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007422:Intestines / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000276:immunology*; D010539:Permeability / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics / Q000276:immunology; D019108:Tight Junctions / Q000235:genetics / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology*
chemical_list: D008070:Lipopolysaccharides; C507779:MYD88 protein, human; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse