title: Transforming growth factor-β1 protects against intestinal epithelial barrier dysfunction caused by hypoxia-reoxygenation.
abstract: Intestinal epithelia regulate barrier integrity when challenged by inflammation, oxidative stress, and microbes. Transforming growth factor-β1 (TGF-β1) is a cytokine with known beneficial effects on intestinal epithelia, including barrier enhancement, after exposure to proinflammatory cytokines and infectious agents. The aim of this study was to determine whether TGF-β1 directly protects intestinal epithelia during hypoxia-reoxygenation (HR). Intestinal epithelial monolayers (T84, Caco-2) were exposed to either hypoxia (1% O2, 1 h) or oxidative stress (hydrogen peroxide, 1 mM), followed by normoxic atmosphere for different time points in the absence and presence of varying concentrations of TGF-β1. Transepithelial electrical resistance (TER) assessed barrier function, with RNA extracted for reverse transcription polymerase chain reaction analysis of GPx-1, HIF-1, heme-oxygenase-1 (HO-1), and NOX-1. In some experiments, intestinal epithelia were exposed to enterohemorrhagic Escherichia coli (EHEC) O157:H7 during the reoxygenation period and TER recorded 7 h after the infectious challenge. Hypoxia-reoxygenation significantly decreased TER in intestinal epithelia compared with normoxic controls. Transforming growth factor-β1 pretreatment ameliorated HR-induced epithelial barrier dysfunction in T84 (at 1 - 3 h) and Caco-2 (1 h) monolayers. Transforming growth factor-β1 preserved barrier integrity for up to 16 h after challenge with hydrogen peroxide. In TGF-β1-treated epithelial monolayers, only HO-1 mRNA significantly increased after HR (P < 0.05 vs. normoxic controls). The EHEC-induced epithelial barrier dysfunction was significantly worsened by intestinal HR (P < 0.05 vs. normoxia-EHEC-infected cells), but this was not protected by TGF-β1 pretreatment. Transforming growth factor-β1 preserves loss of epithelial barrier integrity caused by the stress of HR via a mechanism that may involve the upregulation of HO-1 transcription. Targeted treatment with TGF-β could lead to novel therapies in enteric diseases characterized by HR injury.
authors.affiliation: *Cell Biology Program, Research Institute, Hospital for Sick Children, University of Toronto, Toronto; †Faculty of Health Sciences, Department of Surgery, Division of General Surgery, McMaster University, Hamilton, Ontario; and ‡Department of Paediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Howe
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lorentz
authors.forename: Amit
authors.initials: A
authors.lastname: Assa
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Pinnell
authors.forename: Kathene C
authors.initials: KC
authors.lastname: Johnson-Henry
authors.forename: Philip M
authors.initials: PM
authors.lastname: Sherman
mesh_terms: D018938:Caco-2 Cells; D015687:Cell Hypoxia; D016207:Cytokines / Q000378:metabolism; D017097:Electric Impedance; D054324:Enterohemorrhagic Escherichia coli / Q000472:pathogenicity; D004847:Epithelial Cells / Q000187:drug effects; D004848:Epithelium / Q000378:metabolism; D015870:Gene Expression; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D007410:Intestinal Diseases / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000473:pathology; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D016207:Cytokines; D012333:RNA, Messenger; D011994:Recombinant Proteins; D053773:Transforming Growth Factor beta1; D006861:Hydrogen Peroxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D010100:Oxygen