title: Tumor necrosis factor-α induces a biphasic change in claudin-2 expression in tubular epithelial cells: role in barrier functions.
abstract: The inflammatory cytokine tumor necrosis factor-α (TNF-α) is a pathogenic factor in acute and chronic kidney disease. TNF-α is known to alter expression of epithelial tight junction (TJ) proteins; however, the underlying mechanisms and the impact of this effect on epithelial functions remain poorly defined. Here we describe a novel biphasic effect of TNF-α on TJ protein expression. In LLC-PK1 tubular cells, short-term (1-6 h) TNF-α treatment selectively elevated the expression of the channel-forming TJ protein claudin-2. In contrast, prolonged (>8 h) TNF-α treatment caused a marked downregulation in claudin-2 and an increase in claudin-1, -4, and -7. The early increase and the late decrease in claudin-2 expression involved distinct mechanisms. TNF-α slowed claudin-2 degradation through ERK, causing the early increase. This increase was also mediated by the EGF receptor and RhoA and Rho kinase. In contrast, prolonged TNF-α treatment reduced claudin-2 mRNA levels and promoter activity independent from these signaling pathways. Electric Cell-substrate Impedance Sensing measurements revealed that TNF-α also exerted a biphasic effect on transepithelial resistance (TER) with an initial decrease and a late increase. Thus there was a good temporal correlation between TNF-α-induced claudin-2 protein and TER changes. Indeed, silencing experiments showed that the late TER increase was at least in part caused by reduced claudin-2 expression. Surprisingly, however, claudin-2 silencing did not prevent the early TER drop. Taken together, the TNF-α-induced changes in claudin-2 levels might contribute to TER changes and could also play a role in newly described functions of claudin-2 such as proliferation regulation.
authors.affiliation: Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Yasaman
authors.initials: Y
authors.lastname: Amoozadeh
authors.affiliation: Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Qinghong
authors.initials: Q
authors.lastname: Dan
authors.affiliation: Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Jenny
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Faiza
authors.initials: F
authors.lastname: Waheed
authors.affiliation: Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada szaszik@smh.ca.
authors.forename: Katalin
authors.initials: K
authors.lastname: Szászi
mesh_terms: D000818:Animals; D057167:Claudins / Q000235:genetics / Q000378:metabolism*; D017097:Electric Impedance; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D019073:HT29 Cells; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D018374:LLC-PK1 Cells; D010539:Permeability; D059748:Proteolysis; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013552:Swine; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: C491875:CLDN2 protein, human; D057167:Claudins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C066737:RHOA protein, human; C541485:EGFR protein, mouse; D066246:ErbB Receptors; D054460:rho-Associated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020742:rhoA GTP-Binding Protein
keywords: ECIS; tight junction; transepithelial resistance; tubular epithelial cells; tumor necrosis factor