Novel mechanism of cytokine-induced disruption of epithelial barriers

Abstract

The ductal epithelium plays a key role in physiological secretion of pancreatic enzymes into the digestive system. Loss of barrier properties of the pancreatic duct may contribute to the development of pancreatitis and metastatic dissemination of pancreatic tumors. Proinflammatory cytokines are essential mediators of pancreatic inflammation and tumor progression; however, their effects on the integrity and barrier properties of the ductal epithelium have not been previously addressed. In the present study, we investigate mechanisms of cytokine-induced disassembly of tight junctions (TJs) and adherens junctions (AJs) in a model pancreatic epithelium. Exposure of HPAF-II human pancreatic epithelial cell monolayers to interferon (IFN)γ disrupted integrity and function of apical junctions as manifested by increased epithelial permeability and cytosolic translocation of AJ and TJ proteins. Tumor necrosis factor (TNF)α potentiated the effects of IFNγ on pancreatic epithelial junctions. The cytokine-induced increase in epithelial permeability and AJ/TJ disassembly was attenuated by pharmacological inhibition of Janus kinase (JAK) and protein kinase D (PKD). Loss of apical junctions in IFNγ/TNFα-treated HPAF-II cells was accompanied by JAK and PKD dependent decrease in expression of AJ (E-cadherin, p120 catenin) and TJ (occludin, ZO-1) proteins. Depletion of E-cadherin or p120 catenin recapitulated the effects of cytokines on HPAF-II cell permeability and junctions. Our data suggests that proinflammatory cytokines disrupt pancreatic epithelial barrier via expressional downregulation of key structural components of AJs and TJs. This mechanism is likely to be important for pancreatic inflammatory injury and tumorigenesis.

Disruption of the epithelial barrier during intestinal inflammation: Quest for new molecules and mechanisms

“…By contrast, inducible ablation of intestinal epithelial β-catenin, while blocking cell proliferation, did not impair the integrity of epithelial junctions [53]. Consistently, downregulation of E-cadherin and p120-catenin expression was shown to increase paracellular permeability and to disrupt TJ integrity in model epithelial cell monolayers [52, 54]. Together, these data strongly suggest that expressional downregulation of AJ proteins represents an important mechanism of epithelial barrier disruption during intestinal inflammation.…”

“…Indeed, translation of E-cadherin and p120-catenin is decreased in inflammatory breast cancer [60] and cytokine-exposed model pancreatic epithelium [54]. These effects are associated with defects in the translation initiation machinery.…”

F-actin binding protein, anillin, regulates integrity of intercellular junctions in human epithelial cells

“…Knockdown of γ-adducin was achieved using siRNA SmartPool (Dharmacon). Cells were transfected using DharmaFect 1 transfection reagent (Dharmacon) with a final siRNA concentration of 50 nM, as described previously [41, 42]. For knockdown/overexpression experiments, DU145 cells plated on coverslips were transfected with either control or anillin-specific siRNAs and 24 h later, were subjected to a second round of transfection with either GFP-γ-adducin plasmid (gift from Dr. Y. Peng Loh, Eunice Kennedy Shriver National Institute of Child Health, Bethesda, MD [43]), or a control GFP plasmid (gift from Dr. Andrei Budanov, VCU, Richmond, VA).…”

Tissue Barriers: Introducing an exciting new journal

“…We reflected on this by publishing papers that target controversial issues in the field. Examples of such controversial issue include the nature and origin of intestinal stem cells, 31 the roles of haptoglobin/zonulin proteins in inflammatory bowel diseases, 32 and transcriptional versus translational mechanisms of junctional protein downregulation by proinflammatory cytokines 21 . As for many other extensive research fields, there are some segments of tissue barrier research that are overshadowed by more popular subjects.…”