Proinflammatory cytokines tumor necrosis factor-α and interferon-γ modulate epithelial barrier function in Madin-Darby canine kidney cells through mitogen activated protein kinase signaling
1 Southwestern Graduate School of Biomedical Sciences, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9004, USA
2 UT Medical School, UTHSCSA, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
3 Trinity University, Biology Department, One Trinity Place, San Antonio, TX 78212, USA
BMC Physiology 2006, 6:2 doi:10.1186/1472-6793-6-2Published: 21 February 2006
The tight junction is a dynamic structure that is regulated by a number of cellular signaling processes. Occludin, claudin-1, claudin-2 and claudin-3 are integral membrane proteins found in the tight junction of MDCK cells. These proteins are restricted to this region of the membrane by a complex array of intracellular proteins which are tethered to the cytoskeleton. Alteration of these tight junction protein complexes during pathological events leads to impaired epithelial barrier function that perturbs water and electrolyte homeostasis. We examined MDCK cell barrier function in response to challenge by the proinflammatory cytokines tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ).
Exposure of MDCK cells to TNFα/IFNγ resulted in a marked sustained elevation of transepithelial electrical resistance (TER) as well as elevated paracellular permeability. We demonstrate that the combination of TNFα/IFNγ at doses used in this study do not significantly induce MDCK cell apoptosis. We observed significant alterations in occludin, claudin-1 and claudin-2 protein expression, junctional localization and substantial cytoskeletal reorganization. Pharmacological inhibition of ERK1/2 and p38 signaling blocked the deleterious effects of the proinflammatory cytokines on barrier function.
These data strongly suggest that downstream effectors of MAP kinase signaling pathways mediate the TNFα/IFNγ-induced junctional reorganization that modulates MDCK cell barrier function.