A role for hypoxia inducible factor in the junctional integrity and barrier function of intestinal epithelial cells (60.1)

Abstract

The gastrointestinal mucosa provides the primary physical barrier against gut luminal contents. In mucosal diseases such as inflammatory bowel disease, hypoxia and inflammation occur coincidentally at the level of the epithelium. Adaptive transcriptional responses to oxygen deprivation are mediated primarily through the hypoxia‐inducible factor complex (HIF), comprised of an oxygen‐labile ‘ Α’ subunit and constitutively expressed ‘Β’ subunit. A role for HIF has been implicated in orchestrating a signaling program that promotes intestinal epithelial function and homeostasis. Using lentiviral shRNA‐mediated knockdown of HIF1Β in T84 epithelial cells we sought to define the contribution of HIF signaling to epithelial barrier function. HIF1β knockdown resulted in significantly increased permeability, as measured by transepithelial resistance and FITC‐dextran flux assays. Immunolocalization studies of tight junction and adherens junction markers ZO1 and E‐cadherin, respectively, revealed non‐uniform, undulating junctions in HIF1Β depleted T84 monolayers. RT‐PCR and western blot analysis of HIF1Β‐depleted T84 monolayers revealed significantly reduced levels of claudin‐1, a transmembrane tight junction protein that is important for junctional integrity. To date, little is known concerning the transcriptional regulation of claudin‐1, and this work provides an important mechanistic link between the observed influences of HIF signaling on epithelial barrier function, the formation and maintenance of the apical junction complex and ultimately intestinal tissue integrity.Grant Funding Source: Supported by NIH and CCFA