Selective induction of Mucin‐3 by hypoxia in intestinal epithelia

Abstract

Epithelia line mucosal surfaces, serving as semi-permeable barriers to the outside world. Mucosal organs are highly vascular with extensive metabolic demands and are particularly vulnerable to ischemia and tissue hypoxia. We hypothesized that intestinal barrier function is protectively regulated by hypoxia responsive genes. We demonstrate by microarray, PCR and avidin blotting of immunoprecipitated human Mucin 3 (MUC3), that MUC3 RNA (evident by 8 hours) and surface protein (maximal at 24 hours) are induced in hypoxic T84 intestinal epithelial cells. This MUC3 induction is associated with a transient increase in the barrier restorative peptide, intestinal trefoil factor (ITF). ITF colocalizes with MUC3 to the apical surface of hypoxic T84 cells, and is also found to be physically associated with MUC3, following 24 hours of hypoxia. In exploration of the mechanism of hypoxic regulation of MUC3 expression, we found the mouse mucin 3 promoter to be hypoxia-responsive (5.08 + 1.76-fold increased after 24 hours). Further analyses of both the human and mouse mucin 3 promoters revealed potential HIF1 binding sites which were shown by chromatin immunoprecipitation to bind the pivotal hypoxia-regulating transcription factor HIF-1-α. These studies implicate the HIF-1-α mediated hypoxic induction of MUC3 and associated ITF in the maintenance of intestinal barrier function in hypoxia.