Reduced epithelial sodium channel function might contribute to chronic diarrhea in inflammatory bowel disease

Introduction: The incidence of inflammatory bowel diseases (IBD) has increased significantly in the last decades. Recent data indicate that abnormal Na+ transport contributes to diarrhea, a leading symptom in patients with IBD. The aim of this study was to compare epithelial sodium channel (ENaC)-mediated ion transport in enterocytes isolated from individuals with and without IBD. Materials and methods: Crypts of Lieberkühn were isolated from biopsies taken from patients with Crohn-disease (CD) and ulcerative colitis (UC), as well as from control subjects. Cells were seeded on glass coverslips covered by Matrigel and cultured in standard medium. Cells were used for experiments 2–5 days after isolation. We used whole cell configuration of the patch clamp technique and measured ion currents in voltage clamp mode. Sodium currents were detected by blocking K+ currents with TEA and applying low Cl- concentrations in both pipette and bath solutions. Statistical analysis were performed using Student t-test (p<0.05). Results: Amiloride insensitive basal current density was low in cells isolated from control subjects. Similar data were obtained in cells from CD and UC patients exhibiting even smaller inward currents then in control cells. However, these differences did not reach the level of significance. In control but not in CD and UC cells, administration of the serine protease trypsin significantly stimulated the inward currents. Trypsin shifted the reversal potential of the current towards the equilibrium potential of Na+ suggesting opening of ENaCs. In addition, the trypsin-induced Na+ current were blocked by amiloride. Discussion: Our results show that diarrhea in CD and UC could be due to impaired ENaC-mediated Na+ transport. Nevertheless, we think that alteration of other ion transport mechanisms and accumulation of local inflammatory mediators also contribute to development of symptoms in IBD.

Supported by OTKA 43066, 69008 and 79189 and MTA.