Basolateral potassium (IK_Ca) channel inhibition prevents increased colonic permeability induced by chemical hypoxia

Abstract

Loganathan A, Linley JE, Rajput I, Hunter M, Lodge JP, Sandle GI. Basolateral potassium (IKCa) channel inhibition prevents increased colonic permeability induced by chemical hypoxia. Am J Physiol Gastrointest Liver Physiol 300: G146 -G153, 2011. First published October 21, 2010 doi:10.1152/ajpgi.00472.2009.-Major liver resection is associated with impaired intestinal perfusion and intestinal ischemia, resulting in decreased mucosal integrity, increased bacterial translocation, and an increased risk of postoperative sepsis. However, the mechanism by which ischemia impairs intestinal mucosal integrity is unclear. We therefore evaluated the role of Ca 2ϩ -sensitive, intermediate-conductance (IKCa) basolateral potassium channels in enhanced intestinal permeability secondary to chemical hypoxia. The effects of chemical hypoxia induced by 100 M dinitrophenol (DNP) and 5 mM deoxyglucose (DG) on basolateral IKCa channel activity and whole cell conductance in intact human colonic crypts, and paracellular permeability (GS) in isolated colonic sheets, were determined by patch-clamp recording and transepithelial electrical measurements, respectively. DNP and DG rapidly stimulated IKCa channels in cell-attached basolateral membrane patches and elicited a twofold increase (P ϭ 0.004) in whole cell conductance in amphotericin B-permeabilized membrane patches, changes that were inhibited by the specific IKCa channel blockers TRAM-34 (100 nM) and clotrimazole (CLT; 10 M). In colonic sheets apically permeabilized with nystatin, DNP elicited a twofold increase (P ϭ 0.005) in GS, which was largely inhibited by the serosal addition of 50 M CLT. We conclude that, in intestinal epithelia, chemical hypoxia increases GS through a mechanism involving basolateral IKCa channel activation. Basolateral IKCa channel inhibition may prevent or limit increased intestinal permeability during liver surgery. Ca 2ϩ -sensitive intermediate-conductance basolateral potassium channels

Priming approaches to improve the efficacy of mesenchymal stromal cell-based therapies

“…Chemicals that inhibit the electron transportation chain, such as 2,4-dinitrophenol (DNP) [ 88 ], hypoxia-inducible factors (HIF-1, HIF-1α, HIF-1β), or prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) [ 89 ], also induce hypoxic environments. Preconditioning with DNP induces upregulation of adhesion and homing genes in MSC, as well as increased secretion of cardiomyogenic factors.…”

Evidence that two distinct crypt cell types secrete chloride and potassium in human colon

“…This was accompanied by a positive shift in E rev of 21±5 mV, consistent with K + channel inhibition. We have previously shown that inwardly rectifying K + (IK) channels in human colonic crypt cells are inhibited by CLT,28 and also by 100 nM TRAM-34, a potent and selective IK channel inhibitor 29. By contrast, CLT had no effect on whole-cell currents (figure 2A) or whole-cell conductance (figure 2B) in OR K cells (n=3).…”

Hypoxia/Reoxygenation Effects on Ion Transport across Rat Colonic Epithelium

“…This process is supported by the transient opening of Ca 2+ -dependent Cl − channels in the apical membrane (Hennig et al, 2008 ). Indeed, in human colonic epithelium chemically induced hypoxia has been shown to activate intermediate conductance Ca 2+ -dependent K + channels (Loganathan et al, 2011 ). An increase in the cytosolic Ca 2+ concentration will also stimulate apical Ca 2+ -dependent K + channels, which are found in the brushborder membrane, too (Schultheiss and Diener, 1997 ).…”

“…In T84 cells, a release of epithelial cytokines such as tumor necrosis factor-α has been shown to play a role in the increase in G t during hypoxia, which probably reflects an increased permeability of the tight junctions (Taylor et al, 1998a ). However, this does not necessarily represent only an unspecific damage of the epithelium due to hypoxia, but may in addition involve a regulated process as inhibition of Ca 2+ -dependent K + channels has been shown to reduce the increase in the paracellular permeability during energy depletion in human colon (Loganathan et al, 2011 ).…”