Inhibition of heterologously expressed cystic fibrosis transmembrane conductance regulator Cl channels by non-sulphonylurea hypoglycaemic agents

Authors

  • Z Cai,

    1. Human Genetics Unit, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU
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  • K A Lansdell,

    1. Human Genetics Unit, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU
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    • 2

      Current address: Department of Pharmacology, Quintiles Scotland Ltd, Heriot-Watt University Research Park, Riccarton, Edinburgh EH14 4AP

  • D N Sheppard

    Corresponding author
    1. Human Genetics Unit, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU
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Human Genetics Unit, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU. E-mail: D.N.Sheppard@ed.ac.uk

Abstract

  • Hypoglycaemia-inducing sulphonylureas, such as glibenclamide, inhibit cystic fibrosis transmembrane conductance regulator (CFTR) Cl channels. In search of modulators of CFTR, we investigated the effects of the non-sulphonylurea hypoglycaemic agents meglitinide, repaglinide, and mitiglinide (KAD-1229) on CFTR Cl channels in excised inside-out membrane patches from C127 cells expressing wild-type human CFTR.

  • When added to the intracellular solution, meglitinide and mitiglinide inhibited CFTR Cl currents with half-maximal concentrations of 164±19 μM and 148±36 μM, respectively. However, repaglinide only weakly inhibited CFTR Cl currents.

  • To understand better how non-sulphonylurea hypoglycaemic agents inhibit CFTR, we studied single channels. Channel blockade by both meglitinide and mitiglinide was characterized by flickery closures and a significant decrease in open probability (Po). In contrast, repaglinide was without effect on either channel gating or Po, but caused a small decrease in single-channel current amplitude.

  • Analysis of the dwell time distributions of single channels indicated that both meglitinide and mitiglinide greatly decreased the open time of CFTR. Mitiglinide-induced channel closures were about 3-fold longer than those of meglitinide.

  • Inhibition of CFTR by meglitinide and mitiglinide was voltage-dependent: at positive voltages channel blockade was relieved.

  • The data demonstrate that non-sulphonylurea hypoglycaemic agents inhibit CFTR. This indicates that these agents have a wider specificity of action than previously recognized. Like glibenclamide, non-sulphonylurea hypoglycaemic agents may inhibit CFTR by occluding the channel pore and preventing Cl permeation.

British Journal of Pharmacology (1999) 128, 108–118; doi:10.1038/sj.bjp.0702748

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