Inhibition of heterologously expressed cystic fibrosis transmembrane conductance regulator Cl- channels by non-sulphonylurea hypoglycaemic agents.
1. 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. 2. When added to the intracellular solution, meglitinide and mitiglinide inhibited CFTR Cl- currents with half-maximal concentrations of 164+/-19 microM and 148+/-36 microM, respectively. However, repaglinide only weakly inhibited CFTR Cl- currents. 3. 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. 4. 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. 5. Inhibition of CFTR by meglitinide and mitiglinide was voltage-dependent: at positive voltages channel blockade was relieved. 6. 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.
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Human Genetics Unit, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU.
Lansdell
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Sheppard
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001549:Benzamides / Q000737:chemistry / Q000494:pharmacology; D002219:Carbamates / Q000737:chemistry / Q000494:pharmacology; D002460:Cell Line; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D054833:Isoindoles; D007700:Kinetics; D051379:Mice; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000737:chemistry / Q000494:pharmacology; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D014162:Transfection
D001549:Benzamides; C505032:CFTR protein, human; D002219:Carbamates; D018118:Chloride Channels; D007004:Hypoglycemic Agents; D007211:Indoles; D054833:Isoindoles; D010880:Piperidines; D013453:Sulfonylurea Compounds; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C072379:repaglinide; D000255:Adenosine Triphosphate; C030516:meglitinide; C087255:mitiglinide; D017868:Cyclic AMP-Dependent Protein Kinases; D005905:Glyburide