Differentiation between human ClC-2 and CFTR Cl- channels with pharmacological agents

Am J Physiol Cell Physiol. 2014 Sep 1;307(5):C479-92. doi: 10.1152/ajpcell.00077.2014. Epub 2014 Jul 9.

Abstract

It has been difficult to separate/identify the roles of ClC-2 and CFTR in Cl(-) transport studies. Using pharmacological agents, we aimed to differentiate functionally between ClC-2 and CFTR Cl(-) channel currents. Effects of CFTR inhibitor 172 (CFTRinh172), N-(4-methylphenylsulfonyl)-N'-(4-trifluoromethylphenyl)urea (DASU-02), and methadone were examined by whole cell patch clamp on Cl(-) currents in recombinant human ClC-2/human embryonic kidney 293 (ClC-2/HEK293) cells stably transformed with Epstein-Barr nuclear antigen 1 (hClC-2/293EBNA) and human CFTR/HEK293 (hCFTR/HEK293) cells and by short-circuit current (Isc) measurements in T84 cells. Lubiprostone and forskolin-IBMX were used as activators. CFTRinh172 inhibited forskolin-IBMX-stimulated recombinant human CFTR (hCFTR) and lubiprostone-stimulated recombinant human ClC-2 (hClC-2) Cl(-) currents in a concentration-dependent manner equipotently. DASU-02 inhibited forskolin-IBMX-stimulated Cl(-) currents in hCFTR/HEK293 cells, but not lubiprostone-stimulated Cl(-) currents in hClC-2/293EBNA cells. In T84 cells with basolateral nystatin or 1-ethyl-2-benzimidazolinone (1-EBIO), lubiprostone-stimulated and forskolin-IBMX-cyclosporin A (FICA)-stimulated Isc components were observed. CFTRinh172 inhibited major portions of both components. DASU-02 had no effect on lubiprostone-stimulated Isc but partially inhibited FICA-stimulated Isc. T84 cells in which ClC-2 or CFTR was knocked down using siRNAs were constructed. T84 ClC-2 knockdown cells did not respond to lubiprostone but did respond to forskolin-IBMX in a methadone-insensitive, DASU-02-sensitive manner, indicating CFTR function. T84 CFTR knockdown cells responded separately to lubiprostone and forskolin-IBMX in a methadone-sensitive and DASU-02-insensitive manner, indicating ClC-2 function. Low lubiprostone concentrations activated ClC-2, but not CFTR, and both channels were activated by forskolin-IBMX but have different inhibitor sensitivities. Methadone, but not DASU-02, inhibited ClC-2. DASU-02, but not methadone, inhibited CFTR. In T84 cells, both ClC-2 and CFTR are present and likely play roles in Cl(-) secretion.

Keywords: CFTR inhibitor 172; DASU-02; forskolin; lubiprostone; methadone.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Cell Line
  • Chloride Channels / antagonists & inhibitors*
  • Chloride Channels / physiology*
  • Cystic Fibrosis Transmembrane Conductance Regulator / antagonists & inhibitors*
  • Cystic Fibrosis Transmembrane Conductance Regulator / physiology*
  • Dose-Response Relationship, Drug
  • Epithelial Cells / drug effects
  • HEK293 Cells
  • Humans
  • Methadone / pharmacology
  • Urea / analogs & derivatives
  • Urea / pharmacology

Substances

  • CFTR protein, human
  • Chloride Channels
  • ClC-2 chloride channels
  • N-(4-methylphenylsulfonyl)-N'-(4-trifluoromethylphenyl)urea
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Urea
  • 1-Methyl-3-isobutylxanthine
  • Methadone