xe-991--anthracenone and Long-QT-Syndrome

The slow delayed rectifier K+ current, Iks, encoded by KCNQ1 (KvLQT1)/KCNE1 (mink) genes, contributes to cardiac action potential repolarization and determines the heartbeat rate. Mutations in either KCNQ1 or KCNE1 that reduce Iks cause long-QT syndrome (LQTS), a disorder of ventricular repolarization that results in cardiac arrhythmia and sudden death. A well-recognized potential treatment for LQTS caused by reduction of Iks is to enhance functional activation of cardiac KCNQ1/KCNE1 channels. In the present study, we generated a stable Chinese hamster ovary cell line that expresses KCNQ1/KCNE1 channels confirmed by electrophysiology. Using a pharmacological tool compound R-L3 (L-364,373 [(3-R)-1,3-dihydro-5-(2-fluorophenyl)-3-(1H-indol- 3-ylmethyl)-1-methyl-2H-1,4-benzodiazepin-2-one]), which activates KCNQ1/mink channels, we then developed and validated a non-radioactive rubidium (Rb+) efflux assay that directly measures the functional activity of KCNQ1/KCNE1 channels by atomic absorption spectroscopy. Our results show that the validated Rb+ efflux assay can be used for screening of KCNQ1/KCNE1 openers that potentially treat LQTS in both inherited and acquired forms. In addition, the assay also can be used for evaluation of possible long-QT liability during cardiac selectivity of new chemical entities.

Topics: Animals; Anthracenes; Benzodiazepines; CHO Cells; Chromans; Cricetinae; Cyclic Nucleotide-Gated Cation Channels; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Gene Expression; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; Ion Channels; KCNQ1 Potassium Channel; Long QT Syndrome; Membrane Potentials; Myocardium; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Voltage-Gated; Potassium Chloride; Rats; Reproducibility of Results; Risk Factors; Rubidium; Spectrophotometry, Atomic; Tetraethylammonium