Fluoxetine blocks Nav1.5 channels via a mechanism similar to that of class 1 antiarrhythmics.

TitleFluoxetine blocks Nav1.5 channels via a mechanism similar to that of class 1 antiarrhythmics.
Publication TypeJournal Article
Year of Publication2014
AuteursPoulin, H, Bruhova, I, Timour, Q, Thériault, O, Beaulieu, J-M, Frassati, D, Chahine, M
JournalMol Pharmacol
Volume86
Issue4
Pagination378-89
Date Published2014 Oct
ISSN1521-0111
KeywordsAmino Acid Sequence, Anti-Arrhythmia Agents, Binding Sites, Fluoxetine, HEK293 Cells, Humans, Inhibitory Concentration 50, Ion Channel Gating, Molecular Sequence Data, Mutation, NAV1.5 Voltage-Gated Sodium Channel, Protein Binding, Serotonin Uptake Inhibitors, Sodium Channel Blockers
Abstract

The voltage-gated Nav1.5 channel is essential for the propagation of action potentials in the heart. Malfunctions of this channel are known to cause hereditary diseases. It is a prime target for class 1 antiarrhythmic drugs and a number of antidepressants. Our study investigated the Nav1.5 blocking properties of fluoxetine, a selective serotonin reuptake inhibitor. Nav1.5 channels were expressed in HEK-293 cells, and Na(+) currents were recorded using the patch-clamp technique. Dose-response curves of racemic fluoxetine (IC50 = 39 μM) and its optical isomers had a similar IC50 [40 and 47 μM for the (+) and (-) isomers, respectively]. Norfluoxetine, a fluoxetine metabolite, had a higher affinity than fluoxetine, with an IC50 of 29 μM. Fluoxetine inhibited currents in a frequency-dependent manner, shifted steady-state inactivation to more hyperpolarized potentials, and slowed the recovery of Nav1.5 from inactivation. Mutating a phenylalanine (F1760) and a tyrosine (Y1767) in the S6 segment of domain (D) IV (DIVS6) significantly reduced the affinity of fluoxetine and its frequency-dependent inhibition. We used a noninactivating Nav1.5 mutant to show that fluoxetine displays open-channel block behavior. The molecular model of fluoxetine in Nav1.5 was in agreement with mutational experiments in which F1760 and Y1767 were found to be the key residues in binding fluoxetine. We concluded that fluoxetine blocks Nav1.5 by binding to the class 1 antiarrhythmic site. The blocking of cardiac Na(+) channels should be taken into consideration when prescribing fluoxetine alone or in association with other drugs that may be cardiotoxic or for patients with conduction disorders.

DOI10.1124/mol.114.093104
Alternate JournalMol. Pharmacol.
PubMed ID25028482
PubMed Central IDPMC4164981
Grant ListR01 NS064969 / NS / NINDS NIH HHS / United States
MOP-111072 / / Canadian Institutes of Health Research / Canada
NS-064969 / NS / NINDS NIH HHS / United States