Back to Search Start Over

Flecainide induces a sustained countercurrent dependent effect on RyR2 in permeabilized WT ventricular myocytes but not in intact cells

Authors :
Emma J. Steer
Zhaokang Yang
Moza M. Al-Owais
Hannah M. Kirton
Edward White
Derek S. Steele
Source :
Frontiers in Pharmacology, Vol 14 (2023)
Publication Year :
2023
Publisher :
Frontiers Media S.A., 2023.

Abstract

Background and purpose: While flecainide is now an accepted treatment for arrhythmias associated with catecholaminergic polymorphic ventricular tachycardia (CPVT), its mechanism of action remains controversial. In studies on myocytes from CPVT mice, inhibition of proarrhythmic Ca2+ waves was initially attributed to a novel action on the type-2 ryanodine receptor (RyR2). However, subsequent work on wild type (WT) myocytes questioned the conclusion that flecainide has a direct action on RyR2. In the present study, the effects of flecainide were compared in intact and permeabilized WT myocytes.Experimental approach: Intracellular Ca2+ was measured using confocal microscopy in intact or saponin permeabilized adult rat ventricular myocytes (ARVM). In some experiments on permeabilized cells, flecainide was studied following partial inhibition of the sarcoplasmic reticulum (SR) counter-current.Key results: Flecainide induced sustained changes Ca2+ sparks and waves in permeabilized ARVM, which were comparable to those reported in intact or permeabilized myocytes from CPVT mice. However, a relatively high level of flecainide (25 μM) was required to induce these effects. Inhibition of the SR counter-current potentiated the effects of flecainide on SR Ca2+ waves. In intact field stimulated ARVM, prolonged exposure to 15 μM flecainide decreased wave frequency but RyR2 dependent effects on Ca2+ sparks were absent; higher drug concentrations blocked field stimulation, consistent with inhibition of Nav1.5.Conclusions and implications: In intact ARVM, the absence of effects on Ca2+ sparks suggests that the intracellular flecainide concentration was insufficient to influence RyR2. Wave inhibition in intact ARVM may reflect secondary effects of Nav1.5 inhibition. Potentiation of flecainide’s action by counter-current inhibition can be explained if transient polarization of the SR membrane during SR Ca2+ release facilitates its action on RyR2.

Details

Language :
English
ISSN :
16639812
Volume :
14
Database :
Directory of Open Access Journals
Journal :
Frontiers in Pharmacology
Publication Type :
Academic Journal
Accession number :
edsdoj.67857d3bbcf941a2ace61eb090bed825
Document Type :
article
Full Text :
https://doi.org/10.3389/fphar.2023.1155601