AAV9-Mediated Overexpression of TRPM4 Increases the Incidence of Stress-Induced Ventricular Arrhythmias in Mice

Abstract

Ca 2+ activated non-selective (CAN) cation channels have been described in cardiomyocytes since the advent of the patch clamp technique. It has been hypothesized that this type of ion channel contributes to the triggering of cardiac arrhythmias. TRPM4 is to date the only molecular candidate for a CAN cation channel in cardiomyocytes. Its significance for arrhythmogenesis in living animals remains, however, unclear. In this study, we have tested whether increased expression of wild-type (WT) TRPM4 augments the risk of arrhythmias in living mice. Overexpression of WT TRPM4 was achieved via tail vein injection of adeno-associated viral vector serotype 9 (AAV9) particles, which have been described to be relatively cardiac specific in mice. Subsequently, we performed ECG-measurements in freely moving mice to determine their in vivo cardiac phenotype. Though cardiac muscle was transduced with TRPM4 viral particles, the majority of viral particles accumulated in the liver. We did not observe any difference in arrhythmic incidents during baseline conditions. Instead, WT mice that overexpress TRPM4 were more vulnerable to develop premature ventricular ectopic beats during exercise-induced β-adrenergic stress. Conduction abnormalities were rare and not more frequent in transduced mice compare to WT mice. Taken together, we provide evidence that overexpression of TRPM4 increases the susceptibility of living mice to stress-induced arrhythmias.

Electrophysiological Effects of the Transient Receptor Potential Melastatin 4 Channel Inhibitor (4-Chloro-2-(2-chlorophenoxy)acetamido) Benzoic Acid (CBA) in Canine Left Ventricular Cardiomyocytes

“…Similar results were obtained in mouse as 9-phenanthrol abolished hypoxia and re-oxygenation induced early afterdepolarization in a dose-dependent manner [21]. Cardiac specific overexpression of TRPM4 in mice increased the occurrence of ectopic ventricular beats during stress conditions (evoked by heavy exercise and β-adrenergic stimulation), but not in baseline [55], which highlights the possibility that TRPM4 can indeed generate DADs in calcium overloaded cells in vivo. Similarly, TRPM4 could be involved in aldosterone-induced atrial arrhythmias in mice [56].…”

Inherited Cardiac Arrhythmia Syndromes: Focus on Molecular Mechanisms Underlying TRPM4 Channelopathies

“…TRPM4 gain-of-function may inactivate the sodium channels via the depolarization of the resting membrane potential, while a loss-of-function could induce a hyperpolarization of the membrane potential, leading to a reduced cellular excitability and conduction [ 42 , 69 ]. These hypotheses were partially supported by some recent in vivo studies [ 18 , 40 , 72 ]. Regarding TRPM4 loss-of-function, the invalidation of the TRPM4 gene in mice induced a multilevel conduction block without any modification of the ventricular AP characteristics [ 40 ].…”

“…As regards the TRPM4 gain-of-function, Pironet and colleagues have overexpressed wild-type TRPM4 channels in living mice via tail vein injection of AAV9 particles. The authors did not observe any increase in conduction abnormalities in mice overexpressing TRPM4 [ 72 ].…”

Whole-Exome Sequencing Identifies a Novel TRPM4 Mutation in a Chinese Family with Atrioventricular Block

“…The current study further supported the idea of the role of TRPM4 in AVB. A developed ventricular fibrillation and idioventricular rhythm had been recorded in overexpression of TRPM4 [21]. Thus, our study regards TRPM4 mutation as the result of AVB among 10 identified mutations.…”