Modulation of action potential duration on myocyte hypertrophic pathways

Area of Science:

• Cardiology
• Molecular Biology
• Electrophysiology

Background:

• Cardiac hypertrophy and failure are linked to prolonged action potential duration (APD).
• Reduced hyperpolarizing current from calcium-independent transient outward K+ channels (I(to)) contributes to APD prolongation.
• Angiotensin II (AngII) is a key mediator of cardiac hypertrophy.

Purpose of the Study:

• To investigate the impact of manipulating I(to) and sodium/calcium exchanger (NCX) currents on cardiomyocyte hypertrophy induced by AngII.
• To determine if distinct intracellular calcium patterns influence MAPkinase activation and cellular hypertrophy.
• To explore the role of action potential duration in AngII-mediated cardiac hypertrophy.

Main Methods:

• Cultured neonatal rat ventricular myocytes (NRVMs) were infected with adenoviruses for Kv4.3, Kv4.3 antisense, or NCX.
• Hypertrophy was induced by incubating NRVMs with AngII.
• Measurements included I(to) density, APD, Ca(2+) influx, protein expression (ANF, beta-MHC), and MAPkinase/calcineurin activation.

Main Results:

• Overexpression of Kv4.3 increased I(to), shortened APD, reduced Ca(2+) influx, and inhibited AngII-induced hypertrophy markers.
• Kv4.3 overexpression blocked ERK MAP kinases and calcineurin expression.
• These effects were reversed by Kv4.3 antisense and NCX gene transfer.

Conclusions:

• Enhanced I(to) function via Kv4.3 overexpression abrogates AngII-mediated hypertrophy in NRVMs.
• Modulating action potential duration is a significant factor in cardiac hypertrophy development.
• Targeting I(to) channels offers a potential therapeutic strategy for cardiac hypertrophy.