Inhibition of late sodium current attenuates ionic arrhythmia mechanism in ventricular myocytes expressing LaminA-N195K mutation.

BACKGROUND: Lamin A and C are nuclear filament proteins encoded by the LMNA gene. Mutations in the LMNA gene cause many congenital diseases known as laminopathies, including Emery-Dreifuss muscular dystrophy, Hutchinson-Gilford progeria syndrome, and familial dilated cardiomyopathy (DCM) with conduction disease. A missense mutation (N195K) in the A-type lamins results in familial DCM and sudden arrhythmic death.

OBJECTIVE: The purpose of this study was to investigate the ion current mechanism of arrhythmia and DCM caused by the LaminA-N195K variant.

METHODS: A homozygous mouse line expressing the Lmna-N195K mutation (LmnaN195K/N195K ) that exhibited arrhythmia, DCM, and sudden death was used. Using whole cell patch-clamp technique, we measured action potential duration (APD), Na+ currents (INa ) in ventricular myocytes isolated from LmnaN195K/N195K , and wild-type mice.

RESULTS: Both peak and late INa were significantly (P <.05) increased in LmnaN195K/N195K ventricular myocytes. Similarly, LmnaN195K/N195K ventricular myocytes exhibited significant (P <.005) prolongation of APD (time to 50% [APD50 ] and 90% [APD90 ] repolarization) and triggered activity. Acute application of ranolazine inhibited late INa , shortened APD, and abolished triggered activity in LmnaN195K/N195K ventricular myocytes.

CONCLUSION: Inhibition of late INa may be an effective therapy in preventing arrhythmia in patients with LmnaN195K mutation-related DCM.