Cellular redox state protects acetaldehyde-induced alteration in cardiomyocyte function by modifying Ca2+ release from sarcoplasmic reticulum

Departments of 1 Cell Physiology, 2 Forensic Medicine, and 3 Cardio-Renal Medicine and Hypertension, Nagoya City University Graduate School of Medical Sciences, Nagoya; and 4 Department of Pharmacology, Juntendo University School of Medicine, Tokyo, Japan Submitted 1 May 2007 ; accepted in final form 30 October 2007 Recent studies indicate that low concentrations of acetaldehyde may function as the primary factor in alcoholic cardiomyopathy by disrupting Ca 2+ handling or disturbing cardiac excitation-contraction coupling. By producing reactive oxygen species, acetaldehyde shifts the intracellular redox potential from a reduced state to an oxidized state. We examined whether the redox state modulates acetaldehyde-induced Ca 2+ handling by measuring Ca 2+ transient using a confocal imaging system and single ryanodine receptor type 2 (RyR2) channel activity using the planar lipid bilayer method. Ca 2+ transient was recorded in isolated rat ventricular myocytes with incorporated fluo 3. Intracellular reduced glutathione level was estimated using the monochlorobimane fluorometric method. Acetaldehyde at 1 and 10 µM increased Ca 2+ transient amplitude and its relative area in intact myocytes, but acetaldehyde at 100 µM decreased Ca 2+ transient area significantly. Acetaldehyde showed a minor effect on Ca 2+ transient in myocytes in which intracellular reduced glutathione content had been decreased against challenge of diethylmaleate to a level comparable to that induced by exposure to 50 µM acetaldehyde. Channel activity of the RyR2 with slightly reduced cytoplasmic redox potential from near resting state (–213 mV) or without redox fixation was augmented by all concentrations of acetaldehyde (1–100 µM) used here. However, acetaldehyde failed to activate the RyR2 channel, when the cytoplasmic redox potential was kept with a reduced (–230 mV) or markedly oxidized (–180 mV) state. This result was similar to effects of acetaldehyde on Ca 2+ transient in diethylmaleate-treated myocytes, probably being in oxidized redox potential. The present results suggest that acetaldehyde acts as an RyR2 activator to disturb cardiac muscle function, and redox potential protects the heart from acetaldehyde-induced alterations in myocytes. Ca 2+ transient; single ryanodine receptor type 2 channel activity; intracellular glutathione level; intracellular redox state Address for reprint requests and other correspondence: T. Oba, Dept. of Cell Physiology, Nagoya City Univ. Graduate Sch