Requirement of intracellular free thiols for hydrogen peroxide-induced hypertrophy in cardiomyocytes

Reactive oxygen species (ROS) are by‐products of aerobic metabolism and are implicated in the pathogenesis of several diseases. H2O2 produces oxidative stress and acts as a second messenger in several cell types. We tested whether the effect of H2O2 on cellular events could be altered by changes in the intracellular redox status in a cardiomyocyte cell line. Using flow cytometric measurements, we found that adding H2O2 induced hypertrophy in control cells in a time‐dependent manner. Pre‐incubation of the cells with buthionine sulfoximine (BSO), an inhibitor of de novo GSH synthesis, induced increase in the number of cells of small sizes by the addition of H2O2 as compared to non‐BSO pre‐incubated control cells, and exacerbated the decrease in viability. Total thiol and GSH levels in H9c2 cells pre‐incubated with BSO were about 75 and 30% of control, respectively, and GSH levels fell to below the limitation of detection after the addition of H2O2, although total thiol levels were not markedly decreased. In the cells pre‐incubated with BSO, hypertrophy was not observed by the addition of H2O2 at any level of concentration. N‐acetyl‐l‐cysteine and cysteine not only prevented increase in the number of cells of small sizes caused by H2O2 but also induced hypertrophy in cells pre‐incubated with BSO. These results suggest that the intracellular free thiol levels determine whether cell death or hypertrophy occurs in cardiomyocytes in the presence of H2O2. On the other hand, the hypertrophied cells did not become larger by adding H2O2, but had high levels of cellular GSH, suggesting the possibility that the hypertrophied cells have tolerance to oxidative stress. J. Cell. Biochem. 89: 944–955, 2003. © 2003 Wiley‐Liss, Inc.