Pro-oxidant effect of transforming growth factor- beta1 mediates contractile dysfunction in rat ventricular myocytes

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional cytokine that contributes to pathogenic cardiac remodelling via mechanisms that involve oxidative stress. However, the direct impact of TGF-beta1 on contractile function of ventricular myocytes is incompletely understood.

Reactive oxygen species (ROS) production and intracellular glutathione (GSH) were measured by fluorescence microscopy in isolated rat ventricular myocytes pretreated with TGF-beta1 (0.1-10 ng/mL). In separate studies, video edge detection measurements were made to evaluate myocyte contractile function, and confocal microscopy was used to monitor evoked Ca2+ transients. TGF-beta1 (1 ng/mL) for 3-4 h significantly increased ROS production by 90% (P < 0.05) and decreased GSH by 34% (P < 0.05) compared with control. These changes paralleled a significant decrease in the rate of myocyte shortening and relaxation by 33% and 43%, respectively (0.5 Hz; P < 0.05), whereas fractional shortening was not altered. Ca2+ transients in TGF-beta1-treated myocytes were characterized by a delayed peak and slowing in the rate of decay but no change in peak Ca2+ amplitude. Increased ROS production and GSH depletion by TGF-beta1 were prevented by an NAD(P)H oxidase inhibitor or a free radical scavenger, both of which significantly mitigated TGF-beta1-induced myocyte contractile dysfunction. Moreover, pretreating myocytes with exogenous GSH or the GSH precursor N-acetylcysteine also prevented myocyte contractile impairment and abnormal Ca2+ transients elicited by TGF-beta1.

Our data suggest that TGF-beta1-induced cardiomyocyte contractile dysfunction is associated with enhanced ROS production and oxidative alterations in Ca2+ handling proteins regulated by endogenous GSH.