Abstract
Apoptosis is essential for normal tissue development and homeostasis. The apoptotic volume decrease (AVD), which is induced by KCl efflux due to activation of K+ and Cl− channels, is an early-phase, prerequisite component of apoptosis. We previously demonstrated that volume-sensitive Cl− currents are activated after application either of a mitochondrion-mediated inducer, staurosporine (STS), or of a death receptor-mediated inducer, TNF-α or Fas ligand, in HeLa cells without showing cell swelling. Here, we investigated a role of reactive oxygen species (ROS) in STS-induced activation of Cl− channel. STS was found to increase the intracellular ROS level by using 2', 7'-dichlorofluorescein diacetate. The rise in ROS was inhibited by a ROS scavenger, N-acetyl-cysteine (NAC), or an NAD(P)H oxidase inhibitor, diphenylene-iodonium chloride (DPI). In the presence of NAC or DPI, STS failed to activate Cl− currents. In addition, extracellular application of hydrogen peroxide directly increased Cl− currents, which exhibited properties identical to those of volume-sensitive Cl− currents. NAC and DPI could abolish the AVD induced by STS. STS-induced caspase-3 activation and reduction of cell viability were also suppressed by NAC and DPI. These results suggest that ROS is a key mediator for activation of volume-sensitive Cl− channel during a mitochondrion-mediated apoptosis. [Jpn J Physiol 54 Suppl:S83 (2004)]
