CFTR mediates apoptotic volume decrease and cell death by controlling glutathione efflux and ROS production in cultured mice proximal tubules

Abstract

We have previously shown that despite the presence of mRNA encoding CFTR, renal proximal cells do not exhibit cAMP-sensitive Cl(-) conductance (Rubera I, Tauc M, Bidet M, Poujeol C, Cuiller B, Watrin A, Touret N, Poujeol P. Am J Physiol Renal Physiol 275: F651-F663, 1998). Nevertheless, in these cells, CFTR plays a crucial role in the control of the volume-sensitive outwardly rectifying (VSOR) activated Cl(-) currents during hypotonic shock. The aim of this study was to determine the role of CFTR in the regulation of apoptosis volume decrease (AVD) and the apoptosis phenomenon. For this purpose, renal cells were immortalized from primary cultures of proximal convoluted tubules from cftr(+/+) and cftr(-/-) mice. Apoptosis was induced by staurosporine (STS; 1 microM). Cell volume, Cl(-) conductance, caspase-3 activity, intracellular level of reactive oxygen species (ROS), and glutathione content (GSH/GSSG) were monitored during AVD. In cftr(+/+) cells, AVD and caspase-3 activation were strongly impaired by conventional Cl(-) channel blockers and by a specific CFTR inhibitor (CFTR(inh)-172; 5 microM). STS induced activation of CFTR conductance within 15 min, which was progressively replaced by VSOR Cl(-) currents after 60 min of exposure. In parallel, STS induced an increase in ROS content in the time course of VSOR Cl(-) current activation. This increase was impaired by CFTR(inh)-172 and was not observed in cftr(-/-) cells. Furthermore, the intracellular GSH/GSSG content decreased during STS exposure in cftr(+/+) cells only. In conclusion, CFTR could play a key role in the cascade of events leading to apoptosis. This role probably involves control of the intracellular ROS balance by some CFTR-dependent modulation of GSH concentration.