Mitochondrial-derived ROS in edelfosine-induced apoptosis in yeasts and tumor cells

Abstract

To investigate whether a similar process mediates cytotoxicity of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3, edelfosine) in both yeasts and human tumor cells. A modified version of a previously described assay for the intracellular conversion of nitro blue tetrazolium to formazan by superoxide anion was used to measure the generation of reactive oxygen species (ROS). Apoptotic yeast cells were detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. DNA fragmentation and the generation of ROS were measured by cytofluorimetric analysis in Jurkat cells. Edelfosine induced apoptosis in Saccharomyces cerevisiae, as assessed by TUNEL assay. Meanwhile, edelfosine induced a time- and concentration-dependent generation of ROS in yeasts. Rotenone, an inhibitor of the mitochondrial electron transport chain, prevented ROS generation and apoptosis in response to edelfosine in S cerevisiae. alpha-Tocopherol abrogated the edelfosine-induced generation of intracellular ROS and apoptosis. Edelfosine also induced an increase of ROS in human leukemic cells that preceded apoptosis. The overexpression of Bcl-2 by gene transfer abrogated both ROS generation and apoptosis induced by edelfosine in leukemic cells. Changes in the relative mitochondrial membrane potential were detected in both yeasts and Jurkat cells. These results indicate that edelfosine induces apoptosis in yeasts in addition to human tumor cells, and this apoptotic process involves mitochondria, likely through mitochondrial-derived ROS. These data also suggest that yeasts can be used as a suitable cell model in elucidating the antitumor mechanism of action of edelfosine.