Trans-Resveratrol Induces Apoptosis through ROS-Triggered Mitochondria-Dependent Pathways in A549 Human Lung Adenocarcinoma Epithelial Cells

Resveratrol has been shown to be a potential chemopreventive and anticancer agent, inducing apoptosis in a variety of cancer cells. The present study was performed to evaluate the effect of resveratrol on A549 human lung adenocarcinoma epithelial cells. 3-(4,5-Dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide evaluation demonstrated that the exposure of cells to increasing concentrations of resveratrol (0-175 mu M) for 24h resulted in a decrease in cell viability (IC50 85.5 mu M). Annexin V/propidium iodide double stain verified apoptosis in A549 cells, while negligible cell cytotoxity (0.5%) was observed in all untreated incubations. Using colorimetric assay kits, induction of caspase-3, but not of caspase-8, activity was detected in response to resveratrol (>130 mu M). Confirmatory evidence of this finding was provided by Western blotting, indicating expression of cleaved caspase-3 levels in a concentration-dependent manner with a minimum resveratrol concentration of 65 mu M required for activation of this protease, while that of caspase-8 remained unaffected. The apoptotic process was associated with reactive oxygen species production in a concentration-dependent manner, evidenced by microscopic examination and fluorescence-activated cell sorting analysis using the 2,7-dichlorofluorescein diacetate assay. In the presence of the mitochondrial electron transport chain inhibitor rotenone, reactive oxygen species production and the concomitant apoptotic cell population were significantly reduced. This finding suggested that the resveratrol-induced apoptosis was mediated via a mitochondrial pathway alignment in human A549 cells. Although effective levels were observed at high concentrations, the outcome may well differ under in vivo conditions. Finally, experiments reaffirmed the chemical instability of trans-resveratrol, suggesting the need for protection of the solutions from extended exposure to light.