Apoptosis in Respiratory Epithelial Cells: Triggering by Paraquat and Modulation by L-ascorbic acid

ABSTRACT

PURPOSE: Apoptosis is a programmed cell death that is a selective process of physiological cell deletion. This study was undertaken to evaluate a paraquat-triggered apoptosis and the ability of ascorbic acid to modulate the process in the A549 cell line, a well-characterized cellular model of human lung alveolar cells. METHODS: A 549 cells were incubated with different concentrations of paraquat for up to 24 hour, followed by 24, 48, and 72 hours of recovery in paraquat-free medium. To test the abilities of antioxidants as modulators of paraquatinduced apoptosis, we pre-treated the cells for 4 hours with 250 micrometer L-ascorbic acid (vitamin C) before exposure to paraquat, and we incubated cells with paraquat in the presence of 250 micrometer L-ascorbic acid. Apoptosis was assayed by staining the cells with FITC-annexin V, and the cells were analyzed by using flow cytometry. RESULTS: Paraquat was inducer of apoptosis. A549 cells incubated with paraquat for up to 24 hour showed no apoptotic features, but the following incubation in a paraquat-free medium resulted in a time-dependent appearance of apoptosis. The ascorbic acid proved effective in reducing paraquat-induced apoptosis. CONCLUSION: We propose an experimental model for investigating the steps and mechanism of paraquat-induced apoptosis in alveolar cells