Iron chelators induce apoptosis in thymocytes.
(A) Agarose gel electrophoresis of DNA extracted from fresh murine thymocytes (lane 2) or after 24 hours of incubation with media alone (lane 3) or either CP20, DFO (300 μM IBE, lanes 4 and 6, respectively), HU (1 mM, lane 5), or dexamethasone (DEX) (10−7 M, lane 7). (B) Flow cytometric profiles of freshly isolated thymocytes or thymocytes incubated for 24 hours with either PBS, CP20 (300 μM IBE), or dexamethsone (10−7 M). The cells were washed, fixed in 70% cold ethanol, and stained with propidium iodide for apoptosis measurement by flow cytometry. The data shown are typical flow cytometric profiles obtained following addition of the respective drugs, and the percent of nuclei with less than 2N DNA is given. (C) Thymocytes were incubated for 0, 4, 8, or 24 hours with PBS (control), dexamethasone (10−7 M), or the iron chelators CP20 or DFO (300 μM IBE). The percent apoptosis was measured as indicated in panel B. (D) Thymocytes were incubated for 24 hours with chelator concentrations of 0, 11, 33, 100, 300, and 900 μM IBE and prepared for flow cytometric analysis as indicated above. The data shown are the mean ± SD of 4 independent experiments.
