OXYGEN-TENSION INFLUENCES DNA FRAGMENTATION AND CELL-DEATH IN GLUCOCORTICOID-TREATED THYMOCYTES

Internucleosomal DNA fragmentation and cell death induced by dexametha sone in rat thymocytes were inhibited when cells were cultured in 95% N-2/5% CO2 atmosphere, in which oxygen was rapidly reduced to under 0. 5%. DNA fragmentation was delayed by a less severe hypoxia in 5% oxyge n whilst in cell cultured in high oxygen atmosphere (95% O-2) cell dea th was increased. On the other hand, prolonged oxygen deprivation caus ed an increase of spontaneous apoptotic cell death. Hypoxia also inhib ited DNA fragmentation induced by calcium ionophore A23187, but not by topoisomerase inhibitor camptothecin. These data support the hypothes is of the involvement of oxygen reactive species in calcium-mediated a poptosis and suggest a complex role of oxygen in the modulation of pro grammed cell death. (C) 1995 Academic Press, Inc.