Oxidized glucocorticoids counteract glucocorticoid-induced apoptosis in murine thymocytes in vitro

11 beta -hydroxyglucocorticoids (HGCs) are known to induce apoptosis in imm ature T cells. Here we show that 11-oxoglucocorticoids (OGCs), which are ox idized metabolites of HGCs, counteract the apoptosis-inducing effects of HG C in murine thymocytes in vitro. Corticosterone at concentrations ranging f rom 0.1-100 muM induced apoptosis in thymocytes obtained from C57BL/6J mice aged 4 weeks, as demonstrated by cell staining with anti-phosphatidylserin e antibody, a decrease in mitochondrial membrane potential, and DNA fragmen tation. Go-culture of the cells with 10-100 muM of OGCs, dehydrocorticoster one, cortisone, and prednisone significantly inhibited thymocyte apoptosis induced by 1 muM corticosterone, (p<0.006). Among the other 6 physiological metabolites of the HGCs we tested, 20<alpha>-dehydrocortisol also showed c onsiderable inhibitory effect on corticosterone-induced thymocyte apoptosis . Corticosterone-treatment of thymocytes in vitro decreased the number of C D4 and CD8 double positive cells, while co-culturing the cells with dehydro corticosterone significantly attenuated this corticosterone effect (p<0.000 1). Numbers of double-negative cells and single-positive cells were not sig nificantly affected by corticosterone, dehydrocorticosterone, or both toget her. These results raised the possibility that OGCs and probably other HGC metabolites can regulate apoptotic cell death of immature double-positive t hymocytes induced by HGC. (C) 2001 Elsevier Science Inc. All rights reserve d.