Glucocorticoids protect against apoptosis induced by serum deprivation, cyclic adenosine 3',5'-monophosphate and p53 activation in immortalized human granulosa cells: involvement of Bcl-2.
Glucocorticoid hormones are known to enhance gonadotropin/cAMP-induced steroidogenesis in rat and human granulosa cells. As glucocorticoids induce apoptosis in numerous cell types, we investigated the role of glucocorticoids in the control of apoptosis in immortalized human granulosa cells (HO-23) transfected with a temperature-sensitive mutant of p53 (Val(135)). When HO-23 were incubated with forskolin in the presence or absence of dexamethasone (Dex) at 32 or 37 C, progesterone production was higher by 4- and 8-fold in the presence of Dex at 37 or 32 C, respectively (P: < 0. 01). The expression of adrenodoxin (ADX), which is an intrinsic part of the cytochrome P450 side-chain cleavage enzyme system, remained the same in the presence or absence of Dex in forskolin-stimulated cells. Dex reduced apoptosis (to 33% of control) in cultures after activation of p53 by shifting the temperature from 37 to 32 C. Moreover, Dex suppressed apoptosis induced by serum deprivation (to 40% of control) or forskolin stimulation (to 28% and 40% at 37 and at 32 C, respectively). The protective effect of Dex on cAMP-, p53-, and serum deprivation-induced apoptosis was confirmed by both 4',6-diamido-2-phenylindole hydrochloride DNA staining and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling with an ED(50) of 7 nM Dex. Hydrocortisone showed a similar antiapoptotic effect. The protective effect of glucocorticoids against apoptosis was completely abolished by RU486 when cells were coincubated with 10 nM Dex and 10-100 nM RU486. The protection against apoptosis by glucocorticoid involved a sharp elevation in intracellular levels of Bcl-2 (3-7.6 fold; P: < 0.01). In contrast to the effect of Dex in the prevention of apoptosis in HO-23 granulosa cells, Dex dramatically stimulated apoptosis by 3-fold in LTR-6 myeloid leukemia cells expressing the same temperature-sensitive mutant (Val(135) p53) and the same amount of glucocorticoid receptor-alpha. Forskolin did not stimulate apoptosis when incubated with these cells. However, it augmented by 1.2-fold the p53-induced apoptosis in cells shifted from 37 to 32 C. Dex further enhanced apoptosis by 1.9-fold in p53-activated cultures (32 C). Incubation of the cells with Dex dramatically reduced Bcl-2 levels to 15% of control at 37 C (P: < 0.01) or 32 C in the presence or absence of forskolin (P: < 0.01). Our data suggest that glucocorticoids exert a protective effect against induced apoptosis in immortalized granulosa cells and a stimulatory effect on apoptosis in myeloid leukemia cells. Moreover, modulation of Bcl-2 levels plays an important role in mediating the glucocorticoid effect on cell survival. The opposite effect of glucocorticoids on Bcl-2 levels in the two cell lines may be due to the different ontogeneses of the two cell types: epithelial for granulosa cells vs. mesenchymal for myeloid cells studied in the present work.
Sasson
R
R
Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
Tajima
K
K
Amsterdam
A
A
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001790:Blood Physiological Phenomena; D002461:Cell Line, Transformed; D000242:Cyclic AMP / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005938:Glucocorticoids / Q000502:physiology*; D006107:Granulosa Cells / Q000502:physiology*; D006801:Humans; D011374:Progesterone / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D005938:Glucocorticoids; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D011374:Progesterone; D003907:Dexamethasone; D000242:Cyclic AMP