17-β-estradiol alters Jurkat lymphocyte cell cycling and induces apoptosis through suppression of Bcl-2 and cyclin A

In this investigation, the effects and potential mechanisms of female sex steroid action on proliferation, cell cycling, and apoptosis in Jurkat CD4 + T lymphocytes were examined. 17-beta -Estradiol (estrogen) inhibited Jurkat T cell proliferation, stimulated accumulation of cells in S and G(2)/M Phases of the cell cycle, and induced apoptosis over 72 h in a dose-dependent manner. 4-Pregnene-3,20-dione (progesterone) did not induce redistribution of the cells in the cell cycle but did induce cytostasis and slightly increased apoptosis. Simultaneous staining with anti-BrDU and propidium iodide indicated that estrogen-treated Jurkat T cells proceeded through S phase prior to apoptosis. Progesterone halted cell cycle progression; cells did not progress through S phase or incorporate BrDU. Both hormones decreased the percentage of cells in S or G(2)/M expressing cyclin A protein, but did not affect cyclin D protein expression. Cyclin A mRNA was markedly decreased by estrogen. Bcl-2 protein and mRNA were also reduced in estrogen but not progesterone-treated Jurkat T lymphocytes. This data shows that high concentrations of estrogen or progesterone significantly suppress lymphoproliferation in association with suppression of cyclin A. Additionally, bcl-2 protein levels were suppressed in association with estrogen-induced apoptosis. These findings demonstrate direct, hormone-specific effects on lymphocytes that may provide insight into their role in immunomodulation or the development of autoimmunity. (C) 2001 Elsevier Science B.V. All rights reserved.