Abstract
We have investigated the effects of sex steroids, estradiol (E2), and testosterone (T) on the synthesis of tumor necrosis factor alpha (TNF‐α) and interleukin‐10 (IL‐10) in phorbol‐myristate‐acetate (PMA)‐differentiated human monoblastic U937 cells. The ability of both hormones to modulate the viability and programmed cell death of macrophage‐like PMA‐differentiated U937 cells was also inspected. E2 increased TNF‐α synthesis, whereas T had no effect on the production of this cytokine. The combination of E2 and its antagonist tamoxifen or ICI‐182,789 completely abolished the induction of TNF‐α, while combination of T and its antagonist Casodex (CSDX) did not significantly affect TNF‐α production by U937 cells. Exposure of cells to E2 resulted in a dose‐dependent decrease of IL‐10 synthesis, while again T did not show any detectable effect. In addition, E2 induced a significant increase of apoptosis in macrophage‐like U937 cells and this increase was inhibited by the simultaneous addition of either tamoxifen or ICI‐182. In contrast, T alone or in combination with CSDX did not modify apoptotic rates of U937 cells. This evidence, taken together, suggests that estrogens, but not androgens, exert a pro‐inflammatory action through the modulation of TNF‐α and IL‐10, and regulate the immune effector cells by the induction of programmed cell death. J. Cell. Biochem. 90: 187–196, 2003. © 2003 Wiley‐Liss, Inc.