Effect of estrogens on IL-1β promoter activity

It is well documented that steroid hormones modulate cytokine gene expression. In some tissues estrogens are known to suppress cytokine production while in other tissue types, cytokine expression is enhanced by the hormone. This study was conducted to investigate the regulatory mechanisms which underlie the modulation of the interleukin-1 beta (IL-1 beta) gene at the transcription level. To accomplish this, the macrophage cell line RAW264.7, which appeared insensitive to 17 beta-estradiol (E-2) treatment, was stably transfected with the human estrogen receptor (ER) and an IL-1 beta promoter-CAT reporter construct. E-2 markedly enhanced LPS-induced IL-1 beta promoter-driven CAT activity in an E-2 dose dependent manner. This responsiveness was estrogen specific since no synergism was observed between LPS and the sex steroids testosterone or progesterone while the estrogen analogue 17 alpha-estradiol stimulated only at 10 to 100 times the amount required for 17 beta-E-2. Several antiestrogens, H1285, ICI 182 780, and tamoxifen inhibited the estrogen stimulated enhancement of IL-1 beta promoter activity in a dose-dependent manner, indicating that this effect was indeed mediated through the ER in a ligand dependent manner. The estrogenic effect appeared to be indirect and time dependent since the addition of E-2 was required hours prior to LPS stimulation; addition of E-2 and LPS at the same time resulted in a greatly reduced estrogenic effect. The estrogen metabolites 17-epiestriol and 16-keto-17 beta-E-2 displayed an estrogenic response virtually indistinguishable from E-2. 4-Hydroxyestradiol displayed activity only at 100-fold the concentration of E-2 while 2-hydroxyestrone showed no activity at any of the concentrations tested. Overall the results demonstrate that E-2 and some metabolites of E-2 synergize with LPS to markedly enhance IL-1 beta promoter activity through ER mediated processes. (C) 1998 Elsevier Science Ltd. All rights reserved.