17β-Estradiol utilizes the estrogen receptor to regulate CD16 expression in monocytes

Estrogen can significantly influence CD16 expression and alter monocytic cytokine release upon CD16 receptor activation. However, the function of the estrogen receptor (ER)alpha and beta in this response is unclear. To test whether estrogen binds ER alpha and/or ER beta to affect CD16 expression, monocytic cells were treated with and without physiological levels of 17 beta-estradiol and various doses of the ER alpha and ER beta antagonist fulvestrant followed by measurement of CD16 transcript levels. To determine how estrogen induced changes in TNF-alpha and IL-1 beta release due to CD16 activation we quantitated the amount of cytokines after treatment with estrogen, fulvestrant and antibodies that specifically bind and activate the CD16receptor. Interactionof ER alpha and the CD16 promoter was then determinedbychromatin immunoprecipitation. Furthermore, specific promoter elements utilized by estrogen to control CD 16 expression were mutated and expression from a luciferase reporter quantitated after transfection. Using the luciferase reporter construct containing a wild type CD 16 promoter, the role of ERa and ER beta in the estrogen response was tested by treating transfected monocytes with an ERa specific agonist or an ER beta specific agonist and measuring expression. Our results show that CD16 transcript levels significantly decreased in monocytic cells due to estrogen and that the observed decrease in message was blocked by the antagonist fulvestrant. Estrogen reduced CD16 expression and decreased TNF-alpha and IL-1 beta release upon CD 16 activation but the administration of fulvestrant blocked this decrease. ER alpha was found to interact with a region 5' of the CD16 gene in the presence of estrogen, and site-directed mutational analysis of this region indicated the necessity for an estrogen response element in modulating estrogen effects on CD16 expression. Moreover, both an ERa and an ER beta agonist reduced expression of the CD16 reporter construct suggesting both receptors can play a role in CD16 regulation. In conclusion, CD16 expression can be altered by the activity of ER alpha or ER beta and our results also show that ERa can associate with a region within the CD16 promoter that is important in production of transcript. (c) 2007 Elsevier Ireland Ltd. All riahts reserved.