Repression of interleukin-6 gene expression by 17 beta-estradiol: inhibition of the DNA-binding activity of the transcription factors NF-IL6 and NF-kappa B by the estrogen receptor.

The cytokine interleukin-6 (IL-6), a key mediator of immune and acute phase responses of the liver, has also been implicated in uterine functions. Estrogens are potent repressors of IL-6 production by uterine stromal cells. In the endometrial adenocarcinoma cell line Ishikawa, phorbol ester-induced activation of the IL-6 promoter was inhibited to basal levels by 17 beta-estradiol (E2) in a wild-type receptor-dependent fashion. Although tamoxifen has been shown to have estrogenic effects on the endometrium, it did not inhibit induction of the IL-6 promoter. We previously showed that inhibition of IL-6 gene expression by E2 does not involve high-affinity binding of the estrogen receptor (ER) to IL-6 DNA. We now report that the ER can directly interact with the transcription factors NF-IL6 and NF-kappa B and can inhibit their ability to bind DNA which might be the molecular basis for repression of IL-6 gene expression by estrogens.