Kurebayashi S, Miyashita Y, Hirose T, Kasayama S, Akira S, Kishimoto T
Department of Medicine III, Osaka University Medical School, Suita, Japan.
J Steroid Biochem Mol Biol. 1997 Jan;60(1-2):11-7. doi: 10.1016/s0960-0760(96)00175-6.
Estrogens are the most effective agents available for preventing osteoporosis, and their principal role in bone metabolism is the inhibition of interleukin-6 (IL-6) production in osteoblasts and bone marrow stromal cells. We examined the mechanism of inhibitory effect of estrogens on the 190 bp proximal promoter of the IL-6 gene. Promoter activity induced by transfection of both NF-kappaB p65 subunit and NF-IL6 was decreased by 45% by estradiol (E2)-estrogen receptor (ER) complexes. The inhibitory effect of E2 was also observed on a mutant IL-6 promoter in which the NF-IL6 binding site was disrupted. E2 repressed the wild-type promoter activity induced by NF-kappaB p65 subunit alone, but had no effect on that induced by NF-IL6 alone. These findings suggested that estrogens inhibit IL-6 production by interfering with the function of NF-kappaB rather than that of NF-IL6. The ER mutant, HE19, which does not contain the A/B domain, repressed the induction by NF-kappaB to the same extent as wild-type ER HE0, whereas the effect of C-terminal deletion mutant, HE21, was only marginal. The antiestrogen, 4-hydroxytamoxifen (OHT), had no effect on IL-6 promoter activity, suggesting that E2-induced conformational change of the hormone binding domain plays an important role in protein-protein interaction between ER and NF-kappaB. E2 had no effect on the nuclear translocation of NF-kappaB, and electrophoretic mobility shift assay showed that the presence of E2-ER complexes did not affect the ability of NF-kappaB to bind to specific DNA sequences.
雌激素是预防骨质疏松症最有效的药物，其在骨代谢中的主要作用是抑制成骨细胞和骨髓基质细胞中白细胞介素-6（IL-6）的产生。我们研究了雌激素对IL-6基因190 bp近端启动子的抑制作用机制。雌二醇（E2）-雌激素受体（ER）复合物使NF-κB p65亚基和NF-IL6转染诱导的启动子活性降低了45%。在NF-IL6结合位点被破坏的突变型IL-6启动子上也观察到了E2的抑制作用。E2抑制了单独由NF-κB p65亚基诱导的野生型启动子活性，但对单独由NF-IL6诱导的活性没有影响。这些发现表明，雌激素通过干扰NF-κB的功能而非NF-IL6的功能来抑制IL-6的产生。不含A/B结构域的ER突变体HE19对NF-κB诱导的抑制作用与野生型ER HE0相同，而C末端缺失突变体HE21的作用仅为边缘性。抗雌激素药物4-羟基他莫昔芬（OHT）对IL-6启动子活性没有影响，这表明E2诱导的激素结合结构域构象变化在ER与NF-κB之间的蛋白质-蛋白质相互作用中起重要作用。E2对NF-κB的核转位没有影响，电泳迁移率变动分析表明，E2-ER复合物的存在不影响NF-κB与特定DNA序列结合的能力。
