Lacey Michael, Bohday Jemma, Fonseka Shamara M R, Ullah Amer I, Whitehead Saffron A
Department of Basic Medical Sciences: Physiology, St. George's Hospital Medical School, Cranmer Terrace, London SW17 OAW, UK.
J Steroid Biochem Mol Biol. 2005 Aug;96(3-4):279-86. doi: 10.1016/j.jsbmb.2005.03.006.
There is evidence that certain phytoestrogens can inhibit key steroidogenic enzymes although most studies have been carried out on microsomal or purified enzyme preparations, some using cell lines. This study was designed to test the hypothesis that low doses of phytoestrogens, at concentrations that would be attained through the diet, could inhibit 3beta-hydroxysteroid dehydrogenase (HSD) and/or aromatase in primary cultures of human granulosa-luteal (GL) cells and that this effect was due to a decrease in the expression of these proteins. Based on published evidence, eight compounds were selected for investigation and these included the flavones apigenin and quercetin, the isoflavones genistein, biochanin A and daidzein, the lignans, enterodiol and enterolactone, and the mycotoxin zearalenone. Human GL cells were cultured for 48 h in the presence of these phytoestrogens at concentrations ranging from 0.01 to 100 microM and after addition of fresh media the conversion of pregnenolone to progesterone or androstenedione to oestradiol over a 4h period was measured. Biochanin A was the only phytoestrogen that displayed any dose-dependent inhibition of 3beta-HSD, others showing inhibition at doses >/=10 microM. Apigenin and quercetin only inhibited aromatase/17beta-HSD at high doses as did genistein, biochanin A and daidzein. The lignans had weak inhibitory effects on aromatase/17beta-HSD, whilst zearalenone showed potent inhibition at 0.1 microM. Phytoestrogens did not exert any significant effects on protein expression of 3beta-HSD or aromatase as determined by Western blots. It is concluded that steroidogenic enzymes are inhibited by phytoestrogens in primary cultures of human GL cells but these cells are less sensitive to the effects of phytoestrogens than cell-free systems. This may be due to poor lipid solubility or cellular metabolism. We have also shown for the first time that phytoestrogens do not act by inhibiting the cellular concentration of 3beta-HSD and aromatase even though exposure time would have allowed for changes in gene expression.
有证据表明某些植物雌激素可以抑制关键的类固醇生成酶，尽管大多数研究是在微粒体或纯化的酶制剂上进行的，有些研究使用了细胞系。本研究旨在检验以下假设：低剂量的植物雌激素，在通过饮食可达到的浓度下，能够抑制人颗粒黄体（GL）细胞原代培养物中的3β-羟基类固醇脱氢酶（HSD）和/或芳香化酶，且这种作用是由于这些蛋白质的表达减少所致。基于已发表的证据，选择了8种化合物进行研究，包括黄酮类的芹菜素和槲皮素、异黄酮类的染料木黄酮、鹰嘴豆芽素A和大豆苷元、木脂素类的肠二醇和肠内酯，以及霉菌毒素玉米赤霉烯酮。人GL细胞在这些植物雌激素存在的情况下培养48小时，浓度范围为0.01至100微摩尔，添加新鲜培养基后，测量4小时内孕烯醇酮向孕酮或雄烯二酮向雌二醇的转化。鹰嘴豆芽素A是唯一显示出对3β-HSD有任何剂量依赖性抑制作用的植物雌激素，其他植物雌激素在剂量≥10微摩尔时显示出抑制作用。芹菜素和槲皮素仅在高剂量时抑制芳香化酶/17β-HSD，染料木黄酮、鹰嘴豆芽素A和大豆苷元也是如此。木脂素类对芳香化酶/17β-HSD有较弱的抑制作用，而玉米赤霉烯酮在0.1微摩尔时显示出强效抑制作用。通过蛋白质免疫印迹法测定，植物雌激素对3β-HSD或芳香化酶的蛋白质表达没有产生任何显著影响。得出的结论是，在人GL细胞原代培养物中，类固醇生成酶受到植物雌激素的抑制，但这些细胞对植物雌激素的作用比无细胞系统更不敏感。这可能是由于脂溶性差或细胞代谢所致。我们还首次表明，即使暴露时间足以使基因表达发生变化，植物雌激素也不是通过抑制3β-HSD和芳香化酶的细胞浓度来发挥作用的。
