In vivo characterization of estrogen receptor modulators with reduced genomic versus nongenomic activity in vitro

Estrogen receptor (ER) ligands that are able to prevent postmenopausal bone loss, but have reduced activity in the uterus and the mammary gland might be of great value for hormone therapy. It is well established that the classical ER can activate genomic as well as nongenomic signal transduction pathways. In this study, we analyse the in vivo behaviour of ER ligands that stimulate nongenomic ER effects to the same extent as estradiol, but show clearly reduced activation of genomic ER effects in vitro. Using different readout parameters such as morphological changes, cellular proliferation, and target gene induction, we are able to demonstrate that ER ligands with reduced genomic activity in vitro show a better dissociation of bone versus uterine and mammary gland effects than estradiol that stimulates genomic and nongenomic effects to the same extent. We conclude that pathway-selective ER ligands may represent an interesting option for hormone therapy.     

Mechanisms of genomic and non-genomic actions of carotenoids

Carotenoids are highly bioactive dietary compounds that have the potential to have significant effects on human health. It is becoming increasingly clear that the various biological effects that carotenoids exert could be driven via a number of different mechanisms. These include direct pro- and antioxidant effects, redox sensitive cell signalling, vitamin A signalling pathways and other as yet unidentified mechanisms. This article provides an overview of the known effects of carotenoids and discusses the use of model systems and functional genomic approaches further to elucidate their modes of action.     

膜雌激素受体介导一氧化氮合酶活性增高的快速非基因效应

实验利用新生小牛胸主动脉内皮细胞(BAECs)作为模型,观察17β-雌二醇(E2)、E2BSA对BAECs中内皮型一氧化氯合酶(eNOS)的快速激活作用,并探讨了丝裂素活化蛋白激酶(MAPK)信号通路在其中的作用。结果显示,不同浓度的E2(0．001—1lμmol/L)作用于BAECs l5 min均能快速激活eNOS;0．01μmol/L浓度的E2作用于BAECs,5min即能激活eNOS,15min达到最大效应,随后eNOS快速失活;E2BSA(17．5ng／m1)作用于BAECs,15min同样可激活eNOS。E2、E2BSA激活eNOS的作用均能被雌激素受体(ER)拮抗剂tamoxifen(0．1μmol/L)或MAPK激酶特异抑制剂PD98059(50μmol/L)所阻断。放线菌素D(25μg/ml)不能阻断E2、E2BSA对eNOS的激活作用。E2(0．01μmol/L)、E2BSA(17．5ng/ml)作用于BAECs l5 min后可明显促进p42／p44磷酸化MAPK蛋白表达,而对p42／p44 MAPK总蛋白表达无影响。Tamoxifen可部分阻断E2;E2BSA激活p42／p44磷酸化MAPK的作用。这些结果提示,BAECs膜上可能存在膜雌激素受体(membrane estrogen receptor,mER),E2、E2BSA作用于mER后可通过MAPK信号途径快速激活eNOS。     

Steroidal androgens and nonsteroidal, tissue-selective androgen receptor modulator, S-22, regulate androgen receptor function through distinct genomic and nongenomic signaling pathways

Androgen receptor (AR) ligands are important for the development and function of several tissues and organs. However, the poor oral bioavailability, pharmacokinetic properties, and receptor cross-reactivity of testosterone, coupled with side effects, place limits on its clinical use. Selective AR modulators (SARMs) elicit anabolic effects in muscle and bone, sparing reproductive organs like the prostate. However, molecular mechanisms underlying the tissue selectivity remain ambiguous. We performed a variety of in vitro studies to compare and define the molecular mechanisms of an aryl propionamide SARM, S-22, as compared with dihydrotestosterone (DHT). Studies indicated that S-22 increased levator ani muscle weight but decreased the size of prostate in rats. Analysis of the upstream intracellular signaling events indicated that S-22 and DHT mediated their actions through distinct pathways. Modulation of these pathways altered the recruitment of AR and its cofactors to the PSA enhancer in a ligand-dependent fashion. In addition, S-22 induced Xenopus laevis oocyte maturation and rapid phosphorylation of several kinases, through pathways distinct from steroids. These studies reveal novel differences in the molecular mechanisms by which S-22, a nonsteroidal SARM, and DHT mediate their pharmacological effects.     

Coumestrol antagonizes neuroendocrine actions of estrogen via the estrogen receptor alpha

The phytoestrogen coumestrol has estrogenic actions on peripheral reproductive tissues. Yet in the brain this compound has both estrogenic and anti-estrogenic effects. We used estrogen receptor alpha knockout mice (ERalphaKO) to determine whether coumestrol has estrogenic actions in mice and also if these effects are mediated by the classic ERalpha. Female wild-type (WT) and ERalphaKO mice were ovariectomized and treated with estradiol (E2), dietary coumestrol, both, or neither compound. Ten days later the animals were sacrificed, blood was collected, and brain tissues were perfused. Fixed brains were sectioned and immunocytochemistry was employed to quantify progesterone receptors (PR) in the medial preoptic (POA) and ventromedial nucleus of the hypothalamus (VMN). Plasma was assayed for luteinizing hormone (LH). Estrogen treatment induced PR immunoreactivity in both regions in brains of WT females. In ERalphaKO mice, lower levels of PR were induced. The stimulatory effects of E2 on PR were attenuated in the POA by cotreatment with coumestrol, and the same trend was noted in the VMN. WT ovariectomized females treated with E2 had low levels of LH, while LH was high in untreated females and even higher in ovariectomized females treated with coumestrol. ERalphaKO females in all treatment groups had high levels of LH. Taken together, the results show that coumestrol has anti-estrogenic actions in the brain and pituitary and that ERalpha mediates these effects.