Assuntos
Antimetabólitos Antineoplásicos/farmacologia , Neoplasias do Colo/tratamento farmacológico , Neoplasias do Colo/genética , Fluoruracila/farmacologia , Perfilação da Expressão Gênica , Análise de Sequência com Séries de Oligonucleotídeos , Neoplasias do Colo/patologia , Resistencia a Medicamentos Antineoplásicos , Humanos , Metástase Neoplásica , RNA Mensageiro/análise , Células Tumorais CultivadasRESUMO
Isoflavones are the most potent estrogenic compounds in red clover extracts. Standardized extracts have been discussed as an alternative for hormone replacement therapy. Variation due to extraction procedure and natural seasonal variation and variations originating from agricultural conditions have prevented the large scale use of such phytochemicals. An improved extraction procedure and careful analysis of the raw material yielded in a highly standardized preparation (Menoflavon) with an average isoflavone content of approximately 9% (dry weight) determined by HPLC. The estrogenic activity has been further evaluated by a yeast two plasmid system using estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta). An estrogenic activity corresponding to a transactivational capacity of ca. 18 microg 17 beta-estradiol per g red clover extract for ER alpha and ca. 78 microg 17 beta-estradiol per g red clover for ER beta was obtained. The difference is explained by the higher affinity of ER beta to isoflavones than that observed for ER alpha. Calculation of potency from isoflavone content measured by HPLC yielded a comparable potency to that experimentally determined by the bioassay. The high content of isoflavones as well as the higher transactivational potency for ER beta than ER alpha make these extracts interesting candidates for HRT.
Assuntos
Estrogênios/metabolismo , Terapia de Reposição Hormonal/métodos , Isoflavonas/farmacologia , Extratos Vegetais/farmacologia , Bioensaio , Cromatografia Líquida de Alta Pressão , Relação Dose-Resposta a Droga , Receptor alfa de Estrogênio , Receptor beta de Estrogênio , Estrogênios não Esteroides/metabolismo , Genes Reporter , Isoflavonas/metabolismo , Modelos Químicos , Fitoestrógenos , Preparações de Plantas , Receptores de Estrogênio/metabolismo , Saccharomyces cerevisiae/metabolismo , Ativação Transcricional , Técnicas do Sistema de Duplo-Híbrido , beta-Galactosidase/metabolismoRESUMO
Raloxifene represents a potent compound for the prevention and treatment of osteoporosis and cardiovascular disease in postmenopausal women. Raloxifene exhibits targeted antiestrogenicity in breast and uterus, but acts as an agonist in bone and liver. This synthetic selective estrogen receptor modulator binds both estrogen receptors alpha and beta. The molecular mechanisms by which raloxifene exerts agonistic or antagonistic activity are still not resolved. Therefore, the binding behavior of raloxifene to estrogen receptors and its effects on DNA binding and transactivation were studied. The equilibrium binding affinity of raloxifene by displacing radiolabeled 17beta-estradiol exhibited a similar affinity behavior to that of its natural ligand. Using BIACORE technology with an immobilized estrogen response element, we showed that 17beta-estradiol and raloxifene increased the binding of estrogen receptor alpha to the DNA, suggesting a ligand-dependent dimerization. The influence of the ligands to the binding of estrogen receptor beta was lower. We may conclude that unliganded estrogen receptor alpha binds as a monomer whereas in the presence of 10(-8) M 17beta-estradiol or higher, homodimers are formed that interact with the estrogen response element. Transactivation studies in a yeast reporter system in a ligand-dependent manner resulted in a similar potency of raloxifene to estrogen receptor beta compared to the control testosterone. Subeffective doses of raloxifene combined with 17beta-estradiol did not shift the efficiency, whereas saturating concentrations of 17beta-estradiol combined with increasing concentrations of raloxifene altered the response induced by 17beta-estradiol. In this pure system, the antagonistic activity of raloxifene could not be detected as was expected by the results from ligand competition analysis.
Assuntos
Antagonistas de Estrogênios/farmacologia , Cloridrato de Raloxifeno/farmacologia , Receptores de Estrogênio/genética , Saccharomyces cerevisiae/efeitos dos fármacos , Transcrição Gênica/efeitos dos fármacos , Receptor alfa de Estrogênio , Receptor beta de Estrogênio , Humanos , Receptores de Estrogênio/efeitos dos fármacos , Saccharomyces cerevisiae/genética , TransfecçãoRESUMO
It has been suspected that beer drinking may change the hormonal status of men caused by phytoestrogens. Five different Austrian lager beers have been investigated for estrogenic activity by a yeast two-plasmid system harboring the human estrogen receptor alpha, after concentration by solid phase extraction. The beer concentrate was further fractionated by reversed phase HPLC, and then the fractions were characterized by the biological assay and GC-MS. The most potent fraction did not contain a known phytoestrogen. The total activity corresponded to an average of 43 ng of 17beta-estradiol/L of beer. It was concluded that the human health hazard of beer drinking originating from compounds activity on the estrogen receptor alpha is negligible.
