Structure activity relationship of some 2,3-diaryl-2H-1-benzopyrans to their anti-implantation, estrogenic and antiestrogenic activities in rat

Modulation of AP-1 mediated estrogenic response by ormeloxifene in rat uterus

Ormeloxifene is a selective estrogen receptor modulator that exerts antiestrogenic effects and thereby inhibits growth in uterus. The present study was undertaken to examine the AP-1 protein interaction with AP-1 enhancer DNA elements in rat uterus in vivo and in vitro with a view to explore the modulation of estrogen action mediated via alternative pathway under the influence of ormeloxifene (Orm). In addition, the changes in expression of c-fos and c-jun transcription factors and mRNA expression of growth factor (IGF-1) were investigated with a view to assess the AP-1 mediated transcription. Ovariectomizedoung adult rats were administered with estradiol-17beta (5 microg/100 g body weight) or Orm (200 microg/100 g body weight) or vehicle for 3 days and sacrificed on fourth day. Electrophoretic mobility shift assay using uterine nuclear fraction from various treatment groups demonstrated that Orm caused a significant reduction in E2 induced AP-1 DNA binding. In vitro study revealed that Orm promotes AP-1 complex formation whereas its 7-hydroxy derivative inhibits it significantly. Uterine expression of c-fos and c-jun was increased significantly in Orm treated rats as compared to vehicle treated rats. However, the expression of c-fos and c-jun was decreased in rats receiving Orm plus E2. Semi-quantitative RT-PCR analysis revealed that mRNA expression of IGF-1 was increased in E2 treated group as compared to control group whereas reduced expression was observed in Orm treated rats as compared to E2 treated rats. The uterine weight and IGF-1 mRNA showed similar pattern, indicating that IGF-1 is involved in regulation of uterine weight. These results indicate that 7-hydroxy ormeloxifene (an active metabolite of Orm) is a potent antagonist at AP-1 sites. It inhibits the function of AP-1 transcription factors rather than their expression as evident by downregulation of mRNA expression of AP-1 regulated gene IGF-1, thereby inhibits proliferation in rat uterus. Study suggested a non-classicalregulation of estrogen action on uterus by ormeloxifene.

Modulation of estrogen receptor transactivation and estrogen-induced gene expression by ormeloxifene-a triphenylethylene derivative

The study was aimed to investigate the interaction of D,L-ormeloxifene (Orm), a triphenylethylene and its hydroxy derivative with estrogen receptor subtypes alpha and beta, its influence on ERE-driven transcriptional activation and progesterone receptor expression. In competitive binding experiments using human recombinant ERalpha and ERbeta, Orm showed interaction with both ER subtypes, with more selectivity and higher affinity towards ERalpha (8.8%) as compared to ERbeta (3%). In case of 7-hydroxy derivative, the relative binding affinity for both ERs was enhanced several folds. Orm showed lower Ki, i.e. higher affinity for ERalpha (250 nM) than for ERbeta (750 nM). It was observed that Orm promoted the formation of ER-ERE complexes in uterine tissue extract whereas its hydroxy derivative showed inhibitory effects. Transient co-transfection assay in COS-1 cells using ERE-luciferase reporter construct, revealed that Orm showed estrogenic response whereas its hydroxy-derivative was potent antiestrogen at ERalpha at transcription level. In immature rats, Orm (2 mg/kg) was associated with less increase in uterine weight and in luminal epithelial cell height than E2 or Tam. Orm also induced the expression of PR mRNA but the expression level was significantly less than estradiol treated group. These results suggest that ER-ERE complexes formed under the influence of 7-hydroxy Orm appear to be transcriptionally less effective hence antagonizing the E2-regulated gene expression in this target tissue.

Amide derivatives of 9,11-seco-estra-1,3,5(10)-trien-11-oic acid as modified orally active estrogen agonists with moderate antagonistic activity

Synthesis of amide derivatives of 9,11-seco-estra-1,3,5(10)-trien-11-oic acid containing alkyl and aromatic amine residues has been carried out with an aim to prepare orally active estrogen antagonists. Modification of the estradiol molecule in the form of C-seco-amide derivatives has led to their high oral absorption. Compounds 7 an n-propyl amide, 8 an n-butyl amide, and 16 a p-anisidyl amide of C-seco-estrane showed significant estrogen antagonistic activity (>20%), while, the majority of compounds possessed high estrogen agonistic activity on oral administration at 10mg/kg dose in rats.

Synthesis and biological activities of some new dibenzopyranones and dibenzopyrans: search for potential oestrogen receptor agonists and antagonists

Continuing our search for newer oestrogen agonists or antagonists and extending our work on the exploration of benzopyran related compounds, some new tricyclic molecules bridged between the active molecules of 3,4-diaryl chroman and 2,3-diaryl benzopyrans have been synthesised. Structural modifications at different positions with elements known to impart agonist or antagonist activities have been carried out to prepare the desired molecules. The target compounds were screened for their anti-osteoporotic (agonist) and anti-uterotrophic (antagonist) activities and were found to be moderately active.

Estrogen receptors in rat bone: their interaction with estrogen receptor modulators

Estrogen receptors (ER) were studied in rat bone cytosol using immunoprecipitation, and Western blot technique. Ligand specificity of bone ER was studied using various known modulators of ER. Competitive experiments were performed under exchange conditions in bone tissue obtained from one day old rats. ER alpha and beta subtypes were identified using immunoblotting experiments compared with that of ovarian and uterine tissues. In competitive binding assay, maximum inhibition in specific 3H-E2 binding was shown by E2 followed by tamoxifen and diethylstilbestrol. 7-Hydroxycentchroman and 85/287 also inhibited specific 3H-E2 binding but were less potent as compared to tamoxifen and diethylstilbestrol. However, 85/287 was less effective (81%) as compared to 7-hydroxycentchroman. Polyacrylamide gel electrophoresis of cytosol and Western blot analysis revealed the presence of 55 kD and 66 kD ER immunoreactive bands corresponding to alpha and beta subtypes, respectively, in bone as well as in uterus. Interestingly, the concentration of 55 kD ER was 3-fold higher than that of 66 kD ER. Ovarian cytosol revealed the presence of a 55 kD band only in Western blot analysis. These studies suggest the action of estrogens/ER modulators on osteoblasts which contain a limited number of classical alpha as well as beta sub types of ER that are known to be structurally different in their hormone-binding domains.

Resolution, molecular structure and biological activities of the D- and L-enantiomers of potent anti-implantation agent, DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran

Compound 1 (DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran, CDRI 85/287) a potent anti-estrogen and anti-implantation agent has been successfully resolved into its pure D- and L-enantiomers. Biological studies showed L-enantiomer to be the active form, exhibiting a fivefold higher receptor affinity for the rat uterine cytosolic estrogen receptor, 100% contraceptive efficacy at 1.3 mg/kg dose in single day schedule and 89% inhibition of estradiol induced increase of uterine weight at its contraceptive dose. The absolute stereochemistry determined by X-ray crystallographic analysis showed that the L-enantiomer has 2R configuration at its asymmetric centre.

Liquid chromatographic determination of a non-steroidal oral contraceptive CDRI-85/287 in rat serum

A precise and sensitive high performance liquid chromatographic (HPLC) assay method was developed and validated for the quantitation of 2-[4-(2-piperidinoethoxy) phenyl]-3-phenyl-(2H)-1-benzo(b)pyran (compound CDRI-85/287) in rat serum. This method, applicable to 0.5 ml volumes of serum, was validated according to GLP guidelines. It involved double extraction of serum samples with a mixture of hexane and iso-propanol (98:2 v/v) at alkaline pH and the use of UV detection at 332 nm. Linearity, precision and accuracy were acceptable (5-200 ng ml-1. The absolute recovery was more than 75% and the lower limit of quantitation was 5 ng ml-1. Freeze-thaw stability studies up to four cycles showed no apparent differences in the calculated spiked concentrations. However, in-process stability evaluation showed the stability of the processed samples lasted up to 85 h.