Direct evidences for the groove binding of the Clomifene to double stranded DNA

It has been reported that the antiestrogen Tamoxifen induces liver tumors in rats and genotoxic effects in vitro through DNA interaction. So, it can be proposed that its structural analogue, Clomifene, also can bind to DNA. To test this hypothesis, the DNA binding properties of Clomifene have been studied by absorption spectroscopy, fluorescence spectroscopy, cellular uptake, cell viability, cell proliferation and molecular modeling techniques. Evidences are provided that Clomifene could interact with DNA via minor groove interaction mode. The negative ΔG value implied that the interaction occurred between DNA and Clomifene spontaneously. Also, the positive ΔH and positive ΔS values indicated that the binding of Clomifene with DNA is mainly entropy driven and the enthalpy is unfavorable parameter. This also suggests that the hydrophobic interaction plays a major role in the binding with overall binding constant of K=5.645×10⁷M^-1 at 298K. From the results of docking, it can be concluded that Hydrogen bonds is also one of the most important interactions. The increase in entropy of system after binding might be due to the destruction of the DNA structure.

Determination by liquid chromatography-mass spectrometry of clomiphene isomers in the plasma of patients undergoing treatment for the induction of ovulation

A rapid, sensitive and selective LC-MS method is described for the simultaneous determination of zuclomiphene and enclomiphene in plasma from patients undergoing treatment with clomiphene citrate for the induction of ovulation. Samples spiked with N-didesmethyltamoxifen, the internal standard, were extracted into methyl tertiary butyl ether. The compounds were separated on a Luna C(18) analytical column, and a mobile phase of methanol-water (70:30 v/v) containing 0.05% trifluoroacetic acid at a flow rate of 1ml/min. The limits of determination were 35pg/ml and 7pg/ml for zu- and enclomiphene, respectively. Within-day coefficients of variation ranged from 2.1% to 7.2%.

Target specificity of selective estrogen receptor modulators within human endometrial cancer cells

Selective estrogen receptor modulators (SERMs) are estrogen receptor (ER) ligands that function as antagonists in some tissues, but have either partial or full agonist activity in others. SERMs often display variable partial agonist activity in uterine tissues and this activity can be displayed in uterine cell lines such as the human Ishikawa endometrial adenocarcinoma cell line. In this study, we compared the effects of several ER ligands including some SERMs on alkaline phosphatase (AP) activity and the expression of an ER target gene, the progesterone receptor (PR), in Ishikawa cells. As expected, estradiol (E2) was a potent and efficacious activator of both AP activity and PR mRNA expression. 4-Hydroxytamoxifen (4OHT) stimulated AP activity to a level 47% of that of E2 (100nM), while CP 336156 (lasofoxifene) increased AP activity 18%. A benzothiophene, such as LY 117018, a raloxifene analog, stimulated AP even less with values approximately 11% of E2-stimulated levels. A pure antiestrogen, ICI 182,780 did not stimulate AP activity. Interestingly, when we examined the ability of these compounds to increase the expression of the ER target gene, PR, a different rank order of efficacy was detected. After E2, CP 336156 was the most efficacious in increasing PR mRNA with a maximal stimulation of 20% of E2 levels, while 4OHT stimulated only 17%. LY 117018 increased PR mRNA expression 8% while ICI 182,780 did not increase PR mRNA expression at all. These data illustrate the target specificity that a SERM is able to display within a single cell type independent of "tissue specificity" and differential levels of expression of various cofactors. While 4OHT is 160% more active than CP 336156 in terms of inducing AP activity in the Ishikawa cells, CP 336156 has equivalent activity as 4OHT when one examines the ability of these SERMs to induce PR mRNA expression. Since the stimulation of Ishikawa cells by ER ligands is often used to assess the potential in vivo uterotrophic activity, these data indicate that examination of several endpoints in these cells may be necessary in order to fully characterize the activity of SERMs.

Electrostatic interactions of androgens and progesterone derivatives with rainbow trout estrogen receptor

In primary cultures of immature male rainbow trout (rt) hepatocytes, vitellogenin (Vg) gene expression is regulated by E(2) via the estrogen receptor (ER). However, steroids other than estrogens can also stimulate Vg gene expression. These steroids are hardly converted into E(2) during incubation and their stimulatory activity is completely inhibited by tamoxifen implying rtER involvement. These steroids have no or a slightly positive charge on the Connolly surface. In contrast, steroids that failed to stimulate Vg gene expression had a strong positive or negative charge around rings C and D due to polarization. The amino acid sequences of the ligand binding domains (LBD) of rtER and human ER alpha have 57.7% homology; only one amino acid differs in the presumed steroid binding site. We modeled the three-dimensional structure of the LBD of rtER using X-ray crystallographic data for hER alpha in order to investigate the fit (structural and electrostatic) between steroid and rtER. Two factors are essential for binding to rtER: (i) hydroxyl or carbonyl groups near C3 and C17 of the steroids (hydrophilic regions) that can form hydrogen bonds with His(489), Arg(359), and Glu(318), (ii) a hydrophobic steroid nucleus that interacts with a hydrophobic region of the rtER LBD through van der Waals forces. If polar functional groups are present, the hydrophobic interaction between steroid and the rtER LBD is considerably weakened.

Studies of protein binding to nonpolar solutes by using zonal elution and high-performance affinity chromatography: interactions of cis- and trans-clomiphene with human serum albumin in the presence of beta-cyclodextrin

High-performance affinity chromatography and zonal elution studies were used to examine the binding that takes place between the drug clomiphene and the protein human serum albumin (HSA). Equations were derived to describe the behavior of zonal elution experiments in which a solubilizing agent is present in the mobile phase to aid in the dissolution of a competing agent or injected analyte. These equations were then used to determine the association equilibrium constants for the clomiphene/HSA system, with beta-cyclodextrin being used as a complexation agent to improve the water solubility of cis- and trans-clomiphene without affecting the nature of their binding to HSA. It was found in these studies that both cis- and trans-clomiphene have 1:1 interactions at a common binding region on HSA (association constants at pH 7.4 and 37 degrees C: cis, 7.5 x 10(6) M-1; trans, 1.3 x 10(6) M-1). Further competition experiments between cis- or trans-clomiphene and various site-selective probes indicated that the clomiphene-binding region is the same as the proposed tamoxifen site of HSA. The approach and equations used within this report are general ones that can be applied to zonal elution studies of other solute-ligand systems in which one or more of the test components have limited solubility in the desired mobile phase.

Multivariate analysis of capillary electrophoresis separation conditions for Z-E isomers of clomiphene

Plackett-Burman (P-B) experimental design has been used to optimize the factors affecting separation of Z and E isomers of clomiphene (zuclomiphene and enclomiphene respectively) using capillary electrophoresis. The P-B design was used to simultaneously investigate the following five factors: buffer ionic strength, buffer pH, heptakis (2,3,6-tri-o-methyl) beta-cyclodextrin (TMCD) concentration, methanol concentration and injection time, each at three levels. In addition to these, a dummy variable was added to estimate the variability of the system. Effects on resolution and analysis time were calculated. Based on the information gained from the P-B design, the following set of conditions was chosen: 100 mM phosphate buffer pH 2.3, 5 mM TMCD, 5% methanol, and 1.7 s hydrodynamic injection time. These conditions gave well-resolved peaks for zuclomiphene and enclomiphene.

Development, pharmacology and clinical experience with clomiphene citrate

This review describes the development and pharmacology of clomiphene and those specific characteristics of both drug and patients which determine its clinical efficacy. The studies reviewed describe clinical observation of patient characteristics (age, additional infertility diagnosis, semen quality), vaginal ultrasound observations of ovaries (number and size of pre-ovulatory follicles) and endometrial lining (thickness, pattern) in 2841 clomiphene cycles in patients who required intrauterine insemination (IUI) because of poor sperm quality or an unsatisfactory postcoital test. They show that (i) conception in clomiphene cycles is related to the number and size of pre-ovulatory follicles, endometrial thickness, patient age, pelvic adhesions, type of anovulatory disorder and semen quality; (ii) pregnancy rates per clomiphene-IUI cycle are constant through at least six cycles; (iii) multiple births cannot be prevented by withholding human chorionic gonadotrophin or advising against coitus when multiple pre-ovulation follicles are present unless all follicles down to 10-12 mm diameter are counted. We also reviewed pregnancy outcome (number of gestational sacs, babies, preclinical and clinical abortion, ectopic pregnancy and birth sex) in 1744 clomiphene pregnancies from our clinic. We found that (i) preclinical and clinical abortions are increased only slightly by clomiphene use, compared to spontaneous pregnancy; (ii) clinical abortions are decreased in patients with polycystic ovaries and luteal insufficiency who use clomiphene; (iii) conception and preclinical abortions are related to endometrial thickness prior to ovulation; (iv) ectopic pregnancies are not increased by clomiphene and (v) the ratio of male births is not altered by clomiphene, except possibly in timed insemination cycles. These studies repudiate many misconceptions regarding clomiphene. They also show that clinical outcome may be improved by pre-ovulation ultrasound monitoring of ovarian and endometrial response.

Capillary electrophoretic separation of clomiphene isomers using various cyclodextrins as additives

The cis (Z) and trans (E) isomers of clomiphene were separated using capillary electrophoresis. Various derivatives of cyclodextrins (CDs) were applied as buffer additives, achieving a resolution of greater than 18. The effect of various parameters, type and concentration of CDs, type and concentration of background electrolytes (BGEs), pH, and organic modifiers has been studied systematically. Migration reversal was observed in several cases. The load ability of the various buffer systems was also taken into account.

The effect of clomiphene citrate isomers on human granulosa-lutein cells in culture

The effect of racemic clomiphene citrate and its two individual isomeric forms (i.e. en and zu) on corpus luteum function was evaluated. Granulosa-lutein cells were obtained from three normal ovulatory women undergoing oocyte retrieval following ovulation induction with agents other than clomiphene citrate for in vitro fertilization--embryo transfer (IVF-ET). The granulosa cells were cultured in the presence and absence of the three forms of clomiphene citrate, and in the presence and absence of human chorionic gonadotropin (hCG). Patients were recruited from the unit for assisted reproductive technology in a university hospital. The main outcome measured was the production of estradiol and progesterone by cultured human granulosa cells under the various conditions described above. The production of estradiol and progesterone by the cultured granulosa cells was dose-dependently reduced to a similar extent by all three forms of clomiphene citrate. The addition of hCG augmented steroidogenesis in all groups at all concentrations, but this still remained lower in all clomiphene citrate-treated groups compared to controls. The data suggest that all three types of clomiphene citrate (racemic, en, and zu) have inhibitory effects on the production of estradiol and progesterone by cultured human granulosa-lutein cells.

The effect of clomiphene citrate and its Zu or En isomers on the reproductive system of the immature male rat

The effect of clomiphene citrate (CC) and of its Zuclomiphene (ZuC) and Enclomiphene (EnC) isomers on the reproductive organs of immature male rats under different experimental conditions is reported. CC, ZuC, and EnC were administered daily to groups of either intact or castrated rats between the age of 21-44 d. This led to inhibition of weight increase of testis and accessory glands in the intact group. Spermatogenesis was arrested at the stage of primary spermatocyte following CC and ZuC treatment, and at the stage of young spermatids by EnC treatment. In the castrated group clomiphenes significantly stimulated weight increase of seminal vesicles (SV) compared with castrated control animals, but the former group were unable to achieve organ weight gain comparable to that in normal controls. Administration of human Chorionic Gonadotropin (hCG) together with CC or each of its isomers to intact animals, abolished the drug effect on spermatogenesis and on reproductive organ growth. Administration of CC, ZuC, and EnC together with testosterone to castrated animals, abolished the drug effect on growth inhibition of accessory glands. In intact treated rats LH and testosterone secretion were suppressed by all forms of clomiphenes. In the castrated group ZuC proved to be the most potent inhibitor of LH secretion. Therefore, it is inferred that ZuC and EnC have different potencies as far as their biological activity in the immature male rat is expressed.