Multiple pathways for the oxidative metabolism of estrogens in Syrian hamster and rabbit kidney

Equol: A Microbiota Metabolite Able to Alleviate the Negative Effects of Zearalenone during In Vitro Culture of Ovine Preantral Follicles

The impact of zearalenone (ZEN) on female reproduction remains an issue, since its effects may differ among exposed cell types. Besides the use of decontaminants in animal diet, other approaches should be considered to minimise ZEN effects after exposure. Since the first organ in contact with ZEN is the gastrointestinal tract, we hypothesise that products of microbiota metabolism may play a role in ZEN detoxification. We aimed to evaluate the effect of 1 µmol/L ZEN and 1 µmol/L equol (a microbial metabolite), alone or in combination, on the survival and morphology of in vitro cultured ovarian preantral follicles. Ovaries from 12 sheep were collected at a local abattoir and fragmented, and the ovarian pieces were submitted to in vitro culture for three days in the presence or absence of the test compounds. The follicular morphology was impaired by ZEN, but equol could alleviate the observed degeneration rates. While ZEN decreased cell proliferation in primary and secondary follicles, as well as induced DNA double-strand breaks in primordial follicles, all these observations disappeared when equol was added to a culture medium containing ZEN. In the present culture conditions, equol was able to counteract the negative effects of ZEN on ovarian preantral follicles.

2-Methoxymethylestradiol: a new 2-methoxy estrogen analog that exhibits antiproliferative activity and alters tubulin dynamics

An estradiol metabolite, 2-methoxyestradiol (2-MeOE(2)), has shown antiproliferative effects in both hormone-dependent and hormone-independent breast cancer cells. Previously, a series of 2-hydroxyalkyl estradiol analogs had been synthesized in our laboratories as potential probes for comparison of estrogen receptor (ER)-mediated versus non-ER-mediated effects in breast cancer cells. A methoxy derivative of 2-hydroxymethyl estradiol was prepared for biological evaluation and comparison with 2-MeOE(2). Estrogenic activity of the synthetic analogs was evaluated in two ways, one by examining affinity of the analogs for the estrogen receptor in MCF-7 cells and the other by examining the ability of the analogs to induce estrogen-responsive gene expression. The analog, 2-methoxymethyl estradiol (2-MeOMeE(2)), demonstrated weak affinity for the estrogen receptor (0.9% of estradiol) and weak ability to stimulate estrogen-induced expression of the pS2 gene (0.02% of estradiol). Antitumor activity was evaluated both in vitro and in vivo. The steroidal nucleus seems to be an attractive target for developing novel tubulin polymerization inhibitors. Additionally, such steroidal compounds may have low toxicity compared to the natural products known to interact with tubulin. Interestingly, 2-MeOMeE(2) inhibited tubulin polymerization in vitro at concentrations of 1 and 3 microM and was more effective than 2-MeOE(2). In cells, 2-MeOMeE(2) was effective in suppressing growth and inducing cytotoxicity in MCF-7 and MDA-MB-231 breast cancer cells. The cytotoxic effects of 2-MeOMeE(2) are associated with alterations in tubulin dynamics, with the frequent appearance of misaligned chromosomes, a significant mitotic delay, and the formation of multinucleated cells. In comparison, 2-MeOE(2) was more effective than 2-MeOMeE(2) in producing cytotoxicity and altering tubulin dynamics in intact cells. Assessment of in vivo antitumor activity was performed in athymic mice containing human breast tumor xenografts. Nude mice bearing MDA-MB-435 tumor xenografts were treated i.p. with 50 mg/kg per day of 2-MeOMeE(2) or vehicle control for 45 days. Treatment with 2-MeOMeE(2) resulted in an approximate 50% reduction in mean tumor volume at treatment day 45 when compared to control animals and had no effect on animal weight. Thus, 2-MeOMeE(2) is an estrogen analog with minimal estrogenic properties that demonstrates antiproliferative effects both in vitro and in the human xenograft animal model of human breast cancer.

Prostaglandin-H synthase containing cell lines as tools for studying metabolism and toxicity of xenobiotics

Prostaglandin-H synthase (PHS) can oxidize many xenobiotics and carcinogens (chemicals) in vitro and has been suggested to serve as an alternative metabolic activation enzyme, particularly in tissues low in monooxygenase activity. This article briefly describes types of PHS-catalyzed xenobiotic oxidations and discusses its determinants in cells. Methods employed for studying the involvement of PHS in the bioactivation of chemicals are reviewed with special emphasis on a cell culture system derived from ram seminal vesicles which has been used in studies on the metabolism and the genotoxicity of diethylstilbestrol.

SEMV cell cultures: a model for studies of prostaglandin-H synthase-mediated metabolism and genotoxicity of xenobiotics

Many xenobiotics and carcinogens are oxidized in vitro by prostaglandin-H synthase (PHS) in the presence of arachidonic acid or lipid peroxides. PHS has been suggested to serve as an alternative metabolic activation enzyme to the cytochrome P-450 isoenzymes, particularly in tissues low in monooxygenase activity. This article briefly describes PHS-catalyzed oxidations and reviews methods available for investigating the involvement of PHS in mediating the toxicity of certain chemicals. Since in vivo systems impose certain limitations on such studies, particular emphasis is placed on a specialized cell system which can serve as a model for investigating the PHS-dependent bioactivation of xenobiotics, its determinants and toxicological significance. This is exemplified by experiments conducted with the carcinogenic estrogen diethylstilbestrol (DES) in cell cultures derived from ram seminal vesicles which express PHS but lack monooxygenase activity. DES is oxidized by PHS in seminal vesicle (SEMV) cells and DES can induce micronuclei in this model; both processes are inhibited by indomethacin. These data support the hypothesis that PHS-dependent oxidation of DES plays a role in its genotoxicity.

Prostaglandin H synthase dependent metabolism of diethylstilbestrol by ram seminal vesicle cell cultures

Prostaglandin H synthase (PHS) peroxidase dependent metabolic activation has been suggested to play a role in mediating adverse effects of various carcinogens. Recently, we derived a cell line from ram seminal vesicles (SEMV cells) to conduct studies on the PHS-mediated metabolism of estrogens and xenobiotics in intact cells with the goal of relating this to an endpoint for genotoxicity inducible in this in vitro model. The present paper describes the drug-metabolizing capability of SEMV cells which has been investigated using radiolabeled diethylstilbestrol (DES) and analysing culture extracts by means of reverse phase HPLC with on-line radioactivity detection and after enzymatic hydrolysis of conjugate fractions. The synthetic estrogen DES is converted to sulfate conjugates and to the oxidative metabolite Z,Z-dienestrol (Z,Z-DIES) in a time-dependent manner. Compounds expected to modulate PHS-dependent co-oxidation of DES increased (arachidonic acid) or inhibited (indomethacin) Z,Z-DIES formation of SEMV cells in culture. A comparison of rates of arachidonic acid turnover to prostaglandins on the one hand and DES oxidation on the other reveals that DES is oxidized despite the presence of competing endogenous cosubstrates of PHS peroxidase. The results clearly indicate that SEMV cells catalyze PHS-dependent oxidation of DES as well as carrying out phase II metabolism in the absence of detectable monooxygenase activity. These features and recent data showing that DES can induce micronuclei in SEMV cells makes them an attractive model for further investigations of the role of PHS in mediating the genotoxicity of DES and other xenobiotics.