Changes in thyroid hormone concentrations over time in dogs with autoimmune thyroiditis

OBJECTIVE

The objective of this study was to follow long-term changes in the concentration of thyroid hormones in dogs with subclinical thyroiditis.

SAMPLES

Samples were obtained from 125 dogs with subclinical thyroiditis. The study population included 70 female and 55 male dogs. The mean testing interval was 3.9 years from initial testing (SD, 2.3 years; range, 1 to 9 years).

METHODS

Dogs with subclinical thyroiditis were identified retrospectively using results from the Orthopedic Foundation for Animals Canine Thyroid Profile performed by the Endocrinology Section of the Michigan State University Veterinary Diagnostic Lab. Owners were invited to submit follow-up serum samples with their veterinarian along with a medical history form, including subsequent treatments.

RESULTS

At the time of retesting, 30% of the dogs had progressed to hypothyroidism and/or were treated with thyroxine. Fifty percent maintained positive or equivocal thyroglobulin autoantibody (TgAA) results while remaining euthyroid. Fourteen percent of the dogs became TgAA negative and remained euthyroid. In 6% of the cases tested, proper medical histories were not available, and a final classification could not be determined.

CLINICAL RELEVANCE

These results indicate that most dogs with elevated thyroglobulin autoantibodies either exhibit persistent autoimmune thyroiditis with continued risk of hypothyroidism or progress to hypothyroidism when monitored for more than 1 year. Thyroid function in dogs with subclinical thyroiditis should be monitored every 12 months or if there is change in the clinical presentation.

Molecular Action of Tamoxifen in the Ovaries of Rats with Mammary Neoplasia

Tamoxifen (TAM) is a drug commonly used in patients with breast cancer. The anticancer effect of TAM occurs via its ability to antagonize estrogen-dependent growth of mammary epithelial cells. Previously, we demonstrated that TAM prevented the chemotherapy-induced loss of ovarian follicular reserves in both cancer-free rats and rats with cancer. Such follicular loss is a main cause of infertility in young women treated for cancer. The current study was undertaken to discover the molecules and intracellular pathways involved in the action of TAM in the ovaries of rats with mammary tumors. To meet this goal we used transcriptomic (RNA-Seq) and proteomic (2D-DIGE/MS) approaches. TAM inhibited the expression of genes and lncRNAs involved in ovarian steroidogenesis. Moreover, TAM altered the expression of genes related to primordial follicle activation or arrest. In addition, proteomic screening indicated the importance of basic metabolic processes in the ovarian actions of TAM. Although simple extrapolation of these data to humans is not possible, the results of this study emphasize the need to explore the ability of TAM to affect ovarian function in women undergoing cancer treatment.

Relationship between serum magnesium, calcium, and parathyroid concentrations in dogs with abnormally low serum 25-hydroxyvitamin D concentration and chronic or protein-losing enteropathy

BACKGROUND

The relationship between the development of SHPT and ionized magnesium (iMg) concentrations in blood of dogs with chronic gastrointestinal (GI) disease and abnormally low 25(OH)D is undefined.

OBJECTIVES

Evaluate relationships between ionized magnesium (iMg), PTH, ionized calcium (iCa), and 25(OH)D in dogs with chronic enteropathy (CE) with or without protein-losing enteropathy (PLE) and abnormal 25(OH)D. Determine whether dogs with CE or PLE, decreased 25(OH)D and SHPT have differences in iMg, iCa, or 25(OH)D when compared to dogs that do not have SHPT.

ANIMALS

Fifty dogs with CE +/- PLE and abnormally low serum 25(OH)D.

METHODS

Retrospective search of submissions database at a veterinary diagnostic laboratory for vitamin D profiles submitted in years 2017 to 2020. Cases were excluded if supplemented with Ca, Mg, or vitamin D. Spearman correlation was performed to evaluate relationships between iMg, PTH, 25(OH)D, and iCa. Ionized Mg, iCa, and 25(OH)D concentrations were compared between dogs with SHPT and those with normal PTH concentrations.

RESULTS

Concentrations of iMg were weakly negatively correlated with PTH (rho, -.31; P = .03), and weakly positively correlated with serum 25(OH)D (rho, .34, P = .02) and iCa (rho, .42, P = .003). Ionized magnesium concentrations were lower in dogs with abnormally low 25(OH)D and SHPT compared to dogs with abnormally low 25(OH)D and normal parathyroid hormone concentrations (P = .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Hypomagnesemia might contribute to alterations in iCa and parathyroid hormone in dogs with CE +/- PLE and abnormally low 25(OH)D.

Multiple Lesions Contribute to Infertility in Males Lacking Autoimmune Regulator

Male factors, including those of autoimmune origin, contribute to approximately 50% of infertility cases in humans. However, the mechanisms underlying autoimmune male infertility are poorly understood. Deficiency in autoimmune regulator (AIRE) impairs central immune tolerance because of diminished expression of self-antigens in the thymus. Humans with AIRE mutations and mice with engineered ablation of Aire develop multiorgan autoimmunity and infertility. To determine the immune targets contributing to infertility in male Aire-deficient (-/-) mice, Aire-/- or wild-type (WT) males were paired with WT females. Aire-/- males exhibited dramatically reduced mating frequency and fertility, hypogonadism, and reduced serum testosterone. Approximately 15% of mice exhibited lymphocytic infiltration into the testis, accompanied by atrophy, azoospermia, and reduced numbers of mitotically active germ cells; the remaining mice showed normal testicular morphology, sperm counts, and motility. However, spermatozoa from all Aire-/- mice were defective in their ability to fertilize WT oocytes in vitro. Lymphocytic infiltration into the epididymis, seminal vesicle, and prostate gland was evident. Aire-/- male mice generated autoreactive antibodies in an age-dependent manner against sperm, testis, epididymis, prostate gland, and seminal vesicle. Finally, expression of Aire was evident in the seminiferous epithelium in an age-dependent manner, as well as in the prostate gland. These findings suggest that Aire-dependent central tolerance plays a critical role in maintaining male fertility by stemming autoimmunity against multiple reproductive targets.

Abstract 1120: Randomized clinical trial of a flaxseed lignan in pre-menopausal women at high risk for development of breast cancer

Breast cancer prevention strategies for young pre-menopausal women must have minimal side effects and accommodate potential future child-bearing. Based on epidemiologic evidence and informed by a single-arm pilot study, we conducted a multi-institutional, placebo-controlled Phase IIB trial of the lignan secoisolariciresinol diglycoside (SDG) found in high concentrations in flaxseed. Benign breast tissue was acquired by random periareolar fine needle aspiration (RPFNA) from pre-menopausal women at increased risk for breast cancer during the follicular phase as estimated by dates. Those with cytologic hyperplasia and ≥2% positive cells by Ki-67 immunocytochemistry were eligible for randomization 2:1 to daily Brevail® (50 mg SDG) or placebo. After 12 months, RPFNA and blood for hormone assays were repeated. The primary endpoint was difference in change in Ki-67 between the randomization groups. A planned accrual of 230 was to provide an 80% power of detecting a 2.5% reduction in Ki-67 for the SDG group vs no reduction in the placebo group. Accrual was slower than anticipated and the study was closed with 180 enrollees at five sites. 152 (51 placebo, 101 SDG) sets of paired specimens were evaluable for the primary endpoint. Baseline Ki-67 was a median of 4.1% (range, 2.0 - 26.8%), with no difference between arms (Mann-Whitney nonparametric test, p=0.34). Both arms showed a decrease in percent Ki-67 over time (Wilcoxon signed rank test; p=0.034 for placebo, p=0.001 for SDG). Although Ki-67 reduction was greater in the SDG arm (median of -1.8% vs -1.2%), there was no statistically significant difference between the two arms (Mann-Whitney, p=0.72). Since luteal phase progesterone affects proliferation, we excluded 35 women that by serum progesterone levels could not be confirmed to be in the same phase of the menstrual cycle at baseline and off-study. Analyzing the remaining 117 for Ki-67 (42 placebo, 75 SDG), there was no significant change for the placebo arm (Wilcoxon, p=0.14) but the significant change in the SDG arm persisted (p=0.002). As an exploratory analysis, assessment of gene expression was performed by RT-qPCR on 77 pairs of non-bloody RPFNA specimens. 22 had significant ERα gene expression changes (defined <0.5 or >2.0 fold changes). There was no significant change over time for the placebo group (7/10 increases, Wilcoxon, p=0.16), but there was significant change for the SDG group (10/12 decreases, p=0.027). There was also a significant difference between the groups (Mann-Whitney, p=0.018). While the primary trial result is null, there is supportive evidence SDG may favorably affect cell proliferation and estrogen signaling in premenopausal women at high risk for development of breast cancer. Supported by Susan G. Komen Promise Grant KG101039. Study agent (Brevail®, placebo) provided by Lignan Research Inc. (later Barlean's Oils) which was otherwise not involved in the design, conduct, or analysis of the study.

Citation Format: Carol J. Fabian, Seema A. Khan, Judy E. Garber, William C. Dooley, Lisa D. Yee, Carola M. Zalles, Trina Metheny, Teresa A. Phillips, Jinxiang Hu, Brian K. Petroff, Stephen D. Hursting, Bruce F. Kimler. Randomized clinical trial of a flaxseed lignan in pre-menopausal women at high risk for development of breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1120.

Randomized Phase IIB Trial of the Lignan Secoisolariciresinol Diglucoside in Premenopausal Women at Increased Risk for Development of Breast Cancer

We conducted a multiinstitutional, placebo-controlled phase IIB trial of the lignan secoisolariciresinol diglucoside (SDG) found in flaxseed. Benign breast tissue was acquired by random periareolar fine needle aspiration (RPFNA) from premenopausal women at increased risk for breast cancer. Those with hyperplasia and ≥2% Ki-67 positive cells were eligible for randomization 2:1 to 50 mg SDG/day (Brevail) versus placebo for 12 months with repeat bio-specimen acquisition. The primary endpoint was difference in change in Ki-67 between randomization groups. A total of 180 women were randomized, with 152 ultimately evaluable for the primary endpoint. Median baseline Ki-67 was 4.1% with no difference between arms. Median Ki-67 change was -1.8% in the SDG arm (P = 0.001) and -1.2% for placebo (P = 0.034); with no significant difference between arms. As menstrual cycle phase affects proliferation, secondary analysis was performed for 117 women who by progesterone levels were in the same phase of the menstrual cycle at baseline and off-study tissue sampling. The significant Ki-67 decrease persisted for SDG (median = -2.2%; P = 0.002) but not placebo (median = -1.0%). qRT-PCR was performed on 77 pairs of tissue specimens. Twenty-two had significant ERα gene expression changes (<0.5 or >2.0) with 7 of 10 increases in placebo and 10 of 12 decreases for SDG (P = 0.028), and a difference between arms (P = 0.017). Adverse event incidence was similar in both groups, with no evidence that 50 mg/day SDG is harmful. Although the proliferation biomarker analysis showed no difference between the treatment group and the placebo, the trial demonstrated use of SDG is tolerable and safe.

Autoimmune Regulator is required in female mice for optimal embryonic development and implantation†

Autoimmune Regulator (AIRE) regulates central immune tolerance by inducing expression of tissue-restricted antigens in thymic medullary epithelial cells, thereby ensuring elimination of autoreactive T cells. Aire mutations in humans and targeted Aire deletion in mice result in multiorgan autoimmune disease, known in humans as autoimmune polyglandular syndrome type 1 (APS-1). APS-1 is characterized by the presence of adrenal insufficiency, chronic mucosal candidiasis, and/or hypoparathyroidism. Additionally, females often present with gonadal insufficiency and infertility. Aire-deficiency (KO) in mice results in oophoritis and age-dependent depletion of follicular reserves. Here, we found that while the majority of young 6-week-old Aire-KO females had normal follicular reserves, mating behavior, and ovulation rates, 50% of females experienced embryonic loss between gestation day (GD) 5.5 and 7.5 that could not be attributed to insufficient progesterone production or decidualization. The quality of GD0.5 embryos recovered from Aire KO mice was reduced, and when cultured in vitro, embryos displayed limited developmental capacity in comparison to those recovered from wild-type (WT) mice. Further, embryos flushed from Aire KO dams at GD3.5 were developmentally delayed in comparison to WT controls and had reduced trophoblastic outgrowth in vitro. We conclude that AIRE does not play a direct role in uterine decidualization. Rather, reduced fertility of Aire-deficient females is likely due to multiple factors, including oophoritis, delayed preimplantation development, and compromised implantation. These effects may be explained by autoimmune targeting of the ovary, embryo, or both. Alternatively, altered embryonic development could be due to a direct role for AIRE in early embryogenesis.

Radioactive iodine uptake in hyperthyroid cats after administration of recombinant human thyroid stimulating hormone

BACKGROUND

Radioactive iodine therapy is considered the treatment of choice for hyperthyroidism in cats, but the availability of this modality is limited by costs and hospitalization requirements. Administration of recombinant human thyroid stimulating hormone (rh-TSH) to humans with thyroid neoplasia or nodular goiter can increase thyroidal iodine uptake, thereby allowing the use of lower radioactive iodine doses for treatment. Veterinary studies of this subject are limited, and results are conflicting.

OBJECTIVE

To investigate the effects of rh-TSH administration on thyroidal iodine uptake in hyperthyroid cats.

ANIMALS

Ten client-owned hyperthyroid cats.

METHODS

In this prospective clinical study, cats were administered saline (placebo), 50 μg rh-TSH (low-dose), and 100 μg rh-TSH (high-dose) in randomized crossover design with treatments separated by 7-10 days. After each treatment, thyroid scintigraphy was performed by administering 300 μCi 123 I and assessing radionuclide uptake 8 and 24 hours later. Serum thyroid hormone concentrations were measured at each visit.

RESULTS

Thyroidal percent iodine uptakes (mean ± SD at 8 and 24 hours) in cats treated with placebo (25.2 ± 13.4%, 30.0 ± 12.8%), low-dose (24.1 ± 12.5%, 29.4 ± 13.7%), and high-dose rh-TSH (24.2 ± 16.3%, 30.8 ± 15.3%) were not different (P = .76). Independent of rh-TSH administration, percent iodine uptakes were positively correlated with serum thyroid hormone concentrations.

CONCLUSIONS AND CLINICAL IMPORTANCE

One-time administration of rh-TSH, even at high doses, would not be expected to lower radioactive iodine doses needed for treatment of hyperthyroidism in cats. Investigations of alternate strategies to increase thyroidal uptake of radioactive iodine are warranted.

Immune response to a model shared placenta/tumor-associated antigen reduces cancer risk in parous mice

During human pregnancy, paternally inherited antigens expressed by the fetal-placental unit can elicit expansion of antigen-specific CD8+ T cells. These cells can persist for years as memory T cells, but their effects on long-term maternal health are unknown. Shared placenta/tumor-associated antigens are expressed by placenta and tumors, but are minimally expressed or absent in normal adult tissues. We hypothesized that maternal T cells elicited against these antigens can alter risk of cancers expressing the same antigen after pregnancy, and tested this in mice using chicken ovalbumin (OVA) as a surrogate shared placenta/tumor antigen. Hemizygous OVA transgenic males were bred to wild-type C57BL/6 females (H2b haplotype) such that the fetuses inherited and expressed OVA. Maternal OVA/H2Kb-specific CD8+ T cells became detectable during gestation, and persisted in some animals for up to 24 weeks. To determine whether these cells might influence growth of OVA-expressing tumors in OVA-bred females, E.G7-OVA thymoma cells were inoculated subcutaneously in OVA-bred, wild-type bred, and virgin females, and monitored for growth. OVA-bred mice had prolonged survival as compared to virgin mice and the progression of tumors was delayed in comparison to wild-type bred and virgin females. Thus, paternally inherited OVA antigen elicited a CD8+ T cell response during pregnancy that was associated with delayed growth of OVA-expressing tumors following pregnancy. These data suggest a possible role of antigen-specific T cells in protecting parous females against tumors bearing shared placenta/tumor antigens.

Trophoblast Glycoprotein (TPGB/5T4) in Human Placenta: Expression, Regulation, and Presence in Extracellular Microvesicles and Exosomes

BACKGROUND

Many parallels exist between growth and development of the placenta and that of cancer. One parallel is shared expression of antigens that may have functional importance and may be recognized by the immune system. Here, we characterize expression and regulation of one such antigen, Trophoblast glycoprotein (TPGB; also called 5T4), in the placenta across gestation, in placentas of preeclamptic (PE) pregnancies, and in purified microvesicles and exosomes.

METHODS

Trophoblast glycoprotein expression was analyzed by real-time reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry. Regulation of 5T4 in cytotrophoblast cells was examined under either differentiating conditions of epidermal growth factor or under varying oxygen conditions. Microvesicles and exosomes were purified from supernatant of cultured and perfused placentas.

RESULTS

Trophoblast glycoprotein expression was prominent at the microvillus surface of syncytiotrophoblast and on the extravillous trophoblast cells, with minimal expression in undifferentiated cytotrophoblasts and normal tissues. Trophoblast glycoprotein expression was elevated in malignant tumors. In cytotrophoblasts, 5T4 was induced by in vitro differentiation, and its messenger RNA (mRNA) was increased under conditions of low oxygen. PE placentas expressed higher 5T4 mRNA than matched control placentas. Trophoblast glycoprotein was prominent within shed placental microvesicles and exosomes.

CONCLUSION

Given the potential functional and known immunological importance of 5T4 in cancer, these studies reveal a class of proteins that may influence placental development and/or sensitize the maternal immune system. In extravillous trophoblasts, 5T4 may function in epithelial-to-mesenchymal transition during placentation. The role of syncytiotrophoblast 5T4 is unknown, but its abundance in shed syncytial vesicles may signify route of sensitization of the maternal immune system.

The combined effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and the phytoestrogen genistein on steroid hormone secretion, AhR and ERβ expression and the incidence of apoptosis in granulosa cells of medium porcine follicles

Low doses of endocrine disrupting chemicals (EDCs) used in combination may act in a manner different from that of individual compounds. The objective of the study was to examine in vitro effects of low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 100 pM) and genistein (500 nM) on: 1) progesterone (P₄) and estradiol (E₂) secretion (48 h); 2) dynamic changes in aryl hydrocarbon receptor (AhR) mRNA and protein expression (1, 3, 6, 24 and 48 h); 3) dynamic changes in estrogen receptor β (ERβ) mRNA and protein expression (1, 3, 6, 24 and 48 h); and 4) induction of apoptosis in porcine granulosa cells derived from medium follicles (3, 6 and 24 h). TCDD had no effect on P₄ or E₂ production, but potentiated the inhibitory effect of genistein on P₄ production. In contrast to the individual treatments which did not produce any effects, TCDD and genistein administered together decreased ERβ and AhR protein expression in granulosa cells. Moreover, the inhibitory effect of TCDD on AhR mRNA expression was abolished by genistein. The treatments did not induce apoptosis in the cells. In summary, combined effects of low concentrations of TCDD and genistein on follicular function of pigs differed from that of individual compounds. The results presented in the current paper clearly indicate that effects exerted by low doses of EDCs applied in combination must be taken into consideration when studying potential risk effects of EDCs on biological processes.

Modulation of Breast Cancer Risk Biomarkers by High-Dose Omega-3 Fatty Acids: Phase II Pilot Study in Premenopausal Women

Higher intakes of the omega-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) relative to the omega-6 arachidonic acid (AA) have been variably associated with reduced risk of premenopausal breast cancer. The purpose of this pilot trial was to assess feasibility and explore the effects of high-dose EPA and DHA on blood and benign breast tissue risk biomarkers before design of a placebo-controlled phase IIB trial. Premenopausal women with evidence of hyperplasia ± atypia by baseline random periareolar fine needle aspiration were given 1860 mg of EPA + 1500 mg of DHA ethyl esters daily for 6 months. Blood and benign breast tissue were sampled during the same menstrual cycle phase prestudy and a median of 3 weeks after last dose. Additional blood was obtained within 24 hours of last dose. Feasibility, which was predefined as 50% uptake, 85% retention, and 70% compliance, was demonstrated with 46% uptake, 94% completion, and 85% compliance. Cytologic atypia decreased from 77% to 38% (P = 0.002), and Ki-67 from a median of 2.1% to 1.0% (P = 0.021) with an increase in the ratio of EPA + DHA to AA in erythrocyte phospholipids but no change in blood hormones, adipokines, or cytokines. Exploratory breast proteomics assessment showed decreases in several proteins involved in hormone and cytokine signaling with mixed effects on those in the AKT/mTOR pathways. Further investigation of EPA plus DHA for breast cancer prevention in a placebo-controlled trial in premenopausal women is warranted.

Clinical Trial of Acolbifene in Premenopausal Women at High Risk for Breast Cancer

The purpose of this study was to assess the feasibility of using the selective estrogen receptor modulator (SERM) acolbifene as a breast cancer prevention agent in premenopausal women. To do so, we assessed change in proliferation in benign breast tissue sampled by random periareolar fine-needle aspiration (RPFNA) as a primary endpoint, along with changes in other risk biomarkers and objective and subjective side effects as secondary endpoints. Twenty-five women with cytologic hyperplasia ± atypia and ≥2% of breast epithelial cells staining positive for Ki-67, received 20 mg acolbifene daily for 6-8 months, and then had benign breast tissue and blood risk biomarkers reassessed. Ki-67 decreased from a median of 4.6% [interquartile range (IQR), 3.1%-8.5%] at baseline to 1.4% (IQR, 0.6%-3.5%) after acolbifene (P < 0.001; Wilcoxon signed-rank test), despite increases in bioavailable estradiol. There were also significant decreases in expression (RT-qPCR) of estrogen-inducible genes that code for pS2, ERα, and progesterone receptor (P ≤ 0.026). There was no significant change in serum IGF1, IGFBP3, IGF1:IGFBP3 ratio, or mammographic breast density. Subjective side effects were minimal with no significant increase in hot flashes, muscle cramps, arthralgias, or fatigue. Objective measures showed a clinically insignificant decrease in lumbar spine bone density (DEXA) and an increase in ovarian cysts but no change in endometrial thickness (sonography). In summary, acolbifene was associated with favorable changes in benign breast epithelial cell proliferation and estrogen-inducible gene expression but minimal side effects, suggesting a phase IIB placebo-controlled trial evaluating it further for breast cancer prevention.

Modulation of Breast Cancer Risk Biomarkers by High-Dose Omega-3 Fatty Acids: Phase II Pilot Study in Postmenopausal Women

Associational studies suggest higher intakes/blood levels of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) relative to the omega-6 arachidonic acid (AA) are associated with reduced breast cancer risk. We performed a pilot study of high-dose EPA + DHA in postmenopausal women to assess feasibility before initiating a phase IIB prevention trial. Postmenopausal women with cytologic evidence of hyperplasia in their baseline random periareolar fine needle aspiration (RPFNA) took 1,860 mg EPA +1500 mg DHA ethyl esters daily for 6 months. Blood and breast tissue were sampled at baseline and study conclusion for exploratory biomarker assessment, with P values uncorrected for multiple comparisons. Feasibility was predefined as 50% uptake, 80% completion, and 70% compliance. Trial uptake by 35 study entrants from 54 eligible women was 65%, with 97% completion and 97% compliance. Favorable modulation was suggested for serum adiponectin (P = 0.0027), TNFα (P = 0.016), HOMA 2B measure of pancreatic β cell function (P = 0.0048), and bioavailable estradiol (P = 0.039). Benign breast tissue Ki-67 (P = 0.036), macrophage chemoattractant protein-1 (P = 0.033), cytomorphology index score (P = 0.014), and percent mammographic density (P = 0.036) were decreased with favorable effects in a proteomics array for several proteins associated with mitogen signaling and cell-cycle arrest; but no obvious overall effect on proteins downstream of mTOR. Although favorable risk biomarker modulation will need to be confirmed in a placebo-controlled trial, we have demonstrated feasibility for development of high-dose EPA and DHA ethyl esters for primary prevention of breast cancer.

Effects of Flaxseed Lignan Secoisolariciresinol Diglucosideon Preneoplastic Biomarkers of Cancer Progression in a Model of Simultaneous Breast and Ovarian Cancer Development

Breast cancer prevention efforts are focused increasingly on potentially beneficial dietary modifications due to their ease of implementation and wide acceptance. Secoisolariciresinol diglucoside (SDG) is a lignan found in high concentration in flaxseed that may have selective estrogen receptor modulator-like effects resulting in antiestrogenic activity in a high estrogen environment. In parallel with a human phase II prevention trial, female ACI rats (n = 8-10/group) received 0, 10, or 100 ppm SDG in the feed. The 100 ppm SDG treatment produced similar blood lignan levels as those observed in our human pilot study. Mammary and ovarian cancer progression were induced using local ovarian DMBA treatment and subcutaneous sustained release 17β-estradiol administered starting at 7 weeks of age. Mammary gland and ovarian tissues were collected at 3 mo after initiation of treatment and examined for changes in epithelial cell proliferation (Ki-67, cell counts), histopathology, and dysplasia scores, as well as expression of selected genes involved in proliferation, estrogen signaling, and cell adhesion. Treatment with SDG normalized several biomarkers in mammary gland tissue (dysplasia, cell number, and expression of several genes) that had been altered by carcinogen. There is no indication that SDG promotes preneoplastic progression in the ovarian epithelium.

Abstract P5-12-03: Initial report of a randomized trial of letrozole in high risk women taking hormone replacement therapy

Background:

On the basis of positive results in a pilot study, we initiated a randomized, double-blind, placebo-controlled trial of the aromatase inhibitor letrozole in post-menopausal women at high risk for development of breast cancer who were taking hormone replacement therapy (HRT). The objective was to determine if risk biomarkers for breast cancer in benign breast tissue sampled by random peri-areolar aspiration (RPFNA) could be favorably modulated.

Methods

Women who exhibited cytologic hyperplasia +/- atypia and Ki-67 immunocytochemistry staining ≥1.5% on screening RPFNA were eligible to be randomized 1:1 between placebo and letrozole (2.5. mg daily) for six months, followed by repeat RPFNA. Women were then given the option to receive open-label letrozole for a second six months, and a third RPFNA. The primary analysis was a difference between the two groups for the change in Ki-67 between baseline and 6 months. The initial accrual goal was 108 subjects, with the expectation of 96 subjects evaluable for the baseline∼6 months comparison.

Results

55 subjects were enrolled between March 2007 and March 2014, when accrual was closed. From the time of our successful pilot study to present, there had been a steady decline in the use of HRT by women in our high risk cohort, both in frequency of women using as well as the type and strength of HRT. The result was fewer potential subjects for screening and fewer still that satisfied the 1.5% Ki-67 criterion. Thus, the trial was closed early. Of 55 enrolled subjects, two dropped out prior to 6 months; 52 completed 6 months and provided evaluable RPFNA specimens for analysis, with one subject scheduled for repeat aspiration in September. Six subjects went off study between 6 and 12 months; 42 have completed the entire 12 month schedule, and 5 are still on trial. At baseline, 18 women displayed hyperplasia (Masood score 13-15) and 37 had hyperplasia with atypia (Masood score 14-17). Median Ki-67 was 3.0%, with a range from 1.6 – 15.4%. For 52 comparisons between baseline and 6 months, 8 women had no change by Masood score, 8 had an increase and 36 exhibited a decrease, i.e., less abnormality. Two women had no change in Ki-67 staining, 13 exhibited increased Ki-67 and 37 showed a decrease; median at 6 months 1.7%, median change -1.4%. For 42 comparisons between baseline and 12 months, 11 women had no change by Massod score, 9 increased, and 22 decreased. One woman had no change in Ki-67 staining, 10 exhibited increased Ki-67 and 31 showed a decrease. The decreases in Masood score and Ki-67 between baseline and 12 months (when all subjects had received letrozole, either for 6 or 12 months) were statistically significant (p&lt;0.005, Wilcoxon signed rank test). When 6-month data are available for the final subject, the randomization will be unblinded by the statistician and the primary study question will be addressed.

Conclusion

While pending final analysis of the primary (blinded) endpoint, preliminary analysis indicates favorable modulation of cytomorphology and proliferation by the aromatase inhibitor letrozole in high risk post-menopausal women taking hormone replacement therapy.

Funding: NIH RO1 CA122577; Novartis Pharmaceuticals Corp.

Citation Format: Carol J Fabian, Bruce F Kimler, Jennifer L Nydegger, Trina Metheny, Carola M Zalles, Brian K Petroff, Hung-wen Yeh, Michael D Alvarado. Initial report of a randomized trial of letrozole in high risk women taking hormone replacement therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-12-03.

Tamoxifen prevents apoptosis and follicle loss from cyclophosphamide in cultured rat ovaries

Recent studies documented that the selective estrogen receptor modulator tamoxifen prevents follicle loss and promotes fertility following in vivo exposure of rodents to irradiation or ovotoxic cancer drugs, cyclophosphamide and doxorubicin. In an effort to characterize the ovarian-sparing mechanisms of tamoxifen in preantral follicle classes, cultured neonatal rat ovaries (Day 4, Sprague Dawley) were treated for 1-7 days with active metabolites of cyclophosphamide (i.e., 4-hydroxycyclophosphamide; CTX) (0, 1, and 10 μM) and tamoxifen (i.e., 4-hydroxytamoxifen; TAM) (0 and 10 μM) in vitro, and both apoptosis and follicle numbers were measured. CTX caused marked follicular apoptosis and follicular loss. TAM treatment decreased follicular loss and apoptosis from CTX in vitro. TAM alone had no effect on these parameters. IGF-1 and IGF-1 receptor were assessed in ovarian tissue showing no impact of TAM or CTX on these endpoints. Targeted mRNA analysis during follicular rescue by TAM revealed decreased expression of multiple genes related to inflammation, including mediators of lipoxygenase and prostaglandin production and signaling (Alox5, Pla2g1b, Ptgfr), cytokine binding (Il1r1, Il2rg ), apoptosis (Tnfrsf1a), second messenger signaling (Mapk1, Mapk14, Plcg1), as well as tissue remodeling and vasodilation (Bdkrb2, Klk15). The results suggest that TAM protects the ovary from CTX-mediated toxicity through direct ovarian actions that oppose follicular loss.

Challenges and Potential for Ovarian Preservation with SERMs

Tamoxifen (TAM) is a selective estrogen receptor modulator with tissue-specific effects on estrogen signaling used predominantly for treatment and chemoprevention of breast cancers. Recent studies have shown that TAM prevents infertility and decreases follicular loss from common cancer chemotherapy and radiation therapy in preclinical models. Here we review current and novel uses of selective estrogen receptor modulator s and advantages and challenges for translation of TAM for human fertility preservation.

Ovarian autoimmune disease: clinical concepts and animal models

The ovary is not an immunologically privileged organ, but a breakdown in tolerogenic mechanisms for ovary-specific antigens has disastrous consequences on fertility in women, and this is replicated in murine models of autoimmune disease. Isolated ovarian autoimmune disease is rare in women, likely due to the severity of the disease and the inability to transmit genetic information conferring the ovarian disease across generations. Nonetheless, autoimmune oophoritis is often observed in association with other autoimmune diseases, particularly autoimmune adrenal disease, and takes a toll on both society and individual health. Studies in mice have revealed at least two mechanisms that protect the ovary from autoimmune attack. These mechanisms include control of autoreactive T cells by thymus-derived regulatory T cells, as well as a role for the autoimmune regulator (AIRE), a transcriptional regulator that induces expression of tissue-restricted antigens in medullary thymic epithelial cells during development of T cells. Although the latter mechanism is incompletely defined, it is well established that failure of either results in autoimmune-mediated targeting and depletion of ovarian follicles. In this review, we will address the clinical features and consequences of autoimmune-mediated ovarian infertility in women, as well as the possible mechanisms of disease as revealed by animal models.

The prognostic value of BRCA1 promoter methylation in early stage triple negative breast cancer

Introduction

Methylation of the BRCA1 promoter is frequent in triple negative breast cancers (TNBC) and results in a tumor phenotype similar to BRCA1-mutated tumors. BRCA1 mutation-associated cancers are more sensitive to DNA damaging agents as compared to conventional chemotherapy agents. It is not known if there is an interaction between the presence of BRCA1 promoter methylation (PM) and response to chemotherapy agents in sporadic TNBC. We sought to investigate the prognostic significance of BRCA1 PM in TNBC patients receiving standard chemotherapy.

Methods

Subjects with stage I-III TNBC treated with chemotherapy were identified and their formalin-fixed paraffin-embedded (FFPE) tumor specimens retrieved. Genomic DNA was isolated and subjected to methylation-specific PCR (MSPCR).

Results

DNA was isolated from primary tumor of 39 subjects. BRCA1 PM was detected in 30% of patients. Presence of BRCA1 PM was associated with lower BRCA1 transcript levels, suggesting epigenetic BRCA1 silencing. All patients received chemotherapy (anthracycline:90%, taxane:69%). At a median follow-up of 64 months, 46% of patients have recurred and 36% have died. On univariate analysis, African-American race, node positivity, stage, and BRCA1 PM were associated with worse RFS and OS. Five year OS was 36% for patients with BRCA1 PM vs. 77% for patients without BRCA1 PM (p=0.004). On multivariable analysis, BRCA1 PM was associated with significantly worse RFS and OS.

Conclusions

We show that BRCA1 PM is common in TNBC and has the potential to identify a significant fraction of TNBC patients who have suboptimal outcomes with standard chemotherapy.

Abstract P4-10-01: High dose omega-3 fatty acid supplementation modulates breast tissue biomarkers in post-menopausal women at high risk for development of breast cancer

Background: We conducted a pilot study of high dose omega-3 fatty acid (FA) supplementation in post-menopausal women to determine if risk biomarkers for breast cancer in benign breast tissue sampled by random peri-areolar aspiration (RPFNA) could be favorably modulated and to acquire preliminary data on possible mechanism of action.

Methods: 35 post-menopausal women at increased risk for breast cancer were accrued to a trial of 6-month intervention with 4 g daily of omega-3-acid ethyl esters [1.86 g eicosapentaenoic acid (EPA), 1.5 g docosahexaenoic acid (DHA)]. Subjects had RPFNA performed pre- and post-intervention and specimens evaluated for cytomorphology and proliferation (Ki-67). FA composition was determined in plasma, red blood cells, and RPFNA specimens. Additional specimens were frozen for assessment of hormones, a panel of 11 adipokines and cytokines by Luminex, and gene expression.

Results: 34 subjects completed study with specimens evaluable for change in biomarkers. The ratio of (EPA+DHA):Arachidonic Acid (AA) levels in erythrocyte phospholipid increased significantly by a median of 2.7-fold. Although there was a significant decrease in blood EPA+DHA between discontinuation at 6 months and 2 weeks later when RPFNA was performed, all ratios were above the baseline value (median 1.6-fold). There was favorable but not statistically significant modulation for cytologic evidence of atypia (53% at baseline to 41% at off-study). However, favorable modulation was exhibited for Masood score (medians of 15 to 14; p = 0.014), number of epithelial cells recovered (p = 0.019) and Ki-67 expression (medians of 1.7% to 0.75%, p = 0.036, despite 8 subjects having no Ki-67 expression at baseline). Luminex assay of serum indicated a statistically significant increase (p = 0.003) for adiponectin and decrease (p = 0.016) for TNF-alpha between baseline and off-study. For RPFNA specimens, there was a significant decrease (P = 0.001) in MCP-1 levels adjusted for protein content. By ELISA, serum high molecular weight adiponection increased (p = 0.046) and molar ratio of IGF-1:IGFBP3 decreased (p = 0.006). Note that all analyses were exploratory and without correction for multiple analyses.

Conclusion: Favorable modulation of a variety of blood and tissue risk biomarkers, including cytomorphology and proliferation, along with good tolerability suggests that high dose omega-3 FA esters should be tested further in a placebo-controlled trial.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-10-01.

Favorable modulation of benign breast tissue and serum risk biomarkers is associated with > 10 % weight loss in postmenopausal women

We conducted a phase II feasibility study of a 6-month behavioral weight loss intervention in postmenopausal overweight and obese women at increased risk for breast cancer and the effects of weight loss on anthropomorphic, blood, and benign breast tissue biomarkers. 67 women were screened by random peri-areolar fine-needle aspiration, 27 were registered and 24 participated in the interventional phase. The 24 biomarker evaluable women had a median baseline BMI of 34.2 kg/m(2) and lost a median of 11 % of their initial weight. Significant tissue biomarker modulation after the 6-month intervention was noted for Ki-67 (if restricted to the 15 women with any Ki-67 at baseline, p = 0.041), adiponectin to leptin ratio (p = 0.003); and cyclin B1 (p = 0.001), phosphorylated retinoblastoma (p = 0.005), and ribosomal S6 (p = 0.004) proteins. Favorable modulation for serum markers was observed for sex hormone-binding globulin (p < 0.001), bioavailable estradiol (p < 0.001), bioavailable testosterone (p = 0.033), insulin (p = 0.018), adiponectin (p = 0.001), leptin (p < 0.001), the adiponectin to leptin ratio (p < 0.001), C-reactive protein (p = 0.002), and hepatocyte growth factor (p = 0.011). When subdivided by <10 or >10 % weight loss, change in percent total body and android (visceral) fat, physical activity, and the majority of the serum and tissue biomarkers were significantly modulated only for women with >10 % weight loss from baseline. Some factors such as serum PAI-1 and breast tissue pS2 (estrogen-inducible gene) mRNA were not significantly modulated overall but were when considering only those with >10 % weight loss. In conclusion, a median weight loss of 11 % over 6 months resulted in favorable modulation of a number of anthropomorphic, breast tissue and serum risk and mechanistic markers. Weight loss of 10 % or more should likely be the goal for breast cancer risk reduction studies in obese women.

High-dose omega-3 fatty acid supplementation to modulate breast tissue biomarkers in premenopausal women at high risk for development of breast cancer

1515

Background: We conducted a pilot study of high dose omega-3 fatty acid (FA) supplementation in pre-menopausal women to determine if risk biomarkers for breast cancer in benign breast tissue sampled by random peri-areolar aspiration (RPFNA) could be favorably modulated and to acquire preliminary data on possible mechanism of action. Methods: 36 pre-menopausal women at increased risk for breast cancer were accrued to a trial of 6-month intervention with 4 g daily of omega-3-acid ethyl esters [1.86 g eicosapentaenoic acid (EPA), 1.5 g docosahexaenoic acid (DHA)]. To date, 31 subjects have completed study with RPFNA performed pre- and post-intervention in the follicular phase of the menstrual cycle and specimens evaluated for cytomorphology and proliferation (Ki-67). FA composition was determined in plasma, red blood cells, and RPFNA specimens. Additional specimens were frozen for assessment of hormones, a panel of 11 adipokines and cytokines, and gene expression. Results: The ratio of (EPA+DHA):Arachidonic Acid (AA) levels increased significantly in plasma and erythrocytes by a median of three-fold. There was a significant decrease in blood EPA+DHA between discontinuation at 6 months and 2 weeks later when RPFNA was performed. Despite that, there was favorable modulation for cytologic evidence of atypia (81% at baseline to 42% at off-study; p=0.003), Masood score (medians of 15 to 14; p=0.001), number of epithelial cells recovered (p=0.004) and Ki-67 expression (p=0.025 for 30 women with any Ki-67 at baseline, medians of 1.9% to 0.9%). Serum assays have been completed for 24 subjects. No statistically significant changes were observed for estradiol, testosterone, progesterone, SHBG, IGF-1, IGFBP-3. There was a trend (p=0.056) towards a decrease in resistin. To date, only two subjects have discontinued the study early; grade 2 or greater gastrointestinal side effects have been reported by only two subjects. Conclusions: Favorable modulation of tissue risk biomarkers, cytologic atypia and proliferation along with good tolerability suggests that high dose omega-3 FA esters should be tested further in a placebo controlled trial. Clinical trial information: NCT01252277.

Assessment of RNA in human breast tissue sampled by random periareolar fine needle aspiration and ductal lavage and processed as fixed or frozen specimens

Ductal lavage (DL) and random periareolar fine needle aspiration (RPFNA) have both been proposed as minimally invasive techniques to sample breast tissue during breast cancer prevention trials. Laser capture microdissection (LCM), linear RNA amplification and quantitative real-time polymerase chain reaction (qPCR) theoretically overcome the limitations of small specimen size obtained with DL and RPFNA. In order to test the yield, relative stability and amplifiability of RNA from fixed and archived RPFNA and DL specimens, breast tissue was sampled from individual high risk women (n=9) by both DL and RPFNA. RPFNA samples showed good RNA/cDNA yield and amplification while only 2 of 9 of the paired DL specimens had cDNA of adequate quality for subsequent PCR. One and two rounds of linear amplification provided approximately a 200- and 20,000-fold enrichment of RNA, respectively. PCR analysis consistently detected ER and COX-1 mRNA in the majority of RPFNA samples examined while pS2, PCNA, VEGF and survivin expression varied with subject. RNA yield and/or stability was greater for fixed and archived RPFNA than DL specimens of breast tissue. In a subsequent study examining an expanded biomarker gene panel in fixed vs. frozen RPFNA samples, mRNA profiles and ranked relative mRNA abundance were similar (r=0.89) for frozen and fixed RPFNA specimens. In summary, frozen RPFNA samples may be optimal for RNA endpoints in human breast cancer prevention trials but fixed RPFNA specimens allow similar analyses with greater convenience.

A case for combined ovarian and breast cancer prevention

Targeted prevention of ovarian cancer is hindered by the inaccessibility of ovarian tissue, lack of accepted biomarkers and low disease incidence. However, ovarian cancer has common risk factors and shared etiologies with breast cancer. Chemoprevention of ovarian cancer has been demonstrated incidentally during testing of novel breast cancer prevention drugs. Here it is hypothesized that the development of combined ovarian and breast cancer prevention strategies is a preferable strategy for ovarian cancer prevention.

Reduction in Ki-67 in benign breast tissue of high-risk premenopausal women with the SERM acolbifene

520

Background: Selective Estrogen Receptor Modulators (SERMs) are approved for reduction of risk for breast cancer; however, uptake and use is limited. We conducted a pilot study of a 4th generation SERM to determine tolerability and effect on tissue biomarkers in healthy women at high risk for development of breast cancer. Methods: Premenopausal women at elevated risk for breast cancer were screened by random periareolar fine needle aspiration (RPFNA) performed during the follicular phase of the menstrual cycle. Women were eligible if breast epithelial cells exhibited evidence of cytologic hyperplasia with or without atypia, as well as Ki-67 ≥2% by immunocytochemistry. Following 6-8 months of open-label acolbifene (20 mg/d), the RPFNA was repeated. The primary endpoint was modulation of the proportion of cells that expressed Ki-67. Body composition (DEXA), pelvic sonography, mammographic breast density, and serum levels of IGF-1/IGFBP3 and several bioavailable hormones were assessed pre and post intervention. Results: 76 women were screened by RPFNA, with 25 eligible and enrolled in the intervention over a 9 month period. All 25 (7 on oral contraceptives) subjects completed the study, had a second RPFNA, and were evaluable. Median Ki-67 at baseline was 4.6% (range 2.4 – 21.9%) and off study 1.4% (range 0 – 6.6%); median change was a reduction of 3.0% (range -20.2% to +2.8%; decreased in 23, increased in 2) or a relative reduction of 77%. The end-of-study Ki-67 was significantly less than baseline (p<0.001, 2-tailed Wilcoxon test). There were no statistically significant changes in cytomorphology over this short intervention period. There was a marginal effect on breast density (16 decreased; 8 increased; p=0.067). Adverse events were minimal with greatest grade of 3 reported by 2 subjects, grade 2 by 7 subjects, and grade 1 by 11 subjects. No serious adverse event was reported and no subject discontinued the study due to an AE. Conclusions: Based on preliminary evaluation showing favorable modulation of proliferation and minimal adverse events, further investigation of acolbifene, a fourth generation SERM, as a breast cancer chemoprevention agent for premenopausal women appears warranted. Supported by NO1-CN-35135.

The autoimmune regulator prevents premature reproductive senescence in female mice

Loss-of-function mutations in the autoimmune regulator (AIRE) gene are responsible for autoimmune polyglandular syndrome type 1 (APS-1), which commonly manifests as infertility in women. AIRE is a transcriptional regulator that promotes expression of tissue-restricted antigens in the thymus, including antigens specific to the ovary. Thymic expression of ovarian genes under AIRE's control may be critical for preventing ovarian autoimmune disease. Because mice lacking Aire are an important APS-1 model, we examined the reproductive properties of female Aire-deficient (Aire(-/-)) mice. Female Aire(-/-) mice on the BALB/c background were examined for reproductive parameters, including fertility, litter sizes, and ovarian follicular reserves. Although delayed puberty was observed in Aire(-/-) mice, all mice entered puberty and exhibited mating behavior. Only 50% of Aire(-/-) females gave an initial litter, and only 16% were able to produce two litters. Ovarian histopathologic examination revealed that 83% of previously bred females lost all ovarian follicular reserves. Among virgin females, follicular depletion was observed in 25% by 8 wk, and by 20 wk, 50%-60% of mice lost all follicles. This was associated with elevated serum follicle-stimulating hormone level and ovarian infiltration of proliferating CD3+ T lymphocytes. Ovulation rates of 6-wk-old Aire(-/-) mice were reduced by 22%, but this difference was not statistically significant. Finally, transplantation experiments revealed that follicular loss depended on factors extrinsic to the ovary. These results suggest that immune-mediated ovarian follicular depletion is a mechanism of infertility in Aire(-/-) mice. The results have important implications in the pathogenesis of ovarian autoimmune disease in women.

The aryl hydrocarbon receptor agonist 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) alters early embryonic development in a rat IVF exposure model

Aryl hydrocarbon receptor (AHR) ligands, including 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD), accelerate reproductive senescence and one proposed target is the early embryo. To discriminate between direct effects on the oocyte and early embryo and those mediated by complex ovarian interactions with TCDD, IVF was carried out in the presence of TCDD (10, 100 nM) and the aryl hydrocarbon antagonist CH-223191 (1 μM) combined factorially. TCDD-induced Cyp1a1 mRNA expression was absent in 2-cell embryos; however morulae exhibit dose-dependent Cyp1a1 expression. TCDD induced accumulation of sperm in the perivitelline space and displacement of blastomere nuclei. At 100 nM TCDD, aberrations in cytokinesis and nuclear positioning were observed 2-cell embryos and morula and these effects were reversed in the presence of CH-223191. Our data suggest that acute exposure to TCDD has direct effects on early development in the rat that permit discrimination of AHR-mediated and AHR-independent mechanisms through which environmental toxicants impair mammalian reproduction.

Reduction in Ki-67 in benign breast tissue of high-risk women with the lignan secoisolariciresinol diglycoside

Preclinical and correlative studies suggest reduced breast cancer with higher lignan intake or blood levels. We conducted a pilot study of modulation of risk biomarkers for breast cancer in premenopausal women after administration of the plant lignan secoisolariciresinol given as the diglycoside (SDG). Eligibility criteria included regular menstrual cycles, no oral contraceptives, a >3-fold increase in 5-year risk, and baseline Ki-67 of ≥2% in areas of hyperplasia in breast tissue sampled by random periareolar fine-needle aspiration (RPFNA) during the follicular phase of the menstrual cycle. SDG (50 mg/d) was given for 12 months, followed by repeat RPFNA. The primary end point was change in Ki-67. Secondary end points included change in cytomorphology, mammographic breast density, serum bioavailable estradiol and testosterone insulin-like growth factor-I and IGF-binding protein-3, and plasma lignan levels. Forty-five of 49 eligible women completed the study with excellent compliance (median = 96%) and few serious side effects (4% grade 3). Median plasma enterolactone increased ∼9-fold, and total lignans increased 16-fold. Thirty-six (80%) of the 45 evaluable subjects showed a decrease in Ki-67, from a median of 4% (range, 2-16.8%) to 2% (range, 0-15.2%; P < 0.001, Wilcoxon signed rank test). A decrease from baseline in the proportion of women with atypical cytology (P = 0.035) was also observed. Based on favorable risk biomarker modulation and lack of adverse events, we are initiating a randomized trial of SDG versus placebo in premenopausal women.

The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin disturbs the establishment and maintenance of cell polarity in preimplantation rat embryos

Maternal exposure to the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces a variety of defects in compaction-stage embryos, including monopolar spindle formation, errors in chromosome segregation, and fragmentation resulting from aberrant cytokinesis. In this study, we investigated the possibility that a failure in centrosome duplication, separation, or positioning within blastomeres might underlie the observed effects of TCDD on early embryos. The subcellular localization of the centrosomal marker TUBG1 was analyzed in preimplantation embryos collected from female rats exposed to either chronic (50 ng kg(-1) wk(-1) for 3 wk) or acute (50 ng/kg or 1 microg/kg at proestrus) doses of TCDD. In treated embryos, interphase TUBG1 foci were more abundant and cortically displaced when compared to those in controls. At prophase, some blastomeres exhibited a single large perinuclear TUBG1 aggregate, suggesting a failure in centrosome duplication or separation. Furthermore, the presence of monopolar spindles at metaphase was confirmed by the localization of TUBG1 to the single spindle pole. Therefore, the misregulation of centrosome number and localization, as indicated by TUBG1 staining, may contribute to errors in chromosome segregation and cytokinesis in embryos following maternal TCDD exposure.

Temporal and anatomical sensitivities to the aryl hydrocarbon receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin leading to premature acyclicity with age in rats

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates diverse dioxin toxicities. While the acute effects of activation of the AhR pathway by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been a focus of past study, the role of this pathway in normal physiology and ageing is unclear. The purpose of this study was to identify the portion of the reproductive axis [ovary vs. hypothalamus and pituitary gland (H-H axis)] and the stages of the reproductive lifespan (foetal and early post-natal life vs. adolescence and adulthood) that are particularly sensitive to the effects of TCDD during female reproductive ageing. Adult pregnant Lewis rat dams were dosed with corn oil vehicle or TCDD (50 ng/kg-week by gavage) on days 14 and 21 of gestation and post-natal days 7 and 14 to provide in utero and lactational (IUL) exposure to pups. Female pups (n = 96) were weaned on post-natal day 21 and dosed with TCDD or vehicle weekly. Half of the pups were used as donors for ovary transplantation while the remainder were recipients. Following ovary transplantation, rats (n = 6-8 per group) received weekly TCDD or vehicle again until sacrifice at 8 months of age. Beginning at vaginal opening, reproductive cycles were monitored by vaginal cytology for 10 days each month. Blood samples were collected at 22.00 h on proestrus to measure concentration of 17beta-oestradiol in serum. Real-time PCR was used to determine differences in Cyp1a1, Cyp19a1, Cyp17a1, LH receptor (LHR), FoxA2 and FoxJ1 genes expression between control and remaining groups. IUL exposure of the H-H axis plus adult exposure of the whole body to TCDD significantly delayed puberty in females rats. Data analysis revealed an accelerated onset of acyclicity by 5 months in all groups involving IUL exposure of the developing ovary to TCDD. 17beta-oestradiol was significantly decreased in animals receiving TCDD during IUL exposure of the H-H axis. CYP1a1 expression was markedly greater in the liver than in ovarian tissue and correlated with ongoing TCDD exposure. Aromatase, 17alpha-hydroxylase and LHR gene expressions were largely unchanged (or occasionally elevated) by TCDD. FoxA2 and FoxJ1 mRNAs were similarly of limited value mechanistically, although FoxJ1 was much higher in TTT females (receiving TCDD as donor, recipient and adult). This study reveals a particular sensitivity of the developing ovary to TCDD leading to early loss of reproductive function with age.

Effects of phytoestrogen daidzein and estradiol on steroidogenesis and expression of estrogen receptors in porcine luteinized granulosa cells from large follicles

The aims of the study were to compare the in vitro effects of daidzein or 17beta-estradiol (E(2)) on: 1) progesterone (P(4)) secretion by luteinized granulosa cells harvested from large porcine follicles, as well as 2) estrogen receptor alpha and beta (ERalpha and ERbeta) mRNA and protein expression in the cells. In addition, the effect of daidzein on E(2) secretion and viability of the granulosa cells was examined. We found that basal and gonadotropin-stimulated P(4) secretion were inhibited in granulosa cells cultured in the presence of daidzein either for 24 or 48 hours. In contrast to daidzein, E(2) reduced P(4) secretion only during 24-hour cell cultures increasing it during longer cultures. Daidzein did not affect E(2) secretion by granulosa cells. The expression of ERalpha and ERbeta mRNA, as well as ERbeta protein, was up-regulated by daidzein but unaffected by E(2). To conclude, the soy estrogen daidzein acts directly on the porcine ovary to decrease progesterone production and to increase expression of ERbeta mRNA and protein. Daidzein actions in porcine luteinized granulosa cells differ from those of estradiol and it may suggest disadvantageous effects of the phytoestrogen on reproductive processes in females.

Effect of chronic exposure to the aryl hydrocarbon receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin in female rats on ovarian gene expression

The aryl hydrocarbon receptor (AHR) mediates the effects of many endocrine disruptors and contributes to the loss of fertility in polluted environments. Female rats exposed chronically to environmentally relevant doses of the AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) across their lifespan experience accelerated reproductive senescence preceded by ovarian endocrine disruption. The purpose of this study was to determine the changes in ovarian gene expression that accompany the loss of ovarian function caused by chronic exposure to TCDD. Beginning in utero, female Sprague-Dawley rats received TCDD (1, 5, 50, or 200 ng/kg-week; n=4 per group) or vehicle weekly throughout their lifespan, and were sacrificed on diestrus just prior to loss of reproductive cyclicity at 11 months of age. Microarray analysis was used to determine differences in ovarian gene expression between control and TCDD-treated (200 ng/kg-week) animals. To confirm microarray results, real-time PCR was used to assess changes in gene expression among treatment groups. TCDD treatment decreased (p<0.05) proestrus serum estradiol concentrations with no effect on serum progesterone. In ovaries from rats treated with 200 ng/kg-week TCDD compared to controls, 19 genes of known function were found to be up-regulated, while 31 ovarian genes were found to be down-regulated >or=1.5-fold (p<or=0.05). Gene expression of 17 alpha-hydroxylase decreased following chronic TCDD treatment, suggesting the decrease in estradiol biosynthesis may be a consequence of decreased substrate. Taken together with past studies indicating a lack of effect on hypothalamus or pituitary function, the apparent regulation of key ovarian genes support the hypothesis that chronic TCDD exposure directly affects ovarian function.

Tamoxifen prevents premalignant changes of breast, but not ovarian, cancer in rats at high risk for both diseases

Women at increased risk for breast cancer are at increased risk for ovarian cancer as well, reflecting common risk factors and intertwined etiology of the two diseases. We previously developed a rat model of elevated breast and ovarian cancer risk, allowing evaluation of dual-target cancer prevention strategies. Tamoxifen, a Food and Drug Administration-approved breast cancer chemoprevention drug, has been shown to promote ovarian cysts in premenopausal women; however, the effect of tamoxifen on ovarian cancer risk is still controversial. In the current experiment, Fischer 344 rats (n = 8 per treatment group) received tamoxifen (TAM) or vehicle (control) in factorial combination with combined breast and ovarian carcinogen (17beta-estradiol and 7,12 dimethylbenza[a]anthracene, respectively). Mammary and ovarian morphologies were normal in the control and TAM groups. Carcinogen (CARC) treatment induced mammary dysplasia with elevated cell proliferation and reduced estrogen receptor-alpha expression and promoted preneoplastic changes in the ovary. In the CARC + TAM group, tamoxifen reduced preneoplastic changes and proliferation rate in the mammary gland, but not in the ovary, compared with rats treated with carcinogen alone. Putative stem cell markers (Oct-4 and aldehyde dehydrogenase 1) were also elevated in the mammary tissue by carcinogen and this expansion of the stem cell population was not reversed by tamoxifen. Our study suggests that tamoxifen prevents early progression to mammary cancer but has no effect on ovarian cancer progression in this rat model.

The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin disrupts morphogenesis of the rat pre-implantation embryo

Background

Environmental toxicants, whose actions are often mediated through the aryl hydrocarbon receptor (AhR) pathway, pose risks to the health and well-being of exposed species, including humans. Of particular concern are exposures during the earliest stages of development that while failing to abrogate embryogenesis, may have long term effects on newborns or adults. The purpose of this study was to evaluate the effect of maternal exposure to the AhR-specific ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the development of rat pre-implantation embryos with respect to nuclear and cytoskeletal architecture and cell lineage allocation.

Results

We performed a systematic 3 dimensional (3D) confocal microscopy analysis of rat pre-implantation embryos following maternal exposure to environmentally relevant doses of TCDD. Both chronic (50 ng/kg/wk for 3 months) and acute (50 ng/kg and 1 μg/kg at proestrus) maternal TCDD exposure disrupted morphogenesis at the compaction stage (8–16 cell), with defects including monopolar spindle formation, f-actin capping and fragmentation due to aberrant cytokinesis. Additionally, the size, shape and position of nuclei were modified in compaction stage pre-implantation embryos collected from treated animals. Notably, maternal TCDD exposure did not compromise survival to blastocyst, which with the exception of nuclear shape, were morphologically similar to control blastocysts.

Conclusion

We have identified the compaction stage of pre-implantation embryogenesis as critically sensitive to the effects of TCDD, while survival to the blastocyst stage is not compromised. To the best of our knowledge this is the first in vivo study to demonstrate a critical window of pre-implantation mammalian development that is vulnerable to disruption by an AhR ligand at environmentally relevant doses.

Ovarian Endocrine Disruption Underlies Premature Reproductive Senescence Following Environmentally Relevant Chronic Exposure to the Aryl Hydrocarbon Receptor Agonist 2,3,7,8-Tetrachlorodibenzo-p-Dioxin1

The aryl hydrocarbon receptor (AHR) mediates the effects of many endocrine disruptors and contributes to the loss of fertility in polluted environments. While previous work has focused on mechanisms of short-term endocrine disruption and ovotoxicity in response to AHR ligands, we have shown recently that chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces premature reproductive senescence in female rats without depletion of ovarian follicular reserves. In the current study, premature reproductive senescence was induced using a range of low-dose exposure to TCDD (0, 1, 5, 50, and 200 ng kg(-1) wk(-1)) beginning in utero and continuing until the transition to reproductive senescence. Doses of 50 and 200 ng TCDD kg(-1) wk(-1) delayed the age at vaginal opening and accelerated the loss of normal reproductive cyclicity with age without depletion of follicular reserves. Serum estradiol concentrations were decreased in a dose-dependent fashion (> or = 5 ng kg(-1) wk(-1)) across the estrous cycle in perisenescent rats still displaying normal cyclic vaginal cytology. Serum FSH, LH, and progesterone profiles were unchanged by TCDD. The loss of reproductive cyclicity following chronic exposure to TCDD was not accompanied by decreased responsiveness to GnRH. Ovarian endocrine disruption is the predominant functional change preceding the premature reproductive senescence induced by chronic exposure to low doses of the AHR-specific ligand TCDD.

Reduction in proliferation with six months of letrozole in women on hormone replacement therapy

The objective of this study was to determine if 6 months of the aromatase inhibitor letrozole, administered to postmenopausal women taking a stable dose of hormone replacement remedy, would be safe and would modulate biomarkers of breast cancer risk. The intent was to reduce the proliferation marker Ki-67 while maintaining adequate systemic levels of estradiol so as to avoid perimenopausal symptoms. Postmenopausal women at high risk for development of breast cancer and taking a stable dose of estrogen or estrogen plus progestin were screened by random periareolar fine needle aspiration (RPFNA). To be eligible, the acquired breast epithelial cells had to be characterized as cytologic atypia or borderline atypia with > or =1,000 epithelial cells on the cytomorphology slide; plus > or =500 epithelial cells on a slide processed for Ki-67 immunocytochemistry. Forty-two women were enrolled in the one arm study and received 2.5 mg letrozole per day for 6 months, followed by repeat assessment of biomarkers. Ki-67 was reduced by a median relative value of 66%. There was no significant change in breast cell cytomorphology; ER weighted index score; serum estradiol, testosterone, or IGF-1:IGFBP-3 ratio; mammographic breast density, or frequency or severity of perimenopausal symptoms. Given the dramatic reduction in proliferation, the effect of letrozole on risk and response biomarkers should be explored further in a randomized, placebo-controlled Phase IIB breast cancer chemoprevention trial.

Optimization of estrogen receptor analysis by immunocytochemistry in random periareolar fine-needle aspiration samples of breast tissue processed as thin-layer preparations

Immunostaining of estrogen receptor alpha (ER) in samples of benign breast tissue obtained by random periareolar fine-needle aspiration (RPFNA) is a practical tool for breast cancer chemoprevention trials. The authors report an optimized method of ER immunostaining for use with thin-layer preparations of modified Cytolyt-fixed benign breast tissue acquired by RPFNA. Samples of benign breast tissue and MCF-7 controls processed as thin-layer preparations were tested for the effects of antibody titer, antigen retrieval temperature (90 degrees or 115 degrees C), buffer (20% nuclear decloaker, pH 9.3; 10 mM citrate buffer, pH 6), and blocking solution (0.01% glucose oxidase or 0.3% H2O2) on ER immunostaining. The prevalence of positively stained breast epithelial cells, mean intensity of ER staining, and composite immunostaining score were evaluated for effect of immunostaining protocol. RPFNA samples and MCF-7 cells processed using nuclear decloaker and low-temperature antigen retrieval had more ER-positive cells (P<0.0001) and increased mean staining intensity and weighted staining indices (P<0.05) compared with samples prepared with citrate buffer and high-temperature antigen retrieval. Glucose oxidase increased ER-positive cells in comparison to hydrogen peroxide (P<0.04) when combined with low-temperature antigen retrieval and the use of nuclear decloaker. Staining was negative for all non-immune controls regardless of protocol. The combination of low-temperature antigen retrieval, diluted commercial nuclear decloaker solution, and a glucose oxidase blocking step yielded optimal ER immunostaining for thin-layer preparations of benign breast tissue harvested by RPFNA.

Detection of biomarker gene expression by real-time polymerase chain reaction using amplified ribonucleic acids from formalin-fixed random periareolar fine needle aspirates of human breast tissue

OBJECTIVE

To address the detection of breast cancer biomarker gene expression in formalin-fixed random periareolar fine needle aspiration (RPFNA) samples of benign breast tissue collected during breast cancer prevention trials by quantitative real-time polymerase chain reaction (qPCR).

STUDY DESIGN

Formalin-fixed breast epithelial cells collected by RPFNA and processed as thin layer preparations were isolated by laser capture microdissection (LCM). Ribonucleic acid (RNA) was extracted and amplified using a single round of T7-based linear amplification followed by quality assessment and biomarker assay using TaqMan chemistry.

RESULTS

More than 80% of RPFNA samples yielded RNA of sufficient quantity and quality for measurement of a panel of biomarker genes following a single round of linear amplification. RNA and protein expression for estrogen receptor alpha, as assessed by LCM/qPCR and immunohistochemistry, were correlated. Amplification plots were similar for cDNA standards and cDNA derived from RPFNA samples.

CONCLUSION

Assessment of gene expression using amplified RNA from microdissected formalin-fixed RPFNAs can increase the number of biomarkers used during breast cancer chemoprevention trials.

Expression of enzymes of cyclooxygenase pathway and secretion of prostaglandin E2 and F2α by porcine myometrium during luteolysis and early pregnancy

Past studies of uterine prostaglandin (PGs) and pig reproduction have focused on endometrial rather than myometrial PGs. This study documents the synthesis and secretion of myometrial prostaglandins (PGs) in pigs and the involvement of oxytocin (OT) in these processes. Cyclooxygenase-2 (COX-2) expression was similar in myometrial explants from cyclic and pregnant pigs (days 14-16) and OT (10(-7) M) in vitro significantly increased COX-2 protein regardless of reproductive state. Basal expression of prostaglandin E2 synthase (PGES) was higher during pregnancy than during luteolysis. Conversely, prostaglandin F synthase (PGFS) was highest during luteolysis and lower in myometrium from gravid animals. OT had no influence on the expression of PGES and PGFS. In another tissue culture experiment, myometrial slices produced more PGE2 than PGF2alpha regardless of reproductive state of the female. OT stimulated PGE2 production in myometrium harvested during luteolysis and increased PGF2alpha production in all tissues examined. Progesterone (P4; 10(-5) M) blocked stimulatory effect of OT on myometrial PG release. Myometrial OTr mRNA was higher (P=0.03) during luteolysis than during pregnancy.

IN CONCLUSION

(1) oxytocin increases myometrial COX-2 expression, but does not influence the expression of terminal enzymes of PGs synthesis (PGES and PGFS); (2) porcine myometrium preferentially produces PGs during early pregnancy and secretes more PGE2 than PGF2alpha; (3) myometrial OT and OTr support secretion of PGs from myometrium during luteolysis.

Characterization of a preclinical model of simultaneous breast and ovarian cancer progression

Women at increased risk for breast cancer are often also at increased risk for ovarian cancer, reflecting common risk factors and intertwined etiologies for both diseases. Unlike breast cancer prevention, primary ovarian cancer prevention has been impractical due to the low incidence, lack of risk and response biomarkers and difficulties in sampling ovarian tissue. Challenges in the development of ovarian cancer prevention drugs, however, may be circumvented through the development of breast cancer prevention strategies that simultaneously decrease ovarian cancer. In the present study, three commonly used mammary cancer carcinogen models [7,12-dimethylbenz[alpha]anthracene (DMBA), N-methyl-N-nitrosourea (MNU) and estradiol (E2)] were combined with local ovarian DMBA administration to induce progression to mammary and ovarian cancer concurrently in the rat. Animals were treated for 3 or 6 months, and tissue histology as well as proliferation, hormonal and inflammation biomarkers were assessed. Mammary and ovarian morphologies (measured as descriptive histology and dysplasia scores) were normal in vehicle controls. Mammary hyperplasia was observed in DMBA/DMBA (mammary carcinogen/ovarian carcinogen) and MNU/DMBA-treated rats; however, ovarian preneoplastic changes were seldom observed after these treatments. All E2/DMBA-treated rats had mammary hyperplasia, atypia, ductal carcinoma in situ and/or invasive adenocarcinoma, while 50% also developed preneoplastic changes in the ovary (ovarian epithelial and stromal hyperplasia and inclusion cyst formation). In both the mammary gland and ovary, decreased estrogen receptor alpha expression was detected, and in the mammary gland elevated Ki-67 and cyclooxygenase-2 expressions were observed. This combined breast and ovarian cancer rat model (systemic E2 treatment and local ovarian DMBA) may be useful for future dual target breast and ovarian cancer prevention studies.

The effect of progesterone on oxytocin-stimulated intracellular mobilization of Ca2+ and prostaglandin E2 and F2alpha secretion from porcine myometrial cells

Our past studies have shown that porcine myometrium produce prostaglandins (PG) during luteolysis and early pregnancy and that oxytocin (OT) and its receptor (OTr) support myometrial secretion of prostaglandins E2 and F2alpha (PGE2 and PGF2alpha) during luteolysis. This study investigates the role of intracellular Ca2+ [Ca2+]i as a mediator of OT effects on PG secretion from isolated myometrial cells in the presence or absence of progesterone (P4). Basal [Ca2+]i was similar in myometrial cells from cyclic and pregnant pigs (days 14-16). OT (10(-7)M) increased [Ca2+]i in myometrial cells of cyclic and pregnant pigs, although this effect was delayed in myometrium from pregnant females. After pre-incubation of the myocytes with P4 (10(-5)M) the influence of OT on [Ca2+]i)was delayed during luteolysis and inhibited during pregnancy. Myometrial cells in culture produce more PGE2 than PGF2alpha regardless of reproductive state of the female. OT (10(-7)M) increased PGE2 secretion after 6 and 12 h incubation for the tissue harvested during luteolysis and after 12 h incubation when myometrium from gravid females was used. In the presence of P4 (10(-5)M), the stimulatory effect of OT on PG secretion was diminished.

IN CONCLUSION

(1) porcine myometrial cells in culture secrete PG preferentially during early pregnancy and produce more PGE2 than PGF2alpha, (2) OT controls myometrial PGF2alpha secretion during luteolysis, (3) release of [Ca2+]i is associated with the influence of OT on PG secretion, and (4) the effects of OT on PG secretion and Ca2+ accumulation are delayed by P4 during luteolysis and completely inhibited by P4 during pregnancy.

Effects of Acute and Chronic Exposure to the Aryl Hydrocarbon Receptor Agonist 2,3,7,8-Tetrachlorodibenzo-p-Dioxin on the Transition to Reproductive Senescence in Female Sprague-Dawley Rats1

Activation of the aryl hydrocarbon receptor (AHR) can occur in polluted environments, either from smoking-related toxicants or from endogenous ligands. We tested whether acute or chronic exposure to the AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters the transition to reproductive senescence in female Sprague-Dawley rats. In experiment 1, rats (n = 6 per experimental group) received a single dose of 0 or 10 mug/kg of TCDD orally (p.o.) on Postnatal Day 29. Vaginal cytology was monitored for 1 wk each month until rats were killed at 1 yr of age. The single prepubertal exposure to TCDD hastened the transition to reproductive senescence in female rats and was associated with delayed puberty, abnormal cyclicity, and premature reproductive senescence. In a second experiment, rats were exposed to TCDD chronically through weekly dosing (0, 50, or 200 ng kg(-1) wk(-1) p.o., n = 7 each dose) beginning in utero. Lifelong exposure to these lower doses of TCDD induced a dose- and time-dependent loss of normal cyclicity and significantly hastened the onset of the transition to reproductive senescence (P < 0.05). This premature transition to reproductive senescence was associated with prolonged estrous cycles and, at the highest dose of TCDD, persistent estrus or diestrus. The number and size of ovarian follicles were not altered by TCDD. Diestrous concentrations of LH in rats exposed chronically to TCDD were similar to those in controls, whereas progesterone tended to be elevated at both doses of the dioxin (P < 0.08). Serum FSH was elevated in the group exposed to 50 ng/kg of TCDD (P < 0.02), whereas estradiol was decreased at both doses of dioxin (P < 0.01). Data thus far support endocrine disruption rather than depletion of follicular reserves as a primary mechanism of the premature transition to reproductive senescence following activation of the AHR pathway by TCDD in female rats.

Potential roles of the aryl hydrocarbon receptor in female reproductive senescence

The transition to reproductive senescence involves changes in neuroendocrine and ovarian functions, and is accelerated by activation of the aryl hydrocarbon pathway by environmental toxicants such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD). In this article, studies which provide evidence as to the possible mechanisms by which the aryl hydrocarbon receptor (AhR) acts in this capacity (i.e. disruption of ovarian, hypothalamic or suprachiasmatic nucleus function, or any combination of these) are reviewed, along with the normal physiological changes that occur during the transition to reproductive senescence in female humans and rodents. Based on findings that the AhR is evolutionarily conserved and necessary for normal fertility, we suggest that the AhR has not only a pathological but also a physiological role in the process of aging. Studies of realistic lifelong AhR activation by dioxins on the hypothalamic-pituitary-ovarian axis and its impact on the transition to reproductive senescence in the aging female are a previously neglected area of research that warrants further consideration.

Pharmacokinetics of ovarian steroids in Sprague-Dawley rats after acute exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces abnormalities in steroid-dependent processes such as mammary cell proliferation, gonadotropin release and maintenance of pregnancy. In the current study, the effects of TCDD on the pharmacokinetics of 17beta-estradiol and progesterone were examined. Adult Sprague-Dawley rats were ovariectomized and pretreated with TCDD (15 microg/kg p.o.) or vehicle. A single bolus of 17beta-estradiol (E2, 0.3 micromol/kg i.v.) or progesterone (P4, 6 micromol/kg i.v.) was administered 24 hours after TCDD and blood was collected serially from 0-72 hours post-injection. Intravenous E2 and P4 in DMSO vehicle had elimination half-lives of approximately 10 and 11 hours, respectively. TCDD had no significant effect on the pharmacokinetic parameters of P4. The elimination constant and clearance of E2 were decreased by TCDD while the elimination half-life, volume of distribution and area under the time*concentration curve were not altered significantly. Overall, these results indicate that diminished serum progesterone and estradiol concentrations following exposure to TCDD are due primarily to actions on steroid synthesis and release rather than any alterations in pharmacokinetics.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) stimulates gonadotropin secretion in the immature female Sprague-Dawley rat through a pentobarbital- and estradiol-sensitive mechanism but does not alter gonadotropin-releasing hormone (GnRH) secretion by immortalized GnRH neurons in vitro

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces aberrant release of gonadotropins, FSH, and LH and blocks ovulation during induced ovarian follicular development in rats by an unknown mechanism. In the current study, TCDD (0, 8, or 32 microg/kg orally) was administered to immature female Sprague-Dawley rats, and synchronous follicular development was induced 24 h later with equine chorionic gonadotropin (eCG, 5 IU s.c.). Both doses of TCDD induced a significant premature increase in serum FSH and LH (P < 0.05) at 12 h post-eCG. This premature gonadotropin surge was facilitated by the administration of a long-acting estradiol (estradiol cypionate, 0.01, 0.1, and 0.5 mg/kg s.c.), whereas the progesterone and cortisol receptor antagonist RU486 (0, 1, and 10 mg/kg s.c.) potentiated the premature release of FSH and LH following TCDD as well. Pentobarbital (32 mg/kg i.p.) administered at 6 or 9 h, but not 0 h, post-eCG ablated the ability of TCDD to stimulate the release of FSH and LH in vivo. TCDD had no significant effect on GnRH accumulation in vitro from immortalized GnRH neuronal (GT1-7) cells and failed to alter the cell number. Transfection of these cells with a rat GnRH promoter-reporter construct revealed no significant acute effect of TCDD on GnRH promoter activity. Aryl hydrocarbon receptor mRNA was not detected in the GT1-7 cells by reverse transcription polymerase chain reaction. TCDD appears to stimulate premature gonadotropin release in the gonadotropin-primed immature rat by interacting with an estradiol- and pentobarbital-sensitive neural signal for GnRH release but not by acting upon the GnRH neuron directly.

Endocrine disruption by indole-3-carbinol and tamoxifen: blockage of ovulation

Immature Sprague-Dawley rats received daily doses of indole-3-carbinol (I3C, 0-1.5 g/kg/day), 3,3'-diindolymethane (DIM, 0-400 mg/kg/day), tamoxifen (TAM, 0-0.5 mg/kg/day), or vehicle to determine if their antiestrogenic effects occur by the same mechanism and whether I3C's action is mediated by DIM. Follicular development was induced on day 24 of age by equine chorionic gonadotropin (eCG, 5 IU) 1 day after the initial dose. In a hormone replacement study, human chorionic gonadotropin (hCG, 10 IU sc, 48 h post-eCG) was used to mimic a normal preovulatoy luteinizing hormone (LH) surge following treatment with either I3C or TAM. Blood and ovaries were collected throughout follicular development and the number of ova shed was measured on the morning following expected ovulation (72 h post-eCG). I3C but not TAM reduced body weight gain at higher doses after 4 days of dosing. Ovarian weight gain and ovulation were inhibited by both I3C and TAM in a dose-dependent fashion. During the preovulatory period, both I3C and TAM blocked normal LH and follicle-stimulating hormone (FSH) surges and suppressed serum progesterone (P(4)) profoundly without changing circulating levels of estrogen (E(2)). At the time of expected ovulation, serum E(2) was increased in rats receiving I3C or tamoxifen, whereas serum P(4) was dose-dependently decreased. DIM exerted no significant effects on any of the endpoints studied, even at the highest dose, indicating that the antiestrogenic effects of I3C are not mediated by this metabolite of I3C. hCG successfully restored ovarian weight gain and ovulation in TAM-treated rats. However, hCG only partially reversed the blockage of ovulation by I3C, although ovarian weight gain was restored to normal. In summary, both I3C and TAM block ovulation by altering preovulatory concentrations of LH and FSH, but I3C appears to exert its effect(s) by (a) different mechanism(s) of action. I3C seems to act at both the ovarian and hypothalamic levels by mechanisms similar to those seen in TCDD-treated rats, whereas TAM appears to act only on the hypothalamic-pituitary axis as an anti-estrogen.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on serum inhibin concentrations and inhibin immunostaining during follicular development in female Sprague-Dawley rats

Intact and hypophysectomized immature rats were pretreated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 0 or 32 microg/kg p.o.) and sacrificed throughout synchronized follicular development (0, 12, 24, 48, and 72 h after equine chorionic gonadotropin, eCG). TCDD administration to intact rats resulted in a premature elevation of serum FSH and LH by 12 h post-eCG. In intact rats pretreated with TCDD, the intensity of ovarian immunoreactivity for inhibin and the number of ovarian follicles staining for inhibin in midsaggital ovarian sections were decreased at the time of eCG administration (24 h post-TCDD) in comparison to controls. However, this decreased ovarian staining for inhibin was not associated with alterations in serum inhibin concentrations. Serum inhibin was suppressed in TCDD-treated rats when compared to intact controls only at 24 h post-eCG. Hypophysectomized animals exhibited no effect of TCDD on serum inhibin at any timepoint but did have decreased estradiol concentrations during follicular development. In summary, TCDD reduced serum concentrations of inhibin after the premature increases in FSH and LH suggesting that inhibin is not important in the initial elevation of FSH following exposure to TCDD.