Bioassay of steroid hormone agonist and antagonist activities of anti-androgens on mammary gland, seminal vesicles and spleen of male mice

Effects of perinatal exposures to a TAML catalyst on the mammary gland and hormone-sensitive outcomes in male mice

Estrogenic chemicals are common pollutants in wastewater and current effluent treatment processes are not typically effective in removing these compounds. Tetra-amido macrocyclic ligands (TAMLs) are catalysts that mimic endogenous peroxidases that may provide a solution to remove environmental pollutants including low concentrations of estrogenic compounds. Yet relatively little is known about the toxicity of TAMLs, and few studies have evaluated whether they may have endocrine disrupting properties. We administered one of three doses of a TAML, NT7, to mice via drinking water throughout pregnancy and lactation. Two pharmacologically active compounds, ethinyl estradiol (EE2) and flutamide were also included to give comparator data for estrogen receptor agonist and androgen receptor antagonist activities. Male pups were evaluated for several outcomes at weaning, puberty, and early adulthood. We found that EE2 exposures during gestation and the perinatal period induced numerous effects that were observed across the three ages including changes to spleen and testis weight and drastic effects on the morphology of the mammary gland. Flutamide had fewer effects but altered anogenital distance at weaning as well as spleen, liver, and kidney weight. In contrast, relatively few effects of NT7 were observed, but included alterations to spleen weight and modest changes to adult testis weight and morphology of the mammary gland at weaning. Collectively, these results provide some of the first evidence suggesting that NT7 may alter some hormone-sensitive outcomes, but that the effects were distinct from either EE2 or flutamide. Additional studies are needed to characterize the biological activity of this and other TAML catalysts.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Developmental exposure to the DE-71 mixture of polybrominated diphenyl ether (PBDE) flame retardants induce a complex pattern of endocrine disrupting effects in rats

Polybrominated diphenyl ethers (PBDEs) are legacy compounds with continued widespread human exposure. Despite this, developmental toxicity studies of DE-71, a mixture of PBDEs, are scarce and its potential for endocrine disrupting effects in vivo is not well covered. To address this knowledge gap, we carried out a developmental exposure study with DE-71. Pregnant Wistar rat dams were exposed to 0, 40 or 60 mg/kg bodyweight/day from gestation day 7 to postnatal day 16, and both sexes were examined. Developmental exposure affected a range of reproductive toxicity endpoints. Effects were seen for both male and female anogenital distances (AGD), with exposed offspring of either sex displaying around 10% shorter AGD compared to controls. Both absolute and relative prostate weights were markedly reduced in exposed male offspring, with about 40% relative to controls. DE-71 reduced mammary gland outgrowth, especially in male offspring. These developmental in vivo effects suggest a complex effect pattern involving anti-androgenic, anti-estrogenic and maybe estrogenic mechanisms depending on tissues and developmental stages. Irrespective of the specific underlying mechanisms, these in vivo results corroborate that DE-71 causes endocrine disrupting effects and raises concern for the effects of PBDE-exposure on human reproductive health, including any potential long-term consequences of disrupted mammary gland development.

Prenatal Exposure to Unconventional Oil and Gas Operation Chemical Mixtures Altered Mammary Gland Development in Adult Female Mice

Unconventional oil and gas (UOG) operations, which combine hydraulic fracturing (fracking) and directional drilling, involve the use of hundreds of chemicals, including many with endocrine-disrupting properties. Two previous studies examined mice exposed during early development to a 23-chemical mixture of UOG compounds (UOG-MIX) commonly used or produced in the process. Both male and female offspring exposed prenatally to one or more doses of UOG-MIX displayed alterations to endocrine organ function and serum hormone concentrations. We hypothesized that prenatal UOG-MIX exposure would similarly disrupt development of the mouse mammary gland. Female C57Bl/6 mice were exposed to ~3, ~30, ~ 300, or ~3000 μg/kg/d UOG-MIX from gestational day 11 to birth. Although no effects were observed on the mammary glands of these females before puberty, in early adulthood, females exposed to 300 or 3000 μg/kg/d UOG-MIX developed more dense mammary epithelial ducts; females exposed to 3 μg/kg/d UOG-MIX had an altered ratio of apoptosis to proliferation in the mammary epithelium. Furthermore, adult females from all UOG-MIX-treated groups developed intraductal hyperplasia that resembled terminal end buds (i.e., highly proliferative structures typically seen at puberty). These results suggest that the mammary gland is sensitive to mixtures of chemicals used in UOG production at exposure levels that are environmentally relevant. The effect of these findings on the long-term health of the mammary gland, including its lactational capacity and its risk of cancer, should be evaluated in future studies.

The mouse mammary gland as a sentinel organ: distinguishing 'control' populations with diverse environmental histories

BACKGROUND

There are numerous examples of laboratory animals that were inadvertently exposed to endocrine disrupting chemicals (EDCs) during the process of conducting experiments. Controlling contaminations in the laboratory is challenging, especially when their source is unknown. Unfortunately, EDC contaminations can interfere with the interpretation of data during toxicological evaluations. We propose that the male CD-1 mouse mammary gland is a sensitive bioassay to evaluate the inadvertent contamination of animal colonies.

METHODS

We evaluated mammary glands collected from two CD-1 mouse populations with distinct environmental histories. Population 1 was born and raised in a commercial laboratory with unknown EDC exposures; Population 2 was the second generation raised in an animal facility with limited exposures to xenoestrogens from caging, feed, etc. Mammary glands were collected from all animals and evaluated using morphometric techniques to quantify morphological characteristics of the mammary gland.

RESULTS

Population 1 (with suspected history of environmental chemical exposure) and Population 2 (with known limited history of xenoestrogen exposure) were morphologically distinguishable in adult males, prepubertal females, and pubertal females. Mammary glands from males raised in the commercial animal facility were significantly more developed, with larger ductal trees and more branching points. The appearance of these mammary glands was consistent with prior reports of male mice exposed to low doses of bisphenol A (BPA) during early development. In females, the two populations were morphologically distinct at both prepuberty and puberty, with the most striking differences observed in the number, size, and density of terminal end buds, e.g. highly proliferative structures found in the developing mammary gland.

CONCLUSIONS

Collectively, these results suggest that the mouse mammary gland has the potential to be used as a sentinel organ to evaluate and distinguish animal colonies raised in different environmental conditions including potential EDC exposures. Our findings could help researchers that wish to perform a posteriori evaluations to determine whether inadvertent contamination with xenoestrogens (and potentially other EDCs) has occurred in their animal colonies, especially after new materials (feed, caging, water bottles) have been introduced. Finally, our results challenge the relatively common practice of using historical controls in toxicological experiments.

PSA-NCAM in the posterodorsal medial amygdala is necessary for the pubertal emergence of attraction to female odors in male hamsters

During puberty, attention turns away from same-sex socialization to focus on the opposite sex. How the brain mediates this change in perception and motivation is unknown. Polysialylated neural cell adhesion molecule (PSA-NCAM) virtually disappears from most of the central nervous system after embryogenesis, but it remains elevated in discrete regions of the adult brain. One such brain area is the posterodorsal subnucleus of the medial amygdala (MePD). The MePD has been implicated in male sexual attraction, measured here as the preference to investigate female odors. We hypothesize that PSA-NCAM gates hormone-dependent plasticity necessary for the emergence of males' attraction to females. To evaluate this idea, we first measured PSA-NCAM levels across puberty in several brain regions, and identified when female odor preference normally emerges in male Syrian hamsters. We found that MePD PSA-NCAM staining peaks shortly before the surge of pubertal androgen and the emergence of preference. To test the necessity of PSA-NCAM for female odor preference, we infused endo-neuraminidase-N into the MePD to deplete it of PSAs before female odor preference normally appears. This blocked female odor preference, which suggests that PSA-NCAM facilitates behaviorally relevant, hormone-driven plasticity.

Mixtures of environmentally relevant endocrine disrupting chemicals affect mammary gland development in female and male rats

Estrogenic chemicals are able to alter mammary gland development in female rodents, but little is known on the effects of anti-androgens and mixtures of endocrine disrupting chemicals (EDCs) with dissimilar modes of action. Pregnant rat dams were exposed during gestation and lactation to mixtures of environmentally relevant EDCs with estrogenic, anti-androgenic or dissimilar modes of action (TotalMix) of 100-, 200- or 450-fold high end human intake estimates. Mammary glands of prepubertal and adult female and male offspring were examined. Oestrogens increased mammary outgrowth in prepubertal females and the mRNA level of matrix metalloproteinase-3, which may be a potential biomarker for increased outgrowth. Mixtures of EDCs gave rise to ductal hyperplasia in adult males. Adult female mammary glands of the TotalMix group showed morphological changes possibly reflecting increased prolactin levels. In conclusion both estrogenic and anti-androgenic chemicals given during foetal life and lactation affected mammary glands in the offspring.

Regulatory decisions on endocrine disrupting chemicals should be based on the principles of endocrinology

For years, scientists from various disciplines have studied the effects of endocrine disrupting chemicals (EDCs) on the health and wellbeing of humans and wildlife. Some studies have specifically focused on the effects of low doses, i.e. those in the range that are thought to be safe for humans and/or animals. Others have focused on the existence of non-monotonic dose-response curves. These concepts challenge the way that chemical risk assessment is performed for EDCs. Continued discussions have clarified exactly what controversies and challenges remain. We address several of these issues, including why the study and regulation of EDCs should incorporate endocrine principles; what level of consensus there is for low dose effects; challenges to our understanding of non-monotonicity; and whether EDCs have been demonstrated to produce adverse effects. This discussion should result in a better understanding of these issues, and allow for additional dialog on their impact on risk assessment.

The male mammary gland: a target for the xenoestrogen bisphenol A

Males of some strains of mice retain their mammary epithelium even in the absence of nipples. Here, we have characterized the mammary gland in male CD-1 mice both in whole mounts and histological sections. We also examined the effects of bisphenol A (BPA), an estrogen mimic that alters development of the female mouse mammary gland. BPA was administered at a range of environmentally relevant doses (0.25-250μg/kg/day) to pregnant and lactating mice and then the mammary glands of male offspring were examined at several periods in adulthood. We observed age- and dose-specific effects on mammary gland morphology, indicating that perinatal BPA exposures alter the male mammary gland in adulthood. These results may provide insight into gynecomastia, the most common male breast disease in humans, where proliferation of the mammary epithelium leads to breast enlargement.

Mouse bioassay for in vivo screening of oestrogen and progesterone antagonists

This study tested and compared the anti-proliferative and proliferative activities of two anti-oestrogens and three anti-progestins on four separate mouse model systems: young intact and adult ovariectomized (OV-X) females, and young intact and adult castrated males. Pure steroidal anti-oestrogen ICI 182,780 (ICI) decreased mammary and uterine growth stimulated by endogenous hormones in young intact females and by exogenous hormones [progesterone (Prog), 17beta-oestradiol (E) or E plus Prog] in both young intact and adult ovariectomized (OV-X) females. Non-steroidal anti-oestrogen EM-800 (EM), on the other hand, had no effect on mammary and uterine growth stimulated by endogenous hormones in young intact females and in adult OV-X females. Uterine growth was even stimulated by EM alone, and a combination of EM plus Prog not only stimulated uterine growth but also mammary growth (an oestrogenic agonistic activity). However, EM showed anti-oestrogenic activities in both mammary and uterine tissues in females treated with E or E plus Prog. In males, ICI and EM decreased mammary growth stimulated by exogenous hormones (E or E plus Prog) in both young intact and adult castrated animals. In young intact, but not in adult castrated males, ICI increased seminal vesicle growth affected by both endogenous and exogenous (Prog, E or E plus Prog) hormones. EM, on the other hand, decreased seminal vesicle weights in E or E plus Prog and increased its weights in Prog-treated young intact males. Thus, under certain conditions EM possess mixed agonist and antagonist activity in the mammary gland, uterus and seminal vesicles. Norethindrone acetate (NA)-stimulated mammary growth was decreased by anti-progestins onapristone (ON), RU 46556 (RU), and RU 38486 (MI) by 34-59% in females and by 35-93% in males. Uterine weights of NA-treated females were decreased by ON and RU by 29-55% but not by MI. In NA-treated young intact males, seminal vesicle weights were stimulated by RU (by 63%) and not affected by ON and MI. In NA-treated adult castrated males, seminal vesicle weights were decreased by ON, increased by RU and not affected by MI. The results obtained in these and our earlier studies show clearly that mouse four-model systems could serve as in vivo tool for the detection of steroid hormone agonist and antagonist activities of natural and man-made chemicals.

Prostate size and risk of high-grade, advanced prostate cancer and biochemical progression after radical prostatectomy: a search database study

PURPOSE

Prostate growth and differentiation are under androgenic control, and prior studies suggested that tumors that develop in hypogonadal men are more aggressive. We examined whether prostate weight was associated with tumor grade, advanced disease, or risk of biochemical progression after radical prostatectomy (RP).

PATIENTS AND METHODS

We evaluated the association of prostate weight with pathologic tumor grade, positive surgical margins, extracapsular disease, and seminal vesicle invasion using logistic regression and with biochemical progression using Cox proportional hazards regression among 1,602 men treated with RP between 1988 and 2003 at five equal-access medical centers, which composed the Shared Equal Access Regional Cancer Hospital (SEARCH) Database.

RESULTS

In outcome prediction models including multiple predictor variables, it was found that the predictor variable of prostate weight was significantly inversely associated with the outcomes of high-grade disease, positive surgical margins, extracapsular extension (all P < or = .004), and biochemical progression (comparing prostate weight < 20 v > or = 100 g: relative risk = 8.43; 95% CI, 2.9 to 24.0; P < .001). Similar associations were seen between preoperative transrectal ultrasound-measured prostate volume and high-grade disease, positive surgical margins, extracapsular extension (all P < or = .005), seminal vesicle invasion (P = .07), and biochemical progression (P = .06).

CONCLUSION

Men with smaller prostates had more high-grade cancers and more advanced disease and were at greater risk of progression after RP. These results suggest that prostate size may be an important prognostic variable that should be evaluated for use pre- and postoperatively to predict biochemical progression.

Mouse Bioassay to Assess Oestrogenic and Anti-oestrogenic Compounds: Hydroxytamoxifen, Diethylstilbestrol and Genistein

Young intact and adult gonadectomized C3H male and female mice were utilized as bioassay models to detect endocrine disruption chemicals. Animals treated with oestradiol (E) or progesterone (Prog) or E plus Prog were used to assess steroid hormone agonist and antagonist activities of 4-OH-tamoxifen (TAM), diethylstilbestrol (DES) and genistein (GEN) by bioassay. The stimulation or inhibition of mammary growth by TAM depended on sex, the state of animal (intact or gonadectomized), hormonal treatment (Prog, E, E plus Prog) and dose of TAM. TAM stimulated mammary growth in untreated ovariectomized (OV-X) females and in Prog-treated intact males and OV-X females. In intact males, mammary growth was increased by TAM at dose 0.1-1 microg day(-1) and decreased at dose 10 microg day(-1). Mammary growth was inhibited by TAM in Prog-treated intact females and in E or E plus Prog-treated intact and gonadectomized males and females. Uterine weights were increased by TAM in both untreated and treated (E, Prog, E plus Prog) intact and OV-X females; however, seminal vesicle weights were decreased by TAM in both untreated and treated (E, Prog, E plus Prog) intact males. DES alone affected mammary growth (an inverted-U-shaped dose-response curve) both in male and female mice. DES increased uterine weights; however, seminal vesicle weights were decreased. GEN increased mammary and uterine growth in OV-X females, GEN plus Prog stimulated mammary growth in intact males. The results obtained in these studies show clearly that only a bioassay consisting of several endpoints reflective to the mechanism of oestrogen and anti-oestrogen action has the ability to evaluate activities of a molecule.