In Utero Exposure to Bisphenol A Shifts the Window of Susceptibility for Mammary Carcinogenesis in the Rat

Background

Bisphenol A (BPA) is a ubiquitous environmental chemical with reported endocrine-disrupting properties.

Objective

Our goal in this study was to determine whether prenatal exposure to BPA predisposes the adult rat mammary gland to carcinogenesis.

Methods

Pregnant rats were treated orally with 0, 25, or 250 μg BPA/kg body weight (BW) from gestation day (GD) 10 to GD21. For tumorigenesis experiments, prenatally exposed female offspring received a single gavage of 7,12-dimethylbenz(a)anthracene (DMBA; 30 mg/kg BW) on postnatal day (PND) 50, or PND100.

Results

Prenatal exposure of the dam to 250 μg BPA/kg BW combined with a single exposure of female offspring to DMBA on PND100, but not on PND50, significantly increased tumor incidence while decreasing tumor latency compared with the control group. Prenatal exposure of the dam to 250 μg BPA/kg BW, in the absence of DMBA to the female offspring, increased cell proliferation and elicited differential effects at the protein level at PND100 compared with PND50. Differentially regulated proteins in the mammary gland included estrogen receptor-α, progesterone receptor-A, Bcl-2, steroid receptor coactivators, epidermal growth factor receptor, phospho-insulin-like growth factor 1 receptor, and phospho-Raf.

Conclusions

Our study demonstrates that oral prenatal exposure to BPA increases mammary cancer susceptibility in offspring and shifts the window of susceptibility for DMBA-induced tumorigenesis in the rat mammary gland from PND50 to PND100. These changes are accompanied by differential effects of prenatal BPA exposure on the expression of key proteins involved in cell proliferation.     

Influence of Prevastein, an isoflavone-rich soy product, on mammary gland development and tumorigenesis in Tg.NK (MMTV/c-neu) mice

We investigated spontaneous mammary tumor development and mammary gland morphogenesis in female Tg.NK mice postnatally exposed to dietary soy isoflavones (0, 11, 39, and 130 mg aglycones/kg diet) added to a Western-style diet. Instead of preventing mammary tumorigenesis, the highest dose of isoflavones was associated with a small but significant increase in the number and size of tumors as compared to mice administered a Western-style control diet (P < 0.05). At postnatal Week 6, dynamic activity (measured as apoptotic density) at the highest dose and the degree of branching of the mammary tree in all isoflavone-exposed groups was increased as compared to controls (P < 0.05). At adulthood, the epithelium appeared more quiescent in the medium- and high-dose groups evident by reduced apoptotic density and a reduction in the percentage of terminal end buds (TEBs), respectively, as compared to controls (P < 0.05). The number of actively dividing cells within the TEBs was unaffected by isoflavone exposure as was the activity of drug-metabolizing and antioxidant enzymes. In conclusion, isoflavones may augment mammary gland and mammary tumor development.     

Influenza subtype-specific maternal antibodies protect offspring against infection but inhibit vaccine-induced immunity and protection in mice

Following influenza A virus (IAV) infection or vaccination during pregnancy, maternal antibodies are transferred to offspring in utero and during lactation. The age and sex of offspring may differentially impact the transfer and effects of maternal immunity on offspring. To evaluate the effects of maternal IAV infection on immunity in offspring, we intranasally inoculated pregnant mice with sublethal doses of mouse-adapted (ma) H1N1, maH3N2, or media (mock) at embryonic day 10. In offspring of IAV-infected dams, maternal subtype-specific antibodies peaked at postnatal day (PND) 23, remained detectable through PND 50, and were undetectable by PND 105 in both sexes. When offspring were challenged with homologous IAV at PND 23, both male and female offspring had greater clearance of pulmonary virus and less morbidity and mortality than offspring from mock-inoculated dams. Inactivated influenza vaccination (IIV) against homologous IAV at PND 23 caused lower vaccine-induced antibody responses and protection following live virus challenge in offspring from IAV than mock-infected dams, with this effect being more pronounced among female than male offspring. At PND 105, there was no impact of maternal infection status, but vaccination induced greater antibody responses and protection against challenge in female than male offspring of both IAV-infected and mock-inoculated dams. To determine if maternal antibody or infection interfered with vaccine-induced immunity and protection in early life, offspring were vaccinated and challenged against a heterosubtypic IAV (i.e., different IAV group than dam) at PND 23 or 105. Heterosubtypic IAV maternal immunity did not affect antibody responses after IIV or protection after live IAV challenge of vaccinated offspring at either age. Subtype-specific maternal IAV antibodies, therefore, provide protection independent of offspring sex but interfere with vaccine-induced immunity and protection in offspring with more pronounced effects among females than males.     

Dietary exposure to whey proteins alters rat mammary gland proliferation, apoptosis, and gene expression during postnatal development

We have found that AIN-93G diets made with whey protein hydrolysate (WPH) reduce 7,12-dimethyl-benz[a]anthracene (DMBA)-induced tumor incidence in Sprague-Dawley (Harlan) rats relative to those fed a diet with casein (CAS). Herein, we replicated these findings in another Sprague-Dawley substrain (Charles River) and examined whether WPH protective effects were associated with altered mammary gland differentiation status and expression of the tumor suppressor phosphatase and tensin homolog deleted in chromosome ten (PTEN). Mammary tumor incidence was lower in DMBA-treated rats fed WPH than in those fed CAS. Mammary glands of WPH- and CAS-fed rats were isolated at weaning [postnatal day (PND) 21-28] and at an early adult stage (PND 50-53) and analyzed for proliferative (proliferating cell nuclear antigen immunoreactivity), apoptotic (terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick-end labeling), and differentiation (beta-casein) indices, as well as for PTEN mRNA and protein levels. PND 50-53 rats fed WPH showed decreased proliferation and increased apoptosis in mammary structures, coincident with increased mammary beta-casein gene expression, decreased terminal end-bud numbers, and increased ductal lengths, relative to same-age CAS-fed rats. When challenged with DMBA for 24 h, mammary glands of PND 53 CAS-fed rats had decreased cell survival in both terminal end buds and ductal epithelium, while the mammary glands of WPH-fed rats were not altered from pre-DMBA levels. At 7 d post-DMBA, mammary glands of CAS- and WPH-fed rats exhibited comparable apoptotic indices. Mammary PTEN expression was higher in WPH- than in CAS-fed rats at PND 21-28, but was not different in young adults fed either diet. Results demonstrate that dietary WPH advances mammary gland differentiation during neonatal development and suggest that the transiently increased expression of the pro-apoptotic signal PTEN during a sensitive developmental window may partly underlie the cancer protective effects of WPH.     

Gestational and chronic low-dose PFOA exposures and mammary gland growth and differentiation in three generations of CD-1 mice

Background: Prenatal exposure to perfluorooctanoic acid (PFOA), a ubiquitous industrial surfactant, has been reported to delay mammary gland development in female mouse offspring (F₁) and the treated lactating dam (P₀) after gestational treatments at 3 and 5 mg PFOA/kg/day.Objective: We investigated the consequences of gestational and chronic PFOA exposure on F₁ lactational function and subsequent development of F₂ offspring.Methods: We treated P₀ dams with 0, 1, or 5 mg PFOA/kg/day on gestation days 1–17. In addition, a second group of P₀ dams treated with 0 or 1 mg/kg/day during gestation and their F₁ and F₂ offspring received continuous PFOA exposure (5 ppb) in drinking water. Resulting adult F₁ females were bred to generate F₂ offspring, whose development was monitored over postnatal days (PNDs) 1–63. F₁ gland function was assessed on PND10 by timed-lactation experiments. Mammary tissue was isolated from P₀, F₁, and F₂ females throughout the study and histologically assessed for age-appropriate development.Results: PFOA-exposed F₁ dams exhibited diminished lactational morphology, although F₁ maternal behavior and F₂ offspring body weights were not significantly affected by P₀ treatment. In addition to reduced gland development in F₁ females under all exposures, F₂ females with chronic low-dose drinking-water exposures exhibited visibly slowed mammary gland differentiation from weaning onward. F₂ females derived from 5 mg/kg PFOA-treated P₀ dams displayed gland morphology similar to F₂ chronic water exposure groups on PNDs 22–63.Conclusions: Gestational PFOA exposure induced delays in mammary gland development and/or lactational differentiation across three generations. Chronic, low-dose PFOA exposure in drinking water was also sufficient to alter mammary morphological development in mice, at concentrations approximating those found in contaminated human water supplies.     

Perinatally Administered Bisphenol A as a Potential Mammary Gland Carcinogen in Rats

Background: Environmental exposure to bisphenol A (BPA) affects mammary gland development in rodents and primates. Prenatal exposure to environmentally relevant doses of BPA increased the number of intraductal hyperplasias and ductal carcinomas in situ by 50 days of age in Wistar-Furth rats.Objective: We aimed to determine whether BPA exposure of dams during gestation only or throughout lactation affects the incidence of mammary gland neoplasia in female offspring.Methods: We treated pregnant Sprague-Dawley rats with BPA at 0, 0.25, 2.5, 25, or 250 μg BPA/kg BW/day from gestational day (GD) 9 to birth and from GD9 to postnatal day (PND) 21. Mammary glands from BPA-exposed offspring were examined at four time points for preneoplastic and neoplastic lesions. To assess circulating BPA levels, we exposed pregnant rats to vehicle or 250 μg BPA/kg BW/day during gestation only or during gestation/lactation and analyzed sera from dams, fetuses, and nursing pups for total and unconjugated BPA.Results: Total and unconjugated BPA were detected in sera from 100% of dams and fetuses and 33% of pups exposed to 250 μg BPA/kg BW/day. Unconjugated BPA levels in exposed dams and fetuses (gestational) and in exposed dams and pups (gestational/lactational) were within levels found in humans. Preneoplastic lesions developed in BPA-exposed female offspring across all doses as early as PND50. Unexpectedly, mammary gland adenocarcinomas developed in BPA-exposed offspring by PND90.Conclusions: Our findings suggest that developmental exposure to environmentally relevant levels of BPA during gestation and lactation induces mammary gland neoplasms in the absence of any additional carcinogenic treatment. Thus, BPA may act as a complete mammary gland carcinogen.Citation: Acevedo N, Davis B, Schaeberle CM, Sonnenschein C, Soto AM. 2013. Perinatally administered bisphenol A acts as a mammary gland carcinogen in rats. Environ Health Perspect 121:1040–1046; http://dx.doi.org/10.1289/ehp.1306734     

Prenatal bisphenol A exposure induces preneoplastic lesions in the mammary gland in Wistar rats

BACKGROUND: Humans are routinely exposed to bisphenol A (BPA), an estrogenic compound that leaches from dental materials, food and beverage containers, and other consumer products. Prenatal exposure to BPA has produced long-lasting and profound effects on rodent hormone-dependent tissues that are manifested 1-6 months after the end of exposure. OBJECTIVE: The aim of the present work was to examine whether in utero exposure to BPA alters mammary gland development and increases its susceptibility to the carcinogen N-nitroso-N-methylurea (NMU). METHODS: Pregnant Wistar rats were exposed to BPA (25 pg/kg body weight per day) or to vehicle. Female offspring were sacrificed on postnatal day (PND) 30, 50, 110, or 180. On PND50 a group of rats received a single subcarcinogenic dose of NMU (25 mg/kg) and they were sacrificed on either PND110 or PND180. RESULTS: At puberty, animals exposed prenatally to BPA showed an increased proliferation/apoptosis ratio in both the epithelial and stromal compartments. During adulthood (PND110 and PND180), BPA-exposed animals showed an increased number of hyperplastic ducts and augmented stromal nuclear density. Moreover, the stroma associated with hyperplastic ducts showed signs of desmoplasia and contained an increased number of mast cells, suggesting a heightened risk of neoplastic transformation. Administration of a subcarcinogenic dose of NMU to animals exposed prenatally to BPA increased the percentage of hyperplastic ducts and induced the development of neoplastic lesions. CONCLUSIONS: Our results demonstrate that the prenatal exposure to low doses of BPA perturbs mammary gland histoarchitecture and increases the carcinogenic susceptibility to a chemical challenge administered 50 days after the end of BPA exposure.     

Emergence of ageing-related changes in insulin secretion by pancreatic islets of male rat offspring of mothers fed a low-protein diet

Maternal low-protein (LP) diets programme β-cell secretion, potentially altering the emergence of ageing of offspring pancreatic function. We hypothesised that isolated pancreatic islet β-cell secretory responses are blunted in offspring exposed to LP during development and age-related reduction is influenced by the developmental stage of exposure to decreased nutrition. We studied male offspring of rats fed control (C) or LP protein (R) diets in pregnancy, first letter and/or lactation second letter of CC, RR, CR or RC groups. Serum glucose, insulin and homeostatic model assessment (HOMA) were measured. Pancreatic islets were isolated and in vitro insulin secretion quantified in low (LG - 5 mM) or high glucose (HG - 11 mM). Body weight and serum values between groups were similar at all ages. Insulin and HOMA rose with age and were highest at postnatal day (PND) 450 in all groups. At PND 36, insulin secretion was greatest in RR and RC. Only CC increased insulin secretion to HG. By PND 110, restricted groups responded less to LG but increased secretion to HG. By PND 450, CC offspring alone increased secretion to HG. Despite minimal differences in circulating insulin and glucose, reduced maternal protein intake affected insulin secretion at all ages. In addition, ageing reduced function in all R groups compared with CC by PND 110 and further by PND 450 most markedly in RC. We conclude that maternal LP diet during pregnancy and/or lactation impairs offspring insulin secretory response to a glucose challenge and alters the trajectory of ageing of pancreatic insulin secretion.     

Maternal protein malnutrition induces autism-like symptoms in rat offspring

Objective: We tested the correlation between maternal protein malnutrition and autistic-like symptoms using behavioral tests in rodents that measure main behavioral characteristics observed in humans with autism spectrum disorder (ASD).

Methods: Pregnant female rats were fed a normal diet or a hypoproteic diet during gestation and lactation periods. The litters were weighed every 3 days during lactation, and the offspring were tested in behavioral tasks during infancy (postnatal day (PND) 5: quantification of ultrasonic vocalizations; PND 13: homing behavior test) and adolescence (PND 30–32: open field, hole-board, play social behavior, and object recognition tests) in order to capture the prevalence of some of the core and associated symptoms of ASD.

Results: Litters of the hypoproteic diet group had a lesser weight gain during lactation. In addition, pups of dams fed with a hypoproteic diet vocalized less compared to those fed with a normal diet, and they showed impaired social discrimination abilities in the homing behavior test. In adolescence, both male and female offspring of the hypoproteic diet group showed no impairment in locomotor activity; however, they exhibited stereotypic behavior in the hole-board test and a decrease in social play behaviors. Male offspring showed increased interest in exploring a familiar object rather than a novel object.

Conclusion: Our results show that maternal protein malnutrition in rats causes offspring behaviors that resemble core and associated ASD symptoms.     

A maternal high-fat/high-caloric diet delays reflex ontogeny during lactation but enhances locomotor performance during late adolescence in rats

Objective: The main goal of the present study was to investigate the effects of two maternal high-fat diets with different energy densities on the somatic growth, reflex ontogeny, and locomotor activity of offspring.

Methods: Twenty-nine female Wistar rats (220–250?g) were mated and grouped into three different dietary conditions: control (n?=?11, AIN-93G diet, 3.6?kcal/g), high-fat/high-caloric (HH, n?=?9, 51% of the calories from fat, 4.62?kcal/g), and high-fat/isocaloric (HI, n?=?9, 51% of the calories from fat, 3.64?kcal/g). The fat source was mainly lard. The dietary groups were maintained during gestation and lactation. From postnatal day 1 (PND1) until weaning, the somatic growth, maturation of physical features, and reflex ontogeny of the male pups were evaluated. The locomotor activity was evaluated in an open field at PND8, PND14, PND17, PND21, PND30, PND45, and PND60.

Results: HH dams had a lower food intake but no difference in caloric intake or body weight gain. The HH pups had higher body weights, greater tail and body lengths, and an increased axis of the head at weaning. The prediction of ear unfolding, delayed palmar grasp, and cliff avoidance maturation were also observed in the HH offspring. At PND60, the HH pups showed an increased average speed as well as an average potency and kinetic energy in the open field.

Conclusion: A high-fat/high-caloric maternal diet increases somatic growth, predicts the maturation of physical features, and delays reflex ontogeny during lactation, and it enhances motor performance during late adolescence. A maternal HI diet does not elicit the same influences on offspring development compared with the HH diet.     

Exposure to flaxseed or purified lignan during lactation influences rat mammary gland structures

Previous investigation demonstrated that feeding a 10% flaxseed (10F) diet during pregnancy and lactation enhanced the differentiation of highly proliferative terminal end bud (TEB) structures of rat mammary gland into less proliferative alveolar buds and lobules. From this study, it was hypothesized that the lignan component in flaxseed mediated the observed effects. Because mammary glands with more TEBs are more susceptible to carcinogens, exposure to flaxseed during early postnatal life may reduce the risk of developing mammary cancer. Our objectives were to elucidate whether exposure to flaxseed during lactation only and during pregnancy and lactation can similarly influence the differentiation of mammary gland structures and also to identify whether the lignan component of flaxseed is the biologically active agent. Offspring were exposed to a 10F diet or a dose of purified lignan equivalent to that in a 10F diet (10S) during lactation only or from lactation to postnatal Day 50. Compared with controls, exposure to 10F or 10S during lactation only or from lactation to postnatal Day 50 reduced the number of TEBs and resulted in a rise in the number of alveolar buds. In conclusion, exposure to flaxseed or its purified lignan during lactation is a critical period in which mammary gland development may be promoted by enhancing the differentiation of the mammary gland structures. However, continuous exposure, particularly to purified lignans, resulted in the most differentiation of the mammary gland. The next step is to determine whether the changes in mammary gland structures are chemopreventive in rats challenged with a carcinogen.     

Maternal High-Fat Diet Reduces Type-2 Neural Stem Cells and Promotes Premature Neuronal Differentiation during Early Postnatal Development

Maternal obesity or exposure to a high-fat diet (HFD) has an irreversible impact on the structural and functional development of offspring brains. This study aimed to investigate whether maternal HFD during pregnancy and lactation impairs dentate gyrus (DG) neurogenesis in offspring by altering neural stem cells (NSCs) behaviors. Pregnant Sprague-Dawley rats were fed a chow diet (CHD) or HFD (60% fat) during gestation and lactation. Pups were collected on postnatal day 1 (PND 1), PND 10 and PND 21. Changes in offspring body weight, brain structure and granular cell layer (GCL) thickness in the hippocampus were analyzed. Hippocampal NSCs behaviors, in terms of proliferation and differentiation, were investigated after immunohistochemical staining with Nestin, Ki67, SOX2, Doublecortin (DCX) and NeuN. Maternal HFD accelerated body weight gain and brain structural development in offspring after birth. It also reduced the number of NSCs and their proliferation, leading to a decrease in NSCs pool size. Furthermore, maternal HFD intensified NSCs depletion and promoted neuronal differentiation in the early postnatal development period. These findings suggest that maternal HFD intake significantly reduced the amount and capability of NSCs via reducing type–2 NSCs and promoting premature neuronal differentiation during postnatal hippocampal development.     

Early Life and Postnatal Western Diet Feeding and Susceptibility to Chemically Induced Colonic Aberrant Crypt Foci in Male Rats Offspring

The modifying effects of a Western diet (WD) during early life on the susceptibility to colon carcinogenesis induced by dimethylhydrazine (DMH) were examined in male rats as later adults. Three groups were studied: a lifetime control diet-fed group, a test group fed WD since pregnancy from dams until postnatal day (PND) 42, and a group fed WD at adulthood. At PND 70, all groups received the carcinogen DMH and were euthanized 10 wk later. Colonic aberrant crypt foci (ACF) were scored (number and crypt multiplicity) and the altered pattern of β-catenin expression was evaluated in the colonic lesions. ACF multiplicity (≥4 crypts) was significantly higher in the group fed WD at early life than in the group fed the control diet. ACF number, crypt multiplicity, and the number of high-grade dysplastic lesions were significantly higher in the group fed WD at adulthood than in the groupfed the control diet. The number of lesions with altered β-catenin expression was higher in the groups receiving WD at early life or at adulthood than in the lifetime control-diet-fed group. These findings indicate that WD exposure at early life increased the susceptibility to colon carcinogenesis at adulthood.     

Whey Protein Hydrolysate but not Whole Whey Protein Protects Against 7,12-Dimethylbenz(a)anthracene-Induced Mammary Tumors in Rats

Effects of intact and processed bovine milk proteins on development of chemically induced mammary tumors in female rats were compared. AIN-93G diets were made with 20% casein (CAS), casein hydrolysate (CASH), intact whey protein (IWP), or whey protein hydrolysate (WPH). Pregnant Sprague-Dawley rats were fed the diets starting at Gestational Day 4. Offspring were fed the same diet. At 50 days, female offspring (44–49/group) were gavaged with sesame oil containing 80 mg/kg of the mammary carcinogen dimethylbenzanthracene (DMBA) and euthanized 62 days posttreatment. Rats fed WPH had an adenocarcinoma incidence of 17% compared to the rats fed CAS, CASH, and IWP diets (34%, 33%, and 36% respectively) (P < 0.001). Median palpable tumor latency for rats fed WPH was greater (61 days, P < 0.001) compared to CAS (44 days), CASH (42 days) and IWP (45 days). Tumor multiplicity was also lower (1.5 vs. 3.0, P < 0.05) in rats fed WPH than in CAS and CASH fed groups. Results demonstrate that hydrolytic processing of whey protein is required for this diet to be effective in reducing DMBA-induced mammary tumors. The bioactive compounds produced during whey protein processing and mechanisms underlying the anticancer effects of WPH are yet to be identified.     

孕哺期PM2.5和高脂饮食联合暴露对大鼠仔鼠血压、血脂、血糖的影响

目的 探讨孕哺期细颗粒物（fine particulate matter,PM2.5）和高脂饮食（high fat diet,HFD）联合暴露对大鼠仔鼠血压、血脂、空腹血糖的影响,观察生命早期同时暴露PM2.5和HFD对子代发育的影响。方法 成年SD大鼠按照雌雄2[DK]∶1进行交配,孕鼠随机分为对照组（CC组）、高脂饮食组（HFD组）、PM2.5低暴露组（L-PM2.5组）、PM2.5高暴露组（H-PM2.5组）、高脂饮食+PM2.5低暴露组（HFD+L-PM2.5组）和高脂饮食+PM2.5高暴露组（HFD+H-PM2.5组）。对照组和PM2.5低、高暴露组给予普通饲料,其余给予高脂饲料。PM2.5染毒采用细颗粒物在线浓缩和动物染毒系统,低、高暴露剂量分别设为室外大气PM2.5浓度的2倍和4倍。母鼠从孕0日开始染毒,每天5h,每周5d,直至仔鼠出生后第21d（Postnatal day,PND21）,记录仔鼠体长和尾长,测量仔鼠的血压、心率,检测空腹血糖、血清甘油三酯、胆固醇水平。结果 PND21雄鼠HFD组、HFD+L-PM2.5组、HFD+H-PM2.5组体长较CC组增加,PND21雌鼠HFD+L-PM2.5组尾长较L-PM2.5组增加（P<0.05）。析因分析显示,PM2.5（F=3.492,P<0.05）和HFD（F=4.346,P<0.05）均使雌鼠收缩压升高,二者不存在交互作用（P>0.05）;HFD使雄鼠收缩压（F=9.259）、舒张压（F=5.981）、平均动脉压（F=7.754）升高（P均<0.05）,HFD+H-PM2.5组雄鼠收缩压、舒张压、平均动脉压均高于CC组（P<0.05）,PM2.5和HFD不存在交互作用（P>0.05）。PM2.5、HFD使雌鼠（F值分别为13.346,32.277,P均<0.05）、雄鼠血清甘油三酯（F值分别为5.723,10.360,P均<0.05）均升高,HFD+H-PM2.5组雌雄仔鼠甘油三酯含量均高于CC组,两者对雌鼠的血清甘油三酯含量存在协同作用（F=8.651,P<0.05）,对雄鼠不存在交互作用（P>0.05）。各组仔鼠空腹血糖水平差异无统计学意义（P>0.05）。结论 PM2.5和HFD联合暴露能引起PND21仔鼠血压、血脂升高,二者对血压的影响不存在交互作用,对雌性仔鼠血脂的影响存在协同作用。PM2.5和HFD对血压的影响存在性别差异。     

Modifying effects of lemongrass essential oil on specific tissue response to the carcinogen N-methyl-N-nitrosurea in female BALB/c mice

Lemongrass (Cymbopogon citratus Stapf) essential oil has been used worldwide because of its ethnobotanical and medicinal usefulness. Regarding its medicinal usefulness, the present study evaluated the beneficial effects of lemongrass essential oil (LGEO) oral treatment on cell proliferation and apoptosis events and on early development of hyperplastic lesions in the mammary gland, colon, and urinary bladder induced by N-methyl-N-nitrosourea (MNU) in female BALB/c mice. The animals were allocated into three groups: G1, treated with LGEO vehicle for 5 weeks (five times per week); G2, treated with LGEO vehicle as for G1 and MNU (two injections each of 30?mg/kg of body weight at weeks 3 and 5); and G3, treated with LGEO (five times each with 500?mg/kg of body weight per week) and MNU as for G2. Twenty-four hours after the last MNU application, all animals were euthanized, and mammary glands, colon, and urinary bladder were collected for histological and immunohistochemical analysis. LGEO oral treatment significantly changed the indexes of apoptosis and/or cellular proliferation for the tissues analyzed. In particular, the treatment reduced the incidence of hyperplastic lesions and increased apoptosis in mammary epithelial cells. This increment in the apoptosis response may be related to a favorable balance in Bcl-2/Bax immunoreactivity in mammary epithelial cells. These findings indicate that LGEO presented a protective role against early MNU-induced mammary gland alterations in BALB/c mice.     

In utero and lactational exposures to low doses of polybrominated diphenyl ether-47 alter the reproductive system and thyroid gland of female rat offspring

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are capable of disrupting thyroid hormone homeostasis. PBDE-47 (2,2',4,4'-tetrabromodiphenyl ether) is one of the most abundant congeners found in human breast adipose tissue and maternal milk samples. OBJECTIVES: We evaluated the effects of developmental exposure to low doses of PBDE-47 on the female reproductive system. METHODS: Pregnant Wistar rats were administered vehicle (peanut oil) or PBDE-47 [140 or 700 microg/kg body weight (bw)] on gestation day (GD) 6, or 5 mg 6-n-propyl-2-thiouracil (PTU)/L in the drinking water from GD7 through postnatal day (PND) 21. RESULTS: In female offspring sacrificed on PND38, there was a significant decrease in ovarian weight after exposure to PTU or 140 microg/kg PBDE-47. Alterations in folliculogenesis were apparent: we observed a decrease in tertiary follicles and serum estradiol concentrations in the offspring exposed to either PTU or 700 microg/kg PBDE-47. PTU exposure also resulted in a decrease in primordial follicles. On PND100, persistent effects on the thyroid glands included histologic and morphometric changes after exposure to either PTU or PBDE-47. No relevant changes in reproductive indices were observed after mating the exposed F1 females with nontreated males. CONCLUSIONS: Administration of PBDE-47 at doses relevant to human exposure led to changes in the rat female reproductive system and thyroid gland.     

Effect of short‐term administration of n‐(4‐hydroxyphenyl)‐all‐trans‐retinamide on chemically induced mammary tumors

Mammary cancer was induced in 50‐day‐old Sprague‐Dawley rats with either 25 mg/kg body weight of N‐methyl‐N‐nitrosourea (MNU) or 10 mg/rat of dimethyl‐benz(a)anthracene (DMBA). The retinoid N‐(4‐hydroxyphenyl)‐all‐trans‐retinamide (RAHA) was begun in the diet (2.0 mmol/kg diet) of MNU‐induced rats at 21, 48, or 52 days of age, and at 21 or 60 days of age for DMBA ‐induced rats. RAHA was terminated 12–17 weeks postinduction, and the animals were sacrificed at 28 weeks postinduction. Significant inhibition of tumor incidence or multiplicity was found in only one group (rats fed RAHA beginning at 48 days of age). This was not considered sufficient evidence to conclude that short‐term administration of RAHA altered mammary tumor development.