Organotin speciation and tissue distribution in rat dams, fetuses, and neonates following oral administration of tributyltin chloride

Long-term tributyltin exposure alters behavior, oocyte maturation, and histomorphology of the ovary due to oxidative stress in adult zebrafish

Tributyltin (TBT), an organotin endocrine-disrupting substance, is recognized as one of the important toxic environmental pollutants. The present study was carried out to investigate the toxic effects of TBT on behavior and the ovary of adult zebrafish with a focus on oxidative stress markers and oocyte maturation. Adult zebrafish were exposed to three different concentrations (125, 250, and 500 ng/L of water) of TBT for 28 days. TBT exposure produced a concentration-dependent negative effect on the body weight and behavior (anxiety-like symptoms) of adult zebrafish. Alterations in the activity of superoxide dismutase (SOD) and catalase (CAT), the total antioxidant capacity of ovarian tissue by the highest exposure level of TBT resulted in lipid peroxidation as indicated by increased malondialdehyde (MDA) level. The numbers of early-vitellogenic oocytes were significantly increased in zebrafish exposed to TBT as low as 125 ng/L. However, the numbers and size of fully-grown (mature) oocytes were significantly reduced in the highest exposure group only. Correlation between the MDA level and pre-vitellogenic oocytes in the 500 ng/L group indicated that lipid peroxidation prevented the maturation of pre-vitellogenic oocytes. TBT exposure produced significant histological changes in the ovary as evidenced by disturbed maturation of oocytes. In conclusion, TBT adversely affected the maturation of oocytes in zebrafish ovary through oxidative stress-mediated mechanisms.

Maternal exposure to tributyltin alters the breast milk, hormonal profile, and thyroid morphology of dams and induces sex-specific changes in neonate rat offspring

Tributyltin (TBT) is the chemical substance commonly used worldwide to prevent biofouling of vessels. Due to its ability to bioaccumulate and biomagnify, even after being banned, significant concentrations of TBT can be detected in sediment, affecting marine and human life. Although studies have shown that direct exposure to TBT alters physiological parameters in mammals, the relationship between exposure to TBT during pregnancy and lactation, considered critical windows for metabolic programming, has not been fully elucidated. Our hypothesis is that offspring whose mothers were exposed to TBT during critical stages of development may exhibit dysfunctions in endocrine-metabolic parameters. We used pregnant Wistar rats that were divided into groups and received the following treatments from gestational day 7 until the end of lactation by intragastric gavage: vehicle (ethanol 0.01%; Control), low TBT dose (100 ng/kg of body weight (bw)/day; TBT100ng) and high TBT dose (1000 ng/kg bw/day; TBT1000ng). Dams and offspring at birth and weaning (21 days old) were studied. Maternal exposure to TBT promoted dose-dependent changes in dams. The findings for adiposity, milk composition and lipid profile were more pronounced in TBT100 ng dam; however, thyroid morphology was altered in TBT1000 ng dam. Female offspring were differentially affected by the dose of exposure. At birth, females in the TBT100ng group had low body weight, lower naso-anal length (NAL), and higher plasma T4, and at weaning, females in the TBT100ng group had lower insulin and leptin levels. Females in the TBT1000ng group had lower NAL at birth and lower leptinemia and weight of white adipose tissue at weaning. Male offspring from TBT groups showed high T3 at birth, without biometric alterations at birth or weaning. Despite these findings, both sexes exhibited dose-dependent morphological changes in the thyroid gland. Thus, maternal exposure to TBT constitutes an important route of contamination for both dams and offspring.

Toxic Relationships: Prediction of TBT's Affinity to the Ecdysteroid Receptor of Triops longicaudatus

Tributyltin (TBT) is a biocide introduced in the 1960s in antifouling paints. Despite legislation banning its use, its persistence in the environment still causes significant harm to organisms. Tributyltin is a ligand of retinoid X receptors (RXR) and ecdysteroid receptors (EcRs), which in arthropods act as homologs of RXR. Focusing on Metazoan species, this study used genomic and proteomic information from different sources to compare their three-dimensional structure, phylogenetic distribution, and amino acid sequence alterations. The objective was to identify possible patterns that relate organisms' sensitivity to TBT using the species Triops longicaudatus as the basis for the comparisons. The results showed great conservation of this protein across several species when comparing the interaction amino acids described to RXR (an EcR analog) in Homo sapiens. The three-dimensional comparison of RXR showed little conformational variation between different sequences by maintaining the interaction pocket. As for the Species Sensitivity Distribution (SSD) curve, an HC05 = 0.2649 [0.0789-0.7082] µg/L was obtained with no specific distribution between the different taxa. Protein-ligand docking analysis was then used to confirm the SSD curve ranking of species. Still, the results showed an opposite trend that may be related, for example, to differences in the LC50 values used in the calculations. This study serves as the first step for applying bioinformatics techniques to produce information that can be used as an alternative to animal or cellular experimentation. These techniques could be adapted to various chemicals and proteins, allowing for observations in a shorter timeframe and providing information on a broader spectrum.

Organotin Antifouling Compounds and Sex-Steroid Nuclear Receptor Perturbation: Some Structural Insights

Organotin compounds (OTCs) are a commercially important group of organometallic compounds of tin used globally as polyvinyl chloride stabilizers and marine antifouling biocides. Worldwide use of OTCs has resulted in their ubiquitous presence in ecosystems across all the continents. OTCs have metabolic and endocrine disrupting effects in marine and terrestrial organisms. Thus, harmful OTCs (tributyltin) have been banned by the International Convention on the Control of Harmful Antifouling Systems since 2008. However, continued manufacturing by non-member countries poses a substantial risk for animal and human health. In this study, structural binding of common commercial OTCs, tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT), monophenyltin (MPT), and azocyclotin (ACT) against sex-steroid nuclear receptors, androgen receptor (AR), and estrogen receptors (ERα, ERβ) was performed using molecular docking and MD simulation. TBT, DBT, DPT, and MPT bound deep within the binding sites of AR, ERα, and Erβ, showing good dock score, binding energy and dissociation constants that were comparable to bound native ligands, testosterone and estradiol. The stability of docking complex was shown by MD simulation of organotin/receptor complex with RMSD, RMSF, Rg, and SASA plots showing stable interaction, low deviation, and compactness of the complex. A high commonality (50-100%) of interacting residues of ERα and ERβ for the docked ligands and bound native ligand (estradiol) indicated that the organotin compounds bound in the same binding site of the receptor as the native ligand. The results suggested that organotins may interfere with the natural steroid/receptor binding and perturb steroid signaling.

Perinatal exposure to tributyltin affects feeding behavior and expression of hypothalamic neuropeptide Y in the paraventricular nucleus of adult mice

Organotins such as tributyltin chloride (TBT), are highly diffused environmental pollutants, which act as metabolism disrupting chemicals, i.e. may interfere with fat tissue differentiation, as well as with neuroendocrine circuits, thus impairing the control of energetic balance. We have previously demonstrated that adult exposure to TBT altered the expression of neuropeptides in the hypothalamus. In this study, we orally administered daily a solution containing oil, or TBT (0.25, 2.5, or 25 μg/kg body weight/day) to pregnant females from gestational day 8 until birth, and to their pups from day 0 until post-natal day 21. Our results showed that TBT exposure of female mice during gestation and of pups during lactation permanently altered the feeding efficiency of pups of both sexes and subcutaneous fat distribution in adult males. In addition, the neuropeptide Y system was affected at the level of the paraventricular nucleus, with a decrease in immunoreactivity in both sexes (significant in females for all TBT doses and in males only for intermediate TBT doses), while no effect was observed in other hypothalamic areas (arcuate, ventromedial and dorsomedial nuclei). Metabolic syndrome, as well as obesity and diabetes, which are significant health issues, are considered multifactorial diseases and may be caused by exposure to metabolic disruptors, both in adults and during perinatal life. In addition, our work indicates that TBT doses defined as the tolerably daily intake had a profound and sex-specific long-term effect.

Evaluation of Fetal Exposures to Metals and Metalloids through Meconium Analyses: A Review

This paper surveys the existing scientific literature on metals concentrations in meconium. We examine some 32 papers that analyzed meconium for aluminum, arsenic, barium, calcium, chromium, copper, iron, lithium, magnesium, manganese, zinc, lead, mercury, manganese, molybdenum, nickel, phosphorus, lead, antimony, selenium, tin, vanadium, and zinc. Because of the lack of detail in the statistics it is not possible to do a rigorous meta-analysis. What stands out is that almost every study had subjects with seemingly large amounts of at least one of the metals. The significance of metals in meconium is not clear beyond an indication of exposure although some studies have correlated metals in meconium to a number of adverse outcomes. A number of outstanding questions have been identified that, if resolved, would greatly increase the utility of meconium analysis for assessment of long-term gestational metals exposures. Among these are questions of the developmental and long-term significance of metals detected in meconium, the kinetics and interactions among metals in maternal and fetal compartments and questions on best methods for meconium analyses.

A novel catalytic two-step process for the preparation of rigid polyurethane foams: synthesis, mechanism and computational studies

Synthesis of polyurethane foams catalyzed by sodium chloride both in prepolymer preparation and elongation step. The reaction mechanism involves the role of a proton shuttle between two terminal OH groups of PEG 400.

Environmental Exposures in the Etiology of Abortion: Placental Toxic and Trace Element Levels

PURPOSE

Intensive research has been conducted on the effects of toxic and trace elements on pregnancy. Previous studies indicated a possible relationship between placental levels of these elements and first-trimester abortion; however, their effects on the further gestational weeks are not clear. This study aimed to investigate the effect of changes in the levels of placental trace and toxic elements on second-trimester abortion.

METHODS

The patient group consisted of 30 women with missed abortion. The control group comprised 60 healthy term and singleton pregnant women who gave birth. Placental samples were obtained from the patients and the healthy controls, and the concentrations of placental elements were measured using inductively coupled plasma mass spectrometry.

RESULTS

In the abortion group, placental arsenic, cadmium, mercury, lead, antimony, tin, cobalt, manganese, and selenium levels were significantly higher than those of the control group (p<0.05). Antimony was determined as an independent predictor with an odds ratio of 6.1 in toxic elements (p=0.025), and selenium was determined as an independent predictor with an odds ratio of 2.3 in trace elements (p=0.015).

CONCLUSION

The changes in trace element and toxic element levels, especially an increase in antimony and selenium, in placental tissue due to environmental exposure may play an important role in second-trimester abortion.

DNA fragmentation factor 40 expression in T cells confers sensibility to tributyltin-induced apoptosis

DNA fragmentation factor 40 (DFF40), an endonuclease, mediates the final and irreversible step of apoptosis by conducting oligonucleosomal DNA fragmentation. New emerging studies have proposed a role of DFF40 in genomic stability, besides its nuclease activity. Overexpression of DFF40 in tumoral cells increases their sensitivity to chemotherapeutic drugs. In this study, we sought to determine if DFF40 expression influences the toxicity of tributyltin (TBT), a well-known immunotoxic and apoptosis-inducing compound. The strategy used was to knockout DFF40 expression by CRISPR-cas9 method in Jurkat T cells and to determine the toxicity of TBT in DFF40 KO cells and DFF40 WT Jurkat cells. DFF40 KO Jurkat cells show an increase of cell viability following a 24-h TBT exposure (p < 0.05). There is a resistance to TBT-induced apoptosis determined by annexin V/PI am labeling (p < 0.05). Interestingly, the basal level of ROS rises in DFF40 KO Jurkat cells, but ROS production levels after TBT exposure remains at the same basal level. Other apoptosis or DNA damage makers (procaspase-3, caspase-6, and PARP cleavage) are significantly delayed and decreased. DFF40 deficient cells do not present histone H2AX phosphorylation, whereas wild-type cells present a phosphorylation following a 6-h exposure to TBT (p < 0.001). The re-expression of DFF40 in DFF40 KO cells restores the cytotoxic effects of TBT. Overall, these data suggest a role of DFF40 in cells sensitivity to TBT and possibly in DNA stability.

Effects of exposure to triphenyltin (TPT) contaminant on sperm activity in adulthood of Calomys laucha exposed through breastfeeding

Triphenyltin (TPT) is an organotin compound (OT), primarily used in agriculture and in the composition of antifouling paints for ships worldwide. Studies have showed its effects as an endocrine disrupter in several organisms by preventing enzymatic expression and causing reproductive toxicity. This study aimed to evaluate the effects of exposure to TPT, via breastfeeding, on reproductive physiology in the Calomys laucha species. The experimental design was compound of five groups, two controls and three with different doses of TPT. Moreover, females were exposed by gavage to the TPT for 20 days, from the 1st day postpartum to the 21st postnatal day (PND). Then, the pups were euthanized and the kinetics, organelles, and biochemistry of the sperm were evaluated. The results presented a reduction in total motility in the groups exposed to TPT. Regarding cellular organelles analysis, a loss in membrane integrity was evidenced; the functionality of mitochondria showed diminution followed by increased acrosome reaction. In conclusion, the TPT causes alteration of the reproductive parameters, decreasing the activity and sperm quality in individuals exposed in the breastfeeding phase.

Effects of tributyltin on placental cytokine production

Objective Tributyltin (TBT) is a persistent pollutant but its effects on placental function are poorly understood as are its possible interactions with infection. We hypothesized that TBT alters the production of sex hormones and biomarkers for inflammation and neurodevelopment in an infection-dependent manner. Methods Placental explant cultures were treated with 0-5000 nM TBT in the presence and absence of Escherichia coli. A conditioned medium was harvested and concentrations of steroids (progesterone, P4; testosterone, T and estradiol, E2) as well as biomarkers of inflammation [interleukin (IL)-1β (IL-1β), tumor necrosis factor (TNF-α), IL-10, IL-6, soluble glycoprotein 130 (sgp-130) and heme oxygenase-1 (HO-1)], oxidative stress [8-iso-prostaglandin (8-IsoP)] and neurodevelopment [brain-derived neurotrophic factor (BDNF)] were quantified. Results TBT increased P4 slightly but had little or no effect on T or E2 production. IL-1β, IL-6, sgp-130, IL-10 and 8-IsoP production was enhanced by TBT. P4 and IL-6 production was also enhanced by TBT for bacteria-stimulated cultures but TBT significantly inhibited bacteria-induced IL-1β and sgp-130 production. High doses of TBT also inhibited BDNF production. Conclusions TBT increases P4 but has minimal effect on downstream steroids. It enhances the production of inflammatory biomarkers such as IL-1β, TNF-α, IL-10 and IL-6. Inhibition of sgp-130 by TBT suggests that TBT may increase bioactive IL-6 production which has been associated with adverse neurodevelopmental outcomes. Reduced expression of BDNF also supports this possibility.

The obesogen tributyltin induces features of polycystic ovary syndrome (PCOS): a review

Polycystic ovary syndrome (PCOS) is a heterogeneous syndrome characterized by abnormal reproductive cycles, irregular ovulation, and hyperandrogenism. This complex disorder has its origins both within and outside the hypothalamic-pituitary-ovarian axis. Cardio-metabolic factors, such as obesity and insulin resistance, contribute to the manifestation of the PCOS phenotype. Polycystic ovary syndrome is one of the most common endocrine disorders among women of reproductive age. Growing evidence suggested an association between reproductive and metabolic features of PCOS and exposure to endocrine-disrupting chemicals (EDC), such as bisphenol A. Further, the environmental obesogen tributyltin (TBT) was shown to induce reproductive, metabolic and cardiovascular abnormalities resembling those found in women and animal models of PCOS. However, the causal link between TBT exposure and PCOS development remains unclear. The objective of this review was to summarize the most recent research findings on the potential association between TBT exposure and development of PCOS-like features in animal models and humans.

From the Cover: Tributyltin Alters the Bone Marrow Microenvironment and Suppresses B Cell Development

Organotins are industrial chemicals and agricultural pesticides, and they contaminate both outdoor and indoor environments. Organotins are detectable in human sera at biologically active concentrations and are immuno-and neuro-toxicants. Triphenyltin, tributyltin (TBT) and dibutyltin activate peroxisome proliferator-activated receptor γ in bone marrow multipotent mesenchymal stromal cells and promote adipogenesis. TBT also has been shown to suppress osteogenesis; osteoblasts not only support bone homeostasis but also support B lymphopoiesis. In addition, developing B cells are highly sensitive to exogenous insults. Thus, we hypothesized that bone marrow B cells may be negatively affected by TBT exposure both directly, through activation of apoptosis, and indirectly, through alterations of the bone marrow microenvironment. TBT activated apoptosis in developing B cells at environmentally relevant concentrations (as low as 80 nM) in vitro, via a mechanism that is distinct from that induced by high dose (μM) TBT and that requires p53. TBT suppressed the proliferation of hematopoietic cells in an ex vivo bone marrow model. Concurrent treatment of stromal cells and B cells or pretreatment of stromal cells with TBT induced adipogenesis in the stromal cells and reduced the progression of B cells from the early pro B (Hardy fraction B) to the pre B stage (Hardy fraction D). In vivo, TBT induced adipogenesis in bone marrow, reduced "aging-sensitive" AA4+CD19+ B cells in bone marrow, and reduced splenic B cell numbers. Immunosenescence and osteoporosis are adverse health effects of aging, we postulate that TBT exposure may mimic, and possibly intensify, these pathologies.

Organotin Exposure and Vertebrate Reproduction: A Review

Organotin (OTs) compounds are organometallic compounds that are widely used in industry, such as in the manufacture of plastics, pesticides, paints, and others. OTs are released into the environment by anthropogenic actions, leading to contact with aquatic and terrestrial organisms that occur in animal feeding. Although OTs are degraded environmentally, reports have shown the effects of this contamination over the years because it can affect organisms of different trophic levels. OTs act as endocrine-disrupting chemicals (EDCs), which can lead to several abnormalities in organisms. In male animals, OTs decrease the weights of the testis and epididymis and reduce the spermatid count, among other dysfunctions. In female animals, OTs alter the weights of the ovaries and uteri and induce damage to the ovaries. In addition, OTs prevent fetal implantation and reduce mammalian pregnancy rates. OTs cross the placental barrier and accumulate in the placental and fetal tissues. Exposure to OTs in utero leads to the accumulation of lipid droplets in the Sertoli cells and gonocytes of male offspring in addition to inducing early puberty in females. In both genders, this damage is associated with the imbalance of sex hormones and the modulation of the hypothalamic-pituitary-gonadal axis. Here, we report that OTs act as reproductive disruptors in vertebrate studies; among the compounds are tetrabutyltin, tributyltin chloride, tributyltin acetate, triphenyltin chloride, triphenyltin hydroxide, dibutyltin chloride, dibutyltin dichloride, diphenyltin dichloride, monobutyltin, and azocyclotin.

Tributyltin: Advancing the Science on Assessing Endocrine Disruption with an Unconventional Endocrine-Disrupting Compound

Tributyltin (TBT) has been recognized as an endocrine disrupting chemical (EDC) for several decades. However, only in the last decade, was its primary endocrine mechanism of action (MeOA) elucidated-interactions with the nuclear retinoid-X receptor (RXR), peroxisome proliferator-activated receptor γ (PPARγ), and their heterodimers. This molecular initiating event (MIE) alters a range of reproductive, developmental, and metabolic pathways at the organism level. It is noteworthy that a variety of MeOAs have been proposed over the years for the observed endocrine-type effects of TBT; however, convincing data for the MIE was provided only recently and now several researchers have confirmed and refined the information on this MeOA. One of the most important lessons learned from years of research on TBT concerns apparent species sensitivity. Several aspects such as the rates of uptake and elimination, chemical potency, and metabolic capacity are all important for identifying the most sensitive species for a given chemical, including EDCs. For TBT, much of this was discovered by trial and error, hence important relationships and important sensitive taxa were not identified until several decades after its introduction to the environment. As recognized for many years, TBT-induced responses are known to occur at very low concentrations for molluscs, a fact that has more recently also been observed in fish species. This review explores the MeOA and effects of TBT in different species (aquatic molluscs and other invertebrates, fish, amphibians, birds, and mammals) according to the OECD Conceptual Framework for Endocrine Disruptor Testing and Assessment (CFEDTA). The information gathered on biological effects that are relevant for populations of aquatic animals was used to construct Species Sensitivity Distributions (SSDs) based on No Observed Effect Concentrations (NOECs) and Lowest Observed Effect Concentrations (LOECs). Fish appear at the lower end of these distributions, showing that they are as sensitive as molluscs, and for some species, even more sensitive. Concentrations in the range of 1 ng/L for water exposure (10 ng/g for whole-body burden) have been shown to elicit endocrine-type responses, whereas mortality occurs at water concentrations ten times higher. Current screening and assessment methodologies as compiled in the OECD CFEDTA are able to identify TBT as a potent endocrine disruptor with a high environmental risk for the original use pattern. If those approaches had been available when TBT was introduced to the market, it is likely that its use would have been regulated sooner, thus avoiding the detrimental effects on marine gastropod populations and communities as documented over several decades.

Prenatal Exposure to Tributyltin Decreases GluR2 Expression in the Mouse Brain

Tributyltin (TBT), a common environmental contaminant, is widely used as an antifouling agent in paint. We previously reported that exposure of primary cortical neurons to TBT in vitro decreased the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit glutamate receptor 2 (GluR2) expression and subsequently increased neuronal vulnerability to glutamate. Therefore, to identify whether GluR2 expression also decreases after TBT exposure in vivo, we evaluated the changes in GluR2 expression in the mouse brain after prenatal or postnatal exposure to 10 and 25 ppm TBT through pellet diets. Although the mean feed intake and body weight did not decrease in TBT-exposed mice compared with that in control mice, GluR2 expression in the cerebral cortex and hippocampus decreased after TBT exposure during the prenatal period. These results indicate that a decrease in neuronal GluR2 may be involved in TBT-induced neurotoxicity, especially during the fetal period.

A Short-Term Exposure to Tributyltin Blocks Leydig Cell Regeneration in the Adult Rat Testis

Background: Tributyltin (TBT) is widely used as an antifouling agent that may cause reproductive toxicity. The mechanism of TBT on Leydig cell development is still unknown. The objective of the present study was to investigate whether a brief exposure to low doses of TBT permanently affects Leydig cell development and to clarify the underlying mechanism. Methods: Adult male Sprague Dawley rats were randomly assigned into four groups and gavaged normal saline (control), 0.1, 1.0, or 10.0 mg/kg/day TBT for a consecutive 10 days, respectively. At the end of TBT treatment, all rats received a single intraperitoneal injection of 75 mg/kg ethane dimethane sulfonate (EDS) to eliminate all of adult Leydig cells. Leydig cells began a developmental regeneration process on post-EDS day 35. The Leydig cell regeneration was evaluated by measuring serum testosterone, luteinizing hormone, and follicle-stimulating hormone levels on post-EDS day 7, 35, and 56, the expression levels of Leydig cell genes, Leydig cell morphology and number and proliferation on post-EDS day 56. Results: TBT significantly reduced serum testosterone levels on post-EDS day 35 and 56 and increased serum luteinizing hormone and follicle-stimulating hormone levels on post-EDS day 56 at ≥1 mg/kg/day. Immunohistochemical staining showed that there were fewer regenerated Leydig cells in the TBT-treated testis on post-EDS day 56. Further study demonstrated that the mRNA or protein levels of Leydig (Lhcgr, Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3) and Sertoli cells (Fshr, Dhh, and Sox9) were significantly down-regulated in the TBT-treated testes when compared to the control. Immunofluorescent staining showed that TBT inhibited Leydig cell proliferation as judged by the reduced number of proliferating cyclin nuclear antigen-positive Leydig cells on post-EDS day 35. Conclusion: The present study demonstrated that a short-term TBT exposure blocked Leydig cell developmental regeneration process via down-regulating steroidogenesis-related proteins and inhibiting the proliferation of Leydig cells.

Adult exposure to tributyltin affects hypothalamic neuropeptide Y, Y1 receptor distribution, and circulating leptin in mice

Tributyltin (TBT), a pesticide used in antifouling paints, is toxic for aquatic invertebrates. In vertebrates, TBT may act in obesogen- inducing adipogenetic gene transcription for adipocyte differentiation. In a previous study, we demonstrated that acute administration of TBT induces c-fos expression in the arcuate nucleus. Therefore, in this study, we tested the hypothesis that adult exposure to TBT may alter a part of the nervous pathways controlling animal food intake. In particular, we investigated the expression of neuropeptide Y (NPY) immunoreactivity. This neuropeptide forms neural circuits dedicated to food assumption and its action is mediated by Y1 receptors that are widely expressed in the hypothalamic nuclei responsible for the regulation of food intake and energy homeostasis. To this purpose, TBT was orally administered at a dose of 0.025 mg/kg/day/body weight to adult animals [male and female C57BL/6 (Y1-LacZ transgenic mice] for 4 weeks. No differences were found in body weight and fat deposition, but we observed a significant increase in feed efficiency in TBT-treated male mice and a significant decrease in circulating leptin in both sexes. Computerized quantitative analysis of NPY immunoreactivity and Y1-related β-galactosidase activity demonstrated a statistically significant reduction in NPY and Y1 transgene expression in the hypothalamic circuit controlling food intake of treated male mice in comparison with controls. In conclusion, the present results indicate that adult exposure to TBT is profoundly interfering with the nervous circuits involved in the stimulation of food intake.

Effects of 13 developmentally toxic chemicals on the migration of rat cephalic neural crest cells in vitro

The inhibition of neural crest cell (NCC) migration has been considered as a possible pathogenic mechanism underlying chemical developmental toxicity. In this study, we examined the effects of 13 developmentally toxic chemicals on the migration of rat cephalic NCCs (cNCCs) by using a simple in vitro assay. cNCCs were cultured for 48 h as emigrants from rhombencephalic neural tubes explanted from rat embryos at day 10.5 of gestation. The chemicals were added to the culture medium at 24 h of culture. Migration of cNCCs was measured as the change in the radius (radius ratio) calculated from the circular spread of cNCCs between 24 and 48 h of culture. Of the chemicals examined, 13-cis-retinoic acid, ethanol, ibuprofen, lead acetate, salicylic acid, and selenate inhibited the migration of cNCCs at their embryotoxic concentrations; no effects were observed for acetaminophen, caffeine, indium, phenytoin, selenite, tributyltin, and valproic acid. In a cNCC proliferation assay, ethanol, ibuprofen, salicylic acid, selenate, and tributyltin inhibited cell proliferation, suggesting the contribution of the reduced cell number to the inhibited migration of cNCCs. It was determined that several developmentally toxic chemicals inhibited the migration of cNCCs, the effects of which were manifested as various craniofacial abnormalities.

The Mammalian "Obesogen" Tributyltin Targets Hepatic Triglyceride Accumulation and the Transcriptional Regulation of Lipid Metabolism in the Liver and Brain of Zebrafish

Recent findings indicate that different Endocrine Disrupting Chemicals (EDCs) interfere with lipid metabolic pathways in mammals and promote fat accumulation, a previously unknown site of action for these compounds. The antifoulant and environmental pollutant tributyltin (TBT), which causes imposex in gastropod snails, induces an “obesogenic” phenotype in mammals, through the activation of the nuclear receptors retinoid X receptor (RXR) and peroxisome proliferator-activated receptor gamma (PPARγ). In teleosts, the effects of TBT on the lipid metabolism are poorly understood, particularly following exposure to low, environmental concentrations. In this context, the present work shows that exposure of zebrafish to 10 and 50 ng/L of TBT (as Sn) from pre-hatch to 9 months of age alters the body weight, condition factor, hepatosomatic index and hepatic triglycerides in a gender and dose related manner. Furthermore, TBT modulated the transcription of key lipid regulating factors and enzymes involved in adipogenesis, lipogenesis, glucocorticoid metabolism, growth and development in the brain and liver of exposed fish, revealing sexual dimorphic effects in the latter. Overall, the present study shows that the model mammalian obesogen TBT interferes with triglyceride accumulation and the transcriptional regulation of lipid metabolism in zebrafish and indentifies the brain lipogenic transcription profile of fish as a new target of this compound.

Effects of Tributyltin and Other Retinoid Receptor Agonists in Reproductive-Related Endpoints in the Zebrafish (Danio rerio)

Both field and experimental data examined the influence of exposure to environmental contaminant tributyltin (TBT) on marine organisms. Although most attention focused on the imposex phenomenon in gastropods, adverse effects were also observed in other taxonomic groups. It has been shown that imposex induction involves modulation of retinoid signaling in gastropods. Whether TBT influences similar pathways in fish is yet to be addressed. In this study, larvae of the model teleost Danio rerio were exposed to natural retinoids, all-trans-retinoic acid, 9-cis-retinoic acid, and all-trans-retinol, as well as to the RXR synthetic pan-agonist methoprene acid (MA) and to TBT. Larvae were exposed to TBT from 5 days post fertilization (dpf) to adulthood, and reproductive capacity was assessed and correlated with mode of action. TBT significantly decreased fecundity at environmentally relevant levels at 1 μg TBT Sn/g in diet. Interestingly, in contrast to previous reports, TBT altered zebrafish sex ratio toward females, whereas MA exposure biased sex toward males. Since fecundity was significantly altered in the TBT-exposed group with up to 62% decrease, the potentially affected pathways were investigated. Significant downregulation was observed in brain mRNA levels of aromatase b (CYP19a1b) in females and peroxisome proliferator activated receptor gamma (PPARg) in both males and females, suggesting an involvement of these pathways in reproductive impairment associated with TBT.

Sexual maturation and fertility of mice exposed to triphenyltin during prepubertal and pubertal periods

This study investigated the effects of pre- and peripubertal exposure (PND 15-45) to triphenyltin hydroxide (TPT: 0, 1.875, 3.75, 7.5 and 15 mg/kg bw/d po) on mouse sexual maturation and fertility. Half of the mice were euthanized on PND 46 and the remaining mice were submitted to fertility tests on PND 65-75. TPT caused a transient decrease of weight gain at 3.75 mg/kg bw/d, and deaths and body weight deficits at higher doses. Delays of testes descent (TD), vaginal opening (VO) and first estrus (FE) occurred at doses ≥3.75 (TD) and ≥7.5 mg/kg bw/d (VO, FE), respectively. Body weight on the days of TD, VO and FE did not differ among groups. TPT at doses ≥3.75 mg/kg decreased sperm and spermatid counts at the end of treatment (PND 46) but no alteration was noted later on PND 75. Testicular histopathology (PND 46) showed a dose-dependent reduction of seminiferous tubules diameter, a greater degree of vacuolation in Sertoli cells and germ cell degeneration and necrosis in TPT-treated mice. TPT did not affect the outcome of fertility tests. Study-derived NOAEL was 1.875 mg TPT/kg bw/d for males and 3.75 mg TPT/kg bw/d for females. The detrimental effects of TPT on spermatogenesis were reversed after treatment discontinuation.

Association of placenta organotin concentrations with growth and ponderal index in 110 newborn boys from Finland during the first 18 months of life: a cohort study

BACKGROUND

Humans are exposed to tributyltin (TBT), previously used as an antifouling paint in ships, mainly through fish consumption. As TBT is a known obesogen, we studied the association of placenta TBT and other organotin compounds (OTCs) with ponderal index (PI) and growth during the first 18 months of life in boys.

METHODS

In a prospective Finnish study, 110 placenta samples were collected from mothers of boys born in 1997-1999 with (n = 55) and without (n = 55) cryptorchidism. To account for the original study design, linear regression, weighted for sampling fractions of boys with (121/55) and without (5677/55) cryptorchidism from the total cohort, was used to study the association between placenta OTCs and children's weight, length, growth rates and PI up to 18 months of age.

RESULTS

Placenta TBT concentrations were above the limit of quantification (LOQ) in 99% of the samples. However, monobutyltin (MBT), dibutyltin (DBT) and triphenyltin (TPhT) concentrations were below LOQ in 90%, 35% and 57% of samples, respectively. Placenta TBT was positively associated (p = 0.024) with weight gain during the first three months of life, but no other significant associations were observed for weight or length gain. Also, no significant associations between placenta OTC concentrations and child length, weight or PI at any time point were found.

CONCLUSIONS

We observed a trend towards higher weight gain from birth to 3 months of age with increasing placenta TBT concentration. These results should be interpreted with caution because obesogenic effects in animal experiments were seen after in-utero TBT exposures to doses that were orders of magnitude higher. Also the number of study subjects included in this study was limited.

Environmental pollutants and lifestyle factors induce oxidative stress and poor prenatal development

Developmental toxicity caused by exposure to a mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviours, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase susceptibility of offspring to diseases. There is evidence to suggest that the developmental toxicological mechanisms of chemicals and lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased ROS generation overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Data on the involvement of oxidative stress in the mechanism of developmental toxicity following exposure to environmental pollutants are reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on post-natal development and health outcomes. Developmental toxicity caused by exposure to mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviors, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase the susceptibility of offspring to development complications and diseases. There is evidence to suggest that the developmental toxicological mechanisms of human-made chemicals and unhealthy lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased generation of ROS overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Exposure to various environmental pollutants induces synergic and cumulative dose-additive adverse effects on prenatal development, pregnancy outcomes and neonate health. Data from the literature on the involvement of oxidative stress in the mechanism of developmental toxicity following in vivo exposure to environmental pollutants will be reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on postnatal development and health outcomes.

Stimulation of estradiol biosynthesis by tributyltin in rat hippocampal slices

Hippocampal functions are influenced by steroid hormones, such as testosterone and estradiol. It has been demonstrated that hippocampus-derived steroid hormones play important roles in neuronal protection and synapse formation. Our research groups have demonstrated that estradiol is de novo synthesized in the rat hippocampus. However, the mechanism(s) regulating this synthesis remains unclear. It has been reported that tributyltin, an environmental pollutant, binds to the retinoid X receptor (RXR) and modifies estrogen synthesis in human granulosa-like tumor cells. This compound can penetrate the blood brain barrier, and tends to accumulate in the brain. Based on these facts, we hypothesized that tributyltin could influence the hippocampal estradiol synthesis. A concentration of 0.1 μM tributyltin induced an increase in the mRNA content of P450(17α) and P450arom in hippocampal slices, as determined using real-time PCR. The transcript levels of other steroidogenic enzymes and a steroidogenic acute regulatory protein were not affected. The estradiol level in rat hippocampal slices was subsequently determined using a radioimmunoassay. We found that the estradiol synthesis was stimulated by ∼2-fold following a 48-h treatment with 0.1 μM tributyltin, and this was accompanied by transcriptional activation of P450(17α) and P450arom. Tributyltin stimulated de novo hippocampal estradiol synthesis by modifying the transcription of specific steroidogenic enzymes.

Association of placenta organotin concentrations with congenital cryptorchidism and reproductive hormone levels in 280 newborn boys from Denmark and Finland

STUDY QUESTION

Is the placental burden of organotin compounds (OTCs) associated with congenital cryptorchidism in infant offspring from Finland and Denmark?

SUMMARY ANSWER

Increasing concentrations of OTCs had a negative association with cryptorchidism in Finland, whereas a positive association was found in Denmark.

WHAT IS KNOWN ALREADY

The rapid increase in the prevalence of cryptorchidism suggests that environmental factors, such as endocrine disruptors, may be involved. OTCs are endocrine disruptors at very low concentrations due to activation of the retinoid X receptor (RXR).

STUDY DESIGN, SIZE, DURATION

Between the years 1997 and 2001, placentas from mothers of cryptorchid boys and from healthy controls were collected from Denmark (39 cases, 129 controls) and Finland (56 cases, 56 controls). In Denmark 33 and 6 boys, and in Finland 22 and 34 boys had mild or severe cryptorchidism, respectively. The association between concentrations of four OTCs [monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT) and triphenyltin (TPhT)] and case-control status was estimated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In both countries, placenta samples were selected from larger cohorts. In Finland placenta samples were collected from boys with cryptorchidism at birth and matched controls (nested case-control design). Matching criteria were parity, maternal smoking (yes/no), diabetes (yes/no), gestational age (±7 days) and date of birth (±14 days). Numbers of controls per case was 1. In Denmark, all available placentas from cryptorchid boys were chosen and control placentas were selected randomly from the total Danish cohort (case-cohort design). The average number of controls per case was 3.3. OTCs in placenta samples were analysed with liquid extraction, ethylation and gas chromatography-mass spectrometry determination and coded by country-specific tertiles.

MAIN RESULTS AND THE ROLE OF CHANCE

Generally, the concentrations of OTCs were very low. For most analytes, a large proportion of samples (29-96% depending on the country and case-control status) had OTC concentrations below the limit of quantification (LOQ). As an exception, the concentration of TBT was >LOQ in 99% of Finnish placentas. The mean concentrations of DBT and TBT were 1.5 and 7 times higher in Finland than in Denmark, respectively. For DBT in Danish placentas, the odds ratio (OR) for cryptorchidism in the second tertile (0.10-0.14 ng/g) when compared with the first tertile (<0.10 ng/g, <LOQ) was 3.13 (95% CI 1.19-8.26) and the OR for the third tertile (≥0.15 ng/g) when compared with the first tertile was 4.01 (95% CI 1.42-11.33). For TBT in Finnish placentas, the OR for cryptorchidism in the second tertile (0.10-0.39 ng/g) when compared with the first tertile (<0.1 ng/g) was 0.61 (95% CI 0.18-2.01) and the OR for the third tertile (≥0.40 ng/g) when compared with the first tertile was 0.13 (95% CI 0.03-0.54).

LIMITATIONS, REASONS FOR CAUTION

The main limitation of the study was the relatively small number of mother-boy pairs that limits the extrapolation of the study results to the general population. Also misclassification of exposure is a reason for caution for two reasons: because the concentrations of most OTCs were below or only barely above the LOQ in a large proportion of samples and because it is not known how well OTCs measured from placenta represent exposure at the time window that is relevant for cryptorchidism occurrence.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to measure the concentrations of OTCs from human placenta samples, and to associate these concentrations to cryptorchidism. As opposite results were obtained with regard to OTC concentration in placenta and cryptorchidism status in Finland and Denmark, and no mechanism is known at the moment by which OTCs could affect testicular descent, these results cannot be generalized to other populations. However, some animal tests described in the literature show opposite effects of OTCs on fat deposition at different ranges of exposure. It is also clearly shown in the literature that TBT has an impact on sexual development of gastropods through RXR. As TBT is known to activate human RXR, further laboratory studies should be designed to explore the potential impact of TBT on male sexual development.

Effects of oral exposure to arsenobetaine during pregnancy and lactation in Sprague-Dawley rats

Arsenobetaine (ASB) is the major form of arsenic (As) in seafood sources such as molluscs and fish. Limited data demonstrated that ASB toxicity in mammals is minimal; however, data on possible reproductive effects are lacking. This study investigated the tissue distribution and developmental effects of ASB during pregnancy, early postnatal life, and development to adulthood. Pregnant rats were randomly assigned to 3 cohorts and gavaged daily from gestational day 8 (GD8) with ASB in deionized water at 0, 0.1, 1, or 10 mg/kg body weight (bw)/d. Cohort 1 dams were sacrificed on GD20 (n = 6 per dose group), cohort 2 dams and pups were sacrificed on postnatal day 13 (PND13; n = 4 dams per dose group), and cohort 3 pups (n = 2 dams per dose group) were sacrificed on PND90. Residue analysis detected significant levels of ASB in livers of cohort 1 dams and lower levels in cohort 1 GD20 fetuses, as well as in cohort 2 male and female offspring, indicating placental transfer from the maternal circulation in utero. Trace amounts of ASB in dams' milk were found only in the 10-mg/kg bw/d dose cohort 2 (PND13), demonstrating that lactational transfer was limited. ASB levels in liver varied during pregnancy, lactation, and postweaning, with levels falling rapidly as these physiological states progress. Although transfer of ASB through the placenta to the fetuses and to a limited extent through milk was confirmed, ASB exposure during pregnancy and lactation appeared to produce no teratogenic or deleterious effects on reproductive development.

The epigenetic lorax: gene-environment interactions in human health

Over the last decade, we have witnessed an explosion of information on genetic factors underlying common human diseases and disorders. This 'human genomics' information revolution has occurred as a backdrop to a rapid increase in the rates of many human disorders and diseases. For example, obesity, Type 2 diabetes, asthma, autism spectrum disorder and attention deficit hyperactivity disorder have increased at rates that cannot be due to changes in the genetic structure of the population, and are difficult to ascribe to changes in diagnostic criteria or ascertainment. A likely cause of the increased incidence of these disorders is increased exposure to environmental factors that modify gene function. Many environmental factors that have epidemiological association with common human disorders are likely to exert their effects through epigenetic alterations. This general mechanism of gene-environment interaction poses special challenges for individuals, educators, scientists and public policy makers in defining, monitoring and mitigating exposures.

Perinatal exposure to low doses of tributyltin chloride advances puberty and affects patterns of estrous cyclicity in female mice

Tributyltin (TBT), a proven endocrine-disrupting chemical, is well known to induce imposex in female gastropods. Herein we demonstrate the effects of low doses of tributyltin chloride (TBTCl) on the female offspring of KM mice. Pregnant mice were administered by gavage with 0, 1, 10, or 100 μg TBTCl/kg body weight/day from day 6 of pregnancy through the period of lactation. TBTCl dramatically advanced the age of onset of vaginal opening (VO) and first vaginal estrus, and reduced body weights at VO and first estrus. Furthermore, perinatal treatment with TBTCl significantly reduced the number of days between VO and first estrus. In addition, female offspring from dams exposed to 10 and 100 μg kg(-1) TBTCl exhibited altered patterns of estrous cyclicity in adulthood. In conclusion, perinatal exposure to low doses TBTCl result in early puberty and impaired estrous cyclicity in female mice, which suggest that TBTCl might act as an estrogen agonist or/and a disruptor on hypothalamic-pituitary function in the present study.

Tributyltin impairs the reproductive cycle in female rats

Triorganotins are environmental contaminants, commonly used in antifouling agents for boats, that bioaccumulate and thus are found in mammals and humans due to ingestion of contaminated seafood diets. The importance of triorganotins as environmental endocrine disruptors and consequent reproductive toxicity in different animal models is well known; however, the adverse effects on reproductive cycle are less well understood. The potential reproductive toxicity of tributyltin (TBT) on regular reproductive cycling of female rats was examined. Wistar female rats (12 wk old, weighing approximately 230 g) were divided into two groups: control (vehicle, ethanol 0.4%) and tributyltin (100 ng/kg/d, 7 d/wk, for 16 d by gavage). Tributyltin significantly decreased the cycle regularity (%), duration of the reproductive cycle, the proestrus and diestrus phases, and number of epithelial cell in proestrus phase. TBT also increased the duration of metestrus and the number of cornified cells in this phase. Ovary weight and serum 17β-estradiol levels decreased markedly, accompanied by a significant increase in progesterone levels. Histological analysis showed apoptotic cells in corpus luteum and granulosa cells layer, with cystic follicles after TBT exposure. Tributyltin also elevated number of atretic follicles and corpoa lutea. The micronucleus (MN) test, using Chinese hamster ovary cells, demonstrated a concentration-dependent mutagenic effect of TBT, and at 2.0 × 10(-2)ng/ml most of the cells were nonviable. The toxic potential of TBT over the reproductive cycle may be attributed to changes found in the ovarian weight, unbalanced levels of sexual female hormones, and number of ovarian follicles and corpora lutea.

Endocrine disrupters: a review of some sources, effects, and mechanisms of actions on behaviour and neuroendocrine systems

Some environmental contaminants interact with hormones and may exert adverse consequences as a result of their actions as endocrine disrupting chemicals (EDCs). Exposure in people is typically a result of contamination of the food chain, inhalation of contaminated house dust or occupational exposure. EDCs include pesticides and herbicides (such as dichlorodiphenyl trichloroethane or its metabolites), methoxychlor, biocides, heat stabilisers and chemical catalysts (such as tributyltin), plastic contaminants (e.g. bisphenol A), pharmaceuticals (i.e. diethylstilbestrol; 17α-ethinylestradiol) or dietary components (such as phytoestrogens). The goal of this review is to address the sources, effects and actions of EDCs, with an emphasis on topics discussed at the International Congress on Steroids and the Nervous System. EDCs may alter reproductively-relevant or nonreproductive, sexually-dimorphic behaviours. In addition, EDCs may have significant effects on neurodevelopmental processes, influencing the morphology of sexually-dimorphic cerebral circuits. Exposure to EDCs is more dangerous if it occurs during specific 'critical periods' of life, such as intrauterine, perinatal, juvenile or puberty periods, when organisms are more sensitive to hormonal disruption, compared to other periods. However, exposure to EDCs in adulthood can also alter physiology. Several EDCs are xenoestrogens, which can alter serum lipid concentrations or metabolism enzymes that are necessary for converting cholesterol to steroid hormones. This can ultimately alter the production of oestradiol and/or other steroids. Finally, many EDCs may have actions via (or independent of) classic actions at cognate steroid receptors. EDCs may have effects through numerous other substrates, such as the aryl hydrocarbon receptor, the peroxisome proliferator-activated receptor and the retinoid X receptor, signal transduction pathways, calcium influx and/or neurotransmitter receptors. Thus, EDCs, from varied sources, may have organisational effects during development and/or activational effects in adulthood that influence sexually-dimorphic, reproductively-relevant processes or other functions, by mimicking, antagonising or altering steroidal actions.

Neurotoxicity of endocrine disruptors: possible involvement in brain development and neurodegeneration

Environmental chemicals that act as endocrine disruptors do not appear to pose a risk to human reproduction; however, their effects on the central nervous systems are less well understood. Animal studies suggested that maternal exposure to endocrine-disrupting chemicals (EDC) produced changes in rearing behavior, locomotion, anxiety, and learning/memory in offspring, as well as neuronal abnormalities. Some investigations suggested that EDC exert effects on central monoaminergic neurons, especially dopaminergic neurons. Our data demonstrated that EDC attenuate the development of dopaminergic neurons, which might be involved in developmental disorders. Perinatal exposure to EDC might affect neuronal plasticity in the hippocampus, thereby potentially modulating neuronal development, leading to impaired cognitive and memory functions. Endocrine disruptors also attenuate gender differences in brain development. For example, the locus ceruleus is larger in female rats than in males, but treatments with bisphenol-A (BPA) enlarge this region in males. Some reports indicated that EDC induce hypothyroidism, which might be evidenced as abnormal brain development. Endocrine disruptors might also affect mature neurons, resulting in neurodegenerative disorders such as Parkinson's disease. The current review focused on alterations in the brain induced by EDC, specifically on the possible involvement of EDC in brain development and neurodegeneration.

Acute exposure to tributyltin induces c-fos activation in the hypothalamic arcuate nucleus of adult male mice

Tributyltin (TBT) is a largely diffused environmental pollutant, banned from paints in the European Union from 2003. However, the level of TBT (and other organotins) in food, particularly fish and shellfish, remains still high. Several studies demonstrated that TBT is involved in the development of obesity, via peripheral action, but currently, there are only a few data illustrating effects of TBT on the nervous system. In the present study, we tested the hypothesis that acute exposure to TBT may directly activate brain cells in particular, in those hypothalamic nuclei regulating the food intake. To this purpose, TBT was orally administered at a single dose (10 mg/kg/body weight) to two groups of adult male mice: regularly fed or fasted for 24 h. Mice were sacrificed 90 min after the TBT administration and perfused by 4% paraformaldehyde. Brains were quickly dissected, frozen and sectioned for immunocytochemical detection of c-fos, a common marker of cell activation. In both, fed or fasted mice, exposure to TBT induced a significant increase of c-fos expression in the arcuate nucleus in comparison to control mice. The other nuclei involved in the control of feeding behavior did not show any significant increase. These data are the first in vivo demonstration that TBT has not only peripheral effects, but also may activate elements in the brain, in particular in a crucial region for the regulation of food intake like the arcuate nucleus.

Postnatal development and fertility of offspring from mice exposed to triphenyltin (fentin) hydroxide during pregnancy and lactation

Fentin or triphenylthin (TPT) is an organotin compound (OTC) widely used as an agricultural fungicide and miticide. It is well known that TPT exerts adverse effects on the reproductive and immune systems and may disrupt the endocrine system, raising concerns regarding the risks posed by exposure to this metal on environmental and human health. In this study the effects of maternal exposure to TPT at doses of control (0), 1.875, 3.75, or 7.5 mg/kg body weight/d, po, were examined during gestation and lactation on offspring growth, organ weights, and fertility. Except for a significant liver enlargement at the highest dose, TPT produced no maternal toxicity. Increased neonatal mortality (death of 3 entire litters from a total of 18 treated litters) was noted at 7.5 mg/kg. Pup body weight at birth was significantly reduced at all dose levels, but no marked weight loss was found on postnatal day (PND) 5 and thereafter. Offspring maturation (ear unfolding, incisor eruption, vagina opening, and testes descent) and fertility in adulthood were not significantly affected by maternal exposure to TPT. In conclusion, data provided by this study indicate that maternal treatment with TPT during pregnancy and lactation delayed prenatal growth but did not impair postnatal development and fertility in exposed offspring in adulthood.

Endocrine disrupters as obesogens

The recent dramatic rise in obesity rates is an alarming global health trend that consumes an ever increasing portion of health care budgets in Western countries. The root cause of obesity is thought to be a prolonged positive energy balance. Hence, the major focus of preventative programs for obesity has been to target overeating and inadequate physical exercise. Recent research implicates environmental risk factors, including nutrient quality, stress, fetal environment and pharmaceutical or chemical exposure as relevant contributing influences. Evidence points to endocrine disrupting chemicals that interfere with the body's adipose tissue biology, endocrine hormone systems or central hypothalamic-pituitary-adrenal axis as suspects in derailing the homeostatic mechanisms important to weight control. This review highlights recent advances in our understanding of the molecular targets and mechanisms of action for these compounds and areas of future research needed to evaluate the significance of their contribution to obesity.

Minireview: the case for obesogens

Obesity and obesity-related disorders, such as type 2 diabetes, hypertension, and cardiovascular disease, are epidemic in Western countries, particularly the United States. The conventional wisdom holds that obesity is primarily the result of a positive energy balance, i.e. too many calories in and too few calories burned. Although it is self-evident that fat cannot be accumulated without a higher caloric intake than expenditure, recent research in a number of laboratories suggests the existence of chemicals that alter regulation of energy balance to favor weight gain and obesity. These obesogens derail the homeostatic mechanisms important for weight control, such that exposed individuals are predisposed to weight gain, despite normal diet and exercise. This review considers the evidence for obesogens, how they might act, and where future research is needed to clarify their relative contribution to the obesity epidemic.