Gestational 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) exposure disrupts fetoplacental unit: Fetal thyroid-cytokines dysfunction

Exploring Prenatal Exposure to Halogenated Compounds and Its Relationship with Birth Outcomes Using Nontarget Analysis

Halogenated organic compounds (HOCs) are a class of contaminants showing high toxicity, low biodegradability, and high bioaccumulation potential, especially chlorinated and brominated HOCs (Cl/Br-HOCs). Knowledge gaps exist on whether novel Cl/Br-HOCs could penetrate the placental barrier and cause adverse birth outcomes. Herein, 326 cord blood samples were collected in a hospital in Jinan, Shandong Province from February 2017 to January 2022, and 44 Cl/Br-HOCs were identified with communicating confidence level above 4 based on a nontarget approach, covering veterinary drugs, pesticides, and their transformation products, pharmaceutical and personal care products, disinfection byproducts, and so on. To our knowledge, the presence of closantel, bromoxynil, 4-hydroxy-2,5,6-trichloroisophthalonitrile, 2,6-dibromo-4-nitrophenol, and related components in cord blood samples was reported for the first time. Both multiple linear regression (MLR) and Bayesian kernel machine regression (BKMR) models were applied to evaluate the relationships of newborn birth outcomes (birth weight, length, and ponderal index) with individual Cl/Br-HOC and Cl/Br-HOCs mixture exposure, respectively. A significantly negative association was observed between pentachlorophenol exposure and newborn birth length, but the significance vanished after the false discovery rate correction. The BKMR analysis showed that Cl/Br-HOCs mixture exposure was significantly associated with reduced newborn birth length, indicating higher risks of fetal growth restriction. Our findings offer an overview of Cl/Br-HOCs exposome during the early life stage and enhance the understanding of its exposure risks.

The Role of Endocrine Disrupting Chemicals in Gestation and Pregnancy Outcomes

Endocrine disrupting chemicals (EDCs) are exogenous substances widely disseminated both in the environment and in daily-life products which can interfere with the regulation and function of the endocrine system. These substances have gradually entered the food chain, being frequently found in human blood and urine samples. This becomes a particularly serious issue when they reach vulnerable populations such as pregnant women, whose hormones are more unstable and vulnerable to EDCs. The proper formation and activity of the placenta, and therefore embryonic development, may get seriously affected by the presence of these chemicals, augmenting the risk of several pregnancy complications, including intrauterine growth restriction, preterm birth, preeclampsia, and gestational diabetes mellitus, among others. Additionally, some of them also exert a detrimental impact on fertility, thus hindering the reproductive process from the beginning. In several cases, EDCs even induce cross-generational effects, inherited by future generations through epigenetic mechanisms. These are the reasons why a proper understanding of the reproductive and gestational alterations derived from these substances is needed, along with efforts to establish regulations and preventive measures in order to avoid exposition (especially during this particular stage of life).

Polychlorinated biphenyls and thyroid function: a scoping review

OBJECTIVE

Numerous evidence indicates the association between polychlorinated biphenyls (PCBs), an endocrine disrupter, with thyroid hormone disruption, contradictory findings also exist. Herein, we tried to address this question by performing a scoping review.

CONTENT

The search was performed on PubMed, Scopus, Web of Science, and Google Scholar databases from 2010 onwards. Animal studies on PCBs' effect on thyroid function were searched. The SYRCLE's RoB scale assessed the risk of bias. I2 and Q tests are used for investigating heterogeneity. A random-effects model with the pooled standard means difference (SMD) and 95 % confidence interval (CI) was performed for the TSH, TT4, TT3, and FT4 outcomes using Comprehensive Meta-Analyses (CMA) Software version 3. Also, we conducted subgroup analyses based on the different types of PCB. The initial search identified 1,279 publications from the main databases 26 of them fulfilled our eligibility criteria for the study, and then five studies among selected studies had sufficient data for analysis. Meta-analysis of data revealed that Aroclor 1260 (SDM: -0.47, 95 % CI: -0.92, -0.01, p=0.044) and PCB 126 (SDM: 0.17, 95 % CI: -0.40, 0.75, p=0.559) significantly increased TSH concentration in the exposed groups vs. the control groups. Related to the effects of PCBs on the TT4, our findings indicated a significant reduction the TT4 concentration of animals exposed to Aroclor 1260 (SDM: -5.62, 95 % CI: -8.30, -2.94, p=0.0001), PCB 118 (SDM: -6.24, 95 % CI: -7.76, -4.72, p=0.0001), PCB 126 (SDM: -1.81, 95 % CI: -2.90, -0.71, p=0.001), and PCB 153 (SDM: -1.32, 95 % CI: -2.29, -0.35, p=0.007) vs. the controls. Our meta-analysis indicated a significant increase in TT3 concentration following exposure to PCB 118 and PCB 153 (SDM: -0.89, 95 % CI: -1.36, -0.42, p=0.0001, and SDM: -1.45, 95 % CI: -2.15, -0.75, p=0.0001, respectively). Aroclor 1254 and PCB 126 significantly decreased TT3 concentration (SDM: 1.25, 95 % CI: 0.29, 2.21, p=0.01 and SDM: 3.33, 95 % CI: 2.49, 4.18, p=0.0001, respectively). PCB 126 significantly decreased FT4 in the exposed groups vs. the control groups (SDM: -7.80, 95 % CI: -11.51, -5.35, p=0.0001).

SUMMARY

Our findings showed an association between PCBs exposure and hypothyroidism in rodents, fish, and chicken embryos.

OUTLOOK

Regarding to the most evidence of hypothyroidism effects of PCBs in animal species, it is necessary to consider large cohort studies to address the association between PCBs exposure and thyroid function impairment in humans.

Exposure to PCB126 during the nursing period reversibly impacts early-life glucose tolerance

Polychlorinated biphenyls (PCBs) are persistent environmental organic pollutants known to have detrimental health effects. Using a mouse model, we previously demonstrated that PCB126 exposure before and during pregnancy and throughout the perinatal period adversely affected offspring glucose tolerance and/or body composition profiles. The purpose of this study was to investigate the glucose tolerance and body composition of offspring born to dams exposed to PCB126 during the nursing period only. Female ICR mice were bred, and half of the dams were exposed to either vehicle (safflower oil) or 1 µmole PCB126 per kg of body weight via oral gavage on postnatal days (PND) 3, 10, and 17 (n = 9 per group). Offspring body weight, lean and fat mass, and glucose tolerance were recorded every three weeks. PCB126 treatment did not alter dam nor offspring body weight (p > 0.05). PCB126-exposed male and female offspring displayed normal body composition (p > 0.05) relative to vehicle-exposed offspring. However, both male and female offspring that were exposed to PCB126 during the nursing period had significantly impaired glucose tolerance at 3 and 9 weeks of age (p < 0.05). At 6 and 12 weeks of age, no impairments in glucose tolerance existed in offspring (p > 0.05). Our current study demonstrates that exposure to PCB126 through the mother's milk does not affect short- or long-term body composition but impairs glucose tolerance in the short-term.

Gene×environment interactions in autism spectrum disorders

There is credible evidence that environmental factors influence individual risk and/or severity of autism spectrum disorders (hereafter referred to as autism). While it is likely that environmental chemicals contribute to the etiology of autism via multiple mechanisms, identifying specific environmental factors that confer risk for autism and understanding how they contribute to the etiology of autism has been challenging, in part because the influence of environmental chemicals likely varies depending on the genetic substrate of the exposed individual. Current research efforts are focused on elucidating the mechanisms by which environmental chemicals interact with autism genetic susceptibilities to adversely impact neurodevelopment. The goal is to not only generate insights regarding the pathophysiology of autism, but also inform the development of screening platforms to identify specific environmental factors and gene×environment (G×E) interactions that modify autism risk. Data from such studies are needed to support development of intervention strategies for mitigating the burden of this neurodevelopmental condition on individuals, their families and society. In this review, we discuss environmental chemicals identified as putative autism risk factors and proposed mechanisms by which G×E interactions influence autism risk and/or severity using polychlorinated biphenyls (PCBs) as an example.

Gestational exposure to PCB-118 impairs placental angiogenesis and fetal growth

Maternal exposure to polychlorinated biphenyls (PCBs) results in adverse effects on fetal development. However, the underlying mechanism has not been sufficiently explored in respect to particular PCBs. Placental angiogenesis plays a crucial role in feto-maternal substances transportation and fetal development. The present study was conducted to investigate the effects of prenatal PCB118 exposure on placental angiogenesis and fetal growth. The pregnant dam received PCB118 at environmentally relevant doses (0, 20, or 100 μg/kg/day) intragastrically from gestational day (GD) 7.5-18.5 to establish an in vivo model. Compared with the control group, the fetal body and placental weights of the PCB118 (100 μg/kg/day) group were significantly decreased and the intrauterine growth retardation (IUGR) rates were increased both in the female and male fetus. Furthermore, we found that placental histology was significantly impaired and the number of blood vessels was decreased in the PCB118 group. Additionally, gestational exposure to PCB118 caused anomalous mRNA expression of the genes in the placenta regarding angiogenesis. These findings indicate that PCB118 may contribute to the occurrence of IUGR by provoking placental angiogenesis dysfunction. This study clarified the adverse effects and potential mechanism of prenatal PCBs exposure on fetal growth, providing a new theoretical and experimental basis for future treatment and prevention.

Gaps in the knowledge of thyroid hormones and placental biology

Thyroid hormones (THs) are required for the growth and development of the foetus, stimulating anabolism and oxygen consumption from the early stages of pregnancy to the period of foetal differentiation close to delivery. Maternal changes in the hypothalamic–pituitary thyroid axis are also well known. In contrast, several open questions remain regarding the relationships between the placenta and the maternal and foetal TH systems. The exact mechanism by which the placenta participates in regulating the TH concentration in the foetus and mother and the role of TH in the placenta are still poorly studied. In this review, we aim to summarize the available data in the area and highlight significant gaps in our understanding of the ontogeny and cell-specific localization of TH transporters, TH receptors and TH metabolic enzymes in the placenta in both human and rodent models. Significant deficiencies also exist in knowledge of the contribution of genomic and nongenomic effects of TH on the placenta and finally how the placenta reacts during pregnancy when the mother has thyroid disease. By addressing these key knowledge gaps, improved pregnancy outcomes and management of women with thyroid alterations may be possible.

Lack of Offspring Nrf2 Does Not Exacerbate the Detrimental Metabolic Outcomes Caused by In Utero PCB126 Exposure

Human environmental exposures to toxicants, such as polychlorinated biphenyls (PCBs), increase oxidative stress and disease susceptibility. Such exposures during pregnancy and/or nursing have been demonstrated to adversely affect offspring health outcomes. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the antioxidant response and is involved in the detoxification of coplanar PCBs, like PCB126. The purpose of this study was to investigate glucose tolerance and body composition in PCB-exposed offspring expressing or lacking Nrf2. We hypothesized that offspring lacking Nrf2 expression would be more susceptible to the long-term health detriments associated with perinatal PCB exposure. During gestation, whole-body Nrf2 heterozygous (Het) and whole-body Nrf2 knockout (KO) mice were exposed to vehicle or PCB126. Shortly after birth, litters were cross-fostered to unexposed dams to prevent PCB exposure during nursing. Offspring were weaned, and their body weight, body composition, and glucose tolerance were recorded. At two months of age, PCB exposure resulted in a significant reduction in the average body weight of offspring born to Nrf2 Het dams (p < 0.001) that primarily arose from the decrease in average lean body mass in offspring (p < 0.001). There were no differences in average body weight of PCB-exposed offspring born to Nrf2 KO dams (p > 0.05), and this was because offspring of Nrf2 KO dams exposed to PCB126 during pregnancy experienced a significant elevation in fat mass (p = 0.002) that offset the significant reduction in average lean mass (p < 0.001). Regardless, the lack of Nrf2 expression in the offspring themselves did not enhance the differences observed. After an oral glucose challenge, PCB-exposed offspring exhibited significant impairments in glucose disposal and uptake (p < 0.05). Offspring born to Nrf2 Het dams exhibited these impairments at 30 min and 120 min, while offspring born to Nrf2 KO dams exhibited these impairments at zero, 15, 30, 60 and 120 min after the glucose challenge. Again, the interactions between offspring genotype and PCB exposure were not significant. These findings were largely consistent as the offspring reached four months of age and demonstrate that the lack of offspring Nrf2 expression does not worsen the metabolic derangements caused by in utero PCB exposure as we expected. Future directions will focus on understanding how the observed maternal Nrf2 genotypic differences can influence offspring metabolic responses to in utero PCB exposure.

Relationship between endocrine disruptors and obesity with a focus on bisphenol A: a narrative review

Introduction: Scientific data suggest that early exposure to endocrine-disrupting chemicals (EDCs) affect -repro, -neuro, -metabolic systems, to which are added other notions such as mixtures, window and duration of exposure, trans-generational effects, and epigenetic mechanisms. Methods: In the present narrative review, we studied the relationship between exposure to EDCs with the appearance and development of obesity. Results: Exposure to EDCs like Bisphenol A during the early stages of development has been shown to lead to weight gain and obesity. EDCs can interfere with endocrine signaling, affect adipocytes differentiation and endocrine function and disrupt metabolic processes, especially if exposure occurs at very low doses, in the mixture, during early development stages for several generations. Conclusion: Exposure to EDCs is positively associated with obesity development. Moreover, the use of integrative approaches which mimicking environmental conditions are necessary and recommended to evaluate EDCs' effects in future studies.

Maternal LiCl exposure disrupts thyroid-cerebral axis in neonatal albino rats

This work aimed to elucidate whether maternal lithium chloride (LiCl) exposure disturbs the thyroid-cerebral axis in neonatal albino rats. 50 mg of LiCl/kg b.wt. is orally given for pregnant Wistar rats from gestational day (GD) 1 to lactation day (LD) 28. The maternal administration of LiCl induced follicular dilatation and degeneration, hyperplasia, lumen obliteration and colloid vacuolation in the maternal and neonatal thyroid gland at postnatal days (PNDs) 14, 21 and 28. Neuronal degeneration (spongiform), gliosis, nuclear pyknosis, perivascular oedema, and meningeal hyperaemia were observed in the neonatal cerebral cortex of the maternal LiCl-treated group at examined PNDs. This disturbance appears to depend on intensification in the neonatal cerebral malondialdehyde (MDA), nitric oxide (NO), and hydrogen peroxide (H₂ O₂ ) levels, and attenuation in the glutathione (GSH), total thiol (t-SH), catalase (CAT), and superoxide dismutase (SOD) levels. In the neonatal cerebrum, the fold change in the relative mRNA expression of deiodinases (DII and DIII) increased significantly at PNDs 21 and 14, respectively, in the maternal LiCl-treated group. These data suggest that maternal LiCl may perturb the thyroid-cerebrum axis generating neonatal neurodevelopmental disorder.

The Bladder Is a Novel Target of Developmental Polychlorinated Biphenyl Exposure Linked to Increased Inflammatory Cells in the Bladder of Young Mice

Bladder inflammation is associated with several lower urinary tract symptoms that greatly reduce quality of life, yet contributing factors are not completely understood. Environmental chemicals are plausible mediators of inflammatory reactions within the bladder. Here, we examine whether developmental exposure to polychlorinated biphenyls (PCBs) leads to changes in immune cells within the bladder of young mice. Female mice were exposed to an environmentally relevant mixture of PCBs through gestation and lactation, and bladders were collected from offspring at postnatal day (P) 28-31. We identify several dose- and sex-dependent PCB effects in the bladder. The lowest concentration of PCB (0.1 mg/kg/d) increased CD45+ hematolymphoid immune cells in both sexes. While PCBs had no effect on CD79b+ B cells or CD3+ T cells, PCBs (0.1 mg/kg/d) did increase F4/80+ macrophages particularly in female bladder. Collagen density was also examined to determine whether inflammatory events coincide with changes in the stromal extracellular matrix. PCBs (0.1 mg/kg/d) decreased collagen density in female bladder compared to control. PCBs also increased the number of cells undergoing cell division predominantly in male bladder. These results implicate perturbations to the immune system in relation to PCB effects on the bladder. Future study to define the underlying mechanisms could help understand how environmental factors can be risk factors for lower urinary tract symptoms.

Endocrine disrupting chemicals (EDCs) and placental function: Impact on fetal brain development

Pregnancy is a critical time of vulnerability for the development of the fetal brain. Exposure to environmental pollutants at any point in pregnancy can negatively impact many aspects of fetal development, especially the organization and differentiation of the brain. The placenta performs a variety of functions that can help protect the fetus and sustain brain development. However, disruption of any of these functions can have negative impacts on both the pregnancy outcome and fetal neurodevelopment. This review presents current understanding of how environmental exposures, specifically to endocrine disrupting chemicals (EDCs), interfere with placental function and, in turn, neurodevelopment. Some of the key differences in placental development between animal models are presented, as well as how placental functions such as serving as a xenobiotic barrier and exchange organ, immune interface, regulator of growth and fetal oxygenation, and a neuroendocrine organ, could be vulnerable to environmental exposure. This review illustrates the importance of the placenta as a modulator of fetal brain development and suggests critical unexplored areas and possible vulnerabilities to environmental exposure.

Perinatal effects of persistent organic pollutants on thyroid hormone concentration in placenta and breastmilk

Thyroid hormones (TH) are known to play a critical role in regulating many biological processes including growth and development, energy homeostasis, thermogenesis, lipolysis and metabolism of cholesterol. Severe TH deficiency especially during fetal development results in cretinism, but can also lead to an imbalance in metabolism with, among others, an alteration in body weight composition. Over the past two decades, increasing evidence has shown that certain persistent organic pollutants (POP) can interfere with the endocrine system. These POP referred to as "endocrine disrupting chemicals" are widely present in the environment and populations are exposed globally. Moreover, epidemiological studies have shown that a particularly sensitive period is the pre- and postnatal time. Indeed, perinatal exposure to such chemicals could lead to the onset diseases in later life. It is known, that, maternal thyroid hormones are transported by the placenta to the fetus from 6 weeks of gestation and it seems that during the first trimester, and part of the second, the fetus is entirely dependent on maternal TH supply for its development. Interferences in the TH-network as a consequence of the exposure to such pollutants could cause variations in TH concentration. Only small changes in maternal thyroid hormone levels in early stages of pregnancy can influence fetal neurological and cardiovascular development, as well as according to recent studies, have effect on childhood body composition. With this review, we will report the most recent and important studies concerning the association between thyroid hormone concentration and POP levels measured during the perinatal period. We will mostly focus on the data recently reported on placenta and breastmilk as main sources for understanding the potential consequences of exposure. The possible link between exposure to pollutants, TH dysregulation and possible adverse outcome will also be briefly discussed. From our literature search, several studies support the hypothesis that pre- and postnatal exposure to different pollutants might play a role in causing variation in thyroid hormone concentration. However, few research papers have so far studied the relationship linking exposure to pollutants, TH concentration and possible health consequences. Therefore, this review highlights the need for further research in this direction.

Perspective on prenatal polychlorinated biphenyl exposure and the development of the progeny nervous system (Review)

The developmental origins of health and disease concept illustrates that exposure in early life to various factors may affect the offspring's long-term susceptibility to disease. During development, the nervous system is sensitive and vulnerable to the environmental insults. Polychlorinated biphenyls (PCBs), which are divided into dioxin-like (DL-PCBs) and non-dioxin-like PCBs (NDL-PCBs), are synthetic persistent environmental endocrine-disrupting chemicals. The toxicological mechanisms of DL-PCBs have been associated with the activation of the aryl hydrocarbon receptor and NDL-PCBs have been associated with ryanodine receptor-mediated calcium ion channels, which affect neuronal migration, promote dendritic growth and alter neuronal connectivity. In addition, PCB accumulation in the placenta destroys the fetal placental unit and affects endocrine function, particularly thyroid hormones and the dopaminergic system, leading to neuroendocrine disorders. However, epidemiological investigations have not achieved a consistent result in different study cohorts. The present review summarizes the epidemiological differences and possible mechanisms of the effects of intrauterine PCB exposure on neurological development.

The insulin-like growth factor system: A target for endocrine disruptors?

The insulin-like growth factor (IGF) system is a critical regulator of growth, especially during fetal development, while also playing a central role in metabolic homeostasis. Endocrine disruptors (EDs) are ubiquitous compounds able to interfere with hormone action and impact human health. For example, exposure to EDs is associated with decreased birthweight and increased incidence of metabolic disorders. Therefore, the IGF system is a potential target for endocrine disruption. This review summarises the state of the science regarding effects of exposure to major classes of endocrine disruptors (dioxins and dioxin-like compounds, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, phthalates, perfluoroalkyl substances and bisphenol A) on the IGF system. Evidence from both experimental models (in vitro and in vivo) and epidemiological studies is presented. In addition, possible molecular mechanisms of action and effects on methylation are discussed. There is a large body of evidence supporting the link between dioxins and dioxin-like compounds and IGF disruption, but mixed findings have been reported in human studies. On the other hand, although only a few animal studies have investigated the effects of phthalates on the IGF system, their negative association with IGF levels and methylation status has been more consistently reported in humans. For polybrominated diphenyl ethers, perfluoroalkyl substances and bisphenol A the evidence is still limited. Despite a lack of studies for some ED classes linking ED exposure to changes in IGF levels, and the need for further research to improve reproducibility and determine the degree of risk posed by EDs to the IGF system, this is clearly an area of concern.

The influence of sex, genotype, and dose on serum and hippocampal cytokine levels in juvenile mice developmentally exposed to a human-relevant mixture of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are pervasive environmental contaminants implicated as risk factors for neurodevelopmental disorders (NDDs). Immune dysregulation is another NDD risk factor, and developmental PCB exposures are associated with early life immune dysregulation. Studies of the immunomodulatory effects of PCBs have focused on the higher-chlorinated congeners found in legacy commercial mixtures. Comparatively little is known about the immune effects of contemporary, lower-chlorinated PCBs. This is a critical data gap given recent reports that lower-chlorinated congeners comprise >70% of the total PCB burden in serum of pregnant women enrolled in the MARBLES study who are at increased risk for having a child with an NDD. To examine the influence of PCBs, sex, and genotype on cytokine levels, mice were exposed throughout gestation and lactation to a PCB mixture in the maternal diet, which was based on the 12 most abundant PCBs in sera from MARBLES subjects. Using multiplex array, cytokines were quantified in the serum and hippocampus of weanling mice expressing either a human gain-of-function mutation in ryanodine receptor 1 (T4826I mice), a human CGG premutation repeat expansion in the fragile X mental retardation gene 1 (CGG mice), or both mutations (DM mice). Congenic wildtype (WT) mice were used as controls. There were dose-dependent effects of PCB exposure on cytokine concentrations in the serum but not hippocampus. Differential effects of genotype were observed in the serum and hippocampus. Hippocampal cytokines were consistently elevated in T4826I mice and also in WT animals for some cytokines compared to CGG and DM mice, while serum cytokines were usually elevated in the mutant genotypes compared to the WT group. Males had elevated levels of 19 cytokines in the serum and 4 in the hippocampus compared to females, but there were also interactions between sex and genotype for 7 hippocampal cytokines. Only the chemokine CCL5 in the serum showed an interaction between PCB dose, genotype, and sex. Collectively, these findings indicate differential influences of PCB exposure and genotype on cytokine levels in serum and hippocampal tissue of weanling mice. These results suggest that developmental PCB exposure has chronic effects on baseline serum, but not hippocampal, cytokine levels in juvenile mice.

Placenta Disrupted: Endocrine Disrupting Chemicals and Pregnancy

Endocrine disrupting chemicals (EDCs) are chemicals that can interfere with normal endocrine signals. Human exposure to EDCs is particularly concerning during vulnerable periods of life, such as pregnancy. However, often overlooked is the effect that EDCs may pose to the placenta. The abundance of hormone receptors makes the placenta highly sensitive to EDCs. We have reviewed the most recent advances in our understanding of EDC exposures on the development and function of the placenta such as steroidogenesis, spiral artery remodeling, drug-transporter expression, implantation and cellular invasion, fusion, and proliferation. EDCs reviewed include those ubiquitous in the environment with available human biomonitoring data. This review also identifies critical gaps in knowledge to drive future research in the field.

Maternal lithium chloride exposure alters the neuroendocrine-cytokine axis in neonatal albino rats

The aim of this work was to clarify whether maternal lithium chloride (LiCl) exposure disrupts the neonatal neuroendocrine-cytokine axis. Pregnant Wistar rats were orally administrated 50 mg LiCl/kg b.wt. from gestational day (GD) 1 to postpartum day 28. Maternal administration of LiCl induced a hypothyroid state in both dams and their neonates compared to the control dams and neonates at lactation days (LDs) 14, 21 and 28, where the levels of serum free triiodothyronine (FT3) and free thyroxin (FT4) were decreased and the level of serum thyrotropin (TSH) level was increased. A noticeable depression in maternal body weight gain, neonatal body weight and neonatal serum growth hormone (GH) was observed on all examined postnatal days (PNDs; 14, 21 and 28). A single abortion case was recorded at GD 17, and three dead neonates were noted at birth in the LiCl-treated group. Maternal administration of LiCl disturbed the levels of neonatal serum tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta (TGF-β), interleukin-1 beta (IL-1β), interferon-gamma (INF-γ), leptin, adiponectin and resistin at all tested PNDs compared to the control group. This administration produced a stimulatory action on the level of neonatal cerebral serotonin (5-HT) at PND 14 and on the level of neonatal cerebral norepinephrine (NE) at PNDs 21 and 28. However, this administration produced an inhibitory action on the level of neonatal cerebral dopamine (DA) at all examined PNDs and on the level of neonatal cerebral NE at PND 14 and the level of neonatal cerebral 5-HT at PNDs 21 and 28 compared to the corresponding control group. Thus, maternal LiCl exposure-induced hypothyroidism disrupts the neonatal neuroendocrine-cytokine system, which delay cerebral development.

Overdoses of Acetaminophen Disrupt the Thyroid-Liver Axis in Neonatal Rats

OBJECTIVE

The aim of the study was to examine the impact of neonatal acetaminophen (APAP; paracetamol) administrations on the thyroid-liver axis in male Wistar rats.

METHODS

APAP (100 or 350mg/kg) was orally administered to neonates from Postnatal Day (PND) 20 to 40.

RESULTS

Both APAP doses elicited a substantial increase in serum TSH, albumin, AST, ALT, and ALP values, and a profound decrease in serum FT4 and FT3 values at PND 40 relative to those in the control group. Additionally, the hypothyroid state in both APAP-treated groups may increase the histopathological variations in the neonatal liver, such as destructive degeneration, fibrosis, fatty degeneration, fibroblast proliferation, haemorrhage, oedema, and vacuolar degeneration, at PND 40. Moreover, in the APAP groups, a marked depression was recorded in the t-SH and GSH levels and GPx and CAT activities at PND 40 in the neonatal liver compared to those in the control group. However, the levels of hepatic LPO, H2O2, and NO were increased in both APAP-treated groups at PND 40. All previous alterations were dose- dependent.

CONCLUSION

Neonatal APAP caused a hypothyroidism and disturbed hepatic cellular components by increasing prooxidant markers and decreasing antioxidant markers, causing hepatotoxicity. Thus, neonatal administrations of APAP may act as a neonatal thyroid-liver disruptor.

Gestational Arsenic Trioxide Exposure Acts as a Developing Neuroendocrine-Disruptor by Downregulating Nrf2/PPARγ and Upregulating Caspase-3/NF-ĸB/Cox2/BAX/iNOS/ROS

The goal of this investigation was to evaluate the effects of gestational administrations of arsenic trioxide (ATO; As₂O₃) on fetal neuroendocrine development (the thyroid-cerebrum axis). Pregnant Wistar rats were orally administered ATO (5 or 10 mg/kg) from gestation day (GD) 1 to 20. Both doses of ATO diminished free thyroxine and free triiodothyronine levels and augmented thyrotropin level in both dams and fetuses at GD 20. Also, the maternofetal hypothyroidism in both groups caused a dose-dependent reduction in the fetal serum growth hormone, insulin growth factor-I (IGF-I), and IGF-II levels at embryonic day (ED) 20. These disorders perturbed the maternofetal body weight, fetal brain weight, and survival of pregnant and their fetuses. In addition, destructive degeneration, vacuolation, hyperplasia, and edema were observed in the fetal thyroid and cerebrum of both ATO groups at ED 20. These disruptions appear to depend on intensification in the values of lipid peroxidation, nitric oxide, and H₂O₂, suppression of messenger RNA (mRNA) expression of nuclear factor erythroid 2-related factor 2 and peroxisome proliferator-activated receptor gamma, and activation of mRNA expression of caspase-3, nuclear factor kappa-light-chain-enhancer of activated B cells, cyclooxygenase-2, Bcl-2–associated X protein, and inducible nitric oxide synthase in the fetal cerebrum. These data suggest that gestational ATO may disturb thyroid-cerebrum axis generating fetal neurodevelopmental toxicity.

Assessment of epigenetic changes and oxidative DNA damage in rat pups exposed to polychlorinated biphenyls and the protective effect of curcumin in the prenatal period

Background Polychlorinated biphenyls (PCBs) are persistent organic chemicals that exert neurotoxic and endocrine disrupting effects. The aims of this study were to examine the effects of prenatal Aroclor 1254 (PCBs mixture) exposure on central nervous system tissues DNA and to evaluate the effects of curcumin. Methods Rat pups were assigned to three groups: [Group 1], Aroclor 1254 administrated group; [Group 2], Aroclor 1254 and curcumin administrated group; and [Group 3], control group. Plasma, cerebrum, cerebellum, pons and medulla oblongata tissue homogenates 8-hydroxy-2'-deoxyguanosine [8-(OH)DG] levels and plasma freeT4 levels were determined. Global DNA methylation and hydroxymethylation status were determined in cerebrum, cerebellum, pons and medulla oblongata. To this aim, DNA 5-hydroxymethylcytosine and 5-methylcytosine levels were measured, respectively. Results Mean cerebellum and cerebral cortex 5-hydroxymethylcytosine and 5-methylcytosine levels were higher in the control group than in the experimental groups. Mean plasma, cerebellum and cerebral cortex 8-(OH)DG concentrations were higher in Group 1 than the control group. No statistically significant difference was observed between Group 2 and the control group in terms of cerebellum and cerebral cortex 8-(OH)DG concentrations. Histopathological changes were also observed in the cerebral cortex and cerebellum of rat pups exposed to Aroclor 1254. PCBs exposure changes both DNA methylation and hypomethylation status and induces cerebellar and cerebral cortex DNA damage in the prenatal period. Exogenous curcumin may have protective effect on PCBs-induced DNA damage in cerebellum and cerebral cortex.

Gestational caffeine exposure acts as a fetal thyroid-cytokine disruptor by activating caspase-3/BAX/Bcl-2/Cox2/NF-κB at ED 20

The objective of this examination was to explore the impact of gestational caffeine (1,3,7-trimethylxanthine) exposure on the maternofetal thyroid axis and fetal thyroid-cytokine communications during gestation. Pregnant rats (Rattus norvegicus) were intraperitoneally administered caffeine (120 or 150 mg kg-1) from gestation day (GD) 1 to 20. Both doses of caffeine resulted in maternal hyperthyroidism, whereas the elevation in the concentration of serum free triiodothyronine (FT3) and free thyroxine (FT4) was related to a depletion in the level of TSH at GD 20. Maternal body weight gain and food consumption were markedly increased, while fetal body weight was significantly reduced. These alterations caused fetal hypothyroidism and several pathological lesions in the fetal thyroid gland including a vacuolar colloid, destructive degeneration, atrophy and hyperplasia at embryonic day (ED) 20. The abnormalities in the fetal thyroid gland seemed to depend on the activation of caspase-3, Bcl-2, BAX, Cox2, and NF-κB mRNA expression. Both maternal caffeine doses caused a marked attenuation in the values of fetal serum GH, IGF-II, VEGF, TGF-β, TNF-α, IL-1β, IL-6, leptin and MCP-1, and a noticeable elevation in the value of fetal serum adiponectin at ED 20. Thus, gestational caffeine exposure might disrupt the fetal thyroid-cytokine axis.

WITHDRAWN: Toxic effects of gestational arsenic trioxide on the neuroendocrine axis of developing rats

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Suppressive effects of neonatal bisphenol A on the neuroendocrine system

The aim of this study was to assess the effects of neonatal bisphenol A (BPA) administration on neuroendocrine features (the thyroid–brain axis). BPA (20 or 40 µg/kg) was orally administered to juvenile male albino rats ( Rattus norvegicus) from postnatal days (PNDs) 15 to 30. Both doses resulted in lower serum thyroxine (T4), triiodothyronine (T3), and growth hormone levels and higher thyrotropin level than the control levels at PND 30. In the neonatal cerebellum and cerebrum, vacuolation, pyknosis, edema, degenerative changes, and reductions in the size and number of the cells were observed in both treated groups. Alternatively, elevations in oxidative markers (lipid peroxidation, nitric oxide, and hydrogen peroxide [H2O2]) at both dose levels were recorded at PND 30, along with decreased activities of antioxidant markers (ascorbic acid, total thiol [t-SH], glutathione, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, and catalase) with respect to control levels. Thus, the BPA-induced hypothyroid state may disturb the neonatal thyroid–brain axis via production of free radicals, and this could damage the plasma membrane and cellular components, delaying cerebrum and cerebellum development.