Neurodevelopmental and behavioral toxicity via lactational exposure to the sum of six indicator non-dioxin-like-polychlorinated biphenyls (∑6 NDL-PCBs) in mice

Prenatal exposure to persistent organic pollutants and emotional and behavioral outcomes from early childhood to adolescence: Rhea Cohort Study in Crete, Greece

Background

Persistent organic pollutants (POPs) are widespread, hazardous chemicals, but their impact on emotional and behavioral development is not well understood. This study aimed to investigate whether prenatal exposure to POPs influences internalizing, externalizing, and attention deficit hyperactivity disorder (ADHD) symptoms from early childhood to adolescence.

Methods

We utilized longitudinally collected data from 467 mother-child pairs in the Rhea study. Concentrations of hexachlorobenzene, dichlorodiphenyldichloroethylene, and six polychlorinated biphenyl congeners (PCBs) were determined in maternal serum samples collected during early pregnancy. Mothers reported their children's internalizing, externalizing, and ADHD symptoms at ages 4 (Strengths and Difficulties Questionnaire, ADHD Test), 6, 11, and 15 years (Child Behavior Checklist, Conners' Parent Rating Scale). The associations between prenatal pollutant exposure and longitudinally studied outcomes were assessed using generalized estimating equation models.

Results

In utero exposure to hexachlorobenzene and dichlorodiphenyldichloroethylene was not associated with emotional or behavioral outcomes. Prenatal exposure to PCBs was associated with decreased internalizing symptoms from childhood through adolescence and reduced ADHD symptoms at age 4 (adjusted β [95% confidence interval]: -0.17 [-0.29, -0.05], and -0.16 [-0.30, -0.02], per doubling of exposure, respectively). Sensitivity analyses confirmed these findings, though the association between PCB exposure and internalizing symptoms was not observed in women with sufficient gestational weight gain.

Conclusions

Our findings suggest that prenatal POP exposure does not adversely affect emotional and behavioral development from preschool age through adolescence. Further research is warranted to elucidate the potential impact of gestational POP exposure on developmental trajectories.

Effects of 28-day nose-only inhalation of PCB52 (2,2',5,5'-Tetrachlorobiphenyl) on the brain transcriptome

A semi-volatile polychlorinated biphenyl (PCB) congener, PCB52, is present in the indoor air of schools; however, the effects of inhaled PCB52 on the brain have not been investigated. This study exposed male Sprague-Dawley rats at 39 days of age and female rats at 42 days of age to PCB52 for 4 hours per day over 28 consecutive days through nose-only inhalation. Neurobehavioral tests were conducted during the last 5 days of exposure. The total estimated PCB52 exposures after 28 days were 1080±20 µg/kg BW for male rats and 1140±10 µg/kg BW for female rats. PCB52 and its metabolites were detected by gas chromatography-tandem mass spectrometry in the brain, lung, and serum, with the lung showing the highest concentrations. PCB52 levels were higher in the brains of females than males. Males showed increased exploratory behavior compared to controls, whereas females exhibited decreased exploratory behavior compared to controls in the same tests. PCB52 exposure did not impact locomotor activity or working memory. Gene expression and pathway analysis in the striatum and cerebellum suggest that PCB52 inhalation causes mitochondrial dysfunction. No significant differences were observed by immunohistochemical evaluation in the density and percent area of total cells, astrocytes, or microglia in the striatum and cerebellar cortex. Our results indicate multilevel effects of inhaled PCB52 on the rat brain, from gene expression to behavioral effects.

Sex-specific Effects of Endocrine-disrupting Chemicals on Brain Monoamines and Cognitive Behavior

The period of brain sexual differentiation is characterized by the development of hormone-sensitive neural circuits that govern the subsequent presentation of sexually dimorphic behavior in adulthood. Perturbations of hormones by endocrine-disrupting chemicals (EDCs) during this developmental period interfere with an organism's endocrine function and can disrupt the normative organization of male- or female-typical neural circuitry. This is well characterized for reproductive and social behaviors and their underlying circuitry in the hypothalamus and other limbic regions of the brain; however, cognitive behaviors are also sexually dimorphic, with their underlying neural circuitry potentially vulnerable to EDC exposure during critical periods of brain development. This review provides recent evidence for sex-specific changes to the brain's monoaminergic systems (dopamine, serotonin, norepinephrine) after developmental EDC exposure and relates these outcomes to sex differences in cognition such as affective, attentional, and learning/memory behaviors.

Prenatal exposure to a mixture of organochlorines and metals and internalizing symptoms in childhood and adolescence

BACKGROUND

Although prenatal chemical exposures influence neurobehavior, joint exposures are not well explored as risk factors for internalizing disorders through adolescence.

OBJECTIVE

To evaluate associations of prenatal organochlorine and metal exposures, considered individually and as a mixture, with mid-childhood and adolescent internalizing symptoms.

METHODS

Participants were 468 children from a prospective cohort recruited at birth (1993-1998) in New Bedford, Massachusetts. Organochlorines (hexachlorobenzene, p,p'-dichlorodiphenyl dichloroethylene, polychlorinated biphenyls) and metals (lead, manganese) were analyzed in cord blood. Internalizing symptoms (anxiety, depressive, somatic) were assessed via multiple informants on the Conners' Rating Scale (CRS) at 8-years and Behavior Assessment System for Children, Second Edition (BASC-2) at 15-years; higher T-scores indicate greater symptoms. Overall and sex-specific covariate-adjusted associations were evaluated using Bayesian Kernel Machine Regression (BKMR) and five-chemical linear regression models.

RESULTS

The cohort was socioeconomically diverse (35% household income <$20,000; 55% maternal ≤ high school education at birth). Most chemical concentrations were consistent with background levels [e.g., median (range) cord blood lead: 1.1 (0-9.4) μg/dL]. BKMR suggested linear associations and no interactions between chemicals. The overall mixture was positively associated with Conners' Parent Rating Scale (CPRS) and BASC-2 Self Report of Personality (SRP) anxiety and depressive symptoms, and negatively with somatic symptoms. Prenatal lead was positively associated with adolescent anxiety symptoms [1.56 (95% CI: 0.50, 2.61) BASC-2 SRP Anxiety score increase per doubling lead]. For CRPS and BASC-2 SRP, a doubling of cord blood manganese was positively associated with internalizing symptoms for girls [e.g., 3.26 (95% CI: 0.27, 6.25) BASC-2 SRP Depression score increase], but not boys. Organochlorine exposures were not adversely associated with internalizing symptoms.

DISCUSSION

Low-level prenatal lead exposure was positively associated with adolescent anxiety symptoms, and prenatal manganese exposure was positively associated with internalizing symptoms for girls from mid-childhood through adolescence. In utero neurotoxicant metal exposures may contribute to the emergence of anxiety and depression.

Environmental pollution, a hidden culprit for health issues

The environmental and health impacts from the massive discharge of chemicals and subsequent pollution have been gaining increasing public concern. The unintended exposure to different pollutants, such as heavy metals, air pollutants and organic chemicals, may cause diverse deleterious effects on human bodies, resulting in the incidence and progression of different diseases. The article reviewed the outbreak of environmental pollution-related public health emergencies, the epidemiological evidence on certain pollution-correlated health effects, and the pathological studies on specific pollutant exposure. By recalling the notable historical life-threatening disasters incurred by local chemical pollution, the damning evidence was presented to criminate certain pollutants as the main culprit for the given health issues. The epidemiological data on the prevalence of some common diseases revealed a variety of environmental pollutants to blame, such as endocrine-disrupting chemicals (EDCs), fine particulate matters (PMs) and heavy metals. The retrospection of toxicological studies provided illustrative clues for evaluating ambient pollutant-induced health risks. Overall, environmental pollution, as the hidden culprit, should answer for the increasing public health burden, and more efforts are highly encouraged to strive to explore the cause-and-effect relationships through extensive epidemiological and pathological studies.

Toxicity Assessment of 91-Day Repeated Inhalation Exposure to an Indoor School Air Mixture of PCBs

School indoor air contaminated with polychlorinated biphenyls (PCBs) released from older building materials and paint pigments may pose health risks to children, as well as teachers and staff, by inhalation of PCBs. The health effects of long-term inhalation exposure to PCBs are poorly understood. We conducted a comprehensive toxicity assessment of 91-day repeated inhalation exposure to a lab-generated mixture of PCBs designed to emulate indoor school air, combining transcriptomics, metabolomics, and neurobehavioral outcomes. Female Sprague-Dawley rats were exposed to school air mixture (SAM+) at a concentration of 45.5 ± 5.9 μg/m3 ∑209PCB or filtered air 4 h/day, 6 days/week for 13 weeks using nose-only exposure systems. The congener-specific PCB body burden was quantified in major tissues using GC-MS/MS. The generated SAM+ vapor recapitulated the target school air profile with a similarity coefficient, cos θ of 0.91. PCB inhalation yielded 875-9930 ng/g ∑209PCBlipid weight levels in tissues in the following ascending order: brain < liver < lung < serum < adipose tissue. We observed that PCB exposure impaired memory, induced anxiety-like behavior, significantly reduced white blood cell counts, mildly disrupted metabolomics in plasma, and influenced transcription processes in the brain with 274 upregulated and 58 downregulated genes. With relatively high exposure and tissue loading, evidence of toxicity from half the end points tested was seen in the rats.

Spatial distribution of pesticides, organochlorine compounds, PBDEs, and metals in surface marine sediments from Cartagena Bay, Colombia

Cartagena Bay is an estuarine system located in the Caribbean Sea (Colombia, South America), that receives fresh water from Canal del Dique, which is connected to the Magdalena River, the most important river of Colombia, with some of the most prominent Colombian cities located in its watershed, which has a high sediment yield. An analysis of persistent organic pollutants and heavy metals was carried out on marine sediments from Cartagena Bay. Cartagena Bay sediments deployed the occurrence of total levels of pesticides (thiocarbamates, bromacil, triazines, organochlorines, and organophosphorus), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), in sediments ranging from 0.83-33.67 ng/g dry-weight, 0.05-0.34 ng/g dry-weight, and 0.06-19.58 ng/g dry-weight, respectively. Their concentrations were lower than those reported in NOAA Screening Quick Reference Tables. DDTs and PCBs are banned organochlorine compounds, since, even at low levels, their presence in sediments represents a threat to aquatic organisms and, therefore, to human health through the trophic chain. Sediments showed high concentrations of strontium (50-959.6 mg/kg). All metals evaluated in the marine sediments were found in the S6 sampling point; this was near tannery and hydrocarbon industries (Pb 37.1 mg/kg, Cr 137.2 mg/kg, Cd 1.7 mg/kg, Cu 64.4 mg/kg, As 13.1 mg/kg, Sr 318.9 mg/kg); these results exceeded the accepted values of threshold effect levels (TEL) used as an indicator of their potential risk on marine life.

In utero and lactational PCB exposure drives anatomic changes in the juvenile mouse bladder

Bladder dysfunction, including incontinence, difficulty emptying the bladder, or urgency to urinate is a pervasive health and quality of life concern. However, risk factors for developing these symptoms are not completely understood, and the influence of exposure to environmental chemicals, especially during development, on the formation and function of the bladder is understudied. Environmental contaminants such as polychlorinated biphenyls (PCBs) are known to pose a risk to the developing brain; however, their influence on the development of peripheral target organs, such as bladder, are unknown. To address this data gap, C57Bl/6J mouse dams were exposed to an environmentally-relevant PCB mixture at 0, 0.1, 1 or 6 mg/kg daily beginning two weeks prior to mating and continuing through gestation and lactation. Bladders were collected from offspring at postnatal days (P) 28-31. PCB concentrations were detected in bladders in a dose-dependent manner. PCB effects on the bladder were sex- and dose-dependent. Overall, PCB effects were observed in male, but not female, bladders. PCBs increased bladder volume and suburothelial βIII-tubulin-positive nerve density compared to vehicle control. A subset of these nerves were sensory peptidergic axons indicated by increased calcitonin gene-related protein (CGRP) positive nerve fibers in mice exposed to the highest PCB dose compared to the lowest PCB dose. PCB-induced increased nerve density was also positively correlated with the number of mast cells in the bladder, suggesting inflammation may be involved. There were no detectable changes in epithelial composition or apoptosis as indicated by expression of cleaved caspase 3, suggesting PCBs do not cause overt toxicity. Bladder volume changes were not accompanied by changes in bladder mass or epithelial thickness, indicating that obstruction was not likely involved. Together, these results are the first to suggest that following developmental exposure, PCBs can distribute to the bladder and alter neuroanatomic development and bladder volume in male mice.

Chronic depression-like phenotype in male offspring mice following perinatal exposure to naturally contaminated eels with a mixture of organic and inorganic pollutants

Previously, we demonstrated that maternal exposure to high, intermediate, or lowly contaminated European eels with a mixture of chemicals, during pregnancy and lactation, resulted in adult despair-like behavior, selectively in male offspring mice. Here, we investigate if depression-like behavior in offspring males was transient or permanent by monitoring immobility behavior, a measure of behavioral despair, at three distinct stages of life, including young adult (post-natal day (PND) 55), mature adult (PND 200) and middle (PNDs 335-336) age, in the forced swimming (FST) and the tail suspension (TST) tests. Oxidative stress markers including malondialdehyde (MDA) levels and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were evaluated in the hippocampus, prefrontal cortex, and cerebellum of middle-aged animals. Findings showed a significant enhancement of immobility behavior in the TST performed at young adult age (all p < 0.05) in the FST carried out at mature adult age (all p < 0.001) and in both behavioral tests realized at middle age (all p < 0.05, except one p = 0.06) in mice perinatally exposed to eels compared with non-exposed controls. Antioxidant-related enzyme activities, including SOD and CAT, were only elevated in the hippocampus of middle-aged males perinatally exposed to the two more polluted eels (all p < 0.05). Further, lipid peroxidation, assessed by MDA levels, was not found to be differentially regulated in the selected areas of middle-aged brains of exposed mice (all p > 0.05). Collectively, this suggested limited oxidative metabolism disturbances in middle-aged brains exposed to eels. In summary, our results highlighted that offspring males perinatally exposed to naturally contaminated reared and river eels with persistent organic pollutants (POPs) and heavy metals displayed chronic depression-like phenotype. As extrapolation of data to humans should be done with precaution, retrospective and prospective epidemiological studies are needed to clarify this potential relationship, stressed in our animal model, between maternal polluted fish consumption and chronically low mood in offspring.

Sex-specific effects of developmental exposure to polychlorinated biphenyls on neuroimmune and dopaminergic endpoints in adolescent rats

Exposure to environmental contaminants early in life can have long lasting consequences for physiological function. Polychlorinated biphenyls (PCBs) are a group of ubiquitous contaminants that perturb endocrine signaling and have been associated with altered immune function in children. In this study, we examined the effects of developmental exposure to PCBs on neuroimmune responses to an inflammatory challenge during adolescence. Sprague Dawley rat dams were exposed to a PCB mixture (Aroclor 1242, 1248, 1254, 1:1:1, 20 μg/kg/day) or oil control throughout pregnancy, and adolescent male and female offspring were injected with lipopolysaccharide (LPS, 50 μg/kg, ip) or saline control prior to euthanasia. Gene expression profiling was conducted in the hypothalamus, prefrontal cortex, striatum, and midbrain. In the hypothalamus, PCBs increased expression of genes involved in neuroimmune function, including those within the nuclear factor kappa b (NF-κB) complex, independent of LPS challenge. PCB exposure also increased expression of receptors for dopamine, serotonin, and estrogen in this region. In contrast, in the prefrontal cortex, PCB exposure blunted or induced irregular neuroimmune gene expression responses to LPS challenge. Moreover, neither PCB nor LPS exposure altered expression of neurotransmitter receptors throughout the mesocorticolimbic circuit. Almost all effects were present in males but not females, in agreement with the idea that male neuroimmune cells are more sensitive to perturbation and emphasizing the importance of studying both male and female subjects. Given that altered neuroimmune signaling has been implicated in mental health and substance abuse disorders that often begin during adolescence, these results highlight neuroimmune processes as another mechanism by which early life PCBs can alter brain function later in life.

Evaluating the Role of the Steroid and Xenobiotic Receptor (SXR/PXR) in PCB-153 Metabolism and Protection against Associated Adverse Effects during Perinatal and Chronic Exposure in Mice

BACKGROUND

Polychlorinated biphenyls (PCBs) are environmental toxicants; PCB exposure has been associated with adverse effects on wildlife and humans. However, the mechanisms underlying these adverse effects are not fully understood. The steroid and xenobiotic receptor [SXR; also known as the pregnane X receptor (PXR) and formally known as NR1I2] is a nuclear hormone receptor that regulates inducible metabolism of drugs and xenobiotics and is activated or inhibited by various PCB congeners.

OBJECTIVES

The aim of this study was to investigate the effects of exposure to PCB-153, the most prevalent PCB congener in human tissues, on SXR knockout mice (SXRKO) and to elucidate the role of SXR in PCB-153 metabolism and promotion of its harmful effects.

METHODS

Wild-type (WT) and SXRKO mice were chronically or perinatally exposed to a low dose (54μg/kg/d) of PCB-153. Blood, livers, and spleens were analyzed using transcriptome sequencing (RNA-seq) and molecular techniques to investigate the impacts of exposure on metabolism, oxidative stress, and hematological parameters.

RESULTS

SXRKO mice perinatally exposed to PCB-153 displayed elevated oxidative stress, symptoms of hemolytic anemia, and premature death. Transcriptomal analysis revealed that expression of genes involved in metabolic processes was altered in SXRKO mice. Elevated levels of the PCB-153 metabolite, 3-OH-PCB-153, were found in exposed SXRKO mice compared to exposed WT mice. Blood hemoglobin (HGB) levels were lower throughout the lifespan, and the occurrence of intestinal tumors was larger in SXRKO mice chronically exposed to PCB-153 compared to vehicle and WT controls.

DISCUSSION

Our results suggest that altered metabolism induced by SXR loss of function resulted in the accumulation of hydroxylated metabolites upon exposure to PCB-153, leading to oxidative stress, hemolytic anemia, and tumor development in a mouse model. These results support a major role for SXR/PXR in protection against xenobiotic-induced oxidative stress by maintaining proper metabolism in response to PCB-153 exposure. This role of SXR could be generally applicable to other environmental toxicants as well as pharmaceutical drugs. https://doi.org/10.1289/EHP6262.

Long Term Pharmacological Perturbation of Autophagy in Mice: Are HCQ Injections a Relevant Choice?

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved catabolic process whose loss-of-function has been linked to a growing list of pathologies. Knockout mouse models of key autophagy genes have been instrumental in the demonstration of the critical functions of autophagy, but they display early lethality, neurotoxicity and unwanted autophagy-independent phenotypes, limiting their applications for in vivo studies. To avoid problems encountered with autophagy-null transgenic mice, we investigated the possibility of disturbing autophagy pharmacologically in the long term. Hydroxychloroquine (HCQ) ip injections were done in juvenile and adult C57bl/6j mice, at range doses adapted from the human malaria prophylactic treatment. The impact on autophagy was assessed by western-blotting, and juvenile neurodevelopment and adult behaviours were evaluated for four months. Quite surprisingly, our results showed that HCQ treatment in conditions used in this study neither impacted autophagy in the long term in several tissues and organs nor altered neurodevelopment, adult behaviour and motor capabilities. Therefore, we recommend for future long-term in vivo studies of autophagy, to use genetic mouse models allowing conditional inhibition of selected Atg genes in appropriate lineage cells instead of HCQ treatment, until it could be successfully revisited using higher HCQ doses and/or frequencies with acceptable toxicity.

Evidence Implicating Non-Dioxin-Like Congeners as the Key Mediators of Polychlorinated Biphenyl (PCB) Developmental Neurotoxicity

Despite being banned from production for decades, polychlorinated biphenyls (PCBs) continue to pose a significant risk to human health. This is due to not only the continued release of legacy PCBs from PCB-containing equipment and materials manufactured prior to the ban on PCB production, but also the inadvertent production of PCBs as byproducts of contemporary pigment and dye production. Evidence from human and animal studies clearly identifies developmental neurotoxicity as a primary endpoint of concern associated with PCB exposures. However, the relative role(s) of specific PCB congeners in mediating the adverse effects of PCBs on the developing nervous system, and the mechanism(s) by which PCBs disrupt typical neurodevelopment remain outstanding questions. New questions are also emerging regarding the potential developmental neurotoxicity of lower chlorinated PCBs that were not present in the legacy commercial PCB mixtures, but constitute a significant proportion of contemporary human PCB exposures. Here, we review behavioral and mechanistic data obtained from experimental models as well as recent epidemiological studies that suggest the non-dioxin-like (NDL) PCBs are primarily responsible for the developmental neurotoxicity associated with PCBs. We also discuss emerging data demonstrating the potential for non-legacy, lower chlorinated PCBs to cause adverse neurodevelopmental outcomes. Molecular targets, the relevance of PCB interactions with these targets to neurodevelopmental disorders, and critical data gaps are addressed as well.

Comparative evaluation of influence of aging, soil properties and structural characteristics on bioaccessibility of polychlorinated biphenyls in soil

Though bioaccessibility commonly recognized as a guideline for risk assessment is closely related with pollution occurrence and chemical species of compounds, the mechanistic links are barely evaluated particularly for widespread polychlorinated biphenyls (PCBs) in soil. With the biomimetic extraction of hydroxypropyl-β-cyclodextrin (β-HPCD), the temporal and spatial influences of soil properties, aging and structural characteristics, e.g. polarity of PCB congeners on bioaccessibility were investigated for PCBs. Sensitive variation of bioaccessibility with aging, soil organic matter (SOM), particle size and soil moisture were clearly evidenced for different PCB congeners. Due to aging, the bioaccessibility decreased in the long term after stabilization for 36 h. In concert with the first-order kinetics, the decay rates of bioaccessibility were shown with congener-specificity and were well correlated with dipoles of PCBs. The increment of SOM diminished the bioaccessibility for the strengthened adsorption while the increased particle size and soil moisture elevated it possibly due to the less adsorption on soil particles and more accommodation of PCBs in soil pore water. Except the positive correlations with particle size, soil moisture and dipole moment, the greater dependency on aging and SOM was highlighted for bioaccessibility by partial least squares (PLS) analysis. The mutual relationship with influential factors was quantitatively formulated for accelerative prediction of bioaccessibility, and the comparative evaluation and detailed insights into the mechanistic links would thus help enhance the precise determination of bioaccessibility and risk assessment of PCBs in soil.

Ryanodine receptor and FK506 binding protein 1 in the Atlantic killifish (Fundulus heteroclitus): A phylogenetic and population-based comparison

Non-dioxin-like polychlorinated biphenyls (NDL PCBs) activate ryanodine receptors (RyR), microsomal Ca²⁺ channels of broad significance. Teleost fish may be important models for NDL PCB neurotoxicity, and we used sequencing databases to characterize teleost RyR and FK506 binding protein 12 or 12.6kDa (genes FKBP1A; FKBP1B), which promote NDL PCB-triggered Ca²⁺ dysregulation. Particular focus was placed on describing genes in the Atlantic killifish (Fundulus heteroclitus) genome and searching available RNA-sequencing datasets for single nucleotide variants (SNV) between PCB tolerant killifish from New Bedford Harbor (NBH) versus sensitive killifish from Scorton Creek (SC), MA. Consistent with the teleost whole genome duplication (tWGD), killifish have six RyR genes, corresponding to a and b paralogs of mammalian RyR1, 2 and 3. The presence of six RyR genes was consistent in all teleosts investigated including zebrafish. Killifish have four FKBP1; one FKBP1b and three FKBP1a named FKBP1aa, FKBP1ab, likely from the tWGD and a single gene duplicate FKBP1a3 suggested to have arisen in Atherinomorphae. The RyR and FKBP1 genes displayed tissue and developmental stage-specific mRNA expression, and the previously uncharacterized RyR3, herein named RyR3b, and all FKBP1 genes were prominent in brain. We identified a SNV in RyR3b encoding missense mutation E1458D. In NBH killifish, 57% were heterozygous and 28% were homozygous for this SNV, whereas almost all SC killifish (94%) lacked the variant (n≥39 per population). The outlined sequence differences between mammalian and teleost RyR and FKBP1 together with outlined population differences in SNV frequency may contribute to our understanding of NDL PCB neurotoxicity.

Perinatal effects of exposure to PCBs on social preferences in young adult and middle-aged offspring mice

In social species, social interactions between conspecifics constitute a fundamental component to establish relations, provide best chances to reproduce, and even improve survival rates. In this study, a three-chambered social approach test was used to estimate the level of sociability and level of preference for social novelty in both male and female young adult (postnatal day (PND) 50) and middle-aged (PND 330) offspring mice (n=10 per group) that were perinatally exposed to a mixture of six polychlorinated biphenyls (PCBs), 28, 52, 101, 138, 153, and 180, at environmentally low doses (10 and 1000ng/kg b.w. for dams during gestation and lactation), a profile that closely mimics human exposure to contaminated fish. Our results showed that PCBs bidirectionally modulated social preferences in offspring mice, and the effects were sex and age dependent. However, increased levels of social interactions were rather frequently detected in both assays of the three-chambered test. Reduced social interaction was only induced in 1000ng/kg PCB-exposed middle-aged males, which exhibited similar preferences to social and non-social stimuli when compared to middle-aged controls. Furthermore, results showed that plasma levels of both corticosterone and acetylcholinesterase activity were higher in all PCB-exposed middle-aged males and females than in their control counterparts. In summary, although the effects of PCBs were only of moderate magnitude, our results suggest that a PCB mixture can act as an endocrine disruptor in offspring mice, disturbing the formation of normal social habits.

Hippocampal-dependent memory deficit induced by perinatal exposure to polutted eels in middle-aged offspring mice: Sex differential effects

The effects of perinatal exposure to low, intermediate, or highly polluted eels on neonatal, postnatal, adult and middle-aged brain inflammation, and on cognitive performances of middle-aged offspring mice were compared to those of offspring controls. Inflammatory markers in microglia were assessed in offspring on the postnatal days-PNDs 1, 21, 100 and 330. Activated p38MAPK, ERK-1/2 and p65, and acetylcholine levels were assessed in the middle-aged hippocampus. Plasma myeloperoxidase and corticosterone levels were evaluated at PND 330. Learning and its retention, and working memory in middle-aged offspring were assessed using the Morris water maze, and Y-maze. Our results showed enhanced microglia production of inflammatory markers across the lifespan of male as well as female exposed offspring. Inflammation and increased p38 MAPK activation were detected in the exposed middle-aged hippocampus of both exposed sexes. Significant levels of MPO, but not corticosterone, were found in middle-aged males and females perinatally exposed to eels. However, decreases in ERK1/2 and p65 activation, and acetylcholine levels were only detected in female hippocampus exposed to either intermediately or highly polluted eels. Sex selective effects were also detected with regard to memory, the only altered cognitive function. Thus, middle-aged females, but not males, perinatally exposed to either intermediately or highly polluted eels take longer to locate the escape platform, spend considerably less time in the platform and perform less visit to the platform in the retention test. Our results suggest perinatal programming of hippocampal-dependent memory deficit by inflammation in middle-aged offspring, in sex and dose dependent manner.

Endocrine-disrupting chemicals and the regulation of energy balance

Energy balance involves the adjustment of food intake, energy expenditure and body fat reserves through homeostatic pathways. These pathways include a multitude of biochemical reactions, as well as hormonal cues. Dysfunction of this homeostatic control system results in common metabolism-related pathologies, which include obesity and type 2 diabetes mellitus. Metabolism-disrupting chemicals (MDCs) are a particular class of endocrine-disrupting chemicals that affect energy homeostasis. MDCs affect multiple endocrine mechanisms and thus different cell types that are implicated in metabolic control. MDCs affect gene expression and the biosynthesis of key enzymes, hormones and adipokines that are essential for controlling energy homeostasis. This multifaceted spectrum of actions precludes compensatory responses and favours metabolic disorders. Herein, we review the main mechanisms used by MDCs to alter energy balance. This work should help to identify new MDCs, as well as novel targets of their action.

Relative toxicity for indoor semi volatile organic compounds based on neuronal death

BACKGROUND

Semi Volatile Organic Compounds (SVOCs) are contaminants commonly found in dwellings as a result of their use as plasticizers, flame retardants, or pesticides in building materials and consumer products. Many SVOCs are suspected of being neurotoxic, based on mammal experimentation (impairment of locomotor activity, spatial learning/memory or behavioral changes), raising the question of cumulative risk assessment. The aim of this work is to estimate the relative toxicity of such SVOCs, based on neuronal death.

METHOD

SVOCs fulfilling the following conditions were included: detection frequency >10% in dwellings, availability of data on effects or mechanism of action for neurotoxicity, and availability of dose-response relationships based on cell viability assays as a proxy of neuronal death. Benchmark concentration values (BMC) were estimated using a Hill model, and compared to assess relative toxicity.

RESULTS

Of the 58 SVOCs selected, 28 were suspected of being neurotoxic in mammals, and 21 have been documented as inducing a decrease in cell viability in vitro. 13 have at least one dose-response relationship that can be used to derive a BMC based on a 10% fall in neuronal viability. Based on this in vitro endpoint, PCB-153 appeared to be the most toxic compound, having the lowest BMC₁₀ (0.072μM) and diazinon the least toxic compound, having the highest BMC₁₀ (94.35μM). We showed that experimental designs (in particular choice of cell lines) had a significant influence on BMC calculation.

CONCLUSION

For the first time, the relative in vitro toxicity of 13 indoor contaminants belonging to different chemical families has been assessed on the basis of neuronal cell viability. Lack of comparable toxicity datasets limits the number of SVOCs that can be included. More standardized protocols in terms of cell lines, species and exposure duration should be developed with a view to cumulative risk assessment.

Perinatal programming of depressive-like behavior by inflammation in adult offspring mice whose mothers were fed polluted eels: Gender selective effects

Several lines of evidence indicate that early-life inflammation may predispose to mental illness, including depression, in later-life. We investigated the impact of perinatal exposure to polluted eels on neonatal, postnatal, and adult brain inflammation, and on the resignation behavior of male and female adult offspring mice. The effects of maternal standard diet (laboratory food) were compared to the same diet enriched with low, intermediate, or highly polluted eels. Brain inflammatory markers including cytokines were assessed in offspring mice on the day of birth (i.e., on the postnatal day-PND 1), upon weaning (PND 21) and at adulthood (PND 100). Plasma myeloperoxidase and corticosterone levels were evaluated at PND 100. Immobility behavior of offspring was assessed in adulthood (i.e., at PNDs 95-100), using the tail suspension and forced swimming tests. Chronic brain inflammation was found in male and female offspring mice compared to controls, as assessed at PNDs 1, 21, and 100. The level of myeloperoxidase was found to be significantly higher in both adult males and females vs. control offspring. However, high corticosterone levels were only found in male offspring mice that were perinatally exposed to eels, suggesting a gender-selective dysregulation of the adult hypothalamic-pituitaryadrenal (HPA) axis. Gender-specific differences were also detected in adulthood in regard to offspring resignation behavior. Thus, compared to controls, males, but not females, whose mothers were fed eels during pregnancy and lactation exhibited a depressive-like behavior in adult age in both behavioral models of depression. Depressive symptoms were more pronounced in male mice perinatally exposed to either intermediate or highly polluted eels than those exposed to only lowly polluted eels. Our results indicate that early-life inflammatory insult is a plausible causative factor that induces the depressive phenotype exhibited by male adult offspring mice, most likely through a gender-specific HPA axis enhanced activation.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Anxiety-like behaviors in adulthood are altered in male but not female rats exposed to low dosages of polychlorinated biphenyls in utero

Exposure to polychlorinated biphenyls (PCBs), a class of endocrine-disrupting chemicals, can result in altered reproductive behavior in adulthood, especially when exposure occurs during critical periods of brain sexual differentiation in the fetus. Whether PCBs alter other sexually dimorphic behaviors such as those involved in anxiety is poorly understood. To address this, pregnant rat dams were injected twice, on gestational days 16 and 18, with the weakly estrogenic PCB mixture Aroclor 1221 (A1221) at one of two low dosages (0.5mg/kg or 1.0mg/kg, hereafter 1.0 and 0.5), estradiol benzoate (EB; 50μg/kg) as a positive estrogenic control, or the vehicle (3% DMSO in sesame oil). We also conducted a comprehensive assessment of developmental milestones of the F1 male and female offspring. There were no effects of treatment on sex ratio at birth and age at eye opening. Puberty, assessed by vaginal opening in females and preputial separation in males, was not affected in females but was advanced in males treated with A1221 (1.0). Males and females treated with A1221 (both dosages) were heavier in early adulthood relative to controls. The earliest manifestation of this effect developed in males prior to puberty and in females slightly later, during puberty. Anxiety-like behaviors were tested using the light:dark box and elevated plus maze tests in adulthood. In females, anxiety behaviors were unaffected by treatment. Males treated with A1221 (1.0) showed reduced indices of anxiety and increased activity in the light:dark box but not the elevated plus maze. EB failed to replicate the phenotype produced by A1221 for any of the developmental and behavioral endpoints. Collectively, these results indicate that PCBs increase body weight in both sexes, but their effects on anxiety-like behaviors are specific to males. Furthermore, differences between the results of A1221 and EB suggest that the PCBs are likely acting through mechanisms distinct from their estrogenic activity.

POPs in the South Latin America: Bioaccumulation of DDT, PCB, HCB, HCH and Mirex in blubber of common dolphin (Delphinus delphis) and Fraser's dolphin (Lagenodelphis hosei) from Argentina

Organic compounds, in particular organochlorines, are highly persistent compounds which accumulate in biotic and abiotic substrates. Marine mammals bioaccumulate and biomagnify persistent organic pollutants (POPs) through diet. ∑PCB (26 PCB congeners), ∑DDT (pp-DDT, pp-DDD, pp-DDE), ∑HCH (α-HCH, β-HCH, γ-HCH, δ-HCH), HCB and mirex were analyzed from samples of subcutaneous adipose tissue of common dolphins, Delphinus delphis, and Fraser's dolphins, Lagenodelphis hosei, obtained in 1999 and 2012. The aim of this study was to determine the concentrations of POPs to get baseline information on the current state of pollution by these compounds in these two species in South Atlantic. At the same time, to assess concentrations of POPs in relation to age, the total length and sexual maturity in common dolphins. Organochlorine pesticides dominated Fraser's dolphins, DDT being the most abundant, while PCBs were mostly present in common dolphins. In both species, the distributions of isomers or metabolites followed the order: β-HCH>δ-HCH>γ-HCH>α-HCH and pp-DDE>pp-DDD>pp-DDT. As for ∑PCB, the largest contribution was given by congeners of high molecular weight, particularly by hexa and hepta - CBs. Common dolphins did not show effects on sexual maturity, age and standard length in the concentration of organochlorines. The mean concentrations found in this study are lower compared to those reported in other studies performed in dolphins elsewhere. This study provides new information regarding levels of organochlorines in common dolphins for the Southwestern Atlantic.

Neurobehavioral deficits and brain oxidative stress induced by chronic low dose exposure of persistent organic pollutants mixture in adult female rat

Persistent organic pollutants (POPs) are long-lived organic compounds that are considered one of the major risks to ecosystem and human health. Recently, great concerns are raised about POPs mixtures and its potential toxicity even in low doses of daily human exposure. The brain is mostly targeted by these lipophilic compounds because of its important contain in lipids. So, it would be quite interesting to study the effects of exposure to these mixtures and evaluate their combined toxicity on brain cells. The present study was designed to characterize the cognitive and locomotors deficits and brain areas redox status in rat model. An orally chronic exposure to a representative mixture of POPs composed of endosulfan (2.6 μg/kg), chlorpyrifos (5.2 μg/kg), naphthalene (0.023 μg/kg) and benzopyrane (0.002 μg/kg); the same mixture with concentration multiplied by 10 and 100 was also tested. Exposed rats have shown a disturbance of memory and a decrease in learning ability concluded by Morris water maze and the open field tests results and anxiolytic behaviour in the test of light/dark box compared to control. Concerning brain redox homeostasis, exposed rats have shown an increased malondialdehyde (MDA) amount and an alteration in glutathione (GSH) levels in both the brain mitochondria and cytosolic fractions of the cerebellum, striatum and hippocampus. These effects were accompanied by a decrease in levels of cytosolic glutathione S-transferase (GST) and a highly significant increase in superoxide dismutase (SOD) and catalase (CAT) activities in both cytosolic and mitochondrial fractions. The current study suggests that environmental exposure to daily even low doses of POPs mixtures through diet induces oxidative stress status in the brain and especially in the mitochondria with important cognitive and locomotor behaviour variations in the rats.

An Extended Structure-Activity Relationship of Nondioxin-Like PCBs Evaluates and Supports Modeling Predictions and Identifies Picomolar Potency of PCB 202 Towards Ryanodine Receptors

Nondioxin-like polychlorinated biphenyls (NDL PCBs) activate ryanodine-sensitive Ca²⁺channels (RyRs) and this activation has been associated with neurotoxicity in exposed animals. RyR-active congeners follow a distinct structure-activity relationship and a quantitative structure-activity relationship (QSAR) predicts that a large number of PCBs likely activate the receptor, which requires validation. Additionally, previous structural based conclusions have been established using receptor ligand binding assays but the impact of varying PCB structures on ion channel gating behavior is not understood. We used [³H]Ryanodine ([³H]Ry) binding to assess the RyR-activity of 14 previously untested PCB congeners evaluating the predictability of the QSAR. Congeners determined to display widely varying potency were then assayed with single channel voltage clamp analysis to assess direct influences on channel gating kinetics. The RyR-activity of individual PCBs assessed in in vitro assays followed the general pattern predicted by the QSAR but binding and lipid bilayer experiments demonstrated higher potency than predicted. Of the 49 congeners tested to date, tetra-ortho PCB 202 was found to be the most potent RyR-active congener increasing channel open probability at 200 pM. Shifting meta-substitutions to the para-position resulted in a > 100-fold reduction in potency as seen with PCB 197. Non-ortho PCB 11 was found to lack activity at the receptor supporting a minimum mono-ortho substitution for PCB RyR activity. These findings expand and support previous SAR assessments; where out of the 49 congeners tested to date 42 activate the receptor demonstrating that the RyR is a sensitive and common target of PCBs.

Exposure to endocrine disrupting chemicals and neurodevelopmental alterations

The developing brain is remarkably malleable as neural circuits are formed and these circuits are strongly dependent on hormones for their development. For those reasons, the brain is very vulnerable to the effects of endocrine-disrupting chemicals (EDCs) during critical periods of development. This review focuses on three ubiquitous endocrine disruptors that are known to disrupt the thyroid function and are associated with neurobehavioral deficits: polychlorinated biphenyls, polybrominated diphenyl ethers, and bisphenol A. The human and rodent data suggesting effects of those EDCs on memory, cognition, and social behavior are discussed. Their mechanisms of action go beyond relative hypothyroidism with effects on neurotransmitter release and calcium signaling.

Two-hit exposure to polychlorinated biphenyls at gestational and juvenile life stages: 1. Sexually dimorphic effects on social and anxiety-like behaviors

Endocrine disrupting chemicals (EDCs) are widespread environmental contaminants that affect many neuroendocrine functions. The brain is particularly vulnerable to EDCs during critical periods of gestational development when gonadal hormones exert organizational effects on sexually dimorphic behaviors later in life. Peripubertal development is also a time of continued neural sensitivity to organizing effects of hormones, yet little is known about EDC actions at these times. We sought to determine effects of prenatal or juvenile exposures to a class of EDCs, polychlorinated biphenyls (PCBs) at human-relevant dosages on development, physiology, and social and anxiety-related behaviors later in life, and the consequences of a second juvenile "hit" following prenatal treatment. We exposed male and female Sprague-Dawley rats to PCBs (Aroclor 1221, 1mg/kg/day, ip injection) and/or vehicle during prenatal development (embryonic days 16, 18, 20), juvenile development (postnatal days 24, 26, 28), or both. These exposures had differential effects on behaviors in sex and age-dependent ways; while prenatal exposure had more effects than juvenile, juvenile exposure often modified or unmasked the effects of the first hit. Additionally, females exhibited altered social and anxiety behavior in adolescence, while males displayed small but significant changes in sociosexual preferences in adulthood. Thus, the brain continues to be sensitive to organizing effects of EDCs through juvenile development. As humans are exposed to EDCs throughout multiple periods in their life, these findings have implications for our understanding of EDC effects on physiology and behavior.

Two-hit exposure to polychlorinated biphenyls at gestational and juvenile life stages: 2. Sex-specific neuromolecular effects in the brain

Exposures to polychlorinated biphenyls (PCBs) during early development have long-lasting, sexually dimorphic consequences on adult brain and behavior. However, few studies have investigated their effects during juvenile development, a time when increases in pubertal hormones influence brain maturation. Here, male and female Sprague Dawley rats were exposed to PCBs (Aroclor 1221, 1 mg/kg/day) or vehicle prenatally, during juvenile development, or both, and their effects on serum hormone concentrations, gene expression, and DNA methylation were assessed in adulthood. Gene expression in male but not female brains was affected by 2-hits of PCBs, a result that paralleled behavioral effects of PCBs. Furthermore, the second hit often changed the effects of a first hit in complex ways. Thus, PCB exposures during critical fetal and juvenile developmental periods result in unique neuromolecular phenotypes, with males most vulnerable to the treatments.

Butyltins, polyaromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls in sediments and bivalve mollusks in a mid-latitude environment from the Patagonian coastal zone

Butyltins (BTs), polyaromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) were assessed in a mid-latitude environment of the Patagonian coast, distant from significant pollutant sources. Bioaccumulation processes through bottom sediment resuspension were suggested by BTs level (expressed as ng of tin [Sn] g(-1) dry wt) found in surface sediment (<limit of detection [LOD]-166.5 ng [Sn] g(-1) dry wt) and bivalve mollusks (29.4-206.0 ng [Sn] g(-1) dry wt); whereas imposex incidence was only 15% in the gastropod Pareuthria plumbea collected near a harbor. Low hydrocarbon pollution was found in sediments and bivalves with ∑PAHs(16) ranging from <LOD to 94.9 ng g(-1) dry weight and from <LOD to 54.9 ng g(-1) dry weight, respectively. Values were typical of locations distant from pollutant sources and showed different compositional patterns for both substrates. However, concentrations for some individual PAHs in sediments were found over the threshold effect level. On average, ΣPCB did not exceed the sediment quality guidelines being 0.57 ± 0.88 ng g(-1) dry weight in sediments and 0.41 ± 0.26 ng g(-1) dry weight in bivalves. Average ΣOCPs in sediments were 0.53 ± 0.34 ng g(-1) dry weight and ranged from <LOD to 0.22 ng g(-1) dry weight in bivalves, showing a different pattern and suggesting a different accumulation pathway as was found for PAHs. Although both discrete and atmospheric sources can be considered for PAHs, organochlorines pollution was clearly related to atmospheric global transport, indicating that in the studied area, OCPs and PCBs experience permanent or temporal deposition during their migration to southern zones.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

Lactational exposure of mice to low levels of non-dioxin-like polychlorinated biphenyls increases susceptibility to neuronal stress at a mature age

Lactational exposure to low levels of the sum of the six indicator polychlorinated biphenyls (Σ6 NDL-PCBs, 10ng/kg/day) is known to lead to persistent anxious behavior in young and adult offspring mice at postnatal days 40 and 160, respectively. At more advanced life stages, we evaluated the effects on the mouse brain of neuronal stress induced by the synaptotoxic amyloid-beta (Aβ) peptide. Perinatal exposure of lactating mice to Σ6 NDL-PCBs did not affect short-term memory performances of their offspring male mice aged 14 months as compared to control PCB-naive mice. However, following intracerebroventricular injection of soluble Aβ oligomers, significant impairments in long-term memory were detected in the mice that had been lactationally treated with Σ6 NDL-PCBs. In addition, immunoblot analyses of the synaptosomal fraction of hippocampal tissues from treated mice revealed a lower expression of the synaptic proteins synaptophysin and PSD-95. Though preliminary, our findings suggest for the first time that early exposure to low levels of NDL-PCBs induce late neuronal vulnerability to amyloid stress. Additional experiments are needed to confirm whether early environmental influences are involved in the etiology of brain aging and cognitive decline.

Organochlorine pesticides and PCBs in Southern Right Whales (Eubalaena australis) breeding at Península Valdés, Argentina

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were assessed in blubber from 35 dead Southern Right Whales (SRW - Eubalaena australis) stranded at Península Valdés, Argentina. The life cycle includes a feeding period in high productivity areas of the South West Atlantic and a reproductive period in coastal template waters of Argentina. Organochlorine pesticides showed higher concentrations (22.6±13.8 ng·g(-1)ww) than PCBs (7.5±10 ng·g(-1)ww). Among pesticides, HCHs, DDTs, endosulfans, dieldrin, chlordans, heptachlor epoxide, and trans-nonachlor were detected. p,p'-DDE and p,p'-DDT were present in 69% and 26% of samples, respectively. p,p'-DDT/p,p'-DDE ratio showed low values (<0.33) as a result of aged DDT inputs. However, the occurrence of only p,p'-DDT in some samples suggests a recent pesticide input. α-HCH/γ-HCH ratio (<DL-0.37) indicated no recent contribution of technical HCH mixture and/or current use of lindane. Dieldrin was present in 77% of the samples and endosulfan was detected in all samples with predominance of α- (75%) over β-endosulfan (19%) and scarce contribution of endosulfan sulphate (7%), suggesting a recent input of this insecticide to the environment in the SRW foraging area. A predominance of pentachlorobiphenyls was observed. In 21 samples at least one PCB indicator was found and PCB #118, highly toxic, contributed in 5% to total PCBs. Although all these organochlorine compounds are forbidden they were bioaccumulated in the blubber of SRW with a predominance of endosulfans, the more recently used pesticide. The absence of data on chemical pollutants in stranded dead whales is highlighted as a priority for research. This is the first study on levels, compositional patterns, and organochlorine sources in SRW. Moreover, more research including milk, and other tissues/organs is recommended considered that in the studied specimens, mostly calves, pollutants are likely transferred from the mother during pregnancy and nursing.

Effects of standard humic materials on relative bioavailability of NDL-PCBs in juvenile swine

Young children with their hand-to-mouth activity may be exposed to contaminated soils. However few studies assessing exposure of organic compounds sequestrated in soil were realized. The present study explores the impact of different organic matters on retention of NDL-PCBs during digestive processes using commercial humic substances in a close digestive model of children: the piglet. Six artificial soils were used. One standard soil, devoid of organic matter, and five amended versions of this standard soil with either fulvic acid, humic acid, Sphagnum peat, activated carbon or a mix of Sphagnum peat and activated carbon (95∶5) (SPAC) were prepared. In order to compare the different treatments, we use spiked oil and negative control animals. Forty male piglets were randomly distributed in 7 contaminated and one control groups (n = 5 for each group). During 10 days, the piglets were fed artificial soil or a corn oil spiked with 19,200 ng of Aroclor 1254 per g of dry matter (6,000 ng.g⁻¹ of NDL-PCBs) to achieve an exposure dose of 1,200 ng NDL-PCBs.Kg⁻¹ of body weight per day. NDL-PCBs in adipose tissue were analyzed by GC-MS. Fulvic acid reduced slightly the bioavailability of NDL-PCBs compared to oil. Humic acid and Sphagnum peat reduced it significantly higher whereas activated carbon reduced the most. Piglets exposed to soil containing both activated carbon and Shagnum peat exhibited a lower reduction than soil with only activated carbon. Therefore, treatment groups are ordered by decreasing value of relative bioavailability as following: oil ≥ fulvic acid>Sphagnum peat ≥ Sphagnum peat and activated carbon ≥ Humic acid>>activated carbon. This suggests competition between Sphagnum peat and activated carbon. The present study highlights that quality of organic matter does have a significant effect on bioavailability of sequestrated organic compounds.

Lactational exposure to low levels of the six indicator non-dioxin-like polychlorinated biphenyls induces DNA damage and repression of neuronal activity, in juvenile male mice

Previously, we evaluated the effects of lactational exposure to a representative mixture of the six indicator non-dioxin-like polychlorinated biphenyls (∑6 NDL-PCBs) at low levels on the neurobiological changes and developmental/behavioral performances in mice. In this study, we analyzed the global gene expression profile in cerebellar neurons isolated from male mice presenting the most significant induction of anxiety-like behavior in our previous study (10 ng/kg ∑6 NDL-PCBs). Our results revealed changes in the expression of 16658 genes in the neurons of the exposed mice. Among these, 693 upregulated [fold change (FC)>2; p<0.05] and 665 downregulated (FC<2; p<0.05) genes were statistically linked to gene ontology terms (GO). Overexpressed genes belonged to GO terms involved with the cell cycle, DNA replication, cell cycle checkpoint, response to DNA damage stimulus, regulation of RNA biosynthetic processes, and microtubule cytoskeleton organization. Downregulated genes belonged to terms involved with the transmission of nerve impulses, projection neurons, synapse hands, cell junctions, and regulation of RNA biosynthetic processes. Using qPCR, we quantified gene expression related to DNA damage and validated the transcriptomic study, as a significant overexpression of Atm-Atr Bard1, Brca2, Fancd2, Figf, Mycn, p53 and Rad51 was observed between groups (p<0.001). Finally, using immunoblots we determined the expression level of six selected proteins. We found that changes in the protein expression of Atm Brca1, p53, Kcnma1, Npy4r and Scn1a was significant between exposed and control groups (p<0.05), indicating that the expression pattern of these proteins agreed with the expression pattern of their genes by qPCR, further validating our transcriptomic findings. In conclusion, our study showed that early life exposure of male mice to a low level of ∑6 NDL-PCBs induced p53-dependent responses to cellular stress and a decrease in the expression of proteins involved in the generation, conduction, and transmission of electrical signals in neurons.

Endocrine-disrupting actions of PCBs on brain development and social and reproductive behaviors

Polychlorinated biphenyls are among the most well-studied endocrine-disrupting chemicals (EDCs) for their neurobehavioral effects, especially neurodevelopment and cognitive performance. In addition, past research has demonstrated effects of PCBs on circulating hormones and associated changes in reproductive behaviors. This article will focus on recent advances that have been made in characterizing developmental PCB effects on reproductive function, broader social and affective behaviors, and the neuroendocrine mechanisms behind such changes. In general, PCBs seem to inhibit reproductive function by suppressing multiple aspects of the associated hypothalamic circuitry. Additionally, PCBs may also reduce motivation for social behaviors and induce depressive-like symptoms via overall reductions in dopaminergic and glutamatergic functions in the limbic system. However, more work with human-relevant exposure paradigms is needed to fully support these conclusions.

Signaling mechanisms and disrupted cytoskeleton in the diphenyl ditelluride neurotoxicity

Evidence from our group supports that diphenyl ditelluride (PhTe)₂ neurotoxicity depends on modulation of signaling pathways initiated at the plasma membrane. The (PhTe)₂-evoked signal is transduced downstream of voltage-dependent Ca²⁺ channels (VDCC), N-methyl-D-aspartate receptors (NMDA), or metabotropic glutamate receptors activation via different kinase pathways (protein kinase A, phospholipase C/protein kinase C, mitogen-activated protein kinases (MAPKs), and Akt signaling pathway). Among the most relevant cues of misregulated signaling mechanisms evoked by (PhTe)₂ is the cytoskeleton of neural cells. The in vivo and in vitro exposure to (PhTe)₂ induce hyperphosphorylation/hypophosphorylation of neuronal and glial intermediate filament (IF) proteins (neurofilaments and glial fibrillary acidic protein, resp.) in different brain structures of young rats. Phosphorylation of IFs at specific sites modulates their association/disassociation and interferes with important physiological roles, such as axonal transport. Disrupted cytoskeleton is a crucial marker of neurodegeneration and is associated with reactive astrogliosis and apoptotic cell death. This review focuses the current knowledge and important results on the mechanisms of (PhTe)₂ neurotoxicity with special emphasis on the cytoskeletal proteins and their differential regulation by kinases/phosphatases and Ca²⁺-mediated mechanisms in developmental rat brain. We propose that the disrupted cytoskeletal homeostasis could support brain damage provoked by this neurotoxicant.

Effects of condensed organic matter on PCBs bioavailability in juvenile swine, an animal model for young children

The exposure assessment of polychlorinated biphenyls (PCBs) contaminated soils is a critical issue in terms of human health, especially since little reliable information on transfer of PCBs to humans via involuntary soil ingestion is available. Indeed, young children with their hand-to-mouth activity may be exposed to contaminated soils. The current study addresses the impact of soil organic matter (OM) condensation on bioavailability of sequestrated NDL-PCBs. Three artificial soils (ASs) were prepared according to OECD guideline 207. One standard soil (SS), devoid of OM, and two amended versions of this SS with fulvic acid (FA) or activated carbon (AC) were prepared to obtain 1% organic mass. This study involved fourteen juvenile male swine as a digestive physiology model of young children. Animals were randomly distributed into 4 contaminated groups (3 replicates) and a control one (2 replicates). During 10d, the piglets were fed AS or a corn oil spiked with 19200 ng of Aroclor 1254 per g of dry matter (6000 ng g(-1) of NDL-PCBs) to achieve an exposure dose of 1200 ng NDL-PCBskg(-1) of body weight per day. After 10d of oral exposure, NDL-PCBs in adipose tissue, liver and muscles were analyzed by GC-MS, after extraction and purification. Two distinct groups of treatments were found: on the one hand oil, SS and FA, on the other hand C and AC. This study highlights that condensed OM (AC) strongly reduces bioavailability whereas the less condensed one (FA) does not seem to have a significant effect. This result has to be considered as a first major step for further relative bioavailability studies involving mixture of different humic substances.

The dynamics of autism spectrum disorders: how neurotoxic compounds and neurotransmitters interact

In recent years concern has risen about the increasing prevalence of Autism Spectrum Disorders (ASD). Accumulating evidence shows that exposure to neurotoxic compounds is related to ASD. Neurotransmitters might play a key role, as research has indicated a connection between neurotoxic compounds, neurotransmitters and ASD. In the current review a literature overview with respect to neurotoxic exposure and the effects on neurotransmitter systems is presented. The aim was to identify mechanisms and related factors which together might result in ASD. The literature reported in the current review supports the hypothesis that exposure to neurotoxic compounds can lead to alterations in the GABAergic, glutamatergic, serotonergic and dopaminergic system which have been related to ASD in previous work. However, in several studies findings were reported that are not supportive of this hypothesis. Other factors also might be related, possibly altering the mechanisms at work, such as time and length of exposure as well as dose of the compound. Future research should focus on identifying the pathway through which these factors interact with exposure to neurotoxic compounds making use of human studies.