Further analysis of behavioral and endocrine consequences of chronic exposure of male Wistar rats to subtoxic doses of endocrine disruptor chlorobenzenes

Study of endocrine disruptor effects in AVP and OT mediated behavioral and reproductive processes in female rat models

Environmental exposures may have endocrine disruptor (ED) effects, e.g., a role for halogenated hydrocarbon chlorobenzenes in increasing vasopressin (AVP), oxytocin (OT) secretion and, in association, anxiety and aggression in male rats has been shown. Our aim is to investigate whether 1,2,4-trichlorobenzenehexachlorobenzene= 1:1 (mClB) treatment of female rats also shows ED effects and reproductive biology differences, and whether AVP may have a mediator role in this? Female Wistar rats were treated (0.1; 1.0; 10.0 μg/bwkg/day) with mClB (by gastrictube) and then 30; 60; 90 days after treatment anxiety (open field test) and aggressive (resident intruder test) behaviors AVP, OT concentrations from blood plasma samples were detected by radioimmunoassay on 30; 60; 90 days. Treated female rats were mated with untreated males. Mating success, number of newborn and maternal aggression on the neonates were monitored. Results showed that AVP, OT levels; and anxiety, aggressive behaviors; and mothers' aggression towards their offspring increased significantly in relation to the duration and the dose of mClB treatment. But mating propensity and number of offspring decreased. Patterns of AVP, OT release and anxiety, aggression behaviors, and reproductive-related behaviors were correlated. Consistent with the literature, our studies confirmed the role of AVP and OT in different behavioral effects.

Combining computational tools and experimental studies towards endocrine disruptors mitigation: A review of biocatalytic and adsorptive processes

The endocrine disruptors (EDCs) are an important group of emerging contaminants, and their mitigation has been a huge challenge due to their chemistry complexity and variety of these compounds. The traditional treatments are inefficient to completely remove EDCs, and adsorptive processes are the major alternative investigated on their removal. Also, the use of EDCs degrading enzymes has been encouraged due to ecofriendly approach of biocatalytic processes. This paper highlights the occurrence, classification, and toxicity of EDCs with special focus in the use of enzyme-based and adsorptive technologies in the elimination of EDCs from ambiental matrices. Numerous prior reviews have focused on the discussions toward these technologies. However, the literature lacks theoretical discussions about important aspects of these methods such as the mechanisms of EDCs adsorption on the adsorbent surface or the interactions between degrading enzymes - EDCs. In this sense, theoretical calculations combined to experimental studies may help in the development of more efficient technologies to EDCs mitigation. In this review, we point out how computational tools such as molecular docking and molecular dynamics have to contribute to the design of new adsorbents and efficient catalytic processes towards endocrine disruptors mitigation.

Study of the Potential Endocrine-Disrupting Effects of Phenylurea Compounds on Neurohypophysis Cells In Vitro

Homeostatic disruptor agents, and endocrine disruptor compounds (EDC) specifically, can originate from agricultural and industrial chemicals. If they modify the adaptation of living organisms as direct (e.g., by altering hormone regulation, membrane functions) and/or indirect (e.g., cell transformation mechanisms) factors, they are classified as EDC. We aimed to examine the potential endocrine-disrupting effects of phenylurea herbicides (phenuron, monuron, and diuron) on the oxytocin (OT) and arginine-vasopressin (AVP) release of neurohypophysis cell cultures (NH). In our experiments, monoamine-activated receptor functions of neurohypophyseal cells were used as a model. In vitro NH were prepared by enzymatic (trypsin, collagenase) and mechanical dissociation. In the experimental protocol, the basal levels of OT and AVP were determined as controls. Later, monoamine (epinephrine, norepinephrine, serotonin, histamine, and dopamine) activation (10^-6 M, 30 min) and the effects of phenylurea (10^-6 M, 60 min) alone and in combination (monoamines 10^-6 M, 30 min + phenylureas 10^-6 M, 60 min) with monoamine were studied. OT and AVP hormone contents in the supernatant media were measured by radioimmunoassay. The monoamine-activated receptor functions of neurohypophyseal cells were modified by the applied doses of phenuron, monuron, and diuron. It is concluded that the applied phenylurea herbicides are endocrine disruptor agents, at least in vitro for neurohypophysis function.

The Role of Uron and Chlorobenzene Derivatives, as Potential Endocrine Disrupting Compounds, in the Secretion of ACTH and PRL

Uron herbicides polluting the environment represent a serious concern for environmental health and may be regarded as endocrine-disrupting compounds (EDCs), which influence the regulation of human homeostasis. We aimed to investigate the effect of EDC urons (phenuron: PU, monuron: MU, and diuron: DU) and chlorobenzenes on the basal release of the adrenocorticotropic hormone (ACTH), which is a part of the adenohypophysis-adrenocortical axis. Hormone secretion in the presence of EDC was studied in two cell types: normal adenohypophysis cells (AdH) and cells of prolactinomas (PRLOMA). PRLOMA was induced in female Wistar rats by subcutaneously injecting them with estrone acetate for 6 months. AdH and PRLOMA were separated from treated and untreated experimental animals, dissociated enzymatically and mechanically in order to create monolayer cell cultures, which served as an experimental in vitro model. We investigated the effects of ED agents separately and in combination on ACTH and prolactin (PRL) release through the hypophyseal-adrenal axis. Hormone determination was carried out by the luminescent immunoassay and the radioimmunoassay methods. Our results showed that (1) uron agents separately did not change ACTH and PRL release in AdH culture; (2) ACTH secretion in arginine vasopressin- (AVP-) activated AdH cells was significantly increased by EDC treatment; (3) ED agents increased the basal hormone release (ACTH, PRL) in PRLOMA cells; and (4) EDC exposure increased ACTH release in AVP-activated PRLOMA cells. We conclude that the herbicides PU, MU, and DU carry EDC effects and show human toxicity potential.

Transgenerational effects of 17α-ethinyl estradiol on anxiety behavior in the guppy, Poecilia reticulata

Environmental contaminants can cause alterations that can be transgenerationally transmitted to subsequent generations. Estrogens are among those contaminants shown to induce heritable changes that persist over generations in mammals. Results in other vertebrates are few. We have analyzed the effects on anxiety of 17α-ethinyl estradiol (EE2) in the F1 and F2 generations in guppies, Poecilia reticulata, obtained from F0 fish maternally exposed to 0 or 20ng/L EE2 until birth. F0 males and females were bred with fish of the same treatment but different families producing F1 offspring. Behavior in the novel tank test at 6months revealed that males with EE2-exposed parents had significantly longer latency to the upper half of the tank than control males, while no EE2 effects were observed in females. Also in F2, obtained from F1 as above, males in the EE2 group had longer latency time compared to control males, with no differences due to EE2-exposure of F0 observed in females. In the scototaxis (light/dark preference) test, latency to first transition to black compartment and total transitions to black were significantly altered in females due to EE2 exposure of F0 while the total time in black was higher in males with EE2-exposed F0 compared with controls. The increased anxiety in the F2 generation demonstrates a transgenerational anxiety phenotype and shows that non-reproductive behavior can be transgenerationally modified by estrogens in fish.

Effects of chronic and subtoxic chlorobenzenes on adrenocorticotrophic hormone release

Many environmental chemicals and pesticides have been found to alter neuroendocrine communication in exposed biological objects. The environmental loads have primary and secondary effects that can alter the homeostatic regulation potential. Since it is difficult to avoid human exposition, a potentially important area of research to develop in vivo and in vitro experimental models. In this context, the primary aim of this study was to demonstrate the effects of chlorobenzenes on adrenocorticotrophic hormone (ACTH) release. In our experimental study, male Wistar rats were exposed to 0.1, 1.0 and 10 μg/b.w. (body weight)kg of 1,2,4- trichlorobenzene and hexachlorobenzene (ClB) mix via gastric tube for 30, 60 or 90 days. At the endpoints of the experiment blood samples were taken and animals were decapitated. Primary, monolayer adenohypophysis cell cultures were prepared by enzymatic and mechanical digestion. The ACTH hormone content in serum and supernatant media was measured by immuno-chemiluminescence assay. The Mg(2+)-dependent ATPase activity was determined by modified method of Martin and Dotty. Significant differences were detected in the hormone release between the control and treated groups. The hormone release was enhanced characteristically in exposed groups depending upon the dose and duration of exposure. The Mg(2+)-ATPase activity enhanced after chronic and subtoxic ClB exposition. Light microscopy revealed that the adenohypophysis seemed to be more abundant. Results indicate that Wistar rats exposed to subtoxic ClB have direct and indirect effects on hypothalamus-hypophysis-adrenal axis.

Effects of Endocrine Disruptor Compounds, Alone or in Combination, on Human Macrophage-Like THP-1 Cell Response

The aim of the present study was to evaluate the immunological effects on human macrophages of four endocrine disruptor compounds (EDCs) using the differentiated human THP-1 cell line as a model. We studied first the effects of these EDCs, including Bisphenol A (BPA), di-ethylhexyl-phthalate (DEHP), dibutyl phthalate (DBP) and 4-tert-octylphenol (4-OP), either alone or in combination, on cytokine secretion, and phagocytosis. We then determined whether or not these effects were mediated by estrogen receptors via MAPK pathways. It was found that all four EDCs studied reduced strongly the phagocytosis of the differentiated THP-1 cells and that several of these EDCs disturbed also TNF-α, IL-1 β and IL-8 cytokine secretions. Furthermore, relative to control treatment, decreased ERK 1/2 phosphorylation was always associated with EDCs treatments-either alone or in certain combinations (at 0.1 μM for each condition). Lastly, as treatments by an estrogen receptor antagonist suppressed the negative effects on ERK 1/2 phosphorylation observed in cells treated either alone with BPA, DEHP, 4-OP or with the combined treatment of BPA and DEHP, we suggested that estrogen receptor-dependent pathway is involved in mediating the effects of EDCs on human immune system. Altogether, these results advocate that EDCs can disturb human immune response at very low concentrations.

Risk assessment's insensitive toxicity testing may cause it to fail

BACKGROUND

Risk assessment of chemicals and other agents must be accurate to protect health. We analyse the determinants of a sensitive chronic toxicity study, risk assessment's most important test. Manufacturers originally generate data on the properties of a molecule, and if government approval is needed to market it, laws globally require toxicity data to be generated using Test Guidelines (TG), i.e. test methods of the Organisation for Economic Cooperation and Development (OECD), or their equivalent. TGs have advantages, but they test close-to-poisonous doses for chronic exposures and have other insensitivities, such as not testing disease latency. This and the fact that academic investigators will not be constrained by such artificial methods, created a de facto total ban of academia's diverse and sensitive toxicity tests from most risk assessment.

OBJECTIVE

To start and sustain a dialogue between regulatory agencies and academic scientists (secondarily, industry and NGOs) whose goals would be to (1) agree on the determinants of accurate toxicity tests and (2) implement them (via the OECD).

DISCUSSION

We analyse the quality of the data produced by these incompatible paradigms: regulatory and academic toxicology; analyse the criteria used to designate data quality in risk assessment; and discuss accurate chronic toxicity test methods.

CONCLUSION

There are abundant modern experimental methods (and rigorous epidemiology), and an existing systematic review system, to at long last allow academia's toxicity studies to be used in most risk assessments.

Effect of the environmental pollutant hexachlorobenzene (HCB) on the neuronal differentiation of mouse embryonic stem cells

Exposure to persistent environmental pollutants may constitute an important factor on the onset of a number of neurological disorders such as autism, Parkinson’s disease, and Attention Deficit Disorder (ADD), which have also been linked to reduced GABAergic neuronal function. GABAergic neurons produce γ-aminobutyric acid (GABA), which is the main inhibitory neurotransmitter in the brain. However, the lack of appropriate models has hindered the study of suspected environmental pollutants on GABAergic function. In this work, we have examined the effect of hexachlorobenzene (HCB), a persistent and bioaccumulative environmental pollutant, on the function and morphology of GABAergic neurons generated in vitro from mouse embryonic stem (ES) cells. We observed that: (1) treatment with 0.5 nM HCB did not affect cell viability, but affected the neuronal differentiation of ES cells; (2) HCB induced the production of reactive oxygen species (ROS); and (3) HCB repressed neurite outgrowth in GABAergic neurons, but this effect was reversed by the ROS scavenger N-acetylcysteine (NAC). Our study also revealed that HCB did not significantly interfere with the function of K⁺ ion channels in the neuronal soma, which indicates that this pollutant does not affect the maturation of the GABAergic neuronal soma. Our results suggest a mechanism by which environmental pollutants interfere with normal GABAergic neuronal function and may promote the onset of a number of neurological disorders such as autism and ADD.

Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of "the dose makes the poison," because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.