The endocrine disruptor atrazine accounts for a dimorphic somatostatinergic neuronal expression pattern in mice

Endocrine toxicity of atrazine and its underlying mechanisms

Atrazine (ATR) is one of the most widely utilized herbicides globally and is prevalent in the environment due to its extensive use and long half-life. It can infiltrate the human body through drinking water, ingestion, and dermal contact, and has been recognized as an environmental endocrine disruptor. This study aims to comprehensively outline the detrimental impacts of ATR on the endocrine system. Previous research indicates that ATR is harmful to various bodily systems, including the reproductive system, nervous system, adrenal glands, and thyroi d gland. The toxic effects of ATR on the endocrine system and its underlying molecular mechanisms are summarized as follows: influencing the expression of kisspeptin in the HPG axis, consequently affecting steroid synthesis; disrupting DNA synthesis and meiosis, as well as modifying DNA methylation levels, leading to reproductive and developmental toxicity; impacting dopamine by altering Nurr1, VMAT2, and DAT expression, consequently affecting dopamine synthesis and transporter expression, and influencing other neurotransmitters, resulting in neurotoxicity; and changing adipose tissue synthesis and metabolism by reducing basal metabolism, impairing cellular oxidative phosphorylation, and inducing insulin resistance. Additionally, a compilation of natural products used to mitigate the toxic effects of ATR has been provided, encompassing melatonin, curcumin, quercetin, lycopene, flavonoids, vitamin C, vitamin E, and other natural remedies. It is important to note that existing research predominantly relies on in vitro and ex vivo experiments, with limited population-based empirical evidence available.

Peripubertal exposure of atrazine cause decrease in exploratory activity, deficits in sociability and few alterations on brain monoaminergic systems of rats

Atrazine is a pesticide used to control weeds in both in pre- and post-emergence crops. The chronic exposure to atrazine can lead to severe damage in animals, especially in the endocrine and reproduction systems, leading to the inclusion of this pesticide into the endocrine disrupting chemicals group. Studies with rats showed that atrazine exposure during lactation in dams caused changes in the juvenile offspring, however; there is still limited information regarding the effects of atrazine during puberty. Thus, the aim of this study is to evaluate the effects of peripubertal exposure of atrazine in rats, assessing motor activity, social behavior and neurochemical alterations. Juvenile rats were treated with different doses of atrazine (0, 10, 30 or 100 mg/kg) by gavage from postnatal day 22 to 41. Behavioral tests were conducted for the evaluation of motor activity and social behavior, and neurochemical evaluation was done in order to assess monoamine levels. Atrazine caused behavioral alterations, evidenced by decrease in the exploratory activity (p values variation between 0.05 and 0.0001) and deficits in the social behavior of both male and females as adults (p values variation between 0.01 and 0.0001). As for the monoaminergic neurotransmission, atrazine led to very few alterations on the dopamine and serotonin systems that were limited to the females (p < 0.05). Altogether, the results suggests that peripubertal exposure of atrazine cause behavioral and neurochemical alterations. More studies need to be conducted to fully understand the differences in atrazine's effects and its use should be considered carefully.

Molecular mechanisms of atrazine toxicity on H19-7 hippocampal neurons revealed by integrated miRNA and mRNA "omics"

Atrazine (ATR) is a widely applied herbicide in Asia and South America with slow natural degradation and documented deleterious effects on human and animal health, including hippocampal toxicity. However, relatively little is known about the molecular mechanisms responsible for ATR-induced hippocampal damage. Screening for differentially expressed mRNAs and microRNAs (miRNAs), and construction of potential miRNA-mRNA regulatory networks can reveal such mechanisms, so we analyzed the mRNA and miRNA expression profiles of rat hippocampus-derived H19-7 cells in response to ATR (500 μM) and conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment (KEGG) analyses. Integration of miRNA sequencing (miRNA-seq) and mRNA sequencing (mRNA-seq) results identified 114 differentially expressed miRNAs (DEMIs, 40 upregulated and 74 downregulated), and 510 differentially expressed mRNAs (DEMs, 177 upregulated and 333 downregulated) targeted by these DEMIs. The top 10 hub mRNAs (Fos, Prkcb, Ncf1, Vcam1, Atf3, Pak3, Pak1, Cacna1s, Junb, and Ccl2) and 19 related miRNAs (rno-miR-194-5p, rno-miR-24-3p, rno-miR-3074, rno-miR-1949, rno-miR-218a-1-3p, rno-miR-1843a-5p, rno-miR-1843b-5p, rno-miR-296-3p, rno-miR-320-3p, rno-miR-219a-1-3p, rno-miR-122-5p, rno-miR-1839-5p, rno-miR-1843a-3p, rno-miR-215, rno-miR-3583-3p, rno-miR-194-3p, rno-miR-128-1-5p, rno-miR-1956-5p, and rno-miR-466b-2-3p) were validated by quantitative real-time PCR. GO analysis indicated that these DEMs were enriched in genes associated with synaptic plasticity and antioxidant capacity, while KEGG analysis suggested that enriched DEMs were involved in calcium signaling, axon guidance, MAPK signaling, and glial carcinogenesis. The miRNA-mRNA regulatory network identified here may provide potential biomarkers and novel strategies for the treatment of hippocampal neurotoxicity induced by ATR.

Association Mechanism and Conformational Changes in Trypsin on Its Interaction with Atrazine: A Multi- Spectroscopic and Biochemical Study with Computational Approach

Atrazine (ATR) is a herbicide globally used to eliminate undesired weeds. Herbicide usage leads to various adverse effects on human health and the environment. The primary source of herbicides in humans is the food laced with the herbicides. The ATR binding to trypsin (TYP) was investigated in this study to explore its binding potential and toxicity. In vitro interaction of ATR with TYP was studied using multi-spectroscopic methods, molecular docking, and enzyme kinetics to explore the mechanism of binding for the TYP-ATR system. The TYP-ATR complex revealed binding constants (10³ M^-1), suggesting a moderate binding. The free energy for the TYP-ATR complexes was negative, suggesting a spontaneous interaction. Thermodynamic parameters enthalpy (ΔH) and entropy (ΔS) obtained positive values for the TYP-ATR system suggesting hydrophobic interactions in the binding process. Micro-environmental and conformational changes in TYP molecules were induced on interaction with ATR. Reduced catalytic activity of TYP was observed after interaction with ATR owing to the changes in the secondary structure of the TYP.

Integrating network pharmacology and in vitro model to investigate hippocampal neurotoxicity induced by atrazine

Atrazine (ATR), a commonly applied herbicide in agriculture, has been found to cause hippocampal injury in rodents. However, the underlying toxicological targets and mechanisms are unclear. In this study, network pharmacology analysis and in vitro model were integrated to investigate the effect and mechanism of ATR-induced hippocampal neurotoxicity. In total, 71 targets of hippocampal neurotoxicity induced by ATR were predicted. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment (KEGG) enrichment analysis suggested that these targets were related to multiple GO terms and signaling pathways. To further investigate the underlying mechanisms, the top 10 hub targets were screened and included tumor protein p53 (Tp53), caspase 3 (Casp3), prostaglandin-endoperoxide synthase 2 (Ptgs2), cAMP-responsive element-binding protein 1 (Creb1), estrogen receptor 1 (Esr1), Jun proto-oncogene (Jun), brain-derived neurotrophic factor (Bdnf), catalase (Cat), sirtuin 1 (Sirt1) and Fos proto-oncogene (Fos). Moreover, the cell counting kit-8 (CCK8) and lactate dehydrogenase (LDH) assay showed that ATR had time and dose-dependent cytotoxicity on H19-7 cells. TUNEL staining revealed that ATR increased the apoptotic ratio. In addition, Real-time quantitative polymerase chain reaction (RT-qPCR) results indicated that the mRNA expression levels of all hub targets showed significant changes, except Esr1 and Jun. Our study demonstrated that ATR mainly acted on multiple targets and signaling pathways to exert its hippocampal neurotoxicity. These results provided initial evidence for the further exploration of the toxicological mechanism of ATR.

Stability of Atrazine–Smectite Intercalates: Density Functional Theory and Experimental Study

Atrazine (A) is one of the most applied herbicides and has a negative impact on the environment and health. Density functional theory (DFT) and experimental methods were used in the study of the immobilization of atrazine in two smectites, montmorillonite (Mt) and beidellite (Bd), as well as in their organically modified structures. Four systems were examined: A-Mt and A-Bd, as well as the structures modified by tetramethylphosphonium cation (TMP), A-TMP-Mt and A-TMP-Bd. The calculations revealed a flat arrangement of the atrazine in the interlayer space of both smectites with higher stability of beidellite structures. The presence of the TMP cation increased the fixation of atrazine in both organically modified smectites. The calculated vibrational spectra allowed a detailed analysis of the overlapping bands observed in the experimental FTIR spectra and their correct assignment. Further, selected FTIR bands unambiguously assigned to atrazine and both smectites served for the estimation of the adsorbed amount of atrazine. It was shown that the adsorption capacity of both TMP-modified smectites did not increase in comparison to the adsorption capacity of unmodified smectite samples.

Pre-differentiation exposure to low-dose of atrazine results in persistent phenotypic changes in human neuronal cell lines

Exposures to organic pesticides, particularly during a developmental window, have been associated with various neurodegenerative diseases later in life. Atrazine (ATZ), one of the most used pesticides in the U.S., is suspected to be associated with increased neurodegeneration later in life but few studies assessed the neurotoxicity of developmental ATZ exposure using human neuronal cells. Here, we exposed human SH-SY5Y cells to 0.3, 3, and 30 ppb of ATZ prior to differentiating them into dopaminergic-like neurons in ATZ-free medium to mimic developmental exposure. The differentiated neurons exhibit altered neurite outgrowth and SNCA pathology depending on the ATZ treatment doses. Epigenome changes, such as decreases in 5mC (for 0.3 ppb only), H3K9me3, and H3K27me3 were observed immediately after exposure. These alterations persist in a compensatory manner in differentiated neurons. Specifically, we observed significant reductions in 5mC and H3K9me3, as well as, an increase in H3K27me3 in ATZ-exposed cells after differentiation, suggesting substantial chromatin rearrangements after developmental ATZ exposure. Transcriptional changes of relevant epigenetic enzymes were also quantified but found to only partially explain the observed epigenome alteration. Our results thus collectively suggest that exposure to low-dose of ATZ prior to differentiation can result in long-lasting changes in epigenome and increase risks of SNCA-related Parkinson's Disease.

Spatial and Temporal Distribution Characteristics of Triazine Herbicides in Typical Agricultural Regions of Liaoning, China

The aim of the current study was to track the composition, spatial and temporal distribution charactistics of triazine herbicides in arable soils and corns in typical agricultural regions of Liaoning Province, China. All samples were analyzed using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Twelve kinds of triazine herbicides were found including atrazine, simazine, prometryn, propazine, ametryn, metribuzin, simetryn, aziprotryne, cyanizine, atrazine-desethyl, atrazine-desisopropyl and atrazine-desethyl-desisopropyl in the soil samples, of which atrazine, simazine, prometryn, atrazine-desethyl and atrazine-desethyl-desisopropyl were proved to be the predominant species with a high incidence though relatively low contamination level. The maximum concentration of atrazine in the soils was 73.80 µg·kg^-1. Five kinds of triazine herbicides were found in corns in the region including atrazine, simazine, prometryn, atrazine-desethyl and atrazine-desethyl-desisopropyl with the detection rate 96.4%, 17.8%, 14.3%, 60.7% and 46.4%, respectively. The maximum contaminant level of atrazine in corns was 12.52 µg·kg^-1, which is lower than that regulated in the National Standard of the People's Republic of China (GB2763-2012).

The impact of endocrine-disrupting chemical exposure in the mammalian hypothalamic-pituitary axis

The hypothalamic-pituitary axis (HP axis) plays a critical and integrative role in the endocrine system control to maintain homeostasis. The HP axis is responsible for the hormonal events necessary to regulate the thyroid, adrenal glands, gonads, somatic growth, among other functions. Endocrine-disrupting chemicals (EDCs) are a worldwide public health concern. There is growing evidence that exposure to EDCs such as bisphenol A (BPA), some phthalates, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and biphenyls (PBBs), dichlorodiphenyltrichloroethane (DDT), tributyltin (TBT), and atrazine (ATR), is associated with HP axis abnormalities. EDCs act on hormone receptors and their downstream signaling pathways and can interfere with hormone synthesis, metabolism, and actions. Because the HP axis function is particularly sensitive to endogenous hormonal changes, disruptions by EDCs can alter HP axis proper function, leading to important endocrine irregularities. Here, we review the evidence that EDCs could directly affect the mammalian HP axis function.

Brain alterations in GABA, glutamate and glutamine markers after chronic atrazine exposure in the male albino rat

Atrazine (ATR; 2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is an herbicide widely used to kill annual grasses and broadleaf weeds in crops such as corn, sorghum, and sugarcane. Studies in rodents have shown that chronic ATR exposure is associated with alterations in the nigrostriatal dopaminergic pathway such as hyperactivity, decreased striatal dopamine levels, and diminished numbers of tyrosine hydroxylase positive cells in substantia nigra pars compacta. However, the effects of ATR on neurotransmitters such as GABA and glutamate have been scarcely studied. To evaluate the impact of ATR on motor and anxiety tasks, tissue levels of GABA, glutamate, glutamine, and extracellular and potassium-evoked release of glutamate in the striatum, we daily exposed Sprague-Dawley male rats to 1 or 10 mg ATR/kg of body weight for 12-14 months. As previously reported, chronic ATR exposure causes hyperactivity in the group exposed to 10 mg ATR/kg and increased anxiety in both groups exposed to ATR. GABA, glutamate, and glutamine levels were differentially altered in brain regions related to nigrostriatal and mesolimbic systems, the amygdala, and the prefrontal cortex. The groups exposed to 10 mg ATR/kg showed increased extracellular levels and release of glutamate in the striatum. These neurochemical alterations could underlie the behavioral changes observed in rats. These results indicate that chronic exposure to the herbicide ATR disrupts the neurochemistry of several brain structures and could be a risk factor for the development of neurodegenerative diseases.

Potential Health Risks Linked to Emerging Contaminants in Major Rivers and Treated Waters

The presence of endocrine-disrupting chemicals (EDCs) in our local waterways is becoming an increasing threat to the surrounding population. These compounds and their degradation products (found in pesticides, herbicides, and plastic waste) are known to interfere with a range of biological functions from reproduction to differentiation. To better understand these effects, we used an in silico ontological pathway analysis to identify the genes affected by the most commonly detected EDCs in large river water supplies, which we grouped together based on four common functions: Organismal injuries, cell death, cancer, and behavior. In addition to EDCs, we included the opioid buprenorphine in our study, as this similar ecological threat has become increasingly detected in river water supplies. Through the identification of the pleiotropic biological effects associated with both the acute and chronic exposure to EDCs and opioids in local water supplies, our results highlight a serious health threat worthy of additional investigations with a potential emphasis on the effects linked to increased DNA damage.

Effects of Atrazine and Fenoxaprop-Ethyl on Capacitation and the Acrosomal Reaction in Boar Sperm

Atrazine is a herbicide of the chloro-s-triazine family. It inhibits photosynthesis in plants and is an endocrine disruptor, but its effects on human health are controversial. Fenoxaprop-ethyl, an aryloxy phenoxyalkanoic acid herbicide, inhibits the biosynthesis of fatty acids and provokes depolarization of membranes. The aim of this study is to evaluate the in vitro effects of both herbicides on capacitation, spontaneous acrosome reaction (SAR) and progesterone-induced acrosome reaction (PIAR) in boar sperm. Sperm capacitation is done in TALP-HEPES media for 4 hours. Capacitation and SAR are evaluated immediately; PIAR, 30 minutes later. LC50 for fenoxaprop-ethyl is 60 mM and 40 mM for atrazine. Fenoxaprop-ethyl induces capacitation at 60 mM and SAR at all concentrations, also increases significantly PIAR. Atrazine decreased capacitation whereas increase significantly SAR and PIAR at all concentrations. It seems that fenoxaprop-ethyl and atrazine accelerate the capacitation and the acrosomal reaction, possibly via plasma membrane destabilization.

Monitoring Histone Methylation (H3K9me3) Changes in Live Cells

H3K9me3 (methylation of lysine 9 of histone H3) is an epigenetic modification that acts as a repressor mark. Several diseases, including cancers and neurological disorders, have been associated with aberrant changes in H3K9me3 levels. Different tools have been developed to enable detection and quantification of H3K9me3 levels in cells. Most techniques, however, lack live cell compatibility. To address this concern, we have engineered recombinant protein sensors for probing H3K9me3 in situ. A heterodimeric sensor containing a chromodomain and chromo shadow domain from HP1a was found to be optimal in recognizing H3K9me3 and exhibited similar spatial resolution to commercial antibodies. Our sensor offers similar quantitative accuracy in characterizing changes in H3K9me3 compared to antibodies but claims single cell resolution. The sensor was applied to evaluate changes in H3K9me3 responding to environmental chemical atrazine (ATZ). ATZ was found to result in significant reductions in H3K9me3 levels after 24 h of exposure. Its impact on the distribution of H3K9me3 among cell populations was also assessed and found to be distinctive. We foresee the application of our sensors in multiple toxicity and drug-screening applications.

The MEK/ERK/CREB signaling pathway is involved in atrazine induced hippocampal neurotoxicity in Sprague Dawley rats

Atrazine (ATR) is a commonly used artificial synthetic herbicide world-wide, which has been implicated as a potential threat to human health. Previous studies have demonstrated that exposure to ATR affects hippocampus-dependent learning and memory in rodents, but the exact molecular mechanism remains to be elucidated. In this study, we investigated the effect of ATR on the hippocampus of postnatal day 35 male Sprague Dawley (SD) rats administered doses of either 10 or 100 mg/kg body weight (BW)/day of ATR for a period of 30 days. A Morris water maze (MWM) test revealed that ATR treatment impaired memory performance in the spatial probe test, especially amongst the high-dose group. Moreover, analysis by electron microscopy showed that hippocampal neuron ultrastructure in the dentate gyrus (DG) and cornu ammonis 1 (CA1) sub-regions was impaired in the ATR-treated groups. Finally, a downregulation in the mRNA and protein expression levels of members of the MEK/ERK/CREB pathway and downstream factors brain-derived neurotrophic factor (BDNF) and Zif268 was observed in hippocampal tissue following ATR treatment. Taken together, these results suggest that developmental exposure to ATR is able to induce functional and morphological lesions in the hippocampus of SD rats, and that the MEK/ERK/CREB signaling pathway may be involved in this process.

Developmental Exposure to Atrazine Impairs Spatial Memory and Downregulates the Hippocampal D1 Dopamine Receptor and cAMP-Dependent Signaling Pathway in Rats

Atrazine (ATR) is a widely used herbicide that has been implicated as a neurotoxicant. Recent experimental evidence has implicated that ATR exposure also appears to have adverse effects on the hippocampus, which is a critical region for learning and memory. The aim of the present study was to investigate the effects of ATR toxicity on the hippocampus of developing rats. Postnatal day (PND) 28 male Sprague⁻Dawley (SD) rats received ATR by oral gavage at 10 or 100 mg/kg bodyweight (BW) for 30 consecutive days and were sacrificed at PND 90. Behavioral test results indicated that spatial learning and memory were affected by ATR treatment. Electron microscopy analysis showed that the ultrastructures of the hippocampus were altered in the ATR-treated groups, as compared to the control group. Additionally, ATR treatment impacted dopamine and D1 dopamine receptor (D1DR) contents through different mechanisms. Reduced mRNA and protein expression levels of factors involved in the cAMP-dependent signaling pathway were also detected. These results indicate that the developmental exposure of rats to ATR can damage the hippocampus and spatial memory, which might be related to the downregulation of expression levels of the D1DR and its downstream signaling pathway.

The effects of gestational and chronic atrazine exposure on motor behaviors and striatal dopamine in male Sprague-Dawley rats

This study sought to investigate the effects of environmentally relevant gestational followed by continued chronic exposure to the herbicide, atrazine, on motor function, cognition, and neurochemical indices of nigrostriatal dopamine (DA) activity in male rats. Dams were treated with 100 μg/kg atrazine, 10mg/kg atrazine, or vehicle on gestational day 1 through postnatal day 21. Upon weaning, male offspring continued daily vehicle or atrazine gavage treatments for an additional six months. Subjects were tested in a series of behavioral assays, and 24h after the last treatment, tissue samples from the striatum were analyzed for DA and 3,4-dihydroxyphenylacetic acid (DOPAC). At 10mg/kg, this herbicide was found to produce modest disruptions in motor functioning, and at both dose levels it significantly lowered striatal DA and DOPAC concentrations. These results suggest that exposures to atrazine have the potential to disrupt nigrostriatal DA neurons and behaviors associated with motor functioning.

Gestational and lactational exposure to atrazine via the drinking water causes specific behavioral deficits and selectively alters monoaminergic systems in C57BL/6 mouse dams, juvenile and adult offspring

Atrazine (ATR) is one of the most frequently detected pesticides in the U.S. water supply. This study aimed to investigate neurobehavioral and neurochemical effects of ATR in C57BL/6 mouse offspring and dams exposed to a relatively low (3 mg/l, estimated intake 1.4 mg/kg/day) concentration of ATR via the drinking water (DW) from gestational day 6 to postnatal day (PND) 23. Behavioral tests included open field, pole, grip strength, novel object recognition (NOR), forced swim, and marble burying tests. Maternal weight gain and offspring (PND21, 35, and 70) body or brain weights were not affected by ATR. However, ATR-treated dams exhibited decreased NOR performance and a trend toward hyperactivity. Juvenile offspring (PND35) from ATR-exposed dams were hyperactive (both sexes), spent less time swimming (males), and buried more marbles (females). In adult offspring (PND70), the only behavioral change was a sex-specific (females) decreased NOR performance by ATR. Neurochemically, a trend toward increased striatal dopamine (DA) in dams and a significant increase in juvenile offspring (both sexes) was observed. Additionally, ATR exposure decreased perirhinal cortex serotonin in the adult female offspring. These results suggest that perinatal DW exposure to ATR targets the nigrostriatal DA pathway in dams and, especially, juvenile offspring, alters dams' cognitive performance, induces sex-selective changes involving motor and emotional functions in juvenile offspring, and decreases cognitive ability of adult female offspring, with the latter possibly associated with altered perirhinal cortex serotonin homeostasis. Overall, ATR exposure during gestation and lactation may cause adverse nervous system effects to both offspring and dams.

Differentiation state-dependent effects of in vitro exposure to atrazine or its metabolite diaminochlorotriazine in a dopaminergic cell line

AIMS

This study sought to determine the impact of in vitro exposure to the herbicide atrazine (ATR) or its major mammalian metabolite diaminochlorotriazine (DACT) on dopaminergic cell differentiation.

MAIN METHODS

N27 dopaminergic cells were exposed for 24 or 48 h to ATR or DACT (12-300 μM) and their effects on cell viability, ATP levels, ADP:ATP ratio and differentiation markers, such as soma size and neurite outgrowth, were assessed.

KEY FINDINGS

Overall, intracellular ATP levels and soma size (decreased by ATR at ≥12 μM; 48 h) were the two parameters most sensitive to ATR exposure in undifferentiated and differentiating dopaminergic cells, respectively. At the morphological level, ATR, but not DACT, increased the percentage of morphologically abnormal undifferentiated N27 cells. On the other hand, exposure to DACT (300 μM; 48 h), but not ATR, increased the ADP:ATP ratio regardless of the differentiation state and it moderately disrupted thin neurite outgrowth. Only the highest concentration of ATR or DACT (300 μM) was cytotoxic after a longer exposure (48 h) and undifferentiated N27 cells were the least sensitive to the cytotoxic effects of ATR or DACT.

SIGNIFICANCE

Our results suggest that the energy perturbation and morphological disruption of dopaminergic neuronal differentiation induced by ATR and, to a lesser extent, DACT, may be associated with reported neurological deficits caused by developmental ATR exposure in rodents.

Repeated exposure to the herbicide atrazine alters locomotor activity and the nigrostriatal dopaminergic system of the albino rat

Atrazine (ATR) is used as a pre- and post-emergent herbicide; although banned in several countries of the European Community, it is still used extensively around the world. A recent study in rats has shown that chronic, daily exposure to 10 mg ATR/kg BW causes hyperactivity, disrupts motor coordination and learning of behavioral tasks, and decreases dopamine levels in the brain. In order to evaluate the short-term effect of ATR exposure on locomotor activity, monoamine markers, and antioxidants, adult male Sprague-Dawley rats received six IP injections of 100 mg ATR/kg BW or vehicle over two weeks. After every ATR injection we found hypoactivity that lasted up to five days, and it was accompanied by reductions in levels of striatal DA, DOPAC, and HVA without any alteration in the striatal expression of the mRNAs for Mn-SOD, Trx-1, DAR-D(1), or DAR-D(2). In contrast, in the nucleus accumbens no changes in monoamine markers were observed, and a down-regulation of Trx-1 expression was detected shortly after the ATR treatment. Moreover, in the ventral midbrain, we found that ATR induced a down-regulation of mRNA for Th and DAT, but it increased VMAT2 mRNA expression. Decreases of monoamine levels and of locomotor activity disappeared three months after ATR treatment; however, an amphetamine challenge (1 mg/kg) given two months after the ATR treatment resulted in a significant stimulation in the exposed group, revealing hidden effects of ATR on dopaminergic systems. These results indicate that ATR exposure differentially modifies the dopaminergic systems, and these modifications may underlie the behavioral changes observed.

Impact of endocrine-disrupting compounds (EDCs) on female reproductive health

Evidence is accumulating that environmental chemicals (ECs) including endocrine-disrupting compounds (EDCs) can alter female reproductive development, fertility and onset of menopause. While not as clearly defined as in the male, this set of abnormalities may constitute an Ovarian Dysgenesis Syndrome with at least some origins of the syndrome arising during foetal development. ECs/EDCs have been shown to affect trophoblast and placental function, the female hypothalamo-pituitary-gonadal axis, onset of puberty and adult ovarian function. The effects of ECs/EDCs are complex, not least because it is emerging that low-level, 'real-life' mixtures of ECs/EDCs may carry significant biological potency. In addition, there is evidence that ECs/EDCs can alter the epigenome in a sexually dimorphic manner, which may lead to changes in the germ line and perhaps even to transgenerational effects. This review summarises the evidence for EC, including EDC, involvement in female reproductive dysfunction, it highlights potential mechanisms of EC action in the female and emphasises the need for further research into EC effects on female development and reproductive function.

Demasculinization and feminization of male gonads by atrazine: consistent effects across vertebrate classes

Atrazine is the most commonly detected pesticide contaminant of ground water, surface water, and precipitation. Atrazine is also an endocrine disruptor that, among other effects, alters male reproductive tissues when animals are exposed during development. Here, we apply the nine so-called "Hill criteria" (Strength, Consistency, Specificity, Temporality, Biological Gradient, Plausibility, Coherence, Experiment, and Analogy) for establishing cause-effect relationships to examine the evidence for atrazine as an endocrine disruptor that demasculinizes and feminizes the gonads of male vertebrates. We present experimental evidence that the effects of atrazine on male development are consistent across all vertebrate classes examined and we present a state of the art summary of the mechanisms by which atrazine acts as an endocrine disruptor to produce these effects. Atrazine demasculinizes male gonads producing testicular lesions associated with reduced germ cell numbers in teleost fish, amphibians, reptiles, and mammals, and induces partial and/or complete feminization in fish, amphibians, and reptiles. These effects are strong (statistically significant), consistent across vertebrate classes, and specific. Reductions in androgen levels and the induction of estrogen synthesis - demonstrated in fish, amphibians, reptiles, and mammals - represent plausible and coherent mechanisms that explain these effects. Biological gradients are observed in several of the cited studies, although threshold doses and patterns vary among species. Given that the effects on the male gonads described in all of these experimental studies occurred only after atrazine exposure, temporality is also met here. Thus the case for atrazine as an endocrine disruptor that demasculinizes and feminizes male vertebrates meets all nine of the "Hill criteria".

Bisphenol A: developmental toxicity from early prenatal exposure

Bisphenol A (BPA) exposure has been documented in pregnant women, but consequences for development are not yet widely studied in human populations. This review presents research on the consequences for offspring of BPA exposure during pregnancy. Extensive work in laboratory rodents has evaluated survival and growth of the conceptus, interference with embryonic programs of development, morphological sex differentiation, sex differentiation of the brain and behavior, immune responsiveness, and mechanism of action. Sensitive measures include RAR, aryl hydrocarbon receptor, and Hox A10 gene expression, anogenital distance, sex differentiation of affective and exploratory behavior, and immune hyperresponsiveness. Many BPA effects are reported at low doses (10-50 µg/kg d range) by the oral route of administration. At high doses (>500,000 µg/kg d) fetal viability is compromised. Much of the work has centered around the implications of the estrogenic actions of this agent. Some work related to thyroid mechanism of action has also been explored. BPA research has actively integrated current knowledge of developmental biology, concepts of endocrine disruption, and toxicological research to provide a basis for human health risk assessment.

A physiologically based pharmacokinetic model for atrazine and its main metabolites in the adult male C57BL/6 mouse

Atrazine (ATR) is a chlorotriazine herbicide that is widely used and relatively persistent in the environment. In laboratory rodents, excessive exposure to ATR is detrimental to the reproductive, immune, and nervous systems. To better understand the toxicokinetics of ATR and to fill the need for a mouse model, a physiologically based pharmacokinetic (PBPK) model for ATR and its main chlorotriazine metabolites (Cl-TRIs) desethyl atrazine (DE), desisopropyl atrazine (DIP), and didealkyl atrazine (DACT) was developed for the adult male C57BL/6 mouse. Taking advantage of all relevant and recently made available mouse-specific data, a flow-limited PBPK model was constructed. The ATR and DACT sub-models included blood, brain, liver, kidney, richly and slowly perfused tissue compartments, as well as plasma protein binding and red blood cell binding, whereas the DE and DIP sub-models were constructed as simple five-compartment models. The model adequately simulated plasma levels of ATR and Cl-TRIs and urinary dosimetry of Cl-TRIs at four single oral dose levels (250, 125, 25, and 5mg/kg). Additionally, the model adequately described the dose dependency of brain and liver ATR and DACT concentrations. Cumulative urinary DACT amounts were accurately predicted across a wide dose range, suggesting the model's potential use for extrapolation to human exposures by performing reverse dosimetry. The model was validated using previously reported data for plasma ATR and DACT in mice and rats. Overall, besides being the first mouse PBPK model for ATR and its Cl-TRIs, this model, by analogy, provides insights into tissue dosimetry for rats. The model could be used in tissue dosimetry prediction and as an aid in the exposure assessment to this widely used herbicide.

Atrazine binds to the growth hormone-releasing hormone receptor and affects growth hormone gene expression

BACKGROUND

Atrazine (ATR), a commonly used herbicide in the United States, is widely distributed in water and soil because of its mobility through ecosystems and its persistence in the environment. ATR has been associated with defects in sexual development in animals, but studies on mammalian systems have failed to clearly identify a cellular target.

OBJECTIVES

Our goal in this study was to identify a ligand-binding receptor for ATR in pituitary cells that may explain the mechanism of action at the gene expression level.

METHODS

We used pituitary cells from postnatal day 7 male rats and pituitary cell lines to study the effect of ATR on gene expression of growth hormone (GH), luteinizing hormone (LH), and prolactin (PRL) at RNA and protein levels. 14C-ATR was used to determine its specific binding to the growth hormone-releasing hormone receptor (GHRHR). The effect of ATR on structural proteins was visualized using immunofluorescent in situ staining.

RESULTS

The treatment of rat pituitary cells with ATR, at environmentally relevant concentrations (1 ppb and 1 ppm), resulted in a reduction of GH expression. This effect appeared to result from the inhibition of GH gene transcription due to ATR binding to the GHRHR of the pituitary cells.

CONCLUSIONS

Identification of GHRHR as the target of ATR is consistent with the myriad effects previously reported for ATR in mammalian systems. These findings may lead to a better understanding of the hazards of environmental ATR contamination and inform efforts to develop guidelines for establishing safe levels in water systems.

Chronic atrazine exposure causes disruption of the spontaneous locomotor activity and alters the striatal dopaminergic system of the male Sprague-Dawley rat

The herbicide atrazine (ATR) is widely used around the world, and is a potential toxicant of the dopaminergic systems. Nigrostriatal and mesolimbic systems are the two major dopaminergic pathways of the central nervous system; they play key roles mediating a wide array of critical motor and cognitive functions. We evaluated the effects of exposing male rats for one year to 10 mg ATR/kg B.W. on these systems using motor and cognitive tasks and measuring monoamine content in the striatum, nucleus accumbens, prefrontal cortex, and hypothalamus. ATR administration resulted in impaired motor coordination and greater spontaneous locomotor activity only after 10 to 12 months of exposure. Chronic exposure to 10 mg ATR decreased striatal dopamine, but had no effect on accumbal, hypothalamic or cortical monoamine content. Chronic ATR exposure caused discrete changes in learning tasks that involve either the striatum or the nucleus accumbens. These results indicate that chronic exposure to ATR preferentially targets the nigrostriatal dopaminergic pathway, in comparison to the other dopaminergic pathways evaluated in this study, inducing behavioral and neurochemical alterations. In order to unveil the full extent of atrazine's effects on the nervous system, other neurochemical systems should be considered in future studies.

P19 neuronal differentiation and retinoic acid metabolism as criteria to investigate atrazine, nitrite, and nitrate developmental toxicity

Atrazine and nitrogenous fertilizers are agrochemical contaminants frequently detected in water systems in North America. Several studies reported their ability to affect amphibian and mammalian development. Retinoids, supplied in the diet or synthesized by cells, are essential to embryogenesis. Disturbance of their homeostasis may lead to teratogenic effects. Retinoic acid (RA) is a major retinoid regulator of cell proliferation and differentiation. Previous studies reported alterations of retinoid stores in bullfrogs of Yamaska River subwatersheds (Québec, Canada), a region of intensive agricultural activities associated with atrazine, nitrate, and nitrite contaminants. These contaminants could affect RA metabolism and RA-mediated processes. Mouse P19 embryonic stem cells, which can differentiate to neurons in response to RA, were used to test this hypothesis. Cells were cultured in the absence or presence of contaminants during neuroinduction with RA and assayed by flow cytometry for expression of stage-specific embryonic antigen-1 (SSEA1) (embryonic marker) and betaIII-tubulin (neuronal marker). Cell cultures were also analyzed for RA metabolism by high performance liquid chromotagraphy (HPLC). Downregulation of SSEA1 paralleled betaIII-tubulin upregulation in an RA concentration-dependent manner. Atrazine, nitrate, and nitrite did not affect differentiation at environmentally encountered micromolar concentrations. However, low molar nitrite prevented RA-induced SSEA1 downregulation and decreased betaIII-tubulin appearance. Decreased cell viability/proliferation accompanied these differentiation effects. P19 cells metabolized RA to polar retinoids. RA metabolism was not affected at any concentration of atrazine, nitrate, or nitrite. Environmentally relevant levels of these contaminants, thus, had no gross effect on neurodifferentiation and RA catabolism of embryonic stem cells. P19 cell-based bioassays may provide valuable tools in monitoring developmental toxicity.

Disposition of the herbicide 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (Atrazine) and its major metabolites in mice: a liquid chromatography/mass spectrometry analysis of urine, plasma, and tissue levels

2-Chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine, ATR) is a toxicologically important and widely used herbicide. Recent studies have shown that it can elicit neurological, immunological, developmental, and biochemical alterations in several model organisms, including in mice. Because disposition data in mice are lacking, we evaluated ATR's metabolism and tissue dosimetry after single oral exposures (5-250 mg/kg) in C57BL/6 mice using liquid chromatography/mass spectrometry (Ross and Filipov, 2006). ATR was metabolized and cleared rapidly; didealkyl ATR (DACT) was the major metabolite detected in urine, plasma, and tissues. Plasma ATR peaked at 1 h postdosing and rapidly declined, whereas DACT peaked at 2 h and slowly declined. Most ATR and metabolite residues were excreted within the first 24 h. However, substantial amounts of DACT were still present in 25- to 48-h and 49- to 72-h urine. ATR reached maximal brain levels (0.06-1.5 microM) at 4 h (5-125 mg/kg) and 1 h (250 mg/kg) after dosing, but levels quickly declined to <0.1 microM by 12 h in all the groups. In contrast, strikingly high concentrations of DACT (1.5-50 microM), which are comparable with liver DACT levels, were detectable in brain at 2 h. Brain DACT levels slowly declined, paralleling the kinetics of plasma DACT. Our findings suggest that in mice ATR is widely distributed and extensively metabolized and that DACT is a major metabolite detected in the brain at high levels and is ultimately excreted in urine. Our study provides a starting point for the establishment of models that link target tissue dose to biological effects caused by ATR and its in vivo metabolites.

Improved methods for urinary atrazine mercapturate analysis—Assessment of an enzyme-linked immunosorbent assay (ELISA) and a novel liquid chromatography–mass spectrometry (LC–MS) method utilizing online solid phase extraction (SPE)

Elimination of interfering substances in urine by solid phase extraction (SPE) prior to analysis resulted in 10-fold improvement in the sensitivity of atrazine mercapturate (AM) enzyme-linked immunosorbent assay (ELISA) compared to previous reports. Of the two tested SPE systems, Oasis HLB and MCX, the mixed-mode MCX gave good recoveries (82%) of AM in spiked samples measured by ELISA, whereas the reverse-phase HLB phase was not compatible with the immunochemical method. At relatively high concentrations of urinary AM (>20 ng mL(-1)), sample dilution was effective enough for the elimination of interfering substances. The new liquid chromatography-mass spectrometry (LC-MS) method developed for AM utilizes online-SPE with Oasis HLB, column switching and a stable-isotope internal standard. The limit of quantification (0.05 ng mL(-1)) indicates improved sensitivity compared with most previously published LC-MS methods for AM. Validation of all three methods, LC-MS, ELISA+SPE and ELISA+dilution with spiked urine samples showed good correlation between the known and measured concentrations with R2 values of 0.996, 0.957 and 0.961, respectively. When a set (n=70 plus 12 blind duplicates) of urine samples from farmers exposed to atrazine was analyzed, there was a good agreement (R2=0.917) between the log normalized data obtained by ELISA+SPE and LC-MS. High correlation among the data obtained by the two tested methods and the LC-MS method by the Center of Disease Control and Prevention (CDC), together with low variability among the blind duplicates, suggests that both methods reported here would be suitable for the analysis of urinary AM as a biomarker for human exposure of atrazine.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.