Atrazine acts as an endocrine disrupter by inhibiting cAMP-specific phosphodiesterase-4

A review on toxic effects of pesticides in Zebrafish, Danio rerio and common carp, Cyprinus carpio, emphasising Atrazine herbicide

The widespread use of pesticides has emerged as a pressing environmental concern nowadays. These chemical compounds pose a significant threat to aquatic organisms due to their toxic effects. Zebrafish and common carp are two common species used in pesticide toxicity studies. Atrazine, a widely used herbicide, is one of the most prevalent globally, detectable in nearly all surface waters. This article examines existing literature to provide a comprehensive review of the toxic effects of Atrazine on Zebrafish and common carp. The findings reveal that exposure to atrazine triggers a range of biochemical, physiological, behavioral, and genetic alterations in these fish species, even at concentrations deemed environmentally relevant. These changes could have severe consequences, including increased mortality rates, reproductive failures, and potentially leading to fish populations decline. It is, therefore, imperative to prioritize stringent regulatory measures to curb the usage of this herbicide and safeguard fish species as unintended victims of aquatic ecosystems.

Acute effects of atrazine on the immunoexpressions of sertoli and germ cells molecular markers, cytokines, chemokines, and sex hormones levels in mice testes and epididymides

Atrazine is currently one of the most commonly used agrochemicals in the United States and elsewhere. Here, we studied the immunoexpression of molecular markers of mammalian testicular functions: androgen receptor (AR), promyelocytic leukemia zinc finger (PLZF), GDNF family receptor alpha-1 (GFRA1), VASA/DDX4 (DEAD-Box Helicase 4) as well as the levels of intratesticular and intra-epididymal estradiol (E2) and dihydrotestosterone (DHT), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukins (IL-1β and IL-6, IL-10) and testicular chemokines (CXCL-1, CCL-2 and CCL3) in BalB/c mice after a sub-acute gavage treatment with a gonado-toxin, atrazine (50 mg/kg body wt.) for three days. We found high numbers of AR immunopositive Sertoli cells and low numbers of GFRA1, PLZF and VASA/DDX4-positive germ cells in the seminiferous tubule regions of the testes. While TNF-α level in the testes fell and remained unchanged in the epididymides, IFN-γ levels in the testes remained constant but increased in the epididymides. E2 and DHT concentrations remained unaltered in the testes but were changed in the epididymides. There were no significant changes in the levels of interleukins in the testis and epididymis. Intratesticular chemokines were also not significantly altered, except for CCL-4, which was increased in the testis. Light microscopy of the epididymis showed detached epithelium and some detached cells in the lumen. It is concluded that atrazine changed the inflammatory status of the gonads and highlighted Sertoli and undifferentiated spermatogonia as important targets for atrazine's toxic effects in the testis of mice. Concerning the epididymis, atrazine altered the epididymal hormonal concentrations and promoted histopathological modifications in its parenchyma.

Atrazine degradation through a heterogeneous dual-effect process using Fe-TiO2-allophane catalysts under sunlight

This study investigated the novel application of Fe-TiO2-allophane catalysts with 6.0 % w/w of iron oxide and two TiO2 proportions (10 % and 30 % w/w) for degrading atrazine (ATZ) using the heterogeneous dual-effect (HDE) process under sunlight. Comparative analyses with Fe-allophane and TiO2-allophane catalysts were conducted in both photocatalysis (PC) and HDE processes. FTIR spectra reveal the unique hydrous feldspathoids structure of allophane, showing evidence of new bond formation between Si-O groups of allophane clays and iron hydroxyl species, as well as Si-O-Ti bonds that intensified with higher TiO2 content. The catalysts exhibited an anatase structure. In Fe-TiO2-allophane catalysts, iron oxide was incorporated through the substitution of Ti4+ by Fe3+ in the anatase crystal lattice and precipitation on the surface of allophane clays, forming small iron oxide particles. Allophane clays reduced the agglomeration and particle size of TiO2, resulting in an enhanced specific surface area and pore volume for all catalysts. Iron oxide incorporation decreased the band gap, broadening the photoresponse to visible light. In the PC process, TiO2-allophane achieves 90 % ATZ degradation, attributed to radical species from the UV component of sunlight. In the HDE process, Fe-TiO2-allophane catalysts exhibit synergistic effects, particularly with 30 % w/w TiO2, achieving 100 % ATZ degradation and 85 % COD removal, with shorter reaction time as TiO2 percentage increased. The HDE process was performed under less acidic conditions, achieving complete ATZ degradation after 6 h without iron leaching. Consequently, Fe-TiO2-allophane catalysts are proposed as a promising alternative for degrading emerging pollutants under environmentally friendly conditions.

Association of Atrazine-Induced Overexpression of Aldo-Keto-Reductase 1C2 (AKR1C2) with Hypoandrogenism and Infertility: An Experimental Study in Male Wistar Rat

Atrazine (ATZ, C8H14ClN5) is a widely used synthetic herbicide that contaminates drinking water. It is a known endocrine disruptor that disrupts various molecular pathways involved in hormone signaling, and DNA damage, and can cause reproductive disorders, including decreased fertility, and abnormal development of reproductive organs, as revealed in animal model studies. However, the effect of ATZ on steroidogenesis in the male reproductive system, especially reduction of ketosteroids to hydroxysteroids, remains unclear. This study investigated the toxicity of ATZ on the male reproductive system in the Wistar rat model, with an emphasis on its adverse effect on aldo-ketoreductase family 1 member C2 (AKR1C2). Male Wistar rats were administered ATZ for 56 days (duration of one spermatogenic cycle) through oral route, at 20, 40 and 60 mg/kg body weight (bw) doses. The results indicate that ATZ exposure affects the body weight, impairs sperm production, and decrease FSH, LH, and testosterone levels. Additionally, the down-regulation of key steroidogenic enzymes by ATZ disrupted the synthesis of testosterone, leading to decreased levels of this essential male hormone. On the other hand, the expression of AKR1C2 (mRNA and protein) in the testis was upregulated. The findings suggest that AKR1C2 plays a role in androgen metabolism. Furthermore, its overexpression may lead to alteration in the expression of genes in the connected pathway, causing an increase in the breakdown or inactivation of androgens, which would result in lower androgen levels and, thereby, lead to hypoandrogenism, as the combined effects of down-regulation of steroidogenic genes and up-regulation of AKR1C2. These findings reveal direct implication of disrupted AKR1C2 in male reproductive health and highlight the need for further research on the impact of environmental toxins on human fertility, ultimately providing for better patient care.

Exposure to Pesticides and Breast Cancer in an Agricultural Region in Brazil

Rural workers are disproportionally exposed to pesticides and might be at an increased risk of developing chronic diseases. Here, we investigated the impact of pesticide exposure on breast cancer (BC) risk and disease profile in rural female workers. This is a case-control study that prospectively included 758 individuals. The study was conducted in the Southwest region of Paraná state in Brazil, a region characterized by family-based agriculture and intensive use of pesticides. We found that this region has a 41% higher BC diagnosis rate and 14% higher BC mortality rate than the mean rates in Brazil, as well as a pesticide trade volume about 6 times higher than the national average. We showed substantial exposure in this population and found that even women who did not work in the fields but performed equipment decontamination and clothes washing of male partners who worked in the fields had urine samples positive for glyphosate, atrazine, and/or 2,4-D. The crude association showed a significantly higher risk of BC among women exposed to pesticides (OR: 1.58, 95% CI 1.18-2.13). Adjusted analyses showed a lower and nonstatistically significant association (OR: 1.30, 95% CI 41 0.87-1.95). Stratification on disease profile showed a significantly higher risk of lymph node metastasis (adjusted OR: 2.19, 95% CI 1.31-3.72) in women exposed to pesticides. Our findings suggest that female populations exposed to pesticides are at a higher risk of developing BC with a more aggressive profile and draw attention to the need to monitor rural populations potentially exposed to pesticides in the field or at home.

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.

Endocrine Disruptors and Metabolic Changes: Impact on Puberty Control

OBJECTIVE

This study aims to explore the significant impact of environmental chemicals on disease development, focusing on their role in developing metabolic and endocrine diseases. The objective is to understand how these chemicals contribute to the increasing prevalence of precocious puberty, considering various factors, including epigenetic changes, lifestyle, and emotional disturbances.

METHODS

The study employs a comprehensive review of descriptive observational studies in both human and animal models to identify a degree of causality between exposure to environmental chemicals and disease development, specifically focusing on endocrine disruption. Due to ethical constraints, direct causation studies in human subjects are not feasible; therefore, the research relies on accumulated observational data.

RESULTS

Puberty is a crucial life period with marked physiological and psychological changes. The age at which sexual characteristics develop is changing in many regions. The findings indicate a correlation between exposure to endocrine-disrupting chemicals and the early onset of puberty. These chemicals have been shown to interfere with normal hormonal processes, particularly during critical developmental stages such as adolescence. The research also highlights the interaction of these chemical exposures with other factors, including nutritional history, social and lifestyle changes, and emotional stress, which together contribute to the prevalence of precocious puberty.

CONCLUSION

Environmental chemicals significantly contribute to the development of certain metabolic and endocrine diseases, particularly in the rising incidence of precocious puberty. Although the evidence is mainly observational, it adequately justifies regulatory actions to reduce exposure risks. Furthermore, these findings highlight the urgent need for more research on the epigenetic effects of these chemicals and their wider impact on human health, especially during vital developmental periods.

An Updated Evaluation of Atrazine-Cancer Incidence Associations among Pesticide Applicators in the Agricultural Health Study Cohort

BACKGROUND

Atrazine is a common agricultural herbicide in the United States. Few epidemiologic studies have evaluated cancer risks. Previous analyses within the Agricultural Health Study (AHS) have found some evidence of associations with cancer at some sites.

OBJECTIVE

We updated exposure information, incident cases, and follow-up time to assess the associations between atrazine use and cancer at specific sites in the AHS.

METHODS

Information about lifetime pesticide use was reported at enrollment (1993-1997) and follow-up (1999-2005). Among 53,562 pesticide applicators in North Carolina and Iowa, we identified 8,915 incident cases through cancer registry linkages through 2014 (North Carolina)/2017 (Iowa). We used Poisson regression to evaluate the association between ever/never and intensity-weighted lifetime days of atrazine use and incident cancer risk controlling for several confounders. We also evaluated lagged exposures and age-stratified risk.

RESULTS

Approximately 71.2% of applicators reported ever using atrazine, which was associated with lung cancer [rate ratios  ( RR ) = 1.24 ; 95% confidence interval (CI): 1.04, 1.46]. Aggressive prostate cancer risk was increased in the highest quartile (RR Q 4 = 1.20 ; 95% CI: 0.95, 1.52; p -trend = 0.19 ), particularly among those < 60 years old (RR Q 4 = 3.04 ; 95% CI: 1.61, 5.75; p -trend < 0.001 ; p -interaction = 0.04 ). Among applicators < 50 years of age, ever-atrazine use was associated with non-Hodgkin lymphoma (NHL) (RR = 2.43 ; 95% CI: 1.10, 5.38; p -interaction = 0.60 ). For soft tissue sarcoma, there was an elevated risk in the highest tertile of exposure (RR T 3 : 2.54; 95% CI: 0.97, 6.62; p -trend = 0.31 ). In analyses with exposure lagged by 25 years, there was an elevated risk of pharyngeal (RR T 3 = 3.04 ; 95% CI: 1.45, 6.36; p -trend = 0.07 ) and kidney (RR Q 4 = 1.62 ; 95% CI: 1.15, 2.29; p -trend < 0.005 ) cancers.

DISCUSSION

We observed suggestive associations with some malignancies in overall, age-specific, and lagged analyses. Associations with aggressive prostate cancer and NHL were apparent among those diagnosed at younger ages and with cancers of the pharynx and kidney, and soft tissue sarcomas were observed in lagged analyses. Further work is needed to confirm these observed associations and elucidate potential underlying mechanisms. https://doi.org/10.1289/EHP13684.

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.

Brief research report pesticide occupational exposure leads to significant inflammatory changes in normal mammary breast tissue

Studies have documented the high occurrence of several tumors, including female breast cancer, in populations occupationally exposed to pesticides worldwide. It is believed that in addition to direct DNA damage, other molecular alterations that indicate genomic instability are associated, such as epigenetic modifications and the production of inflammation mediators. The present study characterized the profile of inflammatory changes in the breast tissue of women without cancer occupationally exposed to pesticides. In samples of normal breast tissue collected during biopsy and evaluated as negative for cancer by a pathologist, oxidative stress levels were assessed as inflammatory markers through measurements of lipoperoxides and total antioxidant capacity of the sample (TRAP) by high-sensitivity chemiluminescence, as well as levels of nitric oxide (NOx) metabolites. The levels of inflammation-modulating transcription factors PPAR-γ (peroxisome proliferator-activated receptor gamma) and NF-κB (nuclear factor kappa B) were also quantified, in addition to the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin 12 (IL-12). The levels of lipoperoxides, TRAP, and NOx were significantly lower in the exposed group. On the other hand, PPAR-γ levels were increased in the breast tissue of exposed women, with no variation in NF-κB. There was also a rise of TNF-α in exposed women samples without significant variations in IL-12 levels. These findings suggest an inflammatory signature of the breast tissue associated with pesticide exposure, which may trigger mechanisms related to mutations and breast carcinogenesis.

Atrazine Toxicity: The Possible Role of Natural Products for Effective Treatment

There are various herbicides which were used in the agriculture industry. Atrazine (ATZ) is a chlorinated triazine herbicide that consists of a ring structure, known as the triazine ring, along with a chlorine atom and five nitrogen atoms. ATZ is a water-soluble herbicide, which makes it capable of easily infiltrating into majority of the aquatic ecosystems. There are reports of toxic effects of ATZ on different systems of the body but, unfortunately, majority of these scientific reports were documented in animals. The herbicide was reported to enter the body through various routes. The toxicity of the herbicide can cause deleterious effects on the respiratory, reproductive, endocrine, central nervous system, gastrointestinal, and urinary systems of the human body. Alarmingly, few studies in industrial workers showed ATZ exposure leading to cancer. We embarked on the present review to discuss the mechanism of action of ATZ toxicity for which there is no specific antidote or drug. Evidence-based published literature on the effective use of natural products such as lycopene, curcumin, Panax ginseng, Spirulina platensis, Fucoidans, vitamin C, soyabeans, quercetin, L-carnitine, Telfairia occidentalis, vitamin E, Garcinia kola, melatonin, selenium, Isatis indigotica, polyphenols, Acacia nilotica, and Zingiber officinale were discussed in detail. In the absence of any particular allopathic drug, the present review may open the doors for future drug design involving the natural products and their active compounds.

Prolonged exposure to the herbicide atrazine promotes kidney fibrosis by activating Wnt/β-catenin signaling in rats

Exposure to atrazine (ATR), a widely-used herbicide, is a potential harmful to human health due to its long-term environmental persistence and bioaccumulation. The effects of chronic exposure to ATR on renal function in rats were evaluated in this research. Female Sprague-Dawley rats at 4 weeks of age were treated with different concentrations of ATR for 6 months. No significant differences  in terms of renal functions were observed after ATR treatment. In histopathological examination of the kidney, Hematoxylin-Eosin staining indicated the development of degenerative changes in a dose-dependent manner. The results revealed that ATR exposure leads to renal fibrosis and that activation of the Wnt/β-catenin pathway plays a potential role in ATR-related renal fibrosis. Levels of transforming growth factor (TGF)-β and TGF-β1 levels and the reactive oxygen species were significantly upregulated after ATR treatment. In conclusion, long-term exposure to ATR could cause kidney fibrosis, which is the result of epithelial-mesenchymal transition caused by inflammation and oxidative stress.

Impact of Chronic Multi-Generational Exposure to an Environmentally Relevant Atrazine Concentration on Testicular Development and Function in Mice

A common herbicide, atrazine, is associated with poor health. Atrazine acts as an endocrine disruptor at supra-environmental levels. Little research, however, has been conducted regarding chronic exposure to environmental atrazine concentrations across generations. This study utilized comprehensive endpoint measures to investigate the effects of chronic exposure to a conservative atrazine concentration (0.02 ng/mL), measured in Australian waterways, on male mice fertility across two generations. Mice were exposed through the maternal line, from the pre-conception period and through the F1 and F2 generations until three or six months of age. Atrazine did not impact sperm function, testicular morphology nor germ cell parameters but did alter the expression of steroidogenic genes in the F1, down-regulating the expression of Cyp17a1 (Cytochrome P450 family 17, subfamily A member 1; p = 0.0008) and Ddx4 (DEAD-box helicase 4; p = 0.007), and up-regulating the expression of Star (Steroidogenic acute regulatory protein; p = 0.017). In the F2, atrazine induced up-regulation in the expression of Star (p = 0.016). The current study demonstrates that chronic exposure to an environmentally relevant atrazine concentration perturbs testicular steroid-associated gene expression that varies across generations. Future studies through the paternal and combined parental lineages should be undertaken to further elucidate the multigenerational effects of atrazine on male fertility.

Anxiety-related behavior and associated brain transcriptome and epigenome alterations in adult female zebrafish exposed to atrazine during embryogenesis

Atrazine often contaminates drinking water sources, exceeding the maximum contaminant level established by the US Environmental Protection Agency at 3 parts per billion (ppb; μg/L). Atrazine is linked to endocrine disruption, neurotoxicity, and cancer, with delayed health effects observed after developmental exposure in line with the developmental origins of health and disease (DOHaD) hypothesis. To test the hypothesis that embryonic atrazine exposure induces delayed neurotoxicity in adult female zebrafish (Danio rerio), embryos were exposed to 0, 0.3, 3, or 30 ppb atrazine during embryogenesis (1-72 h post fertilization (hpf)) and raised to adults with no additional atrazine exposure. Behavioral outcomes were tested through a novel tank test, light-dark box, and open field test and indicated female zebrafish had more anxious phenotypes at 9 months post fertilization (mpf). Female brain transcriptomic analysis at 9 mpf found altered gene expression pathways related to organismal injury and cancer with beta-estradiol and estrogen receptor as top upstream regulators. These results were compared to 9 mpf male and 6 mpf female groups with the same atrazine embryonic exposures and showed differences in specific genes that were altered, but similarities in top molecular pathways. Molecular pathways associated with behavior were observed only in the 6 mpf transcriptomic profiles, suggesting prediction of observed behavioral outcomes at 9 mpf. The expression of genes associated with serotonin neurotransmission was also evaluated at 14 mpf to determine persistence; however, no significant changes were observed. Brain global methylation in 12 mpf zebrafish observed an increased percent 5 mC in females with embryonic 0.3 ppb atrazine exposure. Finally, the body length, body weight, and brain weight were determined at 14 mpf and were altered in all treatment groups. These results indicate that embryonic atrazine exposure does cause delayed neurotoxicity within the DOHaD framework, which is significant given atrazine's presence and persistence in the environment.

Tox21-Based Comparative Analyses for the Identification of Potential Toxic Effects of Environmental Pollutants

Chemical pollution has become a prominent environmental problem. In recent years, quantitative high-throughput screening (qHTS) assays have been developed for the fast assessment of chemicals' toxic effects. Toxicology in the 21st Century (Tox21) is a well-known and continuously developing qHTS project. Recent reports utilizing Tox21 data have mainly focused on setting up mathematical models for in vivo toxicity predictions, with less attention to intuitive qHTS data visualization. In this study, we attempted to reveal and summarize the toxic effects of environmental pollutants by analyzing and visualizing Tox21 qHTS data. Via PubMed text mining, toxicity/structure clustering, and manual classification, we detected a total of 158 chemicals of environmental concern (COECs) from the Tox21 library that we classified into 13 COEC groups based on structure and activity similarities. By visualizing these COEC groups' bioactivities, we demonstrated that COECs frequently displayed androgen and progesterone antagonistic effects, xenobiotic receptor agonistic roles, and mitochondrial toxicity. We also revealed many other potential targets of the 13 COEC groups, which were not well illustrated yet, and that current Tox21 assays may not correctly classify known teratogens. In conclusion, we provide a feasible method to intuitively understand qHTS data.

Widespread pesticide contamination of drinking water and impact on cancer risk in Brazil

Pesticides, which are associated with endocrine dysfunction, immunological dysregulation, and cancer, are widespread sources of drinking water contamination. The state of Paraná has a population of 11 million, is the second largest grain producer in Brazil and is a leading consumer of pesticides. In this study, we analyzed the extent of drinking water contamination from 11 proven, probable, or potentially carcinogenic pesticides (alachlor, aldrin-dieldrin, atrazine, chlordane, DDT-DDD-DDE, diuron, glyphosate-AMPA, lindane-γ-HCH, mancozeb-ETU, molinate, and trifluralin) in 127 grain-producing municipalities in the state of Paraná. Extensive contamination of drinking water was found, including legacy pesticides such as aldrin-dieldrin (mean 0.047 ppb), DDT-DDD-DDE (mean: 0.07), chlordane (mean: 0.181), and lindane-HCH (mean: 2.17). Most of the municipalities were significantly above the maximum limits for each one of the currently allowed pesticides (67% for alachlor, 9.44% for atrazine, 96.85% for diuron, 100% for glyphosate-AMPA, 80.31% for mancozeb-ETU, 91.33% for molinate, and 12.6% for trifluralin). Ninety-seven percent of municipalities presented a sum of all pesticides at levels significantly above (189.84 ppb) the European Union preconized limits (<0.5 ppb). Using the mean pesticide concentration in water (ppb), the exposed population for each municipality, and the benchmark cancer risk for pesticides, we estimated the minimum number of cancer cases attributable to pesticide-contaminated drinking water during the period (total of 542 cases). More than 80% were attributed to mancozeb-ETU and diuron. Glyphosate-AMPA and diuron-attributable cases strongly correlated with the total cancer cases in the same period (R = 0.8117 and 0.8138, respectively) as well as with breast cancer cases (R = 0.7695 and 0.7551, respectively). Water contamination was significantly correlated with the sum of the estimated cancer cases for all 11 pesticides detected in each city (R = 0.58 and p < 0.0001). These findings reveal extensive contamination of drinking water in the state of Paraná and suggest that contamination may increase the risk of cancer in this region.

Membrane Hormone Receptors and Their Signaling Pathways as Targets for Endocrine Disruptors

The endocrine disruptors are mostly small organic molecules developed for numerous and very diverse industrial applications. They essentially act through nuclear receptors with small and hydrophobic endogenous ligands. Nevertheless, potential adverse effects through membrane hormone receptors cannot be ruled out, and have indeed been observed. The present paper reviews how orthosteric and allosteric binding sites of the different families of membrane receptors can be targets for man-made hydrophobic molecules (components of plastics, paints, flame retardants, herbicides, pesticides, etc.). We also review potential target proteins for such small hydrophobic molecules downstream of membrane receptors at the level of their intracellular signaling pathways. From the currently available information, although endocrine disruptors primarily affect nuclear receptors’ signaling, membrane receptors for hormones, cytokines, neuro-mediators, and growth factors can be affected as well and deserve attention.

Use of Chicken Embryo Model in Toxicity Studies of Endocrine-Disrupting Chemicals and Nanoparticles

Lab animals such as mice and rats are widely used in toxicity research of food additive and pharmaceutics, despite the well-recognized research limitation such as the inability to simulate human neurological diseases, faster absorption of chemicals, big variations among species, and high cost when using a large number of animals. The Society of Toxicology's guidance now focuses on minimizing discomfort and distress of lab animals, finding alternative ways to reduce animal number, replacing animals with in vitro models, and complying to the animal welfare policies. The chicken embryonic model can be a better alternative to mice and rats because of its abundant availability and cost-effectiveness. It can be studied in both laboratory and natural environment, with easy manipulation in ovo or in vivo. The objective of this review paper is to evaluate the use of chicken embryonic model in toxicity evaluation for endocrine-disrupting chemicals (EDCs) and nanoparticles (NPs) by different end points to determine more comprehensive toxic responses. The end points include chicken embryonic mortality and hatchability, developmental malformation analysis, hormonal imbalance, physiological changes in endocrine organs, and antiangiogenesis. Major research methodologies using chicken embryos are also summarized to demonstrate their versatile practice and valuable application in modern toxicity evaluation of EDCs and NPs.

Glyphosate vs. Glyphosate-Based Herbicides Exposure: A Review on Their Toxicity

Glyphosate-based herbicide has been the first choice for weed management worldwide since the 1970s, mainly due to its efficacy and reported low toxicity, which contributed to its high acceptance. Many of the recent studies focus solely on the persistence of pesticides in soils, air, water or food products, or even on the degree of exposure of animals, since their potential hazards to human health have raised concerns. Given the unaware exposure of the general population to pesticides, and the absence of a significant number of studies on occupational hazards, new glyphosate-induced toxicity data obtained for both residual and acute doses should be analyzed and systematized. Additionally, recent studies also highlight the persistence and toxicity of both glyphosate metabolites and surfactants present in herbicide formulations. To renew or ban the use of glyphosate, recently published studies must be taken into account, aiming to define new levels of safety for exposure to herbicide, its metabolites, and the toxic excipients of its formulations. This review aims to provide an overview of recent publications (2010–present) on in vitro and in vivo studies aimed at verifying the animal toxicity induced by glyphosate, its metabolite aminomethylphosphonic acid (AMPA) and glyphosate-based formulations, evaluated in various experimental models. Apart from glyphosate-induced toxicity, recent data concerning the role of surfactants in the toxicity of glyphosate-based formulations are discussed.

Exposure to Atrazine through gestation and lactation period led to impaired sexual maturation and subfertility in F1 male rats with congenital deformities in F2 progeny

Several scientific reports suggest perturbed reproductive and developmental defects associated with environmental exposure to Atrazine (ATR). ATR has been associated with altered endocrine and reproductive functioning in-vivo exposed during the critical window of development. Thus, the present study investigates the effect of ATR exposure on F1-F2 male progeny exposed through gestation and lactation. F0 dams administered with ATR at doses 2, 10, 70, and 100 mg/kg b. wt/day from gestation day 6 to postnatal day 21. The F1 male rats were monitored for sexual maturation and subjected to fertility assessment on PND75. Delayed testicular descent was observed in 10, 70, and 100 mg/kg b. wt/day ATR dose with significantly lower serum testosterone, sperm count, and motility with testicular defects in F1 male. Expression of Androgen receptor (AR), Estrogen receptors (ER α and ER β), StAR, Aromatase, and INSL-3 were upregulated at all doses indicating estrogenic/anti-androgenic activity of ATR. Fertility assessment revealed subfertility in F1 males with high (%) pre- and post-implantation loss at 10, 70, and 100 mg/kg b. wt/day dose as compared to control. Further, F2 fetuses exhibited congenital disabilities viz. decreased weight, crown-rump length, and anogenital distance with several other morphological deformities. To conclude, ATR exerted estrogenic and/or anti-androgenic activity with fetotoxic effects through the male germline.

Pesticide use and kidney function among farmers in the Biomarkers of Exposure and Effect in Agriculture study

BACKGROUND

Pesticides have been reported to be associated with malignant and non-malignant kidney disease. Few studies have examined the relationship between individual pesticides and kidney dysfunction.

OBJECTIVE

We evaluated the associations of pesticide use with measured kidney function among male pesticide applicators in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study, a subcohort in the Agricultural Health Study.

METHODS

Serum creatinine was measured in 1545 BEEA participants and estimated glomerular filtration rate (eGFR) was calculated with the chronic kidney disease epidemiology collaboration (CKD-EPI) equation. Using reported information on lifetime use of 41 pesticides, multivariable linear and logistic regression was used to examine associations with eGFR modeled continuously and with CKD (eGFR <60 mL/min/1.73 m²), respectively. Models were adjusted for possible confounding factors related to kidney function and correlated pesticides.

RESULTS

Lower eGFR was observed among pesticide applicators who ever used the herbicides pendimethalin (-3.7%, 95% confidence interval (CI): 5.8%, -1.5%), atrazine (-3.7%, 95% CI: 6.9%, -0.4%), and dicamba (-2.8%, 95% CI: 5.3%, -0.2%) compared with never users of each pesticide. Ever use of pendimethalin (odds ratio (OR)=1.6, 95% CI: 1.1, 2.2) and atrazine (OR=1.8, 95% CI: 1.0, 3.0) was also associated with elevated odds of CKD, with an exposure-response association between intensity-weighted lifetime days of pendimethalin use and CKD among active farmers (N=1302; p_trend=0.04). Atrazine use within the last year was associated with lower eGFR and elevated odds of CKD when compared with never users, and we observed exposure-response associations with intensity-weighted lifetime days among recent users. Use of several other pesticides was associated with higher eGFR.

DISCUSSION

These results suggest that two widely used herbicides, pendimethalin and atrazine, may be associated with altered kidney function among pesticide applicators. Our findings for these herbicides are consistent with observed associations with end-stage renal disease in the Agricultural Health Study.

Honey bee queen health is unaffected by contact exposure to pesticides commonly found in beeswax

Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. Prior research has investigated the effects of indirect pesticide exposure on queens via workers, as well as direct effects on queens during development. However, as adults, queens are in constant contact with wax as they walk on comb and lay eggs; therefore, direct pesticide contact with adult queens is a relevant but seldom investigated exposure route. Here, we conducted laboratory and field experiments to investigate the impacts of topical pesticide exposure on adult queens. We tested six pesticides commonly found in wax: coumaphos, tau-fluvalinate, atrazine, 2,4-DMPF, chlorpyriphos, chlorothalonil, and a cocktail of all six, each administered at 1, 4, 8, 16, and 32 times the concentrations typically found in wax. We found no effect of any treatment on queen mass, sperm viability, or fat body protein expression. In a field trial testing queen topical exposure of a pesticide cocktail, we found no impact on egg-laying pattern, queen mass, emergence mass of daughter workers, and no proteins in the spermathecal fluid were differentially expressed. These experiments consistently show that pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics at the doses tested. We suggest that previously reported associations between high levels of pesticide residues in wax and queen failure are most likely driven by indirect effects of worker exposure (either through wax or other hive products) on queen care or queen perception.

The use of different sublethal endpoints to monitor atrazine toxicity in nematode Caenorhabditis elegans

In this work, Caenorhabditis elegans was employed as an in vivo model to determine the toxic effects of atrazine at different concentrations. After the exposure period from the larval stage L1 to adulthood day 1, atrazine (10 mg/L) significantly decreased the body length and lifespan of nematodes. In addition, exposure to ≥0.01 mg/L atrazine remarkably increased the intestinal reactive oxygen species (ROS) levels and reduced locomotion behavior of nematodes, while exposure to ≥ 1 mg/L atrazine decreased the brood size of nematodes. Moreover, atrazine (0.001-0.1 mg/L) upregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes, indicating the activation of mitochondrial unfolded protein response (mtUPR). On the contrary, atrazine (1-10 mg/L) downregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes. Furthermore, mtUPR induction governed by the RNAi knockdown of atfs-1 could increase the vulnerability of nematodes against atrazine toxicity. Overall, our findings highlighted the dynamic responses of nematodes toward different concentrations of atrazine, which could be monitored using different sublethal endpoints as bioindicators.

Chloro-s-triazines-toxicokinetic, Toxicodynamic, Human Exposure, and Regulatory Considerations

Chloro-s-triazines-atrazine, cyanazine, propazine, simazine, and terbuthylazine-are structurally similar herbicides, differing only in specific s-triazine4-and 6-N alkyl substituents. It is generally regarded that their toxicokinetics, such as, metabolic pathways, biological effects and toxicities, also share more similar features than the differences. Consequently, it is useful to compare their characteristics to potentially find useful structure-activity relationships or other similarities or differences regarding different active compounds, their metabolites, and biological effects including toxic outcomes. The ultimate goal of these exercises is to apply the summarized knowledge-as far as it is possible regarding a patchy and often inadequate database-to cross the in vitro-in vivo and animal-human borders and integrate the available data to enhance toxicological risk assessment for the benefit of humans and ecosystems.

The Herbicide Atrazine Potentiates Angiotensin II-Induced Aldosterone Synthesis and Release From Adrenal Cells

Atrazine is one of the most commonly used pre-emergence and early post-emergence herbicides in the world. We have shown previously that atrazine does not directly stimulate the pituitary or adrenal to trigger hormone release but acts centrally to activate a stress-like activation of the hypothalamic-pituitary-adrenal axis. In doing so, atrazine treatment has been shown to cause adrenal morphology changes characteristic of repeated stress. In this study, adrenals from atrazine treated and stressed animals were directly compared after 4 days of atrazine treatment or restraint stress. Both atrazine and stressed animals displayed reduced adrenocortical zona glomerulosa thickness and aldosterone synthase (CYP11B2) expression, indicative of repeated adrenal stimulation by adrenocorticotropic hormone. To determine if reduced CYP11B2 expression resulted in attenuated aldosterone synthesis, stressed and atrazine treated animals were challenged with angiotensin II (Ang II). As predicted, stressed animals produced less aldosterone compared to control animals when stimulated. However, atrazine treated animals had higher circulating aldosterone concentrations compared to both stressed and control groups. Ang II-induced aldosterone release was also potentiated in atrazine pretreated human adrenocortical carcinoma cells (H295R). Atrazine pretreated did not alter the expression of the rate limiting steroidogenic StAR protein or angiotensin II receptor 1. Atrazine treated animals also presented with higher basal blood pressure than vehicle treated control animals suggesting sustained elevations in circulating aldosterone levels. Our results demonstrate that treatment with the widely used herbicide, atrazine, directly increases stimulated production of aldosterone in adrenocortical cells independent of expression changes to rate limiting steroidogenic enzymes.

Non-targeted metabolomic profiling of atrazine in Caenorhabditis elegans using UHPLC-QE Orbitrap/MS

The widespread use of the herbicides Atrazine (ATR) has been raised attention due to its ubiquitous occurrence in the environment. As an endocrine disruptor, ATR causes reproductive, immune, nervous system toxicity in biota. In this study, we aimed to investigate metabolic profile characteristics and potential metabolic biomarker that reflects specific damage in toxic effect after ATR exposure. Hence, a metabolomics study was performed to determine the significantly affected metabolites and the reproduction and locomotion of C. elegans were investigated. Mediation analysis was used to evaluate the mediating effect of metabolites on association between ATR exposure and toxic effect. ATR (≥0.04 mg/L) caused the significant dose dependent reduction of brood size and locomotion behavior, however, the body length and width were significantly decreased only in 40 mg/L group. These results suggesting that brood size, head thrashes and body bends are more sensitive indictor to assessment ATR toxicity in C. elegans. Meanwhile, metabolomics analysis revealed that ATR exposure can induce metabolic profiles significant alterations in C. elegans. We found that 9 metabolites significantly increased and 18 metabolites significantly decreased, such as phosphatidylcholine, GMP, CDP-choline, neopterin etc. Those alteration of metabolites were mainly involved in the pathways: glycerophospholipid metabolism, glycolysis/gluconeogenesis, folate biosynthesis, glycine, serine and threoninemetabolism, pyrimidine and purine metabolism. Overall, these changes are signs of possible oxidative stress and ATP synthesis disruption modification. Mediation analysis showed a significant indirect effect of ATR exposure on brood size, via 7,8-dihydroneopterin 2',3'-cyclic-p, and phosphatidylcholine might mediate association between ATR exposure and body bends, suggesting that 7,8-dihydroneopterin 2',3'-cyclic-p and phosphatidylcholine might be potentially specificity marker for brood size and body bend respectively. This preliminary analysis investigates metabolic characteristics in C. elegans after ATR exposure, helping to understand the pathways involved in the response to ATR exposure and provide potential biomarkers for the safety evaluation of ATR.

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.

Embryonic atrazine exposure and later in life behavioral and brain transcriptomic, epigenetic, and pathological alterations in adult male zebrafish

Atrazine (ATZ), a commonly used pesticide linked to endocrine disruption, cancer, and altered neurochemistry, frequently contaminates water sources at levels above the US Environmental Protection Agency's 3 parts per billion (ppb; μg/L) maximum contaminant level. Adult male zebrafish behavior, brain transcriptome, brain methylation status, and neuropathology were examined to test the hypothesis that embryonic ATZ exposure causes delayed neurotoxicity, according to the developmental origins of health and disease paradigm. Zebrafish (Danio rerio) embryos were exposed to 0 ppb, 0.3 ppb, 3 ppb, or 30 ppb ATZ during embryogenesis (1-72 h post fertilization (hpf)), then rinsed and raised to maturity. At 9 months post fertilization (mpf), males had decreased locomotor parameters during a battery of behavioral tests. Transcriptomic analysis identified altered gene expression in organismal development, cancer, and nervous and reproductive system development and function pathways and networks. The brain was evaluated histopathologically for morphometric differences, and decreased numbers of cells were identified in raphe populations. Global methylation levels were evaluated at 12 mpf, and the body length, body weight, and brain weight were measured at 14 mpf to evaluate effects of ATZ on mature brain size. No significant difference in genome methylation or brain size was observed. The results demonstrate that developmental exposure to ATZ does affect neurodevelopment and neural function in adult male zebrafish and raises concern for possible health effects in humans due to ATZ's environmental presence and persistence. Graphical abstract.

Impact of pesticide exposure on adipose tissue development and function

Obesity is a leading cause of morbidity, mortality and health care expenditure whose incidence is rapidly rising across the globe. Although the cause of the obesity epidemic is typically viewed as a product of an increased availability of high calorie foods and/or a reduction in physical activity, there is mounting evidence that exposure to synthetic chemicals in our environment may play an important role. Pesticides, are a class of chemicals whose widespread use has coincided with the global rise of obesity over the past two decades. Importantly, given their lipophilic nature many pesticides have been shown to accumulate with adipose tissue depots, suggesting they may be disrupting the function of white adipose tissue (WAT), brown adipose tissue (BAT) and beige adipose tissue to promote obesity and metabolic diseases such as type 2 diabetes. In this review, we discuss epidemiological evidence linking pesticide exposure with body mass index (BMI) and the incidence of diabetes. We then review preclinical studies in rodent models which have directly evaluated the effects of different classes of insecticides and herbicides on obesity and metabolic dysfunction. Lastly, we review studies conducted in adipose tissue cells lines and the purported mechanisms by which pesticides may induce alterations in adipose tissue function. The review of the literature reveals major gaps in our knowledge regarding human exposure to pesticides and our understanding of whether physiologically relevant concentrations promote obesity and elicit alterations in key signaling pathways vital for maintaining adipose tissue metabolism.

Endocrine disruption and obesity: A current review on environmental obesogens

Obesity represents an important public health concern because it substantially increases the risk of multiple chronic diseases and thereby contributing to a decline in both quality of life and life expectancy. Besides unhealthy diet, physical inactivity and genetic susceptibility, environmental pollutants also contribute to the rising prevalence of obesity epidemic. An environmental obesogen is defined as a chemical that can alter lipid homeostasis to promote adipogenesis and lipid accumulation whereas an endocrine disrupting chemical (EDC) is defined as a synthetic chemical that can interfere with the endocrine function and cause adverse health effects. Many obesogens are EDCs that interfere with normal endocrine regulation of metabolism, adipose tissue development and maintenance, appetite, weight and energy balance. An expanding body of scientific evidence from animal and epidemiological studies has begun to provide links between exposure to EDCs and obesity. Despite the significance of environmental obesogens in the pathogenesis of metabolic diseases, the contribution of synthetic chemical exposure to obesity epidemic remains largely unrecognised. Hence, the purpose of this review is to provide a current update on the evidences from animal and human studies on the role of fourteen environmental obesogens in obesity, a comprehensive view of the mechanisms of action of these obesogens and current green and sustainable chemistry strategies to overcome chemical exposure to prevent obesity. Designing of safer version of obesogens through green chemistry approaches requires a collaborative undertaking to evaluate the toxicity of endocrine disruptors using appropriate experimental methods, which will help in developing a new generation of inherently safer chemicals.

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Many environmental obesogens are endocrine disrupting chemicals that interfere with normal endocrine regulation of metabolism.

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Understanding the role of environmental obesogens in the epidemics of obesity is in an infant stage.

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Green chemistry approach aims to design a safer version of these chemicals by understanding their hazardous effects.

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Further studies are necessary to fully establish the hazardous effects of obesogens and their association to human obesity.

Occupational Pesticide Use and Risk of Renal Cell Carcinoma in the Agricultural Health Study

BACKGROUND

Agricultural work and occupational pesticide use have been associated with increased risk of renal cell carcinoma (RCC), the most common form of kidney cancer. However, few prospective studies have investigated links to specific pesticides.

OBJECTIVE

We evaluated the lifetime use of individual pesticides and the incidence of RCC.

METHODS

We evaluated the associations between intensity-weighted lifetime days (IWDs) of 38 pesticides and incident RCC in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in Iowa and North Carolina. Among 55,873 applicators, 308 cases were diagnosed between enrollment (1993-1997) and the end of follow-up (2014-2015). We estimated incidence rate ratios (RRs) and 95% confidence intervals (CIs) using Poisson regression, controlling for potential confounding factors, with lagged and unlagged pesticide exposures.

RESULTS

There was a statistically significant increased risk of RCC among the highest users of 2,4,5-T compared with never users [unlagged RR IWD Tertile  3 = 2.92 (95% CI: 1.65, 5.17; p trend = 0.001 )], with similar risk estimates for lagged exposure [20-y lag RR IWD Tertile  3 = 3.37 (95% CI: 1.83, 6.22; p trend = 0.001 )]. In 20-y lagged analyses, we also found exposure-response associations with chlorpyrifos [RR IWD Quartile  4 = 1.68 (95% CI: 1.05, 2.70; p trend = 0.01 )], chlordane [RR IWD Tertile  3 = 2.06 (95% CI: 1.10, 3.87; p trend = 0.02 )], atrazine [RR IWD Quartile  4 = 1.43 (95% CI: 1.00, 2.03; p trend = 0.02 )], cyanazine [RR IWD Quartile  4 = 1.61 (95% CI: 1.03, 2.50; p trend = 0.02 )], and paraquat [RR IWD > Median = 1.95 (95% CI: 1.03, 3.70; p trend = 0.04 )].

CONCLUSIONS

This is, to our knowledge, the first prospective study to evaluate RCC risk in relation to various pesticides. We found evidence of associations with RCC for four herbicides (2,4,5-T, atrazine, cyanazine, and paraquat) and two insecticides (chlorpyrifos and chlordane). Our findings provide insights into specific chemicals that may influence RCC risk among pesticide applicators. Confirmation of these findings and investigations of the biologic plausibility and potential mechanisms underlying the observed associations are warranted. https://doi.org/10.1289/EHP6334.

Paternal exposure to a common herbicide alters the behavior and serotonergic system of zebrafish offspring

Increasingly, studies are revealing that endocrine disrupting chemicals (EDCs) can alter animal behavior. Early life exposure to EDCs may permanently alter phenotypes through to adulthood. In addition, the effects of EDCs may not be isolated to a single generation − offspring may indirectly be impacted, via non-genetic processes. Here, we analyzed the effects of paternal atrazine exposure on behavioral traits (distance moved, exploration, bottom-dwelling time, latency to enter the top zone, and interaction with a mirror) and whole-brain mRNA of genes involved in the serotonergic system regulation (slc6a4a, slc6a4b, htr1Aa, htr1B, htr2B) of zebrafish (Danio rerio). F0 male zebraFIsh were exposed to atrazine at 0.3, 3 or 30 part per billion (ppb) during early juvenile development, the behavior of F1 progeny was tested at adulthood, and the effect of 0.3 ppb atrazine treatment on mRNA transcription was quantified. Paternal exposure to atrazine significantly reduced interactions with a mirror (a proxy for aggression) and altered the latency to enter the top zone of a tank in unexposed F1 offspring. Bottom-dwelling time (a proxy for anxiety) also appeared to be somewhat affected, and activity (distance moved) was reduced in the context of aggression. slc6a4a and htr1Aa mRNA transcript levels were found to correlate positively with anxiety levels in controls, but we found that this relationship was disrupted in the 0.3 ppb atrazine treatment group. Overall, paternal atrazine exposure resulted in alterations across a variety of behavioral traits and showed signs of serotonergic system dysregulation, demonstrating intergenerational effects. Further research is needed to explore transgenerational effects on behavior and possible mechanisms underpinning behavioral effects.

Electrospun CNT embedded ZnO nanofiber based biosensor for electrochemical detection of Atrazine: a step closure to single molecule detection

In this study we have reported the design and development of a facile, sensitive, selective, and label-free electrochemical sensing platform for the detection of atrazine based on MWCNT-embedded ZnO nanofibers. Electrospun nanofibers were characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), UV-Visible spectroscope (UV-VIS), and Fourier-transform infrared spectroscope (FTIR). Electrochemical properties of MWCNT-ZnO nanofiber-modified electrodes were assessed using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Binding event of atrazine to anti-atrazine antibody, which immobilized on nanofiber-modified electrode via EDC and NHS chemistry, was transduced with EIS. Due to high conductivity, surface area, and low bandgap of MWCNT-ZnO nanofibers, we have achieved the sensitivity and limit of detection (LoD) of sensor as 21.61 (KΩ μg^-1 mL^-1) cm^-2 and 5.368 zM for a wide detection range of 10 zM-1 µM. The proposed immunosensing platform has good stability, selectivity, repeatability, and reproducibility, and are less prone to interference.

In-Solution Molecular Recognition Comparison of Aptamers against the Herbicide Atrazine

Atrazine is a common herbicide that is widely used to control weed growth in both agricultural and residential settings. It has been shown to act as an endocrine disruptor that affects aquatic organisms. Rapid and low-cost monitoring methods for atrazine is the first step to mitigate its widespread persistency. Aptamers are small synthetic oligonucleotides that can assume a 3D structure to act as the molecular recognition element for a specific target of interest. Two different atrazine binding aptamers (R12.23 Trunc. and R12.45 Trunc.) have been identified from the same library design but with fundamentally different in vitro selection methodologies. While the R12.23 Trunc. has been utilized in immobilized biosensing platforms, it is unclear if in-solution-based applications would be suitable for both atrazine binding aptamers. This study provides the first insight of comparative in-solution binding profiles of the two atrazine binding aptamers. Based on our results, this information will be useful for future biosensing platform development utilizing the two aptamers.

Nitrogen-dependent induction of atrazine degradation pathway in Pseudomonas sp. strain AKN5

Soil isolate Pseudomonas sp. strain AKN5 degrades atrazine as the sole source of nitrogen. The strain showed expeditious growth on medium containing citrate as the carbon source and ammonium chloride as the nitrogen source as compared to citrate plus atrazine or cyanuric acid. Biochemical and nitrogen-source-dependent enzyme induction studies revealed that atrazine is metabolized through hydrolytic pathway and has two segments: the upper segment converts atrazine into cyanuric acid while the lower segment metabolizes cyanuric acid to CO2 and ammonia. Bioinformatics and co-transcriptional analyses suggest that atzA, atzB and atzC were transcribed as three independent transcripts while atzDEF were found to be transcribed as a single polycistronic mRNA indicating operonic arrangement. Transcriptional analysis showed inducible expression of atzA/B/C/DEF from atrazine grown cells while cyanuric acid grown cells showed significantly higher expression of atzDEF. Interestingly, growth profiles and enzyme activity measurements suggests that strain utilizes a simple nitrogen source (ammonium chloride) over the complex (atrazine or cyanuric acid) when grown on dual nitrogen source. These results suggest that atrazine degradation genes were up-regulated in the presence of atrazine but repressed in the presence of simple nitrogen source like ammonium chloride.

Xenobiotic mediated diabetogenesis: Developmental exposure to dichlorvos or atrazine leads to type 1 or type 2 diabetes in Drosophila

The increased incidence of diabetes to the magnitude of a global epidemic is attributed to non-traditional risk factors, including exposure to environmental chemicals. However, the contribution of xenobiotic exposure during the development of an organism to the etiology of diabetes is not fully addressed. Developing stages are more susceptible to chemical insult, but knowledge on the consequence of the same to the onset of diabetes is residual. In this context, by using Drosophila melanogaster having conserved Insulin/Insulin growth factor-like signaling (IIS) as well as glucose homeostasis as a model, we evaluated the potential of developmental exposure to dichlorvos (DDVP, an organophosphorus pesticide) or atrazine (herbicide) to cause diabetes in exposed organisms. Flies exposed to DDVP during their development display insulin deficiency or type 1 diabetes (T1D) while those exposed to atrazine show insulin resistance or type 2 diabetes (T2D), suggesting that exposure to these xenobiotics during organismal development can result in diabetes and that different mechanisms underlie pesticide mediated diabetes. We show that oxidative stress-mediated c-Jun N-terminal kinase (JNK) signaling activation underlies insulin resistance in flies exposed to atrazine during their development while DDVP-mediated T1D involves activation of caspase-mediated cell death pathway. Mitigation of oxidative stress through over-expression of SOD2 in atrazine (20μg/ml) exposed flies, revealed significantly decreased oxidative stress levels and reduced phosphorylation of JNK. Moreover, glucose and Akt phosphorylation levels in SOD2 over-expression flies exposed to atrazine were comparable to those in controls, suggesting restoration in insulin sensitivity. Therefore, exposure to xenobiotics during development is a common risk factor for the development of type 1 or type 2 diabetes. Accordingly, the present study cautions against the use of such diabetogenic pesticides. Also, mitigation of oxidative stress or anti-oxidant supplementation could be a potential therapy for xenobiotic mediated type 2 diabetes.

Atrazine induced transgenerational reproductive effects in medaka (Oryzias latipes)

Atrazine is presently one of the most abundantly used herbicides in the United States, and a common contaminant of natural water bodies and drinking waters in high-use areas. Dysregulation of reproductive processes has been demonstrated in atrazine exposed fish, including alteration of key endocrine pathways on hypothalamic-pituitary-gonadal (HPG) axis. However, the potential for atrazine-induced transgenerational inheritance of reproductive effects in fish has not been investigated. The present study examined the effects of early developmental atrazine exposure on transgenerational reproductive dysregulation in Japanese medaka (Oryzias latipes). F0 medaka were exposed to atrazine (ATZ, 5 or 50 μg/L), 17α-ethinylestradiol (EE2, 0.002 or 0.05 μg/L), or solvent control during the first twelve days of development with no subsequent exposure over three generations. This exposure overlapped with the critical developmental window for embryonic germ cell development, gonadogenesis, and sex determination. Exposed males and females of the F0 generation were bred to produce an F1 generation, and this was continued until the F2 generation. Sperm count and motility were not affected in F0 males; however, both parameters were significantly reduced in the males from F2 Low EE2 (0.002 μg/L), Low ATZ (5 μg/L), and High ATZ (50 μg/L) lineages. Fecundity was unaffected by atrazine or EE2 in F0 through F2 generations; however, fertilization rate was decreased in low atrazine and EE2 exposure lineages in the F2 generation. There were significant transgenerational differences in expression of the genes involved in steroidogenesis and DNA methylation. These results suggest that although early life exposure to atrazine did not cause significant phenotypes in the directly exposed F0 generation, subsequent generations of fish were at greater risk of reproductive dysfunction.

Effects of short-time exposure to atrazine on miRNA expression profiles in the gonad of common carp (Cyprinus carpio)

BACKGROUND

Atrazine is widely used in agriculture and is a known endocrine disrupting chemical. Atrazine can seep into the water body through surface, posing a potential threat to the aquatic ecological environment and human drinking water source. In vertebrate, studies have shown that it can affect reproduction and development seriously, but its molecular mechanism for aquatic animals is unknown. Aquaculture is very common in China, especially common carp, whose females grow faster than males. However, the effects of atrazine on the reproduction of carp, especially miRNA, have not been investigated.

RESULTS

In this study, common carp (Cyprinus carpio) at two key developmental stages were exposed to atrazine in vitro. Sex ratio was observed to analyze the effect of atrazine on the sex. MiRNA expression profiles were analysed to identify miRNAs related to gonad development and to reveal the atrazine mechanisms interfering with gonad differentiation. The results showed that the sex ratio was biased towards females. Atrazine exposure caused significant alteration of multiple miRNAs. Predicted targets of differently-expressed miRNAs were involved in many reproductive biology signalling pathways.

CONCLUSIONS

Our results indicate that atrazine promoted the expression of female-biased genes by decreasing miRNAs in primordial gonad. In addition, our results indicate that atrazine can up-regulate aromatase expression through miRNAs, which supports the hypothesis that atrazine has endocrine-disrupting activity by altering the gene expression profile of the Hypothalamus-Pituitary-Gonad axis through its corresponding miRNAs.

Long-term Immunotoxic Effects of Oral Prenatal and Neonatal Atrazine Exposure

Atrazine and its metabolites are present at high concentrations in many water supplies in agro-intensive areas. Because residents in these areas drink water from sources fed from these contaminated supplies, we investigated the long-term immunotoxicity of combined prenatal and neonatal (perinatal) exposure to atrazine via drinking water, on the immune system in mice. At 6 months of age, upon immunization with heat-killed Streptococcus pneumoniae, the serum IgG antibody response against the T independent antigen phosphorylcholine was significantly higher in male, but not female, atrazine-exposed mice as compared with that in untreated controls. No alterations were present in all offspring in the serum antibody response against the T-dependent antigen pneumococcal surface protein A (PspA). ELISpot analysis showed only a small, insignificant reduction in PspA-specific IgG producing splenocytes in atrazine-treated male offspring. Interestingly, upon ex vivo stimulation with anti-CD3 and anti-CD28 antibodies, significant decreases in interleukin (IL)-2, tumor necrosis factor-α, interferon-γ, and IL-17A and a decreasing trend in IL-10 were observed in splenocytes from atrazine-exposed male, but not female mice. Analysis of thymic and splenic cell populations showed no effects of atrazine exposure in either sex. This is the first time that long-term changes in the immune response were observed after a perinatal exposure to atrazine and it demonstrates that these early life exposures can result in permanent changes to the immune system as well as a male bias in these effects.

Comparative Overview of the Mechanisms of Action of Hormones and Endocrine Disruptor Compounds

Endocrine Disruptor Compounds (EDCs) are synthetic or natural molecules in the environment that promote adverse modifications of endogenous hormone regulation in humans and/or in wildlife animals. In the present paper, we review the potential mechanisms of EDCs and point out the similarities and differences between EDCs and hormones. There was only one mechanism, out of nine identified, in which EDCs acted like hormones (i.e. binding and stimulated hormone receptor activity). In the other eight identified mechanisms of action, EDCs exerted their effects either by affecting endogenous hormone concentration, or its availability, or by modifying hormone receptor turn over. This overview is intended to classify the various EDC mechanisms of action in order to better appreciate when in vitro tests would be valid to assess their risks towards humans and wildlife.

Characterization of Activation of the Hypothalamic-Pituitary-Adrenal Axis by the Herbicide Atrazine in the Female Rat

Atrazine (ATR) is a commonly used pre-emergence and early postemergence herbicide. Rats gavaged with ATR and its chlorometabolites desethylatrazine (DEA) and deisopropylatrazine (DIA) respond with a rapid and dose-dependent rise in plasma corticosterone, whereas the major chlorometabolite, diaminochlorotriazine (DACT), has little or no effect on corticosterone levels. In this study, we investigated the possible sites of ATR activation of the hypothalamic-pituitary-adrenal (HPA) axis. ATR treatment had no effect on adrenal weights but altered adrenal morphology. Hypophysectomized rats or rats under dexamethasone suppression did not respond to ATR treatment, suggesting that ATR does not directly stimulate the adrenal gland to induce corticosterone synthesis. Immortalized mouse corticotrophs (AtT-20) and primary rat pituitary cultures were treated with ATR, DEA, DIA, or DACT. None of the compounds induced an increase in ACTH secretion or potentiated ACTH release in conjunction with CRH on ACTH release. In female rats gavaged with ATR, pretreatment with the CRH receptor antagonist astressin completely blocked the ATR-induced rise in corticosterone concentrations, implicating CRH release in ATR-induced HPA activation. Intracerebroventricular infusion of ATR, DEA, and DIA but not DACT at concentrations equivalent to peak plasma concentrations after gavage dosing resulted in an elevation of plasma corticosterone concentrations. However, ATR did not induce c-Fos immunoreactivity in the paraventricular nucleus of the hypothalamus. These results indicate that ATR activates the HPA axis centrally and requires CRH receptor activation, but it does not stimulate cellular pathways associated with CRH neuronal excitation.

Embryonic atrazine exposure elicits proteomic, behavioral, and brain abnormalities with developmental time specific gene expression signatures

Atrazine (ATZ), the second most commonly used herbicide in the United States, is an endocrine disrupting chemical linked to cancer and a common drinking water contaminant. This study further investigates ATZ-related developmental toxicity by testing the following hypotheses in zebrafish: the effects of embryonic ATZ exposure are dependent on timing of exposure; embryonic ATZ exposure alters brain development and function; and embryonic ATZ exposure changes protein abundance in carcinogenesis-related pathways. After exposing embryos to 0, 0.3, 3, or 30 parts per billion (ppb) ATZ, we monitored the expression of cytochrome P450 family 17 subfamily A member 1 (cyp17a1), glyoxalase I (glo1), ring finger protein 14 (rnf14), salt inducible kinase 2 (sik2), tetratricopeptide domain 3 (ttc3), and tumor protein D52 like 1 (tpd52l1) at multiple embryonic time points to determine normal expression and if ATZ exposure altered expression. Only cyp17a1 had normal dynamic expression, but ttc3 and tpd52l1 had ATZ-related expression changes before 72 h. Larvae exposed to 0.3 ppb ATZ had increased brain length, while larvae exposed to 30 ppb ATZ were hypoactive. Proteomic analysis identified altered protein abundance in pathways related to cellular function, neurodevelopment, and genital-tract cancer. The results indicate embryonic ATZ toxicity involves interactions of multiple pathways.

SIGNIFICANCE

This is the first report of proteomic alterations following embryonic exposure to atrazine, an environmentally persistent pesticide and common water contaminant. Although the transcriptomic alterations in larval zebrafish with embryonic atrazine exposure have been reported, neither the time at which gene expression changes occur nor the resulting proteomic changes have been investigated. This study seeks to address these knowledge gaps by evaluating atrazine's effect on gene expression through multiple time points during embryogenesis, and correlating changes in gene expression to pathological alterations in brain length and functional changes in behavior. Finally, pathway analysis of the proteomic alterations identifies connections between the molecular changes and functional outcomes associated with embryonic atrazine exposure.

Toxicity of atrazine- and glyphosate-based formulations on Caenorhabditis elegans

Atrazine and Glyphosate are herbicides massively used in agriculture for crop protection. Upon application, they are available to the biota in different ecosystems. The aim of this research was to evaluate the toxicity of Glyphosate and Atrazine based formulations (GBF and ABF, respectively). Caenorhabditis elegans was exposed to different concentrations of each single formulation, and to the mixture. Lethality, locomotion, growth, and fertility were measured as endpoints. Effects on gene expression were monitored utilizing green fluorescence protein transgenic strains. ABF caused lethality of 12%, 15%, and 18% for 6, 60, and 600 μM, respectively, displaying a dose dependence trend. GBF produced lethality of 20%, 50%, and 100% at 0.01, 10, and 100 μM, respectively. Locomotion inhibition ranged from 21% to 89% at the lowest and maximum tested concentrations for Atrazine; whereas for Glyphosate, exposure to 10 μM inhibited 87%. Brood size was decreased by 67% and 93% after treatment to 0.06 and 6 μM Atrazine, respectively; and by 23% and 93% after exposure to 0.01 and 10 μM Glyphosate, respectively. There were no significant differences in growth. Changes in gene expression occurred in all genes, highlighting the expression of sod-1, sod-4, and gpx-4 that increased more than two-fold after exposure to 600 μM ABF and 10 μM GBF. The effects observed for the mixture of these formulations were additive for lethality, locomotion and fertility. In short, GBF, ABF, and their mixture induced several toxic responses related to oxidative stress on C. elegans.

High-Throughput H295R Steroidogenesis Assay: Utility as an Alternative and a Statistical Approach to Characterize Effects on Steroidogenesis

The U.S. Environmental Protection Agency Endocrine Disruptor Screening Program and the Organization for Economic Co-operation and Development (OECD) have used the human adrenocarcinoma (H295R) cell-based assay to predict chemical perturbation of androgen and estrogen production. Recently, a high-throughput H295R (HT-H295R) assay was developed as part of the ToxCast program that includes measurement of 11 hormones, including progestagens, corticosteroids, androgens, and estrogens. To date, 2012 chemicals have been screened at 1 concentration; of these, 656 chemicals have been screened in concentration-response. The objectives of this work were to: (1) develop an integrated analysis of chemical-mediated effects on steroidogenesis in the HT-H295R assay and (2) evaluate whether the HT-H295R assay predicts estrogen and androgen production specifically via comparison with the OECD-validated H295R assay. To support application of HT-H295R assay data to weight-of-evidence and prioritization tasks, a single numeric value based on Mahalanobis distances was computed for 654 chemicals to indicate the magnitude of effects on the synthesis of 11 hormones. The maximum mean Mahalanobis distance (maxmMd) values were high for strong modulators (prochloraz, mifepristone) and lower for moderate modulators (atrazine, molinate). Twenty-five of 28 reference chemicals used for OECD validation were screened in the HT-H295R assay, and produced qualitatively similar results, with accuracies of 0.90/0.75 and 0.81/0.91 for increased/decreased testosterone and estradiol production, respectively. The HT-H295R assay provides robust information regarding estrogen and androgen production, as well as additional hormones. The maxmMd from this integrated analysis may provide a data-driven approach to prioritizing lists of chemicals for putative effects on steroidogenesis.

Atrazine suppresses FSH-induced steroidogenesis and LH-dependent expression of ovulatory genes through PDE-cAMP signaling pathway in human cumulus granulosa cells

Atrazine (ATR) alters female reproductive functions in different animal species. Here, we analyzed whether ATR disturbs steroidogenic and ovulatory processes in hormone-stimulated human cumulus granulosa cells and mechanism of its action. Results showed that treatment of human cumulus granulosa cells with 20 μM ATR for 48 h resulted in lower FSH-stimulated estradiol and progesterone production. ATR reduced mRNA levels of aromatase (CYP19A1), steroidogenic acute regulatory protein (STAR) and luteinizing hormone/choriogonadotropin receptor (LHCGR). Addition of hCG 48 h after FSH and ATR treatment did not trigger maximal expression of the ovulatory genes amphiregulin (AREG) and epiregulin (EREG). Mechanistic experiments showed that ATR activated cPDE and decreased cAMP level. Addition of total PDE and specific PDE4 inhibitors, IBMX and rolipram, prevented ATR's action on CYP19A1 and STAR mRNA expression in FSH-stimulated human cumulus granulosa cells. This study suggests that ATR alters steroidogenesis and ovulatory process in human cumulus granulosa cells jeopardizing female reproduction.

Identification of candidate reference chemicals for in vitro steroidogenesis assays

The Endocrine Disruptor Screening Program (EDSP) is transitioning from traditional testing methods to integrating ToxCast/Tox21 in vitro high-throughput screening assays for identifying chemicals with endocrine bioactivity. The ToxCast high-throughput H295R steroidogenesis assay may potentially replace the low-throughput assays currently used in the EDSP Tier 1 battery to detect chemicals that alter the synthesis of androgens and estrogens. Herein, we describe an approach for identifying in vitro candidate reference chemicals that affect the production of androgens and estrogens in models of steroidogenesis. Candidate reference chemicals were identified from a review of H295R and gonad-derived in vitro assays used in methods validation and published in the scientific literature. A total of 29 chemicals affecting androgen and estrogen levels satisfied all criteria for positive reference chemicals, while an additional set of 21 and 15 chemicals partially fulfilled criteria for positive reference chemicals for androgens and estrogens, respectively. The identified chemicals included pesticides, pharmaceuticals, industrial and naturally-occurring chemicals with the capability to increase or decrease the levels of the sex hormones in vitro. Additionally, 14 and 15 compounds were identified as potential negative reference chemicals for effects on androgens and estrogens, respectively. These candidate reference chemicals will be informative for performance-based validation of in vitro steroidogenesis models.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Toxic effects of atrazine on porcine oocytes and possible mechanisms of action

Because atrazine is a widely used herbicide, its adverse effects on the reproductive system have been extensively researched. In this study, we investigated the effects of atrazine exposure on porcine oocyte maturation and the possible mechanisms. Our results showed that the rates of oocyte maturation significantly decreased after treatment with 200 μM atrazine in vitro. Atrazine treatment resulted in abnormal spindle morphology but did not affect actin distribution. Atrazine exposure not only triggered a DNA damage response but also decreased MPF levels in porcine oocytes. Our results also revealed that atrazine worsened porcine oocyte quality by causing excessive accumulation of superoxide radicals, increasing cathepsin B activity, and decreasing the GSH level and mitochondrial membrane potential. Furthermore, atrazine decreased developmental competence of porcine oocytes up to the blastocyst stage and changed some properties: cell numbers, apoptosis, and related gene expression levels. Collectively, our results indicate that porcine oocyte maturation is defective after atrazine treatment at least through disruption of spindle morphology, MPF activity, and mitochondrial function and via induction of DNA damage, which probably reduces developmental competence.