In vitro atrazine-exposure inhibits human natural killer cell lytic granule release

Atrazine: cytotoxicity, oxidative stress, apoptosis, testicular effects and chemopreventive Interventions

Atrazine (ATZ) is an environmental pollutant that interferes with several aspects of mammalian cellular processes including germ cell development, immunological, reproductive and neurological functions. At the level of human exposure, ATZ reduces sperm count and contribute to infertility in men. ATZ also induces morphological changes similar to apoptosis and initiates mitochondria-dependent cell death in several experimental models. When in vitro experimental models are exposed to ATZ, they are faced with increased levels of reactive oxygen species (ROS), cytotoxicity and decreased growth rate at dosages that may vary with cell types. This results in differing cytotoxic responses that are influenced by the nature of target cells, assay types and concentrations of ATZ. However, oxidative stress could play salient role in the observed cellular and genetic toxicity and apoptosis-like effects which could be abrogated by antioxidant vitamins and flavonoids, including vitamin E, quercetin, kolaviron, myricetin and bioactive extractives with antioxidant effects. This review focuses on the differential responses of cell types to ATZ toxicity, testicular effects of ATZ in both in vitro and in vivo models and chemopreventive strategies, so as to highlight the current state of the art on the toxicological outcomes of ATZ exposure in several experimental model systems.

Immunotoxicity studies of sulfolane following developmental exposure in Hsd:Sprague Dawley SD rats and adult exposure in B6C3F1/N mice

Sulfolane is a solvent used in the petrochemical industry and a groundwater contaminant in areas near refineries. The current studies were conducted to assess the impact of oral exposure to sulfolane on the immune system using two models: (1) a perinatal drinking water exposure to 0, 30, 100, 300, or 1000 mg/L from gestation day (GD) 6 until ∼13 weeks-of-age in Harlan Sprague Dawley rats; and, (2) a 90-day gavage exposure of adult female B6C3F1/N mice to 0, 1, 10, 30, 100, or 300 mg/kg/day. Immune parameters evaluated included measurement of antibody production against sheep red blood cells (SRBC) and keyhole limpet hemocyanin (KLH), ex vivo measurements of natural killer (NK) cell activity, cytotoxic T-cell (CTL) activity, and T-cell proliferation, as well as measures of splenic immune cell populations, hematological parameters, and histopathology of immune tissues. A decrease in ex vivo NK cell activity was observed in cells from female - but not male - F1 rats following developmental exposure. In adult female mice, splenic NK cell number was lower than the vehicle controls at doses ≥ 100 mg/kg; however, ex vivo NK cell activity was not affected by sulfolane treatment. In female mice, a decrease in the number of large unstained cells at doses ≥ 30 mg/kg was observed. In F1 rats, effects on white blood cells (WBC) were limited to a decreasing trend in leukocytes in females; no effects were observed in males. Under the conditions of this study, a no-observed-effect level (NOEL) of 3 mg/kg/day was identified based on reduced NK cell activity in female F1 rats. Overall, these findings suggest that oral exposure to sulfolane in rodents had minimal effects on the immune system.

Endocrine Disruptor Compounds-A Cause of Impaired Immune Tolerance Driving Inflammatory Disorders of Pregnancy?

Endocrine disrupting compounds (EDCs) are prevalent and ubiquitous in our environment and have substantial potential to compromise human and animal health. Amongst the chronic health conditions associated with EDC exposure, dysregulation of reproductive function in both females and males is prominent. Human epidemiological studies demonstrate links between EDC exposure and infertility, as well as gestational disorders including miscarriage, fetal growth restriction, preeclampsia, and preterm birth. Animal experiments show EDCs administered during gestation, or to either parent prior to conception, can interfere with gamete quality, embryo implantation, and placental and fetal development, with consequences for offspring viability and health. It has been presumed that EDCs operate principally through disrupting hormone-regulated events in reproduction and fetal development, but EDC effects on maternal immune receptivity to pregnancy are also implicated. EDCs can modulate both the innate and adaptive arms of the immune system, to alter inflammatory responses, and interfere with generation of regulatory T (Treg) cells that are critical for pregnancy tolerance. Effects of EDCs on immune cells are complex and likely exerted by both steroid hormone-dependent and hormone-independent pathways. Thus, to better understand how EDCs impact reproduction and pregnancy, it is imperative to consider how immune-mediated mechanisms are affected by EDCs. This review will describe evidence that several EDCs modify elements of the immune response relevant to pregnancy, and will discuss the potential for EDCs to disrupt immune tolerance required for robust placentation and optimal fetal development.

Adverse effects of pesticides on the functions of immune system

Pesticides are chemical substances used to kill unwanted fungi, weeds and insects. In many countries, there is currently concern regarding the adverse effects of pesticides on health. It has been reported that pesticides may cause cancer, respiratory diseases, organ diseases, system failures, nervous system disorders and asthma, which are closely connected with immune disorders. Therefore, this study reviewed the immunotoxicity of pesticides that are currently used or prohibited from being used, especially their effects on leukocytes such as T cells, B cells, NK cells and macrophages. These immune cells play crucial roles in innate and adaptive immune systems to protect hosts. Pesticides are known to have possible toxicological modes of action to induce oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress in living organisms. According to previous studies, pesticides such as atrazine (ATR), organophophorus (OP) compounds, carbamates, and pyrethroids were shown to inhibit the survival and growth of leukocytes by inducing apoptosis or cell cycle arrest and interfering with the specific immunological functions of each type of immune cells. These results suggest the immunotoxicity of pesticides toward specific immune cells. To substantiate the overall immunocompromised effects of pesticides, there is a need to collect and thoroughly analyze additional information regarding other immunological toxicities.

Atrazine Bioremediation and Its Influence on Soil Microbial Diversity by Metagenomics Analysis

Pesticide accumulation in agricultural soils is an environmental concern, often addressed through distinct bioremediation strategies. This study has tried to analyze various soil bioremediation options viz., biostimulation, bioaugmentation, and natural attenuation in terms of efficiency and the response of autochthonous microbial flora by using atrazine as a model contaminant. Soil mesocosms were established with 100 kg of soil simulating the field conditions. The soil previously exposed to the herbicide was used for the bioaugmentation strategy undertaken in this study. We have tried to analyze how the microbial community responds to a foreign compound, both in terms of taxonomic and functional capacities? To answer this, we have analyzed metagenome of the mesocosms at a time point when 90% atrazine was degraded. Bioaugmentation for bioremediation proved to be efficient with a DT90 value of 15.48 ± 0.79 days, in comparison to the natural attenuation where the DT90 value was observed to be 41.20 ± 1.95 days. Metagenomic analysis revealed the abundance of orders Erysipelotrichales, Selemonadales, Clostridiales, and Thermoanaerobacterales exclusively in SBS mesocosm. Besides Pseudomonas, bacterial genera such as Achromobacter, Xanthomonas, Stenotrophomonas, and Cupriavidus have emerged as the dominant members in various bioremediation strategies tested in this study. Inclusive results suggest that inherent microbial flora adjust their community and metabolic machinery upon exposure to the pollutant. The site under pollutant stress showed efficient microbial communities to bio-remediate the newly polluted terrestrial ecologies in relatively less time and by economic means.

Immunomodulatory effects of synthetic endocrine disrupting chemicals on the development and functions of human immune cells

Endocrine disrupting chemicals (EDCs) are added to food, cosmetics, plastic packages, and children's toys and have thus become an integral part of the human environment. In the last decade, there has been increasing interest in the effect of EDCs on human health, including their impact on the immune system. So far, researchers have proved that EDCs (e.g. bisphenols, phthalates, triclosan, phenols, propanil, tetrachlorodibenzo-p-dioxin, diethylstilbestrol, tributyltin (TBT), and parabens) affect the development, functions, and lifespan of immune cells (e.g., monocytes, neutrophils, mast cells, eosinophils, lymphocytes, dendritic cells, and natural killers). In this review, we have summarized the current knowledge of the multivariable influence of EDCs on immune cells and underlined the novel approach to EDC studies, including dose-dependent effects and low-dose effects. We discuss critically the possible relationship between exposure to EDCs and immunity related diseases (e.g. allergy, asthma, diabetes, and lupus). Moreover, based on the literature, we construct a model of possible mechanisms of EDC action on immune cells at cellular, molecular, and epigenetic levels.

Lack of immunotoxic effects of repeated exposure to atrazine associated with the adaptation of adrenal gland activation

T cell-dependent IgM antibody production and natural killer cell (NKC) activity were assessed in SD rats orally administered atrazine for 28 days to males (0, 6.5, 25, or 100 mg/kg/day) or females (0, 3, 6, or 50 mg/kg/day), or 30 or 500 ppm in diet (3 or 51 mg/kg/day). Anti-asialo GM1 antibodies (NKC) and cyclophosphamide (antibody-forming cell assay [AFC]) served as positive controls. Pituitary (ACTH, prolactin), adrenal (corticosterone, progesterone, aldosterone), and gonadal (androgens, estrogens) hormones were assessed after 1, 7, and/or 28 days of treatment. Food intake and body weights were significantly reduced in the highest dosed males, and transiently affected in females. Urinary corticosterone levels were not increased in atrazine-treated groups in either sex at any time point measured (10, 22, or 24 days). Corticosterone and progesterone were elevated in males after a single atrazine dose ≥6.5 mg/kg/day, but not after 7, 14, or 28 doses. There were no effects on adrenal, pituitary, or gonadal hormones in females. Atrazine did not suppress the AFC response or decrease NKC function after 28 days in males or females. Atrazine had no effect on spleen weights or spleen cell numbers in males or females, although thymus weights were elevated in males receiving the highest dose. The lack of immunotoxic effect of atrazine was associated with diminished adrenal activation over time in males, and no effects on adrenal hormones in females.

Pesticide Exposure and Risk of Rheumatoid Arthritis among Licensed Male Pesticide Applicators in the Agricultural Health Study

BACKGROUND

The occupation of farming has been associated with rheumatoid arthritis (RA); pesticides may account for this association, but there are few studies.

OBJECTIVES

We investigated associations between RA and use of pesticides in the Agricultural Health Study.

METHODS

The study sample was drawn from male pesticide applicators enrolled in 1993–1997 who provided questionnaire data at baseline and at least once during follow-up (over a median 18 y; interquartile range 16–19). Incident RA cases (n=220), confirmed by physicians or by self-reported use of disease-modifying antirheumatic drugs, were compared with noncases (n=26,134) who did not report RA. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression, adjusting for enrollment age, state, smoking pack-years, and education. We evaluated the association of RA with the use of 46 pesticides and across 4 levels (never use and tertiles) of lifetime days of use for 16 pesticides with OR≥1.2 for ever use.

RESULTS

Incident RA was associated with ever use of fonofos (OR = 1.70; 95% CI: 1.22, 2.37), carbaryl (OR = 1.51; 95% CI: 1.03, 2.23), and chlorimuron ethyl (OR = 1.45; 95% CI: 1.01, 2.07) compared with never use. Statistically significant exposure–response trends in association with RA were observed for lifetime days of use of atrazine [OR_tertile3= 1.62 (95% CI: 1.09, 2.40); p_trend=0.01] and toxaphene [OR_tertile3= 2.42 (95% CI: 1.03, 5.68); p_trend=0.02]. Exposure–response was nonlinear for fonofos [OR_tertile1= 2.27 (95% CI: 1.44, 3.57); OR_tertile2= 0.98 (95% CI: 0.54, 1.80); OR_tertile3= 2.10 (95% CI: 1.32, 3.36); p_trend=0.005] and suggestive for carbaryl (p_trend=0.053).

CONCLUSIONS

Our results provide novel evidence of associations between exposure to some pesticides and RA in male farmers. https://doi.org/10.1289/EHP1013.

Atrazine exposure causes mitochondrial toxicity in liver and muscle cell lines

Objective:

Chronic exposure to atrazine and other pesticides is reported to cause metabolic disorders, yet information on effects of atrazine on expression of genes relevant to mitochondrial function is largely missing. In the present study, therefore, we investigated the expression of a battery of nuclear- and mitochondrial-encoded genes involved in oxidative phosphorylation (OXPHOS) in human liver (HepG2) and rat muscle (L6) cell lines due to short-term atrazine exposure.

Materials and Methods:

We have determined the EC₅₀ values of atrazine for cytotoxicity and mitochondrial toxicity (mitotoxicity) in terms of adenosine triphosphate (ATP) content in HepG2 and L6 cells. Further, the mRNA expression of nuclear- and mitochondrial-encoded genes was analyzed using quantitative real-time polymerase chain reaction.

Results:

The EC₅₀ value of atrazine for mitotoxicity in HepG2 and L6 cells was found to be about 0.162 and 0.089 mM, respectively. Mitochondrial toxicity was indicated by reduction in ATP content following atrazine exposure. Atrazine exposure resulted in down-regulation of many OXPHOS subunits expression and affected biogenesis factors’ expression. Most prominently, superoxide dismutase (SOD) and sirtuin 3 (SIRT3) expressions were up-regulated in HepG2 cells, whereas SIRT3 expression was alleviated in L6 cells, without significant changes in SOD levels. Mitochondrial transcription factor A (TFAM) and SIRT1 expression were significantly down-regulated in both cell lines.

Conclusion:

Results suggest that TFAM and SIRT1 could be involved in atrazine-induced mitochondrial dysfunction, and further studies can be taken up to understand the mechanism of mitochondrial toxicity. Further study can also be taken up to explore the possibility of target genes as biomarkers of pesticide toxicity.

Gene expression profiles in testis of developing male Xenopus laevis damaged by chronic exposure of atrazine

As a widely used herbicide, atrazine (AZ) has been extensively studied for its adverse effects on the reproductive system, especially feminization in male animals. However, the relationship of gene expression changes and associated toxicological endpoints remains unclear. In this study, developing Xenopus laevis tadpoles were exposed to concentration of AZ at 0.1, 1, 10 or 100 μg/L continuously. Compared with froglets in the control group, there were no significant differences in body length, body weight, liver weight and hepatosomatic index (HSI) of males in groups treated with AZ for 90 d. At 100 μg/L AZ treatment caused a significant reduction of gonad weight and gonadosomatic index (GSI) of males (p < 0.01). In addition, AZ at all dose levels caused testicular degeneration, especially in froglets from the groups with 0.1 and 100 μg/L which exhibited U-shaped dose-response trend. We further investigated the gene expression changes associated with the testicular degeneration induced by AZ. We found that the expression of 1165 genes was significantly altered with 616 upregulated and 549 downregulated compared to the expression profile of the control animals. KEGG analysis showed that genes which were significantly affected by AZ are mainly involved in arginine and proline metabolism, cell cycle, riboflavin metabolism, spliceosome, base excision repair and progesterone-mediated oocyte maturation pathway. Our results show that AZ may affect reproductive and immune systems by interference with the related gene expression changes during the male X. laevis development. The findings may help to clarify the feminization mechanisms of AZ in male X. laevis.

A comprehensive review of pesticides and the immune dysregulation: mechanisms, evidence and consequences

Nowadays, in many communities, there is a growing concern about possible adverse effects of pesticides on human health. Reports indicate that during environmental or occupational exposure, pesticides can exert some intense adverse effects on human health through transient or permanent alteration of the immune system. There is evidence on the relation between pesticide-induced immune alteration and prevalence of diseases associated with alterations of the immune response. In the present study, direct immunotoxicity, endocrine disruption and antigenicity have been introduced as the main mechanisms working with pesticides-induced immune dysregulation. Moreover, the evidence on the relationship between pesticide exposure, dysregulation of the immune system and predisposition to different types of psychiatric disorders, cancers, allergies, autoimmune and infectious diseases are criticized.

Assessment of pesticide residues and gene expression in common carp exposed to atrazine and chlorpyrifos: Health risk assessments

This study assessed the impacts of atrazine (ATR), chlorpyrifos (CPF) and combined ATR/CPF exposure on the kidney of common carp (Cyprinus carpio L.). The carp were sampled after a 40-d exposure to CPF and ATR, individually or in combination, followed by a 40-d recovery to measure the expression levels of heat shock proteins genes (HSP60, HSP70 and HSP90) and pesticide residues in the kidney tissue. The results revealed that the mRNA and protein levels of HSP60, HSP70 and HSP90 were induced in the kidney of common carp by ATR, CPF, and ATR/CPF mixture. The accumulated amounts of ATR, CPF, and their metabolites in the kidney tissues exhibited dose-dependency. These results exhibited that increasing concentration of ATR and CPF in the environment causes considerable stress for common carp, suggesting that the expression levels of HSP60, HSP70 and HSP90 may act as potential biomarkers for assessing the environmental ATR and CPF risk for carp.

Atrazine and chlorpyrifos exposure induces liver autophagic response in common carp

Under normal conditions, autophagy occurs at basal levels but can be induced rapidly in response to stress conditions and extracellular signals. Increasing experimental evidence indicates that the expression of autophagy-related genes play very important roles in toxicology. Atrazine (ATR) and chlorpyrifos (CPF) are the most common agrochemical in the freshwater ecosystems of the world. This study assessed the effects of ATR, CPF and combined ATR/CPF exposure on the liver of common carp. Carp were sampled after a 40-d exposure to ATR and CPF, individually or in combination, followed by a 40-d recovery to measure the mRNA and protein levels of autophagy-related genes in the liver. In addition, we also investigated the change in ultrastructure in the liver. The results revealed that the mRNA and protein levels of microtubule-associated protein 1 light chain 3 B (LC3B) and dynein were significantly induced in the treated groups compared to the solvent control group. Transmission electron microscope assays indicated that autolysosomes were observed in the exposure and recovery groups. These results indicated that ATR and CPF could induce autophagy in carp liver. To the best of our knowledge, this is the first report to study the autophagy effects caused by sub-chronic exposure to ATR, CPF and the ATR/CPF combination in common carp. The information presented in the present study may provide new insights into the mechanisms used by fish to adapt to stressful environments.

Effects of atrazine and chlorpyrifos on DNA methylation in the brain and gonad of the common carp

DNA methylation is known to play an important role in the regulation of gene expression in animal. The purpose of the present study was to examine the effect of atrazine (ATR), chlorpyrifos (CPF) and combined ATR/CPF exposure on DNA methylation in the brain and gonad of common carp (Cyprinus carpio L.). The carp were sampled after a 40-d exposure to CPF and ATR, individually or in combination, followed by a 40-d recovery to measure the levels of global DNA methylation and the expression of methylation enzymes (DNA methyltransferases (DNMTs) and methylcytosine binding domain 2 (MBD2)) in the brain and gonad tissues. The results revealed that a significant global DNA hypomethylation in the common carp exposed to ATR, CPF and their mixture was observed compared to the control fish. The MBD2 mRNA expression was up-regulated in the brain and gonad of the common carp exposed to ATR, CPF and their mixture, in contrast, the DNMTs mRNA expression was down-regulated. The information regarding the effects of ATR and CPF on DNA methylation status generated in this study is important for pesticides toxicology evaluation. However, the effect of ATR and CPF on the methylation status of specific genes, as well as its detailed mechanism requires further investigation.

In vitro exposure to the herbicide atrazine inhibits T cell activation, proliferation, and cytokine production and significantly increases the frequency of Foxp3+ regulatory T cells

The herbicide atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-s-triazine) is the most common water contaminant in the United States. Atrazine is a phosphodiesterase inhibitor and is classified as an estrogen disrupting compound because it elevates estrogen levels via induction of the enzyme aromatase. Previous studies have shown that atrazine exposure alters the function of innate immune cells such as NK cells, DC, mast cells, and macrophages. In this study we have examined the impact of in vitro atrazine exposure on the activation, proliferation, and effector cytokine production by primary murine CD4(+) T lymphocytes. We found that atrazine exposure significantly inhibited CD4(+) T cell proliferation and accumulation as well as the expression of the activation markers CD25 and CD69 in a dose-dependent manner. Interestingly, the effects were more pronounced in cells from male animals. These effects were partially mimicked by pharmacological reagents that elevate intracellular cAMP levels and addition of exogenous rmIL-2 further inhibited proliferation and CD25 expression. Consistent with these findings, atrazine exposure during T cell activation resulted in a 2- to 5-fold increase in the frequency of Foxp3(+) CD4(+) T cells.

Alterations in activity and mRNA expression of acetylcholinesterase in the liver, kidney and gill of common carp exposed to atrazine and chlorpyrifos

Insecticides and herbicides are widely used in modern agricultural production. The intensive use of insecticide chlorpyrifos (CPF) and herbicide atrazine (ATR) has resulted in serious environmental problems. Herein, we investigated alteration in activity and mRNA levels of AChE in the liver, kidney and gill from common carp after 40d exposure to CPF and ATR alone or in combination and 20d recovery treatment. Results indicated that activity and mRNA levels of AChE at all high-dose groups have been significantly decreased after CPF and ATR alone or ATR/CPF mixture exposure, and the changes were improved in the end of recovery tests in varying degrees, the activity and gene expression of AChE in the joint toxicity of ATR and CPF groups were significantly lower than that in the single toxicant group. Our study suggests that the decrease of AChE activity observed at all high-dose groups (CPF and ATR alone or in combination) may be directly related to a lower AChE expression, and the joint toxicity of ATR and CPF is higher than ATR and CPF alone.

The epigenetic lorax: gene-environment interactions in human health

Over the last decade, we have witnessed an explosion of information on genetic factors underlying common human diseases and disorders. This 'human genomics' information revolution has occurred as a backdrop to a rapid increase in the rates of many human disorders and diseases. For example, obesity, Type 2 diabetes, asthma, autism spectrum disorder and attention deficit hyperactivity disorder have increased at rates that cannot be due to changes in the genetic structure of the population, and are difficult to ascribe to changes in diagnostic criteria or ascertainment. A likely cause of the increased incidence of these disorders is increased exposure to environmental factors that modify gene function. Many environmental factors that have epidemiological association with common human disorders are likely to exert their effects through epigenetic alterations. This general mechanism of gene-environment interaction poses special challenges for individuals, educators, scientists and public policy makers in defining, monitoring and mitigating exposures.

Effects of atrazine and chlorpyrifos on activity and transcription of glutathione S-transferase in common carp (Cyprinus carpio L.)

Glutathione S-transferase isoenzymes (GSTs) play a critical role in detoxification pathways. Here we report the tissue distribution of four antioxidant GSTs gene in common carp, and their expression profiles. We also investigated the GSTs activity in different tissues after exposure to the agricultural chemicals atrazine (ATR), chlorpyrifos (CPF), and their mixture. Relative changes in the mRNA abundance of the GST isoforms were examined by real time PCR in liver, brain, kidney and gill of common carp. After exposure and recovery, we observed a statistically significant decrease in the GSTs activity in animals exposed to high concentrations of ATR (428 μg/L), CPF (116 μg/L), and their mixture (113 μg/L). At basal levels of tissue expression, four GSTs transcript were detected in liver, brain, kidney, and gill. High expression levels were found in all examined tissues. Transcription of some GST isoforms, GST kappa (GSTK), GST theta (GSTT) and GST rho (GSTR), decreased after exposure to CPF and ATR for the entire experimental period in both the kidney and gill. However, increased transcription of GST mu (GSTM) was observed in the kidney or gill 20 d after exposure to ATR or CPF, respectively. Transcription of both GSTT and GSTR was inhibited for the entire experimental period in the brain, kidney and gill of animals exposed to the ATR/CPF mixture, but transcription of GSTM was induced in the liver after 40 d of exposure. In summary, changes in the GSTs activity and their transcription varied within each organ and among organs of common carp after exposure to ATR, CPF, and their mixture.

Exposure to atrazine affects the expression of key genes in metabolic pathways integral to energy homeostasis in Xenopus laevis tadpoles

In our laboratory, Xenopus laevis tadpoles exposed throughout development to 200 or 400 μg/L atrazine, concentrations reported to periodically occur in puddles, vernal ponds and runoff soon after application, were smaller and had smaller fat bodies (the tadpole's lipid storage organ) than controls. It was hypothesized that these changes were due to atrazine-related perturbations of energy homeostasis. To investigate this hypothesis, selected metabolic responses to exposure at the transcriptional and biochemical levels in atrazine-exposed tadpoles were measured. DNA microarray technology was used to determine which metabolic pathways were affected after developmental exposure to 400 μg/L atrazine. From these data, genes representative of the affected pathways were selected for assay using quantitative real time polymerase chain reaction (qRT-PCR) to measure changes in expression during a 2-week exposure to 400 μg/L. Finally, ATP levels were measured from tadpoles both early in and at termination of exposure to 200 and 400 μg/L. Microarray analysis revealed significant differential gene expression in metabolic pathways involved with energy homeostasis. Pathways with increased transcription were associated with the conversion of lipids and proteins into energy. Pathways with decreased transcription were associated with carbohydrate metabolism, fat storage, and protein synthesis. Using qRT-PCR, changes in gene expression indicative of an early stress response to atrazine were noted. Exposed tadpoles had significant decreases in acyl-CoA dehydrogenase (AD) and glucocorticoid receptor protein (GR) mRNA after 24 h of exposure, and near-significant (p=0.07) increases in peroxisome proliferator-activated receptor β (PPAR-β) mRNA by 72 h. Decreases in AD suggested decreases in fatty acid β-oxidation while decreases in GR may have been a receptor desensitization response to a glucocorticoid surge. Involvement of PPAR-β, an energy homeostasis regulatory molecule, also suggested changes in energy status. Despite, or possibly because of, these early gene changes, there were no differences in either absolute ATP levels or ADP:ATP ratios early in the exposure. However, livers from animals exposed to 200 μg/L atrazine had near-significant (p=0.06) increases in ADP:ATP ratios at the end of exposure suggesting tadpoles may have had difficulty maintaining energy homeostasis. Perturbations in the expression of genes regulating energy metabolism by 24 h into exposure to 400 μg/L atrazine was noteworthy, especially since these tadpoles were significantly smaller than controls by 72 h of exposure.

Chronic exposure to high levels of atrazine alters expression of genes that regulate immune and growth-related functions in developing Xenopus laevis tadpoles

Atrazine is the most commonly detected pesticide in ground and surface waters, with seasonal spikes that often exceed the Environmental Protection Agency's "Recommended Water Quality Criterion" of 350 parts per billion (ppb). Although numerous studies have shown atrazine produces adverse effects on growth, development, immune and endocrine system functions in a wide range of species, few describe gene expression changes concurrent with atrazine-induced changes in phenotype during development. In this report, developing Xenopus laevis tadpoles were chronically exposed to 400 ppb atrazine, an environmentally relevant concentration. Affymetrix microarrays and Taqman qRT-PCR were used to define gene expression changes that underlie atrazine-induced phenotypic alterations. Atrazine significantly reduced survival and growth (weight, length and fat body size) in male and female tadpoles. Microarray analysis showed atrazine altered expression of 44 genes in male tadpoles (18 upregulated, 26 downregulated) and 77 genes in female tadpoles (23 upregulated, 54 downregulated). Classification of the genes into functional groups showed the majority of genes were associated with the following biological functions: growth and metabolism, proteolysis, fibrinogen complex formation and immune regulation. Seven genes associated with immune system function, specifically defense molecules present in the skin (e.g. magainin II, levitide A, preprocarulein, skin granule protein), were significantly downregulated in female tadpoles. These results support the idea that environmental contaminants such as atrazine compromise important gene pathways during frog development that may, ultimately, be relevant to global amphibian decline.

Combined in utero and juvenile exposure of mice to arsenate and atrazine in drinking water modulates gene expression and clonogenicity of myeloid progenitors

The effects of arsenate (As) and atrazine (Atr) on myeloid progenitors (colony-forming unit-granulocyte/macrophage, CFU-GM) cells derived from bone marrow were studied in male and female mice after combined in utero and juvenile exposure. Female adult mice were treated with arsenate in drinking water during gestation. Then, separate groups of males and females' offspring were exposed for 4 months to atrazine, to additional arsenate or to co-exposure of atrazine and arsenate together in drinking water. In male mice, arsenate and the combined exposure did not modulate the percentage of CFU-GM progenitors, whereas atrazine significantly decreases the clonogenicity of myeloid cells. In females, the percentage of CFU-GM significantly decreased after atrazine exposure did not change with arsenate treatment, but dramatically increased after the combined exposure. The expression of estrogen receptors alpha (ERalpha) and beta (ERbeta) in bone marrow cells was investigated, and an up-regulation of receptor beta was observed in both genders. A gene expression profile was generated using nylon membranes spotted with 1185 cancer-related genes. Results from microarrays indicate that atrazine alone did not stimulate the expression of any of the genes analysed in both male and female. Arsenic induced gene expression modulation only in female. Major significant changes on the gene expression resulted following the co-exposure to arsenic and atrazine in both male and female.

Developmental immunotoxicity of atrazine in rodents

There is a substantial literature reporting that the developing immune system is more sensitive to toxic insult and that the measurable phenotype resulting from prenatal/neonatal exposure often differs from that seen in adult exposure models (reviewed in Holladay and Steven, and Smialowicz et al.). Atrazine is a common herbicidal contaminant of groundwater in agricultural areas in the USA. The potential immunotoxicity of atrazine has been extensively studied using adult-exposure models; however, few studies have explored its immunotoxicity in a prenatal and/or lactational exposure model. Prenatal/lactational atrazine exposure affects the function of young adult rodent immune systems in both sex- and age-dependant manners. In our studies, the humoural and cell-mediated immune responses of offspring from atrazine-exposed dams were assessed at two ages, 3 and 6 months of age to test the hypothesis that prenatal/lactational atrazine exposure would cause greater health complications as the mice aged. Male offspring showed a significant immunopotentiation at three moa that was not apparent at 6 months. Three-month-old female offspring showed no significant difference in immune response from controls. However, at 6 months, female litter mates showed a significant depression in their immune function. These results indicate a decreasing trend in immune capacity. Rooney et al. showed a significant depression of the immune function of young male rat exposure prenatally and lactationally to atrazine. These results demonstrate a sex- and age-dependant effect of prenatal exposure to atrazine on the immune system of the adult offspring using two rodent strains.