Genome-wide study of DNA methylation alterations in response to diazinon exposure in vitro

Identification of common genetic factors and immune-related pathways associating more than two autoimmune disorders: implications on risk, diagnosis, and treatment

Autoimmune disorders (ADs) are chronic conditions resulting from failure or breakdown of immunological tolerance, resulting in the host immune system attacking its cells or tissues. Recent studies report shared effects, mechanisms, and evolutionary origins among ADs; however, the possible factors connecting them are unknown. This study attempts to identify gene signatures commonly shared between different autoimmune disorders and elucidate their molecular pathways linking the pathogenesis of these ADs using an integrated gene expression approach. We employed differential gene expression analysis across 19 datasets of whole blood/peripheral blood cell samples with five different autoimmune disorders (rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, Crohn's disease, and type 1 diabetes) to get nine key genes-EGR1, RUNX3, SMAD7, NAMPT, S100A9, S100A8, CYBB, GATA2, and MCEMP1 that were primarily involved in cell and leukocyte activation, leukocyte mediated immunity, IL-17, AGE-RAGE signaling in diabetic complications, prion disease, and NOD-like receptor signaling confirming its role in immune-related pathways. Combined with biological interpretations such as gene ontology (GO), pathway enrichment, and protein-protein interaction (PPI) network, our current study sheds light on the in-depth research on early detection, diagnosis, and prognosis of different ADs.

Exploring RNA methylation as a promising biomarker for assessing sublethal effects of fipronil on honeybees (Apis mellifera L.)

Honeybees play a crucial role as pollinators for crops and are regarded as sensitive bioindicators of environmental health. The widespread use of pesticides poses a severe threat to honeybee survival. However, there is limited information available on the specific risks associated with fipronil exposure in honeybees, particularly concerning the impact on RNA methylation throughout their lifespan. This study aimed to evaluate the effects of sublethal concentrations of fipronil on RNA m⁶A and m⁵C methylations, along with the associated genes in honeybee larvae and newly emerged adults. LC-MS/MS analysis revealed a notable hypomethylation of m⁵C in larvae, while hypermethylation of m⁶A was observed in the adult brain. Significant changes in the expression of genes such as AmWTAP, AmYTHDF, AmALKBH4, AmALKBH6, AmALKBH8, AmNSUN5, AmNOP2, AmTET1, and AmYBX1 were observed in the adult brain, whereas alterations in the expression of AmNSUN2, AmMETTL14, AmALKBH1, AmALKBH4, AmALKBH6 AmALYREF, AmTET1, and AmYBX1 were observed in the larvae. Notably, the expression of AmALKBH1 was not detected in any fipronil-treated larvae, suggesting its potential as an early risk indicator for honeybee larvae in future assessments. This pioneering study provides insights into the effects of fipronil on RNA methylations in honeybees and explores the possibility of employing RNA methylation as a tool for assessing pesticide risks in this important pollinator species. These findings offer new perspectives on honeybee protection and the development of toxicity evaluation systems for pesticides.

Coenzyme Q10 treatment and diazinon exposure in parental male rats: effects of the exposure on their neonatal brains

Prenatal acute and chronic exposure to organophosphorus pesticides may evoke physical and behavioral impairments in offspring development. However, the mechanism of antioxidant consumption repair to cure these impairments remains unclear. This study aimed to investigate the protective effects of COQ10 against DZN toxicity by measuring Malondialdehyde (MDA) level, superoxide dismutase (SOD) activity, the expression of MH2A, DNMT1, H2AZ, and HDAC3, and the histopathology in the brain of neonatal Wistar albino rats whose male parents were exposed to DZN and COQ10. The results showed that COQ10 could significantly decrease MDA level, histopathological alteration, and expression of DNMT1 and HDAC3 in the neonatal brain (P < 0.05). Also, an increase in SOD activity and expression of MH2A and H2AZ were observed in the neonatal brain of this group (P < 0.05). These investigations suggest that COQ10 can reduce the effects of DZN on neuronal oxidative stress and its damage to the neonatal brain.

Monoclonal antibody-based icELISA for the screening of diazinon in vegetable samples

Diazinon (DAZ) is an organophosphorus pesticide (OP), which is commonly used to prevent and control harmful pests that endanger agricultural products. In this study, we developed a novel heterology coating strategy for the immunoassay of DAZ. The DAZ coating hapten can be directly conjugated to the carrier protein without requiring a spacer arm. This proposed hapten coating strategy is time-saving and significantly improves the sensitivity of the immunoassay due to the lack of a spacer arm. The as-synthesized coating antigen was used to screen the monoclonal antibody (mAb). Finally, the developed indirect competitive enzyme-linked immunoassay (icELISA) showed IC₅₀ and limit of detection (LOD) values of 0.58 ng mL^-1 and 8 pg mL^-1, respectively. This method exhibited negligible cross-reactivity towards other analogues, and the recoveries of samples (cucumber, cabbage, and lettuce) ranged from 92.6% to 125.4%, with coefficients of variance (CV) below 12%. Good correlation between icELISA and high-performance liquid chromatography mass spectrometry (HPLC-MS/MS) was obtained. The proposed icELISA was an ideal tool for monitoring DAZ residues in food samples.

Ferulago angulata extract improves the quality of buck spermatozoa post-thaw and counteracts the harmful effects of diazinon and lead

During cryopreservation, spermatozoa are exposed to chemical or physical stress that has adverse effects on the quality of mammalian spermatozoa. Recently, much attention has been paid to environmental contaminants (ECs) in livestock, because of their detrimental effects on livestock productivity and fertility. ECs like diazinon (DZN) and lead acetate (LA) are considered ubiquitous and induced oxidative stress, which decreases spermatozoa quality. Since Ferulago angulata extract (FAE) has antioxidant properties, the present study investigated the effect of FAE supplementation in a freezing extender, in the presence or absence of DZN + LA, during cryopreservation, on the quality and fertility ability of buck spermatozoa after thawing. Pooled ejaculates were diluted with a freezing extender and supplemented with FAE (0.002%, w/v) in the presence or absence of DZN (100 μM) + LA (12.5 μM). Post-thaw spermatozoa parameters, ROS production, fertilization ability, and developmental competence of oocytes inseminated with FAE/DZN + LA treated spermatozoa were calculated. The results demonstrated that FAE improves cryopreserved spermatozoa motility, viability, membrane integrity, fertilizability, and developmental competence, and reduced spermatozoa ROS production in the presence or absence of DZN + LA. Besides, FAE significantly restored the adverse effects of DZN + LA exposure during cryopreservation on inner cell mass (ICM) count, trophectoderm (TE) cell count, total cell number (TCN), and the ratio between ICM to TCN. In conclusion, FAE on its own resulted in an improvement in the buck spermatozoa's quality and fertility. Therefore, the addition of FAE, as a natural antioxidant to buck semen extender, can increase spermatozoa cryotolerance and post-thaw resistance even when exposed to ECs.

Environmental and socio-cultural impacts on global DNA methylation in the indigenous Huichol population of Nayarit, Mexico

Alterations of global DNA methylation have been evaluated in several studies worldwide; however, Long Interspersed Nuclear Elements-1 (LINE-1) methylation in genetically conserved populations such as indigenous communities have not, to our knowledge, been reported. The aim of this study was to evaluate the relationship between LINE-1 methylation patterns and factors such as pesticide exposure and socio-cultural characteristics in the Indigenous Huichol Population of Nayarit, Mexico. A cross-sectional study was conducted in 140 Huichol indigenous individuals. A structured questionnaire was used to determine general and anthropometric characteristics, diet, harmful habits, and pesticide exposure. DNA methylation was determined by pyrosequencing of bisulfite-treated DNA. A lower level of LINE-1 methylation was found in the indigenous population when compared to a Mestizo population previously studied by our group. This difference might be due to the influence of the genetic admixture and differing dietary and lifestyle habits. The males in the indigenous population exhibited increased LINE-1 methylation in comparison to the females. Sex and alcohol consumption showed positive associations with LINE-1 methylation, while weight, current work in the field, current pesticide usage, and folate intake exhibited negative associations with LINE-1 methylation. The results suggest that ethnicity, as well as other internal and environmental factors, might influence LINE-1 methylation.

Autoencoded DNA methylation data to predict breast cancer recurrence: Machine learning models and gene-weight significance

Breast cancer is the most frequent cancer in women and the second most frequent overall after lung cancer. Although the 5-year survival rate of breast cancer is relatively high, recurrence is also common which often involves metastasis with its consequent threat for patients. DNA methylation-derived databases have become an interesting primary source for supervised knowledge extraction regarding breast cancer. Unfortunately, the study of DNA methylation involves the processing of hundreds of thousands of features for every patient. DNA methylation is featured by High Dimension Low Sample Size which has shown well-known issues regarding feature selection and generation. Autoencoders (AEs) appear as a specific technique for conducting nonlinear feature fusion. Our main objective in this work is to design a procedure to summarize DNA methylation by taking advantage of AEs. Our proposal is able to generate new features from the values of CpG sites of patients with and without recurrence. Then, a limited set of relevant genes to characterize breast cancer recurrence is proposed by the application of survival analysis and a pondered ranking of genes according to the distribution of their CpG sites. To test our proposal we have selected a dataset from The Cancer Genome Atlas data portal and an AE with a single-hidden layer. The literature and enrichment analysis (based on genomic context and functional annotation) conducted regarding the genes obtained with our experiment confirmed that all of these genes were related to breast cancer recurrence.

Environmental epitranscriptomics

Chemical modifications of RNA molecules have gained increasing attention since evidence emerged for their substantive roles in a range of biological processes, such as the stability and translation of mRNA transcripts. More than 150 modifications have been identified in different organisms to date, collectively known as the 'epitranscriptome', with 6-methyladenosine (m⁶A), 5-methylcytidine (m⁵C), pseudouridine and N1-methyladenosine (m¹A) the most extensively investigated. Although we are just beginning to elucidate the roles of these modifications in cellular functions, there is already evidence for their dysregulation in diseases such as cancer and neurodevelopmental disorders. There is currently more limited knowledge regarding how environmental exposures affect the epitranscriptome and how this may mediate disease risk, but evidence is beginning to emerge. Here, we review the current evidence for the impact of environmental exposures such as benzo[a]pyrene, bisphenol A, pesticides, metals and nanoparticles upon RNA modifications and the expression of their 'writers' (methyl transferases), 'erasers' (demethylases) and 'readers'. We discuss future directions of the field and identify areas of particular promise and consider the technical challenges that are faced.

Pesticides, cognitive functions and dementia: A review

Pesticides are widely-used chemicals commonly applied in agriculture for the protection of crops from pests. Depending on the class of pesticides, the specific substances may have a specific set of adverse effects on humans, especially in cases of acute poisoning. In past years, evidence regarding sequelae of chronic, low-level exposure has been accumulating. Cognitive impairment and dementia heavily affect a person's quality of life and scientific data has been hinting towards an association between them and antecedent chronic pesticide exposure. Here, we reviewed animal and human studies exploring the association between pesticide exposure, cognition and dementia. Additionally, we present potential mechanisms through which pesticides may act neurotoxically and lead to neurodegeneration. Study designs rarely presented homogeneity and the estimation of the exposure to pesticides has been most frequently performed without measuring the synergic effects and the possible interactions between the toxicants within mixtures, and also overlooking low exposures to environmental toxicants. It is possible that a Real-Life Risk Simulation approach would represent a robust alternative for future studies, so that the safe exposure limits and the net risk that pesticides confer to impaired cognitive function can be examined. Previous studies that evaluated the effect of low dose chronic exposure to mixtures of pesticides and other chemicals intending to simulate real life exposure scenarios showed that hormetic neurobehavioral effects can appear after mixture exposure at doses considered safe for individual compounds and these effects can be exacerbated by a coexistence with specific conditions such as vitamin deficiency. However, there is an overall indication, derived from both epidemiologic and laboratory evidence, supporting an association between exposure to neurotoxic pesticides and cognitive dysfunction, dementia and Alzheimer's disease.

Diuron exposure and Akt overexpression promote glioma formation through DNA hypomethylation

BACKGROUND

Diuron is an environmental component listed as a likely human carcinogen. Several other studies report that diuron can be oncogenic for bladder, urothelial, skin, and mammary cells. No study mentions the putative effect of diuron on the glioma occurrence.

OBJECTIVES

We here wanted to investigate the effects of diuron exposure on the glioma occurrence while wishing to incriminate a putative implication of DNA methylation modulation in this process.

METHODS

In in vivo model of glioma, diuron exposure was firstly compared or combined with oncogenic overexpressions already known to promote gliomagenesis. ELISA quantifying the 5-methylcytosine level on DNA was performed to examine the global DNA methylation level. Quantitative real-time polymerase chain reaction and proximity ligation in situ assay were performed to identify the molecular causes of the diuron-induced changes of DNA methylation. The signatures diuron-induced changes of DNA methylation were analyzed in a cohort of 23 GBM patients.

RESULTS

Diuron exposure is not sufficient to promote glioma, such as the oncogenic overexpression of Akt or Ras. However, the combination of diuron exposure and Akt overexpression promotes glioma. We observed that the diuron/Akt-induced glioma is characterized by three phenotypic signatures characterizing cancer cells: a global DNA hypomethylation, a loss of sensitivity to cell death induction, and a gain of signals of immune escape. Our data associated these phenotypes with three aberrant DNA methylation signatures: the LLT1, PD-L1, and Bcl-w hypomethylations. Strikingly, we observed that these three concomitant hypomethylations were only observed in GBM patients having a potential exposure to diuron via their professional activity.

CONCLUSIONS

As single player, diuron is not an oncogenic of glioma, but it can participate to the glioma formation in association with other events (also devoid of oncogenic property as single player) such as Akt overexpression.

Environmental monitoring and the developmental origins of health and disease

Early-life chronic exposure to environmental contaminants, such as bisphenol-A, particulate matter air pollution, organophosphorus pesticides, and pharmaceutical drugs, among others, may affect central tissues, such as the hypothalamus, and peripheral tissues, such as the endocrine pancreas, causing inflammation and apoptosis with severe implications to the metabolism. The Developmental Origins of Health and Disease (DOHaD) concept articulates events in developmental phases of life, such as intrauterine, lactation, and adolescence, to later-life metabolism and health. These developmental phases are more susceptible to environmental changes, such as those caused by environmental contaminants, which may predispose individuals to obesity, metabolic syndrome, and chronic noncommunicable diseases later in life. Alterations in the epigenome are explored as an underlying mechanism to the programming effects on metabolism, as the expression of key genes related with central and peripheral metabolic functions may be altered in response to environmental disturbances. Studies show that environmental contaminants may affect gene expressions in mammals, especially when exposed to during the developmental phases of life, leading to metabolic disorders in adulthood. In this review, we discuss the current obesity epidemics, the DOHaD concept, pollutants' toxicology, environmental control, and the role of environmental contaminants in the central and peripheral programming of obesity and metabolic syndrome. Improving environmental monitoring may directly affect the quality of life of the population and help protect the future generations from metabolic diseases.

Modified CDKN2B (p15) and CDKN2A (p16) DNA methylation profiles in urban pesticide applicators

Gene-specific changes in DNA methylation by pesticides in occupationally exposed populations have not been studied extensively. Of particular concern are changes in the methylation profile of tumor-suppressor, such as CDKN2B and CDKN2A, genes involved in oncogenesis. The aim of this study was to evaluate the methylation profiles of CDKN2B and CDKN2A genes in urban pesticide applicators and their relationship with occupational exposure to pesticides. A cross-sectional study was conducted in 186 urban pesticide applicators (categorized as high or moderate exposures) and 102 participants without documented occupational exposures to pesticides. Acute and chronic pesticide exposures were evaluated by direct measurement of urinary dialkylphosphates, organophosphate metabolites, and a structured questionnaire, respectively. Anthropometric characteristics, diet, clinical histories, and other variables were estimated through a validated self-reported survey. DNA methylation was determined by pyrosequencing of bisulfite-treated DNA. Decreased DNA methylation of the CDKN2B gene was observed in pesticide-exposed groups compared to the non-exposed group. In addition, increased methylation of the CDKN2A promoter was observed in the moderate-exposure group compared to the non-exposed group. Bivariate analysis showed an association between CDKN2B methylation and pesticide exposure, general characteristics, smoking status, and micronutrients, while changes in CDKN2A methylation were associated with pesticide exposure, sex, educational level, body mass index, smoking status, supplement intake, clinical parameters, and caffeine consumption. These data suggest that pesticide exposure modifies the methylation pattern of CDKN2B and CDKN2A genes and raise important questions about the role that these changes may play in the regulation of cell cycle activities, senescence, and aging.

Organophosphate pesticide exposure and differential genome-wide DNA methylation

BACKGROUND

Organophosphates (OP) are widely used insecticides that acutely inhibit acetylcholinesterase enzyme activity. There is great interest in improving the understanding of molecular mechanisms related to chronic OP exposure induced toxicity. We aim to elucidate epigenetic changes associated with OP exposure, using untargeted analysis of genome-wide DNA methylation data.

METHODS

In a population-based case control study of Parkinson's disease (PD), we assessed ambient OP exposure via residential and workplace proximity to commercial applications. We investigated associations between OP exposure and genome-wide DNA methylation (Illumina 450 k) in 580 blood samples (342 PD patients, 238 controls) and 259 saliva samples (128 patients, 131 controls). To identify differential methylation related to OP exposure, we controlled for age, sex, European ancestry, and PD status; in addition, we stratified by disease status.

RESULTS

We identified 70 genome-wide significant CpGs, including cg01600516 in ALOX12 (cor = 0.27, p = 1.73E-11) and two CpGs in HLA genes, cg01655658 (cor = -0.24, p = 2.80E-09) in HLA-L (pseudogene) and cg15680603 (cor = 0.20, p = 7.94E-07) in HLA-DPA1. Among the 70 CpGs located in 41 genes, 14 were also differentially methylated in saliva samples. The most overrepresented pathway was the nicotinic acetylcholine receptor signaling pathway (fold enrichment = 15.63, p = 1.01E-03, FDR = 1.64E-01). Expanding to a larger number of genes (CpG p < 5E-04, FDR < 2.25E-01; 1077 CpGs, 662 genes), the most enriched pathway shifted to the muscarinic acetylcholine receptor 1 and 3 signaling pathway (p-value = 5.36E-04, FDR = 4.73E-02). When we stratified by PD status, results were similar. Of the 70 significant CpGs, 63 were detected among both patients and controls and 7 were only associated with OP exposure among patients.

CONCLUSIONS

This study finds chronic low-level OP exposure is associated with differential DNA methylation in blood and saliva, both in elderly population controls and PD patients. Our study results suggest that long-term sub-acute OP exposure influences methylation in genes enriched for muscarinic and nicotinic acetylcholine receptor pathways.

Mechanisms of organophosphorus pesticide toxicity in the context of airway hyperreactivity and asthma

Numerous epidemiologic studies have identified an association between occupational exposures to organophosphorus pesticides (OPs) and asthma or asthmatic symptoms in adults. Emerging epidemiologic data suggest that environmentally relevant levels of OPs may also be linked to respiratory dysfunction in the general population and that in utero and/or early life exposures to environmental OPs may increase risk for childhood asthma. In support of a causal link between OPs and asthma, experimental evidence demonstrates that occupationally and environmentally relevant OP exposures induce bronchospasm and airway hyperreactivity in preclinical models. Mechanistic studies have identified blockade of autoinhibitory M2 muscarinic receptors on parasympathetic nerves that innervate airway smooth muscle as one mechanism by which OPs induce airway hyperreactivity, but significant questions remain regarding the mechanism(s) by which OPs cause neuronal M2 receptor dysfunction and, more generally, how OPs cause persistent asthma, especially after developmental exposures. The goals of this review are to 1) summarize current understanding of OPs in asthma; 2) discuss mechanisms of OP neurotoxicity and immunotoxicity that warrant consideration in the context of OP-induced airway hyperreactivity and asthma, specifically, inflammatory responses, oxidative stress, neural plasticity, and neurogenic inflammation; and 3) identify critical data gaps that need to be addressed in order to better protect adults and children against the harmful respiratory effects of low-level OP exposures.

The link of organophosphorus pesticides with neurodegenerative and neurodevelopmental diseases based on evidence and mechanisms

Organophosphorus (OP) compounds have been known as the most widely used pesticides during the past half century and there have been a huge body of literature regarding their association with human chronic diseases. Neurodegenerative and neurodevelopmental disorders including Alzheimer, Parkinson, amyotrophic lateral sclerosis (ALS), attention deficit hyperactivity disorder (ADHD), and autism are among the afflicting neurological diseases which overshadow human life and their higher risk in relation to OP exposures have been uncovered by epidemiological studies. In addition, experimental studies exploring the underlying mechanisms have provided some evidence for involvement of cholinergic deficit, oxidative stress, neuro-inflammation, and epigenetic modifications as the processes which are common in the toxicity of the OP and pathophysiology of the mentioned diseases. In addition, genetic mutations and polymorphisms of different variants of some genes like paraoxonase have been shown to be implicated in both susceptibility to OPs toxicity and neurological diseases. In this article, we reviewed the epidemiological as well as experimental studies evidencing the association of exposure to OPs and incidence of neurodegenerative and neurodevelopmental diseases.

Mechanisms of diazinon effects on impaired spermatogenesis and male infertility

Diazinon (DZN) is an organophosphate insecticide that has cytotoxic and pathological effects on the reproductive system. It causes a wide variety of pathological effects on the reproductive system such as testicular atrophy, disturbance in sex hormones, impaired spermatogenesis, low quality of sperm, and fertility problems. However, molecular and cellular mechanisms of its adverse effects are not well understood. General events such as testicular damage, inflammation, mitochondrial deficiency, DNA fragmentation, disintegration of sperm plasma membrane, apoptosis, and cell death are observed in DZN-exposed animals. Oxidative stress (OS) induced by reactive oxygen species may be a main mechanism, which can be associated with sperm DNA fragmentation, reduced integrity of sperm cell membrane, apoptosis, depletion of antioxidants, and subsequently poor sperm quality and male infertility. Therefore, identification of these pathways may provide valuable information regarding the mechanisms of DZN action on the male reproductive system. In this review, we aim to discuss the proposed cellular and molecular mechanisms of DZN action on male reproductive system, the importance of OS and mechanisms by which DZN induces OS and depletion of other antioxidants.

Endosulfan causes the alterations of DNA damage response through ATM-p53 signaling pathway in human leukemia cells

Exposure to pesticides results in DNA damage and genomic instability. We previously predicted that endosulfan might be associated with leukemia, but the role of endosulfan in leukemia cells has been unexplored. The aim of this study is to elucidate molecular mechanism of endosulfan-induced DNA damage response in human leukemia cells. We performed endosulfan exposure experiments in K562 cells with varying concentrations of endosulfan for 48 h and found that endosulfan lowered cell viability in a dose-dependent manner. We observed the dramatic DNA damage using comet assay and the increase of micronucleus in 75 μM endosulfan-exposed cells. Endosulfan at 75 μM caused the expression alterations of ATM and DNA repair genes such as FANCD2, and BRCA1/2 at different exposure time points (12, 24, 48 h), which was reversed by ATM inhibitor KU-55933. Endosulfan significantly increased the mRNA expression levels of p53 and GADD45A, and decreased PCNA and XRCC2 at 48 h after exposure. Flow cytometric analysis showed that endosulfan at 50 and 75 μM induced cell cycle G1 arrest, a response attributed to down-regulation of CDK6 and up-regulation of p21. We also observed that endosulfan at 50 and 75 μM induced a considerable percentage of cells to undergo apoptosis, as detected by Annexin-V binding assays. Endosulfan resulted in the activation of caspase-3, and elevated the expression levels of PUMA and the ratio of BAX/Bcl-2. These findings suggest that endosulfan caused DNA damage response throughATM-p53 signaling pathway, implicating the potential correlation between endosulfan and leukemia.

Epigenetic modulation of Nrf2 and Ogg1 gene expression in testicular germ cells by methyl parathion exposure

Methyl parathion (Me-Pa) is an oxidizing organophosphate (OP) pesticide that generates reactive oxygen species (ROS) through its biotransformation. Some studies have also suggested that OP pesticides have the capacity to alkylate biomolecules, including DNA. In general, DNA methylation in gene promoters represses transcription. NRF2 is a key transcription factor that regulates the expression of antioxidant, metabolic and detoxifying genes through the antioxidant response element (ARE) situated in promoters of regulated genes. Furthermore, DNA repair genes, including 8-oxoguanine DNA glycosidase (OGG1), have been proposed as NRF2 target genes. Me-Pa exposure produces poor semen quality, genetic and oxidative damage in sperm cells, and reduced fertility. However, the Me-Pa effects on the methylation status and the expression of antioxidant (Nrf2) or DNA repair (Ogg1) genes in male germ cells have not been investigated. Therefore, mice were exposed to Me-Pa to evaluate the global (%5-mC) and specific methylation of Nrf2 and Ogg1 genes using pyrosequencing, gene expression, and total protein carbonylation in male germ cells. The results showed that Me-Pa significantly decreased the global DNA methylation pattern and significantly increased the methylation of two CpG sites within Ogg1 promoter and one CpG site within Nrf2 promoter. In addition, Ogg1 or Nrf2 expression did not change after Me-Pa exposure despite the oxidative damage produced. Altogether, our data suggest that Me-Pa toxicity alters Ogg1 and Nrf2 promoter methylation in male germ cells that may be modulating their gene expression.

Combined Prenatal Pesticide Exposure and Folic Acid Intake in Relation to Autism Spectrum Disorder

BACKGROUND

Maternal folic acid (FA) protects against developmental toxicity from certain environmental chemicals.

OBJECTIVE

We examined combined exposures to maternal FA and pesticides in relation to autism spectrum disorder (ASD).

METHODS

Participants were California children born from 2000-2007 who were enrolled in the Childhood Autism Risks from Genetics and the Environment (CHARGE) case-control study at age 2-5 y, were clinically confirmed to have ASD (n=296) or typical development (n=220), and had information on maternal supplemental FA and pesticide exposures. Maternal supplemental FA and household pesticide product use were retrospectively collected in telephone interviews from 2003-2011. High vs. low daily FA intake was dichotomized at 800μg (median). Mothers' addresses were linked to a statewide database of commercial applications to estimate agricultural pesticide exposure.

RESULTS

High FA intake (≥800μg) during the first pregnancy month and no known pesticide exposure was the reference group for all analyses. Compared with this group, ASD was increased in association with <800μg FA and any indoor pesticide exposure {adjusted odds ratio [OR]=2.5 [95% confidence interval (CI): 1.3, 4.7]} compared with low FA [OR=1.2 (95% CI: 0.7, 2.2)] or indoor pesticides [OR=1.7 (95% CI: 1.1, 2.8)] alone. ORs for the combination of low FA and regular pregnancy exposure (≥6 mo) to pet pesticides or to outdoor sprays and foggers were 3.9 (95% CI: 1.4, 11.5) and 4.1 (95% CI: 1.7, 10.1), respectively. ORs for low maternal FA and agricultural pesticide exposure 3 mo before or after conception were 2.2 (95% CI: 0.7, 6.5) for chlorpyrifos, 2.3 (95% CI: 0.98, 5.3) for organophosphates, 2.1 (95% CI: 0.9, 4.8) for pyrethroids, and 1.5 (95% CI: 0.5, 4.8) for carbamates. Except for carbamates, these ORs were approximately two times greater than those for either exposure alone or for the expected ORs for combined exposures under multiplicative or additive models.

CONCLUSIONS

In this study population, associations between pesticide exposures and ASD were attenuated among those with high versus low FA intake during the first month of pregnancy. Confirmatory and mechanistic studies are needed. https://doi.org/10.1289/EHP604.

DNA damage and methylation induced by glyphosate in human peripheral blood mononuclear cells (in vitro study)

Glyphosate is a very important herbicide that is widely used in the agriculture, and thus the exposure of humans to this substance and its metabolites has been noted. The purpose of this study was to assess DNA damage (determination of single and double strand-breaks by the comet assay) as well as to evaluate DNA methylation (global DNA methylation and methylation of p16 (CDKN2A) and p53 (TP53) promoter regions) in human peripheral blood mononuclear cells (PBMCs) exposed to glyphosate. PBMCs were incubated with the compound studied at concentrations ranging from 0.1 to 10 mM for 24 h. The study has shown that glyphosate induced DNA lesions, which were effectively repaired. However, PBMCs were unable to repair completely DNA damage induced by glyphosate. We also observed a decrease in global DNA methylation level at 0.25 mM of glyphosate. Glyphosate at 0.25 mM and 0.5 mM increased p53 promoter methylation, while it did not induce statistically significant changes in methylation of p16 promoter. To sum up, we have shown for the first time that glyphosate (at high concentrations from 0.5 to 10 mM) may induce DNA damage in leucocytes such as PBMCs and cause DNA methylation in human cells.

Pesticide use and LINE-1 methylation among male private pesticide applicators in the Agricultural Health Study

Cancer risk may be associated with DNA methylation (DNAm) levels in Long Interspersed Nucleotide Element 1 (LINE-1), a surrogate for global DNAm. Exposure to certain pesticides may increase risk of particular cancers, perhaps mediated in part through global DNAm alterations. To date, human data on pesticide exposure and global DNAm alterations are limited. The goal of this study was to evaluate alterations of LINE-1 DNAm by pesticides in a variety of classes. Data from 596 cancer-free male participants enrolled in the Agricultural Health Study (AHS) were used to examine associations between use of 57 pesticides and LINE-1 DNAm measured via Pyrosequencing in peripheral blood leucocytes. Participants provided information on pesticide use at three contacts between 1993 and 2010. Associations of ever/never pesticide use and lifetime days of application (years of use × days per year) and LINE-1 DNAm level were assessed using linear regression, adjusting for potential confounders (race, age at blood draw, and frequency of drinking alcohol) and other moderately correlated pesticides. After adjustment, ever application of 10 pesticides was positively associated and ever application of eight pesticides was negatively associated with LINE-1 DNAm. In dose-response analyses, increases in five pesticides (imazethapyr, fenthion, EPTC, butylate, and heptachlor) were associated with increasing LINE-1 DNAm (p_trend < 0.05) and increases in three pesticides (carbaryl, chlordane, and paraquat) were associated with decreasing LINE-1 DNAm (p_trend < 0.05). This study provides some mechanistic insight into the pesticide-cancer relationship, which may be mediated in part by epigenetics.

Investigation into experimental toxicological properties of plant protection products having a potential link to Parkinson's disease and childhood leukaemia

In 2013, EFSA published a literature review on epidemiological studies linking exposure to pesticides and human health outcome. As a follow up, the EFSA Panel on Plant Protection Products and their residues (PPR Panel) was requested to investigate the plausible involvement of pesticide exposure as a risk factor for Parkinson's disease (PD) and childhood leukaemia (CHL). A systematic literature review on PD and CHL and mode of actions for pesticides was published by EFSA in 2016 and used as background documentation. The Panel used the Adverse Outcome Pathway (AOP) conceptual framework to define the biological plausibility in relation to epidemiological studies by means of identification of specific symptoms of the diseases as AO. The AOP combines multiple information and provides knowledge of biological pathways, highlights species differences and similarities, identifies research needs and supports regulatory decisions. In this context, the AOP approach could help in organising the available experimental knowledge to assess biological plausibility by describing the link between a molecular initiating event (MIE) and the AO through a series of biologically plausible and essential key events (KEs). As the AOP is chemically agnostic, tool chemical compounds were selected to empirically support the response and temporal concordance of the key event relationships (KERs). Three qualitative and one putative AOP were developed by the Panel using the results obtained. The Panel supports the use of the AOP framework to scientifically and transparently explore the biological plausibility of the association between pesticide exposure and human health outcomes, identify data gaps, define a tailored testing strategy and suggests an AOP's informed Integrated Approach for Testing and Assessment (IATA).

Avermectin induced global DNA hypomethylation and over-expression of heat shock proteins in cardiac tissues of pigeon

Despite increasing evidences pointing to residues of avermectin (AVM) pose toxic effects on non-target organisms in environment, but the data in pigeon is insufficient. The alteration of global DNA methylation and response of heat shock proteins (Hsps) are important for assessing the AVM toxicity in cardiac tissues of pigeon (Columba livia). To investigate the effects of AVM exposure in cardiac tissues of pigeon, we detected the expression levels of DNA methyltransferases (Dnmts), methylated DNA-binding domain protein 2 (MBD2), and Hsp 60, 70 and 90. Pigeons were exposed to feed containing AVM (0, 20, 40 and 60mg/kg diet) for 30, 60, 90days respectively, and cardiac tissues were collected and analyzed. We found the transcriptional levels of Dnmt1, Dnmt3_a and Dnmt3_b mRNA were down-regulated, but the transcriptional levels of MBD2 mRNA were up-regulated by AVM exposure in cardiac tissues of pigeon. Necrocytosis, hemorrhage, infiltration of inflammatory cells and abundant vacuoles appeared in cardiac tissues after AVM exposure. Accompanying this phenotype, the mRNA transcriptional and/or protein levels of Hsp30, Hsp60, Hsp70 and Hsp90 increased. In conclusion, these results underscored AVM exposure caused DNA methylation machinery malfunctions, and induced over-expression of Hsps to improve the protective function against cardiac injury.

Lactobacillus Casei Decreases Organophosphorus Pesticide Diazinon Cytotoxicity in Human HUVEC Cell Line

PURPOSE

Exposure to diazinon can trigger acute and chronic toxicity and significantly induces DNA damage and proapoptotic effects in different human cells. Due to the significance of probiotic bacteria antitoxin effect, this study aimed to investigate the effect of Lactobacillus casei on diazinon (DZN) cytotoxicity in human umbilical vein endothelial cells (HUVEC) in vitro.

METHODS

The cytotoxicity assessments were performed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, DAPI (4',6-diamidino-2-phenylindole) staining and flow cytometric methodologies.

RESULTS

Cytotoxic assessments through flow cytometry/ DAPI staining demonstrated that apoptosis is the main cytotoxic mechanism of diazinon in HUVEC cells and L. casei could decrease the diazinon cytotoxic effects on toxicants.

CONCLUSION

the screen of total bacterial secreted metabolites can be considered as a wealthy source to find the new active compounds to introduce as reducing agricultural remained pesticide cytotoxicity effects on the human food chain.

Toxicopathic changes and genotoxic effects in liver of rat following exposure to diazinon

In general, people may come in contact with mixtures of insecticides through domestic use, consumption of contaminated food or drinks, and/or living close to treated areas. We analyzed the toxic effects of diazinon on histological structure of liver and hematological parameters in male rats. DNA-damaging potential of diazinon was also investigated using the comet assay in blood cells and the micronucleus test in bone marrow. Two groups of six male rats orally received different amounts of diazinon: 1/50 and 1/25 LD 50 for 4 weeks (5 day/week). The present study showed that diazinon caused hypertrophy of sinusoids, central vein, and portal triad, in addition to the formation of oedema, vacuoles, hemorrhage, necrosis, and lymphoid infiltration in rats' liver. A significant decrease in red blood cells, hemoglobin, hematocrite levels, and platelet counts was observed in the treated groups. However, the white blood cell count increased. Micronucleus test results revealed aneugenic effects of diazinon. Furthermore, we noticed an increase in comet tail length in treated groups. So, the comet assay confirmed the genotoxic potential of diazinon in vivo. On the assumption that all alterations observed in rats could be observed in human, it is necessary to raise the awareness about the health risk posed by this insecticide.

Linking Pesticide Exposure with Pediatric Leukemia: Potential Underlying Mechanisms

Leukemia is the most common cancer in children, representing 30% of all childhood cancers. The disease arises from recurrent genetic insults that block differentiation of hematopoietic stem and/or progenitor cells (HSPCs) and drives uncontrolled proliferation and survival of the differentiation-blocked clone. Pediatric leukemia is phenotypically and genetically heterogeneous with an obscure etiology. The interaction between genetic factors and environmental agents represents a potential etiological driver. Although information is limited, the principal toxic mechanisms of potential leukemogenic agents (e.g., etoposide, benzene metabolites, bioflavonoids and some pesticides) include topoisomerase II inhibition and/or excessive generation of free radicals, which may induce DNA single- and double-strand breaks (DNA-DSBs) in early HSPCs. Chromosomal rearrangements (duplications, deletions and translocations) may occur if these lesions are not properly repaired. The initiating hit usually occurs in utero and commonly leads to the expression of oncogenic fusion proteins. Subsequent cooperating hits define the disease latency and occur after birth and may be of a genetic, epigenetic or immune nature (i.e., delayed infection-mediated immune deregulation). Here, we review the available experimental and epidemiological evidence linking pesticide exposure to infant and childhood leukemia and provide a mechanistic basis to support the association, focusing on early initiating molecular events.

Zebrafish as a model to study the role of DNA methylation in environmental toxicology

Environmental epigenetics is a rapidly growing field which studies the effects of environmental factors such as nutrition, stress, and exposure to compounds on epigenetic gene regulation. Recent studies have shown that exposure to toxicants in vertebrates is associated with changes in DNA methylation, a major epigenetic mechanism affecting gene transcription. Zebra fish, a well-known model in toxicology and developmental biology, are emerging as a model species in environmental epigenetics despite their evolutionary distance to rodents and humans. In this review, recent insights in DNA methylation during zebra fish development are discussed and compared to mammalian models in order to evaluate zebra fish as a model to study the role of DNA methylation in environmental toxicology. Differences exist in DNA methylation reprogramming during early development, whereas in later developmental stages, tissue distribution of both 5-methylcytosine and 5-hydroxymethylcytosine seems more conserved between species, as well as basic DNA (de)methylation mechanisms. All DNA methyl transferases identified so far in mammals are present in zebra fish, as well as a number of major demethylation pathways. However, zebra fish appear to lack some methylation pathways present in mammals, such as parental imprinting. Several studies report effects on DNA methylation in zebra fish following exposure to environmental contaminants, such as arsenic, benzo[a]pyrene, and tris(1,3-dichloro-2-propyl)phosphate. Though more research is needed to examine heritable effects of contaminant exposure on DNA methylation, recent data suggests the usefulness of the zebra fish as a model in environmental epigenetics.

Longitudinal Study of DNA Methylation of Inflammatory Genes and Cancer Risk

BACKGROUND

Chronic inflammation plays a key role in cancer etiology. DNA methylation modification, one of the epigenetic mechanisms regulating gene expression, is considered a hallmark of cancer. Human and animal models have identified numerous links between DNA methylation and inflammatory biomarkers. Our objective was to prospectively and longitudinally examine associations between methylation of four inflammatory genes and cancer risk.

METHODS

We included 795 Normative Aging Study participants with blood drawn one to four times from 1999 to 2012 (median follow-up, 10.6 years). Promoter DNA methylation of IL6, ICAM-1, IFN, and TLR2 in blood leukocytes was measured using pyrosequencing at multiple CpG sites and averaged by gene for data analysis. We used Cox regression models to examine prospective associations of baseline and time-dependent methylation with cancer risk and compared mean methylation differences over time between cancer cases and cancer-free participants.

RESULTS

Baseline IFN hypermethylation was associated with all-cancer (HR, 1.49; P = 0.04) and prostate cancer incidence (HR, 1.69; P = 0.02). Baseline ICAM-1 and IL6 hypermethylation were associated with prostate cancer incidence (HR, 1.43; P = 0.02; HR, 0.70; P = 0.03, respectively). In our time-dependent analyses, IFN hypermethylation was associated with all-cancer (HR, 1.79; P = 0.007) and prostate cancer (HR, 1.57; P = 0.03) incidence; and ICAM-1 and IL6 hypermethylation were associated with prostate cancer incidence (HR, 1.39; P = 0.02; HR, 0.69; P = 0.03, respectively). We detected significant ICAM-1 hypermethylation in cancer cases (P = 0.0003) 10 to 13 years prediagnosis.

CONCLUSION

Hypermethylation of IFN and ICAM-1 may play important roles in early carcinogenesis, particularly that of prostate cancer.

IMPACT

These methylation changes could inform the development of early detection biomarkers and potential treatments of inflammation-related carcinogenesis.

Organophosphate insecticide use and cancer incidence among spouses of pesticide applicators in the Agricultural Health Study

OBJECTIVES

Organophosphates (OPs) are among the most commonly used insecticides. OPs have been linked to cancer risk in some epidemiological studies, which have been largely conducted in predominantly male populations. We evaluated personal use of specific OPs and cancer incidence among female spouses of pesticide applicators in the prospective Agricultural Health Study cohort.

METHODS

At enrolment (1993-1997), spouses provided information about ever use of specific pesticides, including 10 OPs, demographic information, reproductive health history and other potential confounders. We used Poisson regression to estimate relative risks (RRs) and 95% CIs for all cancers diagnosed through 2010 for North Carolina and through 2011 for Iowa.

RESULTS

Among 30,003 women, 25.9% reported OP use, and 718 OP-exposed women were diagnosed with cancer during the follow-up period. Any OP use was associated with an elevated risk of breast cancer (RR=1.20, 95% CI 1.01 to 1.43). Malathion, the most commonly reported OP, was associated with increased risk of thyroid cancer (RR=2.04, 95% CI 1.14 to 3.63) and decreased risk of non-Hodgkin lymphoma (RR=0.64, 95% CI 0.41 to 0.99). Diazinon use was associated with ovarian cancer (RR=1.87, 95% CI 1.02 to 3.43).

CONCLUSIONS

We observed increased risk with OP use for several hormonally-related cancers, including breast, thyroid and ovary, suggesting potential for hormonally-mediated effects. This study represents the first comprehensive analysis of OP use and cancer risk among women, and thus demonstrates a need for further evaluation.

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.

Effects of atrazine and chlorpyrifos on DNA methylation in the liver, kidney and gill of the common carp (Cyprinus carpio L.)

Pesticide exposure has repeatedly been associated with cancers, although the molecular mechanisms behind this association are largely undetermined. Abnormal DNA methylation plays a key role in the process of some disease. However, little was known about the effect of pesticides on DNA methylation in the common carp. In this study, we investigated the mRNA levels of DNA methyltransferases (DNMTs) and methyl-CpG-binding protein DNA-binding domain protein 2 (MBD2) as well as the DNA methylation levels in the liver, kidney and gill of the common carp (Cyprinus carpio L.) after 40-d exposure to atrazine (ATR) and chlorpyrifos (CPF) alone or in combination, and a 40-d recovery period. Juvenile common carp were exposed to various concentrations of ATR (at concentrations of 4.28, 42.8 and 428μg/L), CPF (1.16, 11.6 and 116μg/L), and an ATR/CPF mixture (at concentrations of 1.13, 11.3 and 113μg/L). The results revealed that the levels of genomic DNA methylation decreased in all tissues after 40d of exposure to ATR and CPF either individually or in combination. Moreover, the mRNA expression of DNMTs was down-regulated in all treatment groups. In contrast, the mRNA expression of MBD2 was up-regulated. These results demonstrated that long-term exposure to ATR, CPF and ATR/CPF mixtures could disrupt genomic DNA. It might imply that DNA methylation is involved in the toxicity caused by ATR and CPF in the common carp.

Brain cancer mortality in an agricultural and a metropolitan region of Rio de Janeiro, Brazil: a population-based, age-period-cohort study, 1996-2010

BACKGROUND

Individuals who live in rural areas are at greater risk for brain cancer, and pesticide exposure may contribute to this increased risk. The aims of this research were to analyze the mortality trends and to estimate the age-period-cohort effects on mortality rates from brain cancer in two regions in Rio de Janeiro, Brazil.

METHODS

This descriptive study examined brain cancer mortality patterns in individuals of both sexes, >19 years of age, who died between 1996 and 2010. They were residents of a rural (Serrana) or a non-rural (Metropolitan) area of Rio de Janeiro, Brazil. We estimated mortality trends using Joinpoint Regression analysis. Age-period-cohort models were estimated using Poisson regression analysis.

RESULTS

The estimated annual percentage change in mortality caused by brain cancer was 3.8% in the Serrana Region (95% confidence interval (CI): 0.8-5.6) and -0.2% (95% CI: -1.2-0.7) in the Metropolitan Region. The results indicated that the relative risk was higher in the rural region for the more recent birth cohorts (1954 and later). Compared with the reference birth cohort (1945-49, Serrana Region), the relative risk was four times higher for individuals born between 1985 and 1989.

CONCLUSIONS

The results of this study indicate that there is an increasing trend in brain cancer mortality rates in the rural Serrana Region in Brazil. A cohort effect occurred in the birth cohorts born in this rural area after 1954. At the ecological level, different environmental factors, especially the use of pesticides, may explain regional disparities in the mortality patterns from brain cancers.

A systematic review of neurodevelopmental effects of prenatal and postnatal organophosphate pesticide exposure

Agricultural and residential use of organophosphate (OP) pesticides has increased in recent decades after banning some persistent pesticides. Although there is evidence of the effects of OPs on neurodevelopment and behaviour in adults, limited information is available about their effects in children, who might be more vulnerable to neurotoxic compounds. This paper was aimed at analysing the scientific evidence published to date on potential neurodevelopmental and behavioural effects of prenatal and postnatal exposure to OPs. A systematic review was undertaken to identify original articles published up to December 2012 evaluating prenatal or postnatal exposure to OPs in children and effects on neurodevelopment and/or behaviour. Articles were critically compared, focusing on the methodology used to assess exposure and adverse effects, as well as potential contributing factors that may modify both exposure and outcomes, such as genetic susceptibility to certain enzymes involved in OPs metabolisation (e.g. paraoxonase-1) and gender differences. Twenty articles met the inclusion criteria, 7 of which evaluated prenatal exposure to OPs, 8 postnatal exposure and 5 both pre- and postnatal exposure. Most of the studies evaluating prenatal exposure observed a negative effect on mental development and an increase in attention problems in preschool and school children. The evidence on postnatal exposure is less consistent, although 2 studies found an increase in reaction time in schoolchildren. Some paraoxonase-1 polymorphisms could enhance the association between OPs exposure and mental and psychomotor development. A large variability in epidemiological designs and methodologies used for assessing exposure and outcome was observed across the different studies, which made comparisons difficult. Prenatal and to a lesser extent postnatal exposure to OPs may contribute to neurodevelopmental and behavioural deficits in preschool and school children. Standardised methodologies are needed to allow results to be better compared and to perform a quantitative meta-analysis before drawing any final conclusions.

Hazard-ranking of agricultural pesticides for chronic health effects in Yuma County, Arizona

With thousands of pesticides registered by the United States Environmental Protection Agency, it not feasible to sample for all pesticides applied in agricultural communities. Hazard-ranking pesticides based on use, toxicity, and exposure potential can help prioritize community-specific pesticide hazards. This study applied hazard-ranking schemes for cancer, endocrine disruption, and reproductive/developmental toxicity in Yuma County, Arizona. An existing cancer hazard-ranking scheme was modified, and novel schemes for endocrine disruption and reproductive/developmental toxicity were developed to rank pesticide hazards. The hazard-ranking schemes accounted for pesticide use, toxicity, and exposure potential based on chemical properties of each pesticide. Pesticides were ranked as hazards with respect to each health effect, as well as overall chronic health effects. The highest hazard-ranked pesticides for overall chronic health effects were maneb, metam-sodium, trifluralin, pronamide, and bifenthrin. The relative pesticide rankings were unique for each health effect. The highest hazard-ranked pesticides differed from those most heavily applied, as well as from those previously detected in Yuma homes over a decade ago. The most hazardous pesticides for cancer in Yuma County, Arizona were also different from a previous hazard-ranking applied in California. Hazard-ranking schemes that take into account pesticide use, toxicity, and exposure potential can help prioritize pesticides of greatest health risk in agricultural communities. This study is the first to provide pesticide hazard-rankings for endocrine disruption and reproductive/developmental toxicity based on use, toxicity, and exposure potential. These hazard-ranking schemes can be applied to other agricultural communities for prioritizing community-specific pesticide hazards to target decreasing health risk.