Potential effects of chlorpyrifos on fetal growth outcomes: implications for risk assessment

Evaluation of developmental toxicity of chlorpyrifos through new approach methodologies: a systematic review

Chlorpyrifos (CPF) is an organophosphorus pesticide of concern because many in vivo animal studies have demonstrated developmental toxicity exerted by this substance; however, despite its widespread use, evidence from epidemiological studies is still limited. In this study, we have collected all the information generated in the twenty-first century on the developmental toxicity of CPF using new approach methodologies. We have critically evaluated and integrated information coming from 70 papers considering human, rodent, avian and fish models. The comparison of the collected evidence with available adverse outcome pathways allows us to conclude that adverse outcomes observed in animals, such as memory and learning impairments as well as reduction in cognitive function, could involve several mechanisms of action including inhibition of acetylcholinesterase, overactivation of glutamate receptors and activation of mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2, followed by both disruption of neurotransmitter release and increase in oxidative stress and apoptosis.

Analysis of Chlorpyrifos Pesticide Residue in Locally Grown Cauliflower, Cabbage, and Eggplant Using Gas Chromatography-Mass Spectrometry (GC-MS) Technique: A Bangladesh Perspective

Pesticides are chemical substances used to kill or control various types of pests, which are hazardous for crops and animals. Pesticides may remain on or in foods after these are applied to crops. Pesticide residue in food has been a major global concern since there are direct and indirect health hazards associated with the regular consumption of foods with pesticide residues. Chlorpyrifos is one of the most used pesticides that has received much attention worldwide due to its detrimental health impact. The presence of chlorpyrifos residue in food crops can have both long-term and short-term effects on consumer health. Bangladesh is an agricultural country that uses a high volume of pesticides every year including chlorpyrifos. This experimental study aimed to analyze chlorpyrifos pesticide residue in locally grown cauliflower, cabbage, and eggplant samples by gas chromatography-mass spectrometry (GC-MS) technique followed by a suitable extraction process. Commercially available cauliflower, cabbage, and eggplant samples along with samples cultivated with the recommended pesticide dose were collected for qualitative and quantitative analysis. Samples cultivated without chlorpyrifos were collected as control samples for the validation study. The method was validated with respect to accuracy, recovery, reproducibility, linearity, limit of detection, and limit of quantification. The method has a limit of detection (LOD) of 0.011 mg/kg and a limit of quantification (LOQ) of 0.034 mg/kg. The experimental results were compared to the maximum residue level (MRL) to assess the human health impact. Chlorpyrifos residue was found in 44% of cauliflower samples with 91% of samples higher than MRL. The residue was found in 68% of cabbage samples with 53% of samples higher than MRL. For eggplant, the residue was found in 80% of the samples with 65% of samples higher than MRL. The risk assessment based on the residue level found in this study shows a potential health hazard of having a high concentration of chlorpyrifos residue in locally grown vegetables.

Metabolome-wide association study of the relationship between chlorpyrifos exposure and first trimester serum metabolite levels in pregnant Thai farmworkers

INTRODUCTION

Organophosphate (OP) insecticides, including chlorpyrifos, have been linked with numerous harmful health effects on maternal and child health. Limited data are available on the biological mechanisms and endogenous pathways underlying the toxicity of chlorpyrifos exposures on pregnancy and birth outcomes. In this study, we measured a urinary chlorpyrifos metabolite and used high-resolution metabolomics (HRM) to identify biological perturbations associated with chlorpyrifos exposure among pregnant women in Thailand, who are disparately exposed to high levels of OP insecticides.

METHODS

This study included 50 participants from the Study of Asian Women and their Offspring's Development and Environmental Exposures (SAWASDEE). We used liquid chromatography-high resolution mass spectrometry to conduct metabolic profiling on first trimester serum samples collected from participants to evaluate metabolic perturbations in relation to chlorpyrifos exposures. We measured 3,5,6-trichloro-2-pyridinol (TCPy), a specific metabolite of chlorpyrifos and chlorpyrifos-methyl, in first trimester urine samples to assess the levels of exposures. Following an untargeted metabolome-wide association study workflow, we used generalized linear models, pathway enrichment analyses, and chemical annotation to identify significant metabolites and pathways associated with urinary TCPy levels.

RESULTS

In the 50 SAWASDEE participants, the median urinary TCPy level was 4.36 μg TCPy/g creatinine. In total, 691 unique metabolic features were found significantly associated with TCPy levels (p < 0.05) after controlling for confounding factors. Pathway analysis of metabolic features associated with TCPy indicated perturbations in 24 metabolic pathways, most closely linked to the production of reactive oxygen species and cellular damage. These pathways include tryptophan metabolism, fatty acid oxidation and peroxisome metabolism, cytochromes P450 metabolism, glutathione metabolism, and vitamin B3 metabolism. We confirmed the chemical identities of 25 metabolites associated with TCPy levels, including glutathione, cystine, arachidic acid, itaconate, and nicotinamide adenine dinucleotide.

DISCUSSION

The metabolic perturbations associated with TCPy levels were related to oxidative stress, cellular damage and repair, and systemic inflammation, which could ultimately contribute to health outcomes, including neurodevelopmental deficits in the child. These findings support the future development of sensitive biomarkers to investigate the metabolic underpinnings related to pesticide exposure during pregnancy and to understand its link to adverse outcomes in children.

The association between organophosphate insecticides and blood pressure dysregulation: NHANES 2013-2014

BACKGROUND

Organophosphate (OP) insecticides represent one of the largest classes of sprayed insecticides in the U.S., and their use has been associated with various adverse health outcomes, including disorders of blood pressure regulation such as hypertension (HTN).

METHODS

In a study of 935 adults from the NHANES 2013-2014 cycle, we examined the relationship between systolic and diastolic blood pressure changes and urinary concentrations of three OP insecticides metabolites, including 3,5,6-trichloro-2-pyridinol (TCPy), oxypyrimidine, and para-nitrophenol. These metabolites correspond to the parent compounds chlorpyrifos, diazinon, and methyl parathion, respectively. Weighted, multivariable linear regression analysis while adjusting for potential confounders were used to model the relationship between OP metabolites and blood pressure. Weighted, multivariable logistic regression analysis was used to model the odds of HTN for quartile of metabolites.

RESULTS

We observed significant, inverse association between TCPy on systolic blood pressure (β-estimate = -0.16, p < 0.001) and diastolic blood pressure (β-estimate = -0.15, p < 0.001). Analysis with para-nitrophenol revealed a significant, positive association with systolic blood pressure (β-estimate = 0.03, p = 0.02), and an inverse association with diastolic blood pressure (β-estimate = -0.09, p < 0.001). For oxypyrimidine, we observed significant, positive associations between systolic blood pressure (β-estimate = 0.58, p = 0.03) and diastolic blood pressure (β-estimate = 0.31, p < 0.001). Furthermore, we observed significant interactions between TCPy and ethnicity on systolic blood pressure (β-estimate = 1.46, p = 0.0036). Significant interaction terms were observed between oxypyrimidine and ethnicity (β-estimate = -1.73, p < 0.001), as well as oxypyrimidine and BMI (β-estimate = 1.51 p < 0.001) on systolic blood pressure, and between oxypyrimidine and age (β-estimate = 1.96, p = 0.02), race (β-estimate = -3.81 p = 0.004), and BMI on diastolic blood pressure (β-estimate = 0.72, p = 0.02). A significant interaction was observed between para-nitrophenol and BMI for systolic blood pressure (β-estimate = 0.43, p = 0.01), and between para-nitrophenol and ethnicity on diastolic blood pressure (β-estimate = 2.19, p = 0.006). Lastly, we observed a significant association between the odds of HTN and TCPy quartiles (OR = 0.65, 95% CI [0.43,0.99]).

CONCLUSION

Our findings support previous studies suggesting a role for organophosphate insecticides in the etiology of blood pressure dysregulation and HTN. Future studies are warranted to corroborate these findings, evaluate dose-response relationships between organophosphate insecticides and blood pressure, determine clinical significance, and elucidate biological mechanisms underlying this association.

Health risk assessment of exposure to chlorpyrifos in pregnant women using deterministic and probabilistic approaches

Since chlorpyrifos (CPF), a major organophosphorus pesticide, is widely used for agricultural and domestic purposes, thus, humans may be exposed to these toxic compounds through multiple sources. In recent years, significant concerns have been raised regarding the deleterious effects of exposure to CPF on human health, especially growing fetus. Therefore, in this study, we aimed to evaluate the health risks of exposure to CPF among pregnant women living in Isfahan province, Iran, using deterministic and probabilistic approaches. The urinary concentration of 3, 5, 6-trichloro-2-pyridinol (TCP), the most common metabolite of CPF, was measured as the biomarker of current exposure to CPF. For this purpose, spot urine samples were taken from 110 pregnant women and the urinary concentrations of TCP were quantified. The estimated daily intake and hazard quotient (HQ) for CPF exposure were measured according to the reference values set by World Health Organization (WHO) and United States Environmental Protection Agency (US EPA) for acute and chronic exposure to CPF. Based on the results, TCP was detected in more than 70% of samples (3.8 ± 2.72 μg/L). The estimated daily intake for some participants was found to be higher than the suggested reference dose by USEPA for chronic exposure to CPF. Furthermore, the HQ>1 was obtained for 20% of the study population in Monte-Carlo analysis using USEPA chronic reference dose, indicating that chronic toxic effects are expected at least for a part of the target population. Based on the findings, proper measures should be taken to reduce the exposure of Iranian pregnant women to CPF and resultant health risks.

Prenatal exposure to organophosphate and pyrethroid insecticides and the herbicide 2,4-dichlorophenoxyacetic acid and size at birth in urban pregnant women

BACKGROUND

Organophosphate insecticides and the herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D) are used to protect crops or control weeds. Pyrethroids are used to manage pests both in agriculture and in residences, and to reduce the transmission of insect-borne diseases. Several studies have reported inverse associations between exposure to organophosphates (as a larger class) and birth outcomes but these associations have not been conclusive for pyrethroids or 2,4-D, specifically. We aimed to investigate the association between birth outcomes and urinary biomarkers of pyrethroids, organophosphates and 2,4-D among healthy pregnant women living in New York City.

METHODS

We quantified urinary biomarkers of 2,4-D and of organophosphate and pyrethroid insecticides from 269 women from two cohorts: a) Thyroid Disruption And Infant Development (TDID) and b) Sibling/Hermanos cohort (S/H). We used weighted quantile sum regression and multivariable linear regression models to evaluate the associations between a mixture of urinary creatinine-adjusted biomarker concentrations and birth outcomes of length, birthweight and head circumference, controlling for covariates. We also used linear regression models and further classified biomarkers concentrations into three categories (i: non-detectable; ii: between the limit of detection and median; and iii: above the median) to investigate single pesticides' association with these birth outcomes. Covariates considered were delivery mode, ethnicity, marital status, education, income, employment status, gestational age, maternal age and pre-pregnancy BMI. Analyses were conducted separately for each cohort and stratified by child sex within each cohort.

RESULTS

In TDID cohort, we found a significant inverse association between weighted quantile sum of mixture of pesticides and head circumference among boys. We found that the urinary biomarkers of organophosphate chlorpyrifos, TCPy, and 2,4-D had the largest contribution to the overall mixture effect in the TDID cohort among boys (b = -0.57, 95%CI: -0.92, -0.22) (weights = 0.81 and 0.16 respectively) but not among girls. In the multivariable linear regression models, we found that among boys, for each log unit increase in 3,5,6-trichloro-2-pyridinol (TCPy, metabolite of organophosphate chlorpyrifos) in maternal urine, there was a -0.56 cm decrease in head circumference (95%CI: -0.92, -0.19). Among boys in the TDID cohort, 2,4-D was associated with smaller head circumference in the second (b = -1.57; 95%CI: -2.74, -0.39) and third (b = -1.74, 95%CI: -2.98, -0.49) concentration categories compared to the first. No associations between pyrethroid and organophosphate biomarkers and birth outcomes were observed in girls analyzed in WQS regression or individually in linear regression models in TDID cohort. In the S/H cohort, head circumference increased with higher concentrations of 3-phenoxybenzoic acid (3-PBA, a biomarker of several pyrethroids) (b = 0.53, 95%CI: 0.03, 1.04) among boys and head circumference was lower among girls in the high compared to low category of 2,4-D (b = -2.27, 95%CI: - 3.98, -0.56). Birth length was also positively associated with the highest concentration of 2,4-D compared to the lowest among boys (b = 4.01, 95%CI: 0.02,8.00).

CONCLUSIONS

Weighted quantile sum of pesticides was negatively associated with head circumference among boys in one cohort. Nonetheless, due to directional homogeneity assumption in WQS no positive associations were detected. In linear regression models with individual pesticides, concentrations of TCPy were inversely associated with head circumference in boys and higher concentrations of 2,4-D was inversely associated with head circumference among girls; 2,4-D concentrations were also associated with higher birth length among boys. Concentrations of 3-PBA was positively associated with head circumference among boys.

Protective effects of curcumin and Ganoderma lucidum on hippocampal damage caused by the organophosphate insecticide chlorpyrifos in the developing rat brain: Stereological, histopathological and immunohistochemical study

The aim of this study is to draw attention to the possible effects of chlorpyrifos exposure on the developing rat hippocampus in the prenatal period and to determine whether these effects can be reduced with various antioxidant substances. Pregnant rats were divided into 7 groups.; Chlorpyrifos (CPF), Curcumin (CUR), Ganoderma lucidum (GNL), Chlorpyrifos + Curcumin (CPF + CUR), Chlorpyrifos + Ganoderma lucidum, (CPF + GNL), SHAM and Control (C). After the experiments, brain tissues were evaluated by stereological and immunohistochemical methods. As a result of the stereological analyzes, it was determined that the number of pyramidal neurons in the hippocampus of the CPF group decreased significantly from all other groups. In contrast, the number of neurons in the CPF + CUR and CPF + GNL groups was significantly higher than the CPF group. In addition, immunohistochemical analyzes showed that the density of cells stained with glial fibrillar acidic protein (GFAP) positive in all areas in the hippocampus of the rats in the CPF group was significantly higher compared to the control group, whereas in the CPF + CUR and CPF + GNL groups were less than the CPF group. As a result, the exposure of CPF in the prenatal period caused neurotoxicity in the brain hippocampus, whereas CUR and GNL reduced this toxicity caused by CPF.

Genome-wide analysis of DNA methylation in testis of male rat exposed to chlorpyrifos

In our previous study, we found that subchronic exposure of chlorpyrifos (CPF) can cause reproductive damage in male rats. However, the mechanisms underlying the reproductive effects of CPF are not well understood. DNA methylation is essential for epigenetic gene regulation in development and disease. Therefore, we aim to compare DNA methylation profiles between controls and CPF-treated rats in order to identify the epigenetic mechanism of male reproductive toxicity induced by CPF. Methylated DNA immunoprecipitation with high-throughput sequencing (MeDIP-seq) was used to investigate the genome-wide DNA methylation pattern in testes of control and CPF-treated rats for 90 days. We identified 27 019 differentially methylated regions (DMRs) (14 150 upmethylated and 12 869 downmethylated) between CPF-exposed and control groups. The DMR-related genes are mainly involved in 113 pathways predicted by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The result showed that high methylation gene PIK3CD may play a key role in epigenetic regulation of multiple pathways, such as Ras signaling pathway, AGE-RAGE signaling pathway in diabetic complications, HIF-1 signaling pathway, VEGF signaling pathway, and glioma and Fc epsilon RI signaling pathway in rats exposed to CPF. Our study provides significant explanations for the epigenetic mechanism of male reproductive toxicology induced by CPF.

Associations of prenatal and childhood chlorpyrifos exposure with Neurodevelopment of 3-year-old children

Chlorpyrifos (CPF), an organophosphate insecticide, has been linked to adverse neurodevelopmental effects in animal studies. However, little is known about long-term neurotoxicity of early-life CPF exposure in humans. We aimed to evaluate the associations of both prenatal and early childhood CPF exposure with neurodevelopment of children. In this observational study based on Sheyang Mini Birth Cohort, pregnant women were recruited from an agricultural region between June 2009 and January 2010, and their children were followed up from birth to age three. Urinary 3,5,6-Trichloro-2-pyridinol (TCPy), a specific metabolite of CPF, was quantified using large-volume-injection gas chromatography-tandem mass spectrometry. Developmental quotients (DQs) of children in motor, adaptive, language, and social areas were assessed by trained pediatricians. Data from 377 mother-child pairs were used in the current study. Associations between CPF exposure and neurodevelopmental indicators were estimated using generalized linear models with adjustment for potential confounders. The median concentrations of TCPy in maternal and children's urine were 5.39 μg/L and 5.34 μg/L, respectively. No statistically significant association was found between maternal urinary TCPy concentrations and children neurodevelopment. While for postnatal exposure, we found lower motor area DQ score 0.61 [95% confidence interval (CI): -1.13, -0.09; p = 0.02] and social area DQ score 0.55 (95% CI: -1.07, -0.03; p = 0.04) per one-unit increase in the ln-transformed childhood urinary TCPy concentrations. Further stratification by sex indicated that the inverse associations were only observed in boys, but not in girls. Our findings suggest that adverse neurodevelopmental effects were associated with early childhood CPF exposure, but not prenatal exposure. Additional longitudinal studies are needed to replicate these results and to further understand the toxicological mechanisms of CPF.

Impaired innate and conditioned social behavior in adult C57Bl6/J mice prenatally exposed to chlorpyrifos

Background

Signs of pervasive developmental disorder and social deficits were reported in toddlers and children whose mothers were exposed to organophosphate pesticides during pregnancy. Deficits in social preference were reported in adult male mice exposed to chlorpyrifos on gestational days 12–15. This study aimed (a) to test the hypothesis that adult female and male mice that were exposed prenatally to subtoxic doses of chlorpyrifos would be impaired in social behavior and (b) to determine if prenatal chlorpyrifos altered the expression of transcripts for oxytocin in the hypothalamus. Pregnant mice were treated by gavage with corn oil vehicle or 2.5 mg/kg or 5 mg/kg of CPF on gestational days 12–15. Social preference, social and non-social conditioned place preference tasks were tested in adults. Expression of oxytocin transcripts in hypothalamus was measured by qPCR.

Results

Chlorpyrifos (5 mg/kg on GD 12–15) reduced the innate preference for a conspecific in a dose and sex dependent manner. Adult males exposed prenatally to 5 mg/kg CPF showed a reduction in social preference. Socially conditioned place preference was impaired in offspring of dams treated with either dose of CPF. Non-social appetitive place conditioning was impaired in offspring of dams exposed to 2.5 mg/kg, but not to 5 mg/kg chlorpyrifos. Prenatal chlorpyrifos treatment did not alter the expression of the oxytocin mRNA in the hypothalamus, although expression was significantly lower in females.

Conclusions

Prenatal chlorpyrifos induced innate and learned social deficits and non-specific conditioning deficits in adult mice in a sex-dependent manner. Males showed specific social deficits following the higher dose whereas both males and females showed a more generalized conditioning deficit following the intermediate dose.

Effects of Chlorpyrifos or Methyl Parathion on Regional Cholinesterase Activity and Muscarinic Receptor Subtype Binding in Juvenile Rat Brain

The effects of developmental exposure to two organophosphorus (OP) insecticides, chlorpyrifos (CPF) and methyl parathion (MPS), on cholinesterase (ChE) activity and muscarinic acetylcholine receptor (mAChR) binding were investigated in preweanling rat brain. Animals were orally gavaged daily with low, medium, and high dosages of the insecticides using an incremental dosing regimen from postnatal day 1 (PND1) to PND20. On PND12, PND17 and PND20, the cerebral cortex, corpus striatum, hippocampus, and medulla-pons were collected for determination of ChE activity, total mAChR density, and the density of the individual mAChR subtypes. ChE activity was inhibited by the medium and high dosages of CPF and MPS at equal levels in all four brain regions at all three ages examined. Exposure to both compounds decreased the levels of the M1, M2/M4, and M3 subtypes and the total mAChR level in all brain regions, but the effects varied by dosage group and brain region. On PND12, only the high dosages induced receptor changes while on PND17 and PND20, greater effects became evident. In general, the effects on the M1 subtype and total receptor levels appeared to be greater in the cerebral cortex and hippocampus than in the corpus striatum and medulla-pons. This did not appear to be the case for the M2/M4 and M3 subtypes effects. The differences between CPF and MPS were minimal even though in some cases, CPF exerted statistically greater effects than MPS did. In general, repeated exposure to organophosphorus insecticides can alter the levels of the various mAChR subtypes in various brain regions which could induce perturbation in cholinergic neurochemistry during the maturation of the brain regions.

Naturally Occurring Genetic Variants of Human Acetylcholinesterase and Butyrylcholinesterase and Their Potential Impact on the Risk of Toxicity from Cholinesterase Inhibitors

Acetylcholinesterase (AChE) is the physiologically important target for organophosphorus toxicants (OP) including nerve agents and pesticides. Butyrylcholinesterase (BChE) in blood serves as a bioscavenger that protects AChE in nerve synapses from inhibition by OP. Mass spectrometry methods can detect exposure to OP by measuring adducts on the active site serine of plasma BChE. Genetic variants of human AChE and BChE do exist, but loss of function mutations have been identified only in the BCHE gene. The most common AChE variant, His353Asn (H322N), also known as the Yt blood group antigen, has normal AChE activity. The most common BChE variant, Ala567Thr (A539T) or the K-variant in honor of Werner Kalow, has 33% reduced plasma BChE activity. The genetic variant most frequently associated with prolonged response to muscle relaxants, Asp98Gly (D70G) or atypical BChE, has reduced activity and reduced enzyme concentration. Early studies in young, healthy males, performed at a time when it was legal to test nerve agents in humans, showed that individuals responded differently to the same low dose of sarin with toxic symptoms ranging in severity from minimal to moderate. Additionally, animal studies indicated that BChE protects from toxicants that have a higher reactivity with AChE than with BChE (e.g., nerve agents) but not from toxicants that have a higher reactivity with BChE than with AChE (e.g., OP pesticides). As a corollary, we hypothesize that individuals with genetic variants of BChE may be at increased risk of toxicity from nerve agents but not from OP pesticides.

Effects of mipafox, paraoxon, chlorpyrifos and its metabolite chlorpyrifos-oxon on the expression of biomarker genes of differentiation in D3 mouse embryonic stem cells

Chlorpyrifos (CPS) is an organophosphorus compound (OP) capable of causing well-known cholinergic and delayed syndromes through the inhibition of acetylcholinesterase and Neuropathy Target Esterase (NTE), respectively. CPS is also able to induce neurodevelopmental toxicity in animals. NTE is codified by the Pnpla6 gene and plays a central role in differentiation and neurodifferentiation. We tested, in D3 mouse embryonic stem cells under differentiation, the effects of the NTE inhibition by the OPs mipafox, CPS and its main active metabolite chlorpyrifos-oxon (CPO) on the expression of genes Vegfa, Bcl2, Amot, Nes and Jun, previously reported to be under- or overexpressed after Pnpla6 silencing in this same cellular model. Mipafox did not significantly alter the expression of such genes at concentrations that significantly inhibited NTE. However, CPS and CPO at concentrations that caused NTE inhibition at similar levels to mipafox statistically and significantly altered the expression of most of these genes. Paraoxon (another OP with capability to inhibit esterases but not NTE) caused similar effects to CPS and CPO. These findings suggest that the molecular mechanism for the neurodevelopmental toxicity induced by CPS is not based on NTE inhibition, and that other unknown esterases might be potential targets of neurodevelopmental toxicity.

Prenatal exposure to persistent organic pollutants and organophosphate pesticides, and markers of glucose metabolism at birth

BACKGROUND

Experimental evidence suggests that developmental exposure to persistent organic pollutants (POP) and to some non persistent pesticides may disrupt metabolic regulation of glucose metabolism and insulin secretion, and thereby contribute to the current epidemic of obesity and metabolic disorders. Quasi-experimental situations of undernutrition in utero have provided some information. However, the evidence in humans concerning the role of the prenatal environment in these disorders is contradictory, and little is known about long-term outcomes, such as type 2 diabetes, of prenatal exposure.

OBJECTIVES

Our aim was to evaluate the effects of prenatal exposure to POP and organophosphate pesticides on fetal markers of glucose metabolism in a sample of newborns from the Pelagie mother-child cohort in Brittany (France).

METHODS

Dialkylphosphate (DAP) metabolites of organophosphate pesticides were measured in maternal urine collected at the beginning of pregnancy. Cord blood was assayed for polychlorinated biphenyl congener 153 (PCB153), p,p'-dichlorodiphenyl dichloroethene (DDE) and other POP. Insulin and adiponectin were determined in cord blood serum (n=268).

RESULTS

A decrease in adiponectin and insulin levels was observed with increasing levels of DDE, but only in girls and not boys. Adiponectin levels were not related to the concentrations of other POP or DAP metabolites. Decreasing insulin levels were observed with increasing PCB153 concentrations. Insulin levels increased with DAP urinary levels. Additional adjustment for BMI z-score at birth modified some of these relations.

CONCLUSIONS

Our observations bring support for a potential role of organophosphate pesticides and POP in alterations to glucose metabolism observable at birth.

Disruption of iron homeostasis and resultant health effects upon exposure to various environmental pollutants: A critical review

Environmental pollution has become one of the greatest problems in the world, and the concerns about environmental pollutants released by human activities from agriculture and industrial production have been continuously increasing. Although intense efforts have been made to understand the health effects of environmental pollutants, most studies have only focused on direct toxic effects and failed to simultaneously evaluate the long-term adaptive, compensatory and secondary impacts on health. Burgeoning evidence suggests that environmental pollutants may directly or indirectly give rise to disordered element homeostasis, such as for iron. It is crucially important to maintain concerted cellular and systemic iron metabolism. Otherwise, disordered iron metabolism would lead to cytotoxicity and increased risk for various diseases, including cancers. Thus, study on the effects of environmental pollutants upon iron homeostasis is urgently needed. In this review, we recapitulate the available findings on the direct or indirect impacts of environmental pollutants, including persistent organic pollutants (POPs), heavy metals and pesticides, on iron homeostasis and associated adverse health problems. In view of the unanswered questions, more efforts are warranted to investigate the disruptive effects of environmental pollutants on iron homeostasis and consequent toxicities.

Chlorpyrifos Induces MLL Translocations Through Caspase 3-Dependent Genomic Instability and Topoisomerase II Inhibition in Human Fetal Liver Hematopoietic Stem Cells

Household pesticide exposure during pregnancy has been associated with a more than 2-fold increased risk in infant leukemia, and chlorpyrifos (CPF) is among the most frequently applied insecticides. During early fetal development, liver is a hematopoietic organ with majority of cells being CD34(+) hematopoietic stem cells (CD34(+)HSC). The in utero injury to CD34(+)HSC has been known to underlie the pathogenesis of several blood disorders, often involving rearrangements of the mixed-lineage leukemia (MLL) gene on 11q23. In this study, we evaluated the leukemogenic potential of CPF in human fetal liver-derived CD34(+)HSC. Specifically, exposure to 10 μM CPF led to decrease in viability, inhibition in proliferation and induction of DNA double-strand breaks (DSBs) and occurrence of MLL(+) rearrangements. In particular, we observed CPF-mediated cell cycle disturbance as shown by G0/G1 arrest, in contrast to etoposide (VP-16), an anticancer drug used as a positive control and known to induce G2/M arrest. Further study on mechanisms underlying DNA DSBs and MLL(+) rearrangements revealed that CPF might act as topoisomerase II poison, a mechanism of action similar to VP-16. On the other hand, CPF was also shown to induce early apoptosis through active caspase-3 activation, a pathway known to underlie DNA DSBs and MLL(+) translocations. Our data indicate that in utero injury of CD34(+)HSC by CPF may contribute to the increased risk of infant leukemia. Future work will elucidate the mechanism and the type of CPF-induced MLL(+) translocations in HSC.

Chlorpyrifos Exposure During Perinatal Period Affects Intestinal Microbiota Associated With Delay of Maturation of Digestive Tract in Rats

OBJECTIVES

Pesticide exposure via residues in food may be especially harmful when it takes place in the developing child. The present study was designed to assess the impact of perinatal exposure to chlorpyrifos (CPF, an insecticide known to cross the placental barrier).

METHODS

Female rats were exposed to oral CPF (1 or 5 mg kg day vs vehicle controls) from gestation onset up to weaning of the pups that were individually gavaged (CPF or vehicle) thereafter. Two developmental time points were studied: weaning (day 21) and adulthood (day 60). After sacrifice, samples from the intestinal tract and other organs underwent microbiological and histological analyses.

RESULTS

Rat pups exposed to 5 mg kg day CPF were both significantly smaller (body length) and lighter than controls. Exposure to CPF was associated with changes in the histological structures (shorter and thinner intestinal villosities), an intestinal microbial dysbiosis, and increased bacterial translocation in the spleen and liver. These significant microbial changes in the gut were associated with impaired epithelium protection (mucin-2) and microbial pattern recognition receptor (Toll-like 2 and 4) gene expression.

CONCLUSIONS

Exposure to CPF during gestation and development affected the pups' intestinal development, with morphological alteration of the structures involved in nutrient absorption, intestinal microbial dysbiosis, alteration of mucosal barrier (mucin-2), stimulation of the innate immune system, and increased bacterial translocation. Perinatal exposure to CPF may therefore have short- and long-term impacts on the digestive tract.

Organophosphorus pesticide chlorpyrifos and its metabolites alter the expression of biomarker genes of differentiation in D3 mouse embryonic stem cells in a comparable way to other model neurodevelopmental toxicants

There are discrepancies about whether chlorpyrifos is able to induce neurodevelopmental toxicity or not. We previously reported alterations in the pattern of expression of biomarker genes of differentiation in D3 mouse embryonic stem cells caused by chlorpyrifos and its metabolites chlorpyrifos-oxon and 3,5,6-trichloro-2-pyridinol. Now, we reanalyze these data comparing the effects on these genes with those caused in the same genes by retinoic acid, valproic acid, and penicillin-G (model compounds considered as strong, weak, and non-neurodevelopmental toxicants, respectively). We also compare the effects of chlorpyrifos and its metabolites on the cell viability of D3 cells and 3T3 mouse fibroblasts with the effects caused in the same cells by the three model compounds. We conclude that chlorpyrifos and its metabolites act, regarding these end-points, as the weak neurodevelopmental toxicant valproic acid, and consequently, a principle of caution should be applied avoiding occupational exposures in pregnant women. A second independent experiment run with different cellular batches coming from the same clone obtained the same result as the first one.

Placental oxidative status in rural residents environmentally exposed to organophosphates

The impact of environmental organophosphate pesticide exposure on the placenta oxidative status was assessed. Placental samples were collected from women residing in an agricultural area during pesticide pulverization period, non-pulverization period and from control group. Carboxylesterase activity was significantly decreased in pulverization period group. Enzymatic and non-enzymatic defense system, the oxidative stress biomarkers and the nuclear factor erythroid 2-related factor levels showed no differences among groups. However, in the pulverization period group, an inverse association between catalase activity and placental index, a useful metric for estimating placental inefficiency, was found. This result suggests that catalase may serve as a potential placental biomarker of susceptibility to pesticides. Further studies designed from a gene-environment perspective are needed.

Pesticide exposure and neurodevelopmental outcomes: review of the epidemiologic and animal studies

Assessment of whether pesticide exposure is associated with neurodevelopmental outcomes in children can best be addressed with a systematic review of both the human and animal peer-reviewed literature. This review analyzed epidemiologic studies testing the hypothesis that exposure to pesticides during pregnancy and/or early childhood is associated with neurodevelopmental outcomes in children. Studies that directly queried pesticide exposure (e.g., via questionnaire or interview) or measured pesticide or metabolite levels in biological specimens from study participants (e.g., blood, urine, etc.) or their immediate environment (e.g., personal air monitoring, home dust samples, etc.) were eligible for inclusion. Consistency, strength of association, and dose response were key elements of the framework utilized for evaluating epidemiologic studies. As a whole, the epidemiologic studies did not strongly implicate any particular pesticide as being causally related to adverse neurodevelopmental outcomes in infants and children. A few associations were unique for a health outcome and specific pesticide, and alternative hypotheses could not be ruled out. Our survey of the in vivo peer-reviewed published mammalian literature focused on effects of the specific active ingredient of pesticides on functional neurodevelopmental endpoints (i.e., behavior, neuropharmacology and neuropathology). In most cases, effects were noted at dose levels within the same order of magnitude or higher compared to the point of departure used for chronic risk assessments in the United States. Thus, although the published animal studies may have characterized potential neurodevelopmental outcomes using endpoints not required by guideline studies, the effects were generally observed at or above effect levels measured in repeated-dose toxicology studies submitted to the U.S. Environmental Protection Agency (EPA). Suggestions for improved exposure assessment in epidemiology studies and more effective and tiered approaches in animal testing are discussed.

Chlorpyrifos and its metabolites alter gene expression at non-cytotoxic concentrations in D3 mouse embryonic stem cells under in vitro differentiation: considerations for embryotoxic risk assessment

The effects of organophosphate insecticide chlorpyrifos (CPF) on development are currently under discussion. CPF and its metabolites, chlorpyrifos-oxon (CPO) and 3,5,6-trichloro-2-pyridinol (TClP), were more cytotoxic for D3 mouse embryonic stem cells than for differentiated fibroblasts 3T3 cells. Exposure to 10 μM CPF and TClP and 100 μM CPO for 12 h significantly altered the in vitro expression of biomarkers of differentiation in D3 cells. Similarly, exposure to 20 μM CPF and 25 μM CPO and TClP for 3 days also altered the expression of the biomarkers in the same model. These exposures caused no significant reduction in D3 viability with mild inhibition of acetylcholinesterase and neuropathy target esterase by CPF and severe inhibition by CPO. We conclude that certain in vivo exposure scenarios are possible, which cause inhibition of acetylcholinesterase but without clinical symptoms that reach high enough systemic CPF concentrations able to alter the expression of genes involved in cellular differentiation with potentially hazard effects on development. Conversely, the risk for embryotoxicity by CPO and TClP was very low because the required exposure would induce severe cholinergic syndrome.