Prenatal exposure to the organophosphate insecticide chlorpyrifos enhances brain oxidative stress and prostaglandin E2 synthesis in a mouse model of idiopathic autism

Prenatal Organophosphate Pesticide Exposure and Traits Related to Autism Spectrum Disorders in a Population Living in Proximity to Agriculture

BACKGROUND

Prenatal exposure to organophosphate (OP) pesticides has been linked with poorer neurodevelopment and behaviors related to autism spectrum disorders (ASD) in previous studies, including in the Center for Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a birth cohort living in the agricultural Salinas Valley in California.

OBJECTIVES

To investigate the association of prenatal exposure to OP pesticides with traits related to ASD, in childhood and adolescents in CHAMACOS.

METHODS

We assessed OP exposure during pregnancy with measurements of dialkyl phosphates (DAP) metabolites in urine, and residential proximity to OP use during pregnancy using California's Pesticide Use Reporting (PUR) data and estimated associations with ASD-related traits using linear regression models. We measured traits reported by parents and teachers as well as the child's performance on tests that evaluate the ability to use facial expressions to recognize the mental state of others at 7, 10¹/₂, and 14 years of age.

RESULTS

Prenatal DAPs were associated with poorer parent and teacher reported social behavior [e.g., a 10-fold DAP increase was associated with a 2.7-point increase (95% confidence interval (CI): 0.9, 4.5) in parent-reported Social Responsiveness Scale, Version 2, T-scores at age 14]. We did not find clear evidence of associations between residential proximity to OP use during pregnancy and ASD-related traits.

CONCLUSIONS

These findings contribute mixed evidence linking OP pesticide exposures with traits related to developmental disorders like ASD. Subtle pesticide-related effects on ASD-related traits among a population with ubiquitous exposure could result in a rise in cases of clinically diagnosed disorders like ASD. https://doi.org/10.1289/EHP2580.

High expression of Endogenous Retroviruses from intrauterine life to adulthood in two mouse models of Autism Spectrum Disorders

Retroelements, such as Human Endogenous Retroviruses (HERVs), have been implicated in many complex diseases, including neurological and neuropsychiatric disorders. Previously, we demonstrated a distinctive expression profile of specific HERV families in peripheral blood mononuclear cells from Autistic Spectrum Disorders (ASD) patients, suggesting their involvement in ASD. Here we used two distinct ASD mouse models: inbred BTBR T+tf/J mice and CD-1 outbred mice prenatally exposed to valproic acid. Whole embryos, blood and brain samples from the offspring were collected at different ages and the expression of several ERV families (ETnI, ETnII-α, ETnII-β, ETnII-γ, MusD and IAP), proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and Toll-like receptors (TLR3 and TLR4) was assessed. In the two distinct mouse models analysed, the transcriptional activity of the ERV families was significant higher in comparison with corresponding controls, in whole embryos, blood and brain samples. Also the expression levels of the proinflammatory cytokines and TLRs were significantly higher than controls. Current results are in agreement with our previous findings in ASD children, supporting the hypothesis that ERVs may serve as biomarkers of atypical brain development. Moreover, the changes in ERVs and proinflammatory cytokines expression could be related with the autistic-like traits acquisition in the two mouse models.

Association of maternal diabetes with autism spectrum disorders in offspring: A systemic review and meta-analysis

Studies on the association of maternal diabetes with autism spectrum disorders (ASDs) in offspring provide inconsistent findings; therefore an updated and comprehensive literature review and meta-analysis is necessary to perform in order to evaluate the available evidences.After searching databases systematically, we established the inclusion criteria and selected the eligible studies. In both overall and stratified analyses, the estimated effects were synthesized dependent on the presence or absence of heterogeneity.Twelve articles involving 16 studies were included and synthesized, demonstrating a significant association of maternal diabetes with ASDs among children (relative risk [RR] = 1.48). However, high heterogeneity was observed (I = 56.3%) and publication bias was identified. In terms of the analyses on reliable evidences from case-control studies, heterogeneity and publication bias disappeared, and the risk of ASDs was increased by 62% among diabetic mothers compared with non-diabetic mothers.Maternal diabetes, especially gestational diabetes mellitus, is associated with ASDs in offspring based on a limited number of convincing case-control studies. More large-scale population-based prospective studies are still needed to draw firm conclusions.

Specific Effects of Chronic Dietary Exposure to Chlorpyrifos on Brain Gene Expression-A Mouse Study

Chlorpyrifos (CPF) is an organophosphate insecticide used to control pests on a variety of food and feed crops. In mammals, maternal exposure to CPF has been reported to induce cerebral cortex thinning, alteration of long-term brain cognitive function, and Parkinson-like symptoms, but the mechanisms of these processes are not fully understood. In this study, we aimed to gain a deeper understanding of the alterations induced in the brains of mice chronically exposed to CPF by dietary intake. For our purpose, we analysed F1 offspring (sacrificed at 3 and 8 months) of Mus musculus, treated in utero and postnatally with 3 different doses of CPF (0.1-1-10 mg/kg/day). Using RT² Profiler PCR Arrays, we evaluated the alterations in the expression of 84 genes associated with neurodegenerative diseases. In the brains of exposed mice, we evidenced a clear dose–response relationship for AChE inhibition and alterations of gene expression. Some of the genes that were steadily down-regulated, such as Pink1, Park 2, Sv2b, Gabbr2, Sept5 and Atxn2, were directly related to Parkinson’s onset. Our experimental results shed light on the possibility that long-term CPF exposure may exert membrane signalling alterations which make brain cells more susceptible to develop neurodegenerative diseases.

Isoprostanes, neuroprostanes and phytoprostanes: An overview of 25years of research in chemistry and biology

Since the beginning of the 1990's diverse types of metabolites originating from polyunsaturated fatty acids, formed under autooxidative conditions were discovered. Known as prostaglandin isomers (or isoprostanoids) originating from arachidonic acid, neuroprostanes from docosahexaenoic acid, and phytoprostanes from α-linolenic acid proved to be prevalent in biology. The syntheses of these compounds by organic chemists and the development of sophisticated mass spectrometry methods has boosted our understanding of the isoprostanoid biology. In recent years, it has become accepted that these molecules not only serve as markers of oxidative damage but also exhibit a wide range of bioactivities. In addition, isoprostanoids have emerged as indicators of oxidative stress in humans and their environment. This review explores in detail the isoprostanoid chemistry and biology that has been achieved in the past three decades.

Involvement of superoxide in malaoxon-induced toxicity in primary cultures of cortical neurons

Organophosphorus compounds (OP) represent a class of insecticides that are used most globally. The neurotoxic effects are attributed mainly to acetylcholinesterase (AChE) enzyme inhibition, which is responsible for cholinergic manifestations in individuals acutely exposed to OP. However, AChE inhibition alone cannot account for the wide range of symptoms that were reported following OP exposures. In agreement with this, evidence shows that non-cholinergic events may be mechanistically linked to OP-induced neurotoxicity. The aim of this study was to investigate the potential occurrence of oxidative stress as a critical step in the toxicity induced by the OP malaoxon(MAL) using primary cultures of mouse cortical neurons, as well as to distinguish MAL-induced oxidative stress and cell toxicity from an action on AChE blockade. Primary cultures of mouse cortical neurons were treated with MAL (0.01; 0.1; 1; 10; or 100 µM) at varying time points (1, 3, 6, 24, 48, or 144 hr) and the following biochemical parameters determined including cell viability, AChE activity, and superoxide production. MAL significantly reduced cell viability in a concentration- and time-dependent manner. Of note, 1 µM MAL significantly inhibited (approximately 75%) AChE activity after 48 hr incubation. Pralidoxime (PRAL) (600 µM), a classical AChE reactivator, significantly protected against MAL-induced AChE blockade; however, PRAL did not affect MAL-mediated fall in cellular viability, indicating that AChE inhibition is not necessarily correlated with insecticide-induced decrease in cell survival. MAL-induced diminished cell viability was preceded by a significant increase in superoxide anion production. The antioxidant agent ascorbic acid (AA) (200 µM), which significantly protected against MAL-induced superoxide anion production, did not alter MAL-induced AChE inhibition and significantly prevented insecticide-mediated fall in cell survival. Data show that increased superoxide anion production is an event that precedes MAL-induced cell toxicity in primary cultures of mouse cortical neurons. Based on the preventative effects of AA against MAL-mediated superoxide anion production and reduced cell viability, evidence indicates that oxidative stress represents an important step mediating MAL-induced toxicity in neurons and that AChE inhibition is not necessarily correlated with lowered cell survival noted in insecticide-exposed cells.

Impaired Redox Control in Autism Spectrum Disorders: Could It Be the X in GxE?

PURPOSE OF REVIEW

This review aims to provide a brief description of the complex etiology of autism spectrum disorders (ASD), with special emphasis on the recent findings of impaired redox control in ASD, and to suggest a possible model of oxidative stress-specific gene-environment interaction in this group of disorders.

RECENT FINDINGS

Recent findings point out to the significance of environmental, prenatal, and perinatal factors in ASD but, at the same time, are in favor of the potentially significant oxidative stress-specific gene-environment interaction in ASD. Available evidence suggests an association between both the identified environmental factors and genetic susceptibility related to the increased risk of ASD and the oxidative stress pathway. There might be a potentially significant specific gene-environment interaction in ASD, which is associated with oxidative stress. Revealing novel susceptibility genes (including those encoding for antioxidant enzymes), or environmental factors that might increase susceptibility to ASD in carriers of a specific genotype, might enable the stratification of individuals more prone to developing ASD and, eventually, the possibility of applying preventive therapeutic actions.

Developmental Neurotoxicity of Traffic-Related Air Pollution: Focus on Autism

PURPOSE OF REVIEW

Epidemiological and animal studies suggest that air pollution may negatively affect the central nervous system (CNS) and contribute to CNS diseases. Traffic-related air pollution is a major contributor to global air pollution, and diesel exhaust (DE) is its most important component.

RECENT FINDINGS

Several studies suggest that young individuals may be particularly susceptible to air pollution-induced neurotoxicity and that perinatal exposure may cause or contribute to developmental disabilities and behavioral abnormalities. In particular, a number of recent studies have found associations between exposures to traffic-related air pollution and autism spectrum disorders (ASD), which are characterized by impairment in socialization and in communication and by the presence of repetitive and unusual behaviors. The cause(s) of ASD are unknown, and while it may have a hereditary component, environmental factors are increasingly suspected as playing a pivotal role in its etiology, particularly in genetically susceptible individuals. Autistic children present higher levels of neuroinflammation and systemic inflammation, which are also hallmarks of exposure to traffic-related air pollution. Gene-environment interactions may play a relevant role in determining individual susceptibility to air pollution developmental neurotoxicity. Given the worldwide presence of elevated air pollution, studies on its effects and mechanisms on the developing brain, genetic susceptibility, role in neurodevelopmental disorders, and possible therapeutic interventions are certainly warranted.

Autism genes are selectively targeted by environmental pollutants including pesticides, heavy metals, bisphenol A, phthalates and many others in food, cosmetics or household products

The increasing incidence of autism suggests a major environmental influence. Epidemiology has implicated many candidates and genetics many susceptibility genes. Gene/environment interactions in autism were analysed using 206 autism susceptibility genes (ASG's) from the Autworks database to interrogate ∼1 million chemical/gene interactions in the comparative toxicogenomics database. Any bias towards ASG's was statistically determined for each chemical. Many suspect compounds identified in epidemiology, including tetrachlorodibenzodioxin, pesticides, particulate matter, benzo(a)pyrene, heavy metals, valproate, acetaminophen, SSRI's, cocaine, bisphenol A, phthalates, polyhalogenated biphenyls, flame retardants, diesel constituents, terbutaline and oxytocin, inter alia showed a significant degree of bias towards ASG's, as did relevant endogenous agents (retinoids, sex steroids, thyroxine, melatonin, folate, dopamine, serotonin). Numerous other suspected endocrine disruptors (over 100) selectively targeted ASG's including paraquat, atrazine and other pesticides not yet studied in autism and many compounds used in food, cosmetics or household products, including tretinoin, soy phytoestrogens, aspartame, titanium dioxide and sodium fluoride. Autism polymorphisms influence the sensitivity to some of these chemicals and these same genes play an important role in barrier function and control of respiratory cilia sweeping particulate matter from the airways. Pesticides, heavy metals and pollutants also disrupt barrier and/or ciliary function, which is regulated by sex steroids and by bitter/sweet taste receptors. Further epidemiological studies and neurodevelopmental and behavioural research is warranted to determine the relevance of large number of suspect candidates whose addition to the environment, household, food and cosmetics might be fuelling the autism epidemic in a gene-dependent manner.