Medium and long-term effects of low doses of Chlorpyrifos during the postnatal, preweaning developmental stage on sociability, dominance, gut microbiota and plasma metabolites

Exploring microbiota-gut-brain axis biomarkers linked to autism spectrum disorder in prenatally chlorpyrifos-exposed Fmr1 knock-out and wild-type male rats

Fmr1 (fragile X messenger ribonucleoprotein 1)-knockout (KO) rats, modeling the human Fragile X Syndrome (FXS), are of particular interest for exploring the ASD-like phenotype in preclinical studies. Gestational exposure to chlorpyrifos (CPF) has been associated with ASD diagnosis in humans and ASD-like behaviors in rodents and linked to the microbiota-gut-brain axis. In this study, we have used both Fmr1-KO and wild-type male rats (F2 generation) at postnatal days (PND) 7 and 40 obtained after F1 pregnant females were randomly exposed to 1 mg/kg/mL/day of CPF or vehicle. A nuclear magnetic resonance (NMR) metabolomics approach together with gene expression profiles of these F2 generation rats were employed to analyze different brain regions (such as prefrontal cortex, hippocampus, and cerebellum), whole large intestine (at PND7) and gut content (PND40). The statistical comparison of each matrix spectral profile unveiled tissue-specific metabolic fingerprints. Significant variations in some biomarker levels were detected among brain tissues of different genotypes, including taurine, myo-inositol, and 3-hydroxybutyric acid, and exposure to CPF induced distinct metabolic alterations, particularly in serine and myo-inositol. Additionally, this study provides a set of metabolites associated with gastrointestinal dysfunction in ASD, encompassing several amino acids, choline-derived compounds, bile acids, and sterol molecules. In terms of gene expression, genotype and gestational exposure to CPF had only minimal effects on decarboxylase 2 (gad2) and cholinergic receptor muscarinic 2 (chrm2) genes.

Sociability: Comparing the Effect of Chlorpyrifos with Valproic Acid

In recent years, exposures to organophosphate pesticide have been highlighted as a possible cause or aggravating factor of autism spectrum disorder (ASD). The present study examined if Wistar rats prenatally exposed to chlorpyrifos (CPF) at a dose of 1 mg/kg in GD 12.5-15.5 could express similar behaviors to those exposed to valproic acid (VPA, 400 mg/kg) during the same administration window, which is an accepted animal model of autism. The 3-chambered test was employed to evaluate sociability and reaction to social novelty in two experiments, the first in adolescence and the second in adulthood. The results obtained in this study show that animals prenatally treated with CPF or VPA show a similar behavioral phenotype compared to the control group (CNT). In adolescence, the CPF animals showed a negative index in the reaction to social novelty, followed closely by the VPA, while both experimental groups showed a recovery in this aspect during adulthood. This study therefore provides evidence to suggest that prenatal exposure to CPF in rats could have similar effects on certain components of sociability to those seen in autistic models.

Multi-omics and gut microbiome: Unveiling the pathogenic mechanisms of early-life pesticide exposure

The extensive application of pesticides in agricultural production has raised significant concerns about its impact on human health. Different pesticides, including fungicides, insecticides, and herbicides, cause environmental pollution and health problems for non-target organisms. Infants and young children are so vulnerable to the harmful effects of pesticide exposure that early-life exposure to pesticides deserves focused attention. Recent research lays emphasis on understanding the mechanism between negative health impacts and early-life exposure to various pesticides. Studies have explored the impacts of exposure to these pesticides on model organisms (zebrafish, rats, and mice), as well as the mechanism of negative health effects, based on advanced methodologies like gut microbiota and multi-omics. These methodologies help comprehend the pathogenic mechanisms associated with early-life pesticide exposure. In addition to presenting health problems stemming from early-life exposure to pesticides and their pathogenic mechanisms, this review proposes expectations for future research. These proposals include focusing on identifying biomarkers that indicate early-life pesticide exposure, investigating transgenerational effects, and seeking effective treatments for diseases arising from such exposure. This review emphasizes how to understand the pathogenic mechanisms of early-life pesticide exposure through gut microbiota and multi-omics, as well as the adverse health effects of such exposure.

An updated systematic review on the maternal exposure to environmental pesticides and involved mechanisms of autism spectrum disorder (ASD) progression risk in children

Autism spectrum disorder (ASD) increased dramatically over the past 25 years because of genetic and environmental factors. This systematic review (SR) aimed to determine the association between maternal exposure during pregnancy to environmental pesticides and other associations with the risk of ASD progression in children. PubMed (MEDLINE), Scopus (Elsevier) and the Institute for Scientific Information (ISI) Web of Science were searched using appropriate keywords up to March 2021. Twenty-four studies met the inclusion/exclusion criteria and were selected. Most studies reported that ASD increases the risk of offspring after prenatal exposure to environmental pesticides in pregnant mother's residences, against offspring of women from the same region without this exposure. The main potential mechanisms inducing ASD progressions are ROS and prostaglandin E2 synthesis, AChE inhibition, voltage-gated sodium channel disruption, and GABA inhibition. According to the included studies, the highest rates of ASD diagnosis increased relative to organophosphates, and the application of the most common pesticides near residences might enhance the prevalence of ASD.

Environmental exposure to chlorpyrifos during gestation, APOE polymorphism and the risk on autistic-like behaviors

Autism spectrum disorder (ASD) encompasses several neurodevelopmental conditions characterized by communication and social impairment, as well as repetitive patterns of behavior. However, it can co-occur with other mental conditions such as anxiety. The massive use of chlorpyrifos (CPF) has been linked to the increased prevalence of developmental disorders. Likewise, ASD has also been closely linked to a wide variety of genetic factors. The aims of the present investigation are to study how gestational CPF exposure and APOE polymorphism affects communication skills, early development and mid-term anxiety-like behaviors, as well as, changes in gene expression related to the cholinergic system. C57BL/6J and humanized apoE3 and apoE4 homozygous mice were exposed to 0 or 1 mg/kg/day of CPF through the diet, from gestational day (GD) 12-18. In addition, a group of C57BL/6J females were injected subcutaneously with 300 mg/kg/day of valproic acid (VPA) on GD 12 and 13. This group was used as a positive control for studying some core and associated autism-like behaviors. Communication skills by means of ultrasonic vocalizations and physical/motor development were assessed during the preweaning period, whereas locomotor activity, anxiety-like behaviors and the gene expression of cholinergic elements were evaluated during adolescence. Our results showed that C57BL/6J mice prenatally exposed to CPF or VPA showed a decrease in body weight and a delay in eye opening. Communication and anxiety behavior were affected differently depending on treatment, while gene expression was altered by sex and treatment. In addition, none of the parameters evaluated in apoE transgenic mice exposed to CPF were affected, but there were differences between genotypes. Therefore, we suggest that prenatal CPF exposure and VPA produce divergent effects on communication and anxiety.

Embryonic development, hatchling performance and metabolic profile after egg exposure to environmentally relevant levels of chlorpyrifos in an aquatic turtle

The extensive use of organophosphorus insecticides poses a threat to the survival of non-target organisms. Ecotoxicological outcomes of embryonic exposure to insecticides are rarely evaluated in various oviparous species. In this study, soft-shelled turtle (Pelodiscus sinensis) eggs were incubated in moist substrate containing different levels (0, 2, 20 and 200 μg/kg) of chlorpyrifos to investigate its toxic effects on embryonic development and survival, and hatchling physiological performance. Chlorpyrifos exposure had no significant impacts on embryonic development rate and egg survival in P. sinensis. Similarly, embryonic chlorpyrifos exposure neither obviously affected the size and locomotor performance of hatchlings, nor changed the activities of superoxide dismutase and catalase, and content of malondialdehyde in their erythrocytes. Based on liquid chromatography-mass spectrometry analysis, minor metabolic perturbations related to amino acid, lipid and energy metabolism in hatchlings after embryonic chlorpyrifos exposure were revealed by hepatic metabolite profiling. Overall, our results suggested that embryonic exposure to environmentally relevant levels of chlorpyrifos had only a limited impact on physiological performances of hatchlings, although it would result in a potential risk of hepatotoxicity in P. sinensis.

Impact of pesticides exposure during neurodevelopmental period on autism spectrum disorders - A focus on gut microbiota

Accumulating evidence indicates exposure to pesticides during the crucial neurodevelopmental period increases susceptibility to many diseases, including the neurodevelopmental disorder known as autism spectrum disorder (ASD). In the last few years, it has been hypothesized that gut microbiota dysbiosis is strongly implicated in the aetiopathogenesis of ASD. Recently, new studies have suggested that the gut microbiota may be involved in the neurological and behavioural defects caused by pesticides, including ASD symptoms. This review highlights the available evidence from recent animal and human studies on the relationship between pesticides that have the potential to disturb intestinal microbiota homeostasis, and ASD symptoms. The mechanisms through which gut microbiota dysbiosis may trigger ASD-like behaviours induced by pesticides exposure during the neurodevelopmental period via the altered production of bacterial metabolites (short chain fatty acids, lipids, retinol, and amino acid) are also described. According to recent research, gut microbiota dysbiosis may be a major contributor to the symptoms of ASD associated with pesticides exposure. However, to determine the detailed mechanism of action of gut microbiota on pesticide-induced ASD behaviours, actual population exposure scenarios from epidemiological studies should be used as the basis for the appropriate exposure pattern and dosage to be used in animal studies.

Neurobehavioral Responses and Toxic Brain Reactions of Juvenile Rats Exposed to Iprodione and Chlorpyrifos, Alone and in a Mixture

Herein, male juvenile rats (23th postnatal days (PND)) were exposed to chlorpyrifos (CPS) (7.5 mg/kg b.wt) and/or iprodione (IPD) (200 mg IPD /kg b.wt) until the onset of puberty (60th day PND). Our results demonstrated that IPD and/or CPS exposure considerably reduced locomotion and exploration. However, CPS single exposure induced anxiolytic effects. Yet, neither IPD nor IPD + CPS exposure significantly affected the anxiety index. Of note, IPD and/or CPS-exposed rats showed reduced swimming time. Moreover, IPD induced significant depression. Nonetheless, the CPS- and IPD + CPS-exposed rats showed reduced depression. The individual or concurrent IPD and CPS exposure significantly reduced TAC, NE, and AChE but increased MDA with the maximum alteration at the co-exposure. Moreover, many notable structural encephalopathic alterations were detected in IPD and/or CPS-exposed rat brain tissues. The IPD + CPS co-exposed rats revealed significantly more severe lesions with higher frequencies than the IPD or CPS-exposed ones. Conclusively, IPD exposure induced evident neurobehavioral alterations and toxic reactions in the brain tissues. IPD and CPS have different neurobehavioral effects, particularly regarding depression and anxiety. Hence, co-exposure to IPD and CPS resulted in fewer neurobehavioral aberrations relative to each exposure. Nevertheless, their simultaneous exposure resulted in more brain biochemistry and histological architecture disturbances.

Perinatal Stressors as a Factor in Impairments to Nervous System Development and Functions: Review of In Vivo Models

The human body is faced with stress throughout ontogeny. At the stage of intrauterine development, the mother’s body serves as a source of resources and most of the humoral factors supporting the development of the fetus. In normal conditions, maternal stress-related humoral signals (e.g., cortisol) regulate fetal development; however, distress (excessive pathological stress) in the perinatal period leads to serious and sometimes irreversible changes in the developing brain. The mother being in an unfavorable psychoemotional state, toxins and teratogens, environmental conditions, and severe infectious diseases are the most common risk factors for the development of perinatal nervous system pathology in the modern world. In this regard, the challenge of modeling situations in which prenatal or early postnatal stresses lead to serious impairments to brain development and functioning is extremely relevant. This review addresses the various models of perinatal pathology used in our studies (hypoxia, exposure to valproate, hyperserotoninemia, alcoholization), and assesses the commonality of the mechanisms of the resulting disorders and behavioral phenotypes forming in these models, as well as their relationship with models of perinatal pathology based on the impact of psychoemotional stressors.

Effect of exposure to endocrine disrupting chemicals in obesity and neurodevelopment: The genetic and microbiota link

Current evidence highlights the importance of the genetic component in obesity and neurodevelopmental disorders (attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD) and intellectual disability (ID)), given that these diseases have reported an elevated heritability. Additionally, environmental stressors, such as endocrine disrupting chemicals (EDCs) have been classified as obesogens, neuroendocrine disruptors, and microbiota disrupting chemicals (MDCs). For this reason, the importance of this work lies in examining two possible biological mechanistic pathways linking obesity and neurodevelopmental/behavioural disorders: EDCs - gene and EDCs - microbiota interactions. First, we summarise the shared mechanisms of action of EDCs and the common genetic profile in the bidirectional link between obesity and neurodevelopment. In relation to interaction models, evidence from the reviewed studies reveals significant interactions between pesticides/heavy metals and gene polymorphisms of detoxifying and neurotransmission systems and metal homeostasis on cognitive development, ASD and ADHD symptomatology. Nonetheless, available literature about obesity is quite limited. Importantly, EDCs have been found to induce gut microbiota changes through gut-brain-microbiota axis conferring susceptibility to obesity and neurodevelopmental disorders. In view of the lack of studies assessing the impact of EDCs - gene interactions and EDCs - mediated dysbiosis jointly in obesity and neurodevelopment, we support considering genetics, EDCs exposure, and microbiota as interactive factors rather than individual contributors to the risk for developing obesity and neurodevelopmental disabilities at the same time.

Developmental exposure to chlorpyrifos causes neuroinflammation via necroptosis in mouse hippocampus and human microglial cell line

Neurodevelopmental exposure to chlorpyrifos (CPF) could increase risks for neurological disorders, such as autism spectrum disorder, cognitive impairment, or attention deficit hyperactivity disorder. The potential involvement of microglia reactive to inflammatory stimuli in these neurological disorders has been generally reported. However, the concrete effects and potential mechanisms of microglia dysfunction triggered by developmental CPF exposure remain unclear. Therefore, we established mouse and human embryonic microglial cells (HMC3 cell) models of developmental CPF exposure to evaluate the effects of developmental CPF exposure on neuroinflammation and underlying mechanisms. The results showed that developmental exposure to CPF enhanced the expression of Iba1 in hippocampus. CPF treatment increased inflammatory cytokines levels and TSPO expression in hippocampus and HMC3 cells. The levels of necroptosis and necroptosis-related signaling RIPK/MLKL were increased in hippocampus and HMC3 cells following CPF exposure. Furthermore, the expression of TLR4/TRIF signaling was increased in hippocampus and HMC3 cells subjected to CPF exposure. Notably, the increased levels of TLR4/TRIF signaling, RIPK/MLKL signaling, necroptosis and pro-inflammatory cytokines induced by CPF treatment were remarkably inhibited by TAK-242 (a specific TLR4 inhibitor). Additionally, the necroptosis and pro-inflammatory cytokines production induced by CPF treatment were significantly relieved by Nec-1 (a specific RIPK1 inhibitor). In general, the above results suggested that activated microglia in hippocampus subjected to developmental CPF exposure underwent RIPK1/MLKL-mediated necroptosis regulated by TLR4/TRIF signaling.

Recent advances in assessment methods and mechanism of microbe-mediated chlorpyrifos remediation

Chlorpyrifos (CP) is one of the Organophosphorus pesticides (OPs) primarily used in agriculture to safeguard crops from pests and diseases. The pervasive use of chlorpyrifos is hazardous to humans and the environment as it inhibits the receptor for acetylcholinesterase activity, leading to abnormalities linked to the central nervous system. Hence, there is an ardent need to develop an effective and sustainable approach to the on-site degradation of chlorpyrifos. The role of microbes in the remediation of pesticides is considered the most effective and eco-friendly approach, as they have strong degradative potential due to their gene and enzymes naturally adapted to these sites. Several reports have previously been published on exploring the role of microbes in the degradation of CP. However, detection of CP as an environmental contaminant is an essential prerequisite for developing an efficient microbial-mediated biodegradation method with less harmful intermediates. Most of the articles published to date discuss the fate and impact of CP in the environment along with its degradation mechanism but still fail to discuss the analytical portion. This review is focused on the latest developments in the field of bioremediation of CP along with its physicochemical properties, toxicity, fate, and conventional (UV-Visible spectrophotometer, FTIR, NMR, GC-MS, etc) and advanced detection methods (Biosensors and immunochromatography-based methods) from different environmental samples. Apart from it, this review explores the role of metagenomics, system biology, in-silico tools, and genetic engineering in facilitating the bioremediation of CP. One of the objectives of this review is to educate policymakers with scientific data that will enable the development of appropriate strategies to reduce pesticide exposure and the harmful health impacts on both Human and other environmental components. Moreover, this review provides up-to-date developments related to the sustainable remediation of CP.

Prenatal, but not postnatal exposure to chlorpyrifos affects social behavior of mice and the excitatory-inhibitory balance in a sex-dependent manner

The balance between excitatory and inhibitory neurotransmitters is essential for proper brain development. An imbalance between these two systems has been associated with neurodevelopmental disorders. On the other hand, literature also associates the massive use of pesticides with the increase of these disorders, with a particular focus on chlorpyrifos (CPF) a world-wide used organophosphate pesticide. This study was aimed at assessing social autistic-like behaviors on mice pre or postnatally exposed to CPF (0 or 1 mg/kg/day), in both sexes. In prenatal exposure, C57BL/6J pregnant mice were exposed to CPF through the diet, between gestational days (GD) 12 and 18, while a positive control group for some autistic behaviors was exposed to valproic acid (VPA) on GD 12 and 13. To assess postnatal exposure, C57BL/6J mice were orally exposed to the vehicle (corn oil) or CPF, from postnatal days (PND) 10-15. Social behavior and gene expression analysis were assessed on PND 45. Results showed social alterations only in males prenatally treated. GABA system was upregulated in CPF-treated females, whereas an increase in both systems was observed in both treated males. These findings suggest that males are more sensitive to prenatal CPF exposure, favoring the sex bias observed in ASD.

The mechanistic basis for the toxicity difference between juvenile rats and mice following exposure to the agricultural insecticide chlorpyrifos

At high exposure levels, organophosphorus insecticides (OPs) exert their toxicity in mammals through the inhibition of brain acetylcholinesterase (AChE) leading to the accumulation of acetylcholine in cholinergic synapses and hyperactivity of the nervous system. Currently, there is a concern that low-level exposure to OPs induces negative impacts in developing children and the chemical most linked to these issues is chlorpyrifos (CPF). Our laboratory has observed that a difference in the susceptibility to repeated exposure to CPF exists between juvenile mice and rats with respect to the inhibition of brain AChE. The basis for this difference is unknown but differences in the levels of the detoxification mechanisms could play a role. To investigate this, 10-day old rat and mice pups were exposed daily for 7 days to either corn oil or a range of dosages of CPF via oral gavage. Four hours following the last administration of CPF on day 16, brain, blood, and liver were collected. The inhibition of brain AChE activity was higher in juvenile rats as compared to juvenile mice. The levels of activity of the detoxification enzymes and the impact of CPF exposure on their activity were determined in the two species at this age. In blood and liver, the enzyme paraoxonase-1 (PON1) hydrolyzes the active metabolite of CPF (CPF-oxon), and the enzymes carboxylesterase (CES) and cholinesterase (ChE) act as alternative binding sites for CPF-oxon removing it from circulation and providing protection. Both species had similar levels of PON1 activity in the liver and serum. Mice had higher ChE activity in liver and serum than rats but, following CPF exposure, the percentage inhibition was similar between species at an equivalent dosage. Even though rats had slightly higher liver CES activity than mice, the level of inhibition following exposure was higher in rats. In serum, juvenile mice had an 8-fold higher CES activity than rats, and exposure to a CPF dosage that almost eliminated CES activity in rats only resulted in 22% inhibition in mice suggesting that the high serum CES activity in mice as compared to rats is a key component in this species difference. In addition, there was a species difference in the sensitivity of CES to inhibition by CPF-oxon with rats having a lower IC₅₀ in both liver and serum as compared to mice. This greater enzyme sensitivity suggests that saturation of CES would occur more rapidly in juvenile rats than in mice, resulting in more CPF reaching the brain to inhibit AChE in rats.

Influence of Gestational Chlorpyrifos Exposure on ASD-like Behaviors in an fmr1-KO Rat Model

Based on previous reports, exposure to pesticides could be linked to the prevalence increase of autism spectrum disorders (ASD). Gestational exposure to chlorpyrifos (CPF) has been associated with ASD diagnosis in humans and ASD-like behaviors in rodents. However, ASD severity degree results from the complex relationship between genetic background and environmental factors. Thus, animals with a genetic vulnerability and prenatally exposed to CPF could have a more severe ASD-like phenotype. Fragile X syndrome is one of the most common monogenic causes of ASD, characterized by a mutation in the X chromosome which alters the expression of the fragile X mental retardation protein (FMRP). Based on this, some fmr1 knockout (KO) rodent models have been developed to study the physiological and genetic basis of ASD. Both fmr1-KO and wild-type male rats (F2 generation) were used in the present study. F1 pregnant females were randomly exposed to 1 mg/kg/mL/day of CPF (s.c.) from GD12.5-15.5 or vehicle. Different behavioral, developmental, and molecular variables were analyzed in F2 males. KO rats were heavier, emitted altered USVs, were socially inefficient, reacted more to a novel stimulus, were hyperactive when exploring a new context, but hypoactive when exploring anxiety-inducing environments, and had an upregulated hippocampal expression of the grin2c gene. When exposed to low doses of CPF during gestation, these KO rats showed decreased climbing capacity, dysfunctional social interaction, and increased hippocampal expression for kcc1 and 5ht2c genes. Gestational CPF exposure increased the ASD-like phenotype in those animals with a genetic vulnerability, although its effect was less generalized than expected. It is the first time that this additive effect of CPF exposure and the fmr1-KO genetic vulnerability model is explored concerning social traits or any other behavior.

Effect of daily co-exposure to inulin and chlorpyrifos on selected microbiota endpoints in the SHIME® model

The intestinal microbiota has a key role in human health via the interaction with the somatic and immune cells in the digestive tract environment. Food, through matrix effect, nutrient and non-nutrient molecules, is a key regulator of microbiota diversity. As a food contaminant, the pesticide chlorpyrifos (CPF) has an effect on the composition of the intestinal microbiota and induces perturbation of microbiota. Prebiotics (and notably inulin) are known for their ability to promote an equilibrium of the microbiota that favours saccharolytic bacteria. The SHIME® dynamic in vitro model of the human intestine was exposed to CPF and inulin concomitantly for 30 days, in order to assess variations in both the bacterial populations and their metabolites. Various analyses of the microbiota (notably temporal temperature gradient gel electrophoresis) revealed a protective effect of the prebiotic through inhibition of the enterobacterial (E. coli) population. Bifidobacteria were only temporarily inhibited at D15 and recovered at D30. Although other potentially beneficial populations (lactobacilli) were not greatly modified, their activity and that of the saccharolytic bacteria in general were highlighted by an increase in levels of short-chain fatty acids and more specifically butyrate. Given the known role of host-microbiota communication, CPF's impact on the body's homeostasis remains to be determined.

Socioemotional deficit and HPA axis time response in high compulsive rats selected by schedule-induced polydipsia

Compulsivity is a failure to stop an ongoing behavior that has become inappropriate to the situation and is recognized as a transdiagnostic trait present in different neuropsychiatric disorders. The implication of motivation and emotion, as well as the stress response in compulsive population has not been fully understood. We assessed the motivation to reward and cues, the emotional response in different contexts and the hypothalamic-pituitary-adrenal (HPA) axis response in rats selected by a preclinical model of compulsive behavior. Firstly, high (HD) or low (LD) drinkers were selected according to their drinking behavior on schedule-induced polydipsia (SIP). Then, we assessed motivation by the propensity to attribute incentive salience to rewards on Pavlovian Conditioned Approach (PavCA) and motivation to gain reward on Progressive Ratio Schedule of Reinforcement (PRSR). Emotion was measured by Social Dominance on the Tube Test (SDTT) and emotional memory on Passive Avoidance (PA). Plasma corticosterone (CORT) levels in response to SIP were assessed. HD rats showed a socioemotional deficit by fewer victories on the SDTT, and an increased latency to enter the dark compartment on the PA. No differences were found between groups regarding to motivational assessment. Moreover, HD rats revealed a blunted time response in the increase of CORT levels at 45 min after SIP compared to LD rats. The findings show that the compulsive phenotype of HD rats exhibit less social dominance, more resistance to extinction and a differential CORT time response to SIP. These findings may contribute to highlight the relevance of assessing socioemotional behaviors and stress response for a better characterization of the vulnerability to compulsive spectrum disorders.

Chronic Perigestational Exposure to Chlorpyrifos Induces Perturbations in Gut Bacteria and Glucose and Lipid Markers in Female Rats and Their Offspring

An increasing burden of evidence is pointing toward pesticides as risk factors for chronic disorders such as obesity and type 2 diabetes, leading to metabolic syndrome. Our objective was to assess the impact of chlorpyrifos (CPF) on metabolic and bacteriologic markers. Female rats were exposed before and during gestation and during lactation to CPF (1 mg/kg/day). Outcomes such as weight, glucose and lipid profiles, as well as disturbances in selected gut bacterial levels, were measured in both the dams (at the end of the lactation period) and in their female offspring at early adulthood (60 days of age). The results show that the weight of CPF dams were lower compared to the other groups, accompanied by an imbalance in blood glucose and lipid markers, and selected gut bacteria. Intra-uterine growth retardation, as well as metabolic disturbances and perturbation of selected gut bacteria, were also observed in their offspring, indicating both a direct effect on the dams and an indirect effect of CPF on the female offspring. Co-treatment with inulin (a prebiotic) prevented some of the outcomes of the pesticide. Further investigations could help better understand if those perturbations mimic or potentiate nutritional risk factors for metabolic syndrome through high fat diet.

NMR-based Metabolomics and Fatty Acid Profiles to Unravel Biomarkers in Preclinical Animal Models of Compulsive Behavior

Compulsivity is a key manifestation of inhibitory control deficit and a cardinal symptom of psychopathological conditions such as obsessive-compulsive and attention-deficit hyperactivity disorders, in which metabolic alterations have raised attention as putative biomarkers for early identification. The present study assessed the metabolic profile in a preclinical model of a compulsive phenotype of rats. We used the schedule-induced polydipsia (SIP) method to classify male Wistar rats into high drinkers (HDs) or low drinkers (LDs) according to their compulsive drinking rate developed by exposure to a fixed-time 60 s (FT-60) schedule of reinforcement with water available ad libitum during 20 sessions. Before and after SIP, blood samples were collected for subsequent serum analysis by nuclear magnetic resonance spectroscopy coupled to multivariate analysis. Although no differences existed in the pre-SIP set, the compulsive drinking behavior induced remarkable metabolic alterations: HD rats selected by SIP exhibited a hyperlipidemic, hypoglycemic, and hyperglutaminergic profile compared with their low-compulsive counterparts. Interestingly, these alterations were not attributable to the mere exposure to reward pellets because a control experiment did not show differences between HDs and LDs after 20 sessions of pellet consumption without intermittent reinforcement. Our results shed light toward the implication of dietary and metabolic factors underpinning the vulnerability to compulsive behaviors.

The relationship between pesticide exposure during critical neurodevelopment and autism spectrum disorder: A narrative review

Agricultural pesticides have been one of the most extensively used compounds throughout the world. The main sources of contamination for humans are dietary intake and occupational exposure. The impairments caused by agricultural pesticide exposure have been a significant global public health problem. Recent studies have shown that low-level agricultural pesticide exposure during the critical period of neurodevelopment (pregnancy and lactation) is closely related to autism spectrum disorder (ASD). Inhibition of acetylcholinesterase, gut microbiota, neural dendrite morphology, synaptic function, and glial cells are targets for the effects of pesticides during nervous system development. In the present review, we summarize the associations between several highly used and frequently studied pesticides (e.g., glyphosate, chlorpyrifos, pyrethroids, and avermectins) and ASD. We also discusse future epidemiological and toxicological research directions on the relationship between pesticides and ASD.

Iprodione and/or chlorpyrifos exposure induced testicular toxicity in adult rats by suppression of steroidogenic genes and SIRT1/TERT/PGC-1α pathway

There is cumulative evidence that iprodione (IPR) fungicide and chlorpyrifos (CPF) insecticide are endocrine disruptors that can evoke reproductive toxicity. Yet, the underlying mechanisms are still unclear. Besides, the outcomes of their co-exposure to male sexual behavior and male fertility are still unknown. The effects of IPR (200 mg/kg b.wt) and CPF (7.45 mg/kg b.wt) single or mutual exposure for 65 days on sexual behavior, sex hormones, testicular enzymes, testis, and accessory sex gland histomorphometric measurements, apoptosis, and oxidative stress biomarkers were investigated. In addition, expression of nuclear receptor subfamily group A (NR5A1), 17β-hydroxysteroid dehydrogenase (HSD17B3), silent information regulator type-1 (SIRT1), telomerase reverse transcriptase (TERT), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) genes has been assessed. Our results revealed that the individual or concurrent IPR and CPF exposure significantly disturb the sexual behavior, semen characteristics, testicular enzymes, and male hormones level. Oxidative stress caused by IPR and CPF activates apoptosis by inducing Caspase-3 and reducing Bcl-2. Downregulation of HSD17B3, NR5A1, and SIRT1/TERT/PGC-1α pathway was evident. Of note, most of these disturbances were exaggerated in rats co-exposed to IPR and CPF compared to IPR or CPF alone. Conclusively, our findings verified that IPR and CPF possibly damage the male reproductive system, and concurrent exposure should be avoided.

Chlorpyrifos and Δ9 Tetrahydrocannabinol exposure and effects on parameters associated with the endocannabinoid system and risk factors for obesity

Marilyn Silva. Retired from a career in toxicology and risk assessment. Increased childhood and adult obesity are associated with chlorpyrifos (CPF), an organophosphate pesticide. Cannabis (Δ9Tetrahydrocannabinol: Δ9THC) use has increased globally with legalization. CPF applications on cannabis crops lacks federally regulated tolerances and may pose health risks through exposure during development and in adulthood. Both CPF and Δ9THC affect the endocannabinoid system (eCBS), a regulator of appetite, energy balance, and gut microbiota, which, if disrupted, increases risk for obesity and related diseases. CPF inhibits eCB metabolism and Δ9THC is a partial agonist/antagonist at the cannabinoid receptor (CB1R). Effects of each on obesogenic parameters were examined via literature search. Male rodents with CPF exposure showed increased body weights, dysbiosis, inflammation and oxidative stress, potentially associated with increased eCBs acting through the gut-microbiota-adipose-brain regulatory loop. Δ9THC generally decreased body weights via partial agonism at the CB1R, lowering levels of eCBs. Dysbiosis and/or oxidative stress associated inflammation occurred with CPF, but these parameters were not tested with Δ9THC. Database deficiencies included limited endpoints to compare between chemicals/age-groups, inter-study variables (dose ranges, dosing vehicle, rodent strain, treatment duration, etc.). CPF and Δ9THC were not tested together, but human co-chemical effects would depend on exposure ratio, subject age, exposure duration, and health status, among others. An overriding concern is that both chemicals are well-documented developmental neurotoxins in addition to their low dose effects on energy balance. A co-exposure risk assessment is warranted with increased use and lack of federal CPF regulation on cannabis.

Pesticides and aging: Preweaning exposure to Chlorpyrifos induces a general hypomotricity state in late-adult rats

The molecular and behavioral effects of the developmental exposure to low doses of Chlorpyrifos (CPF) have been intensively studied in young (neonates and adolescents), and adult animals. However, no study examined influences of developmental CPF exposure in older adult or geriatric rats. This is relevant as such ages are generally linked to cognitive decline and the onset of specific neurodegenerative disorders, some of them previously associated with CPF exposure in both preclinical and human studies. 1 mg/kg/mL of CPF was orally administered to both male and female Wistar rats from Postnatal day 10 to 15. Animals' spatial memory, learning, compulsivity, motricity, and anxiety were analyzed with Morris Water Maze (15-16 months of age) and the Plus-maze (at 18 months of age). Results showed that postnatal CPF exposure did not alter either spatial memory, compulsive-like behaviors, or anxiety levels in late-adult rats. However, CPF exposed rats were hyposensitive to brief disruptions (Probe stage) following the learning phase and showed a general decrease in locomotor activity in both paradigms. These data are relevant as it is the first time that developmental exposure to CPF has been studied at such a late age, observing important effects in locomotor activity that could be linked to specific pathologies previously associated with CPF effects in people. Future studies should extend these findings to other behaviors and molecular outcomes.

Toxicology and Microbiota: How Do Pesticides Influence Gut Microbiota? A Review

In recent years, new targets have been included between the health outcomes induced by pesticide exposure. The gastrointestinal tract is a key physical and biological barrier and it represents a primary site of exposure to toxic agents. Recently, the intestinal microbiota has emerged as a notable factor regulating pesticides’ toxicity. However, the specific mechanisms related to this interaction are not well known. In this review, we discuss the influence of pesticide exposure on the gut microbiota, discussing the factors influencing gut microbial diversity, and we summarize the updated literature. In conclusion, more studies are needed to clarify the host–microbial relationship concerning pesticide exposure and to define new prevention interventions, such as the identification of biomarkers of mucosal barrier function.

NMR-Based Metabolomics Approach to Explore Brain Metabolic Changes Induced by Prenatal Exposure to Autism-Inducing Chemicals

NMR offers the unique potential to holistically screen hundreds of metabolites and has already proved to be a powerful technique able to provide a global picture of a wide range of metabolic processes underlying complex and multifactorial diseases, such as neurodegenerative and neurodevelopmental diseases. The aim of this study was to apply an NMR-based metabolomics approach to explore brain metabolic changes in both male and female rats induced by prenatal exposure to two chemicals associated with autism disorders-the organophosphorus pesticide chlorpyrifos (CPF) and the antiepileptic drug valproic acid (VPA)-at different postnatal ages. Depending on the age and on the brain region (hippocampus and cerebellum), several metabolites were shown to be significantly affected by exposure to both compounds. The evaluation of the spectral profiles revealed that the nervous-system-specific metabolite N-acetylaspartate (NAA), amino acid neurotransmitters (e.g., glutamate, glutamine, GABA, glycine), pyroglutamic acid, unsaturated fatty acids, and choline-based compounds are discriminant biomarkers. Additionally, metabolic changes varied as a function of age, but importantly not of sex.

Chronic oral exposure to pesticides and their consequences on metabolic regulation: role of the microbiota

Pesticides have long been used in agriculture and household treatments. Pesticide residues can be found in biological samples for both the agriculture workers through direct exposure but also to the general population by indirect exposure. There is also evidence of pesticide contamination in utero and trans-generational impacts. Whilst acute exposure to pesticides has long been associated with endocrine perturbations, chronic exposure with low doses also increases the prevalence of metabolic disorders such as obesity or type 2 diabetes. Dysmetabolism is a low-grade inflammation disorder and as such the microbiota plays a role in its etiology. It is therefore important to fully understand the role of microbiota on the genesis of subsequent health effects. The digestive tract and mostly microbiota are the first organs of contact after oral exposure. The objective of this review is thus to better understand mechanisms that link pesticide exposure, dysmetabolism and microbiota. One of the key outcomes on the microbiota is the reduced Bacteroidetes and increased Firmicutes phyla, reflecting both pesticide exposure and risk factors of dysmetabolism. Other bacterial genders and metabolic activities are also involved. As for most pathologies impacting microbiota (including inflammatory disorders), the role of prebiotics can be suggested as a prevention strategy and some preliminary evidence reinforces this axis.

A comprehensive review on chlorpyrifos toxicity with special reference to endocrine disruption: Evidence of mechanisms, exposures and mitigation strategies

Chlorpyrifos (CPF) is a broad-spectrum chlorinated organophosphate (OP) pesticide used for the control of a variety of insects and pathogens in crops, fruits, vegetables, as well as households, and various other locations. The toxicity of CPF has been associated with neurological dysfunctions, endocrine disruption, and cardiovascular diseases (CVDs). It can also induce developmental and behavioral anomalies, hematological malignancies, genotoxicity, histopathological aberrations, immunotoxicity, and oxidative stress as evidenced by animal modeling. Moreover, eye irritation and dermatological defects are also reported due to CPF toxicity. The mechanism of action of CPF involves blocking the active sites of the enzyme, acetylcholinesterase (AChE), thereby producing adverse nervous system effects. Although CPF has low persistence in the body, its active metabolites, 3,5,6-trichloro-2-pyridinol (TCP), and chlorpyrifos-oxon (CPO) are comparatively more persistent, albeit equally toxic, and thus produce serious health complications. The present review has been compiled taking into account the work related to CPF toxicity and provides a brief compilation of CPF-induced defects in animals and humans, emphasizing the abnormalities leading to endocrine disruption, neurotoxicity, reproductive carcinogenesis, and disruptive mammary gland functionality. Moreover, the clinical signs and symptoms associated with the CPF exposure along with the possible pharmacological treatment are reported in this treatise. Additionally, the effect of food processing methods in reducing CPF residues from different agricultural commodities and dietary interventions to curtail the toxicity of CPF has also been discussed.