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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.

Alterations in attention and inhibitory control are common features in several neurological disorders. Environmental factors such as exposure to pesticides have been linked to their appearance. Chlorpyrifos (CPF) is one of the most widely used organophosphate compounds in the world. CPF exposure during development seems to be critical for later behavioral and molecular disruptions during adult ages, although this depends on the specific period of development, where the preweaning period is one of the least studied. Despite the abundant empirical work made in the last decades on developmental CPF exposure, the systematic study of this on attention is sparse, and nonexistent concerning inhibitory control, without a single study on preweaning developmental stages. The present research explored the effects of the exposure to low doses of CPF that do not elicit a significant inhibition of the Cholinesterases during this developmental period on rats' behavior in the five-choice serial reaction time task. Behavioral manipulations (inter-trial interval and stimulus duration), pharmacological manipulations (cholinergic and GABAergic drugs) and brain gene expression analyses were also conducted. Exposure to CPF decreased the locomotor activity and enhanced the learning profile of the female rats, increased the impulsive rates, unmasked by a longer inter-trial interval, hypo-sensitized the cholinergic system and down-regulated the mRNA expression levels of the brain-derived neurotrophic factor in the dorsal striatum of the male rats. This happened without significant inhibition of the brain Acetylcholinesterase. All this new information corroborates that the exposure to a common pesticide at low doses during a key, but under-explored developmental period importantly affects different behaviors, neurotransmitter systems, and molecules that are altered in the main neurological disorders observed nowadays., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The gut microbiota comprises a large number of microorganisms, whose composition can be modified by genetic and environmental factors. The host's genetic background, including the different isoforms of the apolipoprotein E (APOE) gene, can exert an influence over microbiota composition. Exposure to the widely-used pesticide chlorpyrifos (CPF), can lead to dysbiosis and alter the levels of metabolites produced by the microbiota, such as short-chain fatty acids (SCFAs). This study was aimed at assessing the contribution of the APOE genotype and early exposure to CPF on gut microbiota and SCFA in brain. For it, C57BL/6, apoE3-and apoE4-TR mice were orally exposed to CPF from postnatal day (PND) 10 to PND 15. Microbiota in the gut and SCFA in the brain were assessed at PND 15 after CPF exposure. Differences between genotypes at different taxonomic levels were found, A. muciniphila presented greater abundance in APOE4 genotype, but was reduced by CPF exposure. APOE and CPF influenced cerebral SCFAs, with APOE3 genotype showing the highest levels of acetic, propionic and butyric acids and CPF exposure inducing the highest levels of isovaleric and 4-methylvaleric acids. These results provide further knowledge about gut microbiota and cerebral SCFAs composition at early ages and their modulation by APOE and postnatal CPF exposure., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Development is especially sensitive to Chlorpyrifos (CPF) toxicity, associated with several neurodegenerative and neurodevelopmental disorders where motor function dysfunction is a core symptom. Amongst the alternative molecular targets to cholinesterases inhibition, developmental CPF alters different components in the most important neurotransmitter systems, although this depends on the exposure period. Exposure during the late postnatal preweaning stage is the least studied by far. This period includes essential neurodevelopmental processes and has an important translational meaning. The present study analyzed the influence of low doses of CPF on this developmental window on locomotor activity and the state of the different neurotransmitter systems by pharmacological challenges. Brain gene expression and microbiome modulation following CPF were also analyzed. CPF exposure long-term increased spontaneous vertical activity, female's activity following acute stress, hyposensitized the cholinergic system and hypersensitized the GABAergic system, up-regulated both muscarinic 2 receptor and GABA-A-α2 receptor subunit in the dorsal striatum and the frontal cortex, respectively and induced gut microbiota dysbiosis at both genus and species levels. The present study supports alternative molecular targets than the ChEs following late postnatal, preweaning exposure to low doses of CPF, focusing on both cholinergic and GABAergic systems and the gut microbiome as an important factor., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Organophosphate pesticides (OPs) are used extensively throughout the world. The main sources of contamination for humans are dietary ingestion and occupational exposures. The major concerns related to OP exposure are delayed effects following high level exposures as well as the impact of low level exposures during the lifespan which are suggested to be a risk factor for nervous system chronic diseases. Both high and low level exposures may have a particularly high impact in population subgroups such as aged or genetically vulnerable populations. Apart from the principle action of OPs which involves inhibition of the acetylcholinesterase (AChE) enzyme, several molecular targets, such as hormones; neurotransmitters; neurotrophic factors; enzymes related to the metabolism of beta amyloid protein as well as inflammatory changes have been identified for OP compounds. Here we review the main neurological and/or cognitive deficits described and the experimental and epidemiological relationships found between pesticide exposure and Alzheimer's, Parkinson's, and Amyotrophic Lateral Sclerosis (ALS) diseases. This report also focuses on possible individual differences making groups resilient or vulnerable to these toxicants. A critical discussion of the evidence obtained from experimental models and possible sources of bias in epidemiological studies is included. In particular this review aims to discuss common targets and pathways identified which may underlie the functional deficits associated with both pesticide exposure and neurodegeneration., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Chlorpyrifos (CPF) is an organophosphate (OP) insecticide that is metabolically activated to the highly toxic chlorpyrifos oxon. Dietary exposure is the main route of intoxication for non-occupational exposures. However, only limited behavioral effects of chronic dietary exposure have been investigated. Therefore, male Wistar rats were fed a dose of 5mg/kg/day of CPF for thirty-one weeks. Animals were evaluated in spatial learning and impulsivity tasks after 21 weeks of CPF dietary exposure and one week after exposure ended, respectively. In addition, the degree of inhibition of brain acetylcholinesterase (AChE) was evaluated for both the soluble and particulate forms of the enzyme, as well as AChE gene expression. Also, brain acylpeptide hydrolase (APH) was investigated as an alternative target for OP-mediated effects. All variables were evaluated at various time points in response to CPF diet and after exposure ended. Results from behavioral procedures suggest cognitive and emotional disorders. Moreover, low levels of activity representing membrane-bound oligomeric forms (tetramers) were also observed. In addition, increased brain AChE-R mRNA levels were detected after four weeks of CPF dietary exposure. However, no changes in levels of brain APH were observed among groups. In conclusion, our data point to a relationship between cognitive impairments and changes in AChE forms, specifically to a high inhibition of the particulate form and a modification of alternative splicing of mRNA during CPF dietary exposure., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Pesticide exposure has been associated with neuropsychological and psychiatric impairments and neurodegenerative disorders. Pesticide exposure commonly causes a deficit in inhibitory control behaviours. In the present study, we investigated whether acute exposure to organophosphate (OP) chlorpyrifos (CPF) is related to long-term lack of inhibitory control; we also examined the possible neurochemical basis of this association. Lister Hooded rats were exposed to an acute dose of CPF (250 mg/kg). Seven months later, we tested inhibitory control with the 5-choice serial reaction time task (5-CSRTT). We manipulated the baseline conditions of this task and also systemically pre-administered d-amphetamine, quinpirole, dizocilpine (MK-801) or ketanserin. We also analysed the post-mortem baseline levels of monoamines and amino acids in different brain regions. On the 5-CSRT task, CPF-exposed rats showed elevated perseverative responses that persisted across manipulation of baseline conditions of the task and under most of the pharmacological challenges tested. Only D-amphetamine induced a dose-dependent amelioration of the increased perseverative responses in the CPF group. The CPF group also exhibited increased levels of dopamine metabolism in the hippocampus and decreased levels of gamma-aminobutyric acid (GABA) and glutamate in the striatum compared to the vehicle group. These findings suggest that CPF induced a long-term compulsivity that was apparent in the 5-CSRT task and associated with changes in monoaminergic and amino acid brain systems of inhibitory control function. Exposure to high doses of OP should be taken into account in studies of environmental causes for neurodegenerative, neuropsychological and neuropsychiatric disorders., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Organophosphates (OPs) are important toxic compounds commonly used for a variety of purposes in agriculture, industry and household settings. It has been well established that the main mechanism of acute toxic action of OP is the inhibition of acetylcholinesterase (AChE). However, we observed long term deficit after acute subcutaneous exposure to Chlorpyrifos (CPF) even when AChE activity is restored. In fact, besides AChE inhibition, non-AChE targets have also been proposed as an alternative mechanism involved in the acute lethal action and side effects of short or long-term exposure. In this context, our main aim in this research was to establish a dose-response curve of Acylpeptide hydrolase (APH) and AChE regional brain activity after acute CPF administration that could explain these long term effects observed in the literature. Moreover, since available data suggest that long term effects of OPs exposure could involve neuronal cell death, our second aim was to evaluate, assessing by Fluoro-Jade B (FJB) staining, whether CPF produces induced cell death. Our results show that an acute exposure to 250 mg/kg CPF does not induce neuronal death as measured by FJB but produces highest AChE regional brain inhibition after administration. In addition, APH seems to be more sensitive than AChE to CPF exposure because after 31 days of exposure, complete recovery was seen only for APH activity at Frontal Cortex, Cerebellum and Brain Stem.

Preliminary clinical evidence obtained in Gulf War veterans and patients suffering multiple chemical sensitivity points to the existence of a potential link between environmental exposure to organosphosphates (OPs) and the emergence of unspecific sickness syndromes in which associative Pavlovian conditioning might be partly involved. A laboratory animal model might be a useful tool for analyzing the involvement of conditioning in sickness syndromes potentially linked to OP poisoning. The first objective in the present study was to determine if paraoxon (PX), the neuroactive metabolite of the OP parathion, elicits a conditioned avoidance response to a novel stimulus (a taste-odor compound) in a conditioned flavor aversion procedure. Data obtained in Experiment 1 show conditioned flavor avoidance, demonstrative of the associative nature of the sickness properties of PX. The second objective was to characterize the nature of the specific physiological cue serving as the unconditioned stimulus in PX-induced conditioned avoidance. Despite PX administration did induce cholinergic hyperactivity, as measured by body hypothermia and increased jaw movements, lesions of the lateral parabrachial area (lPB) disrupted PX-elicited flavor avoidance responses, indicating that cholinergic signs were not sufficient as unconditioned stimuli supporting avoidance responses. Given that lPB neural integrity is necessary to process aversive interoceptive information, disruption of conditioned flavor avoidance as a result of lPB lesions is consistent with a central interruption of interoceptive processing in PX-poisoned animals. Data are discussed under the light of the hypothesis claiming the importance of associative processes and noncholinesterase targets in sickness syndromes potentially induced by OP exposure.

Chlorpyrifos (CPF) is an organophosphate widely used as an insecticide in agriculture which elicits short- and long-term neurobehavioral deficits after acute administration. Because little is known about the specific brain areas targeted by CPF, investigating for the location of its neuroanatomical targets could help to describe the brain systems involved in the neurobehavioral toxicity developed in CPF-exposed organisms. To meet this objective, in the present study we evaluated CPF-induced c-fos expression. In addition, locomotor behavior and cerebral cholinesterase level were evaluated. We found two main sets of results. First, no significant c-fos expression was found in cholinoceptive regions in CPF-treated rats 2 h or 24 h post-administration, despite the fact that 41% and 62% acetylcholinesterase inhibition, respectively, were present in brain homogenates. These results are consistent with previous reports showing CPF-induced activation of adaptive neural mechanisms re-establishing cholinergic tone. Second, 24 h post-intoxication CPF elicited c-fos expression in cytokine-related areas. Cytokines have been involved in anxiety-like responses and psychiatric stress syndromes. Taking into account that CPF triggers the synthesis of peripheral cytokines, the present data stress the need to further clarify functional relations between organophosphate-triggered peripheral cytokines and emotional disturbances reported in intoxicated organisms.