Pre- and postnatal exposure to glyphosate-based herbicide causes behavioral and cognitive impairments in adult mice: evidence of cortical ad hippocampal dysfunction

Glyphosate as a direct or indirect activator of pro-inflammatory signaling and cognitive impairment

Glyphosate-based herbicides are widely used around the world, making it likely that most humans have significant exposure. Because of habitual exposure, there are concerns about toxicity including neurotoxicity that could result in neurological, psychiatric, or cognitive impairment. We recently found that a single injection of glyphosate inhibits long-term potentiation, a cellular model of learning and memory, in rat hippocampal slices dissected 1 day after injection, indicating that glyphosate-based herbicides can alter cognitive function. Glyphosate-based herbicides could adversely affect cognitive function either indirectly and/or directly. Indirectly, glyphosate could affect gut microbiota, and if dysbiosis results in endotoxemia (leaky gut), infiltrated bacterial by-products such as lipopolysaccharides could activate pro-inflammatory cascades. Glyphosate can also directly trigger pro-inflammatory cascades. Indeed, we observed that acute glyphosate exposure inhibits long-term potentiation in rat hippocampal slices. Interestingly, direct inhibition of long-term potentiation by glyphosate appears to be similar to that of lipopolysaccharides. There are several possible measures to control dysbiosis and neuroinflammation caused by glyphosate. Dietary intake of polyphenols, such as quercetin, which overcome the inhibitory effect of glyphosate on long-term potentiation, could be one effective strategy. The aim of this narrative review is to discuss possible mechanisms underlying neurotoxicity following glyphosate exposure as a means to identify potential treatments.

Evaluation of the potential role of glutamatergic, cholinergic, and nitrergic systems in the dopamine release induced by the pesticide glyphosate in rat striatum

Glyphosate (GLY) is a pesticide that severely alters nigrostriatal dopaminergic neurotransmission, inducing great increases in dopamine release from rat dorsal striatum. This GLY-induced striatal dopamine overflow occurs through mechanisms not yet fully understood, hence the interest in evaluating the role of other neurotransmitter systems in such effects. So, the main objective of this mechanistic study was to evaluate the possible mediation of the glutamatergic, cholinergic, and nitrergic systems in the GLY-induced in vivo dopamine release from rat dorsal striatum. The extracellular dopamine levels were measured by cerebral microdialysis and HPLC with electrochemical detection. Intrastriatal administration of GLY (5 mmol/L) significantly increased the dopamine release (1102%). Pretreatment with MK-801 (50 or 400 μmol/L), a non-competitive antagonist of NMDA receptors, significantly decreased the effect of GLY (by 70% and 74%, respectively), whereas AP-5 (400 μmol/L), a competitive antagonist of NMDA receptors, or CNQX (500 μmol/L), an AMPA/kainate receptor antagonist, had no significant effect. Administration of the nitric oxide synthase inhibitors, L-nitroarginine (L-NAME, 100 μmol/L) or 7-nitroindazole (7-NI, 100 μmol/L), also did not alter the effect of GLY on dopamine release. Finally, pretreatment of the animals with mecamylamine, an antagonist of nicotinic receptors, decreased the effect of GLY on dopamine release by 49%, whereas atropine, a muscarinic antagonist, had no significant effect. These results indicate that GLY-induced dopamine release largely depends on the activation of NMDA and nicotinic receptors in rat dorsal striatum. Future research is needed to determine the effects of this pesticide at environmentally relevant concentrations.

Similar toxicity potential of glyphosate and glyphosate-based herbicide on cerebellar development after maternal exposure in rats

Studies on the effects of glyphosate (GlyP) and glyphosate-based herbicides (GBHs) on cerebellar development are extremely limited. This study examined the effects of maternal exposure to GlyP and GBH on rat cerebellar development in male offspring. From day 6 of gestation until day 21 postpartum at weaning, dams were given GlyP at 1.5% or 3.0% in diet or GBH at 1.0% in drinking water (corresponding to 0.36% GlyP). At weaning, GBH exposure was linked to increased numbers of DCX+ migrating granule cells in the cortex and TUNEL+ apoptotic cells in the internal granular layer (IGL), suggesting the disappearance of mismigrated granule cells via apoptosis. GBH also upregulated Nr4a3 and downregulated Cdk5 in the cerebellar vermis, suggesting a causal relation with the impaired granule cell development at this time. GlyP (3.0%) tended to increase in the number of DCX+ migrating granule cells in the IGL and upregulated Nr4a3 at weaning. Both compounds also upregulated genes related to granule cell migration (Astn1, Astn2, Nfia, and/or Nfix) at weaning and in adulthood, which might be an ameliorative response to delayed granule cell migration. Moreover, GBH induced Purkinje cell misalignment at weaning, which could be the result of delayed granule cell migration. In adulthood, GBH was associated with upregulation of the reelin signaling-related genes Reln, Dab1, and Efnb1, suggesting a compensatory response to Purkinje cell misalignment. GlyP induced the same gene expression changes. These results suggest that GBH reversibly disrupts cerebellar development, primarily by targeting granule cell migration and differentiation, whereas GlyP exhibited similar toxic potential as GBH.

Gestational glyphosate exposure and early childhood neurodevelopment in a Puerto Rico birth cohort

INTRODUCTION

N-(phosphonomethyl)glycine, or glyphosate, is a non-selective systemic herbicide widely used in agricultural, industrial, and residential settings since 1974. Glyphosate exposure has been inconsistently linked to neurotoxicity in animals, and studies of effects of gestational exposure among humans are scarce. In this study we investigated relationships between prenatal urinary glyphosate analytes and early childhood neurodevelopment.

METHODS

Mother-child pairs from the PROTECT-CRECE birth cohort in Puerto Rico with measures for both maternal urinary glyphosate analytes and child neurodevelopment were included for analysis (n = 143). Spot urine samples were collected 1-3 times throughout pregnancy and analyzed for glyphosate and aminomethylphosphonic acid (AMPA), an environmental degradant of glyphosate. Child neurodevelopment was assessed at 6, 12, and 24 months using the Battelle Developmental Inventory, 2nd edition Spanish (BDI-2), which provides scores for adaptive, personal-social, communication, motor, and cognitive domains. We used multivariable linear regression to examine associations between the geometric mean of maternal urinary glyphosate analytes across pregnancy and BDI-2 scores at each follow-up. Results were expressed as percent change in BDI-2 score per interquartile range increase in exposure.

RESULTS

Prenatal AMPA concentrations were negatively associated with communication domain at 12 months (%change = -5.32; 95%CI: 9.04, -1.61; p = 0.007), and communication subdomain scores at 12 and 24 months. At 24 months, four BDI-2 domains were associated with AMPA: adaptive (%change = -3.15; 95%CI: 6.05, -0.25; p = 0.038), personal-social (%change = -4.37; 95%CI: 7.48, -1.26; p = 0.008), communication (%change = -7.00; 95%CI: 11.75, -2.26; p = 0.005), and cognitive (%change = -4.02; 95%CI: 6.72, -1.32; p = 0.005). Similar trends were observed with GLY concentrations, but most confidence intervals include zero. We found no significant associations at 6 months.

CONCLUSIONS

Our results suggest that gestational exposure to glyphosate is associated with adverse early neurodevelopment, with more pronounced delays at 24 months. Given glyphosate's wide usage, further investigation into the impact of gestational glyphosate exposure on neurodevelopment is warranted.

Continuous low-level dietary exposure to glyphosate elicits dose and sex-dependent synaptic and microglial adaptations in the rodent brain

Prolonged exposure to low levels of dietary contaminants is a context in modern life that could alter organ physiology gradually. Here, we aimed to investigate the impact of continuous exposure to acceptable daily intake (ADI) and non-observable adverse effect level (NOAEL) of glyphosate from gestation to adulthood using C57BL/6J mice and incorporating these levels into their food pellets. From adulthood, we analyzed neurophysiological and neuro-glia cellular adaptations in male and female animals. Using ex-vivo hippocampal slice electrophysiology, we found a reduced efficacy of Schaffer collateral-to-CA1 excitatory synapses in glyphosate-exposed dietary conditions, with ADI and NOAEL dose-dependent effects. Short-term facilitation of excitatory synaptic transmission was specifically increased in NOAEL conditions, with a predominant influence in males, suggesting a reduced probability of neurotransmitter release. Long-term synaptic potentiation (LTP) was decreased in NOAEL-exposed mice. Next, we explore whether these neurophysiological modifications are associated with neuro-glia changes in the somatosensory cortex and hippocampus. High-resolution confocal microscopy analyses unveil a dose-dependent increased density of excitatory Vglut1+ Homer1+ synapses. Microglial Iba1+ cells displayed a shortening of their ramifications, a sign of cellular reactivity that was more pronounced in males at NOAEL levels. The morphology of GFAP+ astrocytes was generally not modified. Finally, we asked whether mouse-specific cross-correlations exist among all data sets generated. This examination included the novel object recognition (NOR) test performed before ex vivo functional and immunohistochemical examinations. We report a negative linear regression between the number of synapses and NOR or LTP maintenance when plotting ADI and NOAEL datasets. These results outline synaptic and microglial cell adaptations resulting from prenatal and continuous dietary low levels of glyphosate, discernible in, but not limited to, adult males exposed to the NOAEL. We discuss the potential significance of these findings to real-world consumer situations and long-term brain resilience.

Impact of glyphosate-based herbicide exposure through maternal milk on offspring's antioxidant status, neurodevelopment, and behavior

Glyphosate-based Herbicide (GBH) is a widely used pesticide that functions as a broad-spectrum, non-selective herbicide. Despite advanced research to describe the neurotoxic potential of GBH, the harmful effects on maternal behavior and neurodevelopment of offspring remain unclear. This study was conducted to highlight the effects of GBH on the antioxidant system, anxiety traits, social interaction, and cognitive and sensorimotor functions in pups exposed to 25 or 50 mg/l daily via their mother's milk. Concerning the biochemical biomarkers, GBH administered during the early stages of development negatively affected the status of antioxidant enzymes and lipid peroxidation in the brain structures of the pups. Furthermore, our results showed a significant decrease in acetylcholinesterase (AChE) specific activity within the brains of treated pups. The results of the behavioral tests indicated that the treated offspring developed anxiety, memory, and sociability disorders, as evidenced by the Open Field, Y-maze, object recognition task, and social interaction tests. Through neurodevelopmental testing, we also showed sensorimotor impairment (righting reflex and negative geotaxis) and abnormal maternal behavior. Altogether, our study clearly demonstrates that the developing brain is sensitive to GBH.

Association between urinary glyphosate levels and serum neurofilament light chain in a representative sample of US adults: NHANES 2013-2014

BACKGROUND

Glyphosate, the herbicide with the highest global usage, has been found to have links to neurological impairment in some occupational studies. Neurofilament light chain (NfL) is a protein that is released into the bloodstream following neuroaxonal damage and has emerged as a reliable biomarker for various neurological disorders. However, no research has investigated the potential link between glyphosate exposure and neurological damage or serum NfL levels in the general population.

OBJECTIVE

The objective of this study was to assess the possible correlation between glyphosate exposure and serum NfL levels in a population that is representative of the United States.

METHODS

We analyzed data from 597 adults (aged ≥20 years) from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to explore the potential correlation between urinary glyphosate levels and serum NfL levels.

RESULTS

We found a significant positive association between urinary glyphosate levels and serum NfL levels (ß-coefficient = 0.110; S.E. = 0.040; P = 0.015), indicating that higher levels of glyphosate exposure may be linked to higher levels of neuroaxonal damage. Furthermore, when glyphosate levels were divided into quintiles, we observed a significant trend of increasing mean NfL concentrations with increasing quintiles of glyphosate exposure (P for trend = 0.036). Notably, the association was more pronounced in certain subgroups, including those aged ≥40 years, non-Hispanic whites, and those with a BMI between 25 and 30.

IMPACT STATEMENT

This is the first research to suggest an association between glyphosate exposure and biomarkers indicative of neurological damage in general U.S. adults. If the correlation observed is causal, it raises concerns about the potential effects of glyphosate exposure on neurological health among U.S. adults. The study is noteworthy due to its representation of American adults aged 20 and above, as well as the use of reliable and comprehensive data from the NHANES database.

Neurotoxicity of glyphosate: Focus on molecular mechanisms probably associated with alterations in cognition and behavior

In recent decades, glyphosate and glyphosate-based herbicides (GBH) have been extensively used in agriculture all over the world. Initially, they were considered safe, but rising evidence suggests that these molecules reach the central nervous system producing metabolic, functional, and permanent alterations that impact cognition and behavior. This theoretical and non-systematic review involved searching, integrating, and analyzing preclinical evidence regarding the effects of acute, sub-chronic, and chronic exposure to glyphosate and GBH on cognition, behavior, neural activity, and development in adult and juvenile rodents following perinatal exposition. In addition, this review gathers the mechanisms underlying the neurotoxicity of glyphosate mediating cognitive and behavioral alterations. Furthermore, clinical evidence of the effects of exposition to GBH on human health and its possible link with several neurological disorders was revised.

Maternal exposure to glyphosate-based herbicide causes vascular dysfunction in offspring female rats

This study analyzed how glyphosate exposure in the gestational period affects vascular function in their female offspring and whether oxidative stress is involved in this effect. To this, pregnant Wistar rats were exposed through drinking water to 0.2% of a glyphosate commercial formulation, and we analyzed the response to acetylcholine and phenylephrine in the aorta from offspring of Glyphosate-based herbicide (O-GBH) and controls (O-CON) rats at six months of age. Relaxation to acetylcholine was reduced in O-GBH than in O-CON. Acute Indomethacin and Apocynin increased relaxation to acetylcholine in O-GBH. The aorta from O-GBH was hyperactive to phenylephrine; the preincubation with N-nitro-L-arginine methyl ester (L-NAME) increased contraction to phenylephrine more in O-CON than O-GBH. TEMPOL similarly reduced phenylephrine response, and L-NAME prevented this effect. The TBARS and GSH levels were increased in O-GBH than in O-CON. Results reinforce the concept that oxidative stress during the perinatal period contributes to the development of vascular changes in adulthood. Results also reveal that oxidative stress parameters altered, and the current levels considered safe for exposure to Glyphosate deserve further investigation, especially in the female gender.

Association between urinary glyphosate levels and hand grip strength in a representative sample of US adults: NHANES 2013-2014

Introduction

Glyphosate, a widely utilized herbicide globally, has been linked to various health issues, including cancer, birth abnormalities, and reproductive issues. Additionally, there is growing experimental support indicating potential harm to skeletal muscles. Despite this, the impact of glyphosate on human muscle health remains unclear.

Methods

We examined information gathered from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), which included 1466 adults aged 18 or older. Our primary aim was to investigate the relationship between glyphosate exposure and hand grip strength, as well as its influence on lean muscle mass.

Results and discussion

Our investigation uncovered a detrimental correlation between glyphosate exposure and all measures of grip strength, except for the second test of the first hand. Specifically, we observed a statistically significant adverse association between glyphosate exposure and combined grip strength, which is calculated as the sum of the highest readings from both hands (ß coefficient of -2.000, S.E. = 0.891, p = 0.040). We did not observe a significant correlation between glyphosate levels, lean muscle mass, and the likelihood of reaching maximum grip strength meeting sarcopenia criteria. Additionally, we observed an interaction between age and glyphosate, as well as between body mass index (BMI) and glyphosate, concerning the association with combined grip strength. In this comprehensive analysis of NHANES data, our study reveals a potential association between glyphosate exposure and hand grip strength in the adult population. Our findings suggest the need for deeper exploration into the health effects of glyphosate exposure and its impact on muscle strength, shedding light on possible public health concerns.

Glyphosate: Impact on the microbiota-gut-brain axis and the immune-nervous system, and clinical cases of multiorgan toxicity

Glyphosate (GLP) and GLP-based herbicides (GBHs), such as polyethoxylated tallow amine-based GLP surfactants (GLP-SH), developed in the late 70', have become the most popular and controversial agrochemicals ever produced. Nowadays, GBHs have reached 350 million hectares of crops in over 140 countries, with an annual turnover of 5 billion and 11 billion USD in the U.S.A. and worldwide, respectively. Because of the highly efficient inhibitory activity of GLP targeted to the 5-enolpyruvylshikimate-3-phosphate synthase pathway, present in plants and several bacterial strains, the GLP-resistant crop-based genetic agricultural revolution has decreased famine and improved the costs and quality of living in developing countries. However, this progress has come at the cost of the 50-year GBH overuse, leading to environmental pollution, animal intoxication, bacterial resistance, and sustained occupational exposure of the herbicide farm and companies' workers. According to preclinical and clinical studies covered in the present review, poisoning with GLP, GLP-SH, and GBHs devastatingly affects gut microbiota and the microbiota-gut-brain (MGB) axis, leading to dysbiosis and gastrointestinal (GI) ailments, as well as immunosuppression and inappropriate immunostimulation, cholinergic neurotransmission dysregulation, neuroendocrinal system disarray, and neurodevelopmental and neurobehavioral alterations. Herein, we mainly focus on the contribution of gut microbiota (GM) to neurological impairments, e.g., stroke and neurodegenerative and neuropsychiatric disorders. The current review provides a comprehensive introduction to GLP's microbiological and neurochemical activities, including deviation of the intestinal Firmicutes-to-Bacteroidetes ratio, acetylcholinesterase inhibition, excitotoxicity, and mind-altering processes. Besides, it summarizes and critically discusses recent preclinical studies and clinical case reports concerning the harmful impacts of GBHs on the GI tract, MGB axis, and nervous system. Finally, an insightful comparison of toxic effects caused by GLP, GBH-SH, and GBHs is presented. To this end, we propose a first-to-date survey of clinical case reports on intoxications with these herbicides.

Metabolomic Changes in Rat Serum after Chronic Exposure to Glyphosate-Based Herbicide

Glyphosate-based herbicides (GBHs) have gained extensive popularity in recent decades. For many years, glyphosate has been regarded as harmless or minimally toxic to mammals due to the absence of its primary target, the shikimic acid pathway in humans. Nonetheless, mounting evidence suggests that glyphosate may cause adverse health effects in humans via other mechanisms. In this study, we described the metabolomic changes in the serum of experimental rats exposed to chronic GBH using the highly sensitive LC-MS/MS technique. We investigated the possible relationship between chronic exposure to GBH and neurological disorders. Our findings suggest that chronic exposure to GBH can alter spatial learning memory and the expression of some important metabolites that are linked to neurophysiological disorders in young rats, with the female rats showing higher susceptibility compared to the males. This indicates that female rats are more likely to show early symptoms of the disorder on exposure to chronic GBH compared to male rats. We observed that four important metabolites (paraxanthine, epinephrine, L-(+)-arginine, and D-arginine) showed significant changes and involvement in neurological changes as suggested by ingenuity pathway analysis. In conclusion, our results indicate that chronic exposure to GBH can increase the risk of developing neurological disorders.

Redox imbalance and inflammation: A link to depression risk in brazilian pesticide-exposed farmers

This study aims to elucidate the mechanisms linking occupational pesticide exposure to depression among rural workers from Maravilha, Brazil. We assessed the mental health, oxidative, and inflammatory profiles of farmers exposed to pesticides (N = 28) and compared them to an urban control group without occupational exposure to pesticides (N = 25). Data on sociodemographic, occupational history, and clinical records were collected. Emotional states were evaluated using the State-Trait Anxiety Inventory (STAI) and Beck Depression Inventory (BDI). Biochemical, hematological, inflammatory, and redox parameters were examined in blood samples from both groups. Results showed educational disparities between groups and unveiled a concerning underutilization of personal protective equipment (PPEs) among farmers. Glyphosate was the predominant pesticide used by farmers. Farmers exhibited higher BDI scores, including more severe cases of depression. Additionally, elevated levels of creatinine, ALT, AST, and LDH were observed in farmers, suggesting potential renal and hepatic issues due to pesticide exposure. Oxidative stress markers, such as increased lipid peroxidation and superoxide dismutase (SOD) activity, along with decreased catalase (CAT) activity and ascorbic acid levels, were noted in the pesticide-exposed group compared to controls. Elevated levels of inflammatory cytokines, particularly IL-1β, IL-6 and TNF-α, were also observed in pesticide-exposed group. Our findings suggest that inflammation, oxidative distress and lower educational levels may be associated with depression in pesticide-exposed farmers. This study highlights the impact of occupational pesticide exposure on the mental health of rural workers. The underuse of PPEs and the link between depressive symptoms, inflammation, and oxidative stress underscore the urgent need for improved safety measures in agricultural practices. Addressing these issues will contribute to a deeper understanding of the intricate relationship between environmental exposures and mental health outcomes.

Association between glyphosate exposure and cognitive function, depression, and neurological diseases in a representative sample of US adults: NHANES 2013-2014 analysis

Glyphosate, the most widely used herbicide globally, has been linked to neurological impairments in some occupational studies. However, the potential neurotoxic effects of glyphosate exposure in the general population are still not fully understood. We conducted analyses on existing data collected from 1532 adults of the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to explore the possible relationship between glyphosate exposure and cognitive function, depressive symptoms, disability, and neurological medical conditions. Our results showed a significant negative association between urinary glyphosate levels and the Consortium to Establish a Registry for Alzheimer's Disease Word List Memory Test (CERAD-WLT) trial 3 recall and delayed recall scores in both models, with ß coefficients of -0.288 (S.E. = 0.111, P = 0.021) and -0.426 (S.E. = 0.148, P = 0.011), respectively. Furthermore, the odds ratio did not show a significant increase with the severity of depressive symptoms with a one-unit increase in ln-glyphosate levels. However, the odds ratio for severe depressive symptoms was significantly higher than for no symptoms (odds ratio = 4.148 (95% CI = 1.009-17.133), P = 0.049). Notably, the odds ratio showed a significant increase for individuals with serious hearing difficulty (odds ratio = 1.354 (95% CI = 1.018-1.800), P = 0.039) with a one-unit increase in ln-glyphosate levels, but not for other neurological medical conditions. In conclusion, our findings provide the first evidence that glyphosate exposure may be associated with neurological health outcomes in the US adult population. Additional investigation is necessary to understand the potential mechanisms and clinical significance of these correlations.

The neurobehavioral impacts of typical antibiotics toward zebrafish larvae

Due to the widely usage in livestock, aquaculture and clinics, antibiotic residues are existed in aqueous environments and their potential toxicity to aquatic organisms is concerning. Here, we used zebrafish as the model to investigate the neurotoxicity and involved mechanism of seven antibiotics that were frequently detected in surface waters. The results revealed that the short-term exposure to clarithromycin (CLA), chlortetracycline (CTC) and roxithromycin (ROX) induced behavioral effects, with effective concentration of 1 μg/L (CTC and ROX) and 100 μg/L (CLA, CTC and ROX) respectively. A significant decrease in the travel distance and velocity as well as an increase in turn angle was measured. TUNEL assay identified increased cell apoptosis in brain sections of larvae exposed to three neurotoxic antibiotics, which raised the possibility that the behavioral symptoms were associated with neural damage. Transcriptome sequencing showed that the three antibiotics could affect the nervous system of zebrafish including the alteration of synaptogenesis and neurotransmission. Additionally, ROX and CTC affected pathways involved in mitochondrial stress response and endocrine system in zebrafish larvae. Besides, BDNF, ASCL1, and CREBBP are potential upstream regulatory factors that mediated these impacts. These findings indicated that exposure of CTC, ROX and CLA may cause abnormal behavior toward zebrafish larvae under environmental relevant concentration and revealed the potential role of neural cell apoptosis and synaptogenesis signaling in mediating this effect.

Role of voltage-dependent calcium channels on the striatal in vivo dopamine release induced by the organophosphorus pesticide glyphosate

In the present study, we investigated the role of voltage-sensitive calcium channels (VSCCs) on the striatal dopamine release induced by the pesticide glyphosate (GLY) using selective VSCC inhibitors. The dopamine levels were measured by in vivo cerebral microdialysis coupled to HPLC-ED. Nicardipine (L-type VSCC antagonist) or ω-conotoxin MVIIC (non-selective P/Q-type antagonist) had no effect on dopamine release induced by 5 mM GLY. In contrast, flunarizine (T-type antagonist) or ω-conotoxin GVIA (neuronal N-type antagonist) significantly reduced GLY-stimulated dopamine release. These results suggest that GLY-induced dopamine release depends on extracellular calcium and its influx through the T- and N-type VSCCs. These findings were corroborated by molecular docking, which allowed us to establish a correlation between the effect of GLY on blocked VSCC with the observed dopamine release. We propose new molecular targets of GLY in the dorsal striatum, which could have important implications for the assessment of pesticide risks in non-target organisms.

The herbicide glyphosate inhibits hippocampal long-term potentiation and learning through activation of pro-inflammatory signaling

Glyphosate, a herbicide marketed as Roundup, is widely used but there are concerns this exposure could impair cognitive function. In the CA1 region of rat hippocampal slices, we investigated whether glyphosate alters synaptic transmission and long-term potentiation (LTP), a cellular model of learning and memory. Our hypothesis is that glyphosate alters neuronal function and impairs LTP induction via activation of pro-inflammatory processes. Roundup depressed excitatory synaptic potentials(EPSPs) in a dose-dependent manner with complete suppression at 2000 mg/L. At concentrations ≤ 20 mg/L Roundup did not affect basal transmission, but 4 mg/L Roundup administered for 30 min inhibited LTP induction. Acute administration of 10-100 μM glyphosate also inhibited LTP induction. Minocycline, an inhibitor of microglial activation, and TAK-242, an inhibitor of toll-like receptor 4 (TLR4), both overcame the inhibitory effects of 100 µM glyphosate. Similarly, lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS), a different TLR4 antagonist, overcame the inhibitory effects. In addition, ISRIB (integrated stress response inhibitor) and quercetin, an inhibitor of endoplasmic reticulum stress, overcame the inhibitory effects. We also observed that in vivo glyphosate injection (16.9 mg/kg i.p.) impaired one-trial inhibitory avoidance learning. This learning deficit was overcome by TAK-242. These observations indicate that glyphosate can impair cognitive function through pro-inflammatory signaling in microglia.

Exposure to metam sodium-based pesticide impaired cognitive performances in adult mice: Involvement of oxidative damage and glial activation

Cognitive integrity is a critical aspect of neurological function, and a decline in cognitive function is a hallmark of neurotoxicity. Oxidative stress is a significant pathological feature contributing to cognitive deficits that can arise from exposure to environmental pollutants such as pesticides. Among these, Metam sodium-based pesticides (MS-BP) are an emergent type of pesticide widely used in the agriculture and public health sectors for controlling pests and diseases. Our prior research has shown that animals exposed to MS-BP during the early stages of brain development caused cognitive impairments. In the present study, we tested whether exposure to this compound in a fully matured brain would affect cognitive performance and induce oxidative damage to the central nervous system. In this context, adult mice received chronic treatment with increasing doses of MS-BP and subjected to a set of behavioral paradigms. Following behavioral assessment, oxidative stress and glial activation were evaluated. Our main findings showed that MS-BP chronic exposure impaired recognition and short- and long-term memory. These alterations were accompanied by increased superoxide dismutase activity and malondialdehyde level and a marked decrease in catalase activity in specific brain areas. Moreover, exposure to MS-BP is associated with a significant rise in the density of astrocytic and microglial markers, indicating a possible glial cell response within the prefrontal cortex and hippocampus. The present work demonstrated that MS-BP altered cognitive performance likely through oxidative damage to the brain.

Urinary Glyphosate, 2,4-D and DEET Biomarkers in Relation to Neurobehavioral Performance in Ecuadorian Adolescents in the ESPINA Cohort

BACKGROUND

Herbicides are the most used class of pesticides worldwide, and insect repellents are widely used globally. Yet, there is a dearth of studies characterizing the associations between these chemical groups and human neurobehavior. Experimental studies suggest that glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides can affect neurobehavior and the cholinergic and glutamatergic pathways in the brain. We aim to assess whether herbicides and insect repellents are associated with neurobehavioral performance in adolescents.

METHODS

We assessed 519 participants (11-17 years of age) living in agricultural communities in Ecuador. We quantified urinary concentrations of glyphosate, 2,4-D, and two N,N-diethyl-meta-toluamide (DEET) insect repellent metabolites [3-(diethylcarbamoyl)benzoic acid (DCBA) and 3-(ethylcarbamoyl)benzoic acid (ECBA)] using isotope-dilution mass spectrometry. We assessed neurobehavioral performance using 9 subtests across 5 domains (attention/inhibitory control, memory/learning, language, visuospatial processing, and social perception). We characterized the associations using generalized estimating equations and multiple imputation for metabolites below detection limits. Models were adjusted for demographic and anthropometric characteristics, urinary creatinine, and sexual maturation. Mediation by salivary cortisol, dehydroepiandrosterone, 17 β -estradiol , and testosterone was assessed using structural equation modeling.

RESULTS

The mean of each neurobehavioral domain score was between 7.0 and 8.7 [standard deviation (SD) range: 2.0-2.3]. Glyphosate was detected in 98.3% of participants, 2,4-D in 66.2%, DCBA in 63.3%, and ECBA in 33.4%. 2,4-D was negatively associated with all neurobehavioral domains, but statistically significant associations were observed with attention/inhibition [score difference per 50% higher metabolite concentration ( β ) = - 0.19 95% confidence interval (CI): - 0.31 , - 0.07 ], language [β = - 0.12 (95% CI: - 0.23 , - 0.01 )], and memory/learning [β = - 0.11 (95% CI: - 0.22 , 0.01)]. Glyphosate had a statistically significant negative association only with social perception [β = - 0.08 (95% CI: - 0.14 , - 0.01 )]. DEET metabolites were not associated with neurobehavioral performance. Mediation by gender and adrenal hormones was not observed.

CONCLUSION

This study describes worse neurobehavioral performance associated with herbicide exposures in adolescents, particularly with 2,4-D. Replication of these findings among other pediatric and adult populations is needed. https://doi.org/10.1289/EHP11383.

Influence of pesticide exposure on farmers' cognition: A systematic review

Objectives

Pesticide application has become necessary to increase crop productivity and reduce losses. However, the use of these products can produce toxic effects. Farmers are individuals occupationally exposed to pesticides, thus subject to associated diseases as well as cognitive impairment. However, this relation is not well established in the literature, requiring further investigation. To assess the potential association between farmers' pesticide exposure and cognitive impairment, we followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, considering participants, interventions, comparators, outcomes, and study strategies.

Materials and Methods

This study included articles published between 2000 and 2021 on the Scopus, Web of Science, ScienceDirect, and PubMed databases, retrieved by the terms "pesticides and cognition" and "pesticides and memory."

Results

In total, ten studies fit the established criteria and were included in the sample. All had farmers occupationally exposed to pesticides in their sample and only one study dispensed with a control group. Of the neurobehavioral tests, four studies used mini-mental state examination, six neurobehavioral core test batteries (tests recognized in the area), and the remaining, other tests. We observed that 90% of articles found an association between cognitive impairment and pesticide exposure. Overall, five studies measured the activity of cholinesterases in their sample, of which three found significant differences between groups, confirming intoxication in those exposed.

Conclusion

Despite the limited number of trials, we found scientific evidence to support the existence of adverse effects of pesticides on farmers' cognition. We recommend that future studies research similar projects, expanding knowledge on the subject.

Dual-Hit: Glyphosate exposure at NOAEL level negatively impacts birth and glia-behavioural measures in heterozygous shank3 mutants

The omnipresence of environmental contaminants represents a health danger with ramifications for adverse neurological trajectories. Here, we tested the dual-hit hypothesis that continuous exposure to non-observable adverse effect level (NOAEL) glyphosate from pre-natal to adulthood represents a risk factor for neurological-associated adaptations when in the presence of the heterozygote or homozygote mutation of the Shank3 synaptic gene. Ultrasound analysis of pregnant dams revealed patterns of pre-natal mortality with effects dependent on wild-type, Shank3ΔC/+, or Shank3ΔC/ΔC genotypes exposed to NOAEL glyphosate (GLY) compared to unexposed conditions. The postnatal survival rate was negatively impacted, specifically in Shank3ΔC/+ exposed to GLY. Next, the resulting six groups of pups were tracked into adulthood and analyzed for signs of neuroinflammation and neurological adaptions. Sholl's analysis revealed cortical microgliosis across groups exposed to GLY, with Shank3ΔC/+ mice presenting the most significant modifications. Brain tissues were devoid of astrocytosis, except for the perivascular compartment in the cortex in response to GLY. Distinct behavioral adaptations accompanied these cellular modifications, as locomotion and social preference were decreased in Shank3ΔC/+ mice exposed to GLY. Notably, GLY exposure from weaning did not elicit glial or neurological adaptations across groups, indicating the importance of pre-natal contaminant exposure. These results unveil the intersection between continuous pre-natal to adulthood environmental input and a pre-existing synaptic mutation. In an animal model, NOAEL GLY predominantly impacted Shank3ΔC/+ mice, compounding an otherwise mild phenotype compared to Shank3ΔC/ΔC. The possible relevance of these findings to neurodevelopmental risk is critically discussed, along with avenues for future research.

The herbicides glyphosate and glufosinate and the cyanotoxin β-N-methylamino-l-alanine induce long-term motor disorders following postnatal exposure: the importance of prior asymptomatic maternal inflammatory sensitization

Background

Prenatal maternal immune activation (MIA) and/or perinatal exposure to various xenobiotics have been identified as risk factors for neurological disorders, including neurodegenerative diseases. Epidemiological data suggest an association between early multi-exposures to various insults and neuropathologies. The "multiple-hit hypothesis" assumes that prenatal inflammation makes the brain more susceptible to subsequent exposure to several kinds of neurotoxins. To explore this hypothesis and its pathological consequences, a behavioral longitudinal procedure was performed after prenatal sensitization and postnatal exposure to low doses of pollutants.

Methods

Maternal exposure to an acute immune challenge (first hit) was induced by an asymptomatic lipopolysaccharide (LPS) dose (0.008 mg/kg) in mice. This sensitization was followed by exposing the offspring to environmental chemicals (second hit) postnatally, by the oral route. The chemicals used were low doses of the cyanotoxin β-N-methylamino-l-alanine (BMAA; 50 mg/kg), the herbicide glufosinate ammonium (GLA; 0.2 mg/kg) or the pesticide glyphosate (GLY; 5 mg/kg). After assessing maternal parameters, a longitudinal behavioral assessment was carried out on the offspring in order to evaluate motor and emotional abilities in adolescence and adulthood.

Results

We showed that the low LPS immune challenge was an asymptomatic MIA. Even though a significant increase in systemic pro-inflammatory cytokines was detected in the dams, no maternal behavioral defects were observed. In addition, as shown by rotarod assays and open field tests, this prenatal LPS administration alone did not show any behavioral disruption in offspring. Interestingly, our data showed that offspring subjected to both MIA and post-natal BMAA or GLA exposure displayed motor and anxiety behavioral impairments during adolescence and adulthood. However, this synergistic effect was not observed in the GLY-exposed offspring.

Conclusion

These data demonstrated that prenatal and asymptomatic immune sensitization represents a priming effect to subsequent exposure to low doses of pollutants. These double hits act in synergy to induce motor neuron disease-related phenotypes in offspring. Thus, our data strongly emphasize that multiple exposures for developmental neurotoxicity regulatory assessment must be considered. This work paves the way for future studies aiming at deciphering cellular pathways involved in these sensitization processes.

Effects of Glyphosate on Female Reproductive Output in the Marine Polychaete Worm Ophryotrocha diadema

Glyphosate is a broad-spectrum herbicide widely employed in agriculture. Exposure to this genotoxic and endocrine-disrupting compound has adverse effects on terrestrial and aquatic organisms and on humans as well. Here, we explored the effects of glyphosate on female reproductive output and somatic growth rate in the marine polychaete worm, Ophryotrocha diadema. Adult focal individuals were exposed to different concentrations of pure glyphosate (0.0, 0.125 0.250, 0.500, 1.000 µg/mL) administered once a week for 3 weeks. Toxic effects and mortalities were observed at the three higher concentrations, whereas only a decrease in growth rate was noted after exposure to 0.125 µg/mL, which did not affect female allocation. An area of focus in future studies should be the effects of contaminants, their metabolites, and ecologically relevant human-driven stressors in the context of global warming.

Neurotoxic effects of exposure to glyphosate in rat striatum: Effects and mechanisms of action on dopaminergic neurotransmission

The main objective of this study was to evaluate the effects and possible mechanisms of action of glyphosate and a glyphosate-based herbicide (GBH) on dopaminergic neurotransmission in the rat striatum. Acute exposure to glyphosate or GBH, administered by systemic (75 or 150 mg/kg, i.p.) or intrastriatal (1, 5, or 10 mM for 1 h) routes, produced significant concentration-dependent increases in dopamine release measured in vivo by cerebral microdialysis coupled to HPLC with electrochemical detection. Systemic administration of glyphosate also significantly impaired motor control and decreased striatal acetylcholinesterase activity and antioxidant capacity. At least two mechanisms can be proposed to explain the glyphosate-induced increases in extracellular dopamine levels: increased exocytotic dopamine release from synaptic vesicles or inhibition of dopamine transporter (DAT). Thus, we investigated the effects of intrastriatal administration of glyphosate (5 mM) in animals pretreated with tetrodotoxin (TTX) or reserpine. It was observed that TTX (10 or 20 μM) had no significant effect on glyphosate-induced dopamine release, while reserpine (10 mg/kg i.p) partially but significantly reduced the dopamine release. When glyphosate was coinfused with nomifensine (50 μM), the increase in dopamine levels was significantly higher than that observed with glyphosate or nomifensine alone. So, two possible hypotheses could explain this additive effect: both glyphosate and nomifensine act through different mechanisms at the dopaminergic terminals to increase dopamine levels; or both nomifensine and glyphosate act on DAT, with glyphosate simultaneously inhibiting reuptake and stimulating dopamine release by reversing the DAT function. Future research is needed to determine the effects of this pesticide at environmentally relevant doses.

Pesticides at brain borders: Impact on the blood-brain barrier, neuroinflammation, and neurological risk trajectories

Pesticides are omnipresent, and they pose significant environmental and health risks. Translational studies indicate that acute exposure to high pesticide levels is detrimental, and prolonged contact with low concentrations of pesticides, as single and cocktail, could represent a risk factor for multi-organ pathophysiology, including the brain. Within this research template, we focus on pesticides' impact on the blood-brain barrier (BBB) and neuroinflammation, physical and immunological borders for the homeostatic control of the central nervous system (CNS) neuronal networks. We examine the evidence supporting a link between pre- and postnatal pesticide exposure, neuroinflammatory responses, and time-depend vulnerability footprints in the brain. Because of the pathological influence of BBB damage and inflammation on neuronal transmission from early development, varying exposures to pesticides could represent a danger, perhaps accelerating adverse neurological trajectories during aging. Refining our understanding of how pesticides influence brain barriers and borders could enable the implementation of pesticide-specific regulatory measures directly relevant to environmental neuroethics, the exposome, and one-health frameworks.

Perinatal exposure to high concentration glyphosate-based herbicides induces intestinal apoptosis by activating endoplasmic reticulum stress in offspring

Glyphosate-based herbicides (GBHs), the most widely used pesticide worldwide, have been reported to impair organ function in humans and animals. However, research on the effect of maternal GBHs exposure on the intestinal health of offspring has received little attention. Based on the glyphosate limits defined by Codex Alimentarius Commission and European Food Safety Authority, this study established pregnant sow exposure models to investigate the influence of low (L-GBHs, 20 mg/kg) and high concentration GBHs (H-GBHs, 100 mg/kg) on the intestinal health of offspring and proposed the protective mechanism mediated by betaine. The results showed that the intestinal morphology and barrier function of suckling piglets were damaged in the H-GBHs group. H-GBHs increased the activity of glutathione peroxidase (GPX) and levels of methane dicarboxylic aldehyde (MDA), hydrogen peroxide (H₂O₂) and inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10)) in suckling piglets and activated Nrf2-mediated antioxidant signaling pathway. Subsequently, we found that exposure to H-GBHs triggered endoplasmic reticulum stress (ERS) and further induced apoptosis by upregulating the expression of Bcl-2-associated X protein (Bax), Caspase3, Caspase9 and Caspase12. Moreover, H-GBHs exposure perturbed mitochondrial membrane fusion and electron transport in mitochondrial respiratory chains by increasing the mRNA expression of mitofusin-2 (MFN2) and succinate dehydrogenase subunit A (SDHA), causing mitochondrial dysfunction. Dietary supplementation with betaine provided modest protection against GBHs-induced intestinal damage in suckling piglets. These findings reveal the mechanism of GBHs-induced intestinal damage in offspring, improving our understanding of the risk of GBHs exposure in pregnant women and suggesting the potential protective effects of betaine against GBHs poisoning.

Pesticides as endocrine disruptors: programming for obesity and diabetes

PURPOSE

Exposure to pesticides has been associated with obesity and diabetes in humans and experimental models mainly due to endocrine disruptor effects. First contact with environmental pesticides occurs during critical phases of life, such as gestation and lactation, which can lead to damage in central and peripheral tissues and subsequently programming disorders early and later in life.

METHODS

We reviewed epidemiological and experimental studies that associated pesticide exposure during gestation and lactation with programming obesity and diabetes in progeny.

RESULTS

Maternal exposure to organochlorine, organophosphate and neonicotinoids, which represent important pesticide groups, is related to reproductive and behavioral dysfunctions in offspring; however, few studies have focused on glucose metabolism and obesity as outcomes.

CONCLUSION

We provide an update regarding the use and metabolic impact of early pesticide exposure. Considering their bioaccumulation in soil, water, and food and through the food chain, pesticides should be considered a great risk factor for several diseases. Thus, it is urgent to reformulate regulatory actions to reduce the impact of pesticides on the health of future generations.

Glyphosate affects the neurochemical phenotype of the intramural neurons in the duodenum in the pig

BACKGROUND

Glyphosate-based herbicides have been one of the most intensively used pollutants worldwide and food products containing glyphosate are an essential component of human and animal diet. The aim of present study was to determine the effect of glyphosate intoxication on the neurochemical properties of the enteric nervous system (ENS) neurons located in the wall of the porcine duodenum.

METHODS

Fifteen sexually immature gilts divided into 3 groups were used: control-animals receiving empty gelatin capsules; G1-animals receiving a low dose of glyphosate-corresponding to the theoretical maximum daily intake (TMDI) - 0.05 mg/kg bw/day; G2-animals receiving a higher dose of glyphosate-corresponding to the acceptable daily intake (ADI)-0.5 mg/kg/day in gelatin capsules orally for 28 days. After this time, the animals were euthanized and small intestine samples were collected. Frozen sections were then subjected to the procedure of double immunofluorescent staining.

KEY RESULTS

Glyphosate supplementation led to alterations in the neurochemical code of the ENS neurons in the porcine duodenum. Generally, increased population of neurons immunoreactive to PACAP, CGRP, CART, nNOS, and a decreased number of VAChT-like immunoreactive neurons were noted.

CONCLUSIONS AND INFERENCES

It may be a first preclinical symptom of digestive tract dysfunction in the course of glyphosate intoxication and further studies are needed to assess the toxicity and risks of glyphosate to humans.

Invertebrates as models of learning and memory: investigating neural and molecular mechanisms

In this Commentary, we shed light on the use of invertebrates as model organisms for understanding the causal and conserved mechanisms of learning and memory. We provide a condensed chronicle of the contribution offered by mollusks to the studies on how and where the nervous system encodes and stores memory and describe the rich cognitive capabilities of some insect species, including attention and concept learning. We also discuss the use of planarians for investigating the dynamics of memory during brain regeneration and highlight the role of stressful stimuli in forming memories. Furthermore, we focus on the increasing evidence that invertebrates display some forms of emotions, which provides new opportunities for unveiling the neural and molecular mechanisms underlying the complex interaction between stress, emotions and cognition. In doing so, we highlight experimental challenges and suggest future directions that we expect the field to take in the coming years, particularly regarding what we, as humans, need to know for preventing and/or delaying memory loss. This article has an associated ECR Spotlight interview with Veronica Rivi.

Maternal exposure to glyphosate-based herbicide causes changes in the vascular function of offspring adult rats

This study analyzed how glyphosate exposure in the gestational period affects vascular function in their offspring, focusing on the influence of age and whether oxidative stress is involved in this effect. To this, pregnant Wistar rats were exposed through drinking water to 0.2% of a glyphosate commercial formulation, and we analyzed the response to acetylcholine and phenylephrine in the aorta from offspring of glyphosate herbicide-based (O-GHB) and controls (O-CON) rats at 3, 6, and 12 months of age. O-GHB groups showed no changes in arterial blood pressure or aorta histological analysis. Relaxation to acetylcholine was reduced in O-GHB than O-CON. Acute TEMPOL increased relaxation to acetylcholine in O-GHB at 6 and 12 months of age. The aorta from O-GHB was hyperactive to phenylephrine only at 6 months of age. Preincubation with N-nitro-L-arginine methyl ester (L-NAME) increased contraction to phenylephrine more in O-CON than O-GHB. TEMPOL similarly reduced phenylephrine response. This effect was prevented by L-NAME. Results reinforce the concept that oxidative stress during the perinatal period contributes to the development of vascular changes in adulthood. Results also reveal that although no changes in cardiac or histological parameters have been demonstrated, the current levels considered safe for exposure to glyphosate deserve further investigation, especially during pregnancy.

Amyotrophic Lateral Sclerosis Pathoetiology and Pathophysiology: Roles of Astrocytes, Gut Microbiome, and Muscle Interactions via the Mitochondrial Melatonergic Pathway, with Disruption by Glyphosate-Based Herbicides

The pathoetiology and pathophysiology of motor neuron loss in amyotrophic lateral sclerosis (ALS) are still to be determined, with only a small percentage of ALS patients having a known genetic risk factor. The article looks to integrate wider bodies of data on the biological underpinnings of ALS, highlighting the integrative role of alterations in the mitochondrial melatonergic pathways and systemic factors regulating this pathway across a number of crucial hubs in ALS pathophysiology, namely glia, gut, and the muscle/neuromuscular junction. It is proposed that suppression of the mitochondrial melatonergic pathway underpins changes in muscle brain-derived neurotrophic factor, and its melatonergic pathway mimic, N-acetylserotonin, leading to a lack of metabolic trophic support at the neuromuscular junction. The attenuation of the melatonergic pathway in astrocytes prevents activation of toll-like receptor agonists-induced pro-inflammatory transcription factors, NF-kB, and yin yang 1, from having a built-in limitation on inflammatory induction that arises from their synchronized induction of melatonin release. Such maintained astrocyte activation, coupled with heightened microglia reactivity, is an important driver of motor neuron susceptibility in ALS. Two important systemic factors, gut dysbiosis/permeability and pineal melatonin mediate many of their beneficial effects via their capacity to upregulate the mitochondrial melatonergic pathway in central and systemic cells. The mitochondrial melatonergic pathway may be seen as a core aspect of cellular function, with its suppression increasing reactive oxygen species (ROS), leading to ROS-induced microRNAs, thereby altering the patterning of genes induced. It is proposed that the increased occupational risk of ALS in farmers, gardeners, and sportsmen and women is intimately linked to exposure, whilst being physically active, to the widely used glyphosate-based herbicides. This has numerous research and treatment implications.

Effects of glyphosate and glyphosate-based herbicides like Roundup™ on the mammalian nervous system: A review

Glyphosate is the active ingredient in glyphosate-based herbicides (GBHs), such as Roundup™, the most widely used herbicides in the world. Glyphosate targets an essential enzyme in plants that is not found in animals. However, both glyphosate and GBHs are rated as Group 2A, probable human carcinogens, and also have documented effects on reproduction, acting as endocrine disruptive chemicals. We have reviewed reports of the effects of glyphosate and GBHs on mammalian nervous system function. As with several other herbicides, GBHs exposure has been associated with an increased risk of Parkinson's Disease and death of neurons in the substantia nigra. There is also some evidence implicating Roundup™ in elevated risk of autism. Other studies have shown the effects of GBHs on synaptic transmission in animal and cellular studies. The major mechanism of action appears to be oxidative stress, accompanied by mitochondrial dysfunction. In addition, some gut bacteria utilize the enzyme used by plants, and glyphosate and GBHs use has been shown to alter the gut microbiome. There is a large and growing body of evidence that the gut microbiome alters susceptibility to great number of human diseases, including nervous system function. The weight of the evidence indicates that in addition to cancer and reproductive effects, glyphosate and GBHs have significant adverse effects on the brain and behavior and increase the risk of at least some serious neurological diseases.

Glyphosate, AMPA and glyphosate-based herbicide exposure leads to GFAP, PCNA and caspase-3 increased immunoreactive area on male offspring rat hypothalamus

Glyphosate, aminomethylphosphonic acid (AMPA), and glyphosate-based herbicides altered the neuroendocrine axis, the content of brain neurotransmitters, and behavior in experimental animal models. Glyphosate alone, AMPA or Roundup® Active were administered to postpartum female rats, from P0 to P10, and their water consumption was measured daily. The immunoreactivity for glial fibrillary acidic protein (GFAP), proliferating cell nuclear antigen (PCNA) and caspase-3 was measured in the anterior, medial preoptic, periventricular, supraoptic and lateroanterior hypothalamic nuclei of P0-P10 male pups after exposure, via lactation, to these xenobiotics. Puppies exposed to glyphosate had a moderate level of GFAP with no overlapping astrocyte processes, but this overlapping was observed after Roundup® Active or AMPA exposure. After being exposed to Roundup® Active or AMPA, PCNA-positive cells with strong immunoreactivity were found in some hypothalamic nuclei. Cells containing caspase-3 were found in all hypothalamic nuclei studied, but the labeling was stronger after Roundup® Active or AMPA exposure. Xenobiotics significantly increased the immunoreactivity area for all of the markers studied in the majority of cases (p<0.05). AMPA or Roundup® Active treated animals had a greater area of PCNA immunoreactivity than control or glyphosate alone treated animals (p<0.05). The effects observed after xenobiotic exposure were not due to increased water intake. The increased immunoreactivity areas observed for the markers studied suggest that xenobiotics induced a neuro-inflammatory response, implying increased cell proliferation, glial activation, and induction of apoptotic pathways. The findings also show that glyphosate metabolites/adjuvants and/or surfactants present in glyphosate commercial formulations had a greater effect than glyphosate alone. In summary, glyphosate, AMPA, and glyphosate-based herbicides altered GFAP, caspase-3, and PCNA expression in the rat hypothalamus, altering the neuroendocrine axis.

Glyphosate infiltrates the brain and increases pro-inflammatory cytokine TNFα: implications for neurodegenerative disorders

BACKGROUND

Herbicides are environmental contaminants that have gained much attention due to the potential hazards they pose to human health. Glyphosate, the active ingredient in many commercial herbicides, is the most heavily applied herbicide worldwide. The recent rise in glyphosate application to corn and soy crops correlates positively with increased death rates due to Alzheimer's disease and other neurodegenerative disorders. Glyphosate has been shown to cross the blood-brain barrier in in vitro models, but has yet to be verified in vivo. Additionally, reports have shown that glyphosate exposure increases pro-inflammatory cytokines in blood plasma, particularly TNFα.

METHODS

Here, we examined whether glyphosate infiltrates the brain and elevates TNFα levels in 4-month-old C57BL/6J mice. Mice received either 125, 250, or 500 mg/kg/day of glyphosate, or a vehicle via oral gavage for 14 days. Urine, plasma, and brain samples were collected on the final day of dosing for analysis via UPLC-MS and ELISAs. Primary cortical neurons were derived from amyloidogenic APP/PS1 pups to evaluate in vitro changes in Aβ40-42 burden and cytotoxicity. RNA sequencing was performed on C57BL/6J brain samples to determine changes in the transcriptome.

RESULTS

Our analysis revealed that glyphosate infiltrated the brain in a dose-dependent manner and upregulated TNFα in both plasma and brain tissue post-exposure. Notably, glyphosate measures correlated positively with TNFα levels. Glyphosate exposure in APP/PS1 primary cortical neurons increases levels of soluble Aβ40-42 and cytotoxicity. RNAseq revealed over 200 differentially expressed genes in a dose-dependent manner and cell-type-specific deconvolution analysis showed enrichment of key biological processes in oligodendrocytes including myelination, axon ensheathment, glial cell development, and oligodendrocyte development.

CONCLUSIONS

Collectively, these results show for the first time that glyphosate infiltrates the brain, elevates both the expression of TNFα and soluble Aβ, and disrupts the transcriptome in a dose-dependent manner, suggesting that exposure to this herbicide may have detrimental outcomes regarding the health of the general population.

Glyphosate and neurological outcomes: A systematic literature review of animal studies

Studies of nervous system effects of glyphosate, a widely used herbicide, have not been critically examined. The aim of this paper was to systematically review glyphosate-induced neurotoxicity literature to determine its usefulness in regulatory decision-making. The review was restricted to mammalian studies of behavior, neuropathology, and neuropharmacology; in vitro and other biochemical studies were considered supplementary information. Glyphosate formulation studies were also considered, despite uncertainties regarding toxicities of the formulated products; no studies used a formulation vehicle as the control. Inclusion criteria were developed a priori to ensure consistent evaluation of studies, and in vivo investigations were also ranked using ToxRTool software to determine reliability. There were 27 in vivo studies (open literature and available regulatory reports), but 11 studies were considered unreliable (mostly due to critical methodological deficiencies). There were only seven acceptable investigations on glyphosate alone. Studies differed in terms of dosing scenarios, experimental designs, test species, and commercial product. Limitations included using only one dose and/or one test time, small sample sizes, limited data presentation, and/or overtly toxic doses. While motor activity was the most consistently affected endpoint (10 of 12 studies), there were considerable differences in outcomes. In six investigations, there were no marked neuropathological changes in the central or peripheral nervous system. Other neurological effects were less consistent, and some outcomes were less convincing due to influences including high variability and small effect sizes. Taken together, these studies do not demonstrate a consistent impact of glyphosate on the structure or function of the mammalian nervous system.

Lifelong Exposure to a Low-Dose of the Glyphosate-Based Herbicide RoundUp® Causes Intestinal Damage, Gut Dysbiosis, and Behavioral Changes in Mice

RoundUp® (RUp) is a comercial formulation containing glyphosate (N-(phosphono-methyl) glycine), and is the world's leading wide-spectrum herbicide used in agriculture. Supporters of the broad use of glyphosate-based herbicides (GBH) claim they are innocuous to humans, since the active compound acts on the inhibition of enzymes which are absent in human cells. However, the neurotoxic effects of GBH have already been shown in many animal models. Further, these formulations were shown to disrupt the microbiome of different species. Here, we investigated the effects of a lifelong exposure to low doses of the GBH-RUp on the gut environment, including morphological and microbiome changes. We also aimed to determine whether exposure to GBH-RUp could harm the developing brain and lead to behavioral changes in adult mice. To this end, animals were exposed to GBH-RUp in drinking water from pregnancy to adulthood. GBH-RUp-exposed mice had no changes in cognitive function, but developed impaired social behavior and increased repetitive behavior. GBH-Rup-exposed mice also showed an activation of phagocytic cells (Iba-1-positive) in the cortical brain tissue. GBH-RUp exposure caused increased mucus production and the infiltration of plama cells (CD138-positive), with a reduction in phagocytic cells. Long-term exposure to GBH-RUp also induced changes in intestinal integrity, as demonstrated by the altered expression of tight junction effector proteins (ZO-1 and ZO-2) and a change in the distribution of syndecan-1 proteoglycan. The herbicide also led to changes in the gut microbiome composition, which is also crucial for the establishment of the intestinal barrier. Altogether, our findings suggest that long-term GBH-RUp exposure leads to morphological and functional changes in the gut, which correlate with behavioral changes that are similar to those observed in patients with neurodevelopmental disorders.

Anxiety and Gene Expression Enhancement in Mice Exposed to Glyphosate-Based Herbicide

Growing evidence demonstrates that serotonin (5-HT) depletion increases activity in the amygdala and medial prefrontal cortex (mPFC), ultimately leading to anxiety behavior. Previously, we showed that glyphosate-based herbicides (GBHs) increased anxiety levels and reduced the number of serotoninergic fibers within the mPFCs and amygdalas of exposed mice. However, the impact of this 5-HT depletion following GBH exposure on neuronal activity in these structures is still unknown. In this study, we investigated the effects of GBH on immediate early gene (IEG) activation within the mPFCs and amygdalas of treated mice from juvenile age to adulthood and its subsequent effects on anxiety levels. Mice were treated for subchronic (6 weeks) and chronic (12 weeks) periods with 250 or 500 mg/kg/day of GBH and subjected to behavioral testing using the open field and elevated plus maze paradigms. Then, we analyzed the expression levels of c-Fos and pCREB and established the molecular proxies of neuronal activation within the mPFC and the amygdala. Our data revealed that repeated exposure to GBH triggers anxiogenic behavior in exposed mice. Confocal microscopy investigations into the prelimbic/infralimbic regions of the mPFC and in basolateral/central nuclei of the amygdala disclosed that the behavioral alterations are paralleled by a robust increase in the density and labelling intensity of c-Fos- and pCREB-positive cells. Taken together, these data show that mice exposed to GBH display the hyperactivation of the mPFC–amygdala areas, suggesting that this is a potential mechanism underlying the anxiety-like phenotype.

Toxic Effects of Glyphosate on the Nervous System: A Systematic Review

Glyphosate, a non-selective systemic biocide with broad-spectrum activity, is the most widely used herbicide in the world. It can persist in the environment for days or months, and its intensive and large-scale use can constitute a major environmental and health problem. In this systematic review, we investigate the current state of our knowledge related to the effects of this pesticide on the nervous system of various animal species and humans. The information provided indicates that exposure to glyphosate or its commercial formulations induces several neurotoxic effects. It has been shown that exposure to this pesticide during the early stages of life can seriously affect normal cell development by deregulating some of the signaling pathways involved in this process, leading to alterations in differentiation, neuronal growth, and myelination. Glyphosate also seems to exert a significant toxic effect on neurotransmission and to induce oxidative stress, neuroinflammation and mitochondrial dysfunction, processes that lead to neuronal death due to autophagy, necrosis, or apoptosis, as well as the appearance of behavioral and motor disorders. The doses of glyphosate that produce these neurotoxic effects vary widely but are lower than the limits set by regulatory agencies. Although there are important discrepancies between the analyzed findings, it is unequivocal that exposure to glyphosate produces important alterations in the structure and function of the nervous system of humans, rodents, fish, and invertebrates.

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.

A subchronic low-dose exposure of a glyphosate-based herbicide induces depressive and anxious-like behavior in mice: quercetin therapeutic approach

In this study, we investigated the possible role of pesticide exposure in contributing to neurological diseases such as depression. Here, we evaluated whether a subchronic low dose of a glyphosate-based herbicide (GBH) could induce alterations in the central nervous system, using the flavonoid quercetin as a therapeutic strategy. Forty mice were divided into four treatment groups: control, GBH, quercetin, and GBH+Quer groups and received 50 mg/kg of GBH solution, 30 mg/kg of quercetin, and/or vehicles for 30 days via gavage. After performing behavioral tests, such as the open field (OF), elevated plus maze (EPM), forced swim test (FST), and sucrose preference test (SPT), the mice were euthanized and their hippocampal tissues were collected to measure the levels of oxidative stress markers such as reactive species (RS), total antioxidant capacity (FRAP), reduced glutathione (GSH), and acetylcholinesterase activity (AChE), as well as for histological evaluation. The GBH group showed anxious and depressive-like behavior in the EPM and FST tests, as well as increased levels of RS and decreased GSH levels in the hippocampus. Quercetin treatment in the GBH+Quer group allowed partial or total improvement in behavioral tests (EPM and FST) and in the levels of oxidative stress markers (RS and GSH). However, the quercetin group showed similar behavior to the GBH group after treatment. The results revealed that oral exposure to a subchronic low dose of GBH was capable of promoting effects on behavior and oxidative stress in the hippocampus of mice. In addition, despite quercetin having a neuroprotective role, caution is needed when considering the possible per se effects of its continuous supplementation.

Chronic Dietary Exposure of Roosters to a Glyphosate-Based Herbicide Increases Seminal Plasma Glyphosate and AMPA Concentrations, Alters Sperm Parameters, and Induces Metabolic Disorders in the Progeny

The effects of chronic dietary Roundup (RU) exposure on rooster sperm parameters, fertility, and offspring are unknown. We investigated the effects of chronic RU dietary exposure (46.8 mg kg⁻¹ day⁻¹ glyphosate) for 5 weeks in 32-week-old roosters (n = 5 RU-exposed and n = 5 control (CT)). Although the concentrations of glyphosate and its main metabolite AMPA (aminomethylphosphonic acid) increased in blood plasma and seminal fluid during exposure, no significant differences in testis weight and sperm concentrations were observed between RU and CT roosters. However, sperm motility was significantly reduced, associated with decreased calcium and ATP concentrations in RU spermatozoa. Plasma testosterone and oestradiol concentrations increased in RU roosters. These negative effects ceased 14 days after RU removal from the diet. Epigenetic analysis showed a global DNA hypomethylation in RU roosters. After artificial insemination of hens (n = 40) with sperm from CT or RU roosters, eggs were collected and artificially incubated. Embryo viability did not differ, but chicks from RU roosters (n = 118) had a higher food consumption, body weight and subcutaneous adipose tissue content. Chronic dietary RU exposure in roosters reduces sperm motility and increases plasma testosterone levels, growth performance, and fattening in offspring.

Pleiotropic Outcomes of Glyphosate Exposure: From Organ Damage to Effects on Inflammation, Cancer, Reproduction and Development

Glyphosate is widely used worldwide as a potent herbicide. Due to its ubiquitous use, it is detectable in air, water and foodstuffs and can accumulate in human biological fluids and tissues representing a severe human health risk. In plants, glyphosate acts as an inhibitor of the shikimate pathway, which is absent in vertebrates. Due to this, international scientific authorities have long-considered glyphosate as a compound that has no or weak toxicity in humans. However, increasing evidence has highlighted the toxicity of glyphosate and its formulations in animals and human cells and tissues. Thus, despite the extension of the authorization of the use of glyphosate in Europe until 2022, several countries have begun to take precautionary measures to reduce its diffusion. Glyphosate has been detected in urine, blood and maternal milk and has been found to induce the generation of reactive oxygen species (ROS) and several cytotoxic and genotoxic effects in vitro and in animal models directly or indirectly through its metabolite, aminomethylphosphonic acid (AMPA). This review aims to summarize the more relevant findings on the biological effects and underlying molecular mechanisms of glyphosate, with a particular focus on glyphosate's potential to induce inflammation, DNA damage and alterations in gene expression profiles as well as adverse effects on reproduction and development.

Perinatal exposure to a glyphosate-based herbicide causes dysregulation of dynorphins and an increase of neural precursor cells in the brain of adult male rats

Glyphosate, the most used herbicide worldwide, has been suggested to induce neurotoxicity and behavioral changes in rats after developmental exposure. Studies of human glyphosate intoxication have reported adverse effects on the nervous system, particularly in substantia nigra (SN). Here we used matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) to study persistent changes in peptide expression in the SN of 90-day-old adult male Wistar rats. The animals were perinatally exposed to 3 % GBH (glyphosate-based herbicide) in drinking water (corresponding to 0.36 % of glyphosate) starting at gestational day 5 and continued up to postnatal day 15 (PND15). Peptides are present in the central nervous system before birth and play a critical role in the development and survival of neurons, therefore, observed neuropeptide changes could provide better understanding of the GBH-induced long term effects on SN. The results revealed 188 significantly altered mass peaks in SN of animals perinatally exposed to GBH. A significant reduction of the peak intensity (P < 0.05) of several peptides from the opioid-related dynorphin family such as dynorphin B (57 %), alpha-neoendorphin (50 %), and its endogenous metabolite des-tyrosine alpha-neoendorphin (39 %) was detected in the GBH group. Immunohistochemical analysis confirmed a decreased dynorphin expression and showed a reduction of the total area of dynorphin immunoreactive fibers in the SN of the GBH group. In addition, a small reduction of dynorphin immunoreactivity associated with non-neuronal cells was seen in the hilus of the hippocampal dentate gyrus. Perinatal exposure to GBH also induced an increase in the number of nestin-positive cells in the subgranular zone of the dentate gyrus. In conclusion, the results demonstrate long-term changes in the adult male rat SN and hippocampus following a perinatal GBH exposure suggesting that this glyphosate-based formulation may perturb critical neurodevelopmental processes.

Neurotoxic Effect of Fipronil in Male Wistar Rats: Ameliorative Effect of L-Arginine and L-Carnitine

Simple Summary

Insecticides are widely used in agricultural and household environments. They induce wide range of deleterious effects. Fipronil is one of the most widely used phenylpyrazoles insecticides. The neurotoxic effect of such insecticide was tested in the present study with special emphasis on cognitive deficit as well as testing the possible ameliorative impacts of L-arginine and L-carnitine. The study proposed fipronil-induced cognitive deficit as a reflection to oxidative stress and neuro-inflammation. Moreover, L-arginine and L-carnitine exerted ameliorative influence on fipronil induced oxidative stress and neuro-inflammation. Therefore, L-arginine and L-carnitine can be considered as prospective candidates for mitigation of pesticide induced neurotoxicity especially in people with high-risk exposure to pesticide.

Abstract

The ameliorative effect of L-arginine (LA) and L-carnitine (LC) against fipronil (FPN)-induced neurotoxicity was explored. In this case, 36 adult male rats were randomly divided into six groups: group I received distilled water, group II received 500 mg/kg LA, group III received 100 mg/kg LC, group IV received 4.85 mg/kg FPN, group V received 4.85 mg/kg FPN and 500 mg/kg LA and group VI received 4.85 mg/kg FPN and 100 mg/kg LC for 6 weeks. Cognitive performance was assessed using Barnes maze (BM). Serum corticosterone, brain total antioxidant capacity (TAC), malondialdehyde (MDA) and dopamine were measured. Histopathology and immunohistochemistry of ionized calcium-binding adaptor (Iba-1), doublecortin (DCX) and serotonin (S-2A) receptors were performed. Fipronil induced noticeable deterioration in spatial learning and memory performance. In addition, FPN significantly (p < 0.05) diminished brain antioxidant defense system and dopamine coincide with elevated serum corticosterone level. Histopathological examination revealed degenerative and necrotic changes. Furthermore, Iba-1 and DCX were significantly expressed in cortex and hippocampus whereas S-2A receptors were significantly lowered in FPN group. However, administration of LA or LC alleviated FPN-induced deteriorations. In conclusion, LA and LC could be prospective candidates for mitigation of FPN-induced neurotoxicity via their antioxidant, anti-inflammatory and neuropotentiating effects.

Glyphosate Herbicide: Reproductive Outcomes and Multigenerational Effects

Glyphosate base herbicides (GBHs) are the most widely applied pesticides in the world and are mainly used in association with GBH-tolerant crop varieties. Indiscriminate and negligent use of GBHs has promoted the emergence of glyphosate resistant weeds, and consequently the rise in the use of these herbicides. Glyphosate, the active ingredient of all GBHs, is combined with other chemicals known as co-formulants that enhance the herbicide action. Nowadays, the safety of glyphosate and its formulations remain to be a controversial issue, as evidence is not conclusive whether the adverse effects are caused by GBH or glyphosate, and little is known about the contribution of co-formulants to the toxicity of herbicides. Currently, alarmingly increased levels of glyphosate have been detected in different environmental matrixes and in foodstuff, becoming an issue of social concern. Some in vitro and in vivo studies have shown that glyphosate and its formulations exhibit estrogen-like properties, and growing evidence has indicated they may disrupt normal endocrine function, with adverse consequences for reproductive health. Moreover, multigenerational effects have been reported and epigenetic mechanisms have been proved to be involved in the alterations induced by the herbicide. In this review, we provide an overview of: i) the routes and levels of human exposure to GBHs, ii) the potential estrogenic effects of glyphosate and GBHs in cell culture and animal models, iii) their long-term effects on female fertility and mechanisms of action, and iv) the consequences on health of successive generations.

Relationship between Prenatal or Postnatal Exposure to Pesticides and Obesity: A Systematic Review

In recent years, the worldwide prevalence of overweight and obesity among adults and children has dramatically increased. The conventional model regarding the onset of obesity is based on an imbalance between energy intake and expenditure. However, other possible environmental factors involved, such as the exposure to chemicals like pesticides, cannot be discarded. These compounds could act as endocrine-disrupting chemicals (EDC) that may interfere with hormone activity related to several mechanisms involved in body weight control. The main objective of this study was to systematically review the data provided in the scientific literature for a possible association between prenatal and postnatal exposure to pesticides and obesity in offspring. A total of 25 human and 9 animal studies were analyzed. The prenatal, perinatal, and postnatal exposure to organophosphate, organochlorine, pyrethroid, neonicotinoid, and carbamate, as well as a combined pesticide exposure was reviewed. This systematic review reveals that the effects of pesticide exposure on body weight are mostly inconclusive, finding conflicting results in both humans and experimental animals. The outcomes reviewed are dependent on many factors, including dosage and route of administration, species, sex, and treatment duration. More research is needed to effectively evaluate the impact of the combined effects of different pesticides on human health.

Varying modalities of perinatal exposure to a pesticide cocktail elicit neurological adaptations in mice and zebrafish

Epidemiological indications connect maternal and developmental presence or exposure to pesticides with an increased risk for a spectrum of neurological trajectories. To provide pre-clinical data in support of this hypothesis, we used two distinct experimental models. First, female and male mice were fed immediately prior to mating, and the resulting pregnant dams were continously fed during gestation and lactation periods using chow pellets containing a cocktail of six pesticides at tolerable daily intake levels. Male and female offspring were then tracked for behavioral and in vivo electrophysiological adaptations. Second, a zebrafish model allowed us to screen toxicity and motor-behavior outcomes specifically associated with the developmental exposure to a low-to-high concentration range of the cocktail and of each individual pesticide. Here, we report anxiety-like behavior in aging male mice maternally exposed to the cocktail, as compared to age and gender matched sham animals. In parallel, in vivo electrocorticography revealed a decrease in gamma (40-80 Hz) and an increase of theta (6-9 Hz) waves, delineating a long-term, age-dependent, neuronal slowing. Neurological changes were not accompanied by brain structural malformations. Next, by using zebrafish larvae, we showed an increase of all motor-behavioral parameters resulting from the developmental exposure to 10 μg/L of pesticide cocktail, an outcome that was not associated with midbrain structural or neurovascular modifications as assessed by in vivo 2-photon microscopy. When screening each pesticide, chlorpyrifos elicited modifications of swimming parameters at 0.1 μg/L, while other components provoked changes from 0.5 μg/L. Ziram was the single most toxic component inducing developmental malformations and mortality at 10 μg/L. Although we have employed non-equivalent modalities and timing of exposure in two dissimilar experimental models, these outcomes indicate that presence of a pesticide cocktail during perinatal periods represents an element promoting behavioral and neurophysiological modifications. The study limitations and the possible pertinence of our findings to ecotoxicology and public health are critically discussed.

Glyphosate exposure induces synaptic impairment in hippocampal neurons and cognitive deficits in developing rats

Glyphosate is the active ingredient of several widely used herbicide formulations. Studies based on Glyphosate exposure in different experimental models have suggested that the nervous system represented a key target for its toxicity. Previously, we demonstrated that exposure to glyphosate during gestation induces deficits on behavioral and cognitive function in rats. The aim of the present work was to examine whether cognitive dysfunction induced by Glyphosate was connected to changes on synapse formation and maturation. To understand how glyphosate affects synaptic assembly, we performed in vitro assays on cultured hippocampal neurons that were exposed to the herbicide (0.5 or 1 mg/mL) for 5 or 10 days. Biochemical and immunocytochemical approaches revealed that Glyphosate treated neurons showed a decrease on dendritic complexity and synaptic spine formation and maturation. Moreover, results indicated that Glyphosate decreased synapse formation in hippocampal neurons. To evaluate these effects in vivo, pup rats were treated with 35 or 70 mg/kg of Glyphosate from PND 7 to PND 27, every 48 h. Results indicated that Glyphosate postnatal exposure induced cognitive impairments, since recognition and spatial memory were altered. To go further, we evaluated synaptic protein expression and synaptic organization in hippocampus. Images revealed that Glyphosate treatment downregulates synapsin-1, PSD-95, and CaMKII expression, and also decreased PSD-95 clustering in hippocampus. Taken together, these findings demonstrate for the first time that Glyphosate exposure affects synaptic assembly and reduced synaptic protein expression in hippocampus and that likely triggers the impairment of cognitive function and neuronal connectivity.

Differential impact of dose-range glyphosate on locomotor behavior, neuronal activity, glio-cerebrovascular structures, and transcript regulations in zebrafish larvae

The presence of glyphosate represents a debated ecotoxicological and health risk factor. Here, zebrafish larvae were exposed, from 1.5 to 120 h post-fertilization, to a broad concentration range (0.05-10.000 μg/L) of glyphosate to explore its impact on the brain. We evaluated morphology, tracked locomotor behavior and neurophysiological parameters, examined neuro-glio-vascular cell structures, and outlined transcriptomic outcomes by RNA sequencing. At the concentration range tested, glyphosate did not elicit gross morphological changes. Behavioral analysis revealed a significant decrease in locomotor activity following the exposure to 1000 μg/L glyphosate or higher. In parallel, midbrain electrophysiological recordings indicated abnormal, and variable, spike activity in zebrafish larvae exposed to 1000 μg/L glyphosate. Next, we asked whether the observed neurophysiological outcome could be secondary to brain structural modifications. We used transgenic zebrafish and in vivo 2-photon microscopy to examine, at the cellular level, the effects of the behavior-modifying concentration of 1000 μg/L, comparing to low 0.1 μg/L, and control. We ruled out the presence of cerebrovascular and neuronal malformations. However, microglia morphological modifications were visible at the two glyphosate concentrations, specifically the presence of amoeboid cells suggestive of activation. Lastly, RNAseq analysis showed the deregulation of transcript families implicated in neuronal physiology, synaptic transmission, and inflammation, as evaluated at the two selected glyphosate concentrations. In zebrafish larvae, behavioral and neurophysiological defects occur after the exposure to high glyphosate concentrations while cellular and transcript signatures can be detected in response to low dose. The prospective applicability to ecotoxicology and the possible extension to brain-health vulnerability are critically discussed.

Life-long Dietary Pesticide Cocktail Induces Astrogliosis Along with Behavioral Adaptations and Activates p450 Metabolic Pathways

Exposure to environmental contaminants is a public health concern. However, pre-clinical studies that examine the impact of pesticides at low-dose and the long-term consequences are uncommon. Here, C57BL6/j male and female mice were daily fed from weaning and up to 12 months, corresponding to early-childhood into middle-age in humans, using chow pellets containing a cocktail of pesticides at tolerable daily intake levels. We found that 12 months of dietary exposure to pesticides was associated with a moderate perenchymal or perivascular astrogliosis in specific hippocampal sub-regions. The expression of platelet-derived growth factor receptor beta was modified at the perivascular level. Examination of Iba1⁺ microglial cells did not reveal sizeable changes. Concomitantly to astrogliosis, spontaneous spatial memory and sociability were modified in males at 12 months of dietary exposure to pesticides. Telemetry electrocorticograhic explorations ruled out the presence of epileptiform activity or theta-gamma wave modifications in these conditions. Long-term pesticides impacted the periphery where the hepatic P450 metabolic cytochromes Cyp4a14 and Cyp4a10 were significantly upregulated in male and female mice during the 12 months of exposure. The expression of β-oxidation genes, such as Acox1, Cpt1a and Eci, was also significantly increased in male and female mice in response to pesticides. Collectively, our results indicate that a life-long exposure to a pesticide cocktail elicits sex-dependent, spatio-temporally restricted brain modifications and significant activation of P450 pathways in the periphery. These brain-peripheral adjustments are discussed as time or age-dependent vulnerability elements.