NeuroToxicology

Chlorpyrifos is a widely used organophosphate pesticide that exerts its primary toxic effect through inhibition of acetylcholinesterase (AChE). Although the acute neurotoxicity of chlorpyrifos is well characterized, the lasting biochemical, behavioral, and epigenetic consequences of sub-chronic exposure remain poorly understood, particularly when considering sex-specific differences. Therefore, we exposed male and female C57BL/6J mice to either peanut oil (n=19), low chlorpyrifos exposure (1 mg/kg/day; n=19), or high chlorpyrifos exposure (10 mg/kg/day n=10) repeatedly for 21 days via subcutaneous injection. Blood AChE activity, behavior, and hippocampal DNA methylation were measured across groups. During exposure, AChE activity decreased in both males and females but only returned to baseline after behavioral testing in females exposed to low chlorpyrifos levels. Behavioral tests also revealed a sex-specific phenotype, with females in the low exposure group exhibiting reduced forced swim test immobility and a significant time by exposure interaction in open field habituation. No significant behavioral effects were observed in males. Significant DNA methylation changes were observed at 3,538 CpG sites in male and female mice after high exposure. Sex-specific analyses revealed two female-specific differentially methylated CpGs after high exposure. Pathways enriched for differentially methylated genes included several related to synaptic remodeling, cholinergic synapse, and various endocrine systems. These findings demonstrate that repeated high chlorpyrifos exposure leads to persistent cholinergic disruption and DNA methylation changes. However, the female-specific behavioral changes seen are independent of AChE activity and widespread DNA methylation changes, suggesting additional mechanisms, present only in females, may underlie behavioral sensitivity to chlorpyrifos. New and NoteworthySub-chronic chlorpyrifos exposure in adult mice produced dose-dependent blood AChE suppression and widespread hippocampal DNA methylation changes in both sexes, with pathway enrichment including cholinergic synapse and endocrine systems. Behavioral effects were subtle, with females in the low exposure group showing reduced forced swim immobility and altered locomotor habituation. Notably, the female-specific behavioral changes seen are independent of AChE activity and DNA methylation changes, suggesting novel mechanisms may underlie female behavioral sensitivity to chlorpyrifos.

IntroductionMetal exposure has been associated with higher risk of neurodegenerative disorders such as Alzheimers disease (AD). We examined the potential link between welding-related metal co-exposure (e.g., Fe, Mn, Pb) and AD-related structural and neurobehavioral metrics. MethodsSubjects with (welders; n=42) or without (controls; n=31) a history of welding were examined. Metal exposure was estimated by exposure questionnaires and whole blood metal levels. Brain metal accumulations were estimated by MRI R1 (Mn) and R2* (Fe) in the caudate, putamen, globus pallidus, red nucleus (RN), and hippocampus. AD-related structural differences were assessed by volume and diffusion tensor imaging metrics in the hippocampus, and neurobehavioral aspects by learning/memory task scores. ResultsCompared to controls, welders displayed higher blood metal levels (ps <0.004) and R2* values in the caudate and RN (ps<0.024). Caudate R2* values were associated with blood Fe (p=0.043), whereas RN R2* values were correlated with blood Pb (p=0.003). Welders had higher hippocampal mean diffusivity (MD; p=0.011) and lower Story Recall scores (p=0.049), but no difference in volume or domain-wise learning/memory performance (ps>0.117). Group differences in hippocampal MD and Story Recall scores were greater with higher RN R2* values (ps<0.016). Moreover, RN R2* values reflected an indirect link between blood Pb and hippocampal MD (p=0.036) across both groups. DiscussionWelders had hippocampal structural and learning/memory performance differences similar to those in AD-at-risk populations. These AD-like differences in welders may, in part, be linked to Pb exposure reflected by higher RN R2* levels at the brain level.

Lead (Pb) continues to be a public health burden, in the US and around the world, and yet the effects of historical and current exposure levels on neurogenesis are not fully understood. Here we examine the effects of a range of environmentally relevant Pb concentrations (0.16M, 1.26M, and 10M Pb) relative to control on neural differentiation in the SH-SY5Y cell model. Pb exposure began on Day 5 and continued throughout differentiation at Day 18. We assessed morphological measures related to neurogenesis at several time points during this process, including the expression of proteins key in neural differentiation ({beta}-tubulin III and GAP43), cell number and size, as well as the development of neurites. The bulk of detectable changes occurred with 10M Pb exposure, most notably that of {beta}-tubulin III and GAP43 expression. Effects with the 0.16M and 1.26M Pb exposure conditions increased as differentiation progressed, with significant reductions in cell and nuclear size as well as the number and length of neural projections by Day 18. Best benchmark concentration (BMC) analysis revealed many of these metrics to be susceptible to levels of Pb at or below historically relevant levels. This work highlights the disruption of neurite formation and protein expression as potential new mechanisms by which environmentally relevant Pb exposure impacts neurogenesis and morphology and perturb cognitive health throughout the life course.

Mancozeb, a widely used fungicide composed of manganese ethylene-bis-dithiocarbamate with zinc salts, has raised concerns due to its potential neurotoxic effects. In this study, we investigated how chronic oral administration of mancozeb affects astrocyte function and neurobehavior in mice, focusing on store-operated Ca{superscript 2} entry (SOCE), mediated by Orai1 and STIM1. Mancozeb treatment at 0.5 {micro}g/kg/day for 4 weeks reduced glial fibrillary acidic protein (GFAP) expression in the hippocampus and corpus callosum of mice, indicating astrocyte atrophy. Further, administration at the human acceptable daily intake (30 {micro}g/kg/day) for 1 week induced hippocampal astrocyte atrophy and hyperlocomotor activity in open field tests. In vitro experiments revealed that mancozeb specifically inhibited SOCE in astrocytes by targeting the Orai1/STIM1 complex, as its inhibitory effect was abolished by short hairpin RNA (shRNA)-mediated knockdown of Orai1 or STIM1, but not by knockdown of TRPA1 or scramble shRNA. This demonstrates that mancozeb-mediated SOCE inhibition critically depends on the presence of Orai1 and STIM1, highlighting the molecular specificity of its action. Furthermore, mancozeb diminished endoplasmic reticulum (ER) Ca{superscript 2} stores and P2Y1 receptor agonist-induced Ca{superscript 2} transients. Electrophysiological analyses revealed that mancozeb selectively decreased the inhibitory postsynaptic current frequency without affecting excitatory currents, suggesting reduced astrocyte-mediated GABA release. Collectively, these findings demonstrate that mancozeb disrupts astrocytic Ca{superscript 2} homeostasis through Orai1/STIM1-dependent SOCE inhibition, leading to astrocyte atrophy and altered inhibitory neurotransmission, which may underlie the observed behavioral changes. These results highlight the potential neurotoxic risk posed by mancozeb via the impairment of astrocyte function and intracellular Ca{superscript 2} regulation. Importantly, these neurotoxic effects occurred at concentrations below current regulatory safety limits (ADI), indicating that mancozeb-induced disruption of astrocytic Ca{superscript 2} signaling provides a mechanistic basis for re-evaluating established human safety exposure standards. Environmental ImplicationsOur findings highlight that the widespread use of mancozeb has a significant impact on brain health. Mancozeb was shown to induce astrocyte atrophy even at low concentrations, amounting to six times the human acceptable daily intake. Mancozeb causes impairment of GABAergic synaptic transmission of neurons by disrupting the Ca{superscript 2} homeostasis via inhibition of Orai1 and STIM1 of astrocytes. These findings indicate that current regulatory standards significantly underestimate the risks of long-term mancozeb exposure to brain health. Therefore, this study underscores the risks of astrocyte-mediated neurotoxicity resulting from pesticide residue ingestion and emphasizes the need to rigorously re-evaluate current exposure limits from the perspective of brain health.

Per/polyfluoroalkyl substances (PFAS) are used in a variety of industrial and consumer applications due to their distinctive properties. Nonetheless, these substances are ubiquitous and pose significant risks to the environment, wildlife, and human health. Perfluorooctane sulfonate (PFOS), which was previously one of the most commonly utilized PFAS, has prolonged half-life in both humans and the environment. Despite the cessation of its production, PFOS remains one of the prevalent contaminants amongst PFAS. Recent research demonstrates that PFOS is relatively resistant to elimination from the human body and accumulates to a greater extent in older adults. PFOS has been shown to affect the nervous system and its functions, although the intricate mechanisms underlying its toxicity remain largely obscure. Earlier studies utilizing Caenorhabditis elegans indicated that dopaminergic neurons are particularly vulnerable to PFOS neurotoxicity, with glutathione (GSH) playing a role in mitigating neurodegeneration. Curiously, none of the antioxidant treatments evaluated, including N-acetyl-cysteine, produced favorable outcomes, despite N-acetyl-cysteine being a precursor to GSH. This study investigates the GSH synthesis pathway to elucidate critical mechanisms. We assessed the effects of GSH precursors and intermediates on PFOS neurotoxicity. The GSH precursors, cysteine, glutamate, and the combination of cysteine and glutamate did not demonstrate beneficial effects. However, the crucial GSH synthesis intermediate, {gamma}-glutamyl-cysteine, provided neuroprotection comparable to that of GSH. Notably, no changes were observed at the transcriptomic or proteomic levels of GSH synthesis enzymes in C. elegans and SH-SY5Y cells, respectively. This study effectively uncovers a novel mechanism that addresses existing knowledge gaps pertaining to PFOS neurotoxicity. HighlightsO_LIPFOS elicits dopaminergic neurodegeneration in C. elegans C_LIO_LIPrevious research shows that only GSH ameliorated PFOS-induced neurodegeneration, amongst several antioxidants tested. C_LIO_LIUpon testing the precursors and intermediates in the GSH pathway, GGC was realized as a key intermediate C_LIO_LIThe studies highlight the critical component of GSH pathway in alleviating PFOS neurotoxicity C_LI

Adolescence is a sensitive period of neurodevelopment marked by remodeling of brain circuits that support cognitive development and emotion and behavior regulation. These maturation processes heighten psychiatric vulnerability to environmental exposures, including to toxicants such as insecticides. Epidemiological studies show widespread adolescent insecticide exposure and increasingly link this with psychiatric outcomes, yet underlying neural mechanisms remain poorly understood. Preclinical studies can clarify these associations and identify insecticide-induced mechanisms that may disrupt neurodevelopment and produce consequent long-term behavioral outcomes. Here, we performed a systematic review of rodent studies following PRISMA guidelines. 50 original articles met inclusion criteria, examining neurotoxic outcomes following insecticide exposure during adolescence (postnatal days 21-60). Outcomes were categorized into four domains: neurocognitive, neuropsychiatric, neurobiological, and general neurotoxicity. Risk of bias was assessed using the SYRCLE Risk of Bias tool. Across studies, insecticide exposure during adolescence led to learning and memory impairments and tended to increase depression relevant behaviors, alter locomotor activity, and produce general neurotoxic effects. Mechanistic findings highlighted disruptions in cholinergic and monoaminergic signaling, oxidative stress, neuroimmune changes, and cell death and other neurodegenerative processes. Together, these findings indicate adolescent insecticide exposure disrupts multiple neural systems with behavioral consequences relevant to adolescent development and psychiatric risk. Future research should model real-world exposures (e.g. dose, timing) to better inform translational understanding of adolescent psychiatric vulnerability. Because many life-long neuropsychiatric disorders emerge in adolescence, identifying how modifiable environmental exposures shape risk offers an opportunity for prevention and intervention strategies to alter the course of disease across the lifespan.

BackgroundThe formation of hyperphosphorylated tau (p-tau) protein tangles in neurons is a pathological marker of Alzheimers disease (AD). Exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) has been associated with increased risk of AD. ObjectivesTo determine if there was a connection between DDT exposure and tau toxicity we investigated whether exposure to DDT can exacerbate tau protein toxicity in C. elegans. In addition, we examined the association between p-tau protein and metabolism in a human population study and in a transgenic C. elegans strain neuronally expressing a mutant tau protein fragment that is prone to aggregation. MethodsIn the human population study, we used a metabolome-wide association framework to determine the association between p-tau measured in the cerebrospinal fluid (CSF) and metabolomic features measured in both plasma (n = 142) and CSF (n = 78) using high-resolution metabolomics (HRM). Using the same HRM method, we determined changes in metabolomic features in the transgenic C. elegans strain compared to its control strain. Metabolites associated with p-tau in both species were analyzed for overlap. We also examined the effect of DDT and aggregating tau protein on growth, swim behavior, mitochondrial function, metabolism, learning, and lifespan in C. elegans. ResultsPlasma and CSF-derived features associated with p-tau level were related to drug, amino acid, fatty acid and mitochondrial metabolism pathways. Five metabolites overlapped between plasma and C. elegans, and 4 between CSF and C. elegans. DDT exacerbated the inhibitory effect of aggregating tau protein on growth and basal respiration. In the presence of aggregating tau protein, DDT induced more curling and was associated with reduced levels of amino acids but increased levels of uric acid and adenosylselenohomocysteine. Developmental exposure to DDT blunted the lifespan reduction caused by aggregating tau protein. ConclusionThe model organism C. elegans can complement human studies by providing a means to study mechanisms of environmental toxicants. Specifically, our C. elegans data show that DDT exposure and tau protein aggregation both inhibit mitochondrial function and DDT exposure can exacerbate the mitochondrial inhibitory effects of tau protein aggregation providing a plausible explanation for the observed human associations.

Parabens, particularly methylparaben (MP) and ethylparaben (EP), are extensively used preservatives in cosmetics, foods, and pharmaceuticals. Although considered safe at low concentrations, recent evidence questions their biological inertness under chronic exposure. This study evaluated the developmental, biochemical, and behavioral effects of continuous dietary MP and EP exposure in Drosophila melanogaster, an established in vivo model for toxicological screening. Flies were chronically exposed to MP (0.5-2%) or EP (0.5-1.5%) throughout development and adulthood. Developmental timing, lifespan, oxidative-stress markers (MDA, FRAP, total protein), and locomotor performance (negative geotaxis in adults, crawling in larvae) were quantified. Paraben exposure significantly delayed development ([~]15% increase in eclosion time), reduced median lifespan (up to 50% decrease at 2% MP), and elevated oxidative damage ({uparrow}MDA, {downarrow}FRAP) in a dose-dependent manner. Protein content declined more rapidly with age, suggesting oxidative degradation or proteolysis. Both adult climbing and larval crawling performances were impaired, linking biochemical stress to neuromuscular dysfunction. MP produced stronger oxidative and behavioral effects than EP. Feeding controls confirmed that observed deficits were not due to nutritional differences. Chronic MP and EP exposure induces systemic toxicity in D. melanogaster, integrating endocrine disruption and redox imbalance as plausible mechanisms. Given conserved stress and hormonal pathways, these findings reinforce the need to re-evaluate low-dose paraben safety limits and highlight Drosophila as a rapid, ethically viable platform for screening environmental preservatives and safer substitutes.

Developmental exposure to organophosphate pesticides has been associated with adverse neurodevelopmental outcomes, but the circuit-level mechanisms underlying these effects remain poorly understood. Here, we examined how low-level chlorpyrifos (CPF) exposure affects neural circuit maturation and behavior in Xenopus laevis tadpoles. Tadpoles were exposed to 1 {micro}M CPF from developmental stage 42 to stage 49, spanning a critical period of synaptogenesis and circuit refinement. CPF-exposed tadpoles displayed abnormal schooling behavior, characterized primarily by impaired body-axis alignment despite preserved group aggregation, as well as altered spontaneous swimming marked by reduced looping and increased seizure-like activity. Whole-cell recordings from tectal neurons revealed persistent reductions in inhibitory synaptic drive, consistent with altered excitation-inhibition balance. Although acute CPF exposure transiently increased intrinsic excitability of tectal neurons as well as baseline swimming activity, this effect was not maintained after chronic exposure. Morphological analysis of GFP-labeled tectal neurons revealed altered dendritic branching distribution despite no change in total dendritic length or branch number. Together, these findings suggest that developmental CPF exposure disrupts tectal circuit maturation, leading to abnormal neural connectivity and maladaptive behavioral outcomes relevant to neurodevelopmental dysfunction.

Lead (Pb) poisoning during early development is associated with behavioral and cognitive deficits, but the specific mechanisms by which Pb impairs brain development are not fully understood. One potential mechanism is that Pb poisoning may impair thyroid hormone (TH)- mediated changes in brain development To address this issue, we performed experiments to assess the effects of Pb poisoning on (TH) -dependent changes in cellular and molecular mechanisms in the developing Xenopus laevis tadpole brain. We treated stage 48 tadpoles to combinations of 1000 ppb Pb bath for seven days and added one of three different concentrations of thyroxine (T4) for the final two days of treatment. We found that lead exposure decreased body length, including in T4-treated tadpoles. We also performed immuno-staining for proliferative marker pH3 and found that Pb disrupts T4-induced increases in neuronal proliferation. Finally, we used syGlass VR data visualization software to measure volume of the forebrain, midbrain, and hindbrain in 3D and found that Pb exposure impaired T4-mediated changes in brain volume. Last, we found that Pb poisoning reduced the T4-mediated increase in proliferating cell nuclear antigen (PCNA), a TH-sensitive gene. These results illustrate that Pb poisoning impairs some TH-dependent changes in the developing brain.

BackgroundArsenic is a well-established carcinogen known to increase all-cause mortality, but its effects on the central nervous system are less well understood. Recent epidemiological studies suggest that early life exposure to arsenic is associated with learning deficits and behavioral changes, and increased arsenic exposure continues to affect an estimated 200 million individuals worldwide. Previous studies on arsenic exposure and synaptic function have demonstrated a decrease in synaptic transmission and long-term potentiation in adult rodents, but have relied on in vitro or extended exposure in adulthood. Therefore, little is known about the effect of arsenic exposure in development. ObjectiveHere, we studied the effects of gestational and early developmental arsenic exposure in juvenile mice. Specifically, our objective was to investigate the impact of arsenic exposure on synaptic transmission and plasticity in the hippocampus. MethodsC57BL/6 females were exposed to arsenic (0, 50ppb, 36ppm) in their drinking water two weeks prior to mating and continued to be exposed to arsenic throughout gestation and after parturition. We then performed field recordings in acute hippocampal slices from the juvenile offspring prior to weaning (P17-P23). In this paradigm, the juvenile mice are only exposed to arsenic in utero and via the mothers milk. ResultsHigh (36ppm) and relatively low (50ppb) arsenic exposure both lead to decreased basal synaptic transmission in the hippocampus of juvenile mice. There was a mild decrease in paired-pulse facilitation in juvenile mice exposed to high, but not low, arsenic, suggesting the alterations in synaptic transmission are primarily post-synaptic. Finally, high developmental arsenic exposure led to a significant increase in long-term potentiation. DiscussionThese results suggest that indirect, ecologically-relevant arsenic exposure in early development impacts hippocampal synaptic transmission and plasticity that could underlie learning deficits reported in epidemiological studies.

Chronic exposure to lead (Pb) is known to cause deficits in neuronal function across the nervous system, including the visual nervous system. Visual deficits have been observed in both humans and rodent models following Pb exposure. However, how Pb exposure causes visual deficits is poorly understood. In this study, we evaluated the effects of Pb toxicity on the retina and optic nerve of the mouse visual nervous system. We used C57BL/6 adult mice of both sexes and divided them into one of three different exposure groups. Adult mice received daily oral gavage of 108mg/kg Na-acetate (control), 54mg/kg Pb-acetate (low dose), or 108mg/kg Pb-acetate (high dose) for 4 weeks. At the end of Pb exposure, whole blood, retina, and optic nerve samples were collected for Pb quantification by atomic absorption spectroscopy and tissue immunohistochemical analyses. Cell type specific markers were used to quantify changes in cell density of retinal ganglion cells (RGCs), oligodendrocytes (OLs), oligodendrocyte precursor cells (OPCs), and myelin structure. Following Pb exposure, we observed a small, but significant reduction in the cell density of RGCs in the retina. However, we found no significant changes in branch thickness or coverage of retinal vasculature following Pb exposure. In the optic nerve after Pb exposure, we found a significant reduction in the cell density of OLs and OPCs. Finally, using immunolabeling for Caspr and Nav1.6, we observed significant structural changes in nodes of Ranvier, suggesting a disruption in myelin structure. Our findings suggested that Pb toxicity may impair survival and maturation process of oligodendrocytes, changes in myelin structures, and potential demyelination of the optic nerve. These results provide the foundation for future investigations into the molecular mechanisms of Pb-dependent changes in myelination and visual nervous system function.

Per/polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have shown extensive usage. Owing to widespread use and resistance to environmental degradation, they have become a hazard with respect to the environment and human health. While the legacy PFAS are being phased out, they are being replaced by second-generation PFAS that are considered safer alternatives. However, the lack of information pertaining to the underlying mechanisms for legacy and especially second-generation PFAS exacerbates the risk. This study investigates legacy and second-generation PFAS to determine their individual effects on neurotoxicity and mitochondrial respiration. Legacy PFAS, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and second-generation PFAS, GenX, and ADONA were employed, and studies were conducted using Caenorhabditis elegans and mitochondria isolated from Rat brain for Complex I to IV. It was found that legacy PFAS, PFNA, and PFDA were neurotoxic, with neurotoxicity proportional to chain length. PFOA, PFNA, and PFDA also exhibited significant inhibition to most of the mitochondrial complexes. Whereas in the case of second-generation PFAS ADONA, and GenX, it was only limited to the inhibition of Complex IV. GenX only exhibited neurodegeneration at very high doses. Our findings conclude that the legacy and second-generation PFAS might have significant neurotoxic implications. While the targets are similar to some extent, the mechanisms between the two classes are distinct. Our study the sets the stage to evaluate further the combined effect of PFAS (legacy and emergent) to fill in informational gaps pertaining to their safety.

While a growing number of studies have linked environmental exposures and Parkinsons disease (PD)1-3, the impact of many pesticides remains understudied4,5; for example, neonicotinoids are the most used insecticides in the world, but research into their contribution to PD is limited to a handful of studies6-8. Newer pesticides, such as the butenolide flupyradifurone (FPF), specifically developed to overcome increased pest resistance9 and spurred on by tighter restrictions on neonicotinoids such as imidacloprid (IMI)10, are even less studied. New approach methodologies (NAMs) that allow for rapid evaluation of pesticide exposures are needed to evaluate potential links between the growing number of pesticides and PD11. To this end, we exposed the model nematode Caenorhabditis elegans12 to IMI and FPF. Due to its high degree of tractability, and conservation of many genetic, neuronal, and toxic mode of action processes, C. elegans has been invaluable in both elucidating mechanisms and novel therapeutic targets for PD that can be validated in other models13, and as a complementary tool for early toxicity screening14. Along this line, we found that exposure to IMI, and to a greater extent FPF, in young adult animals causes significant dendritic blebbing, an early sign of neurodegeneration, exclusively in dopaminergic neurons. Blebbing was accompanied by impairment of dopamine-mediated behaviors, changes in neuronal mitochondrial morphology, and elevation of pathways related to reactive oxygen species (ROS). We were able to reduce the blebbing caused by IMI and FPF two ways: 1) pharmacologically via administration of the antioxidant N-acetyl cysteine (NAC); 2) genetically via knockout of a MAP kinase (MAPK) stress response pathway. This suggests that oxidative stress is a key mediator of this insecticide-induced dopaminergic neurodegeneration.

Glyphosate-based herbicides (GBHs), the most recognized of which is Roundup, are the most extensively used herbicides worldwide. GBHs were initially considered safe for animals since the primary target of the active ingredient, glyphosate, is only found in plants. Recent studies show that glyphosate can affect a range of animal physiologies; however, it remains poorly characterized as to whether animal GBH effects are mediated by glyphosate itself or are in response to toxic effects of the adjuvants and surfactants found in GBH formulations. Here we expose embryonic zebrafish to environmentally relevant doses of glyphosate or Roundup and compare effects on two systems in the larvae: cellular bioenergetics, since glyphosate can affect mitochondrial function, and behaviour, as a systems-level readout of lasting developmental changes. We showed that exposure of embryonic zebrafish to low levels of glyphosate resulted in decreased mitochondrially-mediated basal respiration and hypoactive swimming behavior in larval stage, whereas exposure to Roundup in this same treatment paradigm had the opposite effect, causing increased cellular respiration and increased locomotion. In addition, we also explored generational effects of F1 embryonic glyphosate or Roundup exposure in the F2, and showed that offspring born to zebrafish exposed to low-level glyphosate or Roundup during embryogenesis both exhibited reduced mitochondrially-mediated basal respiration and altered locomotion. Combined, these data show that embryonic exposure to glyphosate or the full formulation of GBHs caused differential effects on mitochondrial function and behaviours in vertebrates, with potential lasting effects on future generations. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/510731v1_fig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@93431borg.highwire.dtl.DTLVardef@1aa602org.highwire.dtl.DTLVardef@1890cf5org.highwire.dtl.DTLVardef@b1c655_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Graphical abstract.Zebrafish (F1 generation) were exposed to glyphosate or Roundup from zero to 48 hours, with behaviour and mitochondrial bioenergetics assessed at larval timepoints (2- and 5-dpf). Offspring of glyphosate and Roundup exposed fish (F2 generation) behaviour and mitochondrial bioenergetics were assessed to the same paradigm as F1 fish at 5-dpf. Changes to core metabolic parameters and locomotion was observed in both F1 and F2 generations. C_FIG

Air pollution has been increasingly linked to adverse neurodevelopmental and neurodegenerative outcomes. While experimental and preclinical studies suggest that exposure to particulate matter (PM), particularly during gestation, may disrupt cognitive development, the impact of short-term PM exposure on cognitive and behavioral functioning in healthy young populations remains insufficiently explored in Spain. Moreover, few studies have incorporated individualized dosimetry models to estimate exposure more accurately. This study included 186 healthy young adults (mean age = 20.4 years) recruited from three Spanish cities (Teruel, Almeria, and Talavera) characterized by different pollution levels. Ambient fine and coarse PM concentrations were recorded 8, 15, and 30 days prior to psychological assessment. Instead of relying solely on raw in situ environmental measurements, individualized PM deposition was estimated using the Multiple-Path Particle Dosimetry Model (MPPD), allowing a more biologically meaningful exposure approximation. Psychological outcomes were assessed using validated questionnaires: DASS-21 (depression, anxiety, stress), BIS-11 (impulsivity), UCLA Loneliness Scale, and SWLS (life satisfaction). Behavioral performance was evaluated using computerized versions of the Attentional Network Task (ANT) and the Stroop Task. Blood NRF2 concentrations were analyzed as a biomarker potentially related to oxidative stress mechanisms. In situ data indicated that Talavera presented the highest pollution levels, followed by Almeria and Teruel. Linear regression analyses showed that coarse PM exposure across 8-, 15-, and 30-day windows significantly predicted poorer Executive Control Index performance in the ANT. Additionally, 15-day coarse PM and 30-day fine PM exposure were associated with greater cognitive interference. Oxidative stress markers were significantly associated with PM exposure levels. These findings support emerging evidence that short-term PM exposure may negatively affect executive and attentional processes even in healthy young adults. Further longitudinal research incorporating individualized exposure modeling is warranted to clarify causal pathways and underlying biological mechanisms. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/713644v1_ufig1.gif" ALT="Figure 1"> View larger version (79K): org.highwire.dtl.DTLVardef@1a0ac13org.highwire.dtl.DTLVardef@1812accorg.highwire.dtl.DTLVardef@120bf07org.highwire.dtl.DTLVardef@dd9a7c_HPS_FORMAT_FIGEXP M_FIG C_FIG

IntroductionAir pollution is an environmental factor associated with Alzheimers disease, characterized by decreased cognitive abilities and memory. The limited models of sporadic Alzheimers disease fail to replicate all pathological hallmarks of the disease, making it challenging to uncover potential environmental causes. Environmentally driven models of Alzheimers disease are thus timely and necessary. MethodsWe used live-cell confocal fluorescent imaging combined with high-resolution stimulated emission depletion (STED) microscopy to follow the response of neuron-like cells to nanomaterial exposure. Here, we report that a high dose rate in vitro exposure of neuron-like cells to particulate matter constituents reproduces neurodegenerative phenotype, including extracellular amyloid-{beta} containing plaques and decreased neurite length. ResultsConsistent with the existing in vivo research, we observed detrimental effects, specifically a substantial reduction in neurite length and formation of amyloid beta plaques, after exposure to iron oxide and diesel exhaust particles. Conversely, after exposure to engineered cerium oxide nanoparticles, the lengths of neurites were maintained, and almost no extracellular amyloid beta plaques were formed. DiscussionAlthough the exact mechanism behind this effect remains to be explained, the high dose rate in vitro model, comprising wild-type neuron-like cells, could serve as an alternative environmentally driven model of Alzheimers disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/586796v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@63faf1org.highwire.dtl.DTLVardef@1eff3cdorg.highwire.dtl.DTLVardef@6f3365org.highwire.dtl.DTLVardef@973a78_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO High dose rate in vitro exposure of neuron-like cells to particulate matter constituents, like diesel exhaust and iron oxide nanoparticles, reproduces neurodegenerative phenotype, including extracellular amyloid--containing plaques and reduction in neurite length and density. C_FIG

Neurodegenerative disorders are a debilitating and persistent threat to the global elderly population carrying grim outcomes. Their genesis is often multifactorial, with a history of early exposure to xenobiotics like pesticides or diagnostic exposure to ionizing radiation. A holistic molecular insight into their mechanistic induction is still unclear upon single or combinatorial exposure to different toxicants. In the present study, one-month-old C57/BL-6J male mice were treated orally with malathion (MAL) (50mg/kg body wt. for 14 days) and/or a single whole-body radiation (IR) (0.5 Gy) on the 8th day. Post-treatment, behavioral assays were conducted to assess exploratory behavior, memory, and learning. Following sacrifice, brains were collected for histology, biochemical assays, and transcriptomic analysis. Differential expression analysis, Gene ontology, and pathway enrichment revealed several common and uniquely altered genes, biological processes, and pathways related to neurodegeneration, synaptic transmission and plasticity, neuronal survival, proliferation, and regulation of neuronal death. Increased astrogliosis was observed in the IR and co-exposure groups, with significant neuronal cell death and reduction in the expression of NeuN in all three groups. Sholl analysis and dendritic arborization/ spine density study revealed decreased total apical neuronal path length and dendritic spine density in all three groups. Decreased levels of antioxidant enzymes GST and GSH and acetylcholinesterase enzyme activity were also detected. However, there were no changes in exploratory behavior or learning and memory. Thus, explicating the molecular mechanisms behind MAL and IR can provide novel insights into the genesis of environmental factor-driven neurodegenerative pathogenesis.

BackgroundAlzheimers disease (AD) is characterized by the presence of amyloid-{beta} plaques, neurofibrillary tangles, and neuroinflammation. Previously, we reported serum levels of dichlorodiphenyldichloroethylene (DDE), the primary metabolite of the pesticide dichlorodiphenyltrichloroethane (DDT), were significantly higher in AD patients compared to age-matched controls and that DDT exposure worsened AD pathology in animal models. ObjectiveHere, we investigated the effect of DDT on neuroinflammation in primary mouse microglia (PMG) and C57BL/6J mice. MethodsEffects of DDT on inflammation and disease-associated microglia were determined in primary mouse microglia and C57BL/6J mice. ResultsPMG exposed to DDT (0.5-5.0 {micro}M) elicited a [~]2-3-fold increase in Il-1b mRNA levels, with similar concentration-dependent upregulation in Il-6, Nos2, and Tnfa. These effects were blocked by the sodium channel antagonist tetrodotoxin, demonstrating the role of DDT-microglial sodium channel interactions in mediating this response. Additionally, NOS2 protein levels increased by [~]1.5-2-fold, while TNFa was elevated by 2-4-fold. C57BL/6J male and female mice exposed to DDT (30 mg/kg) demonstrated significantly increased mRNA levels of Nos2, Il-1b, and Il-6 in the frontal cortex (1.5-2.3-fold), and Nos2, Il-1b, and Tnfa (1.5-1.8-fold) in the hippocampus. Furthermore, microglial homeostatic genes, Cx3cr1, P2ry12, and Tmem119, were downregulated, while stage 1 disease-associated microglia genes were upregulated both in vitro and in vivo. Notably, Apoe and Trem2 were only upregulated in the frontal cortex and hippocampus of females. ConclusionThese data indicate that DDT increases neuroinflammation, which may result from direct actions of DDT on microglia, providing a novel pathway by which DDT may contribute to AD risk.

Alzheimers disease (AD) is one of the most prevalent neurodegenerative disorders and one of the leading causes of death in individuals over the age of 65. Most cases of AD develop sporadically, however, there are several risk factors that have been identified which significantly increases an individuals risk for developing AD. The most prominent of these is Apolipoprotein E4 (APOE4), which can potentially result in an up to 10-fold greater risk of developing AD. The presence of APOE4 alone, however, cannot be solely responsible for AD as the disease may occur even in the absence of APOE4. Therefore, there must be other contributing factors such as exposure to environmental toxins including heavy metals and pesticides, which have independently been shown to contribute to AD. Nano- and microplastics (NMPs) are plastic particles less than 1 m and 5 mm in size, respectively, and have only recently been identified as a major environmental pollutant with serious health concerns. Given the adverse health effects that are increasingly being associated with NMPs exposure, we sought to understand how the combination of APOE4 and NMPs exposure may work synergistically to promote cognitive dysfunction and alter key regulatory pathways to impact overall health. Following an acute (3 week) exposure to pristine spherical fluorescently-labeled 0.1 and 2 {micro}m polystyrene (PS) NMPs, we found significant sex-dependent alterations in locomotor and recognition memory in APOE4 mice, but not in APOE3 controls. We additionally found that exposure to PS-NMPs resulted in sex and genotype specific alterations in astrocytic and microglial markers in the brain, and in CYP1A1, a major metabolizer of environmental polycyclic aromatic hydrocarbons, in the liver. These results suggest PS-NMPs may interact with the APOE4 allele to promote cognitive dysfunction and alter immune and metabolic pathways which may contribute to disease-like states.