The impact of environmental metals in young urbanites' brains

Discordant sibling analysis of autism risk associated with prenatal exposure to tailpipe and non-tailpipe particulate matter pollution

BACKGROUND

We previously assessed associations of prenatal exposure to fine particulate matter (PM2.5) tracers reflecting tailpipe (elemental carbon [EC] and organic carbon [OC]) and non-tailpipe emissions (copper [Cu], iron [Fe] and manganese [Mn]) with risk of autism spectrum disorder (ASD) in a large pregnancy cohort. To address genetic and family environment confounding, we conducted an ASD-discordant sibling study.

METHODS

Data included 4024 children (1837 with and 2187 siblings without ASD) born to 1801 unique mothers who had at least one child diagnosed with ASD by age 5, and one child without ASD. Prenatal exposures to total PM2.5, trace elements Cu, Fe, Mn, EC, and OC and dispersion-modeled near-roadway-air-pollution (NRAP) from freeway and non-freeway source were obtained using maternal addresses during pregnancy. Conditional logistic regression was used to assess ASD risk associated with exposures adjusting for covariates. Results were reported as odds ratio (OR, 95 % CI) per inter-quartile increment of each exposure.

RESULTS

In single-pollutant models, child ASD risk (OR; 95 % CI) was associated with gestational exposures to non-tailpipe source Cu (1.17; 1.03-1.33), Fe (1.26; 1.07-1.48), Mn (1.29; 1.11-1.50); but not likewise associated with tailpipe source EC (1.10; 0.92-1.32) and OC (1.10; 0.91-1.32). Total PM2.5 and non-freeway NRAP were both associated with ASD risk. Adjusting for total PM2.5 or NRAP attenuated the ASD associations with Cu, Fe, and Mn but they remained largely statistically significant. By trimester analysis showed the associations with Cu, Fe, and Mn were significant in the first two trimesters.

CONCLUSION

This ASD-discordant sibling study confirmed previously reported ASD risk associated with prenatal exposure to PM2.5, NRAP and non-tailpipe particulate trace-element Cu, Fe, and Mn, particularly in the first two trimesters, thus, increasing evidence of causality.

A peripheral irritant motor response (PIMR) assay to identify chemical-induced locomotor deficits in larval zebrafish (Danio rerio)

Zebrafish (Danio rerio) behavioral assays provide valuable insights into the effects of environmental chemicals on the developing nervous system, primarily through motor responses triggered by stimuli-induced CNS activation. However, as these responses rely on the locomotor integrity of larval zebrafish, chemical-induced impairments to their locomotor capacity could obscure behavioral observations and confound findings concerning the developmental neurotoxicity of the tested chemicals. This limitation emphasizes the need for supporting assays designed to specifically evaluate the locomotor capacity of larval zebrafish. In the present study, we evaluated the use of peripheral irritant-elicited motor responses as a method to identify chemical-induced locomotor deficits. The motor activity of 120 hours post-fertilization (hpf) zebrafish larvae exposed to different concentrations of two peripheral stimulants-mustard oil and cinnamon oil-was evaluated. Subsequently, we assessed changes to central (visual and acoustic) and peripheral (irritant) motor responses after tricaine-s (MS-222; neurodepressant) and tubocurarine (neuromuscular blocker) exposures. Additional investigations were also carried out to assess the central and peripheral motor activity of larvae after developmental exposures (114 h) to lead (Pb) and cadmium (Cd)-two suggested developmental neurotoxic environmental contaminants. Our observations revealed that exposure to mustard oil (12.5 µM) elicits the strongest motor response. Larvae exposed to MS-222 showed decreases in motor responses to visual and acoustic stimuli, but the same exposure induced limited effects on motor responses elicited by the peripheral irritant. Exposure to tubocurarine depressed all motor responses examined. Finally, both Pb and Cd exposures induced hypoactivation of central motor responses, but only Cd showed a significant depression in the peripheral irritant motor response (PIMR) in both intact and developmentally deformed larvae. This finding suggests that loss of locomotor capacity might be confounding the behavioral observations associated with Cd exposures. This research underscores the utility of this zebrafish-based PIMR assay in elucidating locomotor impairments induced by chemicals, which may obscure the behavioral findings of motor response assays designed to evaluate developmental neurotoxicity.

Global trends and projections of Parkinson's disease incidence: a 30-year analysis using GBD 2021 data

BACKGROUND AND OBJECTIVES

Parkinson's disease (PD) is a neurodegenerative disorder marked by the progressive loss of dopaminergic neurons, leading to motor dysfunction and non-motor symptoms like cognitive decline and depression. With the aging global population, PD incidence is anticipated to rise, especially in regions with rapidly growing elderly populations. This study leverages Global Burden of Disease (GBD) 2021 data to analyze the burden of PD by region, sex, and age group, examining trends from 1992 to 2021 and projecting the future burden to 2030.

METHODS

Data from the GBD 2021 database for the years 1992-2021 were analyzed to assess age-standardized incidence rates (ASIR) and mortality of PD across socio-demographic index (SDI) regions, sex, and age groups. The Age-Period-Cohort (APC) model was used to explore temporal trends, while the Bayesian Age-Period-Cohort (BAPC) model projected future PD burden from 2022 to 2030.

RESULTS

From 1992 to 2021, global PD cases increased from 450,000 to 1.34 million, with crude incidence rates rising from 8.19 to 16.92 per 100,000 and ASIR from 11.54 to 15.63 per 100,000, indicating an annual net drift of 1.11% (95% CI 1.06%-1.17%), reflecting a growing burden driven by an aging population. All SDI regions saw a growth in PD burden, with the highest increases in middle- and high-middle-SDI regions, where male incidence was notably higher than female. Incidence rates escalated sharply in individuals aged 60 and older, peaking in those aged 85 and above. Projections suggest that by 2030, global PD cases will reach 1.93 million, with an ASIR of 27 per 100,000.

DISCUSSION

The findings highlight a sustained global increase in PD burden, particularly in middle- and high-income regions and among men. In low-SDI areas, PD burden may be underestimated due to limited healthcare access and diagnostic challenges. These results stress the urgent need for health policies focused on elderly populations, especially men, and call for effective prevention and intervention strategies to mitigate the future impact of PD.

On the origin of metal species in the human brain: a perspective on key physicochemical properties

Normal functioning of the human brain is dependent on adequate regulation of essential metal nutrients. However, it is also highly sensitive to metal-mediated toxicity, linked to various neurodegenerative disorders. Exposure to environmental metal sources (especially to particulate air pollution) can stimulate toxicity and neuropathologic effects, which is particularly evident in populations chronically exposed to high levels of air pollution. Identifying the sources of metal-rich deposits in the human brain is important in not only distinguishing the effects of environmentally acquired metals from endogenous metal dysregulation, but also for tracing pollutant sources which may be subject to exposure control. This perspective reviews evidence for key physicochemical properties (size/morphology, chemical composition, oxidation state, magnetic properties, and isotopic composition) concerning their capacity to distinguish sources of metals in the brain. The scope for combining analytical techniques to study properties in tandem is also discussed.

Brain tissue metal concentrations and Alzheimer's disease neuropathology in total joint arthroplasty patients versus controls

We examined whether total joint arthroplasty (TJA) is associated with increased metal accumulation in the brain and histopathologic changes of Alzheimer's disease. We measured ultra-trace metal concentrations (aluminum, chromium, cobalt, manganese, molybdenum, nickel, titanium, and vanadium) on postmortem frozen tissues of the occipital lobe of 177 subjects (89 non-TJA and 88 TJA) using a triple-quadrupole inductively coupled plasma mass spectrometry and correlated elemental concentrations to the degree of Alzheimer's disease neuropathic change (ADNC). To effectively assess the relationship between TJA and brain metal concentrations, subjects with and without TJA were matched for baseline clinical characteristics and showed no difference in postmortem Alzheimer's disease neuropathic change. TJA subjects had increased concentrations of cobalt and titanium and both metals were associated with increased amyloid plaques. In both the TJA and non-TJA subjects, increased concentrations of cobalt, titanium, manganese, and molybdenum were associated with increased odds of neuritic and diffuse plaques. Lastly, the brain's inter-metal correlations were altered in the presence of increased neuritic plaques and/or implantable artificial joints. These findings suggest that metal concentrations and homeostasis vary in presence of TJA.

Multiphase Radical Chemical Processes Induced by Air Pollutants and the Associated Health Effects

Air pollution is increasingly recognized as a significant health risk, yet our understanding of its underlying chemical and physiological mechanisms remains incomplete. Fine particulate matter (PM2.5) and ozone (O3) interact with biomolecules in intracellular and microenvironments, such as the epithelial lining fluid (ELF), leading to the generation of reactive oxygen species (ROS). These ROS trigger cellular inflammatory responses and oxidative stress, contributing to a spectrum of diseases affecting the respiratory, cardiovascular, and central nervous systems. Extensive epidemiological and toxicological research highlights the pivotal role of ROS in air pollution-related diseases. It is crucial to comprehend the intricate chemical processes and accompanying physiological effects of ROS from air pollutants. This review aims to systematically summarize ROS generation mechanisms in the ELF and measurement techniques of oxidative potential (OP), taking the kinetic reactions of ROS cycling in the ELF as an example, and discusses the general health implications of ROS in respiratory, cardiovascular, and central nervous systems. Understanding these processes through interdisciplinary research is essential to develop effective and precise strategies as well as air quality standards to mitigate the public health impacts of air pollution globally.

Ambient air pollution undermines chemosensory sensitivity - a global perspective

This study offers insights into the complex relationship between chemical species constituting air pollution and chemosensory function. We examined the relationship between chemical species known to contribute to air pollution and assault human health and chemosensory sensitivity. Chemosensory sensitivity data was retrieved from a large-scale study involving 711 urban-dwelling participants inhabiting 10 different regions of the globe. Their olfactory threshold towards phenyl ethyl alcohol (PEA) and olfactory/trigeminal threshold towards Eucalyptol was measured in a multicentre study. We matched the individual chemosensory data with the levels of PM2.5, PM10, O3, NO2, SO2, CO at the location of testing sites, on the exact date of the test, using EMAC (ECHAM5/MESSy for Atmospheric Chemistry) model. Our findings indicate that air pollution negatively affects olfactory function and has cumulative negative effects with aging. The reported patterns are seasonal and increase during Autumn and Winter, and interact with medical conditions related to poorer olfactory function. We extend the current knowledge by demonstrating that olfactory/trigeminal perception is also disrupted by toxic air, albeit in a slightly different manner. The analyzed models promote a more complex perspective on the relationship between air composition and chemosensory sensitivity, but delineate problems related to the interdependence of the levels of chemical species constituting air pollution and using them together to predict chemosensory sensitivity. Conclusions point to the need to investigate the problem of air pollution and chemosensory health from a global perspective, as air quality partly accounts for the differences in chemosensory perception in different regions of the world.

Carcinogenic Mechanisms of Hexavalent Chromium: From DNA Breaks to Chromosome Instability and Neoplastic Transformation

PURPOSE OF REVIEW

Hexavalent chromium [Cr(VI)] is a well-established human carcinogen, yet the mechanisms by which it leads to carcinogenic outcomes is still unclear. As a driving factor in its carcinogenic mechanism, Cr(VI) causes DNA double strand breaks and break-repair deficiency, leading to the development of chromosome instability. Therefore, the aim of this review is to discuss studies assessing Cr(VI)-induced DNA double strand breaks, chromosome damage and instability, and neoplastic transformation including cell culture, experimental animal, human pathology and epidemiology studies.

RECENT FINDINGS

Recent findings confirm Cr(VI) induces DNA double strand breaks, chromosome instability and neoplastic transformation in exposed cells, animals and humans, emphasizing these outcomes as key steps in the mechanism of Cr(VI) carcinogenesis. Moreover, recent findings suggest chromosome instability is a key phenotype in Cr(VI)-neoplastically transformed clones and is an inheritable and persistent phenotype in exposed cells, once more suggesting chromosome instability as central in the carcinogenic mechanism. Although limited, some studies have demonstrated DNA damage and epigenetic modulation are also key outcomes in biopsies from chromate workers that developed lung cancer. Additionally, we also summarized new studies showing Cr(VI) causes genotoxic and clastogenic effects in cells from wildlife, such as sea turtles, whales, and alligators. Overall, across the literature, it is clear that Cr(VI) causes neoplastic transformation and lung cancer. Many studies measured Cr(VI)-induced increases in DNA double strand breaks, the most lethal type of breaks clearly showing that Cr(VI) is genotoxic. Unrepaired or inaccurately repaired breaks lead to the development of chromosome instability, which is a common phenotype in Cr(VI) exposed cells, animals, and humans. Indeed, many studies show Cr(VI) induces both structural and numerical chromosome instability. Overall, the large body of literature strongly supports the conclusion that Cr(VI) causes DNA double strand breaks, inhibits DNA repair and chromosome instability, which are key to the development of Cr(VI)-induced cell transformation.

Exploring the link between the pediatric exposome, respiratory health, and executive function in children: a narrative review

Asthma is a highly prevalent inflammatory condition, significantly affecting nearly six million U.S. children and impacting various facets of their developmental trajectories including neurodevelopment. Evidence supports a link between pediatric environmental exposures in two key areas: asthma and executive function (E.F.). E.F.s are a collective of higher-order cognitive processes facilitating goal-oriented behaviors. Studies also identify asthma-associated E.F. impairments in children. However, limited research has evaluated the inter-relationships among environmental exposures, asthma, and E.F. in children. This review explored relevant research to identify and connect the potential mechanisms and pathways underlying these dynamic associations. The review suggests that the role of the pediatric exposome may function through (1) several underlying biological pathways (i.e., the lung-brain axis, neuroendocrine system, and hypoxia), which could drive asthma and maladaptive E.F. in children and (2) the relationships between the exposome, asthma, and E.F. is a bidirectional linkage. The review reveals essential synergistic links between asthma and E.F. deficits, highlighting the potential role of the pediatric exposome.

Particulate matter 2.5 accelerates aging: Exploring cellular senescence and age-related diseases

Exposure to Particulate matter 2.5 (PM2.5) accelerates aging, causing declines in tissue and organ function, and leading to diseases such as cardiovascular, neurodegenerative, and musculoskeletal disorders. PM2.5 is a major environmental pollutant and an exogenous pathogen in air pollution that is now recognized as an accelerator of human aging and a predisposing factor for several age-related diseases. In this paper, we seek to elucidate the mechanisms by which PM2.5 induces cellular senescence, such as genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, and mitochondrial dysfunction, and age-related diseases. Our goal is to increase awareness among researchers within the field of the toxicity of environmental pollutants and to advocate for personal and public health initiatives to curb their production and enhance population protection. Through these endeavors, we aim to promote longevity and health in older adults.

An Update Overview on Mechanistic Data and Biomarker Levels in Cobalt and Chromium-Induced Neurodegenerative Diseases

There is increasing evidence that the imbalance of metals as cobalt (Co) and chromium (Cr) may increase the risk of development and progression of neurodegenerative diseases (NDDs). The human exposure to Co and Cr is derived mostly from industry, orthopedic implants, and polluted environments. Neurological effects of Co and Cr include memory deficit, olfactory dysfunction, spatial disorientation, motor neuron disease, and brain cancer. Mechanisms of Co and Cr neurotoxicity included DNA damage and genomic instability, epigenetic changes, mitochondrial disturbance, lipid peroxidation, oxidative stress, inflammation, and apoptosis. This paper seeks to overview the Co and Cr sources, the mechanisms by which these metals induce NDDs, and their levels in fluids of the general population and patients affected by NDDs. To this end, evidence of Co and Cr unbalance in the human body, mechanistic data, and neurological symptoms were collected using in vivo mammalian studies and human samples.

Exposure to multiple ambient air pollutants changes white matter microstructure during early adolescence with sex-specific differences

BACKGROUND

Air pollution is ubiquitous, yet questions remain regarding its impact on the developing brain. Large changes occur in white matter microstructure across adolescence, with notable differences by sex.

METHODS

We investigate sex-stratified effects of annual exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) at ages 9-10 years on longitudinal patterns of white matter microstructure over a 2-year period. Diffusion-weighted imaging was collected on 3T MRI scanners for 8182 participants (1-2 scans per subject; 45% with two scans) from the Adolescent Brain Cognitive Development (ABCD) Study®. Restriction spectrum imaging was performed to quantify intracellular isotropic (RNI) and directional (RND) diffusion. Ensemble-based air pollution concentrations were assigned to each child's primary residential address. Multi-pollutant, sex-stratified linear mixed-effect models assessed associations between pollutants and RNI/RND with age over time, adjusting for sociodemographic factors.

RESULTS

Here we show higher PM2.5 exposure is associated with higher RND at age 9 in both sexes, with no significant effects of PM2.5 on RNI/RND change over time. Higher NO2 exposure is associated with higher RNI at age 9 in both sexes, as well as attenuating RNI over time in females. Higher O3 exposure is associated with differences in RND and RNI at age 9, as well as changes in RND and RNI over time in both sexes.

CONCLUSIONS

Criteria air pollutants influence patterns of white matter maturation between 9-13 years old, with some sex-specific differences in the magnitude and anatomical locations of affected tracts. This occurs at concentrations that are below current U.S. standards, suggesting exposure to low-level pollution during adolescence may have long-term consequences.

Study on the metabolic effects of hexavalent chromium [Cr (VI)] on rat astrocytes using un-targeted metabolomics

Introduction: Hexavalent chromium [Cr (VI)] has been identified as a human carcinogen and environmental pollutant capable of affecting multiple systems in the human body. However, the specific mechanisms by which Cr (VI) affects the human nervous system remain unclear. Objective: Following confirmation of Cr (VI)'s toxic effects on rat astrocytes, this study explores the metabolites and associated metabolic pathways of rat astrocytes under different doses of Cr (VI) exposure. Methods: Cell viability was assessed using CCK8 assays, intracellular reactive oxygen species (ROS) levels were measured using DCFH-DA fluorescent probes, intracellular 8-hydroxydeoxyguanosine (8-OHdG) content was determined by Elisa, mitochondrial membrane potential was observed using JC-1 probes, and key metabolites were identified through untargeted metabolomics analysis. Results: With increasing Cr (VI) doses, significant decreases in cell viability were observed in the 4, 8, and 16 mg/L dose groups (p < 0.05). Elevated levels of ROS and 8-OHdG, increased caspase-3 activity, and significant reductions in mitochondrial membrane potential were observed in the 2 and 4 mg/L dose groups (p < 0.05). Untargeted metabolomics analysis revealed Cr (VI)'s impact on key metabolites such as sphingosine and methionine. Enrichment analysis of KEGG pathways highlighted the critical roles of sphingolipid metabolism and the methionine-cysteine cycle in the effects of Cr (VI) on rat astrocytes. Conclusion: Our study underscores the potential neuro-health risks associated with environmental and occupational exposure to Cr (VI) and provides new perspectives and directions for investigating neurotoxic mechanisms.

Association Between Exposure to Particulate Matter and the Incidence of Parkinson's Disease: A Nationwide Cohort Study in Taiwan

OBJECTIVE

Emerging evidence suggests that air pollution exposure may increase the risk of Parkinson's disease (PD). We aimed to investigate the association between exposure to fine particulate matter (PM2.5) and the risk of incident PD nationwide.

METHODS

We utilized data from the Taiwan National Health Insurance Research Database, which is spatiotemporally linked with air quality data from the Taiwan Environmental Protection Administration website. The study population consisted of participants who were followed from the index date (January 1, 2005) until the occurrence of PD or the end of the study period (December 31, 2017). Participants who were diagnosed with PD before the index date were excluded. To evaluate the association between exposure to PM2.5 and incident PD risk, we employed Cox regression to estimate the hazard ratio and 95% confidence interval (CI).

RESULTS

A total of 454,583 participants were included, with a mean (standard deviation) age of 63.1 (9.9) years and a male proportion of 50%. Over a mean follow-up period of 11.1 (3.6) years, 4% of the participants (n = 18,862) developed PD. We observed a significant positive association between PM2.5 exposure and the risk of PD, with a hazard ratio of 1.22 (95% CI, 1.20-1.23) per interquartile range increase in exposure (10.17 μg/m3) when adjusting for both SO2 and NO2.

CONCLUSION

We provide further evidence of an association between PM2.5 exposure and the risk of PD. These findings underscore the urgent need for public health policies aimed at reducing ambient air pollution and its potential impact on PD.

A multi-environmental source approach to explore associations between metals exposure and olfactory identification among school-age children residing in northern Italy

BACKGROUND

Metal exposures can adversely impact olfactory function. Few studies have examined this association in children. Further, metal exposure occurs as a mixture, yet previous studies of metal-associated olfactory dysfunction only examined individual metals. Preventing olfactory dysfunctions can improve quality of life and prevent neurodegenerative diseases with long-term health implications.

OBJECTIVE

We aimed to test the association between exposure to a mixture of 12 metals measured in environmental sources and olfactory function among children and adolescents residing in the industrialized province of Brescia, Italy.

METHODS

We enrolled 130 children between 6 and 13 years old (51.5% females) and used the "Sniffin' Sticks" test to measure olfactory performance in identifying smells. We used a portable X-ray fluorescence instrument to determine concentrations of metals (arsenic (As), calcium, cadmium (Cd), chromium, copper, iron, manganese, lead (Pb), antimony, titanium, vanadium and zinc) in outdoor and indoor deposited dust and soil samples collected from participants' households. We used an extension of weighted quantile sum (WQS) regression to test the association between exposure to metal mixtures in multiple environmental media and olfactory function adjusting for age, sex, socio-economic status, intelligence quotient and parents' smoking status.

RESULTS

A higher multi-source mixture was significantly associated with a reduced Sniffin' Sticks identification score (β = -0.228; 95% CI -0.433, -0.020). Indoor dust concentrations of Pb, Cd and As provided the strongest contributions to this association (13.8%, 13.3% and 10.1%, respectively). The metal mixture in indoor dust contributed more (for 8 metals out of 12) to the association between metals and olfactory function compared to soil or outdoor dust.

IMPACT STATEMENT

Among a mixture of 12 metals measured in three different environmental sources (soil, outdoor and indoor dust), we identified Pb, Cd and As measured in indoor dust as the main contributors to reduced olfactory function in children and adolescents residing in an industrialized area. Exposure to indoor pollution can be effectively reduced through individual and public health interventions allowing to prevent the deterioration of olfactory functions. Moreover, the identification of the factors that can deteriorate olfactory functions can be a helpful instrument to improve quality of life and prevent neurodegenerative diseases as long-term health implications.

Within-city spatial variations in PM2.5 magnetite nanoparticles and brain cancer incidence in Toronto and Montreal, Canada

Magnetite nanoparticles are small, strongly magnetic iron oxide particles which are produced during high-temperature combustion and friction processes and form part of the outdoor air pollution mixture. These particles can translocate to the brain and have been found in human brain tissue. In this study, we estimated associations between within-city spatial variations in concentrations of magnetite nanoparticles in outdoor fine particulate matter (PM2.5) and brain cancer incidence. We performed a cohort study of 1.29 million participants in four cycles of the Canadian Census Health and Environment Cohort in Montreal and Toronto, Canada who were followed for malignant brain tumour (glioma) incidence. As a proxy for magnetite nanoparticle content, we measured the susceptibility of anhysteretic remanent magnetization (χARM) in PM2.5 samples (N = 124 in Montreal, N = 110 in Toronto), and values were assigned to residential locations. Stratified Cox proportional hazards models were used to estimate hazard ratios (per IQR change in volume-normalized χARM). ARM was not associated with brain tumour incidence (HR = 0.998, 95% CI 0.988, 1.009) after adjusting for relevant potential confounders. Although we found no evidence of an important relationship between within-city spatial variations in airborne magnetite nanoparticles and brain tumour incidence, further research is needed to evaluate this understudied exposure, and other measures of exposure to magnetite nanoparticles should be considered.

Evidence for chromium crosses blood brain barrier from the hypothalamus in chromium mice model

It has been shown that exposure to hexavalent Chromium, Cr (Ⅵ), via nasal cavity can have neurotoxicological effects and induces behavioral impairment due to the fact that blood brain barrier (BBB) does not cover olfactory bulb. But whether Cr (Ⅵ) can cross the BBB and have a toxicological effects in central nervous system (CNS) remains unclear. Therefore, we investigated the effects of Cr (Ⅵ) on mice treated with different concentrations and exposure time (14 days and 28 days) of Cr (Ⅵ) via intraperitoneal injection. Results revealed that Cr accumulated in hypothalamus (HY) in a timely dependent manner. Much more severer neuropathologies was observed in the group of mice exposed to Cr (Ⅵ) for 28 days than that for 14 days. Gliosis, neuronal morphological abnormalities, synaptic degeneration, BBB disruption and neuronal number loss were observed in HY. In terms of mechanism, the Nrf2 related antioxidant stress signaling dysfunction and activated NF-κB related inflammatory pathway were observed in HY of Cr (Ⅵ) intoxication mice. And these neuropathologies and signaling defects appeared in a timely dependent manner. Taking together, we proved that Cr (Ⅵ) can enter HY due to weaker BBB in HY and HY is the most vulnerable CNS region to Cr (Ⅵ) exposure. The concentration of Cr in HY increased along with time. The accumulated Cr in HY can cause BBB disruption, neuronal morphological abnormalities, synaptic degeneration and gliosis through Nrf2 and NF-κB signaling pathway. This finding improves our understanding of the neurological dysfunctions observed in individuals who have occupational exposure to Cr (Ⅵ), and provided potential therapeutic targets to treat neurotoxicological pathologies induced by Cr (Ⅵ).

Elossaily G, Vellapandian C, Prajapati B. Investigating the Potential Impact of Air Pollution on Alzheimer's Disease and the Utility of Multidimensional Imaging for Early Detection

Pollution is ubiquitous, and much of it is anthropogenic in nature, which is a severe risk factor not only for respiratory infections or asthma sufferers but also for Alzheimer's disease, which has received a lot of attention recently. This Review aims to investigate the primary environmental risk factors and their profound impact on Alzheimer's disease. It underscores the pivotal role of multidimensional imaging in early disease identification and prevention. Conducting a comprehensive review, we delved into a plethora of literature sources available through esteemed databases, including Science Direct, Google Scholar, Scopus, Cochrane, and PubMed. Our search strategy incorporated keywords such as "Alzheimer Disease", "Alzheimer's", "Dementia", "Oxidative Stress", and "Phytotherapy" in conjunction with "Criteria Pollutants", "Imaging", "Pathology", and "Particulate Matter". Alzheimer's disease is not only a result of complex biological factors but is exacerbated by the infiltration of airborne particles and gases that surreptitiously breach the nasal defenses to traverse the brain, akin to a Trojan horse. Various imaging modalities and noninvasive techniques have been harnessed to identify disease progression in its incipient stages. However, each imaging approach possesses inherent limitations, prompting exploration of a unified technique under a single umbrella. Multidimensional imaging stands as the linchpin for detecting and forestalling the relentless march of Alzheimer's disease. Given the intricate etiology of the condition, identifying a prospective candidate for Alzheimer's disease may take decades, rendering the development of a multimodal imaging technique an imperative. This research underscores the pressing need to recognize the chronic ramifications of invisible particulate matter and to advance our understanding of the insidious environmental factors that contribute to Alzheimer's disease.

Perinatal Exposure to Trace Elements: The Dubious Culprit of Autistic Spectrum Disorder in Children

There is evidence that few trace elements in the environment work as hazardous materials in terms of their exposure in the perinatal period, causing autistic spectrum disorder (ASD) in children, and avoiding these exposures in the environment can reduce the number of new cases. This perspective study provides preliminary evidence to consider a few trace elements as culprits for ASD. More studies with larger cohorts are needed, but meanwhile, as per available evidence, exposure to these hazardous materials must be warranted during pregnancy and early stages of life.

Effects of combined exposure of manganese and iron on serum inflammatory factor levels among workers

OBJECTIVE

The aim of the study is to examine the association between long-term occupational exposure to Mn and Fe and their health effects in workers.

METHODS

108 Mn workers were selected for the Mn exposure groups; 92 non-Mn workers were in the control group. Inductively coupled plasma-mass spectrometry was used to determine the Mn and Fe concentration in the working environment. Graphite furnace-atomic absorption spectroscopy was used to determine the blood Mn concentration of workers. Serum inflammatory factors were measured by enzyme-linked immunosorbent assay.

RESULTS

The blood Mn concentration, positive rate of clinical symptoms and serum inflammatory response in the Mn exposure group was higher than in the control group.

CONCLUSIONS

Low levels of Mn exposure may increase blood Mn concentrations, the rate of complaints of neurological symptoms and promote increased serum inflammatory response in workers.

Sex-specific effects in how childhood exposures to multiple ambient air pollutants affect white matter microstructure development across early adolescence

Ambient air pollution is ubiquitous, yet questions remain as to how it might impact the developing brain. Large changes occur in the brain's white matter (WM) microstructure across adolescence, with noticeable differences in WM integrity in male and female youth. Here we report sex-stratified effects of fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) on longitudinal patterns of WM microstructure from 9-13 years-old in 8,182 (49% female) participants using restriction spectrum imaging. After adjusting for key sociodemographic factors, multi-pollutant, sex-stratified models showed that one-year annual exposure to PM2.5 and NO2 was associated with higher, while O3 was associated with lower, intracellular diffusion at age 9. All three pollutants also affected trajectories of WM maturation from 9-13 years-old, with some sex-specific differences in the number and anatomical locations of tracts showing altered trajectories of intracellular diffusion. Concentrations were well-below current U.S. standards, suggesting exposure to these criteria pollutants during adolescence may have long-term consequences on brain development.

Metal-ion transporter SLC39A8 is required for brain manganese uptake and accumulation

Manganese (Mn) is an essential nutrient, but is toxic in excess. Whole-body Mn levels are regulated in part by the metal-ion influx transporter SLC39A8, which plays an essential role in the liver by reclaiming Mn from bile. Physiological roles of SLC39A8 in Mn homeostasis in other tissues, however, remain largely unknown. To screen for extrahepatic requirements for SLC39A8 in tissue Mn homeostasis, we crossed Slc39a8-inducible global-KO (Slc39a8 iKO) mice with Slc39a14 KO mice, which display markedly elevated blood and tissue Mn levels. Tissues were then analyzed by inductively coupled plasma-mass spectrometry to determine levels of Mn. Although Slc39a14 KO; Slc39a8 iKO mice exhibited systemic hypermanganesemia and increased Mn loading in the bone and kidney due to Slc39a14 deficiency, we show Mn loading was markedly decreased in the brains of these animals, suggesting a role for SLC39A8 in brain Mn accumulation. Levels of other divalent metals in the brain were unaffected, indicating a specific effect of SLC39A8 on Mn. In vivo radiotracer studies using 54Mn in Slc39a8 iKO mice revealed that SLC39A8 is required for Mn uptake by the brain, but not most other tissues. Furthermore, decreased 54Mn uptake in the brains of Slc39a8 iKO mice was associated with efficient inactivation of Slc39a8 in isolated brain microvessels but not in isolated choroid plexus, suggesting SLC39A8 mediates brain Mn uptake via the blood-brain barrier. These findings establish SLC39A8 as a candidate therapeutic target for mitigating Mn uptake and accumulation in the brain, the primary organ of Mn toxicity.

Neurotoxicity of the air-borne particles: From molecular events to human diseases

Exposure to PM_2.5 is associated with an increased incidence of CNS diseases in humans, as confirmed by numerous epidemiological studies. Animal models have demonstrated that PM_2.5 exposure can damage brain tissue, neurodevelopmental issues and neurodegenerative diseases. Both animal and human cell models have identified oxidative stress and inflammation as the primary toxic effects of PM_2.5 exposure. However, understanding how PM_2.5 modulates neurotoxicity has proven challenging due to its complex and variable composition. This review aims to summarize the detrimental effects of inhaled PM_2.5 on the CNS and the limited understanding of its underlying mechanism. It also highlights new frontiers in addressing these issues, such as modern laboratory and computational techniques and chemical reductionism tactics. By utilizing these approaches, we aim to fully elucidate the mechanism of PM_2.5-induced neurotoxicity, treat associated diseases, and ultimately eliminate pollution.

CNS-Related Effects Caused by Vanadium at Realistic Exposure Levels in Humans: A Comprehensive Overview Supplemented with Selected Animal Studies

Neurodegenerative disorders, which are currently incurable diseases of the nervous system, are a constantly growing social concern. They are progressive and lead to gradual degeneration and/or death of nerve cells, resulting in cognitive deterioration or impaired motor functions. New therapies that would ensure better treatment results and contribute to a significant slowdown in the progression of neurodegenerative syndromes are constantly being sought. Vanadium (V), which is an element with a wide range of impacts on the mammalian organism, is at the forefront among the different metals studied for their potential therapeutic use. On the other hand, it is a well-known environmental and occupational pollutant and can exert adverse effects on human health. As a strong pro-oxidant, it can generate oxidative stress involved in neurodegeneration. Although the detrimental effects of vanadium on the CNS are relatively well recognized, the role of this metal in the pathophysiology of various neurological disorders, at realistic exposure levels in humans, is not yet well characterized. Hence, the main goal of this review is to summarize data on the neurological side effects/neurobehavioral alterations in humans, in relation to vanadium exposure, with the focus on the levels of this metal in biological fluids/brain tissues of subjects with some neurodegenerative syndromes. Data collected in the present review indicate that vanadium cannot be excluded as a factor playing a pivotal role in the etiopathogenesis of neurodegenerative illnesses, and point to the need for additional extensive epidemiological studies that will provide more evidence supporting the relationship between vanadium exposure and neurodegeneration in humans. Simultaneously, the reviewed data, clearly showing the environmental impact of vanadium on health, suggest that more attention should be paid to chronic diseases related to vanadium and to the assessment of the dose-response relationship.

Insufficient evidence to link human exposure to heavy metals with biomarkers of glioma

Information on molecular mechanisms has implicated potential association between the concentrations of heavy metals and incidences of glioma, but experimental data on human brain tissue remain sparse. To address this data gap, 13 heavy metals were measured in 137 glioma and 35 non-glioma samples collected from 161 alive patients in Guangdong Province, China in 2019 - 2020. All target heavy metals were detected, suggesting they could cross the blood-brain barrier. Concentrations of Mn, Cu, and Zn were higher in glioma than in non-glioma samples, while those of Ni and Se were higher in non-glioma samples, probably suggesting that these five heavy metals are more prone to be altered by changing pathological conditions. In addition, Cu/Zn, Cr/Mn, Cr/Se, Ni/Se, Pb/Mn, and Pb/Se were statistically different between glioma and non-glioma samples by a difference test and a multiple logistic regression model. These concentration ratios may serve as chemical markers to assist pathological analysis for differentiating between tumor and healthy tissues. However, no direct link between heavy metal concentrations or concentration ratios and biomarkers of glioma (i.e., tumor grade, P53, and Ki-67) was observed. No sufficient evidence was obtained to implicate the role of heavy metals in inducing glioma, largely caused by the limited number of samples. Different concentrations and concentration ratios of heavy metals may be the consequence rather than the cause of pathological changes in brain tumors.

Association of air pollution with olfactory identification performance of São Paulo residents: a cross-sectional study

OBJECTIVE

Exposure to particulate matter of 10 μm or less in diameter (PM₁₀) has been implicated in pulmonary and cardiovascular diseases. However, the effect of PM₁₀ on olfaction has not been well established. We estimated individual acute and chronic PM₁₀ exposure levels in a large Brazilian cohort and related them to the ability to identify odors.

METHODS

Adults from São Paulo (n = 1358) were recruited from areas with different levels of air pollution. To verify individual exposure to air pollution, the averages of 30, 60, 90, 180 and 364 days of PM₁₀ were interpolated to subjects' zip codes using the kriging method. Olfactory identification performance was tested using the University of Pennsylvania Smell Identification Test (UPSIT®). Multiple linear regressions were used to calculate the effect of air pollution on olfactory identification performance, controlling for demographic and other variables that affect the sense of smell.

RESULTS

Acute exposures to PM₁₀ were related to worse UPSIT® scores, including 30- (β =  - 0.94, 95% Confidence Interval [CI]  - 0.98,  - 0.89), 60- (β =  - 1.09, 95% CI = - 1.13,  - 1.04) and 90-day intervals (β =  - 1.06, 95% CI  - 1.10,  - 1.02) (reference for β: 1 µm/m³ increase in PM10 exposure per point decrease in UPSIT® score). Chronic exposures were also associated with worse olfaction for both 180- (β =  - 1.06, 95% CI  - 1.10,  - 1.03) and 364-day (β =  - 0.87, 95% CI  - 0.90,  - 0.84) intervals. As in prior work, men, older, low-income, and low-schooling people demonstrated worse olfactory performance.

CONCLUSION

Acute and chronic exposure to PM₁₀ is strongly associated with olfactory identification performance in Brazilian adults. Understanding the mechanisms which underlie these relationships could help to improve chemosensory function with a large public health impact.

Prenatal exposure to tailpipe and non-tailpipe tracers of particulate matter pollution and autism spectrum disorders

BACKGROUND

Traffic-related air pollution exposure is associated with increased risk of autism spectrum disorder (ASD). It is unknown whether carbonaceous material from vehicular tailpipe emissions or redox-active non-tailpipe metals, eg. from tire and brake wear, are responsible. We assessed ASD associations with fine particulate matter (PM_2.5) tracers of tailpipe (elemental carbon [EC] and organic carbon [OC]) and non-tailpipe (copper [Cu]; iron [Fe] and manganese [Mn]) sources during pregnancy in a large cohort.

METHODS

This retrospective cohort study included 318,750 children born in Kaiser Permanente Southern California (KPSC) hospitals during 2001-2014, followed until age 5. ASD cases were identified by ICD codes. Monthly estimates of PM_2.5 and PM_2.5 constituents EC, OC, Cu, Fe, and Mn with 4 km spatial resolution were obtained from a source-oriented chemical transport model. These exposures and NO₂ were assigned to each maternal address during pregnancy, and associations with ASD were assessed using Cox regression models adjusted for covariates. PM constituent effect estimates were adjusted for PM_2.5 and NO₂ to assess independent effects. To distinguish ASD risk associated with non-tailpipe from tailpipe sources, the associations with Cu, Fe, and Mn were adjusted for EC and OC, and vice versa.

RESULTS

There were 4559 children diagnosed with ASD. In single-pollutant models, increased ASD risk was associated with gestational exposures to tracers of both tailpipe and non-tailpipe emissions. The ASD hazard ratios (HRs) per inter-quartile increment of exposure) for EC, OC, Cu, Fe, and Mn were 1.11 (95% CI: 1.06-1.16), 1.09 (95% CI: 1.04-1.15), 1.09 (95% CI: 1.04-1.13), 1.14 (95% CI: 1.09-1.20), and 1.17 (95% CI: 1.12-1.22), respectively. Estimated effects of Cu, Fe, and Mn (reflecting non-tailpipe sources) were largely unchanged in two-pollutant models adjusting for PM_2.5, NO₂, EC or OC. In contrast, ASD associations with EC and OC were markedly attenuated by adjustment for non-tailpipe sources.

CONCLUSION

Results suggest that non-tailpipe emissions may contribute to ASD. Implications are that reducing tailpipe emissions, especially from vehicles with internal combustion engines, may not eliminate ASD associations with traffic-related air pollution.

Cobalt-mediated oxidative DNA damage and its prevention by polyphenol antioxidants

Although cobalt is a required nutrient, it is toxic due to its ability to generate reactive oxygen species (ROS) and damage DNA. ROS generation by Co²⁺ often has been compared to that of Fe²⁺ or Cu⁺, disregarding the reduction potential differences among these metal ions. In plasmid DNA damage studies, a maximum of 15% DNA damage is observed with Co²⁺/H₂O₂ treatment (up to 50 μM and 400 μM, respectively) significantly lower than the 90% damage observed for Fe²⁺/H₂O₂ or Cu⁺/H₂O₂ treatment. However, when ascorbate is added to the Co²⁺/H₂O₂ system, a synergistic effect results in 90% DNA damage. DNA damage by Fe²⁺/H₂O₂ can be prevented by polyphenol antioxidants, but polyphenols both prevent and promote DNA damage by Cu⁺/H₂O₂. When tested for cobalt-mediated DNA damage affects, eight of ten polyphenols (epicatechin gallate, epigallocatechin gallate, propyl gallate, gallic acid, methyl-3,4,5-trihydroxybenzoate, methyl-4,5-dihydroxybenzoate, protocatechuic acid, and epicatechin) prevent cobalt-mediated DNA damage with IC₅₀ values of 1.3 to 27 μM and two (epigallocatechin and vanillic acid) prevent little to no DNA damage. EPR studies demonstrate cobalt-mediated formation of ^•OH, O₂^•-, and ^•OOH, but not ¹O₂ in the presence of H₂O₂ and ascorbate. Epigallocatechin gallate and methyl-4,5-dihydroxybenzoate significantly reduce ROS generated by Co²⁺/H₂O₂/ascorbate, consistent with their prevention of cobalt-mediated DNA damage. Thus, while cobalt, iron, and copper are all d-block metal ions, cobalt ROS generation and its prevention is significantly different from that of iron and copper.

TDP-43 CSF Concentrations Increase Exponentially with Age in Metropolitan Mexico City Young Urbanites Highly Exposed to PM2.5 and Ultrafine Particles and Historically Showing Alzheimer and Parkinson's Hallmarks. Brain TDP-43 Pathology in MMC Residents Is Associated with High Cisternal CSF TDP-43 Concentrations

Environmental exposures to fine particulate matter (PM2.5) and ultrafine particle matter (UFPM) are associated with overlapping Alzheimer’s, Parkinson’s and TAR DNA-binding protein 43 (TDP-43) hallmark protein pathologies in young Metropolitan Mexico City (MMC) urbanites. We measured CSF concentrations of TDP-43 in 194 urban residents, including 92 MMC children aged 10.2 ± 4.7 y exposed to PM2.5 levels above the USEPA annual standard and to high UFPM and 26 low pollution controls (11.5 ± 4.4 y); 43 MMC adults (42.3 ± 15.9 y) and 14 low pollution adult controls (33.1 ± 12.0 y); and 19 amyotrophic lateral sclerosis (ALS) patients (52.4 ± 14.1 y). TDP-43 neuropathology and cisternal CSF data from 20 subjects—15 MMC (41.1 ± 18.9 y) and 5 low pollution controls (46 ± 16.01 y)—were included. CSF TDP-43 exponentially increased with age (p < 0.0001) and it was higher for MMC residents. TDP-43 cisternal CSF levels of 572 ± 208 pg/mL in 6/15 MMC autopsy cases forecasted TDP-43 in the olfactory bulb, medulla and pons, reticular formation and motor nuclei neurons. A 16 y old with TDP-43 cisternal levels of 1030 pg/mL exhibited TDP-43 pathology and all 15 MMC autopsy cases exhibited AD and PD hallmarks. Overlapping TDP-43, AD and PD pathologies start in childhood in urbanites with high exposures to PM2.5 and UFPM. Early, sustained exposures to PM air pollution represent a high risk for developing brains and MMC UFPM emissions sources ought to be clearly identified, regulated, monitored and controlled. Prevention of deadly neurologic diseases associated with air pollution ought to be a public health priority and preventive medicine is key.

Possible association between PM2.5 and neurodegenerative diseases: A systematic review

Air pollution is one of the most serious environmental problems that afflict our planet and one of the greatest risk factors for human health. In particular, PM_2.5 is able to cross the blood-alveolar and blood-brain barriers, thus increasing the onset of respiratory, cardiovascular and neurodegenerative diseases. Neurodegenerative disease is a progressive neuronal dysfunction that leads to neuronal lesions in both structure and function, and includes several diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), vascular dementia (VaD), multiple sclerosis (MS), and others. We carried out a systematic review using PRISMA approach to investigate on the possible association between exposure to PM_2.5 and neurodegenerative diseases. The international databases (PubMed, Science Direct, Web of Sciences) were used to find published studies on the topic. The search period was between January 2011 and June 2021. About 2000 full research articles were selected, and finally, we included 20 full-research articles. Selected studies have highlighted how PM_2.5 exposure can be associated with the onset of neurodegenerative diseases (AD, PD, MS, VaD). This association depends not only on age, PM_2.5 levels and exposure time, but also on exposure to other air pollutants, proximity to areas with high vehicular traffic, and the presence of comorbidities. Exposure to PM_2.5 promotes neuroinflammation processes, because through breathing the particles can reach the nasal epithelial mucosa and transferred to the brain through the olfactory bulb. Furthermore, exposure to PM_2.5 has been associated with an increased expression of markers of neurodegenerative diseases (e.g. alpha-synuclein or beta-amyloid), which can contribute to the etiopathogenesis of neurodegenerative diseases. Although many studies have revealed the pathological relationship between PM_2.5 exposure and cognitive impairment, the potential cellular and molecular mechanisms of PM_2.5 leading to neurodegenerative disease remain not entirely clear, and then, further studies need to be carried out on the topic.

Metals, Nanoparticles, Particulate Matter, and Cognitive Decline

Exposure to metals is ubiquitous and emission sources include gasoline, diesel, smoke from wildfires, contaminated soil, water and food, medical implants, waste recycling facilities, subway exposures, and occupational environments. PM_2.5 exposure is associated with impaired cognitive performance, neurobehavioral alterations, incidence of dementia, and Alzheimer's disease (AD) risk. Heavy-duty diesel vehicles are major emitters of metal-rich PM_2.5 and nanoparticles in Metropolitan Mexico City (MMC). Cognitive impairment was investigated in 336 clinically healthy, middle-class, Mexican volunteers, age 29.2 ± 13.3 years with 13.7 ± 2.4 years of education using the Montreal Cognitive Assessment (MoCA). MoCA scores varied with age and residency in three Mexican cities with cognition deficits impacting ~74% of the young middle-class population (MoCA ≤ 25). MMC residents ≥31 years (x¯46.2 ± 11.8 y) had MoCA x¯20.4 ± 3.4 vs. low pollution controls 25.2 ± 2.4 (p < 0.0001). Formal education years positively impacted MoCA total scores across all participants (p < 0.0001). Residency in PM_2.5 polluted cities impacts multi-domain cognitive performance. Identifying and making every effort to lower key pollutants impacting neural risk trajectories and monitoring cognitive longitudinal performance are urgent. PM_2.5 emission control should be prioritized, metal emissions targeted, and neuroprevention interventions implemented early.

Current understanding of hexavalent chromium [Cr(VI)] neurotoxicity and new perspectives

Hexavalent chromium [Cr(VI)] is a global environmental pollutant that increases risk for several types of cancers and is increasingly being recognized as a neurotoxicant. Traditionally, the brain has been viewed as a largely post-mitotic organ due to its specialized composition of neurons, and consequently, clastogenic effects were not considered in neurotoxicology. Today, we understand the brain is composed of at least eight distinct cell types - most of which continue mitotic activity throughout lifespan. We have learned these dividing cells play essential roles in brain and body health. This review focuses on Cr(VI), a potent clastogen and known human carcinogen, as a potentially neurotoxic agent targeting mitotic cells of the brain. Despite its well-established role as a human carcinogen, Cr(VI) neurotoxicity studies have failed to find a significant link to brain cancers. In the few studies that did find a link, Cr(VI) was identified as a risk for gliomas. Instead, in the human brain, Cr(VI) appears to have more subtle deleterious effects that can impair childhood learning and attention development, olfactory function, social memory, and may contribute to motor neuron diseases. Studies of Cr(VI) neurotoxicity with animal and cell culture models have demonstrated elevated markers of oxidative damage and redox stress, with widespread neurodegeneration. One study showed mice exposed to Cr(VI)-laden tannery effluent exhibited longer periods of aggressive behavior toward an "intruder" mouse and took longer to recognize mice previously encountered, recapitulating the social memory deficits observed in humans. Here we conducted a critical review of the available literature on Cr(VI) neurotoxicity and synthesize the collective observations to thoroughly evaluate Cr(VI) neurotoxicity - much remains to be understood and recognized.

Lithium administered to pregnant, lactating and neonatal rats: entry into developing brain

Background

Little is known about the extent of drug entry into developing brain, when administered to pregnant and lactating women. Lithium is commonly prescribed for bipolar disorder. Here we studied transfer of lithium given to dams, into blood, brain and cerebrospinal fluid (CSF) in embryonic and postnatal animals as well as adults.

Methods

Lithium chloride in a clinically relevant dose (3.2 mg/kg body weight) was injected intraperitoneally into pregnant (E15–18) and lactating dams (birth-P16/17) or directly into postnatal pups (P0–P16/17). Acute treatment involved a single injection; long-term treatment involved twice daily injections for the duration of the experiment. Following terminal anaesthesia blood plasma, CSF and brains were collected. Lithium levels and brain distribution were measured using Laser Ablation Inductively Coupled Plasma-Mass Spectrometry and total lithium levels were confirmed by Inductively Coupled Plasma-Mass Spectrometry.

Results

Lithium was detected in blood, CSF and brain of all fetal and postnatal pups following lithium treatment of dams. Its concentration in pups’ blood was consistently below that in maternal blood (30–35%) indicating significant protection by the placenta and breast tissue. However, much of the lithium that reached the fetus entered its brain. Levels of lithium in plasma fluctuated in different treatment groups but its concentration in CSF was stable at all ages, in agreement with known stable levels of endogenous ions in CSF. There was no significant increase of lithium transfer into CSF following application of Na⁺/K⁺ ATPase inhibitor (digoxin) in vivo, indicating that lithium transfer across choroid plexus epithelium is not likely to be via the Na⁺/K⁺ ATPase mechanism, at least early in development. Comparison with passive permeability markers suggested that in acute experiments lithium permeability was less than expected for diffusion but similar in long-term experiments at P2.

Conclusions

Information obtained on the distribution of lithium in developing brain provides a basis for studying possible deleterious effects on brain development and behaviour in offspring of mothers undergoing lithium therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00285-w.

Effect of ambient air PM2.5-bound heavy metals on blood metal(loid)s and children's asthma and allergy pro-inflammatory (IgE, IL-4 and IL-13) biomarkers

BACKGROUND

We investigated the concentrations of metals in fine particulate matter PM_2.5 in the outdoor air around the home sites of 123 male children from Ahvaz, average age 7.56, along with their blood samples to measure pro-inflammatory responses (Immunoglobulin E and cytokines: IgE, IL-4 and IL-13).

METHODS

We measured 6 metals (As, Cd, Cr, Hg, Ni and Pb) in three Ahvaz's regions including industrial (Padad), vehicle traffic (Golestan) and control (Kianpars).

RESULTS

The higher concentrations of metals in the Padad as the industrial ambient air i.e., arsenic, cadmium, chromium, mercury and nickel coincided with the higher concentrations of those metals in exposed children (P < 0.05) versus the controls. Children in Golestan, the high traffic air pollution area had the highest lead concentrations (p < 0.05). Also a significant association was shown in Padad between blood arsenic and IgE (β = 26.59, P < 0.001), IL-4 (β = 172.1, P < 0.001) and IL-13 (β = 14.84, P < 0.001), blood chromium and IgE (β = 10.38, P < 0.001), IL-4 (β = 75.27, P < 0.001) and IL-13 (β = 5.27, P < 0.001) and blood mercury and IgE (β = 13.11, P < 0.001), IL-4 (β = 108.09, P < 0.001) and IL-13 (β = 7.96, P < 0.001) and blood lead and IgE(β = 0.92, P = 0.025), IL-4(β = 7.16, P < 0.001) and IL-13(β = 0.58, P = 0.003). However, no significant relation was found for Cadmium, Nickel in blood with IgE, IL-4 and IL-13 levels. Moreover, children from industrial areas showed significantly higher concentrations of IgE (mean = 146.44 pg/200landa, P < 0.001), IL-4 (mean = 548.23 pg/200landa, P < 0.001) and IL-13 (mean = 52.93 pg/200landa, P < 0.001) versus Golestan and Kianpars.

CONCLUSION

Children residing in an industrial area with high concentrations of metals in PM_2.5 had high metals in blood and high production of IgE, IL-4 and IL-13, reflecting an immune dysregulation and brisk inflammatory responses.

Prenatal PM2.5 exposure in the second and third trimesters predicts neurocognitive performance at age 9-10 years: A cohort study of Mexico City children

INTRODUCTION

Prenatal exposure to fine particulate matter air pollution (PM2.5) is an important, under-studied risk factor for neurodevelopmental dysfunction. We describe the relationships between prenatal PM2.5 exposure and vigilance and inhibitory control, executive functions related to multiple health outcomes in Mexico City children.

METHODS

We studied 320 children enrolled in Programming Research in Obesity, GRowth, Environment and Social Stressors, a longitudinal birth cohort study in Mexico City. We used a spatio-temporal model to estimate daily prenatal PM2.5 exposure at each participant's residential address. At age 9-10 years, children performed three Go/No-Go tasks, which measure vigilance and inhibitory control ability. We used Latent class analysis (LCA) to classify performance into subgroups that reflected neurocognitive performance and applied multivariate regression and distributed lag regression modeling (DLM) to test overall and time-dependent associations between prenatal PM2.5 exposure and Go/No-Go performance.

RESULTS

LCA detected two Go/No-Go phenotypes: high performers (Class 1) and low performers (Class 2). Predicting odds of Class 1 vs Class 2 membership based on prenatal PM2.5 exposure timing, logistic regression modeling showed that average prenatal PM2.5 exposure in the second and third trimesters correlated with increased odds of membership in low-performance Class 2 (OR = 1.59 (1.16, 2.17), p = 0.004). Additionally, DLM analysis identified a critical window consisting of gestational days 103-268 (second and third trimesters) in which prenatal PM2.5 exposure predicted poorer Go/No-Go performance.

DISCUSSION

Increased prenatal PM2.5 exposure predicted decreased vigilance and inhibitory control at age 9-10 years. These findings highlight the second and third trimesters of gestation as critical windows of PM2.5 exposure for the development of vigilance and inhibitory control in preadolescent children. Because childhood development of vigilance and inhibitory control informs behavior, academic performance, and self-regulation into adulthood, these results may help to describe the relationship of prenatal PM2.5 exposure to long-term health and psychosocial outcomes. The integrative methodology of this study also contributes to a shift towards more holistic analysis.

Indoor Particulate Matter in Urban Households: Sources, Pathways, Characteristics, Health Effects, and Exposure Mitigation

Particulate matter (PM) is a complex mixture of solid particles and liquid droplets suspended in the air with varying size, shape, and chemical composition which intensifies significant concern due to severe health effects. Based on the well-established human health effects of outdoor PM, health-based standards for outdoor air have been promoted (e.g., the National Ambient Air Quality Standards formulated by the U.S.). Due to the exchange of indoor and outdoor air, the chemical composition of indoor particulate matter is related to the sources and components of outdoor PM. However, PM in the indoor environment has the potential to exceed outdoor PM levels. Indoor PM includes particles of outdoor origin that drift indoors and particles that originate from indoor activities, which include cooking, fireplaces, smoking, fuel combustion for heating, human activities, and burning incense. Indoor PM can be enriched with inorganic and organic contaminants, including toxic heavy metals and carcinogenic volatile organic compounds. As a potential health hazard, indoor exposure to PM has received increased attention in recent years because people spend most of their time indoors. In addition, as the quantity, quality, and scope of the research have expanded, it is necessary to conduct a systematic review of indoor PM. This review discusses the sources, pathways, characteristics, health effects, and exposure mitigation of indoor PM. Practical solutions and steps to reduce exposure to indoor PM are also discussed.

Airborne particulate matter induces oxidative damage, DNA adduct formation and alterations in DNA repair pathways

Air pollution, which includes particulate matter (PM), is classified in group 1 as a carcinogen to humans by the International Agency for Research in Cancer. Specifically, PM exposure has been associated with lung cancer in patients living in highly polluted cities. The precise mechanism by which PM is linked to cancer has not been completely described, and the genotoxicity induced by PM exposure plays a relevant role in cell damage. In this review, we aimed to analyze the types of DNA damage and alterations in DNA repair pathways induced by PM exposure, from both epidemiological and toxicological studies, to comprehend the contribution of PM exposure to carcinogenesis. Scientific evidence supports that PM exposure mainly causes oxidative stress by reactive oxygen species (ROS) and the formation of DNA adducts, specifically by polycyclic aromatic hydrocarbons (PAH). PM exposure also induces double-strand breaks (DSBs) and deregulates the expression of some proteins in DNA repair pathways, precisely, base and nucleotide excision repairs and homologous repair. Furthermore, specific polymorphisms of DNA repair genes could lead to an adverse response in subjects exposed to PM. Nevertheless, information about the effects of PM on DNA repair pathways is still limited, and it has not been possible to conclude which pathways are the most affected by exposure to PM or if DNA damage is repaired properly. Therefore, deepening the study of genotoxic damage and alterations of DNA repair pathways is needed for a more precise understanding of the carcinogenic mechanism of PM.

Air Pollution: A Neglected Risk Factor for Dementia in Latin America and the Caribbean

The risk of dementia and Alzheimer's disease in Latin America and the Caribbean (LAC) rises with increasing age and polluted air. Currently, at least 172 million people breathe unhealthy levels of air pollution in LAC countries. Several cohort studies have indicated that air pollution increases the risk of developing dementia and neurodegenerative diseases, but the mechanisms underlying the association are still not clear. Air pollution causes and aggravates five established risk factors for dementia (obesity, hypertension, stroke, diabetes mellitus, and heart diseases) and is linked to three other risk factors (physical inactivity, cognitive inactivity, and depression). Some of these risk factors could be mediating the association between air pollution and dementia. Reducing the risks for dementia is crucial and urgently needed in LAC countries. There is room for improving air quality in many urban areas in the LAC region and other low- and middle-income countries (LMICs), a routealready explored by many urban areas in developing regions. Moreover, reducing air pollution has proved to improve health outcomes before. In this article, we propose that despite the ongoing and valid scientific discussion, if air pollution can or cannot directly affect the brain and cause or aggravate dementia, we are ready to consider air pollution as a potentially modifiable risk factor for dementia in LAC and possibly in other LMICs. We suggest that controlling and reducing current air pollution levels in LAC and other LMIC regions now could strongly contribute.

The Air We Breathe: Air Pollution as a Prevalent Proinflammatory Stimulus Contributing to Neurodegeneration

Air pollution is regarded as an important risk factor for many diseases that affect a large proportion of the human population. To date, accumulating reports have noted that particulate matter (PM) is closely associated with the course of cardiopulmonary disorders. As the incidence of Alzheimer’s disease (AD), Parkinson’s disease (PD), and autoimmune disorders have risen and as the world’s population is aging, there is an increasing interest in environmental health hazards, mainly air pollution, which has been slightly overlooked as one of many plausible detrimental stimuli contributing to neurodegenerative disease onset and progression. Epidemiological studies have indicated a noticeable association between exposure to PM and neurotoxicity, which has been gradually confirmed by in vivo and in vitro studies. After entering the body directly through the olfactory epithelium or indirectly by passing through the respiratory system into the circulatory system, air pollutants are subsequently able to reach the brain. Among the potential mechanisms underlying particle-induced detrimental effects in the periphery and the central nervous system (CNS), increased oxidative stress, inflammation, mitochondrial dysfunction, microglial activation, disturbance of protein homeostasis, and ultimately, neuronal death are often postulated and concomitantly coincide with the main pathomechanisms of neurodegenerative processes. Other complementary mechanisms by which PM could mediate neurotoxicity and contribute to neurodegeneration remain unconfirmed. Furthermore, the question of how strong and proven air pollutants are as substantial adverse factors for neurodegenerative disease etiologies remains unsolved. This review highlights research advances regarding the issue of PM with an emphasis on neurodegeneration markers, symptoms, and mechanisms by which air pollutants could mediate damage in the CNS. Poor air quality and insufficient knowledge regarding its toxicity justify conducting scientific investigations to understand the biological impact of PM in the context of various types of neurodegeneration.

Anthropogenic Iron Oxide Nanoparticles Induce Damage to Brain Microvascular Endothelial Cells Forming the Blood-Brain Barrier

BACKGROUND

Iron nanoparticles, mainly in magnetite phase (Fe3O4 NPs), are released to the environment in areas with high traffic density and braking frequency. Fe3O4 NPs were found in postmortem human brains and are assumed to get directly into the brain through the olfactory nerve. However, these pollution-derived NPs may also translocate from the lungs to the bloodstream and then, through the blood-brain barrier (BBB), into the brain inducing oxidative and inflammatory responses that contribute to neurodegeneration.

OBJECTIVE

To describe the interaction and toxicity of pollution-derived Fe3O4 NPs on primary rat brain microvascular endothelial cells (rBMECs), main constituents of in vitro BBB models.

METHODS

Synthetic bare Fe3O4 NPs that mimic the environmental ones (miFe3O4) were synthesized by co-precipitation and characterized using complementary techniques. The rBMECs were cultured in Transwell® plates. The NPs-cell interaction was evaluated through transmission electron microscopy and standard colorimetric in vitro assays.

RESULTS

The miFe3O4 NPs, with a mean diameter of 8.45±0.14 nm, presented both magnetite and maghemite phases, and showed super-paramagnetic properties. Results suggest that miFe3O4 NPs are internalized by rBMECs through endocytosis and that they are able to cross the cells monolayer. The lowest miFe3O4 NPs concentration tested induced mid cytotoxicity in terms of 1) membrane integrity (LDH release) and 2) metabolic activity (MTS transformation).

CONCLUSION

Pollution-derived Fe3O4 NPs may interact and cross the microvascular endothelial cells forming the BBB and cause biological damage.

Exposure to Particulate Matter Air Pollution and Anosmia

IMPORTANCE

Anosmia, the loss of the sense of smell, has profound implications for patient safety, well-being, and quality of life, and it is a predictor of patient frailty and mortality. Exposure to air pollution may be an olfactory insult that contributes to the development of anosmia.

OBJECTIVE

To investigate the association between long-term exposure to particulate matter (PM) with an aerodynamic diameter of no more than 2.5 μm (PM2.5) with anosmia.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study examined individuals who presented from January 1, 2013, through December 31, 2016, at an academic medical center in Baltimore, Maryland. Case participants were diagnosed with anosmia by board-certified otolaryngologists. Control participants were selected using the nearest neighbor matching strategy for age, sex, race/ethnicity, and date of diagnosis. Data analysis was conducted from September 2020 to March 2021.

EXPOSURES

Ambient PM2.5 levels.

MAIN OUTCOMES AND MEASURES

Novel method to quantify ambient PM2.5 exposure levels in patients diagnosed with anosmia compared with matched control participants.

RESULTS

A total of 2690 patients were identified with a mean (SD) age of 55.3 (16.6) years. The case group included 538 patients with anosmia (20%), and the control group included 2152 matched control participants (80%). Most of the individuals in the case and control groups were women, White patients, had overweight (BMI 25 to <30), and did not smoke (women: 339 [63.0%] and 1355 [63.0%]; White patients: 318 [59.1%] and 1343 [62.4%]; had overweight: 179 [33.3%] and 653 [30.3%]; and did not smoke: 328 [61.0%] and 1248 [58.0%]). Mean (SD) exposure to PM2.5 was significantly higher in patients with anosmia compared with healthy control participants at 12-, 24-, 36-, 60-month time points: 10.2 (1.6) μg/m3 vs 9.9 (1.9) μg/m3; 10.5 (1.7) μg/m3 vs 10.2 (1.9) μg/m3; 10.8 (1.8) μg/m3 vs 10.4 (2.0) μg/m3; and 11.0 (1.8) μg/m3 vs 10.7 (2.1) μg/m3, respectively. There was an association between elevated PM2.5 exposure level and odds of anosmia in multivariate analyses that adjusted for age, sex, race/ethnicity, body mass index, alcohol or tobacco use, and medical comorbidities (12 mo: odds ratio [OR], 1.73; 95% CI, 1.28-2.33; 24 mo: OR, 1.72; 95% CI, 1.30-2.29; 36 mo: OR, 1.69; 95% CI, 1.30-2.19; and 60 mo: OR, 1.59; 95% CI, 1.22-2.08). The association between long-term exposure to PM2.5 and the odds of developing anosmia was nonlinear, as indicated by spline analysis. For example, for 12 months of exposure to PM2.5, the odds of developing anosmia at 6.0 µg/m3 was OR 0.79 (95% CI, 0.64-0.97); at 10.0 µg/m3, OR 1.42 (95% CI, 1.10-1.82); at 15.0 µg/m3, OR 2.03 (95% CI, 1.15-3.58).

CONCLUSIONS AND RELEVANCE

In this study, long-term airborne exposure to PM2.5 was associated with anosmia. Ambient PM2.5 represents a potentially ubiquitous and modifiable risk factor for the loss of sense of smell.

Metal-mixtures in toenails of children living near an active industrial facility in Los Angeles County, California

BACKGROUND

Children residing in communities near metalworking industries are vulnerable to multiple toxic metal exposures. Understanding biomarkers of exposure to multiple toxic metals is important to characterize cumulative burden and to distinguish potential exposure sources in such environmental justice neighborhoods impacted by industrial operations. Exposure to metal mixtures has not been well-characterized among children residing in the United States, and is understudied in communities of color.

METHODS

In this study we used toenail clippings, a noninvasive biomarker, to assess exposure to arsenic (As), cadmium (Cd), mercury (Hg), manganese (Mn), lead (Pb), antimony (Sb), selenium (Se), and vanadium (V). We used nonnegative matrix factorization (NMF) to identify "source" signatures and patterns of exposure among predominantly working class Latinx children residing near an industrial corridor in Southeast Los Angeles County. Additionally, we investigated the association between participant demographic, spatial, and dietary characteristics with identified metal signatures.

RESULTS

Through NMF, we identified three groupings (source factors) for the metal concentrations in children's toenails. A grouping composed of Sb, Pb, As, and Cd, was identified as a potential industrial source factor, reflective of known airborne elemental emissions in the industrial corridor. We further identified a manganese source factor primarily composed of Mn, and a potential dietary source factor driven by Se and Hg. We observed differences in the industrial source factor by age of participants, while the dietary source factor varied by neighborhood.

CONCLUSION

Utilizing an unsupervised dimension reduction technique (NMF), we identified a "source signature" of contamination in toenail samples from children living near metalworking industry. Investigating patterns and sources of exposures in cumulatively burdened communities is necessary to identify appropriate public health interventions.

Variation in the concentration and regional distribution of magnetic nanoparticles in human brains, with and without Alzheimer's disease, from the UK

The presence of magnetic nanoparticles (MNPs) in the human brain was attributed until recently to endogenous formation; associated with a putative navigational sense, or with pathological mishandling of brain iron within senile plaques. Conversely, an exogenous, high-temperature source of brain MNPs has been newly identified, based on their variable sizes/concentrations, rounded shapes/surface crystallites, and co-association with non-physiological metals (e.g., platinum, cobalt). Here, we examined the concentration and regional distribution of brain magnetite/maghemite, by magnetic remanence measurements of 147 samples of fresh/frozen tissues, from Alzheimer's disease (AD) and pathologically-unremarkable brains (80-98 years at death) from the Manchester Brain Bank (MBB), UK. The magnetite/maghemite concentrations varied between individual cases, and different brain regions, with no significant difference between the AD and non-AD cases. Similarly, all the elderly MBB brains contain varying concentrations of non-physiological metals (e.g. lead, cerium), suggesting universal incursion of environmentally-sourced particles, likely across the geriatric blood-brain barrier (BBB). Cerebellar Manchester samples contained significantly lower (~ 9×) ferrimagnetic content compared with those from a young (29 years ave.), neurologically-damaged Mexico City cohort. Investigation of younger, variably-exposed cohorts, prior to loss of BBB integrity, seems essential to understand early brain impacts of exposure to exogenous magnetite/maghemite and other metal-rich pollution particles.

Brain region- and metal-specific effects of embedded metals in a shrapnel wound model in the rat

The health effects of prolonged exposure to embedded metal fragments, such as those found in shrapnel wounds sustained by an increasing number of military personnel, are not well known. As part of a large collaborative effort to expand this knowledge, we use an animal model of shrapnel wounds originally developed to investigate effects of embedded depleted uranium to investigate effects of military-relevant metals tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium compared to an inert control, tantalum. Rats are surgically implanted with pellets of one of the metals of interest in the gastrocnemius (leg) muscle and tracked until 1 month, 3 months, 6 months, or 12 months from the time of implant, at which point they are euthanized and multiple organs and tissue samples are collected for inspection. Here we focus on four regions of the brain: frontal cortex, hippocampus, amygdala, and cerebellum. We examined changes in accumulated metal concentration in each region as well as changes in expression of proteins related to blood brain barrier tight junction formation, occludin and ZO-1, and synapse function, PSD95, spinophilin, and synaptotagmin. We report few changes in metal accumulation or blood brain barrier protein expression, but a large number of synapse proteins have reduced expression levels, particularly within the first 6 months of exposure, but there are regional and metal-specific differences in effects.

Environmental pollution and mental health: a narrative review of literature

Pollutant agents are exponentially increasing in modern society since industrialization processes and technology are being developed worldwide. Impact of pollution on public health is well known but little has been described on the association between environmental pollutants and mental health. A literature search on PubMed and EMBASE has been conducted and 134 articles published on the issue of pollution and mental health have been included, cited, reviewed, and summarized. Emerging evidences have been collected on association between major environmental pollutants (air pollutants, heavy metals, ionizing radiation [IR], organophosphate pesticides, light pollution, noise pollution, environmental catastrophes) and various mental health disorders including anxiety, mood, and psychotic syndromes. Underlying pathogenesis includes direct and indirect effects of these agents on brain, respectively, due to their biological effect on human Central Nervous System or related to some levels of stress generated by the exposure to the pollutant agents over the time. Most of emerging evidences are still nonconclusive. Further studies should clarify how industrial production, the exploitation of certain resources, the proximity to waste and energy residues, noise, and the change in lifestyles are connected with psychological distress and mental health problems for the affected populations.

A matter of concern - Trace element dyshomeostasis and genomic stability in neurons

Neurons are post-mitotic cells in the brain and their integrity is of central importance to avoid neurodegeneration. Yet, the inability of self-replenishment of post-mitotic cells results in the need to withstand challenges from numerous stressors during life. Neurons are exposed to oxidative stress due to high oxygen consumption during metabolic activity in the brain. Accordingly, DNA damage can occur and accumulate, resulting in genome instability. In this context, imbalances in brain trace element homeostasis are a matter of concern, especially regarding iron, copper, manganese, zinc, and selenium. Although trace elements are essential for brain physiology, excess and deficient conditions are considered to impair neuronal maintenance. Besides increasing oxidative stress, DNA damage response and repair of oxidative DNA damage are affected by trace elements. Hence, a balanced trace element homeostasis is of particular importance to safeguard neuronal genome integrity and prevent neuronal loss. This review summarises the current state of knowledge on the impact of deficient, as well as excessive iron, copper, manganese, zinc, and selenium levels on neuronal genome stability.

•

Post-mitotic neurons show an increased vulnerability to oxidative stress.

•

Trace element dyshomeostasis impairs neuronal genome maintenance, affecting DNA damage response as well as DNA repair.

•

The review summarises the effects of excessive and deficient trace element levels neuronal genome stability maintenance.

Exposure to environmental neurotoxic substances and neurodevelopment in children from Latin America and the Caribbean

Environmental (and occupational) exposure to neurotoxic substances is a worldwide problem that can affect children's neurodevelopment (ND). In Latin American and Caribbean (LAC) countries there are over 300 million children living under the threat of neurodevelopmental delays due to toxic environmental exposure. Large industrial centers, intense mining and agricultural activities, along with changing complex ecosystems constitute a mosaic that drives contamination of air, water and the food chain. Neurotoxic contaminants such as pesticides (organochlorines, organophosphates, carbamates, pyrethroids, neonicotinoids, and manganese fungicides), chemicals of industrial use (phthalates), and metals (Hg, Pb, Al, As, F, Cd, Mo, Mn) are at the center of environmental exposure studies. Exposure to neurotoxic substances singly or in combination with other compounds or socioeconomic stressors (maternal education, socio-economic and nutritional status) intertwined with occupational and para-occupational exposure can affect ND (motor, cognition, behavior) of children. Significant negative effects of pesticides and neurotoxic elements on ND were found in all studied countries, affecting especially the less-privileged children from laboring families. Studies showed that exposures to the neurotoxicants in human milk are secondary to their more lasting effects during prenatal exposure. This review integrates exposure (prenatal and breastfeeding), metabolism, and ND effects of neurotoxicants. It highlights the overwhelming evidence showing that current levels of exposures are hazardous and detrimental to children's ND in LAC countries. The evidence indicates that a reduction in neurotoxicant exposure is essential to protect children's ND. Therefore, it is urgent to adopt policies and actions that prevent and remediate region-specific children's ND issues.

Diet-Induced Obesity Disrupts Trace Element Homeostasis and Gene Expression in the Olfactory Bulb

The aim of this study was to determine the impact of diet-induced obesity (DIO) on trace element homeostasis and gene expression in the olfactory bulb and to identify potential interaction effects between diet, sex, and strain. Our study is based on evidence that obesity and olfactory bulb impairments are linked to neurodegenerative processes. Briefly, C57BL/6J (B6J) and DBA/2J (D2J) male and female mice were fed either a low-fat diet or a high-fat diet for 16 weeks. Brain tissue was then evaluated for iron, manganese, copper, and zinc concentrations and mRNA gene expression. There was a statistically significant diet-by-sex interaction for iron and a three-way interaction between diet, sex, and strain for zinc in the olfactory bulb. Obese male B6J mice had a striking 75% increase in iron and a 50% increase in manganese compared with the control. There was an increase in zinc due to DIO in B6J males and D2J females, but a decrease in zinc in B6J females and D2J males. Obese male D2J mice had significantly upregulated mRNA gene expression for divalent metal transporter 1, alpha-synuclein, amyloid precursor protein, dopamine receptor D2, and tyrosine hydroxylase. B6J females with DIO had significantly upregulated brain-derived neurotrophic factor expression. Our results demonstrate that DIO has the potential to disrupt trace element homeostasis and mRNA gene expression in the olfactory bulb, with effects that depend on sex and genetics. We found that DIO led to alterations in iron and manganese predominantly in male B6J mice, and gene expression dysregulation mainly in male D2J mice. These results have important implications for health outcomes related to obesity with possible connections to neurodegenerative disease.

Intracellular nickel accumulation induces apoptosis and cell cycle arrest in human astrocytic cells

Nickel, a heavy metal found in electronic wastes and fume from electronic cigarettes, induces neuronal cell death and is associated with neurocognitive impairment. Astrocytes are the first line of defense against nickel after entering the brain; however, the effects of nickel on astrocytes remain unknown. Herein, we investigated the effect of nickel exposure on cell survival and proliferation and the underlying mechanisms in U-87 MG human astrocytoma cells and primary human astrocytes. Intracellular nickel levels were elevated in U-87 MG cells in a dose- and time-dependent manner after exposure to nickel chloride. The median toxic concentrations of nickel in astrocytoma cells and primary human astrocytes were 600.60 and >1000 µM at 48 h post-exposure, respectively. Nickel exposure triggered apoptosis in concomitant with the decreased expression of anti-apoptotic B-cell lymphoma protein (Bcl-2) and increased caspase-3/7 activity. Nickel induced reactive oxygen species formation. Additionally, nickel suppressed astrocyte proliferation in a dose- and time-dependent manner by delaying G2 to M phase transition through the upregulation of cyclin B1 and p27 protein expression. These results indicate that nickel-induced cytotoxicity of astrocytes is mediated by the activation of apoptotic pathway and disruption of cell cycle regulation.