Comparative evaluation of the effects of short-term inhalation exposure to diesel engine exhaust on rat lung and brain

From Inhalation to Neurodegeneration: Air Pollution as a Modifiable Risk Factor for Alzheimer's Disease

Air pollution, a growing concern for public health, has been linked to various respiratory and cardiovascular diseases. Emerging evidence also suggests a link between exposure to air pollutants and neurodegenerative diseases, particularly Alzheimer's disease (AD). This review explores the composition and sources of air pollutants, including particulate matter, gases, persistent organic pollutants, and heavy metals. The pathophysiology of AD is briefly discussed, highlighting the role of beta-amyloid plaques, neurofibrillary tangles, and genetic factors. This article also examines how air pollutants reach the brain and exert their detrimental effects, delving into the neurotoxicity of air pollutants. The molecular mechanisms linking air pollution to neurodegeneration are explored in detail, focusing on oxidative stress, neuroinflammation, and protein aggregation. Preclinical studies, including in vitro experiments and animal models, provide evidence for the direct effects of pollutants on neuronal cells, glial cells, and the blood-brain barrier. Epidemiological studies have reported associations between exposure to air pollution and an increased risk of AD and cognitive decline. The growing body of evidence supporting air pollution as a modifiable risk factor for AD underscores the importance of considering environmental factors in the etiology and progression of neurodegenerative diseases, in the face of worsening global air quality.

Reducing Indoor Particulate Air Pollution Improves Student Test Scores: A Randomized Double-Blind Crossover Study

Short-term exposure to air pollution is associated with a decline in cognitive function. Standardized test scores have been employed to evaluate the effects of air pollution exposure on cognitive performance. Few studies aimed to prove whether air pollution is responsible for reduced test scores; none have implemented a "gold-standard" method for assessing the association such as a randomized, double-blind intervention. This study used a "gold-standard" method─randomized, double-blind crossover─to assess whether reducing short-term indoor particle concentrations results in improved test scores in college students in Tianjin, China. Participants (n = 162) were randomly assigned to one of two similar classrooms and completed a standardized English test on two consecutive weekends. Air purifiers with active or sham (i.e., filter removed) particle filtration were placed in each classroom. The filtration mode was switched between the two test days. Linear mixed-effect models were used to evaluate the effect of the intervention mode on the test scores. The results show that air purification (i.e., reducing PM) was significantly associated with increases in the z score for combined (0.11 [95%CI: 0.02, 0.21]) and reading (0.11 [95%CI: 0.00, 0.22]) components. In conclusion, a short-term reduction in indoor particle concentration led to improved test scores in students, suggesting an improvement in cognitive function.

Subchronic exposure to ambient PM 2.5 impairs novelty recognition and spatial memory

Air pollution remains a great challenge for public health, with the detrimental effects of air pollution on cardiovascular, rhinosinusitis, and pulmonary health increasingly well understood. Recent epidemiological associations point to the adverse effects of air pollution on cognitive decline and neurodegenerative diseases. Mouse models of subchronic exposure to PM 2.5 (ambient air particulate matter < 2.5 µm) provide an opportunity to demonstrate the causality of target diseases. Here, we subchronically exposed mice to concentrated ambient PM 2.5 for 7 weeks (5 days/week; 8h/day) and assessed its effect on behavior using standard tests measuring cognition or anxiety-like behaviors. Average daily PM 2.5 concentration was 200 µg/m 3 in the PM 2.5 group and 10 µg/m 3 in the filtered air group. The novel object recognition (NOR) test was used to assess the effect of PM 2.5 exposure on recognition memory. The increase in exploration time for a novel object versus a familiarized object was lower for PM 2.5 -exposed mice (42% increase) compared to the filtered air (FA) control group (110% increase). In addition, the calculated discrimination index for novel object recognition was significantly higher in FA mice (67 %) compared to PM 2.5 exposed mice (57.3%). The object location test (OLT) was used to examine the effect of PM 2.5 exposure on spatial memory. In contrast to the FA-exposed control mice, the PM 2.5 exposed mice exhibited no significant increase in their exploration time between novel location versus familiarized location indicating their deficit in spatial memory. Furthermore, the discrimination index for novel location was significantly higher in FA mice (62.6%) compared to PM 2.5 exposed mice (51%). Overall, our results demonstrate that subchronic exposure to higher levels of PM 2.5 in mice causes impairment of novelty recognition and spatial memory.

Significant association between increased risk of emergency department visits for psychiatric disorders and air pollutants in South Korea

BACKGROUND

The association between air pollutants and psychiatric disorders has been investigated in many countries. However, results for the association between air pollutants and emergency room (ER) visits for psychiatric disorders are inconsistent. Further, systematic large-scale studies relating to the same are lacking, especially in South Korea.

OBJECTIVE

We aimed to investigate the acute and short-term cumulative effect of air pollutants on ER visits for psychiatric disorders in South Korea.

METHODS

The data on nitrogen dioxide (NO2) and particulate matter (PM2.5 and PM10) and ER visits due to nine representative psychiatric disorders were collected from eight major cities in South Korea for three years. We estimated the relative risk (RR) at lag 0 and a cumulative 11-day RR by increasing a 10-unit for PM and 0.01-unit for NO2 using the Distributed Lag Nonlinear Model.

RESULTS

During the study period, a total of 79,092 ER visits for psychiatric disorders were identified and tested for association with NO2, PM2.5, and PM10. The RR at lag 0 of depression per 0.01-unit increase in NO2 was the highest (3.127; 95% confidence interval [CI] 2.933 to 3.332) among the psychiatric disorders. The RRs at lag 0 of anxiety disorders per 10-unit increase in PM2.5 (1.709; 95% CI 1.424 to 2.053) and PM10 (2.168; 95% CI 1.957 to 2.403) were the highest among the psychiatric disorders.

SIGNIFICANCE

Air pollutants increased ER visits for psychiatric disorders with the highest RR of depression due to NO2 and anxiety disorder due to PM2.5 and PM10. These results contribute evidence to the positive association between ambient exposure to air pollution and aggravation of psychiatric disorders, indicating air pollution may be a modifiable risk factor in mental health management.

IMPACT STATEMENT

We investigated the effect of air pollution on emergency room visits caused by major psychiatric disorders in prominent cities in South Korea. Using the Distributed Lag Nonlinear Model, an advanced analysis method, we calculated the acute effect and short-term cumulative effect. Air pollutants increased ER visits for psychiatric disorders with the highest relative risk of depression due to NO2 and anxiety disorder due to PM2.5 and PM10. These results reveal an association between ambient exposure to air pollution and aggravation of psychiatric disorders and suggest that air pollution may be a modifiable risk factor in mental health management.

Air Pollutant impacts on the brain and neuroendocrine system with implications for peripheral organs: a perspective

Air pollutants are being increasingly linked to extrapulmonary multi-organ effects. Specifically, recent studies associate air pollutants with brain disorders including psychiatric conditions, neuroinflammation and chronic diseases. Current evidence of the linkages between neuropsychiatric conditions and chronic peripheral immune and metabolic diseases provides insights on the potential role of the neuroendocrine system in mediating neural and systemic effects of inhaled pollutants (reactive particulates and gases). Autonomically-driven stress responses, involving sympathetic-adrenal-medullary and hypothalamus-pituitary-adrenal axes regulate cellular physiological processes through adrenal-derived hormones and diverse receptor systems. Recent experimental evidence demonstrates the contribution of the very stress system responding to non-chemical stressors, in mediating systemic and neural effects of reactive air pollutants. The assessment of how respiratory encounter of air pollutants induce lung and peripheral responses through brain and neuroendocrine system, and how the impairment of these stress pathways could be linked to chronic diseases will improve understanding of the causes of individual variations in susceptibility and the contribution of habituation/learning and resiliency. This review highlights effects of air pollution in the respiratory tract that impact the brain and neuroendocrine system, including the role of autonomic sensory nervous system in triggering neural stress response, the likely contribution of translocated nano particles or metal components, and biological mediators released systemically in causing effects remote to the respiratory tract. The perspective on the use of systems approaches that incorporate multiple chemical and non-chemical stressors, including environmental, physiological and psychosocial, with the assessment of interactive neural mechanisms and peripheral networks are emphasized.

Air Pollution: Possible Interaction between the Immune and Nervous System?

Exposure to environmental pollutants is a serious and common public health concern associated with growing morbidity and mortality worldwide, as well as economic burden. In recent years, the toxic effects associated with air pollution have been intensively studied, with a particular focus on the lung and cardiovascular system, mainly associated with particulate matter exposure. However, epidemiological and mechanistic studies suggest that air pollution can also influence skin integrity and may have a significant adverse impact on the immune and nervous system. Air pollution exposure already starts in utero before birth, potentially causing delayed chronic diseases arising later in life. There are, indeed, time windows during the life of individuals who are more susceptible to air pollution exposure, which may result in more severe outcomes. In this review paper, we provide an overview of findings that have established the effects of air pollutants on the immune and nervous system, and speculate on the possible interaction between them, based on mechanistic data.

Microglial Activation and Oxidative Stress in PM2.5-Induced Neurodegenerative Disorders

Fine particulate matter (PM_2.5) pollution remains a prominent environmental problem worldwide, posing great threats to human health. The adverse effects of PM_2.5 on the respiratory and cardiovascular systems have been extensively studied, while its detrimental effects on the central nervous system (CNS), specifically neurodegenerative disorders, are less investigated. Neurodegenerative disorders are characterized by reduced neurogenesis, activated microglia, and neuroinflammation. A variety of studies involving postmortem examinations, epidemiological investigations, animal experiments, and in vitro cell models have shown that PM_2.5 exposure results in neuroinflammation, oxidative stress, mitochondrial dysfunction, neuronal apoptosis, and ultimately neurodegenerative disorders, which are strongly associated with the activation of microglia. Microglia are the major innate immune cells of the brain, surveilling and maintaining the homeostasis of CNS. Upon activation by environmental and endogenous insults, such as PM exposure, microglia can enter an overactivated state that is featured by amoeboid morphology, the over-production of reactive oxygen species, and pro-inflammatory mediators. This review summarizes the evidence of microglial activation and oxidative stress and neurodegenerative disorders following PM_2.5 exposure. Moreover, the possible mechanisms underlying PM_2.5-induced microglial activation and neurodegenerative disorders are discussed. This knowledge provides certain clues for the development of therapies that may slow or halt the progression of neurodegenerative disorders induced by ambient PM.

Comparison of exposure to traffic-related pollutants on different commuting routes to a primary school in Jinan, China

Traffic-related pollutants seriously affect human health, and the commute time to and from school is the time when students are exposed greatest to traffic pollution sources. Field measurements were conducted with hand-held instruments while walking along two selected commuting routes in winter and spring. The measured data were then compared with background monitoring data, and the respiratory deposition dose (RDD) was calculated to assess the exposure risk. Particulate matter intake from 2018 to 2020 was calculated. In winter, the average concentrations of PM_2.5 and PM₁₀ were higher in the afternoon than in the morning. The highest concentration was 2.94 times greater than the background value. The low-concentration distribution area of the low-traffic route that is off the main road (route B) was more significant than that of the high-traffic route that is near the main road (route A). Moreover, the RDD of route B was consistently lower than that of route A, while the average annual amount of PM_2.5 inhalation on route B in 3 years was 16.3% lower than that on route A. Overall, route B is more suitable than route A for students to commute on foot. Based on the findings, a walking route located within a community is a good choice.

Effects of reactive oxygen species generation induced by Wonju City particulate matter on mitochondrial dysfunction in human middle ear cell

Atmospheric particulate matter (PM) contains different components that can elicit varying adverse health effects in humans and animals. Studies on PM toxicity and its underlying mechanisms in the middle ear are limited, and they generally use a PM standard. However, as PM composition varies temporally and geographically, it is crucial to identify the toxic PM constituents according to season and region and investigate their associated health effects. Thus, we sought to determine whether PM induces cytotoxicity and inflammatory factor and reactive oxygen species (ROS) generation in human middle ear epithelial cells obtained from patients with otitis media. The cells were treated with both standard urban PM and PM directly captured from the atmosphere in Wonju City. The association between mitochondrial dysfunction and PM was investigated. PM exposure significantly increased COX-2 and TNF-α mRNA expression, increased ROS generation, induced inflammatory responses, and caused abnormalities in mitochondrial motility and function. Furthermore, PM induced cell apoptosis, which consequently reduced cell survival, particularly at the concentration of 100 μg/mL. Overall, our study provides new insights into the toxic effects of standard and atmospheric PM on middle ear cell line.

Evaluating the endothelial-microglial interaction and comprehensive inflammatory marker profiles under acute exposure to ultrafine diesel exhaust particles in vitro

Exposure to combustion-derived particulate matter (PM) such as diesel exhaust particles (DEP) is a public health concern because people in urban areas are continuously exposed, and once inhaled, fine and ultrafine DEP may reach the brain. The blood-brain barrier (BBB) endothelial cells (EC) and the perivascular microglia protect the brain from circulating pathogens and neurotoxic molecules like DEP. While the BBB-microglial interaction is critical for maintaining homeostasis, no study has previously evaluated the endothelial-microglial interaction nor comprehensively characterized these cells' inflammatory marker profiles under ultrafine DEP exposures in vitro. Therefore, the goal of this study was to investigate the in vitro rat EC-microglial co-culture under acute (24 h.) exposure to ultrafine DEP (0.002-20 μg/mL), by evaluating key mechanisms associated with PM toxicity: lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, cell metabolic activity (CMA) changes, and production of 27 inflammatory markers. These parameters were also evaluated in rat microglial and endothelial monocultures to determine whether the EC-microglial co-culture responded differently than the cerebrovasculature and microglia alone. While results indicated that ultrafine DEP exposure caused concentration-dependent increases in LDH leakage and ROS production in all groups, as expected, exposure also caused mixed responses in CMA and atypical cytokine/chemokine profiles in all groups, which was not expected. The inflammation assay results further suggested that the microglia were not classically activated under this exposure scenario, despite previous in vitro studies showing microglial activation (priming) at similar concentrations of ultrafine DEP. Additionally, compared to the cerebrovasculature alone, the EC-microglia interaction in the co-culture did not appear to cause changes in any parameter save in pro-inflammatory marker production, where the interaction appeared to cause an overall downregulation in cytokine/chemokine levels after ultrafine DEP exposure. Finally, to our knowledge, this is the first study to evaluate the influence of microglia on the BBB's ultrafine DEP-induced cytotoxic and inflammatory responses, which are heavily implicated in the pathogenesis of PM-related cerebrovascular dysfunction and neurodegeneration.

Systemic Exposure to Air Pollution Induces Oxidative Stress and Inflammation in Mouse Brain, Contributing to Neurodegeneration Onset

In northern Italy, biomass burning-derived (BB) particles and diesel exhaust particles (DEP) are considered the most significant contributors to ultrafine particle (UFP) emission. However, a comparison between their impact on different brain regions was not investigated until now. Therefore, male BALB/c mice were treated with a single or three consecutive intratracheal instillations using 50 µg of UFPs in 100 µL of isotonic saline solution or 100 µL of isotonic saline solution alone, and brains were collected and analyzed. Proteins related to oxidative stress and inflammation, as well as Alzheimer's disease markers, were examined in the hippocampus, cerebellum, and the rest of the brain (RoB). Histopathological examination of the brain was also performed. Moreover, correlations among different brain, pulmonary, and cardiovascular markers were performed, allowing us to identify the potentially most stressful UFP source. Although both acute exposures induced inflammatory pathways in mouse brain, only DEP showed strong oxidative stress. The sub-acute exposure also induced the modulation of APP and BACE1 protein levels for both UFPs. We observed that DEP exposure is more harmful than BB, and this different response could be explained by this UFP's different chemical composition and reactivity.

Selective memory and behavioral alterations after ambient ultrafine particulate matter exposure in aged 3xTgAD Alzheimer's disease mice

BACKGROUND

A growing body of epidemiological literature indicates that particulate matter (PM) air pollution exposure is associated with elevated Alzheimer's disease (AD) risk and may exacerbate AD-related cognitive decline. Of concern is exposure to the ultrafine PM (UFP) fraction (≤100 nm), which deposits efficiently throughout the respiratory tract, has higher rates of translocation to secondary organs, like brain, and may induce inflammatory changes. We, therefore, hypothesize that exposure to UFPs will exacerbate cognitive deficits in a mouse model of AD. The present study assessed alterations in learning and memory behaviors in aged (12.5 months) male 3xTgAD and non-transgenic mice following a 2-week exposure (4-h/day, 4 days/week) to concentrated ambient UFPs using the Harvard ultrafine concentrated ambient particle system (HUCAPS) or filtered air. Beginning one month following exposure, locomotor activity, spatial learning and memory, short-term recognition memory, appetitive motivation, and olfactory discrimination were assessed.

RESULTS

No effects on locomotor activity were found following HUCAPS exposure (number concentration, 1 × 104-4.7 × 105 particles/cm3; mass concentration, 29-132 μg/m3). HUCAPS-exposed mice, independent of AD background, showed a significantly decreased spatial learning, mediated through reference memory deficits, as well as short-term memory deficits in novel object recognition testing. AD mice displayed diminished spatial working memory, potentially a result of olfactory deficits, and short-term memory. AD background modulated HUCAPS-induced changes on appetitive motivation and olfactory discrimination, specifically enhancing olfactory discrimination in NTg mice. Modeling variation in appetitive motivation as a covariate in spatial learning and memory, however, did not support the conclusion that differences in motivation significantly underlie changes in spatial learning and memory.

CONCLUSIONS

A short-term inhalation exposure of aged mice to ambient UFPs at human-relevant concentrations resulted in protracted (testing spanning 1-6.5 months post-exposure) adverse effects on multiple memory domains (reference and short-term memory) independent of AD background. Impairments in learning and memory were present when accounting for potential covariates like motivational changes and locomotor activity. These results highlight the need for further research into the potential mechanisms underlying the cognitive effects of UFP exposure in adulthood.

Neurobehavioral Consequences of Traffic-Related Air Pollution

Traffic-related air pollution (TRAP) is a major contributor to global air pollution. The World Health Organization (WHO) has reported that air pollution due to gasoline and diesel emissions from internal combustion engines of automobiles, trucks, locomotives, and ships leads to 800,000 premature deaths annually due to pulmonary, cardiovascular, and neurological complications. It has been observed that individuals living and working in areas of heavy vehicle traffic have high susceptibility to anxiety, depression, and cognitive deficits. Information regarding the mechanisms that potentially lead to detrimental mental health effects of TRAP is gradually increasing. Several studies have suggested that TRAP is associated with adverse effects in the central nervous system (CNS), primarily due to increase in oxidative stress and neuroinflammation. Animal studies have provided further useful insights on the deleterious effects of vehicle exhaust emissions (VEEs). The mechanistic basis for these effects is unclear, although gasoline and diesel exhaust-induced neurotoxicity seems the most plausible cause. Several important points emerge from these studies. First, TRAP leads to neurotoxicity. Second, TRAP alters neurobehavioral function. Exactly how that happens remains unclear. This review article will discuss current state of the literature on this subject and potential leads that have surfaced from the preclinical work.

Myo-inositol mediates the effects of traffic-related air pollution on generalized anxiety symptoms at age 12 years

BACKGROUND

Exposure to traffic-related air pollution (TRAP) has been linked to childhood anxiety symptoms. Neuroimaging in patients with anxiety disorders indicate altered neurochemistry.

OBJECTIVES

Evaluate the impact of TRAP on brain metabolism and its relation to childhood anxiety symptoms in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS).

METHODS

Adolescents (n = 145) underwent magnetic resonance spectroscopy. Brain metabolites, including myo-inositol, N-acetylaspartate, creatine, choline, glutamate, glutamate plus glutamine, and glutathione were measured in the anterior cingulate cortex. Anxiety symptoms were assessed using the Spence Children's Anxiety Scale. TRAP exposure in early-life, averaged over childhood, and during the 12 months prior to imaging was estimated using a validated land use regression model. Associations between TRAP exposure, brain metabolism, and anxiety symptoms were estimated using linear regression and a bootstrapping approach for testing mediation by brain metabolite levels.

RESULTS

Recent exposure to high levels of TRAP was associated with significant increases in myo-inositol (β = 0.26; 95%CI 0.01, 0.51) compared to low TRAP exposure. Recent elevated TRAP exposure (β = 4.71; 95% CI 0.95, 8.45) and increased myo-inositol levels (β = 2.98; 95% CI 0.43, 5.52) were also significantly associated with increased generalized anxiety symptoms with 12% of the total effect between TRAP and generalized anxiety symptoms being mediated by myo-inositol levels.

CONCLUSIONS

This is the first study of children to utilize neuroimaging to link TRAP exposure, metabolite dysregulation in the brain, and generalized anxiety symptoms among otherwise healthy children. TRAP may elicit atypical excitatory neurotransmission and glial inflammatory responses leading to increased metabolite levels and subsequent anxiety symptoms.

Exposure to Atmospheric Ultrafine Particles Induces Severe Lung Inflammatory Response and Tissue Remodeling in Mice

Exposure to particulate matter (PM) is leading to various respiratory health outcomes. Compared to coarse and fine particles, less is known about the effects of chronic exposure to ultrafine particles, despite their higher number and reactivity. In the present study, we performed a time-course experiment in mice to better analyze the lung impact of atmospheric ultrafine particles, with regard to the effects induced by fine particles collected on the same site. Trace element and PAH analysis demonstrated the almost similar chemical composition of both particle fractions. Mice were exposed intranasally to FF or UFP according to acute (10, 50 or 100 µg of PM) and repeated (10 µg of PM 3 times a week during 1 or 3 months) exposure protocols. More particle-laden macrophages and even greater chronic inflammation were observed in the UFP-exposed mice lungs. Histological analyses revealed that about 50% of lung tissues were damaged in mice exposed to UFP for three months versus only 35% in FF-exposed mice. These injuries were characterized by alveolar wall thickening, macrophage infiltrations, and cystic lesions. Taken together, these results strongly motivate the update of current regulations regarding ambient PM concentrations to include UFP and limit their emission.

Ambient Air Pollution, Noise, and Late-Life Cognitive Decline and Dementia Risk

Exposure to ambient air pollution and noise is ubiquitous globally. A strong body of evidence links air pollution, and recently noise, to cardiovascular conditions that eventually may also affect cognition in the elderly. Data that support a broader influence of these exposures on cognitive function during aging is just starting to emerge. This review summarizes current findings and discusses methodological challenges and opportunities for research. Although current evidence is still limited, especially for chronic noise exposure, high exposure has been associated with faster cognitive decline either mediated through cerebrovascular events or resulting in Alzheimer's disease. Ambient environmental exposures are chronic and affect large populations. While they may yield relatively modest-sized risks, they nevertheless result in large numbers of cases. Reducing environmental pollution is clearly feasible, though lowering levels requires collective action and long-term policies such as standard setting, often at the national level as well as at the local level.

Physical, chemical, and toxicological characteristics of particulate emissions from current technology gasoline direct injection vehicles

We assessed the physical, chemical and toxicological characteristics of particulate emissions from four light-duty gasoline direct injection vehicles when operated over the LA92 driving cycle. Our results showed that particle mass and number emissions increased markedly during accelerations. For three of the four vehicles tested, particulate matter (PM) mass and particle number emissions were markedly higher during cold-start and the first few accelerations following the cold-start period than during the hot running and hot-start segments of the LA92 cycle. For one vehicle (which had the highest emissions overall) the hot-start and cold-start PM emissions were similar. Black carbon emissions were also much higher during the cold-start conditions, indicating severe fuel wetting leading to slow evaporation and pool burning, and subsequent soot formation. Particle number concentrations and black carbon emissions showed large reductions during the urban and hot-start phases of the test cycle. The oxidative potential of PM was quantified with both a chemical and a biological assay, and the gene expression impacts of the PM in a macrophage model with PCR (polymerase chain reaction) and ELISA (enzyme-linked immunosorbent assay) analyses. Inter- and intra-vehicle variability in oxidative potential per milligram of PM emitted was relatively low for both oxidative assays, suggesting that real-world emissions and exposure can be estimated with distance-normalized emission factors. The PCR response from signaling markers for oxidative stress (e.g., NOX1) was greater than from inflammatory, AhR (aryl hydrocarbon receptor), or MAPK (mitogen-activated protein kinase) signaling. Protein production associated with inflammation (tumor necrosis factor alpha-TNFα) and oxidative stress (HMOX-1) were quantified and displayed relatively high inter-vehicle variability, suggesting that these pathways may be activated by different PM components. Correlation of trace metal concentrations and oxidative potential suggests a role for small, insoluble particles in inducing oxidative stress.

Association between ambient PM2.5 and emergency department visits for psychiatric emergency diseases

Background

Whether or not short-term exposure to particulate matter <2.5 μm in diameter (PM_2.5) increases the risk of psychiatric emergency diseases is unclear.

Methods

The study was performed in a metropolis from January 2015 to December 2016. The exposure was PM_2.5, and the confounders were weather (temperature and humidity) and other pollutants (PM₁₀, SO₂, CO, O₃, and NO₂). The outcomes were emergency department (ED) visits with psychiatric disease codes (F00-F99 in ICD10 codes). General additive models were used for the statistical analysis to calculate the adjusted relative risks (ARRs) and 95% confidence intervals (95% CIs) for the daily number of ED visits with a lag of 1 to 3 days following a 10 μg/m³ increase in PM_2.5.

Results

During the study period, a total of 67,561 ED visits for psychiatric diseases were identified and tested for association with PM_2.5. Daily ED visits for all psychiatric diseases were not associated with PM_2.5 in the model that was not adjusted for other pollutants. The ARR (95% CI) in the model adjusted for SO₂ was 1.011 (1.002–1.021) by 10 μg/m³ of PM_2.5 on Lag 1 for all psychiatric diseases (F00-F99). The ARR (95% CI) in the model adjusted for O₃ was 1.015 (1.003–1.029) by 10 μg/m³ of PM_2.5 on Lag 1 for F40-F49 (Neurotic, stress-related and somatoform disorders).

Conclusion

An increase in PM_2.5 showed a significant association with an increase in ED visits for all psychiatric diseases (F00-F99) and for neurotic, stress-related and somatoform disorders (F40-F49) on lag day 1.

PM2.5 exposure stimulates COX-2-mediated excitatory synaptic transmission via ROS-NF-κB pathway

Long-term exposure to fine particulate matter (PM_2.5) has been reported to be closely associated with the neuroinflammation and synaptic dysfunction, but the mechanisms underlying the process remain unclear. Cyclooxygenase-2 (COX-2) is a key player in neuroinflammation, and has been also implicated in the glutamatergic excitotoxicity and synaptic plasticity. Thus, we hypothesized that COX-2 was involved in PM_2.5-promoted neuroinflammation and synaptic dysfunction. Our results revealed that PM_2.5 elevated COX-2 expression in primary cultured hippocampal neurons and increased the amplitude of field excitatory postsynaptic potentials (fEPSPs) in hippocampal brain slices. And the administration of NS398 (a COX-2 inhibitor) prevented the increased fEPSPs. PM_2.5 also induced intracellular reactive oxygen species (ROS) generation accompanied with glutathione (GSH) depletion and the loss of mitochondrial membrane potential (MMP), and the ROS inhibitor, N-acetyl-L-cystein (NAC) suppressed the COX-2 overexpression and the increased fEPSPs. Furthermore, the nuclear factor kappa B (NF-κB) was involved in ROS-induced COX-2 and fEPSP in response to PM_2.5 exposure. These findings indicated that PM_2.5 activated COX-2 expression and enhanced the synaptic transmission through ROS-NF-κB pathway, and provided possible biomarkers and specific interventions for PM_2.5-induced neurological damage.

Diesel engine exhaust accelerates plaque formation in a mouse model of Alzheimer's disease

Background

Increasing evidence from toxicological and epidemiological studies indicates that the central nervous system is an important target for ambient air pollutants. We have investigated whether long-term inhalation exposure to diesel engine exhaust (DEE), a dominant contributor to particulate air pollution in urban environments, can aggravate Alzheimer’s Disease (AD)-like effects in female 5X Familial AD (5XFAD) mice and their wild-type female littermates. Following 3 and 13 weeks exposures to diluted DEE (0.95 mg/m³, 6 h/day, 5 days/week) or clean air (controls) behaviour tests were performed and amyloid-β (Aβ) plaque formation, pulmonary histopathology and systemic inflammation were evaluated.

Results

In a string suspension task, assessing for grip strength and motor coordination, 13 weeks exposed 5XFAD mice performed significantly less than the 5XFAD controls. Spatial working memory deficits, assessed by Y-maze and X-maze tasks, were not observed in association with the DEE exposures. Brains of the 3 weeks DEE-exposed 5XFAD mice showed significantly higher cortical Aβ plaque load and higher whole brain homogenate Aβ42 levels than the clean air-exposed 5XFAD littermate controls. After the 13 weeks exposures, with increasing age and progression of the AD-phenotype of the 5XFAD mice, DEE-related differences in amyloid pathology were no longer present. Immunohistochemical evaluation of lungs of the mice revealed no obvious genetic background-related differences in tissue structure, and the DEE exposure did not cause histopathological changes in the mice of both backgrounds. Luminex analysis of plasma cytokines demonstrated absence of sustained systemic inflammation upon DEE exposure.

Conclusions

Inhalation exposure to DEE causes accelerated plaque formation and motor function impairment in 5XFAD transgenic mice. Our study provides further support that the brain is a relevant target for the effects of inhaled DEE and suggests that long-term exposure to this ubiquitous air pollution mixture may promote the development of Alzheimer’s disease.

Multiple sclerosis and air pollution exposure: Mechanisms toward brain autoimmunity

The association between neurodegenerative diseases and environmental exposures, in particular air pollution, has been noticed in the last two decades, but the importance of this environmental factor in multiple sclerosis (MS) pathogenesis has not been considered extensively. However, recent evidence suggests that major mechanisms involved in MS pathogenesis, such as inflammatory factors expression, free radicals overproduction, the blood brain barrier (BBB) breakdown, neuroinflammation, vitamin D deficiency and mitochondrial dysfunction could also occur due to exposure to air pollutants. A prospective hypothesis is suggested here in which exposure to air pollutants may initiate destructive mechanisms inducing inflammatory-oxidative cascades, reduction of immunological self-tolerance and neurodegeneration leading to brain autoimmunity.

Sex and genetic differences in the effects of acute diesel exhaust exposure on inflammation and oxidative stress in mouse brain

In addition to increased morbidity and mortality caused by respiratory and cardiovascular diseases, air pollution may also contribute to central nervous system (CNS) diseases. Traffic-related air pollution is a major contributor to global air pollution, and diesel exhaust (DE) is its most important component. DE contains more than 40 toxic air pollutants and is a major constituent of ambient particulate matter (PM), particularly of ultrafine-PM. Limited information suggests that exposure to DE may cause oxidative stress and neuroinflammation in the CNS. We hypothesized that males may be more susceptible than females to DE neurotoxicity, because of a lower level of expression of paraoxonase 2 (PON2), an intracellular anti-oxidant and anti-inflammatory enzyme. Acute exposure of C57BL/6 mice to DE (250-300μg/m3 for 6h) caused significant increases in lipid peroxidation and of pro-inflammatory cytokines (IL-1α, IL-1β, IL-3, IL-6, TNF-α) in various brain regions (particularly olfactory bulb and hippocampus). In a number of cases the observed effects were more pronounced in male than in female mice. DE exposure also caused microglia activation, as measured by increased Iba1 (ionized calcium-binding adapter molecule 1) expression, and of TSPO (translocator protein) binding. Mice heterozygotes for the modifier subunit of glutamate cysteine ligase (the limiting enzyme in glutathione biosynthesis; Gclm+/- mice) appeared to be significantly more susceptible to DE-induced neuroinflammation than wild type mice. These findings indicate that acute exposure to DE causes neuroinflammation and oxidative stress in brain, and suggest that sex and genetic background may play important roles in modulating susceptibility to DE neurotoxicity.

Urinary t,t-muconic acid as a proxy-biomarker of car exhaust and neurobehavioral performance in 15-year olds

INTRODUCTION

Traffic-related air pollution has been shown to induce neurotoxicity in rodents. Several recent epidemiological studies reported negative associations between residential outdoor air pollution and neurobehavioral performance. We investigated in a population of non-smoker adolescents the associations between the urinary concentration of trans, trans-muconic acid (t,t-MA-U), a metabolite of benzene and used as proxy-biomarker of traffic exposure, and two neurobehavioral domains, i.e. sustained attention and short-term memory.

METHODS

In the framework of an environmental health surveillance study in Flanders (Belgium), we examined between 2008 and 2014 grade nine high school students (n=895). We used reaction time, number of omission errors, and number of commission errors in the Continuous Performance Test to evaluate sustained attention, and for the evaluation of short-term memory we used maximum digit span forward and backward of the Digit Span Test. We measured blood lead (PbB) to assess the independent effect of t,t-MA-U on neurobehavioral outcomes.

RESULTS

This neurobehavioral examination study showed that a ten-fold increase in t,t-MA-U was associated with a 0.14 SD lower sustained attention (95% Confidence Interval: -0.26 to -0.019; p=0.02) and a 0.17 SD diminished short-term memory (95% CI: -0.31 to -0.030; p=0.02). For the same increment in t,t-MA-U, the Continuous Performance Test showed a 12.2ms higher mean reaction time (95% CI: 4.86-19.5; p=0.001) and 0.51 more numbers of errors of omission (95% CI: 0.057-0.97; p=0.028), while no significant association was found with errors of commission. For the Digit Span Tests, the maximum digit span forward was associated with a 0.20 lower number of digits (95% CI: -0.38 to -0.026; p=0.025) and maximum digit span backward with -0.15 digits (95% CI: -0.32 to 0.022; p=0.088). These associations were independent of PbB, parental education and other important covariates including gender, age, passive smoking, ethnicity, urinary creatinine, time of the day, and examination day of the week. For PbB, an independent association was only found with mean reaction time of the Continuous Performance Test (19.1ms, 95% CI: 2.43-35.8; p=0.025).

CONCLUSIONS

In adolescents, a ten-fold increase in the concentration of t,t-MA-U, used as a proxy-biomarker for traffic-related exposure, was associated with a significant deficit in sustained attention and short-term memory. The public health implications of this finding cannot be overlooked as the effect-size for these neurobehavioral domains was about 40% of the effect-size of parental education.

Traffic-related air pollution increased the risk of Parkinson's disease in Taiwan: A nationwide study

BACKGROUND

Ambient air pollution has been associated with many health conditions, but little is known about its effects on neurodegenerative diseases, such as Parkinson's disease (PD). In this study, we investigated the influence of ambient air pollution on PD in a nationwide population-based case-control study in Taiwan.

METHODS

We identified 11,117 incident PD patients between 2007 and 2009 from the Taiwanese National Health Insurance Research Database and selected 44,468 age- and gender-matched population controls from the longitudinal health insurance database. The average ambient pollutant exposure concentrations from 1998 through the onset of PD were estimated using quantile-based Bayesian Maximum Entropy models. Basing from logistic regression models, we estimated the odds ratios (ORs) and 95% confidence intervals (CIs) of ambient pollutant exposures and PD risk.

RESULTS

We observed positive associations between NO_x, CO exposures, and PD. In multi-pollutant models, for NO_x and CO above the 75th percentile exposure compared with the lowest percentile, the ORs of PD were 1.37 (95% CI=1.23-1.52) and 1.17 (95% CI=1.07-1.27), respectively.

CONCLUSIONS

This study suggests that ambient air pollution exposure, especially from traffic-related pollutants such as NO_x and CO, increases PD risk in the Taiwanese population.

A Systematic Review and Meta-Analysis of Multiple Airborne Pollutants and Autism Spectrum Disorder

BACKGROUND

Exposure to ambient air pollution is widespread and may be detrimental to human brain development and a potential risk factor for Autism Spectrum Disorder (ASD). We conducted a systematic review of the human evidence on the relationship between ASD and exposure to all airborne pollutants, including particulate matter air pollutants and others (e.g. pesticides and metals).

OBJECTIVE

To answer the question: "is developmental exposure to air pollution associated with ASD?"

METHODS

We conducted a comprehensive search of the literature, identified relevant studies using inclusion/exclusion criteria pre-specified in our protocol (registered in PROSPERO, CRD # 42015017890), evaluated the potential risk of bias for each included study and identified an appropriate subset of studies to combine in a meta-analysis. We then rated the overall quality and strength of the evidence collectively across all air pollutants.

RESULTS

Of 1,158 total references identified, 23 human studies met our inclusion criteria (17 case-control, 4 ecological, 2 cohort). Risk of bias was generally low across studies for most domains; study limitations were related to potential confounding and accuracy of exposure assessment methods. We rated the quality of the body of evidence across all air pollutants as "moderate." From our meta-analysis, we found statistically significant summary odds ratios (ORs) of 1.07 (95% CI: 1.06, 1.08) per 10-μg/m3 increase in PM10 exposure (n = 6 studies) and 2.32 (95% CI: 2.15, 2.51) per 10-μg/m3 increase in PM2.5 exposure (n = 3 studies). For pollutants not included in a meta-analysis, we collectively evaluated evidence from each study in rating the strength and quality of overall evidence considering factors such as inconsistency, imprecision, and evidence of dose-response. All included studies generally showed increased risk of ASD with increasing exposure to air pollution, although not consistently across all chemical components.

CONCLUSION

After considering strengths and limitations of the body of research, we concluded that there is "limited evidence of toxicity" for the association between early life exposure to air pollution as a whole and diagnosis of ASD. The strongest evidence was between prenatal exposure to particulate matter and ASD. However, the small number of studies in the meta-analysis and unexplained statistical heterogeneity across the individual study estimates means that the effect could be larger or smaller (including not significant) than these studies estimate. Our research supports the need for health protective public policy to reduce exposures to harmful airborne contaminants among pregnant women and children and suggests opportunities for optimizing future research.

Combination of chlorogenic acid and salvianolic acid B protects against polychlorinated biphenyls-induced oxidative stress through Nrf2

Caffeic acid derivatives (CADs) are well-known phytochemicals with multiple physiological and pharmacological activities. This study aimed to investigate the combined protective effects of CADs on PCB126-induced liver damages and oxidative stress in mice. Here, we used chemiluminescence and chose chlorogenic acid (CGA), salvianolic acid B (Sal B) as the best antioxidants. Then, mice were intragastrically administered with 60mg/kg/d CGA, Sal B, and CGA plus Sal B (1:1) for 3 weeks before exposing to 0.05mg/kg/d PCB126 for 2 weeks. We found that pretreatment with CGA, Sal B, and CGA plus Sal B effectively attenuated liver injury and cytotoxicity caused by PCB126, but improved the expressions of superoxide dismutase (SOD), glutathione reduced (GSH), heme oxygenase-1 (HO-1) and nuclear factor E2-related factor 2 (Nrf2), CGA plus Sal B especially, was found to have the best effects that indicated a synergetic protective effect. Taken together, as the Nrf2 regulates the cyto-protective response by up-regulating the expression of antioxidant genes, we suggested that CGA plus Sal B had a combined protection on PCB126-induced tissue damages and that the Nrf2 signaling might be involved.

Neurodegenerative and neurological disorders by small inhaled particles

The world's population is steadily ageing and as a result, health conditions related to ageing, such as dementia, have become a major public health concern. In 2001, it was estimated that there were almost 5 million Europeans suffering from Alzheimer's disease (AD) and this figure has been projected to almost double by 2040. About 40% of people over 85 suffer from AD, and another 10% from Parkinson's disease (PD). The majority of AD and PD cases are of sporadic origin and environmental factors play an important role in the aetiology. Epidemiological research identified airborne particulate matter (PM) as one of the environmental factors potentially involved in AD and PD pathogenesis. Also, cumulating evidence demonstrates that the smallest sizes of the inhalable fraction of ambient particulate matter, also referred to as ultrafine particulate matter or nano-sized particles, are capable of inducing effects beyond the respiratory system. Translocation of very small particles via the olfactory epithelium in the nose or via uptake into the circulation has been demonstrated through experimental rodent studies with engineered nanoparticles. Outdoor air pollution has been linked to several health effects including oxidative stress and neuroinflammation that may ultimately result in neurodegeneration and cognitive impairment. This review aims to evaluate the relationship between exposure to inhaled ambient particles and neurodegeneration.

Traffic-Related Air Pollution and Parkinson's Disease in Denmark: A Case-Control Study

BACKGROUND

Very little is currently known about air pollutants' adverse effects on neurodegenerative diseases even though recent studies have linked particulate exposures to brain pathologies associated with Parkinson's and Alzheimer's disease.

OBJECTIVE

In the present study, we investigated long-term exposure to traffic-related air pollution and Parkinson's disease.

METHODS

In a case-control study of 1,696 Parkinson's disease (PD) patients identified from Danish hospital registries and diagnosed 1996-2009 and 1,800 population controls matched by sex and year of birth, we assessed long-term traffic-related air pollutant exposures (represented by nitrogen dioxide; NO2) from a dispersion model, using residential addresses from 1971 to the date of diagnosis or first cardinal symptom for cases and the corresponding index date for their matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated with logistic regression, adjusting for matching factors and potential confounders.

RESULTS

We found ambient air pollution from traffic sources to be associated with risk of PD, with a 9% higher risk (95% CI: 3, 16.0%) per interquartile range increase (2.97 μg/m(3)) in modeled NO2. For participants living for ≥ 20 years in the capital city, ORs were larger (OR = 1.21; 95% CI: 1.11, 1.31) than in provincial towns (OR = 1.10; 95% CI: 0.97, 1.26), whereas there was no association among rural residents.

CONCLUSIONS

Our findings raise concerns about potential effects of air pollution from traffic and other sources on the risk of PD, particularly in populations with high or increasing exposures.

Developmental neurotoxicity of inhaled ambient ultrafine particle air pollution: Parallels with neuropathological and behavioral features of autism and other neurodevelopmental disorders

Accumulating evidence from both human and animal studies show that brain is a target of air pollution. Multiple epidemiological studies have now linked components of air pollution to diagnosis of autism spectrum disorder (ASD), a linkage with plausibility based on the shared mechanisms of inflammation. Additional plausibility appears to be provided by findings from our studies in mice of exposures from postnatal day (PND) 4-7 and 10-13 (human 3rd trimester equivalent), to concentrated ambient ultrafine (UFP) particles, considered the most reactive component of air pollution, at levels consistent with high traffic areas of major U.S. cities and thus highly relevant to human exposures. These exposures, occurring during a period of marked neuro- and gliogenesis, unexpectedly produced a pattern of developmental neurotoxicity notably similar to multiple hypothesized mechanistic underpinnings of ASD, including its greater impact in males. UFP exposures induced inflammation/microglial activation, reductions in size of the corpus callosum (CC) and associated hypomyelination, aberrant white matter development and/or structural integrity with ventriculomegaly (VM), elevated glutamate and excitatory/inhibitory imbalance, increased amygdala astrocytic activation, and repetitive and impulsive behaviors. Collectively, these findings suggest the human 3rd trimester equivalent as a period of potential vulnerability to neurodevelopmental toxicity to UFP, particularly in males, and point to the possibility that UFP air pollution exposure during periods of rapid neuro- and gliogenesis may be a risk factor not only for ASD, but also for other neurodevelopmental disorders that share features with ASD, such as schizophrenia, attention deficit disorder, and periventricular leukomalacia.

In utero exposure of mice to diesel exhaust particles affects spatial learning and memory with reduced N-methyl-D-aspartate receptor expression in the hippocampus of male offspring

Diesel exhaust consists of diesel exhaust particles (DEPs) and gaseous compounds. Previous studies reported that in utero exposure to diesel exhaust affects the central nervous system. However, there was no clear evidence that these effects were caused by diesel exhaust particles themselves, gaseous compounds, or both. Here, we explored the effects of in utero exposure to DEPs on learning and memory in male ICR mice. DEP solutions were administered subcutaneously to pregnant ICR mice at a dose of 0 or 200 μg/kg body weight on gestation days 6, 9, 12, 15, and 18. We examined learning and memory in 9-to-10-week-old male offspring using the Morris water maze test and passive avoidance test. Immediately after the behavioral tests, hippocampi were isolated. Hippocampal N-methyl-D-aspartate receptor (NR) expression was also measured by quantitative RT-PCR analysis. Mice exposed to DEPs in utero showed deficits in the Morris water maze test, but their performance was not significantly different from that of control mice in the passive avoidance test. In addition, DEP-exposed mice exhibited decreased hippocampal NR2A expression. The present results indicate that maternal DEP exposure disrupts learning and memory in male offspring, which is associated with reduced hippocampal NR2A expression.

Toxicology of ambient particulate matter

It is becoming increasingly clear that inhalation exposure to particulate matter (PM) can lead to or exacerbate various diseases, which are not limited to the lung but extend to the cardiovascular system and possibly other organs and tissues. Epidemiological studies have provided strong evidence for associations with chronic obstructive pulmonary disease (COPD), asthma, bronchitis and cardiovascular disease, while the evidence for a link with lung cancer is less strong. Novel research has provided first hints that exposure to PM might lead to diabetes and central nervous system (CNS) pathology. In the current review, an overview is presented of the toxicological basis for adverse health effects that have been linked to PM inhalation. Oxidative stress and inflammation are discussed as central processes driving adverse effects; in addition, profibrotic and allergic processes are implicated in PM-related diseases. Effects of PM on key cell types considered as regulators of inflammatory, fibrotic and allergic mechanisms are described.

Differential proinflammatory responses induced by diesel exhaust particles with contrasting PAH and metal content

Exposure to diesel engine exhaust particles (DEPs), representing a complex and variable mixture of components, has been linked with cellular production and release of several types of mediators related to pulmonary inflammation. A key challenge is to identify the specific components, which may be responsible for these effects. The aim of this study was to compare the proinflammatory potential of two DEP-samples with contrasting contents of polycyclic aromatic hydrocarbons (PAHs) and metals. The DEP-samples were compared with respect to their ability to induce cytotoxicity, expression and release of proinflammatory mediators (IL-6, IL-8), activation of mitogen-activated protein kinases (MAPKs) and expression of CYP1A1 and heme oxygenase-1 (HO-1) in human bronchial epithelial (BEAS-2B) cells. In addition, dithiothreitol and ascorbic acid assays were performed in order to examine the oxidative potential of the PM samples. The DEP-sample with the highest PAH and lowest metal content was more potent with respect to cytotoxicity and expression and release of proinflammatory mediators, CYP1A1 and HO-1 expression and MAPK activation, than the DEP-sample with lower PAH and higher metal content. The DEP-sample with the highest PAH and lowest metal content also possessed a greater oxidative potential. The present results indicate that the content of organic components may be determinant for the proinflammatory effects of DEP. The findings underscore the importance of considering the chemical composition of particulate matter-emissions, when evaluating the potential health impact and implementation of air pollution regulations.

Public health and components of particulate matter: the changing assessment of black carbon

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments. In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries. Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models. Natural "interventions"--reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems--demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g, carbonaceous species, may cause harm, aiding interpretation of epidemiological studies. Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the US. EPA rubric for judging possible causality of PM25. mass concentrations, be used to assess which PM2.5. species are most harmful to public health.

IMPLICATIONS

Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM2.5 species in models; using better measurements of subject exposure) have also occurred. "Natural intervention" studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM2.5 species is suggested.

Prenatal exposure to PM₁₀ and NO₂ and children's neurodevelopment from birth to 24 months of age: mothers and Children's Environmental Health (MOCEH) study

INTRODUCTION

Previous studies have suggested adverse effects of maternal exposure to air pollution on neurodevelopment in early childhood.

OBJECTIVES

We aimed to investigate the association between prenatal exposure to particulates of less than 10 μm in diameter (PM10) and nitrogen dioxide (NO2) and neurodevelopment in children during the first 24 months of their lives.

METHODS

The MOCEH study is a prospective birth cohort study in South Korea. Average exposure levels to PM10 and NO2 during the entire pregnancy were estimated using the inverse distance weighting (IDW) method. A total of 520 mother-child pairs who completed neurodevelopmental assessments using the Korean Bayley Scale of Infant Development II (K-BSID-II) more than once at ages of 6, 12 and 24 months were included. Mental developmental index (MDI) and psychomotor developmental index (PDI) from the K-BSID-II were used as outcome variables.

RESULTS

There were negative associations between maternal exposure to PM10 and MDI (β=-2.83; p=0.003) and PDI (β=-3.00; p=0.002) throughout the first 24 months of life as determined by the generalized estimating equation (GEE) model. Maternal NO2 exposure was related with impairment of psychomotor development (β=-1.30; p=0.05) but not with cognitive function (β=-0.84; p=0.20). In a multiple linear regression model, there were significant effects of prenatal air pollution exposure on MDI (PM10: β=-4.60; p<0.001, NO2: β=-3.12; p<0.001) and PDI (PM10: β=-7.24; p<0.001, NO2: β=-3.01; p<0.001) at 6 months, but no significant association was found at 12 and 24 months of age.

CONCLUSIONS

The findings suggest that exposure to air pollution may result in delayed neurodevelopment in early childhood.

Effect of urban particles on human middle ear epithelial cells

OBJECTIVES

The aim of this study was to examine the cytotoxic effect and inflammatory response of human middle ear epithelial cells (HMEECs) induced by urban particles (UP).

MATERIALS AND METHODS

Cell viability following UP exposure was assessed in HMEECs using the CCK 8 assay. The expression levels of the inflammation-related genes (COX-2 and MUC5AC) were analyzed using semi-quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and COX-2 production was analyzed using western blotting.

RESULTS

Treatment with UP decreased cell viability in HMEECs in a dose- and time-dependent manner. UP exposure induced the significantly increased expression of COX-2 and MUC5AC. Western blotting showed dose dependently increased expression of COX-2 production.

CONCLUSIONS

UP decreased cell viability, increased the inflammatory response, and increased mucin gene production in HMEECs. These findings indicate that exposure to UP can contribute to the development of otitis media.

Investigation of the effects of short-term inhalation of carbon nanoparticles on brains and lungs of c57bl/6j and p47(phox-/-) mice

Recent studies indicate that the brain is a target for toxic carbonaceous nanoparticles present in ambient air. It has been proposed that the neurotoxic effects of such particles are driven by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediated generation of reactive oxygen species (ROS) in activated microglia. In the present study, we have evaluated the effects of short term (4h) nose-only inhalation exposure to carbon NP (CNP) in the brains and lungs of C57BL/6J mice and in p47(phox-/-) mice that lack a functional NADPH oxidase. It was shown that the lungs of the p47(phox-/-) mice are less responsive to CNP inhalation than lungs of the corresponding C57BL/6J control animals. Lung tissue mRNA expression of the oxidative stress/DNA damage response genes 8-oxoguanine glycosylase (OGG1) and apurinic/apyrimidinic endonuclease 1 (APE1) were induced by CNP exposure in C57BL/6J but not in the p47(phox-/-) mice. In contrast, the expression of these genes, as well as Tumor Necrosis Factor-α (TNFα), Cyclooxygenase-2 (COX-2) and Heme Oxygenase-1 (HO-1) was not altered in the olfactory bulb, cerebellum or remaining brain tissue part of either mouse background. This indicates that neuroinflammation was not induced by this exposure. CNP inhalation for 4h or for 4h on three consecutive days also did not affect brain tissue protein expression of interleukin (IL)-1β, while a clear significant difference in constitutive expression level of this pro-inflammatory cytokine was found between C57BL/6J and p47(phox-/-) mice. In conclusion, short-term inhalation exposure to pure carbon nanoparticles can trigger mild p47(phox) dependent oxidative stress responses in the lungs of mice whereas in their brains at the same exposure levels signs of oxidative stress and inflammation remain absent. The possible role of p47(phox) in the neuro-inflammatory effects of nanoparticles in vivo remains to be clarified.

Neurotoxicants are in the air: convergence of human, animal, and in vitro studies on the effects of air pollution on the brain

In addition to increased morbidity and mortality caused by respiratory and cardiovascular diseases, air pollution may also negatively affect the brain and contribute to central nervous system diseases. Air pollution is a mixture comprised of several components, of which ultrafine particulate matter (UFPM; <100 nm) is of much concern, as these particles can enter the circulation and distribute to most organs, including the brain. A major constituent of ambient UFPM is represented by traffic-related air pollution, mostly ascribed to diesel exhaust (DE). Human epidemiological studies and controlled animal studies have shown that exposure to air pollution may lead to neurotoxicity. In addition to a variety of behavioral abnormalities, two prominent effects caused by air pollution are oxidative stress and neuroinflammation, which are seen in both humans and animals and are confirmed by in vitro studies. Among factors which can affect neurotoxic outcomes, age is considered the most relevant. Human and animal studies suggest that air pollution (and DE) may cause developmental neurotoxicity and may contribute to the etiology of neurodevelopmental disorders, including autistic spectrum disorders. In addition, air pollution exposure has been associated with increased expression of markers of neurodegenerative disease pathologies.

Exposure to vehicle emissions results in altered blood brain barrier permeability and expression of matrix metalloproteinases and tight junction proteins in mice

Background

Traffic-generated air pollution-exposure is associated with adverse effects in the central nervous system (CNS) in both human exposures and animal models, including neuroinflammation and neurodegeneration. While alterations in the blood brain barrier (BBB) have been implicated as a potential mechanism of air pollution-induced CNS pathologies, pathways involved have not been elucidated.

Objectives

To determine whether inhalation exposure to mixed vehicle exhaust (MVE) mediates alterations in BBB permeability, activation of matrix metalloproteinases (MMP) -2 and −9, and altered tight junction (TJ) protein expression.

Methods

Apolipoprotein (Apo) E^−/− and C57Bl6 mice were exposed to either MVE (100 μg/m³ PM) or filtered air (FA) for 6 hr/day for 30 days and resulting BBB permeability, expression of ROS, TJ proteins, markers of neuroinflammation, and MMP activity were assessed. Serum from study mice was applied to an in vitro BBB co-culture model and resulting alterations in transport and permeability were quantified.

Results

MVE-exposed Apo E^−/− mice showed increased BBB permeability, elevated ROS and increased MMP-2 and −9 activity, compared to FA controls. Additionally, cerebral vessels from MVE-exposed mice expressed decreased levels of TJ proteins, occludin and claudin-5, and increased levels of inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β in the parenchyma. Serum from MVE-exposed animals also resulted in increased in vitro BBB permeability and altered P-glycoprotein transport activity.

Conclusions

These data indicate that inhalation exposure to traffic-generated air pollutants promotes increased MMP activity and degradation of TJ proteins in the cerebral vasculature, resulting in altered BBB permeability and expression of neuroinflammatory markers.

BaP-induced DNA damage initiated p53-independent necroptosis via the mitochondrial pathway involving Bax and Bcl-2

Benzo(a)pyrene (BaP), a typical environmental carcinogen, can induce cell death both by protein 53 or tumor protein 53 (p53)-independent and -dependent pathways. However, little is known about the molecular mechanisms of p53-independent pathways in BaP-induced cell death. In this study, cells with different genetic background (including p53-proficient human fetal lung fibroblast cell lines (MRC-5), p53-deficient human non-small-cell lung carcinoma cell lines (H1299), and p53-knockdown cell lines (MRC-5 p53−/−)) were used to establish models of BaP-induced cell death. The results showed that BaP (8, 16, 32, and 64 μM) induced necroptotic cell death in the cell lines. The necroptotic cell death and DNA damage were concurrently observed. In the three cell lines, at 24 h after treatment, BaP (8–64 μM) upregulated expressions of BAX, BCL-2, and cleaved caspase-3 proteins, but not their messenger RNA levels. The findings suggested that BaP-induced necroptosis was modulated by the p53-independent pathway, which was related to the induction of BAX, decreased expression of BCL-2, and activation of caspase-3.

Gene expression changes in rat brain after short and long exposures to particulate matter in Los Angeles basin air: Comparison with human brain tumors

Air pollution negatively impacts pulmonary, cardiovascular, and central nervous systems. Although its influence on brain cancer is unclear, toxic pollutants can cause blood-brain barrier disruption, enabling them to reach the brain and cause alterations leading to tumor development. By gene microarray analysis validated by quantitative RT-PCR and immunostaining we examined whether rat (n=104) inhalation exposure to air pollution particulate matter (PM) resulted in brain molecular changes similar to those associated with human brain tumors. Global brain gene expression was analyzed after exposure to PM (coarse, 2.5-10μm; fine, <2.5μm; or ultrafine, <0.15μm) and purified air for different times, short (0.5, 1, and 3 months) and chronic (10 months), for 5h per day, four days per week. Expression of select gene products was also studied in human brain (n=7) and in tumors (n=83). Arc/Arg3.1 and Rac1 genes, and their protein products were selected for further examination. Arc was elevated upon two-week to three-month exposure to coarse PM and declined after 10-month exposure. Rac1 was significantly elevated upon 10-month coarse PM exposure. On human brain tumor sections, Arc was expressed in benign meningiomas and low-grade gliomas but was much lower in high-grade tumors. Conversely, Rac1 was elevated in high-grade vs. low-grade gliomas. Arc is thus associated with early brain changes and low-grade tumors, whereas Rac1 is associated with long-term PM exposure and highly aggressive tumors. In summary, exposure to air PM leads to distinct changes in rodent brain gene expression similar to those observed in human brain tumors.

The role of MAC1 in diesel exhaust particle-induced microglial activation and loss of dopaminergic neuron function

Increasing reports support that air pollution causes neuroinflammation and is linked to central nervous system (CNS) disease/damage. Diesel exhaust particles (DEP) are a major component of urban air pollution, which has been linked to microglial activation and Parkinson's disease-like pathology. To begin to address how DEP may exert CNS effects, microglia and neuron-glia cultures were treated with either nanometer-sized DEP (< 0.22 μM; 50 μg/mL), ultrafine carbon black (ufCB, 50 μg/mL), or DEP extracts (eDEP; from 50 μg/mL DEP), and the effect of microglial activation and dopaminergic (DA) neuron function was assessed. All three treatments showed enhanced ameboid microglia morphology, increased H2 O2 production, and decreased DA uptake. Mechanistic inquiry revealed that the scavenger receptor inhibitor fucoidan blocked DEP internalization in microglia, but failed to alter DEP-induced H2 O2 production in microglia. However, pre-treatment with the MAC1/CD11b inhibitor antibody blocked microglial H2 O2 production in response to DEP. MAC1(-/-) mesencephalic neuron-glia cultures were protected from DEP-induced loss of DA neuron function, as measured by DA uptake. These findings support that DEP may activate microglia through multiple mechanisms, where scavenger receptors regulate internalization of DEP and the MAC1 receptor is mandatory for both DEP-induced microglial H2 O2 production and loss of DA neuron function.

Negative effects of ultrafine particle exposure during forced exercise on the expression of Brain-Derived Neurotrophic Factor in the hippocampus of rats

Exercise improves cognitive function, and Brain-Derived Neurotrophic Factor (BDNF) plays a key role in this process. We recently reported that particulate matter (PM) exposure negatively contributed to the exercise-induced increase in human serum BDNF concentration. Furthermore, PM exposure is associated with neuroinflammation and cognitive decline. The aim of this study was to investigate the effect of exposure to ultrafine particles (UFP) during a single bout of forced exercise on the expression of inflammatory (IL1α, IL1β, TNF, IL6, NOS2, NOS3) and oxidative stress (NFE2L2)-related genes, as well as BDNF in the brain of rats. Four groups (n=6/group) of Wistar rats were exposed for 90 min to one of the following exposure regimes: UFP+exercise, UFP+rest, ambient air+exercise, ambient air+rest (control). Hippocampus, olfactory bulb and prefrontal cortex were collected 24h after exposure. Gene expression changes were analyzed with real-time PCR. In the condition ambient air+exercise, hippocampal expression of BDNF and NFE2L2 was up-regulated, while the expression of IL1α and NOS3 in the prefrontal cortex and IL1α in the olfactory bulb was down-regulated compared to the control. In contrast, gene expression in the condition UFP+exercise did not differ from the control. In the condition UFP+rest, hippocampal expression of NFE2L2 was down-regulated and there was a trend toward down-regulation of BDNF expression compared to the control. This study shows a negative effect of UFP exposure on the exercise-induced up-regulation of BDNF gene expression in the hippocampus of rats.