Exposure to traffic-generated air pollutants mediates alterations in brain microvascular integrity in wildtype mice on a high-fat diet

Traffic-related air pollution in marginalized neighborhoods: a community perspective

OBJECTIVES

Marginalized communities are exposed to higher levels of traffic-related air pollution (TRAP) than the general population. TRAP exposure is linked to pulmonary toxicity, neurotoxicity, and cardiovascular toxicity often through mechanisms of inflammation and oxidative stress. Early life exposure to TRAP is also implicated in higher rates of asthma in these same communities. There is a critical need for additional epidemiological, in vivo, and in vitro studies to define the health risks of TRAP exposure affecting the most vulnerable groups to set strict, protective air pollution standards in these communities.

MATERIALS AND METHODS

A literature review was conducted to summarize recent findings (2010-2024) concerning TRAP exposure and toxic mechanisms that are relevant to the most affected underserved communities.

CONCLUSIONS

Guided by the perspectives of NYC community scientists, this contemporary review of toxicological and epidemiological studies considers how the exposome could lead to disproportionate exposures and health effects in underserved populations.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood-brain barrier co-cultured with microglia

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer's (AD). Considered the brain's first line of defense, the Blood-Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aβ transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 μg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1β and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB's response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB's responses to this environmental chemical.

Histological features of non-alcoholic fatty liver disease revealed in response to mixed vehicle emission exposure and consumption of a high-fat diet in wildtype C57Bl/6 male mice

Non-alcoholic fatty liver disease (NAFLD) is currently plaguing the population at pandemic proportions and is expected to become more prevalent over the next decade. Recent epidemiological studies have demonstrated a correlation between the manifestation of NAFLD and ambient air pollution levels, which is exacerbated by other risk factors, such as diabetes, dyslipidemia, obesity, and hypertension. Exposure to airborne particulate matter has also been associated with inflammation, hepatic lipid accumulation, oxidative stress, fibrosis, and hepatocyte injury. While prolonged consumption of a high-fat (HF) diet is associated with NAFLD, little is known regarding the effects of inhaled traffic-generated air pollution, a ubiquitous environmental pollutant, on the pathogenesis of NAFLD. Therefore, we investigated the hypothesis that exposure to a mixture of gasoline and diesel engine emissions (MVE), coupled with the concurrent consumption of a HF diet, promotes the development of a NAFLD phenotype within the liver. Three-month-old male C57Bl/6 mice were placed on either a low-fat or HF diet and exposed via whole-body inhalation to either filtered (FA) air or MVE (30 µg PM/m³ gasoline engine emissions + 70 µg PM/m³ diesel engine emissions) 6 hr/day for 30 days. Histology revealed mild microvesicular steatosis and hepatocyte hypertrophy in response to MVE exposure alone, compared to FA controls, yielding a classification of "borderline NASH" under the criteria of the modified NAFLD active score (NAS) system. As anticipated, animals on a HF diet exhibited moderate steatosis; however, we also observed inflammatory infiltrates, hepatocyte hypertrophy, and increased lipid accumulation, with the combined effect of HF diet and MVE exposure. Our results indicate that inhalation exposure to traffic-generated air pollution initiates hepatocyte injury and further exacerbates lipid accumulation and hepatocyte injury induced by the consumption of a HF diet, thereby contributing to the progression of NAFLD-related pathologies.

Neurodevelopmental toxicity induced by airborne particulate matter

Airborne particulate matter (PM), the primary component associated with health risks in air pollution, can negatively impact human health. Studies have shown that PM can enter the brain by inhalation, but data on the exact quantity of particles that reach the brain are unknown. Particulate matter exposure can result in neurotoxicity. Exposure to PM poses a greater health risk to infants and children because their nervous systems are not fully developed. This review paper highlights the association between PM and neurodevelopmental toxicity (NDT). Exposure to PM can induce oxidative stress and inflammation, potentially resulting in blood-brain barrier damage and increased susceptibility to development of neurodevelopmental disorders (NDD), such as autism spectrum disorders and attention deficit disorders. In addition, human and animal exposure to PM can induce microglia activation and epigenetic alterations and alter the neurotransmitter levels, which may increase risks for development of NDD. However, the systematic comparisons of the effects of PM on NDD at different ages of exposure are deficient. The elucidation of PM exposure risks and NDT in children during the early developmental stages are of great importance. The synthesis of current research may help to identify markers and mechanisms of PM-induced neurodevelopmental toxicity, allowing for the development of strategies to prevent permanent damage of developing brain.

Recent Advances in Vehicle Exhaust Treatment with Photocatalytic Technology

Vehicle exhaust has been acknowledged as an essential factor affecting human health due to the extensive use of cars. Its main components include volatile organic compounds (VOCs) and nitrogen oxides (NOx), which can cause acute irritation and chronic diseases, and significant research on the treatment of vehicle exhaust has received increasing attention in recent decades. Recently, photocatalytic technology has been considered a practical approach for eliminating vehicle emissions. This review highlights the crucial role of photocatalytic technology in eliminating vehicle emissions using semiconductor catalysts. A particular emphasis has been placed on various photocatalytic materials, such as TiO2-based materials, Bi-based materials, and Metal–Organic Frameworks (MOFs), and their recent advances in the performance of VOC and NOx photodegradation. In addition, the applications of photocatalytic technology for the elimination of vehicle exhaust are presented (including photocatalysts combined with pavement surfaces, making photocatalysts into architectural coatings and photoreactors), which will offer a promising strategy for photocatalytic technology to remove vehicle exhaust.

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

A Critical Review and Meta-Analysis of Impacts of Per- and Polyfluorinated Substances on the Brain and Behavior

Per- and polyfluoroalkyl substances (PFAS) are a class of structurally diverse synthetic organic chemicals that are chemically stable, resistant to degradation, and persistent in terrestrial and aquatic environments. Widespread use of PFAS in industrial processing and manufacturing over the last 70 years has led to global contamination of built and natural environments. The brain is a lipid rich and highly vascularized organ composed of long-lived neurons and glial cells that are especially vulnerable to the impacts of persistent and lipophilic toxicants. Generally, PFAS partition to protein-rich tissues of the body, primarily the liver and blood, but are also detected in the brains of humans, wildlife, and laboratory animals. Here we review factors impacting the absorption, distribution, and accumulation of PFAS in the brain, and currently available evidence for neurotoxic impacts defined by disruption of neurochemical, neurophysiological, and behavioral endpoints. Emphasis is placed on the neurotoxic potential of exposures during critical periods of development and in sensitive populations, and factors that may exacerbate neurotoxicity of PFAS. While limitations and inconsistencies across studies exist, the available body of evidence suggests that the neurobehavioral impacts of long-chain PFAS exposures during development are more pronounced than impacts resulting from exposure during adulthood. There is a paucity of experimental studies evaluating neurobehavioral and molecular mechanisms of short-chain PFAS, and even greater data gaps in the analysis of neurotoxicity for PFAS outside of the perfluoroalkyl acids. Whereas most experimental studies were focused on acute and subchronic impacts resulting from high dose exposures to a single PFAS congener, more realistic exposures for humans and wildlife are mixtures exposures that are relatively chronic and low dose in nature. Our evaluation of the available human epidemiological, experimental, and wildlife data also indicates heightened accumulation of perfluoroalkyl acids in the brain after environmental exposure, in comparison to the experimental studies. These findings highlight the need for additional experimental analysis of neurodevelopmental impacts of environmentally relevant concentrations and complex mixtures of PFAS.

Traffic-generated air pollution - Exposure mediated expression of factors associated with demyelination in a female apolipoprotein E-/- mouse model

Epidemiology studies suggest that exposure to ambient air pollution is associated with demyelinating diseases in the central nervous system (CNS), including multiple sclerosis (MS). The pathophysiology of MS results from an autoimmune response involving increased inflammation and demyelination in the CNS, which is higher in young (adult) females. Exposure to traffic-generated air pollution is associated with neuroinflammation and other detrimental outcomes in the CNS; however, its role in the progression of pathologies associated with demyelinating diseases has not yet been fully characterized in a female model. Thus, we investigated the effects of inhalation exposure to mixed vehicle emissions (MVE) in the brains of both ovary-intact (ov+) and ovariectomized (ov-) female Apolipoprotein (ApoE^-/-) mice. Ov + and ov- ApoE^-/- mice were exposed via whole-body inhalation to either filtered air (FA, controls) or mixed gasoline and diesel vehicle emissions (MVE: 200 PM μg/m³) for 6 h/d, 7 d/wk., for 30 d. We then analyzed MVE-exposure mediated alterations in myelination, the presence of CD4+ and CD8+ T cells, reactive oxygen species (ROS), myelin oligodendrocyte protein (MOG), and expression of estrogen (ERα and ERβ) and progesterone (PROA/B) receptors in the CNS. MVE-exposure mediated significant alterations in myelination across multiple regions in the cerebrum, as well as increased CD4+ and CD8+ staining. There was also an increase in ROS production in the CNS of MVE-exposed ov- and ov + ApoE^-/- mice. Ov- mice displayed a reduction in cerebral ERα mRNA expression, compared to ov + mice; however, MVE exposure resulted in an even further decrease in ERα expression, while ERβ and PRO A/B were unchanged across groups. These findings collectively suggest that inhaled MVE-exposure may mediate estrogen receptor expression alterations associated with increased CD4+/CD8+ infiltration, regional demyelination, and ROS production in the CNS of female ApoE^-/- mice.

In vivo analysis of noise dependent activation of white blood cells and microvascular dysfunction in mice

This article contains supporting information on data collection for the research article entitled “Aircraft noise exposure drives the activation of white blood cells and induces microvascular dysfunction in mice” by Eckrich et al. We found that noise-induced stress triggered microvascular dysfunction via involvement of innate immune-derived reactive oxygen species. In this article, we present the instrumentation of mice with dorsal skinfold chambers for in vivo microscopic imaging of blood flow, interaction of leukocytes with the vascular wall (also by fluorescent labelling of blood cells) and vessel diameter. In addition, we explain the preparation of cerebral arterioles for measurement of vascular reactivity in vitro.•

visualization of noise-dependent effects in dorsal skinfold chamber.

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in vivo microscopy of noise-dependent activation of white blood cells.

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analysis of noise-dependent microvascular dysfunction in dorsal skinfold chamber and cannulated cerebral arterioles.

Short-term exposure to air pollution and biomarkers of cardiovascular effect: A repeated measures study

To help understand the pathophysiologic mechanisms linking air pollutants and cardiovascular disease (CVD), we employed a repeated measures design to investigate the associations of four short-term air pollution exposures - particulate matter less than 2.5 μm in diameter (PM_2.5), nitrogen dioxide (NO₂), ozone (O₃) and sulfur dioxide (SO₂), with two blood markers involved in vascular effects of oxidative stress, soluble lectin-like oxidized LDL receptor-1 (sLOX-1) and nitrite, using data from the Multi-Ethnic Study of Atherosclerosis (MESA). Seven hundred and forty participants with plasma sLOX-1 and nitrite measurements at three exams between 2002 and 2007 were included. Daily PM_2.5, NO₂, O₃ and SO₂ zero to seven days prior to blood draw were estimated from central monitors in six MESA regions, pre-adjusted using site-specific splines of meteorology and temporal trends, and an indicator for day of the week. Unconstrained distributed lag generalized estimating equations were used to estimate net effects over eight days with adjustment for sociodemographic and behavioral factors. The results showed that higher short-term concentrations of PM_2.5, but not other pollutants, were associated with increased sLOX-1 analyzed both as a continuous outcome (percent change per interquartile increase: 16.36%, 95%CI: 0.1-35.26%) and dichotomized at the median (odds ratio per interquartile increase: 1.21, 95%CI: 1.01-1.44). The findings were not meaningfully changed after adjustment for additional covariates or in several sensitivity analyses. Pollutant concentrations were not associated with nitrite levels. This study extends earlier experimental findings of increased sLOX-1 levels following PM inhalation to a much larger population and at ambient concentrations. In light of its known mechanistic role in promoting vascular disease, sLOX-1 may be a suitable translational biomarker linking air pollutant exposures and cardiovascular outcomes.

Vehicle emissions-exposure alters expression of systemic and tissue-specific components of the renin-angiotensin system and promotes outcomes associated with cardiovascular disease and obesity in wild-type C57BL/6 male mice

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Vehicle emission-exposure increases systemic and adipose renin-angiotensin signaling.

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Emission-exposure promotes renal, vascular, and adipocyte AT1 receptor expression.

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Diet and emission-exposure are associated with adipocyte hypertrophy and weight gain.

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Emission-exposure promotes expression of adipokines and adipose inflammatory factors.

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High-fat diet promotes an obese adipose phenotype, exacerbated by emission-exposure.

Exposure to air pollution from traffic-generated sources is known to contribute to the etiology of inflammatory diseases, including cardiovascular disease (CVD) and obesity; however, the signaling pathways involved are still under investigation. Dysregulation of the renin-angiotensin system (RAS) can contribute to CVD and alter lipid storage and inflammation in adipose tissue. Our previous exposure studies revealed that traffic-generated emissions increase RAS signaling, further exacerbated by a high-fat diet. Thus, we investigated the hypothesis that exposure to engine emissions increases systemic and local adipocyte RAS signaling, promoting the expression of factors involved in CVD and obesity. Male C57BL/6 mice (6–8 wk old) were fed either a high-fat (HF, n = 16) or low-fat (LF, n = 16) diet, beginning 30d prior to exposures, and then exposed via inhalation to either filtered air (FA, controls) or a mixture of diesel engine + gasoline engine vehicle emissions (MVE: 100 μg PM/m³) via whole-body inhalation for 6 h/d, 7 d/wk, 30d. Endpoints were assessed via immunofluorescence and RT-qPCR. MVE-exposure promoted vascular adhesion factors (VCAM-1, ICAM-1) expression, monocyte/macrophage sequestration, and oxidative stress in the vasculature, associated with increased angiotensin II receptor type 1 (AT1) expression. In the kidney, MVE-exposure promoted the expression of renin, AT1, and AT2 receptors. In adipose tissue, both HF-diet and MVE-exposure mediated increased epididymal fat pad weight and adipocyte hypertrophy, associated with increased angiotensinogen and AT1 receptor expression; however, these outcomes were further exacerbated in the MVE + HF group. MVE-exposure also induced inflammation, monocyte chemoattractant protein (MCP)-1, and leptin, while reducing insulin receptor and glucose transporter, GLUT4, expression in adipose tissue. Our results indicate that MVE-exposure promotes systemic and local adipose RAS signaling, associated with increased expression of factors contributing to CVD and obesity, further exacerbated by HF diet consumption.

Traffic generated emissions alter the lung microbiota by promoting the expansion of Proteobacteria in C57Bl/6 mice placed on a high-fat diet

Air pollution has been documented to contribute to severe respiratory diseases like asthma and chronic obstructive pulmonary disorder (COPD). Although these diseases demonstrate a shift in the lung microbiota towards Proteobacteria, the effects of traffic generated emissions on lung microbiota profiles have not been well-characterized. Thus, we investigated the hypothesis that exposure to traffic-generated emissions can alter lung microbiota and immune defenses. Since a large population of the Western world consumes a diet rich in fats, we sought to investigate the synergistic effects of mixed vehicle emissions and high-fat diet consumption. We exposed 3-month-old male C57Bl/6 mice placed either on regular chow (LF) or a high-fat (HF: 45% kcal fat) diet to mixed emissions (ME: 30 µg PM/m³ gasoline engine emissions+70 µg PM/m³ diesel engine emissions) or filtered air (FA) for 6 h/d, 7 d/wk for 30 days. Levels of pulmonary immunoglobulins IgA, IgG, and IgM were analyzed by ELISA, and lung microbial profiling was done using qPCR and Illumina 16 S sequencing. We observed a significant decrease in lung IgA in the ME-exposed animals, compared to the FA-exposed animals, both fed a HF diet. Our results also revealed a significant decrease in lung IgG in the ME-exposed animals both on the LF diet and HF diet, in comparison to the FA-exposed animals. We also observed an expansion of Enterobacteriaceae belonging to the Proteobacteria phylum in the ME-exposed groups on the HF diet. Collectively, we show that the combined effects of ME and HF diet result in decreased immune surveillance and lung bacterial dysbiosis, which is of significance in lung diseases.

A mechanistic view on the neurotoxic effects of air pollution on central nervous system: risk for autism and neurodegenerative diseases

Many reports have shown a strong association between exposure to neurotoxic air pollutants like heavy metal and particulate matter (PM) as an active participant and neurological disorders. While the effects of these toxic pollutants on cardiopulmonary morbidity have principally been studied, growing evidence has shown that exposure to polluted air is associated with memory impairment, communication deficits, and anxiety/depression among all ages. So, these toxic pollutants in the environment increase the risk of neurodegenerative disease, ischemia, and autism spectrum disorders (ASD). The precise mechanisms in which air pollutants lead to communicative inability, social inability, and declined cognition have remained unknown. Various animal model studies show that amyloid precursor protein (APP), processing, oxidant/antioxidant balance, and inflammation pathways change following the exposure to constituents of polluted air. In the present review study, we collect the probable molecular mechanisms of deleterious CNS effects in response to various air pollutants.

Exposure to traffic-generated air pollution promotes alterations in the integrity of the brain microvasculature and inflammation in female ApoE-/- mice

Traffic-generated air pollutants have been correlated with alterations in blood-brain barrier (BBB) integrity, which is associated with pathologies in the central nervous system (CNS). Much of the existing literature investigating the effects of air pollution in the CNS has predominately been reported in males, with little known regarding the effects in females. As such, this study characterized the effects of inhalation exposure to mixed vehicle emissions (MVE), as well as the presence of female sex hormones, in the CNS of female ApoE^-/- mice, which included cohorts of both ovariectomized (ov-) and ovary-intact (ov+) mice. Ov + and ov- were placed on a high-fat diet and randomly grouped to be exposed to either filtered-air (FA) or MVE (200 PM/m³: 50 μg PM/m³ gasoline engine + 150 μg PM/m³ from diesel engine emissions) for 6 h/d, 7d/wk, for 30d. MVE-exposure resulted in altered cerebral microvascular integrity and permeability, as determined by the decreased immunofluorescent expression of tight junction (TJ) proteins, occludin, and claudin-5, and increased IgG extravasation into the cerebral parenchyma, compared to FA controls, regardless of ovary status. Associated with the altered cerebral microvascular integrity, we also observed an increase in matrix metalloproteinases (MMPs) -2/9 activity in the MVE ov+, MVE ov-, and FA ov- groups, compared to FA ov+. There was also elevated expression of intracellular adhesion molecule (ICAM)-1, inflammatory interleukins (IL-1, IL-1β), and tumor necrosis factor (TNF-α) mRNA in the cerebrum of MVE ov + and MVE ov- animals. IκB kinase (IKK) subunits IKKα and IKKβ mRNA expressions were upregulated in the cerebrum of MVE ov- and FA ov- mice. Our findings indicate that MVE exposure mediates altered integrity of the cerebral microvasculature correlated with increased MMP-2/9 activity and inflammatory signaling, regardless of female hormones present.

Exposure to Traffic-Generated Pollutants Exacerbates the Expression of Factors Associated with the Pathophysiology of Alzheimer’s Disease in Aged C57BL/6 Wild-Type Mice

Background: Multiple studies report a strong correlation between traffic-generated air pollution-exposure and detrimental outcomes in the central nervous system (CNS), including Alzheimer’s disease (AD). Incidence of AD is rapidly increasing and, worldwide, many live in regions where pollutants exceed regulatory standards. Thus, it is imperative to identify environmental pollutants that contribute to AD, and the mechanisms involved. Objective: We investigated the effects of mixed gasoline and diesel engine emissions (MVE) on the expression of factors involved in progression of AD in the hippocampus and cerebrum in a young versus aged mouse model. Methods: Young (2 months old) and aged (18 months old) male C57BL/6 mice were exposed to either MVE (300μg/m3 PM) or filtered air (FA) for 6 h/d, 7 d/wk, for 50 d. Immunofluorescence and RT-qPCR were used to quantify oxidative stress (8-OHdG) and expression of amyloid-β protein precursor (AβPP), β secretase (BACE1), amyloid-β (Aβ), aryl hydrocarbon receptor (AhR), cytochrome P450 (CYP) 1B1, angiotensin-converting enzyme (ACE1), and angiotensin II type 1 (AT1) receptor in the cerebrum and hippocampus, in addition to cerebral microvascular tight junction (TJ) protein expression. Results: We observed age-related increases in oxidative stress, AhR, CYP1B1, Aβ, BACE1, and AT1 receptor in the CA1 region of the hippocampus, and elevation of cerebral AβPP, AhR, and CYP1B1 mRNA, associated with decreased cerebral microvascular TJ protein claudin-5. MVE-exposure resulted in further promotion of oxidative stress, and significant increases in AhR, CYP1B1, BACE1, ACE1, and Aβ, compared to the young and aged FA-exposed mice. Conclusion: Such findings suggest that MVE-exposure exacerbates the expression of factors in the CNS associated with AD pathogenesis in aged populations.

Neuropathology changed by 3- and 6-months low-level PM2.5 inhalation exposure in spontaneously hypertensive rats

BACKGROUND

Epidemiological evidence has linked fine particulate matter (PM2.5) to neurodegenerative diseases; however, the toxicological evidence remains unclear. The objective of this study was to investigate the effects of PM2.5 on neuropathophysiology in a hypertensive animal model. We examined behavioral alterations (Morris water maze), lipid peroxidation (malondialdehyde (MDA)), tau and autophagy expressions, neuron death, and caspase-3 levels after 3 and 6 months of whole-body exposure to urban PM2.5 in spontaneously hypertensive (SH) rats.

RESULTS

SH rats were exposed to S-, K-, Si-, and Fe-dominated PM2.5 at 8.6 ± 2.5 and 10.8 ± 3.8 μg/m3 for 3 and 6 months, respectively. We observed no significant alterations in the escape latency, distance moved, mean area crossing, mean time spent, or mean swimming velocity after PM2.5 exposure. Notably, levels of MDA had significantly increased in the olfactory bulb, hippocampus, and cortex after 6 months of PM2.5 exposure (p < 0.05). We observed that 3 months of exposure to PM2.5 caused significantly higher expressions of t-tau and p-tau in the olfactory bulb (p < 0.05) but not in other brain regions. Beclin 1 was overexpressed in the hippocampus with 3 months of PM2.5 exposure, but significantly decreased in the cortex with 6 months exposure to PM2.5. Neuron numbers had decreased with caspase-3 activation in the cerebellum, hippocampus, and cortex after 6 months of PM2.5 exposure.

CONCLUSIONS

Chronic exposure to low-level PM2.5 could accelerate the development of neurodegenerative pathologies in subjects with hypertension.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

NLRP3 Inflammasome: A Potential Therapeutic Target in Fine Particulate Matter-Induced Neuroinflammation in Alzheimer's Disease

As one of the most harmful air pollutants, fine particulate matter (PM2.5) has been implicated as a risk factor for multiple diseases, which has generated widespread public concern. Accordingly, a growing literature links PM2.5 exposure with Alzheimer's disease (AD). A critical gap in our understanding of the adverse effects of PM2.5 on AD is the mechanism triggered by PM2.5 that contributes to disease progression. Recent evidence has demonstrated that PM2.5 can activate NLRP3 inflammasome-mediated neuroinflammation. In this review, we highlight the novel evidence between PM2.5 exposure and AD incidence, which is collected and summarized from neuropathological, epidemiological, and neuroimaging studies to in-depth deciphering molecular mechanisms. First, neuropathological, epidemiological, and neuroimaging studies will be summarized. Then, the transport pathway for central nervous system delivery of PM2.5 will be presented. Finally, the role of NLRP3 inflammasome-mediated neuroinflammation in PM2.5 induced-effects on AD will be recapitulated.

Pathogenic Role of Air Pollution Particulate Matter in Cardiometabolic Disease: Evidence from Mice and Humans

Significance: Air pollution is a considerable global threat to human health that dramatically increases the risk for cardiovascular pathologies, such as atherosclerosis, myocardial infarction, and stroke. An estimated 4.2 million cases of premature deaths worldwide are attributable to outdoor air pollution. Among multiple other components, airborne particulate matter (PM) has been identified as the major bioactive constituent in polluted air. While PM-related illness was historically thought to be confined to diseases of the respiratory system, overwhelming clinical and experimental data have now established that acute and chronic exposure to PM causes a systemic inflammatory and oxidative stress response that promotes cardiovascular disease. Recent Advances: A large body of evidence has identified an impairment of redox metabolism and the generation of oxidatively modified lipids and proteins in the lung as initial tissue response to PM. In addition, the pathogenicity of PM is mediated by an inflammatory response that involves PM uptake by tissue-resident immune cells, the activation of proinflammatory pathways in various cell types and organs, and the release of proinflammatory cytokines as locally produced tissue response signals that have the ability to affect organ function in a remote manner. Critical Issues: In the present review, we summarize and discuss the functional participation of PM in cardiovascular pathologies and its risk factors with an emphasis on how oxidative stress, inflammation, and immunity interact and synergize as a response to PM. Future Directions: The impact of PM constituents, doses, and novel anti-inflammatory therapies against PM-related illness is also discussed.

Mixed Vehicle Emissions Induces Angiotensin II and Cerebral Microvascular Angiotensin Receptor Expression in C57Bl/6 Mice and Promotes Alterations in Integrity in a Blood-Brain Barrier Coculture Model

Exposure to traffic-generated pollution is associated with alterations in blood-brain barrier (BBB) integrity and exacerbation of cerebrovascular disorders. Angiotensin (Ang) II signaling through the Ang II type 1 (AT1) receptor is known to promote BBB disruption. We have previously reported that exposure to a mixture of gasoline and diesel vehicle engine emissions (MVE) mediates alterations in cerebral microvasculature of C57Bl/6 mice, which is exacerbated through consumption of a high-fat (HF) diet. Thus, we investigated the hypothesis that inhalation exposure to MVE results in altered central nervous system microvascular integrity mediated by Ang II-AT1 signaling. Three-month-old male C57Bl/6 mice were placed on an HF or low-fat diet and exposed via inhalation to either filtered air (FA) or MVE (100 μg/m3 PM) 6 h/d for 30 days. Exposure to HF+MVE resulted in a significant increase in plasma Ang II and expression of AT1 in the cerebral microvasculature. Results from a BBB coculture study showed that transendothelial electrical resistance was decreased, associated with reduced expression of claudin-5 and occludin when treated with plasma from MVE+HF animals. These effects were attenuated through pretreatment with the AT1 antagonist, Losartan. Our BBB coculture showed increased levels of astrocyte AT1 and decreased expression of aryl hydrocarbon receptor and glutathione peroxidase-1, associated with increased interleukin-6 and transforming growth factor-β in the astrocyte media, when treated with plasma from MVE-exposed groups. Our results indicate that inhalation exposure to traffic-generated pollutants results in altered BBB integrity, mediated through Ang II-AT1 signaling and inflammation, which is exacerbated by an HF diet.

Ambient Air Pollution Increases the Risk of Cerebrovascular and Neuropsychiatric Disorders through Induction of Inflammation and Oxidative Stress

Exposure to ambient air pollution is a well-established determinant of health and disease. The Lancet Commission on pollution and health concludes that air pollution is the leading environmental cause of global disease and premature death. Indeed, there is a growing body of evidence that links air pollution not only to adverse cardiorespiratory effects but also to increased risk of cerebrovascular and neuropsychiatric disorders. Despite being a relatively new area of investigation, overall, there is mounting recent evidence showing that exposure to multiple air pollutants, in particular to fine particles, may affect the central nervous system (CNS) and brain health, thereby contributing to increased risk of stroke, dementia, Parkinson's disease, cognitive dysfunction, neurodevelopmental disorders, depression and other related conditions. The underlying molecular mechanisms of susceptibility and disease remain largely elusive. However, emerging evidence suggests inflammation and oxidative stress to be crucial factors in the pathogenesis of air pollution-induced disorders, driven by the enhanced production of proinflammatory mediators and reactive oxygen species in response to exposure to various air pollutants. From a public health perspective, mitigation measures are urgent to reduce the burden of disease and premature mortality from ambient air pollution.

Reducing residual antibiotic levels in animal feces using intestinal Escherichia coli with surface-displayed erythromycin esterase

Antibiotics are widely used in livestock and poultry industries, which results in large quantities of antibiotic residues in manure that influences subsequent treatments. In this study, an Escherichia coli strain was engineered to display erythromycin esterase on its cell surface. The engineered strain (E. coli ereA) efficiently degraded erythromycin by opening the macrocyclic 14-membered lactone ring in solution. Erythromycin (50 mg/L) was completely degraded in a solution by E. coli ereA (1 × 10⁹ CFU/mL) within 24 h. E. coli ereA retained over 86.7 % of the initial enzyme activity after 40 days of storage at 25 °C, and 78.5 % of the initial activity after seven repeated batch reactions in solution at 25 °C. Mice were fed with E. coli ereA and real-time quantitative PCR data showed that E. coli ereA colonized in the mice large intestine. The mice group fed E. coli ereA exhibited 83.13 % decrease in erythromycin levels in their feces compared with the mice group not fed E. coli ereA. E. coli ereA eliminated antibiotics from the source preventing its release into the environment. The surface-engineered strain therefore is an effective alternative agent for treating recalcitrant antibiotics, and has the potential to be applied in livestock and poultry industries.

Effects of inhaled air pollution on markers of integrity, inflammation, and microbiota profiles of the intestines in Apolipoprotein E knockout mice

Air pollution exposure is known to contribute to the progression of cardiovascular disease (CVD) and there is increasing evidence that dysbiosis of the gut microbiome may also play a role in the pathogenesis of CVD, including atherosclerosis. To date, the effects of inhaled air pollution mixtures on the intestinal epithelial barrier (IEB), and microbiota profiles are not well characterized, especially in susceptible individuals with comorbidity. Thus, we investigated the effects of inhaled ubiquitous air-pollutants, wood-smoke (WS) and mixed diesel and gasoline vehicle exhaust (MVE) on alterations in the expression of markers of integrity, inflammation, and microbiota profiles in the intestine of atherosclerotic Apolipoprotein E knockout (ApoE^-/-) mice. To do this, male 8 wk-old ApoE^-/- mice, on a high-fat diet, were exposed to either MVE (300 μg/m³ PM), WS; (∼450 μg/m³ PM), or filtered air (FA) for 6 h/d, 7 d/wk, for 50 d. Immunofluorescence and RT-PCR were used to quantify the expression of IEB components and inflammatory factors, including mucin (Muc)-2, tight junction (TJ) proteins, matrix metalloproteinase (MMP)-9, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β, as well as Toll-like receptor (TLR)-4. Microbial profiling of the intestine was done using Illumina 16S sequencing of V4 16S rRNA PCR amplicons. We observed a decrease in intestinal Muc2 and TJ proteins in both MVE and WS exposures, compared to FA controls, associated with a significant increase in MMP-9, TLR-4, and inflammatory marker expression. Both WS and MVE-exposure resulted in decreased intestinal bacterial diversity, as well as alterations in microbiota profiles, including the Firmicutes: Bacteroidetes ratio at the phylum level. Our findings suggest inhalation exposure to either MVE or WS result in alterations in components involved in mucosal integrity, and also microbiota profiles and diversity, which are associated with increased markers of an inflammatory response.

Susceptibility Variations in Air Pollution Health Effects: Incorporating Neuroendocrine Activation

Diverse host factors/phenotypes may exacerbate or diminish biological responses induced by air pollutant exposure. We lack an understanding of biological indicators of environmental exposures that culminate in a physiological response versus those that lead to adversity. Variations in response phenotype might arise centrally and/or at the local tissue level. In addition to genetic differences, the current evidence supports the roles of preexisting cardiopulmonary diseases, diabetes, diet, adverse prenatal environments, neurobehavioral disorders, childhood infections, microbiome, sex, and psychosocial stressors in modifying the susceptibility to air pollutant exposures. Animal models of human diseases, obesity, nutritional inadequacies, and neurobehavioral conditions have been compared with healthy controls to understand the causes of variations in susceptibility. Although psychosocial stressors have been associated with increased susceptibility to air pollutant effects, the contribution of neuroendocrine stress pathways in mediating these effects is just emerging. The new findings of neuroendocrine activation leading to systemic metabolic and immunological effects of air pollutants, and the potential contribution to allostatic load, emphasize the consideration of these mechanisms into susceptibility. Variations in susceptibility to air pollution health effects are likely to underlie host genetic and physiological conditions in concert with disrupted neuroendocrine circuitry that alters physiological stability under the influence of stressors.

Blood-brain barrier function, cell viability, and gene expression of tight junction-associated proteins in the mouse are disrupted by crude oil, benzo[a]pyrene, and the dispersant COREXIT

Exposure to crude oil, its components, and oil dispersants during a major crude oil spill, such as the Deepwater Horizon Oil Spill, can elicit behavioral changes in animals and humans. However, the underlying mechanisms by which oil spill-related compounds alters behavior remains largely unknown. A major cause of behavioral changes generally is dysfunction of the blood-brain barrier (BBB). We investigated the impact of a crude oil high energy water accommodated fraction (HEWAF), benzo[a] pyrene (BaP; a major component of crude oil), and the oil dispersant COREXIT, on BBB function. BBB function was assessed by measuring transendothelial electrical resistance (TEER) of mouse brain microvascular endothelial cells (BMECs). Within 3 h after treatment, TEER was significantly reduced by exposure to high concentrations of all test compounds. TEER remained reduced in response to COREXIT after 48 h, but this effect waned in BMECs treated with HEWAF and BaP, with low-mid range concentrations inducing increased TEER compared to vehicle controls. At 48 h of treatment, BMEC viability was significantly reduced in response to 2% HEWAF, but was increased in response to BaP (25 and 50 μM). BMEC viability was increased with 80 ppm COREXIT, but was reduced with 160 ppm. Gene expression of tight junction-associated proteins (claudin-5 and tight junction protein-1), and cell adhesion receptor (vascular cell adhesion molecule-1) was reduced in response to HEWAF and COREXIT, but not BaP. Taken together, these data suggest that oil spill-related compounds markedly affect BBB function, and that these changes may underlie the observed behavioral changes due to crude oil exposure.

Neuroendocrine Regulation of Air Pollution Health Effects: Emerging Insights

Air pollutant exposures are linked to cardiopulmonary diseases, diabetes, metabolic syndrome, neurobehavioral conditions, and reproductive abnormalities. Significant effort is invested in understanding how pollutants encountered by the lung might induce effects in distant organs. The role of circulating mediators has been predicted; however, their origin and identity have not been confirmed. New evidence has emerged which implicates the role of neuroendocrine sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) stress axes in mediating a wide array of systemic and pulmonary effects. Our recent studies using ozone exposure as a prototypical air pollutant demonstrate that increases in circulating adrenal-derived stress hormones (epinephrine and cortisol/corticosterone) contribute to lung injury/inflammation and metabolic effects in the liver, pancreas, adipose, and muscle tissues. When stress hormones are depleted by adrenalectomy in rats, most ozone effects including lung injury/inflammation are diminished. Animals treated with antagonists for adrenergic and glucocorticoid receptors show inhibition of the pulmonary and systemic effects of ozone, whereas treatment with agonists restore and exacerbate the ozone-induced injury/inflammation phenotype, implying the role of neuroendocrine activation. The neuroendocrine system is critical for normal homeostasis and allostatic activation; however, chronic exposure to stressors may lead to increases in allostatic load. The emerging mechanisms by which circulating mediators are released and are responsible for producing multiorgan effects of air pollutants insists upon a paradigm shift in the field of air pollution and health. Moreover, since these neuroendocrine responses are linked to both chemical and nonchemical stressors, the interactive influence of air pollutants, lifestyle, and environmental factors requires further study.

LOX-1 and atherosclerotic-related diseases

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a scavenger receptor of oxidized low-density lipoprotein (ox-LDL) found in various cells, plays a crucial role in the formation and progression of atherosclerotic plaques. Animal studies have suggested that LOX-1 mediates the balance between internalization and degeneration of endothelial cells, thereby contributing to various steps in the atherosclerotic process, from initiation to plaque rupture. Under pathological conditions, the extracellular domain of membrane bound LOX-1 can be largely proteolytically cleaved into a soluble form (sLOX-1), which is proportional and linked to the LOX-1 expression level. Circulating levels of sLOX-1 are regarded as a risk biomarker for plaque rupture and acute coronary syndrome (ACS). Recently, studies have shown that sLOX-1 is also elevated in patients with acute stroke and can be a predictive biomarker for acute stroke. With the discovery of the vital role of LOX-1 in atherosclerosis, there is growing focus on the influence of LOX-1 in atherosclerotic-related diseases, including coronary arterial disease(CAD), stroke, and other cardiovascular events. Genetic polymorphisms of LOX-1 have been investigated and have been found to modulate the risk of these diseases. Most polymorphisms have been found to be risk factors, except for the splicing isoform LOXIN. This review concludes with a discussion of the potential future applications of LOX-1 for atherosclerotic-related diseases.

Chronic pulmonary exposure to traffic-related fine particulate matter causes brain impairment in adult rats

BACKGROUND

Effects of air pollution on neurotoxicity and behavioral alterations have been reported. The objective of this study was to investigate the pathophysiology caused by particulate matter (PM) in the brain. We examined the effects of traffic-related particulate matter with an aerodynamic diameter of < 1 μm (PM₁), high-efficiency particulate air (HEPA)-filtered air, and clean air on the brain structure, behavioral changes, brainwaves, and bioreactivity of the brain (cortex, cerebellum, and hippocampus), olfactory bulb, and serum after 3 and 6 months of whole-body exposure in 6-month-old Sprague Dawley rats.

RESULTS

The rats were exposed to 16.3 ± 8.2 (4.7~ 68.8) μg/m³ of PM₁ during the study period. An MRI analysis showed that whole-brain and hippocampal volumes increased with 3 and 6 months of PM₁ exposure. A short-term memory deficiency occurred with 3 months of exposure to PM₁ as determined by a novel object recognition (NOR) task, but there were no significant changes in motor functions. There were no changes in frequency bands or multiscale entropy of brainwaves. Exposure to 3 months of PM₁ increased 8-isoporstance in the cortex, cerebellum, and hippocampus as well as hippocampal inflammation (interleukin (IL)-6), but not in the olfactory bulb. Systemic CCL11 (at 3 and 6 months) and IL-4 (at 6 months) increased after PM₁ exposure. Light chain 3 (LC3) expression increased in the hippocampus after 6 months of exposure. Spongiosis and neuronal shrinkage were observed in the cortex, cerebellum, and hippocampus (neuronal shrinkage) after exposure to air pollution. Additionally, microabscesses were observed in the cortex after 6 months of PM₁ exposure.

CONCLUSIONS

Our study first observed cerebral edema and brain impairment in adult rats after chronic exposure to traffic-related air pollution.

Chronic pulmonary exposure to traffic-related fine particulate matter causes brain impairment in adult rats

Background

Effects of air pollution on neurotoxicity and behavioral alterations have been reported. The objective of this study was to investigate the pathophysiology caused by particulate matter (PM) in the brain. We examined the effects of traffic-related particulate matter with an aerodynamic diameter of < 1 μm (PM₁), high-efficiency particulate air (HEPA)-filtered air, and clean air on the brain structure, behavioral changes, brainwaves, and bioreactivity of the brain (cortex, cerebellum, and hippocampus), olfactory bulb, and serum after 3 and 6 months of whole-body exposure in 6-month-old Sprague Dawley rats.

Results

The rats were exposed to 16.3 ± 8.2 (4.7~ 68.8) μg/m³ of PM₁ during the study period. An MRI analysis showed that whole-brain and hippocampal volumes increased with 3 and 6 months of PM₁ exposure. A short-term memory deficiency occurred with 3 months of exposure to PM₁ as determined by a novel object recognition (NOR) task, but there were no significant changes in motor functions. There were no changes in frequency bands or multiscale entropy of brainwaves. Exposure to 3 months of PM₁ increased 8-isoporstance in the cortex, cerebellum, and hippocampus as well as hippocampal inflammation (interleukin (IL)-6), but not in the olfactory bulb. Systemic CCL11 (at 3 and 6 months) and IL-4 (at 6 months) increased after PM₁ exposure. Light chain 3 (LC3) expression increased in the hippocampus after 6 months of exposure. Spongiosis and neuronal shrinkage were observed in the cortex, cerebellum, and hippocampus (neuronal shrinkage) after exposure to air pollution. Additionally, microabscesses were observed in the cortex after 6 months of PM₁ exposure.

Conclusions

Our study first observed cerebral edema and brain impairment in adult rats after chronic exposure to traffic-related air pollution.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0281-1) contains supplementary material, which is available to authorized users.

An air quality index-based multistage type-2-fuzzy interval-stochastic programming model for energy and environmental systems management under multiple uncertainties

In this study, a multistage type-2-fuzzy interval-stochastic programming (MTIP) method is developed, which extends upon the existing multistage stochastic programming (MSP) by allowing uncertainties expressed as probabilistic distributions, interval values and type-2 fuzzy sets to be effectively incorporated within the optimization framework. Through coupling air quality index (AQI) with MTIP, an AQI-MTIP model is formulated for energy and environmental systems (EES) management of Tianjin. A number of scenarios based on changed AQIs are examined to analyze the impacts of environmental requirements on the city's energy system. Results indicate that (i) with the improvement of environmental requirement, utilization of clean energies (especially natural gas) is provoked markedly; (ii) PM_2.5 is the primary pollutant, 64.50% of which should be reduced each period to maintain the city's air quality at a health-safe level. These findings can help decision makers adjust energy structure, make effective mitigation strategy, and gain deep insight into the relationship between energy consumption and environmental requirement.

In utero exposure to fine particulate matter results in an altered neuroimmune phenotype in adult mice

Environmental exposure to air pollution has been linked to a number of health problems including organ rejection, lung damage and inflammation. While the deleterious effects of air pollution in adult animals are well documented, the long-term consequences of particulate matter (PM) exposure during animal development are uncertain. In this study we tested the hypothesis that environmental exposure to PM 2.5 μm in diameter in utero promotes long term inflammation and neurodegeneration. We evaluated the behavior of PM exposed animals using several tests and observed deficits in spatial memory without robust changes in anxiety-like behavior. We then examined how this affects the brains of adult animals by examining proteins implicated in neurodegeneration, synapse formation and inflammation by western blot, ELISA and immunohistochemistry. These tests revealed significantly increased levels of COX2 protein in PM2.5 exposed animal brains in addition to changes in synaptophysin and Arg1 proteins. Exposure to PM2.5 also increased the immunoreactivity for GFAP, a marker of activated astrocytes. Cytokine concentrations in the brain and spleen were also altered by PM2.5 exposure. These findings indicate that in utero exposure to particulate matter has long term consequences which may affect the development of both the brain and the immune system in addition to promoting inflammatory change in adult animals.