The role of pro-/anti-inflammation imbalance in Aβ42 accumulation of rat brain co-exposed to fine particle matter and sulfur dioxide

Neurotoxicity of fine and ultrafine particulate matter: A comprehensive review using a toxicity pathway-oriented adverse outcome pathway framework

Fine particulate matter (PM2.5) can cause brain damage and diseases. Of note, ultrafine particles (UFPs) with an aerodynamic diameter less than or equal to 100 nm are a growing concern. Evidence has suggested toxic effects of PM2.5 and UFPs on the brain and links to neurological diseases. However, the underlying mechanism has not yet been fully illustrated due to the variety of the study models, different endpoints, etc. The adverse outcome pathway (AOP) framework is a pathway-based approach that could systematize mechanistic knowledge to assist health risk assessment of pollutants. Here, we constructed AOPs by collecting molecular mechanisms in PM-induced neurotoxicity assessments. We chose particulate matter (PM) as a stressor in the Comparative Toxicogenomics Database (CTD) and identified the critical toxicity pathways based on Ingenuity Pathway Analysis (IPA). We found 65 studies investigating the potential mechanisms linking PM2.5 and UFPs to neurotoxicity, which contained 2, 675 genes in all. IPA analysis showed that neuroinflammation signaling and glucocorticoid receptor signaling were the common toxicity pathways. The upstream regulator analysis (URA) of PM2.5 and UFPs demonstrated that the neuroinflammation signaling was the most initially triggered upstream event. Therefore, neuroinflammation was recognized as the MIE. Strikingly, there is a clear sequence of activation of downstream signaling pathways with UFPs, but not with PM2.5. Moreover, we found that inflammation response and homeostasis imbalance were key cellular events in PM2.5 and emphasized lipid metabolism and mitochondrial dysfunction, and blood-brain barrier (BBB) impairment in UFPs. Previous AOPs, which only focused on phenotypic changes in neurotoxicity upon PM exposure, we for the first time propose AOP framework in which PM2.5 and UFPs may activate pathway cascade reactions, resulting in adverse outcomes associated with neurotoxicity. Our toxicity pathway-based approach not only advances risk assessment for PM-induced neurotoxicity but shines a spotlight on constructing AOP frameworks for new chemicals.

Early-life exposure to ambient air pollutants and kidney function in adolescents: a cohort study based on the 'Children of 1997' Hong Kong birth cohort

OBJECTIVES

Air pollution is increasingly linked to impaired kidney function in adults. However, little is known about how early-life exposure to air pollutants affects kidney function in adolescents.

STUDY DESIGN

Cohort study.

METHODS

We leveraged data from the 'Children of 1997' Hong Kong population-representative birth cohort (N = 8327). Residential exposure to average ambient levels of four air pollutants, including inhalable particle (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and nitrogen monoxide (NO), during in utero, infancy, and childhood periods was estimated using the inverse distance weighting. Kidney function was assessed using estimated glomerular filtration rate (eGFR) calculated from age-adjusted equations for adolescents. Generalized linear regression was used to examine the association of air pollutant exposure in each period with kidney function at 17.6 years. Two-pollutant models tested the robustness of the association.

RESULTS

Of the 3350 participants included, 51.4% were boys. Exposure to PM10 was associated with poorer kidney function. Each interquartile range increment in PM10 was inversely associated with eGFR (β: -2.933, 95% confidence interval -4.677 to -1.189) in utero, -2.362 (-3.992 to -0.732) infancy, -2.708 (-4.370 to -1.047) childhood, and -2.828 (-4.409 to -1.247) overall. Exposure to PM10 and SO2in utero had a stronger inverse association with kidney function in males. The associations were robust to PM10 exposure in two-pollutant models.

CONCLUSIONS

Our findings suggest that early-life exposure to ambient PM10 and SO2 is associated with reduced kidney function in adolescents, especially exposure in utero.

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

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

Air pollution, depressive and anxiety disorders, and brain effects: A systematic review

Accumulating data suggest that air pollution increases the risk of internalizing psychopathology, including anxiety and depressive disorders. Moreover, the link between air pollution and poor mental health may relate to neurostructural and neurofunctional changes. We systematically reviewed the MEDLINE database in September 2021 for original articles reporting effects of air pollution on 1) internalizing symptoms and behaviors (anxiety or depression) and 2) frontolimbic brain regions (i.e., hippocampus, amygdala, prefrontal cortex). One hundred and eleven articles on mental health (76% human, 24% animals) and 92 on brain structure and function (11% human, 86% animals) were identified. For literature search 1, the most common pollutants examined were PM2.5 (64.9%), NO2 (37.8%), and PM10 (33.3%). For literature search 2, the most common pollutants examined were PM2.5 (32.6%), O3 (26.1%) and Diesel Exhaust Particles (DEP) (26.1%). The majority of studies (73%) reported higher internalizing symptoms and behaviors with higher air pollution exposure. Air pollution was consistently associated (95% of articles reported significant findings) with neurostructural and neurofunctional effects (e.g., increased inflammation and oxidative stress, changes to neurotransmitters and neuromodulators and their metabolites) within multiple brain regions (24% of articles), or within the hippocampus (66%), PFC (7%), and amygdala (1%). For both literature searches, the most studied exposure time frames were adulthood (48% and 59% for literature searches 1 and 2, respectively) and the prenatal period (26% and 27% for literature searches 1 and 2, respectively). Forty-three percent and 29% of studies assessed more than one exposure window in literature search 1 and 2, respectively. The extant literature suggests that air pollution is associated with increased depressive and anxiety symptoms and behaviors, and alterations in brain regions implicated in risk of psychopathology. However, there are several gaps in the literature, including: limited studies examining the neural consequences of air pollution in humans. Further, a comprehensive developmental approach is needed to examine windows of susceptibility to exposure and track the emergence of psychopathology following air pollution exposure.

Different components of air pollutants and neurological disorders

The harmful effects of air pollution can cause various diseases. Most research on the hazards of air pollution focuses on lung and cardiovascular diseases. In contrast, the impact of air pollution on neurological disorders is not widely recognized. Air pollution can cause various neurological conditions and diseases, such as neural inflammation, neurodegeneration, and cerebrovascular barrier disorder; however, the mechanisms underlying the neurological diseases induced by various components of air pollutants remain unclear. The present paper summarizes the effects of different components of air pollutants, including particulate matter, ozone, sulfur oxides, carbon oxides, nitrogen oxides, and heavy metals, on the nervous system and describes the impact of various air pollutants on neurological disorders, providing ideas for follow-up research.

Association between gaseous air pollutants and idiopathic nephrotic syndrome in children: a 12-year population-based cohort study

Background

To date, there is insufficient knowledge about the association of air pollution and childhood nephrotic syndrome in the real world. This study aimed to evaluate the effects of the three common gaseous air pollutants, including sulfur dioxide, total hydrocarbon, and methane, on the risk of idiopathic nephrotic syndrome (INS) in children.

Methods

We collected data from the Taiwan National Health Insurance Research Database and Taiwan Air Quality-Monitoring Database. Children younger than 18 years old, identified from January 1, 2000, were followed up until the first diagnosis of INS was established or until December 31, 2012. We measured the incidence rates and hazard ratios for INS stratified based on the quartiles (Q1–Q4) of air pollutant concentration. Multivariate Cox proportional hazards models were also applied by adjusting age, sex, monthly income, and urbanization.

Results

Compared with participants exposed to Q1 concentrations, the adjusted hazard ratios (aHRs) for INS increased progressively along the four quartiles of sulfur dioxide, total hydrocarbon, and methane, from 1 (Q1) to 1.78 (Q4), 1 (Q1) to 3.49 (Q4), 1 (Q1) to 7.83 (Q4), respectively.

Conclusions

Our study revealed that children with exposure to higher concentrations of sulfur dioxide, total hydrocarbon, and methane was associated with an increased risk of INS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-022-01269-8.

Short-term exposure to ambient air pollution and risk of daily hospital admissions for anxiety in China: A multicity study

The potential impact of short-term exposure to ambient air pollution on risk of anxiety remains uncertain. We performed a detailed evaluation based on data from national insurance databases in China. Daily hospital admissions for anxiety disorders were identified in 2013-2017 from the national insurance databases covering up to 261 million urban residents in 56 cities in China. A two-stage time-series study was conducted to evaluate the associations between short-term exposure to major ambient air pollutants, including fine particles, inhalable particles, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone, and carbon monoxide, and risk of daily hospital admissions for anxiety. Significant associations between short-term exposures to ambient NO₂ and SO₂ and risk of daily hospital admissions for anxiety were found in the overall analysis. Per 10 μg/m³ increases in NO₂ at lag0 and SO₂ at lag6 were associated with significant increases of 1.37% (95% CI: 0.14%, 2.62%) and 1.53% (95% CI: 0.59%, 2.48%) in anxiety admissions, respectively. Stronger associations were found in the southern region and patients <65 years for SO₂. Short-term exposure to ambient air pollution is associated with increased risk of anxiety admissions, which may provide important implications for promotion of mental health in the public.

Impact of Long-Term Exposure to Air Pollution on Cognitive Decline in Older Adults Without Dementia

Background: Air pollution control is necessary to decrease the burden on older adults with cognitive impairment, especially in low- and middle-income countries (LMICs). Objective: This study retrospectively examined the effect of cumulative exposure to air pollution, including NO2, SO2, CO, fine particulate matter (PM)10, PM2.5, and O3, on cognitive function in older individuals. Methods: Community-dwelling older adults who underwent the Mini-Mental State Examination (MMSE) from 2007 to 2018 were included in the analyses. We excluded older individuals diagnosed with dementia at baseline, while those who had completed more than two MMSE tests were included in the longitudinal analyses. Baseline MMSE and changes in MMSE scores were analyzed according to 5-year average concentrations of the district-level air pollutants, after controlling for covariates associated with cognitive decline in older adults. Results: In total, 884,053 (74.3±7.1 years; 64.1% females) and 398,889 (72.3±6.4 years; 67.0% females) older individuals were included in the cross-sectional and longitudinal analyses, respectively. Older individuals exposed to higher levels of NO2, SO2, CO, and PM10 showed lower baseline MMSE scores. During follow-up, exposure to higher levels of NO2, SO2, CO, and PM10 was associated with greater decreases in MMSE scores in older individuals; for O3, the opposite pattern was observed. Conclusion: Our findings suggest that exposure to high levels of air pollutants can worsen the cognitive performance of older adults without dementia. Efforts to reduce air pollution in LMICs that have similar levels of pollutants to South Korea are necessary to reduce the burden on older adults with cognitive impairment.

Air Pollution and Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Ambient air pollution has been associated with Alzheimer's disease (AD) in the elderly. However, its effects on AD have not been meta-analyzed comprehensively.

OBJECTIVE

We conducted a systematic review and meta-analysis to assess the associations between air pollution and AD incidence.

METHODS

We searched PubMed and Web of Science for indexed publications up to March 2020. Odds risk (OR) and confidence intervals (CI) were estimated for particulate matter (PM)10 (PM10), PM2.5, ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). The subgroup analysis was conducted based on the pollution levels.

RESULTS

Nine studies were included in the meta-analysis and review. The OR per 10μg/m3 increase of PM2.5 was 1.95 (95% CI: 0.88-4.30). The corresponding values per 10μg/m3 increment of other pollutants were 1.03 (95% CI: 0.68-1.57) for O3, 1.00 (95% CI: 0.89-1.13) for NO2, and 0.95 (95% CI: 0.91-0.99) for PM10 (only one study), respectively. Overall OR of the five air pollutants above with AD was 1.32 (95% CI: 1.09-1.61), suggesting a positive association between ambient air pollution and AD incidence. The sub-analysis indicated that the OR (2.20) in heavily polluted regions was notably higher than that in lightly polluted regions (1.06). Although AD risk rate data related to SO2 or CO exposure are still limited, the epidemiologic and toxicological evidence indicated that higher concentration of SO2 or CO exposure increased risks of dementia, implying that SO2 or CO might have a potential impact on AD.

CONCLUSION

Air pollution exposure may exacerbate AD development.

Air Pollution Is Associated with Cognitive Deterioration of Alzheimer's Disease

INTRODUCTION

Dementia is one of the major causes of disability and dependency among older people worldwide. Alz-heimer's disease (AD), the most common cause of dementia among the elderly, has great impact on the health-care system of developed nations. Several risk factors are suggestive of an increased risk of AD, including APOE-ε4, male, age, diabetes mellitus, hypertension, and low social engagement. However, data on risk factors of AD progression are limited. Air pollution is revealed to be associated with increasing dementia incidence, but the relationship between air pollution and clinical AD cognitive deterioration is unclear.

METHODS

We conducted a case-control and city-to-city study to compare the progression of AD patients in different level of air-polluted cities. Clinical data of a total of 704 AD patients were retrospectively collected, 584 residences in Kaohsiung and 120 residences in Pingtung between 2002 and 2018. An annual interview was performed with each patient, and the Clinical Dementia Rating score (0 [normal] to 3 [severe stage]) was used to evaluate their cognitive deterioration. Air pollution data of Kaohsiung and Pingtung city for 2002-2018 were retrieved from Taiwan Environmental Protection Administration. Annual Pollutant Standards Index (PSI) and concentrations of particulate matter (PM10), sulfur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO) were obtained.

RESULTS

The PSI was higher in Kaohsiung and compared with Pingtung patients, Kaohsiung patients were exposed to higher average annual concentrations of CO, NO2, PM10, and SO2. AD patients living in Kaohsiung suffered from faster cognitive deterioration in comparison with Pingtung patients (log-rank test: p = 0.016). When using multivariate Cox proportional hazards regression analysis, higher levels of CO, NO2, PM10, and SO2 exposure were associated with increased risk of AD cognitive deterioration. Among all these air pollutants, high SO2 exposure has the greatest impact while O3 has a neutral effect on AD cognitive deterioration.

CONCLUSIONS

Air pollution is an environment-related risk factor that can be controlled and is associated with cognitive deterioration of AD. This finding could contribute to the implementation of public intervention strategies of AD.

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.

Identifying circRNA- and lncRNA-associated-ceRNA networks in the hippocampi of rats exposed to PM2.5 using RNA-seq analysis

Non-coding RNAs appear to be involved in the regulation of the nervous system. However, no competing endogenous RNA (ceRNA) network related to PM_2.5 damage in the hippocampal function has yet been constructed. Herein, we used whole-transcriptome sequencing technology to systematically study the ceRNA network in rat hippocampi after PM_2.5 exposure. We identified 100 circRNAs, 67 lncRNAs, 28 miRNAs, and 539 mRNAs and constructed the most comprehensive ceRNA network to date, to our knowledge. Gene Ontology and KEGG analyses showed that the network molecules are involved in synapses, neural projections, and neural development and involve signal pathways such as the synaptic vesicle cycle. Finally, the expression of the differentially expressed RNAs confirmed by quantitative real-time PCR was consistent with the sequencing data. This study systematically dissected the ceRNA atlas related to cognitive memory function in the hippocampal tissue of PM_2.5-exposed rats for the first time, to our knowledge, and promotes the development of potential new treatments for cognitive impairment.

Atmospheric nanoparticles affect vascular function using a 3D human vascularized organotypic chip

Inhaled atmospheric nanoparticles (ANPs) can migrate into human blood vessels. However, the exact pathogenesis has not yet been well elucidated. In this study, a perfusable 3D human microvessel network was constructed in a microfluidic device. This functional 3D micro-tissue partly mimicked the physiological response of human vessels. Intravascular nanoparticles tend to adsorb proteins to form a protein corona. Based on this pathological response, vessel permeability and vasoconstriction resulting from ANP stimulation might be related to vascular inflammation. It mediated abnormal expression of nuclear factor-κB (NF-κB) and an influx of intracellular Ca²⁺ ([Ca²⁺]i). This biological behavior disturbed the normal expression of intercellular cell adhesion molecule 1 (ICAM-1) and vascular endothelial growth factor (VEGF). The imbalance of nitric oxide (NO) and endothelin-1 (ET-1) further resulted in endothelial cell contraction. All these bio-events induced the loss of tight junctions (ZO-1) which enhanced vessel permeability. Meanwhile, ANP induced-vascular toxicity was also found in mice. Our observations provide a plausible explanation for how the ANPs affect human vascular function. The vessel-on-chip provides a bridge between in vitro results and human responses. We aimed to use this human 3D functional microvascular model to mimic the physiological responses of human vessels. This model is suitable for the evaluation of vascular toxicity after the human vessel exposure to ANPs.

Arsenic and sulfur dioxide co-exposure induce renal injury via activation of the NF-κB and caspase signaling pathway

Although emerging evidence suggests positive association of arsenic (As) or sulfur dioxide (SO₂) exposure with human diseases, reports concerning the effects of co-exposure of As and SO₂ are lacking. Moreover, there is insufficient information in the literature about As and SO₂ co-exposure to renal injury. In this study, we focus on the environmental problems of excessive As and SO₂ that co-exist in many coal consumption areas. We used both C57BL/6 mice and 293T cells to detect toxicities of As and SO₂ exposure alone or in combination. Our results showed that co-exposure significantly increased the hazard compared with exposure to As or SO₂ alone. Mouse kidney tissue slices showed that co-exposure caused more severe diffuse sclerosing glomerulonephritis than As and SO₂ exposure alone. Meanwhile experiments showed that apoptosis was aggravated by co-exposure of As and SO₂ in 293T cells. Because As and SO₂ cause cell toxicity through increasing oxidative stress, next we detected ROS and other oxidative stress parameters, and the results showed oxidative stress was increased by co-exposure compared with the other three groups. The expression levels of downstream genes in the NF-κB and caspase pathways were higher in the co-exposure group than in the groups of As or SO₂ exposure alone in mice and 293T cells. Based on the above results, co-exposure could induce higher toxicity in vitro and in vivo compared with single exposure to As or SO₂, indicating that people living in places that contaminated by As and SO₂ may have higher chance to get renal injury.

Integrated communications between cyclooxygenase-2 and Alzheimer's disease

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.

Effects of inhaled particulate matter on the central nervous system in mice

Little is known regarding the adverse effects of chronic particulate matter (PM) inhalation on the central nervous system (CNS). The present study aimed to examine how PM exposure impacts on oxidative stress and inflammatory processes, as well as the expression of interneurons and perineuronal nets (PNNs) in the CNS. BALB/c mice (6-week-old females, n = 32) were exposed to 1 to 5 μm size diesel-extracted particles (DEPs) (100 μg/m³, 5 d/week, 5 h/day) and categorized into the following four groups: 1) 4-week DEP (n = 8); 2) 4-week control (n = 8), 3) 8-week DEP (n = 8); and 4) 8-week control (n = 8). The olfactory bulb, prefrontal cortex, temporal cortex, striatum, and cerebellum were harvested from the animals in each group. The expression of antioxidants (heme oxygenase 1 [HO-1] and superoxide dismutase 2 [SOD-2]), and markers of the unfolded protein response (X-box binding protein [XBP]-1S), inflammation (tumor necrosis factor-alpha [TNF-α]), and proliferation (neurotrophin-3 and brain-derived neurotrophic factor [BDNF]) were measured using reverse transcription polymerase chain reaction (PCR) and Western blotting. The expression levels of HO-1, SOD-2, XBP-1S, TNF-α, neurotrophin-3, and BDNF were compared among groups using the Mann-Whitney U test. The temporal cortex was immunostained for parvalbumin (PV) and Wisteria floribunda agglutinin (WFA). The numbers of PV- and WFA-positive cells were counted using a confocal microscope and analyzed with the Mann-Whitney U test. HO-1 expression was elevated in the prefrontal cortex, temporal cortex, striatum, and cerebellum of mice in the 8-week DEP group compared with the control group. Expression of SOD-2 and XBP-1S was elevated in the prefrontal cortex and striatum of the 8-week DEP group compared with the control group. TNF-α expression was elevated in the prefrontal cortex, temporal cortex, striatum, and cerebellum in the 4- and 8-week DEP groups compared with the control group. Neurotrophin-3 expression was decreased in the olfactory bulb and striatum of the 8-week DEP group compared with the control group. WFA density was increased in the 8-week DEP group compared with the control group. The PV and PV + WFA densities were decreased in the 4-week DEP group compared with the control group. Chronic DEP inhalation activated oxidative stress and inflammation in multiple brain regions. Chronic DEP inhalation increased PNNs and decreased the number of interneurons, which may contribute to PM exposure-related CNS dysfunction.