Redox and inflammatory mechanisms linking air pollution particulate matter with cardiometabolic derangements

Synergistic Toxicity of Fine Particulate Matter and Ozone and Their Underlying Mechanisms

The co-occurrence of fine particulate matter (PM2.5) and ozone has emerged as a critical environmental challenge in recent years. The individual harmful impacts of PM2.5 and ozone exposure have been well studied; however, their combined toxicity under co-exposure conditions remains mechanistically undefined. This paper provides an extensive evaluation of the current pollution levels, epidemiological investigation, and new findings on the toxicological mechanisms of combined exposure to PM2.5 and ozone. The synergistic toxicity of PM2.5 and ozone depends on different factors, including the physicochemical properties of PM2.5, the dose and duration of exposure, and the specific target organs. Through extensive research, we identified the main targets of toxic responses to PM2.5 and ozone exposure and summarized their synergistic toxic mechanisms. Given the current research priorities, there is an urgent need to improve scientific research regarding PM2.5 and ozone co-exposure with priority given to characterizing their properties and toxicological responses while updating relevant guidelines and standards.

Environmentally persistent free radicals stimulate CYP2E1-mediated generation of reactive oxygen species at the expense of substrate metabolism

Environmentally persistent free radicals (EPFRs) are a recently recognized component of particulate matter that cause respiratory and cardiovascular toxicity. The mechanism of EPFR toxicity appears to be related to their ability to generate reactive oxygen species (ROS), causing oxidative damage. EPFRs were shown to affect cytochrome P450 (P450) function, inducing the expression of some forms through the Ah receptor. However, another characteristic of EPFRs is their ability to inhibit P450 activities. CYP2E1 is one of the P450s that is inhibited by EPFR (MCP230, the laboratory-generated EPFR made by heating silica 5% copper oxide, and silica [<0.2 μm in diameter] and 2-monochlorophenol at ≥230 °C) exposure. Because CYP2E1 is also known to generate ROS, it is important to understand the ability of EPFRs to influence the function of this enzyme and to identify the mechanisms involved. CYP2E1 was shown to be inhibited by EPFRs and to a lesser extent by non-EPFR particles. Because EPFR-mediated inhibition was more robust at subsaturating NADPH-P450 reductase (POR) concentrations, disruption of POR•CYP2E1 complex formation and electron transfer were examined. Surprisingly, neither complex formation nor electron transfer between POR and CYP2E1 was inhibited by EPFRs. Examination of ROS production showed that MCP230 generated a greater amount of ROS than the non-EPFR control particle (CuO-Si). When a POR/CYP2E1-containing reconstituted system was added to the pollutant-particle systems, there was a synergistic stimulation of ROS production. The results indicate that EPFRs cause inhibition of CYP2E1-mediated substrate metabolism, yet do not alter electron transfer and actually stimulate ROS generation. Taken together, the results are consistent with EPFRs affecting CYP2E1 function by inhibiting substrate metabolism and increasing the generation of ROS. SIGNIFICANCE STATEMENT: Environmentally persistent free radicals affect CYP2E1 function by inhibition of monooxygenase activity. This inhibition is not due to disruption of the POR•CYP2E1 complex or inhibition of electron transfer but due to the uncoupling of NADPH and oxygen consumption from substrate metabolism to the generation of reactive oxygen species. These results show that environmentally persistent free radicals block the metabolism of foreign compounds and synergistically stimulate the formation of reactive oxygen species that lead to oxidative damage within the organism.

Impact of the environmental pollution on cardiovascular diseases: From epidemiological to molecular evidence

Environmental pollution poses a significant threat to human health, particularly concerning its impact on cardiovascular diseases (CVDs). This review synthesizes epidemiological and molecular evidence to elucidate the intricate relationship between environmental pollutants and CVDs. Epidemiological studies highlight the association between exposure to air, water, and soil pollutants and increased CVD risk, including hypertension, coronary artery disease, and stroke. Furthermore, molecular investigations unravel the underlying mechanisms linking pollutant exposure to CVD pathogenesis, such as oxidative stress, inflammation, endothelial dysfunction, and autonomic imbalance. Understanding these molecular pathways is crucial for developing targeted interventions and policy strategies to mitigate the adverse effects of environmental pollution on cardiovascular health. By integrating epidemiological and molecular evidence, this review provides insights into the complex interplay between environmental factors and CVDs, emphasizing the urgent need for comprehensive preventive measures and environmental policies to safeguard public health.

The mediating effect of TyG-related indicators between long-term exposure to particulate matter and cardiovascular disease: evidence from a national longitudinal cohort study

BACKGROUND

Ambient particulate matter (PM) exposure is recognized as a risk factor for cardiovascular disease (CVD). However, the extent to which PM exposure is associated with CVD via triglyceride glucose (TyG)-related indicators remains unknown. This study examines the relationship between long-term PM exposure and CVD events, further assessing whether TyG-related indicators mediate this association.

METHODS

This cohort study involved 7,532 individuals aged at least 45 years who were not diagnosed with CVD in 2011 from the China Longitudinal Study of Health and Retirement (CHARLS) and were followed up for the occurrence of CVD until 2020. The annual PM concentration data at the city level, with aerodynamic diameters ≤ 1 μm (PM1), ≤ 2.5 μm (PM2.5), and ≤ 10 μm (PM10), were obtained from the ChinaHighAirPollutants (CHAP). The average concentration of PM in the 3 years before the baseline survey in 2011 was defined as the long-term exposure level of the individual. The relationship between PM exposure and CVD incidence was examined via Cox proportional hazards models, with a focus on probing the role of TyG-related indicators through mediation analysis.

RESULTS

A total of 1,865 individuals with CVD were diagnosed over the span of a 7.4-year follow-up period. The 3-year average concentrations before baseline were 31.29 µg/m³ for PM1, 56.03 µg/m³ for PM2.5, and 95.73 µg/m³ for PM10. In fully adjusted model, the Cox proportional hazards models revealed that an increase of 10 µg/m³ in the PM1, PM2.5, and PM10 exposure concentrations corresponded to elevated CVD risk, with HRs (95% CI) of 1.135 (1.078-1.195), 1.092 (1.062-1.123), and 1.075 (1.059-1.090), respectively. Mediation analyses further suggested that the correlation between PM exposure and CVD could be partly mediated via TyG-BMI, TyG-WC, and TyG-WHtR, with mediation proportions varying from 5.54 to 15.30%.

CONCLUSION

A significant correlation was observed between long-term PM exposure and increased CVD risk, with TyG-related indicators, such as TyG-BMI, TyG-WC, and TyG-WHtR, partially mediating this relationship.

The Possible Role of PM2.5 Chronic Exposure on 5-Year Survival in Patients with Left Ventricular Dysfunction Following Coronary Artery Bypass Grafting

BACKGROUND

The survival benefit of surgical revascularization in multivessel coronary artery disease is well understood, though it can be modified by left ventricular dysfunction. Chronic exposure to air pollutants has gained more attention recently as a possible non-traditional morbidity and mortality cardiovascular risk factor. This study identified possible 5-year mortality risk factors related to postoperative left ventricular performance, including air pollutants.

PATIENTS

There were 283 patients (244 (86%) males) with a median age of 65 (60-70) years enrolled in the retrospective analysis. All patients were referred for off-pump coronary artery revascularization due to chronic coronary syndrome that presented as a multivessel coronary artery disease. They were divided into three groups depending on the postoperative course of left ventricular fraction (LVEF 50% or more (169 patients), LVEF between 41 and 49% (61 patients), and LVEF 40% or less (53 patients)).

RESULTS

The overall survival rate was 84% (237 patients) in a median follow-up time of 5.3 (4.8-6.1) years. The median (Q1-Q3) chronic air pollution exposures for the analyzed group were 19.3 (16.9-22.4) μg/m3 for fine particles such as PM2.5, 25.8 (22.5-29.4) μg/m3 for coarse particles such as PM10, and 12.2 (9.7-14.9) μg/m3 for nitric dioxide (NO2). The mortality in the first group (LVEF at least 50%) was 23 (13.6%), in the second group (LVEF 41-49%) was 9 (15%), and in the third group (LVEF 40% or less) was 14 (26%). The multivariable regression analysis for the five-year mortality risk in the first group revealed the predictive value of dyslipidemia (HR: 3.254, 95% CI: 1.008-10.511, p = 0.049). The multivariable regression analysis for five-year mortality risk in the second group revealed the predictive value of dyslipidemia (HR: 3.391, 95% CI: 1.001-11.874, p = 0.050) and PM2.5 (HR: 1.327, 95% CI: 1.085-1.625, p = 0.006). In the third group (severely decreased LVEF), chronic PM2.5 exposure was found to be significant (HR: 1.518, 95% CI: 1.50-2.195, p = 0.026) for 5-year mortality prediction.

CONCLUSIONS

Traditional risk factors, such as dyslipidemia, are pivotal in the 5-year mortality risk following surgical revascularization. Chronic exposure to ambient air pollutants such as PM2.5 may be an additional risk factor in patients with left ventricular dysfunction.

Aqueous PM2.5 promotes lipid accumulation, classical macrophage polarisation and heat shock response

Fine particulate matter (PM2.5) is an air pollutant that enhances susceptibility to cardiovascular diseases. Macrophages are the first immune cells to encounter the inhaled particles and orchestrate an inflammatory response. Given their role in atherosclerosis development, we investigated whether aqueous PM2.5 could elicit atherogenic effects by polarising macrophages to a pro-oxidative and pro-inflammatory phenotype and enhancing foam cell formation. The RAW264.7 macrophage cell line was exposed to PM2.5 for 48 h, with PBS as the control. Aqueous PM2.5 induced apoptosis and reduced cell proliferation. In surviving cells, we observed morphological, phagocytic, oxidative, and inflammatory features (i.e. enhanced iNOS, Integrin-1β, IL-6 expression), indicative of classical macrophage activation. We also detected an increase in total and surface HSP70 levels, suggesting macrophage activation. Further, exposure of high-cholesterol diet-fed mice to PM2.5 resulted in aortic wall enlargement, indicating vascular lesions. Macrophages exposed to PM2.5 and non-modified low-density lipoprotein (LDL) showed exacerbated lipid accumulation. Given the non-oxidised LDL used and the evidence linking inflammation to disrupted cholesterol negative feedback, we hypothesise that PM2.5-induced inflammation in macrophages enhances their susceptibility to transforming into foam cells. Finally, our results indicate that exposure to aqueous PM2.5 promotes classical macrophage activation, marked by increased HSP70 expression and that it potentially contributes to atherosclerosis.

Unresolved questions in the regulation of skeletal muscle insulin action by reactive oxygen species

Reactive oxygen species (ROS) are well-established signaling molecules implicated in a wide range of cellular processes, including both oxidative stress and intracellular redox signaling. In the context of insulin action within its target tissues, ROS have been reported to exert both positive and negative regulatory effects. However, the precise molecular mechanisms underlying this duality remain unclear. This Review examines the complex role of ROS in insulin action, with a particular focus on skeletal muscle. We aim to address three critical aspects: (a) the proposed intracellular pro-oxidative redox shift elicited by insulin, (b) the evidence supporting that redox-sensitive cysteine modifications impact insulin signaling and action, and (c) cellular mechanisms underlying how ROS can paradoxically act as both enhancers and inhibitors of insulin action. This Review underscores the urgent need for more systematic research to identify specific reactive species, redox targets, and the physiological significance of redox signaling in maintaining insulin action and metabolic health, with a particular emphasis on human skeletal muscle.

A case-crossover study of ST-elevation myocardial infarction and organic carbon and source-specific PM2.5 concentrations in Monroe County, New York

Background

Previous work reported increased rates of cardiovascular hospitalizations associated with increased source-specific PM2.5 concentrations in New York State, despite decreased PM2.5 concentrations. We also found increased rates of ST elevation myocardial infarction (STEMI) associated with short-term increases in concentrations of ultrafine particles and other traffic-related pollutants in the 2014-2016 period, but not during 2017-2019 in Rochester. Changes in PM2.5 composition and sources resulting from air quality policies (e.g., Tier 3 light-duty vehicles) may explain the differences. Thus, this study aimed to estimate whether rates of STEMI were associated with organic carbon and source-specific PM2.5 concentrations.

Methods

Using STEMI patients treated at the University of Rochester Medical Center, compositional and source-apportioned PM2.5 concentrations measured in Rochester, a time-stratified case-crossover design, and conditional logistic regression models, we estimated the rate of STEMI associated with increases in mean primary organic carbon (POC), secondary organic carbon (SOC), and source-specific PM2.5 concentrations on lag days 0, 0-3, and 0-6 during 2014-2019.

Results

The associations of an increased rate of STEMI with interquartile range (IQR) increases in spark-ignition emissions (GAS) and diesel (DIE) concentrations in the previous few days were not found from 2014 to 2019. However, IQR increases in GAS concentrations were associated with an increased rate of STEMI on the same day in the 2014-2016 period (Rate ratio [RR] = 1.69; 95% CI = 0.98, 2.94; 1.73 μg/m3). In addition, each IQR increase in mean SOC concentration in the previous 6 days was associated with an increased rate of STEMI, despite imprecision (RR = 1.14; 95% CI = 0.89, 1.45; 0.42 μg/m3).

Conclusion

Increased SOC concentrations may be associated with increased rates of STEMI, while there seems to be a declining trend in adverse effects of GAS on triggering of STEMI. These changes could be attributed to changes in PM2.5 composition and sources following the Tier 3 vehicle introduction.

Toxicity of airborne nanoparticles: Facts and challenges

Air pollution is one of the most severe environmental healthhazards, and airborne nanoparticles (diameter <100 nm) are considered particularly hazardous to human health. They are produced by various sources such as internal combustion engines, wood and biomass burning, and fuel and natural gas combustion, and their origin, among other parameters, determines their intrinsic toxicity for reasons that are not yet fully understood. Many constituents of the nanoparticles are considered toxic or at least hazardous, including polycyclic aromatic hydrocarbons (PAHs) and heavy metal compounds, in addition to gaseous pollutants present in the aerosol fraction, such as NOx, SO2, and ozone. All these compounds can cause oxidative stress, mitochondrial damage, inflammation in the lungs and other tissues, and cellular organelles. Epidemiological investigations concluded that airborne pollution may affect the respiratory, cardiovascular, and nervous systems. Moreover, particulate matter has been linked to an increased risk of lung cancer, a carcinogenic effect not related to DNA damage, but to the cellular inflammatory response to the pollutants, in which the release of cytokines promotes the proliferation of pre-existing mutated cancer cells. The mechanisms behind toxicity can be investigated experimentally using cell cultures or animal models. Methods for gathering particulate matter have been explored, but standardized protocols are needed to ensure that the samples accurately represent chemical mixtures in the environment. Toxic constituents of nanoparticles can be studied in animal and cellular models, but designing realistic exposure settings is challenging. The air-liquid interface (ALI) system directly exposes cells, mimicking particle inhalation into the lungs. Continuous research and monitoring of nanoparticles and other airborne pollutants is essential for understanding their effects and developing active strategies to mitigate their risks to human and environmental health.

Fine particulate matter-sudden death association modified by ventricular hypertrophy and inflammation: a case-crossover study

Background

Sudden death accounts for approximately 10% of deaths among working-age adults and is associated with poor air quality. Objectives: To identify high-risk groups and potential modifiers and mediators of risk, we explored previously established associations between fine particulate matter (PM2.5) and sudden death stratified by potential risk factors.

Methods

Sudden death victims in Wake County, NC, from 1 March 2013 to 28 February 2015 were identified by screening Emergency Medical Systems reports and adjudicated (n = 399). Daily PM2.5 concentrations for Wake County from the Air Quality Data Mart were linked to event and control periods. Potential modifiers included greenspace metrics, clinical conditions, left ventricular hypertrophy (LVH), and neutrophil-to-lymphocyte ratio (NLR). Using a case-crossover design, conditional logistic regression estimated the OR (95%CI) for sudden death for a 5 μg/m3 increase in PM2.5 with a 1-day lag, adjusted for temperature and humidity, across risk factor strata.

Results

Individuals having LVH or an NLR above 2.5 had PM2.5 associations of greater magnitude than those without [with LVH OR: 1.90 (1.04, 3.50); NLR > 2.5: 1.25 (0.89, 1.76)]. PM2.5 was generally less impactful for individuals living in areas with higher levels of greenspace.

Conclusion

LVH and inflammation may be the final step in the causal pathway whereby poor air quality and traditional risk factors trigger arrhythmia or myocardial ischemia and sudden death. The combination of statistical evidence with clinical knowledge can inform medical providers of underlying risks for their patients generally, while our findings here may help guide interventions to mitigate the incidence of sudden death.

Pollutants, microbiota and immune system: frenemies within the gut

Pollution is a critical concern of modern society for its heterogeneous effects on human health, despite a widespread lack of awareness. Environmental pollutants promote several pathologies through different molecular mechanisms. Pollutants can affect the immune system and related pathways, perturbing its regulation and triggering pro-inflammatory responses. The exposure to several pollutants also leads to alterations in gut microbiota with a decreasing abundance of beneficial microbes, such as short-chain fatty acid-producing bacteria, and an overgrowth of pro-inflammatory species. The subsequent intestinal barrier dysfunction, together with oxidative stress and increased inflammatory responses, plays a role in the pathogenesis of gastrointestinal inflammatory diseases. Moreover, pollutants encourage the inflammation-dysplasia-carcinoma sequence through various mechanisms, such as oxidative stress, dysregulation of cellular signalling pathways, cell cycle impairment and genomic instability. In this narrative review, we will describe the interplay between pollutants, gut microbiota, and the immune system, focusing on their relationship with inflammatory bowel diseases and colorectal cancer. Understanding the biological mechanisms underlying the health-to-disease transition may allow the design of public health policies aimed at reducing the burden of disease related to pollutants.

Implications of climatic change on sickle cell anemia: A review

Sickle cell anemia (SCA) is a hereditary blood disorder characterized by abnormal hemoglobin, causing red blood cells to assume a sickle shape, leading to various complications. Climate change has emerged as a significant global challenge, influencing environmental conditions worldwide. This paper explores the implications of climatic variations on the prevalence, management, and outcomes of SCA. Climate change affects weather patterns, leading to altered temperatures, increased frequency of extreme weather events, and variations in humidity levels. These changes can have a profound impact on individuals living with SCA. High temperatures exacerbate the symptoms of SCA, potentially triggering painful vaso-occlusive crises due to dehydration and increased blood viscosity. Conversely, cold temperatures may induce vaso-occlusion by causing blood vessels to constrict. Changes in rainfall patterns might also affect water accessibility, which is crucial for maintaining adequate hydration, particularly in regions prone to droughts. The management of SCA is multifaceted, involving regular medical care, hydration, and avoiding triggers that could precipitate a crisis. Adverse weather events and natural disasters can disrupt healthcare infrastructure and access to essential medications and resources for SCA patients, especially in vulnerable communities. To mitigate the implications of climatic change on SCA, interdisciplinary strategies are essential. These strategies may include enhancing healthcare systems' resilience to climate-related disruptions, implementing adaptive measures to address changing environmental conditions, and promoting public awareness and education on managing SCA amidst climate variability. In conclusion, climatic variations pose significant challenges for individuals with SCA, affecting the prevalence, management, and outcomes of the disease.

Molecular mechanisms underlying NLRP3 inflammasome activation and IL-1β production in air pollution fine particulate matter (PM2.5)-primed macrophages

Exposure to air pollution fine particulate matter (PM2.5) aggravates respiratory and cardiovascular diseases. It has been proposed that PM2.5 uptake by alveolar macrophages promotes local inflammation that ignites a systemic response, but precise underlying mechanisms remain unclear. Here, we demonstrate that PM2.5 phagocytosis leads to NLRP3 inflammasome activation and subsequent release of the pro-inflammatory master cytokine IL-1β. Inflammasome priming and assembly was time- and dose-dependent in inflammasome-reporter THP-1-ASC-GFP cells, and consistent across PM2.5 samples of variable chemical composition. While inflammasome activation was promoted by different PM2.5 surrogates, significant IL-1β release could only be observed after stimulation with transition-metal rich Residual Oil Fly Ash (ROFA) particles. This effect was confirmed in primary human monocyte-derived macrophages and murine bone marrow-derived macrophages (BMDMs), and by confocal imaging of inflammasome-reporter ASC-Citrine BMDMs. IL-1β release by ROFA was dependent on the NLRP3 inflammasome, as indicated by lack of IL-1β production in ROFA-exposed NLRP3-deficient (Nlrp3-/-) BMDMs, and by specific NLRP3 inhibition with the pharmacological compound MCC950. In addition, while ROFA promoted the upregulation of pro-inflammatory gene expression and cytokines release, MCC950 reduced TNF-α, IL-6, and CCL2 production. Furthermore, inhibition of TNF-α with a neutralizing antibody decreased IL-1β release in ROFA-exposed BMDMs. Using electron tomography, ROFA particles were observed inside intracellular vesicles and mitochondria, which showed signs of ultrastructural damage. Mechanistically, we identified lysosomal rupture, K+ efflux, and impaired mitochondrial function as important prerequisites for ROFA-mediated IL-1β release. Interestingly, specific inhibition of superoxide anion production (O2•-) from mitochondrial respiratory Complex I, but not III, blunted IL-1β release in ROFA-exposed BMDMs. Our findings unravel the mechanism by which PM2.5 promotes IL-1β release in macrophages and provide a novel link between innate immune response and exposure to air pollution PM2.5.

Particulate air pollution and cardiovascular disease mortality in Jiangsu Province, China: a time-series analysis between 2015 and 2021

Introduction

Previous time-series studies have revealed a positive association between particulate matter (PM) and acute cardiovascular effects. However, the evidence mostly comes from developed countries and regions, while the majority of air-pollution-related deaths occur in developing countries. To assess the effect of short-term exposure to PM on daily cause-specific cardiovascular disease (CVD) mortality in Jiangsu Province, China, we investigated 1,417,773 CVD deaths from 2015 to 2021 in Jiangsu.

Methods

The city-specific association was estimated using generalized additive models with quasi-Poisson regression, and then, random effects meta-analysis was performed to estimate the pooled provincial-average associations between acute exposure to PM2.5 and PM10 and cardiovascular disease mortality. To test the independence of PM from gaseous pollutants, we fitted two-pollutant models. Mortality data were also stratified by sex, age, and region to investigate the modification of associations. The exposure-response (E-R) curve from each city was combined using meta-analysis to drive the provincial-level E-R curve.

Results

The results showed that each 10-μg/m3 increase in the PM2.5 concentration was associated with a 0.723% [95% confidence interval (CI): 0.512, 0.935] increase in daily total CVD mortality, a 0.669% (95% CI: 0.461, 0.878) increase in CHD mortality, a 0.758% (95% CI: 0.584, 0.931) increase in stroke mortality, a 0.512% (95% CI: 0.245, 0.780) increase in ICH mortality, and a 0.876% (95% CI: 0.637, 1.116) increase in CI mortality. The corresponding increases in daily mortality rates for the same increase in the PM10 concentration were 0.424% (95% CI: 0.293, 0.556), 0.415% (95% CI: 0.228, 0.602), 0.444% (95% CI: 0.330, 0.559), 0.276% (95% CI: 0.026, 0.526), and 0.510% (95% CI: 0.353, 0.667), respectively. The association between PM and total CVD mortality remained significant after adjusting for gaseous pollutants. Females, older adults and districts with lower average PM levels are more sensitive, especially for PM10. The E-R curve for PM on CVD mortality is steeper at lower concentrations and flattens out at higher concentrations. The estimates remained generally consistent in sensitivity analyses when excluding the data during the COVID-19 pandemic period.

Discussion

Our time-series study provides evidence of positive associations between acute exposure to PM2.5 and PM10 and total and cause-specific cardiovascular disease mortality in developing countries.