Ambient Particulate Matter Induces In Vitro Toxicity to Intestinal Epithelial Cells without Exacerbating Acute Colitis Induced by Dextran Sodium Sulfate or 2,4,6-Trinitrobenzenesulfonic Acid.

Inflammatory bowel disease (IBD) is an immunologically complex disorder involving genetic, microbial, and environmental risk factors. Its global burden has continued to rise since industrialization, with epidemiological studies suggesting that ambient particulate matter (PM) in air pollution could be a contributing factor. Prior animal studies have shown that oral PM10 exposure promotes intestinal inflammation in a genetic IBD model and that PM2.5 inhalation exposure can increase intestinal levels of pro-inflammatory cytokines. PM10 and PM2.5 include ultrafine particles (UFP), which have an aerodynamic diameter of <0.10 µm and biophysical and biochemical properties that promote toxicity. UFP inhalation, however, has not been previously studied in the context of murine models of IBD. Here, we demonstrated that ambient PM is toxic to cultured Caco-2 intestinal epithelial cells and examined whether UFP inhalation affected acute colitis induced by dextran sodium sulfate and 2,4,6-trinitrobenzenesulfonic acid. C57BL/6J mice were exposed to filtered air (FA) or various types of ambient PM reaerosolized in the ultrafine size range at ~300 µg/m3, 6 h/day, 3-5 days/week, starting 7-10 days before disease induction. No differences in weight change, clinical disease activity, or histology were observed between the PM and FA-exposed groups. In conclusion, UFP inhalation exposure did not exacerbate intestinal inflammation in acute, chemically-induced colitis models.

Diesel exhaust particle extract elicits an oxPAPC-like transcriptomic profile in macrophages across multiple mouse strains.

Air pollution is a prominent cause of cardiopulmonary illness, but uncertainties remain regarding the mechanisms mediating those effects as well as individual susceptibility. Macrophages are highly responsive to particles, and we hypothesized that their responses would be dependent on their genetic backgrounds. We conducted a genome-wide analysis of peritoneal macrophages harvested from 24 inbred strains of mice from the Hybrid Mouse Diversity Panel (HMDP). Cells were treated with a DEP methanol extract (DEPe) to elucidate potential mechanisms that mediate acute responses to air pollution exposures. This analysis showed that 1,247 genes were upregulated and 1,383 genes were downregulated with DEPe treatment across strains. Pathway analysis identified oxidative stress responses among the most prominent upregulated pathways; indeed, many of the upregulated genes included antioxidants such as Hmox1, Txnrd1, Srxn1, and Gclm, with NRF2 (official gene symbol: Nfe2l2) being the most significant driver. DEPe induced a Mox-like transcriptomic profile, a macrophage subtype typically induced by oxidized phospholipids and likely dependent on NRF2 expression. Analysis of individual strains revealed consistency of overall responses to DEPe and yet differences in the degree of Mox-like polarization across the various strains, indicating DEPe x genetic interactions. These results suggest a role for macrophage polarization in the cardiopulmonary toxicity induced by air pollution.

Subchronic inhalation exposure to ultrafine particulate matter alters the intestinal microbiome in various mouse models.

Exposure to ultrafine particles (UFPs) has been associated with multiple adverse health effects. Inhaled UFPs could reach the gastrointestinal tract and influence the composition of the gut microbiome. We have previously shown that oral ingestion of UFPs alters the gut microbiome and promotes intestinal inflammation in hyperlipidemic Ldlr-/- mice. Particulate matter (PM)2.5 inhalation studies have also demonstrated microbiome shifts in normolipidemic C57BL/6 mice. However, it is not known whether changes in microbiome precede or follow inflammatory effects in the intestinal mucosa. We hypothesized that inhaled UFPs modulate the gut microbiome prior to the development of intestinal inflammation. We studied the effects of UFP inhalation on the gut microbiome and intestinal mucosa in two hyperlipidemic mouse models (ApoE-/- mice and Ldlr-/- mice) and normolipidemic C57BL/6 mice. Mice were exposed to PM in the ultrafine-size range by inhalation for 6 h a day, 3 times a week for 10 weeks at a concentration of 300-350 µg/m3.16S rRNA gene sequencing was performed to characterize sequential changes in the fecal microbiome during exposures, and changes in the intestinal microbiome at the end. PM exposure led to progressive differentiation of the microbiota over time, associated with increased fecal microbial richness and evenness, altered microbial composition, and differentially abundant microbes by week 10 depending on the mouse model. Cross-sectional analysis of the small intestinal microbiome at week 10 showed significant changes in α-diversity, ß-diversity, and abundances of individual microbial taxa in the two hyperlipidemic models. These alterations of the intestinal microbiome were not accompanied, and therefore could not be caused, by increased intestinal inflammation as determined by histological analysis of small and large intestine, cytokine gene expression, and levels of fecal lipocalin. In conclusion, 10-week inhalation exposures to UFPs induced taxonomic changes in the microbiome of various animal models in the absence of intestinal inflammation.

Ectodomain shedding of proteins important for SARS-CoV-2 pathogenesis in plasma of tobacco cigarette smokers compared to electronic cigarette vapers: a cross-sectional study.

The impact of tobacco cigarette (TCIG) smoking and electronic cigarette (ECIG) vaping on the risk of development of severe COVID-19 is controversial. The present study investigated levels of proteins important for SARS-CoV-2 pathogenesis present in plasma because of ectodomain shedding in smokers, ECIG vapers, and non-smokers (NSs). Protein levels of soluble angiotensin-converting enzyme 2 (ACE2), angiotensin (Ang) II (the ligand of ACE2), Ang 1-7 (the main peptide generated from Ang II by ACE2 activity), furin (a protease that increases the affinity of the SARS-CoV-2 spike protein for ACE2), and products of ADAM17 shedding activity that predict morbidity in COVID-19 (IL-6/IL-6R alpha (IL-6/IL-6Rα) complex, soluble CD163 (sCD163), L-selectin) were determined in plasma from 45 NSs, 30 ECIG vapers, and 29 TCIG smokers using ELISA. Baseline characteristics of study participants did not differ among groups. TCIG smokers had increased sCD163, L-selectin compared to NSs and ECIG vapers (p < 0.001 for all comparisons). ECIG vapers had higher plasma furin compared to both NSs (p < 0.001) and TCIG smokers (p < 0.05). ECIG vaping and TCIG smoking did not impact plasma ACE2, Ang 1-7, Ang II, and IL-6 levels compared to NSs (p > 0.1 for all comparisons). Further studies are needed to determine if increased furin activity and ADAM17 shedding activity that is associated with increased plasma levels of sCD163 and L-selectin in healthy young TCIG smokers may contribute to the future development of severe COVID-19 and cardiovascular complications of post-acute COVID-19 syndrome.

Passive smoking and urinary oxidative biomarkers: A pilot study of healthy travelers from Los Angeles to Beijing.

There is a great heterogeneity in smoking prevalence and tobacco control policy across different countries. However, it is unknown whether this heterogeneity could cause increased passive smoking and adverse health effects among international travelers. In this pilot study, we collected 190 urine samples from 26 Los Angeles residents before (LA-before), during (Beijing), and after (LA-after) a 10-week visit to Beijing to measure biomarkers of passive smoking (cotinine), exposure to polycyclic aromatic hydrocarbons (OH-PAHs), and oxidative stress (malondialdehyde, 8-isoprostane, and uric acid). The geometric mean concentrations of urinary cotinine were 0.14, 1.52, and 0.22 µg/g creatinine in LA-before, Beijing, and LA-after, respectively. Likewise, OH-PAH levels were significantly higher in Beijing as compared to LA-before or LA-after, in association with the urinary cotinine levels. One-fold increase in urinary cotinine levels was associated with 10.1% (95% CI: 5.53-14.8%), 8.75% (95% CI: 2.33-15.6%), and 25.4% (95%CI: 13.1-39.1%) increases in urinary levels of malondialdehyde, 8-isoprotane, and uric acid, respectively. OH-PAHs mediated 9.1-23.3% of the pro-oxidative effects associated with passive smoking. Taken together, our findings indicate that traveling to a city with higher smoking prevalence may increase passive smoking exposure, in association with pro-oxidative effects partially mediated by PAHs.

Arachidonic acid metabolism and inflammatory biomarkers associated with exposure to polycyclic aromatic hydrocarbons.

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with systemic inflammation, yet what mechanisms regulate PAHs' inflammatory effects are less understood. This study evaluated the change of arachidonic acid (ARA) metabolites and inflammatory biomarkers in response to increased exposure to PAHs among 26 non-smoking healthy travelers from Los Angeles to Beijing. Traveling from Los Angeles to Beijing significantly increased urinary metabolites of dibenzofuran (800%), fluorene (568%), phenanthrene (277%), and pyrene (176%), accompanied with increased C-reactive protein, fibrinogen, IL-8, and IL-10, and decreased MCP-1, sCD40L, and sCD62P levels in the blood. Meanwhile, the travel increased the levels of ARA lipoxygenase metabolites that were positively associated with a panel of pro-inflammatory biomarkers. Concentrations of cytochrome P450 metabolite were also increased in Beijing and were negatively associated with sCD62P levels. In contrast, concentrations of ARA cyclooxygenase metabolites were decreased in Beijing and were negatively associated with anti-inflammatory IL-10 levels. Changes in both inflammatory biomarkers and ARA metabolites were reversed 4-7 weeks after participants returned to Los Angeles and were associated with urinary PAH metabolites, but not with other exposures such as secondhand smoke, stress, or diet. These results suggested possible roles of ARA metabolic alteration in PAHs-associated inflammatory effects.

Triglyceride profiles are associated with subacute exposure to bisphenol A in healthy young adults.

Conflicted results from previous epidemiological studies call for mechanistic evidence to associate exposure to bisphenol A (BPA) with cardiometabolic diseases. In this natural experiment among healthy travelers from Los Angeles (LA) to Beijing, we collected paired urine and blood samples before their departure, 6-8 weeks after their arrival to Beijing, and 4-7 weeks after their return to LA for the assessment of urinary BPA and lipidome in the serum fraction of blood, to study the effects of drastically changed BPA exposure on the lipid metabolism in relation to the development of cardiometabolic disorders. We used linear mixed-effects models with random intercepts for participant and phase to examine the associations between urinary BPA and serum lipidome. Among 744 lipid species from seven classes, triglyceride (TGs) species showed the strongest associations with BPA exposure. The elevation in BPA exposure was associated with increases in TGs with short carbon chains or few double bonds, and decreases in TGs with long carbon chains or many double bonds. A significant linear relationship was observed between BPA-associated TG changes and the number of carbons and double-bonds in the acyl chain. No modification effects of gender but of body mass index (BMI) were observed on the associations between BPA exposure and TGs. This interdisciplinary environmental research substantiated the cardiometabolic effects of BPA according to the perturbations of TG profiling.

Differential Effects of Electronic Hookah Vaping and Traditional Combustible Hookah Smoking on Oxidation, Inflammation, and Arterial Stiffness.

BACKGROUND: Traditional hookah smoking has grown quickly to become a global tobacco epidemic. More recently, electronic hookahs (e-hookahs)-vaped through traditional water pipes-were introduced as healthier alternatives to combustible hookah. With combustible tobacco smoking, oxidative stress, inflammation, and vascular stiffness are key components in the development and progression of atherosclerosis. The comparable effects of hookah are unknown. RESEARCH QUESTION: What is the differential acute effect of e-hookah vaping vs combustible hookah smoking on oxidation, inflammation, and arterial stiffness? STUDY DESIGN AND METHODS: In a randomized crossover design study, among a cohort of 17 healthy young adult chronic hookah smokers, we investigated the effect of e-hookah vaping and hookah smoking on measures of conduit arterial stiffness, including carotid-femoral pulse wave velocity (PWV), augmentation index-corrected for heart rate before and after a 30-min exposure session. We assessed a panel of circulating biomarkers indicative of inflammation and oxidants and measured plasma nicotine and exhaled carbon monoxide (CO) levels before and after the sessions. RESULTS: e-Hookah vaping tended to lead to a larger acute increase in PWV than hookah smoking (mean ± SE: e-hookah, +0.74 ± 0.12 m/s; combustible hookah, +0.57 ± 0.14 m/s [P < .05 for both]), indicative of large artery stiffening. Compared with baseline, only e-hookah vaping induced an acute increase in augmentation index (e-hookah, +5.58 ± 1.54% [P = .004]; combustible hookah, +2.87 ± 2.12% [P = not significant]). These vascular changes were accompanied by elevation of the proinflammatory biomarkers high-sensitivity C-reactive protein, fibrinogen, and tumor necrosis factor α after vaping (all P < .05). No changes in biomarkers of inflammation and oxidants were observed after smoking. Compared with baseline, exhaled CO levels were higher after smoking than after vaping (+36.81 ± 6.70 parts per million vs -0.38 ± 0.22 parts per million; P < .001), whereas plasma nicotine concentrations were comparable (+6.14 ± 1.03 ng/mL vs +5.24 ± 0.96 ng/mL; P = .478). INTERPRETATION: Although advertised to be "safe," flavored e-hookah vaping exerts injurious effects on the vasculature that are, at least in part, mediated by inflammation. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT03690427; URL: www.clinicaltrials.gov.

Key Characteristics of Cardiovascular Toxicants.

BACKGROUND: The concept of chemical agents having properties that confer potential hazard called key characteristics (KCs) was first developed to identify carcinogenic hazards. Identification of KCs of cardiovascular (CV) toxicants could facilitate the systematic assessment of CV hazards and understanding of assay and data gaps associated with current approaches. OBJECTIVES: We sought to develop a consensus-based synthesis of scientific evidence on the KCs of chemical and nonchemical agents known to cause CV toxicity along with methods to measure them. METHODS: An expert working group was convened to discuss mechanisms associated with CV toxicity. RESULTS: The group identified 12 KCs of CV toxicants, defined as exogenous agents that adversely interfere with function of the CV system. The KCs were organized into those primarily affecting cardiac tissue (numbers 1-4 below), the vascular system (5-7), or both (8-12), as follows: 1) impairs regulation of cardiac excitability, 2) impairs cardiac contractility and relaxation, 3) induces cardiomyocyte injury and death, 4) induces proliferation of valve stroma, 5) impacts endothelial and vascular function, 6) alters hemostasis, 7) causes dyslipidemia, 8) impairs mitochondrial function, 9) modifies autonomic nervous system activity, 10) induces oxidative stress, 11) causes inflammation, and 12) alters hormone signaling. DISCUSSION: These 12 KCs can be used to help identify pharmaceuticals and environmental pollutants as CV toxicants, as well as to better understand the mechanistic underpinnings of their toxicity. For example, evidence exists that fine particulate matter [PM ≤2.5µm in aerodynamic diameter (PM2.5)] air pollution, arsenic, anthracycline drugs, and other exogenous chemicals possess one or more of the described KCs. In conclusion, the KCs could be used to identify potential CV toxicants and to define a set of test methods to evaluate CV toxicity in a more comprehensive and standardized manner than current approaches. https://doi.org/10.1289/EHP9321.

Electronic and Tobacco Cigarettes Alter Polyunsaturated Fatty Acids and Oxidative Biomarkers.

[Figure: see text].

Metabolomic Changes after Subacute Exposure to Polycyclic Aromatic Hydrocarbons: A Natural Experiment among Healthy Travelers from Los Angeles to Beijing.

Emerging epidemiological evidence has associated exposure to polycyclic aromatic hydrocarbons (PAHs) with chronic diseases including cardiometabolic diseases and neurodegeneration. However, little information is available about their subacute effects, which may accumulate over years and contribute to chronic disease development. To fill this knowledge gap, we designed a natural experiment among 26 healthy young adults who were exposed to elevated PAHs for 10 weeks after traveling from Los Angeles to Beijing in 2014 and 2015. Serum was collected before, during, and after the trip for metabolomics analysis. We identified 50 metabolites that significantly changed 6-8 weeks after the travel to Beijing (FDR < 5%). The network analysis revealed two main independent modules. Module 1 was allocated to oxidative homeostasis-related response and module 2 to delayed enzymatic deinduction response. Remarkably, the module 1 metabolites were recovered 4-7 weeks after participants' return, while the module 2 metabolites were not. Urinary hydroxylated PAHs were significantly associated with metabolites from both modules, while PAH carboxylic acids, likely metabolites of alkylated PAHs, were only associated with antioxidation-related metabolites. These results suggested differential subacute effects of unsubstituted and alkylated PAHs. Further studies are warranted to elucidate the role of the reversibility of metabolite changes in adverse health effects of PAHs.

Ascorbic Acid Prevents Vascular Endothelial Dysfunction Induced by Electronic Hookah (Waterpipe) Vaping.

Background Electronic hookah (e-hookah) vaping has increased in popularity among youth, who endorse unsubstantiated claims that flavored aerosol is detoxified as it passes through water. However, e-hookahs deliver nicotine by creating an aerosol of fine and ultrafine particles and other oxidants that may reduce the bioavailability of nitric oxide and impair endothelial function secondary to formation of oxygen-derived free radicals. Methods and Results We examined the acute effects of e-hookah vaping on endothelial function, and the extent to which increased oxidative stress contributes to the vaping-induced vascular impairment. Twenty-six healthy young adult habitual hookah smokers were invited to vape a 30-minute e-hookah session to evaluate the impact on endothelial function measured by brachial artery flow-mediated dilation (FMD). To test for oxidative stress mediation, plasma total antioxidant capacity levels were measured and the effect of e-hookah vaping on FMD was examined before and after intravenous infusion of the antioxidant ascorbic acid (n=11). Plasma nicotine and exhaled carbon monoxide levels were measured before and after the vaping session. Measurements were performed before and after sham-vaping control experiments (n=10). E-hookah vaping, which increased plasma nicotine (+4.93±0.92 ng/mL, P<0.001; mean±SE) with no changes in exhaled carbon monoxide (-0.15±0.17 ppm; P=0.479), increased mean arterial pressure (11±1 mm Hg, P<0.001) and acutely decreased FMD from 5.79±0.58% to 4.39±0.46% (P<0.001). Ascorbic acid infusion, which increased plasma total antioxidant capacity 5-fold, increased FMD at baseline (5.98±0.66% versus 9.46±0.87%, P<0.001), and prevented the acute FMD impairment by e-hookah vaping (9.46±0.87% versus 8.74±0.84%, P=0.002). All parameters were unchanged during sham studies. Conclusions E-hookah vaping has adverse effects on vascular function, likely mediated by oxidative stress, which overtime could accelerate development and progression of cardiovascular disease. Registration URL: https://ClinicalTrials.gov. Unique identifier: NCT03690427.

Urinary carboxylic acid metabolites as possible novel biomarkers of exposures to alkylated polycyclic aromatic hydrocarbons.

Previous studies have found that alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) were more abundant in petrogenic sources (e.g., crude oil and its refined products) than pyrogenic sources of incomplete combustion. While urinary hydroxylated metabolites of unsubstituted PAHs have been widely used as biomarkers of PAHs exposures, little information is available as to the occurrence of alkyl-PAH metabolites. In this study, we have detected carboxylic acid metabolites of alkyl-naphthalene (2-NAPCA) and alkyl-phenanthrene (2-PHECA) in 314 urine samples repeatedly collected from 45 Los Angeles residents before, during, and after they spent ten weeks in Beijing in summers of 2014-2017. We found that traveling from Los Angeles to Beijing led to 348% (95% CI: 243 to 485%) and 209% (95% CI: 149 to 282%) increases in 2-NAPCA and 2-PHECA concentrations, respectively, which returned to baseline levels after participants came back to Los Angeles. The concentration ratio between 2-PHECA and hydroxy-phenanthrenes was significantly (p < 0.05) lower in Beijing (median: 0.40, IQR: 0.27-0.53) than in Los Angeles (median: 0.51, IQR: 0.32-0.77), where more than 5,000 active gas and oil wells were located. From 2014 to 2017, the concentration ratio of 2-PHECA to hydroxy-phenanthrenes increased by 28.7 (95%CI: 12.3 to 47.6) %/yr in Los Angeles and 18.6 (95%CI: 7.9 to 30.3) %/yr in Beijing, likely resulted from both cities' efforts to reduce pyrogenic emissions (e.g. vehicle exhaust). These results provided indirect evidence supporting the use of 2-PHECA to hydroxy-phenanthrene ratio as an index to reflect the relative exposure contributions from petrogenic and pyrogenic sources. While our study suggested that urinary PAHCAs may be novel biomarkers of exposure to alkyl-PAHs, future studies with external exposure characterization are warranted to further validate these biomarkers.

Changes in lipid composition associated with electronic cigarette use.

BACKGROUND: Electronic cigarette use is on the rise despite a number of reports linking electronic cigarettes with adverse health outcomes. Recent studies have suggested that alterations in lipid signaling may be one mechanism by which electronic cigarettes contribute to lung pulmonary function. Vitamin E acetate, for example, is synthetic form of Vitamin E transported via lipids, found to be associated with electronic cigarette associated lung injury. Lipids are absolutely critical for normal lung physiology and perturbations in a number of lipid pathways have been associated with respiratory illness. Is it conceivable that electronic cigarette use even in seemingly healthy cohorts are associated with alterations in lipid pathways? METHODS: To investigate quantitative alterations in the plasma lipidome associated with electronic cigarette use in healthy we obtained plasma samples from 119 male and female participants with who were either: (1) chronic tobacco cigarette (TC) smokers (> 12 months of self-reported TC use), (2) chronic Electronic cigarette (EC) users (> 12 months of self-reported EC use), or (3) non-users. We measured quantitative lipid species across different lipid sub-classes from plasma samples using the Sciex Lipidyzer. RESULTS: We found that male and female tobacco and electronic cigarette users had distinct lipidome signatures across a number of lipid species although the vast majority of lipids were unchanged when compared to non-users. Intriguingly, we found that female but not male electronic cigarette users had lower levels of plasmalogens, critical glycerophospholipids secreted by alveoli and required for normal surfactant function. CONCLUSIONS: In summary, our study does not reveal striking changes associated with electronic cigarette use but we observed sex-specific changes in lipids known to be critical for lung function.

Different temporal trends of exposure to Bisphenol A among international travelers between Los Angeles and Beijing.

Recent studies suggested a significant downward trend in population's exposure to bisphenol A (BPA) in the United States. However, the temporal trend of BPA exposure remains unclear in China - a populous country with substantial industrial activities but less efforts made to phase out BPA in consumer products. In addition, it is unclear to what extent a visit from the United States to China could affect human exposure to BPA. In this natural experiment, we measured the concentration of total BPA in 418 urine samples repeatedly collected from 55 Los Angeles residents before, during, and after they spent 10 weeks in Beijing from 2012 to 2017. We found that traveling from Los Angeles to Beijing led to a 2.91-fold (95% CI: 2.43 to 3.50) increase in urinary BPA levels, which fully returned to baseline after study participants came back to Los Angeles. From 2012 to 2017, urinary BPA concentrations decreased in Los Angeles by 25.5% per year (95% CI: -30.8% to -19.8%; p < 0.001) but did not change in Beijing (p = 0.24). Consequently, the concentration ratio of urinary BPA between Beijing and Los Angeles increased from 1.23 (95% CI: 0.82 to 1.85) in 2012 to 4.05 (95% CI: 2.75 to 5.97) in 2017. These results indicate that BPA exposures may increase among international travelers to China. Additional efforts are needed to reduce population's exposure to BPA in China.

Diesel Exhaust Extract Exposure Induces Neuronal Toxicity by Disrupting Autophagy.

The vast majority of neurodegenerative disease cannot be attributed to genetic causes alone and as a result, there is significant interest in identifying environmental modifiers of disease risk. Epidemiological studies have supported an association between long-term exposure to air pollutants and disease risk. Here, we investigate the mechanisms by which diesel exhaust, a major component of air pollution, induces neurotoxicity. Using a zebrafish model, we found that exposure to diesel exhaust particulate extract caused behavioral deficits and a significant decrease in neuron number. The neurotoxicity was due, at least in part, to reduced autophagic flux, which is a major pathway implicated in neurodegeneration. This neuron loss occurred alongside an increase in aggregation-prone neuronal protein. Additionally, the neurotoxicity induced by diesel exhaust particulate extract in zebrafish was mitigated by co-treatment with the autophagy-inducing drug nilotinib. This study links environmental exposure to altered proteostasis in an in vivo model system. These results shed light on why long-term exposure to traffic-related air pollution increases neurodegenerative disease risk and open up new avenues for exploring therapies to mitigate environmental exposures and promote neuroprotection.

Pro-Oxidative and Proinflammatory Effects After Traveling From Los Angeles to Beijing: A Biomarker-Based Natural Experiment.

BACKGROUND: Exposure to air pollution increases cardiovascular morbidity and mortality. Preventing chronic cardiovascular diseases caused by air pollution relies on detecting the early effects of pollutants on the risk of cardiovascular disease development, which is limited by the lack of sensitive biomarkers. We have previously identified promising biomarkers in experimental animals but comparable evidence in humans is lacking. METHODS: Air pollution is substantially worse in Beijing than in Los Angeles. We collected urine and blood samples from 26 nonsmoking, healthy adult residents of Los Angeles (mean age, 23.8 years; 14 women) before, during, and after spending 10 weeks in Beijing during the summers of 2014 and 2015. We assessed a panel of circulating biomarkers indicative of lipid peroxidation and inflammation. Personal exposure to polycyclic aromatic hydrocarbons (PAHs), a group of combustion-originated air pollutants, was assessed by urinary PAH metabolite levels. RESULTS: Urinary concentrations of 4 PAH metabolites were 176% (95% CI, 103% to 276%) to 800% (95% CI, 509% to 1780%) greater in Beijing than in Los Angeles. Concentrations of 6 lipid peroxidation biomarkers were also increased in Beijing, among which 5-, 12-, and 15-hydroxyeicosatetraenoic acid and 9- and 13-hydroxyoctadecadienoic acid levels reached statistical significance (false discovery rate <5%), but not 8-isoprostane (20.8%; 95% CI, -5.0% to 53.6%). The antioxidative activities of paraoxonase (-9.8%; 95% CI, -14.0% to -5.3%) and arylesterase (-14.5%; 95% CI, -22.3% to -5.8%) were lower and proinflammatory C-reactive protein (101%; 95% CI, 3.3% to 291%) and fibrinogen (48.3%; 95% CI, 4.9% to 110%) concentrations were higher in Beijing. Changes in all these biomarkers were reversed, at least partially, after study participants returned to Los Angeles. Changes in most outcomes were associated with urinary PAH metabolites (P<0.05). CONCLUSIONS: Traveling from a less-polluted to a more-polluted city induces systemic pro-oxidative and proinflammatory effects. Changes in the levels of 5-, 12-, and 15-hydroxyeicosatetraenoic acid and 9- and 13-hydroxyoctadecadienoic acid as well as paraoxonase and arylesterase activities in the blood, in association with exposures to PAH metabolites, might have important implications in preventive medicine as indicators of increased cardiovascular risk caused by air pollution exposure.

Diesel exhaust particles dysregulate multiple immunological pathways in murine macrophages: Lessons from microarray and scRNA-seq technologies.

Exposure to ambient particulate matter has been shown to promote a variety of disorders, including cardiovascular diseases predominantly of ischemic etiology. However, the mechanisms linking inhaled particulates with systemic vascular effects, resulting in worsened atherosclerosis, are not well defined. We assessed the potential role of macrophages in translating these effects by analyzing gene expression patterns in response to diesel exhaust particles (DEP) at the average cell level, using Affymetrix microarrays in peritoneal macrophages in culture (in vitro), and at the individual cell level, using single-cell RNA sequencing (scRNA-seq) in alveolar macrophages collected from exposed mice (in vivo). Peritoneal macrophages were harvested from C57BL/6J mice and treated with 25 µg/mL of a DEP methanol extract (DEPe). These cells exhibited significant (FDR < 0.05) differential expression of a large number of genes and enrichment in pathways, especially engaged in immune responses and antioxidant defense. DEPe led to marked upregulation of heme oxygenase 1 (Hmox1), the most significantly upregulated gene (FDR = 1.75E-06), and several other antioxidant genes. For the in vivo work, C57BL/6J mice were subjected to oropharyngeal aspiration of 200 µg of whole DEP. The gene expression profiles of the alveolar macrophages harvested from these mice were analyzed at the single-cell level using scRNA-seq, which showed significant dysregulation of a broad number of genes enriched in immune system pathways as well, but with a large heterogeneity in how individual alveolar macrophages responded to DEP exposures. Altogether, DEP pollutants dysregulated immunological pathways in macrophages that may mediate the development of pulmonary and systemic vascular effects.

Diesel Exhaust Induces Mitochondrial Dysfunction, Hyperlipidemia, and Liver Steatosis.

OBJECTIVE: Air pollution is associated with increased cardiovascular morbidity and mortality, as well as dyslipidemia and metabolic syndrome. Our goal was to dissect the mechanisms involved. Approach and Results: We assessed the effects of exposure to air pollution on lipid metabolism in mice through assessment of plasma lipids and lipoproteins, oxidized fatty acids 9-HODE (9-hydroxyoctadecadienoic) and 13-HODE (13-hydroxyoctadecadienoic), lipid, and carbohydrate metabolism. Findings were corroborated, and mechanisms were further assessed in HepG2 hepatocytes in culture. ApoE knockout mice exposed to inhaled diesel exhaust (DE, 6 h/d, 5 days/wk for 16 weeks) exhibited elevated plasma cholesterol and triglyceride levels, increased hepatic triglyceride content, and higher hepatic levels of 9-HODE and 13-HODE, as compared to control mice exposed to filtered air. A direct effect of DE exposure on hepatocytes was demonstrated by treatment of HepG2 cells with a methanol extract of DE particles followed by loading with oleic acid. As observed in vivo, this led to increased triglyceride content and significant downregulation of ACAD9 mRNA expression. Treatment of HepG2 cells with DE particles and oleic acid did not alter de novo lipogenesis but inhibited total, mitochondrial, and ATP-linked oxygen consumption rate, indicative of mitochondrial dysfunction. Treatment of isolated mitochondria, prepared from mouse liver, with DE particles and oleic acid also inhibited mitochondrial complex activity and ß-oxidation. CONCLUSIONS: DE exposure leads to dyslipidemia and liver steatosis in ApoE knockout mice, likely due to mitochondrial dysfunction and decreased lipid catabolism.

Exposure to Nanoscale Particulate Matter from Gestation to Adulthood Impairs Metabolic Homeostasis in Mice.

Emerging evidence from epidemiological and animal studies suggests that exposure to traffic-related air pollutants and particulate matter less than 2.5 µm in diameter (PM2.5) contributes to development of obesity and related metabolic abnormalities. However, it is not known whether nanoscale particulate matter (nPM) with aerodynamic diameter ≤200 nm have similar adverse metabolic effects. The goal of the present study was to determine the effects of prenatal and early life exposure to nPM on metabolic homeostasis in mice. C57BL/6 J mice were exposed to nPM or filtered air from gestation until 17 weeks of age and characterized for metabolic and behavioral parameters. In male mice, nPM exposure increased food intake, body weight, fat mass, adiposity, and whole-body glucose intolerance (p < 0.05). Consistent with these effects, male mice exposed to nPM displayed alterations in the expression of metabolically-relevant neuropeptides in the hypothalamus and decreased expression of insulin receptor signaling genes in adipose (p < 0.05). There were no differences in exploratory behavior or motor function, fasting lipid levels, or the inflammatory profile of adipose tissue. Our results provide evidence that chronic nPM exposure from gestation to early adulthood in male mice promotes metabolic dysregulation in part through modulation of feeding behavior and in the absence of an obesogenic diet.