Effects of PM2.5 collected from Cache Valley Utah on genes associated with the inflammatory response in human lung cells

Attenuation of PM2.5-induced alveolar epithelial cells and lung injury through regulation of mitochondrial fission and fusion

BACKGROUND

Exposure to particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM_2.5) is a risk factor for developing pulmonary diseases and the worsening of ongoing disease. Mitochondrial fission and fusion are essential processes underlying mitochondrial homeostasis in health and disease. We examined the role of mitochondrial fission and fusion in PM_2.5-induced alveolar epithelial cell damage and lung injury. Key genes in these processes include dystrophin-related protein 1 (DRP1) and optic atrophy 1 (OPA1) respectively.

METHODS

Alveolar epithelial (A549) cells were treated with PM_2.5 (32 µg/ml) in the presence and absence of Mdivi-1 (10µM, a DRP1 inhibitor) or BGP-15 (10µM, an OPA1 activator). Results were validated using DRP1-knockdown (KD) and OPA1-overexpression (OE). Mice were injected intraperitoneally with Mdivi-1 (20 mg/kg), BGP-15 (20 mg/kg) or distilled water (control) one hour before intranasal instillation of PM_2.5 (7.8 mg/kg) or distilled water for two consecutive days.

RESULTS

PM_2.5 exposure of A549 cells caused oxidative stress, enhanced inflammation, necroptosis, mitophagy and mitochondrial dysfunction indicated by abnormal mitochondrial morphology, decreased mitochondrial membrane potential (ΔΨm), reduced mitochondrial respiration and disrupted mitochondrial fission and fusion. Regulating mitochondrial fission and fusion pharmacologically using Mdivi-1 and BGP-15 and genetically using DRP1-KD and OPA1-OE prevented PM_2.5-induced celluar damage in A549 cells. Mdivi-1 and BGP-15 attenuated PM_2.5-induced acute lung injury in mice.

CONCLUSION

Increased mitochondrial fission and decreased mitochondrial fusion may underlie PM_2.5-induced alveolar epithelial cell damage in vitro and lung injury in vivo.

Ozone-oxidized black carbon particles change macrophage fate: Crosstalk between necroptosis and macrophage extracellular traps

The impacts of environmental PM 2.5 on public health have become a major concern all over the world. Many studies have shown that PM 2.5 still poses a threat to public health even at very low levels. Physical or chemical reactions occur between primary particles and other components in the environment, which changes the properties of primary particles. Such newly formed particles with changed properties are called secondary particles. Ozone-oxidized black carbon (oBC) is a key part of PM 2.5 and a representative secondary particle. Macrophages extracellular traps (METs) is a means for macrophages to capture and destroy invading pathogens, thereby exercising innate immunity. Necroptosis is a kind of programmed cell death, which is accompanied by the destruction of membrane integrity, thus inducing inflammatory reaction. However, there is no research on the crosstalk mechanism between necroptosis and MET after oBC exposure. In our study, AO/EB staining, SYTOX Green staining, fluorescent probe, qPCR, Western blot, and immunofluorescence were applied. This experiment found that under normal physiological conditions, when macrophages receive external stimuli (such as pathogens; in our experiment: phorbol 12-myristate 13-acetate (PMA)), they will form METs, capture and kill pathogens, thus exerting innate immune function. However, exposure to oBC can cause necroptosis in macrophages, accompanied by increased levels of reactive oxygen species (ROS) and cytosolic calcium ions, as well as the expression disorder of inflammatory factors and chemokines, and prevent the formation of METs, lose the function of capturing and killing pathogens, and weaken the innate immune function. Notably, inhibition of necroptosis restored the formation of METs, indicating that necroptosis inhibited the formation of METs. This study was the first to explore the crosstalk mechanism between necroptosis and METs after oBC exposure.

Black carbon nanoparticles activate the crosstalk mechanism between necroptosis and macrophage extracellular traps to change macrophages fate

PM2.5 still poses a threat to public health even at very low levels. Black carbon (BC) is a key component of PM2.5. Macrophage extracellular traps (METs) are a means by which macrophages capture and destroy invading pathogens. Necroptosis is an inflammatory programmed cell death. However, there is no research on the crosstalk mechanism between necroptosis and METs after BC exposure. In our study, fluorescence labeling, fluorescent probes, qPCR, and immunofluorescence were applied. Our research found that under normal physiological conditions, when macrophages receive external stimuli (in our experiment, phorbol 12-myristate 13-acetate (PMA)), they will form METs, thus exhibiting innate immune function. However, exposure to BC can cause necroptosis in macrophages accompanied by increased levels of ROS and cytosolic calcium ions as well as altered expression of inflammatory factors and chemokines that prevent the formation of METs, and weakening innate immune function. Notably, inhibition of necroptosis restored the formation of METs, indicating that necroptosis inhibits the formation of METs. Our experiment will enrich the understanding of the mechanism of macrophage injury caused by BC exposure, provide a new direction for studying harmful atmospheric particle toxicity, and propose new therapeutic insights for diseases caused by atmospheric particulate matter. This study is the first to explore the crosstalk mechanism between necroptosis and METs after BC exposure.

The pathophysiological and molecular mechanisms of atmospheric PM2.5 affecting cardiovascular health: A review

BACKGROUND

Exposure to ambient fine particulate matter (PM2.5, with aerodynamic diameter less than 2.5 µm) is a leading environmental risk factor for global cardiovascular health concern.

OBJECTIVE

To provide a roadmap for those new to this field, we reviewed the new insights into the pathophysiological and cellular/molecular mechanisms of PM2.5 responsible for cardiovascular health.

MAIN FINDINGS

PM2.5 is able to disrupt multiple physiological barriers integrity and translocate into the systemic circulation and get access to a range of secondary target organs. An ever-growing body of epidemiological and controlled exposure studies has evidenced a causal relationship between PM2.5 exposure and cardiovascular morbidity and mortality. A variety of cellular and molecular biology mechanisms responsible for the detrimental cardiovascular outcomes attributable to PM2.5 exposure have been described, including metabolic activation, oxidative stress, genotoxicity, inflammation, dysregulation of Ca2+ signaling, disturbance of autophagy, and induction of apoptosis, by which PM2.5 exposure impacts the functions and fates of multiple target cells in cardiovascular system or related organs and further alters a series of pathophysiological processes, such as cardiac autonomic nervous system imbalance, increasing blood pressure, metabolic disorder, accelerated atherosclerosis and plaque vulnerability, platelet aggregation and thrombosis, and disruption in cardiac structure and function, ultimately leading to cardiovascular events and death. Therein, oxidative stress and inflammation were suggested to play pivotal roles in those pathophysiological processes.

CONCLUSION

Those biology mechanisms have deepen insights into the etiology, course, prevention and treatment of this public health concern, although the underlying mechanisms have not yet been entirely clarified.

The effect of air pollution on systemic lupus erythematosus: A systematic review and meta-analysis

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease resulting from impaired inflammatory responses. Given the role of air pollution on increasing inflammatory mediators, thus, we aimed to systematically review and meta-analyze evidence regarding an association between short-term exposure to air pollution and SLE onset, activity, and hospitalization.

METHODS

Electronic databases including Web of Science, PubMed, Scopus, and Embase were searched for all published articles until July 5, 2021. Newcastle Ottawa Scale (NOS) checklist was used to assess the quality of individual studies. Relevant demographic data and the intended results of the selected studies were extracted, and their adjusted risk ratios (RRs) were pooled using random and fixed effect analysis based on the heterogeneity index.

FINDINGS

Twelve studies were entered in our systematic review, and finally, six publications were enrolled in meta-analysis. Overall, Meta-analysis showed no significant association between an increase of PM_2.5 on the third day and SLEDAI score with pooled adjusted RR of 1.212 (95% CI, 0,853-1.721), p-value = 0.284. However, there was a positive relationship between 6 days increase of Particulate matter (PM) 2.5 and the systemic lupus erythematosus disease activity Index (SLEDAI) score (pooled adjusted RR 1.112; 95% CI, 1.005-1.231), p-value = 0.040. There was no significant association between carbon monoxide (CO), nitrogen dioxide (NO₂), PM_2.5, and PM₁₀ increase in the air and hospitalization of SLE patients with pooled RR of 1.021 (95% CI, 0,986-1.1.057), p-value = 0.249, 1.034 (95% CI, 0.996-1.068); p-value = 0.079, 1.042 (95% CI, 0.994-1.092); p-value = 0.084 and 1.004 (95% CI, 0.996-1.013); p-value = 0.323, respectively. Also, analysis showed a significant relation between ozone (O₃) increase and hospitalization with a pooled RR of 1.076 (95% CI, 1.009-1.147); p-value = 0.025. Finally, analysis of SO₂ increase and risk of hospitalization demonstrated no significant relationship with the pooled RR of 1.011; (95% CI, 0.962-1.062), p-value = 0.0.671.

CONCLUSION

Our findings prove that PM_2.5 was associated with increased SLE risk. We also showed that only O₃ was associated with increased hospital admissions of SLE patients.

Exposure to traffic-related fine particulate matter 2.5 causes respiratory damage via peroxisome proliferator-activated receptor gamma-regulated inflammation

Exposure to particulate matter 2.5 (PM2.5) potentially triggers airway inflammation. Peroxisome proliferator-activated receptor gamma (PPARγ) has been reported to regulate inflammatory responses in diverse cell types. Therefore, this work investigated the mechanisms of PPARγ in regulating traffic-related PM2.5-induced airway inflammation. Using the diffusion flame burner soot generation, traffic-related PM2.5 was generated and adsorbed. BALB/c male mice and human bronchial epithelial cells (16-HBE) were exposed to PM2.5 alone or co-treatment with rosiglitazone (RSG), an agonist of PPARγ. To the end of exposure, bronchoalveolar lavage fluid (BALF), venous blood and arterial blood, trachea, bronchus and lung tissues were collected. The levels of IL-1β, IL-6, and IL-17 were detected by ELISA, and the cell types in BALF were counted. Hematoxylin-eosin (H&E) assay were used to analyze the pathological conditions of lung, bronchus, and pulmonary artery. Apoptosis was detected by TUNEL, and PPARγ expression in lung and bronchus was detected by immunohistochemical (IHC) staining. Western Blot was used to detect PPARγ, NF-kB, AP-1 and STAT3 expression in lung and bronchus. The viability was detected by MTT method. PM2.5 exposure caused pathological damage to the lung, bronchus and pulmonary artery tissue, which induced apoptosis of bronchial epithelial cells. PM2.5 exposure caused local inflammation of the whole body and airway. PPARγ expression increased after PM2.5 exposure. PM2.5 exposure regulated the downstream signaling pathways to affect the inflammatory response through PPARγ. Exposure to traffic-related PM2.5 caused respiratory damage via PPARγ-regulated inflammation.

Potential cytotoxicity of trace elements and polycyclic aromatic hydrocarbons bounded to particulate matter: a review on in vitro studies on human lung epithelial cells

A large number of studies have been conducted for clarifying toxicological mechanisms of particulate matter (PM) aimed to investigate the physicochemical properties of PM and providing biological endpoints such as inflammation, perturbation of cell cycle, oxidative stress, or DNA damage. However, although several studies have presented some effects, there is still no consensus on the determinants of biological responses. This review attempts to summarize all past research conducted in recent years on the physicochemical properties of environmental PM in different places and the relationship between different PM components and PM potential cytotoxicity on the human lung epithelial cells. Among 447 papers with our initial principles, a total of 50 articles were selected from 1986 to April 2020 based on the chosen criteria for review. According to the results of selected studies, it is obvious that cytotoxicity in human lung epithelial cells is created both directly or indirectly by transition metals (such as Cu, Cr, Fe, Zn), polycyclic aromatic hydrocarbons (PAH), and ions that formed on the surface of particles. In the selected studies, the findings of the correlation analysis indicate that there is a significant relationship between cell viability reduction and secretion of inflammatory mediators. As a result, it seems that the observed biological responses are related to the composition and the physicochemical properties of the PMs. Therefore, the physicochemical properties of PM should be considered when explaining PM cytotoxicity, and long-term research data will lead to improved strategies to reduce air pollution.

Inhalation of ammonium sulfate and ammonium nitrate adversely affect sperm function

Among the components of air pollution in developing countries and Asia, (NH₄)₂SO₄ and NH₄NO₃ are known as major water-soluble in-organic compounds that cause particulate matter. Several researchers have been reported that the (NH₄)₂SO₄ and NH₄NO₃ induce abnormal decreases in body weight, as well as pneumotoxic, and immunotoxic. Moreover, while it has been reported that (NH₄)₂SO₄ and NH₄NO₃ have detrimental effects on reproduction, specific effects on male fertility have not been addressed in depth. Therefore, the present study evaluated the reproductive toxicity of (NH₄)₂SO₄ and NH₄NO₃ in spermatozoa under the capacitation condition. Results showed that various sperm motion parameters were significantly altered after inhalation of (NH₄)₂SO₄ and NH₄NO₃. In particular, alterations to a range of motion kinematic parameters and to capacitation status were observed after capacitation. In addition, protein kinase A (PKA) activity and tyrosine phosphorylation were altered by (NH₄)₂SO₄ and NH₄NO₃ regardless of capacitation. Taken together, our results show that inhalation of (NH₄)₂SO₄ and NH₄NO₃ may induce adverse effects on male fertility such as sperm motility, motion kinematics, and capacitation status via unusual tyrosine phosphorylation by abnormal PKA activity. Therefore, we suggest that exposure to (NH₄)₂SO₄ and NH₄NO₃ should be highlighted as a health risk, as it may lead to male reproductive toxicity in humans and animals.

Extracellular Vesicles Derived from Adipose Mesenchymal Stem Cells Alleviate PM2.5-Induced Lung Injury and Pulmonary Fibrosis

Background

Exposure to PM2.5 (fine particulate matter ≤2.5 μm in aerodynamic diameter) in air increases the risk of lung injury and pulmonary fibrosis (PF). Extracellular vesicles (EVs) derived from adipose mesenchymal stem cells (ADSCs) have been identified as a potential treatment based on the proteins or RNAs delivery and immunomodulatory properties. Here, we assessed the protective effects and mechanisms of ADSCs-EVs on PM2.5-induced lung injury or PF.

Material/Methods

Rats (male, 6 weeks old) were exposed to PBS or PM2.5 (1.5 mg/kg/day) for 3 days a week for 4 weeks. ADSCs-EVs were extracted by ultracentrifugation. PBS and ADSCs-EVs were administrated through intratracheal instillation. After the end of exposure, the rats were anesthetized and killed. Lung tissues with different treatments were collected for Western blot analysis and HE, IHC, and IF staining analysis. Cells exposed to PM2.5 or “PM2.5+ADSCs-EVs” in vitro were also collected for further Western blotting, qRT-PCR, and IF staining evaluation.

Results

The results indicated that the initial response of lungs exposed to PM2.5 was lung injury with oxidative stress and inflammation. Long-term PM2.5 exposure resulted in obvious PF in rats. Treatment with ADSCs-EVs decreased PM2.5-induced apoptosis and necrosis in type II alveolar epithelial cells and alleviated lung injury and PF in rats. ADSCs-EVs suppressed reactive oxygen species (ROS) levels and inflammation induced by PM2.5. Furthermore, ADSCs-EVs inhibited TGF-βRI by transferring let-7d-5p and further mitigated PF.

Conclusions

Our results suggest that EVs derived from ADSCs can alleviate PM2.5-induced lung injury and PF.

Exercise in Thermal Inversions: PM2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance

INTRODUCTION

Wintertime thermal inversions can lead to the accumulation of small particulate matter (PM_2.5). Despite an association between respiratory hospital admissions and elevated PM_2.5 levels, many people continue to exercise outdoors during inversions. This study compared pulmonary function and exercise performance during periods of low and high ambient PM_2.5 concentrations.

METHODS

Forced vital capacity and forced expiratory volume in 1 s were measured outdoors before and after two 3200 m running time trials: one with low ambient PM_2.5 (0.6-14.7 microgram·m^-3), and the other during high PM_2.5 (19.1-42.5 micrograms·m^-3). A 10 cm visual analog scale (VAS) administered postexercise quantified subjective ratings of respiratory discomfort.

RESULTS

The PM_2.5 differential between trials was ≥18 micrograms·m^-3 for 10 healthy runners. Despite feeling more respiratory discomfort (P=0.044) during the bad air trial (VAS: 4.6±1.8 cm) compared with the good air trial (VAS: 2.9±1.8 cm), the 3200 m run time (low PM_2.5: 13:54±1:34 min:s; high PM_2.5: 14:07±1:44 min:s) was not different (P=0.261) between trials. Postexercise forced vital capacity was not significantly different (P=0.846) between the low (4.86±1.00 L) and high (4.84±0.95 L) PM_2.5 conditions. Similarly, the difference in postexercise forced expiratory volume in 1 s was not significant (P=0.750) between trials (4.22±0.89 L vs 4.23±0.85 L).

CONCLUSIONS

Neither run time nor pulmonary function of healthy adults were adversely affected by an acute bout of exercise in elevated ambient PM_2.5, equivalent to yellow or orange on the air quality index.

A novel inhibitory role of microRNA-224 in particulate matter 2.5-induced asthmatic mice by inhibiting TLR2

Epidemiological studies have shown that elevated concentrations of particulate matter 2.5 (PM2.5) correlate with increased incidence of asthma. Studies have highlighted the implication of microRNAs (miRNAs) in asthmatic response. Here, the objective of this study is to explore the effect of miR-224 on PM2.5-induced asthmatic mice. Ovalbumin (OVA) was utilized to establish asthmatic mouse models, which were then exposed to PM2.5, followed by miR-224 expression detection. Next, lesions and collagen deposition area in lung tissue, ratio Treg/Th17, the expression of TLR4 and MYD88, inflammation, eosinophils (EOS) and airway remodelling were evaluated in OVA mice after injection with miR-224 agomir. Following isolation of mouse primary bronchial epithelial cells, miR-224 mimic and TLR2/TLR4 inhibitor were introduced to assess inflammation and the expression of TGF-β, MMP9, TIMP-1, Foxp3, RORγt, TLR2, TLR4 and MYD88. After exposure to PM2.5, lesions and collagen deposition were promoted in lung tissues, inflammation and EOS were increased in bronchoalveolar lavage fluid (BALF), and airway remodelling was enhanced in OVA mice. miR-224 was down-regulated, whereas TLR2/TLR4/MYD88 was up-regulated in OVA mice after treatment with PM2.5, accompanied by Treg/Th17 immune imbalance. Of note, bioinformatic prediction and dual luciferase reporter gene assay confirmed that TLR2 was a target gene of miR-224. Overexpressed miR-224 reduced expression of TGF-β, MMP9, TIMP-1 and RORγt and inflammation but increased Foxp3 expression in bronchial epithelial cells through down-regulating TLR2. In summary, overexpressed miR-224 suppressed airway epithelial cell inflammation and airway remodelling in PM2.5-induced asthmatic mice through decreasing TLR2 expression.

PM2.5 induced pulmonary fibrosis in vivo and in vitro

Epidemiological studies have revealed positive correlation between particulate matter with an aerodynamic diameter of < 2.5 µm (PM_2.5) and pulmonary fibrosis (PF). As etiology and pathogenesis of PF have not been fully elucidated, this study was to investigate the potential mechanism by which PM_2.5 exposure adversely induced PF in vivo and in vitro. In the present study, 6-week-old C57/BL6J mice were intranasally administrated with PM_2.5 (100 μg/day) for 4 weeks. Micro-CT and hematoxylin-eosin (HE) staining analysis showed that lung inflammation and incipient fibrosis symptoms were induced after PM_2.5 exposure. The expression of Transforming growth factor-β1 (TGF-β1), α-Smooth muscle actin (α-SMA), and Collagen type I (COL1) in mice lung was increased. Upregulation of TGF-β1 in mice serum was also detected by ELISA after exposure to PM_2.5. Moreover, chronic PM_2.5 exposure on human bronchial epithelial cell line BEAS-2B cells led to activation of TGF-β1/SMAD3 pathway, TGF-β1 excretion and epithelial-mesenchymal transition (EMT), while PM_2.5 also triggered the activation of TGF-β1/SMAD3 pathway, TGF-β1 excretion as well as differentiation of human pulmonary fibroblast cell line HFL-1 cells, and TGF-β1 production in mouse macrophage cell line RAW264.7 cells. Furthermore, cell culture medium of PM_2.5-treated BEAS-2B and RAW264.7 cells could both activate TGF-β1/SMAD3 signaling, α-SMA and COL1 upregulation in HFL-1 cells. Therefore, we concluded that PM_2.5 could induce PF by targeting pulmonary epithelium, macrophages and fibroblasts, suggesting that PM_2.5 was a potent initiator of PF.

Chemical Characterization and Source Apportionment of PM2.5 in a Nonattainment Rocky Mountain Valley

Severe air pollution has significant adverse health effects and poses a threat to public health in many communities, including nonattainment areas in the Unites States. To develop effective control strategies to reduce air pollution with minimum economic cost, one of the biggest challenges is to quantify the contributions from different sources. By combining chemical analyses, Positive Matrix Factorization modeling, and emission inventory development, this study identified primary and secondary sources of particulate matter with a diameter of <2.5 μm (PM) in a nonattainment Rocky Mountain valley (i.e., West Silver Valley [WSV]) in Idaho. The results show that biomass burning is the dominant source and contributes ∼84% of the PM concentration in the valley. The study also identified influences on the WSV PM concentrations from traffic (7.4%), soil dust (3.4%), and secondary aerosols (4.8%). The results of this paper represent the first report on the chemical composition and source apportionment of PM in mountain valleys of northern Idaho and have been used to develop effective strategies to reduce the PM concentrations in the WSV. Moreover, this study provides detailed equations and methods in PM speciation, accounting for artifacts of the chemical analysis, Positive Matrix Factorization modeling, and emission inventory development, which can be used for source apportionment of severe air pollution in other regions.

SGK1 inhibits PM2.5-induced apoptosis and oxidative stress in human lung alveolar epithelial A549 cells

Emerging evidence demonstrated that particulate matter 2.5 (PM2.5) is an important environmental risk factor for lung diseases. Serum- and glucocorticoid-inducible kinase 1(SGK1) was reported to be a crucial factor for cell survival. However, the role of SGK1 in PM2.5-induced cell injury is still unclear. In this work, we firstly found that the expression of SGK1 was decreased in PM2.5-treated human lung alveolar epithelial (A549) cells by western blot. In addition, overexpression of SGK1 significantly attenuated A549 cell apoptosis and reduced the reactive oxygen species (ROS) generation induced by PM2.5. Moreover, we found that PM2.5 exposure significantly promoted the ERK1/2 activation and inhibited the AKT activation, whereas overexpression of SGK1 could reverse that. Finally, the results of the rescue experiment showed that MK2206 (AKT inhibitor) could rescue the impact of SGK1 on A549 cell apoptosis, while PD98059 (ERK1/2 inhibitor) could not further aggravate the impact. Taken together, our results suggest that SGK1 inhibits PM2.5-induced cell apoptosis and ROS generation via ERK1/2 and AKT signaling pathway in human lung alveolar epithelial A549 cells.

Gasoline particle filter reduces oxidative DNA damage in bronchial epithelial cells after whole gasoline exhaust exposure in vitro

A substantial amount of traffic-related particle emissions is released by gasoline cars, since most diesel cars are now equipped with particle filters that reduce particle emissions. Little is known about adverse health effects of gasoline particles, and particularly, whether a gasoline particle filter (GPF) influences the toxicity of gasoline exhaust emissions. We drove a dynamic test cycle with a gasoline car and studied the effect of a GPF on exhaust composition and airway toxicity. We exposed human bronchial epithelial cells (ECs) for 6 hours, and compared results with and without GPF. Two hours later, primary human natural killer cells (NKs) were added to ECs to form cocultures, while some ECs were grown as monocultures. The following day, cells were analyzed for cytotoxicity, cell surface receptor expression, intracellular markers, oxidative DNA damage, gene expression, and oxidative stress. The particle amount was significantly reduced due to GPF application. While most biological endpoints did not differ, oxidative DNA damage was significantly reduced in EC monocultures exposed to GPF compared to reference exhaust. Our findings indicate that a GPF has beneficial effects on exhaust composition and airway toxicity. Further studies are needed to assess long-term effects, also in other cell types of the lung.

Effects of ambient particulate matter on aerobic exercise performance

Background/Objective

Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM_2.5). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM_2.5 exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation.

Methods

Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM_2.5 concentrations (<12 μg/m³), and 2) an air quality index (AQI) ranking of “yellow.” Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV₁).

Results

Despite a significant difference in mean PM_2.5 concentration of 9.3 ± 3.0 μg/m³ between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM_2.5 conditions (9.9 ± 1.7 km) compared to high PM_2.5 conditions (10.1 ± 1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV₁. Additionally, there were no dose-response relationships (p > .05) for PM_2.5 concentration and the measured variables.

Conclusion

An acute bout of vigorous exercise during an AQI of “yellow” did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM_2.5 exposure.

Gene expression profiles and bioinformatics analysis of human umbilical vein endothelial cells exposed to PM2.5

Cardiovascular system is demonstrated the main target of PM_2.5 and the objective of this study was to explore the toxic effect and molecular mechanisms caused by PM_2.5 in primary human umbilical vein endothelial cells (HUVECs) using microarray and bioinformatics analysis. The results showed that 591 genes were differentially expressed triggered by PM_2.5, of which 174 genes were down-regulated, while 417 genes were up-regulated. Gene ontology analysis revealed that PM_2.5 caused significant changes in gene expression patterns, including response to stimuli, immune response, and cellular processes. Pathway analysis and Signal-net analysis suggested that endocytosis, chemokine signaling pathway, RNA transport, protein processing in endoplasmic reticulum (ER) and autophagy regulation were the most critical pathways in PM_2.5-induced toxicity in HUVECs. Moreover, gene expression confirmation of LIF, BCL2L1, CSF3, HMOX1, RPS6, PFKFB, CAPN1, HSPBP1, MOGS, PREB, TUBB2A, GABARAP by qRT-PCR indicated that endocytosis might be involved in the cellular uptake of PM_2.5 by forming phagosomes, and subsequently inflammation, hypoxia and ER stress was occurred, which finally activated autophagy after PM_2.5 exposure in HUVECs. In summary, our data can serve as fundamental research clues for further studies of PM_2.5-induced toxicity in HUVECs.

Comparison of gene expression profiles induced by fresh or ozone-oxidized black carbon particles in A549 cells

Epidemiological studies have showed an association between black carbon (BC) exposure and adverse health effects. This study intends to investigate the influence of oxidation processes in atmosphere on the initial cellular responses of BC. The changes of gene expressions induced by fresh BC (FBC) and ozone-oxidized BC (OBC) in human lung epithelial A549 cells were analyzed. And their toxic effects presented by viability, LDH release and DNA damage were compared. Totally 47, 000 genes in A549 cells were examined using Affymetrix Human U133 plus 2.0 chips. Some of the differentially expressed genes were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results showed that 1446 genes (including 756 up-regulated and 690 down-regulated) and 1594 genes (including 788 up-regulated and 806 down-regulated genes) were significantly changed by FBC and OBC respectively. Only 4 of 14 (FBC)/15 (OBC) oxidative stress related genes, up- or down-regulated by FBC and OBC, were identical; 13 of 29 (FBC)/31 (OBC) inflammation related genes, and 6 of 20 (FBC)/18 (OBC) autophagy related genes were identical. No obvious differences were observed between the toxic effects of FBC and OBC. The cytotoxicity of OBC and FBC in A549 cells is at least partially induced by oxidative stress and consequent inflammation or autophagy process. Previous studies indicated that OBC may be more toxic than FBC. However, our results suggested that FBC and OBC might lead to diverse toxic endpoints through activating different molecular pathways.

Association of IL-6 with PM2.5 Components: Importance of Characterizing Filter-Based PM2.5 Following Extraction

Filter-based toxicology studies are conducted to establish the biological plausibility of the well-established health impacts associated with fine particulate matter (PM_2.5) exposure. Ambient PM_2.5 collected on filters is extracted into solution for toxicology applications, but frequently, characterization is nonexistent or only performed on filter-based PM_2.5, without consideration of compositional differences that occur during the extraction processes. To date, the impact of making associations to measured components in ambient instead of extracted PM_2.5 has not been investigated. Filter-based PM_2.5 was collected at locations (n = 5) and detailed characterization of both ambient and extracted PM_2.5 was performed. Alveolar macrophages (AMJ2-C11) were exposed (3, 24, and 48 h) to PM_2.5 and the pro-inflammatory cytokine interleukin (IL)-6 was measured. IL-6 release differed significantly between PM_2.5 collected from different locations; surprisingly, IL-6 release was highest following treatment with PM_2.5 from the lowest ambient concentration location. IL-6 was negatively correlated with the sum of ambient metals analyzed, as well as with concentrations of specific constituents which have been previously associated with respiratory health effects. However, positive correlations of IL-6 with extracted concentrations indicated that the negative associations between IL-6 and ambient concentrations do not accurately represent the relationship between inflammation and PM_2.5 exposure. Additionally, seven organic compounds had significant associations with IL-6 release when considering ambient concentrations, but they were not detected in the extracted solution. Basing inflammatory associations on ambient concentrations that are not necessarily representative of in vitro exposures creates misleading results; this study highlights the importance of characterizing extraction solutions to conduct accurate health impact research.

Gene expression network analyses in response to air pollution exposures in the trucking industry

BACKGROUND

Exposure to air pollution, including traffic-related pollutants, has been associated with a variety of adverse health outcomes, including increased cardiopulmonary morbidity and mortality, and increased lung cancer risk.

METHODS

To better understand the cellular responses induced by air pollution exposures, we performed genome-wide gene expression microarray analysis using whole blood RNA sampled at three time-points across the work weeks of 63 non-smoking employees at 10 trucking terminals in the northeastern US. We defined genes and gene networks that were differentially activated in response to PM_2.5 (particulate matter ≤ 2.5 microns in diameter) and elemental carbon (EC) and organic carbon (OC).

RESULTS

Multiple transcripts were strongly associated (p_adj < 0.001) with pollutant levels (48, 260, and 49 transcripts for EC, OC, and PM_2.5, respectively), including 63 that were statistically significantly correlated with at least two out of the three exposures. These genes included many that have been implicated in ischemic heart disease, chronic obstructive pulmonary disease (COPD), lung cancer, and other pollution-related illnesses. Through the combination of Gene Set Enrichment Analysis and network analysis (using GeneMANIA), we identified a core set of 25 interrelated genes that were common to all three exposure measures and were differentially expressed in two previous studies assessing gene expression attributable to air pollution. Many of these are members of fundamental cancer-related pathways, including those related to DNA and metal binding, and regulation of apoptosis and also but include genes implicated in chronic heart and lung diseases.

CONCLUSIONS

These data provide a molecular link between the associations of air pollution exposures with health effects.

The health effects of ambient PM2.5 and potential mechanisms

The impacts of ambient PM2.5 on public health have become great concerns worldwide, especially in the developing countries. Epidemiological and toxicological studies have shown that PM2.5 does not only induce cardiopulmonary disorders and/or impairments, but also contributes to a variety of other adverse health effects, such as driving the initiation and progression of diabetes mellitus and eliciting adverse birth outcomes. Of note, recent findings have demonstrated that PM2.5 may still pose a hazard to public health even at very low levels (far below national standards) of exposure. The proposed underlying mechanisms whereby PM2.5 causes adverse effects to public health include inducing intracellular oxidative stress, mutagenicity/genotoxicity and inflammatory responses. The present review aims to provide an brief overview of new insights into the molecular mechanisms linking ambient PM2.5 exposure and health effects, which were explored with new technologies in recent years.

A common functional variant on the pro-inflammatory Interleukin-6 gene may modify the association between long-term PM10 exposure and diabetes

BACKGROUND

Air pollutants have been linked to type 2 diabetes (T2D), hypothesized to act through inflammatory pathways and may induce interleukin-6 gene (IL6) in the airway epithelium. The cytokine interleukin-6 may impact on glucose homeostasis. Recent meta-analyses showed the common polymorphisms, IL6 -572G > C and IL6 -174G > C to be associated with T2D risk. These IL6 variants also influence circulatory interleukin-6 levels. We hypothesize that these common functional variants may modify the association between air pollutants and T2D.

METHODS

We cross-sectionally studied 4410 first follow-up participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases (SAPALDIA), aged 29 to 73 years who had complete data on genotypes, diabetes status and covariates. We defined diabetes as self-reported physician-diagnosed, or use of diabetes medication or non-fasting glucose >11.1 mmol/L or HbA1c > 0.065. Air pollution exposure was 10-year mean particulate matter <10 μm in diameter (PM10) assigned to participants' residences using a combination of dispersion modelling, annual trends at monitoring stations and residential history. We derived interaction terms between PM10 and genotypes, and applied mixed logistic models to explore genetic interactions by IL6 polymorphisms on the odds of diabetes.

RESULTS

There were 252 diabetes cases. Respective minor allele frequencies of IL6 -572G > C and IL6 -174G > C were 7 and 39 %. Mean exposure to PM10 was 22 μg/m(3). Both variants were not associated with diabetes in our study. We observed a significant positive association between PM10 and diabetes among homozygous carriers of the pro-inflammatory major G-allele of IL6 -572G > C [Odds ratio: 1.53; 95 % confidence interval (1.22, 1.92); P interaction (additive) = 0.003 and P interaction (recessive) = 0.006]. Carriers of the major G-allele of IL6 -174G > C also had significantly increased odds of diabetes, but interactions were statistically non-significant.

CONCLUSIONS

Our results on the interaction of PM10 with functionally well described polymorphisms in an important pro-inflammatory candidate gene are consistent with the hypothesis that air pollutants impact on T2D through inflammatory pathways. Our findings, if confirmed, are of high public health relevance considering the ubiquity of the major G allele, which puts a substantial proportion of the population at risk for the development of diabetes as a result of long-term exposure to air pollution.

Characterization of ambient and extracted PM2.5 collected on filters for toxicology applications

Research on the health effects of fine particulate matter (PM2.5) frequently disregards the differences in particle composition between that measured on an ambient filter versus that measured in the corresponding extraction solution used for toxicological testing. This study presents a novel method for characterizing the differences, in metallic and organic species, between the ambient samples and the corresponding extracted solutions through characterization of extracted PM2.5 suspended on filters. Removal efficiency was found to be 98.0 ± 1.4% when measured using pre- and post-removal filter weights, however, this efficiency was significantly reduced to 80.2 ± 0.8% when measured based on particle mass in the extraction solution. Furthermore, only 47.2 ± 22.3% of metals and 24.8 ± 14.5% of organics measured on the ambient filter were found in the extraction solution. Individual metallic and organic components were extracted with varying efficiency, with many organics being lost entirely during extraction. Finally, extraction efficiencies of specific PM2.5 components were inversely correlated with total mass. This study details a method to assess compositional alterations resulting from extraction of PM2.5 from filters, emphasizing the need for standardized procedures that maintain compositional integrity of ambient samples for use in toxicology studies of PM2.5.

Toxicology of ambient particulate matter

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

Health risk assessment for air pollutants: alterations in lung and cardiac gene expression in mice exposed to Milano winter fine particulate matter (PM2.5)

Oxidative stress, pulmonary and systemic inflammation, endothelial cell dysfunction, atherosclerosis and cardiac autonomic dysfunction have been linked to urban particulate matter exposure. The chemical composition of airborne pollutants in Milano is similar to those of other European cities though with a higher PM2.5 fraction. Milano winter fine particles (PM2.5win) are characterized by the presence of nitrate, organic carbon fraction, with high amount of polycyclic aromatic hydrocarbons and elements such as Pb, Al, Zn, V, Fe, Cr and others, with a negligible endotoxin presence. In BALB/c mice, we examined, at biochemical and transcriptomic levels, the adverse effects of repeated Milano PM2.5win exposure in lung and heart. We found that ET-1, Hsp70, Cyp1A1, Cyp1B1 and Hsp-70, HO-1, MPO respectively increased within lung and heart of PM2.5win-treated mice. The PM2.5win exposure had a strong impact on global gene expression of heart tissue (181 up-regulated and 178 down-regulated genes) but a lesser impact on lung tissue (14 up-regulated genes and 43 down-regulated genes). Focusing on modulated genes, in lung we found two- to three-fold changes of those genes related to polycyclic aromatic hydrocarbons exposure and calcium signalling. Within heart the most striking aspect is the twofold to threefold increase in collagen and laminin related genes as well as in genes involved in calcium signaling. The current study extends our previous findings, showing that repeated instillations of PM2.5win trigger systemic adverse effects. PM2.5win thus likely poses an acute threat primarily to susceptible people, such as the elderly and those with unrecognized coronary artery or structural heart disease. The study of genomic responses will improve understanding of disease mechanisms and enable future clinical testing of interventions against the toxic effects of air pollutant.

Peak expiratory flow, breath rate and blood pressure in adults with changes in particulate matter air pollution during the Beijing Olympics: a panel study

OBJECTIVES

This study aims to examine whether changes in short-term exposures to particulate matter are associated with changes in lung function, breath rate, and blood pressure among healthy adults and whether smoking status modifies the association.

METHODS

We took advantage of the artificially controlled changes in air pollution levels that occurred during the 2008 Olympic Games in Beijing, China and conducted a panel study of 201 Beijing residents. Data were collected before, during, and after the Olympics, respectively. Linear mixed-effect models and generalized estimating equation models were used to compare measurements of peak expiratory flow, breath rate and blood pressure across three time points.

RESULTS

The mean values of peak expiratory flow were 346.0 L/min, 399.3 L/min, and 364.1L/min over the three study periods. Peak expiratory flow levels increased in 78% of the participants when comparing the during- with pre- Olympics time points, while peak expiratory flow levels decreased in 80% of participants for the post- and during-Olympic periods comparison. In subgroup analyses comparing the during-Olympic to pre-Olympic time points, we found a larger percentage change in peak expiratory flow (+17%) among female, younger and non-smoking participants than among male, elderly and smoking participants (+12%). The percentage of participants with a fast breath rate (>20/min) changed from 9.7% to 4.9% to 30.1% among females, and from 7.9% to 2.6% to 27.3% among males over the three time points. The changes in blood pressure over the three study periods were not very clear, although there is an increase in diastolic pressure and a decrease in pulse pressure among males during the games.

CONCLUSIONS

The results suggest that exposure to different air pollution levels has significant effects on respiratory function. Smoking, age and gender appear to modify participants' biological response to changes in air quality.

Sensing biophysical alterations of human lung epithelial cells (A549) in the context of toxicity effects of diesel exhaust particles

Diesel exhaust particles (DEP) in urban air are associated with numerous respiratory diseases. The role of underlying biomechanics in cytotoxicity of individual lung cells relating to DEP exposure is unclear. In this study, atomic force microscopy (AFM), confocal Raman microspectroscopy (RM), and fluorescence (FL) microscopy were used to monitor alterations of single A549 cells exposed to DEP. Results revealed a significant decrease in membrane surface adhesion force and a significant change in cell elasticity as a function of DEP-cell interaction time, and the dynamic changes in cellular biocomponents which were reflected by changes of characteristic Raman bands: 726 cm(-1) (adenine), 782 cm(-1) (uracil, cytosine, thymine), 788 cm(-1) (O-P-O), 1006 cm(-1) (phenylalanine), and 1320 cm(-1) (guanine) after DEP exposure. These findings suggest that the combination of multi-instruments (e.g., AFM/FL) may offer an exciting platform for investigating the roles of biophysical and biochemical responses to particulate matter-induced cell toxicity.

The role of in vitro gene expression profiling in particulate matter health research

Exposure to particulate matter (PM) is consistently associated with increased morbidity and mortality rate. The mechanisms for these adverse health effects have been vigorously investigated for many years, but remain uncertain, in part due to the complex interactions between host and exposure. Over the past decade, the use of global gene expression profiling has increased to investigate molecular changes in an attempt to gain more insight into the complex mechanisms that underlie the adverse health effects induced by PM. These experiments have been performed mostly in cell cultures, in part due to the easy availability and maneuverability of different cell types. Whether or not the results obtained from these in vitro experiments are relevant to human exposure is unclear. In this study, cell culture studies were reviewed that used microarray technology to measure global gene expression in response to PM and the findings discussed in the context of global gene expression results obtained from animal and human exposure studies. Ten in vitro studies were identified from PubMed that reported global gene expression results in response to PM exposure. Despite difference in cell types, microarray platforms, incubation time, and PM sources and doses, these experiments showed commonality in the expression of genes and pathways, especially xenobiotic metabolism, oxidative stress, and inflammation. These gene expression profiles were consistent with results from animal and human controlled exposure experiments. The in vitro experiments also uncovered novel biological mechanisms that may be important in PM-induced health effects reported in epidemiological studies. Data indicate that in vitro microarray experiments complement animal and human exposure studies and allow the PM-associated health research to focus on the "toxic" components in PM and novel mechanisms, and may enhance risk assessment beyond the current mass-based standards.

Epigenetic Regulation in Particulate Matter-Mediated Cardiopulmonary Toxicities: A Systems Biology Perspective

Particulate matter (PM) air pollution exerts significant adverse health effects in global populations, particularly in developing countries with extensive air pollution. Understanding of the mechanisms of PM-induced health effects including the risk for cardiovascular diseases remains limited. In addition to the direct cellular physiological responses such as mitochondrial dysfunction and oxidative stress, PM mediates remarkable dysregulation of gene expression, especially in cardiovascular tissues. The PM-mediated gene dysregulation is likely to be a complex mechanism affected by various genetic and non-genetic factors. Notably, PM is known to alter epigenetic markers (e.g., DNA methylation and histone modifications), which may contribute to air pollution-mediated health consequences including the risk for cardiovascular diseases. Notably, epigenetic changes induced by ambient PM exposure have emerged to play a critical role in gene regulation. Though the underlying mechanism(s) are not completely clear, the available evidence suggests that the modulated activities of DNA methyltransferase (DNMT), histone acetylase (HAT) and histone deacetylase (HDAC) may contribute to the epigenetic changes induced by PM or PM-related chemicals. By employing genome-wide epigenomic and systems biology approaches, PM toxicogenomics could conceivably progress greatly with the potential identification of individual epigenetic loci associated with dysregulated gene expression after PM exposure, as well the interactions between epigenetic pathways and PM. Furthermore, novel therapeutic targets based on epigenetic markers could be identified through future epigenomic studies on PM-mediated cardiopulmonary toxicities. These considerations collectively inform the future population health applications of genomics in developing countries while benefiting global personalized medicine at the same time.

Gene expression profiling and pathway analysis of human bronchial epithelial cells exposed to airborne particulate matter collected from Saudi Arabia

Epidemiological studies have established a positive correlation between human mortality and increased concentration of airborne particulate matters (PM). However, the mechanisms underlying PM related human diseases, as well as the molecules and pathways mediating the cellular response to PM, are not fully understood. This study aims to investigate the global gene expression changes in human cells exposed to PM(10) and to identify genes and pathways that may contribute to PM related adverse health effects. Human bronchial epithelial cells were exposed to PM(10) collected from Saudi Arabia for 1 or 4 days, and whole transcript expression was profiled using the GeneChip human gene 1.0 ST array. A total of 140 and 230 genes were identified that significantly changed more than 1.5 fold after PM(10) exposure for 1 or 4 days, respectively. Ingenuity Pathway Analysis revealed that different exposure durations triggered distinct pathways. Genes involved in NRF2-mediated response to oxidative stress were up-regulated after 1 day exposure. In contrast, cells exposed for 4 days exhibited significant changes in genes related to cholesterol and lipid synthesis pathways. These observed changes in cellular oxidative stress and lipid synthesis might contribute to PM related respiratory and cardiovascular disease.

Genomics and the respiratory effects of air pollution exposure

Adverse health effects from air pollutants remain important, despite improvement in air quality in the past few decades. The exact mechanisms of lung injury from exposure to air pollutants are not yet fully understood. Studying the genome (e.g. single-nucleotide polymorphisms (SNP) ), epigenome (e.g. methylation of genes), transcriptome (mRNA expression) and microRNAome (microRNA expression) has the potential to improve our understanding of the adverse effects of air pollutants. Genome-wide association studies of SNP have detected SNP associated with respiratory phenotypes; however, to date, only candidate gene studies of air pollution exposure have been performed. Changes in epigenetic processes, such DNA methylation that leads to gene silencing without altering the DNA sequence, occur with air pollutant exposure, especially global and gene-specific methylation changes. Respiratory cell line and animal models demonstrate distinct gene expression signatures in the transcriptome, arising from exposure to particulate matter or ozone. Particulate matter and other environmental toxins alter expression of microRNA, which are short non-coding RNA that regulate gene expression. While it is clearly important to contain rising levels of air pollution, strategies also need to be developed to minimize the damaging effects of air pollutant exposure on the lung, especially for patients with chronic lung disease and for people at risk of future lung disease. Careful study of genomic responses will improve our understanding of mechanisms of lung injury from air pollution and enable future clinical testing of interventions against the toxic effects of air pollutants.

Urban particulate matter activates Akt in human lung cells

The normally picturesque Cache Valley in northern Utah is frequently reported to have the worst particulate (PM) air pollution in the United States. Numerous epidemiological studies conducted elsewhere have associated PM exposure to a variety of cardiovascular diseases and early mortality. We have previously shown that Cache Valley PM (CVPM) is pro-inflammatory, through a variety of mechanisms involving the release of inflammatory cytokines, unfolded protein response, ER stress, and C-reactive protein (CRP). This study was undertaken to determine whether Cache Valley PM (CVPM) would activate Akt, an upstream mechanism common to these events. Human lung (BEAS-2B) cells were treated with either fine (PM(2.5)) or coarse (PM(10)) particles (12.5 and 25 μg/ml) for periods up to 24 h. PM-exposed cells exhibited Akt activation as evidenced by phosphorylation at Thr(308) and Ser(473). Events downstream of Akt activation such as NF-κB activation were observed at 1 and 24 h, but IκB phosphorylation occurred only at 24 h, indicating that mechanisms of PM-mediated NF-κB activation are time dependent. Akt and NF-κB related inflammatory cytokine IL-1α, and IL-6 and the chemokine IL-8 were upregulated in treated cells at 6 and 24 h. The calpain inhibitor leupeptin limited Akt phosphorylation to Ser(473) and reduced release of IL-1α, IL-6, and IL-8, indicating that calpain or similar protease(s) are involved in PM-induced activation of Akt and subsequent release of inflammatory cytokines. Our data indicate that PM activates Akt, which may play a role in the pro-inflammatory response to PM exposure.

Molecular cloning and expression of interleukin-1 receptor-associated kinase 4, an important mediator of Toll-like receptor signal pathway, from small abalone Haliotis diversicolor

Mammal interleukin-1 receptor-associated kinases (IRAKs) have been demonstrated to play important functions in TLRs (Toll-like receptor) signal pathway and T cell proliferation, but there is less knowledge available on mollusc IRAKs. In this study, a molluscan IRAK-4 gene, saIRAK-4, was cloned for the first time from the small abalone (Haliotis diversicolor). Its full-length cDNA sequence was 2062 bp, with a 1548 bp open reading frame encoding a protein of 516 aa. The molecular mass of the deduced protein was approximately 57.8 kDa with an estimated pI of 5.23, and showed highest identity (47%) to acorn worm Saccoglossus kowalevskii. Amino acid sequence analysis revealed saIRAK-4 shares conserved signature motifs with other IRAK-4 proteins, including the death domain (DD), serine/threonine/tyrosine protein kinase domain (STYKc), protein kinases ATP-binding region signature, serine/threonine protein kinases active-site signature and prokaryotic membrane lipoprotein lipid attachment site. Quantitative real-time PCR was employed to investigate the tissue distribution of saIRAK-4 mRNA, and its expression in abalone under bacteria challenge and larvae at different developmental stages. The saIRAK-4 mRNA could be detected in all examined tissues, with the highest expression level in gills, and was up-regulated in hemocytes and gills after bacteria injection. Additionally, saIRAK-4 was constitutively expressed at all examined developmental stages. These results indicate that saIRAK-4 could respond to pathogenic infection and may play an important role in the adult abalone immune system and early innate immunity in the process of abalone larval development.

Associations between ambient fine particulate levels and disease activity in patients with systemic lupus erythematosus (SLE)

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic disease of unclear etiology, characterized by an overactive immune system and the production of antibodies that may target normal tissues of many organ systems, including the kidneys. It can arise at any age and occurs mainly in women.

OBJECTIVE

Our aim was to evaluate the potential influence of particulate matter (PM) air pollution on clinical aspects of SLE.

METHODS

We studied a clinic cohort of SLE patients living on the island of Montreal, followed annually with a structured clinical assessment. We assessed the association between ambient levels of fine PM [median aerodynamic diameter ≤ 2.5 μm (PM2.5)] measured at fixed-site monitoring stations and SLE disease activity measured with the SLE Disease Activity Index, version 2000 (SLEDAI-2K), which includes anti-double-stranded DNA (anti-dsDNA) serum-specific autoantibodies and renal tubule cellular casts in urine, which reflects serious renal inflammation. We used mixed effects regression models that we adjusted for daily ambient temperatures and ozone levels.

RESULTS

We assessed 237 patients (223 women) who together had 1,083 clinic visits from 2000 through 2007 (mean age at time of first visit, 41.2 years). PM2.5 levels were associated with anti-dsDNA and cellular casts. The crude and adjusted odds ratios (reflecting a 10-μg/m3 increase in PM2.5 averaged over the 48 hr prior to clinical assessment) were 1.26 [95% confidence interval (CI), 0.96-1.65] and 1.34 (95% CI, 1.02-1.77) for anti-dsDNA antibodies and 1.43 (95% CI, 1.05-1.95) and 1.28 (0.92-1.80) for cellular casts. The total SLEDAI-2K scores were not associated with PM2.5 levels.

CONCLUSIONS

We provide novel data that suggest that short-term variations in air pollution may influence disease activity in established autoimmune rheumatic disease in humans. Our results add weight to concerns that pollution may be an important trigger of inflammation and autoimmunity.

In vitro assessment of the inflammatory response of respiratory endothelial cells exposed to particulate matter

Particulate matter (PM) is a ubiquitous environmental pollutant that has been associated with increased risk of cardiopulmonary mortality and morbidity in urban communities. An increasing body of evidence suggests that inflammation induced by PM may play an important role in the development of cardiovascular diseases. However, airway epithelial cell lines, instead of vascular endothelial cells, are commonly used to investigate the effects of PM with respect to cardiovascular effects. Thus, the present study was conducted using primary human vascular endothelial cells (HMVEC-LB1), human white blood cells (WBC), and their cocultures to evaluate their inflammatory responses to various PM exposures. Enzyme-linked immunosorbent assay (ELISA) kits were used to measure the concentrations of interleukin (IL)-6, soluble intercellular adhesion marker (sICAM-1), and soluble vascular cell adhesion marker (sVCAM-1) in HMVEC-LB1, WBC, and their cocultures after exposure to size-fractionated PM. Pretreatment of cells with inhibitors was performed in order to examine pathways involved in PM-induced cellular responses. IL-6 levels increased significantly in HMVEC-LB1 cells exposed to PM in both a time- and concentration-dependent manner. However, particle exposure for up to 24 h failed to induce any detectable production of sICAM-1 or sVCAM-1 in HMVEC-LB1 cells. IL-6 production in response to size-fractioned PM exposures failed to show evidence of relative importance of particle sizes in their abilities to induce proinflammatory responses. Lastly, cocultures with WBC significantly enhanced particle induced IL-6 release in HMVEC-LB1 cells in a synergistic manner. The present study suggests that HMVEC-LB1 cells can be successfully used as an in vitro model to examine effects of PM exposure.

Modification of the interleukin-6 response to air pollution by interleukin-6 and fibrinogen polymorphisms

BACKGROUND

Evidence suggests that cardiovascular effects of air pollution are mediated by inflammation and that air pollution can induce genetic expression of the interleukin-6 gene (IL6).

OBJECTIVES

We investigated whether IL6 and fibrinogen gene variants can affect plasma IL-6 responses to air pollution in patients with cardiovascular disease.

METHODS

We repeatedly determined plasma IL-6 in 955 myocardial infarction survivors from six European cities (n = 5,539). We conducted city-specific analyses using additive mixed models adjusting for patient characteristics, time trend, and weather to assess the impact of air pollutants on plasma IL-6. We pooled city-specific estimates using meta-analysis methodology. We selected three IL6 single-nucleotide polymorphisms (SNPs) and one SNP each from the fibrinogen alpha-chain gene (FGA) and beta-chain gene (FGB) for gene-environment analyses.

RESULTS

We found the most consistent modifications for variants in IL6 rs2069832 and FBG rs1800790 after exposure to carbon monoxide (CO; 24-hr average; p-values for interaction, 0.034 and 0.019, respectively). Nitrogen dioxide effects were consistently modified, but p-values for interaction were larger (0.09 and 0.19, respectively). The strongest effects were seen 6-11 hr after exposure, when, for example, the overall effect of a 2.2% increase in IL-6 per 0.64 mg/m(3) CO was modified to a 10% (95% confidence interval, 4.6-16%) increase in IL-6 (p-value for interaction = 0.002) for minor homozygotes of FGB rs1800790.

CONCLUSIONS

The effect of gaseous traffic-related air pollution on inflammation may be stronger in genetic subpopulations with ischemic heart disease. This information could offer an opportunity to identify postinfarction patients who would benefit more than others from a cleaner environment and antiinflammatory treatment.

Urban particulate matter causes ER stress and the unfolded protein response in human lung cells

Because of its presumed adverse health effects, particulate air pollution (PM) has received growing attention, but the cellular mechanisms by which PM exerts toxicity are not well elucidated. PM has been associated with early mortality from illnesses that share endoplasmic reticulum (ER) stress as a mechanism of pathogenesis. In this study, we examined whether PM would induce the unfolded protein response (UPR) which is a cellular response to ER stress. Coarse (PM(10)) and fine (PM(2.5)) PM was collected from a single location in Northern Utah's Cache Valley during atmospheric inversions occurring in January 2002 and January 2003. Extracts of PM samples were added (12.5 and 25 microg/ml) to cultured human bronchial epithelial (BEAS-2B) cells for 24 h. At these concentrations neither PM nor LPS exhibited demonstrable cytotoxicity by the neutral red assay. However, PM elicited significant increases of unfolded protein response (UPR)-related post-translational modifications, such as S6 ribosomal protein, heat-shock protein (Hsp)27, and protein kinase related protein phosphorylation and cleavage of activating transcription factor (ATF)-6. PM exposure also resulted in significant increases in the UPR-associated proteins ATF-4, Hsp70, Hsp90, and binding immunoglobulin protein. PM also interfered with the export of Hsp70 from the cells in a concentration-dependent manner and resulted in release of C-reactive protein. Calpain was upregulated and activated in PM-treated cultures, though these events were not proapoptotic. This study demonstrates that PM is capable of inducing ER stress and the UPR in vitro and may be a mechanism by which PM exerts toxicity.

Airborne particulate matter PM2.5 from Mexico City affects the generation of reactive oxygen species by blood neutrophils from asthmatics: an in vitro approach

Background

The Mexico City Metropolitan Area is densely populated, and toxic air pollutants are generated and concentrated at a higher rate because of its geographic characteristics. It is well known that exposure to particulate matter, especially to fine and ultra-fine particles, enhances the risk of cardio-respiratory diseases, especially in populations susceptible to oxidative stress. The aim of this study was to evaluate the effect of fine particles on the respiratory burst of circulating neutrophils from asthmatic patients living in Mexico City.

Methods

In total, 6 subjects diagnosed with mild asthma and 11 healthy volunteers were asked to participate. Neutrophils were isolated from peripheral venous blood and incubated with fine particles, and the generation of reactive oxygen species was recorded by chemiluminescence. We also measured plasma lipoperoxidation susceptibility and plasma myeloperoxidase and paraoxonase activities by spectrophotometry.

Results

Asthmatic patients showed significantly lower plasma paraoxonase activity, higher susceptibility to plasma lipoperoxidation and an increase in myeloperoxidase activity that differed significantly from the control group. In the presence of fine particles, neutrophils from asthmatic patients showed an increased tendency to generate reactive oxygen species after stimulation with fine particles (PM_2.5).

Conclusion

These findings suggest that asthmatic patients have higher oxidation of plasmatic lipids due to reduced antioxidant defense. Furthermore, fine particles tended to increase the respiratory burst of blood human neutrophils from the asthmatic group.

On the whole, increased myeloperoxidase activity and susceptibility to lipoperoxidation with a concomitant decrease in paraoxonase activity in asthmatic patients could favor lung infection and hence disrupt the control of asthmatic crises.

Fine ambient particles induce oxidative stress and metal binding genes in human alveolar macrophages

Exposure to pollutant particles increased respiratory morbidity and mortality. The alveolar macrophages (AMs) are one cell type in the lung directly exposed to particles. Upon contact with particles, AMs are activated and produce reactive oxygen species, but the scope of this oxidative stress response remains poorly defined. In this study, we determined the gene expression profile in human AMs exposed to particles, and sought to characterize the global response of pro- and antioxidant genes. We exposed AMs obtained by bronchoscopy from normal individuals to Chapel Hill particulate matter of 2.5-microm diameter or smaller (PM(2.5); 1 microg/ml) or vehicle for 4 hours (n = 6 independent samples). mRNAs were extracted, amplified, and hybridized to Agilent human 1A microarray. Significant genes were identified by significance analysis of microarrays (false discovery rate, 10%; P < or = 0.05) and mapped with Gene Ontology in the Database for Annotation, Visualization, and Integrated Discovery. We found 34 and 41 up- and down-regulated genes, respectively; 22 genes (approximately 30%) were involved in metal binding, and 11 were linked to oxidative stress, including up-regulation of five metallothionein (MT)-1 isoforms. Exogenous MT1 attenuated PM(2.5)-induced H2O2 release. PM(2.5) premixed with MT1 stimulated less H2O2 release. Knockdown of MT1F gene increased PM(2.5)-induced H2O2 release. PM(2.5) at 1 microg/ml did not increase H2O2 release. Mount St. Helens PM(2.5) and acid-extracted Chapel Hill PM(2.5), both poor in metals, did not induce MT1F or H2O2 release. Our results show that PM(2.5) induced a gene expression profile prevalent with genes related to metal binding and oxidative stress in human AMs, independent of oxidative stress. Metals associated with PM may play an important role in particle-induced gene changes.

Regulation of COX-2 expression and IL-6 release by particulate matter in airway epithelial cells

Particulate matter (PM) in ambient air is a risk factor for human respiratory and cardiovascular diseases. The delivery of PM to airway epithelial cells has been linked to release of proinflammatory cytokines; however, the mechanisms of PM-induced inflammatory responses are not well-characterized. This study demonstrates that PM induces cyclooxygenase (COX)-2 expression and IL-6 release through both a reactive oxygen species (ROS)-dependent NF-kappaB pathway and an ROS-independent C/EBPbeta pathway in human bronchial epithelial cells (HBEpCs) in culture. Treatment of HBEpCs with Baltimore PM induced ROS production, COX-2 expression, and IL-6 release. Pretreatment with N-acetylcysteine (NAC) or EUK-134, in a dose-dependent manner, attenuated PM-induced ROS production, COX-2 expression, and IL-6 release. The PM-induced ROS was significantly of mitochondrial origin, as evidenced by increased oxidation of the mitochondrially targeted hydroethidine to hydroxyethidium by reaction with superoxide. Exposure of HBEpCs to PM stimulated phosphorylation of NF-kappaB and C/EBPbeta, while the NF-kappaB inhibitor, Bay11-7082, or C/EBPbeta siRNA attenuated PM-induced COX-2 expression and IL-6 release. Furthermore, NAC or EUK-134 attenuated PM-induced activation of NF-kappaB; however, NAC or EUK-134 had no effect on phosphorylation of C/EBPbeta. In addition, inhibition of COX-2 partly attenuated PM-induced Prostaglandin E2 and IL-6 release.

The involvement of the interleukin-1 receptor-associated kinases (IRAKs) in cellular signaling networks controlling inflammation

Innate immunity and inflammation plays a key role in host defense and wound healing. However, Excessive or altered inflammatory processes can contribute to severe and diverse human diseases including cardiovascular disease, diabetes and cancer. The interleukin-1 receptor-associated kinases (IRAKs) are critically involved in the regulation of intracellular signaling networks controlling inflammation. Collective studies indicate that IRAKs are present in many cell types, and can mediate signals from various cell receptors including toll-like-receptors (TLRs). Consequently, diverse downstream signaling processes can be elicited following the activation of various IRAKs. Given the critical and complex roles IRAK proteins play, it is not surprising that genetic variations in human IRAK genes have been found to be linked with various human inflammatory diseases. This review intends to summarize the recent advances regarding the regulations of various IRAK proteins and their cellular functions in mediating inflammatory signaling processes.

Particulate matter, oxidative stress and neurotoxicity

Particulate matter (PM), a component of air pollution has been epidemiologically associated with sudden deaths, cardiovascular and respiratory illnesses. The effects are more pronounced in patients with pre-existing conditions such as asthma, diabetes or obstructive pulmonary disorders. Clinical and experimental studies have historically focused on the cardiopulmonary effects of PM. However, since PM particles carry numerous biocontaminants that are capable of triggering free radical production and cytokine release, the possibility that PM may affect organs systems sensitive to oxidative stress must be considered. Four independent studies that summarize the neurochemical and neuropathological changes found in the brains of PM exposed animals are described here. These were recently presented at two 2007 symposia sponsored by the Society of Toxicology (Charlotte, NC) and the International Neurotoxicology Association (Monterey, CA).