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

Degenerative and Regenerative Actin Cytoskeleton Rearrangements, Cell Death, and Paradoxical Proliferation in the Gills of Pearl Gourami (Trichogaster leerii) Exposed to Suspended Soot Microparticles

The effect is studied of water-suspended soot microparticles on the actin cytoskeleton, apoptosis, and proliferation in the gill epithelium of pearl gourami. To this end, the fish are kept in aquariums with 0.005 g/L of soot for 5 and 14 days. Laser confocal microscopy is used to find that at the analyzed times of exposure to the pollutant zones appear in the gill epithelium, where the actin framework of adhesion belts dissociates and F-actin either forms clumps or concentrates perinuclearly. It is shown that the exposure to soot microparticles enhances apoptosis. On day 5, suppression of the proliferation of cells occurs, but the proliferation increases to the control values on day 14. Such a paradoxical increase in proliferation may be a compensatory process, maintaining the necessary level of gill function under the exposure to toxic soot. This process may occur until the gills' recovery reserve is exhausted. In general, soot microparticles cause profound changes in the actin cytoskeleton in gill cells, greatly enhance cell death, and influence cell proliferation as described. Together, these processes may cause gill dysfunction and affect the viability of fish.

Insight into the oxidation of glutathione mediated by black carbon from three typical emission sources

Black carbon (BC) is released into the atmosphere in large quantities from different emission sources each year and poses a serious threat to human health. These BC possessed a variety of characteristics and different mediation abilities for the reactive oxygen species (ROS) generation. In this study, we collected BC (i.e., diesel BC, coal BC and wood BC) from three typica emission sources, and examined their mediation abilities to the oxidation of glutathione (GSH). Results showed that all three BC significantly promoted the GSH oxidation, and the mediation efficiencies were as follows: diesel BC > coal BC > wood BC. In comparison with the water-soluble fraction, the mediation abilities of three BC mainly came from their solid phase fractions. In the coal BC and wood BC systems, the oxidation of GSH was attributed to the catalysis of transition metals in BC. By contrast, the transition metals, phenolic -OH and persistent free radicals in diesel BC were identified as the active sites responsible for the GSH oxidation. In addition, the graphitic surface of diesel BC could synergize with these active sites to accelerate the oxidation of GSH. Under the catalysis of BC, dissolved oxygen was first reduced to ROS (O₂^•- and H₂O₂) and then caused the GSH oxidation. These findings not only help to better assess the adverse health effects of different BC, but also deepen the understanding of the reaction mechanisms.

Integrated proteomic analysis to explore the molecular regulation mechanism of IL-33 mRNA increased by black carbon in the human endothelial cell line EA.hy926

Black carbon (BC) correlates with the occurrence and progression of atherosclerosis and other cardiovascular diseases. Increasing evidence has demonstrated that BC could impair vascular endothelial cells, but the underlying mechanisms remain obscure. It is known that IL-33 exerts a significant biological role in cardiovascular disease, but little is known about the molecular regulation of IL-33 expression at present. We first found that BC significantly increased IL-33 mRNA in EA.hy926 cells in a concentration and time-dependent manner, and we conducted this study to explore its underlying mechanism. We identified that BC induced mitochondrial damage and suppressed autophagy function in EA.hy926 cells, as evidenced by elevation of the aspartate aminotransferase (GOT2), reactive oxygen species (ROS) and p62, and the reduction of mitochondrial membrane potential (ΔΨm). However, ROS cannot induce IL-33 mRNA-production in BC-exposed EA.hy926 cells. Further, experiments revealed that BC could promote IL-33 mRNA production through the PI3K/Akt/AP-1 and p38/AP-1 signaling pathways. It is concluded that BC could induce oxidative stress and suppress autophagy function in endothelial cells. This study also provided evidence that the pro-cardiovascular-diseases properties of BC may be due to its ability to stimulate the PI3K/AKT/AP-1 and p38/AP-1 pathway, further activate IL-33 and ultimately result in a local vascular inflammation.

RIPK1 is a key factor in black carbon-induced cell death

Air pollution is associated with increased morbidity and mortality and with cell death at a cellular level. However, the exact mechanism of particulate matter-induced cell death remains to be elucidated. The aim of the present in vitro study using human alveolar epithelial cells (A549) was to determine the cell death pathway(s) induced by black carbon (BC) and ozone oxidized-black carbon (O-BC). BC and O-BC induced A549 cell death and the cytotoxic effect was dose-dependent. Cell death was significantly abrogated by inhibitor of receptor protein interacting kinase 1 (RIPK1) but only mildly inhibited by apoptosis inhibitor and RIPK3. BC- and O-BC-treated cells showed RIPK1 and RIPK3 protein overexpression and high phosphorylated levels of these proteins, as well as detectable levels of caspase-8 active form. BC- and O-BC-triggered cell death was also fully rescued in A549 cells that under-expressed RIPK1 with RIPK1 siRNA. Our results indicated that BC and O-BC could induce cell death through a multitude of pathways including apoptotic and necroptotic pathways and that RIPK1 is the upstream signal protein of these cell death pathways, with an important role in the regulation of BC-induced cell death.

Oxidized carbon black nanoparticles induce endothelial damage through C-X-C chemokine receptor 3-mediated pathway

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CBox) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CBox particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CBox particles. Treatment with CBox demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CBox-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CBox particles and established the role of macrophage-released chemical mediators in endothelial damage.

Long-term carbon black inhalation induced the inflammation and autophagy of cerebellum in rats

Carbon black (CB) has been demonstrated to have adverse effects on the lung tissue. Few studies explored the effects of CB on the cerebellum, widely recognized to contribute to gait and balance coordination and timing in the motor domain. Some studies have reported that inflammatory response and damaged autophagy are important mechanisms of CB toxicity and can be repaired after the recovery. The present study aimed to determine whether long-term CB exposure could induce the inflammation and damaged autophagy of the cerebellum. The rats were randomly divided into four groups. The control group received the filtered air for 90 days; the carbon black (CB) group received CB particles for 90 days; the recovery (R) group received CB for 90 days and recovered for another 14 days; the recovery control (RC) group received filtered air for 104 days. The purpose of the R group was to test whether neuroinflammation and autophagy could be repaired after short-term recovery. The western blot and immunohistochemistry revealed that long-term CB exposure induced augmented level of pro-inflammatory cytokines (Interleukin-1β, IL-1β; Interleukin-6, IL-6; and Tumor Necrosis Factor-α, TNF-α) and anti-inflammatory cytokine (Interleukin-10, IL-10). The autophagic markers (Beclin1 and LC3) were increased in both CB group and R group. These findings clearly demonstrated that long-term CB exposure induced inflammation and autophagy in the cerebellum, which were not obviously improved after short-term recovery.

Black carbon induces complement activation via NLRP3 inflammasome in human corneal epithelial cells

PURPOSE

To investigate the effect of black carbon (BC) particles on complement activation in human corneal epithelial cells (HCECs), and determine whether this effect can be attenuated by inhibiting the NLPR3 inflammasome pathway.

MATERIALS AND METHODS

HCECs were treated with fresh BC (FBC) or ozone-oxidized BC (OBC) particles at a concentration of 200 μg/ml for 72hours. Complement activation was observed by detecting C5b-9 protein level in cell culture supernatant using ELISA. HCECs were transfected with duplexes of siRNA targeting NLRP3 (NLRP3-siRNA) at 0.1 pmol/µL for 24 hours to inhibit the NLPR3 inflammasome pathway. RT-qPCR was performed to examine the efficacy of NLRP3-siRNA for inhibition; a random siRNA duplex was used for control siRNA.

RESULTS

Both FBC exposure and OBC exposure for 72 hours significantly increased the C5b-9 protein level compared to negative control cells (all P < .05). However, the difference in C5b-9 level after FBC exposure and OBC exposure was not statistically significant (P> .05). NLRP3-siRNA transfection reduced C5b-9 protein levels in FBC treated and OBC treated HCECs compared to control (lowered by 27% in the FBC treated group and by 23% in the OBC treated group, all P < .05).

CONCLUSIONS

BC particles, including FBC and OBC, triggered complement activation, increasing the protein level of C5b-9 in cultured HCECs. siRNA targeting NLRP3 to inhibit NLRP3 generation reduced C5b-9 protein level in HCECs treated with FBC or OBC particles, indicating that BC induces complement activation potentially through the NLRP3 inflammasome in HCECs.

Assessment of changes in genetic transcriptome in nasal epithelial cells exposed to ozone-aged black carbon and pollen allergen by high-throughput transcriptomics

Background

Air pollution may be associated with increased airway responsiveness to allergens in allergic rhinitis (AR). Ozone-aged environmental black carbon (O₃BC) is an important constituent of atmospheric particulate matter (PM), for which the mechanisms underlying its effects have not been fully elucidated in AR. The objective of the present study was to determine the O₃BC and pollen-induced alterations in the transcriptome in human nasal epithelial cells (hNECs) in vitro.

Methods

hNECs from nasal epithelial mucosal samples of healthy individuals undergoing nasal surgery (turbinoplasty or septoplasty) were established as air–liquid interface (ALI) cultures and exposed to O₃BC, pollen, or a combination of O₃BC+ pollen. Changes in cell viability were analyzed by fluorescence and changes in the transcriptome by high-throughput RNA sequencing (RNA-seq). Several differentially expressed genes were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Enrichment analysis, based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) database, was performed to determine major biological functions and pathways involved.

Results

Exposure to ≥ 50 μg/ml O₃BC or 25 μg/ml O₃BC+ 200 μg /ml pollen significantly decreased cell viability of the hNECs compared to control (p < 0.05) or 25 μg/ml O₃BC alone (p < 0.05); whereas exposure to pollen alone did not alter cell viability at any concentration investigated. High-throughput RNA sequencing analysis indicated that there was significant difference in gene expression between pollen or O₃BC alone and O₃BC+ pollen exposed cells. Exposure to 200 μg/ml O₃BC was associated with hypoxia stress response GO terms, whereas exposure to 25 μg/ml O₃BC+ 200 μg/ml pollen was associated with inflammatory response GO terms; including regulation of neutrophil migration and chemotaxis, macrophage differentiation and chemotaxis, mast cell activation, and phagocytosis. KEGG pathway analysis indicated the top 10 upstream regulators to be IL1B, CSF1, CCL2, TLR2, LPL, IGF8, SPP1, CXCL8, FCER1G and IL1RN; of which expressions of inflammation-related genes IL1B, CSF1 and FCER1G were significantly increased.

Conclusion

O₃BC and pollen allergen combined exposure may induce innate immune and allergic inflammation in hNECs, and therefore potentially exacerbate the symptoms of AR in affected individuals.

Low-dose combined exposure of carboxylated black carbon and heavy metal lead induced potentiation of oxidative stress, DNA damage, inflammation, and apoptosis in BEAS-2B cells

Black carbon (BC) and heavy metal lead (Pb), as typical components of atmospheric PM_2.5, have been shown to cause a variety of adverse health effects. However, co-exposure to BC and Pb may induce pulmonary damage by aggravating toxicity via an unknown mechanism. This study aimed to investigate the combined toxicity of carboxylated black carbon (c-BC) and lead acetate (Pb) on human bronchial epithelial cells (BEAS-2B) at the no-observed-adverse-effect level (NOAEL). Cells were exposed to c-BC (6.25 μg/mL) and Pb (4 μg/mL) alone or their combination, and their combined toxicity was investigated by focusing on cell viability, oxidative stress, DNA damage, mitochondrial membrane potential (MMP), apoptosis, and cellular inflammation. Factorial analyses were also used to determine the potential interactions between c-BC and Pb. The results suggested that the combination of c-BC and Pb could significantly increase the production of reactive oxygen species (ROS), malondialdehyde (MDA), and lactate dehydrogenase leakage (LDH) and decrease the activities of glutathione (GSH) and superoxide dismutase (SOD). The excessive oxidative stress could increase the levels of inflammatory cytokine IL-6 and TNF-α, and induce oxidative DNA damage and dissipation of MMP. Moreover, the results also suggested that the combined group could enhance the cellular apoptotic rate and the activation of apoptotic markers like caspase-3, caspase-8, and caspase-9. The factorial analysis further demonstrated that synergistic interaction was responsible for the combined toxicity of c-BC and Pb co-exposure. Most noticeably, the co-exposure of c-BC and Pb could induce some unexpected toxicity, even beyond the known toxicities of the individual compounds in BEAS-2B cells at the NOAEL.

Removal of polycyclic aromatic hydrocarbon (PAH)-contaminated sediments by persulfate oxidation and determination of degradation product cytotoxicity based on HepG2 and ZF4 cell lines

This study evaluated the use of magnetite (Fe₃O₄), carbon black (CB), and Fe₃O₄-CB composites activated by persulfate (PS) at circumneutral pH to oxidize polycyclic aromatic hydrocarbons (PAHs) in marine sediments. In addition, the in vitro cytotoxic activity and apoptotic response of the obtained degradation products were investigated. Chemical analyses showed that the total PAH concentration was 26,263 ng/g for sediment samples from an industrial port area. Highly toxic BaP was the main contributor to the TEQ in sediments. Source analyses demonstrated that the PAHs in the sediment were derived from coal combustion. In this study, we found that the PS oxidation processes effectively degrade PAHs at concentration levels of 1.7 × 10^-5 M at pH 6.0. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the cytotoxicity of the PAH degradation products before and after Fe₃O₄/PS, CB/PS, and Fe₃O₄-CB/PS oxidation treatment using a human hepatoma carcinoma cell line (HepG2) and a zebrafish (Danio rerio) embryonic cell line (ZF4). Each sample extract showed a marked dose-related response, with the cell viability reduced by 82% in the case of HepG2 and 58% in the case of ZF4 at 100 μg/mL after the Fe₃O₄-CB/PS process. The PAH degradation products had different effects on the cell morphologies of the two cell lines. The results suggested that the ZF4 cell model is more sensitive than HepG2 to the toxicity of the PAH samples.

Evaluation of oxidative damage and Nrf2 activation by combined pollution exposure in lung epithelial cells

The lungs are one the main organs exposed to environmental pollutants, such as tropospheric ozone (O3) and particulate matter (PM), which induce lung pathologies through similar mechanisms, resulting in altered redox homeostasis and inflammation. Although numerous studies have investigated the effects of these pollutants in the respiratory tract, there are only a few evidences that have evaluated the combined effects of outdoor stressors, despite the fact that humans are consistently exposed to more pollutants simultaneously. In this study, we wanted to investigate whether exposure to PM and O3 could have an additive, noxious effect in lung epithelial cells by measuring oxidative damage and the activity of redox-sensitive nuclear factor erythroid 2-related factor 2 (Nrf2) which is a master regulator of cellular antioxidant defenses. First, we measured the cytotoxic effects of O3 and PM individually and in combination. We observed that both pollutants alone increased LDH release 24 h post-exposure. Interestingly, we did observe via TEM that combined exposure to O3 and PM resulted in increased cellular penetration of PM particles. Furthermore, we found that levels of 4-hydroxy-nonenal (4HNE), a marker of oxidative damage, significantly increased 24 h post-exposure, in response to the combined pollutants. In addition, we observed increased levels of Nrf2, in response to the combined pollutants vs. either pollutant, although this effect was not followed by the increase in Nrf2-responsive genes expression HO1, SOD1, GPX, or GR nor enzymatic activity. Despite these observations, our study suggests that O3 exposure facilitate the cellular penetration of the particles leading to an increased oxidative damage, and additive defensive response.

Comparison of Transcriptomics Changes Induced by TCS and MTCS Exposure in Human Hepatoma HepG2 Cells

Triclosan (TCS) has been a widely used antibacterial agent in medical and personal care products in the last few decades. Methyl TCS (MTCS) is the major biotransformation product of TCS through replacement of the hydroxyl group with methoxy. Previous studies revealed that MTCS showed reduced toxicity but enhanced environmental persistence, when compared with TCS. Till date, the toxicological molecular mechanisms of TCS and MTCS remain to be clarified. This study aimed to investigate the transcriptomic changes in HepG2 cells induced by TCS and MTCS using microarray chips and to identify key target genes and related signal pathways. The microarray data showed that there were 1664 and 7144 differentially expressed genes (DEGs) in TCS- and MTCS-treated groups, respectively. Gene ontology (GO) enrichment and Kyoto Encyclopedia of genes and genomes (KEGG) analysis revealed that TCS and MTCS induced overlapping as well as distinct transcriptome signatures in HepG2 cells. Both TCS and MTCS could result in various biological responses in HepG2 cells mainly responding to biosynthetic and metabolic processes but probably through different regulatory pathways. Among the selected 50 GO terms, 9 GO terms belonging to the cellular component category were only enriched in the MTCS group, which are mainly participating in the regulation of cellular organelle's function. KEGG analysis showed that 19 and 59 pathway terms were separately enriched in TCS and MTCS groups, with only seven identical pathways. The selected 10 TCS-specific signal pathways are mainly involved in cell proliferation and apoptosis, while the selected 10 MTCS-specific pathways mainly take part in the regulation of protein synthesis and modification. The overall data suggested that MTCS induced more enriched DEGs, GO terms, and pathway terms than TCS. In conclusion, compared with TCS, MTCS presents lower polarity and stronger lipophilicity, enabling MTCS to cause more extensive transcriptomic changes in HepG2 cells, activate differentiated signal pathways, and finally lead to differences in biological responses.

PI3K/Akt/FoxO pathway mediates glycolytic metabolism in HepG2 cells exposed to triclosan (TCS)

Triclosan (TCS) has been widely used as an antibacterial agent for the last several decades in personal care products. The toxicological effect of TCS has attracted more and more attention of researchers. The purpose of this study is to evaluate the cytotoxic effects of TCS in HepG2 cells and to elucidate the molecular mechanism focusing on regulation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/forkhead box O (FoxO) pathway in the glycolytic metabolism. In this study, we evaluated the adverse effect of TCS exposure on cell viability, reactive oxygen species (ROS) generation, superoxide dismutase (SOD) activity and mitochondrial membrane potential (MMP). In addition, the glycolysis process in HepG2 cells exposed to TCS was examined in terms of glucose consumption, lactate production and ATP generation. Furthermore, Affymetrix Human U133 plus 2.0 gene chips and gene function enrichment analysis were conducted to screen differential expression genes (DEGs) and potential signaling pathway. Expressions of the glycolysis-related proteins were measured and quantified with Western Blotting. The results showed that TCS could suppress the cell viability, induce oxidative stress, and cause mitochondrial damage. In addition, TCS exposure promoted the glycolysis process, as manifested by accelerated conversion of glucose to lactate and increased energy release. Western Blotting results confirmed that the expression levels of glycolysis related proteins were significantly elevated. The PI3K/Akt/FoxO pathway was identified to play a pivot role in TCS-induced glycolysis, which was further confirmed by inhibitor tests using specific inhibitors LY294002 and MK2206. In general, TCS can induce oxidative stress, cause oxidative damages and promote glycolysis in HepG2 cells, which was mediated by the PI3K/Akt/FoxO pathway.

Airborne Particulate Matter: Human Exposure and Health Effects

OBJECTIVE

Exposure to airborne particulate matter (PM) is estimated to cause millions of premature deaths annually. This work conveys known routes of exposure to PM and resultant health effects.

METHODS

A review of available literature.

RESULTS

Estimates for daily PM exposure are provided. Known mechanisms by which insoluble particles are transported and removed from the body are discussed. Biological effects of PM, including immune response, cytotoxicity, and mutagenicity, are reported. Epidemiological studies that outline the systemic health effects of PM are presented.

CONCLUSION

While the integrated, per capita, exposure of PM for a large fraction of the first-world may be less than 1 mg per day, links between several syndromes, including attention deficit hyperactivity disorder (ADHD), autism, loss of cognitive function, anxiety, asthma, chronic obstructive pulmonary disease (COPD), hypertension, stroke, and PM exposure have been suggested. This article reviews and summarizes such links reported in the literature.

Transcriptomic analyses of the biological effects of black carbon exposure to A549 cells

Ambient black carbon (BC) is found to be associated with increased risk of diverse pulmonary diseases, including acute respiratory inflammation and decreased lung function. Freshly emitted BC (FBC) can be transformed into oxidized BC (OBC) through the photochemical oxidization in the air. How this oxidization process influences the toxicity of BC particles is unclear. Previous studies found FBC and OBC could induce oxidative stress and inflammation. This study aimed to further compare the regulating pathways and tried to reveal the crucial target genes caused by FBC and OBC in A549 cells based on transcriptomic data. A total of 47,000 genes in A549 cells after treated with FBC and OBC were examined using Affymetrix Human U133 plus 2.0 chips. Gene ontology (GO) classification (functional enrichment of differentially expressed genes) and Kyoto encyclopedia of genes and genomes (KEGG) classification (pathway enrichment of differentially expressed genes) were conducted and crucial genes were screened. The results showed that top 50 GO terms of FBC and OBC were not completely consistent. The Go term of cation channel was only identified in OBC group, probably caused by the characteristic that zeta potential of OBC is negative, while, that of FBC is positive. In addition transient receptor potential melastatin 7 (trpm7) gene was suggested to be closely related to this process caused by OBC. There are 47 identical pathways in FBC and OBC group among the top 50 KEGG. The inconsistent pathways are mostly related to inflammation with different up-regulation or down-regulation trends of crucial genes. The KEGG results suggested that FBC and OBC both cause inflammatory responses, but through different regulating pathways. In conclusion, OBC and FBC could induce similar toxic endpoints in A549 cells, but the underline regulating processes are not exactly the same.

Oxidation Potential Reduction of Carbon Nanomaterials during Atmospheric-Relevant Aging: Role of Surface Coating

Carbon nanomaterials from various sources are the important component of PM_2.5 and have many adverse effects on human health. They are prone to interact with other pollutants and subsequently age, defined here as changes in chemical properties. In this work, we investigated the aging process of various carbon nanoparticle samples such as Special Black 4A, Printex U, single-walled carbon nanotubes, and hexane flame soot by ambient air and studied the evolution of their oxidation potential. We found that coatings of inorganic and organic species dominated the aging process of carbonaceous particles by ambient air. The amounts of disordered carbon and C-H functional groups of aged carbonaceous particles decreased during the aging process; meanwhile, the contents of sulfate and nitrate showed significant increases. In addition, the oxidation potential measured by the dithiothreitol assay remarkably declined as a function of aging time with ambient air evidently because of heterogeneous reactions between SO₂ and NO₂, as well as the coating with organic vapors. This work is important for understanding the oxidation potential changes of carbonaceous particles during atmospheric transport.

Transcriptional Effects of Ozone and Impact on Airway Inflammation

Epidemiological and challenge studies in healthy subjects and in individuals with asthma highlight the health impact of environmental ozone even at levels considered safe. Acute ozone exposure in man results in sputum neutrophilia in 30% of subjects particularly young children, females, and those with ongoing cardiopulmonary disease. This may be associated with systemic inflammation although not in all cases. Chronic exposure amplifies these effects and can result in the formation of asthma-like symptoms and immunopathology. Asthmatic patients who respond to ozone (responders) induce a greater number of genes in bronchoalveolar (BAL) macrophages than healthy responders with up-regulation of inflammatory and immune pathways under the control of cytokines and chemokines and the enhanced expression of remodeling and repair programmes including those associated with protease imbalances and cell-cell adhesion. These pathways are under the control of several key transcription regulatory factors including nuclear factor (NF)-κB, anti-oxidant factors such as nuclear factor (erythroid-derived 2)-like 2 NRF2, the p38 mitogen activated protein kinase (MAPK), and priming of the immune system by up-regulating toll-like receptor (TLR) expression. Murine and cellular models of acute and chronic ozone exposure recapitulate the inflammatory effects seen in humans and enable the elucidation of key transcriptional pathways. These studies emphasize the importance of distinct transcriptional networks in driving the detrimental effects of ozone. Studies indicate the critical role of mediators including IL-1, IL-17, and IL-33 in driving ozone effects on airway inflammation, remodeling and hyperresponsiveness. Transcription analysis and proof of mechanisms studies will enable the development of drugs to ameliorate the effects of ozone exposure in susceptible individuals.

Cytotoxicity comparison between fine particles emitted from the combustion of municipal solid waste and biomass

Fine particles (PM_2.5) emitted from municipal solid waste incineration (MSWI) contain high amounts of toxic compounds and pose a serious threat to environment and human health. In this study, entire particles as well as extracted water-soluble and -insoluble fractions of PM_2.5 collected from MSWI and biomass incineration (BMI) were subjected to physiochemical characterization and cytotoxic tests in A549 and BEAS-2B cells. MSWI PM_2.5 had higher contents of heavy metals (including Pb, Zn, and Cu) and dioxins (PCDD/Fs) than did BMI PM_2.5. The metals were enriched in the water-insoluble fraction, as measured by inductively coupled plasma-atomic emission spectrometry. BMI PM_2.5 had a higher content of endotoxin, which was also enriched in the water-insoluble fraction. MSWI PM_2.5 caused more serious cell injuries, as indicated by the lower viability, higher ROS generation, and DNA damage, whereas BMI PM_2.5 presented higher pro-inflammatory potential, as indicated by increased mRNA levels of interleukin 6. Normal human BEAS-2B cells were more sensitive than A549 cells in all these tests. Toxic effects caused by MSWI and BMI PM_2.5 were mostly attributable to their water-insoluble fractions. Our results indicate different chemical and biological compositions in MSWI and BMI PM_2.5 probably dominate in different toxic endpoints in vitro.

Fresh and ozonized black carbon promoted DNA damage and repair responses in A549 cells

Nano-sized ambient black carbon (BC) is hypothesized to pose a serious threat to human health. After emission into the air, the atmospheric oxidation process can modify its physiochemical properties and change its biological responses. In this study, we aimed to compare different DNA damage and repair responses promoted by fresh BC (FBC) and ozone oxidized-BC (OBC). The cell apoptosis, cell arrest, DNA damage and repair were investigated in A549 cells after treatment with FBC and OBC. Associated gene expressions were measured with the reverse transcription quantitative polymerase chain reaction (RT-qPCR) method. Both FBC and OBC could induce cell apoptosis in A549 cells with up-regulated gene of promyelocytic leukemia protein (pml) and down-regulated gene of anti-apoptotic B-cell lymphoma-2 (bcl-2). FBC caused cell cycle arrest at S and G2/M phases, which was associated with up-regulated ataxia telangiectasia mutated (atm), checkpoint kinase 2 (chk2), structural maintenance of chromosomes 1 (smc1) and cell division cycle 25 homolog A (cdc25a) genes. OBC promoted cell cycle arrest at the S phase with up-regulated genes of atm, chk2 and smc1. Both FBC and OBC induced oxidative DNA damage and time-dependent DNA repair responses with increased gene expressions of breast cancer susceptibility protein 1 (brca1), recombination protein A paralog B (rad51b), methyl methanesulfonate-sensitivity protein 22-like and tonsoku-like (mms22l). Compared to FBC, OBC could cause more sufficient DNA damage repair responses through cell cycle arrest at the S phase, resulting in relatively weaker DNA damages.

Interactions between oxidative stress, autophagy and apoptosis in A549 cells treated with aged black carbon

After emitted from incomplete combustion of fossil fuels and biomass, ambient black carbon (BC) was then undergone photochemical oxidization processes in the air to form aged BC particles, also called oxidized BC (OBC). This study aimed to investigate the interactions between oxidative stress, autophagy and apoptosis induced by OBC in A549 cells and to explore associated molecular mechanisms. First, OBC could stimulate oxidative stress, autophagy and apoptosis dose-dependently, as evidenced by increased intercellular reactive oxygen species (ROS) levels, up-regulated autophagosome markers (light chain 3, LC3), and elevated apoptosis rate. Inhibitors of oxidative stress (N-acetylcysteine, NAC), autophagy (bafilomycin A1, Baf) and apoptosis (Z-DEVD-FMK) were used to investigate their interactions. NAC pretreatment could significantly reduce autophagy and apoptosis. Additionally, pretreatment with Baf or Z-DEVD-FMK could also significantly suppress the other two biological effects. Furthermore, OBC up regulated the expressions of DNA-dependent protein kinase catalytic subunit (DNA-PKcs), phosphorylated protein kinase B (Akt) and mammalian target of rapamycin (mTOR). The Akt inhibitor (MK-2206) significantly reduced both autophagy and apoptosis. Taken together, dual-direction regulation existed between each two of oxidative stress, autophagy, and apoptosis in A549 cells exposed to OBC. In addition, the autophagy process is modulated by the PI3K/Akt pathway regardless of mTOR activity.