Incinerator fly ash provokes alteration of redox equilibrium and liberation of arachidonic acid in vitro

Human Monocyte-Derived Macrophages Demonstrate Distinct Responses to Ambient Particulate Matter in a Polarization State- and Particle Seasonality-Specific Manner

Macrophages are professional phagocytic immune cells that, following activation, polarize on a spectrum between the proinflammatory M1 and the proresolution M2 states. Macrophages have further been demonstrated to retain plasticity, allowing for the reprogramming of their polarization states following exposure to new stimuli. Particulate matter (PM) has been repeatedly shown to modify macrophage function and polarization while also inducing worsening respiratory infection morbidity and mortality. However, limited work has considered the impact of the initial macrophage polarization state on subsequent responses to PM exposure. PM composition can demonstrate seasonality-specific compositional changes based on differences in seasonal weather patterns and energy needs, introducing the need to consider the seasonality-specific effects of airborne PM when investigating its impact on human health. This study sought to determine the impact of airborne PM collected during different seasons of the year in Xinxiang, China, on macrophage function in a polarization state-dependent manner. Macrophages were differentiated using the macrophage colony-stimulating factor (M-CSF) on CD14+CD16- monocytes isolated from the blood of healthy human volunteers. The resulting macrophages were polarized into indicated states using well-characterized polarization methods and assessed for phagocytic function, bioenergetic properties, and secretory profile following exposure to PM collected during a single day during each season of the year. Macrophages demonstrated clear polarization state-dependent phagocytic, bioenergetic, and secretory properties at the baseline and following PM exposure. Specific PM seasonality had a minimal impact on phagocytic function and a minor effect on bioenergetic properties but had clear impacts on the secretory profile as demonstrated by the enriched secretion of well-characterized mediator clusters by particle season. Together, these data suggest that both particle seasonality and macrophage polarization state must be considered when investigating the impact of PM on macrophage function. These factors may contribute to the negative outcomes linked to PM exposure during respiratory infections.

Trichloroethylene-mediated cytotoxicity in human epidermal keratinocytes is mediated by the rapid accumulation of intracellular calcium: Interception by naringenin

Industrial solvents pose a significant threat to the humankind. The mechanisms of their toxicity still remain in debate. Trichloroethylene (TCE) is a widespread industrial solvent responsible for severe liver dysfunction, cutaneous toxicity in occupationally exposed humans. We utilized an in vitro system of human epidermal keratinocyte (HaCaT) cells in this study to avoid complex cell and extracellular interactions. We report the cytotoxicity of organic solvent TCE in HaCaT and its reversal by a natural flavanone, naringenin (Nar). The cytotoxicity was attributed to the rapid intracellular free calcium (Ca(2+)) release, which might lead to the elevation of protein kinase C along with robust free radical generation, instability due to energy depletion, and sensitization of intracellular stress signal transducer nuclear factor κB. These effects were actually seen to induce significant amount of genomic DNA fragmentation. Furthermore, all these effects of TCE were effectively reversed by the treatment of Nar, a natural flavanone. Our studies identify intracellular Ca as a unique target used by organic solvents in the cytotoxicity and highlight the Ca(2+) ion stabilizer properties of Nar.

Low cytotoxicity of inorganic nanotubes and fullerene-like nanostructures in human bronchial epithelial cells: relation to inflammatory gene induction and antioxidant response

The cytotoxicity of tungsten disulfide nano tubes (INT-WS2) and inorganic fullerene-like molybdenum disulfide (IF-MoS2) nanoparticles (NPs) used in industrial and medical applications was evaluated in comparison to standard environmental particulate matter. The IF-MoS2 and INT-WS2 reside in vesicles/inclusion bodies, suggestive of endocytic vesicles. In cells representing the respiratory, immune and metabolic systems, both IF-MoS2 and INT-WS2 NPs remained nontoxic compared to equivalent concentrations (up to 100 μg/mL in the medium) of silica dioxide (SiO2), diesel engine-derived and carbon black NPs, which induced cell death. Associating with this biocompatibility of IF-MoS2\INT-WS2, we demonstrate in nontransformed human bronchial cells (NL-20) relative low induction of the pro-inflammatory cytokines IL-1β, IL-6, IL-8, and TNF-α. Moreover, IF-MoS2 and INT-WS2 activated antioxidant response as measured by the antioxidant response element (ARE) using a luciferase reporter, and induced Nrf2-mediated Phase II detoxification genes. Collectively, our findings suggest that the lower cytotoxicity of IF-MoS2 and INT-WS2 NPs does not reflect general biological inertness. Rather, compared to other NP's, it likely results from decreased pro-inflammatory activation, but a comparable significant capacity to induce protective antioxidant/detoxification defense mechanisms.

Coal and tire burning mixtures containing ultrafine and nanoparticulate materials induce oxidative stress and inflammatory activation in macrophages

Ultra-fine and nano-particulate materials resulting from mixtures of coal and non-coal fuels combustion for power generation release to the air components with toxic potential. We evaluated toxicological and inflammatory effects at cellular level that could be induced by ultrafine/nanoparticles-containing ashes from burning mixtures of coal and tires from an American power plant. Coal fly ashes (CFA) samples from the combustion of high-S coal and tire-derived fuel, the latter about 2-3% of the total fuel feed, in a 100-MW cyclone utility boiler, were suspended in the cell culture medium of RAW 264.7 macrophages. Cell viability, assessed by MTT reduction, SRB incorporation and contrast-phase microscopy analysis demonstrated that CFA did not induce acute toxicity. However, CFA at 1mg/mL induced an increase of approximately 338% in intracellular TNF-α, while release of this proinflammatory cytokine was increased by 1.6-fold. The expression of the inflammatory mediator CD40 receptor was enhanced by 2-fold, the receptor for advanced glycation endproducts (RAGE) had a 5.7-fold increase and the stress response protein HSP70 was increased nearly 12-fold by CFA at 1mg/mL. Although CFA did not induce cell death, parameters of oxidative stress and reactive species production were found to be altered at several degrees, such as nitrite accumulation (22% increase), DCFH oxidation (3.5-fold increase), catalase (5-fold increase) and superoxide dismutase (35% inhibition) activities, lipoperoxidation (4.2 fold-increase) and sulfhydryl oxidation (40% decrease in free SH groups). The present results suggest that CFA containing ultra-fine and nano-particulate materials from coal and tire combustion may induce sub-chronic cell damage, as they alter inflammatory and oxidative stress parameters at the molecular and cellular levels, but do not induce acute cell death.

Regulation of the arachidonic acid mobilization in macrophages by combustion-derived particles

BACKGROUND

Acute exposure to elevated levels of environmental particulate matter (PM) is associated with increasing morbidity and mortality rates. These adverse health effects, e.g. culminating in respiratory and cardiovascular diseases, have been demonstrated by a multitude of epidemiological studies. However, the underlying mechanisms relevant for toxicity are not completely understood. Especially the role of particle-induced reactive oxygen species (ROS), oxidative stress and inflammatory responses is of particular interest.In this in vitro study we examined the influence of particle-generated ROS on signalling pathways leading to activation of the arachidonic acid (AA) cascade. Incinerator fly ash particles (MAF02) were used as a model for real-life combustion-derived particulate matter. As macrophages, besides epithelial cells, are the major targets of particle actions in the lung murine RAW264.7 macrophages and primary human macrophages were investigated.

RESULTS

The interaction of fly ash particles with macrophages induced both the generation of ROS and as part of the cellular inflammatory responses a dose- and time-dependent increase of free AA, prostaglandin E2/thromboxane B2 (PGE2/TXB2), and 8-isoprostane, a non-enzymatically formed oxidation product of AA. Additionally, increased phosphorylation of the mitogen-activated protein kinases (MAPK) JNK1/2, p38 and ERK1/2 was observed, the latter of which was shown to be involved in MAF02-generated AA mobilization and phosphorylation of the cytosolic phospolipase A2. Using specific inhibitors for the different phospolipase A2 isoforms the MAF02-induced AA liberation was shown to be dependent on the cytosolic phospholipase A2, but not on the secretory and calcium-independent phospholipase A2. The initiation of the AA pathway due to MAF02 particle exposure was demonstrated to depend on the formation of ROS since the presence of the antioxidant N-acetyl-cysteine (NAC) prevented the MAF02-mediated enhancement of free AA, the subsequent conversion to PGE2/TXB2 via the induction of COX-2 and the ERK1/2 and JNK1/2 phosphorylation. Finally we showed that the particle-induced formation of ROS, liberation of AA and PGE2/TXB2 together with the phosphorylation of ERK1/2 and JNK1/2 proteins was decreased after pre-treatment of macrophages with the metal chelator deferoxamine mesylate (DFO).

CONCLUSIONS

These results indicate that one of the primary mechanism initiating inflammatory processes by incinerator fly ash particles seems to be the metal-mediated generation of ROS, which triggers via the MAPK cascade the activation of AA signalling pathway.

Anti-oxidative and inflammatory responses induced by fly ash particles and carbon black in lung epithelial cells

Combustion-derived nanoparticles as constituents of ambient particulate matter have been shown to induce adverse health effects due to inhalation. However, the components inducing these effects as well as the biological mechanisms are still not fully understood. The fine fraction of fly ash particles collected from the electrostatic precipitator of a municipal solid waste incinerator was taken as an example for real particles with complex composition released into the atmosphere to study the mechanism of early biological responses of BEAS-2B human lung epithelial cells. The studies include the effects of the water-soluble and -insoluble fractions of the fly ash and the well-studied carbon black nanoparticles were used as a reference. Fly ash induced reactive oxygen species (ROS) and increased the total cellular glutathione (tGSH) content. Carbon black also induced ROS generation; however, in contrast to the fly ash, it decreased the intracellular tGSH. The fly ash-induced oxidative stress was correlated with induction of the anti-oxidant enzyme heme oxygenase-1 and increase of the redox-sensitive transcription factor Nrf2. Carbon black was not able to induce HO-1. ROS generation, tGSH increase and HO-1 induction were only induced by the insoluble fraction of the fly ash, not by the water-soluble fraction. ROS generation and HO-1 induction were markedly inhibited by pre-incubation of the cells with the anti-oxidant N-acetyl cysteine which confirmed the involvement of oxidative stress. Both effects were also reduced by the metal chelator deferoxamine indicating a contribution of bioavailable transition metals. In summary, both fly ash and carbon black induce ROS but only fly ash induced an increase of intracellular tGSH and HO-1 production. Bioavailable transition metals in the solid water-insoluble matrix of the fly ash mostly contribute to the effects.

Comparison of gene expression profiles induced by coarse, fine, and ultrafine particulate matter

Coarse, fine, and ultrafine particulate matter (PM) fractions possess different physical properties and chemical compositions and may produce different adverse health effects. Studies were undertaken to determine whether or not gene expression patterns may be used to discriminate among the three size fractions. Airway epithelial cells obtained from 6 normal individuals were exposed to Chapel Hill coarse, fine or ultrafine PM (250 μg/ml) for 6 and 24 h (n=3 different individuals each). RNA was isolated and hybridized to Affymetrix cDNA microarrays. Significant genes were identified and mapped to canonical pathways. Expression of selected genes was confirmed by reverse-transcription polymerase chain reaction (RT-PCR). The numbers of genes altered by coarse, fine, and ultrafine PM increased from 0, 6, and 17 at 6 h to 1281, 302, and 455 at 24 h, respectively. The NRF2-mediated oxidative stress response, cell cycle:G2/M DNA damage checkpoint regulation, and mitotic roles of polo-like kinase were the top three pathways altered by all three fractions. Fine and ultrafine PM displayed more similar gene expression patterns. One example was the increased expression of metallothionein isoforms, reflecting the higher zinc content associated with fine and ultrafine fractions. A set of 10 genes was identified that could discriminate fine and ultrafine PM from coarse PM. These results indicate that common properties shared by the three size fractions as well as size-specific factors, e.g., compositions, may determine the effects on gene expression. Genomic markers may be used to discriminate coarse from fine and ultrafine PM.

Agents associated with lung inflammation induce similar responses in NCI-H292 lung epithelial cells

The aim of this study was to investigate an in vitro lung epithelial model for assessment of potential inhalation toxicity. The selected NCI-H292 lung carcinoma cell line is sensitive to cigarette smoke, responds in a similar manner to primary human lung epithelial cells and produces airway mucins. The following agents associated with inhalation toxicity were tested in the model: cigarette smoke total particulate matter, fly ash, bleomycin, lipopolysaccharide, vanadyl sulphate, diesel exhaust particles and carbon black. Polystyrene, poly-methylmethacrylate and dimethyl sulphoxide were used as negative controls. Response markers were chosen on the basis of reported injurious effects of lung toxicants in humans, and included pro-inflammatory cytokines, matrix metalloprotease-1, the airway mucin MUC5AC and heparin-binding epidermal growth factor-like growth factor. Markers were quantified at the mRNA and/or protein level in control and treated cells. Many of the selected markers were regulated in a similar manner by cigarette smoke and the other toxic substances in the H292 cell model. By comparison, the negative control agents were largely ineffective. We conclude that, with further validation, this assay may form part of a tiered strategy for toxicological assessment of inhaled agents prior to more complex primary cell models and animal inhalation studies.

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.

A new method for quantifiable and controlled dosage of particulate matter for in vitro studies: the electrostatic particulate dosage and exposure system (EPDExS)

An exposure chamber is described for the quantifiable addition of fine and ultrafine aerosol particulate matter directly to cells and used to demonstrate the in vitro cytotoxicity of fine 1,4-naphthoquinone particles to murine lung epithelial cells. The electrostatic particulate dosage and exposure system (EPDExS) operates on the principle of electrostatic precipitation and is shown to deposit fine and ultrafine aerosol particles directly to cells with 100% efficiency for particle diameters in the range of 40-530nm. This range is not limited by the EPDExS, but rather by the aerosolization method used for this study. Numbers of particles deposited onto the cells are counted with a condensation particle counter, negating any need to calculate or estimate particle exposure. The process of particle introduction, assessed using Trypan blue dye exclusion, had no effect on cell viability. In combination with a differential mobility classifier, the EPDExS can deliver select particle diameters to cells. The ability to control the diameter and number of particles deposited permits in vitro toxicity studies of particulate matter using different particle dosage metrics, i.e., particle number and size, surface area and mass. Finally, because EPDExS introduces particles directly from the aerosol, it can be used to expose cells grown at air/liquid interfaces.