Cooperation of the inducible nitric oxide synthase and cytochrome P450 1A1 in mediating lung inflammation and mutagenicity induced by diesel exhaust particles

A comparative study of persistent DNA oxidation and chromosomal instability induced in vitro by oxidizers and reference airborne particles

Adverse health effects driven by airborne particulate matter (PM) are mainly associated with reactive oxygen species formation, pro-inflammatory effects, and genome instability. Therefore, a better understanding of the underlying mechanisms is needed to evaluate health risks caused by exposure to PM. The aim of this study was to compare the genotoxic effects of two oxidizing agents (menadione and 3-chloro-1,2-propanediol) with three different reference PM (fine dust ERM-CZ100, urban dust SRM1649, and diesel PM SRM2975) on monocytic THP-1 and alveolar epithelial A549 cells. We assessed DNA oxidation by measuring the oxidized derivative 8-hydroxy-2'-deoxyguanosine (8-OHdG) following short and long exposure times to evaluate the persistency of oxidative DNA damage. Cytokinesis-block micronucleus cytome assay was performed to assess chromosomal instability, cytostasis, and cytotoxicity. Particles were characterized by inductively coupled plasma mass spectrometry in terms of selected elemental content, the release of ions in cell medium and the cellular uptake of metals. PM deposition and cellular dose were investigated by a spectrophotometric method on adherent A549 cells. The level of lipid peroxidation was evaluated via malondialdehyde concentration measurement. Despite differences in the tested concentrations, deposition efficiency, and lipid peroxidation levels, all reference PM samples caused oxidative DNA damage to a similar extent as the two oxidizers in terms of magnitude but with different oxidative DNA damage persistence. Diesel SRM2975 were more effective in inducing chromosomal instability with respect to fine and urban dust highlighting the role of polycyclic aromatic hydrocarbons derivatives on chromosomal instability. The persistence of 8-OHdG lesions strongly correlated with different types of chromosomal damage and revealed distinguishing sensitivity of cell types as well as specific features of particles versus oxidizing agent effects. In conclusion, this study revealed that an interplay between DNA oxidation persistence and chromosomal damage is driving particulate matter-induced genome instability.

Low doses of imidacloprid induce disruption of intercellular adhesion and initiate proinflammatory changes in Caco-2 cells

Imidacloprid is the most widely used pesticide of the neonicotinoid class. Neonicotinoid toxicities against various insects are well known. Nevertheless, there are rising evidences that neonicotinoids exert cytotoxic effects on different non-target organisms including mammals, fish, birds etc. Besides, depending on pesticide application, the exposed plants absorb some part of used neonicotinoids and their residues are detected in agricultural products worldwide. Thus, the continuous consumption of fruits and vegetables contaminated with neonicotinoids is a high risk factor for humans despite the low doses. Intestine epithelial cells are the first targets of the neonicotinoid cytotoxicity in humans because of its direct way of administration. The epithelial cells provide the barrier function of the intestinal system via specialized intercellular adhesion. The effects of imidacloprid on the intestine barrier function and inflammatory cytokines production are still unknown. In the present study, we exposed the human Caucasian colon adenocarcinoma (Caco-2) epithelial cells to low doses (0.10–0.75 µg/mL) of imidacloprid in order to assess the expression of tight and adherens junctions proteins, occludin and E-cadherin, and production of proinflammatory cytokine TNF α and iNOS. Imidacloprid induced dose-dependent decline in both occludin and E-cadherin levels. By contrast, TNF-α and iNOS contents were upregulated in imidacloprid-exposed Caco-2 cells. Decrease in tight and adherens junctions proteins indicates that the barrier function of intestine epithelial cells could be damaged by imidacloprid administration. In addition, TNF-α and iNOS upregulation indicates that imidacloprid is potent to activate proinflammatory response in enterocytes. Thus, imidacloprid can affect intestine barrier function through the increase of proinflammatory cytokine production and decrease in adhesiveness of enterocytes. The further assessment of the role of adhesion proteins and inflammatory cytokines in neonicotinoid pesticide cytotoxicity as it affects enterocyte barrier function is required to highlight the risk factor of use of neonicotinoids.

Knockout of cytochrome P450 1A1 enhances lipopolysaccharide-induced acute lung injury in mice by targeting NF-κB activation

Acute lung injury (ALI) is accompanied by overactivation of multiple pro-inflammatory factors. Cytochrome P450 1A1 (CYP1A1) has been shown to aggravate lung injury in response to hyperoxia. However, the relationship between CYP1A1 and lipopolysaccharide (LPS)-induced ALI is unknown. In this study, CYP1A1 was shown to be upregulated in mouse lung in response to LPS. Using CYP1A1-deficient (CYP1A1-/-) mice, we found that CYP1A1 knockout enhanced LPS-induced ALI, as evidenced by increased TNF-α, IL-1β, IL-6, and nitric oxide in lung; these effects were mediated by overactivation of NF-κB and iNOS. Furthermore, we found that aspartate aminotransferase, lactate dehydrogenase, creatine kinase, and creatinine levels were elevated in serum of LPS-induced CYP1A1-/- mice. Altogether, these data provide novel insights into the involvement of CYP1A1 in LPS-induced lung injury.

The role of NF-κB and AhR transcription factors in lead-induced lung toxicity in human lung cancer A549 cells

Lead (Pb) is recognized as the first heavy metal of the top six toxic air pollutants threatening human health and the second hazardous substance. Pb exposure is associated with lung impairment and high incidences of lung cancer. Nuclear factor kappa B (NF-κB) and aryl hydrocarbon receptor (AhR) signaling pathways are known to be expressed and play an important role in the lung. However, the link between Pb lung toxicity and NF-κB and/or AhR pathways remains unclear. This study was established to explore the role of NF-κB and AhR modulation in Pb-induced lung toxicity in human lung cancer A549 cells. In the current study, treatment of A549 cells with Pb significantly induced cell apoptosis as evidenced by increasing a) the percentage of cells underwent apoptosis determined by flow cytometry and b) p53 mRNA level. Pb treatment induced oxidative stress by a) increasing the formation of reactive oxygen species and b) decreasing GSTA1 mRNA levels. The toxic effects of Pb on the lung was associated with significant increases in NF-κB and AhR levels which was accompanied with increases in downstream targets genes, iNOS and CYP1A1, respectively. Inhibition of NF-κB or AhR either chemically using resveratrol or genetically using small interfering RNA (siRNA) significantly rescued A549 cells from Pb-mediated lung toxicity. The results clearly indicate that Pb-mediated lung toxicities are NF-κB and AhR-dependent mechanism.

Low dose of chlorine exposure exacerbates nasal and pulmonary allergic inflammation in mice

Work-exacerbated asthma (WEA) is defined as preexisting asthma that worsens with exposure to irritants [e.g., chlorine (Cl2) derivatives] in the workplace. The maximum allowable concentration in the workplace of Cl2 exposure is 3 mg/ m3 (described in OSHA). We investigated in an experimental asthma model in mice the effects of a single exposure to a sodium hypochlorite dose with this allowed chlorine concentration and a tenfold higher dose. Acute chlorine exposure at 3.3 mg/m3 in the OVA-sensitized group increased eosinophils in the peribronquial infiltrate, cytokine production, nasal mucus production and the number of iNOS positive cells in the distal lung compared to only sensitized mice. The exposure to a higher dose of 33.3 mg/m3 in the OVA-sensitized group resulted in an increase in respiratory system elastance, in the total and differential numbers of inflammatory cells in bronchoalveolar lavage fluid, IL-4, IL-5, and IL-17 in the lungs, eosinophils in peribronquial infiltrate and mucus content in nasal compared to non-exposed and sensitized animals. In this asthma model, chorine exposures at an allowable dose, contributed to the potentiation of Th2 responses. The functional alterations were associated with increased iNOS and ROCK-2 activation in the distal lung.

Effects of High-Intensity Swimming on Lung Inflammation and Oxidative Stress in a Murine Model of DEP-Induced Injury

Studies have reported that exposure to diesel exhaust particles (DEPs) induces lung inflammation and increases oxidative stress, and both effects are susceptible to changes via regular aerobic exercise in rehabilitation programs. However, the effects of exercise on lungs exposed to DEP after the cessation of exercise are not clear. Therefore, the aim of this study was to evaluate the effects of high-intensity swimming on lung inflammation and oxidative stress in mice exposed to DEP concomitantly and after exercise cessation. Male Swiss mice were divided into 4 groups: Control (n = 12), Swimming (30 min/day) (n = 8), DEP (3 mg/mL-10 μL/mouse) (n = 9) and DEP+Swimming (n = 8). The high-intensity swimming was characterized by an increase in blood lactate levels greater than 1 mmoL/L between 10th and 30th minutes of exercise. Twenty-four hours after the final exposure to DEP, the anesthetized mice were euthanized, and we counted the number of total and differential inflammatory cells in the bronchoalveolar fluid (BALF), measured the lung homogenate levels of IL-1β, TNF-α, IL-6, INF-ϫ, IL-10, and IL-1ra using ELISA, and measured the levels of glutathione, non-protein thiols (GSH-t and NPSH) and the antioxidant enzymes catalase and glutathione peroxidase (GPx) in the lung. Swimming sessions decreased the number of total cells (p<0.001), neutrophils and lymphocytes (p<0.001; p<0.05) in the BALF, as well as lung levels of IL-1β (p = 0.002), TNF-α (p = 0.003), IL-6 (p = 0.0001) and IFN-ϫ (p = 0.0001). However, the levels of IL-10 (p = 0.01) and IL-1ra (p = 0.0002) increased in the swimming groups compared with the control groups, as did the CAT lung levels (p = 0.0001). Simultaneously, swimming resulted in an increase in the GSH-t and NPSH lung levels in the DEP group (p = 0.0001 and p<0.002). We concluded that in this experimental model, the high-intensity swimming sessions decreased the lung inflammation and oxidative stress status during DEP-induced lung inflammation in mice.

Cytotoxicity and genotoxicity of urban particulate matter in mammalian cells

Ambient air particulate matter (PM)-associated reactive oxygen species (ROS) have been linked to a variety of altered cellular outcomes. In this study, three different PM samples from diesel exhaust particles (DEPs), urban dust standard reference material SRM1649a and air collected in Manchester have been tested for their ability to oxidise DNA in a cell-free assay, to increase intracellular ROS levels and to induce CYP1A1 gene expression in mammalian cells. In addition, the cytotoxicity and genotoxicity of PM were assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and alkaline comet assay, respectively. All PM samples catalysed the Fenton reaction in a cell-free assay, but only DEP resulted in the generation of ROS as measured by dichlorodihydrofluorescein diacetate oxidation in mammalian cells. However, there was no evidence that increased ROS was a consequence of polycyclic aromatic hydrocarbon metabolism via CYP1A1 induction as urban dust, the Manchester dust samples but not DEP-induced CYP1A1 expression. Urban dust was more cytotoxic in murine embryonic fibroblasts (MEFs) than the other PM samples and also induced expression of GADD45a in the GreenScreen Human Cell assay without S9 activation suggesting the presence of a direct-acting genotoxicant. Urban dust and DEP produced comparable levels of DNA damage, as assessed by the alkaline comet assay, in MEFs at higher levels than those induced by Manchester PM. In conclusion, results from the cytotoxic and genotoxic assays are not consistent with ROS production being the sole determinant of PM-induced toxicity. This suggests that the organic component can contribute significantly to this toxicity and that further work is required to better characterise the extent to which ROS and organic components contribute to PM-induced toxicity.

The Effect of Aerobic Exercise in Ambient Particulate Matter on Lung Tissue Inflammation and Lung Cancer

Background:

Exposure to Air pollution PM10 results in lung inflammation increased risk of lung cancer. Regular aerobic exercise improves the inflammatory status in different lung diseases. However, the effects of long-term aerobic exercise on the pulmonary response to PM10 have not been investigated.

Objectives:

The present study evaluated the effect of aerobic exercise on the lung inflammatory and risk of lung cancer of rat exposed to PM10 carbon black.

Materials and Methods:

Twenty four adult male Wistar rats were divided into 4 groups: A: control (without exposure PM10 and aerobic exercise; n = 6), B: aerobic exercise (five times per week for 4 weeks; n = 6), C: exposure to PM10 carbon black (5 mg/m³; per rat; n = 6), D: and aerobic exercise concomitantly with exposure to PM10 carbon black (n = 6). The gene expression of TLR4, NF-κB and TNF-α were analyzed in lung tissue by Real time-PCR. In order to determine the significant differences between groups, one way ANOVA and LSD post hoc and Kruskal-Vallis test were used.

Results:

Aerobic exercise inhibited the PM10 -induced increase in the gene expression of TLR4, NF-κB and TNF-α. But there was significant different only between B and C groups for TNF-α and NF-κB (P = 0.047, 0.014, respectively).

Conclusions:

We conclude that four week aerobic exercise presents protective effects in a rat model of PM10 carbon black-induced lung inflammation and risk of lung cancer. Our results indicate a need for human studies that evaluate the lung Responses to aerobic exercise chronically performed in polluted areas.

Gene expression profiling of candidate genes in peripheral blood mononuclear cells for predicting toxicity of diesel exhaust particles

To validate gene expression profiling of peripheral blood mononuclear cells (PBMCs) as a surrogate for monitoring tissue expression, this study using RT-PCR-based TaqMan low-density array (TLDA) was initiated to investigate similarities in the mRNA expression of target genes altered by exposure to diesel exhaust particles (DEPs) in freshly prepared PBMCs and in lungs. Adult Wistar rats were treated transtracheally with a single dose of 7.5 or 15 or 30mg/kg DEPs and sacrificed 24h later. Blood and lungs were immediately taken out and processed for RT-PCR. DEP treatment induced similar patterns of increase in the expression of polycyclic aromatic hydrocarbon-responsive cytochrome P450s, the phase II enzymes, and their associated transcription factors in both lungs and PBMCs, at all doses. Similar to that seen in lungs, a dose-dependent increase was observed in the expression of genes involved in inflammation, such as cytokines, chemokines, and adhesion molecules, in PBMCs. The expression of various genes involved in DNA repair and apoptosis was also increased in a dose-dependent manner in PBMCs and lungs. The present TLDA data indicating similarities in the responsiveness of candidate genes involved in the toxicity of DEPs between PBMCs and lungs after exposure to DEPs demonstrate that expression profiles of genes in PBMCs could be used as a surrogate for monitoring the acute toxicity of fine and ultrafine particulate matter present in vehicular emissions.

Inflammation-related effects of diesel engine exhaust particles: studies on lung cells in vitro

Diesel exhaust and its particles (DEP) have been under scrutiny for health effects in humans. In the development of these effects inflammation is regarded as a key process. Overall, in vitro studies report similar DEP-induced changes in markers of inflammation, including cytokines and chemokines, as studies in vivo. In vitro studies suggest that soluble extracts of DEP have the greatest impact on the expression and release of proinflammatory markers. Main DEP mediators of effects have still not been identified and are difficult to find, as fuel and engine technology developments lead to continuously altered characteristics of emissions. Involved mechanisms remain somewhat unclear. DEP extracts appear to comprise components that are able to activate various membrane and cytosolic receptors. Through interactions with receptors, ion channels, and phosphorylation enzymes, molecules in the particle extract will trigger various cell signaling pathways that may lead to the release of inflammatory markers directly or indirectly by causing cell death. In vitro studies represent a fast and convenient system which may have implications for technology development. Furthermore, knowledge regarding how particles elicit their effects may contribute to understanding of DEP-induced health effects in vivo, with possible implications for identifying susceptible groups of people and effect biomarkers.

Nitric oxide and superoxide mediate diesel particle effects in cytokine-treated mice and murine lung epithelial cells--implications for susceptibility to traffic-related air pollution

Background

Epidemiologic studies associate childhood exposure to traffic-related air pollution with increased respiratory infections and asthmatic and allergic symptoms. The strongest associations between traffic exposure and negative health impacts are observed in individuals with respiratory inflammation. We hypothesized that interactions between nitric oxide (NO), increased during lung inflammatory responses, and reactive oxygen species (ROS), increased as a consequence of traffic exposure ─ played a key role in the increased susceptibility of these at-risk populations to traffic emissions.

Methods

Diesel exhaust particles (DEP) were used as surrogates for traffic particles. Murine lung epithelial (LA-4) cells and BALB/c mice were treated with a cytokine mixture (cytomix: TNFα, IL-1β, and IFNγ) to induce a generic inflammatory state. Cells were exposed to saline or DEP (25 μg/cm²) and examined for differential effects on redox balance and cytotoxicity. Likewise, mice undergoing nose-only inhalation exposure to air or DEP (2 mg/m³ × 4 h/d × 2 d) were assessed for differential effects on lung inflammation, injury, antioxidant levels, and phagocyte ROS production.

Results

Cytomix treatment significantly increased LA-4 cell NO production though iNOS activation. Cytomix +  DEP-exposed cells incurred the greatest intracellular ROS production, with commensurate cytotoxicity, as these cells were unable to maintain redox balance. By contrast, saline + DEP-exposed cells were able to mount effective antioxidant responses. DEP effects were mediated by: (1) increased ROS including superoxide anion (O₂˙^-), related to increased xanthine dehydrogenase expression and reduced cytosolic superoxide dismutase activity; and (2) increased peroxynitrite generation related to interaction of O₂˙^- with cytokine-induced NO. Effects were partially reduced by superoxide dismutase (SOD) supplementation or by blocking iNOS induction. In mice, cytomix +  DEP-exposure resulted in greater ROS production in lung phagocytes. Phagocyte and epithelial effects were, by and large, prevented by treatment with FeTMPyP, which accelerates peroxynitrite catalysis.

Conclusions

During inflammation, due to interactions of NO and O₂˙^-, DEP-exposure was associated with nitrosative stress in surface epithelial cells and resident lung phagocytes. As these cell types work in concert to provide protection against inhaled pathogens and allergens, dysfunction would predispose to development of respiratory infection and allergy. Results provide a mechanism by which individuals with pre-existing respiratory inflammation are at increased risk for exposure to traffic-dominated urban air pollution.

Anti-inflammatory effects of aerobic exercise in mice exposed to air pollution

PURPOSE

Exposure to diesel exhaust particles (DEP) results in lung inflammation. Regular aerobic exercise improves the inflammatory status in different pulmonary diseases. However, the effects of long-term aerobic exercise on the pulmonary response to DEP have not been investigated. The present study evaluated the effect of aerobic conditioning on the pulmonary inflammatory and oxidative responses of mice exposed to DEP.

METHODS

BALB/c mice were subjected to aerobic exercise five times per week for 5 wk, concomitantly with exposure to DEP (3 mg·mL(-1); 10 μL per mouse). The levels of exhaled nitric oxide, reactive oxygen species, cellularity, interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) were analyzed in bronchoalveolar lavage fluid, and the density of neutrophils and the volume proportion of collagen fibers were measured in the lung parenchyma. The cellular density of leukocytes expressing IL-1β, keratinocyte chemoattractant (KC), and TNF-α in lung parenchyma was evaluated with immunohistochemistry. The levels of IL-1β, KC, and TNF-α were also evaluated in the serum.

RESULTS

Aerobic exercise inhibited the DEP-induced increase in the levels of reactive oxygen species (P < 0.05); exhaled nitric oxide (P < 0.01); total (P < 0.01) and differential cells (P < 0.01); IL-6 and TNF-α levels in bronchoalveolar lavage fluid (P < 0.05); the level of neutrophils (P < 0.001); collagen density in the lung parenchyma (P < 0.05); the levels of IL-6, KC, and TNF-α in plasma (P < 0.05); and the expression of IL-1β, KC, and TNF-α by leukocytes in the lung parenchyma (P < 0.01).

CONCLUSIONS

We conclude that long-term aerobic exercise presents protective effects in a mouse model of DEP-induced lung inflammation. Our results indicate a need for human studies that evaluate the pulmonary responses to aerobic exercise chronically performed in polluted areas.

Similarities in diesel exhaust particles induced alterations in expression of cytochrome P-450 and glutathione S-transferases in rat lymphocytes and lungs

Freshly prepared peripheral blood lymphocytes (PBL) are known to express cytochrome P450s (CYPs) and glutathione S-transferases (GSTs) involved in the bioactivation and detoxification of organic components of diesel exhaust particles (DEPs). To validate that blood lymphocyte expression profiles could be used as a biomarker to predict exposure to vehicular emissions, similarities in the alterations in the mRNA expression of CYPs and GSTs were studied in PBL and lungs of rats exposed to DEPs. Adult male Wistar rats were treated transtracheally with different doses of DEPs (3.75- or 7.5- or 15- or 30-mg/kg b.wt.). The animals were anaesthetized after 24 h and blood was drawn and lungs were taken out and processed. DEP produced a similar pattern of increase in the mRNA expression of CYPs (CYP1A1, 1A2, 1B1, 2E1), associated arylhydrocarbon receptor (Ahr) and arylhydrocarbon nuclear translocator (Arnt) and GSTs (GSTPi, GSTM1 and GSTM2) at all the doses in lungs and PBL. The protein expression of CYP1A1/1A2 and 2E1 and catalytic activity of CYPs and GSTs also showed a similar pattern of increase in blood lymphocyte and in lungs isolated from DEP treated rats. Our data indicating similarities in the alterations in the expression of carcinogen metabolizing CYPs and GSTs in PBL with the lung enzymes suggests the suitability of using expression profiles of blood lymphocyte CYPs and GSTs as a biomarker to predict exposure to vehicular emissions.

Oxidative stress and DNA damage responses in rat and mouse lung to inhaled carbon nanoparticles

We have investigated whether short-term nose-only inhalation exposure to electric spark discharge-generated carbon nanoparticles (∼60 nm) causes oxidative stress and DNA damage responses in the lungs of rats (152 μg/m(3); 4 h) and mice (142 μg/m(3); 4 h, or three times 4 h). In both species, no pulmonary inflammation and toxicity were detected by bronchoalveolar lavage or mRNA expression analyses. Oxidative DNA damage (measured by fpg-comet assay), was also not increased in mouse whole lung tissue or isolated lung epithelial cells from rat. In addition, the mRNA expressions of the DNA base excision repair genes OGG1, DNA Polβ and XRCC1 were not altered. However, in the lung epithelial cells isolated from the nanoparticle-exposed rats a small but significant increase in APE-1 mRNA expression was measured. Thus, short-term inhalation of carbon nanoparticles under the applied exposure regimen, does not cause oxidative stress and DNA damage in the lungs of healthy mice and rats.

Comparative evaluation of the effects of short-term inhalation exposure to diesel engine exhaust on rat lung and brain

Combustion-derived nanoparticles, such as diesel engine exhaust particles, have been implicated in the adverse health effects of particulate air pollution. Recent studies suggest that inhaled nanoparticles may also reach and/or affect the brain. The aim of our study was to comparatively evaluate the effects of short-term diesel engine exhaust (DEE) inhalation exposure on rat brain and lung. After 4 or 18 h recovery from a 2 h nose-only exposure to DEE (1.9 mg/m(3)), the mRNA expressions of heme oxygenase-1 (HO-1), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and cytochrome P450 1A1 (CYP1A1) were investigated in lung as well as in pituitary gland, hypothalamus, olfactory bulb, olfactory tubercles, cerebral cortex, and cerebellum. HO-1 protein expression in brain was investigated by immunohistochemistry and ELISA. In the lung, 4 h post-exposure, CYP1A1 and iNOS mRNA levels were increased, while 18 h post-exposure HO-1 was increased. In the pituitary at 4 h post-exposure, both CYP1A1 and HO-1 were increased; HO-1 was also elevated in the olfactory tuberculum at this time point. At 18 h post-exposure, increased expression of HO-1 and COX-2 was observed in cerebral cortex and cerebellum, respectively. Induction of HO-1 protein was not observed after DEE exposure. Bronchoalveolar lavage analysis of inflammatory cell influx, TNF-alpha, and IL-6 indicated that the mRNA expression changes occurred in the absence of lung inflammation. Our study shows that a single, short-term inhalation exposure to DEE triggers region-specific gene expression changes in rat brain to an extent comparable to those observed in the lung.

Acute effects of diesel emission from the urea selective catalytic reduction engine system on male rats

Short-term inhalation experiments were performed using Fischer 344 rats exposed to emission from the urea selective catalytic reduction (SCR) diesel engine system to identify health effects and compare them to those of the conventional diesel engine system. Rats were exposed to high-, middle-, or low-concentration emission (dilution ratio 1:29, 1:290, or 1:580) or clean air (control) for 1, 3, or 7 days (6 h/day), under driving conditions at a speed of 1320 rpm and a torque of 840 Nm. For the high-concentration group, the major components of the urea SCR emission were 0.04 mg/m(3) particulate matter (PM) and 0.78 ppm nitrogen dioxide (NO(2)); those of the conventional emission were 0.95 mg/m(3) PM and 0.31 ppm NO(2). The authors evaluated the respiratory effects of each emission on rats. Lymphocytes for 3-day exposure of both emissions significantly increased in bronchoalveolar lavage fluid, but there were slight differences. With an increase in potential antioxidant (PAO), 8-hydroxy-2'-deoxyguanosine for the urea SCR emission was significantly decreased, but that of the conventional emission was highest among all groups and did not show a response to PAO. In lungs, heme oxygenase (HO)-1 and tumor necrosis factor (TNF)-alpha mRNA expressions for the urea SCR emission showed a tendency to increase compared to those of the conventional emission. Thus, gene analysis results suggested that NO(2) from the urea SCR emission affected the expressions of mRNAs in lungs. However, as a whole, the results suggested that the health effects of the urea SCR emission might be less than the conventional emission on rats.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Reactive oxygen species- and nitric oxide-mediated lung inflammation and mitochondrial dysfunction in wild-type and iNOS-deficient mice exposed to diesel exhaust particles

Pulmonary responses to diesel exhaust particles (DEP) exposure are mediated through enhanced production of reactive oxygen species (ROS) and nitric oxide (NO) by alveolar macrophages (AM). The current study examined the differential roles of ROS and NO in DEP-induced lung injury using C57B/6J wild-type (WT) and inducible NO synthase knockout (iNOS KO) mice. Mice exposed by pharyngeal aspiration to DEP or carbon black particles (CB) (35 mg/kg) showed an inflammatory profile that included neutrophil infiltration, increased lactate dehydrogenase (LDH) activity, and elevated albumin content in bronchoalveolar lavage fluid (BALF) at 1, 3, and 7 d postexposure. The organic extract of DEP (DEPE) did not induce an inflammatory response. Comparing WT to iNOS KO mice, the results show that NO enhanced DEP-induced neutrophils infiltration and plasma albumin content in BALF and upregulated the production of the pro-inflammatory cytokine interleukin 12 (IL-12) by AM. DEP-exposed AM from iNOS KO mice displayed diminished production of IL-12 and, in response to ex vivo lipopolysaccharide (LPS) challenge, decreased production of IL-12 but increased production of IL-10 when compared to cells from WT mice. DEP, CB, but not DEPE, induced DNA damage and mitochondria dysfunction in AM, however, that is independent of cellular production of NO. These results demonstrate that DEP-induced immune/inflammatory responses in mice are regulated by both ROS- and NO-mediated pathways. NO did not affect ROS-mediated mitochondrial dysfunction and DNA damage but upregulated IL-12 and provided a counterbalance to the ROS-mediated adaptive stress response that downregulates IL-12 and upregulates IL-10.

Diesel exhaust particles induce matrix metalloprotease-1 in human lung epithelial cells via a NADP(H) oxidase/NOX4 redox-dependent mechanism

Chronic exposure to particulate air pollution is associated with lung function impairment. To determine the molecular mechanism(s) of this phenomenon, we investigated, in an alveolar human epithelial cell line (A549), whether diesel exhaust particles (DEPs), a main component of particulate air pollution, modulates the expression and activity of the matrix metalloprotease (MMP)-1, a collagenase involved in alveolar wall degradation. Interaction of DEPs with cigarette smoke, which also produces structural and functional lung alterations, was also investigated. A noncytotoxic concentration of DEPs induced an increase in MMP-1 mRNA and protein expression and activity in A549 cells without modifying the expression of the MMP inhibitors TIMP-1 and -2. This effect was not potentiated when cells were coexposed to noncytotoxic concentrations of cigarette smoke condensate. DEP-induced MMP-1 was associated with increased ERK 1/2 phosphorylation and upregulation of expression and activity of the NADPH oxidase analog NOX4. Cell transfection with a NOX4 small interfering RNA prevented these phenomena, showing the critical role of a NOX4 ERK 1/2 pathway in DEP-induced MMP-1 expression and activity. Similar results to those observed in A549 cells were obtained in another human lung epithelial cell line, NCI-H292. Furthermore, experiments in mice intratracheally instilled with DEPs confirmed the in vitro findings, showing the induction of NOX4 and MMP-1 protein expression in alveolar epithelial cells. We conclude that alveolar alterations secondary to MMP-1 induction could explain lung function impairment associated with exposure to particulate pollution.