Comparison of inducible nitric oxide synthase gene expression and lung inflammation following intratracheal instillation of silica, coal, carbonyl iron, or titanium dioxide in rats

Pulmonary oxidative stress in wild bats exposed to coal dust: A model to evaluate the impact of coal mining on health

This study aimed to verify possible alterations involving histological and oxidative stress parameters in the lungs of wild bats in the Carboniferous Basin of Santa Catarina (CBSC) state, Southern Brazil, as a means to evaluate the impact of coal dust on the health of wildlife. Specimens of frugivorous bat species Artibeus lituratus and Sturnira lilium were collected from an area free of coal dust contamination and from coal mining areas. Chemical composition, histological parameters, synthesis of oxidants and antioxidant enzymes, and oxidative damage in the lungs of bats were analyzed. Levels of Na, Cl, Cu, and Br were higher in both species collected in the CBSC than in the controls. Levels of K and Rb were higher in A. lituratus, and levels of Si, Ca, and Fe were higher in S. lilium collected in the carboniferous basin. Both bat species inhabiting the CBSC areas exhibited an increase in the degree of pulmonary emphysema compared to their counterparts collected from control areas. Sturnira lilium showed increased reactive oxygen species (ROS) and 2',7'-dichlorofluorescein (DCF) levels, while A. lituratus showed a significant decrease in nitrite levels in the CBSC samples. Superoxide dismutase (SOD) activity did not change significantly; however, the activity of catalase (CAT) and levels of glutathione (GSH) decreased in the A. lituratus group from CBSC compared to those in the controls. There were no differences in NAD(P)H quinone dehydrogenase 1 protein (NQO1) abundance or nitrotyrosine expression among the different groups of bats. Total thiol levels showed a significant reduction in A. lituratus from CBSC, while the amount of malondialdehyde (MDA) was higher in both A. lituratus and S. lilium groups from coal mining areas. Our results suggested that bats, especially A. lituratus, living in the CBSC could be used as sentinel species for harmful effects of coal dust on the lungs.

Particle toxicology and health - where are we?

BACKGROUND

Particles and fibres affect human health as a function of their properties such as chemical composition, size and shape but also depending on complex interactions in an organism that occur at various levels between particle uptake and target organ responses. While particulate pollution is one of the leading contributors to the global burden of disease, particles are also increasingly used for medical purposes. Over the past decades we have gained considerable experience in how particle properties and particle-bio interactions are linked to human health. This insight is useful for improved risk management in the case of unwanted health effects but also for developing novel medical therapies. The concepts that help us better understand particles' and fibres' risks include the fate of particles in the body; exposure, dosimetry and dose-metrics and the 5 Bs: bioavailability, biopersistence, bioprocessing, biomodification and bioclearance of (nano)particles. This includes the role of the biomolecule corona, immunity and systemic responses, non-specific effects in the lungs and other body parts, particle effects and the developing body, and the link from the natural environment to human health. The importance of these different concepts for the human health risk depends not only on the properties of the particles and fibres, but is also strongly influenced by production, use and disposal scenarios.

CONCLUSIONS

Lessons learned from the past can prove helpful for the future of the field, notably for understanding novel particles and fibres and for defining appropriate risk management and governance approaches.

Fine chalk dust induces inflammatory response via p38 and ERK MAPK pathway in rat lung

Chalk teaching is widely used in the world due to low cost, especially in some developing countries. During teaching with chalks, a large amount of fine chalk dust is produced. Although exposure to chalk dust is associated with respiratory diseases, the mechanism underlying the correlation between chalk dust exposure and adverse effects has not fully been elucidated. In this study, inflammation and its signal pathway in rat lungs exposed to fine chalk dust were examined through histopathology analyses; pro-inflammatory gene transcription; and protein levels measured by HE staining, RT-PCR, and western blot analysis. The results demonstrated that fine chalk dust increased neutrophils and up-regulated inflammatory gene mRNA levels (TNF-α, IL-6, TGF-β1, iNOS, and ICAM-1), and oxidative stress marker (HO-1) level, leading to the increase of inflammatory cell infiltration and inflammatory injury on the lungs. These inflammation responses were mediated, at least in part, via p38 and extracellular regulated proteinase (ERK) mitogen-activated protein kinase (MAPK) signaling mechanisms. In contrast, N-acetyl-L-cysteine (NAC) supplement significantly ameliorated these changes in inflammatory responses. Our results support the hypothesis that fine chalk dust can damage rat lungs and the NAC supplement may attenuate fine chalk dust-associated lung inflammation.

Role of nitric oxide in pathological responses of the lung to exposure to environmental/occupational agents

Conflicting evidence exists as to whether nitric oxide expresses damaging/inflammatory or antioxidant/anti-inflammatory properties. Data presented in this review indicate that in vitro or in vivo exposure to selected environmental or occupational agents, such as asbestos, silica, ozone or lipopolysaccharide, can result in up-regulation of inducible nitric oxide synthase by alveolar macrophages and pulmonary epithelial cells. In the case of silica exposure, evidence consistently supports a damaging/inflammatory role of nitric oxide and/or peroxynitrite in the pathogenesis of lung disease. Although conflicting data have been reported, the majority of published studies suggest that nitric oxide plays a damaging role in pulmonary injury resulting from exposure to ozone or asbestos. In contrast, most information supports an anti-inflammatory role of nitric oxide following exposure to lipopolysaccharide. Further investigation is required to elucidate fully the mechanisms involved in determining the role of nitric oxide in the initiation and progression of various pulmonary diseases.

Particle stimulation dephosphorylates glutathione S-transferase π1 of epithelial cells

Environmental pollutant exposure is associated with adverse respiratory outcomes. The phosphorylation of enzymes activates or deactivates many cellular processes and is related to the development of lung diseases such as asthma and chronic obstructive pulmonary disease. However, little is known about protein phosphorylation of bronchial epithelial cells in response to airborne particulates. Herein, we screened differentially phosphorylated proteins in TiO₂-treated epithelial cells and validated the change in GSTP1 protein phosphorylation. Two-dimensional electrophoresis was adopted for differential display proteomics of TiO₂-treated BEAS-2B cell lysates. Phosphoproteins were screened using Pro-Q® Diamond phosphoprotein gel stain and identified by MALDI-TOF/TOF analysis. Immunoprecipitation and immunoblotting were performed for quantitative measurement of GSTP1 phosphorylation in cell lysates. Normalized relative intensities of nine phosphorylated proteins increased after TiO₂ treatment, whereas those of 12 proteins decreased in the BEAS-2B cell lysates. From gene ontology and pathway analysis, proteins involved in signal transduction were commonly identified, followed by cytoskeletal proteins, proteins from oxidation and antioxidation pathways, proteins catalyzing reductions, and those involved in cellular process, transport, and modification. Immunoblotting with anti-GSTP1 antibody demonstrated no change in GSTP1 protein levels in the lysates of BEAS-2B cells after treatment with TiO₂ particles; blotting with anti-phosphoserine and anti-phosphotyrosine antibodies showed dose-dependent decreases in phosphoserine and phosphotyrosine proteins. Stimulation with particulates phosphorylated and dephosphorylated several proteins in epithelial cells, and serine and tyrosine protein phosphorylation of GSTP1 decreased. These data indicate that airborne particles affect the pattern of phosphorylation of proteins involved in defense or apoptosis of respiratory epithelium.

NF-kappaB dependent and independent mechanisms of quartz-induced proinflammatory activation of lung epithelial cells

In the initiation and progression of pulmonary inflammation, macrophages have classically been considered as a crucial cell type. However, evidence for the role of epithelial type II cells in pulmonary inflammation has been accumulating. In the current study, a combined in vivo and in vitro approach has been employed to investigate the mechanisms of quartz-induced proinflammatory activation of lung epithelial cells. In vivo, enhanced expression of the inflammation- and oxidative stress-related genes HO-1 and iNOS was found on the mRNA level in rat lungs after instillation with DQ12 respirable quartz. Activation of the classical NF-kappaB pathway in macrophages and type II pneumocytes was indicated by enhanced immunostaining of phospho-IkappaBalpha in these specific lung cell types. In vitro, the direct, particle-mediated effect on proinflammatory signalling in a rat lung epithelial (RLE) cell line was compared to the indirect, macrophage product-mediated effect. Treatment with quartz particles induced HO-1 and COX-2 mRNA expression in RLE cells in an NF-kappaB independent manner. Supernatant from quartz-treated macrophages rapidly activated the NF-kappaB signalling pathway in RLE cells and markedly induced iNOS mRNA expression up to 2000-fold compared to non-treated control cells. Neutralisation of TNFalpha and IL-1beta in macrophage supernatant did not reduce its ability to elicit NF-kappaB activation of RLE cells. In addition the effect was not modified by depletion or supplementation of intracellular glutathione. The results from the current work suggest that although both oxidative stress and NF-kappaB are likely involved in the inflammatory effects of toxic respirable particles, these phenomena can operate independently on the cellular level. This might have consequences for in vitro particle hazard testing, since by focusing on NF-kappaB signalling one might neglect alternative inflammatory pathways.

Endotoxin promotes adverse effects of amorphous silica nanoparticles on lung epithelial cells in vitro

Amorphous silica engineered nanoparticles (ENP) are used for drug delivery and food additive under current regulations. Although the adverse effects of amorphous silica ENP may be negligible, contamination by bacterium products may enhance the toxic potential of these so-called safe products. Lipopolysaccharide (LPS), an endotoxin component generated by gram-negative bacteria, is a potential contaminant of amorphous silica ENP due to its ubiquitous presence in the environment. The combined effects of amorphous silica ENP and LPS are therefore of particular concern. In this study, A549 cells were exposed to amorphous silica ENP in combination with LPS for comparison with the cells treated with ENP. Measurements of MTT assay and lactate dehydrogenase (LDH) activity indicated that the toxicity of amorphous silica ENP was low but co-treatment of the cells with LPS significantly enhanced this toxicity. Decreased cell viability and increased LDH activity release occurred earlier and at lower concentration levels in co-treated cells. Co-treatment of LPS with amorphous silica ENP might also enhance the increase in oxidative stress produced by amorphous silica ENP. However, there were no detectable changes in nitric oxide generation and 8-hydroxy-2-deoxy guanosine formation in the cells treated with either ENP or ENP plus LPS, indicating low effect on oxidative DNA damage. These results showed that LPS may enhance the oxidative stress induced by amorphous silica ENP to initiate cytotoxicity of these engineered nanoparticles.

Exhaled nitric oxide levels and lung function changes of underground coal miners in Newcastle, Australia

The possibility of exhaled nitric oxide (eNO) in combination with lung function as a marker of airway inflammation produced by coal mining exposure was determined presuming that workers exposed to airborne hazards would possess different concentrations of eNO and decreased lung function indices, relative to control subjects recruited from the same area. The effect of smoking was also considered. A study (exposed) group comprising 186 male subjects (aged 19-58 yr) was recruited from Newcastle coal mining companies with 86 male subjects (aged 20-64 yr) from the same area, but working outside of the coal mining location, serving as controls. The parameters examined were eNO, lung function, and variables derived from an interview-administered questionnaire survey. After adjustment for age, body weight, and smoking status, no significant differences between exposed coal mining workers and controls were found for various lung function parameters. However, the exposed group was shown to have significantly lower concentrations of eNO. In the exposed group, forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), and FEV(1) (%) predicted were found to be significantly different between nonsmokers and smokers. The concentrations of eNO were not significantly different between smoking and nonsmokers within the exposed group. The consideration of nonsmokers alone showed that eNO was significantly lower in the exposed group compared to the control group. The consideration of smokers alone found that eNO was significantly lower in exposed subjects. In the exposed group, no significant association was detected between eNO levels and underground work duration but a significant negative association was shown between eNO and age. Data suggest that exposure to airborne hazards in coal mining is not significantly associated with lung function changes but is correlated with decreased eNO concentrations in exposed workers. While underground work duration was not found to be significantly associated with eNO concentrations in coal mining workers in this study, the potential for using eNO as a monitoring marker still exists and further studies are needed to establish its importance.

Effects of particulate matter on genomic DNA methylation content and iNOS promoter methylation

BACKGROUND

Altered patterns of gene expression mediate the effects of particulate matter (PM) on human health, but mechanisms through which PM modifies gene expression are largely undetermined.

OBJECTIVES

We aimed at identifying short- and long-term effects of PM exposure on DNA methylation, a major genomic mechanism of gene expression control, in workers in an electric furnace steel plant with well-characterized exposure to PM with aerodynamic diameters < 10 microm (PM(10)).

METHODS

We measured global genomic DNA methylation content estimated in Alu and long interspersed nuclear element-1 (LINE-1) repeated elements, and promoter DNA methylation of iNOS (inducible nitric oxide synthase), a gene suppressed by DNA methylation and induced by PM exposure in blood leukocytes. Quantitative DNA methylation analysis was performed through bisulfite PCR pyrosequencing on blood DNA obtained from 63 workers on the first day of a work week (baseline, after 2 days off work) and after 3 days of work (postexposure). Individual PM(10) exposure was between 73.4 and 1,220 microg/m(3).

RESULTS

Global methylation content estimated in Alu and LINE-1 repeated elements did not show changes in postexposure measures compared with baseline. PM(10) exposure levels were negatively associated with methylation in both Alu [beta = -0.19 %5-methylcytosine (%5mC); p = 0.04] and LINE-1 [beta = -0.34 %5mC; p = 0.04], likely reflecting long-term PM(10) effects. iNOS promoter DNA methylation was significantly lower in postexposure blood samples compared with baseline (difference = -0.61 %5mC; p = 0.02).

CONCLUSIONS

We observed changes in global and gene specific methylation that should be further characterized in future investigations on the effects of PM.

State-of-the-science review of the occupational health hazards of crystalline silica in abrasive blasting operations and related requirements for respiratory protection

Excessive exposures to airborne crystalline silica have been known for over 100 years to pose a serious health hazard. Work practices and regulatory standards advanced as the knowledge of the hazards of crystalline silica evolved. This article presents a comprehensive historical examination of the literature on exposure, health effects, and personal protective equipment related to silica and abrasive blasting operations over the last century. In the early 1900s, increased death rates and prevalence of pulmonary disease were observed in industries that involved dusty operations. Studies of these occupational cohorts served as the basis for the first occupational exposure limits in the 1930s. Early exposure studies in foundries revealed that abrasive blasting operations were particularly hazardous and provided the basis for many of the engineering control and respiratory protection requirements that are still in place today. Studies involving abrasive blasters over the years revealed that engineering controls were often not completely effective at reducing airborne silica concentrations to a safe level; consequently, respiratory protection has always been an important component of protecting workers. During the last 15-20 yr, quantitative exposure-response modeling, experimental animal studies, and in vitro methods were used to better understand the relationship between exposure to silica and disease in the workplace. In light of Occupational Safety and Health Administration efforts to reexamine the protectiveness of the current permissible exposure limit (PEL) for crystalline silica and its focus on protecting workers who are known to still be exposed to silica in the workplace (including abrasive blasters), this state-of-the-science review of one of the most hazardous operations involving crystalline silica should provide useful background to employers, researchers, and regulators interested in the historical evolution of the recognized occupational health hazards of crystalline silica and abrasive blasting operations and the related requirements for respiratory protection.

Oxidative stress, plasminogen activator inhibitor 1, and lung fibrosis

Fibrosis is characterized by excessive accumulation of extracellular matrix (ECM) in basement membranes and interstitial tissues, resulting from increased synthesis or decreased degradation of ECM or both. The plasminogen activator/plasmin system plays an important role in ECM degradation, whereas the plasminogen activator inhibitor 1 (PAI-1) is a physiologic inhibitor of plasminogen activators. PAI-1 expression is increased in the lung fibrotic diseases and in experimental fibrosis models. The deletion of the PAI-1 gene reduces, whereas the overexpression of PAI-1 enhances, the susceptibility of animals to lung fibrosis induced by different stimuli, indicating an important role of PAI-1 in the development of lung fibrosis. Many growth factors, including transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha), as well as other chemicals/agents, induce PAI-1 expression in cultured cells and in vivo. Reactive oxygen and nitrogen species (ROS/RNS) have been shown to mediate the induction of PAI-1 by many of these stimuli. This review summarizes some recent findings that help us to understand the role of PAI-1 in the development of lung fibrosis and ROS/RNS in the regulation of PAI-1 expression during fibrogenesis.

Understanding the chemical properties of macerals and minerals in coal and its potential application for occupational lung disease prevention

Recent increases in oil price further strengthen the argument that coal and coal products will play an increasingly important role in fulfilling the energy needs of our society. Coal is an aggregate of heterogeneous substances composed of organic (macerals) and inorganic (minerals) materials. The objective of this review was to assess whether some chemical parameters in coal play a role in producing environmental health problems. Basic properties of coal--such as chemical forms of the organic materials, structure, compositions of minerals--vary from one coal mine region to another as well as from coals of different ranks. Most importantly, changes in chemical properties of coals due to exposure to air and humidity after mining--a dynamic process--significantly affect toxicity attributed to coal and environmental fate. Although coal is an extremely complex and heterogeneous material, the fundamental properties of coal responsible for environmental and adverse health problems are probably related to the same inducing components of coal. For instance, oxidation of pyrite (FeS2) in the coal forms iron sulfate and sulfuric acid, which produces occupational lung diseases (e.g., pneumoconiosis) and other environmental problems (e.g., acid mine drainage and acid rain). Calcite (CaCO3) contained in certain coals alters the end products of pyrite oxidation, which may make these coals less toxic to human inhalation and less hazardous to environmental pollution. Finally, knowledge gained on understanding of the chemical properties of coals is illustrated to apply for prediction of toxicity due to coal possibly before large-scale mining and prevention of occupational lung disease during mining.

Cell- and isoform-specific increases in arginase expression in acute silica-induced pulmonary inflammation

Arginase induction was reported in several inflammatory lung diseases, suggesting that this may be a common feature underlying the pathophysiology of such diseases. As little is known regarding arginase expression in silicosis, the induction and cellular localization of arginase were elucidated in lungs of Sprague-Dawley rats 24 h following exposure to varying doses of silica by intratracheal instillation. Arginase expression was evaluated by activity assay, quantification of arginase I and arginase II mRNA levels using real-time polymerase chain reaction (PCR), and immunohistochemistry. Analyses of cells and fluid obtained by bronchoalveolar lavage (BAL) showed that markers of pulmonary inflammation, tissue damage, activation of alveolar macrophages (AM) and NO production were significantly increased by all silica doses. Arginase activity was increased also in AMs isolated from BAL fluid of silica-treated rats. Silica produced two- and three-fold increases in arginase activity of whole lung at doses of 1 and 5 mg/100 g body weight, respectively. Levels of arginase I mRNA, but not of arginase II mRNA, were similarly elevated. In control lungs, arginase I immunoreactivity was observed only in AMs sparsely dispersed throughout the lung; no inducible nitric oxide synthase (iNOS) immunoreactivity was detected. In silica-treated lungs, arginase I and iNOS were co-expressed in most AMs that were abundantly clustered at inflammatory foci. The rapid induction of arginase I expression in inflammatory lung cells, similar to induction of arginase in other inflammatory lung diseases, implicates elevated arginase activity as a factor in the development of lung damage following exposure to silica.

Proteomic identification of macrophage migration-inhibitory factor upon exposure to TiO2 particles

Inhalation of particulate matter aggravates respiratory symptoms in patients with chronic airway diseases, but the mechanisms underlying this response remain poorly understood. We used a proteomics approach to examine this phenomenon. Treatment of epithelial cells with BSA-coated titanium dioxide (TiO(2)) particles altered 20 protein spots on the two-dimensional gel, and these were then analyzed by nano-LC-MS/MS. These proteins included defense-related, cell-activating, and cytoskeletal proteins implicated in the response to oxidative stress. The proteins were classified into four groups according to the time course of their expression patterns. For validation, RT-PCR was performed on extracts of in vitro TiO(2)-treated cells, and lung issues from TiO(2)-treated rats were analyzed by immunohistochemical staining and enzyme immunoassay. TiO(2) treatment was found to increase the amount of mRNA for macrophage migration-inhibitory factor (MIF). MIF was expressed primarily in epithelium and was elevated in lung tissues and bronchoalveolar lavage fluids of TiO(2)-treated rats as compared with sham-treated rats. Carbon black and diesel exhaust particles also induced expression of MIF protein in the epithelial cells.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Increased susceptibility of the lungs of hyperthyroid rats to oxidant injury: specificity of effects

Results from previous studies indicate that hyperthyroidism increases the risk of ozone-induced lung toxicity. This observation raised the possibility that pulmonary damage from other oxidant substances might be greater in a hyperthyroid state. To address this hypothesis, pulmonary responses to crystalline silica, a particulate with oxidant properties, were evaluated in normal or hyperthyroid adult male rats. To induce a hyperthyroid condition, time-release pellets containing thyroxine were implanted subcutaneously; control rats received placebo pellets. After 7 days, the animals were exposed to saline or silica (0.1mg/100g BW or 1.0mg/100g BW) by intratracheal instillation. Following silica treatment, there was a dose-related increase in bronchoalveolar lavage (BAL) albumin levels and neutrophil numbers. However, the effects of silica were similar in both normal and hyperthyroid rats. These findings were confirmed and contrasted with those regarding ozone (1ppm, 4h inhalation) in a subsequent experiment. The results indicated that, although exposure to either ozone or silica resulted in increases in BAL albumin levels and neutrophil numbers, only responses to ozone were enhanced in hyperthyroid rats. These findings suggest that specificity exists in regards to the modulation of oxidant-induced lung damage and inflammation by thyroid hormones.

Enhanced oxidative stress and endothelial dysfunction in streptozotocin-diabetic rats exposed to fine particles

The association between ambient particulate matter (PM) and cardiovascular diseases has been demonstrated in epidemiological studies. Recent studies suggest that diabetic patients are at greater risk for PM-associated cardiovascular events. Although diabetes and PM exposure individually have been reported to be associated with increased oxidative stress, inflammation, and endothelial dysfunction, it is not clear whether PM may induce synergistic interaction effects on these parameters in diabetics. Strepotozotocin-induced diabetic (n=4) and healthy (n=4) rats were intratracheally administered with PM2.5 collected from a busy traffic area in a dose of 200 microg suspended in 0.5 mL phosphate-buffered saline (PBS). The same number of rats was exposed to PBS as controls. Cell and differential counts and protein and lactate dehydrogenase activity were determined in bronchoalveolar lavage. Markers of 8-hydroxydeoxy-guanosine (8-OHdG), endothelin-1 (ET-1), and [nitrate+nitrite], an indicator of nitric oxide (NO) production, in addition to C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) in peripheral blood were also determined. Our results showed that diabetic rats were associated with increased 8-OHdG, IL-6, and ET-1 decreased [nitrate+nitrite]. In nondiabetic rats PM exposure was also associated with increased 8-OHdG, IL-6, TNF-alpha, and CRP but decreased [nitrate+nitrite]. Interestingly, increases of 8-OHdG and ET-1 after PM exposure were more prominent in diabetic rats than in nondiabetic rats. The general linear model further indicated that there were interactions between diabetes and PM on 8-OHdG (P<0.01) and ET-1 (P=0.08). We suggest that PM exposure may enhance the risk of cardiovascular diseases through interaction between PM and diabetes on excess reactive oxygen species generation and endothelial dysfunction. These findings provide further support for previous epidemiological studies.

N-acetylcysteine and deferoxamine reduce pulmonary oxidative stress and inflammation in rats after coal dust exposure

Coal dust inhalation induces oxidative damage and inflammatory infiltration on lung parenchyma. Thus, the aim of this study was to determine whether N-acetylcysteine (NAC) administered alone or in combination with deferoxamine (DFX), significantly reduced the inflammatory infiltration and oxidative damage in the lungs of rats exposed to coal dust. Forty-two male Wistar rats (200-250 g) were exposed to the coal dust (3mg/0.5 mL saline, 3 days/week, for 3 weeks) by intratracheal instillation. The animals were randomly divided into three groups: saline 0.9% (n=8), supplemented with NAC (20mg/kg of body weight/day, intraperitoneal injection (i.p.)) (n=8), and supplemented with NAC (20 mg/kg of body weight/day, i.p.) plus DFX (20 mg/kg of body weight/week) (n=8). Control animals received only saline solution (0.5 mL). Lactate dehydrogenase activity and total cell number were determined in the bronchoalveolar lavage fluid. We determined lipid peroxidation and oxidative protein damage parameters and catalase and superoxide dismutase activities in the lungs of animals. Intratracheal instillation of coal dust in the lungs of rats led to an inflammatory response and induced significant oxidative damage. The administration of NAC alone or in association with DFX reduced the inflammatory response and the oxidative stress parameters in rats exposed to coal dust.

Lung oxidative response after acute coal dust exposure

Coal dust exposure can induce an acute alveolar and interstitial inflammation that can lead to chronic pulmonary diseases. The objective of this study was to describe the acute and later effects of acute coal dust exposure in lung parenchyma and the involvement of reactive oxygen species in coal dust effects. Forty-eight male Wistar rats (200-250 mg) were separated into four groups: 48 h, 7 days, 30 days, and 60 days after coal dust instillation. Gross mineral coal dust (3 mg/0.5 mL saline) was administered directly in the lungs of the treatment group by intratracheal instillation. Control animals received only saline solution (0.5 mL). Lipid peroxidation was determined by the quantity of thiobarbituric acid-reactive species (TBARS), oxidative damage to protein was obtained by the determination of carbonyl groups, the total radical-trapping antioxidant parameter (TRAP) was estimated by luminol chemoluminescence emission, catalase activity was measured by the rate of decrease in hydrogen peroxide, and superoxide dismutase activity was assayed by the inhibition of adrenaline autooxidation. Histological evaluation of coal dust-treated rats demonstrated an inflammatory infiltration after 48 h of the exposure. Initially, this was a cellular infiltration suggestive of lymphocyte infiltration with lymphoid hyperplasia that remained until 7 days after induction. This initial response was followed by a chronic inflammatory infiltration characterized by aggregates of macrophages 30 days after induction. This inflammatory response tended to resolve 60 days after induction, being similar to that of control animals. During both the acute and chronic phases of lung inflammation we observed a decrease in the TRAP in the lung of coal dust-exposed animals compared to that in control animals. We also observed an activation of superoxide dismutase 60 days after coal dust exposition. TBARS were increased 60 days after coal dust exposure and protein carbonyl groups increased at all times after coal dust exposure (48 h, 7 days, 30 days, and 60 days). These data suggested a biphasic inflammatory response and the involvement of oxidative damage in coal dust-induced lung damage.

Role of inducible nitric oxide synthase-derived nitric oxide in silica-induced pulmonary inflammation and fibrosis

Inhalation of crystalline silica can produce lung inflammation and fibrosis. Inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) is believed to be involved in silica-induced lung disease. To investigate the role of iNOS-derived NO in this disease, the responses of iNOS knockout (KO) versus C57Bl/6J wild-type (WT) mice to silica were compared. Male mice (8-10 wk old, mean body weight 24.0 g) were anesthetized and exposed, by aspiration, to silica (40 mg/kg) or saline. At 24 h and 42 d postexposure, lungs were lavaged with saline. The first bronchoalveolar lavage (BAL) fluid supernatant was analyzed for lactate dehydrogenase (LDH) activity, levels of albumin, tumor necrosis factor-alpha (TNF-alpha), and macrophage inflammatory protein-2 (MIP-2), as well as total antioxidant capacity (TAC). The cellular fraction of the total BAL was used to determine alveolar macrophage (AM) and polymorphonuclear leukocyte (PMN) counts, and zymosanstimulated AM chemiluminescence (AM-CL). In separate mice, lung histopathological changes were evaluated 42 d postexposure. Acute (24-h) silica exposure decreased AMs, increased PMNs, increased LDH activity and levels of albumin, TNF-alpha, and MIP-2 in BAL fluid, and enhanced AM-CL in both iNOS KO and WT mice. However, iNOS KO mice exhibited less AM activation (defined as increased AM-CL and decreased AM yield) than WT. Furthermore, TAC following acute silica decreased in WT but was maintained in iNOS KO mice. Pulmonary reactions to subchronic (42 d) silica exposure were similar to acute. However, histopathological and BAL fluid indices of lung damage and inflammation, AM activation, and lung hydroxyproline levels were significantly less in iNOS KO compared to WT mice. These results suggest that iNOS-derived NO contributes to the pathogenesis of silica-induced lung disease in this mouse model.

Role of substrate on larval development of the freshwater teleostPelvicachromis pulcher

It is known that, in an aquatic environment, the mineralogical composition of the substrate can affect the structure of settled communities. In marine environments, the presence of quartz negatively influences the formation of biofilm, as well as the selection and the colonization of the substrate by benthic organisms. Direct laboratory observation revealed that the freshwater teleost Pelivicachromis pulcher selects, when available, nonquartzitic brooding substrate. To monitor the effects of substrate on larvae development, ten lots of embryos were distributed in grid nurseries; carbonatic gravel was laid in five of the nurseries, while freshly fractured quartz gravel was used in the remaining ones. All the embryos laid in the two nurseries hatched, and 90% of the carbonate developing larvae reached adulthood, while 100% of those reared on quartz grain died 120 hr post hatching. Examination was made, both in larvae developed on carbonatic substrates and in those developed on quartz substrates, of the expression of the fetal growth factor, the insulin growth factor-II (IGF-II), of the molecular chaperone, the heat shock protein 70 (HSP70), which is involved in the folding of the nascent polypeptide chain, of the key enzyme of the glycolytic pathway, the glyceraldehyde-3-phosphate dehydrogenase (GADPH), and of the housekeeping gene, the beta-actin. All the data were normalized against 18S RNA expression. In larvae reared on quartz substrate, the genes IGF-II and the beta-actin showed a lower expression, while the GADPH was totally suppressed and the expression of HSP70 increased. In conclusion, the data presented in this article demonstrated, for the first time, that the presence of quarzitic substrates is sufficient to stop larvae development through the inhibition of gene transcription in this African cichlid, leading to its death.

Gene expression of primary human bronchial epithelial cells in response to coal dusts with different prevalence of coal workers' pneumoconiosis

Striking regional differences in the prevalence of coal workers' pneumoconiosis (CWP) have been observed but not fully understood. This study investigated the early biological responses of primary lung cells to treatment with coal dusts from various seams. High-density oligoarray technology (GeneChip, Affymetrix, Santa Clara, CA) was used to compile gene expression profiles of primary human bronchial epithelial cells to low concentrations (2 microg/cm(2)) of coals for 6 h or 24 h of treatment. Data showed that a total of 1050 out of 12,000 genes on the chip were altered by 2 coal dusts. The coal from the Pennsylvania (PA) coal-mine region with a high prevalence of CWP altered 908 genes, many more than the coal from Utah (UT) with a low prevalence of CWP, which affected 356 genes. Many genes decreased their expression levels in response to the PA coal at 6 h and/or 24 h of treatment. For example, transferrin receptor, a gene known to control cellular iron uptake, was downregulated in the cells treated with the iron-containing PA coal in order to protect cells from iron overload. The UT coal without bioavailable iron had no such effect. The downregulation patterns of genes were confirmed by reverse-transcription polymerase chain reaction (RT-PCR). This study is one of the first in profiling gene expressions of primary bronchial epithelial cells treated with coals from various seams, which may set stages for future studies on specific genes.

Response of alveolar macrophages from inducible nitric oxide synthase knockout or wild-type mice to an in vitro lipopolysaccharide or silica exposure

The role of nitric oxide (NO) in pulmonary disease has been controversial with both antiinflammatory (scavenging radicals and inhibiting NF-êB activation) and proinflammatory (forming highly reactive peroxynitrite and augmenting NF-êB activation by inflammatory agents) actions reported. Therefore, a study has been initiated to determine whether deletion of the inducible nitric oxide synthase (iNOS) gene in the C57BL/6J mouse alters the pulmonary macrophage response to lipopolysaccharide (LPS) or silica. The objective of the initial phase of this study was to determine the difference in responsiveness of alveolar macrophages (AMs), harvested from naive wild-type (WT) or iNOS knockout (iNOS KO) mice, to an in vitro LPS or silica exposure. Primary AMs were obtained by bronchoalveolar lavage (BAL) from age- and weight-matched iNOS KO and WT mice. The cells were treated with interferon-gamma (IFN-ã) (50 U/ml), IFN-ã (50 U/ml) + LPS (1 microg/ml), LPS (0.01-100 microg/ml), or silica (25-250 microg/ml). The following parameters were measured: nitrate and nitrite (NOx), tumor necrosis factor-á (TNF-á), macrophage inflammatory protein-2 (MIP-2), intracellular generation of the reactive oxygen species (ROS) hydrogen peroxide (H(2)O(2) and superoxide (O(*-2)), and basal (unstimulated) total antioxidant capacity. Data show a significant increase in NOx production upon exposure to IFN-ã +/- LPS in the WT but not iNOS KO AMs. NOx production by iNOS KO or WT AMs was not altered by in vitro exposure to LPS or silica alone. LPS, but not silica, induced TNF-á and MIP-2 production in both iNOS KO and WT AMs. Statistical analysis of concentration response curves found a significant tendency for greater mediator production in the iNOS KO versus WT AMs. Basal intracellular production of H(2)O(2) and O(*- 2) was significantly greater in the iNOS KO compared to WT AMs. In contrast, LPS- (10 microg/ml) or silica- (100 microg/ml) stimulated intracellular oxidant production was lower in iNOS KO AMs, but overall (basal + stimulated) inflammatory capacity was similar between the cell types. The basal total antioxidant production of the iNOS KO AMs was approximately twofold higher than the WT AMs. In conclusion, certain compensatory changes appear to occur in AMs from iNOS KO mice. In response to the inability to induce NO production, iNOS KO AMs exhibit significantly higher basal generation of H(2)O(2) and (O(*- 2)) as well as higher total antioxidant levels. In addition, LPS induced TNF-á and MIP-2 production tend to be higher in AMs from iNOS KO mice. Such compensatory changes in the AM response may affect the response of iNOS KO mice to inflammatory exposures.

Health effects and time course of particulate matter on the cardiopulmonary system in rats with lung inflammation

Recent epidemiological studies associate health effects and particulate matter in ambient air. Exacerbation of the particle-induced inflammation can be a mechanism responsible for increased hospitalization and death due to cardiopulmonary events in high-risk groups of the population. Systems regulating blood pressure that depend on lung integrity can be involved in progression of cardiovascular diseases. This study focused on the expression levels of various genes involved in cardiovascular and pulmonary diseases to assess their role in the onset of cardiovascular problems due to ambient particulate matter and compared these with the corresponding products. Rats with ozone-induced (1600 microg/m(3); 8 h) pulmonary inflammation were exposed to 0.5 mg, 1.5 mg, or 5 mg of particulate matter (PM) from Ottawa Canada (EHC-93) by intratracheal instillation. mRNA levels of various genes and their products were measured 2, 4, and 7 d after instillation. At 2 d after exposures to PM, tumor necrosis factor (TNF)-alpha levels in bronchoalveolar lavage fluid (BALF) were elevated approximately 4 times for the highest EHC-93 dose. MIP-2 protein levels in BALF were elevated approximately three times during the entire time period studied, whereas IL-6 levels were not affected compared to control groups. The MIP-2 mRNA levels revealed a similar pattern of induction. A twofold increase in endothelin (ET)-1 levels at d 2 and a 20% decrease in angiotensin-converting enzyme (ACE) activity at d 7 were measured in plasma. A 60% decrease of ACE and ET-1 mRNA levels suggested a possible endothelial damage in the lung blood vessels. Inducible nitric oxide synthase (iNOS) mRNA was found to be increased 3.5 times 2 d after instillation of the particles. Therefore, the endothelial damage could have been caused by large amounts of the free radical NO. Also, plasma levels of fibrinogen were elevated (20%), which could presumably increase blood viscosity, leading to decreased tissue blood flow. These changes in hematological and hemodynamic parameters observed in our study are in line with heart failure in high-risk groups of the population after high air pollution episodes.

Differences in the effects of fibrous and particulate titanium dioxide on alveolar macrophages of Fischer 344 rats

Alveolar macrophages are considered to play a major role in the pathophysiology of lung diseases caused by exposure to various kinds of pathogens and particles. In this study, the cytotoxic effect of different shapes of titanium dioxide (TiO(2)) was evaluated on macrophages using a unique magnetometry method and was compared with conventional methods of lactate dehydrogenase (LDH) release, apoptosis measurement, and morphological observations. Alveolar macrophages obtained from Fischer rats (F344) by bronchoalveolar lavage were incubated in vitro for 18 h with Fe(3)O(4) as a magnetometric indicator and fibrous and particulate forms of TiO(2) as test materials. In the control and particulate exposed group, rapid attenuation of the residual magnetic field, so-called "relaxation," was observed immediately after cessation of the external magnetic field. In comparison, a delay of relaxation was observed in alveolar macrophages exposed to fibrous TiO(2). LDH released into serum-free medium induced by exposure to TiO(2) increased significantly in a concentration-dependent manner in macrophages exposed to fibrous TiO(2), while negligible LDH release was observed in macrophages exposed to particulate TiO(2). The DNA ladder detection method and morphological examination detected no apoptosis in macrophages exposed to 60 micro g/ml of fibrous or particulate TiO(2). Electron microscopic examination revealed vacuolar changes and cell surface damage in macrophages exposed to fibrous TiO(2), but no significant changes in macrophages exposed to particulate TiO(2). The results of magnetometry, LDH release, and electron microscopy suggest that cytotoxicity of TiO(2) depends on the shape of the material.

Early inflammatory response to asbestos exposure in rat and hamster lungs: role of inducible nitric oxide synthase

Recent studies have suggested that inducible nitric oxide synthase (iNOS) plays a role in the development of asbestos-related pulmonary disorders. The pulmonary reactions of rats and hamsters upon exposure to asbestos fibers are well known to be disparate. In addition, in vitro experiments have indicated that mononuclear phagocytes from hamsters, in contrast to those from rats, lack the iNOS pathway. Therefore, the purpose of this study was to investigate whether rats and hamsters differ in lung iNOS expression in vivo upon exposure to asbestos fibers and whether differences in iNOS induction are associated with differences in the acute pulmonary inflammatory reaction. Body weight, alveolar-arterial oxygen difference, differential cell count in bronchoalveolar lavage fluid, total protein leakage, lung myeloperoxidase activity and lipidperoxidation, wet/dry ratio, iNOS mRNA and protein expression, and nitrotyrosine staining of lung tissue were determined 1 and 7 days after intratracheal instillation of asbestos fibers in CD rats and Syrian golden hamsters. Exposure of rats to asbestos fibers resulted in enhanced pulmonary iNOS expression and nitrotyrosine staining together with an acute inflammation that was characterized by an influx of neutrophils, enhanced myeloperoxidase activity and lipid peroxidation, damage of the alveolar-capillary membrane, edema formation, and impairment of gas exchange. In comparison, instillation of asbestos fibers in hamsters resulted in a significantly milder inflammatory reaction of the lung with no induction of iNOS in pulmonary cells. The data obtained provide important information to understand the underlying mechanisms of species differences in the pulmonary response upon exposure to asbestos fibers.

The two PM(2.5) (fine) and PM(2.5-10) (coarse) fractions: evidence of different biological activity

Recent studies have shown that an increased concentration of environmental particulate matter (PM(10)) is related to many respiratory diseases. One major issue is whether the toxicity of the particles resides in some particular fraction as defined by chemical composition and size. The overall purpose of this study was to compare the in vitro toxicity of coarse (PM(2.5-10)) and fine (PM(2.5)) particulate matter, collected in an urban area of Rome, in relation to their physicochemical composition as assessed by analytic electron microscopy and atomic absorption spectroscopy. In particular, our aim was to evaluate the importance of particle physicochemical components in the induced toxicity. The in vitro toxicity assays used included human red blood cell hemolysis, cell viability, and nitric oxide (NO) release in the RAW 264.7 macrophage cell line. The hemolytic potential has been widely used as an in vitro toxicity screen and as a useful indicator of oxidative damage to biomembranes. We found that human erythrocytes underwent dose-dependent hemolysis when they were incubated with varying concentrations of fine and coarse particles. The hemolytic potential was greater for the fine particles than for the coarse particles in equal mass concentration. However, when data were expressed in terms of PM surface per volume unit of suspension, the two fractions did not show any significant hemolytic differences. This result suggested that the oxidative stress induced by PM on the cell membranes could be due mainly to the interaction between the particle surfaces and the cell membranes. RAW 264.7 macrophage cells challenged with particles showed decreased viability and an increased release of NO, a key inflammatory mediator, and both effects were not dose dependent in the tested concentration range. The fine particles were the most effective and the differences between the two size fractions in inducing these biological effects remained unchanged when the basis of comparison was changed from weight to surface measures. It seemed therefore that these differences relied on the different physicochemical nature of the particles. The main chemical difference between the two fractions resided in a greater abundance of C-rich particles with S traces in the fine fraction. Therefore, we cautiously suggest a role for these particles in the induction of toxicity.

Interaction of alveolar macrophages with inhaled mineral particulates

Pulmonary disorders triggered by inhalation of occupational and environmental mineral particulates can be endpoints of a chronic inflammatory process in which alveolar macrophages (AMs), as a first line of defense, play a crucial role. The biological processes involved in particulate-induced activation of AMs include indirect or direct interactions of particulates with the cell membrane, subsequent stimulation of signal transduction pathways, and activation of gene transcription. Depending on the nature of particulate involved, particulate-induced activation of AMs has been shown to result in the release of potent mediators, such as reactive oxygen and nitrogen species, cytokines, eicosanoids, and growth factors. The prolonged and enhanced production of such effector molecules may result in a complex cascade of events that can contribute to the development of pulmonary disorders. This paper will give a short review of the present knowledge of AM interaction with inhaled mineral particulates and of the possible implications these interactions may have in the development of pulmonary disorders.

Adenovirus infection increases iNOS and peroxynitrite production in the lung

Host inflammatory and immune responses limit viral gene expression after administration of replication-deficient adenoviruses to the lung. The current study asks whether inducible nitric oxide synthase (iNOS) expression and peroxynitrite generation accompanied the inflammatory response following intratracheal administration of adenovirus. Pulmonary iNOS mRNA and protein were increased 2, 7, and 14 days following administration of 2 x 10(9) plaque-forming units of recombinant adenovirus (Av1Luc1) to BALB/c mice. Adenovirus infection was associated with a marked increase in nitrotyrosine staining. Intense nitrotyrosine staining was observed in alveolar macrophages, respiratory epithelial cells, conducting airways, and alveolar spaces 2 days postinfection. Two weeks after exposure to adenovirus, nitrotyrosine staining was detected within alveolar macrophages, suggesting adenovirus enhanced the nitration of proteins that were subsequently taken up by alveolar macrophages. Western blot analysis using anti-nitrotyrosine antibody did not demonstrate accumulation of nitrated surfactant protein A (SP-A), although a small fraction of aggregated SP-A comigrated with a nitrotyrosine-positive protein. iNOS expression, peroxynitrite, and nitrotyrosine generation accompany and may contribute to inflammatory responses to adenovirus in the lung.

IgE adjuvant effect caused by particles - immediate and delayed effects

Diesel exhaust particles are reported to increase the specific IgE response to ovalbumin (OVA) and pollen. Evidence has been provided that the particle core contributes to this adjuvant activity. The purpose of our study was to investigate the effect of well-defined simple particles, polystyrene particles (PSP), on the production of allergen-specific IgE in a mouse model. The IgE adjuvant effect of PSP was investigated in experiments using intranasal (i.n.) instillation, intratracheal (i.t.) instillation or intraperitoneal (i.p.) injection. Delayed and cumulative adjuvant effects were investigated by giving mice i.p. injections with PSP 1-3 days, or on 4 consecutive days before OVA, respectively. The levels of allergen-specific and total IgE were measured. Irrespectively of immunisation route and protocol, OVA in combination with PSP elicited increased levels of both allergen-specific and total IgE when compared with OVA alone. Therefore, in the experimental model, particles were found to augment the specific IgE response to an allergen even when the allergen was introduced several days after the particles. These findings imply that individuals exposed to particulate air pollution at one point of time may develop an increased reaction towards allergens inhaled later that day or even several days after the particle exposure.

Nitric oxide up-regulates DNA-binding activity of nuclear factor-kappaB in macrophages stimulated with silica and inflammatory stimulants

Nitric oxide (NO), a reactive nitrogen species, plays an important role in inflammatory lung damage. In the present study, we investigated the role of NO in DNA-binding activity of NF-kappaB in macrophages stimulated with silica or other inflammatory stimulants. Treatment of mouse macrophages (RAW264.7 cells) with a selective inhibitor of inducible nitric oxide synthase (iNOS), L-N6-(1-iminoethyl) lysine (L-NIL), or a nonselective iNOS inhibitor, N omega-nitro-L-arginine methylester (L-NAME), resulted in inhibition of silica-induced nitric oxide production as well as silica-induced NF-kappaB activation. L-NIL also effectively inhibited NF-kappaB activation induced by other inflammatory stimulants, such as lipopolysaccharide (LPS) or muramyl dipeptide (MDP). These inhibitory effects of L-NIL and L-NAME on silica- or LPS-induced NF-kappaB activation were also observed in primary rat alveolar macrophages. Furthermore, NO generating compounds, such as sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), caused a dose-dependent increase in NF-kappaB activation, which was positively correlated with the level of NO production. Specific inhibitors of protein tyrosine kinase, such as genistein and AG494, prevented NF-kappaB activation in SNP- or SIN-1 treated cells, suggesting involvement of tyrosine kinase in the NO signaling pathway leading to NF-kappaB activation. In contrast, inhibitors of protein kinase C or A, such as staurosporine or H89, had no inhibitory effect on SIN-1 induced NF-kappaB activation. Metalloporphyrins, such as tetrakis (N-methyl-4'-pyridyl) porphyrinato iron (III) (Fe-TMPyP) and Zn-TMPyP which are known to alter NO-dependent activity, markedly inhibited silica- and LPS-induced NF-kappaB activation. The results suggest that NF-kappaB activation in macrophages can be induced under certain conditions by nitric oxide and that nitric oxide produced by phagocytes exposed to inflammatory agents may up-regulate the activation of NF-kappaB.

Peroxynitrite formation by diesel exhaust particles in alveolar cells: Links to pulmonary inflammation

Diesel exhaust particles (DEP) are assumed to be a causal substance for pulmonary inflammation. As peroxynitrite is recently implicated in inflammation and cytotoxity, the hypothesis was tested that instillation of DEP induces formation of peroxynitrite in cells migrated in lung. Rats were intratracheally instilled with DEP suspension (2 mg/0.5 ml/kg) and killed 24 h later. Alveolar cells were collected by broncho-alveolar lavage. Population of alveolar cells increased more than twice by DEP exposure, mainly due to a large increase of neutrophils. Peroxynitrite formation (N(G)-nitro-L-arginine methylester and superoxide dismutase inhibitable chemiluminescence) was detected in alveolar cells from treated rats, and 12-O-tetradecanoylphorbol 13-acetate-stimulation enhanced it. In addition, DEP induced expression of inducible NO synthase mRNA in these cells. But peroxynitrite was not detectable in cells from control. These results indicate that DEP exposure results in peroxynitrite formation in migrated cells, which leads to pulmonary inflammation.

Persistent depletion of I kappa B alpha and interleukin-8 expression in human pulmonary epithelial cells exposed to quartz particles

Chronic inflammation and fibrosis following quartz inhalation has been associated with persistent up-regulation of several "pro-inflammatory" genes, which are commonly regulated by nuclear factor kappa-B (NF-kappaB). Transcription of the NF-kappaB-inhibitor IkappaBalpha is also under NF-kappaB control, and its de novo synthesis is considered to comprise a negative feedback loop in transient inflammation. To investigate this mechanism in particle inflammation, we have studied IkappaBalpha degradation in A549 cells exposed to DQ12-quartz or TiO(2), in relation to the expression of IL-8. Although both quartz and TiO(2) were found to cause IkappaBalpha degradation, only quartz elicited a mild IkappaBalpha depletion, first appearing at 4 h. TiO(2) was found to cause a higher short-term increase in IkappaBalpha mRNA-expression compared to quartz, whereas the early enhancement of IL-8 expression and release was similar for both particles. Up-regulation of IL-8 expression was found to persist with quartz only. Cotreatment with PDTC and curcumin reduced particle-elicited IL-8 response, whereas cycloheximide caused enhancement of IL-8 mRNA expression in both the quartz- and TiO(2)-treated cells. Our results demonstrate that mineral dusts cause IkappaBalpha degradation, a transient increase in de novo synthesis of IkappaBalpha, and enhanced IL-8 expression in human pulmonary epithelial cells. While IkappaBalpha degradation and early IL-8 expression seem to be general particle phenomena, particle-specific characteristics impact on activation of IkappaBalpha gene transcription, apparently accounting for the different proinflammatory IL-8 responses seen with quartz and TiO(2) in the longer term. These observations may provide an explanation for the transient versus the persistent pulmonary inflammatory status and subsequent differences in pathogenic potency of TiO(2) and quartz.

Silicosis and coal workers' pneumoconiosis

Exposure to coal mine dust and/or crystalline silica results in pneumoconiosis with initiation and progression of pulmonary fibrosis. This review presents characteristics of simple and complicated coal workers' pneumoconiosis (CWP) as well as pathologic indices of acute and chronic silicosis by summarizing results of in vitro, animal, and human investigations. These results support four basic mechanisms in the etiology of CWP and silicosis: a) direct cytotoxicity of coal dust or silica, resulting in lung cell damage, release of lipases and proteases, and eventual lung scarring; b) activation of oxidant production by pulmonary phagocytes, which overwhelms the antioxidant defenses and leads to lipid peroxidation, protein nitrosation, cell injury, and lung scarring; c) activation of mediator release from alveolar macrophages and epithelial cells, which leads to recruitment of polymorphonuclear leukocytes and macrophages, resulting in the production of proinflammatory cytokines and reactive species and in further lung injury and scarring; d) secretion of growth factors from alveolar macrophages and epithelial cells, stimulating fibroblast proliferation and eventual scarring. Results of in vitro and animal studies provide a basis for proposing these mechanisms for the initiation and progression of pneumoconiosis. Data obtained from exposed workers lend support to these mechanisms.

Effects of xenobiotics on macrophage function: evaluation in vitro

Macrophages participate in a variety of inflammatory and immunologic functions (e.g., phagocytosis, cytokine production, killing of microbes and tumor cells, and processing and presentation of antigen to T lymphocytes). Because these cells are widely distributed in the circulation and throughout tissue, the effects of xenobiotics on macrophage function can be significant. Measures in vitro of altered function elicited by xenobiotic exposure can include changes in expression of cell surface proteins, in production of oxygen and nitrogen free radicals, in production of cytokines [interleukin (IL)-1, IL-6, IL-12, tumor necrosis factor alpha (TNFalpha)], in expression of adhesion molecules (ICAM-1), in phagocytosis and intracellular killing, and in antigen presentation.

Genes of chicken MHC regulate the adherence activity of blood monocytes in Rous sarcomas progressing and regressing lines

The influence of the chicken major histocompatibility (B) complex (MHC) on the adherence potential of monocyte-derived macrophages was examined using the congenic chicken lines CB and CC. These lines represent well-defined genetic models for the study of resistance (CB) or susceptibility (CC) to the progressive growth of Rous sarcomas. Using a monoclonal antibody specific for chicken monocytes/macrophages, CB and CC chickens were shown by flow cytometry analyses to have similar proportions of peripheral blood monocytes. However, when the glass-adherence potential of these cells was compared during incubation in tissue culture medium over 24, 48 and 72 h at 40 degrees C, significant differences were seen between cells from these two inbred lines. After 24 and 48 h, glass-adherence by CB cells was 2-3 fold higher than that of CC cells. After 72 h this difference decreased to 1.5 fold. At 24 and 48 h, the adherent CB macrophages also appeared about 1.5 times larger than those of CC chickens. Genetic analysis using F1 hybrids (CBxCC) showed that this trait is regulated by a dominant gene that segregates with the B12 haplotype in the backcross generation F1xCC. From the results obtained with the recombinant congenic lines CB.R1 and CC.R1, we conclude that the gene regulating adherence potential is localized within the B-F/L region of the chicken MHC. About 50% of adherent cells were able to phagocytose opsonised FITC-labelled Zymosan particles. The level of nitric oxide production in vitro by CB and CC macrophages was equal. The importance of cells of the mononuclear phagocyte system for the response to Rous sarcoma virus (RSV) infection was studied in CB chickens using the anti-macrophage agents silica, carrageenan, and C12MDP, encapsulated in liposomes. In those chickens treated with silica and carrageenan, we observed progressive growth of RSV-induced tumors. The graft-versus-host reactivity of peripheral blood lymphocytes (PBL) of treated chickens was comparable to controls. In vitro nitric oxide production by macrophages from silica-treated chickens was higher than by macrophages from untreated controls.

Enhancement of nitric oxide production by pulmonary cells following silica exposure

In vivo exposure of rat lungs to crystalline silica either by intratracheal instillation or by inhalation results in an increase in mRNA levels for inducible nitric oxide synthase (iNOS) in bronchoalveolar lavage cells (BALC), elevated nitric oxide (.NO) production by BALC, and an increase in .NO-dependent chemiluminescence (CL) from alveolar macrophages (AM). Induction of iNOS message occurs in both AM and polymorphonuclear leukocytes (PMN) harvested from silica-exposed lungs but is not significantly elevated in lavaged lung tissue. In vitro exposure of AM to silica does not stimulate .NO production or enhance iNOS message. However, treatment of naive AM with conditioned media from BALC harvested from silica-exposed rats does increase iNOS message and .NO production by these AM. The potency of this conditioned medium is dependent on interaction between AM and PMN. In the rat model, a relationship exists between the ability of various dusts to cause PMN recruitment or protein leakage into the alveolar space and the induction of iNOS message in BALC, i.e., silica > coal mine dust > carbonyl iron > titanium dioxide. Similarly, a comparison of BALC from a healthy volunteer, a silica-exposed coal miner with a normal chest radiograph, and a silica-exposed coal miner with an abnormal chest radiograph shows a correlation between pathology and both the level of iNOS message in BALC and the magnitude of .NO-dependent CL from AM. These data suggest that .NO may play a role in silicosis and that human pulmonary phagocytes exhibit enhanced .NO production in response to an inflammatory insult.

Reactive oxygen species and silica-induced carcinogenesis

Although silica has recently been designated as a carcinogen, its mechanism of carcinogenesis is not fully understood. Recent studies suggest that free-radical reactions may play an important role in the initiation and progression of cancer. This article summarizes literature on the generation of reactive oxygen species (ROS) directly from silica and from silica-stimulated cells. It also summarizes information concerning the role of ROS in silica-induced DNA damage as well as in silica-induced cell proliferation, including the effects of silica on the activation of nuclear transcription factors, induction of growth factors and oncogene expression, redox regulation of the p53 tumor suppressor gene, induction of apoptosis, and division of damaged cells. Understanding the role of ROS in silica-mediated reactions may help develop therapeutic agents to block silica-induced free radical reactions and thus prevent or attenuate silica-induced carcinogenesis.