Comparative performance of a panel of commercially available antimicrobial nanocoatings in Europe

Background

Bacterial resistance against the classic antibiotics is posing an increasing challenge for the prevention and treatment of infections in health care environments. The introduction of antimicrobial nanocoatings with active ingredients provides alternative measures for active killing of microorganisms, through a preventive hygiene approach.

Purpose

The purpose of this study was to investigate the antimicrobial activity of a panel of antimicrobial coatings available on the European market.

Methods

A comparative, biased selection of commercially available antimicrobial coatings was tested for antimicrobial efficiency. Suppliers were contacted to deliver their coatings on glass and/or stainless steel substrates. In total, 23 coatings from eleven suppliers were received, which were investigated for their effect on the growth of Escherichia coli, using the International Organization for Standardization (ISO) 22196 protocol.

Results

The majority of nanomaterial-containing coatings (n=13) contained nanosilver (n=12), while only one had photocatalytic TiO₂ as the active particle. The differences in antimicrobial activity among all of the coatings, expressed as log reduction values, varied between 1.3 and 6.6, while the variation within the nanomaterial-based group was between 2.0 and 6.2. Although nanosilver coatings were on average very effective in reducing the number of viable bacteria after challenge, the strongest log reduction (6.6) was seen with a coating that has immobilized, covalently bound quaternary ammonium salt in its matrix. Besides these two compounds, coatings containing TiO₂, poly(dimethylsiloxane), triclosan, or zinc pyrithione evoked 100% killing of E. coli.

Conclusion

Our findings indicate that nanosilver dominates the nanoparticle-based coatings and performs adequately. However, considering the unknowns in relation to ecotoxicological emission and effects, it needs further consideration before widespread application into different environments.

The limits of testing particle-mediated oxidative stress in vitro in predicting diverse pathologies; relevance for testing of nanoparticles

In vitro studies with particles are a major staple of particle toxicology, generally used to investigate mechanisms and better understand the molecular events underlying cellular effects. However, there is ethical and financial pressure in nanotoxicology, the new sub-specialty of particle toxicology, to avoid using animals. Therefore an increasing amount of studies are being published using in vitro approaches and such studies require careful interpretation. We point out here that 3 different conventional pathogenic particle types, PM₁₀, asbestos and quartz, which cause diverse pathological effects, have been reported to cause very similar oxidative stress effects in cells in culture. We discuss the likely explanation and implications of this apparent paradox, and its relevance for testing in nanotoxicology.

Exposure to diesel exhaust induces changes in EEG in human volunteers

Background

Ambient particulate matter and nanoparticles have been shown to translocate to the brain, and potentially influence the central nervous system. No data are available whether this may lead to functional changes in the brain.

Methods

We exposed 10 human volunteers to dilute diesel exhaust (DE, 300 μg/m³) as a model for ambient PM exposure and filtered air for one hour using a double blind randomized crossover design. Brain activity was monitored during and for one hour following each exposure using quantitative electroencephalography (QEEG) at 8 different sites on the scalp. The frequency spectrum of the EEG signals was used to calculate the median power frequency (MPF) and specific frequency bands of the QEEG.

Results

Our data demonstrate a significant increase in MPF in response to DE in the frontal cortex within 30 min into exposure. The increase in MPF is primarily caused by an increase in fast wave activity (β2) and continues to rise during the 1 hour post-exposure interval.

Conclusion

This study is the first to show a functional effect of DE exposure in the human brain, indicating a general cortical stress response. Further studies are required to determine whether this effect is mediated by the nanoparticles in DE and to define the precise pathways involved.

Calcium and ROS-mediated activation of transcription factors and TNF-alpha cytokine gene expression in macrophages exposed to ultrafine particles

Ultrafine (Uf) particles are a component of particulate air pollution suggested to be responsible for the health effects associated with elevations of this pollutant. We have previously suggested that Uf particles, through the induction of oxidative stress, may induce inflammation in the lung, thus exacerbating preexisting illness in susceptible individuals. Alveolar macrophages are considered to play a key role in particlemediated inflammation and lung disease. The effect of Uf particles on rat alveolar macrophages and human blood monocytes was investigated with reference to the roles of calcium and reactive oxygen species (ROS). TNF-alpha protein release, intracellular calcium concentration, TNF-alpha mRNA expression, and transcription factor activation were studied as end points after treatment of rat alveolar macrophages or peripheral blood monocytes. The calcium channel blocker verapamil, the intracellular calcium chelator BAPTA-AM, the calmodulin inhibitor W-7, and the antioxidants Trolox and Nacystelin (NAL) were included in combination with Uf particles. Verapamil reduced intracellular calcium concentration in rat alveolar macrophages on stimulation with Uf particles. This effect was also apparent with transcription factor AP-1 activation. All antagonists and antioxidants reduced Uf-stimulated nuclear localization of the p50 and p65 subunits of NF-kappaB in human monocytes. Verapamil, BAPTA-AM, and NAL reduced Uf-stimulated TNF-alpha protein release, whereas only verapamil reduced Uf-stimulated mRNA expression in rat alveolar macrophages. In human monocytes, verapamil, Trolox, BAPTA-AM, and W-7 reduced Uf-stimulated TNF-alpha protein release. These findings suggest that Uf particles may exert proinflammatory effects by modulating intracellular calcium concentrations, activation of transcription factors, and cytokine production through a ROS-mediated mechanism.

Associations between infections and fatigue in a Dutch working population: results of the Maastricht Cohort Study on Fatigue at Work

The relationship between fatigue and common infections was further explored, as part of a 3 year prospective cohort study on Fatigue at Work. The current study is based on seven successive questionnaires, covering the first 2 years of follow-up. The overall response at baseline was 45% (n = 12,140). On T1 10,592 (87.2% compared to baseline response) employees returned the questionnaire. For T2, T3, T4, T5 and T6, 10,270 (84.6%), 9655 (79.5%), 8956 (73.8%), 8692 (71.6%) and 8070 (66.5%) employees respectively returned the questionnaire. Self-administered questionnaires were used to determine the level of fatigue with the Checklist Individual Strength (CIS) and the occurrence of common cold, flu-like illness and gastroenteritis. Regression analysis using generalized estimated equations (GEE) were used for data analysis. We found a cross-sectional relationship between fatigue and the infections flu-like illness and gastroenteritis, and a longitudinal relationship between an infection as a predictor of fatigue. For fatigue as a predictor of an infection, we found odds ratios (ORs) of 1.35 (confidence interval (CI) 1.28-1.42) for flu-like illness and 1.33 (CI: 1.25-1.42) for gastroenteritis. The highest incidence of infections was found among employees who reported high fatigue levels on two successive occasions. The increased incidence of infections, is regarded as a substantial effect of fatigue because it is associated with significant absenteeism from work and leads to discomfort.

Aluminium lactate treatment of DQ12 quartz inhibits its ability to cause inflammation, chemokine expression, and nuclear factor-kappaB activation

In 1997, an IARC Working Group classified quartz (crystalline silica) as a Group 1 lung carcinogen, but only in some industries, i.e., the quartz hazard is a variable entity. The reactivity of the quartz surface may underlie its ability to cause inflammation, and treatments that ameliorate this reactivity will reduce the quartz hazard. In this study we treated quartz (Q) with aluminium lactate (AL), a procedure that is reported to decrease the quartz hazard, and explored the effect this had on the highly reactive quartz surface and on proinflammatory events in rat lungs. Aluminium lactate-treated quartz showed a reduced surface reactivity as measured by electron spin resonance and the hemolysis assay. Eighteen hours after instillation of Q into the rat lung, there was massive inflammation as indicated by the number of neutrophils in the bronchoalveolar lavage (BAL). In addition, Q induced an increase in BAL macrophage inflammatory protein-2 (MIP-2) while ALQ had no significant effect compared to control. Epithelial damage, as indicated by BAL protein and gamma glutamyl transpeptidase, also increased with Q but not with ALQ. Furthermore, Q induced an increase in MIP-2 mRNA by BAL cells while ALQ had no effect compared to controls. There was an increase in nuclear binding of the transcription nuclear factor kappaB (NF-kappaB) in the Q-exposed BAL cells and again no effect on nuclear NF-kappaB binding in BAL cells from ALQ-exposed rats. In conclusion, treatment of the quartz surface with aluminium lactate reduced the reactivity of the particles both in terms of hydroxyl radical generation and in terms of the induction of molecular signaling events leading to inflammation.

Genotype and phenotype in susceptibility to coal workers' pneumoconiosis. the use of cytokines in perspective

The readily available technique of screening for gene polymorphisms could be used to explain inter-individual variability in a classic occupational interstitial lung disease, such as coal workers' pneumoconiosis (CWP). The objective of this paper is to describe candidate genes selected from the wide pool of cytokines and growth factors, and to discuss the applications and pitfalls when using them as biomarkers for susceptibility to CWP. The selection of candidate genes is mainly based on observed phenotypic changes in bronchoalveolar lavage (BAL) fluid or BAL cells of patients with CWP, or on animal experiments that use quartz as the fibrogenic agent. This paper also reviews the studies that have been performed to validate tumour necrosis factor genotype and phenotype with respect to CWP. Finally, it is proposed that a multiple marker approach to susceptibility to CWP should be used. This involves the measurement of two cytokines (tumour necrosis factor and transforming growth factor-beta) to improve denomination of high- and low-risk groups.

Interstitial lung disease induced by exogenous agents: factors governing susceptibility

The purpose of this review is to describe the present state of knowledge regarding host susceptibility factors that may determine the occurrence, development and severity of interstitial lung disease (ILD) caused by exogenous agents. First, host susceptibility may pertain to differences in the delivery and/or persistence of the noxious agent in the lung. The deposition and clearance of inhaled particles or fibres may vary depending on innate anatomical or physiological characteristics, and on acquired changes, such as nasal disease or smoking-induced alterations. Genetically- or environmentally-induced interindividual differences in the expression of pulmonary biotransformation enzymes may form the basis for, or contribute to the risk of, drug-induced interstitial lung disease. Secondly, there are genetic and acquired variations in various enzymatic and nonenzymatic defence systems that protect cells and tissues against oxidative stress, which is often involved in the pathogenesis of interstitial lung disease caused by particles, fibres, metals, organic agents and drugs. Thirdly, the occurrence of immunological sensitization is dependent on both genetic and environmental factors. This has been demonstrated in chronic beryllium lung disease and in hypersensitivity pneumonitis. Fourthly, the propensity of individuals to develop particular types of inflammation, such as granulomas, is probably under genetic control. The regulation and resolution of inflammation and fibrogenesis caused by dust particles are also partly determined by genetic factors, involving cytokine networks and growth factors. In conclusion, although the issue of genetics pervades the entire discussion of host susceptibility, genes are not the only determinants of health and disease. Environmental factors may be equally important in shaping host susceptibility. Therefore, research must be focused on both the genetic bases and the environmental determinants of interstitial lung disease, in order to provide mechanism-based prevention strategies, early detection of, and improved therapy for these conditions.

Ambient particulate matter induces relaxation of rat aortic rings in vitro

Epidemiological studies have shown an association between ambient levels of particulate matter (PM) and increased mortality from cardiovascular diseases. However, the underlying mechanisms are still not clear. We hypothesised that PM, when translocated after inhalation, could affect vascular smooth muscle function. Therefore, total suspended particulate matter (TSP) was sampled and investigated for its ability to affect aortic muscle contraction. Both TSP and TSP supernatant (TSP-sup) induced a concentration-dependent relaxation of phenylephrine (PE)-precontracted aortic rings. Relaxation induced by 100 microg/ml TSP was 51.5 +/- 3.1% of total contraction. At 60 and 100 microg/ml, relaxation induced by TSP was significantly higher compared to TSP-sup. Ultrafine TiO2, used as a model to investigate the role of ultrafine particles, did not show an effect. Soluble iron, present in TSP suspensions, seems not to be involved, as chelating with deferoxamine did not affect TSP-induced relaxation. However, TSP effects were inhibited by Trolox, suggesting a role of oxidants. Nudation of aortic rings showed that effects of TSP were only partly endothelium-dependent, while preincubation with L-NAME increased TSP-induced relaxation. From these data, we conclude that both the particle core and soluble components of TSP can affect the smooth muscle function, leading to changes in the vascular contractile response.

Clara-cell hyperplasia after quartz and coal-dust instillation in rat lung

Bronchiolo-alveolar hyperplasia of type II cells in rat lungs after particle exposure is a well-known preneoplastic lesion. The Clara cell, stem cell of the bronchiolar epithelium and the main carrier of cytochrome P-450 isoenzyme system in the lung, has barely been evaluated with regard to this effect. The aim of this study was to examine Clara-cell hyperplasia after particle exposure and to characterize cell proliferation and its normal function. Female Wistar rats were intratracheally instilled with coal dust samples of variable quartz content, quartz (DQ12), titanium dioxide, or saline solution containing 0.5% Tween 80. After 126-129 wk, all coal mine dust- and quartz-exposed animals developed Clara-cell hyperplasia: up to 0.48% of the total lung area, which was significantly increased compared to titanium dioxide (p <.05) and control (p <.03) animals. Proliferation and hyperplasia of bronchiolar Clara cells by coal dusts was independent of their quartz content. The lack of proliferating cell nuclear antigen staining in most of the hyperplastic Clara cells suggests that following damage of alveolar epithelial cells, Clara cells migrate in and remodulate the alveolar epithelium. After the migration they keep their function in the xenobiotic metabolism, as shown by expansion of CYP2E1 active Clara cells. The minor development of Clara-cell hyperplasia in titanium dioxide-treated rats indicates that this is not a general particle effect, and is possibly due to its lower toxicity to epithelial cells.

Psychological job demands as a risk factor for common cold in a Dutch working population

OBJECTIVE

We investigated the effect of Psychological Job Demands (PJD) on the occurrence of the clinical symptoms of common cold.

METHODS

Subjects, participating in a large prospective cohort study on psychological determinants of fatigue at work, were asked to fill in a questionnaire on the occurrence of common cold during the previous four months. High PJD were considered as a potential risk factor. Other factors such as age, gender, and having young children were considered as potential confounders.

RESULTS

In logistic regression analysis, the adjusted odds ratio (OR) for having a recent cold in subjects reporting high PJD vs. those reporting low PJD was 1.20 (95% confidence interval (CI), 1.08-1.33). A higher risk emerged among those with young children (OR, 1.70; 95% CI, 1.47-1.96), those having a history of asthma (OR, 1.69; 95% CI, 1.28-2.22), or being under the age of 40 (OR, 1.28; 95% CI, 1.14-1.43) and among smokers (OR, 1.23; 95% CI, 1.09-1.38).

CONCLUSION

The results support an association between PJD and common cold. In spite of the almost inevitable shortcoming of a large cohort study using questionnaires, this study gave us the opportunity to study the relationship between common cold and work-related factors in a nonexperimental setting with participants observed in a natural environment with all the normal everyday hassles.

Nasal inflammatory and respiratory parameters in human volunteers during and after repeated exposure to chlorine

The objectives of this study were: 1) to determine if chlorine exposure at low levels induces nasal effects in humans as it does in rodents; and 2) to establish a possible occurrence of respiratory effects in human volunteers exposed to chlorine vapour at concentrations of 0, 0.1, 0.3 and 0.5 ppm. The study was conducted in a double-blind fashion in 8 male volunteers using a repeated measures design, with randomly selected exposure sequences. Subjects were exposed for 6 h x day(-1) on 3 consecutive days to each of the 4 exposure conditions. In nasal lavage, interleukin-8 (IL-8), albumin, total cell number, and percentages of neutrophils, lymphocytes, monocytes, eosinophils, and epithelial cells were determined. The lung function parameters that were analysed included forced vital capacity (FVC), forced expiratory volume in first second (FEV1), FEV1/FVC ratio, and maximal mid expiratory flow (MMEF). Data analysis was limited to 7 subjects since one volunteer decided to stop participating for reasons not related to the study. Nasal lavage measurements did not support an inflammatory response or irritant effects on the nasal epithelium. For FVC, FEV1, and FEV1/FVC, no significant differences were found. MMEF was significantly different between the 0 and 0.5 ppm exposure, but this was attributed to an unexplained shift in baseline values during control (0 ppm) exposure. The present data does not support an inflammatory effect in the nose nor shows changes in respiratory function at repeated exposure up to 0.5 ppm. This discrepancy with previous data in rodents can be attributed at least in part to differences in respiratory tract airflow characteristics.

In vitro effects of coal fly ashes: hydroxyl radical generation, iron release, and DNA damage and toxicity in rat lung epithelial cells

Oxygen radical generation due to surface radicals, inflammation, and iron release has been suggested as the mechanism of adverse effects of quartz, such as emphysema, fibrosis, and carcinogenic effects. Therefore, we measured iron release, acellular generation of hydroxyl radicals, and oxidative DNA damage and cytotoxicity in rat lung epithelial (RLE) cells by different coal fly ashes (CFA) that contain both quartz and iron. Seven samples of CFA with different particle size and quartz content (up to 14.1%) were tested along with silica (alpha-quartz), ground coal, and coal mine dust (respirable) as positive control particles, and fine TiO(2) (anatase) as a negative control. Five test samples were pulverized fuel ashes (PFA), two samples were coal gasification (SCG) ashes (quartz content <0.1%), and one sample was a ground coal. No marked differences between SCG and PFA fly ashes were observed, and toxicity did not correlate with physicochemical characteristics or effect parameters. Stable surface radicals were only detected in the reference particles silica and coal mine dust, but not in CFA. On the other hand, hydroxyl radical generation by all fly ashes was observed in the presence of hydrogen peroxide, which was positively correlated with iron mobilization and inhibited by deferoxamine, but not correlated with iron or quartz content. Also a relationship between acellular hydroxyl radical generation and oxidative DNA damage in RLE cells by CFA was observed. Differences in hydroxyl radical generation and oxidative damage by the CFA were not related to iron and quartz content, but the respirable ashes (MAT023, 38, and 41) showed a very extensive level of hydroxyl radical generation in comparison to nonrespirable fly ashes and respirable references. This radical generation was clearly related to the iron mobilization from these particles. In conclusion, the mechanisms by which CFA and the positive references (silica, coal mine dust) affect rat lung epithelial cells seem to be different, and the data suggest that quartz in CFA does not act the same as quartz in silica or coal mine dust. On the other hand, the results indicate an important role for size and iron release in generation and subsequent effects of reactive oxygen species caused by CFA.

Priming of cytokine release and increased levels of bactericidal permeability-increasing protein in the blood of animal facility workers

OBJECTIVE

To investigate cellular immune responses in laboratory animal workers who are exposed to high levels of animal allergens but also to other biologically active substances containing lipopolysaccharides (LPS), i.e., endotoxins.

METHODS

A survey among 20 animal facility workers and 20 matched (gender, smoking) controls was conducted using exposure measurements (endotoxin, colony-forming units of bacteria and fungi) and a questionnaire on respiratory symptoms. Blood samples were taken to determine the ex vivo whole-blood release of tumor necrosis factor-alpha (TNF) and interleukin-8 (IL-8) as well as plasma levels of LPS-binding protein (LBP), bactericidal permeability-increasing protein (BPI), the 75-kDa soluble TNF receptor (sTNFR75), and total/specific IgE.

RESULTS

Although exposure to endotoxin was low (range 0.05-2.8 ng/m(3)), a significant (P < 0.05) increase in plasma BPI (4-fold) and srTNF75 (1.2-fold) was found, suggesting a response to inhalation of LPS. Also, the capacity of blood leukocytes to release TNF and IL-8 in response to ex vivo exposure to workplace dust was increased. Data were not confounded by specific allergies, levels of IgE, smoking, or respiratory symptoms.

CONCLUSIONS

A profound effect on the cellular immune response was seen in animal workers with low endotoxin exposure and a high antigenic load. It remains to be determined which other biologically active substance(s) are involved in this effect.

Neutrophils cause oxidative DNA damage in alveolar epithelial cells

Inflammation has been recognized as a contributing factor in the pathogenesis of some cancers. In the lung, inflammation is characterized by an influx of polymorphonuclear leukocytes (PMN) that release a variety of reactive oxygen species (ROS). The aim of the present study was to investigate the direct effect of PMN on oxidative DNA damage in lung target cells. Therefore, rat alveolar epithelial cells (RLE) were coincubated with PMN or hydrogen peroxide. Known to be correlated with the incidence of cancer, 7-hydro-8-oxo-2'deoxyguanosine (8-oxodG) was used as an effect marker for oxidative damage. Viability of the RLE, when coincubated with PMN, decreased to 43%, dependent on the ratio between PMN and RLE. After washing off PMN, 8-oxodG levels were significantly increased in RLE, but the highest levels were observed in the washed off PMN fraction. In addition, to avoid washing off procedures, immunohistochemical analysis was used to measure the 8-oxodG levels specifically in the RLE and similar results were obtained. In addition, inhibitor experiments showed that antioxidants ameliorated oxidative DNA damage. Our data provide evidence that ROS released by PMN as well as H2O2, cause oxidative DNA damage in epithelial cells.

Changes in levels of catalase and glutathione in erythrocytes of patients with stable asthma, treated with beclomethasone dipropionate

In asthmatic patients, antioxidant defence is decreased. Although inhaled corticosteroids decrease asthmatic inflammation and modulate reactive oxygen species (ROS) generation, little is known of their effect on cellular antioxidant levels. The aim of this study was to evaluate the effect of inhaled beclomethasone dipropionate (BDP; 1,000 microg x day(-1)) on erythrocyte antioxidant levels in stable asthmatic patients. Forty patients with stable, mild asthma were treated in a double-blind, placebo-controlled, parallel-group study with BDP 250 microg, two puffs b.i.d. for 6 weeks. At entry and every 2 weeks during treatment, erythrocyte antioxidant levels, haematological parameters, pulmonary function tests and asthma symptoms were determined. The results show that during treatment with BDP, erythrocyte catalase levels increased (at entry (mean +/-SEM) 41+/-4, after 6 weeks 54+/-4 micromol H2O2 x min(-1) x g haemoglobin (Hb)(-1), p = 0.05 in comparison with placebo). Erythrocyte total glutathione levels significantly decreased after 6 weeks treatment with BDP (from 7.0+/-0.4 to 6.6+/-0.3 micromol x g Hb(-1) (p = 0.04)). In the BDP-treated patients, blood eosinophil counts were higher in patients who responded with an increase in erythrocyte catalase levels during BDP treatment, as compared to those not responding ((mean +/-SEM) 340+/-39 and 153+/-52x10(6) cells x L(-1), respectively, p = 0.05). The present study shows that treatment with inhaled bedomethasone dipropionate results in changes in antioxidant levels in erythrocytes of patients with stable, mild asthma.

Mechanisms and mediators in coal dust induced toxicity: a review

Chronic inhalation of coal dust can cause several lung disorders, including simple coal workers pneumoconiosis (CWP), progressive massive fibrosis (PMF), chronic bronchitis, lung function loss, and emphysema. This review focuses on the cellular actions and interactions of key inflammatory cells and target cells in coal dust toxicity and related lung disorders, i.e. macrophages and neutrophils, epithelial cells, and fibroblasts. Factors released from or affecting these cells are outlined in separate sections, i.e. (1) reactive oxygen species (ROS) and related antioxidant protection mechanisms, and (2) cytokines, growth factors and related proteins. Furthermore, (3) components of the extracellular matrix (ECM), including the modifying role of ROS, cytokines, proteases and antiproteases are discussed in relation to tissue damage and remodelling in the respiratory tract. It is recognised that inhaled coal dust particles are important non-cellular and cellular sources of ROS in the lung, and may be significantly involved in the damage of lung target cells as well as important macromolecules including alpha-1-antitrypsin and DNA. In vitro and in vivo studies with coal dusts showed the up-regulation of important leukocyte recruiting factors, e.g. Leukotriene-B4 (LTB4), Platelet Derived Growth Factor (PDGF), Monocyte Chemotactic Protein-1 (MCP-1), and Tumor Necrosis Factor-alpha (TNF alpha), as well as the neutrophil adhesion factor Intercellular Adhesion Molecule-1 (ICAM-1). Coal dust particles are also known to stimulate the (macrophage) production of various factors with potential capacity to modulate lung cells and/or extracellular matrix, including O2-., H2O2, and NO, fibroblast chemoattractants (e.g. Transforming Growth Factor-beta (TGF beta), PDGF, and fibronectin) and a number of factors that have been shown to stimulate and/or inhibit fibroblast growth or collagen production such as (TNF alpha, TGF beta, PDGF, Insulin Like Growth Factor, and Prostaglandin-E2). Further studies are needed to clarify the in vivo kinetics and relative impact of these factors.

Polymorphisms in the promoter of the tumor necrosis factor-alpha gene in coal miners

Tumor necrosis factor-alpha (TNF) is recognized as a central mediator of mineral dust-induced lung fibrosis, and genetic polymorphisms of the TNF promoter have been reported to influence levels of TNF production. To assess whether polymorphisms within the TNF promoter gene are associated with susceptibility to coal workers' pneumoconiosis (CWP), the DNA of 78 coal miners was typed for G-to-A transitions at positions -238 and -308. Our results show that frequency of A-308 genotype (T2) is significantly overpresented in coal miners with CWP (50%), as compared with miners without CWP (25%) and controls (29%). After correction for cumulative dust exposure and smoking, the A-308 transition genotype is still associated with the presence of CWP (OR = 3.0, 95% CI = 1.0-9.0). Both A-238 and A-308 transition genotypes were related to TNF release from endotoxin-stimulated blood monocytes; only the A-238 transition and not the A-308 transition was associated to coal dust-induced TNF release. In summary, this study shows that the A-308 transition is related to CWP, but this relation is not paralleled by a different TNF release in this genotype. A larger number of patients coupled to frequent TNF release are required to evaluate genotype screening to estimate individual health risks for effects of coal mine dust exposure.

The quartz hazard: a variable entity

An IARC Working Group recently classified crystalline silica (quartz) into IARC's Group 1, i.e. a carcinogen. This classification is based on evidence of carcinogenicity in experimental animals and in humans. However, the evaluation stated that in making the overall evaluation, the Working Group noted that carcinogenicity to humans was not detected in all industrial circumstances studied and that carcinogenicity may be dependent on inherent characteristics of the crystalline silica or on external factors affecting its biological activity. The present review seeks to put the apparently conflicting findings of cancer incidence in quartz-exposed industries into a unifying thesis, based on mechanistic studies. These mechanistic studies have enabled the events leading from deposition of quartz to silicosis and cancer to be partially elucidated and have demonstrated that the biological effects of quartz can be understood in terms of surface reactivity. We particularly emphasise the ability of quartz to generate free radicals and cause oxidative stress and the fact that this could be modified by a range of substances that affect the quartz surface; some of these modifying substances could originate from other minerals. We therefore propose that the hazard posed by quartz is not a constant entity, but one that may vary dramatically depending on the origin of the silica sample or its contact with other chemicals/minerals within its complex constitution. The mechanistic data described here could assist in the interpretation of epidemiological studies and pose further hypotheses that could be tested in order to help resolve the quartz carcinogenesis anomaly. The data suggest that quartz cannot be death with as a single hazard entity, as is the case with most other chemicals.

The effect of hyperoxia on embryonic and organ mass in the developing chick embryo

It is known that hyperoxia stimulates growth late in incubation when the chick embryo outgrows the O2 diffusion capacity. We wondered whether hyperoxia could have an effect in the early period prior to the stage where metabolism exceeds the oxygen diffusion capacity of the eggshell. For this we studied four groups of chicken eggs: control group (CG; n = 100) and three test groups (TGs) exposed during 48 h to 60% O2 on days 10, 14, and 18. In the CG, embryonic and organ mass (brain, heart, lungs, liver and intestine) were measured from day 10 until day 21 of incubation. In the TGs embryonic and organ mass were obtained from 24 h after the start of hyperoxia exposure until the end of incubation. In all TGs the most striking growth rate acceleration was observed in the liver and intestine, maximum growth rate accelerations were respectively, 19 and 42% in TG1, 43 and 173% in TG2 and 39% and 84 in TG3. In contrast, the brain was little affected by the hyperoxia exposure, the maximum growth rate acceleration was 14% in TG2. The results suggest that also in the middle of the incubation period O2 availability can be a limiting factor for growth, before metabolism exceeds the oxygen diffusion capacity of the eggshell.

Induction of antioxidant enzyme activity by hyperoxia (60 % O2) in the developing chick embryo

1. At premature birth, man and animals are exposed to relatively high oxygen levels, compared with intra-uterine conditions, at a time when their antioxidant enzyme (AOE) system is still immature. Using the chick embryo as a study model, we investigated changes in the AOE system in response to hyperoxia applied at different time points during the incubation period. Relations between hyperoxia and AOE activity were studied in selected organs (brain, heart, liver, intestine and lungs) of developing chick embryos (during the second half of the incubation period). 2. Incubated White Leghorn eggs were divided into four groups: control (n = 100) and three test groups exposed for 48 h to 60 % O2 on day 10 (test group 1, n = 80), day 14 (test group 2, n = 60) and day 18 (test group 3, n = 30). Superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) enzyme activities were measured in homogenates of the brain, heart, liver, intestine and lungs. 3. Exposure to hyperoxia at different time points during incubation resulted in a 2- to 10-fold increase in SOD activity in all organs except the brain. Catalase and GPx enzyme activities were only induced in test group 1, 48 h after initiation of hyperoxia. 4. In the developing chick embryo, hyperoxia can produce a temporary induction of AOE activity, which is dependent on the AOE, organ, incubation time and time point of exposure.

Differences in aromatic-DNA adduct levels between alveolar macrophages and subpopulations of white blood cells from smokers

The 32P-post-labelling assay for DNA adduct quantification gives the opportunity to examine endogenous exposure to DNA reactive compounds. Most human biomonitoring studies applied white blood cells (WBC) or cells obtained by broncho-alveolar lavages (BAL) as source of DNA, but still it is not clear what cell type represents the most reliable indicator for exposure to cigarette smoke-associated genotoxins. At first, we examined DNA adduct levels by means of nuclease P1 (NP1) enriched 32P-post-labelling in separated WBC subpopulations after in vitro incubations for 18 h with 10 microM benzo[a]pyrene (B[a]P). DNA adduct levels were highest in monocytes (10.7 +/- 2.9 adducts/10(8) nucleotides, n = 8), followed by lymphocytes (5.9 +/- 1.7, n = 8), and granulocytes (0.5 +/- 0.2, n = 8). Secondly, aromatic-DNA adduct levels were determined in BAL cells and WBC-subsets from (non-)smoking volunteers. In smoking individuals, adduct levels were in the ranking order: BAL cells (3.7 +/- 1.0, n = 5) > monocytes (2.0 +/- 0.5, n = 8) > or = lymphocytes (1.6 +/- 0.4, n = 8) > granulocytes (0.8 +/- 0.2, n = 8) by NP1-enrichment and monocytes (9.0 +/- 3.2, n = 5) > or = lymphocytes (8.0 +/- 2.1, n = 6) > granulocytes (2.1 +/- 0.3, n = 7) by butanol-enriched 32P-post-labelling. Aromatic-DNA adduct levels were significantly higher in WBC-subsets of smokers as compared with non-smokers, except for DNA adducts in granulocytes using butanol enrichment. Thirdly, dose-response relationships were investigated in mononuclear white blood cells (MNC, i.e. monocytes plus lymphocytes) and BAL-cells of a larger group of smoking individuals (n = 78). Adduct levels in MNC were related to daily exposure to cigarette-tar (r = 0.31, P < 0.01). Adduct levels in BAL cells seemed to be correlated with pack-years, but after correction for age this relationship was lost. Butanol extraction resulted in 5-6-fold higher DNA adduct levels in MNC, whereas butanol extraction of BAL-DNA of the same individuals yielded only 2-fold higher adduct levels. The two enrichment procedures of 32P-post-labelling were correlated in BAL cells (r = 0.86, P < 0.001, n = 12). We conclude that particularly MNC are good surrogates for the detection of smoking-related DNA adducts.

Longitudinal changes in inflammatory markers in nasal lavage of cotton workers. Relation to endotoxin exposure and lung function changes

OBJECTIVES

The aim of this study was to evaluate time-related changes in inflammatory markers in nasal lavage (NAL) in relation to endotoxin exposure and lung function changes.

METHODS

Endotoxin in cotton dust is well known to elicit proinflammatory mediators involved in acute or chronic respiratory inflammation due to cotton dust. We applied nasal lavage as well as lung function and exposure measurements in a small group (n = 11) of cotton workers during 6 weeks of observation (after 2 weeks free of exposure). Several inflammatory markers in NAL, such as interleukin 8 (IL-8), IL-6, and down-stream mediators, including soluble tumor necrosis factor receptor 75 (sTNF-R75) and soluble intercellular adhesion molecule 1 (ICAM-1), cell counts, marker of epithelial response (uric acid), and marker of plasma exudation (albumin) were measured.

RESULTS

At the exposure levels examined in this study [cotton dust, geometric mean (GM) = 1.10 mg/m3; endotoxin, GM = 2,869 EU/m3], several inflammatory markers in NAL such as IL-8, sTNF-R75, and albumin tended to increase through the measurement period with increasing airborne endotoxin concentration (in six workers who had paired measurements in weeks 1 and 6). Although no statistical significance was reached, airborne endotoxin exposure and all inflammatory markers in NAL were relatively higher in cotton workers with a 6-week lung function decrease.

CONCLUSION

The data suggest that inflammatory markers in NAL are associated with repeated airborne endotoxin exposure.

Blood interleukin-8 production is increased in chemical workers with bronchitic symptoms

Chemical exposure may result in respiratory conditions such as chronic bronchitis, bronchial hyperresponsiveness, and chronic airway obstruction. Clinical studies have shown that during the course of disease, cytokine networks are changed. In order to study the relationship between blood cytokines and respiratory symptoms in an occupational setting, we investigated 106 chemical workers during a routine yearly medical examination in 1995. Lung function was measured with flow volume curves and impedance using the forced oscillation technique (FOT). Smoking-status and respiratory symptoms were determined by questionnaires. Cytokines were selected on biological plausibility and measured both in a whole blood assay (TNF-alpha, IL-8) and in serum (IL-4, IL-5, IL-6, IFN-gamma). The hypothesis is that blood levels of TNF-alpha and IL-8 are increased in bronchitis, while serum levels of IL4, IL-5 are increased and IFN-gamma is decreased in asthmatic workers. Spontaneous IL-8 release was significantly higher in workers with bronchitis (P < 0.05) or chronic bronchitis (P < 0.01) compared to workers without those respiratory symptoms, also after correction for age, pack-years, and blood lymphocyte numbers or compared to a matched control group. No correlation was present between specific cytokines and asthmatic symptoms. These data suggest that blood IL-8 may be considered as a useful marker for bronchitis.

Toxicity and occupational health hazards of coal fly ash (CFA). A review of data and comparison to coal mine dust

Coal fly ashes (CFA) are complex particles of a variable composition, which is mainly dependent on the combustion process, the source of coal and the precipitation technique. Toxic constituents in these particles are considered to be metals, polycyclic aromatic hydrocarbons and silica. The purpose of this review was to study the in vitro and in vivo data on coal fly ash and relate the studied endpoints to the role of (crystalline) silica, considering its recent classification as a human carcinogen. For most of the effects coal mine dust was chosen as a reference, since it contains up to 10% of crystalline silica (alpha-quartz) and is well studied both in vivo and in vitro. Most studies on fly ash toxicity were not designed to elucidate the effect of its silica-content nor did they include coal mine dust as a reference. Taking this into account, both in vitro and in vivo experimental studies show lower toxicity, inflammatory potential and fibrogenicity of CFA compared to silica and coal mine dust. Although in vitro and in vivo studies suggest genotoxic effects of fly ash, the data are limited and do not clarify the role of silica. Epidemiological studies in fly ash exposed working populations have found no evidence for effects commonly seen in coal workers (pneumoconiosis, emphysema) with the exception of airway obstruction at high exposure. In conclusion, the available data suggest that the hazard of coal fly ash is not to be assessed by merely adding the hazards of individual components. A closer investigation of 'matrix' effects on silica's toxicity in general seems an obligatory step in future risk assessment on fly ashes and other particles that incorporate silica as a component.

Neutrophils amplify the formation of DNA adducts by benzo[a]pyrene in lung target cells

Inflammatory cells and their reactive oxygen metabolites can cause mutagenic effects in lung cells. The purpose of this study was to investigate the ability of activated neutrophils to modulate DNA binding of benzo[a]pyrene (B[a]P), a known carcinogen, in lung target cells. Equivalent numbers of rat lung epithelial cells (RLE-6TN cell line) and freshly isolated human blood neutrophils (PMN) were coincubated in vitro for 2 hr after addition of benzo[a]pyrene (0.5 microM) or two of its trans-diol metabolites, with or without stimulation with phorbol myristate acetate (PMA). DNA adducts of B[a]P-metabolites were determined in target cells using 32P-postlabeling; oxidative DNA damage (7-hydro-8-oxo-2'-deoxyguanosine [8-oxodG]) was evaluated by high performance liquid chromatography with electrochemical detection. Increased DNA adducts were observed in lung cells coincubated with polymorphonuclear leukocytes (PMN). Activation of PMN with PMA, or addition of more activated PMN in relation to the number of lung cells, further increased the number of adducts, the latter in a dose-response manner. Incubation with B[a]P-4,5-diol did not result in any adduct formation, while B[a]P-7,8-diol led to a significant number of adducts. Moreover, PMA-activated PMN strongly enhanced adduct formation by B[a]P-7,8-diol, but not 8-oxodG, in lung cells. The addition of antioxidants to the coincubations significantly reduced the number of adducts. Results suggest that an inflammatory response in the lung may increase the biologically effective dose of polycyclic aromatic hydrocarbons (PAHs), and may be relevant to data interpretation and risk assessment of PAH-containing particulates.

Particles, inflammation and respiratory tract carcinogenesis

Particle-induced carcinogenesis is a non-specific outcome of many different particles. It was the purpose of this study, (i) to comprehensively review some of the mechanisms through which particles and particle-associated carcinogens can cause mutagenic/carcinogenic effects, and (ii) to indicate how this affects risk assessment studies. Data are presented that demonstrate the crucial role of a chronic inflammatory response in mutagenic effects of both silica and carbon black particles on the HPRT gene in lung target cells. The concept of inflammation in particle-induced genotoxicity is put into the context of other mechanisms, such as the release of cytokines and reactive oxygen species. It is concluded that interpretation of rat inhalation studies should certainly include this concept.

A five year follow-up of lung function among chemical workers using flow-volume and impedance measurements

Impedance of the respiratory system, measured using the forced oscillation technique (FOT), has repeatedly been proposed as a tool for occupational health screening. The aim of this study was to compare the outcome of impedance measurements and flow-volume curves, and to study relationships between lung function decline and specific exposures and smoking. Both measurements were applied in 136 chemical workers from seven main production/personnel groups during a 5 year follow-up (1990-1995). The prevalence of airway obstruction (forced expiratory volume in one second (FEV1) < 80% of predicted) at both time-points was about 5% but did not necessarily include the same subjects. The average decline in FEV1 over 5 yrs was 200 mL (predicted decline 160 mL). Although most impedance parameters correlated to flow-volume parameters in both years, a rapid 5 year decline of FEV1 (> 330 mL) was only accompanied by a significant decrease in the reactance at 8 Hz (X8) and an increase in the resonance frequency (f0). Interestingly, decline in FEV1 was significantly dependent on age, years of employment, pack-years, FEV1, and all impedance parameters at the start in 1990 (r = 0.35; p = 0.01). Similarly, the increase in f0 was significantly dependent on age, years of employment, pack-years, f0, FEV1, forced vital capacity (FVC), peak expiratory flow (PEF) and maximal mid-expiratory flow (MMEF) at the start (r = 0.56; p < 0.01). Those with a rapid decline in FEV1, were relatively more represented among acid workers (relative risk (RR) = 2.14), maintenance workers (RR = 2.1) and bulk/transport workers (RR = 1.78), but none of these was significant. Lung function, however, was significantly lower in the bulk/transport workers (n = 14) compared to the rest, based both on flow-volume (FEV1, FVC) and impedance (X8, f0) measurements. Smoking had a significant effect on most flow-volume parameters but only for frequency dependence among the impedance outcomes. It is concluded that alterations in impedance parameters do reflect changes in flow-volume curves induced by age. smoking and occupational exposure. Therefore, these data are a valuable extension to current cross-sectional data.

Cross-shift changes in blood inflammatory markers occur in the absence of airway obstruction in workers exposed to grain dust

Grain dust is well known to cause both acute and chronic respiratory disorders, and endotoxins are considered key components in this. Since endotoxins are known to elicit proinflammatory mediators, we investigated cytokine (tumor necrosis factor [TNF], interleukin-6, interleukin-8) release and a number of proinflammatory and anti-inflammatory proteins (soluble TNF receptors, lipopolysaccharide (LPS) binding protein, bactericidal permeability increasing protein (BPI), C-reactive protein) in plasma of workers exposed to grain dust. In two surveys during 1 week, lung function was measured daily before and after the shift, using flow-volume curves and/or forced oscillation measurements. On Monday and Friday, blood samples (30 mL) were drawn and cytokine release was determined by enzyme-linked immunosorbent assay in supernatant of isolated monocytes or whole blood culture, either unstimulated or on the ex vivo stimulation with 3 ng/mL or 1,000 ng/mL endotoxin. Individual exposures were determined from stationary dust measurements at every workplace combined with personal task analysis during all shifts. In both surveys, no cross-week change in lung function parameters was observed. In the first survey (average exposure: 20.2 mg/m3), monocyte spontaneous TNF release was increased sevenfold cross week (p<0.001) and was significantly related both to individual dust exposure (r=0.62) of that week and the increase in soluble TNF receptor 75 kD (r=0.85). In the second survey, where average exposure was much lower (3.67 mg/m3), impedance parameters indicated a significant improvement of airway function, and cross-week changes in inflammatory markers were minimal. Therefore, we conclude that inflammatory events can be used to monitor adverse respiratory effects of moderate grain dust exposure.

Plasma levels of soluble tumour necrosis factor receptors are increased in coal miners with pneumoconiosis

Among other cytokines, tumour necrosis factor (TNF)-alpha is considered to play a key role in the development of mineral dust related fibrosis. Previously, we showed that ex-vivo release of TNF by peripheral blood monocytes is a marker for progression of coal workers' pneumoconiosis (CWP). Since soluble TNF receptors (sTNF-Rs) are believed to play an important regulatory role in systemic effects of TNF, we measured plasma levels of sTNF-R55 and sTNF-R75 in coal miners with (n = 28) or without (n = 76) CWP and in nonexposed controls (n = 29). sTNF-R75 levels were significantly increased in miners with CWP (2.09 +/- 0.44 ng.mL-1) versus the nonexposed controls (1.86 +/- 0.23 ng.mL-1). Neither sTNF-R55 nor sTNF-R75 were related to exposure, stage of pneumoconiosis, smoking, or (spontaneous or ex-vivo induced) monocyte TNF-release. sTNF-R55 was increased in subjects with medication (especially those using cardiovascular drugs); upon exclusion of these subjects, sTNF-R55 was found also to be significantly increased in CWP. In conclusion, bearing in mind a confounding effect of medication, soluble TNF receptors are elevated in plasma of retired miners with coal workers' pneumoconiosis. These observations further support the important role of TNF-mediated pathways in the pathogenesis of mineral dust related fibrosis.

Epidemiological evaluation of release of monocyte TNF-alpha as an exposure and effect marker in pneumoconiosis: a five year follow up study of coal workers

OBJECTIVES

To determine (a) reproducibility with previous cross sectional findings, and (b) the predictive value of initial release of tumour necrosis factor-alpha (TNF-alpha) towards later progression of coalworkers' pneumoconiosis (CWP).

METHODS

Release of monocyte TNF-alpha after in vitro stimulation with coal mine dust, silica, and endotoxin was measured in 104 retired miners and was related to stage of CWP (chest radiograph) and cumulative exposure. A subgroup of 46 miners was screened by high resolution computed tomography (HRCT). Prospective analysis of TNF-alpha (40 out of 104 miners involved in the previous TNF-alpha study) was done by relating initial TNF-alpha to five year progression of CWP measured by comparison of paired chest radiographs.

RESULTS

As observed previously, dust stimulated release of TNF-alpha was increased in miners, especially in the early stages of pneumoconiosis. Cumulative exposure was related to pneumoconiotic stage but not to release of TNF-alpha. This excluded TNF-alpha as an exposure marker. Initial concentrations (1987) of TNF-alpha were related to later progression of CWP. Miners who showed abnormally high dust stimulated release of TNF-alpha had an increased risk of progression in CWP (relative risk 8.1).

CONCLUSIONS

These results show (a) the significant involvement of TNF-alpha in pneumoconiosis in humans induced by coal dust and (b) that this routine test possibly constitutes a powerful tool to estimate individual prognosis of pneumoconiotic disease, even after the end of occupational exposure.

Oxidant resistance of cadmium-adapted human lung fibroblasts

Metallothionein (MT) is a metal and thiol-rich protein readily induced by cadmium (Cd) exposure. In vitro experiments have demonstrated that MT is able to serve as a scavenger of hydroxyl radicals as well as superoxide anions, albeit to a lesser extent. The role of MT as a mediator in Cd induced oxidant resistance was investigated in a nontransformed human lung fibroblast cell line (IMR-90). Cells were passaged three times either in a Cd-containing medium (8.9 microM CdCl2) or in a medium which lacked Cd. Cellular MT content, as quantitated by a modification of the heme/109Cd binding assay, increased significantly with each passage in Cd. Immunocytochemistry studies revealed that all Cd-pretreated cells contained MT and that MT was localized in both cytoplasmic and nuclear compartments. Immunolabeling was more intense in some cells compared to others. Very slight immunolabeling was observed in physiological control cells, grown in the absence of Cd, and virtually no staining was observed in Cd-adapted or non-adapted cells when primary antibody was omitted. Using the xanthine/xanthine oxidase system as a generating system for active oxygen species, we found that the magnitude of cell injury for Cd-adapted and non-adapted fibroblasts was dependent upon oxidant concentration and duration of oxidant exposure. Cd-adapted fibroblasts, which were characterized by over-expression of MT, were significantly more resistant to injury by active oxygen species and also exhibited a greater ability to scavenge extracellular hydrogen peroxide compared to cells with no previous history of Cd exposure. Experiments with aminotriazole demonstrated that catalase was not a major contributor to the additional hydrogen peroxide scavenging capacity of Cd-adapted cells. The data presented in this report are consistent with involvement of MT in protecting critical cellular targets from reactive oxygen species.

Evaluation of serum type III procollagen peptide as an exposure marker in retired coal workers

Serum type III procollagen peptide (PIIIP), a degradation product of the type III collagen precursor, has been put forward as an exposure marker for mineral dust. We evaluated PIIIP levels as a marker of exposure to and effects of coal dust in retired coal miners (n = 104). To this end: (a) the individual cumulative dust exposure was calculated from job-exposure matrices, and (b) in addition to routine chest radiography (CR) of all miners according to the criteria of the International Labour Organisation (ILO), a subgroup (n = 46) was screened by high-resolution computed tomography (HRCT). Profusion score (CR and HRCT) tended to increase with cumulative dust exposure, even in the absence of CR evidence for pneumoconiosis (i.e. CR < or = 0/1, n = 35). In contrast to our previous findings in active miners, PIIIP levels were not increased in miners as compared with non-dust-exposed controls (n = 29), and no differences were observed between miners without (ILO = 0/0) and miners with coal workers' pneumoconiosis (CWP; ILO > or = 0/1). No trend in PIIIP versus pneumoconiosis stage was present, either by CR or by the more sensitive HRCT score. PIIIP was also unrelated to any lung function parameter (FEV1, FVC, impedance, diffusion capacity). Age, medication, medical history and smoking habits had no significant effect on PIIIP levels. In the miners with CWP (i.e. ILO > 0/0, n = 28) a significant negative correlation was present between PIIIP values and (log) cumulative dust exposure. This decrease in serum PIIIP levels with increasing cumulative exposure may be due to chronic adaptive changes in type III collagen deposition and/or breakdown. Other relations between exposure and PIIIP were not observed. In conclusion, the present findings do not support the use of serum type III procollagen peptide as a marker of exposure to and (early) interstitial or respiratory effects of coal dust.

Induction of c-fos and c-jun proto-oncogenes in target cells of the lung and pleura by carcinogenic fibers

To study mechanisms of cell proliferation by asbestos and nonasbestos fibers, we examined the effects of these agents on the mRNA levels of c-fos and c-jun and ornithine decarboxylase (ODC) in hamster tracheal epithelial (HTE) cells and rat pleural mesothelial (RPM) cells, the progenitor cells of bronchogenic carcinoma and mesothelioma, respectively. In comparison with crocidolite asbestos, increases in c-jun mRNA were less striking in HTE cells after exposure to man-made vitreous fiber-10 (MMVF-10) or refractory ceramic fiber-1 (RCF-1). No c-fos mRNA was detected in HTE cells after exposure to particulates, but exposure of HTE cells to H2O2 caused striking increases in c-fos and c-jun, which preceded increases in ODC mRNA. Increases in ODC mRNA were also observed in HTE cells after exposure to nonasbestos fibers, whereas only crocidolite asbestos caused elevations in ODC mRNA in RPM cells. In RPM cells, crocidolite and chrysotile asbestos caused increases in mRNA levels of both c-fos and c-jun. No increases in proto-oncogene induction were observed using MMVF-10 or RCF-1 at nontoxic concentrations (< or = 5 micrograms/cm2 dish). Moreover, erionite, a fiber extremely potent in the causation of mesothelioma in humans, caused more dramatic elevations in c-fos and c-jun. Nonfibrous particles (riebeckite, polystyrene beads) did not alter proto-oncogene expression in these cell types, suggesting that the fibrous geometry of particulates is critical in the induction of c-fos and c-jun.

Respiratory symptoms and lung function in animal feed workers

In a study among 194 male workers exposed to endotoxin-containing organic dust in animal feed mills, lung function was measured by flow volume curves and impedance measurements and respiratory symptoms were recorded by means of a validated questionnaire. The aims were to detect and localize airway obstruction caused by fodder dust and endotoxin, and to relate respiratory symptoms to both types of lung function measurements. Flow volume and impedance parameters were significantly related to present exposure. All impedance parameters, of the spirometric measures only FEF25, were significantly related to cumulative dust or endotoxin exposure. The changes in impedance parameters were for overall increasing resistance at 8 Hz and decreasing reactance at 8 Hz, reflecting an increase in peripheral airflow obstruction, with increasing exposure. The changes in all lung function parameters were more strongly related to (cumulative) endotoxin exposure than to inspirable dust exposure. All impedance parameters and FEV1 showed a good correlation with complaints of chronic bronchitis and breathlessness. Impedance measurement of the respiratory system proved to be a useful tool for objectively assessing (early) airflow obstruction in workers exposed to inspirable dust and endotoxin and in localizing airflow obstruction.

Respiratory effects and serum type III procollagen in potato sorters exposed to diatomaceous earth

Exposure to diatomaceous earth with low crystalline silica content (< 1%) is rarely reported to cause pneumoconiotic disease, whereas airway obstruction and bronchitis are more frequently reported. We investigated the occurrence of pneumoconiosis and airflow limitation in 172 male workers from 5 potato sorting plants (55 controls, 29 salesmen, 72 currently exposed, and 16 retired exposed) exposed to inorganic dust from former sea terraces (7.7-15.4 mg/m3), high in diatomaceous earth. The presence of fibrosis was evaluated by chest radiographs (exposed only) and serum levels of type III procollagen (P-III-P) were measured as an estimate of fibrogenetic activity. Lung function was assessed by flow volume curves and impedance measurements. A validated questionnaire was used to record respiratory symptoms. No pneumoconiotic abnormalities were demonstrated by chest radiographs. In line with this finding, serum P-III-P levels were not elevated in exposed workers as compared to controls, suggesting no differences in fibrogenetic activity. In fact, serum P-III-P levels decreased significantly (P < 0.03) with increasing cumulative exposure. Flow volume parameters indicated airflow obstruction, dose-related to (cumulative) dust exposure; the annual decline in forced expiratory flow volume (FEV1) was estimated at 10.5 ml/year (P < 0.05). Airway obstruction was confirmed by impedance analysis: In the retired group impedance changes were compatible with airway obstruction extending into the peripheral airways. We conclude that this exposure to quartz during potato sorting does not result in an increased risk for pneumoconiosis, but that (prolonged) surveillance in this group is desirable in order to detect early indications of airflow obstruction.

Biological markers and occupational lung disease: mineral dust-induced respiratory disorders

There is a need for methods to monitor early adverse effects, exposure, and/or susceptibility of individual subjects due to occupational and environmental causes. This paper discusses the experimental origin, value, and validity of several biological indicators, termed biomarkers, that were used to study coal dust-induced respiratory disorders. The findings are presented in a framework to visualize problems and challenges when developing biomarkers. Taking the framework of mineral dust-induced lung disorders as an example, it is demonstrated how carefully designed follow-up studies are a prerequisite to test the validity and use of events often put forward as biomarkers. It is concluded from the data that serum type III procollagen is neither an exposure nor an (early) effect marker, antioxidant enzyme expression is related to the early inflammatory response after mineral dust inhalation, while the evidence is accumulating that tumor necrosis factor-alpha is a susceptibility marker for progression in mineral dust-induced lung fibrosis.

Airflow obstruction and monocyte TNF release in coal workers

Respiratory health of 102 retired coal miners was assessed by chest radiographs, lung function measurements, and questionnaires, and related to tumor necrosis factor-alpha (TNF-alpha) production by blood monocytes upon priming with different stimuli. The objective was to assess a possible relationship between airflow obstruction and TNF-alpha production in retired coal workers. No significant differences in lung function were observed between cases of coal workers' pneumoconiosis (CWP) (n = 27; > %) and references (n = 75; = > %), nor was the effect of cumulative exposure on flow volume or impedance parameters significant. TNF-alpha release upon stimulation of blood monocytes with coal mine dust was significantly increased in cases with International Labour Organisation (ILO) score 0/1 (doubtful cases) compared to references and cases with a higher ILO score. Airflow limitation defined either as a FEV1 < 80% (N = 10; 5 cases of CWP) or as a resonance frequency > 15 Hz accompanied by a negative frequency dependence of resistance (N = 9; 4 cases of CWP) was significantly related to high levels of TNF-alpha release upon stimulation with endotoxin and silica, with silica showing the strongest relation. These data suggest that in this group airflow limitation is associated with an increased expression of inflammatory mediators indifferent of the presence of pneumoconiosis.

Serum procollagen type III peptide in coal workers' pneumoconiosis: a five-year follow-up study

Several studies have suggested the use of serum type III procollagen peptide (PIIIP) as a marker in fibrotic lung disease. To test serum PIIIP as a biomarker for progression of coal workers' pneumoconiosis (CWP), a follow-up study was conducted among 156 coal miners. A five-year progression of simple CWP was determined from paired chest X-ray readings and related to serum PIIIP measured in 1987 (n = 73) and in 1992 (n = 104). Although in eight subjects CWP had progressed, none of these subjects had abnormal levels of serum PIIIP, nor were they different from nonprogressed miners with regard to exposure, age, or smoking habits. The results suggest that the use of serum PIIIP as a biomarker to screen for coal workers' pneumoconiosis is limited.

Oxidant stress responses in human pleural mesothelial cells exposed to asbestos

The generation of oxidants is a proposed mechanism of cell injury by asbestos fibers. To determine whether human pleural mesothelial cells (HMC) respond to asbestos and active oxygen species (AOS) by induction of antioxidant enzymes, cells obtained from pleural effusion were exposed to crocidolite or chrysotile asbestos or xanthine/xanthine oxidase (X/XO), a chemical-generating system of AOS. Gene expression of manganese-containing superoxide dismutase (MnSOD) and heme oxygenase (HO), endogenous enzymes involved in cell defense against oxidant stresses, was then determined. Dosage-dependent increases in steady-state mRNA levels of MnSOD and HO were observed in HMC exposed to asbestos or X/XO. However, increases in gene expression of MnSOD or HO did not occur in HMC after exposure to particulates such as polystyrene beads or riebeckite, the nonfibrous analog of crocidolite asbestos. Comparative experiments with human adult lung fibroblasts (HAL) showed less striking increases in mRNA levels of MnSOD and HO in response to asbestos, but steady-state mRNA levels for HO were increased more than fivefold in response to X/XO. To determine whether increases in mRNA levels of MnSOD were translated into protein, Western blot analyses were performed on HMC and HAL cells exposed to asbestos or X/XO. Slight increases in MnSOD immunoreactive protein were observed in HMC in response to both agents. In contrast, X/XO caused striking elevations in MnSOD protein levels in HAL cells. These results suggest that certain antioxidant enzymes are inducible in HMC after exposure to asbestos and other oxidants.

Increased expression of manganese-containing superoxide dismutase in rat lungs after inhalation of inflammatory and fibrogenic minerals

Steady-state mRNA levels and immunoreactive protein for manganese-containing superoxide dismutase (MnSOD) were assayed in rat lungs after subchronic inhalation of the fibrogenic silicon dioxide, cristobalite, or preparations of titanium dioxide (TiO2) of different inflammatory and fibrogenic potential. Total and differential cell counts recoverable by bronchoalveolar lavage (BAL) were also measured to ascertain whether induction of certain antioxidant enzymes (AOE) correlated with inflammatory responses. Inhalation of cristobalite and ultra-fine TiO2, a particle causing pulmonary inflammation and fibrosis, caused dramatic increases in MnSOD mRNA levels in rat lung which correlated with increases in MnSOD immunoreactive protein. Increases in gene expression of other AOE [catalase, glutathione peroxidase (GPX), copper-zinc containing superoxide dismutase (CuZnSOD)] were less striking and did not correlate precisely with inflammatory potential of minerals. Inflammatory changes in BAL correlated directly with steady-state MnSOD mRNA levels in lung. Inhalation of TiO2-F, a noninflammatory, nonfibrogenic mineral, failed to induce MnSOD or mRNAs for other AOE. Our data suggest that particles causing inflammation and pulmonary fibrosis increase expression of AOE in lung, most notably MnSOD. Thus, elevations of MnSOD mRNA levels in lung or BAL may be predictive of lung disease.

Effects of Aramid, a high strength synthetic fiber, on respiratory cells in vitro

Industry continues to develop synthetic fibers for new technologies and as replacements for asbestos, a toxic and carcinogenic fiber. To determine whether the in vitro effects of the aromatic polyamide fiber, Aramid (Kevlar, Twaron), resembled those induced by asbestos, fibers were surveyed for (1) cytotoxicity as measured by total cell protein, and (2) proliferative capacity as measured by [3H]thymidine incorporation, colony forming efficiency (CFE), and ornithine decarboxylase (ODC) activity in two target cells of mineral dust-induced lung damage, hamster tracheal epithelial (HTE) cells and rat lung (RL90) fibroblasts. Results of cytotoxicity tests indicated that Aramid was as toxic to HTE and RL90 cells as were crocidolite and chrysotile asbestos when expressed on both an equal mass and equal fiber number basis. In HTE cells, Aramid caused a statistically significant increase in [3H]thymidine incorporation and CFE and produced a dose-dependent induction of ODC enzyme activity. Proliferative effects by asbestos or Aramid were not observed in RL90 fibroblasts. Thus, when tested over a respirable size range, Aramid exhibited many of the same effects on epithelial cells in vitro as did asbestos, including increased radiolabeled nucleotide incorporation into DNA and induction of ODC enzyme activity.

Physiologically based toxicokinetic modeling of 1,3-butadiene lung metabolism in mice becomes more important at low doses

This paper describes a physiologically based toxicokinetic model for 1,3-butadiene uptake, distribution, and metabolic clearance in mice. Model parameters for metabolic activity were estimated from the correspondence between computer simulation studies and experimental results as published in the literature. The parameterized model was validated with independent literature data. With the resulting model, the relative importance of lung metabolism as compared to metabolism in the liver increased with decreasing ambient air concentrations. This was due to saturation of metabolism in the alveolar area of the lung, which occurred in the simulations at ambient air concentrations well below current threshold limit values. At higher air concentration, liver metabolism became relatively more important. The tendency toward increased importance of lung metabolism at low doses indicates the necessity of careful extrapolation of in vivo results to low doses. Moreover, this trend may also contribute to species difference in susceptibility to the carcinogenic activity of butadiene.

Cell and tissue responses to oxidative damage

A broad array of oxidative stresses modulates gene expression in a variety of mammalian cells. One goal of this review was to characterize cellular responses to oxidative injury, how these processes are regulated, and the outcome for a particular cell or tissue. Many genes induced in response to specific oxidant stresses have been identified and include transcription factors, replication proteins, proteases, protease inhibitors, proteins affecting cell proliferation and various antioxidants, i.e. heme oxygenase, MT, and MnSOD. The latter enzyme is induced after a number of cytokines and oxidant stresses including hyperoxia and mineral dusts causing inflammation. Moreover, increases in mRNA levels of TNF and IL-1, cytokines inducing MnSOD, are observed after exposure to UV and ionizing radiation. Since increased electron flow could lead to generation of more AOS within mitochondria, increased levels of MnSOD might be necessary to maintain normal functioning of the mitochondria after oxidative stress. Alterations in cell growth are intrinsically related to the pathogenesis of many diseases. Paradoxically, some of the responses of cells to oxidative stress reflect cytotoxicity and cytostasis, whereas others result in increased cell proliferation. For example, induction of gadd genes observed after oxidative stress is related to growth arrest of cells, a response which might enable the cell to repair oxidative damage prior to replication. This phenomenon might prevent fixation of mutations associated with oxidative DNA damage. On the other hand, increased mRNA expression and activity of ODC, observed after exposure of cells to UV or asbestos is associated with increased cell proliferation. In addition, increased mRNA expression of cellular proto-oncogenes observed after exposure to oxidants could also be related to increased DNA synthesis or proliferation. Figure 5 provides a general scheme of cell responses to oxidative stress and possible ramifications. AOS can react with a number of target molecules including proteins, lipids, and DNA. These interactions elicit a number of signals including activation of gene regulatory factors (transcription factors) which in turn activate oxidative stress-responsive genes or regulons. Consequently, a number of proteins are produced with distinctive functions including DNA repair enzymes, antioxidants, proteases inhibitors, cytokines and proteins affecting cell proliferation. These cellular responses to AOS can lead to restoration of normal cellular function and adaptation to oxidative stress, cell death or aberrant proliferation. It is the latter two responses which can lead to a variety of disease states including cancer.(ABSTRACT TRUNCATED AT 400 WORDS)

Decreased glutathione content and glutathione S-transferase activity in red blood cells of coal miners with early stages of pneumoconiosis

Blood samples of miners heavily exposed to coal dust were examined for changes in glutathione S-transferase (GST) activity. Decreased GST activity was found in red blood cells of subjects with early stages of coal workers' pneumoconiosis (International Labour Office classification 0/1-1/2) when compared with control miners. At further progression of coal workers' pneumoconiosis (> or = 2/1), the activity of GST was not different from controls. In the same group with moderate coal workers' pneumoconiosis a decrease in GSH in red blood cells occurred. Decreases in GST activity in early stages of coal workers' pneumoconiosis, as well as the decreases in glutathione peroxidase (GPx) activity and in GSH concentrations reported earlier, may originate from damage caused by reactive oxygen species. These changes might imply an impairment of the detoxification capacity for electrophilic and oxidative compounds during this stage of the disease.