Role of bioavailable iron in coal dust-induced activation of activator protein-1 and nuclear factor of activated T cells: difference between Pennsylvania and Utah coal dusts

Time-/dose- series transcriptome data analysis and traditional Chinese medicine treatment of pneumoconiosis

Pneumoconiosis' pathogenesis is still unclear and specific drugs for its treatment are lacking. Analysis of series transcriptome data often uses a single comparison method, and there are few reports on using such data to predict the treatment of pneumoconiosis with traditional Chinese medicine (TCM). Here, we proposed a new method for analyzing series transcriptomic data, series difference analysis (SDA), and applied it to pneumoconiosis. By comparison with 5 gene sets including existing pneumoconiosis-related genes and gene set functional enrichment analysis, we demonstrated that the new method was not inferior to two existing traditional analysis methods. Furthermore, based on the TCM-drug target interaction network, we predicted the TCM corresponding to the common pneumoconiosis-related genes obtained by multiple methods, and combined them with the high-frequency TCM for its treatment obtained through literature mining to form a new TCM formula for it. After feeding it to pneumoconiosis modeling mice for two months, compared with the untreated group, the coat color, mental state and tissue sections of the mice in the treated group were markedly improved, indicating that the new TCM formula has a certain efficacy. Our study provides new insights into method development for series transcriptomic data analysis and treatment of pneumoconiosis.

The impact of coal mine dust characteristics on pathways to respiratory harm: investigating the pneumoconiotic potency of coals

Exposure to dust from the mining environment has historically resulted in epidemic levels of mortality and morbidity from pneumoconiotic diseases such as silicosis, coal workers' pneumoconiosis (CWP), and asbestosis. Studies have shown that CWP remains a critical issue at collieries across the globe, with some countries facing resurgent patterns of the disease and additional pathologies from long-term exposure. Compliance measures to reduce dust exposure rely primarily on the assumption that all "fine" particles are equally toxic irrespective of source or chemical composition. For several ore types, but more specifically coal, such an assumption is not practical due to the complex and highly variable nature of the material. Additionally, several studies have identified possible mechanisms of pathogenesis from the minerals and deleterious metals in coal. The purpose of this review was to provide a reassessment of the perspectives and strategies used to evaluate the pneumoconiotic potency of coal mine dust. Emphasis is on the physicochemical characteristics of coal mine dust such as mineralogy/mineral chemistry, particle shape, size, specific surface area, and free surface area-all of which have been highlighted as contributing factors to the expression of pro-inflammatory responses in the lung. The review also highlights the potential opportunity for more holistic risk characterisation strategies for coal mine dust, which consider the mineralogical and physicochemical aspects of the dust as variables relevant to the current proposed mechanisms for CWP pathogenesis.

Elucidation of alveolar macrophage cell response to coal dusts: Role of ferroptosis in pathogenesis of coal workers' pneumoconiosis

Causal factors underlying coal workers' pneumoconiosis (CWP) have been variously attributed to the presence of carbon, crystalline silica and reduced iron (Fe) minerals, especially pyrite and Fe/Si-amorphous compounds. The aim of this research was to assess the role of iron in CWP and, more specifically, the cytotoxicity of coal dusts with different elemental composition towards alveolar macrophages (AMs). Survival rate of AMs, alteration in the production of pro-inflammatory cytokine TNF-α, MDA (the lipid peroxidation product) and intracellular GSH were assessed using commercial assay kits. The quantitative interaction between iron and GSH was investigated by developing a numerical model. The presence of various reduced Fe minerals (viz. pyrite and siderite) in coal dusts exhibited a consistently acute adverse impact on the viability of AMs and enhanced the production of TNF-α. The presence of the clinically available Fe chelator deferiprone (DFP) and the cytosolic antioxidant glutathione (GSH) significantly increased the viability of AMs exposed to Fe bearing coal dusts, suggesting coal dusts containing reduced Fe minerals were likely contributors to the initial stages of AM cytotoxicity via a ferroptosis related pathway. Chemical kinetic modeling indicated that these results may be attributed to an enhanced consumption of GSH as a result of Fe redox cycling. Fe^IIGSH and GS^• produced from the interaction between ferric Fe and GSH facilitated the production of O₂^•- which further oxidized GSH via a direct reaction between GSH and GS^• or GSO^•. These results suggest that coal dusts containing reduced Fe minerals and Fe compounds may elevate acute inflammation levels in AMs, indicating that crystalline silica may not be the only hazard of concern in mining environments.

Frequency of Pulmonary Anthracosis and its Related Factors in Autopsy Specimens in Guilan, Iran, in 2019

Background

Anthracosis is caused by several factors and is a risk factor for cancer and tuberculosis. This study investigated the prevalence of anthracosis and the associated factors in autopsy specimens from the Guilan Office of the Iranian Legal Medicine Organization.

Materials and Methods

This retrospective study examined the medical records of autopsy specimens (>18 years) in the Guilan Office of the Iranian Legal Medicine Organization in 2019 for pulmonary anthracosis. Data were extracted from the autopsy findings, and demographic characteristics, occupational information, tuberculosis or pulmonary cancer history, and anthracosis were recorded in a checklist. SPSS version 16 was used to analyze the collected data.

Results

The study included 190 autopsy specimens with a 32.1% anthracosis prevalence. Forty-five (23.7%) subjects had anthracofibrosis. Individuals with agricultural carriers or who worked in tobacco fields had the highest prevalence of anthracosis. The frequency of pulmonary cancer and tuberculosis was significantly higher in the specimens with anthracosis (anthracosis group) than in the non-anthracosis group (P<0.05). The use of traditional cooking and heating methods, as well as exposure to carbon and smoke in the workplace, were significantly higher in the anthracosis group than in the non-anthracosis group (P<0.05).

Conclusion

The results of the current study revealed that occupational exposure, tuberculosis, pulmonary cancer, and traditional indoor cooking and heating methods were all associated with anthracosis.

Impact of reactive iron in coal mine dust on oxidant generation and epithelial lung cell viability

Coal workers' pneumoconiosis (CWP) is a preventable occupational lung disease caused by the chronic inhalation of coal mine dust. The inhalation of coal mine dusts can result in the development of a range of lung diseases termed coal mine dust lung diseases, which is not limited to CWP and includes silicosis, bronchitis, emphysema and cancer. For decades, the presence of elemental Fe, C and Si has been proposed to be the causal factors underlying CWP. The recent resurgence of CWP globally with examination of cases in the United States suggesting a potential but inconclusive role of Fe(II)-sulfide minerals. To obtain a better understanding of Australian coals, the existence and potential adverse impacts of iron minerals were examined using 24 representative Australian coal samples. The results of this work revealed that reduced iron minerals were widely distributed within samples obtained from Australian coal mines with pyrite and siderite being particularly abundant. Compared with carbon and crystalline silica, the presence of these specific iron minerals were negatively correlated to the viability of both alveolar macrophages (NR8383) and human lung epithelial cells (A549) (R² = 0.689) under scenarios reflecting biologically-relevant inflammatory response conditions. Further analysis using Welch's unpaired t-test indicated that the presence of reduced iron minerals statistically enhanced acellular oxidant production (90% CI [0.74 to 2.55]) and inflammatory response (90% CI [0.15 to 36.96]). Compared with Fe(II)-hydroxide, Fe(II)- and Fe(III)-(phyllo)silicate and Fe(II)-sulfate mineralogies, pyrite and siderite bearing dusts are likely to have greater adverse impacts on epithelial lung cells under inflammatory response conditions in view of both their iron content and reactivity.

Anti-Inflammatory and Anti-Remodelling Potential of Ethanol Extract Rhodomyrtus Tomentosa in Combination of Asthma and Coal Dust Models

BACKGROUND

Combination of asthma and coal dust is a chronic and recurring airway disease related to inflammation cell activation. The Rhodomyrtus tomentosa flowering plants native to South Kalimantan exhibit a broad therapeutic potential, like anti-inflammatory and anti-remodelling properties. This study aims to analyze the effect of ethanol extract of R. tomentosa leaves (EERTL) nebulizer on the number of inflammatory cells and histomorphometry of lung tissue in a mice-like model of a combination of asthma and coal dust.

METHODS

The 24 BALB/c mice were divided into four treatment groups (n= 6 per group), were sensitized with normal saline (K), OVA + coal dust (P1), OVA + coal dust + salbutamol (P2), and OVA + coal dust + EERTL (P3). Eosinophil cells, neutrophils, lymphocytes, epithelial thickness, smooth muscle, fibrosis subepithelial bronchioles, and the number of goblet cells as indicators of anti-inflammatory and anti-remodelling airways.

RESULTS

The number of eosinophils, neutrophils, and lymphocytes cells are given salbutamol or EERTL was significantly lower than the OVA-sensitized and coal dust exposure group only. There are meaningful differences in the average thickness of the epithelium, smooth muscle, and subepithelial fibrosis of bronchiolus. The histopathology picture of goblet cells showed an increase in the number and size (hyperplasia) in OVA-sensitized and coal dust exposure compared to another group.

CONCLUSION

It was concluded that the EERTL nebulizer could reduce inflammatory cells and remodelling process from bronchoalveolar lavage in the mice combination of asthma and coal dust models.

Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals

This study evaluates geochemical and oxidative potential (OP) properties of the respirable (finer than 4 μm) fractions of 22 powdered coal samples from channel profiles (CP₄) in Chinese mined coals. The CP₄ fractions extracted from milled samples of 22 different coals were mineralogically and geochemically analysed and the relationships with the OP evaluated. The evaluation between CP₄/CP demonstrated that CP₄ increased concentrations of anatase, Cs, W, Zn and Zr, whereas sulphates, Fe, S, Mo, Mn, Hf and Ge decreased their CP₄ concentrations. OP results from ascorbic acid (AA), glutathione (GSH) and dithiothreitol (DTT) tests evidenced a clear link between specific inorganic components of CP₄ with OP^AA and the organic fraction of OP^GSH and OP^DTT. Correlation analyses were performed for OP indicators and the geochemical patterns of CP₄. These were compared with respirable dust samples from prior studies. They indicate that Fe (r = 0.83), pyrite (r = 0.66) and sulphate minerals (r = 0.42) (tracing acidic species from pyrite oxidation), followed by S (r = 0.50) and ash yield (r = 0.46), and, to a much lesser extent, Ti, anatase, U, Mo, V and Pb, are clearly linked with OP^AA. Moreover, OP^GSH correlation was identified by organic matter, as moisture (r = 0.73), Na (r = 0.56) and B (r = 0.51), and to a lesser extent by the coarse particle size, Ca and carbonate minerals. In addition, Mg (r = 0.70), B (r = 0.47), Na (r = 0.59), Mn, Ba, quartz, particle size and Sr regulate OP^DTT correlations. These became more noticeable when the analysis was done for samples of the same type of coal rank, in this case, bituminous.

Role of iron in cancer development by viruses

Increased levels of iron in body are attributed to higher cancer risk. Given the fact that 16% of all human cancers are caused by viral infections, iron is suggested to play an important role in carcinogenesis particularly those induced by viral infections. The present study provides an updated summary of the literature and the plausible mechanisms of iron involvement in cancer development by viruses. Our understanding about the interplay between viral infections and iron in different settings particularly cancer development is yet to be improved as it may shed a new light in development of new therapeutic strategies.

High Expression of Nuclear Factor of Activated T Cells in Chinese Primary Non-Small Cell Lung Cancer Tissues

Purpose

Nuclear factor of activated T cells (NFAT) has been reported to be involved in the development of various types of cancer including adenocarcinoma of the breast. This research was the first to investigate NFAT protein expression in primary non-small cell lung cancer (NSCLC) tissues from Chinese patients.

Methods

NFAT protein expression was determined in 130 surgically resected primary NSCLC and matched normal tissues by immunohistochemical analysis. The association between NFAT expression and clinical categorical variables was further analyzed with the SPSS software.

Results

We found that NFAT expression was much higher in 85 tumor tissues (65.4%) and lower in 45 tumor tissues (34.6%) compared with the matched normal tissues. Further statistical analysis by the chi-square test showed that high expression of NFAT proteins was significantly associated with tumor differentiation (p=0.045), invasion (p=0.031), histology (p<0.0001), tumor size (p=0.038) and cigarette smoking history (p=0.024). However, there was no correlation between the expression of NFAT proteins and pTNM classification, and no difference in 5-year survival rate between patients with high or low expression of NFAT proteins. Multivariate logistic regression analysis for the correlation between NFAT protein expression levels and various characteristics showed a significant association with histology (p=0.008, OR=0.273).

Conclusion

Our results revealed that high NFAT expression was present in Chinese NSCLCs and that NFAT expression might be involved in the process of human lung cancer development.

Lithium suppression of tau induces brain iron accumulation and neurodegeneration

Lithium is a first-line therapy for bipolar affective disorder. However, various adverse effects, including a Parkinson-like hand tremor, often limit its use. The understanding of the neurobiological basis of these side effects is still very limited. Nigral iron elevation is also a feature of Parkinsonian degeneration that may be related to soluble tau reduction. We found that magnetic resonance imaging T₂ relaxation time changes in subjects commenced on lithium therapy were consistent with iron elevation. In mice, lithium treatment lowers brain tau levels and increases nigral and cortical iron elevation that is closely associated with neurodegeneration, cognitive loss and parkinsonian features. In neuronal cultures lithium attenuates iron efflux by lowering tau protein that traffics amyloid precursor protein to facilitate iron efflux. Thus, tau- and amyloid protein precursor-knockout mice were protected against lithium-induced iron elevation and neurotoxicity. These findings challenge the appropriateness of lithium as a potential treatment for disorders where brain iron is elevated (for example, Alzheimer's disease), and may explain lithium-associated motor symptoms in susceptible patients.

Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors

Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function, and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of deferoxamine is mediated via Wnt signaling, we performed a Wnt profiler array of deferoxamine-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated 2-fold after 48 h at 50 μM deferoxamine. Pathway analysis using specific inhibitors revealed that deferoxamine utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cell pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the deferoxamine-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The promoting effect of deferoxamine on matrix mineralization in wild-type cells was completely abolished in Wnt5a^-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using deferoxamine.

Differential protein folding and chemical changes in lung tissues exposed to asbestos or particulates

Environmental and occupational inhalants may induce a large number of pulmonary diseases, with asbestos exposure being the most risky. The mechanisms are clearly related to chemical composition and physical and surface properties of materials. A combination of X-ray fluorescence (μXRF) and Fourier Transform InfraRed (μFTIR) microscopy was used to chemically characterize and compare asbestos bodies versus environmental particulates (anthracosis) in lung tissues from asbestos exposed and control patients. μXRF analyses revealed heterogeneously aggregated particles in the anthracotic structures, containing mainly Si, K, Al and Fe. Both asbestos and particulates alter lung iron homeostasis, with a more marked effect in asbestos exposure. μFTIR analyses revealed abundant proteins on asbestos bodies but not on anthracotic particles. Most importantly, the analyses demonstrated that the asbestos coating proteins contain high levels of β-sheet structures. The occurrence of conformational changes in the proteic component of the asbestos coating provides new insights into long-term asbestos effects.

Effects of strain and age on hepatic gene expression profiles in murine models of HFE-associated hereditary hemochromatosis

Hereditary hemochromatosis is an iron overload disorder most commonly caused by a defect in the HFE gene. While the genetic defect is highly prevalent, the majority of individuals do not develop clinically significant iron overload, suggesting the importance of genetic modifiers. Murine hfe knockout models have demonstrated that strain background has a strong effect on the severity of iron loading. We noted that hepatic iron loading in hfe-/- mice occurs primarily over the first postnatal weeks (loading phase) followed by a timeframe of relatively static iron concentrations (plateau phase). We thus evaluated the effects of background strain and of age on hepatic gene expression in Hfe knockout mice (hfe-/-). Hepatic gene expression profiles were examined using cDNA microarrays in 4- and 8-week-old hfe-/- and wild-type mice on two different genetic backgrounds, C57BL/6J (C57) and AKR/J (AKR). Genes differentially regulated in all hfe-/- mice groups, compared with wild-type mice, including those involved in cell survival, stress and damage responses and lipid metabolism. AKR strain-specific changes in lipid metabolism genes and C57 strain-specific changes in cell adhesion and extracellular matrix protein genes were detected in hfe-/- mice. Mouse strain and age are each significantly associated with hepatic gene expression profiles in hfe-/- mice. These affects may underlie or reflect differences in iron loading in these mice.

Coal mine dust lung disease. New lessons from old exposure

Coal mining remains a sizable industry, with millions of working and retired coal miners worldwide. This article provides an update on recent advances in the understanding of respiratory health issues in coal miners and focuses on the spectrum of disease caused by inhalation of coal mine dust, termed coal mine dust lung disease. In addition to the historical interstitial lung diseases (coal worker's pneumoconiosis, silicosis, and mixed dust pneumoconiosis), coal miners are at risk for dust-related diffuse fibrosis and chronic airway diseases, including emphysema and chronic bronchitis. Recent recognition of rapidly progressive pneumoconiosis in younger miners, mainly in the eastern United States, has increased the sense of urgency and the need for vigilance in medical research, clinical diagnosis, and exposure prevention. Given the risk for disease progression even after exposure removal, along with few medical treatment options, there is an important role for chest physicians in the recognition and management of lung disease associated with work in coal mining.

Coal dust exposure and mortality from ischemic heart disease among a cohort of U.S. coal miners

BACKGROUND

Particulate exposure from air pollution increases the risk of ischemic heart disease (IHD) mortality. Although coal miners are highly exposed to coal dust particulate, studies of IHD mortality risk among coal miners have had inconsistent results. Previous studies may have been biased by the healthy worker effect.

METHODS

We examined the dose-response relationship between cumulative coal dust exposure, coal rank, and IHD mortality among a cohort of underground coal miners who participated in the National Study of Coal Workers' Pneumoconiosis.

RESULTS

After adjusting for age, smoking, and body mass index, risk of IHD mortality increased at higher levels of coal dust exposure. Mortality risk was also associated with coal rank region.

CONCLUSION

There was an increased risk of mortality from IHD associated with cumulative exposure to coal dust, and with coal rank. The effect of coal rank may be due differences in the composition of coal mine dust particulate. The association of risk of IHD mortality with cumulative particulate exposure is consistent with air pollution studies.

Inhibitory effects of iron on bone morphogenetic protein 2-induced osteoblastogenesis

Postmenopausal osteoporosis is characterized by an imbalance of bone resorption exceeding bone formation, resulting in a net loss of bone mineral density (BMD). Estrogen deficiency is known to promote bone resorption. However, the causative factors that impair bone formation have not been identified. Women after menopause experience not only estrogen deficiency but also iron accumulation as a result of cessation of menstruation. In this study we investigated whether increased iron plays a role in osteoporosis. By growing primary mouse osteoclast and osteoblast progenitor cells as well as immortalized cell lines in the presence of iron, we found that increased iron had minimal effects on osteoclast cell differentiation. Interestingly, iron, particularly in its inorganic form, and to a lesser extent ferritin and transferrin all suppressed alkaline phosphatase (ALP) activities in osteoblasts. Moreover, iron downregulated mRNA levels of several other osteoblastogenic markers such as Runx2, osterix, osteopontin, and osteocalcin. To further show that this in vitro finding is relevant to the in vivo condition, we demonstrated that iron-accumulated mice with intact ovaries exhibited a significant decrease in BMD. Although iron inhibited preosteoblast cell differentiation, it did enhance preosteoblast cell proliferation, as evidenced by increased cell growth and expression of cell cycle regulator genes such as CDK4, CDK6, cyclin D1, and cyclin D3 and G(2) /M phase cell population. Taken together, our results suggest that increased iron could be a factor that slows down bone formation in postmenopausal women.

What component of coal causes coal workers' pneumoconiosis?

OBJECTIVE

To evaluate the component of coal responsible for coal workers' pneumoconiosis (CWP).

METHODS

A literature search of PubMED was conducted to address studies that have evaluated the risk of CWP based on the components of coal.

RESULTS

The risk of CWP (CWP) depends on the concentration and duration of exposure to coal dust. Epidemiology studies have shown inverse links between CWP and quartz content. Coal from the USA and Germany has demonstrated links between iron content and CWP; these same studies indicate virtually no role for quartz. In vitro studies indicate strong mechanistic links between iron content in coal and reactive oxygen species, which play a major role in the inflammatory response associated with CWP.

CONCLUSIONS

The active agent within coal appears to be iron, not quartz. By identifying components of coal before mining activities, the risk of developing CWP may be reduced.

Evidence of Health Impacts of Sulfate-and Nitrate-Containing Particles in Ambient Air

Ambient particulate matter (PM) is a complex mixture of inorganic and organic compounds. The U.S. Environmental Protection Agency (EPA) regulates PM as a criteria pollutant and promulgates National Ambient Air Quality Standards for it. The PM indicator is based on mass concentration, unspecified as to chemical composition, for specific size fractions. The numerical standards are based on epidemiologic evidence of associations between the various size-related particle mass concentrations as indicators and excess mortality and cardiorespiratory health effects as endpoints. The U.S. National Research Council has stated that more research is needed to differentiate the apparent health effects associated with different particle chemical constituents. Sulfate and nitrate constitute a significant portion of the particle mass in the atmosphere, but are accompanied by similar amounts of carbonaceous material, along with low concentrations of various species, including bioactive organic compounds and redox cycling metals. Extensive animal and human toxicology data show no significant effects for particles consisting only of sulfate and nitrate compounds at levels in excess of ambient air concentrations. A few epidemiologic studies, including both short-term time-series studies and long-term cohort studies, have included the sulfate content of PM as a specific variable in health effect analyses. There are much less data for nitrate. The results from the epidemiologic studies with PM sulfate are inconsistent. A detailed analysis of the time-series epidemiological studies shows that PM sulfate has a weaker "risk factor" than PM2.5 for health effects. Since sulfate is correlated with PM2.5, this result is inconsistent with sulfate having a strong health influence. However, there are many limitations with these types of studies that warrant caution for any comparison between a chemical component and mass concentration. In total, the epidemiologic and toxicologic evidence provide little or no support for a causal association of PM sulfate and health risk at ambient concentrations. For nitrate-containing PM, virtually no epidemiological data exist. Limited toxicological evidence does not support a causal association between particulate nitrate compounds and excess health risks. There are some possible indirect processes through which sulfate and nitrate in PM may affect health-related endpoints, including interactions with certain metal species and a linkage with production of secondary organic matter. There is insufficient evidence to include or exclude these processes as being potentially important to PM-associated health risk.

Activation of oxidative stress-responsive signaling pathways in early splenotoxic response of aniline

Aniline exposure causes toxicity to the spleen, which leads to a variety of sarcomas, and fibrosis appears to be an important preneoplastic lesion. However, early molecular mechanisms in aniline-induced toxicity to the spleen are not known. Previously, we have shown that aniline exposure results in iron overload and induction of oxidative stress in the spleen, which can cause transcriptional upregulation of fibrogenic/inflammatory cytokines via activation of oxidative stress (OS)-responsive signaling pathways. To test this mechanism, male SD rats were treated with aniline (1mmol/kg/day via gavage) for 7 days, an experimental condition that precedes the appearance of fibrosis. Significant increases in both NF-kappaB and AP-1 binding activity was observed in the nuclear extracts of splenocytes from aniline-treated rats as determined by ELISAs, and supported by Western blot data showing increases in p-IkappaBalpha, p-p65 and p-c-Jun. To understand the upstream signaling events which could account for the activation of NF-kappaB and AP-1, phosphorylation patterns of IkappaB kinases (IKKalpha and IKKbeta) and mitogen-activated protein kinases (MAPKs) were pursued. Our data showed remarkable increases in both p-IKKalpha and p-IKKbeta in the splenocytes from aniline-treated rats, suggesting their role in the phosphorylation of both IkappaBalpha and p65 subunits. Furthermore, aniline exposure led to activation of all three classes of MAPKs, as evident from increased phosphorylation of extracellular-signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK1/2) and p38 MAPKs, which could potentially contribute to the observed activation of both AP-1 and NF-kappaB. Activation of upstream signaling molecules was also associated with simultaneous increases in gene transcription of cytokines IL-1, IL-6 and TNF-alpha. The observed sequence of events following aniline exposure could initiate a fibrogenic and/or tumorigenic response in the spleen.

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.

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.

Effects of select PM-associated metals on alveolar macrophage phosphorylated ERK1 and -2 and iNOS expression during ongoing alteration in iron homeostasis

It was hypothesized that relative mass relationships among select constituent metals and iron (Fe3+) govern the pulmonary immunotoxic potential of any PM(2.5) sample, as these determine the extent to which Fe3+ binding by transferrin is affected (resulting in altered alveolar macrophage [AM] Fe status and subsequent antibacterial function). Iron response protein (IRP) binding activity is a useful indirect measurement of changes in Fe status, as reductions in cell Fe levels lead to increases in IRP binding. However, AM IRP activity can be affected by an increased presence of nitric oxide generated by inducible nitric oxide synthase (iNOS). This study sought to determine if any changes in AM IRP activity induced by PM(2.5) constituents V, Mn, or Al were independent from effects of the metals on cell NO formation. NR8383 rat AM were exposed to Fe3+ alone or combined with V, Mn, or Al at metal:Fe ratios representative of those in PM(2.5) collected in New York City, Los Angeles, and Seattle during fall 2001. Cells were then assessed for changes in IRP activity and iNOS expression. Phosphorylated extracellular signal-regulated kinase (ERK) 1 and 2 levels were also measured since activated ERKs are involved in signaling pathways that lead to increased iNOS expression. The results indicate that V and Al, and to a lesser extent Mn, altered IRP activity, though the effects were not consistently concentration dependent. Furthermore, while V and Mn treatments did not induce iNOS expression, Al did. These results confirmed our hypothesis that certain metals associated with PM(2.5) might alter the pulmonary immunocompetence of exposed hosts by affecting the Fe status of AM, a major class of deep lung defense cells.

Conference overview: Molecular mechanisms of metal toxicity and carcinogenesis

Chronic exposure to many heavy metals and metal-derivatives is associated with an increased risk of cancer, although the mechanisms of tumorigenesis are largely unknown. Approximately 125 scientists attended the 3rd Conference on Molecular Mechanisms of Metal Toxicity and Carcinogenesis and presented the latest research concerning these mechanisms. Major areas of focus included exposure assessment and biomarker identification, roles of ROS and antioxidants in carcinogenesis, mechanisms of metal-induced DNA damage, metal signalling, and the development of animal models for use in metal toxicology studies. Here we highlight some of the research presented, and summarize the conference proceedings.

Addition of calcite reduces iron's bioavailability in the Pennsylvania coals--potential use of calcite for the prevention of coal workers' lung diseases

In the present study, a hypothesis was tested that the addition of calcite into the Pennsylvania coals may reduce levels of bioavailable iron (BAI), an important component in the mixed coal dust that may contribute to coal workers' lung diseases. Predetermined proportions of calcite (0, 1, 2, 5, 10% w/w) were added into three PA coals. After suspending the mixtures in an aqueous phosphate solution (10 mM, pH 4.5), which mimics the phagolysosomal conditions of the cells, levels of pH as well as calcium ions (Ca2+) in the coals were increased in a calcite concentration-dependent manner. In contrast, levels of BAI (both Fe2+ and Fe3+) were decreased. The inhibitory effects of calcite on the bioavailability of iron in human lung epithelial A549 cells and primary rat alveolar macrophages (AMs) were also examined. It was found that levels of low-molecular-weight (LMW) iron were significantly decreased in both A549 cells and AMs treated with the 10% calcite-PA coal mixture compared to those treated with the PA coal alone, while calcite itself had no effect on intracellular LMW iron. Calcite also showed a significant inhibitory effect on PA coal-induced ferritin synthesis in A549 cells. Reverse-transcription polymerase chain reaction (RT-PCR) studies revealed that the iron-containing PA coal downregulated levels of transferrin receptor (TfR) mRNA in A549 cells, which was partially restored by the addition of calcite. Our results indicate that calcite can inhibit the bioavailability of iron in the iron-containing PA coals.

Activation of transcription factor AP-1 and mitogen-activated protein kinases in aniline-induced splenic toxicity

Signaling mechanisms in aniline-induced fibrogenic and/or tumorigenic response in the spleen are not known. Previous studies have shown that aniline exposure leads to iron accumulation and oxidative stress in the spleen, which may cause activation of redox-sensitive transcription factors and regulate the transcription of genes involved in fibrosis and/or tumorigenesis. To test this, male SD rats were treated with 0.5 mmol/kg/day aniline via drinking water for 30 days, and activation of transcription factor AP-1 was determined in the splenocyte nuclear extracts (NEs). AP-1 DNA-binding activity in the NEs of freshly isolated splenocytes from aniline-treated rats increased in comparison to the controls, as determined by electrophoretic mobility shift assay (EMSA). AP-1 binding was also determined in the NEs of cultured splenocytes (2 h and 24 h), which showed even a greater increase in binding activity at 2 h. The specificity of AP-1 binding for relevant DNA motifs was confirmed by competition EMSA and by supershift EMSA using antibodies specific to c-Jun and c-Fos. To further explore the signaling mechanisms in the AP-1 activation, phosphorylation patterns of mitogen-activated protein kinases (MAPKs) were pursued. Aniline exposure induced increases in the phosphorylation of the three classes of MAPKs: extracellular-signal-regulated kinase (ERK 1/2), c-Jun N-terminal kinase (JNK 1/2), and p38 MAPKs. Furthermore, TGF-beta1 mRNA expression showed a 3-fold increase in the spleens of aniline-treated rats. These observations suggest a strong association among MAPK phosphorylation, AP-1 activation, and enhanced TGF-beta1 gene expression. The observed sequence of events subsequent to aniline exposure could regulate genes that lead to fibrogenic and/or tumorigenic response in the spleen.

Mapping and prediction of coal workers' pneumoconiosis with bioavailable iron content in the bituminous coals

Based on the first National Study of Coal Workers' Pneumoconiosis (CWP) and the U.S. Geological Survey database of coal quality, we show that the prevalence of CWP in seven coal mine regions correlates with levels of bioavailable iron (BAI) in the coals from that particular region (correlation coefficient r = 0.94, p < 0.0015). CWP prevalence is also correlated with contents of pyritic sulfur (r = 0.91, p < 0.0048) or total iron (r = 0.85, p < 0.016) but not with coal rank (r = 0.59, p < 0.16) or silica (r = 0.28, p < 0.54). BAI was calculated using our model, taking into account chemical interactions of pyrite, sulfuric acid, calcite, and total iron. That is, iron present in coals can become bioavailable by pyrite oxidation, which produces ferrous sulfate and sulfuric acid. Calcite is the major component in coals that neutralizes the available acid and inhibits iron's bioavailability. Therefore, levels of BAI in the coals are determined by the available amounts of acid after neutralization of calcite and the amount of total iron in the coals. Using the linear fit of CWP prevalence and the calculated BAI in the seven coal mine regions, we have derived and mapped the pneumoconiotic potencies of 7,000 coal samples. Our studies indicate that levels of BAI in the coals may be used to predict coal's toxicity, even before large-scale mining.

Metal-induced oxidative stress and signal transduction

Occupational and environmental exposures to metals are associated with the development of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the mechanisms of action, especially at the molecular level, are still unclear. Accumulating evidence indicates that reactive oxygen species generated by metals may play an important role in the etiology of disease. This review covers recent advances in (1) metal-induced generation of reactive oxygen species; (2) the receptors, kinases, and nuclear transcription factors affected by metals and metal-induced oxidative stress, including growth factor receptors, src kinase, ras signaling, mitogen-activated protein kinases, the phosphoinositide 3-phosphate/Akt pathway, nuclear transcription factor kappaB, activator protein 1, p53, nuclear factor of activated T cells, and hypoxia-inducible factor 1; and (3) global cellular phenomena (signal transduction, cell cycle regulation, and apoptosis) associated with metal-induced ROS production and gene expression.

Coal-induced interleukin-6 gene expression is mediated through ERKs and p38 MAPK pathways

In the present study, we have tested the ability of coal dust to stimulate kinase phosphorylation of activator protein-1 (AP-1) signal transduction pathways and production of interleukin-6 (IL-6) in both mouse epidermal JB6 and human lung epithelial A549 cells. Seven coal samples from three coalmine regions of Pennsylvania (PA), West Virginia (WV), and Utah (UT) with high, medium, and low prevalence of coal workers' pneumoconiosis (CWP), respectively, were investigated. Results from the present study indicate that three PA coals stimulated the mitogen-activated protein kinase (MAPK) family of extracellular signal-regulated kinases (ERKs) and p38 MAPK, but not c-Jun-NH2-terminal kinases (JNKs) in human lung A549 cells. The effects of three UT coals on the kinase phosphorylation were less as compared to those of the PA coals. Coal dusts from three coalmine regions induced IL-6 in a dose-dependent manner in both JB6 and A549 cells. Interestingly, levels of IL-6 in both cells treated with coals from three coalmine regions correlated well with CWP prevalence from that region. To assess the role of AP-1 pathways in coal-mediated transcriptional activation of IL-6, various inhibitors were used in cells treated with one PA coal, which induced a maximal response. It was found that the increase in IL-6 protein and mRNA by the PA coal was completely eliminated by the pretreatment of both cell types with PD98059, a specific MEK1 inhibitor, and SB202190, a p38 kinase inhibitor. Our results indicate that coal dust can stimulate IL-6 release from mouse epidermal JB6 cells and human lung epithelial A549 cells, and the coal-induced IL-6 increase may involve ERKs and p38 MAPK pathways.

Induction of interleukin-6 by coal containing bioavailable iron is through both hydroxyl radical and ferryl species

Coal mining causes health problems, such as pneumoconiosis. We have previously shown that prevalence of pneumoconiosis in workers from various coalmine regions positively correlates with levels of bioavailable iron (BAI) in the coals from that region. In the present study, the nature of reactive oxygen species formed by BAI in the coals and its mechanisms of the induction of biological responses were investigated. Human lung epithelial cell line, A549 cells, were used to examine the induction of interleukin-6 (IL-6), a pro-inflammatory cytokine, which is known to play a crucial role in the development of pneumoconiosis. We found that levels of IL-6 protein as well as its mRNA were significantly increased in the cells treated for 24 h with 20 microg/cm2 of the BAI-containing Pennsylvania (PA) coal; for example we observed 6.7-fold increase in IL-6 protein. Levels of IL-6 protein in cells treated with the Utah (UT) coal containing low-BAI were only 1.9-fold of the control levels. The enhancing effect on the IL-6 by the PA coal was similar to that caused by hydrogen peroxide. Superoxide dismutase (SOD), catalase (CAT), and N-acetyl-L-cysteine (NAC) all had inhibitory effects on the PA coal-induced IL-6 formation. However, CAT had the least protective effect as compared to SOD and NAC. Our results indicate that BAI in the PA coal may induce IL-6 through both ferryl species (via iron autoxidation) and hydroxyl radicals (via the Fenton/Haber Weiss reactions).