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

Saharan dust induces NLRP3-dependent inflammatory cytokines in an alveolar air-liquid interface co-culture model

BACKGROUND

Epidemiological studies have related desert dust events to increased respiratory morbidity and mortality. Although the Sahara is the largest source of desert dust, Saharan dust (SD) has been barely examined in toxicological studies. Here, we aimed to assess the NLRP3 inflammasome-caspase-1-pathway-dependent pro-inflammatory potency of SD in comparison to crystalline silica (DQ12 quartz) in an advanced air-liquid interface (ALI) co-culture model. Therefore, we exposed ALI co-cultures of alveolar epithelial A549 cells and macrophage-like differentiated THP-1 cells to 10, 21, and 31 µg/cm² SD and DQ12 for 24 h using a Vitrocell Cloud system. Additionally, we exposed ALI co-cultures containing caspase (CASP)1-/- and NLRP3-/- THP-1 cells to SD.

RESULTS

Characterization of nebulized DQ12 and SD revealed that over 90% of agglomerates of both dusts were smaller than 2.5 μm. Characterization of the ALI co-culture model revealed that it produced surfactant protein C and that THP-1 cells remained viable at the ALI. Moreover, wild type, CASP1-/-, and NLRP3-/- THP-1 cells had comparable levels of the surface receptors cluster of differentiation 14 (CD14), toll-like receptor 2 (TLR2), and TLR4. Exposing ALI co-cultures to non-cytotoxic doses of DQ12 and SD did not induce oxidative stress marker gene expression. SD but not DQ12 upregulated gene expressions of interleukin 1 Beta (IL1B), IL6, and IL8 as well as releases of IL-1β, IL-6, IL-8, and tumor necrosis factor α (TNFα). Exposing wild type, CASP1-/-, and NLRP3-/- co-cultures to SD induced IL1B gene expression in all co-cultures whereas IL-1β release was only induced in wild type co-cultures. In CASP1-/- and NLRP3-/- co-cultures, IL-6, IL-8, and TNFα releases were also reduced.

CONCLUSIONS

Since surfactants can decrease the toxicity of poorly soluble particles, the higher potency of SD than DQ12 in this surfactant-producing ALI model emphasizes the importance of readily soluble SD components such as microbial compounds. The higher potency of SD than DQ12 also renders SD a potential alternative particulate positive control for studies addressing acute inflammatory effects. The high pro-inflammatory potency depending on NLRP3, CASP-1, and IL-1β suggests that SD causes acute lung injury which may explain desert dust event-related increased respiratory morbidity and mortality.

Superparamagnetic Iron Oxide Nanoparticles: Cytotoxicity, Metabolism, and Cellular Behavior in Biomedicine Applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely investigated and applied in the field of biomedicine due to their excellent superparamagnetic properties and reliable traceability. However, with the optimization of core composition, shell types and transfection agents, the cytotoxicity and metabolism of different SPIONs have great differences, and the labeled cells also show different cellular behaviors. Therefore, a holistic review of the construction and application of SPIONs is desired. This review focuses the advances of SPIONs in the field of biomedicine in recent years. After summarizing the toxicity of different SPIONs, the uptake, distribution and metabolism of SPIONs in vitro were discussed. Then, the regulation of labeled-cells behavior is outlined. Furthermore, the major challenges in the optimization process of SPIONs and insights on its future developments are proposed.

Physiological function and inflamed-brain migration of mouse monocyte-derived macrophages following cellular uptake of superparamagnetic iron oxide nanoparticles-Implication of macrophage-based drug delivery into the central nervous system

This study was designed to use superparamagnetic iron oxide nanoparticles (SPIONs) as evaluating tools to study monocyte-derived macrophages (MDM)-mediated delivery of small molecular agents into the diseased brains. MDM were tested with different-configured SPIONs at selected concentrations for their impacts on carrier cells' physiological and migratory properties, which were found to depend largely on particle size, coating, and treatment concentrations. SHP30, a SPION of 30-nm core size with oleic acids plus amphiphilic polymer coating, was identified to have high cellular uptake efficiency and cause little cytotoxic effects on MDM. At lower incubation dose (25μg/mL), few alteration was observed in carrier cells' physiological and in vivo migratory functions, as tested in a lipopolysaccharide-induced acute neuroinflammation mouse model. Nevertheless, significant increase in monocyte-to-macrophage differentiation, and decrease in in vivo carrier MDM inflamed-brain homing ability were found in groups treated with a higher dose of SHP30at 100μg/mL. Overall, our results have identified MDM treatment at 25μg/mL SHP30 resulted in little functional changes, provided valuable parameters for using SPIONs as evaluating tools to study MDM-mediated therapeutics carriage and delivery, and supported the concepts of using monocytes-macrophages as cellular vehicles to transport small molecular agents to the brain.

Length-dependent effect of single-walled carbon nanotube exposure in a dynamic cell growth environment of human alveolar epithelial cells

Despite the great use of nanomaterials for engineering and medical applications, nanomaterials may have adverse consequences by accidental exposure, because of their nanoscale size, composition and shape. Like many nanomaterials, carbon nanotubes (CNTs) have been used for many proven applications, but the size of the CNTs makes them more readily become airborne and can therefore create the risk of being inhaled by a worker. In this study, we evaluated single-walled CNT (SWCNT)-induced effects on cellular responses such as cell proliferation, inflammatory response and oxidative stress in dynamic cell growth condition. A dynamic cell growth environment was established to mimic the dynamic changes in the amount of circumferential and longitudinal expansion and contraction occurred during normal breathing movement in the lung. Two different length (short: outer diameter (OD) 1-2 nm, length 0.5-2 μm; long: OD 1-2 nm, length 5-30 μm) of SWCNTs were used at different exposure concentrations (5, 10 and 20 μg/ml) during the different exposure duration (24, 48 and 72 h). Dynamic environment facilitated altered interaction between SWCNTs and A549 monolayer. Cellular responses in dynamic condition were significantly different from those in static condition. Moreover, cellular responses were dependent on the length of SWCNTs both in static and dynamic cell growth conditions.

Cement-related particles interact with proinflammatory IL-8 chemokine from human primary oropharyngeal mucosa cells and human epithelial lung cancer cell line A549

Epidemiological studies have shown that respirable exposure to emitted cement particulate matter is associated with adverse health risk for human. The underlying mechanisms, however, are poorly understood. To examine the effect of cement, nine blinded cement-related particulates (<10 μm) were assessed with regard to their induction of the proinflammatory cytokines IL-6 and IL-8 in human primary epithelial cells (pEC) from oropharyngeal mucosa as well as from nonsmall-cell lung carcinoma (non-SCLC) cells A549. It was demonstrated that the cement specimens did not act cytotoxic as assessed by the lactate dehydrogenase (LDH) assay. The basal and IL-1β-induced IL-8 expression was suppressed, in contrast to an unchanged IL-6. At the transcript level the basal and induced IL-6 and IL-8 gene expression was not influenced by cement dust. To discover the mechanism by which cement influenced the IL-8 expression the following experiments were performed. Submerse exposure experiments have shown that the release of IL-8 was suppressed by cement dust. Furthermore, the incubation of IL-8 with cement-related specimens under cell-free condition led to a loss of immunoreactive IL-8. An immunological masking of IL-8 by free soluble components of respiratory epithelial cells was excluded. Thus, the decrease of IL-8 protein content after cement exposure seems to be a result of the adsorption of IL-8 protein to cement particles and the inhibition of IL-8 release. In conclusion, due to absent cytotoxic and inflammatory effects of cement-related specimens in both human pEC and A549 cell models it remains open how cement exposure may lead to the respiratory adverse effects in humans.

Differential pro-inflammatory effects of metal oxide nanoparticles and their soluble ions in vitro and in vivo; zinc and copper nanoparticles, but not their ions, recruit eosinophils to the lungs

Abstract Nickel, zinc, and copper oxide nanoparticles (NiONP, ZnONP, and CuONP) and their aqueous extracts (AEs) were applied to A549 lung epithelial cells to determine the cytotoxicity, IL-8 production, and activation of transcription factors. Nanoparticles (NPs) and their AEs were also instilled into rat lungs to evaluate acute and chronic inflammatory effects. In vitro AEs had specific effects; for example NiOAE had no effect and ZnOAE affected all parameters measured. NPs themselves all had cytotoxic effects but only ZnONP and CuONP impacted pro-inflammatory endpoints. The inflammatory cells in the BAL were also different from AEs and NPs with ZnONP and CuONP recruiting eosinophils and neutrophils whilst ZnOAE and CuOAE elicited only mild neutrophilic inflammation that had resolved by four weeks. NiONP recruited neutrophils only whilst NiOAE did not cause any inflammation. Understanding differences in the toxic role of the ionic components of metal oxide NPs will contribute to full hazard identification and characterisation.

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

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

Systemic inhibition of NF-kappaB activation protects from silicosis

Background

Silicosis is a complex lung disease for which no successful treatment is available and therefore lung transplantation is a potential alternative. Tumor necrosis factor alpha (TNFα) plays a central role in the pathogenesis of silicosis. TNFα signaling is mediated by the transcription factor, Nuclear Factor (NF)-κB, which regulates genes controlling several physiological processes including the innate immune responses, cell death, and inflammation. Therefore, inhibition of NF-κB activation represents a potential therapeutic strategy for silicosis.

Methods/Findings

In the present work we evaluated the lung transplant database (May 1986–July 2007) at the University of Pittsburgh to study the efficacy of lung transplantation in patients with silicosis (n = 11). We contrasted the overall survival and rate of graft rejection in these patients to that of patients with idiopathic pulmonary fibrosis (IPF, n = 79) that was selected as a control group because survival benefit of lung transplantation has been identified for these patients. At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFα expressing macrophage and NF-κB activation in epithelial cells. Patients with silicosis had poor survival (median survival 2.4 yr; confidence interval (CI): 0.16–7.88 yr) compared to IPF patients (5.3 yr; CI: 2.8–15 yr; p = 0.07), and experienced early rejection of their lung grafts (0.9 yr; CI: 0.22–0.9 yr) following lung transplantation (2.4 yr; CI:1.5–3.6 yr; p<0.05). Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-κB activation with a pharmacologic inhibitor (BAY 11-7085) of IκBα phosphorylation decreased silica-induced inflammation and collagen deposition. In contrast, transgenic mice expressing a dominant negative IκBα mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.

Conclusions

Although limited by its size, our data support that patients with silicosis appear to have poor outcome following lung transplantation. Experimental data indicate that while the systemic inhibition of NF-κB protects from silica-induced lung injury, epithelial cell specific NF-κB inhibition appears to aggravate the outcome of experimental silicosis.

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.

ROS and NF-kappaB are involved in upregulation of IL-8 in A549 cells exposed to multi-walled carbon nanotubes

Carbon nanotubes (CNTs) have potential applications in biosensors, tissue engineering, and biomedical devices because of their unique physico-chemical, electronic and mechanical properties. However, there is limited literature data available concerning the biological properties and toxicity of CNTs. This study aimed to assess the toxicity exhibited by multi-walled CNTs (MWCNTs) and to elucidate possible molecular mechanisms underlying the biological effects of MWCNTs in A549 cells. Exposing A549 cells to MWCNTs led to cell death, changes in cell size and complexity, reactive oxygen species (ROS) production, interleukin-8 (IL-8) gene expression and nuclear factor (NF)-kappaB activation. Treatment of A549 cells with antioxidants prior to adding MWCNTs decreased ROS production and abrogated expression of IL-8 mRNA. Pretreatment of A549 cells with NF-kappaB inhibitors suppressed MWCNTs-induced IL-8 mRNA expression. These results indicate that MWCNTs are able to induce expression of IL-8 in A549 cells, at least in part, mediated by oxidative stress and NF-kappaB activation.

Air pollution, ultrafine and nanoparticle toxicology: cellular and molecular interactions

Nanotechnology is involved with the creation and/or manipulation of materials at the nanometer (nm) scale, and has arisen as a consequence of the novel properties that materials exhibit within the "nano" size range. The attraction of producing, and exploiting nanparticles (NPs; one dimension less than 100 nm) is a consequence of the fact that the properties are often strikingly different from bulk forms composed from the same material. As a consequence, the field of nanotechnology has generated substantial interest resulting in incorporation of NPs into a wide variety of products including electronics, food, clothing, medicines, cosmetics and sporting equipment. While there is general recognition that nanotechnology has the potential to advance science, quality of life and to generate substantial financial gains, a number of reports suggest that potential toxicity should be considered in order to allow the safe and sustainable development of such products. For example, substances which are ordinarily innocuous can elicit toxicity due to the altered chemical and physical properties that become evident within nano dimensions leading to potentially detrimental consequences for the producer, consumer or environment. Research into respirable air pollution particles (PM10) has focused on the role of ultrafine particle (diameter less than 100 nm) in inducing oxidative stress leading to inflammation and resulting in exacerbation of preexisting respiratory and cardiovascular disease. Epidemiological studies have repeatedly found a positive correlation between the level of particulate air pollution and increased morbidity and mortality rates in both adults and children. Such studies have also identified a link between respiratory ill health and the number of ambient ultrafine particles. In vivo and in vitro toxicology studies confirm that for low solubility, low toxicity materials such as TiO2, carbon black and polystyrene beads, ultrafine particles are more toxic and inflammogenic than fine particles. In many of these studies the term "ultrafine particle" can be directly exchanged for nanoparticle, as these particles are manufactured industrially. In such studies the NPs generate reactive oxygen species (ROS) to a greater extent than larger particles leading to increased transcription of pro-inflammatory mediators via intracellular signaling pathways including calcium and oxidative stress. To date, only limited NP compositions and structures have been tested, including materials such as carbon, polystyrene beads and TiO2 as surrogate particles that aimed to represent particulate air pollution. All of these materials are generally low toxicity and low solubility. Much work is required to identify whether the conclusions made for such materials can be extrapolated to engineered nanoparticles varying not only in size but also, shape, composition, structure, surface area, surface coating, and aggregation state. Therefore, it is necessary to reveal if the diversity of NPs available will confer to a varied extent and mechanisms of toxicity.

Curcumin protects against cytotoxic and inflammatory effects of quartz particles but causes oxidative DNA damage in a rat lung epithelial cell line

Chronic inhalation of high concentrations of respirable quartz particles has been implicated in various lung diseases including lung fibrosis and cancer. Generation of reactive oxygen species (ROS) and oxidative stress is considered a major mechanism of quartz toxicity. Curcumin, a yellow pigment from Curcuma longa, has been considered as nutraceutical because of its strong anti-inflammatory, antitumour and antioxidant properties. The aim of our present study was to investigate whether curcumin can protect lung epithelial cells from the cytotoxic, genotoxic and inflammatory effects associated with quartz (DQ12) exposure. Electron paramagnetic resonance (EPR) measurements using the spin-trap DMPO demonstrated that curcumin reduces hydrogen peroxide-dependent hydroxyl-radical formation by quartz. Curcumin was also found to reduce quartz-induced cytotoxicity and cyclooxygenase 2 (COX-2) mRNA expression in RLE-6TN rat lung epithelial cells (RLE). Curcumin also inhibited the release of macrophage inflammatory protein-2 (MIP-2) from RLE cells as observed upon treatment with interleukin-1 beta (IL-1beta) and tumour necrosis factor-alpha (TNFalpha). However, curcumin failed to protect the RLE cells from oxidative DNA damage induced by quartz, as shown by formamidopyrimidine glycosylase (FPG)-modified comet assay and by immunocytochemistry for 8-hydroxydeoxyguanosine. In contrast, curcumin was found to be a strong inducer of oxidative DNA damage itself at non-cytotoxic and anti-inflammatory concentrations. In line with this, curcumin also enhanced the mRNA expression of the oxidative stress response gene heme oxygenase-1 (ho-1). Curcumin also caused oxidative DNA damage in NR8383 rat alveolar macrophages and A549 human lung epithelial cells. Taken together, these observations indicate that one should be cautious in considering the potential use of curcumin in the prevention or treatment of lung diseases associated with quartz exposure.

Proinflammogenic effects of low-toxicity and metal nanoparticles in vivo and in vitro: highlighting the role of particle surface area and surface reactivity

Different particle types cause excessive lung inflammation that is thought to play a role in the various types of pathology they produce. Recently attention has been focused on nanoparticles due to their presence in environmental particulate air pollution, their use and exposure in occupational settings, and their potential use in nanotechnology and novel therapeutics. We have shown previously that the surface area metric drives the overload response. We have instilled a number of low-toxicity dusts of various particle sizes and assessed neutrophil influx into the lung at 18-24 h postinstillation. The extent of inflammation was demonstrated as being a function not of the mass dose instilled but interestingly of the surface area dose instilled. Since low-toxicity nanoparticles present a "special" case of high surface area, they are relatively inflammogenic. We tested whether we could use this approach to model the reactivity of highly toxic dusts. Rats were instilled with either DQ12 quartz or aluminum lactate-treated DQ12 and, as anticipated, the high specific surface toxicity of DQ12 meant that it was much more inflammogenic (63 times more) than the surface area alone would have predicted. By contrast, aluminum lactate-treated DQ12 fell into the line of "low-toxicity" dusts. In addition, as an in vitro testing alternative to that of in vivo testing, interleukin (IL)-8 production in A549 cells exposed to the panel of various particles clearly demonstrated the ability to also identify a relationship between surface area dose and reactivity. These approaches present the possibility of modelling potential toxicity of nanoparticles and nuisance dusts based on the inflammatory response of a given instilled surface area dose.

Protection from acute and chronic lung diseases by curcumin

The aim of this review has been to describe the current state of the therapeutic potential of curcumin in acute and chronic lung injuries. Occupational and environmental exposures to mineral dusts, airborne pollutants, cigarette smoke, chemotherapy, and radiotherapy injure the lungs, resulting in acute and chronic inflammatory lung diseases. Despite major advances in treating lung diseases, until now disease-modifying efficacy has not been demonstrated for any of the existing drugs. Current medical therapy offers only marginal benefit; therefore, there is an essential need to develop new drugs that might be of effective benefit in clinical settings. Over the years, there has been increasing evidence that curcumin, a phytochemical present in turmeric (Curcuma longa), has a wide spectrum of therapeutic properties and a remarkable range of protective effects in various diseases. Several experimental animal models have tested curcumin on lung fibrosis and these studies demonstrate that curcumin attenuates lung injury and fibrosis caused by radiation, chemotherapeutic drugs, and toxicants. The growing amount of data from pharmacological and animal studies also supports the notion that curcumin plays a protective role in chronic obstructive pulmonary disease, acute lung injury, acute respiratory distress syndrome, and allergic asthma, its therapeutic action being on the prevention or modulation of inflammation and oxidative stress. These findings give substance to the possibility of testing curcumin in patients with lung diseases.

The pro-inflammatory effects of low-toxicity low-solubility particles, nanoparticles and fine particles, on epithelial cells in vitro: the role of surface area

OBJECTIVE

Rats exposed to high airborne mass concentrations of low-solubility low-toxicity particles (LSLTP) have been reported to develop lung disease such as fibrosis and lung cancer. These particles are regulated on a mass basis in occupational settings, but mass might not be the appropriate metric as animal studies have shown that nanoparticles (ultrafine particles) produce a stronger adverse effect than fine particles when delivered on an equal mass basis.

METHODS

This study investigated whether the surface area is a better descriptor than mass of LSLTP of their ability to stimulate pro-inflammatory responses in vitro. In a human alveolar epithelial type II-like cell line, A549, we measured interleukin (IL)-8 mRNA, IL8 protein release and glutathione (GSH) depletion as markers of pro-inflammatory effects and oxidative stress after treatment with a range of LSLTP (fine and nanoparticles) and DQ12 quartz, a particle with a highly reactive surface.

RESULTS

In all the assays, nanoparticle preparations of titanium dioxide (TiO2-np) and of carbon black (CB-np) produced much stronger pro-inflammatory responses than the same mass dose of fine TiO2 and CB. The results of the GSH assay confirmed that oxidative stress was involved in the response to all the particles, and two ultra-fine metal dusts (cobalt and nickel) produced GSH depletion similar to TiO2-np, for similar surface-area dose. As expected, DQ12 quartz was more inflammatory than the low toxicity dusts, on both a mass and surface-area basis.

CONCLUSION

Dose-response relationships observed in the in vitro assays appeared to be directly comparable with dose-response relationships in vivo when the doses were similarly standardised. Both sets of data suggested a threshold in dose measured as surface area of particles relative to the surface area of the exposed cells, at around 1-10 cm2/cm2. These findings are consistent with the hypothesis that surface area is a more appropriate dose metric than mass for the pro-inflammatory effects of LSLTP in vitro and in vivo, and consequently that the high surface area of nanoparticles is a key factor in their inflammogenicity.

Nanoparticles: pharmacological and toxicological significance

Nanoparticles are tiny materials (<1000 nm in size) that have specific physicochemical properties different to bulk materials of the same composition and such properties make them very attractive for commercial and medical development. However, nanoparticles can act on living cells at the nanolevel resulting not only in biologically desirable, but also in undesirable effects. In contrast to many efforts aimed at exploiting desirable properties of nanoparticles for medicine, there are limited attempts to evaluate potentially undesirable effects of these particles when administered intentionally for medical purposes. Therefore, there is a pressing need for careful consideration of benefits and side effects of the use of nanoparticles in medicine. This review article aims at providing a balanced update of these exciting pharmacological and potentially toxicological developments. The classes of nanoparticles, the current status of nanoparticle use in pharmacology and therapeutics, the demonstrated and potential toxicity of nanoparticles will be discussed.

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.

Signal transduction pathways relevant for neoplastic effects of fibrous and non-fibrous particles

Apart from their genotoxic effects, both fibrous and non-fibrous particles are known to induce signalling pathways involved in the development of malignant lung diseases. Different direct effects of particles as well as indirect cellular effects are believed to induce changes in apoptosis or proliferation in target cells. Signalling events, e.g. the induction of mitogen-activated protein kinase (MAPK) cascades resulting in the activation of the transcription factor AP-1, as well as the induction of the transcription factor NFkappaB which mainly mediates the expression of pro-inflammatory genes are discussed. There is some insight into the molecular mechanisms eliciting these pathways. Therefore, this review aims to give an overview on signalling pathways as well as initial events including effects of reactive oxygen and nitrogen species, membrane receptors and particle uptake.

Inflammatory Time Course after Quartz Instillation

Inflammation has been suggested as the key factor in the development of quartz-induced fibrosis and carcinogenesis, and particle surface properties are argued as an important characteristic responsible for these pathologic alterations. To evaluate the effect of surface modification on acute and subchronic inflammation, female Wistar rats were intratracheally instilled with 2 mg native quartz, or quartz coated either with polyvinyl-pyridine-N-oxide or with aluminium lactate. Various markers of lung toxicity, inflammation, and oxidative stress were found to be enhanced at 3, 7, 21, and 90 d after instillation of native quartz. Quartz-treated animals also showed enhanced immunostaining of nuclear factor-kappaB (NF-kappaB) in alveolar macrophages and lung epithelium, as well as reduced IkappaBalpha levels in whole lung homogenate. Both surface modifications were found to inhibit most of the effects as observed with native quartz. NF-kappaB activation was also observed in vitro in rat lung epithelial cells following treatment with lavage fluid from quartz-treated animals, as well as with conditioned medium of quartz-treated macrophages, and these effects appeared to be at least partly tumor necrosis factor-alpha-independent. In conclusion, the persistent subchronic inflammatory lung response after quartz exposure appears to be particle surface-driven and is associated with NF-kappaB activation in both alveolar macrophages and the lung epithelium.

The surface area rather than the surface coating determines the acute inflammatory response after instillation of fine and ultrafine TiO2 in the rat

Alterations in the hydrophobic status of particle surfaces have been suggested to modify the toxic properties of ultrafine TiO2. We investigated the acute inflammatory responses and cell damage after intratracheal instillation of surface modified (hydrophilic and hydrophobic) fine (180 nm) and ultrafine (20-30 nm) TiO2 particles 16 h at equivalent mass (1 or 6 mg) and surface doses (100, 500, 600 and 3000 cm2) in rats. Inflammatory response and most enzyme levels were significantly related to the administered surface dose. The hydrophobic surface of the TiO2 particles, achieved by methylation, induced a lower total cell number and influx of neutrophils (PMN) compared to rats instilled with the 1 mg of the untreated, fine or ultrafine TiO2 but the outcomes were not statistically significant. No differences were observed between fine/ultrafine and hydophilic/hydrophobic TiO2 at the high dose (6 mg) or surface dose over 600 cm2. The differences in BAL cellularity at the low dose were reflected in changes in the chemokine MIP-2, but no differences were seen in levels of macrophage cytokines. Considering the large influx of PMN little cell damage was seen when studying enzyme leakage in lavage fluid, although PMNs appeared to be activated as suggested by increased myeloperoxidase (MPO) activity in the lavage fluid. We conclude that the surface area rather than the hydrophobic surface determines the acute, pulmonary inflammation induced by both fine and ultrafine TiO2.

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.

Alpha-1-antitrypsin and a broad spectrum metalloprotease inhibitor, RS113456, have similar acute anti-inflammatory effects

There is increasing evidence that antiproteases are able to affect the inflammatory response. To further examine this question, we administered human alpha-1-antitrypsin (alpha1AT) or a synthetic metalloprotease inhibitor (RS113456) to C57 mice followed by a single intratracheal dose of quartz, a dust that evokes a marked, lasting, polymorphonuclear leukocyte (PMN) infiltrate. At 2 hours after dust administration, both antiproteases completely suppressed silica-induced PMN influx into the lung and macrophage inflammatory protein-2 (MIP-2)/monocyte chemotactic protein-1 (MCP-1) (neutrophil/macrophage chemoattractant) gene expression, partially suppressed nuclear transcription factor kappaB (NF-kappaB) translocation, and increased inhibitor of NF-kappaB (IkappaB) levels. By 24 hours, PMN influx and connective tissue breakdown measured as lavage desmosine or hydroxyproline were still at, or close to, control levels after antiprotease treatment, and increases in NF-kappaB translocation and MIP-2/MCP-1 gene expression were variably suppressed. At both time points, neither agent prevented silica-induced increases in amount of whole lung MIP-2 or MCP-1 protein, but both did prevent increases in whole lung intercellular adhesion molecule-1 (ICAM-1) at 24 hours. Inactivating the alpha1AT by oxidation to the point that it no longer possessed antiproteolytic properties did not affect its ability to suppress inflammation. Both antiproteases also prevented the silica-induced acute inflammatory response in mice with knocked out genes for macrophage metalloelastase (MME -/-), mice that develop inflammation, but not connective tissue breakdown, and the pattern of alpha1AT breakdown fragments was identical in control and MME -/- animals. These findings suggest that, in this model of acute PMN mediated inflammation, a serine protease inhibitor and a metalloprotease inhibitor have similar anti-inflammatory properties, that inflammation is not mediated by proteolysis with generation of chemotactic matrix fragments, and that classic antiproteolysis (complexing of protease to antiprotease) probably does not play a role in suppression of inflammation. The antiproteolytic effects of these agents do not seem to be mediated by protection of endogenous alpha1AT.