Reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation by silica in inflammation and fibrosis

Dextran sulfate sodium enhances interleukin-1 beta release via activation of p38 MAPK and ERK1/2 pathways in murine peritoneal macrophages

Interleukin (IL)-1 beta is a pro-inflammatory cytokine that has been shown to play a pivotal role in the onset of inflammatory bowel disease (IBD), however, the molecular mechanisms underlying the production of IL-1 beta in IBD are not fully understood. We investigated dextran sulfate sodium (DSS)-induced IL-1 beta production and caspase-1 activities in murine peritoneal macrophages (pM phi). Further, the activation status of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun NH(2)-terminal kinase (JNK1/2), as well as their upstream target kinases, were examined by Western blotting. In addition, mRNA expression was assessed by RT-PCR and CXC chemokine ligand 16 (CXCL16) protein was detected by immunocytochemistry. DSS-treated pM phi released IL-1 beta protein in a time-dependent manner without affecting mRNA levels during 3-24 h, and caspase-1 activity peaked at 5 min (29-fold). IL-1 beta release and caspase-1 activity induced by DSS were significantly inhibited by a MAPK kinase 1/2 inhibitor, a p38 MAPK inhibitor, and NAC, however, not by JNK1/2 or a protein kinase C inhibitor. In addition, DSS strikingly induced the phosphorylation of p38 MAPK and ERK1/2 within 2 and 10 min, respectively. DSS also induced intracellular generation of reactive oxygen species (ROS). Pre-treatment with anti-CXCL16 for 24 h, but not anti-scavenger receptor-A, anti-CD36, or anti-CD68 antibodies, significantly suppressed DSS-induced IL-1 beta production. Our results suggest that DSS triggers the release of IL-1 beta protein from murine pM phi at a post-translational level through binding with CXCL16, ROS generation, and resultant activation of both p38 MAPK and ERK1/2 pathways, and finally caspase-1 activation.

Cystic fibrosis and normal human airway epithelial cell response to influenza a viral infection

Viral infections produce severe respiratory morbidity in children with cystic fibrosis (CF). CF cells are more susceptible to virus in part because of impaired airway epithelial activation of signal transducer and activator of transcription 1 (Stat1). As Stat1 is a fundamental regulator of antiviral defenses, we hypothesized that there may be multiple alterations in the antiviral defense of CF epithelium compared with normal (NL). To obtain a comprehensive view of mucosal host responses to influenza and characterize the difference between CF and NL responses to influenza, gene expression profiles of primary human airway epithelial cells (HAEC) were evaluated using an interferon (IFN)-stimulated genes/AU/double-stranded RNA (dsRNA) microarray or quantitative real-time polymerase chain reaction (PCR) following influenza A infection. Gene expression was significantly modified by influenza in NL (228 genes) and CF (101 genes), with a similar pattern of gene response but with overall less numbers of responsive genes in CF (p < 0.05). Moreover, CF cells had less IFN-related antiviral gene induction at 24 h but greater inflammatory cytokine gene induction at 1 h after infection. Taken together, the lesser antiviral and greater early inflammatory response likely contribute to the severe respiratory illness of CF patients with viral infections.

Oxidative stress biology and cell injury during type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) affects approximately 170 million individuals worldwide and is expected to alter the lives of at least 366 million individuals within a future span of 25 years. Of even greater concern is the premise that these projections are underestimated since they assume obesity levels will remain constant. Type 1 insulin-dependent DM accounts for only 5-10 percent of all diabetics but represents a highly significant health concern, since this disorder begins early in life and leads to long-term complications. In contrast, Type 2 DM is recognized as the etiology of over 80 percent of all diabetics and is dramatically increasing in incidence as a result of changes in human behavior and increased body mass index. Yet, the pathological consequences of these disorders that involve the both the neuronal and vascular systems are intimately linked through the pathways that mediate oxidative stress. Here we highlight some of the relevant oxidative pathways that determine insulin resistance through reactive oxygen species, mitochondrial dysfunction, uncoupling proteins, and endoplasmic reticulum stress. These pathways are ultimately linked to protein kinase B (Akt) and the insulin signaling pathways that determine the initial onset of glucose intolerance and the subsequent course to apoptotic cell injury. Through the elucidation of these targets, improvement in current strategies as well as the development of future clinical applications can move forward for both the prevention and treatment of Type 1 and Type 2 DM.

Aggregated ursolic acid, a natural triterpenoid, induces IL-1beta release from murine peritoneal macrophages: role of CD36

IL-1beta has been shown to play a pivotal role in the development of inflammatory disorders. We recently found that a natural triterpene, ursolic acid (UA), enhanced MIF release from nonstimulated macrophages. In this study, we examined the effects of UA on the production of several cytokines in resident murine peritoneal macrophages (pMphi). UA increased the protein release of IL-1beta, IL-6, and MIF, but not of TNF-alpha, in dose- and time-dependent manners. This triterpene also strikingly induced the activation of p38 MAPK and ERK1/2 together with that of upstream kinases. The release of UA-induced IL-1beta was significantly inhibited by the inhibitors of p38 MAPK, MEK1/2, ATP-binding cassette transporter, and caspase-1. Furthermore, UA induced intracellular ROS generation for IL-1beta production, which was suppressed by an antioxidant. Pretreatment with an anti-CD36 Ab significantly suppressed IL-1beta release, and surface plasmon resonance assay results showed that UA bound to CD36 on macrophages. In addition, the amount of IL-1beta released from UA-treated pMphi of CD36-deficient mice was markedly lower than that from those of wild-type mice. Interestingly, UA was found to aggregate in culture medium, and the aggregates were suggested to be responsible for IL-1beta production. In addition, i.p. administration of UA increased the levels of IL-1beta secretion and MPO activity in colonic mucosa of ICR mice. Taken together, our results indicate that aggregated UA is recognized, in part, by CD36 on macrophages for generating ROS, thereby activating p38 MAPK, ERK1/2, and caspase-1, as well as releasing IL-1beta protein via the ATP-binding cassette transporter.

Radical oxygen species production induced by advanced oxidation protein products predicts clinical evolution and response to treatment in systemic sclerosis

OBJECTIVES

To investigate the role of reactive oxygen species (ROS) in the development of the various patterns of systemic sclerosis (SSc) and the mechanisms of ROS production by endothelial cells and fibroblasts.

METHODS

Production of hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and cellular proliferation were determined following incubation of endothelial cells and fibroblasts with 56 SSc and 30 healthy sera. Correlations were established between those markers, the type and the severity of the clinical involvements, and the response to treatment. The factors leading to ROS production were determined.

RESULTS

H(2)O(2) production by endothelial cells and fibroblasts was higher after incubation with SSc sera than with normal sera (p<0.001) and with sera from SSc patients with severe complications than sera from other patients (p<0.05). Sera from patients with lung fibrosis triggered the proliferation of fibroblasts more than other SSc sera (p<0.001), whereas sera from patients with vascular complications exerted no proliferative effect on fibroblasts, but inhibited endothelial cell growth (p<0.05) and induced NO overproduction (p<0.05). Bosentan reduced NO release by 32%, whereas N-acetylcystein potentiated 5-fluorouracil (5FU) to inhibit fibroblast proliferation by 78%. Those serum-mediated effects did not involve antibodies but advanced oxidation protein products that selectively triggered cells to produce H(2)O(2) or NO.

CONCLUSIONS

SSc sera induce the production of different types of ROS that selectively activate endothelial cells or fibroblasts, leading to vascular or fibrotic complications. Assaying serum-induced ROS production allows clinical activity of the disease to be followed and appropriate treatments to be selected.

Nitrotyrosine and protein carbonyls are equally distributed in HT22 cells after nitrosative stress

The generation of reactive oxygen and nitrogen species is an inevitable result of cellular metabolism and environmental influence. Such oxidation processes are always combined with the formation of various protein oxidation products. Environmental oxidants might either be activated inside the cell or act by themselves. Therefore, differences in the localization of oxidant formation might change the major compartment of oxidant action. Therefore, we employed NO donors (SNOC, DETA/NO, and Spe/NO) alone or in combination with the redox-cycling bipyridinium compound paraquat, the superoxide- and NO-releasing compound SIN-1, the relatively more lipophilic oxidants tert-butyl and cumene hydroperoxide, and peroxynitrite itself to test the ability of these compounds to generate oxidized and nitrated proteins in various cellular compartments. Combined treatment with oxidants and nitrating compounds led to the formation of protein carbonyls and nitrotyrosine with a severalfold higher concentration in the cytosol, compared to the nucleus. In fluorescence microscopy studies, the resulting protein modifications show a similar distribution of oxidized proteins and nitrotyrosine with highest concentrations in the perinuclear area. Studying the time- and concentration-dependent formation and degradation of protein carbonyls and nitrated proteins large similarities could be measured. Therefore, it can be concluded that formation, localization, and kinetics of protein carbonyl and nitrotyrosine formation parallel each other depending on the stress-inducing agent.

Nitric oxide in the pathogenesis of diffuse pulmonary fibrosis

By studying the responses of nitric oxide in pulmonary fibrosis, the role of inducible nitric oxide synthase in diffuse pulmonary fibrosis as caused by lipopolysaccharide (LPS) treatment was investigated. When compared to rats treated with LPS only, the rats pretreated with 1400W (an iNOS-specific inhibitor) were found to exhibit a reduced level in: (i) NOx (nitrate/nitrite) production, (ii) collagen type I protein expression, (iv) soluble collagen production, and (iv) the loss of body weight and carotid artery PO2. In the pulmonary fibroblast culture, exogenous NO from LPS-stimulated secretion by macrophages or from a NO donor, such as DETA NONOate, was observed to induce the expression of TIMP-1, HSP47, TGF-beta1, and collagen type I as well as the phosphorylation of SMAD-2. After inhalation of NO for 24 h, an up-regulation of collagen type I protein was also noted to occur in rat pulmonary tissue. The results suggest that the NO signal pathway enhanced the expression of TGF-beta1, TIMP-1, and HSP47 in pulmonary fibroblasts, which collectively demonstrate that the NO signal pathway could activate the SMAD-signal cascade, by initiating a rapid increase in TGF-beta1, thereby increasing the expression of TIMP-1 and HSP47 in pulmonary fibroblasts, and play an important role in pulmonary fibrosis.

Cytotoxicity and genotoxicity of ultrafine crystalline SiO2 particulate in cultured human lymphoblastoid cells

Respirable crystalline silica has been classified as a human lung carcinogen. Ultrafine (diameter < 100 nm) silica particles may be important in carcinogenesis, although the mechanisms remain unclear. In the present study, WIL2-NS cells were incubated for 6, 24, and 48 hr with 0, 30, 60, and 120 microg/ml ultrafine crystalline SiO(2) (UF-SiO(2)). The cytotoxic and genotoxic effects caused by UF-SiO(2) in cultured human cells were investigated via a set of bioassays. Significant dose- dependent decreases in percent cell viability were seen with increasing dose of UF-SiO(2) in the methyl tetrazolium assay. Significant decreases were seen at 120 microg/ml (58, 38, and 57% for 6, 24, and 48-hr exposure, respectively). During 4 days growth in the flasks, there was a slight recovery observed after washing off UF-SiO(2) as measured by the population growth assay. Significant dose-dependent reduction in the cytokinesis block proliferation index was observed by the cytokinesis block micronucleus assay. Treatment with 120 microg/ml UF-SiO(2) for 24 hr produced a fourfold increase in the frequency of micronucleated binucleated cells (MNBNC). The increase in MNBNC was dose-dependent. The lowest dose that gave a statistically significant increase in MNBNC was 30 microg/ml (24-hr treatment), which had cytotoxicity of less than 10%. There was no significant difference in DNA strand breakage as measured by the Comet assay. A significant increase in induced mutant frequency was found at 120 microg/ml as detected by the hypoxanthine guanine phosphoribosyltransferase mutation assay. The results indicate that UF-SiO(2) is cytotoxic and genotoxic in cultured human cells.

Cytokine responses of human lung cells (BEAS-2B) treated with micron-sized and nanoparticles of metal oxides compared to soil dusts

BACKGROUND

The induction of cytokines by airway cells in vitro has been widely used to assess the effects of ambient and occupational particles. This study measured cytotoxicity and the release of the proinflammatory cytokines IL-6 and IL-8 by human bronchial epithelial cells treated with manufactured nano- and micron-sized particles of Al2O3, CeO2, Fe2O3, NiO, SiO2, and TiO2, with soil-derived particles from fugitive dust sources, and with the positive controls LPS, TNF-alpha, and VOSO4.

RESULTS

The nano-sized particles were not consistently more potent than an equal mass of micron-sized particles of the same nominal composition for the induction of IL-6 and IL-8 secretion in the in vitro models used in this study. The manufactured pure oxides were much less potent than natural PM2.5 particles derived from soil dust, and the cells were highly responsive to the positive controls. The nano-sized particles in the media caused artifacts in the measurement of IL-6 by ELISA due to adsorption of the cytokine on the high-surface-area particles. The potency for inducing IL-6 secretion by BEAS-2B cells did not correlate with the generation of reactive oxygen species in cell-free media.

CONCLUSION

Direct comparisons of manufactured metal oxide nanoparticles and previously studied types of particles and surrogate proinflammatory agonists showed that the metal oxide particles have low potency to induce IL-6 secretion in BEAS-2B cells. Particle artifacts from non-biological effects need to be considered in experiments of this type, and the limitations inherent in cell culture studies must be considered when interpreting in vitro results. This study suggests that manufactured metal oxide nanoparticles are not highly toxic to lung cells compared to environmental particles.

Cytokine responses of human lung cells (BEAS-2B) treated with micron-sized and nanoparticles of metal oxides compared to soil dusts

BACKGROUND

The induction of cytokines by airway cells in vitro has been widely used to assess the effects of ambient and occupational particles. This study measured cytotoxicity and the release of the proinflammatory cytokines IL-6 and IL-8 by human bronchial epithelial cells treated with manufactured nano- and micron-sized particles of Al2O3, CeO2, Fe2O3, NiO, SiO2, and TiO2, with soil-derived particles from fugitive dust sources, and with the positive controls LPS, TNF-alpha, and VOSO4.

RESULTS

The nano-sized particles were not consistently more potent than an equal mass of micron-sized particles of the same nominal composition for the induction of IL-6 and IL-8 secretion in the in vitro models used in this study. The manufactured pure oxides were much less potent than natural PM2.5 particles derived from soil dust, and the cells were highly responsive to the positive controls. The nano-sized particles in the media caused artifacts in the measurement of IL-6 by ELISA due to adsorption of the cytokine on the high-surface-area particles. The potency for inducing IL-6 secretion by BEAS-2B cells did not correlate with the generation of reactive oxygen species in cell-free media.

CONCLUSION

Direct comparisons of manufactured metal oxide nanoparticles and previously studied types of particles and surrogate proinflammatory agonists showed that the metal oxide particles have low potency to induce IL-6 secretion in BEAS-2B cells. Particle artifacts from non-biological effects need to be considered in experiments of this type, and the limitations inherent in cell culture studies must be considered when interpreting in vitro results. This study suggests that manufactured metal oxide nanoparticles are not highly toxic to lung cells compared to environmental particles.

Association of silica exposure with anti-neutrophil cytoplasmic autoantibody small-vessel vasculitis: a population-based, case-control study

Anti-neutrophil cytoplasmic autoantibodies (ANCA) are associated with a category of small-vessel vasculitis (SVV) with frequent glomerulonephritis. The goal of this study was to evaluate the association of lifetime silica exposure with development of ANCA-SVV, with particular attention to exposure dosage, intensity, and time since last exposure. A southeastern United States, population-based, case-control study was conducted. Case patients had ANCA-SVV with pauci-immune crescentic glomerulonephritis. Population-based control subjects were frequency-matched to case patients by age, gender, and state. Jobs were assessed in a telephone interview. Silica exposure scores incorporated exposure duration, intensity, and probability for each job and then were categorized as none, low/medium, or high lifetime exposure. Logistic regression models were used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). Silica exposure was found in 78 (60%) of 129 case patients and in 49 (45%) of 109 control subjects. There was no increased risk for disease from low/medium exposure relative to no exposure (OR 1.0; 95% CI 0.4 to 2.2) but increased risk with high exposure (OR 1.9; 95% CI 1.0 to 3.5; P = 0.05). Crop harvesting was associated with elevated risk (OR 2.5; 95% CI 1.1 to 5.4; P = 0.03). However, both agricultural and traditional occupational sources contributed to the cumulative silica exposure scores; therefore, the overall effect could not be attributed to agricultural exposures alone. There was no evidence of decreasing by duration of time since last exposure. High lifetime silica exposure was associated with ANCA-SVV. Exposure to silica from specific farming tasks related to harvesting may be of particular importance in the southeastern United States. Interval of time since last exposure did not influence development of ANCA-SVV.

Effects of Gymnadenia conopsea alcohol extract on collagen synthesis in rat lungs exposed to silica and its mechanism of antioxidative stress

OBJECTIVE

To explore the effects of Gymnadenia conopsea alcohol extract (GcAE) on the collagen synthesis in rat lungs exposed to silica and the influence on antioxidase activities, level of lipid peroxidation (LPO).

METHODS

One hundred and twenty rats were randomly divided into control group, silica group, and GcAE-treated group. Silicotic animal models were established by direct tracheal instillation of silica into rat lungs surgically. From the second day of model establishment, rats in GcAE-treated group were orally given GcAE [8 g/(kg x d) corresponding to raw herb]. At 7, 14, 21, 28 and 60 days after establishment of the animal model, eight rats in each group were sacrificed, and samples were collected. The malondialdehyde (MDA) content, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in plasma were assayed by a spectrophotometer. Types I and III collagen were detected by Sirius red polarization and microscopy, and measuered by Image-Pro Plus Version 4.5 for Windows software.

RESULTS

GcAE could reduce the lung/body weight ratio of rats exposed to silica, the synthesis of types I and III collagen of the lungs and the level of lipid peroxidation, increase the activities of SOD and GPx.

CONCLUSION

GcAE can ameliorate the silica-induced pulmonary fibrosis by increasing the activities of antioxidase and alleviating the damage of lipid peroxidation to the lungs.

Cellular evaluation of the toxicity of combustion derived particulate matter: influence of particle grinding and washing on cellular response

There is increasing interest in continual monitoring of air for the presence of inhalation health hazards, such as particulate matter, produced through combustion of fossil fuels. Currently there are no means to rapidly evaluate the relative toxicity of materials or to reliably predict potential health impact due to the complexity of the composition, size, and physical properties of particulate matter. This research evaluates the feasibility of utilizing cell cultures as the biological recognition element of an inhalation health monitoring system. The response of rat lung type II epithelial (RLE-6TN) cells to a variety of combustion derived particulates and their components has been evaluated. The focus of the current work is an evaluation of how particles are delivered to a cellular sensing array and to what degree does washing or grinding of the particles impacts the cellular response. There were significant differences in the response of these lung cells to PM's of varying sources. Mechanical grinding or washing was found to alter the toxicity of some of these particulates; however these effects were strongly dependent on the fuel source. Washing reduced toxicity of oil PM's, but had little effect on those from diesel or coal. Mechanical grinding could significantly increase the toxicity of coal PM's, but not for oil or diesel.

Mechanistic insights into diabetes mellitus and oxidative stress

Diabetes mellitus (DM) is a significant healthcare concern worldwide that affects more than 165 million individuals leading to cardiovascular disease, nephropathy, retinopathy, and widespread disease of both the peripheral and central nervous systems. The incidence of undiagnosed diabetes, impaired glucose tolerance, and impaired fasting glucose levels raises future concerns in regards to the financial and patient care resources that will be necessary to care for patients with DM. Interestingly, disease of the nervous system can become one of the most debilitating complications and affect sensitive cognitive regions of the brain, such as the hippocampus that modulates memory function, resulting in significant functional impairment and dementia. Oxidative stress forms the foundation for the induction of multiple cellular pathways that can ultimately lead to both the onset and subsequent complications of DM. In particular, novel pathways that involve metabotropic receptor signaling, protein-tyrosine phosphatases, Wnt proteins, Akt, GSK-3beta, and forkhead transcription factors may be responsible for the onset and progression of complications form DM. Further knowledge acquired in understanding the complexity of DM and its ability to impair cellular systems throughout the body will foster new strategies for the treatment of DM and its complications.

Role of pyrite in formation of hydroxyl radicals in coal: possible implications for human health

BACKGROUND

The harmful effects from inhalation of coal dust are well-documented. The prevalence of lung disease varies by mining region and may, in part, be related to regional differences in the bioavailable iron content of the coal. Pyrite (FeS2), a common inorganic component in coal, has been shown to spontaneously form reactive oxygen species (ROS) (i.e., hydrogen peroxide and hydroxyl radicals) and degrade nucleic acids. This raises the question regarding the potential for similar reactivity from coal that contains pyrite. Experiments were performed to specifically evaluate the role of pyrite in coal dust reactivity. Coal samples containing various amounts of FeS2 were compared for differences in their generation of ROS and degradation of RNA.

RESULTS

Coals that contain iron also show the presence of FeS2, generate ROS and degrade RNA. Coal samples that do not contain pyrite do not produce ROS nor degrade RNA. The concentration of generated ROS and degradation rate of RNA both increase with greater FeS2 content in the coals.

CONCLUSION

The prevalence of coal workers' pneumoconiosis can be correlated to the amount of FeS2 in the coals. Considering the harmful effects of generation of ROS by inhaled particles, the results presented here show a possible mechanism whereby coal samples may contribute to CWP. This suggests that the toxicity of coal may be explained, in part, by the presence of FeS2.

Silica induces macrophage cytokines through phosphatidylcholine-specific phospholipase C with hydrogen peroxide

Silica particle-associated inflammation is implicated in the genesis of several pulmonary diseases, including silicosis and lung cancer. In this study we investigated the role of phosphatidylcholine-specific phospholipase C (PC-PLC) in silica-stimulated induction of TNF-alpha and IL-1beta and how PC-PLC activity is regulated by silica in a rat alveolar macrophage model. We demonstrated that inhibition of PC-PLC, which was achieved with tricychodecan-9-yl-xanthate (D609), blocked the silica-stimulated induction of TNF-alpha and IL-1beta in alveolar macrophage, suggesting that PC-PLC is involved in the silica-associated inflammatory response. PC-PLC activity was increased significantly by silica exposure, and this could be inhibited by MnTBAP, which catalyzes both the dismutation of O2.- to O2 and H2O2 and the dismutation of H2O2 to O2 and H2O, revealing that PC-PLC activity is regulated in a redox-dependent manner. This is further confirmed by the finding that PC-PLC activity was increased by exogenous H2O2. The intracellular calcium chelator BAPTA blocked the H2O2-increased PC-PLC activity, while the calcium ionophore, A23187, enhanced PC-PLC activity. The data indicate that PC-PLC plays critical roles in the silica-associated inflammatory response and that PC-PLC is regulated through redox- and calcium-dependent manners in alveolar macrophages.

In vitro toxicity of silica nanoparticles in human lung cancer cells

The cytotoxicity of 15-nm and 46-nm silica nanoparticles was investigated by using crystalline silica (Min-U-Sil 5) as a positive control in cultured human bronchoalveolar carcinoma-derived cells. Exposure to 15-nm or 46-nm SiO(2) nanoparticles for 48 h at dosage levels between 10 and 100 microg/ml decreased cell viability in a dose-dependent manner. Both SiO(2) nanoparticles were more cytotoxic than Min-U-Sil 5; however, the cytotoxicities of 15-nm and 46-nm silica nanoparticles were not significantly different. The 15-nm SiO(2) nanoparticles were used to determine time-dependent cytotoxicity and oxidative stress responses. Cell viability decreased significantly as a function of both nanoparticle dosage (10-100 microg/ml) and exposure time (24 h, 48 h, and 72 h). Indicators of oxidative stress and cytotoxicity, including total reactive oxygen species (ROS), glutathione, malondialdehyde, and lactate dehydrogenase, were quantitatively assessed. Exposure to SiO(2) nanoparticles increased ROS levels and reduced glutathione levels. The increased production of malondialdehyde and lactate dehydrogenase release from the cells indicated lipid peroxidation and membrane damage. In summary, exposure to SiO(2) nanoparticles results in a dose-dependent cytotoxicity in cultural human bronchoalveolar carcinoma-derived cells that is closely correlated to increased oxidative stress.

Physiopathologie de la sclérodermie systémique: état des lieux sur une affection aux multiples facettes

Systemic sclerosis is a rare disease characterized by vascular hyperreactivity and collagen deposition. Endothelial cell, fibroblast and lymphocyte abnormalities have been reported in systemic sclerosis. Fibroblast dysfunction is characterized by uncontrolled activation of the transforming growth factor-beta (TGF-beta) pathway and excess synthesis of both connective tissue growth factor (CTGF) and free radicals. These promote the accumulation of extracellular matrix. Endothelial cells produce excess quantities of endothelin 1 and inducible NO synthase. They also undergo early apoptosis. Oxidative stress appears to play a major role in disease progression. Increased levels of interleukin 4, a profibrotic cytokine, have been detected in plasma and skin of systemic sclerosis patients. Autoantibodies are detectable in the serum of almost all systemic sclerosis patients. Some are directed against well-identified ubiquitous nuclear proteins and have no demonstrated pathogenic role. Other autoantibodies bind to endothelial cells or fibroblasts and may have a pathogenic role.

Effects of nitric oxide synthase inhibitor omega-nitro-L-arginine methyl ester, on silica-induced inflammatory reaction and apoptosis

Background

Although nitric oxide is overproduced by macrophages and neutrophils after exposure to silica, its role in silica-induced inflammatory reaction and apoptosis needs further clarification. In this study, rats were intratracheally instilled with either silica suspension or saline to examine inflammatory reactions and intraperitoneally injected with ω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthases, or saline to examine the possible role of nitric oxide production in the reaction.

Results

Results showed that silica instillation induced a strong inflammatory reaction indicated by increased total cell number, number of neutrophils, protein concentration and lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF). There were no significant differences in these indices between silica-instilled groups with and without L-NAME injection (p > 0.05) except LDH level. The results also showed that apoptotic leucocytes were identified in BALF cells of silica-instilled groups whereas no significant difference was found between silica-instilled groups with and without L-NAME injection in the apoptotic reaction (p > 0.05). Silica instillation significantly increased the level of BALF nitrite/nitrate and L-NAME injection reduced this increase.

Conclusion

Intratracheal instillation of silica caused an obvious inflammatory reaction and leucocyte apoptosis, but these reactions were not influenced by intraperitoneal injection of L-NAME and reduced production of NO. This supports the possibility that silica-induced lung inflammation and BALF cell apoptosis are via NO-independent mechanisms.

Comparative eco-toxicity of nanoscale TiO2, SiO2, and ZnO water suspensions

The potential eco-toxicity of nanosized titanium dioxide (TiO(2)), silicon dioxide (SiO(2)), and zinc oxide (ZnO) water suspensions was investigated using Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as test organisms. These three photosensitive nanomaterials were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO(2) to TiO(2) to ZnO, and B. subtilis was most susceptible to their effects. Advertised nanoparticle size did not correspond to true particle size. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. The presence of light was a significant factor under most conditions tested, presumably due to its role in promoting generation of reactive oxygen species (ROS). However, bacterial growth inhibition was also observed under dark conditions, indicating that undetermined mechanisms additional to photocatalytic ROS production were responsible for toxicity. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management.

Cysteine cathepsins and caspases in silicosis

Silicosis is an occupational pneumoconiosis caused by inhalation of crystalline silica. It leads to the formation of fibrohyalin nodes that result in progressive fibrosis. Alternatively, emphysema may occur, with abnormal destruction of collagen fibres in the advanced stages. Although the pathophysiological mechanisms remain unclear, it has been established that the lung responds to silica by massive enrollment of alveolar macrophages, triggering an inflammatory cascade of reactions. An imbalance in the expression of lung proteases and their inhibitors is implicated in extracellular matrix remodelling and basement membrane disruption. Moreover, exposure to silica can initiate apoptotic cell death of macrophages. This review summarises the current knowledge on cysteine cathepsins that have been ignored so far during silicosis and outlines the recent progress on cellular pathways leading to silica-induced caspase activation, which have been partly delineated.

MARCO mediates silica uptake and toxicity in alveolar macrophages from C57BL/6 mice

Scavenger receptors (SR), on the surface of the macrophage, appear to be responsible for silica uptake and cell death signaling in the macrophage. The purpose of this study was to isolate which SRs (macrophage receptor with collagenous structure (MARCO), CD204, or CD36) were involved using a variety of SR single and double null mice. The findings indicated that MARCO was the critical SR involved in silica uptake and cytotoxicity in the primary alveolar macrophages (AM) from C57BL/6 mice, as there was no particle uptake or cell death in the absence of this SR. The level of MARCO expression on AM changed significantly with the absence of other SR, and silica uptake was proportional to cell surface MARCO expression. In addition, silica uptake and cytotoxicity were completely blocked by an anti-mouse MARCO antibody. Transfection of Chinese hamster ovary cells with human MARCO supported these conclusions, as silica particles bound to and initiated apoptosis in the MARCO-transfected cells. Strain differences with regard to SR distribution were also examined. There was a differential expression of these SR on AM from each strain, with MARCO dominant for C57BL/6, CD36 dominant on BALB/c, and all three SR expressed on 129/SvJ mice. Similar to the results with C57BL/6 AM, MARCO was involved with silica-induced cell death in the 129/SvJ strain. In contrast, BALB/c AM used an unidentified mechanism for silica uptake because the SR antibodies failed to block particle internalization. Taken together, these results indicate MARCO is the primary AM receptor interacting with silica, depending on mouse strain and level of constitutive expression.

Preventing or reducing late side effects of radiation therapy: radiobiology meets molecular pathology

Radiation therapy has curative or palliative potential in roughly half of all incident solid tumours, and offers organ and function preservation in most cases. Unfortunately, early and late toxicity limits the deliverable intensity of radiotherapy, and might affect the long-term health-related quality of life of the patient. Recent progress in molecular pathology and normal-tissue radiobiology has improved the mechanistic understanding of late normal-tissue effects and shifted the focus from initial-damage induction to damage recognition and tissue remodelling. This stimulates research into new pharmacological strategies for preventing or reducing the side effects of radiation therapy.

Toxicological assessment of ambient and traffic-related particulate matter: a review of recent studies

Particulate air pollution (PM) is an important environmental health risk factor for many different diseases. This is indicated by numerous epidemiological studies on associations between PM exposure and occurrence of acute respiratory infections, lung cancer and chronic respiratory and cardiovascular diseases. The biological mechanisms behind these associations are not fully understood, but the results of in vitro toxicological research have shown that PM induces several types of adverse cellular effects, including cytotoxicity, mutagenicity, DNA damage and stimulation of proinflammatory cytokine production. Because traffic is an important source of PM emission, it seems obvious that traffic intensity has an important impact on both quantitative and qualitative aspects of ambient PM, including its chemical, physical and toxicological characteristics. In this review, the results are summarized of the most recent studies investigating physical and chemical characteristics of ambient and traffic-related PM in relation to its toxicological activity. This evaluation shows that, in general, the smaller PM size fractions (<PM(10)) have the highest toxicity, contain higher concentrations of extractable organic matter (comprising a wide spectrum of chemical substances), and possess a relatively high radical-generating capacity. Also, associations between chemical characteristics and PM toxicity tend to be stronger for the smaller PM size fractions. Most importantly, traffic intensity does not always explain local differences in PM toxicity, and these differences are not necessarily related to PM mass concentrations. This implies that PM regulatory strategies should take PM-size fractions smaller than PM(10) into account. Therefore, future research should aim at establishing the relationship between toxicity of these smaller fractions in relation to their specific sources.

Expression of heme oxygenase-1 in the lungs of rats exposed to crystalline silica

Oxidative stress is thought to be the pathogenesis of pulmonary fibrosis induced by particles, and heme oxygenase-1 (HO-1) protects lung tissue against oxidative stress. We hypothesized that HO-1 is also associated with oxidative lung injury caused by exposure to particles. The present study was conducted to investigate the time course of HO-1 expression of lungs exposed to crystalline silica in vivo. Male Wistar rats were administered 1 mg or 2 mg of crystalline silica suspended in saline by a single intratracheal instillation and were sacrificed at 3 d, 1 wk, 1 month, 3 months and 6 months of recovery time. The expression of HO-1 was observed by western blot analysis and immunostaining. Protein levels of HO-1 were increased compared to the controls at 3 d, and from 1 month to 6 months following intratracheal instillation of 2 mg of crystalline silica. The levels of HO-1 were increased compared to the controls from 1 month to 6 months following intratracheal instillation of 1 mg of crystalline silica. Many HO-1 positive cells were found particularly in the alveolar macrophages during immunostaining. These findings suggest that HO-1 is related to lung injury arising from exposure to crystalline silica.

Silica-directed mast cell activation is enhanced by scavenger receptors

Inhalation of crystalline silica results in pulmonary fibrosis and silicosis. It has been suggested that mast cells play a role in these conditions. How mast cells would influence pathology is unknown. We thus explored mast cell interactions with silica in vitro and in B6.Cg-kit(W-sh) mast cell-deficient mice. B6.Cg-kit(W-sh) mice did not develop inflammation or significant collagen deposition after instillation of silica, while C57Bl/6 wild-type mice did have these findings. Given this supporting evidence of a role for mast cells in the development of silicosis, we examined the ability of silica to activate mouse bone marrow-derived mast cells (BMMC), including degranulation (beta-hexosaminidase release); production of reactive oxygen species (ROS) and inflammatory mediators; and the effects of silica on Fc epsilon RI-dependent activation. Silica did not induce mast cell degranulation. However, TNF-alpha, IL-13, monocyte chemotactic protein-1, protease activity, and production of ROS were dose-dependently increased after silica exposure, and production was enhanced after Fc epsilon RI stimulation. This mast cell activation was inhibited by anti-inflammatory compounds. As silica mediates some effects in macrophages through scavenger receptors (SRs), we first determined that mast cells express scavenger receptors; then explored the involvement of SR-A and macrophage receptor with colleagenous structure (MARCO). Silica-induced ROS formation, apoptosis, and TNF-alpha production were reduced in BMMC obtained from SR-A, MARCO, and SR-A/MARCO knockout mice. These findings demonstrate that silica directs mast cell production of inflammatory mediators, in part through SRs, providing insight into critical events in the pathogenesis and potential therapeutic targets in silicosis.

Oxidative stress employs phosphatidyl inositol 3-kinase and ERK signalling pathways to activate cAMP phosphodiesterase-4D3 (PDE4D3) through multi-site phosphorylation at Ser239 and Ser579

RAW macrophages, which express the PDE4D3 and PDE4D5 cAMP phosphodiesterase isoforms, exhibited increased PDE4 activity when challenged with H2O2 in a fashion that was negated by treatment with the cell permeant antioxidant, N-acetyl cysteine and by diphenyleneiodonium chloride, an inhibitor of NADPH oxidase. In Cos1 cells transfected to express PDE4D3, challenge with H2O2 caused a rapid increase in both the activity and phosphorylation of PDE4D3. Lysates from H2O2-treated COS cells caused the phosphorylation of purified, recombinant PDE4D3 at two sites. One was the established ERK phosphorylation site at Ser579, located at the extreme C-terminus of the catalytic unit, and the other was a novel site at Ser239, located at the extreme N-terminus of the catalytic unit. Double Ser239Ala:Ser579Ala mutation of PDE4D3 prevented its H2O2-dependent phosphorylation both in vitro and in intact COS cells. Phosphorylation of PDE4D3 at Ser579 was ablated by treating COS cells with the MEK inhibitor, PD98059, which also negated activation. The activity of the Ser239Ala:Ser579Ala double mutant, and the Ser579Ala single PDE4D3 mutant was unaffected by H2O2 challenge of COS cells, whilst the Ser239Ala mutant was inhibited. Wortmannin inhibited the H2O2-dependent phosphorylation of PDE4D3 in COS cells by around 50%, whilst it fully ablated phosphorylation at Ser239 as well as ablating activation of PDE4D3. Neither immunodepletion of p70S6 kinase nor siRNA-mediated knockdown of mTor inhibited the H2O2-dependent phosphorylation of PDE4D3 at Ser239. Activation of PDE4D3 by challenge with H2O2 was not additive with activation through protein kinase A (PKA)-mediated phosphorylation of PDE4D3. Challenge with H2O2 did not alter PKA-mediated phosphorylation of PDE4D3 at Ser54. H2O2 dependent phosphorylation of PDE4D3, at Ser239 and Ser579, did not alter the sensitivity of PDE4D3 to inhibition by the selective PDE4 inhibitor, rolipram. An unknown protein kinase acting downstream of phosphatidyl inositol 3-kinase phosphorylates PDE4D3 at Ser239. This switches the effect of phosphorylation by ERK at Ser579 from inhibition to activation. We propose that phosphorylation at Ser239 attenuates interaction between either UCR2 or the UCR1/UCR2 module and the PDE4 catalytic unit so as to re-programme the functional outcome effect of phosphorylation by ERK. We identify a novel process through which reactive oxygen species activate long PDE4 isoforms so as to reduce cAMP levels and thereby promote inflammatory responses.

Iron release and ROS generation from mineral particles are not related to cytokine release or apoptosis in exposed A549 cells

The generation of reactive oxygen species (ROS) by mineral particles is believed to be central to their toxicity and their ability to induce inflammation. Surface bound or soluble iron may contribute to the particle-effects by enhancing the ROS generation through the Fenton reaction. Nevertheless, the importance of ROS and transition metals to mineral particle-induced effects is still unclear and further investigations are needed. In the present study we have investigated different mineral particles for their total iron content, amount of soluble iron at pH 7.0 and 4.0, their ability to generate ROS in a cell-free environment, and their ability to induce cytokine release and apoptosis in a human alveolar epithelial cell line (A549). All the investigated parameters varied considerably between the different particles, with the exception of ability to induce apoptosis. Total iron content did not reflect the amount of soluble iron, and neither total nor soluble iron was correlated with ROS generation. Moreover, iron content and ROS was not correlated with the ability of particles to induce cytokine release or apoptosis. The present results suggest that there is no clear relationship between the particles iron content and ability to generate ROS. Moreover, neither iron content nor the ability to induce ROS generation appears to be a prerequisite for the inflammatory potential or cytotoxicity of mineral particles.

NKG2D ligands are expressed on stressed human airway epithelial cells

Immune surveillance of the airways is critical to maintain the integrity and health of the lung. We have identified a family of ligands expressed on the surface of stressed airway epithelial cells whose function is to bind the NKG2D-activating receptor found on several pulmonary lymphocytes, including natural killer cells, γδ+ T cells, and CD8+ T cells. We employed real-time PCR and flow cytometry in normal and transformed airway epithelial cell to demonstrate that major histocompatibility complex class I chain-related (MIC) B and the UL-16 binding protein (ULBP) ligands (ULBP1–4) are ubiquitously expressed at the mRNA level in all cell lines. MICA/B surface expression was present on 70% of transformed cell lines but was undetectable on primary cells. We demonstrate that MICA/B and ULBP 1, 2, 3, and 4 expression is rare or absent on the cell surface of unstimulated normal human bronchial epithelial cells although transcripts and intracellular proteins are present. Normal human bronchial epithelial cells exposed to 0.3 mM hydrogen peroxide exhibit an induction of all ligands examined on the cell surface. Surface expression is independent of changes in transcript level or total cellular protein and is mediated by the ERK family of mitogen-activated protein kinases. The induction of NKG2D ligands on stressed airway epithelial cells represents a potentially important mechanism of immune cell activation in regulation of pulmonary health and disease.

Heme oxygenase-1, a potential biomarker of chronic silicosis, attenuates silica-induced lung injury

RATIONALE

Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, has antioxidative, antiapoptotic, and antiinflammatory activities. We examined whether HO-1 might be involved in silicosis.

OBJECTIVES

To investigate whether HO-1 can reduce silicosis in mice and humans.

METHODS AND MEASUREMENTS

Silicosis was studied using a murine model, and in 46 male patients. Serum HO-1 and 8-hydroxydeoxyguanosine (a marker of oxidative stress) were measured by enzyme-linked immunosorbent assay. Levels of HO-1 were measured by immunohistochemistry and immunoblotting.

MAIN RESULTS

Serum HO-1 levels were significantly elevated in patients with silicosis compared with age-matched control subjects or patients with chronic obstructive pulmonary disease. Serum HO-1 levels also correlated inversely with serum 8-hydroxydeoxyguanosine levels and positively with vital capacity and forced expiratory volume in one second in patients with silicosis. HO-1 was present in the lungs of humans and mice with silicosis, especially at sites of silica particle deposition. In mice, silica exposure was associated with acute leukocyte infiltration, leading to development of silicotic lung lesions. The inflammation was suppressed by treatment with hemin, an inducer of HO-1, and enhanced by zinc protoporphyrin, an inhibitor of HO-1.

CONCLUSIONS

Pulmonary HO-1 expression is increased in silicosis. HO-1 suppresses reactive oxygen species activity, and subsequent pathologic changes, thereby attenuating disease progression.

Guanine nitration in idiopathic pulmonary fibrosis and its implication for carcinogenesis

RATIONALE

Nitric oxide (NO)-induced nitrative stress of nucleic acids, as evidenced by guanine nitration, appears to be involved in inflammation-induced carcinogenesis. A high incidence of lung cancer in idiopathic pulmonary fibrosis (IPF) is the major reason for poor prognosis in patients with IPF.

OBJECTIVES AND METHODS

We immunohistochemically analyzed the formation and localization of 8-nitroguanine in lung tissues from control subjects, patients with IPF, and patients with lung cancer.

MAIN RESULTS

Immunohistochemical analysis of control smoker and nonsmoker lungs showed weak immunoreactivity for 8-nitroguanine, mainly in cytoplasm of bronchial epithelial cells. In addition to the bronchial epithelial cells, metaplastic regenerated epithelial cells overlying dense fibrotic lesions in IPF showed strong 8-nitroguanine staining in the cytoplasm. The staining in these metaplastic cells colocalized with staining of inducible and endothelial NO synthases and 8-oxodeoxyguanosine, as evidenced by double-immunostaining analysis. Confocal and immunoelectron microscopy revealed localization of 8-nitroguanine in metaplastic epithelial cytoplasm, mostly in mitochondria. Appreciable 8-nitroguanine immunostaining was also observed in both nuclei and cytoplasm of malignant epithelial cells in squamous cell carcinoma. No significant difference was found in the epithelial 8-nitroguanine formation between control smokers and nonsmokers, but much higher guanine nitration was observed in patients with IPF than in control subjects and patients with lung cancer, via a quantitative immunofluorescence image analysis.

CONCLUSIONS

The present study indicates that not only oxidative stress but also nitrative stress induced by NO may participate in the pathogenesis of epithelial cell damage and aberrant regeneration occurring in IPF. Thus, guanine nitration may be a major risk factor for lung cancer development in IPF.

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

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

Increased oxidative stress and oxidative damage associated with chronic bacterial prostatitis

AIM

To investigate whether chronic bacterial prostatitis might increase oxidative stress and oxidative damage in chronic bacterial prostatitis patients (CBPP), and to explore its possible mechanism.

METHODS

Enrolled in a case-control study were 70 randomly sampled CBPP and 70 randomly sampled healthy adult volunteers (HAV), on whom plasma nitric oxide (NO), vitamin C (VC), vitamin E (VE) and beta-carotene (beta-CAR) level, erythrocyte malondialdehyde (MDA) level, as well as erythrocyte superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activities were determined by spectrophotometry.

RESULTS

Compared with the HAV group, values of plasma NO and erythrocyte MDA in the CBPP group were significantly increased (P < 0.001); those of plasma VC, VE and beta-CAR as well as erythrocyte SOD, CAT and GPX activities in the CBPP group were significantly decreased (P < 0.001). Findings from partial correlation for the 70 CBPP showed that with prolonged course of disease, values of NO and MDA were gradually increased (P < 0.001), and those of VC, VE, beta-CAR, SOD, CAT and GPX were gradually decreased (P < 0.05-0.001). The findings from stepwise regression for the 70 CBPP suggested that the model was Y = -13.2077 + 0.1894MDA + 0.0415NO - 0.1999GPX, F = 18.2047, P < 0.001, r = 0.6729, P < 0.001.

CONCLUSION

The findings suggest that there exist increased oxidative stress and oxidative damage induced by chronic bacterial prostatitis in the patients, and such phenomenon was closely related to the course of disease.

Using yeast RNA as a probe for generation of hydroxyl radicals by earth materials

Inhalation of certain types of particulate matter can lead to lung disease. The reactivity of these particles and, in part, the pathologic responses that result are dictated by their physicochemical properties. The ability of particles to induce the generation of reactive oxygen species (ROS), especially hydroxyl radicals in vivo, is one property that has been correlated to the development of lung disease. Several minerals, such as quartz and asbestos, are known to generate hydroxyl radicals and cause lung disease, but many other minerals have never been tested. Here, we describe a technique employing yeast RNA as a probe to screen for mineral-generated hydroxyl radicals. The stability of RNA in the presence of hydrogen peroxide, ferrous iron, hydroxyl radicals, and several common minerals (quartz, albite, forsterite, fayalite, hematite, magnetite, coal, and pyrite) was examined. 3'-(p-Aminophenyl) fluorescein (APF) was used to verify mineral generation of ROS. RNA is stable in the presence of hydrogen peroxide, quartz, and albite; while it degrades in the presence of ferrous iron, hydroxyl radicals, and the other minerals. Coal and pyrite are the most reactive both in RNA degradation and hydroxyl radical generation. This noncellular technique provides a straightforward way to compare many different particles simultaneously. Those particles showing reactivity toward RNA using this method are high-priority candidates for further in vitro and possibly in vivo tests.

Reactivity of carbon nanotubes: free radical generation or scavenging activity?

Carbon nanotubes (CNTs) currently attract intense research efforts because of their unique properties which make them suitable for many industrial applications. When inhaled, CNTs constitute a possible hazard to human health. Several studies have shown that when instilled in the lung of experimental animals, CNTs induced an inflammatory and fibrotic response similar to that caused by other toxic particles which might be the result of oxidative stress caused by particle- and/or cell-derived free radicals. There is, however, no direct experimental evidence of a capacity of carbon nanotubes to generate directly free radicals. Here we report that multiwall carbon nanotubes (MWCNT) in aqueous suspension do not generate oxygen or carbon-centered free radicals in the presence of H2O2 or formate, respectively, as detected with the spin-trapping technique. Conversely, we observed that, when in contact with an external source of hydroxyl or superoxide radicals, MWCNT exhibit a remarkable radical scavenging capacity. It is therefore possible that the inflammatory reaction reported in vivo must be ascribed to MWCNT features other than particle-derived free radical generation.

Surface Reactivity, Cytotoxic, and Morphological Transforming Effects of Diatomaceous Earth Products in Syrian Hamster Embryo Cells

In order to evaluate the effect of thermal treatments on the surface reactivity and carcinogenic potential of diatomaceous earth (DE) products, the physicochemical features of some specimens--derived by heating the same original material--were compared with their cytotoxic and transforming potency. The samples were an untreated DE (amorphous) progressively heated in the laboratory at 900 degrees C (DE 900) and 1200 degrees C (DE 1200) and a commercial product manufactured from the same DE (Chd) from which the finer fraction (< 10-microm diameter) was separated (Chd-F). Quartz (Min-U-Sil 5) and a vitreous silica (amorphous) smoothed up with hydrofluoric acid and were used as positive and negative controls, respectively. All samples were analyzed for their degree of crystallization, for their ability to release free radicals and reactive oxygen species, and for their cytotoxic and transforming potencies in Syrian hamster embryo (SHE) cells. X-ray diffractometry showed that DE 900, like DE, was still amorphous, whereas DE 1200 as well as the commercial product (Chd) were partially crystallized into cristobalite. The ability of the dust to release hydroxyl (*OH) radicals in the presence of hydrogen peroxide, as revealed by the spin-trapping technique, was as follows: Chd-F, DE 1200 > Chd > DE 900 > DE, suggesting that on heating, the surface acquires a higher potential for free radical release. Most of the silica samples generated COO* radicals from the formate ion, following homolytic rupture of the carbon-hydrogen bond, in the presence of ascorbic acid. A concentration-dependent decrease in cell proliferation and colony-forming efficiency was observed in SHE cultures treated with Chd-F, Chd, and DE. Heating abolished DE cytotoxicity but conferred a transforming ability to thermal treated particles. DE was the only sample that did not induce morphological transformation of cells. According to their transformation capacity, the samples were classified as follows: Chd-F > Chd, DE 1200 > DE 900 >> DE. Taken together, the reported results suggest that (1) the transforming potential of a biogenic amorphous silica is related to the thermal treatment that transforms the original structure in cristobalite and generates surface active sites; (2) the reactivity of samples in releasing *OH radicals correlates to their transforming ability; (3) the finer fraction of the commercial product is significantly more toxic and transforming than the coarse dust; and (4) opposite to silica dusts of mineral origin, which loose both cytotoxicity and transforming ability upon heating, heated diatomite acquires a cell-transforming potency. DE products should be thus considered a set apart of silica-based potentially toxic materials.

Exposure in vivo to silica or lipopolysaccharide produces transient or sustained upregulation, respectively, of PYPAF7 and MEFV genes in bronchoalveolar lavage cells in rats

A family of proteins containing PAAD [for PYRIN, AIM (absent in melanoma), apoptosis-associated protein speck-like protein containing a caspase recruitment domain, and death domain] domain was found to be involved in modulating inflammatory responses, by its ability to regulate nuclear factor (NF)-kappaB and procaspase-1 activation. In this study, intratracheal instillation of silica in rats was found to produce transient upregulation of mRNA levels of the PAAD family of proteins, PYPAF7 (PYRIN containing Apaf1-like protein; Apaf stands for apoptosis activating factor) and MEFV (for Mediterranean fever), in bronchoalveolar lavage (BAL) cells. The levels were markedly elevated at 4 h, returning to basal levels by 24 h. In contrast, intratracheal instillation of LPS produced a sustained upregulation of the two genes in BAL cells. In vitro exposure of BAL cells to silica or lipopolysaccharide (LPS) produced no changes in the expression of these genes, indicating that silica or LPS exposure in vivo induces some factors that are responsible for the upregulation of PYPAF7 and MEFV. The mRNA levels of these two genes in peripheral blood monocytes and PMN following LPS exposure did not change, indicating that AM and peripheral blood cells show similar response to LPS exposure in vitro. This study provides the basis for a physiological model to study the effects of these two genes in modulating the inflammatory response after particle exposure.

Impaired Progression of Cerebral Aneurysms in Interleukin-1β–Deficient Mice

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage caused by cerebral aneurysm rupture remains a life-threatening emergency despite advances in treatment. However, the mechanisms underlying aneurysm initiation, progression, and rupture remain unclear. We developed a method to induce experimental cerebral aneurysms in rats, monkeys, and mice. Interleukin-1beta (IL-1beta) is a key inflammatory mediator, and it is thought to be a promising target for the treatment of inflammatory diseases. In the present study, we examined the role of IL-1beta in cerebral aneurysm development.

METHODS

Cerebral aneurysms were experimentally induced in 5-week-old male C57BL/6 mice, IL-1beta gene-deficient (IL-1beta-/-) mice, and age-matched control B10 mice (wild-type). Their cerebral arteries were dissected and examined histologically and immunohistochemically.

RESULTS

IL-1beta was expressed in vascular media in mice at an early stage of aneurysmal models' cerebral arteries. No differences were seen in the rate of aneurysm development between IL-1beta-/- and wild-type mice, but the percentage of advanced aneurysm change was significantly larger in wild-type animals. Furthermore, in IL-1beta-/- mice, increased caspase-1 expression was seen compared with wild-type animals. Additionally, the number of apoptotic cells assessed by single-stranded DNA immunoreactivity and TUNEL was significantly reduced in IL-1beta-/- mice compared with wild-type animals.

CONCLUSIONS

IL-1beta is important for the progression of cerebral aneurysms in a mouse model. Disruption of the IL-1beta gene results in the reduced incidence of mature experimental cerebral aneurysms.

Relationship between radical generation by urban ambient particulate matter and pulmonary function of school children

The mechanisms by which particulate matter (PM) produces adverse effects on the respiratory system, such as pulmonary dysfunction in children, are largely unknown. However, oxidative stress is thought to play an important role. Various chemical compounds in ambient particulate matter, including transition metals and aromatic organic compounds, may contribute to adverse effects through intrinsic generation of reactive oxygen species (ROS). It was hypothesized that ROS generation by PM, as determined through electron spin resonance (ESR) spectroscopy, may be negatively associated with pulmonary function in school children. PM(2.5), PM(10), and total suspended particulates (TSP) were sampled at the playgrounds of six elementary schools in the city of Maastricht, the Netherlands. All children (8-13 yr) from the six schools were asked to undergo spirometry. Multivariate linear regression models were constructed to evaluate associations between oxygen radical formation by PM and lung function. The radical-generating capacity per microgram PM correlated negatively to forced expiratory volume in 1 s (FEV(1)) and forced expiratory flow at 50% (FEF(50%)) of forced vital capacity (FVC). The data indicate that chemical features that contribute to intrinsic generation of ROS may be relevant for PM risk assessment.

A Novel Mechanism of Action of Methyl-2-cyano-3,12 Dioxoolean-1,9 Diene-28-oate: Direct Permeabilization of the Inner Mitochondrial Membrane to Inhibit Electron Transport and Induce Apoptosis

Methyl-2-cyano-3,12 dioxoolean-1,9 diene-28-oate (CDDO-Me) is a synthetic oleanolic acid derivative that displays antitumorigenic and anti-inflammatory activities, and we have previously reported that this agent potently activates the intrinsic apoptotic pathway in leukemia cells. In this study, we demonstrate that mitochondrial dysfunction induced by CDDO-Me is mediated by direct permeabilization of the inner mitochondrial membrane, which results in the rapid depletion of mitochondrial glutathione (GSXm), loss of cardiolipin, and inhibition of mitochondrial respiration. More importantly, we demonstrate that in addition to activating the intrinsic apoptotic pathway, the mitochondrial effects of CDDO-Me may mediate its anti-inflammatory activity by modulating the generation of superoxide anion (O2*). It is noteworthy that CDDO-Me did not increase the generation of O2* and pretreatment of leukemia cells with CDDO-Me prevented the increase of this reactive oxygen species elicited by inhibition of complex I or III in the absence of de novo protein synthesis. CDDO-Me, but not other inhibitors of respiration, induced a time- and dose-dependent, cyclosporin A-independent permeability transition (PT) of isolated mitochondria that was sensitive to sulfhydryl antioxidants but not to EDTA. PT induced by CDDO-Me and Ca2+ was accompanied by loss of GSXm, suggesting that the increased permeability of the inner mitochondrial membrane facilitates the loss of this antioxidant. Finally, transmission electron microscopy revealed that CDDO-Me rapidly induced caspase-independent mitochondrial swelling and loss of inner membrane structure before the release of cytochrome c. Taken together, our results indicate that CDDO-Me is a novel mitochondriotoxic agent that induces apoptosis and inhibits mitochondrial electron transport via perturbations in inner mitochondrial membrane integrity.

Signaling pathways regulating intercellular adhesion molecule 1 expression by endothelin 1: Comparison with interleukin-1β in normal and scleroderma dermal fibroblasts

OBJECTIVE

Endothelin 1 (ET-1) has been implicated in the pathogenesis of fibrotic and inflammatory diseases, including scleroderma. In addition to modulating vascular tone and extracellular matrix turnover, ET-1 up-regulates cell surface adhesion molecules including intercellular adhesion molecule 1 (ICAM-1), which is key to cell-cell and cell-matrix adhesion and leukocyte infiltration. This study was undertaken to delineate the signal transduction pathways utilized by ET-1 and compare them with those adopted by proinflammatory cytokine interleukin-1beta (IL-1beta) in normal and scleroderma dermal fibroblasts.

METHODS

Protein expression induced by ET-1 and IL-1beta on normal dermal fibroblasts, with or without signaling inhibitors, was detected by enzyme-linked immunosorbent assay, while messenger RNA (mRNA) levels were analyzed by LightCycler polymerase chain reaction. Expression of protein kinase Cdelta (PKCdelta) and PKCepsilon protein in normal dermal fibroblasts and scleroderma dermal fibroblasts was determined by Western blotting, and PKCepsilon involvement in ET-1 signaling was confirmed through transfection of an ICAM-1 promoter construct into murine PKCepsilon-/- fibroblasts. NF-kappaB activation was confirmed via electrophoretic mobility supershift assay, and analysis of the ICAM-1 promoter region was achieved via transfection of deletion constructs into human dermal fibroblasts.

RESULTS

In normal dermal fibroblasts, ET-1 induced ICAM-1 mRNA and surface protein expression in a dose- and time-dependent manner via both receptor subtypes, ET(A) and ET(B); antagonism of both abolished the ET-1 response. MEK was involved in the signaling cascade, but phosphatidylinositol 3-kinase and p38 MAPK were not. Key to the cascade was activation of NF-kappaB, achieved by ligation of either receptor subtype. PKCepsilon activation led to downstream activation of MEK and, in part, NF-kappaB. IL-1beta signaling required NF-kappaB and MEK activation, along with activation of PKCdelta. ET-1 and IL-1beta each utilized the same ICAM-1 promoter region and the same NF-kappaB site at -157 bp. Responses to ET-1 and IL-1beta differed in scleroderma dermal fibroblasts, with ET-1 sensitivity decreasing and IL-1beta responses remaining intact. Expression of PKCepsilon and PKCdelta in scleroderma dermal fibroblasts was also altered.

CONCLUSION

The findings of this study indicate that differences in sensitivity to ET-1 and IL-1beta in scleroderma dermal fibroblasts may be explained by altered expression of the PKC isoforms and cytokine receptors.

Effects of Silica on Mitochondrial Functions of the Proximal Tubule Cells in Rats

AIM

Despite the belief that silica (Si) is an inert and non-toxic ingredient, latest studies indicated that it is a potent mitochondria activator and Si-induced ROS generation is involved in the inflammatory reactions of silicotic lungs. Si cytotoxicity has been well studied in phagocytic cells, but its effects on the mitochondria of proximal tubule cells which are continuously exposed to filtered blood-borne soluble Si were not known.

METHODS

Using renal cortical slices and isolated mitochondria, the effect of high dietary Si on the mitochondrial functions of proximal tubule cells was studied in rats exposed to 50 mg/kg sodium metasilicate-containing water for 8 days.

RESULTS

Digested Si did not accumulate in kidney cortex, it was totally eliminated in the urine. Glomerular filtration rate as well as urine output were normal. Despite unaltered blood and cortex Si levels, ammonia production of cortical slices and isolated mitochondria was increased significantly and this was further increased by L-NAME pre-treatment. Elevated mitochondrial oxygen utilization was associated with increased ammonia production. Cyclosporin-A-sensitive mtPTP increase was associated with unchanged K(ATP) channels in the mitochondria of Si-exposed rats.

CONCLUSION

These results suggested that dietary Si increases both extracellular and intracellular ammoniagenesis by elevating mitochondrial oxygen utilisation.

The central role of Fas-ligand cell signaling in inflammatory lung diseases

Following inflammation and injury in the lung, loss of epithelial cell precursors could determine the balance between tissue regeneration and fibrosis. This review discusses evidence that proapoptotic Fas‐Fas ligand (FasL) signaling plays a central role in pulmonary inflammation, injury and fibrosis. FasL signaling induces inflammatory apoptosis in epithelial cells and alveolar macrophages, with concomitant IL‐1β and chemokine release, leading to neutrophil infiltration. FasL signaling plays a critical role in models of acute lung injury, idiopathic pulmonary fibrosis and silicosis; blockade of Fas‐FasL interactions either prevents or attenuates pulmonary inflammation and fibrosis. Serologic and immunohistochemical studies in patients support a major pathogenic role of Fas and FasL molecules in inflammatory lung diseases. Identification of the pathogenic role of FasL could facilitate the discovery of more effective treatments for currently untreatable inflammatory lung diseases.

Cysteine cathepsins in human silicotic bronchoalveolar lavage fluids

Mature, active cysteine cathepsins (CPs) were identified in human inflammatory bronchoalveolar lavage fluid (BALF) supernatants from patients suffering from silicosis by both western blot and surface plasmon resonance analyses. BALFs are not a reservoir of activatable proforms, since no autocatalytic maturation at acidic pH occurs. Cathepsin H is the most profuse among studied CPs (median value: 36.5 nM), while cathepsins B and L are the two most abundant thiol-dependent endoproteases. The overall concentration of active cathepsins B, H, K, L, and S is approximately 10-fold lower than their concentration in BALF supernatants from patients suffering from inflammatory acute lung injuries (962+/-347 nM).The cathepsins (approximately 70 nM)/cystatin-like inhibitors (approximately 9 nM) ratio is unbalanced in favor of enzymes ( approximately 8-fold). This presence of uncontrolled CPs suggests that they may contribute, in addition to matrix metalloproteases, to the lung tissue breakdown/remodeling occurring during silicosis, although their exact contribution to interstitial inflammation remains to be evaluated.

The crucial role of particle surface reactivity in respirable quartz-induced reactive oxygen/nitrogen species formation and APE/Ref-1 induction in rat lung

Persistent inflammation and associated excessive oxidative stress have been crucially implicated in quartz-induced pulmonary diseases, including fibrosis and cancer. We have investigated the significance of the particle surface reactivity of respirable quartz dust in relation to the in vivo generation of reactive oxygen and nitrogen species (ROS/RNS) and the associated induction of oxidative stress responses in the lung. Therefore, rats were intratracheally instilled with 2 mg quartz (DQ12) or quartz whose surface was modified by either polyvinylpyridine-N-oxide (PVNO) or aluminium lactate (AL). Seven days after instillation, the bronchoalveolar lavage fluid (BALF) was analysed for markers of inflammation (total/differential cell counts), levels of pulmonary oxidants (H₂O₂, nitrite), antioxidant status (trolox equivalent antioxidant capacity), as well as for markers of lung tissue damage, e.g. total protein, lactate dehydrogenase and alkaline phosphatase. Lung homogenates as well as sections were investigated regarding the induction of the oxidative DNA-lesion/oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) using HPLC/ECD analysis and immunohistochemistry, respectively. Homogenates and sections were also investigated for the expression of the bifunctional apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) by Western blotting and immunohistochemistry. Significantly increased levels of H₂O₂ and nitrite were observed in rats treated with non-coated quartz, when compared to rats that were treated with either saline or the surface-modified quartz preparations. In the BALF, there was a strong correlation between the number of macrophages and ROS, as well as total cells and RNS. Although enhanced oxidant generation in non-coated DQ12-treated rats was paralleled with an increased total antioxidant capacity in the BALF, these animals also showed significantly enhanced lung tissue damage. Remarkably however, elevated ROS levels were not associated with an increase in 8-OHdG, whereas the lung tissue expression of APE/Ref-1 protein was clearly up-regulated. The present data provide further in vivo evidence for the crucial role of particle surface properties in quartz dust-induced ROS/RNS generation by recruited inflammatory phagocytes. Our results also demonstrate that quartz dust can fail to show steady-state enhanced oxidative DNA damage in the respiratory tract, in conditions were it elicits a marked and persistent inflammation with associated generation of ROS/RNS, and indicate that this may relate to compensatory induction of APE/Ref-1 mediated base excision repair.

Development and application of an electron spin resonance spectrometry method for the determination of oxygen free radical formation by particulate matter

Exposure to increased levels of ambient particulate matter (PM) are associated with several health effects, including cardiopulmonary diseases. The formation of reactive oxygen species (ROS) is thought to play an important role in the induction of these health effects. To quantify the ROS generating capacityof PM,we developed an improved electron spin resonance (ESR) spectrometry-based method. ROS formation was measured directly on PM-containing filters, thereby avoiding the selective extraction of components and loss of material or reactivity, which is likely to occur during filter extraction. Also, ascorbic acid was added to stimulate ROS formation. This method was applied to PM10 samples originating from different sources. The radical generating capacity of PM10 from both gasoline and diesel engine exhaust was significantly higher as compared to that of PM10 from ambient or indoor air. Furthermore, in urban PM10 and PM2.5, ROS-generating capacity significantly correlated with concentrations of polycyclic aromatic hydrocarbon content and particular transition metals. This indicates thatthis improved ESR method may be a valuable tool for evaluating the relationship between ROS formation by PM and the adverse health effects associated with this type of air pollution.

Iron-dependent lysosomal destabilization initiates silica-induced apoptosis in murine macrophages

Alveolar macrophages play a critical role in silica-induced lung fibrosis, and apoptotic mechanisms have been implicated in silica-induced pathogenesis. Here, employing a model of murine macrophages (J774 cells), it is shown that serum-coated alpha-quartz silica particles cause lysosomal rupture and apoptosis following endocytotic uptake. The loss of lysosomal integrity involves intralysosomal iron-catalyzed peroxidative damage to lysosomal membranes. Thus, lysosomal damage is most pronounced in cells exposed to silica particles with high amounts of surface-bound iron, whereas silica particles previously treated with the iron chelator desferrioxamine only induce modest rupture. Furthermore, inhibition of intralysosomal Fenton type chemistry, either by pre-treatment with desferrioxamine complexed to starch--an iron chelator targeted to the lysosomal compartment--or by concomitant treatment with diphenylene iodonium--a potent inhibitor of NADPH oxidase --both prevent silica-induced lysosomal leakage and ensuing apoptotic cell death. This study also demonstrates that silica-induced lysosomal rupture is a very early apoptotic event, preceding activation of caspases, disruption of transmembrane mitochondrial potential and DNA fragmentation. Indeed, these later apoptotic events appear to be directly correlated to the magnitude of lysosomal leakage, and are not observed in cells treated with high molecular weight desferrioxamine or diphenylene iodonium.

An update on the detoxification processes for silica particles and asbestos fibers: successess and limitations

Inhalation of asbestos fibers and crystalline silica produces a number of diseases including fibrosis and cancer. Investigations into the mechanisms involved in mineral particle-induced toxicity indicated the importance of their surfaces in the pathological consequences. Masking of the surface sites has therefore featured prominently in a number of detoxification processes that have been investigated. The majority of the detoxification processes were, however, conducted to elucidate the involvement of a particular surface site in the toxicity of a specific mineral. Others were investigated with the aim of large industrial applications to be applied during mining, handling, processing, transporting, and disposing of minerals. It can be concluded that, to date, there is no single detoxification process that could be applied universally to all different types of mineral particles. Those that have shown some success could not completely abolish all adverse effects. Further elucidation of mechanisms of particle-induced toxicity may open new possibilities for detoxification processes.