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

A review of pulmonary neutrophilia and insights into the key role of neutrophils in particle-induced pathogenesis in the lung from animal studies of lunar dusts and other poorly soluble dust particles

The mechanisms of particle-induced pathogenesis in the lung remain poorly understood. Neutrophilic inflammation and oxidative stress in the lung are hallmarks of toxicity. Some investigators have postulated that oxidative stress from particle surface reactive oxygen species (psROS) on the dust produces the toxicopathology in the lungs of dust-exposed animals. This postulate was tested concurrently with the studies to elucidate the toxicity of lunar dust (LD), which is believed to contain psROS due to high-speed micrometeoroid bombardment that fractured and pulverized lunar surface regolith. Results from studies of rats intratracheally instilled (ITI) with three LDs (prepared from an Apollo-14 lunar regolith), which differed 14-fold in levels of psROS, and two toxicity reference dusts (TiO2 and quartz) indicated that psROS had no significant contribution to the dusts' toxicity in the lung. Reported here are results of further investigations by the LD toxicity study team on the toxicological role of oxidants in alveolar neutrophils that were harvested from rats in the 5-dust ITI study and from rats that were exposed to airborne LD for 4 weeks. The oxidants per neutrophils and all neutrophils increased with dose, exposure time and dust's cytotoxicity. The results suggest that alveolar neutrophils play a critical role in particle-induced injury and toxicity in the lung of dust-exposed animals. Based on these results, we propose an adverse outcome pathway (AOP) for particle-associated lung disease that centers on the crucial role of alveolar neutrophil-derived oxidant species. A critical review of the toxicology literature on particle exposure and lung disease further supports a neutrophil-centric mechanism in the pathogenesis of lung disease and may explain previously reported animal species differences in responses to poorly soluble particles. Key findings from the toxicology literature indicate that (1) after exposures to the same dust at the same amount, rats have more alveolar neutrophils than hamsters; hamsters clear more particles from their lungs, consequently contributing to fewer neutrophils and less severe lung lesions; (2) rats exposed to nano-sized TiO2 have more neutrophils and more severe lesions in their lungs than rats exposed to the same mass-concentration of micron-sized TiO2; nano-sized dust has a greater number of particles and a larger total particle-cell contact surface area than the same mass of micron-sized dust, which triggers more alveolar epithelial cells (AECs) to synthesize and release more cytokines that recruit a greater number of neutrophils leading to more severe lesions. Thus, we postulate that, during chronic dust exposure, particle-inflicted AECs persistently release cytokines, which recruit neutrophils and activate them to produce oxidants resulting in a prolonged continuous source of endogenous oxidative stress that leads to lung toxicity. This neutrophil-driven lung pathogenesis explains why dust exposure induces more severe lesions in rats than hamsters; why, on a mass-dose basis, nano-sized dusts are more toxic than the micron-sized dusts; why lung lesions progress with time; and why dose-response curves of particle toxicity exhibit a hockey stick like shape with a threshold. The neutrophil centric AOP for particle-induced lung disease has implications for risk assessment of human exposures to dust particles and environmental particulate matter.

Effect of nanoparticles on gouty arthritis: a systematic review and meta-analysis

OBJECTIVE

The purpose of this study was to explore the effects of nanoparticles on gouty arthritis, and to provide evidence for the preclinical application of nanoparticles in gouty arthritis and ideas for nanomedicine improvement for nanoparticle researchers.

METHODS

Five databases including the Cochrane Library, PubMed, Scopus, Web of Science, and Embase were searched for eligible studies until April 2022. The quality of the selected studies was assessed by SYRCLE's risk of bias (RoB) tool, and the random-effects model was used to calculate the overall effect sizes of weighted mean differences (WMD).

RESULTS

Ten studies met the inclusion criteria. Results showed that nanoparticles were effective in reducing uric acid levels (WMD: -4.91; 95% confidence interval (CI): - 5.41 to - 4.41; p < 0.001), but were not better than allopurinol (WMD: -0.20; 95% CI: - 0.42 to 0.02; p = 0.099). It was worth noting that the nanoparticles were safer than allopurinol. Subgroup analyses indicated that nanoparticle encapsulated substance, animal species, nanoparticle dosage, animal quantity, and animal gender were all sources of heterogeneity.

CONCLUSION

The nanoparticles are safe medications for gouty arthritis which can effectively reduce uric acid levels in rodents. Although the results are still uncertain, it is expected to have certain clinical application value. The nanoparticles may be the preclinical medications for gouty arthritis in the future.

The influence of exposure approaches to in vitro lung epithelial barrier models to assess engineered nanomaterial hazard

Exposure to engineered nanomaterials (ENM) poses a potential health risk to humans through long-term, repetitive low-dose exposures. Currently, this is not commonplace within in vitro lung cell cultures. Therefore, the purpose of this study was to consider the optimal exposure approach toward determining the stability, sensitivity and validity of using in vitro lung cell mono- and co-cultures to determine ENM hazard. A range of exposure scenarios were conducted with DQ₁₂ (previously established as a positive particle control) (historic and re-activated), TiO₂ (JRC NM-105) and BaSO₄ (JRC NM-220) on both monocultures of A549 cells as well as co-cultures of A549 cells and differentiated THP-1 cells. Cell cultures were exposed to either a single, or a repeated exposure over 24, 48- or 72-hours at in vivo extrapolated concentrations of 0-5.2 µg/cm², 0-6 µg/cm² and 0-1µg/cm². The focus of this study was the pro-inflammatory, cytotoxic and genotoxic response elicited by these ENMs. Exposure to DQ₁₂ caused pro-inflammatory responses after 48 hours repeat exposures, as well as increases in micronucleus frequency. Neither TiO₂ nor BaSO₄ elicited a pro-inflammatory response at this time point. However, there was induction of IL-6 after 24 hours TiO₂ exposure. In conclusion, it is important to consider the appropriateness of the positive control implemented, the cell culture model, the time of exposure as well as the type of exposure (bolus or fractionated) before establishing if an in vitro model is appropriate to determine the level of response to the specific ENM of interest.

Characterization and toxicity evaluation of air-borne particles released by grinding from two dental resin composites in vitro

OBJECTIVE

The project aims to evaluate whether inhalation of particles released upon grinding of dental composites may pose a health hazard to dentists. The main objective of the study was to characterize the dust from polymer-based dental composites ground with different grain sized burs and investigate particle uptake and the potential cytotoxic effects in human bronchial cells.

METHODS

Polymerized blocks of two dental composites, Filtek™ Z250 and Filtek™ Z500 from 3M™ ESPE, were ground with super coarse (black) and fine (red) burs inside a glass chamber. Ultrafine airborne dust concentration and particle size distribution was measured real-time during grinding with a scanning mobility particle sizer (SMPS). Filter-collected airborne particles were characterized with dynamic light scattering (DLS) and scanning electron microscopy (SEM). Human bronchial epithelial cells (HBEC-3KT) were exposed to the dusts in dose-effect experiments. Toxicity was measured with lactate dehydrogenase (LDH) assay and cell counting kit-8 (CCK8). Cellular uptake was observed with transmission electron microscopy (TEM).

RESULTS

Airborne ultrafine particles showed that most particles were in the size range 15-35 nm (SMPS). SEM analysis proved that more than 80% of the particles have a minimum Feret diameter less than 1 μm. In solution (DLS), the particles have larger diameters and tend to agglomerate. Cell toxicity (LDH, CCK8) is shown after 48 h and 72 h exposure times and at the highest doses. TEM showed presence of the particles within the cell cytoplasm.

SIGNIFICANCE

Prolonged and frequent exposure through inhalation may have negative health implications for dentists.

Assessing the bioactivity of crystalline silica in heated high-temperature insulation wools

High-Temperature Insulation Wools (HTIW), such as alumino silicate wools (Refractory Ceramic Fibers) and Alkaline Earth Silicate wools, are used in high-temperature industries for thermal insulation. These materials have an amorphous glass-like structure. In some applications, exposure to high temperatures causes devitrification resulting in the formation of crystalline species including crystalline silica. The formation of this potentially carcinogenic material raises safety concerns regarding after-use handling and disposal. This study aims to determine whether cristobalite formed in HTIW is bioactive in vitro. Mouse macrophage (J774A.1) and human alveolar epithelial (A549) cell lines were exposed to pristine HTIW of different compositions, and corresponding heat-treated samples. Cell death, cytokine release, and reactive oxygen species (ROS) formation were assessed in both cell types. Cell responses to aluminum lactate-coated fibers were assessed to determine if responses were caused by crystalline silica. DQ12 α-quartz was used as positive control, and TiO₂ as negative control. HTIW did not induce cell death or intracellular ROS, and their ability to induce pro-inflammatory mediator release was low. In contrast, DQ12 induced cytotoxicity, a strong pro-inflammatory response and ROS generation. The modest pro-inflammatory mediator responses of HTIW did not always coincide with the formation of cristobalite in heated fibers; therefore, we cannot confirm that devitrification of HTIW results in bioactive cristobalite in vitro. In conclusion, the biological responses to HTIW observed were not attributable to a single physicochemical characteristic; instead, a combination of physicochemical characteristics (cristobalite content, fiber chemistry, dimensions and material solubility) appear to contribute to induction of cellular responses.

Phosphonate coating of SiO2 nanoparticles abrogates inflammatory effects and local changes of the lipid composition in the rat lung: a complementary bioimaging study

BACKGROUND

The well-known inflammatory and fibrogenic changes of the lung upon crystalline silica are accompanied by early changes of the phospholipid composition (PLC) as detected in broncho-alveolar lavage fluid (BALF). Amorphous silica nanoparticles (NPs) evoke transient lung inflammation, but their effect on PLC is unknown. Here, we compared effects of unmodified and phosphonated amorphous silica NP and describe, for the first time, local changes of the PLC with innovative bioimaging tools.

METHODS

Unmodified (SiO₂-n), 3-(trihydroxysilyl) propyl methylphosphonate coated SiO₂-n (SiO₂-p) as well as a fluorescent surrogate of SiO₂-n (SiO₂-FITC) nanoparticles were used in this study. In vitro toxicity was tested with NR8383 alveolar macrophages. Rats were intratracheally instilled with SiO₂-n, SiO₂-p, or SiO₂-FITC, and effects on lungs were analyzed after 3 days. BALF from the right lung was analyzed for inflammatory markers. Cryo-sections of the left lung were subjected to fluorescence microscopy and PLC analyses by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MS), Fourier transform infrared microspectroscopy (FT-IR), and tandem mass spectrometry (MS/MS) experiments.

RESULTS

Compared to SiO₂-p, SiO₂-n NPs were more cytotoxic to macrophages in vitro and more inflammatory in the rat lung, as reflected by increased concentration of neutrophils and protein in BALF. Fluorescence microscopy revealed a typical patchy distribution of SiO₂-FITC located within the lung parenchyma and alveolar macrophages. Superimposable to this particle distribution, SiO₂-FITC elicited local increases of phosphatidylglycerol (PG) and phosphatidylinositol (PI), whereas phoshatidylserine (PS) and signals from triacylgyceride (TAG) were decreased in the same areas. No such changes were found in lungs treated with SiO₂-p or particle-free instillation fluid.

CONCLUSIONS

Phosphonate coating mitigates effects of silica NP in the lung and abolishes their locally induced changes in PLC pattern. Bioimaging methods based on MALDI-MS may become a useful tool to investigate the mode of action of NPs in tissues.

Evaluation of the DNA damaging potential of indigenous health hazardous quartz nanoparticles on the cultured lung cells

Quartz nanoparticles (QNPs) cause various diseases in the biological systems and are thus considered as hazardous materials; however, their properties are important in a wide range of biological and pharmaceutical entities. The present study was initiated to enhance the understanding of the genotoxic potential and focused on the mechanism involved in the indigenous quartz nanoparticles induced toxicity in A549 cells. The results show a concentration dependent decrease in the cell viability of A549 cells. Additionally, QNPs exposure results in the concentration dependent toxicity, which intensifies the generation of ROS, which in turn is confirmed by the increased lipid peroxidation and decreased GSH levels. Moreover, it also induces DNA damage in the cells exposed to QNPs as compared to the control cells. The outcome of the results confirms that QNPs have cytotoxic and genotoxic effects on the A549 cells in a concentration and time dependent manner. Western blot analysis indicates the up regulation of LC-3I/II, Beclin-1, and p62 protein levels, which confirms the occurrence of autophagy through the phosphatidylinositol 3-kinase (PI3K)/a threonine kinase (Akt)/mammalian target of rapamycin (mTOR) pathway, as well as the inhibitor of autophagy is also verified. Our study demonstrates that QNPs exposure in human lung cells causes oxidative stress and DNA damage, which leads to autophagy. Hence, from a bioremediation point of view, the remedial strategy that can be adopted from the biological DNA damage from these health hazardous materials will result in a safer environment.

Super-oxidation of silicon nanoclusters: magnetism and reactive oxygen species at the surface

Oxidation of silicon nanoclusters depending on the temperature and oxygen pressure is explored from first principles using the evolutionary algorithm, and structural and thermodynamic analysis. From our calculations of 90 Si_nO_m clusters we found that under normal conditions oxidation does not stop at the stoichiometric SiO₂ composition, as it does in bulk silicon, but goes further placing extra oxygen atoms on the cluster surface. These extra atoms are responsible for light emission, relevant to reactive oxygen species and many of them are magnetic. We argue that the super-oxidation effect is size-independent and discuss its relevance to nanotechnology and miscellaneous applications, including biomedical ones.

Revisiting the paradigm of silica pathogenicity with synthetic quartz crystals: the role of crystallinity and surface disorder

BACKGROUND

Exposure to some - but not all - quartz particles is associated to silicosis, lung cancer and autoimmune diseases. What imparts pathogenicity to any single quartz source is however still unclear. Crystallinity and various surface features are implied in toxicity. Quartz dusts used so far in particle toxicology have been obtained by grinding rocks containing natural quartz, a process which affects crystallinity and yields dusts with variable surface states. To clarify the role of crystallinity in quartz pathogenicity we have grown intact quartz crystals in respirable size.

METHODS

Quartz crystals were grown and compared with a fractured specimen obtained by grinding the largest synthetic crystals and a mineral quartz (positive control). The key physico-chemical features relevant to particle toxicity - particle size distribution, micromorphology, crystallinity, surface charge, cell-free oxidative potential - were evaluated. Membranolysis was assessed on biological and artificial membranes. Endpoints of cellular stress were evaluated on RAW 264.7 murine macrophages by High Content Analysis after ascertaining cellular uptake by bio-TEM imaging of quartz-exposed cells.

RESULTS

Quartz crystals were grown in the submicron (n-Qz-syn) or micron (μ-Qz-syn) range by modulating the synthetic procedure. Independently from size as-grown quartz crystals with regular intact faces did not elicit cellular toxicity and lysosomal stress on RAW 264.7 macrophages, and were non-membranolytic on liposome and red blood cells. When fractured, synthetic quartz (μ-Qz-syn-f) attained particle morphology and size close to the mineral quartz dust (Qz-f, positive control) and similarly induced cellular toxicity and membranolysis. Fracturing imparted a higher heterogeneity of silanol acidic sites and radical species at the quartz surface.

CONCLUSIONS

Our data support the hypothesis that the biological activity of quartz dust is not due to crystallinity but to crystal fragmentation, when conchoidal fractures are formed. Besides radical generation, fracturing upsets the expected long-range order of non-radical surface moieties - silanols, silanolates, siloxanes - which disrupt membranes and induce cellular toxicity, both outcomes associated to the inflammatory response to quartz.

Oxidatively damaged DNA in the nasal epithelium of workers occupationally exposed to silica dust in Tuscany region, Italy

Chronic silica exposure has been associated to cancer and silicosis. Furthermore, the induction of oxidative stress and the generation of reactive oxygen species have been indicated to play a main role in the carcinogenicity of respirable silica. Therefore, we conducted a cross-sectional study to evaluate the prevalence of 3-(2-deoxy-β-D-erythro-pentafuranosyl)pyrimido[1,2-α]purin-10(3H)-one deoxyguanosine (M1dG) adducts, a biomarker of oxidative stress and peroxidation of lipids, in the nasal epithelium of 135 silica-exposed workers, employed in pottery, ceramic and marble manufacturing plants as well as in a stone quarry, in respect to 118 controls living in Tuscany region, Italy. The M1dG generation was measured by the (32)P-postlabelling assay. Significant higher levels of M1dG adducts per 10(8) normal nucleotides were observed in the nasal epithelium of smokers, 77.9±9.8 (SE), and in those of former smokers, 80.7±9.7 (SE), as compared to non-smokers, 57.1±6.2 (SE), P = 0.001 and P = 0.004, respectively. Significant increments of M1dG adducts were found in the nasal epithelium of workers that handle artificial marble conglomerates, 184±36.4 (SE), and in those of quarry workers, 120±34.7 (SE), with respect to controls, 50.6±2.7 (SE), P = 0.014 and P < 0.001, respectively. Null increments were observed in association with the pottery and the ceramic factories. After stratification for different exposures, silica-exposed workers that were co-exposed to organic solvents, and welding and exhaust fumes have significantly higher M1dG levels, 90.4±13.4 (SE), P = 0.014 vs.

CONTROL

Our data suggested that silica exposure might be associated with genotoxicity in the nasal epithelial cells of silica-exposed workers that handle of artificial marble conglomerates and quarry workers. Importantly, we observed that co-exposures to other respiratory carcinogens may have contributed to enhance the burden of M1dG adducts in the nasal epithelium of silica-exposed workers.

Silica-induced NLRP3 inflammasome activation in vitro and in rat lungs

RATIONALE

Mineral particles in the lung cause inflammation and silicosis. In myeloid and bronchial epithelial cells the inflammasome plays a role in responses to crystalline silica. Thioredoxin (TRX) and its inhibitory protein TRX-interacting protein link oxidative stress with inflammasome activation. We investigated inflammasome activation by crystalline silica polymorphs and modulation by TRX in vitro, as well as its localization and the importance of silica surface reactivity in rats.

METHODS

We exposed bronchial epithelial cells and differentiated macrophages to silica polymorphs quartz and cristobalite and measured caspase-1 activity as well as the release of IL-1β, bFGF and HMGB1; including after TRX overexpression or treatment with recombinant TRX. Rats were intratracheally instilled with vehicle control, Dörentruper quartz (DQ12) or DQ12 coated with polyvinylpyridine N-oxide. At days 3, 7, 28, 90, 180 and 360 five animals per treatment group were sacrificed. Hallmarks of silicosis were assessed with Haematoxylin-eosin and Sirius Red stainings. Caspase-1 activity in the bronchoalveolar lavage and caspase-1 and IL-1β localization in lung tissue were determined using Western blot and immunohistochemistry (IHC).

RESULTS

Silica polymorphs triggered secretion of IL-1β, bFGF and HMGB1 in a surface reactivity dependent manner. Inflammasome readouts linked with caspase-1 enzymatic activity were attenuated by TRX overexpression or treatment. At day 3 and 7 increased caspase-1 activity was detected in BALF of the DQ12 group and increased levels of caspase-1 and IL-1β were observed with IHC in the DQ12 group compared to controls. DQ12 exposure revealed silicotic nodules at 180 and 360 days. Particle surface modification markedly attenuated the grade of inflammation and lymphocyte influx and attenuated the level of inflammasome activation, indicating that the development of silicosis and inflammasome activation is determined by crystalline silica surface reactivity.

CONCLUSION

Our novel data indicate the pivotal role of surface reactivity of crystalline silica to activate the inflammasome in cultures of both epithelial cells and macrophages. Inhibitory capacity of the antioxidant TRX to inflammasome activation was evidenced. DQ12 quartz exposure induced acute and chronic functional activation of the inflammasome in the heterogeneous cell populations of the lung in associated with its crystalline surface reactivity.

Variability and consistency in lung inflammatory responses to particles with a geogenic origin

BACKGROUND AND OBJECTIVE

Particulate matter <10 μm (PM10 ) is well recognized as being an important driver of respiratory health; however, the impact of PM10 of geogenic origin on inflammatory responses in the lung is poorly understood. This study aimed to assess the lung inflammatory response to community sampled geogenic PM10 .

METHODS

This was achieved by collecting earth material from two regional communities in Western Australia (Kalgoorlie-Boulder and Newman), extracting the PM10 fraction and exposing mice by intranasal instillation to these particles. The physicochemical characteristics of the particles were assessed and lung inflammatory responses were compared to control particles. The primary outcomes were cellular influx and cytokine production in the lungs of the exposed mice.

RESULTS

The physical and chemical characteristics of the PM10 from Kalgoorlie and Newman differed with the latter having a higher concentration of Fe and a larger median diameter. Control particles (2.5 μm polystyrene) caused a significant influx of inflammatory cells (neutrophils) with little production of proinflammatory cytokines. In contrast, the geogenic particles induced the production of MIP-2, IL-6 and a significant influx of neutrophils. Qualitatively, the response following exposure to particles from Kalgoorlie and Newman were consistent; however, the magnitude of the response was substantially higher in the mice exposed to particles from Newman.

CONCLUSIONS

The unique physicochemical characteristics of geogenic particles induced a proinflammatory response in the lung. These data suggest that particle composition should be considered when setting community standards for PM exposure, particularly in areas exposed to high geogenic particulate loads.

Investigation of the effects of short-term inhalation of carbon nanoparticles on brains and lungs of c57bl/6j and p47(phox-/-) mice

Recent studies indicate that the brain is a target for toxic carbonaceous nanoparticles present in ambient air. It has been proposed that the neurotoxic effects of such particles are driven by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediated generation of reactive oxygen species (ROS) in activated microglia. In the present study, we have evaluated the effects of short term (4h) nose-only inhalation exposure to carbon NP (CNP) in the brains and lungs of C57BL/6J mice and in p47(phox-/-) mice that lack a functional NADPH oxidase. It was shown that the lungs of the p47(phox-/-) mice are less responsive to CNP inhalation than lungs of the corresponding C57BL/6J control animals. Lung tissue mRNA expression of the oxidative stress/DNA damage response genes 8-oxoguanine glycosylase (OGG1) and apurinic/apyrimidinic endonuclease 1 (APE1) were induced by CNP exposure in C57BL/6J but not in the p47(phox-/-) mice. In contrast, the expression of these genes, as well as Tumor Necrosis Factor-α (TNFα), Cyclooxygenase-2 (COX-2) and Heme Oxygenase-1 (HO-1) was not altered in the olfactory bulb, cerebellum or remaining brain tissue part of either mouse background. This indicates that neuroinflammation was not induced by this exposure. CNP inhalation for 4h or for 4h on three consecutive days also did not affect brain tissue protein expression of interleukin (IL)-1β, while a clear significant difference in constitutive expression level of this pro-inflammatory cytokine was found between C57BL/6J and p47(phox-/-) mice. In conclusion, short-term inhalation exposure to pure carbon nanoparticles can trigger mild p47(phox) dependent oxidative stress responses in the lungs of mice whereas in their brains at the same exposure levels signs of oxidative stress and inflammation remain absent. The possible role of p47(phox) in the neuro-inflammatory effects of nanoparticles in vivo remains to be clarified.

Bofutsushosan, a Japanese herbal (Kampo) medicine, attenuates progression of nonalcoholic steatohepatitis in mice

BACKGROUND

Obesity-induced liver disease (nonalcoholic fatty liver disease, NAFLD) is now the commonest cause of chronic liver disease in affluent nations. There are presently no proven treatments for NAFLD or its more severe stage, nonalcoholic steatohepatitis (NASH). Bofutsushosan (BTS), a Japanese herbal (Kampo) medicine, long used as an anti-obesity medicine in Japan and other Asian countries, has been shown to reduce body weight and improve insulin resistance (IR) and hepatic steatosis. The precise mechanism of action of BTS, however, remains unclear. To evaluate the ability of BTS to prevent the development of NASH, and determine the mediators and pathways involved.

METHODS

C57BL/6 mice were injected intra-peritoneally with gold-thioglucose and fed a high-fat diet (HF) or HF diet admixed with either 2 or 5 % BTS for 12 weeks. The effectiveness of BTS in attenuating features of NASH and the mechanisms through which BTS attenuated NASH were then assayed through an assessment of the anthropometric, radiological, biochemical and histological parameters.

RESULTS

BTS attenuated the progression of NASH through induction of adiponectin and its receptors along with an induction of PPAR-α and PPAR-γ, decreased expression of SREBP-1c, increased hepatic fatty acid oxidation and increased hepatic export of triglycerides. BTS moreover, reduced IR through phosphorylation of the protein kinase, Akt.

CONCLUSIONS

BTS through induction of adiponectin signaling and Akt attenuated development of NASH. Identification of the active entity in BTS should allow development of novel treatments for NASH.

Suppression of nuclear factor erythroid 2-related factor 2 via extracellular signal-regulated kinase contributes to bleomycin-induced oxidative stress and fibrogenesis

Pulmonary fibrosis is a serious and irreversible lung injury with obscure etiologic mechanisms and no effective treatment to date. This study explored a crucial link between oxidative stress and pulmonary fibrogenesis, focusing on nuclear factor erythroid 2-related factor 2 (Nrf2), a core transcription factor in antioxidative regulation systems. Treatment of C57 BL/6 mice with bleomycin increased fibroblast viability and collagen production and significantly downregulated Nrf2. In addition, prominent oxidative stress was indicated by changes in superoxide dismutase, catalase activity, and glutathione and thiobarbituric acid-reactive substance levels. In a cell-based model, bleomycin suppressed Nrf2 activation via extracellular signal-related kinase phosphorylation, enhancing intracellular reactive oxygen species in lung fibroblasts and stimulating abnormal cell proliferation and collagen secretion. To confirm this novel mechanism of bleomycin-induced fibrogenesis, we attempted to upregulate Nrf2 and related antioxidant proteins in bleomycin-treated fibroblasts using a putative Nrf2 activator, caffeic acid phenethyl ester, and the results showed that bleomycin-induced fibroblast proliferation and collagen content were attenuated through improved redox balance. Collectively, these results disclose a potential regulatory mechanism in pulmonary fibrosis that will aid the development of new therapies.

Autocrine abscisic acid plays a key role in quartz-induced macrophage activation

Inhalation of quartz induces silicosis, a lung disease where alveolar macrophages release inflammatory mediators, including prostaglandin-E(2) (PGE(2)) and tumor necrosis factor α (TNF-α). Here we report the pivotal role of abscisic acid (ABA), a recently discovered human inflammatory hormone, in silica-induced activation of murine RAW264.7 macrophages and of rat alveolar macrophages (AMs). Stimulation of both RAW264.7 cells and AMs with quartz induced a significant increase of ABA release (5- and 10-fold, respectively), compared to untreated cells. In RAW264.7 cells, autocrine ABA released after quartz stimulation sequentially activates the plasma membrane receptor LANCL2 and NADPH oxidase, generating a Ca(2+) influx resulting in NFκ B nuclear translocation and PGE(2) and TNF-α release (3-, 2-, and 3.5-fold increase, respectively, compared to control, unstimulated cells). Quartz-stimulated RAW264.7 cells silenced for LANCL2 or preincubated with a monoclonal antibody against ABA show an almost complete inhibition of NFκ B nuclear translocation and PGE(2) and TNF-α release compared to controls electroporated with a scramble oligonucleotide or preincubated with an unrelated antibody. AMs showed similar early and late ABA-induced responses as RAW264.7 cells. These findings identify ABA and LANCL2 as key mediators in quartz-induced inflammation, providing possible new targets for antisilicotic therapy.

Evaluation of apoptosis induced by nanoparticles and fine particles in RAW 264.7 macrophages: facts and artefacts

Current hazard characterisation of nanoparticles (NP) is predominantly based on in vitro test systems, being established for small molecules of drugs and chemicals. However, specific physicochemical properties of NP may result in interference with assay components, biomarkers, or detection systems. In the present study, six types of (nano)particles were screened in RAW 264.7 macrophages by common cytotoxicity methods (WST-1, LDH). Our specific focus was on the investigation of apoptosis (analysis of hypodiploid DNA, phosphatidylserine exposure, caspase 3/7 activation, and Cell Death Detection ELISA). Assays were validated by the well-known apoptosis inducer staurosporine. Our results show that ZnO, DQ12 quartz and amorphous silica are cytotoxic with strong indications for apoptotic effects in RAW 264.7 macrophages, whereas toxicity was absent for MgO. For fine as well as ultrafine TiO(2), no apoptotic effects could be detected except for induction of DNA fragmentation. The results of our study demonstrate the necessity to control on a case-by-case basis for assay interference to avoid misinterpretation of specific in vitro test findings. To obtain valid statements on the potential induction of apoptosis by specific NP the measurement of multiple endpoints is a prerequisite.

Contrasting macrophage activation by fine and ultrafine titanium dioxide particles is associated with different uptake mechanisms

Inhalation of (nano)particles may lead to pulmonary inflammation. However, the precise mechanisms of particle uptake and generation of inflammatory mediators by alveolar macrophages (AM) are still poorly understood. The aim of this study was to investigate the interactions between particles and AM and their associated pro-inflammatory effects in relation to particle size and physico-chemical properties.

NR8383 rat lung AM were treated with ultrafine (uf), fine (f) TiO₂ or fine crystalline silica (DQ12 quartz). Physico-chemical particle properties were investigated by transmission electron microscopy, elemental analysis and thermogravimetry. Aggregation and agglomeration tendency of the particles were determined in assay-specific suspensions by means of dynamic light scattering.

All three particle types were rapidly taken up by AM. DQ12 and ufTiO₂ , but not fTiO₂ , caused increased extracellular reactive oxygen species (ROS), heme oxygenase 1 (HO-1) mRNA expression and tumor necrosis factor (TNF)-α release. Inducible nitric oxide synthase (iNOS) mRNA expression was increased most strongly by ufTiO₂ , while DQ12 exclusively triggered interleukin (IL) 1β release. However, oscillations of intracellular calcium concentration and increased intracellular ROS were observed with all three samples. Uptake inhibition experiments with cytochalasin D, chlorpromazine and a Fcγ receptor II (FcγRII) antibody revealed that the endocytosis of fTiO₂ by the macrophages involves actin-dependent phagocytosis and macropinocytosis as well as clathrin-coated pit formation, whereas the uptake of ufTiO₂ was dominated by FcγIIR. The uptake of DQ12 was found to be significantly reduced by all three inhibitors. Our findings suggest that the contrasting AM responses to fTiO₂ , ufTiO₂ and DQ12 relate to differences in the involvement of specific uptake mechanisms.

A novel and comprehensive mouse model of human non-alcoholic steatohepatitis with the full range of dysmetabolic and histological abnormalities induced by gold thioglucose and a high-fat diet

BACKGROUND

The search for effective treatments of non-alcoholic steatohepatitis (NASH), now the most common chronic liver disease in affluent countries, is hindered by a lack of animal models having the range of anthropometric and pathophysiological features as human NASH.

AIMS

To examine if mice treated with gold thioglucose (GTG) - known to induce lesions in the ventromedial hypothalamus, leading to hyperphagia and obesity - and then fed a high-fat diet (HF) had a comprehensive histological and dysmetabolic phenotype resembling human NASH.

METHODS

C57BL/6 mice were injected intraperitoneally with GTG and then fed HF for 12 weeks (GTG+HF). The extent of abdominal adiposity was assayed by CT scanning. A glucose tolerance test and an insulin tolerance test were performed to evaluate insulin resistance (IR). Histological, molecular and biochemical analyses were also performed.

RESULTS

Gold thioglucose+HF induced dysmetabolism, with hyperphagia, obesity with increased abdominal adiposity, IR and consequent steatohepatitis, with hepatocyte ballooning, Mallory-Denk bodies, perivenular and pericellular fibrosis as seen in adult NASH, paralleled by an increased expression of the profibrogenic factors, transforming growth factor-β1 and TIMP-1. Plasma adiponectin and the expression of adiponectin receptor 1 and receptor 2 were decreased, while PPAR-γ and FAS were increased in the livers of GTG+HF mice. In addition, GTG+HF mice showed glucose intolerance and severe IR.

CONCLUSIONS

Treatment with GTG and HF diet induce, in mice, a comprehensive model of human NASH, with the full range of dysmetabolic and histological abnormalities.

Comparative pulmonary toxicity of inhaled nickel nanoparticles; role of deposited dose and solubility

In this pilot study, we investigated which physicochemical properties of nickel hydroxide nanoparticles (nano-NH) were mainly responsible in inducing pulmonary toxicity. First, we studied the role of nickel ions solubilized from nano-NH by comparing the toxic effects of nano-NH to those of readily soluble nickel sulfate nanoparticles (nano-NS). Additionally, to test whether there was a non-specific stress response due to particle morphology, we compared the toxicity of nano-NH with that of carbon nanoparticles (nano-C) and titanium dioxide nanoparticles (nano-Ti), both of which had similar physical properties such as particle size and shape, to nano-NH. We exposed mice to each type of nanoparticles for 4?h via a whole-body inhalation system and examined oxidative stress and inflammatory responses in the lung. We also determined the lung burden and clearance of Ni following nano-NH and nano-NS exposures. The results showed that lung deposition of nano-NH was significantly greater than that of nano-NS and nano-NH appeared to have stronger inflammogenic potential than nano-NS even when lung Ni burden taken into consideration. This suggests that the toxicity of nano-NH is not driven solely by released Ni ions from deposited nano-NH particles. However, it is unlikely that the greater toxic potential of nano-NH is attributable to a generic stress response from any nanoparticle exposure, since nano-C and nano-Ti did not elicit toxic responses similar to those of nano-NH. These results indicate that the observed pulmonary toxicity by inhaled nano-NH were chemical-specific and deposited dose and solubility are key factors to understand toxicity induced by nano-NH.

Oxidative stress and DNA damage responses in rat and mouse lung to inhaled carbon nanoparticles

We have investigated whether short-term nose-only inhalation exposure to electric spark discharge-generated carbon nanoparticles (∼60 nm) causes oxidative stress and DNA damage responses in the lungs of rats (152 μg/m(3); 4 h) and mice (142 μg/m(3); 4 h, or three times 4 h). In both species, no pulmonary inflammation and toxicity were detected by bronchoalveolar lavage or mRNA expression analyses. Oxidative DNA damage (measured by fpg-comet assay), was also not increased in mouse whole lung tissue or isolated lung epithelial cells from rat. In addition, the mRNA expressions of the DNA base excision repair genes OGG1, DNA Polβ and XRCC1 were not altered. However, in the lung epithelial cells isolated from the nanoparticle-exposed rats a small but significant increase in APE-1 mRNA expression was measured. Thus, short-term inhalation of carbon nanoparticles under the applied exposure regimen, does not cause oxidative stress and DNA damage in the lungs of healthy mice and rats.

Effects of combined hyperoxia and cyclooxygenase inhibition in neonatal rat lungs

We examined the hypothesis that persistent pulmonary hypertension of the newborn (PPHN) associated with ibuprofen is due to alterations in biochemical and molecular regulators of oxidative stress and NO signaling. Newborn rats breathing 50% O2 or room air from the first day of life (P1), received early IP injections of: 1) indomethacin (0.2 mg/kg) on P1 and 0.1 mg/kg on P2 and P3; 2) ibuprofen (10 mg/kg) on P1 and 5 mg/kg on P2 and P3; or 3) saline on P1, P2 and P3, then euthanized on P4; or late treatment on P4, P5 and P6, then euthanized on P7. Lung biomarkers for oxidative stress (8- epi-PGF2a), DNA damage (8-hydroxy-2'-deoxyguanosine) and pulmonary hypertension (ET-1, big ET-1, and total NO) were assessed. Despite timing of the dose and oxygen exposure, both drugs resulted in increased alveolar size. Both drugs had no beneficial effects on oxidative stress. Indomethacin treatment in O2 resulted in higher pulmonary levels of 8-epi-PGF2alpha which was associated with downregulation of most antioxidant genes with early treatment and overexpression of GPX5 and 6 with late treatment. Early and late ibuprofen treatment suppressed hyperoxia-induced NOx production and downregulated iNOS. Postponing treatment had no significant beneficial effects on biomolecular regulators of oxidative stress and NO signaling. The effect of ibuprofen on pulmonary NOx may explain in part, the transient PPHN seen in ibuprofen-treated preterm infants.

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.

Role of oxidative damage in toxicity of particulates

Particulates are small particles of solid or liquid suspended in liquid or air. In vitro studies show that particles generate reactive oxygen species, deplete endogenous antioxidants, alter mitochondrial function and produce oxidative damage to lipids and DNA. Surface area, reactivity and chemical composition play important roles in the oxidative potential of particulates. Studies in animal models indicate that particles from combustion processes (generated by combustion of wood or diesel oil), silicate, titanium dioxide and nanoparticles (C60 fullerenes and carbon nanotubes) produce elevated levels of lipid peroxidation products and oxidatively damaged DNA. Biomonitoring studies in humans have shown associations between exposure to air pollution and wood smoke particulates and oxidative damage to DNA, deoxynucleotides and lipids measured in leukocytes, plasma, urine and/or exhaled breath. The results indicate that oxidative stress and elevated levels of oxidatively altered biomolecules are important intermediate endpoints that may be useful markers in hazard characterization of particulates.

Time-response relationship of nano and micro particle induced lung inflammation. Quartz as reference compound

An increasing number of engineered particles, including nanoparticles, are being manufactured, increasing the need for simple low-dose toxicological screening methods. This study aimed to investigate the kinetics of biomarkers related to acute and sub-chronic particle-induced lung inflammation of quartz. Mice were intratracheal instilled with 50 µg of microsized or nanosized quartz. Acute inflammation was assessed 1, 2, 4, 8, 16 or 48 hours post exposure, whereas sub-chronic inflammation was investigated 3 months after exposure. Markers of acute inflammation in the bronchoalveolar lavage fluid (BALF) were neutrophils (PMN), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, macrophage inflammatory protein-2 (MIP-2), keratinocyte derived chemokine (KC) and total protein, which were all close to maximum 16 hours post instillation. No major differences were seen in the time-response profiles of nano- and micro-sized particles. The potency of the two samples cannot be compared; during the milling process, a substantial part of the quartz was converted to amorphous silica and contaminated with corundum. For screening, BALF PMN, either TNF-α or IL-1β at 16 hours post instillation may be useful. At 3 months post instillation, KC, PMN and macrophages were elevated. Histology showed no interstitial inflammation three months post instillation. For screening of sub-chronic effects, KC, PMN, macrophages and histopathology is considered sufficient.

The physicochemistry and toxicology of CFA particles

The term "technogenic particles" is used to describe airborne particulate matter (PM) produced during industrial processes. The most common of these is "fly ash" produced during combustion of solid and liquid fossil fuels. Coal fly ash is derived from the mineral and metal contaminants within coal in which particles (1) are distinctly spherical in shape, (2) are composed of 60-90% glass, and (3) often contain a range of contaminant metals. In addition, particles may contain recrystallized minerals, mainly quartz, mullite, and hematite; both quartz and mullite are recognized respiratory hazards. Fly ash particles from both UK and Chinese coal-burning power stations were characterized by field emission-scanning electron microscopy (morphology and size), x-ray diffraction (crystallinity and minerals), and inductively coupled plasma-mass spectroscopy (elemental composition). PM(10) samples were separated from bulk fly ash by a dry dust separator system. The plasmid scission assay (PSA) was used to measure damage produced by fly ash to plasmid bacteriophage PhiX174 RF DNA. The supercoiled DNA was either damaged or severely damaged by reactive oxygen species (ROS) generated by the fly ash at different concentrations. Geochemical analyses confirmed that the fly ash particles are predominantly glass, with a minor component of the minerals quartz, hematite, and mullite. Fly ash particles also contained a range of metals contaminants; however, these were mostly bound into the glass with only a small proportion potentially bioaccessible. PSA data showed that fly ash exhibited significant oxidative capacity when compared to negative control (MB H(2)O), indicating that ROS are likely to be the driving force underlying fly ash bioreactivity.

Peroxisome proliferator-activated receptor-gamma ligands induce heme oxygenase-1 in lung fibroblasts by a PPARgamma-independent, glutathione-dependent mechanism

Oxidative stress plays an important role in the pathogenesis of pulmonary fibrosis. Heme oxygenase-1 (HO-1) is a key antioxidant enzyme, and overexpression of HO-1 significantly decreases lung inflammation and fibrosis in animal models. Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a transcription factor that regulates adipogenesis, insulin sensitization, and inflammation. We report here that the PPARgamma ligands 15d-PGJ2 and 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), which have potent antifibrotic effects in vitro, also strongly induce HO-1 expression in primary human lung fibroblasts. Pharmacological and genetic approaches are used to demonstrate that induction of HO-1 is PPARgamma independent. Upregulation of HO-1 coincides with decreased intracellular glutathione (GSH) levels and can be inhibited by N-acetyl cysteine (NAC), a thiol antioxidant and GSH precursor. Upregulation of HO-1 is not inhibited by Trolox, a non-thiol antioxidant, and does not involve the transcription factors AP-1 or Nrf2. CDDO and 15d-PGJ2 contain an alpha/beta unsaturated ketone that acts as an electrophilic center that can form covalent bonds with free reduced thiols. Rosiglitazone, a PPARgamma ligand that lacks an electrophilic center, does not induce HO-1. These data suggest that in human lung fibroblasts, 15d-PGJ2 and CDDO induce HO-1 via a GSH-dependent mechanism involving the formation of covalent bonds between 15d-PGJ2 or CDDO and GSH. Inhibiting HO-1 upregulation with NAC has only a small effect on the antifibrotic properties of 15d-PGJ2 and CDDO in vitro. These results suggest that CDDO and similar electrophilic PPARgamma ligands may have great clinical potential as antifibrotic agents, not only through direct effects on fibroblast differentiation and function, but indirectly by bolstering antioxidant defenses.

Apurinic/apyrimidinic endonuclease/redox effector factor-1(APE/Ref-1): a unique target for the prevention and treatment of human melanoma

Management of melanoma is a growing and challenging public health issue requiring novel and multidisciplinary approaches to achieve more efficient prevention and therapeutic benefits. The aim of this article is to show the critical role of APE/Ref-1 on melanomagenesis and progression. APE/Ref-1 serves as a redox-sensitive node of convergence of various signals as well as a DNA-repair enzyme, and its activation protects melanocytes and melanoma cells from chronic oxidative stress and promotes cell survival via mediation of downstream pathways. APE/Ref-1 is a strong candidate as a potential drug-treatable target for the prevention and treatment of human melanoma. Lead compounds exhibiting inhibitory effects on APE/Ref-1 are also reviewed. We anticipate potential clinical benefit in the future through inhibition of APE/Ref-1 and/or Ref-1-mediated signaling.

Surface-Dependent Quartz Uptake by Macrophages: Potential Role in Pulmonary Inflammation and Lung Clearance

Inhalation of quartz particles is associated with a variety of adverse lung effects. Since particle surface is considered to be crucial for particle pathogenicity, we investigated the influence of quartz surface properties on lung burden, inflammation (bronchoalveolar lavage cells), and cytotoxicity (protein, lactate dehydrogenase, beta-glucuronidase) 90 days after a single intratracheal instillation of 2 mg DQ12 into rats. The role of particle surface characteristics was investigated by comparative investigation of native versus surface-modified quartz, using polyvinylpyridine N-oxide (PVNO) or aluminum lactate (AL) coating. Uptake and subcellular localization of quartz samples as well as tumor necrosis factor (TNF)-alpha release were determined using NR8383 rat alveolar macrophages. Surface modification of quartz particles resulted in marked in vivo and in vitro changes. Compared to native quartz, modified quartz samples showed lower lung burden at 90 days, as well as decreased inflammatory and cytotoxic responses. Coating with polyvinylpyridine N-oxide (PVNO) appeared to be more effective than aluminium lactate (AL). PVNO-coating of quartz also resulted in an enhanced particle uptake by macrophages up to 24 h, whereas AL coating caused a transient reduction of quartz uptake at 2 h. At 24 h differences with the native quartz were absent. Subcellular localization of quartz particles was not affected by surface modifications. However, surface modification resulted in a reduced release of TNF-alpha. In conclusion, surface properties of quartz particles appear to be crucial for rate and extent of in vitro particle uptake in macrophages. Our in vivo findings also indicate that quartz surface properties may affect clearance kinetics. Particle surface-specific interactions between quartz and macrophages may therefore play a major role in the pulmonary pathogenicity of quartz.

Drug delivery and nanoparticles:applications and hazards

The use of nanotechnology in medicine and more specifically drug delivery is set to spread rapidly. Currently many substances are under investigation for drug delivery and more specifically for cancer therapy. Interestingly pharmaceutical sciences are using nanoparticles to reduce toxicity and side effects of drugs and up to recently did not realize that carrier systems themselves may impose risks to the patient. The kind of hazards that are introduced by using nanoparticles for drug delivery are beyond that posed by conventional hazards imposed by chemicals in classical delivery matrices. For nanoparticles the knowledge on particle toxicity as obtained in inhalation toxicity shows the way how to investigate the potential hazards of nanoparticles. The toxicology of particulate matter differs from toxicology of substances as the composing chemical(s) may or may not be soluble in biological matrices, thus influencing greatly the potential exposure of various internal organs. This may vary from a rather high local exposure in the lungs and a low or neglectable exposure for other organ systems after inhalation. However, absorbed species may also influence the potential toxicity of the inhaled particles. For nanoparticles the situation is different as their size opens the potential for crossing the various biological barriers within the body. From a positive viewpoint, especially the potential to cross the blood brain barrier may open new ways for drug delivery into the brain. In addition, the nanosize also allows for access into the cell and various cellular compartments including the nucleus. A multitude of substances are currently under investigation for the preparation of nanoparticles for drug delivery, varying from biological substances like albumin, gelatine and phospholipids for liposomes, and more substances of a chemical nature like various polymers and solid metal containing nanoparticles. It is obvious that the potential interaction with tissues and cells, and the potential toxicity, greatly depends on the actual composition of the nanoparticle formulation. This paper provides an overview on some of the currently used systems for drug delivery. Besides the potential beneficial use also attention is drawn to the questions how we should proceed with the safety evaluation of the nanoparticle formulations for drug delivery. For such testing the lessons learned from particle toxicity as applied in inhalation toxicology may be of use. Although for pharmaceutical use the current requirements seem to be adequate to detect most of the adverse effects of nanoparticle formulations, it can not be expected that all aspects of nanoparticle toxicology will be detected. So, probably additional more specific testing would be needed.

Combustion products of 1,3-butadiene inhibit catalase activity and induce expression of oxidative DNA damage repair enzymes in human bronchial epithelial cells

1,3-Butadiene, an important petrochemical, is commonly burned off when excess amounts need to be destroyed. This combustion process produces butadiene soot (BDS), which is composed of a complex mixture of polycyclic aromatic hydrocarbons in particulates ranging in size from <1 microm to 1 mm. An organic extract of BDS is both cytotoxic and genotoxic to normal human bronchial epithelial (NHBE) cells. Based on the oxidizing potential of BDS, we hypothesized that an organic extract of this particulate matter would (1) cause enzyme inactivation due to protein amino acid oxidation and (2) induce oxidative DNA damage in NHBE cells. Thus, our aims were to determine the effect of butadiene soot ethanol extract (BSEE) on both enzyme activity and the expression of proteins involved in the repair of oxidative DNA damage. Catalase was found to be sensitive to BDS as catalase activity was potently diminished in the presence of BSEE. Using Western analysis, both the alpha isoform of human 8-oxoguanine DNA glycosylase (alpha-hOGG1) and human apurinic/apyrimidinic endonuclease (APE-1) were shown to be significantly overexpressed as compared to untreated controls after exposure of NHBE cells to BSEE. Our results indicate that BSEE is capable of effectively inactivating the antioxidant enzyme catalase, presumably via oxidation of protein amino acids. The presence of oxidized biomolecules may partially explain the extranuclear fluorescence that is detected when NHBE cells are treated with an organic extract of BDS. Overexpression of both alpha-hOGG1 and APE-1 proteins following treatment of NHBE cells with BSEE suggests that this mixture causes oxidative DNA damage.

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

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

Study on the oxidative stress status among cement plant workers

The cement industry is considered as a major pollution problem because of dust and particulate matter emitted at various steps of cement production. In the present study, volunteer male workers from a cement factory were studied for oxidative and nitrosative stress biomarkers in relation to their serum levels of aluminum (Al) and chromium (Cr). The subjects were divided into two groups of direct and indirect exposure. Subject who worked in production steps were considered as direct exposure group, and those who worked in administration building were considered as indirect exposure group. For comparison, healthy subjects at the same age and socioeconomic status were tested as a control group. Serum levels of lipid peroxidation (LP), total antioxidant capacity (TAC), total thiol molecules (TTM), and nitric oxide (NO) as well as Al and Cr were measured. The results indicated a significant increase in Al ( P = 0.001) and Cr ( P = 0.009) levels in direct-exposed workers in comparison to healthy control group. Further, a significant increase in Al ( P = 0.002) and Cr ( P = 0.009) levels was observed in direct-exposed workers as compared to indirect-exposed one. Serum levels of TTM and TAC were significantly lower in both direct- and indirect-exposed groups in comparison to healthy control group ( P = 0.00). Serum TTM and TAC were significantly lower in direct-exposed workers as compared to indirect-exposed ones ( P = 0.00 and P = 0.024, respectively). There was no significant difference on the level of LP and NO among groups. A correlation was found between serum level of Cr, TAC, and platelets between direct- and indirect-exposed groups ( P < 0.05). Further correlation was found among serum level of Cr and those of TTM, platelets, and chronic disease ( P < 0.05). Chronic disease had a significant influence adjusted to other predictor variables on the post-shift values of Al ( P < 0.05). Although plasma levels of Al and Cr were found in normal ranges, analyses confirm their role in impairment of TMM and TAC.

Rapid non-genomic effects of glucocorticoids on oxidative stress in a guinea pig model of asthma

BACKGROUND AND OBJECTIVE

Glucocorticoids (GC) may exert therapeutic effects in asthma by a rapid non-genomic mechanism. The lungs of asthmatic patients are exposed to oxidative stress, which is believed to be critical in the pathogenesis of asthma. The aim of this study was to investigate whether GC exert a rapid non-genomic effect on oxidative stress in asthmatic guinea pigs.

METHODS

The guinea pig asthma model was used to assess inhibitory effects of budesonide (BUD) on oxidative stress. BAL fluid (BALF), trolox equivalent antioxidant capacity and lung manganese superoxide dismutase (MnSOD) activity were measured by spectrophotometry. Superoxide anion production was measured by cytochrome c reduction assay.

RESULTS

Oxidative stress occurred within minutes following antigen challenge and BUD reduced the severity of oxidative stress in asthmatic guinea pigs within 15 min. BUD significantly decreased BALF trolox equivalent antioxidant capacity and lung MnSOD activity, as compared with those of vehicle-treated asthmatic guinea pigs (P < 0.05). Additionally, BUD rapidly inhibited in vitro superoxide anion production by BALF cells and bronchi harvested from sensitized animals. These rapid effects were not blocked by the GC receptor antagonist RU486 and/or the protein synthesis inhibitor cycloheximide.

CONCLUSIONS

BUD reduced oxidative stress in a guinea pig model of asthma by a rapid non-genomic mechanism. These data suggest new mechanisms whereby GC treatments may benefit asthma.

Impact of the FcgammaII-receptor on quartz uptake and inflammatory response by alveolar macrophages

The inflammatory response following particle inhalation is described as a key event in the development of lung diseases, e.g., fibrosis and cancer. The essential role of alveolar macrophages (AM) in the pathogenicity of particles through their functions in lung clearance and mediation of inflammation is well known. However, the molecular mechanisms and direct consequences of particle uptake are still unclear. Inhibition of different classic phagocytosis receptors by flow cytometry shows a reduction of the dose-dependent quartz particle (DQ12) uptake in the rat AM cell line NR8383. Thereby the strongest inhibitory effect was observed by blocking the FcgammaII-receptor (FcgammaII-R). Fluorescence immunocytochemistry, demonstrating FcgammaII-R clustering at particle binding sites as well as transmission electron microscopy, visualizing zippering mechanism-like morphological changes, confirmed the role of the FcgammaII-R in DQ12 phagocytosis. FcgammaII-R participation in DQ12 uptake was further strengthened by the quartz-induced activation of the Src-kinase Lyn, the phospho-tyrosine kinases Syk (spleen tyrosine kinase) and PI3K (phosphatidylinositol 3-kinase), as shown by Western blotting. Activation of the small GTPases Rac1 and Cdc42, shown by immunoprecipitation, as well as inhibition of tyrosine kinases, GTPases, or Rac1 provided further support for the role of the FcgammaII-R. Consistent with the uptake results, FcgammaII-R activation with its specific ligand caused a similar generation of reactive oxygen species and TNF-alpha release as observed after treatment with DQ12. In conclusion, our results indicate a major role of FcgammaII-R and its downstream signaling cascade in the phagocytosis of quartz particles in AM as well as in the associated generation and release of inflammatory mediators.

U.S. EPA health assessment for diesel engine exhaust: a review

In 2002 the U.S. Environmental Protection Agency (EPA) released a Health assessment Document for Diesel Engine Exhaust. The objective of this assessment was to examine the possible health hazards associated with exposure to diesel engine exhaust (DE). The assessment concludes that long-term inhalation exposure is likely to pose a lung cancer hazard to humans as inferred from epidemiologic and certain animal studies. Estimation of cancer potency from available epidemiology studies was not attempted because of the absence of a confident cancer dose-response and animal studies were not judged appropriate for cancer potency estimation. A noncancer chronic human health hazard is inferred from rodent studies which show dose-dependent inflammation and histopathology in the rat lung. For these noncancer effects a safe exposure concentration for humans was estimated. Short-term exposures were noted to cause irritation and inflammatory symptoms of a transient nature, these being highly variable across an exposed population. The assessment also indicates that there is emerging evidence for the exacerbation of existing allergies and asthma symptoms; however, as of 2002 the data were inadequate for quantitative dose-response analysis. The assessment conclusions are based on studies that used exposures from engines built prior to the mid 1990s. More recent engines without high-efficiency particle traps would be expected to have exhaust emissions with similar characteristics. With additional cancer epidemiology studies expected in 2007-2008, and a growing body of evidence for allergenicity and cardiovascular effects, future health assessments will have an expanded health effects data base to evaluate.

Genotoxicity of poorly soluble particles

Poorly soluble particles such as TiO2, carbon black, and diesel exhaust particles have been evaluated for their genotoxicity using both in vitro and in vivo assays, since inhalation of these compounds by rats at high concentrations has been found to lead to tumor formation. Two principle modes of genotoxic action can be considered for particles, referred to as primary and secondary genotoxicity. Primary genotoxicity is defined as genetic damage elicited by particles in the absence of pulmonary inflammation, whereas secondary genotoxicity implies a pathway of genetic damage resulting from the oxidative DNA attack by reactive oxygen/nitrogen species (ROS/RNS), generated during particle-elicited inflammation. Conceptually, primary genotoxicity might operate via various mechanisms, such as the actions of ROS (e.g., as generated from reactive particle surfaces), or DNA-adduct formation by reactive metabolites of particle-associated organic compounds (e.g., polycyclic aromatic hydrocarbons). Currently available literature data, however, merely indicate that the tumorigenesis of poorly soluble particles involves a mechanism of secondary genotoxicity. However, further research is urgently required, since (1) causality between pulmonary inflammation and genotoxicity has not yet been established, and (2) effects of inflammation on fundamental DNA damage responses that orchestrate mutagenesis and carcinogenic outcome,that is, cell cycle arrest, DNA repair, proliferation, and apoptosis, are currently poorly understood.

Cytotoxicity and DNA-damage in human lung epithelial cells exposed to respirable α-quartz

Occupational exposure to respirable crystalline silica is associated with the development of silicosis, lung cancer and airways diseases. In order to assess cytotoxic effects and direct-oxidative DNA damage induced by short-term exposure to different doses of respirable alpha-quartz (NIST SRM1878a), we conducted a study using A549 cells. The cells were exposed to alpha-quartz at 25, 50, 100 microg/ml for 4 h and analysed by scanning electron microscope (SEM) and LDH release assay for cytotoxic effect evaluation. Cells were also exposed to 10, 25, 50, 100 microg/ml of alpha-quartz for 2 h and 4 h and analysed by Fpg comet test to evaluate direct and oxidative DNA damage. SEM observations of treated cells showed bleb development at lower doses and alterations of microvilli morphology at the highest dose. A slight LDH release was found only at 100 microg/ml. Fpg comet test showed a dose-related oxidative DNA damage in cells exposed for 2 h to quartz. Cells exposed for 4h at the same concentrations showed a dose-related direct DNA damage and the presence of oxidative DNA damage at lower doses. The bleb induction on cell surface evidenced by SEM at lower doses correlates with the presence of oxidative DNA damage at 4 h. The cell surface modifications observed by SEM at 100 microg/ml indicate that high doses of quartz induce more evident cytotoxic effects confirmed by LDH analysis and correlate with the genotoxicity showed by comet assay.

Angiotensin II type 1 receptor blocker inhibits fibrosis in rat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is now the most frequent cause of chronic liver impairment in developed countries and is a suggested causative factor in the development of cryptogenic cirrhosis and hepatocellular carcinoma. At present there is no effective and accepted therapy for NASH. The renin-angiotensin system is involved in hepatic fibrosis through activation of hepatic stellate cells, major fibrogenic cells in the liver. Hepatic stellate cells are activated by liver injury to express excessive matrix proteins and profibrogenic cytokines such as transforming growth factor-beta 1. Medicines that inhibit this pathway may be of therapeutic potential in NASH. Using a methionine-choline-deficient rat model of NASH, we studied the potential utility of an angiotensin II type 1 receptor blocker (ARB), olmesartan, on biochemical, histologic, and antioxidant measures of disease activity. ARB significantly attenuated increases in aspartate aminotransferase, activation of hepatic stellate cells, oxidative stress, expression of transforming growth factor-beta 1, expression of collagen genes, and liver fibrosis.

CONCLUSION

Our observations strongly suggest a potential preventive role for ARB in the progression of nonalcoholic steatohepatitis.