Ultrafine airborne particles cause increases in protooncogene expression and proliferation in alveolar epithelial cells

Disruption of phosphofructokinase activity and aerobic glycolysis in human bronchial epithelial cells by atmospheric ultrafine particulate matter

Exposure to ambient ultrafine particulate matter (UPM) causes respiratory disorders; however, the underlying molecular mechanisms remain unclear. In this study, we synthesized simulated UPM (sUPM) with controlled physicochemical properties using the spark-discharge method. Subsequently, we investigated the biological effects of sUPM using BEAS-2B human bronchial epithelial cells (HBECs) and a mouse intratracheal instillation model. High throughput RNA-sequencing and bioinformatics analyses revealed that dysregulation of the glycolytic metabolism is involved in the inhibited proliferation and survival of HBECs by sUPM treatment. Furthermore, signaling pathway and enzymatic analyses showed that the treatment of BEAS-2B cells with sUPM induces the inactivation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB, also known as AKT), resulting in the downregulation of phosphofructokinase 2 (PFK2) S483 phosphorylation, PFK enzyme activity, and aerobic glycolysis in HBECs in an oxidative stress-independent manner. Additionally, intratracheal instillation of sUPM reduced the phosphorylation of ERK, AKT, and PFK2, decreased proliferation, and increased the apoptosis of bronchial epithelial cells in mice. The findings of this study imply that UPM induces pulmonary toxicity by disrupting aerobic glycolytic metabolism in lung epithelial cells, which can provide novel insights into the toxicity mechanisms of UPM and strategies to prevent their toxic effects.

Microglial activation and inflammation caused by traffic-related particulate matter

Neurotoxicity caused by particulate matter (PM) has been highlighted as being a potential risk factor for neurodegenerative diseases. However, the effects of brain inflammation in response to traffic-related PM remain unclear. The objective of this study was to investigate the effects of traffic-related PM on microglial responses. We determined the cytotoxicity, oxidative stress, lipid peroxidation, inflammation, activation, autophagy, and apoptosis due to exposure to carbon black (CB) and diesel exhaust particles (DEPs) in Bv2 microglial cells. Additionally, cells were pretreated with corticosteroid to determine alterations in microglial activation and inflammation. For in vivo confirmation, Sprague Dawley (SD) rats were whole-body exposed to traffic-related PM₁ (PM with an aerodynamic diameter of <1 μm) for 3 and 6 months. We observed that a decrease in cell viability and increases in dichlorodihydrofluorescein (DCFH), lactate dehydrogenase (LDH), and thiobarbituric acid-reactive substances (TBARSs) occurred due to CB and DEP. Production of interleukin (IL)-6 and soluble tumor necrosis factor (TNF)-α was significantly stimulated by CB and DEP, whereas production of cellular TNF-α was significantly stimulated by CB. Iba1 and prostaglandin E2 (PGE2) significantly increased due to CB and DEP. Consistently, we observed significant increases in Iba1 in the hippocampus of rats after 3 and 6 months of exposure to traffic-related PM₁. We found that the light chain 3II (LC3II)/LC3I ratio and caspase-3 activity increased due to CB and DEP exposure. Subsequently, LDH, TBARS, LC3II/I, and caspase-3 activities did not clearly respond to corticosteroid pretreatment followed by DEP exposure in BV2 cells. Results of the present study suggested that traffic-related PM induced cytotoxicity, lipid peroxidation, microglial activation, and inflammation as well as autophagy and caspase-3 regulation in microglia. We demonstrated that microglial activation and inflammation may play important roles in the response of the brain to traffic-related PM.

[Study on the Relationship between the Inhalable Fine Particulate Matter of Xuanwei Coal Combustion and Lung Cancer]

背景与目的

云南省宣威地区是中国乃至世界肺癌的高发区，肺癌已成为制约当地社会经济发展和影响社会民生的重要因素。煤炭是当地主要的生活燃料，燃煤是当地室内污染的主要来源。本研究探讨云南宣威不同肺癌发病率地区烟煤燃烧过程中可吸入细颗粒物(fine particulate matter, PM2.5)产出情况，以及不同地区PM2.5成分异同。探讨吸入细颗粒物与当地肺癌高发的关系。

方法

收集宣威市来宾镇老林煤矿C1煤层、宝山镇虎场煤矿K7煤层、文兴镇太平煤矿M30煤层的煤矿进行燃烧试验。收集室内的空气中的PM2.5进行称重，元素分析，用电子显微镜观察其形态，对比三种PM2.5异同。对宣威地区的肺癌患者的术后标本进行电子显微镜观察。

结果

室内空气中的PM2.5浓度分别为C1煤(8.244±1.460)mg/m³，K7煤(5.066±0.984)mg/m³，K7煤(5.071±1.460)mg/m³；三组空气中PM2.5浓度两两比较差异有统计学意义(Ρ=0.029)。C1煤层中滤膜上的杂质有(Silicon, Si)和氧(Oxygen, O)元素富集，三组滤膜上均发现了碳(Carbon, C)，硫(Sulfur, S)的聚集，在部分的滤膜上可见游离的二氧化硅(SiO₂)，部分滤膜上有铝(Aluminium, Al)、钙(Calcium, Ca)元素的聚集。C1煤层与其他煤层相比所产生颗粒物形态不规则，成团块状，杂质较多。在部分的宣威来宾地区的肺癌患者术后标本中，发现纳米级细颗粒的杂质。

结论

C1煤与K7和M30煤燃烧产生的PM2.5不同，PM2.5的成分可能与当地肺癌高发相关。

Meteorological conditions, climate change, new emerging factors, and asthma and related allergic disorders. A statement of the World Allergy Organization

The prevalence of allergic airway diseases such as asthma and rhinitis has increased dramatically to epidemic proportions worldwide. Besides air pollution from industry derived emissions and motor vehicles, the rising trend can only be explained by gross changes in the environments where we live. The world economy has been transformed over the last 25 years with developing countries being at the core of these changes. Around the planet, in both developed and developing countries, environments are undergoing profound changes. Many of these changes are considered to have negative effects on respiratory health and to enhance the frequency and severity of respiratory diseases such as asthma in the general population.

Increased concentrations of greenhouse gases, and especially carbon dioxide (CO₂), in the atmosphere have already warmed the planet substantially, causing more severe and prolonged heat waves, variability in temperature, increased air pollution, forest fires, droughts, and floods – all of which can put the respiratory health of the public at risk. These changes in climate and air quality have a measurable impact not only on the morbidity but also the mortality of patients with asthma and other respiratory diseases. The massive increase in emissions of air pollutants due to economic and industrial growth in the last century has made air quality an environmental problem of the first order in a large number of regions of the world. A body of evidence suggests that major changes to our world are occurring and involve the atmosphere and its associated climate. These changes, including global warming induced by human activity, have an impact on the biosphere, biodiversity, and the human environment. Mitigating this huge health impact and reversing the effects of these changes are major challenges.

This statement of the World Allergy Organization (WAO) raises the importance of this health hazard and highlights the facts on climate-related health impacts, including: deaths and acute morbidity due to heat waves and extreme meteorological events; increased frequency of acute cardio-respiratory events due to higher concentrations of ground level ozone; changes in the frequency of respiratory diseases due to trans-boundary particle pollution; altered spatial and temporal distribution of allergens (pollens, molds, and mites); and some infectious disease vectors. According to this report, these impacts will not only affect those with current asthma but also increase the incidence and prevalence of allergic respiratory conditions and of asthma. The effects of climate change on respiratory allergy are still not well defined, and more studies addressing this topic are needed. Global warming is expected to affect the start, duration, and intensity of the pollen season on the one hand, and the rate of asthma exacerbations due to air pollution, respiratory infections, and/or cold air inhalation, and other conditions on the other hand.

Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) for pulmonary application: a review of the state of the art

Drug delivery by inhalation is a noninvasive means of administration that has following advantages for local treatment for airway diseases: reaching the epithelium directly, circumventing first pass metabolism and avoiding systemic toxicity. Moreover, from the physiological point of view, the lung provides advantages for systemic delivery of drugs including its large surface area, a thin alveolar epithelium and extensive vasculature which allow rapid and effective drug absorption. Therefore, pulmonary application is considered frequently for both, the local and the systemic delivery of drugs. Lipid nanoparticles - Solid Lipid Nanoparticles and Nanostructured Lipid Carriers - are nanosized carrier systems in which solid particles consisting of a lipid matrix are stabilized by surfactants in an aqueous phase. Advantages of lipid nanoparticles for the pulmonary application are the possibility of a deep lung deposition as they can be incorporated into respirables carriers due to their small size, prolonged release and low toxicity. This paper will give an overview of the existing literature about lipid nanoparticles for pulmonary application. Moreover, it will provide the reader with some background information for pulmonary drug delivery, i.e., anatomy and physiology of the respiratory system, formulation requirements, application forms, clearance from the lung, pharmacological benefits and nanotoxicity.

Effect of serum on diesel exhaust particles (DEP)-induced apoptosis of airway epithelial cells in vitro

Patients with chronic airway diseases may be more susceptible to adverse effects of air pollutants including diesel exhaust particles (DEP). We investigated effects of foetal calf serum (FCS) on DEP-induced changes in airway epithelial cell apoptosis and inflammation. DEP (50-200 μg/ml) increased A549 cell viability in the absence of FCS. In the presence of 3.3%FCS, DEP (50-400 μg/ml) decreased A549 cell viability. N-acetylcysteine (NAC, 33 mM) and the c-jun N-terminal kinase (JNK) inhibitor (SP600125, 33 μM) further decreased the viability in the presence of DEP (200 μg/ml) and 3.3% FCS. Under serum-free (SF) condition, DEP (50 μg/ml) reduced apoptotic cells; however, when 3.3% FCS added to the culture medium, this effect was abolished. DEP (200 μg/ml) induced mRNA expression of p21(CIP1/WAF1) both in absence or presence of 3.3% FCS and enhanced JNK2 mRNA expression only in the presence of 3.3% FCS. Under SF condition, DEP (50 μg/ml) induced mRNA expression for p27 and p53, whereas cyclin E mRNA expression was inhibited by DEP (50 and 200 μg/ml). Furthermore, DEP (200 μg/ml) decreased the release of interleukin (IL)-8 in the absence of FCS. In conclusion, FCS modulates effects of DEP on cell death, cell cycle and apoptosis regulating proteins, and IL-8 release by activating oxidant stress pathways, JNK and NF-κB. Extravasation of serum, as occurs in the inflamed airways of patients with chronic airway diseases such as asthma and COPD, may render airway epithelial cells more susceptible to the deleterious effects of DEP.

Combustion particles emitted during church services: implications for human respiratory health

Burning candles and incense generate particulate matter (PM) that produces poor indoor air quality and may cause human pulmonary problems. This study physically characterised combustion particles collected in a church during services. In addition, the emissions from five types of candles and two types of incense were investigated using a combustion chamber. The plasmid scission assay was used to determine the oxidative capacities of these church particles. The corresponding risk factor (CRf) was derived from the emission factor (Ef) and the oxidative DNA damage, and used to evaluate the relative respiratory exposure risks. Real-time PM measurements in the church during candle-incense burning services showed that the levels (91.6 μg/m(3) for PM(10); 38.9 μg/m(3) for PM(2.5)) exceeded the European Union (EU) air quality guidelines. The combustion chamber testing, using the same environmental conditions, showed that the incense Ef for both PM(10) (490.6-587.9 mg/g) and PM(2.5) (290.1-417.2 mg/g) exceeded that of candles; particularly the PM(2.5) emissions. These CRf results suggested that the exposure to significant amounts of incense PM could result in a higher risk of oxidative DNA adducts (27.4-32.8 times) than tobacco PM. The generation and subsequent inhalation of PM during church activities may therefore pose significant risks in terms of respiratory health effects.

Differences in gene expression and cytokine production by crystalline vs. amorphous silica in human lung epithelial cells

Background

Exposure to respirable crystalline silica particles, as opposed to amorphous silica, is associated with lung inflammation, pulmonary fibrosis (silicosis), and potentially with lung cancer. We used Affymetrix/GeneSifter microarray analysis to determine whether gene expression profiles differed in a human bronchial epithelial cell line (BEAS 2B) exposed to cristobalite vs. amorphous silica particles at non-toxic and equal surface areas (75 and 150 × 10⁶μm²/cm²). Bio-Plex analysis was also used to determine profiles of secreted cytokines and chemokines in response to both particles. Finally, primary human bronchial epithelial cells (NHBE) were used to comparatively assess silica particle-induced alterations in gene expression.

Results

Microarray analysis at 24 hours in BEAS 2B revealed 333 and 631 significant alterations in gene expression induced by cristobalite at low (75) and high (150 × 10⁶μm²/cm²) amounts, respectively (p < 0.05/cut off ≥ 2.0-fold change). Exposure to amorphous silica micro-particles at high amounts (150 × 10⁶μm²/cm²) induced 108 significant gene changes. Bio-Plex analysis of 27 human cytokines and chemokines revealed 9 secreted mediators (p < 0.05) induced by crystalline silica, but none were induced by amorphous silica. QRT-PCR revealed that cristobalite selectively up-regulated stress-related genes and cytokines (FOS, ATF3, IL6 and IL8) early and over time (2, 4, 8, and 24 h). Patterns of gene expression in NHBE cells were similar overall to BEAS 2B cells. At 75 × 10⁶μm²/cm², there were 339 significant alterations in gene expression induced by cristobalite and 42 by amorphous silica. Comparison of genes in response to cristobalite (75 × 10⁶μm²/cm²) revealed 60 common, significant gene alterations in NHBE and BEAS 2B cells.

Conclusions

Cristobalite silica, as compared to synthetic amorphous silica particles at equal surface area concentrations, had comparable effects on the viability of human bronchial epithelial cells. However, effects on gene expression, as well as secretion of cytokines and chemokines, drastically differed, as the crystalline silica induced more intense responses. Our studies indicate that toxicological testing of particulates by surveying viability and/or metabolic activity is insufficient to predict their pathogenicity. Moreover, they show that acute responses of the lung epithelium, including up-regulation of genes linked to inflammation, oxidative stress, and proliferation, as well as secretion of inflammatory and proliferative mediators, can be indicative of pathologic potential using either immortalized lines (BEAS 2B) or primary cells (NHBE). Assessment of the degree and magnitude of these responses in vitro are suggested as predictive in determining the pathogenicity of potentially harmful particulates.

Activation of HGF/c-Met signaling by ultrafine carbon particles and its contribution to alveolar type II cell proliferation

Hepatocyte growth factor (HGF) is a potent mitogen and motogen for various epithelial cells. The present study aimed to explore the role of HGF and c-Met receptor in ultrafine carbon particle-induced alveolar type II epithelial (type II) cell proliferation. ICR mice were intratracheally instilled with 100 μg ultrafine carbon black (ufCB) and killed at 21, 48, and 72 days postexposure to examine type II cell proliferation, HGF release, and c-Met activation. In vivo and in vitro applications of neutralizing anti-HGF antibody were used to investigate the causal role of HGF in cell proliferation. The Met kinase inhibitor SU11274 and extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 were used to delineate the involvement of c-Met/ERK1/2 in rat L2 pulmonary epithelial cell proliferation. The results demonstrated that in vivo exposure to 100 μg ufCB caused increased HGF in bronchoalveolar lavage fluid, as well as increased HGF production, c-Met phosphorylation, and cell proliferation in type II cells. In vitro study revealed that ufCB caused a dose-dependent increase in HGF release, c-Met phosphorylation, and cell proliferation. Importantly, treatment with the neutralizing anti-HGF antibody significantly blocked ufCB-induced in vivo and in vitro type II cell proliferation. Moreover, SU11274 and PD98059 significantly reduced ufCB-increased L2 cell proliferation. Results from Western blotting demonstrated that SU11274 successfully suppressed ufCB-induced phosphorylation of c-Met and ERK1/2. In summary, the activation of HGF/c-Met signaling is a major pathway involved in ufCB-induced type II cell proliferation.

c-Src-mediated activation of Erk1/2 is a reaction of epithelial cells to carbon nanoparticle treatment and may be a target for a molecular preventive strategy

Owing to their specific physico/chemical properties, engineered as well as environmental nanoparticles can induce pathogenic endpoints in humans. Earlier studies demonstrated that pure carbon nanoparticles induce cell signaling events at the level of membrane receptor activation in lung epithelial cells. As a possible link between receptor activation and subsequent MAP-kinase signaling, the involvement of Src family kinases was investigated in cell lines of organs potentially exposed to environmental nanoparticles. Human cells from bronchus, intestine, and skin (keratinocytes) as well as rat lung epithelial cells showed similar time patterns for the activation of mitogen-activated protein kinases Erk1/2 as well as Src family kinases (SFK) when treated with carbon nanoparticles. Moreover, c-Src was identified as an integral part of the signaling mediating the transfer of information from membrane receptors to members of the proliferative signaling cascade in lung epithelial cells. Pretreatment of cells with the compatible solute ectoine, which is known to stabilize macromolecules, reduced the nanoparticle specific phosphorylation of SFK. Together with earlier in vivo and in vitro data, this demonstrates that compatible solutes prevent nanoparticle-induced signaling steps at the level of membrane-coupled signaling.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Oxidative stress, calcium homeostasis, and altered gene expression in human lung epithelial cells exposed to ZnO nanoparticles

The influence of 20nm ZnO nanoparticles on cytotoxicity, oxidative stress, intracellular calcium homeostasis, and gene expression was studied in human bronchial epithelial cells (BEAS-2B). ZnO caused a concentration- and time-dependent cytotoxicity while elevating oxidative stress and causing membrane damage (cellular LDH release). There was a remarkably steep relationship between concentration and toxicity at concentrations from 5 to 10microg/ml. Cytotoxicity was completely abolished by the antioxidant N-acetylcysteine (NAC). Exposure to ZnO also increased intracellular calcium levels ([Ca(2+)](in)) in a concentration- and time-dependent manner that was partially attenuated by NAC. Nifedipine, a calcium channel blocker, partially attenuated the elevated [Ca(2+)](in), indicating that some of the excess [Ca(2+)](in) is a result of influx from outside the cell. The relationships between oxidative stress, [Ca(2+)](in), and cytotoxicity are discussed. Exposure to a sublethal concentration of ZnO increased the expression of four genes that are involved in apoptosis and oxidative stress responses BNIP, PRDX3, PRNP, and TXRND1, by at least 2.5-fold. Thus, ZnO alters transcriptional regulation in BEAS-2B cells.

Apoptotic and Inflammatory Effects Induced by Different Particles in Human Alveolar Macrophages

Pollutant particles induce apoptosis and inflammation, but the relationship between these two biological processes is not entirely clear. In this study, we compared the proapoptotic and proinflammatory effects of four particles: residual oil fly ash (ROFA), St. Louis particles SRM 1648 (SL), Chapel Hill PM10 (CHP), and Mount St. Helens dust (MSH). Human alveolar macrophages (AM) were incubated with these particles at 100 microg/ml. Cell death was assessed by annexin V (AV) expression, histone release, nuclear morphology, caspase 3-like activity and release of caspase 1 for apoptosis, and propidium iodide (PI) for necrosis, and inflammation was measured by interleukin (IL)-1beta and IL-6. We found that particle effects on these cell death measurements varied, and ROFA affected most (four out of five) endpoints, including nuclear morphological changes. CHP and SL also caused necrosis. For cytokine release, the potency was CHP > SL > ROFA > MSH. The proapoptotic and proinflammatory effects induced by the whole particles were unaltered after the particles were washed with water. The water-soluble fraction was relatively inactive, as were individual soluble metals (V, Ni, Fe). ROFA-induced nuclear fragmentation was associated with upregulation and mitochondrial release of apoptosis-inducing factor (AIF), a caspase-independent chromatin condensation factor, and upregulation of DNase II, a lysosomal acid endonuclease. These results indicate that the potential for particles to induce apoptosis does not correlate with their proinflammatory properties, although active components for both processes reside in the water-insoluble core. Both apoptosis and inflammatory endpoints should be included when the toxicity of different pollutant particles is assessed.

Nanoparticles-a thoracic toxicology perspective

A substantial literature demonstrates that the main ultrafine particles found in ambient urban air are combustion-derived nanoparticles (CDNP) which originate from a number of sources and pose a hazard to the lungs. For CDNP, three properties appear important-surface area, organics and metals. All of these can generate free radicals and so induce oxidative stress and inflammation. Inflammation is a process involved in the diseases exhibited by the individuals susceptible to the effects of PM- development and exacerbations of airways disease and cardiovascular disease. It is therefore possible to implicate CDNP in the common adverse effects of increased PM. The adverse effects of increases in PM on the cardiovascular system are well-documented in the epidemiological literature and, as argued above, these effects are likely to be driven by the combustion-derived NP. The epidemiological findings can be explained in a number of hypotheses regarding the action of NP:-1) Inflammation in the lungs caused by NP causes atheromatous plaque development and destabilization; 2) The inflammation in the lungs causes alteration in the clotting status or fibrinolytic balance favouring thrombogenesis; 3) The NP themselves or metals/organics released by the particles enter the circulation and have direct effects on the endothelium, plaques, the clotting system or the autonomic nervous system/ heart rhythm. Environmental nanoparticles are accidentally produced but they provide a toxicological model for a new class of purposely 'engineered' NP arising from the nanotechnology industry, whose effects are much less understood. Bridging our toxicological knowledge between the environmental nanoparticles and the new engineered nanoparticles is a considerable challenge.

Effects of dust storm PM2.5 on cell proliferation and cell cycle in human lung fibroblasts

Reports on the effects of PM2.5 from dust storm on lung cells are limited. We compared the effects of PM2.5 collected in dust storm days (dust storm PM2.5) with that in sunshiny and non-dust storm days (normal PM2.5) on cell proliferation and cell cycle in human lung fibroblasts. Our results showed that both dust storm and normal PM2.5 had biphasic effects on cell proliferation, namely, stimulated cell proliferation at lower concentrations while inhibited it at higher concentrations. On the contrary, the organic and inorganic extracts from dust storm and normal PM2.5 significantly inhibited the proliferation in human lung fibroblasts at the concentrations corresponding to their mass contents in PM2.5 samples. The flow cytometry showed that the number of cells in G2/M phase increased significantly after treatment with the dust storm and normal PM2.5. The inorganic and organic extracts from PM2.5, however, induced cell arrest in S phase and G0/G1 phase, respectively. It seems that the biphasic effects of both dust storm and normal PM2.5 on cell proliferation may not be related to their inorganic or organic extractable components.

Amiodarone Induces Angiotensinogen Gene Expression in Lung Alveolar Epithelial Cells through Activation Protein-1

Previous work from this laboratory has shown that amiodarone induces alveolar epithelial cell apoptosis that was abrogated by antagonists of angiotensin II. In this study, amiodarone up-regulated angiotensinogen mRNA and protein in primary cultures of rat type II pneumocytes and in the human A549 cell line. The mechanism of amiodarone-induced angiotensinogen expression was studied in A549 cells with a human angiotensinogen promoter-luciferase reporter (angiotensinogen/luciferase). Amiodarone (3 microg/ml) induced both angiotensinogen/luciferase and endogenous angiotensinogen mRNA; the latter was completely blocked by actinomycin-D. Amiodarone did not affect the half-life of endogenous angiotensinogen mRNA. Deletion analyses of angiotensinogen/luciferase identified at least two amiodarone-responsive domains in the angiotensinogen promoter between -350 to -260 bp and -203 to -46 bp. DNA/Protein array and electrophoretic mobility shift assays showed that amiodarone increases DNA binding of both activation protein-1 and STAT-5 transcription factors. Site-directed mutagenesis of three IL-6-responsive signal transducer activator of transcription (STAT) binding sites within the amiodarone-response domains had no effect on amiodarone-induced angiotensinogen/luciferase expression. In contrast, amiodarone-induced angiotensinogen/luciferase expression was abrogated by a dominant-negative fos construct and was stimulated over five times by c-fos and c-jun expressed together but not separately. Mutagenesis of the activation protein-1 binding site at -15 to -12 bp completely eliminated the response to amiodarone. These data show that activation protein-1 family transcription factors mediate amiodarone-induced angiotensinogen expression in human alveolar epithelial cells and identify an activation protein-1 site, located between the TATA (DNA sequence) box and the transcription initiation site, that is required for the response.

Genotoxicity induced by fine urban air particulate matter in the macrophages cell line RAW 264.7

Recent studies support a participation of fine airborne particulate matter (PM) with an aerodynamic diameter less than 2.5 microm in the effects of air pollutants on health. Particulate matter was collected in an urban area of L'Aquila during the winter 2004. Fine particulate samples were analyzed by X-ray photoelectron spectroscopy (XPS) to determine the chemical inventory of the aerosol particle surfaces and to evaluate the weight of characteristic functional groups of the most frequent carbon-containing organic pollutant compounds (C-C/C-H, C-O/C-N, C=O, COOH). The most important contributor to the mass of fine particulate matter was carbon. The overall purpose of this work was to determine the in vitro toxicity and genotoxicity of fine PM in cultured macrophages (RAW 264.7 cells) since the biological target of inhaled PM are the pulmonary epithelium and resident macrophages. In parallel in vitro toxicity assays were used including cell viability and apoptosis. Genotoxicity was evaluated by the micronucleus (MN) assay. The viability of macrophages was assessed by the MTT method; apoptosis by an ELISA test for programmed cell death (PCD) was determined after RAW 264.7 cells treatment. Concentration of 1, 3 and 10 microg/cm2 of fine particles induced micronuclei in a dose-dependent manner. We also compared the effects of fine PM with those of fine carbon black particles (CB) in similar doses. Fine carbon black particles were consistently less genotoxic than the fine atmospheric particles, suggesting that the contaminants adsorbed on them (i.e. carbon-containing organic compounds in addition to metal oxides and metal salts) are involved in genotoxicity. Fine PM reduced cellular proliferation. Overall, the results presented here demonstrate the utility of in vitro tests in mouse cells for testing genotoxicity of urban air particulate matter.

Ultrafine carbon particles induce apoptosis and proliferation in rat lung epithelial cells via specific signaling pathways both using EGF-R

Apoptosis and proliferation are important causes of adverse health effects induced by inhaled ultrafine particles. The molecular mechanisms of particle cell interactions mediating these end points are therefore a major topic of current particle toxicology and molecular preventive medicine. Initial studies revealed that ultrafine particles induce apoptosis and proliferation in parallel in rat lung epithelial cells, dependent on time and dosage. With these end points, two antagonistic reactions seem to be induced by the same extracellular stimulus. It was therefore investigated whether proliferation is induced directly by the particles or as a compensation of particle-caused cell death. Experimental conditions excluding compensatory proliferation demonstrated that both end points are induced independently by specific signaling pathways. Events eliciting signaling cascades leading to apoptosis and proliferation were studied with specific inhibitors of membrane receptors. Epidermal growth factor receptor (EGF-R) kinase activity was identified as essential for apoptosis as well as for proliferation. As ultrafine particle-induced proliferation alone was dependent on the activation of beta1-integrins, these membrane receptors are suggested to mediate the specificity of EGF-R signaling concerning the decision as to whether apoptosis or proliferation is triggered. Accordingly, MAP kinase signaling downstream of EGF-R showed comparable specificity with regard to receptor-dependent induction of apoptosis and proliferation. As key mediators of signaling cascades, the activation of extracellular signal-regulated kinases 1 and 2 proved to be specific for proliferation in a beta1-integrin-dependent manner, whereas phosphorylation of c-Jun NH2-terminal kinases 1 and 2 was correlated with the induction of apoptosis.

Ultrafine carbon black particles stimulate proliferation of human airway epithelium via EGF receptor-mediated signaling pathway

Exposure to ambient ultrafine particles induces airway inflammatory reactions and tissue remodeling. In this experiment, to determine whether ultrafine carbon black (ufCB) affects proliferation of airway epithelium and, if so, what the mechanism of action is, we studied human primary bronchial epithelial cell cultures. Incubation of cells in the serum-free medium with ufCB increased incorporations of [3H]thymidine and [3H]leucine into cells in a time- and dose-dependent manner. This effect was attenuated by Cu- and Zn-containing superoxide dismutase (Cu/Zn SOD) and apocynin, an inhibitor of NADPH oxidase, and completely inhibited by pretreatment with the epidermal growth factor receptor (EGF-R) tyrosine kinase inhibitors AG-1478 and BIBX-1382, and the mitogen-activated protein kinase kinase inhibitor PD-98059. Transfection of a dominant-negative mutant of H-Ras likewise abolished the effect ufCB. Stimulation with ufCB also induced processing of membrane-anchored proheparin-binding (HB)-EGF, release of soluble HB-EGF into the medium, association of phosphorylated EGF-R and Shc with glutathione- S-transferase-Grb2 fusion protein, and phosphorylation of extracellular signal-regulated kinase (ERK). Pretreatment with AG-1478, [Glu52] Diphtheria toxin, a specific inhibitor of HB-EGF, neutralizing HB-EGF antibody, Cu/Zn SOD, and apocynin each inhibited ufCB-induced ERK activation. These results suggest that ufCB causes oxidative stress-mediated proliferation of airway epithelium, involving processing of HB-EGF and the concomitant activation of EGF-R and ERK cascade.

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

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

Inhaled particles and lung cancer. Part A: Mechanisms

Both occupational and environmental exposure to particles is associated with an increased risk of lung cancer. Particles are thought to impact on genotoxicity as well as on cell proliferation via their ability to generate oxidants such as reactive oxygen species (ROS) and reactive nitrogen species (RNS). For mechanistic purposes, one should discriminate between a) the oxidant-generating properties of particles themselves (i.e., acellular), which are mostly determined by the physicochemical characteristics of the particle surface, and b) the ability of particles to stimulate cellular oxidant generation. Cellular ROS/RNS can be generated by various mechanisms, including particle-related mitochondrial activation or NAD(P)H-oxidase enzymes. In addition, since particles can induce an inflammatory response, a further subdivision needs to be made between primary (i.e., particle-driven) and secondary (i.e., inflammation-driven) formation of oxidants. Particles may also affect genotoxicity by their ability to carry surface-adsorbed carcinogenic components into the lung. Each of these pathways can impact on genotoxicity and proliferation, as well as on feedback mechanisms involving DNA repair or apoptosis. Although abundant evidence suggests that ROS/RNS mediate particle-induced genotoxicity and mutagenesis, little information is available towards the subsequent steps leading to neoplastic changes. Additionally, since most of the proposed molecular mechanisms underlying particle-related carcinogenesis have been derived from in vitro studies, there is a need for future studies that evaluate the implication of these mechanisms for in vivo lung cancer development. In this respect, transgenic and gene knockout animal models may provide a useful tool. Such studies should also include further assessment of the relative contributions of primary (inflammation-independent) and secondary (inflammation-driven) pathways.

Oxidative stress and calcium signaling in the adverse effects of environmental particles (PM10)

This review focuses on the potential role that oxidative stress plays in the adverse effects of PM(10). The central hypothesis is that the ability of PM(10) to cause oxidative stress underlies the association between increased exposure to PM(10) and both exacerbations of lung disease and lung cancer. Pulmonary inflammation may also underlie the cardiovascular effects seen following increased PM(10), although the mechanisms of the cardiovascular effects of PM(10) are not well understood. PM(10) is a complex mix of various particle types and several of the components of PM(10) are likely to be involved in the induction of oxidative stress. The most likely of these are transition metals, ultrafine particle surfaces, and organic compounds. In support of this hypothesis, oxidative stress arising from PM(10) has been shown to activate a number of redox-responsive signaling pathways in lung target cells. These pathways are involved in expression of genes that play a role in responses relevant to inflammation and pathological change, including MAPKs, NF-kappaB, AP-1, and histone acetylation. Oxidative stress from particles is also likely to play an important role in the carcinogenic effects associated with PM(10) and hydroxyl radicals from PM(10) cause DNA damage in vitro.

Role and regulation of activator protein-1 in toxicant-induced responses of the lung

Aberrant cell proliferation and differentiation after toxic injury to airway epithelium can lead to the development of various lung diseases including cancer. The activator protein-1 (AP-1) transcription factor, composed of mainly Jun-Jun and Jun-Fos protein dimers, acts as an environmental biosensor to various external toxic stimuli and regulates gene expression involved in various biological processes. Gene disruption studies indicate that the AP-1 family members c-jun, junB, and fra1 are essential for embryonic development, whereas junD, c-fos, and fosB are required for normal postnatal growth. However, broad or target-specific transgenic overexpression of the some of these proteins gives very distinct phenotype(s), including tumor formation. This implies that, although they are required for normal cellular processes, their abnormal activation after toxic injury can lead to the pathogenesis of the lung disease. Consistent with this view, various environmental toxicants and carcinogens differentially regulate Jun and Fos expression in cells of the lung both in vivo and in vitro. Moreover, Jun and Fos proteins distinctly bind to the promoter regions of a wide variety of genes to differentially regulate their expression in epithelial injury, repair, and differentiation. Importantly, lung tumors induced by various carcinogens display a sustained expression of certain AP-1 family members. Therefore a better understanding of the mechanisms of regulation and functional role(s), as well as identification of target genes of members of the AP-1 family in airway epithelial cells, will provide additional insight into toxicant-induced lung diseases. These studies might offer a unique opportunity to use AP-1 family members and transactivation as potential diagnostic markers or drug targets for early detection and/or prevention of various lung diseases.