PM(10) impairs the antioxidant defense system and exacerbates oxidative stress driven cell death

Pro-inflammatory effects and oxidative stress in lung macrophages and epithelial cells induced by ambient particulate matter

The objective of this study was to compare the toxicological effects of different source-related ambient PM10 samples in regard to their chemical composition. In this context we investigated airborne PM from different sites in Aachen, Germany. For the toxicological investigation human alveolar epithelial cells (A549) and murine macrophages (RAW264.7) were exposed from 0 to 96 h to increasing PM concentrations (0-100 μg/ml) followed by analyses of cell viability, pro-inflammatory and oxidative stress responses. The chemical analysis of these particles indicated the presence of 21 elements, water-soluble ions and PAHs. The toxicological investigations of the PM10 samples demonstrated a concentration- and time-dependent decrease in cell viability and an increase in pro-inflammatory and oxidative stress markers.

Self-assembling nanoparticles containing dexamethasone as a novel therapy in allergic airways inflammation

Nanocarriers can deliver a wide variety of drugs, target them to sites of interest, and protect them from degradation and inactivation by the body. They have the capacity to improve drug action and decrease undesirable systemic effects. We have previously developed a well-defined non-toxic PEG-dendritic block telodendrimer for successful delivery of chemotherapeutics agents and, in these studies, we apply this technology for therapeutic development in asthma. In these proof-of-concept experiments, we hypothesized that dexamethasone contained in self-assembling nanoparticles (Dex-NP) and delivered systemically would target the lung and decrease allergic lung inflammation and airways hyper-responsiveness to a greater degree than equivalent doses of dexamethasone (Dex) alone. We found that ovalbumin (Ova)-exposed mice treated with Dex-NP had significantly fewer total cells (2.78±0.44×10⁵ (n = 18) vs. 5.98±1.3×10⁵ (n = 13), P<0.05) and eosinophils (1.09±0.28×10⁵ (n = 18) vs. 2.94±0.6×10⁵ (n = 12), p<0.05) in the lung lavage than Ova-exposed mice alone. Also, lower levels of the inflammatory cytokines IL-4 (3.43±1.2 (n = 11) vs. 8.56±2.1 (n = 8) pg/ml, p<0.05) and MCP-1 (13.1±3.6 (n = 8) vs. 28.8±8.7 (n = 10) pg/ml, p<0.05) were found in lungs of the Dex-NP compared to control, and they were not lower in the Dex alone group. In addition, respiratory system resistance was lower in the Dex-NP compared to the other Ova-exposed groups suggesting a better therapeutic effect on airways hyperresponsiveness. Taken together, these findings from early-stage drug development studies suggest that the encapsulation and protection of anti-inflammatory agents such as corticosteroids in nanoparticle formulations can improve efficacy. Further development of novel drugs in nanoparticles is warranted to explore potential treatments for chronic inflammatory diseases such as asthma.

Curcumin pretreatment prevents potassium dichromate-induced hepatotoxicity, oxidative stress, decreased respiratory complex I activity, and membrane permeability transition pore opening

Curcumin is a polyphenol derived from turmeric with recognized antioxidant properties. Hexavalent chromium is an environmental toxic and carcinogen compound that induces oxidative stress. The objective of this study was to evaluate the potential protective effect of curcumin on the hepatic damage generated by potassium dichromate (K₂Cr₂O₇) in rats. Animals were pretreated daily by 9-10 days with curcumin (400 mg/kg b.w.) before the injection of a single intraperitoneal of K₂Cr₂O₇ (15 mg/kg b.w.). Groups of animals were sacrificed 24 and 48 h later. K₂Cr₂O₇-induced damage to the liver was evident by histological alterations and increase in the liver weight and in the activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase in plasma. In addition, K₂Cr₂O₇ induced oxidative damage in liver and isolated mitochondria, which was evident by the increase in the content of malondialdehyde and protein carbonyl and decrease in the glutathione content and in the activity of several antioxidant enzymes. Moreover, K₂Cr₂O₇ induced decrease in mitochondrial oxygen consumption, in the activity of respiratory complex I, and permeability transition pore opening. All the above-mentioned alterations were prevented by curcumin pretreatment. The beneficial effects of curcumin against K₂Cr₂O₇-induced liver oxidative damage were associated with prevention of mitochondrial dysfunction.

PM2.5-induced oxidative stress triggers autophagy in human lung epithelial A549 cells

Exposure to higher levels of air pollution particulate matter (PM) with an aerodynamic diameter of less than 2.5 μm (PM2.5) links with an increased risk of cardiovascular and respiratory deaths and hospital admission as well as lung cancer. Although the mechanism underlying the correlation between PM2.5 exposure and adverse effects has not fully elucidated, PM2.5-induced oxidative stress has been considered as an important molecular mechanism of PM2.5-mediated toxicity. In this work, human lung epithelial A549 cells were used to further investigate the biological effects of PM2.5 on autophagy. The cell viability showed both time- and concentration-dependent decrease when exposure to PM2.5, which can be attributed to increase of the levels of extracellular lactate dehydrogenase (LDH) release and intracellular reactive oxygen species (ROS) generation in A549 cells. Moreover, PM2.5-induced oxidative damage in A549 cells was observed through the alteration of superoxide dismutase (SOD) and catalase (CAT) activities compared to the unexposed control cells. PM2.5-induced autophagy was indicated by an increase in microtubule-associated protein light chain-3 (LC3) puncta, and accumulation of LC3 in both time- and concentration-dependent manner. PM2.5-induced mRNA expression of autophagy-related protein Atg5 and Beclin1 was also observed compared with those of the unexposed control cells. These results suggest the possibility that PM2.5-induced oxidative stress probably plays a key role in autophagy in A549 cells, which may contribute to PM2.5-induced impairment of pulmonary function.

Particulate matter promotes in vitro receptor-recognizable low-density lipoprotein oxidation and dysfunction of lipid receptors

Particulate matter may promote cardiovascular disease, possibly as a consequence of its oxidative potential. Studies using susceptible animals indicate that particulate matter aggravates atherosclerosis by increasing lipid/macrophage content in plaques. Macrophage lipid uptake requires oxidized low-density lipoprotein and scavenger receptors; same receptors are involved in particulate matter uptake. We studied in vitro particulate matter potential to oxidize low-density lipoproteins and subsequent cell uptake through scavenger receptors. Particulate matter-induced low-density lipoproteins oxidation was evaluated by the thiobarbituric acid assay. Binding/internalization was tested in wild type and scavenger receptor-transfected Chinese hamster ovary cells, and in RAW264.7 cells using fluorescently labeled low-density lipoproteins. Dose-dependent binding/internalization only occurred in scavenger receptor-transfected Chinese hamster ovary cells and RAW264.7 cells. Competition binding/internalization using particles showed that particulate matter induced decreased binding (∼50%) and internalization (∼70%) of particle-oxidized low-density lipoproteins and native low-density lipoproteins. Results indicate that particulate matter was capable of oxidizing low-density lipoproteins, favoring macrophage internalization, and also altered scavenger and low-density lipoproteins receptor function.

Decrease in respiratory function and electron transport chain induced by airborne particulate matter (PM10) exposure in lung mitochondria

Particulate matter, with a mean aerodynamic diameter of ≤10 µm (PM10), exposure is considered as a risk factor for cardiovascular and respiratory diseases. The mechanism of cell damage induced by PM10 exposure is related to mitochondrial alterations. The aim of this work was to investigate the detailed alterations induced by PM10 on mitochondrial function. Since lung tissue is one of the most important targets of PM10 inhalation, isolated mitochondria from lung rat tissue were exposed to PM10 and structural alterations were analyzed by transmission electron microscopy. Mitochondrial function was evaluated by respiratory control index (RCI), membrane potential, adenosine triphosphate (ATP) synthesis, and activity of respiratory chain. Results showed that exposure to PM10 in isolated mitochondria from lung tissue caused enlarged intermembrane spaces and shape alterations, disruption of cristae, and the decrease in dense granules. Oxygraphic traces showed a concentration-dependent decrease in oxygen consumption and RCI. In addition, mitochondrial membrane potential, ATP synthesis, and activity of complexes II and IV showed an increase and decrease, respectively, after PM10 exposure. PM10 exposure induced disruption in structure and function in isolated mitochondria from lung rat tissue.

Human alveolar epithelial cell injury induced by cigarette smoke

Background

Cigarette smoke (CS) is a highly complex mixture and many of its components are known carcinogens, mutagens, and other toxic substances. CS induces oxidative stress and cell death, and this cell toxicity plays a key role in the pathogenesis of several pulmonary diseases.

Methodology/Principal Findings

We studied the effect of cigarette smoke extract (CSE) in human alveolar epithelial type I-like (ATI-like) cells. These are isolated type II cells that are differentiating toward the type I cell phenotype in vitro and have lost many type II cell markers and express type I cell markers. ATI-like cells were more sensitive to CSE than alveolar type II cells, which maintained their differentiated phenotype in vitro. We observed disruption of mitochondrial membrane potential, apoptosis and necrosis that were detected by double staining with acridine orange and ethidium bromide or Hoechst 33342 and propidium iodide and TUNEL assay after treatment with CSE. We also detected caspase 3 and caspase 7 activities and lipid peroxidation. CSE induced nuclear translocation of Nrf2 and increased expression of Nrf2, HO-1, Hsp70 and Fra1. Moreover, we found that Nrf2 knockdown sensitized ATI-like cells to CSE and Nrf2 overexpression provided protection against CSE-induced cell death. We also observed that two antioxidant compounds N-acetylcysteine and trolox protected ATI-like cells against injury by CSE.

Conclusions

Our study indicates that Nrf2 activation is a major factor in cellular defense of the human alveolar epithelium against CSE-induced toxicity and oxidative stress. Therefore, antioxidant agents that modulate Nrf2 would be expected to restore antioxidant and detoxifying enzymes and to prevent CS-related lung injury and perhaps lessen the development of emphysema.

The oxidative potential and biological effects induced by PM10 obtained in Mexico City and at a receptor site during the MILAGRO Campaign

As part of a field campaign that studied the impact of Mexico City pollution plume at the local, sub-regional and regional levels, we studied transport-related changes in PM(10) composition, oxidative potential and in vitro toxicological patterns (hemolysis, DNA degradation). We collected PM(10) in Mexico City (T(0)) and at a suburban-receptor site (T(1)), pooled according to two observed ventilation patterns (T(0) → T(1) influence and non-influence). T(0) samples contained more Cu, Zn, and carbon whereas; T(1) samples contained more of Al, Si, P, S, and K (p < 0.05). Only SO(4)(-2) increased in T(1) during the influence periods. Oxidative potential correlated with Cu/Zn content (r = 0.74; p < 0.05) but not with biological effects. T(1) PM(10) induced greater hemolysis and T(0) PM(10) induced greater DNA degradation. Influence/non-influence did not affect oxidative potential nor biological effects. Results indicate that ventilation patterns had little effect on intrinsic PM(10) composition and toxicological potential, which suggests a significant involvement of local sources.

Why is particulate matter produced by wildfires toxic to lung macrophages?

The mechanistic basis of the high toxicity to lung macrophages of coarse PM from the California wildfires of 2008 was examined in cell culture experiments with mouse macrophages. Wildfire PM directly killed macrophages very rapidly in cell culture at relatively low doses. The wildfire coarse PM is about four times more toxic to macrophages on an equal weight basis than the same sized PM collected from normal ambient air (no wildfires) from the same region and season. There was a good correlation between the extent of cytotoxicity and the amount of oxidative stress observed at a given dose of wildfire PM in vitro. Our data implicate NF-κB signaling in the response of macrophages to wildfire PM, and suggest that most, if not all, of the cytotoxicity of wildfire PM to lung macrophages is the result of oxidative stress. The relative ratio of toxicity and of expression of biomarkers of oxidant stress between wildfire PM and "normal" PM collected from ambient air is consistent with our previous results in mice in vivo, also suggesting that most, if not all, of the cytotoxicity of wildfire PM to lung macrophages is the result of oxidative stress. Our findings from this and earlier studies suggest that the active components of coarse PM from the wildfire are heat-labile organic compounds. While we cannot rule out a minor role for endotoxin in coarse PM preparations from the collected wildfire PM in our observed results both in vitro and in vivo, based on experiments using the inhibitor Polymyxin B most of the oxidant stress and pro-inflammatory activity observed was not due to endotoxin.

Oxidative stress and air pollution exposure

Air pollution is associated with increased cardiovascular and pulmonary morbidity and mortality. The mechanisms of air pollution-induced health effects involve oxidative stress and inflammation. As a matter of fact, particulate matter (PM), especially fine (PM(2.5), PM < 2.5 μm) and ultrafine (PM(0.1), PM < 0.1 μm) particles, ozone, nitrogen oxides, and transition metals, are potent oxidants or able to generate reactive oxygen species (ROS). Oxidative stress can trigger redox-sensitive pathways that lead to different biological processes such as inflammation and cell death. However, it does appear that the susceptibility of target organ to oxidative injury also depends upon its ability to upregulate protective scavenging systems. As vehicular traffic is known to importantly contribute to PM exposure, its intensity and quality must be strongly relevant determinants of the qualitative characteristics of PM spread in the atmosphere. Change in the composition of this PM is likely to modify its health impact.

Proteomic analysis of the differentially expressed proteins by airborne nanoparticles

Airborne nanoparticles with thermodynamic diameters less than 56 nm (PM(0.056)) were collected using a Moudi cascade impactor, and the differentially expressed proteins upon exposure to the airborne nanoparticles were identified in human bronchial epithelial cells. More than 600 protein spots were detected on the two-dimensional gel, and the identified 13 of these proteins showed notable changes. Nine were up-regulated and four were down-regulated following treatment with the airborne nanoparticles. Notably, malignant transformation-associated multiple forms of keratins, epigenetic regulation-related MBD1-containing chromatin associated factor 2, epithelial malignancy-related vimentin and exocytosis-related annexin A2 were changed upon exposure to airborne nanoparticle PM(0.056).

Effects of diesel particulate matters on inflammatory responses in static and dynamic culture of human alveolar epithelial cells

Diesel particulate matter (DPM) possesses the potential to induce acute and chronic health issues upon occupational and daily exposure. Many recent studies have focused on understanding molecular mechanisms to depict DPM's side effects inside the lung using static in vitro cell culture models. These studies have provided abundant fundamental information on DPM's adverse effects on cellular responses, but these systems were limited by the absence of dynamic nature to access relevant cellular responses and functionality. We hypothesized that the exposure of DPM under dynamic environment may affect the levels of cellular inflammation and reactive oxygen species, which may be different from those under static environments. In this study, we used the dynamic cell growth condition to mimic mechanically dynamic environment similar to the normal breathing in vivo. We also used high (20, 10, and 5 ppm) and low (3, 1, 0.1, and 0.01 ppm) ranges of DPM exposure to mimic different levels of exposure, respectively. Following 24-, 48-, and 72-h exposure of DPM, Interleukin-8 (IL-8), C-reactive protein (CRP), reactive oxygen species (ROS), and total amount of protein were analyzed. Our results demonstrated the distinct differences in the profiles of inflammatory mediators (IL-8, CRP, and ROS) between the static and dynamic cell growth conditions.