Endotoxin Priming Affects the Lung Response to Ultrafine Particles and Ozone in Young and Old Rats

Mortality risk and long-term exposure to ultrafine particles and primary fine particle components in a national U.S. Cohort

The objective of this study was to estimate all-cause, cardiopulmonary, and cancer mortality associations for long-term exposure to ultrafine particles (UFP) and primary PM_2.5 components. We utilized high-resolution, national-scale exposure estimates for UFP (measured as particle number concentration; PNC) and three primary PM_2.5 components, namely black carbon (BC), traffic-emitted organic PM_2.5 (hereafter, hydrocarbon-like organic aerosols; HOA), and cooking-emitted organic PM_2.5 (cooking organic aerosols; COA). Two analytic cohorts were constructed from a nationally representative U.S. health survey. The larger cohort consisted of 617,997 adults with information on a broad set of individual-level risk factors; the smaller cohort was further restricted to those with information on physical activity (n = 396,470). In single-pollutant models, PNC was significantly associated with all-cause (larger cohort HR = 1.03, 95% CI [1.02, 1.04]; smaller cohort HR = 1.02, 95% CI [1.00, 1.04]) and cancer mortality (larger cohort HR = 1.05, 95% CI [1.02, 1.08]; smaller cohort HR = 1.06, 95% CI [1.02, 1.10]). In two-pollutant models, mortality associations varied based on co-pollutant adjustment; PNC mortality associations were generally robust to controlling for PM_10-2.5 and SO₂, but not PM_2.5. In contrast, we found some evidence that the HOA and COA mortality associations are independent of total PM_2.5 mass exposure. Nevertheless, PM_2.5 mass was the most robust predictor of air pollution related mortality, providing some support for current regulatory policies.

Organosilane-Based Coating of Quartz Species from the Traditional Ceramics Industry: Evidence of Hazard Reduction Using In Vitro and In Vivo Tests

The exposure to respirable crystalline silica (RCS), e.g. quartz, in industrial settings can induce silicosis and may cause tumours in chronic periods. Consequently, RCS in the form of quartz and cristobalite has been classified as human lung carcinogen category 1 by the International Agency for Research on Cancer in 1997, acknowledging differences in hazardous potential depending on source as well as chemical, thermal, and mechanical history. The physico-chemical determinants of quartz toxicity are well understood and are linked to density and abundance of surface silanol groups/radicals. Hence, poly-2-vinylpyridine-N-oxide and aluminium lactate, which effectively block highly reactive silanol groups at the quartz surface, have formerly been introduced as therapeutic approaches in the occupational field. In the traditional ceramics industry, quartz-containing raw materials are indispensable for the manufacturing process, and workers are potentially at risk of developing quartz-related lung diseases. Therefore, in the present study, two organosilanes, i.e. Dynasylan® PTMO and Dynasylan® SIVO 160, were tested as preventive, covalent quartz-coating agents to render ceramics production safer without loss in product quality. Coating effectiveness and coating stability (up to 1 week) in artificial alveolar and lysosomal fluids were first analysed in vitro, using the industrially relevant quartz Q1 as RCS model, quartz DQ12 as a positive control, primary rat alveolar macrophages as cellular model system (75 µg cm⁻²; 4 h of incubation ± aluminium lactate to verify quartz-related effects), and lactate dehydrogenase release and DNA strand break induction (alkaline comet assay) as biological endpoints. In vitro results with coated quartz were confirmed in a 90-day intratracheal instillation study in rats with inflammatory parameters as most relevant readouts. The results of the present study indicate that in particular Dynasylan® SIVO 160 (0.2% w/w of quartz) was able to effectively and stably block toxicity of biologically active quartz species without interfering with technical process quality of certain ceramic products. In conclusion, covalent organosilane coatings of quartz might represent a promising strategy to increase workers’ safety in the traditional ceramics industry.

Nanometer-sized emissions from municipal waste incinerators: A qualitative risk assessment

Municipal waste incinerators (MWI) are beneficial alternatives to landfills for waste management. A recent constituent of concern in emissions from these facilities is incidental nanometer-sized particles (INP_MWI), i.e., particles smaller than 1 micrometer in size that may deposit in the deepest parts of the lungs, cross into the bloodstream, and affect different regions of the body. With limited data, the public may fear INP_MWI due to uncertainty, which may affect public acceptance, regulatory permitting, and the increased lowering of air quality standards. Despite limited data, a qualitative risk assessment paradigm can be applied to determine the relative risk due to INP_MWI emissions. This review compiles existing data on nanometer-sized particle generation by MWIs, emissions control technologies used at MWIs, emission releases into the atmosphere, human population exposure, and adverse health effects of nanometer-sized particles to generate a qualitative risk assessment and identify data gaps. The qualitative risk assessment conservatively concludes that INP_MWI pose a low to moderate risk to individuals, primarily due to the lack of relevant toxicological data on INP_MWI mixtures in ambient particulate matter.

MicroRNA-181b stimulates inflammation via the nuclear factor-κB signaling pathway in vitro

Acute lung injury (ALI) is characterized by severe lung edema and an increase in the inflammatory reaction. Considerable evidence has indicated that microRNAs (miRNAs or miRs) are involved in various human diseases; however, the expression profile and function of miRNAs in ALI have been rarely reported. The present study used miRNA microarray and reverse transcription-quantitative polymerase chain reaction to demonstrate that miR-181b is the one of the most significantly upregulated miRNA after lipopolysaccharide (LPS) stimulation in human bronchial epithelial cells, BEAS-2B. To elaborate the role of miR-181b in ALI, an assay was performed to investigate the overexpression of miR-181b in BEAS-2B cells, and the expression of inflammatory factors was then analyzed. The overexpression of miR-181b resulted in the induction of an increment in interleukin (IL)-6 levels. p65 was identified to be a primary component of NF-κB, since it was upregulated in the miR-181b overexpression in the BEAS-2B cells, while pyrrolidine dithiocarbamate, a specific inhibitor of NF-κB, was found to be able to abrogate the upregulation of the expression of p65. In conclusion, the findings of the present study suggested that miR-181b may be involved in the process of LPS-induced inflammation in BEAS-2B cells by activating the NF-κB signaling pathway, which implies that it may serve as a potential therapeutic target for ALI.

INFLAMMATORY CELL RECRUITMENT FOLLOWING THORACIC IRRADIATION

Ionizing radiation leads to a progressive injury in which a monocyte/macrophage-rich pneumonitis is followed by a chronic progressive fibrosis. In the present study, the role of macrophage/monocyte recruitment in the genesis of radiation-induced pulmonary fibrosis was examined. The objectives were threefold: (i) characterize the inflammatory cells recruited into the lung during the development of radiation-induced fibrosis; (ii) investigate changes in lung response following depletion of resident alveolar macrophages in vivo prior to radiation treatment; (iii) assess if inhalation of low levels of endotoxin would potentiate the radiation-initiated injury. One group of fibrosis-sensitive C57BL/6 mice was irradiated with a single dose of 15 Gy to the thorax. In a second group, resident inflammatory cells were depleted using clodronate, encapsulated into liposomes, 48 hours prior to irradiation with a single dose of 15 Gy to the thorax. Control animals were sham irradiated. All groups of animals then were examined 8, 16, or 24 weeks post irradiation. No difference in total cell numbers or cell differentials was observed between irradiated mice or those that were both liposome treated and irradiated at any time point. At 16 weeks, mice that received radiation showed a 5- to 6-fold increase in lymphocytes regardless of treatment as compared to control animals. At 24 weeks post irradiation, select groups were exposed to lipopolysaccharide (LPS) and examined 24 hours post inhalation. Lavageable protein was increased several fold in mice that received both radiation and LPS exposure as compared to 15 Gy or LPS exposure alone. These results demonstrate: (i) macrophages and lymphocytes are the predominately recruited cell types through 24 weeks post irradiation; (ii) recovery of inflammatory cells, regardless of prior macrophage depletion, were similar, suggesting that early responses are primarily driven by parenchymal cell injury; (iii) thoracic irradiation-induced injury can cause sensitization to a secondary stimulus that may result in injuries/responses not predicted by evaluating exposures individually.

Age-related changes in the expression and oxidation of bronchoalveolar lavage proteins in the rat

The incidence and severity of many lung diseases change with age. Some diseases, such as pneumonia, occur with increased frequency in children and the elderly. Proteins obtained by bronchoalveolar lavage (BAL) serve as the first line of defense against inhaled toxins and pathogens. Age-related changes in BAL protein expression and oxidative modification were examined in juvenile (1 mo), young adult (2 mo), and aged (18 mo) F344 rats using two-dimensional difference gel electrophoresis (2D-DIGE), matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-ToF/ToF) tandem mass spectrometry, and carbonyl immunoblotting. Using 2D-DIGE, we detected 563 protein spots, and MALDI-ToF/ToF identified 204 spots comprising 31 proteins; 21 changed significantly (17 increases) between juvenile and young adult or aged rats, but for 12 of these proteins, levels had a biphasic pattern, and levels in aged rats were less than in young adults. Relative carbonylation was determined by comparison of immunostaining with total protein staining on each oxidized protein blot. We found that aged rats had significantly increased oxidation in 13 proteins compared with juvenile rats. Many of the proteins altered in expression or oxidation level had functions in host defense, redox regulation, and protein metabolism. We speculate that low levels of expression of host defense proteins in juvenile rats and decreases in levels of these proteins between young adult and aged rats may predispose these groups to pneumonia. In addition, we have shown age-related increases in protein oxidation that may compromise host defense function in aged rats.

Postnatal lung development: immediate-early gene responses post ozone and LPS exposure

Exposure to environmental pollutants may severely affect lung growth and development. The present study was designed to test the hypothesis that lung damage caused either by ozone or lipopolysaccharide (LPS) occurs through distinct early responses, which are age dependent in the postnatal lung. C57Bl/6 mice ages 4, 10, and 56 days were exposed to inhalation of LPS with an estimated deposited dose of 26 EU and examined 0.5, 1, or 4 h post inhalation exposure; or to 1 or 2.5 ppm ozone for 4 h or sequential exposures of LPS followed by ozone. Abundance of c-fos, c-jun, interleukin (IL)-1beta, Toll-like receptor (TLR) 2, TLR 4, and tumor necrosis factor (TNF) alpha message levels were measured by RNase protection assay. Exposure to ozone for 4 h induced a c-fos and c-jun response in 4-; 10-; and 56-day-old mice in a dose-dependent manner, was localized to conducting and terminal airways, and also induced TLR 4 message abundance in 10- and 56-day-old mice. Exposure to LPS induced c-fos and c-jun 30 and 60 min postinhalation in 10- and 56-day-old mice only. TLR 2 and 4 message abundance was increased at 10 and 56 days, but was undetectable at 4 days of age, and correlated with proinflamatory message induction. Exposure to LPS followed by ozone increased message abundance of IL-1beta, TNFalpha, TLR 2, TLR 4, and c-jun/c-fos at 10 and 56 days, suggesting that combined exposures that induce cellular stresses can regulate gene expression by activating signaling pathways that operate through both transcription factors activator protein (AP)-1 and nuclear factor (NF)-kappaB. However, only c-jun/c-fos and TNFalpha were elevated in 4-day-old mice after sequential exposures, suggesting that the early activation of the inflammatory response after sequential exposures may occur through a TLR-independent pathway. These results suggest that sequential exposures induce multiple signaling pathways that are age dependent.

Sequential exposures to ozone and lipopolysaccharide in postnatal lung enhance or inhibit cytokine responses

Sequential exposures to inhaled environmental pollutants may result in injuries/responses not predicted by evaluating exposures to an individual toxicant. This may indicate that the lung is damaged or primed by earlier events, so exposure to a nontoxic dose of an environmental pollutant may be sufficient to trigger adverse responses. The present study was designed to test the hypothesis that stimulating lung epithelial damage or inflammatory cell activation followed by a second stimulus leads to responses not seen after individual exposures in the postnatal lung. C57Bl/6 mice ages 4, 10, and 56 days were exposed to either a 10-minute inhalation of lipopolysaccharide (LPS), with an estimated deposited dose of 26 EU, followed immediately by 2.5 PPM ozone for 4 hours, or to 2.5 PPM ozone for 4 hours followed immediately by a 10-minute inhalation of LPS and examined 2 hours post exposure. Abundance of proinflammatory cytokine messages was measured by RNase protection assay. Exposure to LPS followed by ozone induced an inflammatory response in 4-day-old mice, which was not detected after LPS or ozone exposure alone. This exposure sequence also generated a synergistic increase in interleukin (IL)-6 mRNA abundance in 10- and 56-day-old mice but not in 4-day-old mice. Exposure to ozone followed by LPS inhibited IL-1alpha and IL-1beta responses in 4-, 10-, and 56-day-old mice; furthermore, this inhibitory effect was observed after 1.0 and 0.5 PPM ozone exposures. These results demonstrate that preexposure to LPS, which primarily activates inflammatory cell recruitment, can cause sensitization to a secondary stimulus. However, preexposure to ozone, which primarily damages the epithelium, inhibited proinflammatory responses. Thus it was concluded that sequential exposures to ozone and LPS resulted in responses not predicted by evaluating individual exposures during postnatal lung development.

Pulmonary function, diffusing capacity, and inflammation in healthy and asthmatic subjects exposed to ultrafine particles

Particulate air pollution is associated with asthma exacerbations and increased morbidity and mortality from respiratory causes. Ultrafine particles (particles less than 0.1 microm in diameter) may contribute to these adverse effects because they have a higher predicted pulmonary deposition, greater potential to induce pulmonary inflammation, larger surface area, and enhanced oxidant capacity when compared with larger particles on a mass basis. We hypothesized that ultrafine particle exposure would induce airway inflammation in susceptible humans. This hypothesis was tested in a series of randomized, double-blind studies by exposing healthy subjects and mild asthmatic subjects to carbon ultrafine particles versus filtered air. Both exposures were delivered via a mouthpiece system during rest and moderate exercise. Healthy subjects were exposed to particle concentrations of 10, 25, and 50 microg/m(3), while asthmatics were exposed to 10 microg/m(3). Lung function and airway inflammation were assessed by symptom scores, pulmonary function tests, and airway nitric oxide parameters. Airway inflammatory cells were measured via induced sputum analysis in several of the protocols. There were no differences in any of these measurements in normal or asthmatic subjects when exposed to ultrafine particles at concentrations of 10 or 25 microg/m(3). However, exposing 16 normal subjects to the higher concentration of 50 microg/m(3) caused a reduction in maximal midexpiratory flow rate (-4.34 +/- 1.78% [ultrafine particles] vs. +1.08 +/- 1.86% [air], p =.042) and carbon monoxide diffusing capacity (-1.76 +/- 0.66 ml/min/mm Hg [ultrafine particles] vs. -0.18 +/- 0.41 ml/min/mm Hg [air], p =.040) at 21 h after exposure. There were no consistent differences in symptoms, induced sputum, or exhaled nitric oxide parameters in any of these studies. These results suggest that exposure to carbon ultrafine particles results in mild small-airways dysfunction together with impaired alveolar gas exchange in normal subjects. These effects do not appear related to airway inflammation. Additional studies are required to confirm these findings in normal subjects, compare them with additional susceptible patient populations, and determine their pathophysiologic mechanisms.

Effect of age on respiratory defense mechanisms: pulmonary bacterial clearance in Fischer 344 rats after intratracheal instillation of Listeria monocytogenes

STUDY OBJECTIVES

To examine the lung defense mechanisms of both young and aged rats before and after pulmonary challenge with a bacterial pathogen.

DESIGN

Male Fischer 344 rats, either 2.5 months or 20 months of age, were intratracheally inoculated with 5 x 10(3), 5 x 10(4), or 5 x 10(5) Listeria monocytogenes, and the effects on mortality, lung inflammation, pulmonary bacterial clearance, alveolar macrophage (AM) function, and T-lymphocyte characterization were determined.

MEASUREMENTS AND RESULTS

In noninfected control animals, the older rats had lower numbers of AMs on lavage and a lower percentage of total T, CD4+, and CD8+ cells. No difference was observed between noninfected young and old rats in AM function, assessing both chemiluminescence and nitric oxide (NO) production. After bacterial challenge, aged rats exhibited an increase in mortality, pulmonary infection, and edema, and lung lesions, which were more extensive than those observed in the younger rats. Interestingly, AM chemiluminescence was enhanced, while AM NO, a highly important antibacterial defense product, was abrogated in the aged rats as compared to the young rats.

CONCLUSIONS

This study demonstrated that advanced age is associated with alterations in lung defense mechanisms and increased susceptibility to pulmonary bacterial infection marked by elevated mortality, slowed pulmonary bacterial clearance, and altered AM function, specifically a decrease in NO production. These observations are indicative of reduced pulmonary defense function in an older population of rats.