Air pollution particles diminish bacterial clearance in the primed lungs of mice

Cough and environmental air pollution in China

With fast-paced urbanization and increased energy consumption in rapidly industrialized modern China, the level of outdoor and indoor air pollution resulting from industrial and motor vehicle emissions has been increasing at an accelerated rate. Thus, there is a significant increase in the prevalence of respiratory symptoms such as coughing, wheezing, and decreased pulmonary function. Experimental exposure research and epidemiological studies have indicated that exposure to particulate matter, ozone, nitrogen dioxide, and environmental tobacco smoke have a harmful influence on development of respiratory diseases and are significantly associated with cough and wheeze. This review mainly discusses the effect of air pollutants on respiratory health, particularly with respect to cough, the links between air pollutants and microorganisms, and air pollutant sources. Particular attention is paid to studies in urban areas of China where the levels of ambient and indoor air pollution are significantly higher than World Health Organization recommendations.

Estimating Causal Associations of Fine Particles With Daily Deaths in Boston

Many studies have reported associations between daily particles less than 2.5 µm in aerodynamic diameter (PM2.5) and deaths, but they have been associational studies that did not use formal causal modeling approaches. On the basis of a potential outcome approach, we used 2 causal modeling methods with different assumptions and strengths to address whether there was a causal association between daily PM2.5 and deaths in Boston, Massachusetts (2004-2009). We used an instrumental variable approach, including back trajectories as instruments for variations in PM2.5 uncorrelated with other predictors of death. We also used propensity score as an alternative causal modeling analysis. The former protects against confounding by measured and unmeasured confounders and is based on the assumption of a valid instrument. The latter protects against confounding by all measured covariates, provides valid estimates in the case of effect modification, and is based on the assumption of no unmeasured confounders. We found a causal association of PM2.5 with mortality, with a 0.53% (95% confidence interval: 0.09, 0.97) and a 0.50% (95% confidence interval: 0.20, 0.80) increase in daily deaths using the instrumental variable and the propensity score, respectively. We failed to reject the null association with exposure after the deaths (P =0.93). Given these results, prior studies, and extensive toxicological support, the association between PM2.5 and deaths is almost certainly causal.

Chronic Household Air Pollution Exposure Is Associated with Impaired Alveolar Macrophage Function in Malawian Non-Smokers

BACKGROUND

Household air pollution in low income countries is an important cause of mortality from respiratory infection. We hypothesised that chronic smoke exposure is detrimental to alveolar macrophage function, causing failure of innate immunity. We report the relationship between macrophage function and prior smoke exposure in healthy Malawians.

METHODS

Healthy subjects exposed daily to cooking smoke at home volunteered for bronchoalveolar lavage. Alveolar macrophage particulate content was measured as a known correlate of smoke exposure. Phagocytosis and intraphagosomal function (oxidative burst and proteolysis) were measured by a flow cytometric assay. Cytokine responses in macrophages were compared following re-exposure in vitro to wood smoke, before and after glutathione depletion.

RESULTS

Volunteers had a range of alveolar macrophage particulate loading. The macrophage capacity for phagosomal oxidative burst was negatively associated with alveolar macrophage particulate content (n = 29, r2 = 0.16, p = 0.033), but phagocytosis per se and proteolytic function were unaffected. High particulate content was associated with lower baseline CXCL8 release (ratio 0.51, CI 0.29-0.89) and lower final concentrations on re-exposure to smoke in vitro (ratio 0.58, CI 0.34-0.97). Glutathione depletion augmented CXCL8 responses by 1.49x (CI 1.02-2.17) compared with wood smoke alone. This response was specific to smoke as macrophages response to LPS were not modulated by glutathione.

CONCLUSION

Chronic smoke exposure is associated with reduced human macrophage oxidative burst, and dampened inflammatory cytokine responses. These are critical processes in lung defence against infection and likely to underpin the relationship between air pollution and pneumonia.

Environmental factors in the relapse and recurrence of inflammatory bowel disease: a review of the literature

INTRODUCTION

The causes of relapse in patients with Crohn's disease (CD) and ulcerative colitis (UC) are largely unknown. This paper reviews the epidemiological and clinical data on how medications (non-steroidal anti-inflammatory drugs, estrogens and antibiotics), lifestyle factors (smoking, psychological stress, diet and air pollution) may precipitate clinical relapses and recurrence. Potential biological mechanisms include: increasing thrombotic tendency, imbalances in prostaglandin synthesis, alterations in the composition of gut microbiota, and mucosal damage causing increased permeability.

RESULTS

The clinical epidemiological data consistently reports positive associations between smoking and relapses in CD, and inverse ones with UC. For NSAIDs and estrogens, the epidemiological findings are inconsistent, although general antibiotic use was associated with a reduced risk of relapse in CD. High levels of stress were positively associated with relapse, although psychological interventions did not have therapeutic benefits. The limited work on diet has reported sulphur-containing foods are positively associated with relapse in UC, but there is no work in CD. Ecological data reported positive correlations between air pollution levels and IBD hospitalisations.

CONCLUSIONS

In the future, to clarify this area, more clinical epidemiological work is required where detailed drug types and doses, and complete dietary intakes are measured, in specific forms of IBD. Such work could provide guidance to both patients and doctors to help maintain remission.

In vivo short-term exposure to residual oil fly ash impairs pulmonary innate immune response against environmental mycobacterium infection

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation induces adverse health effects causing broad ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens that can affect a variety of immune compromised patients, which impacts significantly on human morbidity and mortality. The aim of this study was to evaluate the effect of residual oil fly ash (ROFA) pre-exposure on the pulmonary response after challenge with opportunistic mycobacteria by means of an acute short-term in vivo experimental animal model. We exposed BALB/c mice to ROFA and observed a significant reduction on bacterial clearance at 24 h post infection. To study the basis of this impaired response four groups of animals were instilled with (a) saline solution (Control), (b) ROFA (1 mg kg(-1) BW), (c) ROFA and EM-infected (Mycobacterium phlei, 8 × 10(6) CFU), and (d) EM-infected. Animals were sacrificed 24 h postinfection and biomarkers of lung injury and proinflammatory madiators were examined in the bronchoalveolar lavage. Our results indicate that ROFA was able to produce an acute pulmonary injury characterized by an increase in bronchoalveolar polymorphonuclear (PMN) cells influx and a rise in O2 (-) generation. Exposure to ROFA before M. phlei infection reduced total cell number and caused a significant decline in PMN cells recruitment (p < 0.05), O2 (-) generation, TNFα (p < 0.001), and IL-6 (p < 0.001) levels. Hence, our results suggest that, in this animal model, the acute short-term pre-exposure to ROFA reduces early lung response to EM infection.

Exposure to particular matter increases susceptibility to respiratory Staphylococcus aureus infection in rats via reducing pulmonary natural killer cells

Epidemiological studies have shown a correlation between exposure to fine particular matter (PM2.5) and increased respiratory infection, but the mechanisms have remained poorly defined. By using an experimental system we evaluated the effect of PM2.5 exposure on susceptibility to subsequent pulmonary Staphylococcus aureus (S. aureus) infection and its potential mechanisms. Rats were intratracheally instilled with a single dose of PM2.5 sample or PBS followed by an intratracheal inoculation with bacteria S. aureus at 24h after PM2.5 exposure. The rats were examined at 24h post infection. We found that exposure of rats to PM2.5 significantly increased inflammatory cells and levels of IL-6 and TNF-α in bronchoalveolar lavage fluids (BALF). Prior PM2.5 exposure markedly increased the susceptibility of rats to subsequent S. aureus infection. The mechanistic studies showed that alveolar macrophages (AMs) from PM2.5-experienced lungs had depressed phagocytosis of S. aureus, and prior PM2.5 exposure significantly decreased the natural killer (NK) cells recruited into the airways following subsequent S. aureus infection. Further, adoptive transfer of naive NK cells to the lung of prior PM2.5-exposed rats restored PM2.5-impaired antibacterial host defense. The presence of NK cells markedly enhanced the ability of AMs to phagocytose S. aureus ex vivo. Thus, our study identifies PM2.5-impaired NK cell response in the lung to be a novel critical mechanism for PM2.5-mediated susceptibility to S. aureus bacterial infection, which provides a potential mechanism to explain the epidemiological findings that associate ambient air pollution and increased lung bacterial infections. Our findings also suggest that enhancing pulmonary NK cells may be considered for future therapeutic approaches to clinically antibiotic-resistant S. aureus infection in the lung.

Respiratory risks from household air pollution in low and middle income countries

A third of the world's population uses solid fuel derived from plant material (biomass) or coal for cooking, heating, or lighting. These fuels are smoky, often used in an open fire or simple stove with incomplete combustion, and result in a large amount of household air pollution when smoke is poorly vented. Air pollution is the biggest environmental cause of death worldwide, with household air pollution accounting for about 3·5-4 million deaths every year. Women and children living in severe poverty have the greatest exposures to household air pollution. In this Commission, we review evidence for the association between household air pollution and respiratory infections, respiratory tract cancers, and chronic lung diseases. Respiratory infections (comprising both upper and lower respiratory tract infections with viruses, bacteria, and mycobacteria) have all been associated with exposure to household air pollution. Respiratory tract cancers, including both nasopharyngeal cancer and lung cancer, are strongly associated with pollution from coal burning and further data are needed about other solid fuels. Chronic lung diseases, including chronic obstructive pulmonary disease and bronchiectasis in women, are associated with solid fuel use for cooking, and the damaging effects of exposure to household air pollution in early life on lung development are yet to be fully described. We also review appropriate ways to measure exposure to household air pollution, as well as study design issues and potential effective interventions to prevent these disease burdens. Measurement of household air pollution needs individual, rather than fixed in place, monitoring because exposure varies by age, gender, location, and household role. Women and children are particularly susceptible to the toxic effects of pollution and are exposed to the highest concentrations. Interventions should target these high-risk groups and be of sufficient quality to make the air clean. To make clean energy available to all people is the long-term goal, with an intermediate solution being to make available energy that is clean enough to have a health impact.

Exposure to ingested airborne pollutant particulate matter increases mucosal exposure to bacteria and induces early onset of inflammation in neonatal IL-10-deficient mice

BACKGROUND

Epidemiological associations between early-life air pollution exposure and increased risk of inflammatory bowel diseases have been shown. Our aim was to determine if exposure to airborne particulate matter (PM(10)) during the neonatal period would alter colitis in the interleukin (IL)-10(-/-) mouse model.

METHODS

IL-10(-/-) pregnant dams and pups were fed chow ± PM(10) (9 μg/g) and pups were studied at 10, 14, and 20 weeks. Twenty-week-old mice were given 2% dextran sodium sulfate. Metagenomic analysis of stool was performed. Bacterial translocation was assessed by serum lipopolysaccharide and culturing bacteria from mesenteric lymph nodes and spleen. Cytokine expression was measured in gut homogenates using the MesoScale discovery platform. PM(10) was applied to CMT93 cells ± J744 macrophages, and resistance and cytokine secretion were assessed. THP-1 macrophages were incubated with Escherichia coli HB101 ± PM(10) for assessment of uptake and killing.

RESULTS

PM(10) exposure increased colonic proinflammatory cytokines and bacterial translocation into mesenteric lymph nodes, whereas IL-17A levels were reduced in PM(10)-fed 10-week-old mice. Bifidobacterium was decreased in mice fed PM(10), whereas serum lipopolysaccharide was increased. PM(10) interfered with phagocytosis and killing in THP-1 cells. In coculture, PM(10) increased tumor necrosis factor α and fluorescein isothiocyanate-dextran flux. After dextran sodium sulfate treatment, PM10-fed mice responded with increased colonic tumor necrosis factor α and IL-1β and a larger percentage of PM(10)-fed mice had live bacteria in the mesenteric lymph nodes.

CONCLUSIONS

Our data suggest that early exposure to pollution particulates can result in an earlier onset of intestinal disease in genetically susceptible hosts and can alter responses to gut injury in later life.

Summer appendicitis

Acute appendicitis has been reported to be present throughout the year, but some particular months are associated with higher incidences. The aim of this study was designed to review previous studies and analyze the current knowledge and controversies related to seasonal variability of acute appendicitis, to examine whether appendicitis has an annual seasonal pattern. A search of the MEDLINE databases for English language publications over the period from 1970 to 2012 was conducted. This list was extended by including also references from a recent review of appendicitis epidemiology. We selected the studies, which were published in an English-language peer-reviewed journal, did not have intervention, were conducted for at least one year and had the outcome of histologically-confirmed appendicitis and those which reported case data temporally. A total of 30 titles and abstracts were screened for eligibility. Of these, 11 studies from 8 countries conducted across from 1970 to 2012 met the selection criteria and contributed to the systematic review. A seasonal pattern of appendicitis with a mostly predominant peak is seen during the summer months in all the countries (except Nigeria and Turkey). Appendicitis is more common in summer months. The existence of a seasonal pattern in the onset of appendicitis may be due to exposure to air pollution, decreasing fiber diet and increase in the incidence of gastrointestinal infections in summer.

Possible molecular mechanisms linking air pollution and asthma in children

BACKGROUND

Air pollution has many effects on the health of both adults and children, but children's vulnerability is unique. The aim of this review is to discuss the possible molecular mechanisms linking air pollution and asthma in children, also taking into account their genetic and epigenetic characteristics.

RESULTS

Air pollutants appear able to induce airway inflammation and increase asthma morbidity in children. A better definition of mechanisms related to pollution-induced airway inflammation in asthmatic children is needed in order to find new clinical and therapeutic strategies for preventing the exacerbation of asthma. Moreover, reducing pollution-induced oxidative stress and consequent lung injury could decrease children's susceptibility to air pollution. This would be extremely useful not only for the asthmatic children who seem to have a genetic susceptibility to oxidative stress, but also for the healthy population. In addition, epigenetics seems to have a role in the lung damage induced by air pollution. Finally, a number of epidemiological studies have demonstrated that exposure to common air pollutants plays a role in the susceptibility to, and severity of respiratory infections.

CONCLUSIONS

Air pollution has many negative effects on pediatric health and it is recognised as a serious health hazard. There seems to be an association of air pollution with an increased risk of asthma exacerbations and acute respiratory infections. However, further studies are needed in order to clarify the specific mechanism of action of different air pollutants, identify genetic polymorphisms that modify airway responses to pollution, and investigate the effectiveness of new preventive and/or therapeutic approaches for subjects with low antioxidant enzyme levels. Moreover, as that epigenetic changes are inheritable during cell division and may be transmitted to subsequent generations, it is very important to clarify the role of epigenetics in the relationship between air pollution and lung disease in asthmatic and healthy children.

Indoor air pollution and respiratory health of children in the developing world

Indoor air pollution (IAP) is a key contributor to the global burden of disease mainly in developing countries. The use of solid fuel for cooking and heating is the main source of IAP in developing countries, accounting for an estimated 3.5 million deaths and 4.5% of Disability-Adjusted Life Years in 2010. Other sources of IAP include indoor smoking, infiltration of pollutants from outdoor sources and substances emitted from an array of human utilities and biological materials. Children are among the most vulnerable groups for adverse effects of IAP. The respiratory system is a primary target of air pollutants resulting in a wide range of acute and chronic effects. The spectrum of respiratory adverse effects ranges from mild subclinical changes and mild symptoms to life threatening conditions and even death. However, IAP is a modifiable risk factor having potential mitigating interventions. Possible interventions range from simple behavior change to structural changes and from shifting of unclean cooking fuel to clean cooking fuel. Shifting from use of solid fuel to clean fuel invariably reduces household air pollution in developing countries, but such a change is challenging. This review aims to summarize the available information on IAP exposure during childhood and its effects on respiratory health in developing countries. It specifically discusses the common sources of IAP, susceptibility of children to air pollution, mechanisms of action, common respiratory conditions, preventive and mitigating strategies.

Respiratory burst in alveolar macrophages exposed to urban particles is not a predictor of cytotoxicity

We examined the utility of respiratory burst measurements in alveolar macrophages to assess adverse cellular changes following exposure to urban particles. Cells were obtained by bronchioalveolar lavage of Fisher 344 rats and exposed (0-100 μg/well) to urban particles (EHC-93, SRM-1648, SRM-1649, PM2.5), the soluble (EHC-93sol) and insoluble (EHC-93insol) fractions of EHC-93 (EHC-93tot), mineral particles (TiO(2), SiO(2)) and metal oxides (iron III oxide, iron II/III oxide, copper II oxide, nickel II oxide). The particle-induced respiratory burst was measured by chemiluminescence for 2h after the addition of particles. The cells were then stimulated with phorbol 12-myristate 13-acetate (PMA), yeast Zymosan fragments (Zymosan), or lipopolysaccharide plus interferon-gamma (LPS/IFN-γ) and the stimulant-induced respiratory burst was measured. Independently of the potential of particles to induce directly a respiratory burst, exposure to most particles attenuated the subsequent stimulant-induced burst. The notable exception was SiO(2), which produced a strong respiratory burst upon contact with the macrophages and enhanced the subsequent response to PMA or LPS/IFN-γ. Based on the degree of inhibition of the stimulant-dependent respiratory burst, particles were clustered into groups of high (SRM-1649, iron III oxide), intermediate (EHC-93tot, EHC-93insol, SRM-1648, VERP, iron II/III oxide, copper II oxide), and low (EHC-93sol, SiO(2), TiO2 and nickel II oxide) potency. Across these clusters, the potency of the particles to inhibit the stimulant-dependent respiratory burst showed poor correlation with cytotoxicity determined by XTT reduction assay.

Coal fly ash impairs airway antimicrobial peptides and increases bacterial growth

Air pollution is a risk factor for respiratory infections, and one of its main components is particulate matter (PM), which is comprised of a number of particles that contain iron, such as coal fly ash (CFA). Since free iron concentrations are extremely low in airway surface liquid (ASL), we hypothesize that CFA impairs antimicrobial peptides (AMP) function and can be a source of iron to bacteria. We tested this hypothesis in vivo by instilling mice with Pseudomonas aeruginosa (PA01) and CFA and determine the percentage of bacterial clearance. In addition, we tested bacterial clearance in cell culture by exposing primary human airway epithelial cells to PA01 and CFA and determining the AMP activity and bacterial growth in vitro. We report that CFA is a bioavailable source of iron for bacteria. We show that CFA interferes with bacterial clearance in vivo and in primary human airway epithelial cultures. Also, we demonstrate that CFA inhibits AMP activity in vitro, which we propose as a mechanism of our cell culture and in vivo results. Furthermore, PA01 uses CFA as an iron source with a direct correlation between CFA iron dissolution and bacterial growth. CFA concentrations used are very relevant to human daily exposures, thus posing a potential public health risk for susceptible subjects. Although CFA provides a source of bioavailable iron for bacteria, not all CFA particles have the same biological effects, and their propensity for iron dissolution is an important factor. CFA impairs lung innate immune mechanisms of bacterial clearance, specifically AMP activity. We expect that identifying the PM mechanisms of respiratory infections will translate into public health policies aimed at controlling, not only concentration of PM exposure, but physicochemical characteristics that will potentially cause respiratory infections in susceptible individuals and populations.

Nasopharyngeal carriage of Streptococcus pneumoniae: prevalence and risk factors in HIV-positive children in Tanzania

BACKGROUND

Pneumococcal colonization of the nasopharynx is especially common in young children and is a pre-requisite for pneumococcal disease. Those with immunosuppression, such as HIV, are at higher risk of colonization and disease, especially at older ages. Currently, vaccination schedules are only offered to children under 6 months of age, despite the large impact of pneumococcal disease in older unvaccinated children with HIV. We conducted a study to assess the prevalence of, and risk factors for, pneumococcal carriage in HIV-positive children aged <15 years.

METHODS

We collected a single nasopharyngeal swab from 142 HIV-infected children aged 1-14 years over a 2-month period. To detect carriage of pneumococcus, these samples were cultured and serotyped; PCR was performed on negative samples. We also collected epidemiological data via survey and medical records.

RESULTS

The overall carriage rate was 81% and was at least 76% in those aged 5-14 years. The 7-, 10-, and 13-valent pneumococcal vaccines would cover 37%, 37%, and 49% of children with carriage, respectively. In the multivariate analysis, we identified increase in weight since last visit (p=0.028) and the existence of care-givers who had respiratory symptoms in the past week (p=0.022) as risk factors for carriage. Weight gain was also significantly associated with antiretroviral use (p=0.002).

CONCLUSIONS

These data illuminate the little known area of pneumococcal carriage in older HIV-infected children as well as finding novel risk factors for pneumococcal carriage, namely the association with household members who have respiratory symptoms and with an increase in the child's weight prior to swabbing. Weight gain may be due to an increase in health enabling more mobility and increasing the risk of acquiring carriage. The carriage rate observed (81%) is one of the highest recorded. Further research should address whether vaccination can prevent the acquisition of carriage and so protect against disease.

Effect of residential proximity to major roadways on cystic fibrosis exacerbations

Ambient air pollution has been attributed with an increase in exacerbation frequencies among the cystic fibrosis (CF) population. This study correlates exacerbation frequency with proximity to roadways and two criteria air pollutants. Clinical data was extracted from the Cystic Fibrosis Foundation National Patient Registry and Electronic Medical Records at Children's Hospital Los Angeles (CHLA). Average annual air pollutant levels were obtained from selected US Environmental Protection Agency's monitoring stations. Geographic proximity to monitoring stations and roadways were analyzed using spatial mapping software. A total of 145 patients from the CHLA's CF center were characterized by a dichotomous exacerbation category. No significant association was determined between the frequency of exacerbations and exposure to fine particulate matter and ozone levels. Residential proximity to US-designated highways and freeways also did not achieve significance (p = 0.3777) but was noted to be correlated with major arterial roadways (p = 0.0420). Associations of environmental exposures may have important implications for future predictive models of CF clinical outcomes.

Air pollution and children's respiratory health - gaps in the global evidence

There is now convincing evidence that air pollution, especially the particulate matter (PM) fraction, adversely affects children's health. In general, the health effects of traffic-derived PM are well described in children living in high-income countries. Conversely, studies into the health effects of PM from biomass and solid fuels are limited to children in lower-income countries. As PM from different combustion sources have components in common (e.g. elemental black carbon) - are we able to extrapolate from the research performed in different countries under different exposure conditions? Using lung function growth and vulnerability to infection as examples of health effects of global significance to children, this review addresses the question whether high-income-country research into air pollution can inform effects of pollution in low-income countries and vice versa.

Air pollution and airway disease

Epidemiological and toxicological research continues to support a link between urban air pollution and an increased incidence and/or severity of airway disease. Detrimental effects of ozone (O(3)), nitrogen dioxide (NO(2)) and particulate matter (PM), as well as traffic-related pollution as a whole, on respiratory symptoms and function are well documented. Not only do we have strong epidemiological evidence of a relationship between air pollution and exacerbation of asthma and respiratory morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD), but recent studies, particularly in urban areas, have suggested a role for pollutants in the development of both asthma and COPD. Similarly, while prevalence and severity of atopic conditions appear to be more common in urban compared with rural communities, evidence is emerging that traffic-related pollutants may contribute to the development of allergy. Furthermore, numerous epidemiological and experimental studies suggest an association between exposure to NO(2) , O(3) , PM and combustion products of biomass fuels and an increased susceptibility to and morbidity from respiratory infection. Given the considerable contribution that traffic emissions make to urban air pollution researchers have sought to characterize the relative toxicity of traffic-related PM pollutants. Recent advances in mechanisms implicated in the association of air pollutants and airway disease include epigenetic alteration of genes by combustion-related pollutants and how polymorphisms in genes involved in antioxidant pathways and airway inflammation can modify responses to air pollution exposures. Other interesting epidemiological observations related to increased host susceptibility include a possible link between chronic PM exposure during childhood and vulnerability to COPD in adulthood, and that infants subjected to higher prenatal levels of air pollution may be at greater risk of developing respiratory conditions. While the characterization of pollutant components and sources promise to guide pollution control strategies, the identification of susceptible subpopulations will be necessary if targeted therapy/prevention of pollution-induced respiratory diseases is to be developed.

Adhesion of Streptococcus pneumoniae to human airway epithelial cells exposed to urban particulate matter

BACKGROUND

Epidemiologic studies report an association between pneumonia and urban particulate matter (PM) less than 10 microns (μm) in aerodynamic diameter (PM(10)). Streptococcus pneumoniae is a common cause of bacterial pneumonia worldwide. To date, the mechanism whereby urban PM enhances vulnerability to S pneumoniae infection is unclear. Adhesion of S pneumoniae to host cells is a prerequisite for infection. Host-expressed proteins, including the receptor for platelet-activating factor (PAFR), are co-opted by S pneumoniae to adhere to lower airway epithelial cells.

OBJECTIVES

To define whether inhalable urban PM enhances the adhesion of S pneumoniae to airway epithelial cells.

METHODS

A549 cells were cultured with PM(10) from Leicester (United Kingdom [UK]) and PM(10) and PM less than 2.5 μm in aerodynamic diameter (PM(2.5)) from Accra (Ghana), then infected with S pneumoniae strain D39. Pneumococcal adhesion to human primary bronchial epithelial cells was also assessed. Bacterial adhesion was determined by quantitative culture and confocal microscopy. The role of oxidative stress was assessed by N-acetyl cysteine, and the role of PAFR was assessed by mRNA transcript level, receptor expression, and receptor blocking.

RESULTS

PM(10) (UK) increased S pneumoniae adhesion to both A549 airway epithelial cells and human primary bronchial epithelial cells. PM(10) (Ghana) and PM(2.5) (Ghana) also increased adhesion. Culture of A549 cells by PM(10) (UK) increased PAFR mRNA transcript level and PAFR expression. PM(10) (UK)-stimulated adhesion to A549 cells was attenuated by a PAFR blocker and N-acetyl cysteine.

CONCLUSION

Urban PM increases adhesion of S pneumoniae to human airway epithelial cells. PM-stimulated adhesion is mediated by oxidative stress and PAFR.

The inflammatory bowel diseases and ambient air pollution: a novel association

OBJECTIVES

The inflammatory bowel diseases (IBDs) emerged after industrialization. We studied whether ambient air pollution levels were associated with the incidence of IBD.

METHODS

The health improvement network (THIN) database in the United Kingdom was used to identify incident cases of Crohn's disease (n=367) or ulcerative colitis (n=591), and age- and sex-matched controls. Conditional logistic regression analyses assessed whether IBD patients were more likely to live in areas of higher ambient concentrations of nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), and particulate matter <10 μm (PM(10)), as determined by using quintiles of concentrations, after adjusting for smoking, socioeconomic status, non-steroidal anti-inflammatory drugs (NSAIDs), and appendectomy. Stratified analyses investigated effects by age.

RESULTS

Overall, NO(2), SO(2), and PM(10) were not associated with the risk of IBD. However, individuals ≤23 years were more likely to be diagnosed with Crohn's disease if they lived in regions with NO(2) concentrations within the upper three quintiles (odds ratio (OR)=2.31; 95% confidence interval (CI)=1.25-4.28), after adjusting for confounders. Among these Crohn's disease patients, the adjusted OR increased linearly across quintile levels for NO(2) (P=0.02). Crohn's disease patients aged 44-57 years were less likely to live in regions of higher NO(2) (OR=0.56; 95% CI=0.33-0.95) and PM(10) (OR=0.48; 95% CI=0.29-0.80). Ulcerative colitis patients ≤25 years (OR=2.00; 95% CI=1.08-3.72) were more likely to live in regions of higher SO(2); however, a dose-response effect was not observed.

CONCLUSIONS

On the whole, air pollution exposure was not associated with the incidence of IBD. However, residential exposures to SO(2) and NO(2) may increase the risk of early-onset ulcerative colitis and Crohn's disease, respectively. Future studies are needed to explore the age-specific effects of air pollution exposure on IBD risk.

Acute exposure of mice to high-dose ultrafine carbon black decreases susceptibility to pneumococcal pneumonia

BACKGROUND

Epidemiological studies suggest that inhalation of carbonaceous particulate matter from biomass combustion increases susceptibility to bacterial pneumonia. In vitro studies report that phagocytosis of carbon black by alveolar macrophages (AM) impairs killing of Streptococcus pneumoniae. We have previously reported high levels of black carbon in AM from biomass smoke-exposed children and adults. We therefore aimed to use a mouse model to test the hypothesis that high levels of carbon loading of AM in vivo increases susceptibility to pneumococcal pneumonia.

METHODS

Female outbred mice were treated with either intranasal phosphate buffered saline (PBS) or ultrafine carbon black (UF-CB in PBS; 500 μg on day 1 and day 4), and then infected with S. pneumoniae strain D39 on day 5. Survival was assessed over 72 h. The effect of UF-CB on AM carbon loading, airway inflammation, and a urinary marker of pulmonary oxidative stress was assessed in uninfected animals.

RESULTS

Instillation of UF-CB in mice resulted a pattern of AM carbon loading similar to that of biomass-smoke exposed humans. In uninfected animals, UF-CB treated animals had increased urinary 8-oxodG (P = 0.055), and an increased airway neutrophil differential count (P < 0.01). All PBS-treated mice died within 72 h after infection with S. pneumoniae, whereas morbidity and mortality after infection was reduced in UF-CB treated animals (median survival 48 h vs. 30 h, P < 0.001). At 24 hr post-infection, UF-CB treated mice had lower lung and the blood S. pneumoniae colony forming unit counts, and lower airway levels of keratinocyte-derived chemokine/growth-related oncogene (KC/GRO), and interferon gamma.

CONCLUSION

Acute high level loading of AM with ultrafine carbon black particles per se does not increase the susceptibility of mice to pneumococcal infection in vivo.

Customized PCR-array analysis informed by gene-chip microarray and biological hypothesis reveals pathways involved in lung inflammatory response to titanium dioxide in pregnancy

Validation of gene-chip microarray results is one of the challenges in genomic studies. The successful use of a custom-designed 96-well polymerase chain reaction (PCR) array to study the unexpected inflammatory effect of environmental titanium dioxide (TiO2) particles on the lungs of pregnant mice, with similar results not seen in control mice, is reported. In our approach, selection of candidate genes for the custom PCR array was informed by prior gene-chip microarray profiling. Results demonstrated multiple upregulation of genes in the lungs of pregnant but not control mice produced by TiO2 exposure. Customized PCR array is a flexible tool that offers the ability to combine the "blind" genome-wide scan with a hypothesis-driven approach, by including both the "candidate" genes for validation positively identified by the microarray and biologically relevant "suspects" that failed to be found in the genomic data. Compared to conventional gene-by-gene qPCR or manufacturer-preset pathway kits, this technique provides a cost-effective and time-saving method of analysis and allows for a strong, easily detectable signal. Genes with confirmed differential expression were further used for pathway analysis and indicated involvement in several biologically relevant pathways including allergy mediator signaling in dendritic cells. Finally, an analytical network was created that will inform further mechanistic studies. The dual purpose of the work was to demonstrate that the novel custom PCR array is a convenient approach to validate the microarray results, and to obtain biologically significant data on TiO2-induced inflammation by following the PCR array with pathway analysis, which provided feasible hypotheses to support future experimental studies.

Effect of ambient air pollution on the incidence of appendicitis

BACKGROUND

The pathogenesis of appendicitis is unclear. We evaluated whether exposure to air pollution was associated with an increased incidence of appendicitis.

METHODS

We identified 5191 adults who had been admitted to hospital with appendicitis between Apr. 1, 1999, and Dec. 31, 2006. The air pollutants studied were ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and suspended particulate matter of less than 10 micro and less than 2.5 micro in diameter. We estimated the odds of appendicitis relative to short-term increases in concentrations of selected pollutants, alone and in combination, after controlling for temperature and relative humidity as well as the effects of age, sex and season.

RESULTS

An increase in the interquartile range of the 5-day average of ozone was associated with appendicitis (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.03-1.25). In summer (July-August), the effects were most pronounced for ozone (OR 1.32, 95% CI 1.10-1.57), sulfur dioxide (OR 1.30, 95% CI 1.03-1.63), nitrogen dioxide (OR 1.76, 95% CI 1.20-2.58), carbon monoxide (OR 1.35, 95% CI 1.01-1.80) and particulate matter less than 10 micro in diameter (OR 1.20, 95% CI 1.05-1.38). We observed a significant effect of the air pollutants in the summer months among men but not among women (e.g., OR for increase in the 5-day average of nitrogen dioxide 2.05, 95% CI 1.21-3.47, among men and 1.48, 95% CI 0.85-2.59, among women). The double-pollutant model of exposure to ozone and nitrogen dioxide in the summer months was associated with attenuation of the effects of ozone (OR 1.22, 95% CI 1.01-1.48) and nitrogen dioxide (OR 1.48, 95% CI 0.97-2.24).

INTERPRETATION

Our findings suggest that some cases of appendicitis may be triggered by short-term exposure to air pollution. If these findings are confirmed, measures to improve air quality may help to decrease rates of appendicitis.

Air pollution as a potential contributor to the 'epidemic' of autoimmune disease

There has been remarkable progress over the past 20 years in pushing forward our understanding of many facets of autoimmune disease. Indeed, knowledge of the genetic basis of autoimmunity and the molecular and cellular pathways involved in its pathogenesis has reached an unprecedented level. Yet this knowledge has not served to prevent autoimmune disease nor to curtail the dramatic rise in its incidence over the same interval. Population-level genetic changes cannot explain this trend; thus, environmental factors are strongly implicated. Among the possible environmental contributors to autoimmune disease, air pollution exposure has received very little attention. Although there is only a small amount of published data directly examining a possible causal relationship between air pollution exposure and autoimmunity, data from related fields suggests that it could facilitate autoimmunity as well. If correct, this hypothesis could prove to have sizeable public health implications.

Comparative microarray analysis and pulmonary changes in Brown Norway rats exposed to ovalbumin and concentrated air particulates

The interaction between air particulates and genetic susceptibility has been implicated in the pathogenesis of asthma. The overall objective of this study was to determine the effects of inhalation exposure to environmentally relevant concentrated air particulates (CAPs) on the lungs of ovalbumin (ova) sensitized and challenged Brown Norway rats. Changes in gene expression were compared with lung tissue histopathology, morphometry, and biochemical and cellular parameters in bronchoalveolar lavage fluid (BALF). Ova challenge was responsible for the preponderance of gene expression changes, related largely to inflammation. CAPs exposure alone resulted in no significant gene expression changes, but CAPs and ova-exposed rodents exhibited an enhanced effect relative to ova alone with differentially expressed genes primarily related to inflammation and airway remodeling. Gene expression data was consistent with the biochemical and cellular analyses of the BALF, the pulmonary pathology, and morphometric changes when comparing the CAPs-ova group to the air-saline or CAPs-saline group. However, the gene expression data were more sensitive than the BALF cell type and number for assessing the effects of CAPs and ova versus the ova challenge alone. In addition, the gene expression results provided some additional insight into the TGF-beta-mediated molecular processes underlying these changes. The broad-based histopathology and functional genomic analyses demonstrate that exposure to CAPs exacerbates rodents with allergic inflammation induced by an allergen and suggests that asthmatics may be at increased risk for air pollution effects.

Nickel and the microbial toxin, MALP-2, stimulate proangiogenic mediators from human lung fibroblasts via a HIF-1alpha and COX-2-mediated pathway

Hypoxia-inducible factor (HIF-1alpha) and cyclooxygenase-2 (COX-2) have been implicated in the regulation of inflammatory-like processes that lead to angiogenesis and fibrotic disorders. Here we demonstrate that in human lung fibroblasts (HLFs) treated with mixed exposures to chemical and microbial stimuli, HIF-1alpha stabilization plays a pivotal role in the induction of COX-2 mRNA and protein, driving the release of vascular endothelial growth factor (VEGF) and proangiogenic and profibrotic chemokines. Upon costimulation with Ni and the mycoplasma-derived lipopeptide macrophage-activating lipopeptide-2 (MALP-2), there was a synergistic induction of CXCL1 and CXCL5 mRNA and protein release from HLF, as well as an enhanced response in VEGF compared to either stimulus alone. Consistent with our previous findings that Ni and MALP-2 stimulates the induction of CXCL8 via a COX-2-mediated pathway, CXCL1, CXCL5, and VEGF release were also regulated by COX-2. Ni induced the stabilization of HIF-1alpha protein in HLF, which was further enhanced in the presence of MALP-2. Depletion of HIF-1alpha using siRNA blocked COX-2 induction by Ni and MALP-2 along with the release of VEGF, CXCL1, CXCL5, and CXCL8. Our results indicate that Ni and MALP-2 interact to promote an angiogenic profibrotic phenotype in HLF. Moreover, these findings reveal a potential role for HIF-1alpha in mediating chemical-induced alterations in cellular response to microbial stimuli, modulating pulmonary inflammation and its consequences such as fibrosis and angiogenesis.

Antioxidants and phase 2 enzymes in macrophages: regulation by Nrf2 signaling and protection against oxidative and electrophilic stress

Macrophages play important roles in immunity and other physiological processes. They are also target cells of various toxic agents, including oxidants and electrophiles. However, little is known regarding the molecular regulation and chemical inducibility of a spectrum of endogenous antioxidants and phase 2 enzymes in normal macrophages. Understanding the molecular pathway(s) controlling the coordinated expression of various macrophage antioxidants and phase 2 defenses is of importance for developing strategies to protect against macrophage injury induced by oxidants and electrophiles. Accordingly, this study was undertaken to determine the role of the nuclear factor E2-related factor 2 (Nrf2) in regulating both constitutive and chemoprotectant-inducible expression of various antioxidants and phase 2 enzymes in mouse macrophages. The constitutive expression of a series of antioxidants and phase 2 enzymes was significantly lower in macrophages derived from Nrf2-null (Nrf2(-/-)) mice than those from wild-type (Nrf2(+/+)) littermates. Incubation of wild-type macrophages with 3H-1,2-dithiole-3-thione (D3T) led to significant induction of various antioxidants and phase 2 enzymes, including catalase, glutathione, glutathione peroxidase (GPx), glutathione reductase, glutathione S-transferase, and NAD(P)H:quinone oxidoreductase 1. The inducibility of the above cellular defenses except for GPx by D3T was completely abolished in Nrf2(-/-) macrophages. As compared with wild-type cells, Nrf2(- /-) macrophages were much more susceptible to cell injury induced by reactive oxygen/nitrogen species, as well as two known macrophage toxins, acrolein and cadmium. Up-regulation of the antioxidants and phase 2 enzymes by D3T in wild-type macrophages resulted in increased resistance to the above oxidant-and electrophile-induced cell injury, whereas D3T treatment of Nrf2(- /-) macrophages provided only marginal or no cytoprotec-tion. This study demonstrates that Nrf2 is an indispensable factor in controlling both constitutive and inducible expression of a wide spectrum of antioxidants and phase 2 enzymes in macrophages as well as the susceptibility of these cells to oxidative and electrophilic stress.

PAHs, PAH-induced carcinogenic potency, and particle-extract-Induced cytotoxicity of traffic-related nano/ultrafine particles

Polycyclic aromatic hydrocarbons (PAHs) bound in nano/ ultrafine particles from vehicle emissions may cause adverse health effects. However, little is known about the characteristics of the nanoparticle-bound PAHs and the PAH-associated carcinogenic potency/cytotoxicity; therefore, traffic-related nano/ultrafine particles were collected in this study using a microorifice uniform deposition impactor(MOUDI) and a nano-MOUDI. For PM0.056--18, the difference in size-distribution of particulate total-PAHs between non-after-rain and after-rain samples was statistically significant at alpha = 0.05; however, this difference was not significant for PM0.01--0.056. The PAH correlation between PM0.01--0.1 and PM0.1--1.8 was lower for the after-rain samples than forthe non-after-rain samples. The average particulate total-PAHs in five samplings displayed a trimodal distribution with a major peak in the Aitken mode (0.032--0.056 microm). About half of the particulate total-PAHs were in the ultrafine size range. The BaPeq sums of BaP, IND, and DBA (with toxic equivalence factors > or = 0.1) accounted for approximately 90% of the total-BaPeq in the nano/ultrafine particles, although these three compounds contributed little to the mass of the sampled particles. The mean content of the particle-bound total-PAHs/-BaPeqs and the PAH/BaPeq-derived carcinogenic potency followed the order nano > ultrafine > fine > coarse. For a sunny day sample, the cytotoxicity of particle extracts (using 1:1 (v/v) n-hexane/dichloromethane) was significantly higher (p < 0.05) for the nano (particularly the 10-18 nm)/ultrafine particles than for the coarser particles and bleomycin. Therefore, traffic-related nano and ultrafine particles are possibly cytotoxic.

Nickel alterations of TLR2-dependent chemokine profiles in lung fibroblasts are mediated by COX-2

Particulate matter air pollution (PM) has been linked with chronic respiratory diseases. Real-life exposures are likely to involve a mixture of chemical and microbial stimuli, yet little attention has been paid to the potential interactions between PM components (e.g., Ni) and microbial agents on the development of inflammatory-like conditions in the lung. Using the Toll-like receptor (TLR)-2 agonist MALP-2 as a lipopeptide relevant to microbial colonization, we hypothesized that nickel sensitizes human lung fibroblasts (HLF) for microbial-driven chemokine release through modulation of TLR signaling pathways. NiSO(4) (200 muM) synergistically enhanced CXCL8, yet antagonized CXCL10 mRNA expression and protein release from HLF in response to MALP-2. RT(2)-PCR pathway-focused array results indicated that NiSO(4) exposure did not alter the expression of TLRs or their downstream signaling mediators, yet significantly increased the expression of cyclooxygenase 2 (COX-2). Moreover, when NiSO(4) was given in combination with MALP-2, there was an amplified induction of COX-2 mRNA and protein along with its metabolic product, PGE2, in HLF. The COX-2 inhibitor, NS-398, attenuated NiSO(4) and MALP-2-induced PGE2 and CXCL8 release and partially reversed the NiSO(4)-dependent inhibition of MALP-2-induced CXCL10 release from HLF. These data indicate that NiSO(4) alters the pattern of TLR-2-dependent chemokine release from HLF via a COX-2-mediated pathway. The quantitative and qualitative effects of NiSO(4) on microbial-driven chemokine release from HLF shed new light on how PM-derived metals can exacerbate respiratory diseases.