Respiratory response to endotoxin and dust predicts evidence of inflammatory response in volunteers in a swine barn

Understanding the development of Th2 cell-driven allergic airway disease in early life

Allergic diseases, including atopic dermatitis, allergic rhinitis, asthma, and food allergy, are caused by abnormal responses to relatively harmless foreign proteins called allergens found in pollen, fungal spores, house dust mites (HDM), animal dander, or certain foods. In particular, the activation of allergen-specific helper T cells towards a type 2 (Th2) phenotype during the first encounters with the allergen, also known as the sensitization phase, is the leading cause of the subsequent development of allergic disease. Infants and children are especially prone to developing Th2 cell responses after initial contact with allergens. But in addition, the rates of allergic sensitization and the development of allergic diseases among children are increasing in the industrialized world and have been associated with living in urban settings. Particularly for respiratory allergies, greater susceptibility to developing allergic Th2 cell responses has been shown in children living in urban environments containing low levels of microbial contaminants, principally bacterial endotoxins [lipopolysaccharide (LPS)], in the causative aeroallergens. This review highlights the current understanding of the factors that balance Th2 cell immunity to environmental allergens, with a particular focus on the determinants that program conventional dendritic cells (cDCs) toward or away from a Th2 stimulatory function. In this context, it discusses transcription factor-guided functional specialization of type-2 cDCs (cDC2s) and how the integration of signals derived from the environment drives this process. In addition, it analyzes observational and mechanistic studies supporting an essential role for innate sensing of microbial-derived products contained in aeroallergens in modulating allergic Th2 cell immune responses. Finally, this review examines whether hyporesponsiveness to microbial stimulation, particularly to LPS, is a risk factor for the induction of Th2 cell responses and allergic sensitization during infancy and early childhood and the potential factors that may affect early-age response to LPS and other environmental microbial components.

Establishing farm dust as a useful viral metagenomic surveillance matrix

Farm animals may harbor viral pathogens, some with zoonotic potential which can possibly cause severe clinical outcomes in animals and humans. Documenting the viral content of dust may provide information on the potential sources and movement of viruses. Here, we describe a dust sequencing strategy that provides detailed viral sequence characterization from farm dust samples and use this method to document the virus communities from chicken farm dust samples and paired feces collected from the same broiler farms in the Netherlands. From the sequencing data, Parvoviridae and Picornaviridae were the most frequently found virus families, detected in 85-100% of all fecal and dust samples with a large genomic diversity identified from the Picornaviridae. Sequences from the Caliciviridae and Astroviridae familes were also obtained. This study provides a unique characterization of virus communities in farmed chickens and paired farm dust samples and our sequencing methodology enabled the recovery of viral genome sequences from farm dust, providing important tracking details for virus movement between livestock animals and their farm environment. This study serves as a proof of concept supporting dust sampling to be used in viral metagenomic surveillance.

Pulmonary inflammatory response from co-exposure to LPS and glyphosate

Agricultural airborne work exposures are complex in nature and workplace exposures are a risk for respiratory outcomes in workers. Endotoxin and glyphosate are two common agents in agricultural exposures. While endotoxin (lipopolysaccaride, LPS) is a potent inflammatory agent it explains only a portion of the respiratory inflammatory response. The inflammatory potential when LPS is presented with another common agricultural respiratory agent, glyphosate, is not known.

METHODS

Mice were assigned to four treatment groups: control, LPS alone, glyphosate alone, glyphosate and LPS combined. Treatments were for 1, 5 or 10 days.

RESULTS

Five days of repeated exposure to the comintation of LPS and glyphosate resulted in higher neutrophil counts, myloperoxidase, TNF-α, IL-6, KC levels, and ICAM-1 and TLR-2 expression compared to the same length of treatment to LPS or glyphosate alone. After 10-days of exposure, inflammatory responses decreased, however leukocyte infiltration persisted along with increases in IL-4.

CONCLUSIONS

Glyphosate exposure modified LPS induced lung inflammatory responses and TLR-2 may be important in the modulated inflammatory response.

The impact of bacteria-derived ultrafine dust particles on pulmonary diseases

The relationship between ambient particulate matter exposure and health has been well established. Ultrafine particles (UFP) with a diameter of 100 nm or less are known to increase pulmonary disease risk. Biological factors in dust containing UFP can cause severe inflammatory reactions. Pulmonary diseases develop primarily as a result of chronic inflammation caused by immune dysfunction. Thus, this review focuses on the adverse pulmonary effects of biological UFP, principally lipopolysaccharide (LPS), and bacterial extracellular vesicles (EVs), in indoor dust and the pathophysiological mechanisms involved in the development of chronic pulmonary diseases. The impact of LPS-induced pulmonary inflammation is based primarily on the amount of inhaled LPS. When relatively low levels of LPS are inhaled, a cascade of immune responses leads to Th2 cell induction, and IL-5 and IL-13 released by Th2 cells contributes to asthma development. Conversely, exposure to high levels of LPS induces a Th17 cell response, leading to increased production of IL-17, which is associated with asthma, COPD, and lung cancer incidence. Responses to bacterial EV exposure can similarly be broadly divided based on whether one of two mechanisms, either intracellular or extracellular, is activated, which depends on the type of the parent cell. Extracellular bacteria-derived EVs can cause neutrophilic inflammation via Th17 cell induction, which is associated with asthma, emphysema, COPD, and lung cancer. On the other hand, intracellular bacteria-derived EVs lead to mononuclear inflammation via Th1 cell induction, which increases the risk of emphysema. In conclusion, future measures should focus on the overall reduction of LPS sources in addition to the improvement of the balance of inhaled bacterial EVs in the indoor environment to minimize pulmonary disease risk.

MyD88 controls airway epithelial Muc5ac expression during TLR activation conditions from agricultural organic dust exposure

Inflammation from airborne microbes can overwhelm compensatory mucociliary clearance mechanisms, leading to mucous cell metaplasia. Toll-like receptor (TLR) activation via myeloid differentiation factor 88 (MyD88) signaling is central to pathogen responses. We have previously shown that agricultural organic dust extract (ODE), with abundant microbial component diversity, activates TLR-induced airway inflammation. With the use of an established model, C57BL/6J wild-type (WT) and global MyD88 knockout (KO) mice were treated with intranasal inhalation of ODE or saline, daily for 1 wk. ODE primarily increased mucin (Muc)5ac levels relative to Muc5b. Compared with ODE-challenged WT mice, ODE-challenged, MyD88-deficient mice demonstrated significantly increased Muc5ac immunostaining, protein levels by immunoblot, and expression by quantitative PCR. The enhanced Muc5ac levels in MyD88-deficient mice were not explained by differences in the differentiation program of airway secretory cells in naïve mice. Increased Muc5ac levels in MyD88-deficient mice were also not explained by augmented inflammation, IL-17A, or neutrophil elastase levels. Furthermore, the enhanced airway mucins in the MyD88-deficient mice were not due to defective secretion, as the mucin secretory capacity of MyD88-KO mice remained intact. Finally, ODE-induced Muc5ac levels were enhanced in MyD88-deficient airway epithelial cells in vitro. In conclusion, MyD88 deficiency enhances airway mucous cell metaplasia under environments with high TLR activation.

A systematic review of the public health risks of bioaerosols from intensive farming

BACKGROUND

Population growth, increasing food demands, and economic efficiency have been major driving forces behind farming intensification over recent decades. However, biological emissions (bioaerosols) from intensified livestock farming may have the potential to impact human health. Bioaerosols from intensive livestock farming have been reported to cause symptoms and/or illnesses in occupational-settings and there is concern about the potential health effects on people who live near the intensive farms. As well as adverse health effects, some potential beneficial effects have been attributed to farm exposures in early life. The aim of the study was to undertake a systematic review to evaluate potential for adverse health outcomes in populations living near intensive livestock farms.

MATERIAL AND METHODS

Two electronic databases (PubMed and Scopus) and bibliographies were searched for studies reporting associations between health outcomes and bioaerosol emissions related to intensive farming published between January 1960 and April 2017, including both occupational and community studies. Two authors independently assessed studies for inclusion and extracted data. Risk of bias was assessed using a customized score.

RESULTS

38 health studies met the inclusion criteria (21 occupational and 1 community study measured bioaerosol concentrations, 16 community studies using a proxy measure for exposure). The majority of occupational studies found a negative impact on respiratory health outcomes and increases in inflammatory biomarkers among farm workers exposed to bioaerosols. Studies investigating the health of communities living near intensive farms had mixed findings. All four studies of asthma in children found increased reported asthma prevalence among children living or attending schools near an intensive farm. Papers principally investigated respiratory and immune system outcomes.

CONCLUSIONS

The review indicated a potential impact of intensive farming on childhood respiratory health, based on a small number of studies using self-reported outcomes, but supported by findings from occupational studies. Further research is needed to measure and monitor exposure in community settings and relate this to objectively measured health outcomes.

Pulmonary innate inflammatory responses to agricultural occupational contaminants

Agricultural workers are exposed to many contaminants and suffer from respiratory and other symptoms. Dusts, gases, microbial products and pesticide residues from farms have been linked to effects on the health of agricultural workers. Growing sets of data from in vitro and in vivo models demonstrate the role of the innate immune system, especially Toll-like receptor 4 (TLR4) and TLR9, in lung inflammation induced following exposure to contaminants in agricultural environments. Interestingly, inflammation and lung function changes appear to be discordant indicating the complexity of inflammatory responses to exposures. Whereas the recent development of rodent models and exposure systems have yielded valuable data, we need new systems to examine the combined effects of multiple contaminants in order to increase our understanding of farm-exposure-induced negative health effects.

Toll-like receptor 9 partially regulates lung inflammation induced following exposure to chicken barn air

Background

Exposure to animal barn air is an occupational hazard that causes lung dysfunction in barn workers. Respiratory symptoms experienced by workers are typically associated with endotoxin and TLR4 signalling, but within these environments gram negative bacteria constitute only a portion of the total microbial population. In contrast, unmethylated DNA can be found in all bacteria, some viruses, and mold. We hypothesized that in such environments TLR9, which binds unmethylated DNA, contributes to the overall immune responses in the lung.

Methods

Using a mouse model, wild-type and TLR9^−/− mice were exposed to chicken barn air for 1, 5, or 20 days. Blood serum and bronchiolar lavage fluid was tested against a panel of six TLR9-induced cytokines (IL-1β, IL-6, IL-10, IL-12, TNFα, and IFNγ) for changes in expression. Bronchiolar lavage fluid (BAL) was also tested for macrophage as well as monocyte migration.

Results

There were significant decreases in serum TNFα after a single day exposure in TLR9^−/− mice. BAL concentrations of TNFα and IFNγ, as well as TNFα in serum in TLR9^−/− mice were also reduced after barn exposure for 5 days. After 20 days of exposure IFNγ was significantly reduced in lavage of TLR9^−/− mice. Myeloperoxidase (MPO) accumulation in the lung was reduced at 20 days of exposure in TLR9^−/− mice, as was total lavage cell counts. However, Masson’s staining revealed no apparent lung histological differences between any of the treatment groups.

Conclusions

Taken together our data show TLR9 plays a partial role in lung inflammation induced following exposure to chicken barn air potentially through binding of unmethylated DNA.

Effect of elevated carbon dioxide on bronchial epithelial innate immune receptor response to organic dust from swine confinement barns

Hypercapnia is known to have immunoregulatory effects within the lung. Cell culture systems demonstrate this in both macrophages and alveolar cell lines, suggesting that the alveoli are affected by changes in CO2 levels. We hypothesized that hypercapnia would also modulate human bronchial epithelial cell immune responses. Innate immune responses to Pam3CSK4 (TLR2 ligand), LPS (TLR4 ligand) and a complex innate immune stimulus, an extract from the organic dust of swine confinement barns (barn dust extract or BDE), were tested in a human bronchial epithelial cell line, BEAS-2B. Both TLR ligands showed a decrease in IL-6 and IL-8 production, and an increase in MCP-1 in response to elevated CO2 indicating an enhancement in cytokine production to hypercapnia. This change was not reflected in expression levels of TLR receptor RNA which remained unchanged in response to elevated CO2. Interestingly, barn dust showed an increase in IL-6, IL-8 and MCP-1 response at 9% CO2, suggesting that elevated CO2 exerts different effects on different stimuli. Our results show that airway epithelial cell immune responses to barn dust respond differently to hypercapnic conditions than individual TLR ligands.

Non-culturable bioaerosols in indoor settings: Impact on health and molecular approaches for detection

Despite their significant impact on respiratory health, bioaerosols in indoor settings remain understudied and misunderstood. Culture techniques, predominantly used for bioaerosol characterisation in the past, allow for the recovery of only a small fraction of the real airborne microbial burden in indoor settings, given the inability of several microorganisms to grow on agar plates. However, with the development of new tools to detect non-culturable environmental microorganisms, the study of bioaerosols has advanced significantly. Most importantly, these techniques have revealed a more complex bioaerosol burden that also includes non-culturable microorganisms, such as archaea and viruses. Nevertheless, air quality specialists and consultants remain reluctant to adopt these new research-developed techniques, given that there are relatively few studies found in the literature, making it difficult to find a point of comparison. Furthermore, it is unclear as to how this new non-culturable data can be used to assess the impact of bioaerosol exposure on human health. This article reviews the literature that describes the non-culturable fraction of bioaerosols, focussing on bacteria, archaea and viruses, and examines its impact on bioaerosol-related diseases. It also outlines available molecular tools for the detection and quantification of these microorganisms and states various research needs in this field.

CXCR1/CXCR2 antagonist CXCL8(3-74)K11R/G31P blocks lung inflammation in swine barn dust-instilled mice

Inhalation of agricultural occupational dusts from swine confinement facilities can result in lung inflammation. The innate immune response to organic barn dusts results in production of a number of pro-inflammatory factors in the lungs of barn workers such as cytokines, chemokines, and an influx of neutrophils. Many of these inflammatory factors are influenced by the chemokine CXCL8/IL-8 (KC or MIP-2 in mice). Previously, we have demonstrated that an endotoxin-independent component of swine barn dust extract (SBE) elevates lung chemokines in a protein kinase C (PKC)-dependent manner resulting in the significant formation of lung inflammatory cell infiltrates in a mouse model of SBE injury. In this study we test the ability of a CXCR1/CXCR2 antagonist, CXCL8(3-74)K11R/G31P (G31P) to block many of the features of lung-inflammation in response to challenge with SBE in an established mouse exposure system. Injection of G31P concurrent with SBE nasal instillation over a course of 3 weeks significantly reduced neutrophil accumulation in the lungs of barn dust exposed animals compared to those given SBE alone. There was a similar reduction in pro-inflammatory cytokines and chemokines IL-6, KC, and MIP-2 in SBE plus G31P-treated mice. In addition to excreted products, the receptors ICAM-1, CXCR1, and CXCR2, which all were elevated with SBE exposure, were also decreased with G31P treatment. SBE activation of PKCα and PKCε was reduced as well with G31P treatment. Thus, G31P was found to be highly effective at reducing several features of lung inflammation in mice exposed to barn dust extracts.

A comprehensive review of levels and determinants of personal exposure to dust and endotoxin in livestock farming

The respiratory health effects of livestock farming have been on debate for more than three decades. Endotoxin-contaminated organic dusts are considered as the most important respiratory hazards within livestock environments. A comprehensive review of the knowledge from studies assessing the exposure status of livestock farmers is still to be published. The present study reviews research published within the last 30 years on personal exposure of livestock farmers to organic dust and endotoxin, focusing on studies on pig, poultry and cattle farmers. Applied measurement methods and reported levels of personal exposure for the total, inhalable and respirable fractions are summarized and discussed, with emphasis on the intensity of exposure and the size and distribution of the reported exposure variability. In addition, available evidence on potential determinants of personal exposure to dust and endotoxin among these farmers are documented and discussed, taking results from exposure determinant studies using stationary sampling approaches into consideration. Research needs are addressed from an epidemiological and industrial hygiene perspective. Published studies have been heterogeneous in design, and applied methodologies and results were frequently inadequately reported. Despite these limitations and the presence of an enormous variability in personal exposure to dust and endotoxin, no clear downward trends in exposure with time were observed, suggesting that working environments within stables remains largely uncontrolled. Exposure control and prevention strategies for livestock farmers are urgently required. These should focus on the development of novel and improved methods of controlling dust and endotoxin exposure within stables based on the currently available knowledge on determinants of exposure.

Detection of Streptococcus suis in bioaerosols of swine confinement buildings

Streptococcus suis is an important swine pathogen that can cause septicemia, meningitis, and pneumonia. Also recognized as an emerging zoonotic agent, it is responsible for outbreaks of human infections in Asian countries. Serotype 2 is the predominant isolate from diseased animals and humans. The aerosolization of S. suis in the air of swine confinement buildings (SCB) was studied. The presence of S. suis in bioaerosols was monitored in SCB where cases of infection had been reported and in healthy SCB without reported infections. Using a quantitative-PCR (qPCR) method, we determined the total number of bacteria (1 × 10(8) to 2 × 10(8) airborne/m(3)), total number of S. suis bacteria (4 × 10(5) to 10 × 10(5) airborne/m(3)), and number of S. suis serotype 2 and 1/2 bacteria (1 × 10(3) to 30 × 10(3) airborne/m(3)) present in the air. S. suis serotypes 2 and 1/2 were detected in the air of all growing/finishing SCB that had documented cases of S. suis infection and in 50% of healthy SCB. The total number of bacteria and total numbers of S. suis and S. suis serotype 2 and 1/2 bacteria were monitored in one positive SCB during a 5-week period, and it was shown that the aerosolized S. suis serotypes 2 and 1/2 remain airborne for a prolonged period. When the effect of aerosolization on S. suis was observed, the percentage of intact S. suis bacteria (showing cell membrane integrity) in the air might have been up to 13%. Finally S. suis was found in nasal swabs from 14 out of 21 healthy finishing-SCB workers, suggesting significant exposure to the pathogen. This report provides a better understanding of the aerosolization, prevalence, and persistence of S. suis in SCB.

Organic barn dust extract exposure impairs porcine macrophage function in vitro: implications for respiratory health

Respiratory diseases are responsible for a significant amount of animal morbidity and mortality in the swine industry, including the majority of nursery and grower/finisher deaths. Innate immunity, including the maintenance of lung macrophage health and function, is an important defense mechanism against respiratory pathogens and their associated losses. Chronic exposure of swine industry workers to airborne barn dust results in significant predisposition to airway diseases and impairment of alveolar macrophage (AMφ) function. Because of their importance in maintaining normal respiratory function, this study was designed to evaluate the impact of barn dust on swine macrophages. As measures of macrophage function, we evaluated the activation of NF-κB, cytokine production, cell surface marker expression and the phagocytic and antibacterial capabilities of porcine macrophages after in vitro exposure to an organic swine barn dust extract (ODE). ODE treatment induced AMφ secretion of both pro- and anti-inflammatory cytokines, suggesting a complex activation profile. Additionally, ODE induced expression of genes (TLR2, NOD2) involved in sensing Gram-positive bacteria, a major component of barn dust. ODE exposure also enhanced the expression of several cell surface markers of activation, including a receptor for the porcine reproductive and respiratory syndrome virus. Moreover, two key functions of AMϕ, phagocytosis and bacterial killing, were impaired after exposure to ODE. Treatment with ODE for the first 72 h of differentiation also inhibited the ability of monocyte-derived macrophages to translocate NF-κB to the nucleus following endotoxin stimulation. Taken together, these results demonstrate, for the first time, that organic dust extract exposure negatively affects pig macrophage activation and function, potentially enhancing host susceptibility to a variety of respiratory infections.

Immunopathogenesis of allergic asthma: more than the th2 hypothesis

Asthma is a chronic obstructive airway disease that involves inflammation of the respiratory tract. Biological contaminants in indoor air can induce innate and adaptive immune responses and inflammation, resulting in asthma pathology. Epidemiologic surveys indicate that the prevalence of asthma is higher in developed countries than in developing countries. The prevalence of asthma in Korea has increased during the last several decades. This increase may be related to changes in housing styles, which result in increased levels of indoor biological contaminants, such as house dust mite-derived allergens and bacterial products such as endotoxin. Different types of inflammation are observed in those suffering from mild-to-moderate asthma compared to those experiencing severe asthma, involving markedly different patterns of inflammatory cells and mediators. As described in this review, these inflammatory profiles are largely determined by the involvement of different T helper cell subsets, which orchestrate the recruitment and activation of inflammatory cells. It is becoming clear that T helper cells other than Th2 cells are involved in the pathogenesis of asthma; specifically, both Th1 and Th17 cells are crucial for the development of neutrophilic inflammation in the airways, which is related to corticosteroid resistance. Development of therapeutics that suppress these immune and inflammatory cells may provide useful asthma treatments in the future.

Indoor exposure to airborne endotoxin: a review of the literature on sampling and analysis methods

Assessment of exposure to airborne endotoxins has been studied for several years, especially in occupational environments, but a large number of procedures are used for sampling and analysis. This lack of standardization makes it very difficult to compare results and set internationally accepted threshold limit values (TLVs) or occupational exposure limits (OELs) for endotoxin exposure. This paper reviews the methods reported, using advanced bibliographical search techniques: 82 papers published from 2004 to the present were selected to analyze methods for the assessment of human exposure to airborne endotoxins, with particular reference to occupational settings, and to examine their performance and critical points. Only few studies have focused on the standardization of sampling and analysis methods. The European Committee for Standardization Guidelines coincide with the procedures most frequently applied, but this does not guarantee the best results in terms of recovery and reproducibility. The factor that mainly affects endotoxin measurements is the extraction method, the main concern being the presence in the samples of a fraction insoluble in aqueous media. If substantial differences in the proportions of this fraction in different environments are confirmed in the future, the contribution of insoluble endotoxins cannot be neglected.

Pulmonary function reductions among potentially susceptible subgroups of agricultural workers in Colorado and Nebraska

OBJECTIVE

Organic dust inhalation has been associated with adverse respiratory responses among agricultural workers. We evaluated factors that may confer increased susceptibility to these health effects.

METHODS

We quantified personal work shift exposures to inhalable dust, endotoxin, and its 3-hydroxy fatty acid constituents, and evaluated changes in pulmonary function among 137 grain elevator, cattle feedlot, dairy, and corn farm workers.

RESULTS

Increased dust exposure was associated with work shift reductions in lung function. Although interpretation is limited because of small samples, a suggestion of stronger exposure-response relationships was observed among smokers, as well as workers reporting pesticide/herbicide application, asthma, or allergies, and those with genetic polymorphisms (TLR4) (Pinteraction ≤ 0.05).

CONCLUSIONS

A better understanding of factors leading to increased susceptibility of adverse respiratory outcomes is needed to optimize exposure reduction strategies and develop more comprehensive wellness programs.

CD11c(+)/CD11b(+) cells are critical for organic dust-elicited murine lung inflammation

Organic dust exposure in the agricultural industry results in significant lung disease. Macrophage infiltrates are increased in the lungs after organic dust exposures, yet the phenotype and functional importance of these cells remain unclear. Using an established intranasal inhalation murine model of dust-induced lung inflammation, animals were treated once or daily for 3 weeks with swine confinement organic dust extract (DE). Repetitive DE treatment for 3 weeks resulted in significant increases in CD11c(+)/CD11b(+) macrophages in whole lung-associated tissue. These cells displayed increased costimulatory molecule (CD80 and CD86) expression, enhanced phagocytic ability, and an increased production of IL-6, CXCL1, and CXCL2. Similar findings were observed with the CD11c(+)/CD11b(+) macrophage infiltrate after repetitive exposure to peptidoglycan, a major DE component. To determine the functional importance of macrophages in mediating DE-induced airway inflammation, lung macrophages were selectively depleted using a well-established intranasal clodronate liposome depletion/suicide strategy. First, macrophage depletion by clodronate liposomes resulted in significant reductions in airway neutrophil influx and TNF-α and IL-6 production after a single exposure to DE. In contrast, after repetitive 3-week exposure to DE, airway lavage fluid and lung tissue neutrophils were significantly increased in clodronate liposome-treated mice compared with control mice. A histological examination of lung tissue demonstrated striking increases in alveolar and bronchiolar inflammation, as well as in the size and distribution of cellular aggregates in clodronate-liposome versus saline-liposome groups repetitively exposed to DE. These studies demonstrate that DE elicits activated CD11c(+)/CD11b(+) macrophages in the lung, which play a critical role in regulating the outcome of DE-induced airway inflammation.

Alcohol exposure alters mouse lung inflammation in response to inhaled dust

Alcohol exposure is associated with increased lung infections and decreased mucociliary clearance. Occupational workers exposed to dusts from concentrated animal feeding operations (CAFOs) are at risk for developing chronic inflammatory lung diseases. Agricultural worker co-exposure to alcohol and organic dust has been established, although little research has been conducted on the combination effects of alcohol and organic dusts on the lung. Previously, we have shown in a mouse model that exposure to hog dust extract (HDE) collected from a CAFO results in the activation of protein kinase C (PKC), elevated lavage fluid cytokines/chemokines including interleukin-6 (IL-6), and the development of significant lung pathology. Because alcohol blocks airway epithelial cell release of IL-6 in vitro, we hypothesized that alcohol exposure would alter mouse lung inflammatory responses to HDE. To test this hypothesis, C57BL/6 mice were fed 20% alcohol or water ad libitum for 6 weeks and treated with 12.5% HDE by intranasal inhalation method daily during the final three weeks. Bronchoalveolar lavage fluid (BALF), tracheas and lungs were collected. HDE stimulated a 2–4 fold increase in lung and tracheal PKCε (epsilon) activity in mice, but no such increase in PKCε activity was observed in dust-exposed mice fed alcohol. Similarly, alcohol-fed mice demonstrated significantly less IL-6 in lung lavage in response to dust than that observed in control mice instilled with HDE. TNFα levels were also inhibited in the alcohol and HDE-exposed mouse lung tissue as compared to the HDE only exposed group. HDE-induced lung inflammatory aggregates clearly present in the tissue from HDE only exposed animals were not visually detectable in the HDE/alcohol co-exposure group. Statistically significant weight reductions and 20% mortality were also observed in the mice co-exposed to HDE and alcohol. These data suggest that alcohol exposure depresses the ability of the lung to activate PKCε-dependent inflammatory pathways to environmental dust exposure. These data also define alcohol as an important co-exposure agent to consider in the study of inhalation injury responses.

Chronic obstructive pulmonary disease patients have greater systemic responsiveness to ex vivo stimulation with swine dust extract and its components versus healthy volunteers

Chronic obstructive pulmonary disease (COPD) is characterized by an airway and systemic inflammatory response. Bioaerosols/organic dusts are important agricultural pollutants that may lead to COPD. These environments are complex, containing a rich source of various microbial components. The objective of this study was to determine whether individuals with COPD have enhanced systemic responsiveness to settled swine facility organic dust extract (ODE) or its main pathogenic components (peptidoglycan [PGN], lipopolysaccharide [LPS]) versus healthy volunteers. A modified whole blood assay (WBA) that included occupational levels of ODE and concentrations of LPS and PGN found in ODE was used to determine systemic responsiveness (mediator release), and sputum inflammatory markers were measured to explore for systemic and airway associations. Sputum samples were evaluated for cell counts, and tumor necrosis factor (TNF)-α, interleukin (IL)-8/CXCL8, IL-6, and IL-10. Ex vivo whole blood stimulation with ODE, LPS, and PGN each resulted in significant mediator release in all subjects, with the highest occurring with ODE; PGN resulted in significantly enhanced TNF-α and IL-8 as compared to LPS. COPD subjects demonstrated greater systemic responsiveness using the modified WBA versus healthy controls. Within COPD subjects, blood baseline TNF-α, IL-8, and IL-10 and ODE-, PGN-, and LPS-stimulated IL-8 levels significantly correlated with lung function. In conclusion, dust-induced mediator release was robust, and PGN, in part, resembled dust-induced mediator release. Subjects with COPD demonstrated increased mediator release following ex vivo whole blood stimulation with bioaerosol components, suggesting that circulating blood cells in COPD subjects may be primed to respond greater to microbial/inflammatory insult.

Size distribution of particulate and associated endotoxin and bacteria in traditional swine barn rooms and rooms sprinkled with oil

The objective of this pilot study was to investigate if a once-a-day sprinkling of canola oil in a swine confinement facility alters the airborne concentration and distribution of particulate matter and associated compounds (endotoxin and culturable microbes). Particulate was collected using an eight-stage cascade impactor in four identical swine grower/finisher rooms of a swine barn. Particulate (mg/m(3)) and endotoxin (EU/m(3) and EU/mg) distribution was determined. A six-stage viable cascade impactor was used to quantify total bacteria, enteric bacteria, and fungi. Microbes were characterized from subcultures prepared from the 10 most predominant colony types on each stage 3 (aerodynamic size 3.3-4.7μm) of the collection plates. Results indicated that oil sprinkling reduced total dust by 86% and total endotoxin concentration by 82.5%. However, the distribution patterns indicate that reduction is observed predominantly on large dust particles. In addition, the proportion of endotoxin associated with smaller particulate sizes (i.e., particles <4.7 μm) was higher in the oil-sprinkled rooms. Oil sprinkling does not markedly alter distribution of total bacteria, enteric bacteria, or fungi. The most frequently identified species were gram-positive genera. Oil sprinkling in swine confinement grower/finisher rooms can significantly reduce airborne total dust and endotoxin; however, smaller particles and associated endotoxin appear to remain in suspension, suggesting the overall improvement in air quality is uncertain. Further distribution studies and exposure outcome studies would need to be undertaken to determine the impacts of oil sprinkling.

Gender-related tumor necrosis factor-alpha responses in naïve volunteers with Toll-like receptor 4 polymorphisms exposed in a swine confinement facility

The aim of this work is to better understand the responses of people that are exposed to agricultural organic dust and other factors in modern swine production. We investigated the effects of toll-like receptor 4 (TLR4) genotype and gender on respiratory responses of naïve volunteers (18-28 years) to swine barn exposure. Non-smoking healthy subjects (16 men and 13 women) with TLR4 299 (Asp299Gly) and/or 399 (Thr399Ile) polymorphisms (TLR4 299/399) and age-sex matched subjects with TLR4 wild-type alleles spent 5 h in a nonexposed environment (baseline day) and 5 h in a swine facility (exposure day). The results showed significant decreases between baseline and exposure days in across-shift forced vital capacity (FVC), forced expiratory volume in 1 second (FEV(1)), forced midexpiratory flow rate (FEF(25-75)), and FEV(1)/FVC ratio and in methacholine concentration that reduced FEV1 by 20% (PC(20)) in all groups; however, there were no differences by sex or genotype. Similarly, nasal cytokines, serum cytokines, and blood neutrophil count increased after exposure; in contrast, however, these were influenced by gender. The increase in serum tumor necrosis factor-alpha (TNF-alpha) between baseline and exposure was gender-dependent with male sex associated with a significant increase in the wild-type group and female sex associated with a significant increase in the polymorphic group. These results suggest that for persons exposed to a swine facility, one's immunological response varies with gender as well as TLR4 genotype.

Endotoxin exposure and inflammation markers among agricultural workers in Colorado and Nebraska

The adverse respiratory effects of agricultural dust inhalation are mediated in part by endotoxin, a constituent of gram-negative bacterial cell walls. This study quantified personal work-shift exposures to inhalable dust, endotoxin, and its reactive 3-hydroxy fatty acid (3-OHFA) constituents among workers in grain elevators, cattle feedlots, dairies, and on corn farms. Exposures were compared with post-work-shift nasal lavage fluid inflammation markers and respiratory symptoms. Breathing-zone personal air monitoring was performed over one work shift to quantify inhalable dust (Institute of Medicine samplers), endotoxin (recombinant factor C [rFC] assay), and 3-OHFA (gas chromatography/mass spectrometry). Post-shift nasal lavage fluids were assayed for polymorphonuclear neutrophils (PMN), myeloperoxidase (MPO), interleukin 8 (IL-8), albumin, and eosinophilic cation protein (ECP) concentrations. The geometric mean (GSD) of endotoxin exposure (rFC assay) among the 125 male participants was 888 +/- (6.5) EU/m(3), and 93% exceeded the proposed exposure limit (50 EU/m(3)). Mean PMN, MPO, albumin, and ECP levels were two- to threefold higher among workers in the upper quartile of 3-OHFA exposure compared to the lowest exposure quartile. Even numbered 3-OHFA were most strongly associated with nasal inflammation. Symptom prevalence was not elevated among exposed workers, possibly due to endotoxin tolerance or a healthy worker effect in this population. This is the first study to evaluate the relationship between endotoxin's 3-OHFA constituents in agricultural dust and nasal airway inflammation. More research is needed to characterize the extent to which these agents contribute to respiratory disease among agricultural workers.

Fractionation of swine barn dust and assessment of its impact on the respiratory tract following repeated airway exposure

The effects of repeated exposure to a range of doses of swine barn dust (SBD) on airway hyperresponsiveness (AHR) and inflammation were evaluated using a mouse model system. A number of components, including endotoxin and a number of feed proteins, were identified in SBD, and mice were exposed 20 min/d for 14 d to a log dilution series of nebulized SBD suspensions. AHR to methacholine was measured using head-out whole-body plethysmography, and the methacholine concentration inducing a 20% decrease in pulmonary airflow (PC(20) MCh) was calculated. At the end of the 14-d exposure period, bronchoalveolar lavage (BAL) fluids were recovered, cytokines (interleukin [IL]-1beta, IL-6, keratinocyte-derived chemokine [KC], and tumor necrosis factor [TNF]) in BAL were measured by enzyme-linked immunosorbent assay (ELISA), and leukocytes in BAL were counted. The PC(20) MCh was significantly lower in the group of mice that were exposed to the highest concentration of SBD than in controls or the group exposed to the lowest level of dust. Likewise, the group that was exposed to the highest level of SBD had significantly higher levels of IL-1beta, KC, and TNF than controls and some other groups. There were substantially more lymphocytes and monocytes in the BAL from mice that were exposed to the higher levels of SBD for the 14-d period, but neutrophils were not a part of this response. The SBD exposures used in these experiments induced chronic inflammatory phenotype responses, as indicated by the predominance of lymphocytes and monocytes, but not neutrophils, in BAL and by inflammatory cytokines detected. The association between the PC(20)MCh and dose of SBD suggests that a threshold of susceptibility occurs after a relatively low, chronic exposure to SBD.

Muramic acid, endotoxin, 3-hydroxy fatty acids, and ergosterol content explain monocyte and epithelial cell inflammatory responses to agricultural dusts

In agricultural and other environments, inhalation of airborne microorganisms is linked to respiratory disease development. Bacterial endotoxins, peptidoglycans, and fungi are potential causative agents, but relative microbial characterization and inflammatory comparisons amongst agricultural dusts are not well described. The aim of this study was to determine the distribution of microbial endotoxin, 3-hydroxy fatty acids (3-OHFA), muramic acid, and ergosterol and evaluate inflammatory responses in human monocytes and bronchial epithelial cells with various dust samples. Settled surface dust was obtained from five environments: swine facility, dairy barn, grain elevator, domestic home (no pets), and domestic home with dog. Endotoxin concentration was determined by recombinant factor C (rFC). 3-OHFA, muramic acid, and ergosterol were measured using gas chromatography-mass spectrometry. Dust-induced inflammatory cytokine secretion in human monocytes and bronchial epithelial cells was evaluated. Endotoxin-independent dust-induced inflammatory responses were evaluated. Endotoxin and 3-OHFA levels were highest in agricultural dusts. Muramic acid, endotoxin, 3-OHFA, and ergosterol were detected in dusts samples. Muramic acid was highest in animal farming dusts. Ergosterol was most significant in grain elevator dust. Agricultural dusts induced monocyte tumor necrosis factor (TNF) alpha, interleukin (IL)-6, IL-8, and epithelial cell IL-6 and IL-8 secretion. Monocyte and epithelial IL-6 and IL-8 secretion was not dependent on endotoxin. House dust(s) induced monocyte TNFalpha, IL-6, and IL-8 secretion. Swine facility dust generally produced elevated responses compared to other dusts. Agricultural dusts are complex with significant microbial component contribution. Large animal farming dust(s)-induced inflammation is not entirely dependent on endotoxin. Addition of muramic acid to endotoxin in large animal farming environment monitoring is warranted.

Dietary intake, lung function and airway inflammation in Mexico City school children exposed to air pollutants

INTRODUCTION

Air pollutant exposure has been associated with an increase in inflammatory markers and a decline in lung function in asthmatic children. Several studies suggest that dietary intake of fruits and vegetables might modify the adverse effect of air pollutants.

METHODS

A total of 158 asthmatic children recruited at the Children's Hospital of Mexico and 50 non-asthmatic children were followed for 22 weeks. Pulmonary function was measured and nasal lavage collected and analyzed every 2 weeks. Dietary intake was evaluated using a 108-item food frequency questionnaire and a fruit and vegetable index (FVI) and a Mediterranean diet index (MDI) were constructed. The impact of these indices on lung function and interleukin-8 (IL-8) and their interaction with air pollutants were determined using mixed regression models with random intercept and random slope.

RESULTS

FVI was inversely related to IL-8 levels in nasal lavage (p < 0.02) with a significant inverse trend (test for trend p < 0.001), MDI was positively related to lung function (p < 0.05), and children in the highest category of MDI had a higher FEV1 (test for trend p < 0.12) and FVC (test for trend p < 0.06) than children in the lowest category. A significant interaction was observed between FVI and ozone for FEV1 and FVC as was with MDI and ozone for FVC. No effect of diet was observed among healthy children.

CONCLUSION

Our results suggest that fruit and vegetable intake and close adherence to the Mediterranean diet have a beneficial effect on inflammatory response and lung function in asthmatic children living in Mexico City.

Organic dust exposure alters monocyte-derived dendritic cell differentiation and maturation

Organic dust exposure in agricultural animal environments results in airway diseases. Dendritic cells (DCs) orchestrate inflammatory immune response in the airways, but little is known about how organic dust affects differentiation and maturation of monocyte-derived immature and mature DCs (iDCs, mDCs). Peripheral blood monocytes were differentiated in vitro into iDCs with granulocyte-macrophage colony stimulating factor + IL-4 (6 days) with and without swine facility organic dust extract (ODE, 0.1%). Unlike control iDCs, ODE-conditioned iDCs maintained key monocyte properties (increased mCD14, increased phagocytic ability) while expressing DC features [increased mCD83, HLA-DR, CD80, CD86, diminished cytokine (TNF-alpha, IL-6) responsiveness]. At day 6, iDCs were cultured for an additional 48 h (days 7 and 8) with lipopolysaccharide (LPS) to induce mDCs. ODE-conditioned mDCs maintained high expression of mCD14(+) and elevated phagocytosis while their DC features weakened as evidenced by decreased CD11c, CD83, HLA-DR, CD86, and CCR7 expression and reduced lymphocyte-stimulating capacity. Similar results were observed when monocytes were exposed to ODE for only the first 48 h and with ODE depleted of endotoxin. Control iDCs exposed to ODE during the final 2 days of iDC maturation (days 7 and 8) did not differ from control (no ODE) iDCs in surface marker expression and phagocytic ability, but exhibited enhanced lymphocyte-stimulating capacity. Dust exposure alters monocyte differentiation to iDCs and prevents maturation of iDC to mDCs. The first 48 h of monocyte differentiation appears to be the susceptible period to exposure. Environmental exposures present during early monocyte differentiation may impact the critical balance of DCs in the lung.

Toll-like receptor 4 variants reduce airway response in human subjects at high endotoxin levels in a swine facility

BACKGROUND

Toll-like receptor 4 (TLR4) variants have been shown to reduce the respiratory responses to inhaled LPS in controlled experiments among healthy volunteers.

OBJECTIVE

We sought to investigate whether naive subjects with TLR4 variants showed reduced respiratory response to a complex aerosol including endotoxin as a major constituent.

METHODS

Twenty-nine nonsmoking, nonatopic healthy subjects with TLR4 299/399 polymorphisms and 29 age- and sex-matched, wild-type TLR4 control subjects were exposed for 5 hours each in a noncontaminated environment (baseline day) and in a swine confinement facility (exposure day). There were 16 men and 13 women in each of the 2 age- and sex-matched groups.

RESULTS

TLR4 polymorphic subjects who were exposed to high endotoxin levels (>or=1550 EU/m(3)) had less reduction in the percentage across-shift change in FEV(1) from baseline than did wild-type subjects exposed to similar endotoxin levels. Among subjects exposed to higher endotoxin levels, the mean differences in the percentage across-shift changes between baseline and exposure days were significantly less in TLR4 polymorphic subjects compared with those seen in wild-type subjects in FEV(1) (-8.48% +/- 1.52% [mean +/- SE] vs -11.46% +/- 1.79%, P = .001), forced expiratory flow between 25% and 75% of forced vital capacity (-18.30% +/- 1.99% vs -24.14% +/- 3.28%, P = .009), and FEV(1)/forced vital capacity ratio (-5.40% +/- 0.56% vs -8.53% +/- 1.51%, P = .04). These patterns were not observed in IL-6 levels from serum and nasal lavage fluid, IL-8 levels from nasal lavage fluid, white blood cell counts, or blood differential counts.

CONCLUSION

The association between TLR4 variants and reduced airway responsiveness to inhaled particulate was observed at high endotoxin concentrations, creating the possibility of certain threshold phenomena for the apparent protective effect of TLR4 variants.

Association of Toll-like receptor 4 alleles with symptoms and sensitization to laboratory animals

BACKGROUND

Researchers and technicians working with laboratory animals (LAs) are exposed to animal allergen and endotoxin, which can interact to potentiate or inhibit symptoms or allergic responses. We hypothesized that functional genetic variants of Toll-like receptor 4 (TLR4), a key surface receptor for endotoxin, interface between worker and workplace and affect animal sensitization, symptoms, or both.

OBJECTIVE

We sought to determine whether TLR4/8551 variants alter the risk for LA sensitization, symptoms, or both.

METHODS

Three hundred thirty-five researchers, 195 of whom worked with animals, completed questions on workplace practices and symptoms and underwent skin prick tests or RASTs to common and animal allergens. Real-time PCR assessed TLR4/8551 and TLR4/8851 variants. Nominal logistic regression was used to analyze the contribution of demographic, exposure, and genetic variables to outcomes of interest.

RESULTS

Twenty-one percent of workers were LA sensitized, and 29% reported 1 or more symptoms to LAs. The TLR4/8551 G variant, which is less responsive to endotoxin, was detected in 9% and in linkage disequilibrium with the TLR4/8851 T allele. The G variant significantly associated with atopy and LA sensitization. Workers with the G variant spent significantly longer hours in high endotoxin/animal allergen tasks compared with those with the AA variant, which is perhaps less affected by endotoxin exposures. In multivariate analyses the G variant and longer animal research hours increased the risk of LA sensitization. Job tasks and LA sensitization, but not TLR4 variants, were predictors of LA-induced symptoms.

CONCLUSION

Workers with TLR4 variants that reduce responsiveness to endotoxin have higher risks for LA and other allergen sensitization but spend longer hours in tasks with high endotoxin and animal allergen exposures.

In vitro production of tumor necrosis factor-alpha by human monocytes stimulated with lipopolysaccharide is positively correlated with increased blood monocytes after exposure to a swine barn

Recently there has been interest in the air quality in and around intensive livestock production facilities, such as modern swine production barns, where agricultural workers and surrounding residents may be exposed to elevated levels of organic dusts. The health effects of these exposures are not completely understood. The study that is reported here is a component of a larger investigation of the relationships among the acute effects of high-concentration endotoxin exposure (swine barn dust), polymorphisms in the TLR4 gene, and respiratory outcomes following exposure to swine confinement buildings. The relationships among a mediator of acute lung inflammation, tumor necrosis factor alpha (TNF-alpha), and clinical responses to acute swine barn exposure were characterized. Analysis of the results showed that in vitro stimulation of human monocytes with as little as 1 ng/ml of lipopolysaccharide (LPS) produced a significant increase in the monocytes that produced TNF-alpha. Although the proportion of TNF-alpha-positive monocytes after in vitro stimulation with 1 ng/ml of LPS was not associated with gender or TLR4 genotype, it was positively associated with the concentration of monocytes in blood after barn exposure. Thus, these two responses to different forms of LPS exposure are significantly correlated, and more responsive monocytes in vitro indicate a forthcoming relative monocytosis, post barn exposure, which may initiate a cascade of chronic inflammation.

Repeat organic dust exposure-induced monocyte inflammation is associated with protein kinase C activity

BACKGROUND

Organic dust exposure results in an inflammatory response that attenuates over time, but repetitive exposures can result in chronic respiratory diseases. Mechanisms underlying this modulated response are not clear.

OBJECTIVE

This study investigated the effects of repeat versus single organic dust exposure-induced inflammatory mediators and protein kinase C (PKC) activity in monocytes.

METHODS

Settled organic dust was obtained from swine confinement facilities. Promonocytic THP-1 cells and human peripheral blood monocytes were pretreated with or without dust extract and then restimulated. Culture supernatants were evaluated for TNF-alpha, IL-6, CXCL8, and IL-10. Responses were compared with endotoxin-depleted dust, LPS, and peptidoglycan. PKC isoform (alpha, delta, epsilon, zeta) activation was evaluated by direct kinase activity. PKC isoform inhibitors' effects on TNF-alpha secretion were studied.

RESULTS

Single exposure to organic dust stimulated monocyte secretion of TNF-alpha, IL-6, CXCL8, and IL-10 compared with unstimulated cells. TNF-alpha and IL-6 were diminished in pretreated cells restimulated with dust. Secretion of CXCL8 and IL-10 remained persistently elevated. TNF-alpha responses were retained after marked depletion of endotoxin. Dust exposure induced significant PKC alpha, delta, epsilon, and zeta activation, peaking at 30 to 60 minutes. PKC isoform activation was attenuated in repeat exposed cells. Inhibition of PKCalpha and PKCepsilon reduced dust-induced TNF-alpha secretion.

CONCLUSION

Repeat organic dust exposure modulated inflammatory mediator production in monocytes independent of endotoxin. The inability of PKC to be reactivated may account for this observation.

CLINICAL IMPLICATIONS

Targeting PKC and specific mediators associated with repetitive organic dust exposure may result in novel therapeutic strategies.