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

Use of prototype side stream filtration system to control dust levels in a commercial swine farrowing building

Swine meat provides an essential global food source. Due to economies of scale, modern U.S. swine production primarily occurs indoors to maintain an optimal environment across the stages of swine production. Indoor concentrations of dust and contaminant gases in swine production buildings increase in the winter months due to reduced ventilation to optimal building temperature. In this study, an engineering control technology designed to recirculate the air in a swine farrowing room through a mobile air handling unit containing high-efficiency particulate filters was presented. A mobile solution could be easily deployed as an intervention method if an infectious disease outbreak occurs at a swine operation. The performance of this control technology was evaluated following deployment in a production farrowing barn for a period of 6 weeks during the winter in the Midwestern United States. Contaminant concentrations of inhalable dust, respirable dust, and carbon dioxide were measured in the room treated by the prototype system and compared to contaminant concentrations measured in an untreated "control" room. Over 6 weeks, the mean inhalable and respirable dust concentrations observed during the study period for the "treatment" room were 2.61 and 0.14 mg/m3, respectively, compared to 3.51 and 0.25 mg/m3, respectively, for the control room. The mobile recirculating ventilation system, operating at a flow rate of 45 m3/min (5 room air exchanges per hour), reduced the inhalable dust by 25% and respirable dust by 48% as measured with a real-time aerosol monitor, when compared to the control room. In addition, no concentration differences in carbon dioxide and relative humidity between the treatment and the control rooms were observed. Inhalable and respirable concentrations of dust were significantly reduced (p = 0.001), which demonstrates an essential improvement of the air quality that may prove beneficial to reduce the burden of disease among both workers and animals.

A critical review of advancement in scientific research on food animal welfare-related air pollution

Air pollution generates hazardous pollutants that have resulted in safety, health, and other welfare issues of food animals. This paper reviewed scientific research advancement in food animal welfare-related air pollution based on 219 first-hand research publications in refereed journals (referred to as "RPs") over the past nine decades. Scientific studies in this area began in the 1930s. The number of RPs has increased significantly with each decade from the 1960s to the 1980s, then decreased until the 2010s. Twenty-six countries have contributed to this multidisciplinary research. About 52% of the studies were conducted in the U.S. and U.K. Research activities have surged in China since the 2010s. On-farm discoveries in air toxicity that resulted in animal death or injury were all from observational studies. About 75% of the studies were experimental and conducted primarily under laboratory conditions. Ammonia (NH₃) was the main pollutant in 59% of the RPs, followed by dust, hydrogen sulfide (H₂S), bacteria and endotoxins, carbon dioxide (CO₂), carbon monoxide (CO), silo gas, sulfur dioxide (SO₂), and odor. Approximately 23% of RPs reported multiple pollutants in the same study. The most intensively studied animal species were poultry (broilers, hens, turkeys, ducks, and eggs and embryos in 44% of the RPs) and pigs (also 44%), followed by cattle, and sheep and goats. Scientific investigations in this area were driven by the research focuses in the areas of animal agriculture and industrial air pollution. Some major research teams played important roles in advancing scientific research. However, research in this area is still relatively limited. There is a great need to overcome some technical challenges and reverse the trend of decreasing research activities in North America and Europe.

Particulate matter and airborne endotoxin concentration in calf barns and their association with lung consolidation, inflammation, and infection

Agricultural operations are important sources of organic dust containing particulate matter (PM) and endotoxins, which have possible negative health consequences for both humans and animals. Dust concentrations and composition in calf barns, as well as the potential health effects for these animals, are scarcely documented. The objective of this study was to measure PM fractions and endotoxin concentrations in calf barns and study their associations with lung consolidation, respiratory tract inflammation, and infection in group-housed calves. In this cross-sectional study, samples from 24 dairy farms and 23 beef farms were collected in Belgium from January to April 2017. PM_1.0, PM_2.5 and PM₁₀ (defined as particulate matter passing through a size-selective inlet with a 50% efficiency cut-off at a 1.0-μm, 2.5-μm, and 10-μm aerodynamic diameter, respectively) were sampled during a 24-h period using a Grimm aerosol spectrometer (Grimm Aerosol Technik Ainring GmbH & Co. KG). Endotoxin concentration was measured in the PM₁₀ fraction. Thoracic ultrasonography was performed and broncho-alveolar lavage fluid was collected for cytology and bacteriology. Average PM concentrations were 16.3 µg/m³ (standard deviation, SD: 17.1; range: 0.20-771), 25.0 µg/m³ (SD: 25.3; range: 0.50-144.9), and 70.3 µg/m³ (SD: 54.5; range: 1.6-251.2) for PM_1.0, PM_2.5, and PM₁₀, respectively. Mean endotoxin in the PM₁₀ fraction was 4.2 endotoxin units (EU)/µg (SD: 5.50; range: 0.03-30.3). Concentrations in air were 205.7 EU/m³ (SD: 197.5; range: 2.32-901.0). Lung consolidations with a depth of ≥1, ≥3, and ≥6 cm were present in 43.1% (146/339), 27.4% (93/339), and 15.3% (52/339) of the calves, respectively. Exposure to fine (PM_1.0) PM fractions was associated with increased odds of lung consolidations of ≥1 cm (odds ratio, OR: 3.3; confidence interval (CI): 1.5-7.1), ≥3 cm (OR: 2.8; CI: 1.2-7.1), and ≥6 cm (OR: 12.3; CI: 1.2-125.0). The odds of having lung consolidations of ≥1 cm (OR: 13.9; CI: 3.4-58.8) and ≥3 cm (OR: 6.7; 1.7-27.0) were higher when endotoxin concentrations in the dust mass exceeded 8.5 EU/µg. Broncho-alveolar lavage fluid neutrophil percentage was positively associated with PM₁₀ concentration, and epithelial cell percentage was negatively associated with this fraction. Concentration of PM_2.5 was positively associated with epithelial cell percentage and isolation of Pasteurella multocida. Although concentrations of fine dust are lower in calf barns than in poultry and pig housings, in this study they were associated with pneumonia in calves. Dust control strategies for reducing fine dust fractions in calf barns may benefit human and animal respiratory health.

Particulate matters induce acute exacerbation of allergic airway inflammation via the TLR2/NF-κB/NLRP3 signaling pathway

BACKGROUND

Exposure to particulate matters (PMs) can lead to an acute exacerbation of allergic airway diseases, increasing the severity of symptoms and mortality. However, little is known about the underlying molecular mechanism. This study aimed to investigate the effects of PMs on acute exacerbation of allergic airway inflammation and seek potential therapeutic targets.

METHODS

Non-allergic control and ovalbumin (OVA)-allergic wide-type (WT) and Toll-like receptor 2 knockout (Tlr2-/-) mice were exposed to 100 μg of PM (diameter 5.85 μm) or saline by the oropharyngeal instillation. The responses were examined three days after exposure. In the RAW264.7 macrophage cell line, Tlr2 was knocked down by small-interfering RNA or the NF-κB inhibitor JSH-23 was used, and then the cells were stimulated with PMs for 12 h before comparison of the inflammatory responses.

RESULTS

PM exposure led to increased inflammatory cell recruitment and airway intensity of PAS + staining in OVA-allergic WT mice, accompanied with an accumulation of inflammatory cells and elevated inflammatory cytokines, such as IL-6 and IL-18, in the bronchoalveolar lavage fluid (BALF). Furthermore, the protein levels of TLR2 and the NLRP3 inflammasome were elevated concomitantly with the airway inflammation post-OVA/PMs challenge. Tlr2 deficiency effectively inhibited the airway inflammation, including pulmonary inflammatory cell recruitment, mucus secretion, serum OVA-specific immunoglobulin E (IgE), and BALF inflammatory cytokine production. Additionally, the P-induced NLRP3 activation in the RAW 264.7 cell line was diminished by the knockdown of Tlr2 or JSH-23 treatment in vitro.

CONCLUSION

Our results indicated that PMs exacerbate the allergic airway inflammation mediated by the TLR2/ NF-κB/NLRP3 signaling pathway. Inhibition of NF-κB seems to be a possible treatment.

Haptoglobin and C-Reactive Protein-Non-specific Markers for Nursery Conditions in Swine

A quality concept for production in the pork market includes granting a good health status of pigs from birth to slaughter. This concept is a precondition for animal welfare as well as reducing antibiotic usage in farm animals. The demand for fighting bacterial antimicrobial resistance in humans, animals, and in the environment is one driving force for the development of innovative technical solutions to improve husbandry. Maintenance of a good health status in pigs depends on early detection of a disturbance in homeostasis in critical phases of life. This can be measured by non-specific biomarkers as acute phase proteins. In this project, husbandry conditions and health status in nursery pigs were monitored in an autumn and winter nursery period from weaning to the end of nursery in two compartments with 180 pigs each. It was investigated whether a slight modification in indoor climate achieved by a new ammonia sensory technology coupled with the electronic control unit of the forced ventilation system ensuring ammonia levels lower than 5 ± 3 ppm in one compartment led to a better health status in piglets in comparison to the control compartment. In the examined nursery periods in different seasons, ammonia concentrations in the experimental compartment were significantly lower than in the control compartment, thus proving the functionality and efficacy of the technical system. Production parameters as feed conversion rate and average daily weight gain were slightly improved in the experimental compartment without implementing other measures. Multifactorial analysis of variance resulted in a significant influence of season, daily quarter, and compartment on ammonia concentration. The challenge to preserve a high health status of piglets also during suboptimal outside climate in the transitional season was reflected by an increase in the acute-phase proteins haptoglobin (Hp) and C-reactive protein (CRP) in autumn compared to winter. The seasonal influence on concentrations of CRP and Hp superimposed potential influences of the climate modification. New technological concepts to reduce noxious gases and dust in the animal environment as well as emissions, which in parallel guarantee optimal temperatures also during extreme weather conditions, can be evaluated by clinical data in combination with biomarkers.

Association between endotoxin levels in dust from indoor swine housing environments and the immune responses of pigs

Indoor animal husbandry environments are inevitably contaminated with endotoxins. Endotoxin exposure is associated with various inflammatory illnesses in animals. This cross-sectional study evaluated the relationship between the degree of endotoxin exposure and the cellular and humoral immune profiles of fattening pigs. Blood samples were taken from the jugular vein of 47 pigs from ten pig farms in Korea. Whole blood cell counts and plasma immunoglobulin (Ig) classes were determined. Peripheral-blood mononuclear cells were stimulated in vitro with concanavalin A for 48 h, and cytokines released into culture supernatants were measured. The barns in which the pigs lived were assessed for endotoxin levels in the total and respirable dust by using the limulus amebocyte lysate kinetic QCL method. Low and high endotoxin exposures were defined as ≤ 30 and > 30 EU/m³, respectively. Compared to pigs with low endotoxin exposure (n = 19), highly exposed pigs (n = 28) had higher circulating neutrophil and lymphocyte (particularly B cells) counts, IgG and IgE levels, interferon-gamma (IFNγ) and interleukin (IL)-4 productions, and lower IgA levels and tumor necrosis factor-alpha (TNFα) production. The IL-4, IFNγ, and TNFα levels significantly correlated with endotoxin level and/or pig age. Constant exposure of pigs to high levels of airborne endotoxins can lead to aberrant immune profiles.

Kinome analyses of inflammatory responses to swine barn dust extract in human bronchial epithelial and monocyte cell lines

Exacerbated inflammation upon persistent barn organic dust exposure is a key contributor to the pathogenesis of lung inflammation and lung function decline. Barn dust constituents and the mechanisms contributing to the exacerbated inflammation are not clearly known. We set out to understand the inflammatory effects of Swine Barn Dust Extracts (SBDE) on human lung epithelial (BEAS2B) and macrophage (THP-1 monocyte derived) cell lines on a kinome array to determine phosphorylation events in the inflammatory signaling pathways. Upon identifying events unique to SBDE or those induced by innate immune ligands in each cell line, we validated the signaling pathway activation by transcriptional analyses of downstream inflammatory cytokines. Our findings indicate that SBDE-mediated pro-inflammatory effects are predominantly due to the induction of neutrophilic chemokine IL-8. Differentially phosphorylated peptides implicated in IL-8 induction in BEAS2B cell line include, TLR2, 4, 5, 7, 8, 9, PKC, MAP kinases (p38, JNK), inflammasomes (NLRP1, NLRP3), NF-κB and AP-1. In the THP-1 cell line, in addition to the aforementioned peptides, peptides corresponding to RIG-I-like receptors (RIG-I, MDA5) were found. This is the first report to demonstrate the application of a kinome array to delineate key inflammatory signaling pathways activated upon SBDE exposure in vitro.

A new and efficient culture method for porcine bone marrow-derived M1- and M2-polarized macrophages

BACKGROUND

Macrophages play an important role in the innate immune system as part of the mononuclear phagocyte system (MPS). They have a pro-inflammatory signature (M1-polarized macrophages) or anti-inflammatory signature (M2-polarized macrophages) based on expression of surface receptors and secretion of cytokines. However, very little is known about the culture of macrophages from pigs and more specific about the M1 and M2 polarization in vitro.

METHODS

Porcine monocytes or mononuclear bone marrow cells were used to culture M1- and M2-polarized macrophages in the presence of GM-CSF and M-CSF, respectively. Surface receptor expression was measured with flow cytometry and ELISA was used to quantify cytokine secretion in response to LPS and PAM₃CSK₄ stimulation. Human monocyte-derived macrophages were used as control.

RESULTS

Porcine M1- and M2-polarized macrophages were cultured best using porcine GM-CSF and murine M-CSF, respectively. Cultures from bone marrow cells resulted in a higher yield M1- and M2-polarized macrophages which were better comparable to human monocyte-derived macrophages than cultures from porcine monocytes. Porcine M1-polarized macrophages displayed the characteristic fried egg shape morphology, lower CD163 expression and low IL-10 production. Porcine M2-polarized macrophages contained the spindle-like morphology, higher CD163 expression and high IL-10 production.

CONCLUSION

Porcine M1- and M2-polarized macrophages can be most efficiently cultured from mononuclear bone marrow cells using porcine GM-CSF and murine M-CSF. The new culture method facilitates more refined studies of porcine macrophages in vitro, important for both porcine and human health since pigs are increasingly used as model for translational research.

The Effect of Inhalant Organic Dust on Bone Health

PURPOSE OF REVIEW

Agriculture remains a major economic sector globally, and workers experience high rates of chronic inflammatory lung and musculoskeletal diseases. Whereas obstructive pulmonary diseases are known risk factors for bone loss, the underlying relationship between lung inflammation and bone health is not well known.

RECENT FINDINGS

An agriculture organic dust extract inhalation animal model has recently linked lung injury-induced inflammation to systemic bone loss. This process is dependent upon lipopolysaccharide and the toll-like receptor 4 (TLR4) signaling pathway. Downstream systemic interleukin-6 is a key mediator that subsequently activates osteoclastogenesis. Age is a host factor that impacted bone disease with younger mice demonstrating increased susceptibility to bone loss following inhalant exposures as compared to older mice. Supplemental dietary vitamin D was shown to prevent organic dust-induced bone loss, but not lung disease, in animals. Recent animal studies provide new mechanistic insight into the lung-bone inflammatory axis. Host factors, diet, and lipopolysaccharide/TLR4 signaling pathways play a significant role in explaining how inhalant organic dust exposures impact bone health. These investigations might lead to specific targeted therapeutic approaches.

Methods and Study Designs for Characterizing the Pharmacokinetics and Pharmacodynamics of Carrier-Mediated Agents

Major advances in carrier-mediated agents (CMAs), which include nanoparticles, nanosomes, and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages, such as greater solubility, duration of exposure, and delivery to the site of action over their small molecule counterparts, there is substantial variability in systemic clearance and distribution, tumor delivery, and pharmacologic effects (efficacy and toxicity) of these agents. In this chapter, we focus on the analytical and phenotypic methods required to design a study that characterizes the pharmacokinetics (PK) and pharmacodynamics (PD) of all forms of these nanoparticle-based drug agents. These methods include separation of encapsulated and released drugs, ultrafiltration for measurement of non-protein bound active drug, microdialysis to measure intra-tumor drug concentrations, immunomagnetic separation and flow cytometry for sorting cell types, and evaluation of spatial distribution of drug forms relative to tissue architecture by mass spectrometry imaging and immunohistochemistry.

Airborne Influenza A Is Detected in the Personal Breathing Zone of Swine Veterinarians

The 2009 H1N1 pandemic emphasized a need to evaluate zoonotic transmission of influenza A in swine production. Airborne influenza A virus has been detected in swine facilities during an outbreak. However, the personal exposure of veterinarians treating infected swine has not been characterized. Two personal bioaerosol samplers, the NIOSH bioaerosol sampler and the personal high-flow inhalable sampler head (PHISH), were placed in the breathing zone of veterinarians treating swine infected with either H1N1 or H3N2 influenza A. A greater number of viral particles were recovered from the NIOSH bioaerosol sampler (2094 RNA copies/m3) compared to the PHISH sampler (545 RNA copies/m3). In addition, the majority of viral particles were detected by the NIOSH bioaerosol sampler in the >4 μm size fraction. These results suggest that airborne influenza A virus is present in the breathing zone of veterinarians treating swine, and the aerosol route of zoonotic transmission of influenza virus should be further evaluated among agricultural workers.

Farm animal models of organic dust exposure and toxicity: insights and implications for respiratory health

PURPOSE OF REVIEW

Modern food animal production is a major contributor to the global economy, owing to advanced intensive indoor production facilities aimed at increasing market readiness and profit. Consequences of these advances are accumulation of dusts, gases, and microbial products that diminish air quality within production facilities. Chronic inhalation exposure contributes to onset and exacerbation of respiratory symptoms and diseases in animals and workers. This article reviews literature regarding constituents of farm animal production facility dusts, animal responses to production building and organic dust exposure, and the effect of chronic inhalation exposure on pulmonary oxidative stress and inflammation.

RECENT FINDINGS

Porcine models of production facility and organic dust exposures reveal striking similarities to observations of human cells, tissues, and clinical data. Oxidative stress plays a key role in mediating respiratory diseases in animals and humans, and enhancement of antioxidant levels through nutritional supplements can improve respiratory health.

SUMMARY

Pigs are well adapted to the exposures common to swine production buildings and thus serve as excellent models for facility workers. Insight for understanding mechanisms governing organic dust associated respiratory diseases may come from parallel comparisons between farmers and the animals they raise.

Evaluation of a Shaker Dust Collector for Use in a Recirculating Ventilation System

General ventilation with recirculated air may be cost-effective to control the concentration of low-toxicity, contaminants in workplaces with diffuse, dusty operations, such as in agriculture. Such systems are, however, rarely adopted with little evidence showing improved air quality and ability to operate under harsh conditions. The goal of this work was to examine the initial and long-term performance of a fabric-filter shaker dust collector (SDC) in laboratory tests and as deployed within a recirculating ventilation system in an agricultural building. In laboratory tests, collection efficiency and pressure drop were tracked over several filter loading cycles, and the recovery of filter capacity (pressure drop) from filter shaking was examined. Collection efficiencies of particles larger than 5 μm was high (>95%) even when the filter was pristine, showing effective collection of large particles that dominate inhalable concentrations typical of agricultural dusts. For respirable-sized particles, collection efficiencies were low when the filter was pristine (e.g., 27% for 1 μm) but much higher when a dust cake developed on the filter (>99% for all size particles), even after shaking (e.g., 90% for 1 μm). The first shake of a filter was observed to recovery a substantial fraction of filter capacity, with subsequent shakes providing little benefit. In field tests, the SDC performed effectively over a period of three months in winter when incorporated in a recirculating ventilation system of a swine farrowing room. Trends in collection efficiency and pressure drop with loading were similar to those observed in the laboratory with overall collection efficiencies high (>80%) when pressure drop exceeded 230 Pa, or 23% of the maximum loading recommended by the manufacturer. This work shows that the SDC can function effectively over the harsh winter in swine rearing operations. Together with findings of improved air quality in the farrowing room reported in a companion manuscript, this article provides evidence that an SDC represents a cost-effective solution to improve air quality in agricultural settings.

Immune Control of PRRS: Lessons to be Learned and Possible Ways Forward

Porcine reproductive and respiratory syndrome (PRRS) is an elusive model of host/virus relationship in which disease is determined by virus pathogenicity, pig breed susceptibility and phenotype, microbial infectious pressure, and environmental conditions. The disease can be controlled by farm management programs, which can be supported by vaccination or conditioning of animals to circulating PRRS virus (PRRSV) strains. Yet, PRRS still represents a cause of heavy losses for the pig industry worldwide. Immunological control strategies are often compounded by poor and late development of adaptive immunity in both vaccinated and infected animals. Also, there is evidence that results of field trials can be worse than those of experimental studies in isolation facilities. Neutralizing antibody (NA) was shown to prevent PRRSV infection. Instead, the role of NA and adaptive immunity on the whole in virus clearance after established PRRSV infections is still contentious. Pigs eventually eliminate PRRSV infection, which may be correlated with an “educated,” innate immune response, which may also develop following vaccination. In addition to vaccination, an immunomodulation strategy for PRRS can be reasonably advocated in pig “problem” farms, where a substantial control of disease prevalence and disease-related losses is badly needed. This is not at odds with vaccination, which should be preferably restricted to PRRSV-free animals bound for PRRSV-infected farm units. Oral, low-dose, interferon-α treatments proved effective on farm for the control of respiratory and reproductive disease outbreaks, whereas the results were less clear in isolation facilities. Having in mind the crucial interaction between PRRSV and bacterial lipopolysaccharides for occurrence of respiratory disease, the strong control actions of low-dose type I interferons on the inflammatory response observed in vitro and in vivo probably underlie the rapid clinical responses observed in field trials.