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

Effect of epithelial-specific MyD88 signaling pathway on airway inflammatory response to organic dust exposure

The Toll-like receptor (TLR) adaptor protein MyD88 is integral to airway inflammatory response to microbial-enriched organic dust extract (ODE) exposures. ODE-induced airway neutrophil influx and release of pro-inflammatory cytokines was essentially abrogated in global MyD88-deficient mice, yet these mice demonstrate an increase in airway epithelial cell mucin expression. To further elucidate the role of MyD88-dependent responses specific to lung airway epithelial cells in response to ODE in vivo, the surfactant protein C protein (SPC) Cre+ embryologic expressing airway epithelial cells floxed for MyD88 to disrupt MyD88 signaling were utilized. The inducible club cell secretory protein (CCSP) Cre+, MyD88 floxed, were also developed. Using an established protocol, mice were intranasally instilled with ODE or saline once or daily up to 3 weeks. Mice with MyD88-deficient SPC+ lung epithelial cells exhibited decreased neutrophil influx following ODE exposure once and repetitively for 1 week without modulation of classic pro-inflammatory mediators including tumor necrosis factor (TNF)-α, interleukin (IL)-6, and neutrophil chemoattractants. This protective response was lost after 3 weeks of repetitive exposure. ODE-induced Muc5ac mucin expression at 1 week was also reduced in MyD88-deficient SPC+ cells. Acute ODE-induced IL-33 was reduced in MyD88-deficient SPC+ cells whereas serum IgE levels were increased at one week. In contrast, mice with inducible MyD88-deficient CCSP+ airway epithelial cells demonstrated no significant difference in experimental indices following ODE exposure. Collectively, these findings suggest that MyD88-dependent signaling targeted to all airway epithelial cells plays an important role in mediating neutrophil influx and mucin production in response to acute organic dust exposures.

Reduction of donor mononuclear phagocytes with clodronate-liposome during ex vivo lung perfusion attenuates ischemia-reperfusion injury

OBJECTIVES

Clodronate-liposome is used for depleting mononuclear phagocytes associated with ischemia-reperfusion injury. We hypothesized that administration of clodronate-liposome into the perfusate during ex vivo lung perfusion could reduce mononuclear phagocytes and attenuate ischemia-reperfusion injury.

METHODS

First, the number of mononuclear phagocytes in flushed grafts (minimum cold ischemic time, 6-hour cold ischemic time, 15-hour cold ischemic time, and 18-hour cold ischemic time; n = 6 each) was determined using flow cytometry. Second, grafts (15-hour cold ischemic time) were allocated to control or clodronate (n = 5 each). In the clodronate group, clodronate-liposome is administered into the perfusate. After 4 hours of ex vivo lung perfusion, the number of mononuclear phagocytes in the perfusate and lung tissues was measured. Third, grafts (15-hour cold ischemic time) were allocated to control or clodronate (n = 6 each). After 4 hours of ex vivo lung perfusion, the left lungs were transplanted and reperfused for 2 hours. Lung function was evaluated, and samples were analyzed.

RESULTS

First, mononuclear phagocytes remain in flushed grafts after prolonged cold ischemia. Second, the number of mononuclear phagocytes in lung tissues after ex vivo lung perfusion was significantly reduced in the clodronate group (P = .008). Third, lung compliance and vascular resistance during ex vivo lung perfusion were significantly improved in the clodronate group (P < .001 for both). Blood oxygenation and pulmonary edema were significantly improved in the clodronate group after 2 hours of reperfusion (P = .015 and P = .026, respectively). Histological findings showed reduced lung injury in the clodronate group (P = .013).

CONCLUSIONS

Administration of clodronate-liposome into the perfusate during ex vivo lung perfusion resulted in a significant reduction of mononuclear phagocytes in donor lungs, leading to attenuation of ischemia-reperfusion injury.

Agricultural dust derived bacterial extracellular vesicle mediated inflammation is attenuated by DHA

Dietary long-chain omega-3 polyunsaturated fatty acids (n-3 PUFA) and their pro-resolving metabolites are protective against atherosclerotic disease, and ameliorate systemic inflammatory conditions including lupus erythematosus, psoriasis, and bronchial asthma. Organic bioaerosol inhalation is a common and injurious hazard associated with agricultural occupations such as work in swine concentrated animal feeding operations (CAFOs) and is known to increase the risk for developing respiratory conditions such as asthma and COPD. Nearly all cells secrete membrane-bound vesicles (extracellular vesicles, EVs) that have the capacity to transmit protein, nucleic acid, and lipid signaling mediators between cells. Using a polymer-based isolation technique (ExoQuick, PEG) followed by ultracentrifugation, EVs were isolated from CAFO dust extracts, and were quantified and partially characterized. Here, we investigated the role of the n-3 PUFA docosahexaenoic acid (DHA) as a component of n-6 to n-3 PUFA mixtures used to recapitulate physiologically relevant dietary ratios in the resolution of inflammatory injury caused by exposure to EVs carried by agricultural organic dust in vitro. Primary human bronchial epithelial cells, fibroblasts and monocyte-derived macrophages were exposed to EVs isolated from swine CAFO dust. Cells were treated with mixtures of n-6 and n-3 PUFA during recovery from the EV-induced injury. CAFO dust extract (DE) was found to contain EVs that contributed significantly to the overall consequences of exposure to complete DE. DHA-rich PUFA ratios inhibited DE-derived EV-induced proinflammatory cytokine release dose-dependently. DHA-rich PUFA ratios also reversed the damaging effects of EVs on recellularization of lung matrix scaffolds, accelerated wound healing, and stimulated the release of pro-resolution mediators. These results underscore the importance of n-3 PUFA as anti-inflammatory compounds during recovery from EV-laden environmental dust exposure in the context of cellular responses in vitro, warranting future translational studies.

The influence of exposure approaches to in vitro lung epithelial barrier models to assess engineered nanomaterial hazard

Exposure to engineered nanomaterials (ENM) poses a potential health risk to humans through long-term, repetitive low-dose exposures. Currently, this is not commonplace within in vitro lung cell cultures. Therefore, the purpose of this study was to consider the optimal exposure approach toward determining the stability, sensitivity and validity of using in vitro lung cell mono- and co-cultures to determine ENM hazard. A range of exposure scenarios were conducted with DQ₁₂ (previously established as a positive particle control) (historic and re-activated), TiO₂ (JRC NM-105) and BaSO₄ (JRC NM-220) on both monocultures of A549 cells as well as co-cultures of A549 cells and differentiated THP-1 cells. Cell cultures were exposed to either a single, or a repeated exposure over 24, 48- or 72-hours at in vivo extrapolated concentrations of 0-5.2 µg/cm², 0-6 µg/cm² and 0-1µg/cm². The focus of this study was the pro-inflammatory, cytotoxic and genotoxic response elicited by these ENMs. Exposure to DQ₁₂ caused pro-inflammatory responses after 48 hours repeat exposures, as well as increases in micronucleus frequency. Neither TiO₂ nor BaSO₄ elicited a pro-inflammatory response at this time point. However, there was induction of IL-6 after 24 hours TiO₂ exposure. In conclusion, it is important to consider the appropriateness of the positive control implemented, the cell culture model, the time of exposure as well as the type of exposure (bolus or fractionated) before establishing if an in vitro model is appropriate to determine the level of response to the specific ENM of interest.

Lung Inflammatory Response to Environmental Dust Exposure in Mice Suggests a Link to Regional Respiratory Disease Risk

PURPOSE

The Salton Sea, California's largest lake, is designated as an agricultural drainage reservoir. In recent years, the lake has experienced shrinkage due to reduced water sources, increasing levels of aerosolized dusts in surrounding regions. Communities surrounding the Salton Sea have increased asthma prevalence versus the rest of California; however, a connection between dust inhalation and lung health impacts has not been defined.

METHODS

We used an established intranasal dust exposure murine model to study the lung inflammatory response following single or repetitive (7-day) exposure to extracts of dusts collected in regions surrounding the Salton Sea (SSDE), complemented with in vitro investigations assessing SSDE impacts on the airway epithelium.

RESULTS

In these investigations, single or repetitive SSDE exposure induced significant lung inflammatory cytokine release concomitant with neutrophil influx. Repetitive SSDE exposure led to significant lung eosinophil recruitment and altered expression of genes associated with allergen-mediated immune response, including Clec4e. SSDE treatment of human bronchial epithelial cells (BEAS-2B) induced inflammatory cytokine production at 5- and 24-hours post-treatment. When BEAS-2B were exposed to protease activity-depleted SSDE (PDSSDE) or treated with SSDE in the context of protease-activated receptor-1 and -2 antagonism, inflammatory cytokine release was decreased. Furthermore, repetitive exposure to PDSSDE led to decreased neutrophil and eosinophilic influx and IL-6 release in mice compared to SSDE-challenged mice.

CONCLUSION

These investigations demonstrate potent lung inflammatory responses and tissue remodeling in response to SSDE, in part due to environmental proteases found within the dusts. These studies provide the first evidence supporting a link between environmental dust exposure, protease-mediated immune activation, and respiratory disease in the Salton Sea region.

Neutralization of IL-33 modifies the type 2 and type 3 inflammatory signature of viral induced asthma exacerbation

Background

Respiratory viral infections are one of the leading causes of need for emergency care and hospitalizations in asthmatic individuals, and airway-secreted cytokines are released within hours of viral infection to initiate these exacerbations. IL-33, specifically, contributes to these allergic exacerbations by amplifying type 2 inflammation. We hypothesized that blocking IL-33 in RSV-induced exacerbation would significantly reduce allergic inflammation.

Methods

Sensitized BALB/c mice were challenged with aerosolized ovalbumin (OVA) to establish allergic inflammation, followed by RSV-A2 infection to yield four treatment groups: saline only (Saline), RSV-infected alone (RSV), OVA alone (OVA), and OVA-treated with RSV infection (OVA-RSV). Lung outcomes included lung mRNA and protein markers of allergic inflammation, histology for mucus cell metaplasia and lung immune cell influx by cytospin and flow cytometry.

Results

While thymic stromal lymphopoietin (TSLP) and IL-33 were detected 6 h after RSV infection in the OVA-RSV mice, IL-23 protein was uniquely upregulated in RSV-infected mice alone. OVA-RSV animals varied from RSV- or OVA-treated mice as they had increased lung eosinophils, neutrophils, group 2 innate lymphoid cells (ILC2) and group 3 innate lymphoid cells (ILC3) detectable as early as 6 h after RSV infection. Neutralized IL-33 significantly reduced ILC2 and eosinophils, and the prototypical allergic proteins, IL-5, IL-13, CCL17 and CCL22 in OVA-RSV mice. Numbers of neutrophils and ILC3 were also reduced with anti-IL-33 treatment in both RSV and OVA-RSV treated animals as well.

Conclusions

Taken together, our findings indicate a broad reduction in allergic-proinflammatory events mediated by IL-33 neutralization in RSV-induced asthma exacerbation.

Vitex negundo Linn. extract alleviates inflammatory aggravation and lung injury by modulating AMPK/PI3K/Akt/p38-NF-κB and TGF-β/Smad/Bcl2/caspase/LC3 cascade and macrophages activation in murine model of OVA-LPS induced allergic asthma

ETHNOPHARMACOLOGICAL RELEVANCE

There is growing inclination towards developing bioactive molecule-based strategies for the management of allergic airway inflammation associated respiratory diseases. Vitex negundo Linn., also known as Nirgundi, is one such medicinal plant enriched with phytochemicals and used for inflammatory and respiratory disorders including asthma in traditional system of medicine. Preliminary studies have claimed anti-tussive and bronchodilator potential of V. negundo Linn. However, its attributes as well as molecular mechanism (s) in modulation of asthma mediated by allergic inflammation are yet to be delineated scientifically.

AIM OF THE STUDY

Present study attempted to assess the effectiveness of Vitex negundo leaf extract (VNLE) in mitigation of allergen induced inflammation associated asthmatic lung damage with emphasis to delineate its molecular mechanism (s).

MATERIALS AND METHODS

Allergic lung inflammation was established in Balb/c mice using Ovalbumin-lipopolysaccharide (OVA-LPS). Several allergic inflammatory parameters, histopathological changes, alveolar macrophage activation and signalling pathways were assessed to examine protective effects of VNLE. UHPLC-DAD-QTOF-ESI-IMS was used to characterize VLNE.

RESULTS

VNLE administration effectively attenuated LPS-induced oxi-inflammatory stress in macrophages suggesting its anti-inflammatory potential. Further, VNLE showed protective effect in mitigating asthmatic lung damage as evident by reversal of pathological changes including inflammatory cell influx, congestion, fibrosis, bronchial thickness and alveolar collapse observed in allergen group. VNLE suppressed expressions of inflammatory Th1/Th2 cytokines, chemokines, endopeptidases (MMPs), oxidative effector enzyme (iNOS), adhesion molecules, IL-4/IFN-γ release with simultaneous enhancement in levels of IL-10, IFN-γ, MUC3 and tight junction proteins. Subsequent mechanistic investigation revealed that OVA-LPS concomitantly enhanced phosphorylation of NF-κB, PI3K, Akt and p38MAPKs and downregulated AMPK which was categorically counteracted by VNLE treatment. VNLE also suppressed OVA-LPS induced fibrosis, apoptosis, autophagy and gap junction proteins which were affirmed by reduction in TGF-β, Smad2/3/4, Caspase9/3, Bax, LC3A/B, connexin 50, connexin 43 and enhancement in Bcl2 expression. Additionally, suppression of alveolar macrophage activation, inflammatory cells in blood and elevation of splenic CD8+T cells was demonstrated. UHPLC-DAD-QTOF-ESI-IMS revealed presence of iridoids glycoside and phenolics which might contribute these findings.

CONCLUSION

These findings confer protective effect of VNLE in attenuation of allergic lung inflammation and suggest that it could be considered as valuable medicinal source for developing safe natural therapeutics for mitigation of allergic inflammation during asthma.

High-throughput analysis of lung immune cells in a combined murine model of agriculture dust-triggered airway inflammation with rheumatoid arthritis

Rheumatoid arthritis (RA)-associated lung disease is a leading cause of mortality in RA, yet the mechanisms linking lung disease and RA remain unknown. Using an established murine model of RA-associated lung disease combining collagen-induced arthritis (CIA) with organic dust extract (ODE)-induced airway inflammation, differences among lung immune cell populations were analyzed by single cell RNA-sequencing. Additionally, four lung myeloid-derived immune cell populations including macrophages, monocytes/macrophages, monocytes, and neutrophils were isolated by fluorescence cell sorting and gene expression was determined by NanoString analysis. Unsupervised clustering revealed 14 discrete clusters among Sham, CIA, ODE, and CIA+ODE treatment groups: 3 neutrophils (inflammatory, resident/transitional, autoreactive/suppressor), 5 macrophages (airspace, differentiating/recruited, recruited, resident/interstitial, and proliferative airspace), 2 T-cells (differentiating and effector), and a single cluster each of inflammatory monocytes, dendritic cells, B-cells and natural killer cells. Inflammatory monocytes, autoreactive/suppressor neutrophils, and recruited/differentiating macrophages were predominant with arthritis induction (CIA and CIA+ODE). By specific lung cell isolation, several interferon-related and autoimmune genes were disproportionately expressed among CIA and CIA+ODE (e.g. Oasl1, Oas2, Ifit3, Gbp2, Ifi44, and Zbp1), corresponding to RA and RA-associated lung disease. Monocytic myeloid-derived suppressor cells were reduced, while complement genes (e.g. C1s1 and Cfb) were uniquely increased in CIA+ODE mice across cell populations. Recruited and inflammatory macrophages/monocytes and neutrophils expressing interferon-, autoimmune-, and complement-related genes might contribute towards pro-fibrotic inflammatory lung responses following airborne biohazard exposures in setting of autoimmune arthritis and could be predictive and/or targeted to reduce disease burden.

Organic dust-induced lung injury and repair: Bi-directional regulation by TNFα and IL-10

Exposure to organic dust increases chronic airway inflammatory disorders. Effective treatment strategies are lacking. It has been reported that hog barn dust extracts (HDE) induce TNFα through protein kinase C (PKC) activation and that lung inflammation is enhanced in scavenger receptor A (SRA/CD204) knockout (KO) mice following HDE. Because interleukin (IL)-10 production can limit excessive inflammation, it was hypothesized here that HDE-induced IL-10 would require CD204 to effect inflammatory responses. C57BL/6 wild-type (WT), SRA KO, and IL-10 KO mice were intranasally challenged daily for 8 days with HDE and subsequently rested for 3 days with/without recombinant IL-10 (rIL-10) treatment. Primary peritoneal macrophages (PM) and murine alveolar macrophages (MH-S cells) were treated in vitro with HDE, SRA ligand (fucoidan), rIL-10, and/or PKC isoform inhibitors. HDE induced in vivo lung IL-10 in WT, but not SRA KO mice, and similar trends were demonstrated in isolated PM from same treated mice. Lung lymphocyte aggregates and neutrophils were elevated in in vivo HDE-treated SRA and IL-10 KO mice after a 3-d recovery, and treatment during recovery with rIL-10 abrogated these responses. In vitro rIL-10 treatment reduced HDE-stimulated TNFα release in MH-S and WT PM. In SRA KO macrophages, there was reduced IL-10 and PKC zeta (ζ) activity and increased TNFα following in vitro HDE stimulation. Similarly, blocking SRA (24 hr fucoidan pre-treatment) resulted in enhanced HDE-stimulated macrophage TNFα and decreased IL-10 and PKCζ activation. PKCζ inhibitors blocked HDE-stimulated IL-10, but not TNFα. Collectively, HDE stimulates IL-10 by an SRA- and PKCζ-dependent mechanism to regulate TNFα. Enhancing resolution of dust-mediated lung inflammation through targeting IL-10 and/or SRA may represent new approaches to therapeutic interventions.

A High Docosahexaenoic Acid Diet Alters the Lung Inflammatory Response to Acute Dust Exposure

Agricultural workers are at risk for the development of acute and chronic lung diseases due to their exposure to organic agricultural dusts. A diet intervention using the omega-3 fatty acid docosahexaenoic acid (DHA) has been shown to be an effective therapeutic approach for alleviating a dust-induced inflammatory response. We thus hypothesized a high-DHA diet would alter the dust-induced inflammatory response through the increased production of specialized pro-resolving mediators (SPMs). Mice were pre-treated with a DHA-rich diet 4 weeks before being intranasally challenged with a single dose of an extract made from dust collected from a concentrated swine feeding operation (HDE). This omega-3-fatty-acid-rich diet led to reduced arachidonic acid levels in the blood, enhanced macrophage recruitment, and increased the production of the DHA-derived SPM Resolvin D1 (RvD1) in the lung following HDE exposure. An assessment of transcript-level changes in the immune response demonstrated significant differences in immune pathway activation and alterations of numerous macrophage-associated genes among HDE-challenged mice fed a high DHA diet. Our data indicate that consuming a DHA-rich diet leads to the enhanced production of SPMs during an acute inflammatory challenge to dust, supporting a role for dietary DHA supplementation as a potential therapeutic strategy for reducing dust-induced lung inflammation.

Molecular and cellular mechanisms linking air pollution and bone damage

Air pollution is the second most important risk factor associated with noncommunicable diseases after smoking. The effects of pollution on health are commonly attributable to particulate matter (PM), a complex mixture of particles suspended in the air. PM can penetrate the lower respiratory tract and has harmful direct and indirect effects on different organs and tissues. Direct effects are caused by the ability of PM components to cross the respiratory membrane and enter the bloodstream; indirect effects are systemic consequences of the local airway response. Recent work suggests that PM is an independent risk factor for low bone mineral density and osteoporosis-related fractures. Osteoporosis is a common age-related disease closely linked to bone fractures, with severe clinical consequences affecting quality of life, morbidity, and mortality. In this review, we discuss potential mechanisms behind the association between outdoor air pollution, especially PM, and bone damage. The discussion features four main mechanisms: 1) several different atmospheric pollutants can induce low-grade systemic inflammation, which affects bone metabolism through a specific effect of cytokines such as TNFα, IL-1β, IL-6, and IL-17 on osteoblast and osteoclast differentiation and function; 2) some pollutants, particularly certain gas and metal compounds, can cause oxidative damage in the airway and bone cells; 3) different groups of pollutants can act as endocrine disruptors when binding to the receptors in bone cells, changing their functioning; and 4) air pollution can directly and indirectly cause vitamin D deficiency. Characterizing these mechanisms will better define the physiopathology of bone damage, and recognizing air pollution as a modifiable risk factor for osteoporosis will inform environmental policies. Such knowledge will also guide the prevention of fractures due to fragility and help reduce health-related costs.

MyD88 regulates a prolonged adaptation response to environmental dust exposure-induced lung disease

BACKGROUND

Environmental organic dust exposures enriched in Toll-like receptor (TLR) agonists can reduce allergic asthma development but are associated with occupational asthma and chronic bronchitis. The TLR adaptor protein myeloid differentiation factor88 (MyD88) is fundamental in regulating acute inflammatory responses to organic dust extract (ODE), yet its role in repetitive exposures is unknown and could inform future strategies.

METHODS

Wild-type (WT) and MyD88 knockout (KO) mice were exposed intranasally to ODE or saline daily for 3 weeks (repetitive exposure). Repetitively exposed animals were also subsequently rested with no treatments for 4 weeks followed by single rechallenge with saline/ODE.

RESULTS

Repetitive ODE exposure induced neutrophil influx and release of pro-inflammatory cytokines and chemokines were profoundly reduced in MyD88 KO mice. In comparison, ODE-induced cellular aggregates, B cells, mast cell infiltrates and serum IgE levels remained elevated in KO mice and mucous cell metaplasia was increased. Expression of ODE-induced tight junction protein(s) was also MyD88-dependent. Following recovery and then rechallenge with ODE, inflammatory mediators, but not neutrophil influx, was reduced in WT mice pretreated with ODE coincident with increased expression of IL-33 and IL-10, suggesting an adaptation response. Repetitively exposed MyD88 KO mice lacked inflammatory responsiveness upon ODE rechallenge.

CONCLUSIONS

MyD88 is essential in mediating the classic airway inflammatory response to repetitive ODE, but targeting MyD88 does not reduce mucous cell metaplasia, lymphocyte influx, or IgE responsiveness. TLR-enriched dust exposures induce a prolonged adaptation response that is largely MyD88-independent. These findings demonstrate the complex role of MyD88-dependent signaling during acute vs. chronic organic dust exposures.

Amphiregulin modulates murine lung recovery and fibroblast function following exposure to agriculture organic dust

Exposure to agricultural bioaerosols can lead to chronic inflammatory lung diseases. Amphiregulin (AREG) can promote the lung repair process but can also lead to fibrotic remodeling. The objective of this study was to determine the role of AREG in altering recovery from environmental dust exposure in a murine in vivo model and in vitro using cultured human and murine lung fibroblasts. C57BL/6 mice were intranasally exposed to swine confinement facility dust extract (DE) or saline daily for 1 wk or allowed to recover for 3-7 days while being treated with an AREG-neutralizing antibody or recombinant AREG. Treatment with the anti-AREG antibody prevented resolution of DE exposure-induced airway influx of total cells, neutrophils, and macrophages and increased levels of TNF-α, IL-6, and CXCL1. Neutrophils and activated macrophages (CD11c+CD11bhi) persisted after recovery in lung tissues of anti-AREG-treated mice. In murine and human lung fibroblasts, DE induced the release of AREG and inflammatory cytokines. Fibroblast recellularization of primary human lung mesenchymal matrix scaffolds and wound closure was inhibited by DE and enhanced with recombinant AREG alone. AREG treatment rescued the DE-induced inhibitory fibroblast effects. AREG intranasal treatment for 3 days during recovery phase reduced repetitive DE-induced airway inflammatory cell influx and cytokine release. Collectively, these studies demonstrate that inhibition of AREG reduced, whereas AREG supplementation promoted, the airway inflammatory recovery response following environmental bioaerosol exposure, and AREG enhanced fibroblast function, suggesting that AREG could be targeted in agricultural workers repetitively exposed to organic dust environments to potentially prevent and/or reduce disease.

Identification of an Increased Alveolar Macrophage Subpopulation in Old Mice That Displays Unique Inflammatory Characteristics and Is Permissive to Mycobacterium tuberculosis Infection

The elderly population is more susceptible to pulmonary infections, including tuberculosis. In this article, we characterize the impact of aging on the phenotype of mouse alveolar macrophages (AMs) and their response to Mycobacterium tuberculosis. Uninfected AMs were isolated from bronchoalveolar lavage of young (3 mo) and old (18 mo) C57BL/6 mice. AMs from old mice expressed higher mRNA levels of CCL2, IFN-β, IL-10, IL-12p40, TNF-α, and MIF than young mice, and old mice contained higher levels of CCL2, IL-1β, IFN-β, and MIF in their alveolar lining fluid. We identified two distinct AM subpopulations, a major CD11c⁺ CD11b^- population and a minor CD11c⁺ CD11b⁺ population; the latter was significantly increased in old mice (4-fold). Expression of CD206, TLR2, CD16/CD32, MHC class II, and CD86 was higher in CD11c⁺ CD11b⁺ AMs, and these cells expressed monocytic markers Ly6C, CX3CR1, and CD115, suggesting monocytic origin. Sorted CD11c⁺ CD11b⁺ AMs from old mice expressed higher mRNA levels of CCL2, IL-1β, and IL-6, whereas CD11c⁺ CD11b^- AMs expressed higher mRNA levels of immune-regulatory cytokines IFN-β and IL-10. CD11c⁺ CD11b⁺ AMs phagocytosed significantly more M. tuberculosis, which expressed higher RNA levels of genes required for M. tuberculosis survival. Our studies identify two distinct AM populations in old mice: a resident population and an increased CD11c⁺ CD11b⁺ AM subpopulation expressing monocytic markers, a unique inflammatory signature, and enhanced M. tuberculosis phagocytosis and survival when compared with resident CD11c⁺ CD11b^- AMs, which are more immune regulatory in nature.

Combined Collagen-Induced Arthritis and Organic Dust-Induced Airway Inflammation to Model Inflammatory Lung Disease in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is characterized by extra-articular involvement including lung disease, yet the mechanisms linking the two conditions are poorly understood. The collagen-induced arthritis (CIA) model was combined with the organic dust extract (ODE) airway inflammatory model to assess bone/joint-lung inflammatory outcomes. DBA/1J mice were intranasally treated with saline or ODE daily for 5 weeks. CIA was induced on days 1 and 21. Treatment groups included sham (saline injection/saline inhalation), CIA (CIA/saline), ODE (saline/ODE), and CIA +  ODE (CIA/ODE). Arthritis inflammatory scores, bones, bronchoalveolar lavage fluid, lung tissues, and serum were assessed. In DBA/1J male mice, arthritis was increased in CIA +  ODE >  CIA >  ODE versus sham. Micro-computed tomography (µCT) demonstrated that loss of BMD and volume and deterioration of bone microarchitecture was greatest in CIA +  ODE. However, ODE-induced airway neutrophil influx and inflammatory cytokine/chemokine levels in lavage fluids were increased in ODE >  CIA +  ODE versus sham. Activated lung CD11c+ CD11b+ macrophages were increased in ODE >  CIA +  ODE >  CIA pattern, whereas lung hyaluronan, fibronectin, and amphiregulin levels were greatest in CIA +  ODE. Serum autoantibody and inflammatory marker concentrations varied among experimental groups. Compared with male mice, female mice showed less articular and pulmonary disease. The interaction of inhalation-induced airway inflammation and arthritis induction resulted in compartmentalized responses with the greatest degree of arthritis and bone loss in male mice with combined exposures. Data also support suppression of the lung inflammatory response, but increases in extracellular matrix protein deposition/interstitial disease in the setting of arthritis. This coexposure model could be exploited to better understand and treat RA-lung disease. © 2019 American Society for Bone and Mineral Research.

Organic dust, causing both oxidative stress and Nrf2 activation, is phagocytized by bronchial epithelial cells

Inhalation of organic dust (OD) from swine confinement facilities leads to pulmonary inflammation, airway hyperresponsiveness, and oxidative stress. In mice, pretreatment with a hydroxyl radical scavenger prevents airway inflammation and airway hyperresponsiveness (AHR) induced by OD exposure. We sought to determine a mechanism by which OD could induce oxidative stress in bronchial epithelial cells. Human bronchial epithelial cells (BEAS-2B or NHBE) were treated with various concentrations of OD, followed by evaluation of intracellular oxidative stress using 2',7'-dichlorofluorescein diacetate (DCFDA). After stimulation with OD, gene expression of antioxidant genes was assessed by real-time quantitative PCR followed by quantification of Nrf2 nuclear translocation using a luciferase reporter assay. Phagocytic markers (CD36 and CD68) were analyzed by FACS. Cells were treated with an actin inhibitor, cytochalasin D, before OD exposure and evaluated for Nrf2 nuclear translocation and DCFDA. Mice were pretreated with sulforaphane, the Nrf2 activator, before OD exposure and evaluated for pulmonary inflammation and airway reactivity. OD induced a time- and concentration-dependent increase in DCFDA. mRNA expression levels of Nrf2-dependent genes and Nrf2 nuclear translocation were increased after OD exposure. OD exposure increased the expression of CD68 and CD36. Cytochalasin D prevented oxidative stress and Nrf2 nuclear translocation after OD. Pretreatment with sulforaphane prevented OD-induced inflammation and AHR while increasing the uptake of OD in bronchial epithelial cells. Bronchial epithelial cells can phagocytose OD, resulting in an increase in endogenous oxidative stress. Nrf2-dependent mechanisms mediate the antioxidant response to OD.

Role of Macrophages in Acute Lung Injury and Chronic Fibrosis Induced by Pulmonary Toxicants

A diverse group of toxicants has been identified that cause injury to the lung including gases (eg, ozone, chlorine), particulates/aerosols (eg, diesel exhaust, fly ash, other combustion products, mustards, nanomaterials, silica, asbestos), chemotherapeutics (eg, bleomycin), and radiation. The pathologic response to these toxicants depends on the dose and duration of exposure and their physical/chemical properties. A common response to pulmonary toxicant exposure is an accumulation of proinflammatory/cytotoxic M1 macrophages at sites of tissue injury, followed by the appearance of anti-inflammatory/wound repair M2 macrophages. It is thought that the outcome of the pathogenic responses to toxicants depends on the balance in the activity of these macrophage subpopulations. Overactivation of either M1 or M2 macrophages leads to injury and disease pathogenesis. Thus, the very same macrophage-derived mediators, released in controlled amounts to destroy injurious materials and pathogens (eg, reactive oxygen species, reactive nitrogen species, proteases, tumor necrosis factor α) and initiate wound repair (eg, transforming growth factor β, connective tissue growth factor, vascular endothelial growth factor), can exacerbate acute lung injury and/or induce chronic disease such as fibrosis, chronic obstructive pulmonary disease, and asthma, when released in excess. This review focuses on the role of macrophage subsets in acute lung injury and chronic fibrosis. Understanding how these pathologies develop following exposure to toxicants, and the contribution of resident and inflammatory macrophages to disease pathogenesis may lead to the development of novel approaches for treating lung diseases.

Effects of Agricultural Organic Dusts on Human Lung-Resident Mesenchymal Stem (Stromal) Cell Function

Agricultural organic dust exposures trigger harmful airway inflammation, and workers experiencing repetitive dust exposures are at increased risk for lung disease. Mesenchymal stem/stromal cells (MSCs) regulate wound repair processes in the lung, and may contribute to either proresolution or -fibrotic lung responses. It is unknown how organic dust exposures alter lung-resident MSC activation and proinflammatory versus prorepair programs in the lung. To address this gap in knowledge, we isolated human lung-resident MSC from lung tissue. Cells were stimulated with aqueous extracts of organic dusts (DE) derived from swine confinement facilities and were assessed for changes in proliferative and migratory capacities, and production of proinflammatory and prorepair mediators. Through these investigations, we found that DE induces significant release of proinflammatory mediators TNF-α, IL-6, IL-8, and matrix metalloproteases, while also inducing the production of prorepair mediators amphiregulin, FGF-10, and resolvin D1. In addition, DE significantly reduced the growth and migratory capacities of lung-resident MSC. Together, these investigations indicate lung-resident MSC activation and wound repair activities are altered by organic dust exposures. These findings warrant future investigations to assess how organic dusts affect lung-resident mesenchymal stem/stromal cell function and impact airway inflammation, injury, and repair during agricultural aerosol exposures.

Association Between Organic Dust Exposure and Adult-Asthma: A Systematic Review and Meta-Analysis of Case-Control Studies

Background

Exposure to organic dust has been widely investigated as a potential risk factor for asthma with different results. To clarify a potential relationship, we performed the present meta-analysis to integrate the results of studies examining the association of organic dust exposure with asthma.

Methods

A comprehensive literature search in the electronic databases including EMBASE, PubMed and Cochrane Library databases (up to August 2018) was conducted. The adjusted odds ratios (ORs) with corresponding 95% confidence interval (CI) for organic dust exposure and asthma were retrieved and pooled to generate summary effect estimates in Revman 5.2.

Results

Database searches retrieved 1,016 records. A total of 17 studies containing 3,619 cases and 6,585 controls were finally included in our meta-analysis. The summary estimates suggested that organic dust exposure was positively associated with asthma (OR, 1.48; 95% CI, 1.26–1.75; P < 0.00001), whether among population-based case-control studies (OR, 1.24; 95% CI, 1.13–1.35; P < 0.00001) or hospital-based case-control studies (OR, 2.79; 95% CI, 1.27–6.12; P = 0.01). Subgroup analysis showed that paper/wood (OR, 1.62; 95% CI, 1.38–1.90; P < 0.00001), flour/grain (OR, 1.48; 95% CI, 1.11–1.97; P = 0.008), and textile dust (OR, 1.50; 95% CI, 1.08–2.09; P = 0.02) exposure were significantly associated with asthma.

Conclusions

Based on the studies evaluated, our meta-analysis results prompt that organic dust exposure is a risk factor inducing asthma, although precise analysis focus on specific organic dust materials is still warranted.

Relationship of systemic IL-10 levels with proinflammatory cytokine responsiveness and lung function in agriculture workers

BACKGROUND

Agriculture workers are exposed to microbial component- and particulate matter-enriched organic dust aerosols. Whereas it is clear that exposure to these aerosols can lead to lung inflammation, it is not known how inflammatory responses are resolved in some individuals while others develop chronic lung disease. Interleukin (IL)-10 is an immunomodulatory cytokine that is recognized as a potent anti-inflammatory and pro-resolving factor. The objective of this study was to determine whether there is a relationship of systemic IL-10 and proinflammatory responses and/or respiratory health effects in humans with prior agriculture exposure.

METHODS

This is a cross sectional study of 625 veterans with > 2 years of farming experience. Whole blood was stimulated with or without organic dust and measured for IL-6, TNFα and IL-10. Participants underwent spirometry and respiratory symptoms were assessed by questionnaire.

RESULTS

We found that baseline IL-10 concentration from the whole blood assay was inversely associated with ΔTNF-α (r = - 0.63) and ΔIL-6 (r = - 0.37) levels. Results remained highly significant in the linear regression model after adjusting for age, sex, BMI, race, education, smoking status, and white blood cell count (ΔTNF-α, p < 0.0001; ΔIL-6, p < 0.0001). We found no association between chronic cough (p = 0.18), chronic phlegm (p = 0.31) and chronic bronchitis (p = 0.06) and baseline IL-10 levels using univariate logistic regression models. However, we did find that higher FEV1/FVC was significantly associated with increased baseline IL-10 concentration.

CONCLUSIONS

Collectively, these studies support a potential role for IL-10 in modulating an inflammatory response and lung function in agriculture-exposed persons.

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.

A role for B cells in organic dust induced lung inflammation

BACKGROUND

Agriculture organic dust exposures induce lung disease with lymphoid aggregates comprised of both T and B cells. The precise role of B cells in mediating lung inflammation is unknown, yet might be relevant given the emerging role of B cells in obstructive pulmonary disease and associated autoimmunity.

METHODS

Using an established animal model, C57BL/6 wild-type (WT) and B-cell receptor (BCR) knock-out (KO) mice were repetitively treated with intranasal inhalation of swine confinement organic dust extract (ODE) daily for 3 weeks and lavage fluid, lung tissues, and serum were collected.

RESULTS

ODE-induced neutrophil influx in lavage fluid was not reduced in BCR KO animals, but there was reduction in TNF-α, IL-6, CXCL1, and CXCL2 release. ODE-induced lymphoid aggregates failed to develop in BCR KO mice. There was a decrease in ODE-induced lung tissue CD11c⁺CD11b⁺ exudative macrophages and compensatory increase in CD8⁺ T cells in lavage fluid of BCR KO animals. Compared to saline, there was an expansion of conventional B2-, innate B1 (CD19⁺CD11b⁺CD5^+/-)-, and memory (CD19⁺CD273^+/-CD73^+/-) B cells following ODE exposure in WT mice. Autoreactive responses including serum IgG anti-citrullinated protein antibody (ACPA) and anti-malondialdehyde-acetaldehyde (MAA) autoantibodies were increased in ODE treated WT mice as compared to saline control. B cells and serum immunoglobulins were not detected in BCR KO animals.

CONCLUSIONS

Lung tissue staining for citrullinated and MAA modified proteins were increased in ODE-treated WT animals, but not BCR KO mice. These studies show that agriculture organic dust induced lung inflammation is dependent upon B cells, and dust exposure induces an autoreactive response.

Post-injury and resolution response to repetitive inhalation exposure to agricultural organic dust in mice

Inhalation of organic dusts in agricultural environments causes airway inflammatory diseases. Despite advances in understanding the airway response to dust-induced inflammation, less is known about the transition from lung injury to repair and recovery. The objective of this study was to define the post-inflammation homeostasis events following organic dust-induced lung injury. Using an established protocol, mice were intranasally treated with swine confinement facility organic dust extract (ODE) daily for 3 weeks (repetitive exposure) or treated daily with ODE for 3 weeks followed by no treatment for 1–4 weeks (recovery period) whereupon lavage fluid, lung tissue, and sera were processed. During recovery period, a significant decrease was observed in ODE-induced neutrophil levels after 1 week, lymphocytes at 2 weeks, and macrophages at 4 weeks in the lavage fluid. ODE-induced lung cellular aggregates and bronchiolar compartment inflammation were diminished, but persisted for 4 weeks post-injury. Alveolar inflammation resolved at 3 weeks. ODE-induced lung neutrophils were cleared by 3 weeks, B-cells by 2 weeks, and CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells by 4 week recovery period. Collectively, these results identify important processes during recovery period following agricultural dust-induced inflammation, and present possible strategies for improving lung repair and resolution.

Systemic IL-6 Effector Response in Mediating Systemic Bone Loss Following Inhalation of Organic Dust

Airway and skeletal diseases are prominent among agriculture workers. Repetitive inhalant exposures to agriculture organic dust extract (ODE) induces bone deterioration in mice; yet the mechanisms responsible for connecting the lung-bone inflammatory axis remain unclear. We hypothesized that the interleukin (IL)-6 effector response regulates bone deterioration following inhalant ODE exposures. Using an established intranasal inhalation exposure model, wild-type (WT) and IL-6 knockout (KO) mice were treated daily with ODE or saline for 3 weeks. ODE-induced airway neutrophil influx, cytokine/chemokine release, and lung pathology were not reduced in IL-6 KO animals compared to WT mice. Utilizing micro-computed tomography, analysis of tibia showed that loss of bone mineral density, volume, and deterioration of bone micro-architecture, and mechanical strength induced by inhalant ODE exposures in WT mice were absent in IL-6 KO animals. Compared to saline treatments, bone-resorbing osteoclasts and bone marrow osteoclast precursor populations were also increased in ODE-treated WT but not IL-6 KO mice. These results show that the systemic IL-6 effector pathway mediates bone deterioration induced by repetitive inhalant ODE exposures through an effect on osteoclasts, but a positive role for IL-6 in the airway was not demonstrated. IL-6 might be an important link in explaining the lung-bone inflammatory axis.

Efficacy of β-Lactam-plus-Macrolide Combination Therapy in a Mouse Model of Lethal Pneumococcal Pneumonia

Community-acquired pneumonia is a common disease with considerable morbidity and mortality, for which Streptococcus pneumoniae is accepted as a leading cause. Although β-lactam-plus-macrolide combination therapy for this disease is recommended in several guidelines, the clinical efficacy of this strategy against pneumococcal pneumonia remains controversial. In this study, we examined the effects of β-lactam-plus-macrolide combination therapy on lethal mouse pneumococcal pneumonia and explored the mechanisms of action in vitro and in vivo We investigated survival, lung bacterial burden, and cellular host responses in bronchoalveolar lavage fluids obtained from mice infected with pneumonia and treated with ceftriaxone, azithromycin, or both in combination. Although in vitro synergy was not observed, significant survival benefits were demonstrated with combination treatment. Lung neutrophil influx was significantly lower in the ceftriaxone-plus-azithromycin-treated group than in the ceftriaxone-treated group, whereas no differences in the lung bacterial burden were observed on day 3 between the ceftriaxone-plus-azithromycin-treated group and the ceftriaxone-treated group. Notably, the analysis of cell surface markers in the ceftriaxone-plus-azithromycin combination group exhibited upregulation of presumed immune checkpoint ligand CD86 and major histocompatibility complex class II in neutrophils and CD11b-positive CD11c-positive (CD11b(+) CD11c(+)) macrophages and dendritic cells, as well as downregulation of immune checkpoint receptors cytotoxic-T lymphocyte-associated antigen 4 and programmed death 1 in T helper and T regulatory cells. Our data demonstrate that the survival benefits of ceftriaxone-plus-azithromycin therapy occur through modulation of immune checkpoints in mouse pneumococcal pneumonia. In addition, immune checkpoint molecules may be a novel target class for future macrolide research.

Occupational agriculture organic dust exposure and its relationship to asthma and airway inflammation in adults

OBJECTIVE

Recent studies have made advances into understanding the complex agriculture work exposure environment in influencing asthma in adults. The objective of this study is to review studies of occupational agricultural exposures including dust, animal, and pesticide exposures with asthma in adult populations.

DATA SOURCES

PubMed databases were searched for articles pertaining to farming, agriculture, asthma, occupational asthma, airway inflammation, respiratory disease, lung disease, pesticides, and organic dust.

STUDY SELECTIONS

Studies chosen were published in or after 1999 that included adults and asthma and farming/agricultural work or agricultural exposures and airway inflammatory disease measurements.

RESULTS

The data remain inconclusive. Several retrospective studies demonstrate agricultural work to be protective against asthma in adults, especially with increased farming exposure over time. In contrast, other studies find increased risk of asthma with farming exposures, especially for the non-atopic adult. Mechanistic and genetic studies have focused on defining the wide variety and abundance of microorganisms within these complex organic dusts that trigger several pattern recognition receptor pathways to modulate the hosts' response.

CONCLUSION

Asthma risk depends on the interplay of genetic factors, gender, atopic predisposition, type of livestock, pesticide exposure, and magnitude and duration of exposure in the adult subject. Longer exposure to occupational farming is associated with decreased asthma risk. However, studies also suggest that agricultural work and multiple types of livestock are independent risk factors for developing asthma. Prospective and longitudinal studies focusing on genetic polymorphisms, objective assessments, and environmental sampling are needed to further delineate the influence of agriculture exposure in the adult worker.

Neutrophilic oxidative stress mediates organic dust-induced pulmonary inflammation and airway hyperresponsiveness

Airway exposure to organic dust (OD) from swine confinement facilities induces airway inflammation dominated by neutrophils and airway hyperresponsiveness (AHR). One important neutrophilic innate defense mechanism is the induction of oxidative stress. Therefore, we hypothesized that neutrophils exacerbate airway dysfunction following OD exposure by increasing oxidant burden. BALB/C mice were given intranasal challenges with OD or PBS (1/day for 3 days). Mice were untreated or treated with a neutrophil-depleting antibody, anti-Ly6G, or the antioxidant dimethylthiourea (DMTU) prior to OD exposure. Twenty-four hours after the final exposure, we measured airway responsiveness in response to methacholine (MCh) and collected bronchoalveolar lavage fluid to assess pulmonary inflammation and total antioxidant capacity. Lung tissue was harvested to examine the effect of OD-induced antioxidant gene expression and the effect of anti-Ly6G or DMTU. OD exposure induced a dose-dependent increase of airway responsiveness, a neutrophilic pulmonary inflammation, and secretion of keratinocyte cytokine. Depletion of neutrophils reduced OD-induced AHR. DMTU prevented pulmonary inflammation involving macrophages and neutrophils. Neutrophil depletion and DMTU were highly effective in preventing OD-induced AHR affecting large, conducting airways and tissue elastance. OD induced an increase in total antioxidant capacity and mRNA levels of NRF-2-dependent antioxidant genes, effects that are prevented by administration of DMTU and neutrophil depletion. We conclude that an increase in oxidative stress and neutrophilia is critical in the induction of OD-induced AHR. Prevention of oxidative stress diminishes neutrophil influx and AHR, suggesting that mechanisms driving OD-induced AHR may be dependent on neutrophil-mediated oxidant pathways.

Age Impacts Pulmonary Inflammation and Systemic Bone Response to Inhaled Organic Dust Exposure

Agricultural workers have high rates of airway and skeletal health disease. Studies recently demonstrated that inhaled agricultural organic dust extract (ODE)-induced airway injury is associated with bone deterioration in an animal model. However, the effect of age in governing these responses to organic dusts is unclear, but might be important in future approaches. Young (7-9 wk) and older (12-14,o) male C57BL/6 mice received intranasal (i.n.) inhalation exposure to ODE from swine confinement facilities once or daily for 3 wk. Acute ODE-induced neutrophil influx and cytokine and chemokine (tumor necrosis factor [TNF]-α, interleukin [IL]-6, keratinocyte chemoattractant [CXCL1], macrophage inflammatory protein-2 [CXCL2]) airway production were reduced in older compared to young mice. Repetitive ODE treatment, however, increased lymphocyte recruitment and alveolar compartment histopathologic inflammatory changes in older mice. Whole lung cell infiltrate analysis revealed that young, but not older, mice repetitively treated with ODE demonstrated an elevated CD4:CD8 lymphocyte response. Acute inhalant ODE exposure resulted in a 4-fold and 1.5-fold rise in blood neutrophils in young and older mice, respectively. Serum IL-6 and CXCL1 levels were elevated in young and older mice i.n. exposed once to ODE, with increased CXCL1 levels in younger compared to older mice. Although older mice displayed reduced bone measurements compared to younger mice, younger rodents demonstrated ODE-induced decrease in bone mineral density, bone volume, and bone microarchitecture quality as determined by computed tomography (CT) analysis. Collectively, age impacts the airway injury and systemic inflammatory and bone loss response to inhalant ODE, suggesting an altered and enhanced immunologic response in younger as compared to older counterparts.

Maresin-1 reduces airway inflammation associated with acute and repetitive exposures to organic dust

Agriculture industry workers are at a higher risk for chronic bronchitis and obstructive pulmonary diseases, and current therapeutics are not entirely effective. We previously found that the specialized proresolving lipid mediator maresin-1 (MaR1) reduced proinflammatory cytokine release and intracellular adhesion molecule-1 (ICAM-1) expression in bronchial epithelial cells exposed to extracts of organic dust (DE) derived from swine confinement facilities in vitro. The objective of this study was to determine whether MaR1 is effective at limiting lung inflammation associated with acute and repetitive exposures to DE in an established murine model of inhalant dust exposures. C57Bl/6 mice were treated with MaR1 or vehicle control and intranasally instilled with DE once or daily for 3 weeks. Bronchioalveolar lavage fluid was analyzed for total and differential cell counts and proinflammatory cytokine levels, and lung tissues were assessed for histopathology and ICAM-1 expression. In both single and repetitive DE exposure studies, MaR1 significantly decreased bronchoalveolar lavage neutrophil infiltration, interleukin 6, tumor necrosis factor α, and chemokine C-X-C motif ligand 1 levels without altering repetitive DE-induced bronchioalveolar inflammation or lymphoid aggregate formation. Lung tissue ICAM-1 expression was also reduced in both single and repetitive exposure studies. These data suggest that MaR1 might contribute to an effective strategy to reduce airway inflammatory diseases induced by agricultural-related organic dust environmental exposures.

Pattern recognition scavenger receptor A/CD204 regulates airway inflammatory homeostasis following organic dust extract exposures

Exposure to agriculture organic dusts, comprised of a diversity of pathogen-associated molecular patterns, results in chronic airway diseases. The multi-functional class A macrophage scavenger receptor (SRA)/CD204 has emerged as an important class of pattern recognition receptors with broad ligand binding ability. The objective was to determine the role of SRA in mediating repetitive and post-inflammatory organic dust extract (ODE)-induced airway inflammation. Wild-type (WT) and SRA knockout (KO) mice were intra-nasally treated with ODE or saline daily for 3 weeks and immediately euthanized or allowed to recover for 1 week. Results show that lung histopathologic changes were increased in SRA KO mice as compared to WT following repetitive ODE exposures marked predominately by increased size and distribution of lymphoid aggregates. After a 1-week recovery from daily ODE treatments, there was significant resolution of lung injury in WT mice, but not SRA KO animals. The increased lung histopathology induced by ODE treatment was associated with decreased accumulation of neutrophils, but greater accumulation of CD4(+) T-cells. The lung cytokine milieu induced by ODE was consistent with a TH1/TH17 polarization in both WT and SRA KO mice. Overall, the data demonstrate that SRA/CD204 plays an important role in the normative inflammatory lung response to ODE, as evidenced by the enhanced dust-mediated injury viewed in the absence of this receptor.

Distinct macrophage phenotypes in allergic and nonallergic lung inflammation

Chronic exposure to farm environments is a risk factor for nonallergic lung disease. In contrast to allergic asthma, in which type 2 helper T cell (Th2) activation is dominant, exposure to farm dust extracts (FDE) induces Th1/Th17 lung inflammation, associated with neutrophil infiltration. Macrophage influx is a common feature of both types of lung inflammation, allergic and nonallergic. However, macrophage functions and phenotypes may vary according to their polarized state, which is dependent on the cytokine environment. In this study, we aimed to characterize and quantify the lung macrophage populations in two established murine models of allergic and nonallergic lung inflammation by means of fluorescence-activated cell sorting and immunohistochemistry. We demonstrated that, whereas in allergic asthma M2-dominant macrophages predominated in the lungs, in nonallergic inflammation M1-dominant macrophages were more prevalent. This was confirmed in vitro using a macrophage cell line, where FDE exerted a direct effect on macrophages, inducing M1-dominant polarization. The polarization of macrophages diverged depending on the exposure and inflammatory status of the tissue. Interfering with this polarization could be a target for treatment of different types of lung inflammation.

The omega-3 fatty acid docosahexaenoic acid attenuates organic dust-induced airway inflammation

Workers exposed to organic dusts from concentrated animal feeding operations (CAFOs) are at risk for developing airway inflammatory diseases. Available preventative and therapeutic measures for alleviating dust-induced lung disease are inadequate. Because omega-3 fatty acids can mitigate inflammatory processes, we aimed to determine whether nutritional supplementation with the omega-3 fatty acid docosahexaenoic acid (DHA) could reduce the airway inflammatory consequences of exposures to organic dust. Aqueous extracts of organic dusts from swine CAFOs (ODE) were utilized. In DHA-pretreated human bronchial epithelial cells, lung fibroblasts, monocyte cell cultures, and precision-cut murine lung slices, we found that DHA pretreatment dose-dependently decreased ODE-induced inflammatory cytokine production. To determine the in vivo significance of DHA, C57BL/6 mice were orally administered DHA for seven days prior to treatment with intranasal ODE or saline inhalations. Animals treated with 2 mg DHA demonstrated significant reductions in ODE-induced bronchial alveolar lavage neutrophil influx and pro-inflammatory cytokine/chemokine production compared to mice exposed to ODE alone. Collectively, these data demonstrate that DHA affects several lung cells to reduce the airway inflammatory response to organic dust exposures. Dietary supplementation with DHA may be an effective therapeutic strategy to reduce the airway inflammatory consequences in individuals exposed to agriculture dust environments.

Flow cytometric analysis of macrophages and dendritic cell subsets in the mouse lung

The lung hosts multiple populations of macrophages and dendritic cells, which play a crucial role in lung pathology. The accurate identification and enumeration of these subsets are essential for understanding their role in lung pathology. Flow cytometry is a mainstream tool for studying the immune system. However, a systematic flow cytometric approach to identify subsets of macrophages and dendritic cells (DCs) accurately and consistently in the normal mouse lung has not been described. Here we developed a panel of surface markers and an analysis strategy that accurately identify all known populations of macrophages and DCs, and their precursors in the lung during steady-state conditions and bleomycin-induced injury. Using this panel, we assessed the polarization of lung macrophages during the course of bleomycin-induced lung injury. Alveolar macrophages expressed markers of alternatively activated macrophages during both acute and fibrotic phases of bleomycin-induced lung injury, whereas markers of classically activated macrophages were expressed only during the acute phase. Taken together, these data suggest that this flow cytometric panel is very helpful in identifying macrophage and DC populations and their state of activation in normal, injured, and fibrotic lungs.

Suppression of inflammatory cell trafficking and alveolar simplification by the heme oxygenase-1 product carbon monoxide

Bronchopulmonary dysplasia (BPD), a lung disease of prematurely born infants, is characterized in part by arrested development of pulmonary alveolae. We hypothesized that heme oxygenase (HO-1) and its byproduct carbon monoxide (CO), which are thought to be cytoprotective against redox stress, mitigate lung injury and alveolar simplification in hyperoxia-exposed neonatal mice, a model of BPD. Three-day-old C57BL/6J mice were exposed to air or hyperoxia (FiO2, 75%) in the presence or absence of inhaled CO (250 ppm for 1 h twice daily) for 21 days. Hyperoxic exposure increased mean linear intercept, a measure of alveolar simplification, whereas CO treatment attenuated hypoalveolarization, yielding a normal-appearing lung. Conversely, HO-1-null mice showed exaggerated hyperoxia-induced hypoalveolarization. CO also inhibited hyperoxia-induced pulmonary accumulation of F4/80+, CD11c+, and CD11b+ monocytes and Gr-1+ neutrophils. Furthermore, CO attenuated lung mRNA and protein expression of proinflammatory cytokines, including the monocyte chemoattractant CCL2 in vivo, and decreased hyperoxia-induced type I alveolar epithelial cell CCL2 production in vitro. Hyperoxia-exposed CCL2-null mice, like CO-treated mice, showed attenuated alveolar simplification and lung infiltration of CD11b+ monocytes, consistent with the notion that CO blocks lung epithelial cell cytokine production. We conclude that, in hyperoxia-exposed neonatal mice, inhalation of CO suppresses inflammation and alveolar simplification.

Organic dust, lipopolysaccharide, and peptidoglycan inhalant exposures result in bone loss/disease

Skeletal health consequences associated with chronic inflammatory respiratory disease, and particularly chronic obstructive pulmonary disease (COPD), contribute to overall disease morbidity. Agricultural environmental exposures induce significant airway diseases, including COPD. However, animal models to understand inhalant exposure-induced lung injury and bone disease have not been described. Using micro-computed tomography (micro-CT) imaging technology and histology, bone quantity and quality measurements were investigated in mice after repetitive intranasal inhalation exposures to complex organic dust extracts (ODEs) from swine confinement facilities. Comparison experiments with LPS and peptidoglycan (PGN) alone were also performed. After 3 weeks of repetitive ODE inhalation exposure, significant loss of bone mineral density and trabecular bone volume fraction was evident, with altered morphological microarchitecture changes in the trabecular bone, compared with saline-treated control animals. Torsional resistance was also significantly reduced. Compared with saline treatment, ODE-treated mice demonstrated decreased collagen and proteoglycan content in their articular cartilage, according to histopathology. Significant bone deterioration was also evident after repetitive intranasal inhalant treatment with LPS and PGN. These findings were not secondary to animal distress, and not entirely dependent on the degree of induced lung parenchymal inflammation. Repetitive LPS treatment demonstrated the most pronounced changes in bone parameters, and PGN treatment resulted in the greatest lung parenchymal inflammatory changes. Collectively, repetitive inhalation exposures to noninfectious inflammatory agents such as complex organic dust, LPS, and PGN resulted in bone loss. This animal model may contribute to efforts toward understanding the mechanisms and evaluating the therapeutics associated with adverse skeletal health consequences after subchronic airway injury.

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.

Maresin-1 reduces the pro-inflammatory response of bronchial epithelial cells to organic dust

Background

Exposure to organic dust causes detrimental airway inflammation. Current preventative and therapeutic measures do not adequately treat resulting disease, necessitating novel therapeutic interventions. Recently identified mediators derived from polyunsaturated fatty acids exhibit anti-inflammatory and pro-resolving actions. We tested the potential of one of these mediators, maresin-1 (MaR1), in reducing organic dust-associated airway inflammation.

Methods

As bronchial epithelial cells (BECs) are pivotal in initiating organic dust-induced inflammation, we investigated the in vitro effects of MaR1 on a human BEC cell line (BEAS-2B). Cells were pretreated for 1 hour with 0–200 nM MaR1, followed by 1–24 hour treatment with 5% hog confinement facility-derived organic dust extract (HDE). Alternatively, a mouse lung slice model was utilized in supportive cytokine studies. Supernatants were harvested and cytokine levels determined via enzyme-linked immunosorbent assays. Epithelial cell protein kinase C (PKC) isoforms α and ϵ, and PKA activities were assessed via radioactivity assays, and NFκB and MAPK-related signaling mechanisms were investigated using luciferase vector reporters.

Results

MaR1 dose-dependently reduced IL-6 and IL-8 production following HDE treatment of BECs. MaR1 also reduced HDE-stimulated cytokine release including TNF-α in a mouse lung slice model when given before or following HDE treatment. Previous studies have established that HDE sequentially activates epithelial PKCα and PKCϵ at 1 and 6 hours, respectively that regulated TNF-α, IL-6, and IL-8 release. MaR1 pretreatment abrogated these HDE-induced PKC activities. Furthermore, HDE treatment over a 24-hour period revealed temporal increases in NFκB, AP-1, SP-1, and SRE DNA binding activities, using luciferase reporter assays. MaR1 pretreatment did not alter the activation of NFκB, AP-1, or SP-1, but did reduce the activation of DNA binding at SRE.

Conclusions

These observations indicate a role for MaR1 in attenuating the pro-inflammatory responses of BECs to organic dust extract, through a mechanism that does not appear to rely on reduced NFκB, AP-1, or SP-1-related signaling, but may be mediated partly through SRE-related signaling. These data offer insights for a novel mechanistic action of MaR1 in bronchial epithelial cells, and support future in vivo studies to test MaR1’s utility in reducing the deleterious inflammatory effects of environmental dust exposures.