Search

Concentrated animal feeding operations (CAFOs) are responsible for the production of global greenhouse gases and harmful environmental pollutants including hydrogen sulfide, ammonia, and particulate matter. Swine farmers are frequently exposed to organic dust that is proinflammatory in the lung and are thus at greater risk of developing pneumonia, asthma, and other respiratory conditions. In addition to respiratory disease, air pollutants are directly associated with altered gastrointestinal (GI) physiology and the development of GI diseases, thereby highlighting the gut-lung axis in disease progression. Instillation of hog dust extract (HDE) for 3 wk has been reported to promote the development of chronic airway inflammation in mice, however, the impact of HDE exposure on intestinal homeostasis is poorly understood. We report that 3-wk intranasal exposure of HDE is associated with increased intestinal macromolecule permeability and elevated serum endotoxin concentrations in C57BL/6J mice. In vivo studies also indicated mislocalization of the epithelial cell adhesion protein, E-cadherin, in the colon as well as an increase in the proinflammatory cytokine, Tnfα , in the proximal colon. Moreover, mRNA expression of the Paneth cell-associated marker, Lyz1 , was increased the proximal colon, whereas the expression of the goblet cell marker, Muc2 , was unchanged in the epithelial cells of the ileum, cecum, and distal colon. These results demonstrate that airway exposure to CAFOs dusts promote airway inflammation and modify the gastrointestinal tract to increase intestinal permeability, induce systemic endotoxemia, and promote intestinal inflammation. Therefore, this study identifies complex physiological consequences of chronic exposure to organic dusts derived from CAFOs on the gut-lung axis. NEW & NOTEWORTHY Agricultural workers have a higher prevalence of occupational respiratory symptoms and are at greater risk of developing respiratory diseases. However, gastrointestinal complications have also been reported, yet the intestinal pathophysiology is understudied. This work is novel because it emphasizes the role of an inhaled environmental pollutant on the development of intestinal pathophysiological outcomes. This work will provide foundation for other studies evaluating how agricultural dusts disrupts host physiology and promotes debilitating gastrointestinal and systemic disorders.

IL-22 is a unique cytokine that is upregulated in many chronic inflammatory diseases, including asthma, and modulates tissue responses during inflammation. However, the role of IL-22 in the resolution of inflammation and how this contributes to lung repair processes are largely unknown. Here, we tested the hypothesis that IL-22 signaling is critical in inflammation resolution after repetitive exposure to agricultural dust. Using an established mouse model of organic dust extract-induced lung inflammation, we found that IL-22 knockout mice have an enhanced response to agricultural dust as evidenced by an exacerbated increase in infiltrating immune cells and lung pathology as compared to wild-type controls. We further identified that, in response to dust, IL-22 is expressed in airway epithelium and in Ym1+ macrophages found within the parenchyma in response to dust. The increase in IL-22 expression was accompanied by increases in IL-22 receptor IL-22R1 within the lung epithelium. In addition, we found that alveolar macrophages in vivo as well as THP-1 cells in vitro express IL-22, and this expression is modulated by dust exposure. Furthermore, subcellular localization of IL-22 appears to be in the Golgi of resting THP1 human monocytes, and treatment with dust extracts is associated with IL-22 release into the cytosolic compartment from the Golgi reservoirs during dust extract exposure. Taken together, we have identified a significant role for macrophage-mediated IL-22 signaling that is activated in dust-induced lung inflammation in mice., (Copyright © 2022. Published by Elsevier Inc.)

Agricultural workers, especially those who work in swine confinement facilities, are at increased risk for developing pulmonary diseases including asthma, chronic obstructive pulmonary disease, and chronic bronchitis due to exposures to fumes, vapors, and organic dust. Repetitive exposure to agricultural dust leads to unresolved inflammation, a common underlying mechanism that worsens lung disease. Besides occupational exposure to dusts, diet also significantly contributes to inflammation and disease progression. Since DHA (docosahexaenoic acid), a polyunsaturated omega-3 fatty acid and its bioactive metabolites have key roles in inflammation resolution, we rationalized that individuals chronically exposed to organic dusts can benefit from dietary modifications. Here, we evaluated the role of DHA in modifying airway inflammation in a murine model of repetitive exposure to an aqueous extract of agricultural dust (three-week exposure to swine confinement dust extract, HDE) and after a one-week resolution/recovery period. We found that mice fed a high DHA diet had significantly increased bronchoalveolar lavage fluid (BALF) levels of DHA-derived resolvins and lower TNFα along with altered plasma levels of endocannabinoids and related lipid mediators. Following the one-week recovery we identified significantly reduced BALF cellularity and cytokine/chemokine release along with increased BALF amphiregulin and resolvins in DHA diet-fed versus control diet-fed mice challenged with HDE. We further report observations on the effects of repetitive HDE exposure on lung Ym1+ and Arg-1+ macrophages. Overall, our findings support a protective role for DHA and identify DHA-derived resolvins and endocannabinoids among the potential mediators of DHA in altering airway inflammation in chronic agricultural dust exposure., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

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.

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 + CD11b hi ) 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.

Occupational agricultural dust exposure can cause severe lung injury, including COPD and asthma exacerbations. Cell-derived extracellular vesicles can mediate inflammatory responses and immune activation, but the contribution of diet-derived extracellular vesicles to these processes is poorly understood. We investigated whether bovine milk-derived extracellular vesicles modulate inflammatory responses to agricultural dust exposures in a murine model. C57BL/6 mice were fed either an extracellular vesicle-enriched modification of the AIN-93G diet with lyophilized bovine milk (EV) or a control diet wherein the milk was presonicated, disrupting the milk extracellular vesicles and thereby leading to RNA degradation (DEV). Mice were maintained on the diets for 5-7 weeks and challenged with a single (acute) intranasal instillation of a 12.5% organic dust extract (DE) or with 15 instillations over 3 weeks (repetitive exposure model). Through these investigations, we identified significant interactions between diet and DE when considering numerous inflammatory outcomes, including lavage inflammatory cytokine levels and cellular infiltration into the lung airways. DE-treated peritoneal macrophages also demonstrated altered polarization, with EV-fed mouse macrophages exhibiting an M1 shift compared to an M2 phenotype in DEV-fed mice (IL-6, TNF, IL-12/23 all significantly elevated, and IL-10 and arginase decreased in EV macrophages, ex vivo). In complementary in vitro studies, mouse macrophages treated with purified milk-derived EV were found to express similar polarization phenotypes upon DE stimulation. These results suggest a role for dietary extracellular vesicles in the modulation of lung inflammation in response to organic dust which may involve macrophage phenotype polarization., (Copyright © 2018 Elsevier Inc. All rights reserved.)

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.

Injurious dust exposures in the agricultural workplace involve the release of inflammatory mediators and activation of epidermal growth factor receptor (EGFR) in the respiratory epithelium. Amphiregulin (AREG), an EGFR ligand, mediates tissue repair and wound healing in the lung epithelium. Omega-3 fatty acids such as docosahexaenoic acid (DHA) are also known modulators of repair and resolution of inflammatory injury. This study investigated how AREG, DHA, and EGFR modulate lung repair processes following dust-induced injury. Primary human bronchial epithelial (BEC) and BEAS-2B cells were treated with an aqueous extract of swine confinement facility dust (DE) in the presence of DHA and AREG or EGFR inhibitors. Mice were exposed to DE intranasally with or without EGFR inhibition and DHA. Using a decellularized lung scaffolding tissue repair model, BEC recolonization of human lung scaffolds was analyzed in the context of DE, DHA, and AREG treatments. Through these investigations, we identified an important role for AREG in mediating BEC repair processes. DE-induced AREG release from BEC, and DHA treatment following DE exposure, enhanced this release. Both DHA and AREG also enhanced BEC repair capacities and rescued DE-induced recellularization deficits. In vivo, DHA treatment enhanced AREG production following DE exposure, whereas EGFR inhibitor-treated mice exhibited reduced AREG in their lung homogenates. These data indicate a role for AREG in the process of tissue repair after inflammatory lung injury caused by environmental dust exposure and implicate a role for DHA in regulating AREG-mediated repair signaling in BEC.

Background: Farm workers in rural areas consume more alcohol than those who reside in urban areas. Occupational exposures such as agricultural work can pose hazards on the respiratory system. It is established that hog barn dust induces inflammation in the airway, including the release of cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and IL-8. We have shown that alcohol alters airway epithelial innate defense through changes in both nitric oxide (NO) and cAMP-dependent protein kinase A (PKA). Simultaneous exposure to hog barn dust and alcohol decreases inflammatory mediators, TNF-α, IL-6, and IL-8, in mice. Previously, mice exposed to both alcohol and hog barn dust showed a depleted amount of lymphocytes compared to mice exposed only to hog barn dust. Weakening of the innate immune response could lead to enhanced susceptibility to disease. In addition, mice that were co-exposed to hog barn dust and alcohol also experienced increased mortality., Methods: Because we recently demonstrated that PKA activation inhibits the TNF-α sheddase, TNF-α-converting enzyme (TACE), we hypothesized that an alcohol-mediated PKA pathway blocks TACE activity and prevents the normative inflammatory response to hog barn dust exposure. To delineate these effects, we used PKA pathway inhibitors (adenylyl cyclase [AC], cAMP, and PKA) to modulate the effects of alcohol on dust-stimulated TNF-α release in the bronchial epithelial cell line, BEAS-2B. Alcohol pretreatment blocked TACE activity and TNF-α release in hog barn dust-treated cells., Results: Alcohol continued to block hog barn dust-mediated TNF-α release in the presence of the particulate AC inhibitor, SQ22,536. The soluble adenylyl cyclase inhibitor, KH7, however, significantly increased the inflammatory response to hog barn dust. phosphodiesterase 4 inhibitors significantly elevated cAMP and enhanced alcohol-mediated inhibition of dust-stimulated TNF-α release. In addition, the NO synthase inhibitor, l-NMMA, also reversed the alcohol-blocking effect on dust-stimulated TNF-α., Conclusions: These data suggest that alcohol requires a soluble cyclase-generated cAMP-PKA pathway that is dependent upon the action of NO to inhibit TACE and TNF-α release. These findings support our observations that alcohol functions through a dual NO and PKA pathway in bronchial epithelial cells., (Copyright © 2016 by the Research Society on Alcoholism.)

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., (Copyright © 2015 Elsevier Inc. All rights reserved.)

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.

Lung injury caused by inhalation of dust from swine-concentrated animal-feeding operations (CAFO) involves the release of inflammatory cytokine interleukin 8 (IL-8), which is mediated by protein kinase C-ε (PKC-ε) in airway epithelial cells. Once activated by CAFO dust, PKC-ε is responsible for slowing cilia beating and reducing cell migration for wound repair. Conversely, the cAMP-dependent protein kinase (PKA) stimulates contrasting effects, such as increased cilia beating and an acceleration of cell migration for wound repair. We hypothesized that a bidirectional mechanism involving PKA and PKC regulates epithelial airway inflammatory responses. To test this hypothesis, primary human bronchial epithelial cells and BEAS-2B cells were treated with hog dust extract (HDE) in the presence or absence of cAMP. PKC-ε activity was significantly reduced in cells that were pretreated for 1 h with 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) before exposure to HDE (P < 0.05). HDE-induced IL-6, and IL-8 release was significantly lower in cells that were pretreated with 8-Br-cAMP (P < 0.05). To exclude exchange protein activated by cAMP (EPAC) involvement, cells were pretreated with either 8-Br-cAMP or 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-CPT-2Me-cAMP) (EPAC agonist). 8-CPT-2Me-cAMP did not activate PKA and did not reduce HDE-stimulated IL-6 release. In contrast, 8-Br-cAMP decreased HDE-stimulated tumor necrosis factor (TNF)-α-converting enzyme (TACE; ADAM-17) activity and subsequent TNF-α release (P < 0.001). 8-Br-cAMP also blocked HDE-stimulated IL-6 and keratinocyte-derived chemokine release in precision-cut mouse lung slices (P < 0.05). These data show bidirectional regulation of PKC-ε via a PKA-mediated inhibition of TACE activity resulting in reduced PKC-ε-mediated release of IL-6 and IL-8., (Copyright © 2014 the American Physiological Society.)

Nonmotile primary cilia are recognized as important sensory organelles during development and normal biological functioning. For example, recent work demonstrates that transcriptional regulators of the sonic hedgehog signaling pathway localize to primary cilia and participate in sensing and transducing signals regarding the cellular environment. In contrast, motile cilia are traditionally viewed as mechanical machinery, vital for the movement of solutes and clearance of bacteria and debris, but not participants in cellular sensing and signaling mechanisms. Recently, motile cilia were found to harbor receptors responsible for sensing and responding to environmental stimuli. However, no transcription factors are known to be regulated by cilia localization as a sensing mechanism in vertebrates. Using a mouse model of organic dust-induced airway inflammation, we found that the transcription factor serum response factor (SRF) localizes to motile cilia of airway epithelial cells and alters its localization in response to inflammatory stimuli. Furthermore, inhibition of SRF signaling using the small molecule CCG-1423 reduces organic dust-induced IL-8 release from bronchial epithelial cells and stimulates cilia beat frequency in ciliated mouse tracheal epithelial cells. Immunohistochemical analyses reveal that SRF localizes to the cilia of mouse brain ependymal and ovarian epithelial cells as well. These data reveal a novel mechanism by which a transcription factor localizes to motile cilia and modulates cell activities including cilia motility and inflammation response. These data challenge current dogma regarding motile cilia functioning and may lead to significant contributions in understanding motile ciliary signaling dynamics, as well as mechanisms involving SRF-mediated responses to inflammation and injury.

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.