Bronchoalveolar lavage fluid cytokine, cytology and IgE allergen in horses with equine asthma

Towards personalized medicine for the treatment of equine asthma

Although horses with asthma share similar clinical signs, the heterogeneity of the disease in terms of severity, triggering factors, inflammatory profile, and pathological features has hindered our ability to define biologically distinct subgroups. The recognition of phenotypes and endotypes could enable the development of precision medicine, including personalized, targeted therapy, to benefit affected horses. While in its infancy in horses, this review outlines the phenotypes of equine asthma and discusses how knowledge gained from targeted therapy in human medicine can be applied to evaluate the potential opportunities for personalized medicine in equine asthma and to suggest avenues for research to advance this emerging field.

Cytokine mRNA expression in the bronchoalveolar lavage cells from horses affected by different equine asthma subtypes

Equine asthma (EA) is a respiratory syndrome associated with the increase of different leukocyte populations in the bronchoalveolar lavage fluid (BALF). Its pathogenetic mechanisms remain unclear. This study aimed to evaluate the associations between the mRNA expression of different cytokines in the BALF, different EA subtypes and lung function. Fifteen horses underwent physical examination, airway endoscopy, BALF cytology and lung function testing (8/15). One horse did not have evidence of EA and was used as healthy reference, while the others were classified as affected by neutrophilic or mixed granulocytic EA. Cells isolated from the residual BALF were used for IL-1β, IL-2, IFN-γ, IL-4, IL-17A genes expression by quantitative RT-PCR., Cytokine expression was compared between groups, and their correlations with BALF leukocyte and lung function were evaluated. IL-1β expression was positively correlated with BALF neutrophils count (p=0.038, r=0.56) and with increased expiratory resistance (p=0.047, r=0.76). IFN-γ was correlated with BALF mast cells (p=0.029, r=0.58). IL-4 was higher in horses with mixed granulocytic EA than neutrophilic (p=0.008), positively correlated with BALF mast cells (p=0.028, r=0.59) and inversely with whole-breath (p=0.046, r=-0.76) and expiratory reactance (p=0.003, r=-0.93). Finally, IL-17A was inversely correlated with expiratory reactance (p=0.009, r=-0.92). These results support that multiple immune responses are involved in EA pathogenesis; innate, Th2, and Th17 responses. Innate immunity appeared associated with neutrophilic inflammation, and Th2 response with increased mast cells. The role of Th1 response in EA remains questionable.

Neutrophil gelatinase-associated lipocalin as a potential biomarker for equine asthma

BACKGROUND

Studies in people have found neutrophil gelatinase-associated lipocalin (NGAL) concentrations are increased in asthma and can be used to distinguish between asthma subtypes. NGAL has not yet been investigated in equine asthma (EA).

OBJECTIVES

To investigate the ability of NGAL concentrations in bronchoalveolar lavage (BAL) fluid and serum to distinguish between control horses, horses with mild-moderate EA (MEA) and horses with severe EA (SEA).

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Details of endoscopic examination including tracheal mucus score (TMS, scale 0-5) and BAL cytology performed on 227 horses were extracted from records and NGAL concentrations were measured on stored serum and BAL fluid samples. The horses were divided into groups (control group n = 73, MEA n = 98, SEA n = 56) based on clinical signs and BAL cytology results. Differences between groups were evaluated with the Mann-Whitney test and correlation between BAL NGAL, serum NGAL, and BAL cytology were evaluated using Spearman's correlation.

RESULTS

BAL NGAL concentrations were higher in EA than in control horses (median: 25.6 and 13.3 μg/L, respectively, p < 0.001). Concentrations of NGAL in BAL differed between groups, with higher concentrations in MEA than in control horses (median: 18.5 and 13.3 μg/L, respectively, p < 0.001), and higher concentrations in SEA than in MEA horses (median: 54.1 and 18.5 μg/L, respectively, p < 0.001). BAL NGAL concentration differed between horses with TMS ≤2 an >2 (median 15.6 and 21.1 μg/L, respectively, p = 0.004). No differences were found in serum NGAL concentration between any of the groups.

MAIN LIMITATION

Only 66 of the 227 (29%) horses had haematology and serum NGAL measured.

CONCLUSION

BAL NGAL concentration differed between control and EA and reflected severity of disease. These results justify further research into the potential of NGAL as a biomarker of EA.

Decision Making in Severe Equine Asthma-Diagnosis and Monitoring

Decision making consists of gathering quality data in order to correctly assess a situation and determine the best course of action. This process is a fundamental part of medicine and is what enables practitioners to accurately diagnose diseases and select appropriate treatment protocols. Despite severe equine asthma (SEA) being a highly prevalent lower respiratory disease amongst equids, clinicians still struggle with the optimization of routine diagnostic procedures. The use of several ancillary diagnostic tests has been reported for disease identification and monitoring, but many are only suitable for research purposes or lack practicality for everyday use. The aim of this paper is to assist the equine veterinarian in the process of decision making associated with managing SEA-affected patients. This review will focus on disease diagnosis and monitoring, while also presenting a flow-chart which includes the basic data that the clinician must obtain in order to accurately identify severely asthmatic horses in their everyday routine practice. It is important to note that European and American board-certified specialists on equine internal medicine can provide assistance in the diagnosis and treatment plan of SEA-affected horses.

Immunoproteomics reveal increased serum IgG3/5 binding to Dermatophagoides and yeast protein antigens in severe equine asthma in a preliminary study

Introduction

Severe equine asthma (SEA) is a common, chronic respiratory disease of horses characterized by hyperreactivity to hay dust which has many similarities to severe neutrophilic asthma in humans. SEA-provoking antigens have not been comprehensively characterized, but molds and mites have been suggested as relevant sources. Here, we identified relevant antigen candidates using immunoproteomics with IgG isotype-binding analyses.

Methods

Proteins from Dermatophagoides pteronyssinus (Der p) were separated by two-dimensional gel electrophoresis followed by immunoblotting (2D immunoblots) resulting in a characteristic pattern of 440 spots. After serum incubation, antibody (Ig)-binding of all Ig (Pan-Ig) and IgG isotypes (type-2-associated IgG3/5, type-1-associated IgG4/7) was quantified per each spot and compared between asthmatic and healthy horses' sera (n=5 per group).

Results

Ig binding differences were detected in 30 spots. Pan-Ig binding was higher with asthmatics compared to healthy horses' sera on four spots, and IgG3/5 binding was higher on 18 spots. Small IgG4/7 binding differences were detected on 10 spots with higher binding with asthmatics' sera on four but higher binding with healthy horses' sera on six spots. Proteins from the spots with group differences including mite and yeast proteins were identified by liquid chromatography mass spectrometry. The latter likely originated from the feeding substrate of the Der p culture. Prioritized antigen candidates amongst the proteins identified were Der p 1, Der p 11, group 15 allergens, myosin heavy chain, and uncharacterized Der p proteins. Additionally, yeast enolases, alcohol dehydrogenase (ADH), phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase, and heat shock proteins were prioritized. Eleven antigen candidates were tested for confirmation by ELISAs using the respective proteins separately. Differences in asthmatics vs. healthy horses' serum Ig binding to Der p 1, Der p 18, and three yeast enzymes (enolase, ADH, and PGK) confirmed these as promising antigens of immune responses in SEA.

Discussion

Antigens with relevance in SEA were newly identified by immunoproteomics, and yeast antigens were considered for SEA for the first time. Serum IgG3/5 binding to relevant antigens was increased in SEA and is a novel feature that points to increased type-2 responses in SEA but requires confirmation of the corresponding cellular responses.

Molecular and Cellular Evaluation of Horses With Summer Pasture Associated Asthma Syndrome

Equine asthma is an airway disease that affects a large number of horses annually leading to considerable economic losses in the horse industry. Despite advances in research in this area, there is still a lack of information on its etiology and molecular characterization in pasture associated asthma. The objective of the current study was to characterize the inflammatory disease of lower airways in horses maintained on pasture through cytologic and immunologic profile during the summer in a tropical environment by analysis of the gene expression of Th1 cytokines (IFN- λ, IL-8), Th2 cytokines (IL-4 and IL-5), and pro-inflammatory cytokines (IL-1, TNF-α) in the bronchoalveolar lavage (BAL) fluid in healthy and asthma horses on pasture. A group 39 of clinically healthy horses maintained on native pasture and supplemented with concentrate was evaluated by BAL analyzed for differential cellular count and assigned into a control and an asthma group. The gene expression of pro-inflammatory cytokines was analyzed in the BAL by reverse time PCR (RT-PCR) (IL-1α (alpha), IL-4, IL-5, IL-8, TNF-α alpha and IFN-λ), using β-actin as housekeeping gene. Higher gene expression of IL-1, IL-4, IL-5, IL-8, IFN-λ in the BAL of asthma horses was found. Current results indicate an increase in Th2, characterizing an allergic inflammatory reaction due to the significant increase in IL-5 in asthmatic horses (10.3 ± 1.13), when compared to the values ​​obtained in normal horses (3.27 ± 0.46). The only down regulated cytokine in the asthma group was TNF-α, suggesting a chronic antigenic reaction.

Regulatory T lymphocytes and selected cytokines in horses with mild to severe equine asthma and different inflammatory cytology profiles

This study determined Tregs and inflammatory cytokines in BALF and peripheral blood (PB) of adult horses with mild and severe asthma and different BALF cytological inflammation profiles. Horses of diverse breeds with asthma (age range: 2-20 years, n = 24) were divided into groups according to the number of points obtained in a standardized clinical scoring system (mild-moderate equine asthma - MEA, severe equine asthma - SEA) and according to the inflammation type based on cytological finding. Plasma levels of IFN-γ, IL-4, IL-10, IL-17 and MMP-9 in the BALF were determined by ELISA. Tregs in the BALF and PB were detected by flow cytometry. Horses with SEA were older than horses with MEA and had higher concentrations of MMP-9 in the BALF (P < 0.05). The neutrophilic inflammation group was characterised by higher age, grade of clinical score, percentage of Tregs and MMP-9 concentration in the BALF compared to the mastocytic inflammation group (P < 0.05). Age positively correlated with neutrophils, grade of score, Tregs in the BALF and in the PB. The grade of score positively correlated with MMP-9. The percentage of Tregs in the BALF positively correlated with Tregs in the PB. Tregs in the BALF and PB positively correlated with neutrophils and MMP-9 in the BALF and with IFN-γ, IL-4 and IL-10 in the plasma. IFN-γ and IL-10 in the plasma positively correlated with the age. The results indicate that the evaluation of selected parameters in PB, the collection of which is less invasive than the collection of BALF, is of potential importance.

Effect of Lavage Solution Type on Bronchoalveolar Lavage Fluid Cytology in Clinically Healthy Horses

Equine bronchoalveolar lavage (BAL) is usually performed with 250-500 mL of isotonic saline at pH 5.5. The acidic pH of saline may cause an increase in airway neutrophil count 48 h after BAL. Other isotonic solutions such as Ringer's solution, phosphate-buffered saline (PBS) or Plasma-Lyte 148® have a neutral pH of 7.4 and might be a better choice for BAL by not provoking inflammation and the influx of neutrophils into airways. BAL was performed in four healthy horses in four different lung lobes using four different solutions in a randomized crossover design. In each lobe, BAL was performed twice with a 48 h interval using 250 mL of solution. Automated total nucleated cell counts (TNCs) were recorded, and differential cell counts in lavage fluid were determined by two investigators blinded to treatments. The mean volume of BAL fluid retrieved was 51 ± 14%. The mean neutrophil percentage (%N) increased from 1.5 ± 0.9% to 14.7 ± 9.6% at 48 h (p < 0.001) but was not significantly affected by the solution used or the lung lobe sampled. In conclusion, in this study, the influx of neutrophils into airways after BAL was independent of the type of isotonic solution used and the lung lobe sampled. Saline remains an appropriate solution for BAL in horses.

Asthma: The Use of Animal Models and Their Translational Utility

Asthma is characterized by chronic lower airway inflammation that results in airway remodeling, which can lead to a permanent decrease in lung function. The pathophysiology driving the development of asthma is complex and heterogenous. Animal models have been and continue to be essential for the discovery of molecular pathways driving the pathophysiology of asthma and novel therapeutic approaches. Animal models of asthma may be induced or naturally occurring. Species used to study asthma include mouse, rat, guinea pig, cat, dog, sheep, horse, and nonhuman primate. Some of the aspects to consider when evaluating any of these asthma models are cost, labor, reagent availability, regulatory burden, relevance to natural disease in humans, type of lower airway inflammation, biological samples available for testing, and ultimately whether the model can answer the research question(s). This review aims to discuss the animal models most available for asthma investigation, with an emphasis on describing the inciting antigen/allergen, inflammatory response induced, and its translation to human asthma.

Initial investigation of molecular phenotypes of airway mast cells and cytokine profiles in equine asthma

Equine asthma is a naturally occurring lung disease characterized by chronic, partially reversible airway obstruction, pulmonary remodeling, and lower airway inflammation. Asthma is currently divided into two major groups, mild to moderate asthma (mEA) and severe asthma (sEA), but further subtyping by phenotype (i.e., clinical presentation) and/or endotype (i.e., cellular mechanisms) may be warranted. For this study, we were interested in further investigation of cellular and inflammatory characteristics of EA, including airway mast cells. The purpose of this study was to: (1) compare mast cell protease mRNA expression between healthy and asthmatic horses, (2) analyze the cytokine profile present in BALF of currently defined equine asthma groups, and (3) use these data to evaluate potential biomarkers of defined asthma groups. We hypothesized that there would be significant differences in the cellular mast cell phenotypes (i.e., mucosal vs. connective tissue) and cytokine profiles in the BALF of asthmatic vs. healthy horses and across asthma groups. We assert these characteristics may inform additional subtypes of equine asthma. Adult horses were recruited from the institution's teaching herd and clinical caseload. Mast cell protease gene expression of the BALF cellular component and multiplex bead immunoassay for cytokine concentrations in the BALF supernatant were investigated. Airway mast cells primarily expressed tryptase, with low levels of chymase. No significant changes in protease expression were detected across groups. Horses with severe asthma had increased TNF-α, CXCL-8, and IFN-γ concentrations in BALF supernatant. Multidimensional analysis demonstrated healthy and mEA horses have overlapping characteristics, with sEA separating from the other groups. This difference was primarily due to BALF neutrophil and lymphocyte concentrations. These study results further inform understanding of EA immunopathology, and future studies designed to investigate asthma phenotypes and endotypes. Ultimately, a better understanding of these groups could help identify novel therapeutic strategies.

Protein microarray allergen profiling in bronchoalveolar lavage fluid and serum of horses with asthma

BACKGROUND

The diagnostic value of allergen-specific immunoglobulin E (IgE) in horses with asthma is uncertain. A recently developed protein microarray detected abnormally high latex-specific IgE concentrations in the serum of horses with severe asthma.

OBJECTIVES

The main objective was to characterize the IgE profiles of asthmatic horses in Switzerland using a protein microarray platform in serum and bronchoalveolar lavage fluid (BALF). The secondary objective was to determine whether serological and BALF allergen-specific IgE concentrations correlated.

ANIMALS

Forty-four asthmatic and 39 control horses ≥5 years of age.

METHODS

This prospective cross-sectional study investigated the sensitization profiles of horses with asthma compared with environmentally matched healthy controls. Both serum and BALF were analyzed using the protein microarray. Partial least square-discriminant analysis (PLS-DA) was used to identify and rank the importance of the allergens for class detection (ie, asthma vs control), with a variable influence on the projection (VIP) >1 considered significant.

RESULTS

The allergens that best discriminated (VIP >1) asthmatic horses from controls were proteins derived from fungi (Aspergillus fumigatus), insects (Culicoides spp.), and latex (Hevea brasiliensis). The serological model predictive ability was markedly inferior (area under the curve [AUC] 0.585, 95% confidence interval [CI]: 0.454-0.747) to that of the BALF (AUC 0.751, 95% CI: 0.582-0.866). The two models shared nine allergens, of which eight showed significant weak to moderate correlations.

CONCLUSION AND CLINICAL IMPORTANCE

The concentrations of several allergen-specific IgE were higher in asthmatic horses. The protein microarray performed better on BALF than serum for detection of asthma. Serological IgE concentrations do not closely correlate with BALF concentrations and should be interpreted with caution.

Integrated plasma pharmacochemistry and network pharmacology to explore the mechanism of Gerberae Piloselloidis Herba in treatment of allergic asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Gerberae Piloselloidis Herba (GPH), a commonly used traditional medicine in China, is derived from Gerbera piloselloides (Linn.) Cass. It is featured by its special bioactivities as antitussive, expectorant, anti-asthma, anti-bacterial, anti-tumor, uterine analgesia, and immunity-enhancing. With a long history of medication in ethnic minority areas in China, it is often used as an effective treatment for cough and sore throat as well as allergic asthma. Although our previous investigation also has discovered GPH performed effective treatment on allergic asthma, its underlying mechanism remains unclear.

AIM OF THE STUDY

This research aims to reveal the pharmacological mechanism of GPH in the treatment for allergic asthma through combination of plasma pharmacology and network pharmacology.

MATERIALS AND METHODS

Firstly, the components of GPH in blood samples were identified using UHPLC- Q-Orbitrap HRMS. An interaction network of "compound-target-disease" was constructed based on the compounds confirmed in blood and on their corresponding targets of allergic asthma acquired from disease gene databases, predicting the possible biological targets and potential signal pathways of GPH with the network pharmacology analysis. Then, a molecular docking between the blood ingredients and the core targets was carried out using the Autodock Vina software. Subsequently, after establishing a mouse model with allergic asthma induced by ovalbumin (OVA), the effect of GPH on allergic asthma was evaluated by analyzing a series of indicators including behavior, lung pathological changes, inflammatory factors in serum and bronchoalveolar lavage fluid (BALF). Finally, the key pathway and targets predicted by network pharmacology and molecular docking were further verified using Western blot analysis.

RESULTS

Eleven chemical constituents (such as arbutin, neochlorogenic acid, chlorogenic acid, etc.) were identified through the analysis of plasma samples, on which basis a total of 142 genes intersecting GPH and allergic asthma were collected by network pharmacology. After performing enrichment analysis of these genes in gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG), it was found that arbutin-related targets mainly focused on phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signal pathway, while luteolin and marmesin -related targets tended to locate at Interleukin-17 (IL-17) signal pathway. Meanwhile, the findings of molecular docking suggested that such components as arbutin, luteolin and marmesin entering into blood had good binding with the core targets related to PI3K/Akt and IL-17 pathways. In addition, GPH improved the OVA-induced asthma symptoms, the alveolar septa thickening and the infiltration of inflammatory cell around bronchi and bronchioles as well as reduced the levels of IgE, IL-8 and TNF-α in serum or BALF. Furthermore, GPH could inhibit the phosphorylation level of Akt and the expression of PI3K, an efficacy supported by the findings by way of Western blot which suggests that GPH in the treatment of allergic asthma was linked to PI3K/Akt signal pathway.

CONCLUSION

In this study, a comprehensive strategy to combine the UPLC-Q-Orbitrap HRMS with network pharmacology was employed to clarify the mechanism of GPH against allergic asthma, a finding where GPH may inhibit PI3K/Akt signal pathway to protect mice from OVA-induced allergic asthma. This study provides a deeper understanding of the pharmacological mechanism of GPH in treatment of asthma, offering a scientific reference for further research and clinical application of GPH in terms of allergic asthma.

Neutrophil Extracellular Traps Are Found in Bronchoalveolar Lavage Fluids of Horses With Severe Asthma and Correlate With Asthma Severity

Asthma encompasses a spectrum of heterogenous immune-mediated respiratory disorders sharing a similar clinical pattern characterized by cough, wheeze and exercise intolerance. In horses, equine asthma can be subdivided into severe or moderate asthma according to clinical symptoms and the extent of airway neutrophilic inflammation. While severe asthmatic horses are characterized by an elevated neutrophilic inflammation of the lower airways, cough, dyspnea at rest and high mucus secretion, horses with moderate asthma show a milder neutrophilic inflammation, exhibit intolerance to exercise but no labored breathing at rest. Yet, the physiopathology of different phenotypes of equine asthma remains poorly understood and there is a need to elucidate the underlying mechanisms tailoring those phenotypes in order to improve clinical management and elaborate novel therapeutic strategies. In this study, we sought to quantify the presence of neutrophil extracellular traps (NETs) in bronchoalveolar lavage fluids (BALF) of moderate or severe asthmatic horses and healthy controls, and assessed whether NETs correlated with disease severity. To this end, we evaluated the amounts of NETs by measuring cell-free DNA and MPO-DNA complexes in BALF supernatants or by quantifying NETs release by BALF cells by confocal microscopy. We were able to unequivocally identify elevated NETs levels in BALF of severe asthmatic horses as compared to healthy controls or moderate asthmatic horses. Moreover, we provided evidence that BALF NETs release was a specific feature seen in severe equine asthma, as opposed to moderate asthma, and correlated with disease severity. Finally, we showed that NETs could act as a predictive factor for severe equine asthma. Our study thus uniquely identifies NETs in BALF of severe asthmatic horses using three distinct methods and supports the idea that moderate and severe equine asthma do not rely on strictly similar pathophysiological mechanisms. Our data also suggest that NETs represent a relevant biomarker, a putative driver and a potential therapeutic target in severe asthma disease.

Inflammatory and contractile profile in LPS-challenged equine isolated bronchi: Evidence for IL-6 as a potential target against AHR in equine asthma

BACKGROUND

Airway inflammation and airway hyperresponsiveness (AHR) are pivotal characteristics of equine asthma. Lipopolysaccharide (LPS) may have a central role in modulating airway inflammation and dysfunction. Therefore, the aim of this study was to match the inflammatory and contractile profile in LPS-challenged equine isolated bronchi to identify molecular targets potentially suitable to counteract AHR in asthmatic horses.

METHODS

Equine isolated bronchi were incubated overnight with LPS (0.1-100 ng/ml). The contractile response to electrical field stimulation (EFS) and the levels of cytokines, chemokines, and neurokinin A (NKA) were quantified. The role of capsaicin sensitive-sensory nerves, neurokinin-2 (NK₂) receptor, transient receptor potential vanilloid type 1 receptors (TRPV1), and epithelium were also investigated.

RESULTS

LPS 1 ng/ml elicited AHR to EFS (+238.17 ± 25.20% P < 0.001 vs. control). LPS significantly (P < 0.05 vs. control) increased the levels of IL-4 (+36.08 ± 1.62%), IL-5 (+38.60 ± 3.58%), IL-6 (+33.79 ± 2.59%), IL-13 (+40.91 ± 1.93%), IL-1β (+1650.16 ± 71.16%), IL-33 (+88.14 ± 8.93%), TGF-β (22.29 ± 1.03%), TNF-α (+56.13 ± 4.61%), CXCL-8 (+98.49 ± 17.70%), EOTAXIN (+32.26 ± 2.27%), MCP-1 (+49.63 ± 4.59%), RANTES (+36.38 ± 2.24%), and NKA (+112.81 ± 6.42%). Capsaicin sensitive-sensory nerves, NK₂ receptor, and TRPV1 were generally involved in the LPS-mediated inflammation. Epithelium removal modulated the release of IL-1β, IL-33, and TGF-β. Only the levels of IL-6 fitted with AHR to a wide range of EFS frequencies, an effect significantly (P < 0.05) inhibited by anti-IL-6 antibody; exogenous IL-6 induced significant (P < 0.05) AHR to EFS similar to that elicited by LPS.

CONCLUSION

Targeting IL-6 with specific antibody may represent an effective strategy to treat equine asthma, especially in those animals suffering from severe forms of this disease.

Effect of intrabronchial administration of autologous adipose-derived mesenchymal stem cells on severe equine asthma

BACKGROUND

Severe equine asthma (SEA) is a common chronic respiratory disease and a significant health and well-being problem in horses. Current therapeutic strategies improve pulmonary function and clinical signs in some horses, but in the long-term, return to full athletic function appears to be rare. The aim of this study was to assess the safety and the effect of intrabronchial administration of adipose-derived mesenchymal stem cells (AD-MSC) on pulmonary inflammatory and clinical parameters in horses with SEA.

METHODS

This was a randomized controlled trial. Twenty adult horses diagnosed with SEA were randomly divided into two groups (n = 10), and treated either with a single intrabronchial application of autologous AD-MSC or oral dexamethasone for three weeks. A targeted clinical examination with determination of clinical score, maximal change in pleural pressure during the breathing cycle, and an endoscopic examination of the airways were performed at baseline and three weeks after treatment. Bronchoalveolar lavage fluid was analyzed cytologically, and IL-1β, IL-4, IL-8, IL-17, TNFα and IFNγ mRNA and protein concentrations were measured at baseline and three weeks. The horses were then monitored over one year for recurrence of SEA. A non-inferiority analysis and a linear mixed-effects model were performed to assess differences between treatments.

RESULTS

The non-inferiority of AD-MSC treatment was not established. However, AD-MSC administration significantly ameliorated the clinical score (P = 0.01), decreased the expression of IL-17 mRNA (P = 0.05) and IL-1β (P ≤ 0.001), IL-4 (P ≤ 0.001), TNFα (P = 0.02) protein levels, and had a positive long-term effect on SEA-associated clinical signs (P = 0.02).

CONCLUSIONS

Intrabronchial administration of AD-MSC had limited short-term anti-inflammatory effects but improved the clinical signs of SEA at one year.

Training associated alterations in equine respiratory immunity using a multiomics comparative approach

Neutrophilic airway inflammation is highly prevalent in racehorses in training, with the term mild to moderate equine asthma (MMEA) being applied to the majority of such cases. Our proposed study is largely derived from the strong association between MMEA in racehorses and their entry into a race training program. The objectives of this study are to characterise the effect of training on the local pulmonary immune system by defining the gene and protein expression of tracheal wash (TW) derived samples from Thoroughbred racehorses prior to and following commencement of race training. Multiomics analysis detected 2138 differentially expressed genes and 260 proteins during the training period. Gene and protein sets were enriched for biological processes related to acute phase response, oxidative stress, haemopoietic processes, as well as to immune response and inflammation. This study demonstrated TW samples to represent a rich source of airway cells, protein and RNA to study airway immunity in the horse and highlighted the benefits of a multiomics methodological approach to studying the dynamics of equine airway immunity. Findings likely reflect the known associations between race-training and both airway inflammation and bleeding, offering further insight into the potential mechanisms which underpin training associated airway inflammation.

Dynamics of local gene regulations in synovial fluid leukocytes from horses with lipopolysaccharide-induced arthritis

The role of resident cells such a synoviocytes and chondrocytes in intra-articular inflammation is well-characterized, however the in vivo gene expression patterns of cells (predominantly leukocytes) in the synovial fluid (SF) of an inflamed joint have never previously been investigated. The aim of this study was to investigate gene expression in SF leukocytes from the inflamed joint cavity after intra-articular lipopolysaccharide (LPS) injection in horses to improve our understanding of the temporal regulation of the intra-articular inflammatory response. Gene expression was investigated in SF samples available from six horses 2, 4, 8 16 and 24 h after experimental induction of inflammation in the radiocarpal joint by lipopolysaccharide (LPS) injection. Leukocytic expression of 43 inflammation-related genes was studied using microfluidic high throughput qPCR (Fluidigm®). Expression of 26 genes changed significantly over the 24 h study period, including pro- and anti-inflammatory genes such as interleukin (IL)1, IL6, tumor necrosis factor (TNF), cyclooxygenase 2 (COX2), IL1 receptor antagonist (IL1RN), IL10, and superoxide dismutase 2 (SOD2), chemokine genes, apoptosis-related genes, and genes related to cartilage turnover (matrix metalloproteinase 8 and tissue inhibitor of metalloproteinase 1). The inflammatory responses appeared to be regulated, as an early increase (at 2 h) in expression of the pro-inflammatory genes IL1, IL6, TNF and COX2 was rapidly followed by increased expression (at 4 h) of several anti-inflammatory genes (IL10, IL1RN and SOD2). Similarly, both pro- and anti-apoptotic gene expression as well as expression of chondrodegenerative and chondroprotective genes were activated in SF leukocytes. Thus, the inflammatory response in leukocytes infiltrating the joint in the acute stage of arthritis was well orchestrated in this single-hit LPS-induced arthritis model. This study is the first to describe gene expression patterns in SF-derived leukocytes in vivo during severe joint inflammation, and the results thus expand our knowledge of basic inflammatory mechanisms in the early local response in an inflamed joint.

Immunohistochemical Expression of Neurokinin-A and Interleukin-8 in the Bronchial Epithelium of Horses with Severe Equine Asthma Syndrome during Asymptomatic, Exacerbation, and Remission Phase

Severe equine asthma (EA) syndrome is a chronic obstructive disease characterized by exaggerated contraction, inflammation, and structural alteration of the airways in adult horses, when exposed to airborne molds and particulate material. However, little is known about the relationship between the degree and type of inflammation on one hand, and the severity of the disease and the response to treatment on the other. Furthermore, to date, very few studies evaluate the diagnostic value of histology and immunohistochemical features of endoscopic biopsies on subjects with severe equine asthma. To investigate the expression of two inflammatory markers (NKA and IL-8) before, during, and after the exacerbation of severe EA, a histological and immunohistochemical study was carried out on a series of biopsy samples collected by bronchoscopy from six EA-affected horses subjected to process exacerbation through environmental stimuli and then to pharmacological treatment. The application of a histological biopsy scoring system revealed a significant difference between control cases and the EA-affected horses in all experimental phases (asymptomatic, early exacerbation phase, late exacerbation phase, and remission phase). For immunohistochemistry (IHC), only the intensity of NKA positivity increases significantly between control horses and the EA horses at late exacerbation and remission phases. In EA-affected horses, a difference was detected by comparing histology between asymptomatic and remission phase, meanwhile, NKA and IL-8 showed no differences between the experimental phases. Based on these results we can assert that: (1) The endoscopic biopsies generate reliable and homogeneous samples in the entire bronchial tree; (2) the clinical improvement associated with treatment is characterized by a significant worsening of the histological findings; and (3) the NKA immunopositivity seems to increase significantly rather than decrease, as one would have expected, after pharmacological treatment. Further studies are necessary both to implement the number of samples and to use other markers of inflammation to characterize the potential role of cytokines in the diagnosis and therapeutic approach of severe equine asthma.

Evaluation of Treatment With Respiratory Gene Technology and Serum in a Group of Standard Bred Racehorses With Cytological Evidence of Mild Equine Asthma

Alternative treatment options to glucocorticoids for equine asthma is desirable due to withdrawal time. The objective was to evaluate if serum and Respiratory Gene Technology (RGT), a commercial kit to produce autologous conditioned serum, was effective in reducing bronchoalveolar lavage (BAL) neutrophils and mast cells in racehorses with cytological evidence of mild equine asthma . Thirty-six Standardbred trotters in active training were enrolled in this randomized clinical trial; a healthy control group (n=11), a RGT group (n=12) and a serum group (n=13). Endoscopy including tracheal wash (TW) and BAL was performed before (T0), after a 6-week treatment period including 12 intramuscular injections of RGT or serum (T6) and as a follow-up 10 weeks after treatment (T16). A significant decrease in BAL neutrophils for the RGT group was found between T0 and T6 (P = .002, d=-1.51, CI: -2.43;-0.59) and for the serum group between T0-T6 (P = .002, d=-1.36, CI: -2.26;-0.46). Further, a significant decrease in BAL mast cells between T0-T6 for the both the RGT group (P = .019, d=-1.23, CI: -1.22;-0.34) and the serum group (P= .004, d=-0.81, CI: -1.65;0.04), and further between T0-T16 (RGT P= .011, d=-1.55, CI: -2.62;-0.48; serum P= .044, d=-0.65, CI: -1.68;-0.37). No significant difference in TW cytology was found for any of the time-points. Pro- and anti-inflammatory cytokines were regulated according to treatment. The control group showed no cytological differences between any time-point. Study results showed that intramuscular treatment with both RGT and serum was effective associated with reduction of BAL neutrophils and mast cells in horses with cytological evidence of mild equine asthma. Further large-scale studies are necessary.

Differential gene expression and Ingenuity Pathway Analysis of bronchoalveolar lavage cells from horses with mild/moderate neutrophilic or mastocytic inflammation on BAL cytology

Mild to moderate equine asthma syndrome (mEAS) affects horses of all ages and breeds. To date, the etiology and pathophysiology of mEAS are active areas of research, and it remains incompletely understood whether mEAS horses with different immune cell 'signatures' on BAL cytology represent different phenotypes, distinct pathobiological mechanisms (endotypes), varied environmental conditions, disease severity, genetic predispositions, or all of the above. In this descriptive study, we compared gene expression data from BAL cells isolated from horses with normal BALF cytology (n = 5), to those isolated from horses with mild/moderate neutrophilic inflammation (n = 5), or mild/moderate mastocytic inflammation (n = 5). BAL cell protein lysates were analyzed for cytokine/chemokine levels using Multiplex Bead Immunoassay, and for select proteins using immunoblot. The transcriptome, determined by RNA-seq and analyzed with DEseq2, contained 20, 63, and 102 significantly differentially expressed genes in horses with normal vs. neutrophilic, normal vs. mastocytic, and neutrophilic vs. mastocytic BALF cytology, respectively. Pathway analyses revealed that BAL-isolated cells from horses with neutrophilic vs. normal cytology showed enrichment in inflammation pathways, and horses with mastocytic vs. normal cytology showed enrichment in pathways involved in fibrosis and allergic reaction. BAL cells from horses with mastocytic mEAS, compared to neutrophilic mEAS, showed enrichment in pathways involved in alteration of tissue structures. Cytokine analysis determined that IL-1β was significantly different in the lysates from horses with neutrophilic inflammation compared to those with normal or mastocytic BAL cytology. Immunoblot revealed significant difference in the relative level of MMP2 in horses with neutrophilic vs. mastocytic mEAS. Upregulation of mRNA transcripts involved in the IL-1 family cytokine signaling axis (IL1a, IL1b, and IL1R2) in neutrophilic mEAS, as well as KIT mRNA in mastocytic mEAS, are novel, potentially clinically relevant, findings of this study. These findings further inform our understanding of inflammatory cell subtypes in mEAS.

An Integrative miRNA-mRNA Expression Analysis Reveals Striking Transcriptomic Similarities between Severe Equine Asthma and Specific Asthma Endotypes in Humans

Severe equine asthma is an incurable obstructive respiratory condition affecting 10–15% of horses in temperate climates. Upon exposure to airborne antigens from hay feeding, affected horses show neutrophilic airway inflammation and bronchoconstriction, leading to increased respiratory effort. The resulting implications range from welfare concerns to economic impacts on equestrian sports and horse breeding. Immunological and pathophysiological characteristics of severe equine asthma show important parallels with allergic and severe neutrophilic human asthma. Our study aimed at investigating regulatory networks underlying the pathophysiology of the disease by profiling miRNA and mRNA expression in lung tissue samples from asthmatic horses compared with healthy controls. We sequenced small RNAs and mRNAs from lungs of seven asthmatic horses in exacerbation, five affected horses in remission, and eight healthy control horses. Our comprehensive differential expression analyses, combined with the miRNA–mRNA negative correlation approach, revealed a strong similarity on the transcriptomic level between severe equine asthma and severe neutrophilic asthma in humans, potentially through affecting Th17 cell differentiation. This study also showed that several dysregulated miRNAs and mRNAs are involved in airway remodeling. These results present a starting point for a better transcriptomic understanding of severe equine asthma and its similarities to asthma in humans.

Single Nucleotide and Copy-Number Variants in IL4 and IL13 Are Not Associated with Asthma Susceptibility or Inflammatory Markers: A Case-Control Study in a Mexican-Mestizo Population

BACKGROUND

Asthma is a complex and chronic inflammatory airway disease. Asthma's etiology is unknown; however, genetic and environmental factors could affect disease susceptibility. We designed a case-control study aimed to evaluate the role of single-nucleotide polymorphisms (SNP), and copy-number variants (CNV) in the IL4 and IL13 genes in asthma susceptibility and their participation in plasma cytokine levels depending on genotypes Methods: We include 486 subjects, divided into asthma patients (AP, n = 141) and clinically healthy subjects (CHS, n = 345). We genotyped three SNP, two in the IL4 and two in the IL13 gene; also, two CNVs in IL4. The IL-4, IL-13 and IgE plasma levels were quantified.

RESULTS

Biomass-burning smoke exposure was higher in the AP group compared to CHS (47.5% vs. 20.9%; p < 0.01, OR = 3.4). No statistical differences were found in the genetic association analysis. In both CNV, we only found the common allele. For the analysis of IL-4, IL-13, and IgE measures stratified by genotypes, no significant association or correlation was found.

CONCLUSION

In the Mexican-mestizo population, SNPs neither CNVs in IL4 nor IL13 are associated with asthma susceptibility or involved serum cytokine levels. Biomass-burning smoke is a risk factor in asthma susceptibility.