Severe Equine Asthma Research Articles

Tamoxifen induces apoptosis and inhibits respiratory burst in equine neutrophils independently of estrogen receptors.

Neutrophils play an important role in the exacerbation and maintenance of severe equine asthma; persistent neutrophil activity and delayed apoptosis can be harmful to surrounding tissues. Tamoxifen (TX) is a nonsteroidal estrogen receptor modulator with immunomodulatory effects and induces early apoptosis of blood and bronchoalveolar lavage neutrophils from horses with acute lung inflammation. This study investigated if the in vitro effects of tamoxifen are produced by its action on nuclear (α and β) and membrane (GPR30) estrogen receptors in healthy equine neutrophils. Results showed that TX inhibits neutrophil respiratory burst induced by opsonized zymosan in a dose-dependent manner. Nuclear (17-β-Estradiol) and GPR30 cell membrane (G1) estrogen receptor agonists and their antagonists (ICI 182,780 and G15, respectively) do not block or reproduce the effect of TX. Therefore, TX does not inhibit respiratory burst through estrogen receptors. TX (8.5μM) also increased phosphatidylserine translocation, a marker of early apoptosis, which did not occur with any of the estrogen receptor agonists or antagonists. Thus, tamoxifen generates dose-dependent inhibition of respiratory burst and increased early apoptosis in healthy equine neutrophils, independently of nuclear or membrane estrogen receptors. Further studies are necessary to explore the signaling pathways of tamoxifen-induced ROS inhibition and phosphatidylserine translocation.

Sequence variant analysis of RNA sequences in severe equine asthma.

BackgroundSevere equine asthma is a chronic inflammatory disease of the lung in horses similar to low-Th2 late-onset asthma in humans. This study aimed to determine the utility of RNA-Seq to call gene sequence variants, and to identify sequence variants of potential relevance to the pathogenesis of asthma.MethodsRNA-Seq data were generated from endobronchial biopsies collected from six asthmatic and seven non-asthmatic horses before and after challenge (26 samples total). Sequences were aligned to the equine genome with Spliced Transcripts Alignment to Reference software. Read preparation for sequence variant calling was performed with Picard tools and Genome Analysis Toolkit (GATK). Sequence variants were called and filtered using GATK and Ensembl Variant Effect Predictor (VEP) tools, and two RNA-Seq predicted sequence variants were investigated with both PCR and Sanger sequencing. Supplementary analysis of novel sequence variant selection with VEP was based on a score of <0.01 predicted with Sorting Intolerant from Tolerant software, missense nature, location within the protein coding sequence and presence in all asthmatic individuals. For select variants, effect on protein function was assessed with Polymorphism Phenotyping 2 and screening for non-acceptable polymorphism 2 software. Sequences were aligned and 3D protein structures predicted with Geneious software. Difference in allele frequency between the groups was assessed using a Pearson’s Chi-squared test with Yates’ continuity correction, and difference in genotype frequency was calculated using the Fisher’s exact test for count data.ResultsRNA-Seq variant calling and filtering correctly identified substitution variants in PACRG and RTTN. Sanger sequencing confirmed that the PACRG substitution was appropriately identified in all 26 samples while the RTTN substitution was identified correctly in 24 of 26 samples. These variants of uncertain significance had substitutions that were predicted to result in loss of function and to be non-neutral. Amino acid substitutions projected no change of hydrophobicity and isoelectric point in PACRG, and a change in both for RTTN. For PACRG, no difference in allele frequency between the two groups was detected but a higher proportion of asthmatic horses had the altered RTTN allele compared to non-asthmatic animals.DiscussionRNA-Seq was sensitive and specific for calling gene sequence variants in this disease model. Even moderate coverage (<10–20 counts per million) yielded correct identification in 92% of samples, suggesting RNA-Seq may be suitable to detect sequence variants in low coverage samples. The impact of amino acid alterations in PACRG and RTTN proteins, and possible association of the sequence variants with asthma, is of uncertain significance, but their role in ciliary function may be of future interest.

Equine asthma: Integrative biologic relevance of a recently proposed nomenclature.

The term “equine asthma” has been proposed as a unifying descriptor of inflammatory airway disease (IAD), recurrent airway obstruction (RAO), and summer pasture‐associated obstructive airway disease. Whilst the term will increase comprehensibility for both the lay and scientific communities, its biologic relevance must be compared and contrasted to asthma in human medicine, recognizing the limited availability of peer‐reviewed equine‐derived data, which are largely restricted to clinical signs, measures of airway obstruction and inflammation and response to therapy. Such limitations constrain meaningful comparisons with human asthma phenotypes. Suggested minimum inclusion criteria supporting the term asthma, as well as similarities and differences between IAD, RAO, and multiple human asthma phenotypes are discussed. Furthermore, differences between phenotype and severity are described, and typical features for equine asthma subcategories are proposed. Based on shared features, we conclude that mild/moderate (IAD) and severe (RAO) equine asthma are biologically appropriate models for both allergic and non‐allergic human asthma, with RAO (severe equine asthma) also being an appropriate model for late‐onset asthma. With the development of new biologic treatments in humans and the application of more targeted therapeutic approaches in the horse, it would appear appropriate to further investigate the allergic (Th‐2) and non‐allergic (non‐Th‐2) phenotypes of equine asthma. Further research is required to more fully determine the potential clinical utility of phenotype classification.

EQTL discovery and their association with severe equine asthma in European Warmblood horses

BackgroundSevere equine asthma, also known as recurrent airway obstruction (RAO), is a debilitating, performance limiting, obstructive respiratory condition in horses that is phenotypically similar to human asthma. Past genome wide association studies (GWAS) have not discovered coding variants associated with RAO, leading to the hypothesis that causative variant(s) underlying the signals are likely non-coding, regulatory variant(s). Regions of the genome containing variants that influence the number of expressed RNA molecules are expression quantitative trait loci (eQTLs). Variation associated with RAO that also regulates a gene’s expression in a disease relevant tissue could help identify candidate genes that influence RAO if that gene’s expression is also associated with RAO disease status.ResultsWe searched for eQTLs by analyzing peripheral blood mononuclear cells (PBMCs) from two half-sib families and one unrelated cohort of 82 European Warmblood horses that were previously treated in vitro with: no stimulation (MCK), lipopolysaccharides (LPS), recombinant cyathostomin antigen (RCA), and hay-dust extract (HDE). We identified high confidence eQTLs that did not violate linear modeling assumptions and were not significant due to single outlier individuals. We identified a mean of 4347 high confidence eQTLs in four treatments of PBMCs, and discovered two trans regulatory hotspots regulating genes involved in related biological pathways. We corroborated previous RAO associated single nucleotide polymorphisms (SNPs), and increased the resolution of past GWAS by analyzing 1,056,195 SNPs in 361 individuals. We identified four RAO-associated SNPs that only regulate gene expression of dexamethasone-induced protein (DEXI), however we found no significant association between DEXI gene expression and presence of RAO.ConclusionsThousands of genetic variants regulate gene expression in PBMCs of European Warmblood horses in cis and trans. Most high confidence eSNPs are significantly enriched near the transcription start sites of their target genes. Two trans regulatory hotspots on chromosome 11 and 13 regulate many genes involved in transmembrane cell signaling and neurological development respectively when PBMCs are treated with HDE. None of the top fifteen RAO associated SNPs strongly influence disease status through gene expression regulation.

Tumor necrosis factor-alpha protein concentrations in bronchoalveolar lavage fluid from healthy horses and horses with severe equine asthma

The objective of this study was to determine if TNF-α protein concentration differs in bronchoalveolar lavage fluid (BALF) obtained from healthy horses, horses with naturally occurring exacerbations of severe equine asthma and horses in remission from severe equine asthma. Tumor necrosis factor-alpha (TNF- α) protein concentrations were determined in BALF by commercial equine ELISA. Horses with naturally occurring exacerbation of severe equine asthma were found to have significantly lower BALF TNF-α protein concentrations than healthy horses (p = 0.0026). There was no significant difference in BALF TNF-α concentration between horses in exacerbation and remission from disease, but there was a decrease in median TNF-α concentration between healthy horses and horses with clinical exacerbation of severe equine asthma. These findings suggest, that similar to human asthma, the role of TNF-α in chronic lower airway inflammation of horses may differ between disease phenotypes and disease state. Furthermore, the method with which TNF-α is measured (mRNA expression vs. protein concentration) may affect results when studying the role of TNF-α in horses with severe equine asthma.

Effects of magnesium sulfate infusion on clinical signs and lung function of horses with severe asthma.

OBJECTIVE To evaluate whether MgSO4 solution administered IV would improve the clinical signs and lung function of horses with severe asthma and potentiate the effects of salbutamol inhalation in those horses. ANIMALS 6 adult horses with severe asthma. PROCEDURES Asthmatic horses were used in 3 crossover design experiments (6 treatments/horse). Clinical scores for nasal flaring and the abdominal component associated with breathing and lung function were determined before and after administration of salbutamol (800 μg, by inhalation), MgSO4 solution (2.2 mg/kg/min, IV, over 20 minutes), and combined MgSO4-salbutamol treatment. The data were collected during experimental procedures to assess salbutamol inhalation versus mock inhalation, MgSO4 infusion versus infusion of saline (NaCl) solution (adjusted to the same osmolarity as the MgSO4 solution), and the combined MgSO4-salbutamol treatment versus salbutamol inhalation alone. RESULTS Infusion of MgSO4 significantly improved clinical scores when administered alone or in combination with salbutamol inhalation. With the combination treatment, lung function improved, albeit not significantly. Tidal volume also increased following combined MgSO4-salbutamol treatment. Salbutamol alone significantly improved lung function, whereas saline solution administration and a mock inhalation procedure had no effect on the studied variables. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that MgSO4 infusion alone or in combination with salbutamol inhalation improved the clinical signs of severely asthmatic horses. The effects of MgSO4 were not associated with significant lung function improvement, which suggested that the changes observed were attributable to alterations in the horses' breathing patterns. Infusion of MgSO4 solution at the studied dose offers little advantage over currently used medications for the treatment of severe equine asthma.

Glucocorticosteroids administration is associated with increased regulatory T cells in equine asthmatic lungs

Recurrent inflammation in severe equine asthma causes a remodeling of the airways leading to incompletely reversible airway obstruction. Despite the improvement of clinical signs and lung function with glucocorticoids (GC), inflammation, translated by an increased percentage of neutrophils, persists in the airways. Regulatory T cells (Treg) have been shown to have anti-inflammatory properties and play an important role in balancing the immune response by suppressing effector lymphocyte activity. However, interactions between Treg, neutrophils and glucocorticosteroids in vivo are unclear, particularly in asthma. Furthermore, the effects of GC on Treg in the airway of asthmatic horses have not been investigated. We hypothesized that horses with severe asthma display a decreased population of pulmonary Treg when compared to heathy controls, and that treatment with GC lead to an increased pulmonary Treg cell population only in affected horses. Using lung function measurements and flow cytometry with surface antigens CD4 and FoxP3, we investigated Treg in airway luminal cells obtained by bronchoalveolar lavage fluid (BALF) from 6 asthmatic horses in exacerbation of the disease and 6 aged-match controls, kept in the same environment, before and following a 2-week treatment with dexamethasone. Results showed that the number of Treg increases only in the lungs of asthmatic horses following GC therapy, despite continued presence of increased numbers of neutrophils. Our results support the complexity of the interaction between Treg, neutrophils and GC.

In an Adult Horse With Severe Asthma (Previously Recurrent Airway Obstruction) Does Using Inhaled Corticosteroids Result in an Equal Improvement in Clinical Signs When Compared to Systemic Corticosteroids?

&lt;strong&gt;PICO question&lt;/strong&gt;&lt;br /&gt;&lt;p&gt;In an adult horse with severe asthma (previously recurrent airway obstruction (RAO)) does using inhaled corticosteroids result in an equal improvement in clinical signs when compared to systemic corticosteroids?&lt;/p&gt;&lt;strong&gt;Clinical bottom line&lt;/strong&gt;&lt;br /&gt;&lt;p&gt;The level of confidence in the outcomes from the body of evidence in the 4 papers identified is high. This suggests inhaled corticosteroids (fluticasone and beclomethasone) when used at an appropriate dose can have equivalent effects on severe equine asthma as systemic intravenous dexamethasone. Inhaled corticosteroids can take longer to have the desired effects. &lt;/p&gt;&lt;br /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/oa-icon.jpg" alt="Open Access" /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/pr-icon.jpg" alt="Peer Reviewed" /&gt;

Phagocytosis, bacterial killing, and cytokine activation of circulating blood neutrophils in horses with severe equine asthma and control horses.

OBJECTIVE To evaluate in vitro phagocytosis and bactericidal activity of circulating blood neutrophils in horses with severe equine asthma and control horses and to determine whether circulating blood neutrophils in horses with severe equine asthma have an increase in expression of the proinflammatory cytokine tumor necrosis factor (TNF)-α and the chemokine interleukin (IL)-8 and a decrease in expression of the anti-inflammatory cytokine IL-10 in response to bacteria. ANIMALS 6 horses with severe equine asthma and 6 control horses. PROCEDURES Circulating blood neutrophils were isolated from horses with severe equine asthma and control horses. Phagocytosis was evaluated by use of flow cytometry. Bactericidal activity of circulating blood neutrophils was assessed by use of Streptococcus equi and Streptococcus zooepidemicus as targets, whereas the cytokine mRNA response was assessed by use of a quantitative PCR assay. RESULTS Circulating blood neutrophils from horses with severe equine asthma had significantly lower bactericidal activity toward S zooepidemicus but not toward S equi, compared with results for control horses. Phagocytosis and mRNA expression of TNF-α, IL-8, and IL-10 were not different between groups. CONCLUSIONS AND CLINCAL RELEVANCE Impairment of bactericidal activity of circulating blood neutrophils in horses with severe equine asthma could contribute to an increased susceptibility to infections.

Utility of the Histological Examination of the Bronchial Mucosa in the Diagnosis of Severe Equine Asthma Syndrome in Horses

The severe equine asthma syndrome is one of the most common respiratory problems in older horses. Although epithelial damage and basement membrane thickening are well-known features of airway remodeling in human asthma, pathological features of the bronchial mucosa and their value in the diagnosis of severe equine asthma syndrome are poorly characterized. Therefore, we wanted to determine if classic histologic features characterizing equine asthma are clinically useful. Thirty horses with severe equine asthma and 10 healthy animals were evaluated. A clinical examination, complete blood count, serum chemistry, endoscopic examination, and bronchoalveolar lavage were performed in all the horses. During the bronchoscopy of each horse, three or more biopsies were obtained from either the right or the left first segmental bronchus. The samples were assessed with respect to the surface epithelium, lamina propria, smooth muscle, glands, type of inflammation, and hyperemia. There was a significant difference (P < .05) in all clinical variables between the control and study groups. The horses included in the study group had a mean clinical score of 5.06, wherein the mean clinical score for the control group was 0.7. Cough, nostril flare, and abdominal lift were the components that had the most significant impact on the clinical score. The statistical analysis revealed no statistically significant differences for any histologic variables in the two groups. A classic histological assessment of an endobronchial biopsy is insufficient to differentiate horses with asthma from healthy horses and appears to be less sensitive than the clinical assessment.

Effect of lipopolysaccharide on the responsiveness of equine bronchial tissue

Recurrent airway obstruction (RAO) is a main characteristic of horses with severe equine asthma syndrome. The presence of bacterial lipopolysaccharide (LPS) in the airways of horses is thought to play a crucial role in the clinical expression of this disorder. This study pharmacologically characterized the effect of LPS on the responsiveness of equine bronchial tissue. Equine isolated bronchi were incubated overnight with LPS (0.1–100 ng/ml) and then stimulated by electrical field stimulation (EFS). The role of capsaicin sensitive-sensory nerves (capsaicin desensitization treatment), neurokinin-2 (NK2) receptors (blocked by GR159897), transient receptor potential vanilloid type 1 receptors (TRPV1; blocked by SB366791), and neurokinin A (NKA) were investigated. Untreated bronchi were used as control tissues. LPS (1 ng/ml) significantly increased the EFS-evoked contractility of equine bronchi compared with control tissues (+742 ± 123 mg; P < 0.001). At higher concentrations LPS induced desensitization to airways hyperresponsiveness (AHR; EC50: 5.9 ± 2.6 ng/ml). Capsaicin desensitization and GR159897 significantly prevented AHR induced by LPS at EFS1–50Hz (−197 ± 25%; P < 0.01). SB366791 inhibited AHR at very low EFS frequency (EFS1Hz −193 ± 29%; P < 0.01 vs. LPS-treated bronchi). LPS (1 ng/ml) significantly (P < 0.01) increased 3.7 ± 0.7 fold the release of NKA compared with control bronchi. LPS induces biphasic dysfunctional bronchial contractility due to the stimulation of capsaicin sensitive-sensory nerves, increased release of NKA, and activation of NK2 receptors, whereas TRPV1 receptors appear to play a marginal role in this response. The overnight challenge with low concentrations of LPS represents a suitable model to investigate pharmacological options that may be of value in the treatment of equine RAO.

Influence of bronchoalveolar lavage on thoracic radiography in the horse.

Bronchoalveolar lavage (BAL) and thoracic radiography are routinely performed diagnostic procedures. We hypothesized that BAL increases the interstitial opacity of caudoventral and caudodorsal thoracic radiographs. Fifty-three horses, including 8 clinic owned and 45 from a referral hospital population, were classified as healthy controls (n = 12), severe equine asthma (recurrent airway obstruction, n = 12) or mild-to-moderate equine asthma (inflammatory airway disease, n = 21) based on the results of a clinical scoring system. Eight were excluded due to different diagnoses and poor image quality. Four randomized thoracic radiographs of each horse were scored by two blinded observers, who were also asked to identify the image as obtained before or after a BAL procedure. In severe equine asthma, the chance (adjusted odds) of misinterpretation of the correct imaging time was approximately 5 times higher than in controls (odds ratio [OR] = 5.373, p = 0.028). The chance of misinterpretation was approximately 4 times lower in caudodorsal images than in caudoventral projections (OR = 0.241, p = 0.004). Identification of the correct imaging time was highly correlated with an increase in interstitial opacity (OR = 9.976, p < 0.0001). In conclusion, we recommend performing BAL after thoracic radiography to avoid possible misinterpretation.

Horses With Pasture Asthma Have Airway Remodeling That Is Characteristic of Human Asthma.

Severe equine asthma, formerly recurrent airway obstruction (RAO), is the horse counterpart of human asthma, affecting horses maintained indoors in continental climates. Equine pasture asthma, formerly summer pasture RAO, is clinically similar but affects grazing horses during hot, humid conditions in the southeastern United States and United Kingdom. To advance translational relevance of equine pasture asthma to human asthma, histologic features of airway remodeling in human asthma were scored in lung lobes from 15 pasture asthma-affected and 9 control horses of mixed breeds. All noncartilaginous airways were scored using a standardized grading rubric (0-3) in hematoxylin and eosin (HE) and Movat's pentachrome-stained sections; 15 airways were chosen randomly from each lobe for analysis. Logistic regression identified disease, age, and lobe effects on probability of histologic outcomes. Airway smooth muscle (odds ratio [OR] = 2.5, P < .001), goblet cell hyperplasia/metaplasia (OR = 37.6, P < .0001), peribronchiolar elastic system fibers (OR = 4.2, P < .001), peribronchiolar fibrosis (OR = 3.8, P = .01), airway occlusion by mucus/inflammation (OR = 4.2, P = .04), and airway adventitial inflammation (OR = 3.0, P = .01) were significantly greater in diseased airways. A novel complex tissue disorganization, designated terminal bronchiolar remodeling, was overrepresented in diseased airways (OR = 3.7, P < .0001). Distribution of terminal bronchiolar remodeling corresponded to putative sites of air trapping in human asthma, at secondary pulmonary lobules. Age (>15 years) was an independent risk factor for increased peribronchiolar fibrosis, elastic system fibers, and terminal bronchiolar remodeling. Remodeling differed significantly between lung lobes, congruent with nonhomogeneous remodeling in human asthma. Equine pasture asthma recapitulates airway remodeling in human asthma in a manner not achieved in induced animal asthma models, endorsing its translational relevance for human asthma investigation.

Differential Expression of Serum MicroRNAs Supports CD4⁺ T Cell Differentiation into Th2/Th17 Cells in Severe Equine Asthma.

MicroRNAs (miRNAs) regulate post-transcriptional gene expression and may be exported from cells via exosomes or in partnership with RNA-binding proteins. MiRNAs in body fluids can act in a hormone-like manner and play important roles in disease initiation and progression. Hence, miRNAs are promising candidates as biomarkers. To identify serum miRNA biomarkers in the equine model of asthma we investigated small RNA derived from the serum of 34 control and 37 asthmatic horses. These samples were used for next generation sequencing, novel miRNA identification and differential miRNA expression analysis. We identified 11 significantly differentially expressed miRNAs between case and control horses: eca-miR-128, eca-miR-744, eca-miR-197, eca-miR-103, eca-miR-107a, eca-miR-30d, eca-miR-140-3p, eca-miR-7, eca-miR-361-3p, eca-miR-148b-3p and eca-miR-215. Pathway enrichment using experimentally validated target genes of the human homologous miRNAs showed a significant enrichment in the regulation of epithelial-to-mesenchymal transition (key player in airway remodeling in asthma) and the phosphatidylinositol (3,4,5)-triphosphate (PIP3) signaling pathway (modulator of CD4+ T cell maturation and function). Downregulated miR-128 and miR-744 supports a Th2/Th17 type immune response in severe equine asthma.

Impaired response of the bronchial epithelium to inflammation characterizes severe equine asthma

BackgroundSevere equine asthma is a naturally occurring lung inflammatory disease of mature animals characterized by neutrophilic inflammation, bronchoconstriction, mucus hypersecretion and airway remodeling. Exacerbations are triggered by inhalation of dust and microbial components. Affected animals eventually are unable of aerobic performance. In this study transcriptomic differences between asthmatic and non-asthmatic animals in the response of the bronchial epithelium to an inhaled challenge were determined.ResultsPaired endobronchial biopsies were obtained pre- and post-challenge from asthmatic and non-asthmatic animals. The transcriptome, determined by RNA-seq and analyzed with edgeR, contained 111 genes differentially expressed (DE) after challenge between horses with and without asthma, and 81 of these were upregulated. Genes involved in neutrophil migration and activation were in central location in interaction networks, and related gene ontology terms were significantly overrepresented. Relative abundance of specific gene products as determined by immunohistochemistry was correlated with differential gene expression. Gene sets involved in neutrophil chemotaxis, immune and inflammatory response, secretion, blood coagulation and apoptosis were overrepresented among up-regulated genes, while the rhythmic process gene set was overrepresented among down-regulated genes. MMP1, IL8, TLR4 and MMP9 appeared to be the most important proteins in connecting the STRING protein network of DE genes.ConclusionsSeveral differentially expressed genes and networks in horses with asthma also contribute to human asthma, highlighting similarities between severe human adult and equine asthma. Neutrophil activation by the bronchial epithelium is suggested as the trigger of the inflammatory cascade in equine asthma, followed by epithelial injury and impaired repair and differentiation. Circadian rhythm dysregulation and the sonic Hedgehog pathway were identified as potential novel contributory factors in equine asthma.

Fluticasone/salmeterol reduces remodelling and neutrophilic inflammation in severe equine asthma

Asthmatic airways are inflamed and undergo remodelling. Inhaled corticosteroids and long-acting β2-agonist combinations are more effective than inhaled corticosteroid monotherapy in controlling disease exacerbations, but their effect on airway remodelling and inflammation remains ill-defined. This study evaluates the contribution of inhaled fluticasone and salmeterol, alone or combined, to the reversal of bronchial remodelling and inflammation. Severely asthmatic horses (6 horses/group) were treated with fluticasone, salmeterol, fluticasone/salmeterol, or with antigen avoidance for 12 weeks. Lung function, central and peripheral airway remodelling, and bronchoalveolar inflammation were assessed. Fluticasone/salmeterol and fluticasone monotherapy decreased peripheral airway smooth muscle remodelling after 12 weeks (p = 0.007 and p = 0.02, respectively). On average, a 30% decrease was observed with both treatments. In central airways, fluticasone/salmeterol reversed extracellular matrix remodelling after 12 weeks, both within the lamina propria (decreased thickness, p = 0.005) and within the smooth muscle layer (p = 0.004). Only fluticasone/salmeterol decreased bronchoalveolar neutrophilia (p = 0.03) to the same extent as antigen avoidance already after 8 weeks. In conclusion, this study shows that fluticasone/salmeterol combination decreases extracellular matrix remodelling in central airways and intraluminal neutrophilia. Fluticasone/salmeterol and fluticasone monotherapy equally reverse peripheral airway smooth muscle remodelling.

Characterization of Circulating Low-Density Neutrophils Intrinsic Properties in Healthy and Asthmatic Horses

Low-density neutrophils (LDNs) are a subset of neutrophils first described in the bloodstream upon pathological conditions, and recently, in the blood of healthy humans. LDNs may have an enhanced pro-inflammatory (low-density granulocytes, LDGs) or an immunosuppressive (Granulocytic myeloid-derived suppressor cells, G-MDSCs) profile. Whether these characteristics are specific to LDNs or related to disease states is unknown. Thus, we sought to investigate the properties of LDNs in both health and disease states, and to compare them to those of autologous normal-density neutrophils (NDNs). We studied 8 horses with severe equine asthma and 11 healthy animals. LDNs were smaller and contained more N-formylmethionine-leucyl-phenylalanine receptors than NDNs, but the myeloperoxidase content was similar in both cell populations. They also had an increased capacity to produce neutrophil extracellular traps, and were more sensitive to activation by phorbol-12-myristate-13-acetate. This profile is suggestive of LDGs. These characteristics were similar in both healthy and diseased animals, indicating that these are intrinsic properties of LDNs. Furthermore, these results suggest that LDNs represent a population of primed and predominantly mature cells. This study is the first to characterize LDNs in health, and to compare their properties with those of NDNs and of animals with a naturally occurring disease.

Age associated changes in peripheral airway smooth muscle mass of healthy horses

Peripheral airway smooth muscle (ASM) mass is increased in severe equine asthma, but no information is available on age related changes in ASM. In this study, peripheral ASM dimensions were determined in healthy horses of different ages. The thickness of the peripheral ASM layer was constant in horses of different ages, but ASM occupied a greater proportion of the inner wall area in young horses compared to older horses. This finding suggests that equine airways experience a decrease in the relative abundance of ASM with age.

Severe equine asthma — an overview

Severe equine asthma (EA) is the newly adopted term which defines the syndromes most recently known as recurrent airway obstruction (RAO; syn chronic obstructive pulmonary disease, Heaves) or summer pasture associated recurrent airway obstruction (SPARAO; syn summer pasture associated obstructive pulmonary disease). The adoption of this new nomenclature recognises the clinical phenotypic overlap amongst various non-infectious diseases of the equine lower airways; most notably between severe EA and mild to moderate EA (previously termed inflammatory airway disease). Compared with mild to moderate EA, there is a greater appreciation of the role of genetics in determining susceptibility to severe EA and a better understanding of aetiological triggers and disease pathogenesis. However, despite the relatively well defined clinical phenotype of severe EA, it is increasingly apparent that a significant degree of heterogeneity exists with respect to the susceptibility determinants and underlying immunological mechanisms which ultimately lead to clinical disease.

Mild to moderate equine asthma — an overview

Mild to moderate equine asthma (EA) is the newly adopted term which defines the syndrome previously known as inflammatory airway disease (IAD). The adoption of this new nomenclature recognises the clinical phenotypic overlap amongst various non-infectious diseases of the equine lower airways; most notably between mild to moderate EA and severe EA (previously termed recurrent airway obstruction (RAO)). Despite the high prevalence of mild to moderate EA, particularly within certain horse populations, there remain significant gaps in knowledge, especially with respect to aetiological triggers and pathogenesis, both significant determinants of appropriate therapeutic and prophylactic approaches.