Efficacy of three corticosteroids for the treatment of heaves

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.

Inhalative Nanoparticulate CpG Immunotherapy in Severe Equine Asthma: An Innovative Therapeutic Concept and Potential Animal Model for Human Asthma Treatment

Simple Summary

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory DNA sequences (CpG) bound to nanoparticles were successfully administered by inhalation to severe asthmatic horses in several studies. It was possible to demonstrate a significant, sustained, one-to-eight-week improvement in important clinical parameters: partial oxygen pressure in the blood, quantity and viscosity of tracheal mucus secretion in the airways, and the amount of inflammatory cells in the respiratory tracts of severe asthmatic horses. The immunotherapy with CpG is performed independent of specific allergens. At an immunological level, the treatment leads to decreases in allergic and inflammatory parameters. This innovative therapeutic concept thus opens new perspectives in severe equine asthma treatment and possibly also in human asthma treatment.

Abstract

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory CpG-ODN, bound to gelatin nanoparticles as a drug delivery system, were successfully administered by inhalation to severe equine asthmatic patients in several studies. It was possible to demonstrate a significant, sustained, and allergen-independent one-to-eight-week improvement in key clinical parameters: the arterial partial pressure of oxygen, the quantity and viscosity of tracheal mucus, and neutrophilic inflammatory cells in the respiratory tracts of the severe equine asthmatic subjects. At the immunological level, an upregulation of the regulatory antiallergic and anti-inflammatory cytokine IL-10 as well as a downregulation of the proallergic IL-4 and proinflammatory IFN-γ in the respiratory tracts of the severe equine asthmatic patients were identified in the treatment groups. CD4⁺ T lymphocytes in the respiratory tracts of the asthmatic horses were demonstrated to downregulate the mRNA expression of Tbet and IL-8. Concentrations of matrix metalloproteinase-2 and -9 and tissue inhibitors of metalloproteinase-2 were significantly decreased directly after the treatment as well as six weeks post-treatment. This innovative therapeutic concept thus opens new perspectives in the treatment of severe equine asthma and possibly also that of human asthma.

Glucocorticoid treatment in horses with asthma: A narrative review

Despite substantial research efforts to improve the treatment and outcome of horses with asthma, glucocorticoids (GC) remain the cornerstone of drug treatment of this prevalent disease. The high efficacy of GC to relieve airway obstruction explains their extensive use despite potential deleterious effects. However, much is yet to be uncovered concerning GC use in horses with asthma, including the comparative efficacy of the different drugs, the determination of minimal effective doses and the mechanisms underlying their variable modulation of airway inflammation. The objectives of this structured review were to report and compare the plethora of effects of the various GC used in asthmatic horses with a focus on impact on lung function, airway inflammation, and bronchial remodeling. Adverse effects are also briefly described, with an emphasis on those that have been specifically reported in horses with asthma. Ultimately, we aimed to highlight gaps in the literature and to identify future research areas.

Inhaled ciclesonide is efficacious and well tolerated in the treatment of severe equine asthma in a large prospective European clinical trial

Background

Ciclesonide is a glucocorticoid prodrug, already registered for human use. Due to its mode of action and inhaled route of administration, it was considered an appropriate treatment option for horses with severe equine asthma. Although the efficacy of inhaled ciclesonide has been demonstrated in horses with asthma exacerbations under controlled mouldy hay challenge conditions, it has not yet been reported under field conditions.

Objectives

To assess the effectiveness and safety of inhaled ciclesonide for the treatment of severe equine asthma.

Study design

Prospective, multicentre, placebo‐controlled, randomised, double‐blinded study.

Methods

Two‐hundred and twenty‐four client‐owned horses with severe equine asthma were randomised (1:1 ratio) to receive either ciclesonide inhalation (343 µg/actuation) solution or placebo (0 µg/actuation). Treatments (placebo or ciclesonide) were administered with a nonpressurised Soft Mist™ inhaler specifically developed for horses (Aservo^® EquiHaler^®) at doses of 8 actuations twice daily for the first 5 days and 12 actuations once daily for the following 5 days. Primary outcome was a success/failure analysis with the a priori definition of treatment success as a 30% or greater reduction in weighted clinical score (WCS) between Day 0 and Day 10 (±1).

Results

The treatment success rate (as defined above) in ciclesonide‐treated horses was 73.4% (80/109) after 10 (±1) days of treatment, being significantly higher than in the placebo group with 43.2% (48/111; P < 0.0001). Few systemic and local adverse events of ciclesonide were observed.

Main limitations

The severity of clinical signs of severe equine asthma varies over time; despite the prohibition of environmental management changes during the study, a placebo effect was also identified. This potentially contributed, in part, to the clinical improvement observed in the ciclesonide‐treated group.

Conclusions

Ciclesonide inhalation solution administered by the Aservo^® EquiHaler^® effectively reduced severity of clinical signs in a majority of horses with severe equine asthma and was well tolerated.

Modulation of TNF-α, IL-1Ra and IFN-γ in equine whole blood culture by glucocorticoids

Glucocorticoids are important drugs in the treatment of many inflammatory, autoimmune and allergic diseases in humans and animals. We investigated the effects of hydrocortisone and dexamethasone on TNF-α, IL-1Ra and INF-γ release in stimulated whole blood cell culture from healthy horses. Whole blood cell cultures proved to be useful for the characterization of the anti-inflammatory properties of new drugs. Diluted equine whole blood was exposed to lipopolysaccharide (LPS) and PCPwL (a cocktail consisting of phythemagglutinin E, concanavalin A, pokeweed mitogen and lipopolysaccharide) in the presence or absence of hydrocortisone and dexamethasone (10^-12 - 10^-5 M). TNF-α and IL-1Ra (LPS) as well as IFN-γ (PCPwL) levels were measured in the supernatants using specific enzyme-linked immunosorbent assay (ELISA). The LPS-induced TNF-α and IL-1Ra as well as the PCPwL-induced IFN-γ levels were more potently suppressed by dexamethasone than by hydrocortisone in a concentration-dependent manner. Dexamethasone inhibited TNF-α, IL-1Ra and IFN-γ with the half maximal inhibition concentration (IC₅₀) values of 0.09 μM, 0.453 μM and 0.001 μM, respectively, whereas hydrocortisone inhibited these cytokines with lower IC₅₀ values of 1.45 μM, 2.96 μM and 0.09 μM, respectively. Our results suggest that the equine whole blood test system is useful and reliable to evaluate drug effects and immunological alterations and offers several advantages including simple and cheap performance in physiological and pathological conditions.

Efficacy of inhaled budesonide for the treatment of severe equine asthma

Background

Corticosteroids are the most potent drugs for the control of severe equine asthma, but adverse effects limit their chronic systemic administration. Inhaled medications allow for drug delivery directly into the airways, reducing the harmful effects of these drugs.

Objectives

To evaluate the efficacy of inhaled budesonide specifically formulated for the equine use and administered by a novel inhalation device in horses with severe asthma.

Study design

Experimental studies in horses with naturally occurring asthma with cross‐over, randomised, blinded experimental designs.

Methods

In Study 1, budesonide (1800 μg twice daily) administered using a novel Respimat^® based inhaler was compared to i.v. dexamethasone (0.04 mg/kg). In Study 2, 3 doses of budesonide (450, 900, and 1800 μg) were compared to oral dexamethasone (0.066 mg/kg). Lung function, bronchoalveolar fluid cytology (Study 1), CBC, serum chemistry, and serum cortisol and adrenocorticotropic hormone (ACTH) values were evaluated.

Results

In Study 1, there was a marked and significant improvement in the lung function of all horses treated with budesonide and dexamethasone. Neutrophil percentages in bronchoalveolar fluid decreased in all horses treated with dexamethasone and in four of six horses treated with budesonide. Serum cortisol and blood ACTH concentrations decreased with both treatments. In Study 2, there was a significant improvement in the lung function with all dosages of budesonide, and the effects of higher dosages were comparable to those of dexamethasone. Dexamethasone and budesonide at the two higher dosages induced a significant decrease of cortisol concentrations.

Main limitations

The Respimat^® based inhaler is not currently commercially available.

Conclusions

Administration of budesonide with the Respimat^® based inhaler provided dose‐dependent relief of airway obstruction in horses with severe asthma, but also a suppression of serum cortisol.

Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses

BACKGROUND

Nebulisation of the injectable dexamethasone sodium phosphate (DSP) would offer an inexpensive way of delivering a potent corticosteroid directly to the lungs of horses with asthma. However, this approach would be advantageous only if systemic absorption is minimal and if the preservatives present in the formulation do not induce airway inflammation.

OBJECTIVE

To investigate the bioavailability of nebulised DSP and determine whether it induces airway inflammation or hypothalamic-pituitary-adrenal (HPA) axis suppression in healthy adult horses.

STUDY DESIGN

Randomised crossover experiment.

METHODS

Dexamethasone sodium phosphate was administered to six healthy adult horses at a dose of 5 mg q. 24 h for 5 days via nebulised, or intravenous (i.v.) routes. Plasma dexamethasone concentrations were measured by UPLC/MS-MS to calculate bioavailability. Cytological examination of bronchoalveolar fluid was performed at baseline and after the last dose of DSP. A validated chemiluminescent immunoassay was used to measure basal serum cortisol concentrations.

RESULTS

After nebulisation to adult horses, dexamethasone had a mean (±s.d.) maximum plasma concentration of 0.774 ± 0.215 ng/mL and systemic bioavailability of 4.3 ± 1.2%. Regardless of route of administration, there was a significant decrease in the percentage of neutrophils in bronchoalveolar lavage fluid over time. During i.v. administration, basal serum cortisol concentration decreased significantly from baseline to Day 3 and remained low on Day 5. In contrast, basal serum cortisol concentration did not change significantly during administration via nebulisation.

MAIN LIMITATIONS

Small sample size and short period of drug administration.

CONCLUSIONS

Dexamethasone sodium phosphate administered via nebulisation had minimal systemic bioavailability and did not induce lower airway inflammation or HPA axis suppression in healthy horses.

Corticosteroids and Immune Suppressive Therapies in Horses

Immune suppressive therapies target exaggerated and deleterious responses of the immune system. Triggered by exogenous or endogenous factors, these improper responses can lead to immune or inflammatory manifestations, such as urticaria, equine asthma, or autoimmune and immune-mediated diseases. Glucocorticoids are the most commonly used immune suppressive drugs and the only ones supported by robust evidence of clinical efficacy in equine medicine. In some conditions, combining glucocorticoids with other pharmacologic and nonpharmacologic treatments, such as azathioprine, antihistamine, bronchodilators, environmental management, or desensitization, can help to decrease dosages and associated side effects.

Effect of Dexamethasone and Fluticasone on Airway Hyperresponsiveness in Horses With Inflammatory Airway Disease

Background

Airway hyperresponsiveness (AWHR), expressed as hypersensitivity (PC₇₅R_L) or hyperreactivity (slope of the histamine dose‐response curve), is a feature of inflammatory airway disease (IAD) or mild equine asthma in horses. Glucocorticoids are used empirically to treat IAD.

Objectives

To determine whether dexamethasone (DEX) (0.05 mg/kg IM q24h) and inhaled fluticasone (FLUT) (3,000 μg q12h) administered by inhalation are effective in decreasing AWHR, lung inflammation, and clinical signs in horses with IAD.

Methods

A randomized crossover study design was used. Eight horses with IAD were assigned to a treatment group with either DEX or FLUT. Measured outcomes included lung mechanics during bronchoprovocative challenges, bronchoalveolar lavage fluid (BALF) cytology, and scoring of clinical signs during exercise.

Results

Dexamethasone and FLUT abolished the increase in R_L by 75% at any histamine bronchoprovocative dose in all horses after the first week of treatment. However, after 2 weeks of FLUT treatment, 1 horse redeveloped hypersensitivity. There was a significant decrease in the number of lymphocytes after treatment with both DEX and FLUT (P = .039 for both) but no significant differences in other BALF cell types or total cell counts (P > .05). There was no difference in the scoring of the clinical signs during each treatment and washout period (P > .05).

Conclusions and Clinical Importance

Both DEX and FLUT treatments significantly inhibit airway hypersensitivity and hyperreactivity in horses with IAD. There are no significant effects on the clinical signs or the number of inflammatory cells (except lymphocytes) in BALF. The treatments have no residual effect 3 weeks after discontinuation.

Pharmacological treatments in asthma-affected horses: A pair-wise and network meta-analysis

BACKGROUND

Equine asthma is a disease characterised by reversible airflow obstruction, bronchial hyper-responsiveness and airway inflammation following exposure of susceptible horses to specific airborne agents. Although clinical remission can be achieved in a low-airborne dust environment, repeated exacerbations may lead to irreversible airway remodelling. The available data on the pharmacotherapy of equine asthma result from several small studies, and no head-to-head clinical trials have been conducted among the available medications.

OBJECTIVES

To assess the impact of the pharmacological interventions in equine asthma and compare the effect of different classes of drugs on lung function.

STUDY DESIGN

Pair-wise and network meta-analysis.

METHODS

Literature searches for clinical trials on the pharmacotherapy of equine asthma were performed. The risk of publication bias was assessed by funnel plots and Egger's test. Changes in maximum transpulmonary or pleural pressure, pulmonary resistance and dynamic lung compliance vs. control were analysed via random-effects models and Bayesian networks.

RESULTS

The results obtained from 319 equine asthma-affected horses were extracted from 32 studies. Bronchodilators, corticosteroids and chromones improved maximum transpulmonary or pleural pressure (range: -8.0 to -21.4 cmH₂ O; P<0.001). Bronchodilators, corticosteroids and furosemide reduced pulmonary resistance (range: -1.2 to -1.9 cmH₂ O/L/s; P<0.001), and weakly increased dynamic lung compliance. Inhaled β₂ -adrenoreceptor (β₂ -AR) agonists and inhaled corticosteroids had the highest probability of being the best therapies. Long-term treatments were more effective than short-term treatments.

MAIN LIMITATIONS

Weak publication bias was detected.

CONCLUSIONS

This study demonstrates that long-term treatments with inhaled corticosteroids and long-acting β₂ -AR agonists may represent the first choice for treating equine asthma. Further high quality clinical trials are needed to clarify whether inhaled bronchodilators should be preferred to inhaled corticosteroids or vice versa, and to investigate the potential superiority of combination therapy in equine asthma.

Pulmonary Remodeling in Equine Asthma: What Do We Know about Mediators of Inflammation in the Horse?

Equine inflammatory airway disease (IAD) and recurrent airway obstruction (RAO) represent a spectrum of chronic inflammatory disease of the airways in horses resembling human asthma in many aspects. Therefore, both are now described as severity grades of equine asthma. Increasing evidence in horses and humans suggests that local pulmonary inflammation is influenced by systemic inflammatory processes and the other way around. Inflammation, coagulation, and fibrinolysis as well as extracellular remodeling show close interactions. Cytology of bronchoalveolar lavage fluid and tracheal wash is commonly used to evaluate the severity of local inflammation in the lung. Other mediators of inflammation, like interleukins involved in the chemotaxis of neutrophils, have been studied. Chronic obstructive pneumopathies lead to remodeling of bronchial walls and lung parenchyma, ultimately causing fibrosis. Matrix metalloproteinases (MMPs) are discussed as the most important proteolytic enzymes during remodeling in human medicine and increasing evidence exists for the horse as well. A systemic involvement has been shown for severe equine asthma by increased acute phase proteins like serum amyloid A and haptoglobin in peripheral blood during exacerbation. Studies focusing on these and further possible inflammatory markers for chronic respiratory disease in the horse are discussed in this review of the literature.

Intratracheal therapy with autologous bone marrow-derived mononuclear cells reduces airway inflammation in horses with recurrent airway obstruction

This research evaluated the effects of bone marrow-derived mononuclear cells (BMMCs) on the inflammatory process in the equine recurrent airway obstruction (RAO). Eight horses in RAO clinical score were divided into cell therapy group (Gcel) treated with a single intratracheal dose of BMMCs, and dexamethasone group (Gdex) treated with 21days of oral dexamethasone. The horses were clinically revaluated on days 7 and 21, together with cytological evaluation of the BALF, and detection of inflammatory markers (interleukins [IL]-10, -4, and -17, and interferon γ and α). There were decreases in respiratory effort and clinical score on days 7 and 21(p<0.05) for both groups. The percentage of neutrophils decreased and macrophages increased on days 7 and 21 (p<0.005) in both groups. IL-10 levels increased in the Gcel group on day 21 compared to days 0 and 7 (p<0.05), but this was not observed in the Gdex group. The quantification of IL-4, IL-17, IFN-γ, and IFN-α did not change between evaluations in both groups. These preliminary results suggest that BMMCs may ameliorate the inflammatory response of RAO.

Tamoxifen as a new therapeutic tool for neutrophilic lung inflammation

BACKGROUND AND OBJECTIVE

Neutrophilic asthma is an important disease subgroup, including patients with severe phenotypes and erratic responses to standard treatments. Tamoxifen (TX), a selective estrogen receptor modulator (SERM) used as treatment of human breast cancer, has been shown to induce early apoptosis of equine blood and bronchoalveolar lavage fluid (BALF) neutrophils in vitro. Equine recurrent airway obstruction (RAO) is a naturally occurring neutrophilic condition, closely related with human asthma. Our purpose was to investigate the therapeutic potential of tamoxifen in horses with neutrophilic lung inflammation.

METHODS

Twelve horses underwent acute lung inflammation through exposure to allergens known to cause RAO, after which they received treatment with either tamoxifen or dexamethasone. Outcome measures included evaluation of clinical signs, BALF cytology, and early apoptosis of blood and BALF neutrophils.

RESULTS

Tamoxifen treatment decreased BALF neutrophil counts (65.3 ± 19.38% before treatment; 7.6 ± 4.5% 2 days post-treatment,; and 13.6 ± 9.3% 5 days post-treatment). A similar decrease was observed with dexamethasone treatment (48.6 ± 5.88% before treatment; 11.5 ± 8.1% 2 days post-treatment; 14.6 ± 10.3% 5 days post-treatment). Clinical and endoscopic scores improved in both treatment groups. Tamoxifen treatment significantly increased early apoptosis of peripheral blood neutrophils at 5 days post-treatment (27.04 ± 15.2%), and in BALF neutrophils at 2 and 5 days post-treatment (42.11 ± 11.67% and 48.98 ± 2.6%, respectively).

CONCLUSION

Tamoxifen treatment in horses with induced acute pulmonary inflammation promoted early apoptosis of blood and BALF neutrophils, reduction in BALF neutrophils and improvement in the animals' clinical status.

Investigating the link between particulate exposure and airway inflammation in the horse

Inhalant exposure to airborne irritants commonly encountered in horse stables is implicated in the pathogenesis of inflammatory airway disease (IAD) and recurrent airway obstruction (RAO), non‐infectious, inflammatory pulmonary disorders that impact the health and performance of horses across all equine disciplines. IAD and RAO have overlapping clinical, cytological, and functional manifestations of the pulmonary response to organic dust and noxious gases encountered in the barn environment. Study of these diseases has provided important but incomplete understanding of the effect of air quality upon the respiratory health of horses. In this review, the principles of particulate exposure assessment, including health‐related aerosol size fractions and size‐selective sampling, the factors influencing air quality in equine environments, and the effect of air quality on the equine respiratory tract are discussed. The objective of this review is to provide the reader with a summary of the most common chronic inflammatory airway diseases in the horse and the principles of air sampling that are essential to the planning, interpretation, and assessment of equine respiratory health‐related exposure studies.

The genes of all seven CYP3A isoenzymes identified in the equine genome are expressed in the airways of horses

In the present study, we examined the gene expression of cytochrome P450 3A (CYP3A) isoenzymes in the tracheal and bronchial mucosa and in the lung of equines using TaqMan probes. The results show that all seven CYP3A isoforms identified in the equine genome, that is, CYP3A89, CYP3A93, CYP3A94, CYP3A95, CYP3A96, CYP3A97 and CYP3A129, are expressed in the airways of the investigated horses. Though in previous studies, CYP3A129 was found to be absent in equine intestinal mucosa and liver, this CYP3A isoform is expressed in the airways of horses. The gene expression of the CYP3A isoenzymes varied considerably between the individual horses studied. However, in most of the horses CYP3A89, CYP3A93, CYP3A96, CYP3A97 and CYP3A129 were expressed to a high extent, while CYP3A94 and CYP3A95 were expressed to a low extent in the different parts of the airways. The CYP3A isoenzymes present in the airways may play a role in the metabolic degradation of inhaled xenobiotics. In some instances, the metabolism may, however, result in bioactivation of the xenobiotics and subsequent tissue injury.

Owner assessment in judging the efficacy of airway disease treatment

REASONS FOR PERFORMING STUDY

Efficacy of medications for recurrent airway obstruction is typically tested using clinical, cytological and lung function examinations of severely affected animals. These trials are technically challenging and may not adequately reflect the spectrum of disease and owner complaints encountered in clinical practice.

OBJECTIVE

To determine if owners of horses with chronic airway disease are better able to detect drug efficacy than a veterinarian who clinically examines horses infrequently.

METHOD

In a double-blinded randomised controlled trial, owners and a veterinarian compared the efficacy of dexamethasone (0.1 mg/kg bwt per os, q. 24 h, for 3 weeks; n = 9) to placebo (n = 8) in horses with chronic airway disease. Before and after treatment, owners scored performance, breathing effort, coughing and nasal discharge using a visual analogue scale (VAS). The clinician recorded vital parameters, respiratory distress, auscultation findings, cough and nasal discharge, airway mucus score, bronchoalveolar lavage fluid (BALF) cytology and arterial blood gases.

RESULTS

The VAS score improved significantly in dexamethasone- but not placebo-treated horses. In contrast, the clinician failed to differentiate between dexamethasone- and placebo-treated animals based on clinical observations, BALF cytology or endoscopic mucus score. Respiratory rate (RR) and arterial oxygen pressure (PaO(2)) improved with dexamethasone but not placebo.

CONCLUSIONS AND CLINICAL RELEVANCE

In the design of clinical trials of airway disease treatments, more emphasis should be placed on owner-assessed VAS than on clinical, cytological and endoscopic observations made during brief examinations by a veterinarian. Quantifiable indicators reflecting lung function such as RR and PaO(2) provide a good assessment of drug efficacy.

Fluticasone propionate aerosol is more effective for prevention than treatment of recurrent airway obstruction

BACKGROUND

Efficacy of inhaled fluticasone propionate (FP) for management of recurrent airway obstruction (RAO) has only been evaluated after several weeks' treatment.

OBJECTIVES

To compare efficacy of (1) 3-day treatments with FP to dexamethasone (DEX) for management of RAO; and (2) FP and DEX to no treatment in prevention of acute RAO exacerbations.

ANIMALS

Nine RAO affected horses.

METHODS

Crossover studies in RAO-affected horses compared (a) 3-day treatment of RAO exacerbation with FP (3 and 6 mg q12h) and DEX (0.1 mg/kg q24h) and (b) FP (6 mg q12h) and DEX (0.1 mg/kg q24h) to no treatment for prevention of acute exacerbations of RAO. Treatment efficacy and unwanted effects were judged from maximal change in pleural pressure (DeltaPpl(max)), serum cortisol (COR), bronchoalveolar lavage (BAL) cytology, and subjective scores for respiratory distress and lameness.

RESULTS

In treatment trial, DEX and FP (6 mg) significantly decreased DeltaPpl(max) by 48 and 72 hours, respectively; FP (3 mg) had no significant effect. DEX decreased COR more than did FP. In prevention trial, both DEX and FP (6 mg) prevented the increase in DeltaPpl(max) that occurred in untreated horses. Both treatments decreased COR to the same degree. FP and DEX had no effects on bronchoalveolar lavage fluid (BALF) cytology and there was no evidence of laminitis.

CONCLUSIONS AND CLINICAL IMPORTANCE

FP (6 mg q12h) is as effective as DEX for prevention of acute exacerbations of RAO and lower doses should be evaluated. High-dose FP is not as effective as DEX for treatment of RAO exacerbations.

Characterization of alpha(4)beta(1) (CD49d/CD29) on equine leukocytes: potential utility of a potent alpha(4)beta(1) (CD49d/CD29) receptor antagonist in the treatment of equine heaves (recurrent airway obstruction)

The purpose of this study was to characterize the alpha(4)beta(1) receptor (CD49d/CD29, very late antigen-4, VLA-4) on circulating equine leukocytes and to evaluate the intrinsic potency of an alpha(4)beta(1) receptor antagonist (Compound B) in the horse. Ultimately, these studies would allow us to determine the suitability of treating recurrent airway obstruction (RAO; heaves) affected horses by blocking the cellular recruitment of lymphocytes and neutrophils into the lung. The data demonstrates the alpha(4)beta(1) integrin is present on horse lymphocytes and neutrophils (fluorescence-assisted cell sorter, FACS) and can bind low molecular weight alpha(4)beta(1) antagonists (Compounds A and B) with high affinity. K(D) values for the binding of Compound A to non-activated alpha(4)beta(1) on isolated horse PBMCs (peripheral blood mononuclear cells) and activated neutrophils were 17 pM and 27 pM, respectively. Compound B was identified as a suitable antagonist for performing a series of in vivo experiments. Compound B was found to possess excellent potency in horse whole blood, possessing IC(50) and IC(90) values of 39 pM and 172 pM, respectively. This represents a 3.9-fold molar excess of drug over the alpha(4)beta(1) concentration in blood. Following oral administration of Compound B (5 mg/kg) to beagle dogs and rhesus monkeys, rapid and sustained alpha(4)beta(1) receptor occupancy (>80%) was achieved and maintained for a period of 24 h. When Compound B was administered intravenously to the horse, by either a slow or rapid infusion at a dose of 0.3 mg/kg, receptor blockade of >80% was observed out to 24 h with a concomitant leukocytosis. We believe that Compound B possesses suitable intrinsic and pharmacological properties to be evaluated clinically in horses affected by RAO.

Pulmonary dysfunction and skeletal muscle changes in horses with RAO

BACKGROUND

Chronic pulmonary diseases (recurrent airway obstruction [RAO]) have been reported to alter skeletal muscle cells in humans. The purpose of this study was to evaluate a potential relationship between pulmonary and muscle variables in horses with a clinical diagnosis of RAO. Muscle biopsies from healthy horses and from horses with RAO were investigated and the relationship between the severity of lung disease and the degree of muscular changes was determined.

HYPOTHESIS

We hypothesized that chronic pulmonary disease can lead to changes of the skeletal muscle in horses.

ANIMALS

Fifteen healthy horses (control) and 50 horses with RAO were examined.

METHODS

In a prospective clinical trial, a complete lung examination was performed in all horses. In all horses, muscle enzyme activity at rest and after exercise and muscle biopsies from the M. gluteus medius were examined.

RESULTS

None of the horses had clinical or histologic signs of primary or neurogenic myopathies. According to the clinical, endoscopic, and radiographic findings and with a scoring system, the horses with RAO were grouped according to the severity of pulmonary findings (15 horses mild, 24 horses moderate, 11 horses severe RAO). Pathologic changes of the skeletal muscle (fiber atrophy or fiber hypertrophy, myofibrillar degeneration, hyperplasia of mitochondria, and ragged-red-like fibers) were identified in most horses with RAO but in only a few individual control horses. In addition, a marked depletion of muscle glycogen storage was evident in the RAO horses but not in the control group. Other pathologic changes of skeletal muscle such as centralized nuclei and regenerating fibers were rare, but were more frequent in horses with lung diseases than in the control group. The degree of muscle cell changes was also graded with a scoring system and correlated with the severity of pulmonary disease (r= 0.55).

CONCLUSION

Chronic pulmonary disease in horses is associated with structural changes in skeletal muscle.

CLINICAL IMPORTANCE

Because chronic pulmonary disease may affect muscles, early and effective therapy may prevent these changes. This finding could be of clinical importance but requires further studies.

Genomic and non-genomic effects of dexamethasone on equine peripheral blood neutrophils

BACKGROUND

Glucocorticoids have potent anti-inflammatory properties and are frequently used for the treatment of domestic animal species, including horses. They induce a down-regulation of multiple inflammatory pathways through both genomic and non-genomic effects. Currently, little is known on the effects of glucocorticoids on equine peripheral blood neutrophils.

HYPOTHESIS

Dexamethasone (DEX), a potent synthetic glucocorticoid, inhibits the functions of equine peripheral blood neutrophils through both genomic and non-genomic effects.

ANIMALS

Six healthy adult mixed breed female horses.

METHODS

To assess the genomic effects of DEX, peripheral blood neutrophils were isolated using a gradient technique and incubated 6 h with 100 ng/ml LPS and 10(-6) M DEX alone, or combined with the glucocorticoid receptor (GR) inhibitor RU486 (10(-5) M). Messenger RNA for IL-8, TNF-alpha and TLR-4 were measured using real-time RT-PCR. The non-genomic effects of DEX were studied in neutrophils incubated with 5 microM dichlorodihydrofluorescein (DCF) and 10(-6) M DEX 5, 10 and 15 min prior to being stimulated with 5 ng/ml phorbol myristate acetate. Neutrophils were similarly co-incubated with DEX (10(-6) M, 15 min) and RU486 (10(-5) M) to evaluate the contribution of the GR to these effects. The oxidation of DCF was studied using flow-cytometry.

RESULTS

Neutrophils stimulation with LPS resulted in a significant increase in IL-8, TNF-alpha and TLR-4 mRNA expressions (p<0.0001); incubation with DEX significantly down-regulated this process (p<0.0001). DEX significantly reduced oxidation of DCF after 10 and 15 min of incubation (p<0.0001). Those effects were mediated through the GRs.

CONCLUSION

DEX exerts anti-inflammatory effects on equine peripheral blood neutrophils through both genomic and non-genomic pathways.

Evidence-based respiratory medicine in horses

It is clear from a review of the current scientific literature that an evidence-based approach to medical treatment of equine respiratory disease can be applied, at least in the instance of common lower respiratory diseases. In particular, there is clear evidence for efficacious treatments for recurrent airway obstruction and exercise-induced pulmonary hemorrhage, and with the recognition of this evidence, these treatments should be the first to be considered by a practitioner when treating these conditions. The purpose of this article is not only to identify the existence of relevant high-quality studies for incorporation into an evidence-based veterinary medicine approach to patient care, but to highlight the features of those studies that should be considered when evaluating their value in individual situations.

Obstrução recorrente das vias aéreas em muares: relato de três casos

Relatam-se três casos de obstrução recorrente das vias aéreas em muares com idade média de 10 anos. Os animais eram utilizados para concurso de marcha e criados em campo. Após serem mantidos em cocheiras com cama de serragem e alimentados com feno (tifton e alfafa) e ração comercial, começaram a manifestar intolerância ao exercício e episódios de tosse durante o exercício. Após exames clínico e laboratorial, instituiu-se terapia à base de clenbuterol, dexametazona e bromexina, além de controle ambiental. Após 21 dias de tratamento, ocorreu remissão dos sintomas clínicos. Para comprovação diagnóstica, os animais foram submetidos ao desafio ambiental, por um período de dois dias. Após o tratamento, os três animais voltaram a desempenhar suas atividades atléticas de modo satisfatório.

Comparison of prednisolone and dexamethasone effects in the presence of environmental control in heaves-affected horses

This study was designed to compare the efficacy of oral prednisolone and intramuscular (IM) dexamethasone in heaves-affected horses with environmental control. A total of 16 horses, aged 8-20years, with heaves were included in the study. Complete examinations were performed on Day 0 (before treatment), Day 13 (after treatment) and Day 30. Clinical variables, arterial blood gases, mucus scoring and carina evaluation (during endoscopy), and bronchoalveolar lavage (BAL) cytological analysis were all assessed. The horses were randomly assigned to receive either oral prednisolone (1mg/kg) or IM dexamethasone (0.1mg/kg). The animals were clinically scored and mucus accumulation evaluated. Results were analysed by repeated measures ANOVA with time (days of treatment) and treatment as the main effects. When combined with environmental control, prednisolone and dexamethasone treatments had similar effects on heaves score, blood gases and endoscopic scores. However, dexamethasone had a more beneficial effect on BAL cytology.

Randomized, controlled study of inhaled fluticasone propionate, oral administration of prednisone, and environmental management of horses with recurrent airway obstruction

OBJECTIVE

To determine whether administration of glucocorticoids provides additional benefits to environmental management of horses with recurrent airway obstruction (RAO).

ANIMALS

28 horses with RAO.

PROCEDURE

Horses were classified as having mild, moderate, or severe RAO. Within each category, horses were randomly assigned to receive inhaled fluticasone propionate, inhaled control substance, or oral administration of prednisone. During the 4-week study, horses were maintained outdoors and fed a pelleted feed. Clinical scores, pulmonary function, results of cytologic examination of bronchoalveolar lavage fluid (BALF), and adrenal gland function were determined before and 2 and 4 weeks after initiation of treatment.

RESULTS

Clinical score and pulmonary function of all RAO-affected horses improved during the treatment period. After 4 weeks, clinical scores and pulmonary function of horses treated with a glucocorticoid were not different from those for the control treatment. In horses with severe RAO, treatment with fluticasone for 2 weeks resulted in significantly greater improvement in pulmonary function, compared with pulmonary function after treatment with prednisone or the control substance. Treatment with a glucocorticoid for 4 weeks and a low-dust environment did not have any effect on cellular content of BALF Treatment with prednisone for 2 weeks resulted in a significant decrease in serum cortisol concentration, compared with concentrations after administration of fluticasone or the control substance.

CONCLUSIONS AND CLINICAL RELEVANCE

Environmental management is the most important factor in the treatment of horses with RAO. Early treatment with inhaled fluticasone can help accelerate recovery of horses with severe RAO.

Efficacy of oral and intravenous dexamethasone in horses with recurrent airway obstruction

REASONS FOR PERFORMING STUDY

Although the efficacy of dexamethasone for the treatment of recurrent airway obstruction (RAO) has been documented, the speed of onset of effect and duration of action are unknown, as is the efficacy of orally administered dexamethasone with or without fasting.

OBJECTIVES

To document the time of onset of effect and duration of action of a dexamethasone solution i.v. or orally with and without fasting.

METHODS

Protocol 1 used 8 RAO-affected horses with airway obstruction in a crossover design experiment that compared the effect of i.v. saline and dexamethasone (0.1 mg/kg bwt) on pulmonary function over 4 h. Protocol 2 used 6 similar horses to compare, in a crossover design, the effects of dexamethasone i.v. (0.1 mg/kg bwt), dexamethasone per os (0.164 mg/kg bwt) with and without prior fasting, and dexamethasone per os (0.082 mg/kg) with fasting.

RESULTS

Dexamethasone i.v. caused significant improvement in lung function within 2 h with a peak effect at 4-6 h. Dexamethasone per os was effective within 6 h with peak effect at 24 h at a dose of 0.164 mg/kg bwt prior to feeding. The duration of effect was, for all dexamethasone treatments, statistically significant for 30 h when compared to saline and tended to have a longer duration of effect when used orally. Dexamethasone per os at a dose of 0.164 mg/kg bwt to fed horses had mean effects comparable to dexamethasone at a dose of 0.082 mg/kg bwt per os given to fasted horses, indicating that feeding decreases bioavailability.

CONCLUSIONS

Dexamethasone administered i.v. has a rapid onset of action in RAO-affected horses. Oral administration of a bioequivalent dose of the same solution to fasted horses is as effective as i.v. administration and tends to have longer duration of action. Fasting horses before oral administration of dexamethasone improves the efficacy of treatment.

POTENTIAL RELEVANCE

Oral administration to fasted horses of a dexamethasone solution intended for i.v. use provides an effective treatment for RAO-affected animals.

Comparison of efficacy and tolerability of isoflupredone and dexamethasone in the treatment of horses affected with recurrent airway obstruction ('heaves')

REASONS FOR PERFORMING STUDY

Corticosteroids are currently the most effective drugs for the control of 'heaves' in horses. However, there is limited information concerning the comparative efficacy and tolerability of the various corticosteroids when used for treatment.

OBJECTIVES

To compare the therapeutic and side effects of isoflupredone acetate to those of dexamethasone.

METHODS

A parallel design to compare the effects of 2 corticosteroids by evaluating lung function, serum cortisol and electrolyte concentrations, response to ACTH stimulation and haematology sequentially during a 14 day control period (no treatment), followed by 14 day treatment with either isoflupredone acetate (0.03 mg/kg i.m. s.i.d., n = 6) or dexamethasone (0.04 mg/kg i.v. s.i.d., n = 6) and 7 days of wash-out.

RESULTS

Both drugs were well tolerated clinically and resulted in a significant improvement in lung function that started on Day 3 and lasted for the treatment and wash-out periods. Blood cortisol levels were significantly decreased during the treatment period in both groups of horses, but a normal response to ACTH stimulation was preserved. Serum electrolytes concentration of horses receiving dexamethasone was not affected by the treatment, but horses treated with isoflupredone demonstrated a significant decrease in serum potassium level. Both treatments induced stress changes in haematology.

CONCLUSIONS AND POTENTIAL RELEVANCE

Isoflupredone is as effective as dexamethasone in the treatment of 'heaves'-affected horses but associated with hypokalaemia. Even if clinical signs of hypokalaemia were not observed, this is a side effect that deserves further investigation.

Coughing, mucus accumulation, airway obstruction, and airway inflammation in control horses and horses affected with recurrent airway obstruction

OBJECTIVE

To investigate relationships between cough frequency and mucus accumulation, airway obstruction, and airway inflammation and to determine effects of dexamethasone on coughing and mucus score.

ANIMALS

13 horses with recurrent airway obstruction (RAO) and 6 control horses.

PROCEDURE

6 RAO-affected and 6 control horses were stabled for 3 days. Coughing was counted for 4 hours before and on each day horses were stabled. Before and on day 3 of stabling, tracheal mucus accumulation was scored, airway obstruction was assessed via maximal change in pleural pressure (deltaPpl(max)), and airway inflammation was evaluated by use of cytologic examination of bronchoalveolar lavage fluid (BALF). Effects of dexamethasone (0.1 mg/kg, IV, q 24 h for 7 days) were determined in 12 RAO-affected horses.

RESULTS

To assess frequency, coughing had to be counted for 1 hour. In RAO-affected horses, stabling was associated with increases in cough frequency, mucus score, and deltaPpl(max). Control horses coughed transiently when first stabled. In RAO-affected horses, coughing was correlated with deltaPpl(max), mucus score, and airway inflammation and was a sensitive and specific indicator of deltaPpl(max) > 6 cm H2O, mucus score > 1.0, and > 100 neutrophils/microL and > 20% neutrophils in BALF Dexamethasone reduced cough frequency, mucus score, and deltaPpl(max), but BALF neutrophil count remained increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Because of its sporadic nature, coughing cannot be assessed accurately by counting during brief periods. In RAO-affected horses, coughing is an indicator of airway inflammation and obstruction. Corticosteroid treatment reduces cough frequency concurrently with reductions in deltaPpl(max) and mucus accumulation in RAO-affected horses.

Recurrent airway obstruction--heaves

Heaves, or recurrent airway obstruction (RAO), is a chronic respiratory disease featuring lower airway inflammation, bronchoconstriction, and mucus accumulation. Inhaled organic dusts and T helper 2 type immunologic reactions are involved in the complex pathophysiology of RAO. Clinical signs vary and alternate with remission periods. The diagnosis is often based on history and clinical examination in severe cases, but bronchoalveolar lavage may be useful for the detection of early cases. The most important aspect of treatment is to avoid exposure to allergens. Corticosteroids may be administered systemically or by inhalation in combination with bronchodilators and environmental control.

Prednisone per os is likely to have limited efficacy in horses

Based on its efficacy for the treatment of human asthma, the corticosteroid prednisone is commonly used in horses for treatment of recurrent airway obstruction. However, recent studies have failed to show any benefit of prednisone tablets for the treatment of this condition. The purpose of this study was to determine why oral prednisone has poor efficacy for the treatment of heaves in horses. In a crossover study, 5 horses were given the following treatments: prednisone tablets, prednisone liquid, prednisolone tablets, prednisolone liquid and i.v. prednisolone sodium succinate (positive control). Blood samples were taken before drug administration and at selected time points during a 24 h period. Serum concentrations of prednisone and prednisolone were determined in order to evaluate gastrointestinal absorption and hepatic metabolism. Serum concentrations of the endogenous glucocorticoid hydrocortisone were also determined as an indicator of the biological activity of the drugs. Both prednisolone tablets and liquid were absorbed rapidly, with prednisolone detectable in serum within 15 min of administration and with peak concentrations occurring within 45 min. Small amounts of prednisone were detected in the serum samples after administration of both prednisone tablets and liquid. Prednisolone was not detected in serum samples after administration of prednisone liquid and was detected in serum samples from only one horse after administration of prednisone tablets. Endogenous hydrocortisone production was suppressed when horses received prednisolone. The results of these studies indicate that prednisone has poor efficacy for the treatment of heaves because it is poorly absorbed and the active metabolite prednisolone is rarely produced. In contrast, prednisolone tablets have excellent bioavailability and should be useful as a therapeutic agent in horses.