Chronic Obstructive Pulmonary Disease Horses Research Articles

Differential inhibition of equine neutrophil function by phosphodiesterase inhibitors.

Neutrophils are recruited to the lungs of horses with chronic obstructive pulmonary disease (COPD) and exhibit increased activity after antigen challenge, which may contribute to inflammation and lung damage. Inhibition of phosphodiesterase isoenzymes (PDEs) has been shown to attenuate human neutrophil functions including superoxide production, leukotriene (LT)B4 biosynthesis, enzyme and chemokine release. As equine neutrophils contain predominantly the isoenzyme, PDE4, the present study was undertaken to investigate the effects of rolipram, a PDE4 inhibitor, on equine neutrophil function. For comparison, the effects of the nonselective PDE inhibitor, theophylline, were examined. Cells from both normal horses and COPD horses in remission were used. Superoxide production was significantly inhibited by both rolipram [32.2 +/- 2.6 vs. 10.1 +/- 1.1 nmol/10(6) cells and 49.8 +/- 6.8 vs. 22.7 +/- 2.2 nmol/10(6) cells for normal and COPD susceptible horses, respectively, in response to 10(-7) M human recombinant (hr) C5a] and theophylline (19.0 +/- 0.6 vs. 10.2 +/- 0.6 nmol/10(6) cells and 24.3 +/- 2.1 vs. 10.7 +/- 0.9 nmol/10(6) cells for normal and COPD susceptible horses, respectively, in response to 10(-7) M C5a). However, superoxide production induced by serum treated zymosan was inhibited only by theophylline (10(-3) M). Neither hrC5a- nor platelet activating factor (PAF)-induced neutrophil adherence to fibronectin coated plastic was reduced by rolipram (10(-5) M). These results demonstrate that the effects of PDE inhibitors on equine neutrophils are both stimulus and function dependent. The PDE4 inhibitors may reduce neutrophil activation in vivo in horses with COPD.

MMP-9 as a marker of inflammation in tracheal epithelial lining fluid (TELF) and in bronchoalveolar fluid (BALF) of COPD horses.

Gelatinolytic activity was analysed to study whether elevated activity previously found at the tracheal level of the respiratory tract of horses with chronic obstructive pulmonary disease (COPD) could also be found at the lower part of the respiratory tract. Furthermore, presence and significance of the gelatinolytic matrix metalloproteinases (MMPs) MMP-2 and MMP-9 in respiratory secretions of healthy and COPD horses were determined. Elevated gelatinolytic matrix metalloproteinases were detected in bronchoalveolar and tracheobronchial secretions from COPD horses. The main pathologically elevated MMP was characterised to be MMP-9. Significantly increased MMP-9 activities as measured by gelatin zymography and Western blotting were found in all the respiratory samples from COPD horses compared to healthy horses. Elevation of active MMP-9 paralleled with increased gelatinase-associated lipocalin levels. Bronchoalveolar lavage fluid (BALF) epithelial cells, macrophages, neutrophils and lymphocytes expressed MMP-9 immunoreactivity demonstrated by immunocytochemistry and MMP-9 mRNA was expressed by bronchial epithelial cells of lung tissue section shown by in situ hybridisation. MMP-2 seems not to play a major role in chronic lung inflammation. No clear differences in MMP-2 or MMP-14 (a potent MMP-2 activator) levels were found when comparing the samples from COPD or healthy horses. These results suggests that MMP-9 could serve as a potential diagnostic marker for the active ongoing tissue remodelling in the acute phase of equine COPD. Increased gelatinolytic activity could be found at both tested respiratory tract levels. Therefore, tracheal epithelial lining fluid (TELF) samples can usefully serve as diagnostic material for detection of increased levels of the main gelatinolytic MMP, MMP-9, representing the entire diseased lung.

Forced expiration: a test for airflow obstruction in horses.

The purpose of this study was to assess whether our method of inducing forced expiration detects small airway obstruction in horses. Parameters derived from forced expiratory flow-volume (FEFV) curves were compared with lung mechanics data obtained during spontaneous breathing in nine healthy horses, in three after histamine challenge, and in two with chronic obstructive pulmonary disease (COPD) pre- and posttherapy with prednisone. Parameters measured in the healthy horses included forced vital capacity (FVC = 41.6 +/- 5.8 liters; means +/- SD) and forced expiratory flow (FEF) at various percentages of FVC (range of 20.4-29.7 l/s). Histamine challenge induced a dose-dependent decrease in FVC and FEF at low lung volume. After therapy, lung function of the two COPD horses improved to a point where one horse had normal lung mechanics during tidal breathing; however, FEF at 95% of FVC (4.9 l/s) was still decreased. We concluded that FEFV curve analysis allowed the detection of induced or naturally occurring airway obstruction.

Effect of hyonate administration on pulmonary function and indices of oxidative stress in COPD horses in clinical remission at rest and after exercise

Pulmonary function tests, bronchoalveolar lavages, and venous blood samplings were performed 24 hours before and one hour after a standardized strenous treadmill exercise test on six horses suffering from chronic obstructive pulmonary disease (COPD) in clinical remission. Pulmonary function test consisted of the measurement of the mechanics of breathing and arterial blood gases analyses. During the exercise tests, heart and respiratory rates, and venous plasma lactate, pH and packed cell volume were controlled. Venous blood was analyzed for some markers of the oxidative stress, i.e., hemolysate glutathione redox ratio and oxidized glutathione, and plasma uric acid. BAL was analyzed for cell cytology as well as for markers of oxidative stress, i.e., glutathione redox ratio, and isoprostanes concentration. The procedure was repeated twice, i.e., before and after two IV injections of 40mg hyaluronate administered at seven day intervals. The results were compared to assess a possible influence of the treatment on the pulmonary and systemic inflammatory and/or oxidative status of these horses. Hyaluronate did not influence the pulmonary function test or the physiological parameters recorded during exercise. There was a decrease in the percentage of BAL neutrophils after the treatment, suggesting a possible anti-inflammatory effect at the pulmonary level. As well, the concentration of isoprostanes in the pulmonary epithelium lining fluid was significantly lower after the treatment, which might be either a consequence of the decrease of the BAL neutrophils, or related to a possible antioxidant effect of the treatment. Lastly, the exercise-induced increase in plasma uric acid was significantly less marked after the treatment, which could be due to a systemic antioxidant effect of the hyaluronate. In conclusion, this preliminary study brings some evidence that hyaluronate could have some antiinflammatory and antioxidant effects at the pulmonary—and systemic—level in COPD horses in remission. However, it does not help to understand the possible mechanisms underlying these observations. Further studies are now necessary to better understand its action, to assess the effect of the product on the pulmonary function of horses suffering from other respiratory problems as well as to assess the efficiency of other ways of administration, i.e., nebulization.

Effect of exercise on concentrations of immunoreactive endothelin in bronchoalveolar lavage fluid of normal horses and horses with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) represents a major cause of loss of performance in the horse. The role of endothelin (ET), a potent bronchoconstrictive and vasoactive peptide, is currently being investigated in asthma and other obstructive respiratory diseases in man. We have previously found elevated systemic and pulmonary endothelin levels in horses during exacerbation of COPD. In the present study, our aim was to examine possible variations in ET concentrations occurring during exercise in COPD horses. We compared the effects of intense treadmill exercise on the recovery of endothelin (ET) in the bronchoalveolar lavage fluid (BALF) as well as in arterial and venous blood, in a group of 5 healthy horses and a group of 5 COPD horses studied alternately in remission and while symptomatic. We also investigated the possible correlations between ET levels and pulmonary function tests during the study. While exercise did not affect the ET levels recovered in BALF among controls, it caused a significant increase (P = 0.02) among symptomatic COPD horses. During remission, wide variations of ET levels among horses, at rest and during exercise, made any significant interpretation difficult. No correlation could be found between exercise-induced changes in ET concentrations and pulmonary function tests or changes in arterial oxygen tension with exercise. We conclude that exercise appears to affect the release of ET by the airways in COPD horses, in contrast to healthy horses. It is still unclear, however, whether these differences relate to adjustments of lung function during exercise.

Effects of buprenorphine on cardiovascular and pulmonary function in clinically normal horses and horses with chronic obstructive pulmonary disease

Abstract Objectives To evaluate the cardiovascular and respiratory effects of buprenorphine administered intravenously in clinically normal horses and horses with chronic obstructive pulmonary disease (COPD). Animals 5 clinically normal horses and 5 horses with COPD that were in partial clinical remission (period A) or were having an acute attack of airway obstruction (period B). Procedures Pulmonary function testing, arterial blood gas analysis, and arterial blood pressure measurements were performed before and after a single intravenous bolus of buprenorphine (3 μg/kg of body weight). Respiratory rate (f), tidal volume (VT), expiratory-to-inspiratory time ratio (TE/TI), minute expiratory ventilation (VE), maximal change in transpulmonary pressure (ΔPL), dynamic compliance (Cdyn), and pulmonary resistance (RL) were calculated with a pulmonary function computer. Heart rate (HR) and systolic (SABP), diastolic (DABP), and mean arterial blood pressures (MABP) were measured. Results At baseline, COPD horses in period A had decreased Cdyn and increased f, VE, PL, and HR, whereas COPD horses in period B had decreased TE/TI and Cdyn, arterial blood pH, and Po2, and increased f, vE, ΔPL, and RL, compared with clinically normal horses. After drug administration, SABP, DABP, and MABP increased in all horses, f and VE increased in clinically normal horses, and Pao2 decreased within 60 minutes in horses with COPD. Conclusion and Clinical Relevance Buprenorphine can induce excitement in unsedated horses or horses that do not have signs of pain, but does not seem to induce severe respiratory depression or adverse cardiovascular effects in clinically normal horses or those with COPD. (Am J Vet Res 1998;59:1287–1291)

Does an acute COPD crisis modify the cardiorespiratory and ventilatory adjustments to exercise in horses?

The present study was conducted to understand better the mechanisms leading to the decrease in exercise capacity observed in horses suffering from chronic obstructive pulmonary disease (COPD). Five COPD horses were submitted to a standardized submaximal treadmill exercise test while they were in clinical remission or in acute crisis. Respiratory airflow, O2 and CO2 fractions in the respired gas, pleural pressure changes and heart rate were recorded, and arterial and mixed venous blood were analyzed for gas tensions, hemoglobin, and plasma lactate concentrations. O2 consumption, CO2 production, expired minute ventilation, tidal volume, alveolar ventilation, cardiac output, total pulmonary resistance, and mechanical work of breathing were calculated. The results showed that, when submaximally exercised, COPD horses in crisis were significantly more hypoxemic and hypercapnic and that their total pulmonary resistance and mechanical work of breathing were significantly higher and their expired minute ventilation significantly lower than when they were in remission. However, their O2 consumption remained unchanged, which was probably due to the occurrence of compensatory mechanisms, i.e., higher heart rate, cardiac output, and hemoglobin concentration. Last, their net anaerobic metabolism seemed to be more important.

Effect of a set stabled environmental control on pulmonary function and airway reactivity of COPD affected horses

The aim of this study was to evaluate the respiratory function of horses affected with chronic obstructive pulmonary disease (COPD) when maintained in a barn on wood shavings and fed grass silage for a period of 6 weeks. The mechanics of breathing, blood gas analysis and bronchial reactivity were examined on five horses with COPD at the end of the environment-controlled period (Period B) and the results compared with values obtained after 2 months at pasture (Period A) and after the onset of clinical signs of acute crisis (Period C). The results showed that clinical and functional parameters were similar in healthy horses and in COPD horses placed on pasture or stabled and fed grass silage. Moreover, the bronchial reactivity of COPD horses at pasture was similar to the bronchial reactivity of healthy horses. COPD horses fed grass silage however presented a bronchial reactivity intermediate between those measured after Period A and Period C which suggested they would be more susceptible to develop bronchoconstriction when in contact with inhaled irritants.

Technical validation of a face mask adapted for dry powder inhalation in the equine species.

Development of dry powder inhalation (DPI) for horses requires the use of an adapted face mask. In experiment I, 4 masks (A, B, C and D) were tested and factors influencing the delivery of the dry powder were determined. Mask A was one which is commercially available for metered-dose inhalation. Mask B had the same shape as Mask A but an airtight rubber seal was added for the connection between the mask and horse's head. Mask C was a prototype adapted for DPI with connection for the DPI device between the nostrils, airtight expiratory valves in front of each nostril and airtight rubber seal to attach the mask on the horse's head. Mask D was the same as Mask C but the airtight expiratory valve was situated in front of one nostril and the connection for the DPI device was placed in front of the other nostril. Inhalet emptying and peak inspiratory pressure were measured on 5 healthy horses with each face mask. Both Masks A and B gave a low rate of inhalet emptying. Inspiratory pressures created in Masks C and D were negative enough to ensure inhalet emptying rates of mean +/- s.d. 98.28 +/- 1.79% and 100% respectively. In experiment 2, the face masks giving the greatest inhalet emptying were used to test the therapeutic efficacy of ipratropium bromide DPI. This was tested on 6 horses suffering from acute exacerbation of chronic obstructive pulmonary disease (COPD). At a dose of 200 micrograms/100 kg bwt, ipratropium administered with Mask D improved significantly pulmonary function measurements compared to baseline values and placebo inhalation. With Mask C, a double dose of ipratropium (400 micrograms/100 kg bwt) was necessary to improve these parameters compared to baseline values. This indicated the importance of locating the DPI device in front of one nostril. It was concluded that inhalet emptying is correlated to inspiratory pressures measured in the face masks. Secondly, these pressures are in turn dependent on the air-tightness of the mask, i.e. air-tightness of the expiratory valve and close connection between the horse's head and the mask. Thirdly, position of the DPI device in front of a nostril allows bronchodilation at a dose half that required when the device is placed between the nostrils. Finally DPI using Mask D (EquiPoudre) is a rapid, effective and well tolerated inhalation treatment for COPD horses.

Influence of antigen challenge on platelet responsiveness in horses with chronic obstructive pulmonary disease.

A role for platelets in allergic airways disease has been postulated and changes in the responsiveness of circulating platelets have been demonstrated following antigen challenge of asthmatic human subjects. In this study agonist-induced aggregation of equine platelets in vitro has been compared before and after exposure of horses to a controlled hay and stray challenge. Prior to challenge the response of platelets, from horses with chronic obstructive pulmonary disease (COPD) and normal animals, to adenosine diphosphate (ADP) and platelet activating factor (PAF) did not differ. Five hours after initiation of the challenge, there was a modest but significant decrease in the response of platelets from the COPD horses to PAF, but not to ADP. Platelets from normal horses were not less sensitive to either agonist at this time. Twenty four hours after challenge the responses of platelets from COPD horses to both agonists were the same as pre-challenge values. These results demonstrate that antigen challenge alters the responsiveness of platelets from allergic horses to PAF and this change is suggestive of PAF release accompanying allergen exposure in the horse.

Effect of antigen challenge on the activation of peripheral blood neutrophils from horses with chronic obstructive pulmonary disease

The effect of antigen challenge on the state of activation of peripheral blood neutrophils from horses with chronic obstructive pulmonary disease ( COPD) has been determined by measuring neutrophil superoxide anion formation. Prior to a seven-hour antigen challenge superoxide anion production by neutrophils from asymptomatic horses with COPD and normal horses in response to platelet activating factor ( PAF) (with and without cytochalasin B), serum treated zymosan ( STZ) and phorbol myristate acetate ( PMA) was similar. Agonist-induced superoxide production by neutrophils from symptomatic COPD and normal horses remained unchanged five and 24 hours after antigen challenge. Interestingly, however, superoxide production by neutrophils from symptomatic COPD horses was significantly increased 24 hours after antigen challenge in the control samples for each agonist (basal superoxide production), a five-fold increase being measured in the presence of cytochalasin B. There was a small increase in superoxide production by neutrophils from normal horses but this only reached significance in one set of control samples. The change in activation state of circulating neutrophils during antigen challenge may facilitate the lung neutrophilia and subsequent tissue damage which occur in COPD.

Effects of platelet activating factor on the distribution of radiolabelled leucocytes and platelets in normal horses and asymptomatic horses with chronic obstructive pulmonary disease

Antigen challenge is known to cause the recruitment of neutrophils to the lungs of horses with chronic obstructive pulmonary disease ( COPD). To evaluate a possible role of platelet activating factor ( PAF) in this process, the effects of PAF on the distribution of radiolabelled neutrophils were compared in normal horses and asymptomatic horses with COPD. Changes in lung function, heart rate and the distribution of platelets and eosinophils were also measured. PAF (5 ng kg −1 intravenously) caused immediate but transient increases in the number of radiolabelled neutrophils in the lungs and a concomitant decrease in the peripheral neutrophil count. The total numbers of circulating leucocytes and neutrophils were also significantly decreased by PAF. Rapid and reversible increases in heart rate, respiratory rate and pleural pressure were also observed. In separate experiments, the numbers of radiolabelled eosinophils and platelets in the lungs increased transiently after the administration of PAF The responses to PAF were qualitatively and quantitatively similar in normal horses and asymptomatic COPD horses. The PAF receptor antagonist WEB2086 (3 mg kg −1 intravenously) inhibited the effects of PAF These results suggest that PAF, if released in the lungs of horses with COPD during an antigen challenge, might contribute to the recruitment of leucocytes and the respiratory changes.

A study of the effect of a platelet activating factor (PAF) receptor antagonist on antigen challenge of horses with chronic obstructive pulmonary disease.

Antigen challenge involving exposure to straw and mouldy hay for 7 h produced lung function changes and neutrophil recruitment to the lungs in horses with chronic obstructive pulmonary disease (COPD). During the challenge, an increase in radiolabelled neutrophils in the lungs occurred, together with increased respiratory rate and pleural pressure. The role of platelet activating factor (PAF) in antigen-induced neutrophil accumulation, and increased pleural pressure and respiratory rate was investigated by administering the PAF receptor antagonist WEB 2086 to asymptomatic COPD horses prior to antigen challenge. WEB 2086 (3 mg/kg i.v.) did not affect antigen-induced changes in either neutrophil accumulation or respiratory function. These results suggest that PAF may not be an important mediator of the response to antigen in equine COPD.

Responsiveness of basophil granulocytes of horses suffering from chronic obstructive pulmonary disease to various allergens

As basophils are the major effector cells of allergic reactions, confirmation of the allergic etiology of chronic obstructive pulmonary disease (COPD) was sought by the demonstration of a specific in vitro response of equine basophilic blood cells to some potential allergens (Aspergillus, Cladosporidium, Mucor, Penicillium, extracts of dust particles of hay and straw). The allergen induced degranulation of basophils and the histamine and protease release from basophils during incubation with the allergens were tested. By evaluating the results obtained from 14 COPD horses and eight controls it could be shown that the sensitivity of the basophils of affected horses was increased, particularly against the allergen extract of Mucor mucedo and Mucor spinosus. Further a greater percentage of COPD horses reacted positively with the Mucor allergen extract. The mitogenic stimulation of lymphocytes by PHA and by the allergen extracts used gave comparable results in affected and control horses. Thus the in vitro stimulation of basophils may be an easily to perform testing device for the identification of potential allergens involved in the pathogenesis of equine COPD.

Chronic obstructive pulmonary disease (COPD): effects of bronchodilator drugs on normal and affected horses.

The effects of the bronchodilator drugs, atropine, isoprenaline and terbutaline, on normal horses and on horses affected with chronic obstructive pulmonary disease (COPD), were assessed by pulmonary function tests and clinical examination. Normal horses were not affected but COPD horses responded by a marked decrease in intrathoracic pressure, a decrease in respiratory rate, an initial decrease followed by an increase in arterial oxygen partial pressure and clinical improvement after treatment with all 3 drugs. These changes were temporary.