Bronchial brush cytology, endobronchial biopsy, and SALSA immunohistochemistry in severe equine asthma

Abstract

Horses with severe equine asthma (SEA), also known as heaves and recurrent airway obstruction, have persistent neutrophilic inflammation of the lower airways. Cytologic evaluation of bronchoalveolar lavage (BAL) fluid is commonly used to confirm the clinical diagnosis of SEA. However, the utility of microscopic assessment of bronchial brushings, endobronchial biopsies, and immunohistochemical detection of disease-associated biomarkers for the diagnosis of SEA remain poorly characterized. Salivary scavenger and agglutinin (SALSA) has anti-inflammatory properties and downregulated gene expression in SEA; therefore, it was investigated as a tissue biomarker for airway and systemic inflammation. Six asthmatic and 6 non-asthmatic horses were exposed to an inhaled challenge. Before and after challenge, samples of BAL fluid, bronchial brushing, and endobronchial biopsy were collected. Location of SALSA in biopsies was determined, and immunohistochemical label intensity was computed using image analysis software. Serum amyloid A (SAA) was measured to assess systemic inflammation. After challenge, neutrophil proportions were significantly higher in asthmatic versus non-asthmatic horses in BAL fluid (least squares means, 95% confidence interval: 80.9%, 57.2% to 93.1%, vs 3.6%, 1.1% to 10.7%) and in brush cytology slides (39.5%, 7.7% to 83.6%, vs 0.2%, 0% to 2.3%), illustrating the potential of brush cytology as an alternate modality to BAL for assessing intraluminal inflammation. Bronchial histopathologic findings and intensity of SALSA immunolabeling in surface and glandular epithelium were similar in asthmatic and non-asthmatic horses, indicating limited changes in bronchial tissue from the inhaled challenge. Increases in SAA indicated systemic inflammation, but SALSA immunolabeling did not change significantly.

The amount of hyaluronic acid and airway remodelling increase with the severity of inflammation in neutrophilic equine asthma

“…Our results suggest positive associations between histological scores, airway neutrophilia, and the amount of mucus in the airways. Recent studies have also reported conflicting results on the reliability of EBBs in distinguishing horses with severe EA from control horses, however, the sampling site in these studies was more proximal, closer to the main carina [ 39 , 40 ]. The nonsignificant differences in the histological scores between horses with moderate NAI and control horses in the present study may be related to the low level of neutrophilia in horses with moderate NAI.…”

Decision Making in Severe Equine Asthma—Diagnosis and Monitoring

“…It provides insight into the inflammatory status of airways and although it is not considered the gold standard for the diagnosis of this disease, its practicality in an ambulatory context has rendered this ancillary diagnostic test popular. Cytological samples can be collected using a wide variety of methods, including brush cytology, tracheal wash (TW), bronchoalveolar lavage fluid (BALF) or even bronchial biopsies [118][119][120][121].…”

Effect of budesonide combined with montelukast sodium on pulmonary function parameters and immunoglobulin levels in children with bronchial asthma

“…Hence, budesonide can achieve the dual efficacy of anti-allergy in the process of anti-inflammation. 21 However, atomization inhalation is the most efficient method of delivery due to the drug's significant hepatic first-pass effect.…”