Abstract
Equine asthma is a common chronic respiratory disease characterized by airway inflammation and oxidative imbalance, particularly in its severe form. The aim of this study was to evaluate pro-oxidative substances, oxidative products, and antioxidant defense biomarkers in bronchoalveolar lavage fluid (BALF) from horses with and without a history of severe equine asthma (SEA). This prospective observational study included 21 leisure horses classified as SEA or non-SEA based on clinical history and BALF cytology. Bronchoalveolar lavage fluid was analyzed for derivatives of reactive oxygen metabolites (d-ROMs), non-protein-bound iron (NPBI), advanced oxidation protein products (AOPP), and biological antioxidant potential (BAP) using validated analytical methods. Horses with SEA showed significantly higher NPBI concentrations compared with non-SEA horses, whereas no significant differences were observed for BAP level, AOPP and d-ROMs concentrations between groups. This finding indicates an altered local redox balance in the airways of horses with severe equine asthma, characterized by increased pro-oxidative potential. Overall, the results support the involvement of oxidative mechanisms in the pathophysiology of severe equine asthma and highlight the potential value of bronchoalveolar lavage fluid biomarkers for improving disease characterization.