# Differences in Redox Biomarkers in Bronchoalveolar Lavage Fluid of Leisure Horses With and Without Severe Equine Asthma: Preliminary Results

## TL;DR

This study found higher levels of a harmful form of iron in the lungs of horses with severe asthma, suggesting oxidative stress plays a role in the disease.

## Contribution

The study identifies elevated non-protein-bound iron in bronchoalveolar lavage fluid as a potential biomarker for severe equine asthma.

## Key findings

- Horses with severe equine asthma had significantly higher non-protein-bound iron levels in bronchoalveolar lavage fluid.
- No significant differences were found in antioxidant potential or other oxidative markers between groups.
- The findings suggest a pro-oxidative status in the lungs of horses with severe equine asthma.

## Abstract

Equine asthma is a common long-term respiratory disease in horses that causes breathing difficulty and airway inflammation, particularly in its severe form. Inflammation in the lungs can lead to an imbalance between harmful molecules, known as oxidants, and the body’s natural defenses, called antioxidants. This imbalance may contribute to lung damage and the progression of the disease. The aim of this study was to evaluate markers of oxidative damage and antioxidant protection in fluid collected from the lungs of horses with and without severe equine asthma. We found that horses with severe equine asthma had higher levels of a reactive form of iron that can promote oxidative damage. Other markers showed no clear differences between groups. These results indicate that a pro-oxidative status is present locally in the lungs of affected horses. A better understanding of these processes may help improve disease monitoring and support the development of management strategies, such as nutritional or environmental interventions, to improve respiratory health and welfare in horses.

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.