Redox Biomarker Variations With Severity of Asthma in Horses Across Different Sample Types

Background

The contribution of redox imbalance to equine asthma (EA) pathogenesis remains unclear.

Objectives

(1) validate and measure a panel of redox biomarkers in the tracheal wash (TW) and bronchoalveolar lavage (BAL) samples from horses with neutrophilic and mastocytic mild–moderate EA (MEA) and severe EA. (2) Evaluate the same panel in saliva and serum for comparative purposes.

Animals

A total of 117 horses: 37 healthy, 26 mastocytic MEA, 29 neutrophilic MEA, and 25 severe EA.

Methods

Cross-sectional study using TW, BAL, and serum and saliva sampling. After assay validation, redox biomarkers-ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC), glutathione reductase (GSHred), superoxide dismutase (SOD), and advanced oxidation protein products (AOPP) were quantified.

Results

Assays demonstrated low imprecision, good linearity, and adequate sensitivity in TW and BAL fluid. Bronchoalveolar lavage fluid biomarkers decreased with EA severity for TEAC (healthy horses: median, 0.013; severe EA horses: 0.010; p < 0.001; effect size [ES] = 0.36), SOD (healthy horses: median, 0.95; severe EA horses: 0.70; p < 0.001; ES = 0.39), and AOPP (healthy horses: median, 44.9; severe EA horses: 20; p = 0.05; ES = 0.18).

Bronchoalveolar lavage neutrophil differential counts were negatively correlated with saliva SOD (rho = −52; p = 0.001), GSHred (rho = − 0.46; p = 0.01) and AOPP (rho = − 0.34; p = 0.04).

Conclusions and Clinical Importance

These findings support the potential of redox biomarkers measured in BAL fluid in the characterization of neutrophilic EA and emphasize their value in guiding antioxidant-based therapeutic strategies. Based on our results, redox imbalance is less evident in mastocytic EA compared with neutrophilic EA.