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.