Cytokine mRNA expressions after racing at a high altitude and at sea level in horses with exercise-induced pulmonary hemorrhage.

The research investigates the impact of different altitudes on cytokine mRNA expressions in horses with exercise-induced pulmonary haemorrhage. It states that sea level and high altitudes affect the expression of cytokines like IL-6 and TNF-alpha, but further studies need to be performed to understand this relationship thoroughly.

Objective and Methodology

• The main objective of the research was to analyze the concentrations of cytokine mRNA in horses suffering from exercise-induced pulmonary hemorrhage (EIPH) after racing at different altitudes.
• The study was conducted on 97 Thoroughbreds that had undergone tracheobronchoscopy, and the severity of EIPH was rated on a scale of 0-4. Ten horses from each grade were selected, and their venous blood samples were collected.
• RNA isolation and cDNA synthesis were performed, followed by a real-time PCR assay to detect cytokine-specific mRNA for IL-1, IL-6, and IL-10; interferon (INF)-gamma; and tumor necrosis factor (TNF)-alpha.

Findings

• The results indicated that neither the altitude at which the race took place nor the severity of EIPH influenced the expression of IL-1 and INF-gamma.
• Higher overall expression of IL-6 mRNA was observed at sea level, with grade 4 EIPH horses demonstrating significantly more IL-6 expression compared to horses with grade 0, 1, or 2 EIPH. However, no variation was found in IL-6 expression among the different EIPH grades at high altitude.
• There was a higher overall expression of TNF-alpha mRNA at high altitudes, yet this did not vary among different EIPH grades.
• Significant differences were observed in IL-10 expressions based on EIPH grade, with grade 3 EIPH horses significantly expressing more IL-10 mRNA than grade 0 or 2 EIPH horses, irrespective of the location.

Conclusions

• The study indicates a correlation between sea level altitude and increased IL-6 expression in horses with more severe EIPH. Similarly, racing at high altitudes may influence gene expressions of the proinflammatory cytokine TNF-alpha and anti-inflammatory cytokine IL-6.
• However, the researchers conclude that further studies, particularly on protein concentrations of cytokine expression, are required to enhance the scientific understanding of these findings.
• The pathophysiological significance of these findings still needs to be explained to understand the implications better for equine health and performance at different altitudes.