Effect of chronic airway inflammation and exercise on pulmonary and systemic antioxidant status of healthy and heaves-affected horses.

The study investigates the relationship between oxidant status, airway inflammation, and pulmonary function in horses with a respiratory disease known as heaves. The researchers found that oxidative stress associated with heaves correlated with pulmonary function and airway inflammation and could be measured through various compounds both locally in the lung and systemically in the body.

Objective and Subject of Study

• The primary objective of this study was to explore the relationship between oxidant status, airway inflammation, and pulmonary function of horses suffering from an inflammatory airway disease called ‘heaves,’ both during periods of clinical remission and crisis.
• The researchers conducted their tests on healthy horses as well as horses affected by heaves, during rest, and after exercise. The oxidant status was evaluated by measuring specific chemicals associated with oxidative processes and inflammation.

Method and Measurements

• The oxidant status was assessed in the horses by measuring the levels of reduced and oxidised glutathione, uric acid and 8-epi-PGF2alpha in the blood and pulmonary epithelial lining fluid (PELF). The ratio of oxidised to reduced glutathione (GRR%) was also determined.
• This oxidant status was then related to pulmonary function parameters such as the mechanics of breathing and arterial blood gas tension, along with airway inflammation parameters derived from bronchoalveolar lavage.

Findings

• It was found that the levels of glutathione in the blood were significantly different between the groups of healthy horses and those affected by heaves.
• The glutathione redox ratio in the PELF was found to increase during a crisis state of the disease. This was correlated with changes in pulmonary function and airway inflammation parameters.
• Exercise appeared to cause an increase in plasma uric acid levels, this increase was significantly higher in horses during remission and crisis states of the disease.
• PELF concentrations of 8-epi-PGF2alpha increased significantly during a crisis state and were correlated with pulmonary function and airway inflammation parameters.

Conclusions

• The researchers concluded that oxidative stress during heaves correlates with changes in pulmonary function and airway inflammation. This can be evaluated locally by assessing PELF glutathione status, uric acid, and 8-epi-PGF2alpha concentrations.
• Systemic effects of this oxidative stress, on the other hand, can be evaluated by measuring the GSH levels in restful horses and uric acid levels in horses undergoing exercise.