Antioxidant and inflammatory responses of healthy horses and horses affected by recurrent airway obstruction to inhaled ozone.

This study investigates the effects of inhaled ozone on healthy horses and horses with recurrent airway obstruction (RAO), focusing on oxidative stress and airway inflammation. Contrary to expectation, the results showed that RAO-affected horses in remission did not react more sensitively to ozone despite having reduced pulmonary antioxidant capacity.

Research Objective

• The purpose of the research was to understand whether horses with RAO- a recurring respiratory condition similar to asthma, which reduces the horse’s lung antioxidant capacity – respond differently to inhaled ozone than healthy horses. Specifically, the researchers were interested in knowing if the RAO-affected horses exhibited heightened oxidative stress and airway inflammation after inhaling ozone.

Research Methods

• The study involved seven healthy horses and seven RAO-affected horses for comparison.
• To investigate the effects, all fourteen horses were exposed to 0.8 ppm of ozone for two hours while at rest.
• To measure oxidative stress, the team analyzed the bronchoalveolar lavage fluid (BALF) in each horse. BALF was used to measure the concentration of ascorbic acid (vitamin C) and glutathione, molecules that serve as antioxidants in the horse’s body.

Research Findings

• The BALF results showed that at baseline, RAO-affected horses had lower levels of ascorbic acid compared to healthy horses.
• Ozone was observed to primarily oxidize glutathione over ascorbic acid in the six hours following exposure.
• Both the healthy and RAO-affected horses showed signs of glutathione oxidation in the BALF after ozone exposure, indicating oxidative stress.
• However, RAO-affected horses did not experience more oxidative stress compared to the healthy horses post-ozone exposure.
• No significant airway inflammation was observed in either group post-ozone exposure.

Conclusions

• The findings suggest that despite having reduced pulmonary antioxidant capacity, horses affected by RAO in remission do not respond more sensitively to ozone than healthy horses.
• The study suggests that the initial pulmonary antioxidant status doesn’t determine the vulnerability to ozone.
• The authors recommend considering antioxidant supplementation for horses that exhibit a high susceptibility to oxidative stress. This conclusion is presumably made based on the observation of glutathione oxidation post-ozone exposure in both study groups.