Xanthine oxidase contributes to sustained airway epithelial oxidative stress after scald burn

Respiratory tract infections and pneumonia are major causes of morbidity and mortality in burn victims, however, limited studies have examined the effects of burn injury on airway epithelium. The current study examines the effect of scald burn injury on rat tracheal epithelium at 5 days after injury and tests the hypothesis that treatment with febuxostat (FBX), an inhibitor of xanthine oxidase (XO), can be protective of cell homeostasis. Sprague Dawley rats were randomly divided into uninjured (sham), injured (control) and injured and FBX treated groups, n = 8. Control and FBX treated groups received 60% total body surface area scald burn injury. The FBX group received an i. p. dose (1 mg/kg) at 1 hour after injury and every 24 hours. At 5 days after injury, the animals were sacrificed and tracheal epithelial cell lysates were collected. Malondialdehyde (MDA), ATP, and XO activity were measured. Formation of 8-OHdG in tracheal epithelium was determined using immunohistochemistry (IHC) and immunoreactivity was quantitated. MDA levels were significantly increased in injured control animals (24.8 ± 2.3) compared to sham (7.93 ± 1.2, p = 0.002). FBX treatment attenuated this response (12.6 ± 2.7, p = 0.02). ATP levels were significantly decreased in control (0.7 ± 0.16) compared to sham, (2 ± 0.14, p = 0.01). ATP levels were increased with FBX treatment (1.8 ± 0.1, p = 0.03) compared to controls. There was a significant increase in XO activity in control animals, 1.04 ± 0.06 compared to sham (0.34 ± 0.05, p = 0.03), and this response decreased with FBX treatment 0.46 ± 0.07 (p = 0.04). Immunolabeling of 8-OHdG in control animals was significantly increased (25.1 ± 0.7 compared to the sham group 5.5 ± 1.9 (p = 0.01)), and was decreased with FBX treatment (7.0 ± 2.3 compared to control (p = 0.03)). The current study indicates that lipid peroxidation and ATP depletion persist in tracheal epithelium for 5 days after injury along with increased XO activity and 8-OHdG. These effects were significantly attenuated by FBX treatment, suggesting that reactive oxygen species generated by XO contribute to airway epithelial injury following scald burn.