Abstract：Objective Asthma is recognized as a chronic airway inflammatory disease. Reactive oxygen species can induce airway inflammation. The aim of this study was to explore the effect of melatonin (MT) on the content of reactive oxygen species and airway inflammation in rats with bronchial asthma. Methods Twenty-four Sprague-Dawley (SD) rats were randomly assigned into 3 experimental groups (8 in each): 1) Asthma group: the rats were immunized on day 1 by intraperitoneal injection of 100 mg ovalbumin (OVA) in 1 ml saline with 100 mg of aluminum hydroxide. After 14 days, the rats were challenged with aerosolized 1% OVA for 20 mins per day for 7 consecutive days; 2) MT group: OVA-sensitized rats were given intraperitoneal injection of 10 mg/kg MT 30 mins before each OVA challenge; and 3) Control group: OVA was replaced with normal saline. Airway responsiveness to aerosolized acetylcholine was detected 6 hrs after the last challenge. Then the rats were lavaged and total and differentiated leukocytes counts in bronchoalveolar lavage fluid (BALF) were performed after Wright-Giemsa staining. At the same time, the content of reactive oxygen species (ROS) in the lung tissues was assessed with chemical colorimetry. Results After OVA challenge, there was a significant decrease in airway responsiveness and the number of lymphocytes and eosinophils in the BALF of the MT group compared with the Asthma group (P< 0.05). The MT group also showed a significantly lower ROS level in the lung tissues compared with Asthma group (P< 0.05). Conclusions MT can decrease airway inflammation and the content of ROS in asthmatic rats, which may be the underlying protective mechanisms of MT against asthma.
