A new agent for treatment of acute respiratory distress syndrome: thymoquinone. An experimental study in a rat model.

OBJECTIVE Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are important clinical problems in thoracic surgery and critical care medicine. Most of the treatment methods are still supportive. Thymoquinone has anti-inflammatory, spasmolytic, bronchodilator and antibacterial effects. We studied its effects on ALI/ARDS in a rat model. METHODS ALI/ARDS was developed in 40 Sprague-Dawley male rats (200-250 g in weight) by intratracheal instillation of human gastric juice (pH 1.2). Rats were treated with mechanic ventilator for 3h. There were five groups: Control group (n=11); Steroid group (n=10); Ethanol group (n=5); Thymoquinone group (n=9) and Thymoquinone+Steroid group (n=5). No instillation except gastric juice was applied in the first group. Thymoquinone was given in dosage of 6 mg/kg, metilprednisolone in dosage of 10mg/kg, ethanol 0.75 ml/kg intraperitoneally (IP). Blood gas analysis and compliance measurement were done. At the end of the third hour, rats were sacrificed and their lungs were excised for histopathological examination. RESULTS In the thymoquinone group, the ratio of arterial oxygen to the fraction of inspired oxygen (PO2/FiO2) was significantly better compared to the other groups (P=0.000-0.043). Static compliance measurements revealed higher values in thymoquinone and thymoquinone+steroid groups. Histopathological examinations showed that affected lung tissue is lower in groups 2 and 4 (P=0.000-0.027). CONCLUSIONS This study revealed that thymoquinone improved oxygenation while both thymoquinone and steroids protect lung tissue from hazardous effects of human gastric juice (pH 1.2) histopathologically.