Attenuation of Airway Hyperresponsiveness During Acute Viral Infection Using the 21-Aminosteroid U-83836E in Rats

Respiratory viral infections have been associated with exacerbations of asthma in humans, and are known to produce airway obstruction and hyperresponsiveness in rats. Virus-induced airway dysfunction may result in part from inflammatory cells and their products, and agents that target these mechanisms might therefore attenuate viral airway injury. The 21-aminosteroid class of drugs has been reported to attenuate tissue injury in a variety of models, and we hypothesized that U-83836E, an orally-active aminosteroid, would prevent the development of airway dysfunction during acute viral illness. Adult rats were inoculated with either parainfluenza type 1 (Sendai) virus or sterile vehicle, treated with either U-83836E 20 mg/kg or water by oral gavage twice daily, and studied on postinoculation day 5, 6 or 7. Anesthetized, paralysed, mechanically ventilated rats were placed in a body plethysmograph for measurements of airway obstruction (resistance, dynamic compliance, eucapneic PaO₂), and responsiveness to iv methacholine; lungs were lavaged to obtain inflammatory cells. The water–treated virus group was significantly different from the non-infected controls for all variables. Virus-induced hyperresponsiveness was attenuated (P=0.027) by aminosteroid treatment, although airway obstruction and inflammation were not improved by the treatment. We conclude that 21-aminosteroids may protect airways from virus-induced hyperresponsiveness.