Effects of budesonide and N-acetylcysteine on acute lung hyperinflation, inflammation and injury in rats

Leukocyte activation and production of inflammatory mediators and reactive oxygen species are important in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury. The present study investigated acute lung hyperinflation, edema, and lung inflammation 4 h after an intratracheal instillation of LPS (0.5, 2.5, 5, 10, 50, 100, 500, 1000, and 5000 μg/ml/kg). Effects of budesonide, an inhaled anti-inflammatory corticosteroids, and N-acetylcysteine (NAC), an antioxidant, were evaluated in Wistar rats receiving either low (2.5 μg/ml/kg) or high (50 μg/ml/kg) concentrations of LPS. This study demonstrates that LPS in a concentration-dependent pattern induces acute lung hyperinflation measured by excised lung gas volume (25-45% above control), lung injury indicated by increased lung weight (10-60%), and lung inflammation characterized by the infiltration of leukocytes (40-14000%) and neutrophils (80-17000%) and the production of cytokines (up to 2700%) and chemokines (up to 350%) in bronchoalveolar lavage fluid (BALF). Pretreatment with NAC partially prevented tumor necrosis factor α (TNFα) production induced by the low concentration of LPS, while pretreatment with budesonide totally prevented the increased production of TNFα, interleukin (IL)-1β, IL-6, and monocyte chemoattractive protein (MCP)-1 after LPS challenge at both low and high concentrations. Budesonide failed to prevent BALF levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant 1 (GRO/CINC-1) as well as lung hyperinflation induced by both low and high concentrations of LPS. Pretreatment with budesonide totally prevented the formation of lung edema at the low concentration of LPS and had partial effects on acute lung injury and leukocyte influx at the high concentrations. Thus, our data indicate that therapeutic effects of budesonide and NAC are dependent upon the severity of the disease.