EFFECT OF CIGARETTE-SMOKE EXPOSURE ON BIOMARKERS OF LUNG INJURY IN THE RAT

Rats exposed to tobacco cigarette smoke (CS) via inhalation from a hig h-tar cigarette for 4 h/day over a 14-day period showed measurable cha nges in specific biochemical and immunological markers of lung injury when compared to control rats exposed to clean dry air. We found epith elial cell layer thickening and increased lung permeability as measure d by histopathological examination, and increased levels in hexose and protein exudation present in bronchoalveolar lavage fluid. Exposure t o CS also caused a significant reduction in immunoglobulin A (IgA) lev els (p < .001), which persisted after postexposure recovery. In additi on, alveolar macrophages from rats exposed to CS were unresponsive to lipopolysaccharide stimulation in vitro as shown by reduced expression of cytokine interleukin 1 beta mRNA compared to air controls. These r esults suggest that high-tar cigarette smoke can induce disfunctional changes in immune systems. However, as no reproducible smoke-induced c hanges were seen using medium-tar cigarettes, we have to conclude that the rat may not be the most sensitive species in which to evaluate th e mode of action of cigarette smoke on the lung.