We studied the lungs of 31 patients with ARDS (Pao2/fraction of inspired oxygen ¡Ü 200, 45 ¡À 14 years, 16 men) and 11 controls (52 ¡À 16 years, 7 men) submitted to autopsy and quantified the expression of interleukin (IL) 6, IL-8, surfactant proteins (SP) A and SP-B in the epithelium of small airways using immunohistochemistry and image analysis. In addition, an index of airway epithelial apoptosis was determined by the terminal deoxynucleotidyl transferase-mediated deoxyuridine-triphosphatase nick-end labeling assay, caspase 3, and Fas/Fas ligand expression. The density of inflammatory cells expressing IL-6 and IL-8 within the small airway walls was also quantified.
Acute respiratory distress syndrome airways showed an increase in the epithelial expression of IL-8 (P = .006) and an increased density of inflammatory cells expressing IL-6 (P = .004) and IL-8 (P < .001) compared with controls. There were no differences in SP-A and SP-B epithelium expression or in epithelial apoptosis index between ARDS and controls.
Distal airways are involved in ARDS lung inflammation and show a high expression of proinflammatory interleukins in both airway epithelial and inflammatory cells. Apoptosis may not be a major mechanism of airway epithelial cell death in ARDS.