Cigarette smoking decreases interleukin-8 secretion by human alveolar macrophages

Cigarette smoking can impair pulmonary immune function, and hence influences the development of lung diseases. Interleukin-8 (IL-8) is a proinflammatory peptide and a potent chemotactic factor for neutrophils, and is produced by both immune and non-immune cells including monocytes and alveolar macrophages (AM). We investigated the effect of cigarette smoking on the secretion of IL-8 by human AM. The IL-8 concentration in bronchoalveolar lavage fluid (BALF) was much higher in smokers than in non-smokers (18.4 +/- 3.9 vs 4.1 +/- 1.0 pg ml-1; P < 0.005). However, spontaneous IL-8 secretion by cultured AM was lower in smokers than in non-smokers (46.8 +/- 12.7 vs 124.1 +/- 24.0 ng ml-1; P < 0.01). When stimulated with lipopolysaccharide (LPS), AM from smokers secreted significantly less IL-8 than those from non-smokers at all tested concentrations of LPS. In contrast, the amount of IL-8 secreted by peripheral blood monocytes with or without LPS stimulation was comparable in smokers and non-smokers. These observations indicate that smoking decreases IL-8 secretion by AM, which may modify or decrease the inflammatory response in the lung.