PSEUDOMONAS STIMULATES INTERLEUKIN-8 MESSENGER-RNA EXPRESSION SELECTIVELY IN AIRWAY EPITHELIUM, IN GLAND DUCTS, AND IN RECRUITED NEUTROPHILS

Neutrophils may play important roles in chronic airway diseases. Pseud omonas is a common pathogen in some chronic airway diseases, and expre ssion of the neutrophil chemoattractant interleukin-8 (IL-8) is induce d by Pseudomonas in various cells in vitro. Here we examine the locali zation of IL-8 mRNA expression after incubating human and dog bronchi with Pseudomonas supernatant in vitro. To examine IL-8 expression in r ecruited neutrophils, we also superfused the dog bypassed tracheal seg ment with Pseudomonas supernatant in vivo and measured neutrophil numb er and IL-8 concentration in luminal fluid; simultaneously, we introdu ced Pseudomonas supernatant by catheter in a peripheral airway. After 6 h, we analyzed IL-8 mRNA expression and localization in removed tiss ue. Unincubated bronchi showed no IL-8 mRNA expression, but incubation with Pseudomonas supernatant in vitro resulted in IL-8 mRNA expressio n in surface epithelial, gland duct, and a subpopulation of serous gla nd cells. In vivo, introduction of Pseudomonas supernatant into dog tr achea and peripheral airways caused IL-8 mRNA expression in epithelial and gland duct cells but also in the recruited neutrophils. Pseudomon as lipopolysaccharide alone was without effect in vitro and in vivo. W e conclude that Pseudomonas products, but not lipopolysaccharide, stim ulate IL-8 expression in airways and that this expression occurs prima rily in surface epithelial and gland duct cells, thus bringing the che moattractant to the bacterial site. Furthermore, IL-8 expression in re cruited neutrophils provides a potential mechanism for positive feedba ck of this protective antibacterial response.