Interleukin-8 secretion of human epithelial and monocytic cell lines induced by middle ear pathogens

Otitis media with effusion (OME) is one of the most common diseases in chil dren. Alloiococcus otitidis, a new Gram-positive bacterial species, was iso lated from the middle ear fluid of children with OME; however, the pathogen ic role of this bacteria is yet unknown. In this study, the ability of cult ured epithelial cell lines (Hep-2 and Hela) and monocytic cell lines (THP-1 and U 937) to secrete chemokine interleukin-8 (IL-8) in response to the A. otitidis organism and three bacterial organisms mainly detected from middl e ear fluid in ORLE, and bacterial cell components was investigated. When s timulated with four viable bacterial cells, epithelial cells and monocytes secreted IL-8 in a time-dependent manner. The monocytes produced significan tly higher levels of IL-8 than the epithelial cells. Compared with that by viable bacterial cells, IL-8 secretion by stimulated epithelial cells and m onocytes was reduced when the bacteria were heated and treated with glutara ldehyde. With bacterial stimulations, cell treatment of interferon-gamma ca used monocytes to increase the induction of IL-8 production, however, the i nduction of monocyte differentiation caused monocytes to reduce the inducti on of IL-8 production, Furthermore, epithelial cells and monocytes stimulat ed by four viable bacterial organisms physically separated from cultured ce lls reduced the induction of IL-8 compared with directly stimulated cells, and monocytes stimulated with soluble extracts prepared from A, otitidis or ganisms produced IL-8 in a dose-dependent manner. These results suggest tha t part of the IL-8 stimulation of the A. otitidis organism may exist in a d iffusable factor released by the bacteria or soluble components of the bact eria itself.