Moraxella catarrhalis stimulates the release of proinflammatory cytokines and prostaglandin E2 from human respiratory epithelial cells and monocyte-derived macrophages

The outer membrane proteins of Moraxella catarrhalis, a bacterial pathogen whichcauses disease in both children and adults, play an important role in its phenotypicproperties. However, their proinflammatory potential with regard to respiratoryepithelium and macrophages is unclear. To this end, we examined the cytokine- andmediator-inducing capacity of a heat-killed wild-type M. catarrhalis strain and anonautoagglutinating mutant as well as their outer membrane proteins andsecretory/excretory products using the A549 respiratory epithelial cell line. The outermembrane proteins and secretory/excretory products from both isolates as well asthe heat-killed bacteria all induced interleukin (IL)-6, IL-8 and prostaglandin E2, butnot IL-1b, from the A549 cell line in a dose- and time-dependent manner. Heatkilledbacteria and secretory/excretory products stimulated the release of IL-1b, IL-6,IL-8 and prostaglandin E2 from human monocyte-derived macrophages. Both heatkilledisolates also stimulated nuclear translocation and transactivation of nuclearfactor-kB. The heat-killed wild-type autoagglutinating isolate induced significantlygreater amounts of IL-6 and IL-8 from A549 cells than the nonautoagglutinatingmutant compared with the monocyte-derived macrophages but no significantdifferences in the amounts induced by the two strains were observed. These differenceswere also evident when the respiratory cell line was stimulated with outer membraneproteins as well as in the degree of nuclear factor-kB transactivation. There was littledifference in the stimulatory activity of the secretory/excretory products. Sodiumdodecyl sulphate-polyacrylamide gel electrophoresis analyses revealed some differencesin the outer membrane proteins and secretory excretory products between thetwo isolates. Combined, these data show that M. catarrhalis secretory excretoryproducts and outer membrane proteins are associated with the induction ofinflammatory responses in both respiratory epithelium and macrophages.