Am. J. Respir. Crit. Care Med., Vol 152, No. 3, Sep 1995, 921-926.
Cytokines affect pseudomonas binding to tracheal cells via a neutrophil- mediated process
S Raoof, MM Grant, MS Niederman, MA Poehlman, AF Matin, FA Khan and AM Fein
Department of Medicine, Nassau County Medical Center, East Meadow, New York 11554, USA.
Critical illness is often associated with gram-negative bacterial
colonization of the airways, increasing the risk of nosocomial pneumonia.
Cytokines, released in response to endotoxin, might contribute to this
phenomenon by causing changes in epithelial cell binding of bacteria. To
investigate this possibility, human monocytes and hamster pulmonary
macrophages were cultured without or with Escherichia coli endotoxin (10
micrograms/ml) for 4 and 24 h. Hamster and human tracheal epithelial cells
were treated with supernates from monocyte cultures for 24 h, and
subsequent binding of 14C-labeled Pseudomonas aeruginosa to the epithelial
cells was measured (percent adherence). In separate experiments,
recombinant human (rh) tumor necrosis factor-alpha (TNF-alpha) (25 to 100
ng/ml) and interleukin-1 beta (IL-1 beta) (2,000 to 8,000 pg/ml) were added
to hamster monolayers. Neither monocyte supernates nor purified cytokines
were toxic to the epithelial cells for up to 48 h. There was no significant
change in P. aeruginosa adherence to either hamster or human tracheal
epithelial cells after 24 h of exposure to culture supernates from either
endotoxin-stimulated human monocytes or hamster macrophages. Similarly,
purified rhTNF and rhIL-1 exposure did not increase bacterial adherence.
However, when polymorphonuclear leukocytes were coincubated with the
monocyte supernates and epithelial cells, P. aeruginosa adherence was
significantly increased. Moreover, this effect was enhanced by an
epithelial cell-derived substance. Thus, while inflammatory cytokines may
participate in enhancing bacterial colonization of the lung in vivo, they
do not do so by a direct action on tracheal epithelial cells but can act
via a neutrophil-dependent mechanism.