RAT ALVEOLAR MACROPHAGE CYTOKINE PRODUCTION AND REGULATION OF NEUTROPHIL RECRUITMENT FOLLOWING ACUTE OZONE EXPOSURE

The alveolar macrophage generation of interleukin-1 beta (IL-1 beta) a nd tumor necrosis factor-alpha (TNF-alpha) cytokines has been implicat ed in the recruitment of neutrophils into acutely injured lungs. To ex amine the role of these cytokines in neutrophil chemotaxis, cytokine m RNA transcripts and content were examined in macrophages lavaged from rats immediately following 6 hr exposure to air or 1 ppm ozone. Ozone exposure enhanced the number of lavaged macrophages demonstrating mRNA transcripts and immunocytochemical staining for IL-1 beta and TNF-alp ha. These changes occurred prior to ozone-induced increases in permeab ility and lavageable neutrophils. The supernatant from in vitro macrop hage cultures demonstrated ozone-associated enhancements in neutrophil chemotactic activity and in IL-1 beta and TNF-alpha levels. However, treatment of the macrophage-conditioned media with anti-IL-1 beta and anti-TNF-alpha antibodies separately and in combination demonstrated t hat these cytokines were not directly responsible for the observed neu trophil chemoattraction. However, coculturing the macrophages with ant i-IL-1 beta and anti-TNF-alpha together, but not separately, resulted in a 44% inhibition of media chemotactic activity, suggesting that max imal macrophage generation of chemoattractants was dependent on either IL-1 beta or TNF-alpha. The mRNA transcripts for the neutrophil chemo attractants macrophage inflammatory protein-2 (MIP-2) and cytokine-ind uced neutrophil chemoattractant (CINC) were found to be enhanced in cu ltured macrophages from ozone-exposed rats, but reduced on incubation with anti-IL-1 beta and anti-TNF-alpha together. These results demonst rated that ozone-induced enhancements in IL-1 beta and TNF-alpha produ ctions appear not to be associated directly with neutrophil chemoattra ction, but are more likely involved in stimulating the generation of t he neutrophil chemoattractants MIP-2 and CINC. (C) 1997 Academic Press .