THE EFFECT OF CONDITIONED MEDIUM FROM CULTURED HUMAN BRONCHIAL EPITHELIAL-CELLS ON EOSINOPHIL AND NEUTROPHIL CHEMOTAXIS AND ADHERENCE IN-VITRO

Several studies have demonstrated that bronchial epithelial cells are capable of synthesizing proinflammatory cytokines chat may influence e osinophil and neutrophil activity. We have cultured human bronchial ep ithelial cells to confluence, as explant cultures, and investigated th e effect of conditioned medium from these cells on (I) the chemotaxis of eosinophils and neutrophils and (2) the adherence of these cells to cultured human endothelial cells. Analysis of cytokines, namely inter leukin-1 beta (IL-1 beta), interleukin-8 (IL-8), tumor necrosis factor alpha (TNF alpha), granulocyte/macrophage colony-stimulating factor ( GM-CSF), and RANTES, which are thought to be involved in these process es, demonstrated that all these cytokines were synthesized and release d constitutively from the bronchial epithelial cell cultures. Conditio ned medium obtained after 24 h of incubation significantly increased t he chemotaxis of eosinophils and neutrophils, from median values of 4, 0 cells/per high power field (hpf) (range, 3.0 to 7.0) and 17 cells/hp f (range, 13.0 to 25.0), respectively, for medium 199, to median value s of 11.0 cells/hpf (range, 9 to 12; P = 0.005) and 30 cells/hpf(range , 19 to 33; p = 0.01), Whereas anti-GM-CSF and anti-IL-8 neutralizing monoclonal antibodies significantly attenuated the conditioned medium- induced chemotaxis of eosinophils and neutrophils, anti-RANTES neutral izing antibody significantly attenuated the chemotaxis of only eosinop hils. Conditioned medium also significantly increased the percentage o f eosinophils and neutrophils adhering to endothelial cells in a dose- dependent manner. Both anti-human TNF alpha and anti-human IL-I beta n eutralizing antibodies significantly attenuated the conditioned medium -induced adherence of eosinophils and neutrophils to the endothelial c ells and were found to have an additive effect when studied together. Similarly, treatment of endothelial cells with either anti-ICAM-1 or a nti-E-selectin, for 1 h before co-culture with eosinophils and neutrop hils, significantly attenuated the conditioned medium-induced adherenc e of both eosinophils and neutrophils to endothelial cells. Treatment of endothelial cells with anti-VCAM-1 attenuated the adherence of eosi nophils but not neutrophils. These results suggest that human bronchia l epithelial cells, through their ability to generate proinflammatory mediators, are likely to play a role in the pathogenesis of airway dis ease by influencing chemotaxis and adherence of eosinophils and neutro phils.