EFFECT OF HAEMOPHILUS-INFLUENZAE ENDOTOXIN ON THE SYNTHESIS OF IL-6, IL-8, TNF-ALPHA AND EXPRESSION OF ICAM-1 IN CULTURED HUMAN BRONCHIAL EPITHELIAL-CELLS

Although studies of infective lung diseases have demonstrated that Hae mophilus influenzae is a major pathogen, the mechanisms underlying pat hogenesis by this organism are not clear. We have cultured human bronc hial epithelial cells (HBEC) to confluency and have investigated the e ffect of H. influenzae endotoxin (HIE) on: 1) epithelial permeability, by movement of C-14-bovine serum albumin (C-14-BSA) across HBEC and m easurement of electrical resistance of HBEC; 2) release of interleukin -6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-alpha (TNF- alpha) into the supernatant, by enzyme-linked immunosorbent assay (ELI SA); and 3) expression of intercellular adhesion molecule-1 (ICAM-1), by immunofluorescence staining. HIE did not significantly increase the movement of C-14-BSA across HBEC, In contrast, HIE progressively incr eased the electrical resistance of HBEC, such that this was significan t after 24 h, Compared with untreated cells, 10-100 mu g.ml(-1) HIE-tr eated cells released significantly greater amounts of IL-6, IL-8 and T NF-alpha, after 24 h, which was blocked by 10(-5) M hydrocortisone, Si milarly, incubation of HBEC with 10-100 mu g.ml(-1) HIE, significantly increased the total number of ICAM-1 positive cells, which were signi ficantly decreased on incubation of the cells in the presence 10(-5) M hydrocortisone, Conditioned medium from HIE-exposed HBEC lead to sign ificant increase in neutrophil chemotaxis and adhesion to endothelial cells in vitro. These results suggest that HIE may affect epithelial c ell function and influence inflammation of the airway mucosa via induc tion of proinflammatory mediators.