INTERLEUKIN-6 RECEPTOR EXPRESSION ON HUMAN BRONCHIAL EPITHELIAL-CELLS- REGULATION BY IL-1 AND IL-6

Airway epithelial cells have a potential to participate in regulation of local homeostasis by releasing active compounds including cytokines and growth factors. Several factors such as transforming growth facto r-beta and endothelin have been shown to regulate airway epithelial ce ll functions through an autocrine mechanism. We studied the expression of the specific receptor for a multifunctional cytokine interleukin 6 (IL-6), which is expressed and released by airway epithelial cells. S pecific binding assay demonstrated a single set of binding sites on hu man primary and transformed bronchial epithelial cells. Human recombin ant interleukin-1 alpha (IL-1 alpha) increased maximal binding sites t o IL-6. Northern blot analysis demonstrated that airway epithelial cel ls constitutively expressed mRNA for IL-6 receptor (IL-6R), and IL-1 a lpha and IL-6 itself upregulated IL-6R gene expression. Moreover, exog enously added human recombinant IL-6 had a stimulatory effect on IL-8 release from human bronchial epithelial cells. These results indicated that human bronchial epithelial cells expressed IL-6R, and IL-6 might be involved in the regulation of the epithelial functions via an auto crine as well as a paracrine mechanism.