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 factor-beta and endothelin have been shown to regulate airway epithelial cell 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. Specific binding assay demonstrated a single set of binding sites on human primary and transformed bronchial epithelial cells. Human interleukin-1alpha (IL-1alpha) increased maximal binding sites to IL-6. Northern blot analysis demonstrated that airway epithelial cells constitutively expressed mRNA for IL-6 receptor (IL-6R), and IL-1alpha and IL-6 itself upregulated IL-6R gene expression. Moreover, exogenously 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 autocrine as well as a paracrine mechanism.