ABSTRACT
The surface antigen CD14 plays an important role in innate immunity, serving as a pattern recognition receptor for lipopolysaccharides (LPS). The aim of this study was to investigate the proliferation, NFκB activation, and chemokine secretion of BEAS-2B cells, a human bronchial epithelial cell line, after LPS stimulation, and some details of inVolved signaling. The presence of CD14 was investigated by flow cytometry. Cell proliferation was measured with a [3H]-thymidine incorporation assay. sCD14, RANTES, and IL-8 concentrations in cell supernatants were measured by ELISA. BEAS-2B cells express CD14 on their surface and secrete soluble CD14 into the supernatant. Cells react on LPS with increased proliferation, activation of NFκB, and the secretion of the pro-inflammatory chemotactic cytokines IL-8 and RANTES, which proves the functionality of the CD14 receptor. Neither CD14 nor sCD14 are regulated by LPS. Specific inhibitors of various intracellular signaling pathways diminish the LPS-induced proliferation and IL-8 secretion: Thus MAP-Kinases p38 and JNK, tyrosine kinases, and PI3-kinase are involved in the signaling cascade from the LPS-CD14-complex on the cell surface to the increased cell proliferation and expression of IL-8; furthermore, ERK 1/2, IRAK 1/4, and the NFκB pathway are inVolved in the latter. The data show the existence and functionality of CD14 receptors on BEAS-2B cells and elucidate the signaling pathways inVolved. LPS is able to increase cell prolife-ration, various cytokines which are dependent on endogenous CD14. Three MAPK pathways, PI3 kinase and tyrosine kinase may be involved. Also CD14 is present/involved which was controversial.