LPS-Induced Proliferation and Chemokine Secretion from BEAS-2B Cells

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 [H]-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 proliferation, 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.