Cell-Free Pool of CD14 Mediates Activation of Transcription Factor NF- κB by Lipopolysaccharide in Human Endothelial Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 21; pp. 9887 - 9891
• Main Authors: Read, Margaret A., Cordle, Susan R., Veach, Ruth A., Carlisle, Cherlyn D., Hawiger, Jacek
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.11.1993; National Acad Sciences
• Subjects: Animals; Antigens, CD - biosynthesis; Antigens, CD - metabolism; Antigens, Differentiation, Myelomonocytic - biosynthesis; Antigens, Differentiation, Myelomonocytic - metabolism; Bacteriology; Base Sequence; Binding Sites; Biological and medical sciences; Cell lines; Cell membranes; Cell Nucleus - metabolism; Cells; Cells, Cultured; Endothelial cells; Endothelium, Vascular - drug effects; Endothelium, Vascular - immunology; Endothelium, Vascular - metabolism; Enhancer Elements, Genetic; Fundamental and applied biological sciences. Psychology; Gene Expression; Human umbilical vein endothelial cells; Humans; Immunoglobulin kappa-Chains - genetics; Lipopolysaccharide Receptors; Lipopolysaccharides - pharmacology; Messenger RNA; Mice; Microbiology; Molecular Sequence Data; Monoclonal antibodies; NF-kappa B - metabolism; Oligodeoxyribonucleotides; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Receptors; Recombinant Proteins - metabolism; RNA, Messenger - analysis; RNA, Messenger - biosynthesis; Transcription factors; Umbilical Veins; Ungulates; Human; Toxin; Endothelial cell; Free form; Lipopolysaccharide; Activation; Soluble form; In vitro; Biological activity; Mechanism; Gram negative bacteria; Biological receptor
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.21.9887

Lipopolysaccharide (LPS), a major envelope component of Gram-negative bacteria, is the most frequent causative agent of septic shock and disseminated intravascular coagulation. LPS activates both CD14-positive (monocytes, macrophages, polymorphonuclear leukocytes) and CD14-negative (B-cell lines, endothelial cells) cells. CD14, a 55-kDa glycosyl-phosphatidylinositol-anchored membrane protein present on mature myeloid cells, serves as a receptor for LPS in complex with a soluble (serum-derived) LPS-binding protein (LBP). In this report, we show that human umbilical vein endothelial cells (HUVEC), which do not express measurable CD14 protein, become 3000-fold more sensitive to LPS-induced activation in the presence of serum, as measured by activation of the transcription factor NF-κB and expression of mRNA encoding tissue factor, a procoagulant molecule. This enhanced responsiveness of HUVEC is specifically mediated by the cell-free pool of CD14 (soluble CD14, sCD14) found in serum. The role of sCD14 in HUVEC activation by LPS was established by (i) the blocking effect of monoclonal anti-CD14 antibodies which discriminate between cell-bound and sCD14, (ii) the lack of the serum-enhancing effect after immunodepletion of sCD14, and (iii) establishing a reconstituted system in which recombinant sCD14 was sufficient to enhance the effects of LPS in the absence of serum and without a requirement for LBP. Thus, this mechanism of endothelial cell activation by LPS involves a cell-free pool of sCD14 most likely shed from CD14-positive cells of the monocytic lineage.