Signal transducing mechanism of Porphyromonas gingivalis lipopolysaccharide in expression of monocyte chemoattractant MCP-1 of human monocytic THP-1 cells via CD14.

Abstract

The present study examined the role of CD14 in the signal pathway for expression of Porphyromonas gingivalis lipopolysaccharide (P-LPS) -induced MCP-1, human monocyte chemoattractant protein-1, in human monocytic THP-1 cells. P-LPS, at a concentration of 1μg/ml, induced a maximum MCP-1 gene expression in the cells 3h after initiation of the LPS treatment. A marked chemotactic activity for human monocytes was detected in conditioned medium of the P-LPS-treated cells. The presence of MCP-1 protein in the conditioned medium was indicated by an immunoprecipitation assay and neutralization of the chemotactic activity with the specific antiserum for MCP-1 protein. Anti-CD14 antibody greatly inhibited both gene expression and production of MCP-1 in P-LPS-treated THP-1 cells. The P-LPS-induced MCP-1 gene expression was greatly inhibited by a potent inhibitor of tyrosine kinase, herbimycin A.A Run-on assay showed that the LPS-induced MCP-1 gene expression increased at the transcriptional level. Anti-CD14 antibody also inhibited the increased transcriptional activity of the MCP-1 gene in the LPS-induced cells. Curcumin, a specific inhibitor of transcriptional factor AP-1, strongly inhibited the LPS-induced MCP-1 gene expression. A gel mobility assay showed that P-LPS stimulated the binding of AP-1 to its DNA consensus sequence in the cells and that P-LPS stimulation of the AP-1 binding was markedly inhibited by anti-CD14 antibody and curcumin. Based on these results, we propose a signal transducing mechanism of P-LPS via CD14 in human monocytic cells.