Differential induction of IL-lβand IL-6 production by the nontoxic lipid A fromPorphyromonas gingivalisin comparison with syntheticEscherichia colilipid A in human peripheral blood mononuclear cells

Porphyromonas gingivalis 381 lipid A possesses 1-phospho beta(1-6)-linked glucosamine disaccharide with 3-hydroxy-15-methylhexadecanoyl and 3-hexadecanoyloxy-15-methylhexadecanoyl groups at the 2- and 2'-positions, respectively. P. gingivalis lipid A indicated lower activities in inducing interleukin-1 beta (IL-1 beta) mRNA expression, pro-IL-1 beta protein synthesis and IL-1 beta production than those of synthetic Escherichia coli lipid A (compound 506) in human peripheral blood mononuclear cells (PBMC). The induction of IL-6 mRNA and IL-6 synthesis by P. gingivalis lipid A were comparable to those of compound 506. Herbimycin A, H-7 and H-8, inhibitors of tyrosine kinase, protein kinase C and cyclic nucleotide-dependent protein kinase, inhibited P. gingivalis lipid A- and compound 506-induced IL-1 beta and IL-6 synthesis. W-7, an inhibitor of calmodulin (CaM) kinase, inhibited only P. gingivalis lipid A-induced IL-1 beta production. The result suggests that the CaM kinase-dependent cascade is involved in the down-regulation of IL-1 beta production by P. gingivalis lipid A. P. gingivalis lipid A and compound 506 also functioned in the induction of tyrosine and serine/threonine phosphorylation of several proteins in PBMC. P. gingivalis lipid A inhibited specific binding of fluorescein-labelled E. coli LPS to the PBMC. The nontoxic lipid A of P. gingivalis, having a chemical structure different from toxic compound 506, appears to induce the up- and down-regulation of the differential cytokine-producing activities following the activation of various intracellular enzymes including the CaM kinase through the common receptor sites of LPS.