Interleukin-8 (IL-8) is an important mediator of immune and inflammatory reactions and is produced by a variety of different cell types. This study was undertaken to investigate the effects of lipopolysaccharides (LPSs) from Prevotella intermedia and Prevotella nigrescens , the major causes of inflammatory periodontal disease, on the production of IL-8 and the expression of IL-8 mRNA in differentiated THP-1 cells, a human monocytic cell line.

LPSs from P. intermedia ATCC 25611 and P. nigrescens ATCC 33563 were prepared by the standard hot phenol-water method. THP-1 cells were incubated in the medium supplemented with phorbol myristate acetate to induce differentiation into macrophage-like cells.

We found that LPS preparations from P. intermedia and P. nigrescens can induce IL-8 mRNA expression and stimulate the release of IL-8 in differentiated THP-1 cells without additional stimuli.

There are no previous reports of the ability of P. intermedia and P. nigrescens LPS to stimulate the release of IL-8, and the present study clearly shows, for the first time, that LPSs from P. intermedia and P. nigrescens fully induced IL-8 mRNA expression and IL-8 production in differentiated human monocytic cell line THP-1. The ability of P. intermedia and P. nigrescens LPS to promote the production of IL-8 may be important in the pathogenesis of inflammatory periodontal disease.