STRAIN-DEPENDENT ACTIVATION OF MONOCYTES AND INFLAMMATORY MACROPHAGESBY LIPOPOLYSACCHARIDE OF PORPHYROMONAS-GINGIVALIS

Porphyromonas gingivalis is one of the pathogens associated with perio dontal diseases, and its lipopolysaccharide (LBS) has been suggested a s a possible virulence factor, acting by stimulation of host cells to secrete proinflammatory mediators. However, recent studies have shown that P. gingivalis LPS inhibited some components of the inflammatory r esponse. The present study was designed to test the hypothesis that th ere are strain-dependent variations in the ability of P. gingivalis LP S to elicit the host inflammatory response. By using LPS preparations from two strains of P. gingivalis, W50 and A7346, the responses of mou se macrophages and human monocytes were evaluated by measuring the sec retion of nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha ). Both direct and indirect (priming) effects were investigated. LPS f rom Salmonella typhosa was used as a reference LPS. P. gingivalis A743 6 LPS induced lower secreted levels of NO from the tested cells than S . typhosa LPS but induced similar levels of TNF-alpha. In contrast, LP S from P. gingivalis W50 did not induce NO or TNF-alpha secretion. Pre incubation of macrophages with LPS from S. typhosa or P. gingivalis A7 436 prior to stimulation with S. typhosa LPS upregulated NO secretion and downregulated TNF-alpha secretion, while preincubation with P. gin givalis W50 LPS enhanced both TNF-alpha and NO secretory responses. Th ese results demonstrate that LPSs derived from different strains of P. gingivalis vary in their biological activities in vitro. The findings may have an impact on our understanding of the range of P. gingivalis virulence in vivo.