LIPOPOLYSACCHARIDE ISOLATED FROM PORPHYROMONAS-GINGIVALIS GROWN IN HEMIN-LIMITED CHEMOSTAT CONDITIONS HAS A REDUCED CAPACITY FOR HUMAN NEUTROPHIL PRIMING

One way prokaryotes respond to environmental stresses is by modifying selected outer membrane components. Iron, in the form of hemin, has be en shown to be a significant regulator of Porphyromonas gingivalis gro wth and virulence and of the expression of outer membrane proteins and lipopolysaccharide. Since lipopolysaccharide has profound effects on host immune cells, this study compared the effect of hemin-restricted and hemin-normal P. gingivalis growth conditions on lipopolysaccharide priming of N-formylmethionyl-leucyl-phenylalanine-induced superoxide generation by human neutrophils. P. gingivalis was grown in a chemosta t under normal (5 mu g hemin/ml) and hemin-restricted (0.08 mu g hemin /ml) conditions. Purified lipopolysaccharide from both P. gingivalis n ormal and hemin-limited environments increased N-formylmethionyl-leucy l-phenylalanine-induced superoxide release by neutrophils in a dose-de pendent manner. Lipopolysaccharide isolated from the hemin-normal cond itions was a significantly more potent neutrophil priming agent than t he Lipopolysaccharide isolated from hemin-restricted conditions. Addit ion of normal human serum enhanced the priming effect of both lipopoly saccharide preparations; this effect, however, was more evident with t he hemin-normal lipopolysaccharide. Further, this enhancing effect of serum was partly reduced in the presence of antibodies raised against the serum Lipopolysaccharide-binding protein. The differences in the b iological activity of the two lipopolysaccharide preparations could be associated with structural differences detected by sodium dodecyl sul fate-polyacrylamide gel electrophoresis analysis. These results indica te that hemin availability affects regulation of an aspect of the ging ivalis virulence, lipopolysaccharide-human neutrophils priming. The re duced capacity for neutrophil priming by hemin-restricted Lipopolysacc haride appears to be related to lipopolysaccharide-neutrophil interact ions and not to serum factors. Targeting bacterial cell-surface compon ents involved in hemin transport might be effective therapy for P. gin givalis-associated periodontal diseases.