Neutrophil-mediated damage to human periodontal ligament-derived fibroblasts: role of lipopolysaccharide.

Human periodontal ligament-derived fibroblasts (HPLF) were grown to confluency in culture and were subjected to various combinations of neutrophils (PMNs), lipopolysaccharide (LPS) and the chemoattractant formylmethionyl-leucyl-phenylalanine (FMLP). After treatment, the cells were stained to distinguish between normal and damaged cells. The stain also allowed an estimation of PMN adherence to the HPLF monolayer. We report that FMLP, LPS or PMNs alone did not damage HPLF cells, nor did PMNs when combined with LPS or FMLP separately. However, PMNs subjected to combinations of LPS (10-1000 ng/ml) and FMLP (10(-9)-10(-6) M) caused significant PMN-mediated fibroblast damage. LPS concentrations greater than 1000 ng/ml inhibited the cytotoxic reaction. Furthermore, we found that FMLP alone did not significantly enhance PMN adherence to the HPLF monolayer but that LPS increased PMN adherence 3-fold and the combination of LPS and FMLP enhanced adherence 6-fold. We conclude that LPS promotes PMN adherence to fibroblasts and that such adherence appears to be a crucial, but insufficient stimulus, for the induction of PMN-mediated HPLF injury.