The in vitro effect of Actinobacillus actinomycetemcomitans strain Y4 lipopolysaccharide on murine peritoneal macrophages.

Actinobacillus actinomycetemcomitans strain Y4 lipopolysaccharide (LPS) was examined for its in vitro effect on murine peritoneal macrophage morphology, viability, and lysosomal enzyme activity. Fifty micrograms of Y4 LPS per 10(6) macrophages resulted in macrophage activation, eliciting the release of acid phosphates (AcP), as well as the accumulation of intracellular AcP, without a loss in viability. There was also an increase in the number of organelles and cell-surface ruffles. One hundred or 250 microgram of Y4 LPS caused flattening, rounding, and blebbing of the cell surface, as well as the release of large quantities of AcP and lactate dehydrogenase (LDH), within 5 min of exposure to the LPS. Alteration of cell ultrastructure occurred within 30 min, and extensive autophagocytosis by 24 h, indicative of cell injury. Short-term (less than 24 h) experiments appear necessary to distinguish between the effects of cell activation and cell death caused by A. actinomycetemcomitans Y4 LPS.