Membrane-associated interleukin-1 on macrophages stimulated with Actinobacillus actinomycetemcomitans lipopolysaccharide induces osteoclastic bone resorption in vivo.

The effect of paraformaldehyde-fixed murine macrophage P388D1 cells stimulated with Actinobacillus actinomycetemcomitans Y4 lipopolysaccharide (membrane-associated interleukin-1) on osteoclastic bone resorption was investigated. Both the number of osteoclasts and the bone resorption surfaces increased considerably along the inside of the marrow space of mouse calvaria when membrane-associated interleukin-1 mediated by A. actinomycetemcomitans Y4 lipopolysaccharide were injected into the subcutaneous tissues overlying the central calvaria of 4-week-old C3H/HeJ mice. Membrane-associated interleukin-1 caused hypercalcaemia when injected into C3H/HeJ mice twice a day for 2 days. The calvaria of C3H-HeJ mice injected with membrane-associated interleukin-1 contained less mineral than those of the control mice. These results suggest that membrane-associated interleukin-1 on macrophages stimulated with A. actinomycetemcomitans Y4 lipopolysaccharide plays an important role in inflammatory osteoclastic bone resorption in periodontal diseases.