Functional role of macrophages in periodontal disease: I. Activation of macrophage functions by Bacteroides gingivalis.

Abstract

The present study shows that Bacteroides gingivalis-treated murine peritoneal macrophages produce interleukin-1 (IL-1)-like factor (s) which are stimulatory for the osteoblastic cell line MC3T3 -E1. Macrophage-conditioned medium (MCM) was prepared from peritoneal macrophages harvested from mice on day 3 after injection with B. gingivalis. The MCM was chromatographed by gel filtration and then assayed for IL-1 activity and for its effect on protein synthesis and alkaline phosphatase (ALP) activity of MC3T3-E1 cells. The activities which were stimulatory for protein synthesis and ALP activity in MC3T3-E1 cells and the IL-1 activity cofractionated in fractions with molecular weight (m. w.) of 10, 000-22, 000. On the other hand, a high molecular weight substance corresponding to a m. w. of about 130, 000 exhibited inhibitory activities for protein synthesis and the ALP activity of MC3T3 -E1 cells. Further, the major peak having the stimulatory and IL-1 activity from gel filtration was sequentially purified by isoelectric focusing.Significant stimulatory activity for DNA and protein synthesis of MC3T3-El cells cofractionated with IL-1 activity at pI 5.8. However, no detectable peak of such stimulatory activities was observed at pI 4.6 while significantly increased IL-1 activity occurred in this fraction. These results suggest the possibility that macrophage-derived factors for osteoblasts may play a regulatory role in bone remondeling in periodontal disease.