Characterization of bone-resorbing activity in human periapical lesions

Extracts of human periapical granulomas were tested for the presence of bone-resorbing activity. All granulomas (10 of 10) contained low but significant levels of bone-resorbing activity, ranging from 2.1 to 4.9% treatment-% control/mg specific 45Ca release, as determined by the fetal rat long bone assay. Healthy periodontal ligament and dental pulp had no significant resorbing activity. In characterization studies, the resorbing activity in an extract pool was unaffected by the presence of polymyxin B, indicating an active moiety distinct from lipopolysaccharide. Resorbing activity was also unaffected by heating to 56 degrees C for 30 min, but was completely abolished by proteinase K treatment or heating to 70 degrees C, indicating that activity was largely protein mediated. Fast performance liquid chromatography gel filtration studies demonstrated that activity could be resolved to two major peaks, of M(r) 30,000 to 60,000 (I), and 15,000 to 20,000 (II), with a minor peak present at < 1,000 (III). Peak III was identified as prostaglandin E2 by radioimmunoassay. In inhibition studies, virtually all of the resorbing activity present was inhibited by anti-interleukin 1 beta (69%) and anti-tumor necrosis factor beta (66%) antisera, whereas anti-interleukin 1 alpha and antitumor necrosis factor alpha had no effect. Treatment with the cyclooxygenase inhibitor indomethacin also reduced activity by 74%. Taken together, these data demonstrate that most bone-resorbing activity present in chronic human periapical lesions is attributable to the action of resorptive cytokines interleukin 1 beta and tumor necrosis factor beta, acting via both indomethacin-dependent and independent pathways.(ABSTRACT TRUNCATED AT 250 WORDS)