Interleukin-1 and tumor necrosis factor receptor signaling is not required for bacteria-induced osteoclastogenesis and bone loss but is essential for protecting the host from a mixed anaerobic infection.
Bacterial infection causes significant morbidity, mediated in part by the up-regulation of inflammatory cytokines. Cytokine induction is thought to stimulate osteolysis in conditions such as periodontal disease and otitis media. To establish the relative importance of interleukin-1 (IL-1) and tumor necrosis factor (TNF) in mediating the response to a mixed anaerobic infection, we used an in vivo model in which the dental pulp was inoculated with six anaerobic pathogens, in mice with functional deletions of receptors to IL-1 (IL-1RI(-/-)), TNF (TNFRp55(-/-)-p75(-/-)), or both (TNFRp55(-/-)-IL-1RI(-/-)). Polymorphonuclear and mononuclear phagocyte recruitment occurred to the greatest extent in TNFRp55(-/-)-IL-1RI(-/-) mice, and to a lesser extent in IL-1RI(-/-) or TNFRp55(-/-)-p75(-/-) mice, and the least in wild-type mice, demonstrating that recruitment of these phagocytes is not dependent on IL-1 or TNF receptor signaling. A similar pattern was observed for bacterial penetration into host tissue. Because it had recently been reported that TNF played a critical role in mediating lipopolysaccharide-induced bone loss, we anticipated that mice with targeted deletions of TNFRp55(-/-) would have reduced osteoclastogenesis. Surprisingly, osteolytic lesion formation was greatest in animals lacking TNF and/or IL-1 receptors. These results indicate that IL-1 or TNF receptor signaling is not required for bacteria-induced osteoclastogenesis and bone loss, but does play a critical role in protecting the host against mixed anaerobic infections.
Chen
C P
CP
Department of Periodontology and Oral Biology, Boston University School of Dental Medicine, Boston University, Boston, Massachusetts, USA.
Hertzberg
M
M
Jiang
Y
Y
Graves
D T
DT
D000818:Animals; D001421:Bacteria, Anaerobic / Q000472:pathogenicity*; D001424:Bacterial Infections / Q000150:complications*; D002634:Chemotaxis, Leukocyte; D003782:Dental Pulp / Q000382:microbiology / Q000473:pathology; D007091:Image Processing, Computer-Assisted; D007375:Interleukin-1 / Q000502:physiology*; D051379:Mice; D009336:Necrosis; D010010:Osteoclasts; D010014:Osteolysis / Q000209:etiology / Q000276:immunology* / Q000382:microbiology*; D010586:Phagocytes; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology*; D015398:Signal Transduction
D007375:Interleukin-1; D018124:Receptors, Tumor Necrosis Factor