Murine osteoblasts respond to LPS and IFN-gamma similarly to macrophages.
Osteoblasts are bone-forming mesenchymal cells, while macrophages are cells of hematopoietic origin responsible for innate immunity. Lipopolysaccharide (LPS) can induce tolerance in macrophages, whereas interferon (IFN)-gamma can activate macrophages to produce cytokines, exert bactericidal effects, and present antigens. In this study, we examined such macrophagic phenotypes regulated by LPS and IFN-gamma in murine osteoblasts. In both primary calvarial osteoblasts and osteoblastic MC3T3-E1 cells, LPS pretreatment resulted in reduced production of IL-6 in response to a subsequent LPS stimulation or to Salmonella infection, indicating the existence of LPS-induced tolerance in osteoblasts. Furthermore, IFN-gamma treatment of MC3T3-E1 cells resulted in both enhanced IL-6 production in response to LPS and upregulation of major histocompatibility complex class II (MHC II). Following infection, Salmonella-containing vacuoles (SCVs) were formed in MC3T3-E1 cells, and IFN-gamma pretreatment enhanced bactericidal effects on intracellular Salmonella. Taken together, these observations indicate that osteoblasts can exhibit a subset of phenotypes reminiscent of macrophages in the course of bacterial infection.
Maruyama
Kenta
K
Department of Microbiology and Immunology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
Sano
Gen-Ichiro
G
Matsuo
Koichi
K
D000818:Animals; D002460:Cell Line; D007371:Interferon-gamma / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D046529:Microscopy, Electron, Transmission; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D053244:Osteoprotegerin / Q000096:biosynthesis; D010641:Phenotype; D012475:Salmonella / Q000502:physiology
D015850:Interleukin-6; D008070:Lipopolysaccharides; D053244:Osteoprotegerin; D007371:Interferon-gamma