Lipopolysaccharide- TLR-4 Axis regulates Osteoclastogenesis independent of RANKL/RANK signaling
MetadataShow full item record
AbstractBackground: Lipopolysaccharide (LPS) is an endotoxin and a vital component of gram-negative bacteria’s outer membrane. During gram-negative bacterial sepsis, LPS regulates osteoclast differentiation and activity, in addition to increasing inflammation. This study aimed to investigate how LPS regulates osteoclast differentiation of RAW 264.7 cells in vitro. Results: Herein, we revealed that RAW cells failed to differentiate into mature osteoclasts in vitro in the presence of LPS. However, differentiation occurred in cells primed with receptor activator of nuclear factor-kappa-Β ligand (RANKL) for 24 h and then treated with LPS for 48 h (henceforth, denoted as LPS-treated cells). In cells treated with either RANKL or LPS, an increase in membrane levels of toll-like receptor 4 (TLR4) receptor was observed. Mechanistically, an inhibitor of TLR4 (TAK-242) reduced the number of osteoclasts as well as the secretion of tumor necrosis factor (TNF)-α in LPS-treated cells. RANKL-induced RAW cells secreted a very basal level TNF-α. TAK-242 did not affect RANKL-induced osteoclastogenesis. Increased osteoclast differentiation in LPS-treated osteoclasts was not associated with the RANKL/RANK/OPG axis but connected with the LPS/TLR4/TNF-α tumor necrosis factor receptor (TNFR)-2 axis. We postulate that this is because TAK-242 and a TNF-α antibody suppress osteoclast differentiation. Furthermore, an antibody against TNF-α reduced membrane levels of TNFR-2. Secreted TNF-α appears to function as an autocrine/ paracrine factor in the induction of osteoclastogenesis independent of RANKL. Conclusion: TNF-α secreted via LPS/TLR4 signaling regulates osteoclastogenesis in macrophages primed with RANKL and then treated with LPS. Our findings suggest that TLR4/TNF-α might be a potential target to suppress bone loss associated with inflammatory bone diseases, including periodontitis, rheumatoid arthritis, and osteoporosis. Copyright 2021, The Author(s).
SponsorsDr. Joseph Mauban at Confocal Microscopy Core at the University of Maryland, Baltimore School of Medicine, is gratefully acknowledged for providing technical help using the Nikon Scanning Disk Microscope.
Identifier to cite or link to this itemhttp://hdl.handle.net/10713/15172
- Infection of RANKL-primed RAW-D macrophages with Porphyromonas gingivalis promotes osteoclastogenesis in a TNF-α-independent manner.
- Authors: Kukita A, Ichigi Y, Takigawa I, Watanabe T, Kukita T, Miyamoto H
- Issue date: 2012
- Porphyromonas gingivalis-derived lysine gingipain enhances osteoclast differentiation induced by tumor necrosis factor-α and interleukin-1β but suppresses that by interleukin-17A: importance of proteolytic degradation of osteoprotegerin by lysine gingipain.
- Authors: Akiyama T, Miyamoto Y, Yoshimura K, Yamada A, Takami M, Suzawa T, Hoshino M, Imamura T, Akiyama C, Yasuhara R, Mishima K, Maruyama T, Kohda C, Tanaka K, Potempa J, Yasuda H, Baba K, Kamijo R
- Issue date: 2014 May 30
- Recombinant thrombomodulin lectin-like domain attenuates Porphyromonas gingivalis lipopolysaccharide-induced osteoclastogenesis and periodontal bone resorption.
- Authors: Chang LY, Lai CH, Kuo CH, Chang BI, Wu HL, Cheng TL
- Issue date: 2021 Nov
- Aminothiazoles inhibit RANKL- and LPS-mediated osteoclastogenesis and PGE2 production in RAW 264.7 cells.
- Authors: Kats A, Norgård M, Wondimu Z, Koro C, Concha Quezada H, Andersson G, Yucel-Lindberg T
- Issue date: 2016 Jun
- Macrophage-elicited osteoclastogenesis in response to bacterial stimulation requires Toll-like receptor 2-dependent tumor necrosis factor-alpha production.
- Authors: Ukai T, Yumoto H, Gibson FC 3rd, Genco CA
- Issue date: 2008 Feb