Mohammed S AlQranei1,2, Linda T Senbanjo1, Hanan Aljohani1,3, Therwa Hamza1, Meenakshi A Chellaiah4. 1. Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, 650 W Baltimore Street, Baltimore, MD, 21201, USA. 2. Preventive Dental Sciences Department, School of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. 3. Department of Oral Medicine and Diagnostics Sciences, King Saud University, School of Dentistry, Riyadh, Kingdom of Saudi Arabia. 4. Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, 650 W Baltimore Street, Baltimore, MD, 21201, USA. mchellaiah@umaryland.edu.
Abstract
BACKGROUND: 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.
BACKGROUND: 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.
Entities:
Keywords:
Bone Resorption; Lipopolysaccharides; Osteoclasts; RANK ligand
Authors: K Watanabe; T Iizuka; A Adeleke; L Pham; A E Shlimon; M Yasin; P Horvath; T G Unterman Journal: J Periodontal Res Date: 2010-09-22 Impact factor: 4.419
Authors: Guo-Qing Hou; Chun Guo; Guo-Hua Song; Na Fang; Wen-Juan Fan; Xu-Dong Chen; Lei Yuan; Zhen-Quan Wang Journal: Int J Mol Med Date: 2013-06-05 Impact factor: 4.101
Authors: M A Chellaiah; N Kizer; R Biswas; U Alvarez; J Strauss-Schoenberger; L Rifas; S R Rittling; D T Denhardt; K A Hruska Journal: Mol Biol Cell Date: 2003-01 Impact factor: 4.138
Authors: K Kobayashi; N Takahashi; E Jimi; N Udagawa; M Takami; S Kotake; N Nakagawa; M Kinosaki; K Yamaguchi; N Shima; H Yasuda; T Morinaga; K Higashio; T J Martin; T Suda Journal: J Exp Med Date: 2000-01-17 Impact factor: 14.307
Authors: Charlotte E Roth; Rogerio B Craveiro; Christian Niederau; Hanna Malyaran; Sabine Neuss; Joachim Jankowski; Michael Wolf Journal: Int J Mol Sci Date: 2022-07-22 Impact factor: 6.208