Lipopolysaccharide (LPS) promotes osteoclast differentiation and activation by enhancing the MAPK pathway and COX-2 expression in RAW264.7 cells

Abstract

Bone degradation is a serious complication of chronic inflammatory diseases such as septic arthritis, osteomyelitis and infected orthopedic implant failure. At present, effective therapeutic treatments for lipopolysaccharide (LPS)-induced bone destruction are limited to antibiotics and surgical repair in chronic inflammatory diseases. The present study aimed to evaluate the mechanism of LPS on osteoclast differentiation and activation. RAW264.7 cells were non-induced, or induced by the receptor activator of nuclear factor-κB (RANK) ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and then treated with LPS. Following treatment, the number of osteoclasts and cell viability were measured. The expression of osteoclast-related genes including tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), cathepsin K (CK), carbonic anhydrase II (CAII) and cyclooxygenase-2 (COX-2) was determined by RT-PCR. Protein levels of RANK, tumor necrosis factor receptor-associated factor 6 (TRAF6), COX-2 and mitogen-activated protein kinases (MAPK) were measured using western blotting assays. LPS promoted osteoclast differentiation of RAW264.7 cells and differentiated osteoclasts. LPS significantly increased mRNA expression of osteoclast-related genes in RAW264.7 cells. Differentiated osteoclasts were treated with LPS (100 ng/ml) and the results showed a significantly increased mRNA expression of osteoclast-related genes and protein levels of RANK, TRAF6 and COX-2. Furthermore, LPS at 100 ng/ml significantly promoted the MAPK pathway including increasing the phosphorylation of c-Jun N-terminal kinases (JNK) and the phosphorylation of the extracellular signal-regulated kinase (ERK1/2). In conclusion, LPS promoted osteoclast differentiation and activation by enhancing RANK signaling and COX-2 expression. LPS also promoted osteoclast differentiation via activation of the JNK and ERK1/2 cell proliferation pathways.

Protective Effects of Pretreatment with Quercetin Against Lipopolysaccharide-Induced Apoptosis and the Inhibition of Osteoblast Differentiation via the MAPK and Wnt/β-Catenin Pathways in MC3T3-E1 Cells

“…LPS, a pro-inflammatory glycolipid component of the gram-negative bacterial cell wall, is a well-documented mediator of gram-negative bacterial bone destruction [2-5]. Quercetin, a dietary flavonoid, has been reported anti-inflammatory properties [15, 25-27]; however, whether the effect of quercetin on osteoblastogenesis is suppressive [16-18] or stimulatory [19-21] remains a matter of controversy.…”

“…Lipopolysaccharide (LPS), a component of the outer membrane of all gram-negative bacteria, was shown to be capable of inducing bone resorption in vivo and in vitro [2-5]. Furthermore, LPS is able to inhibit osteoblast differentiation and to induce apoptosis in vitro [6-10].…”

Leakage of Microbial Endotoxin through the Implant-Abutment Interface in Oral Implants: An In Vitro Study

“…According to Hou et al in 2013 [10], it was documented that microbial endotoxin alone proved to be a sufficient stimulus to upregulate the osteoclastic activity in bone metabolism. This interaction initiates a net bone loss in the affected region.…”

“…As a result, studies [8] were conducted on the tightness of implant-abutment connections against corpuscular bodies (viable bacteria). In 2010, Harder et al suggested that the mere ingress of bacterial endotoxins (requiring less of a micro gap) was enough to initiate the inflammatory cascade and tissue destruction that leads to peri-implant bone loss [9]; this concept was demonstrated by Hou et al in 2013 [10] by the upregulation of osteoclasts by bacterial endotoxins. In Harder's study of two internal implant-abutment connections, he showed one to leak after only 5 minutes whilst the hermetic seal of the other remained intact after 168 hours.…”

17β-estradiol attenuates homocysteine-induced oxidative stress and inflammatory response as well as MAPKs cascade via activating PI3-K/Akt signal transduction pathway in Raw 264.7 cells

“…In our previous study, we have found that lipopolysaccharide (LPS) treatment increases the production of NO, the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and up-regulates the phosphorylation of MAPKs in Raw 264.7 cells, which is dependent on the activation of PI3-K/Akt pathway [16]. Additional studies have also demonstrated that ROS formation and inflammation in response to LPS or other stimuli may be regulated via MAPKs or PI3-K/Akt signal pathway in Raw 264.7 cells [17][18][19]. In this study, we proposed that Hcy may stimulate Raw 264.7 cells by activating inflammatory response and MAPKs activation, thereby increasing the generation of intracellular ROS, and that 17β-E 2 may prevent macrophages from Hcy-induced activation via PI3-K/Akt pathway.…”