Magnesium Lithospermate B Protects against Lipopolysaccharide-Induced Bone Loss by Inhibiting RANKL/RANK Pathway.

Jihai Wang,Yongzhuang Duan,Xuejian Wu

doi:10.3389/fphar.2018.00064

Abstract

Lipopolysaccharide (LPS) can induce bone loss by stimulating bone resorption. Natural compounds have great potential for the treatment of osteolytic bone diseases. Magnesium lithospermate B (MLB) plays an important role in protecting against oxidative damage and also has potential anti-inflammatory pharmacological properties. However, its role in LPS-induced bone loss is still unknown. In the present study, we observed the effects of MLB on LPS-induced bone damage and investigated the possible mechanisms. The bone loss models were established by LPS administration in male Sprague–Dawley rats. MLB (200 mg/kg body weight) was given by subcutaneous injection. MicroCT analysis, biomarker assay, histological examination and immunohistochemical staining were performed at the 8th weeks. In addition, RAW264.7 cells were treated with LPS in the presence or absence of MLB. The osteoclast formation, resorption activity and differentiation-related genes [(receptor activator of nuclear factor kappa-B (RANK), Traf6, Fra-1, and c-src)] expression were evaluated. LPS induced bone loss shown as the decrease in bone volume fraction and trabecular number, and increase in trabecular separation. LPS also markedly enhanced the osteoclast formation and resorption activity compared with the control. MLB significantly abolished the LPS-induced bone microstructure damage (p < 0.05) and osteoclast formation. MLB also inhibited the increases of serum tartrate-resistant acid phosphatase 5b, RANK ligand (RANKL) and TNF-α level enhanced by LPS (p < 0.05). Immunohistochemical staining indicated that MLB attenuated the high expression of RANKL and RANK stimulated by LPS. In addition, MLB significantly abolished the LPS-enhanced osteoclast formation, resorption activity, RANK, Traf6, Fra-1, and c-src expression in vitro. Our data demonstrate that MLB can suppress LPS-induced bone loss via inhibiting RANKL/RANK related osteoclast formation.

Highlights

Lipopolysaccharide(LPS) is a component of the outer membranes of the gram-negative bacteria (Kulp and Kuehn, 2010), which has been identified as the critical pathogenic factor in inflammatoryinduced bone resorption (Mori et al, 2013, 2015; Guo et al, 2014)
To gain further insights into the mechanism by which Magnesium lithospermate B (MLB) exerts its inhibitory action on the osteoclast formation and bone resorption, we examined the influence of MLB on the receptor activator of nuclear factor kappa-B (RANK), Traf6, Fra1, and c-src mRNA (Figure 8A) and protein expression in vitro (Figure 8B)
Our data indicate that MLB protects against bone loss induced by LPS via inhibiting osteoclast formation, which demonstrates that MLB might present an efficient therapy against LPS-induced bone loss

Summary

Introduction

Lipopolysaccharide(LPS) is a component of the outer membranes of the gram-negative bacteria (Kulp and Kuehn, 2010), which has been identified as the critical pathogenic factor in inflammatoryinduced bone resorption (Mori et al, 2013, 2015; Guo et al, 2014). The inhibition of LPS-induced osteolysis is critical for the treatment of infective bone diseases (Zhang et al, 2016). Several studies showed that the inhibition of osteoclast formation or activity may be one of treatment strategies (Kim et al, 2014; Zhang et al, 2016). Many studies show that compounds derived from natural products can prevent bone loss by inhibiting osteoclast formation (Hwang et al, 2013; Zhang et al, 2016; Zhou et al, 2016; Chen et al, 2017). Niu et al (2017) showed that Nardosinone, a natural compounds from Nardostachys, could inhibited LPS-induced bone loss by inhibiting osteoclast activity. The effect of MLB on LPS-induced bone loss is not clarified

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Discussion

Conclusion