Hesperetin Prevents Bone Resorption by Inhibiting RANKL-Induced Osteoclastogenesis and Jnk Mediated Irf-3/c-Jun Activation.

Qiang Zhang,Wei Zhu,Xinqiao Tang,Dan Peng,Zhengxiao Ouyang,Wanchun Wang,Zhong Liu,Xiaoxia Song

doi:10.3389/fphar.2018.01028

Abstract

Bone homeostasis and resorption is regulated by the proper activation of osteoclasts, whose stimulation largely depends on the receptor activator of nuclear factor κB ligand (RANKL)-RANK signaling. Herein, for the first time, we showed that interferon regulatory factor (Irf)-3 was intimately involved in RANKL-induced osteoclast formation. In addition, hesperetin (Hes) derived from citrus fruit could inhibit RANKL-induced osteoclast differentiation and maturation among three types of osteoclast precursors with inhibited formation of F-actin rings and resorption pits on bone slices. More importantly, by using SP600125, a selective Jnk inhibitor, we showed that Hes was able to significantly attenuate the Jnk downstream expression of Irf-3 and c-Jun, thereby inactivating NF-κB/MAPK signaling and transcriptional factor NFATc-1, leading to suppression of osteoclast-specific genes, which resulted in impaired osteoclastogenesis and functionality. An ovariectomized (OVX) osteoporosis mouse model demonstrated that Hes could increase trabecular bone volume fractions (BV/TV), trabecular thickness, and trabecular number, whereas it decreased trabecular separation in OVX mice with well-preserved trabecular bone architecture and decreased levels of TRAP-positive osteoclasts. This is further evidenced by the diminished serum expression of bone resorption marker CTX and enhanced production of osteoblastic ALP in vivo. Taken together, these results suggested that Hes could inhibit Jnk-mediated Irf-3/c-Jun activation, thus attenuating RANKL-induced osteoclast formation and function both in vitro and in vivo.

Highlights

Bone is a dynamic tissue that undergoes a series of anabolic and metabolic steps to harbor bone marrow, store minerals, and protect inner organs (Hu et al, 2018)
In order to exclude the possibility of inhibited osteoclastogenesis caused by the decreased number of osteoclasts, we explored nontoxic concentrations of Hes against preosteoclasts for observing its anti-osteoclastogenesis effect
We found that compared with RANKL-treated only, Hes administration could significantly inhibit the expression of TRAF-6 and p-TAK-1, indicating that Hes was capable of targeting upstream TRAF-6 and p-TAK-1 to affect downstream Jun N-terminal kinase (Jnk)/interferon regulatory factor (Irf)-3/c-jun

Summary

Introduction

Bone is a dynamic tissue that undergoes a series of anabolic and metabolic steps to harbor bone marrow, store minerals, and protect inner organs (Hu et al, 2018). It has been demonstrated that MCSF is responsible for osteoclast survival, and supports the increased expression of RANK on osteoclast cell membrane surfaces for RANKL binding (Xing et al, 2012), which, together, are intimately correlated with osteoclastogenesis. Upon binding RANKL to RANK, TNF receptor-associated factor 2/6 (TRAF 2/6) and transforming growth factor β-activated kinase 1 (TAK1) are activated for subsequent phosphorylation of IκB kinase (IKK) complexes, c-Jun N-terminal kinase (Jnk), extracellular-signal regulated kinase (Erk) and p38, activating NF-κB and mitogen-activated protein kinase (MAPK) signaling to facilitate osteoclastogenesis (Boyle et al, 2003; Feng, 2005). It was shown that by targeting TANK-binding kinase (TBK-1) and IKK complex, measles virus nucleocapsid protein (MVNP) could activate both Irf-3 and NFκB to increase osteoclast numbers (Sun et al, 2014). An in-depth insight of Irf-3 during osteoclastogenesis is urgently required, which would undoubtedly provide novel and effective targets for future osteopenia research and clinical practice

Methods

Results

Conclusion