Mun Chual Rho

Oleanolic acid acetate inhibits osteoclast differentiation by downregulating PLCγ2–Ca2 +-NFATc1 signaling, and suppresses bone loss in mice

Owing to their potential pharmacological activities in human disease, natural plant-derived compounds have recently become the focus of increased research interest. In this study, we first isolated oleanolic acid acetate (OAA), a triterpenoid compound, from Vigna angularis (azuki bean) to discover anti-bone resorptive agents. Many studies have identified and described the various medicinal effects of V. angularis extract. However, the pharmacological effect of OAA-derived V. angularis extract, particularly the effect on osteoclastogenesis, is not known. Therefore, we investigated the effect and mechanism of OAA in receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis. OAA inhibited RANKL-induced osteoclast differentiation in bone marrow macrophages (BMMs) without any evidence of cytotoxicity. Interestingly, OAA significantly inhibited Btk phosphorylation, phospholipase Cγ2 (PLCγ2) phosphorylation, calcium ion (Ca(2+)) oscillation, and nuclear factor of activated T cell c1 (NFATc1) expression in RANKL-stimulated BMMs, but did not affect RANKL-induced mitogen-activated protein kinase. OAA also inhibited the bone-resorbing activity of mature osteoclasts. Furthermore, mice treated with OAA demonstrated marked attenuation of lipopolysaccharide-induced bone erosion based on micro-computed tomography and histologic analysis of femurs. Taken together, the results suggested that OAA inhibited RANKL-mediated osteoclastogenesis via PLCγ2-Ca(2+)-NFATc1 signaling in vitro and suppressed inflammatory bone loss in vivo.

Kansuinine A and Kansuinine B from Euphorbia kansui L. inhibit IL-6-induced Stat3 activation.

The current study was performed to examine the mechanisms underlying the potential effects of E. KANSUI on IL-6-induced cellular signaling in human hepatoma cells. We found that two diterpenoids, kansuinine A and B, from E. KANSUI have an inhibitory effect on IL-6-induced Stat3 activation by activating ERK1/2. Inhibition of MEK significantly blocked the effects of kansuinine A and B on IL-6-induced Stat3 activation and tyrosine phosphorylation. These results suggest that blocking of IL-6-induced signal transduction is partially due to the sustained activation of ERK1/2 by kansuinine A and B, which in turn results in an increase of Stat3 serine phosphorylation and SOCS-3 expression. Treatment with kansuinine A and B represents a novel method to block these IL-6-induced effects.

Purslane Suppresses Osteoclast Differentiation and Bone Resorbing Activity via Inhibition of Akt/GSK3β-c-Fos-NFATc1 Signaling in Vitro and Prevents Lipopolysaccharide-Induced Bone Loss in Vivo

Purslane (Portulaca oleracea L.) is popular as a potherb in many areas of Europe, Asia, and the Mediterranean region and is widely distributed around the globe. It has a wide range of pharmacological effects, such as antibacterial, anti-aging, anti-inflammatory, and anti-oxidative properties. Although the extract of purslane has numerous beneficial pharmacological effects, its effect on osteoclasts remains unknown. We aimed to investigate the anti-osteoclastogenic activity in vitro and in vivo and to elucidate the underlying mechanism. The effect of purslane on the differentiation and function of bone marrow-derived macrophages (BMMs) into osteoclasts was examined using a phenotype assay such as tartrate-resistant acid phosphatase (TRAP) staining, F-actin staining, and pit assay and followed by confirmation by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. To address the effect of purslane in vivo, the inflammatory, lipopolysaccharide (LPS)-induced osteolysis mouse model was chosen. Bone volume and bone microarchitecture were evaluated by microcomputed tomography and histologic analysis. Purslane inhibited receptor activator of nuclear factor-kappa B ligand (RANKL)-stimulated osteoclast differentiation accompanied by inhibition of Akt/glycogen synthase kinase 3β (GSK3β) signaling, which could underlie purslane-induced downregulation of c-Fos and nuclear factor of activated T cells 1 (NFATc1) expression levels, transcription factors that regulate osteoclast-specific genes, as well as osteoclast fusion and resorption-related molecules. Moreover, in vivo studies further verified the bone protection activity of purslane in the LPS-induced osteolysis animal model. Purslane could exhibit its anti-osteoclastogenic activity by inhibiting Akt/GSK3β-c-Fos-NFATc1 signaling cascades. Therefore, purslane is a potential natural medicine for the treatment of osteoclast-related diseases.

Ampelopsis brevipedunculata Extract Prevents Bone Loss by Inhibiting Osteoclastogenesis in Vitro and in Vivo

Osteoclasts play a critical role in bone resorbing disorders such as osteoporosis, periodontitis, and rheumatoid arthritis. Therefore, discovery of agents capable of suppressing osteoclast differentiation may aid the development of a therapeutic access for the treatment of pathological bone loss. Ampelopsis brevipedunculata has been used as herbal folk medicine to treat liver diseases and inflammation in Asia. However, its effects on osteoclast differentiation are unknown. We were aimed to investigate the anti-osteoclastogenic activity in vitro and in vivo and to elucidate the underlying mechanism of Ampelopsis brevipedunculata extract (ABE). In this study, ABE inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation, the formation of filamentous actin rings and the bone resorbing activity of mature osteoclasts. ABE inhibited RANKL-induced p38 and IκB phosphorylation and IκB degradation. Also, ABE suppressed the mRNA and protein expression of nuclear factor of activated T cells c1 (NFATc1) and c-Fos, and the mRNA expression of genes required for cell fusion and bone resorption, such as osteoclast-associated receptor (OSCAR), tartrate resistant acid phosphatase (TRAP), cathepsin K, dendritic cell-specific transmembrane protein (DC-STAMP), β3-integrin and osteoclast stimulatory transmembrane protein (OC-STAMP). Furthermore, results of micro-CT and histologic analysis indicated that ABE remarkably prevented lipopolysaccharide (LPS)-induced bone erosion. These results demonstrate that ABE prevents LPS-induced bone erosion through inhibition of osteoclast differentiation and function, suggesting the promise of ABE as a potential cure for various osteoclast-associated bone diseases.