Grape Seed Proanthocyanidin Extract Prevents Bone Loss via Regulation of Osteoclast Differentiation, Apoptosis, and Proliferation.

Dietary procyanidin has been shown to be an important bioactive component that regulates various pharmacological activities to maintain metabolic homeostasis. In particular, grape seed proanthocyanidin extract (GSPE) is a commercially available medicine for the treatment of venous and lymphatic dysfunction. This study aimed to investigate whether GSPE protects against lipopolysaccharide (LPS)-induced bone loss in vivo and the related mechanism of action in vitro. The administration of GSPE restored the inflammatory bone loss phenotype stimulated by acute systemic injection of LPS in vivo. GSPE strongly suppressed receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation and bone resorption activity of mature osteoclasts by decreasing the RANKL-induced nuclear factor-κB transcription activity. GSPE mediates this effect through decreased phosphorylation and degradation of NF-κB inhibitor (IκB) by IκB kinaseß, subsequently inhibiting proto-oncogene cellular Fos and nuclear factor of activated T cells. Additionally, GSPE promotes osteoclast proliferation by increasing the phosphorylation of components of the Akt and mitogen-activated protein kinase signaling pathways and it also inhibits apoptosis by decreasing the activity of caspase-8, caspase-9, and caspase-3, as corroborated by a decrease in the Terminal deoxynucleotidyl transferase dUTP nick end labeling -positive cells. Our study suggests a direct effect of GSPE on the proliferation, differentiation, and apoptosis of osteoclasts and reveals the mechanism responsible for the therapeutic potential of GSPE in osteoclast-associated bone metabolism disease.

Securinine suppresses osteoclastogenesis and ameliorates inflammatory bone loss.

Securinine (Sec) is a naturally derived compound separated from the roots of Securinega suffruticosa, which has long been used as a herbal medicine. Sec is widely known as a GABA receptor antagonist, it is also known as an innate immune cell agonist and has been reported to increase macrophage activity and promote monocyte maturation. On the basis of these studies, we investigated the effect of Sec on osteoclast differentiation and bone resorbing function. We have found that Sec inhibits RANKL-induced osteoclast differentiation, fusion, actin ring formation, and bone resorbing function by the inhibition of gene expression associated with each stage. Moreover, Sec significantly suppressed osteoclastogenesis by decreasing the phosphorylation of p38, Akt, JNK, IκB, and PLCγ2, in pathways involved in early osteoclastogenesis as well as through the subsequent suppression of c-Fos and NFATc1. Finally, Sec effectively protected bone loss induced by the excessive inflammatory responses and activity of osteoclasts in vivo by a micro-CT and histological analysis. In conclusion, our findings suggest that Sec may be a promising drug for bone metabolic diseases such as osteoporosis, which is associated with the excessive activity of osteoclasts.

Effects of Huang Bai (Phellodendri Cortex) and Three Other Herbs on GnRH and GH Levels in GT1-7 and GH3 Cells.

The present study was to evaluate the effects of Huang Bai, Zhi Mu, Mai Ya, and Xia Ku Cao on hormone using the GT1-7 and GH3 cells. The GT1-7 and GH3 cell lines were incubated with DW; DMSO; and 30, 100, or 300 µg/mL of one of the four extract solutions in serum-free media for 24 hours. The MTT assay was performed to determine the cytotoxicity of the four herbs. The GT1-7 and GH3 cells were incubated in DW, estradiol (GT1-7 only), or noncytotoxic herb solutions in serum-free medium for 24 hours. A quantitative RT-PCR and western blot were performed to measure the GnRH expression in GT1-7 cells and GH expression in GH3 cells. Huang Bai, Zhi Mu, Xia Ku Cao, and Mai Ya inhibited the GnRH mRNA expression in GT1-7 cells, whereas Huang Bai enhanced GH mRNA expression in GH3 cells. Additionally, Xia Ku Cao inhibited GnRH protein expression in GT1-7 cells and Huang Bai promoted GH protein expression in GH3 cells. The findings suggest that Huang Bai can delay puberty by inhibiting GnRH synthesis in the hypothalamus while also accelerating growth by promoting GH synthesis and secretion in the pituitary.

Purslane suppresses osteoclast differentiation and bone resorbing activity via inhibition of Akt/GSK3ß-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 3ß (GSK3ß) 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/GSK3ß-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), ß3-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.

Genipin inhibits RANKL-induced osteoclast differentiation through proteasome-mediated degradation of c-Fos protein and suppression of NF-κB activation.

People over the age of 50 are at risk of osteoporotic fracture, which may lead to increased morbidity and mortality. Osteoclasts are responsible for bone resorption in bone-related disorders. Genipin is a well-known geniposide aglycon derived from Gardenia jasminoides, which has long been used in oriental medicine for controlling diverse conditions such as inflammation and infection. We aimed to evaluate the effects of genipin on RANKL-induced osteoclast differentiation and its mechanism of action. Genipin dose-dependently inhibited early stage RANKL-induced osteoclast differentiation in bone marrow macrophages (BMMs) during culture. Genipin inhibited RANKL-induced IκB degradation and suppressed the mRNA expression of osteoclastic markers such as NFATc1, TRAP, and OSCAR in RANKL-treated BMMs, but did not affect c-Fos mRNA expression. Interestingly, genipin markedly inhibited c-Fos protein expression in BMMs, which was reversed in the presence of the proteosome inhibitor MG-132. Furthermore, genipin inhibited RANKL-mediated osteoclast differentiation, which was also rescued by overexpression of c-Fos and NFATc1 in BMMs. Taken together, our findings indicate that genipin down-regulated RANKL-induced osteoclast differentiation through inhibition of c-Fos protein proteolysis as well as inhibition of IκB degradation. Our findings indicate that genipin could be a useful drug candidate that lacks toxic side effects for the treatment of osteoporosis.