Potent osteogenic activity of a novel imidazobenzimidazole derivative, IBIP.

Bone mass is controlled by a balance between bone resorption and formation by osteoclasts and osteoblasts, respectively. An imbalance between osteoblasts and osteoclasts increases the risk of osteoporosis and fractures. Although inhibition of osteoclasts is beneficial for preventing and treating osteoporosis, enhanced bone formation through activation of osteoblast differentiation can be a more promising therapeutic approach. In this study, we attempted to isolate small molecules that promote osteoblast differentiation and found that IBIP (3-(2,3-dimethoxyphenyl)-1-[9-methyl-2-phenyl-9H-imidazo[1,2-a]benzimidazol-3-yl]-2-propen-1-one) was a potent activator of osteoblast differentiation. Upon bone morphogenetic protein-2 (BMP2) stimulation, IBIP promoted osteoblast differentiation and increased the expression of osteoblast-specific gene markers, such as osterix and alkaline phosphatase, in a dose-dependent manner. The phosphorylation of SMADs and extracellular signal-regulated kinase (ERK) increased after IBIP treatment. While enhanced SMAD phosphorylation by IBIP was abolished by a BMP inhibitor, IBIP-induced ERK phosphorylation was sustained in the presence of this inhibitor, but was decreased by an ERK kinase inhibitor. Suppression of IBIP-induced SMAD and ERK phosphorylation diminished osteoblast differentiation. Most importantly, IBIP enhanced bone formation and calcification in a BMP2-independent manner in vitro and advanced the skeletal development of zebrafish larvae in vivo. Collectively, IBIP may have beneficial effects on bone loss through potentiation of bone formation.

Anti-adipogenic activity of the naturally occurring phenanthroindolizidine alkaloid antofine via direct suppression of PPARγ expression.

Antofine (ANTF) is a phenanthroindolizidine alkaloid isolated from the root of Cynanchum paniculatum Kitagawa (Asclepiadaceae), which is used as an herbal remedy for pain and inflammation. ANTF also possesses antiviral and antitumorigenic activities. In this study, we investigated the role of ANTF in adipogenesis. Chronic ABTF administration suppressed adipocyte differentiation and marker expression in a dose-dependent manner. Furthermore, acute administration of ANTF at early stages of differentiation process inhibited lipid droplet formation and adipogenic gene expression. ANTF Treatment decreased expression of PPARγ protein, a master transcription factor in the regulation of adipocyte differentiation, leading to a suppression of aP2 promoter activity. These results suggest that ANTF exerts potent anti-adipogenic effects via direct suppression of PPARγ protein expression, with consequent downregulation of adipogenic gene expression.

In vitro and in vivo osteogenic activity of licochalcone A.

We investigated the in vitro and in vivo osteogenic activity of licochalcone A. At low concentrations, licochalcone A stimulated the differentiation of mouse pre-osteoblastic MC3T3-E1 subclone 4 (MC4) cells and enhanced the bone morphogenetic protein (BMP)-2-induced stimulation of mouse bi-potential mesenchymal precursor C2C12 cells to commit to the osteoblast differentiation pathway. This osteogenic activity of licochalcone A was accompanied by the activation of extracellular-signal regulated kinase (ERK). The involvement of ERK was confirmed in a pharmacologic inhibition study. Additionally, noggin (a BMP antagonist) inhibited the osteogenic activity of licochalcone A in C2C12 cells. Licochalcone A also enhanced the BMP-2-stimulated expression of various BMP mRNAs. This suggested that the osteogenic action of licochalcone A in C2C12 cells could be dependent on BMP signaling and/or expression. We then tested the in vivo osteogenic activity of licochalcone A in two independent animal models. Licochalcone A accelerated the rate of skeletal development in zebrafish and enhanced woven bone formation over the periosteum of mouse calvarial bones. In summary, licochalcone A induced osteoblast differentiation with ERK activation in both MC4 and C2C12 cells and it exhibited in vivo osteogenic activity in zebrafish skeletal development and mouse calvarial bone formation. The dual action of licochalcone A in stimulating bone formation and inhibiting bone resorption, as described in a previous study, might be beneficial in treating bone-related disorders.

Anti-androgen receptor activity of apoptotic CK2 inhibitor CX4945 in human prostate cancer LNCap cells.

Androgen receptor (AR) is crucial for transcriptional signaling in prostate cancers. The anti-cancer activity of protein kinase CK2 (formerly called casein kinase 2)-specific small molecule inhibitors have been reported in several cancers including prostate cancers. The orally available CX4945, a potent and selective small molecule inhibitor of CK2, has advanced into human clinical trials and has exhibited strong anti-tumor activity. The inhibition of CK2 leads to a down-regulation of the AR-dependent transcription, but the functional relevance of CX4945 to AR-dependent transcription in AR-positive LNCap cells has not been studied yet. Our observation of inhibitory effects of CX4945 on the expression or phosphorylation levels of CK2α, Akt and anti-apoptotic molecules including IAP family members agreed with a previous study showing the effect of CK2 inhibition in cancer cells. This study also provides novel information on the impact of CX4945 in the inhibition of AR-dependent transcriptional activation in LNCap cells via its down-regulation. Pharmacologic inhibition experiment revealed that CX4945 could exhibit its anti-cancer activity in LNCap cells via the independent inhibitions of AR and Akt-survivin signalings.

Chemical affinity matrix-based identification of prohibitin as a binding protein to anti-resorptive sulfonyl amidine compounds.

In order to identify the binding proteins to anti-resorptive 5-chloro-1-(2,6-dimethylpiperidin-1-yl)-N-tosylpentan-1-imine (1), the chemical affinity matrix for the compound 1 (2b) was designed and synthesized. Using 2b-based chemical proteomics, prohibitin was identified as one of strong binding proteins for 2b.

Acceleration of osteoblast differentiation by a novel osteogenic compound, DMP-PYT, through activation of both the BMP and Wnt pathways.

Osteoblast differentiation is regulated through the successive activation of signaling molecules by a complex interplay of extracellular signals such as bone morphogenetic protein (BMP) and Wnt ligands. Numerous studies have identified natural as well as synthetic compounds with osteogenic activity through the regulation of either BMP/SMADs or the Wnt/ß-catenin pathway. Here, we attempted to isolate small molecules that concurrently activated both SMADs and ß-catenin, which led to the discovery of a novel potent osteogenic compound, DMP-PYT. Upon BMP2 stimulation, DMP-PYT substantially increased osteoblast differentiation featured by enhanced expression of osteoblast-specific genes and accelerated calcification through activation of BMPs expression. DMP-PYT promoted BMP2-induced SMAD1/5/8 phosphorylation and ß-catenin expression, the latter in a BMP2-independent manner. DMP-PYT alone enhanced nuclear localization of ß-catenin to promote the DNA-binding and transcriptional activity of T-cell factor, thereby resulting in increased osteoblast differentiation in the absence of BMP2. Most importantly, DMP-PYT advanced skeletal development and bone calcification in zebrafish larvae. Conclusively, DMP-PYT strongly stimulated osteoblast differentiation and bone formation in vitro and in vivo by potentiating BMP2-induced activation of SMADs and ß-catenin. These results suggest that DMP-PYT may have beneficial effects for preventing and for treating osteoporosis.

A novel 11ß-HSD1 inhibitor improves diabesity and osteoblast differentiation.

Selective inhibitors of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) have considerable potential as treatment for osteoporosis as well as metabolic syndrome including type 2 diabetes mellitus. Here, we investigated the anti-diabetic, anti-adipogenic, and anti-osteoporotic activity of KR-67500, as a novel selective 11ß-HSD1 inhibitor. Cellular 11ß-HSD1 activity was tested based on a homogeneous time-resolved fluorescence method. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) levels were measured in diet-induced obese (DIO)-C57BL/6 mice administered KR-67500 (50  mg/kg per day, p.o.) for 28 days and, additionally, its anti-diabetic effect was evaluated by OGTT and ITT. The in vitro anti-adipogenic effect of KR-67500 was determined by Oil Red O Staining. The in vitro anti-osteoporotic activity of KR-67500 was evaluated using bone morphogenetic protein 2 (BMP2)-induced osteoblast differentiation and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation model systems. KR-67500 improved the in vivo glucose tolerance and insulin sensitivity in DIO-C57BL/6 mice. KR-67500 suppressed cortisone-induced differentiation of 3T3-L1 cells into adipocytes. KR-67500 enhanced BMP2-induced osteoblastogenesis in C2C12 cells and inhibited RANKL-induced osteoclastogenesis in mouse bone marrow-derived macrophages. KR-67500, a new selective 11ß-HSD1 inhibitor, may provide a new therapeutic window in the prevention and/or treatment of type 2 diabetes, obesity, and/or osteoporosis.

TAZ is required for the osteogenic and anti-adipogenic activities of kaempferol.

Kaempferol (KMP) exerts protective effects against both osteoporosis and obesity by regulating cellular activities, but the underlying molecular mechanisms have not been fully elucidated. TAZ (transcriptional coactivator with PDZ-binding motif) modulates both osteoblast and adipocyte differentiation from mesenchymal stem cells by stimulating the activities of RUNX2 (runt-related transcription factor 2) and suppressing the activities of PPARγ (peroxisome proliferator-activated receptor γ). In this study, we investigated the effects of KMP on TAZ regulated osteoblast and adipocyte differentiation. KMP increased the osteoblast differentiation of mesenchymal cells by facilitating the physical interaction between TAZ and RUNX2, thus the increasing transcriptional activities of RUNX2. KMP also enhanced the association of TAZ with PPARγ, thereby suppressing the gene transcription of PPARγ targets and resulting in diminished adipocyte differentiation. Interestingly, the regulatory effects of kaempferol on RUNX2 and PPARγ-mediated transcriptional activity were impaired in TAZ-null mouse embryonic fibroblasts but recovered by restoration of TAZ expression. Our results demonstrate that KMP fortifies TAZ activity, which enhances RUNX2-mediated osteoblast differentiation and suppresses PPARγ-stimulated adipocyte differentiation, indicating the potential of KMP as an effective therapeutic reagent for controlling bone loss and adiposity through TAZ activation.

Discovery of novel benzopyranyl tetracycles that act as inhibitors of osteoclastogenesis induced by receptor activator of NF-κB ligand.

A novel benzopyran-fused molecular framework 7ai was discovered as a specific inhibitor of RANKL-induced osteoclastogenesis using a cell-based TRAP activity assay from drug-like small-molecule libraries constructed by diversity-oriented synthesis. Its inhibitory activity was confirmed by in vitro evaluations including specific inhibition of RANKL-induced ERK phosphorylation and NF-κB transcriptional activation. 7ai can serve as a specific small-molecule modulator for mechanistic studies of RANKL-induced osteoclast differentiation as well as a potential lead for the development of antiresorptive drugs.