Synthesis and biological evaluation of rhein amides as inhibitors of osteoclast differentiation and bone resorption

Rhein induces bone regeneration via alleviating inflammation in murine periodontitis model

OBJECTIVE

To evaluate the effect of rhein on eliminating the inflammation and promoting bone regeneration of periodontitis after local administration.

MATERIALS AND METHODS

In vivo, periodontitis model was established in murine mandibular first molar by using ligature for 7 days, followed by ligature removal and local administration of rhein/vehicle for 7 consecutive days. In vitro, periodontal ligament fibroblasts were treated by LPS, along with the applications of rhein/vehicle. Histology and molecular biology approaches were applied for analysis.

RESULTS

In vivo, rhein alleviated periodontitis inflammation through downregulating the inflammatory index and promoted the osteogenic potential of PDL fibroblasts in a dosage-dependent manner. The result of micro-CT validated this phenomenon. In vitro, rhein administration inhibited the phosphorylation and nuclear translocation of P65, along with the arose runx2 level of PDL fibroblasts with the stimulus of LPS in mimicking periodontitis.

CONCLUSION

Rhein played its inhibitory role on inflammation via curbing the activation of P65 but uprising the activities of Runx2 in PDL fibroblasts in periodontitis microenvironment. These data suggested that rhein could be an effective and potential clinical choice for the treatment of periodontitis.

m6A demethylase FTO and osteoporosis: potential therapeutic interventions

Osteoporosis is a common bone disease, characterized by a descent in bone mass due to the dysregulation of bone homeostasis. Although different studies have identified an association between osteoporosis and epigenetic alterations in osteogenic genes, the mechanisms of osteoporosis remain unclear. N6-methyladenosine (m6A) modification is a methylated adenosine nucleotide, which regulates the translocation, exporting, translation, and decay of RNA. FTO is the first identified m6A demethylase, which eliminates m6A modifications from RNAs. Variation in FTO disturbs m6A methylation in RNAs to regulate cell proliferation, differentiation, and apoptosis. Besides, FTO as an obesity-associated gene, also affects osteogenesis by regulating adipogenesis. Pharmacological inhibition of FTO markedly altered bone mass, bone mineral density and the distribution of adipose tissue. Small molecules which modulate FTO function are potentially novel remedies to the treatment of osteoporosis by adjusting the m6A levels. This article reviews the roles of m6A demethylase FTO in regulating bone metabolism and osteoporosis.

Rhein-Amino Acid Ester Conjugates as Potential Antifungal Agents: Synthesis and Biological Evaluation

In the search for crop protectants, amino acid ester conjugates have been widely investigated as potential antifungal agents. In this study, a series of rhein-amino acid ester conjugates were designed and synthesized in good yields, and their structures were confirmed by ¹H-NMR, ¹³C-NMR and HRMS. The bioassay results revealed that most of the conjugates exhibited potent inhibitory activity against R. solani and S. sclerotiorum. In particular, conjugate 3c had the highest antifungal activity against R. solani with an EC₅₀ value of 0.125 mM. For S. sclerotiorum, conjugate 3m showed the highest antifungal activity with an EC₅₀ value of 0.114 mM. Satisfactorily, conjugate 3c exhibited better protective effects than that of the positive control, physcion, against powdery mildew in wheat. This research supports the role of rhein-amino acid ester conjugates as potential antifungal agents for plant fungal diseases.

Comparative analysis of an anthraquinone and chalcone derivatives-based virtual combinatorial library. A cheminformatics "proof-of-concept" study

A Laplacian scoring algorithm for gene selection and the Gini coefficient to identify the genes whose expression varied least across a large set of samples were the state-of-the-art methods used here. These methods have not been trialed for their feasibility in cheminformatics. This was a maiden attempt to investigate a complete comparative analysis of an anthraquinone and chalcone derivatives-based virtual combinatorial library. This computational "proof-of-concept" study illustrated the combinatorial approach used to explain how the structure of the selected natural products (NPs) undergoes molecular diversity analysis. A virtual combinatorial library (1.6 M) based on 20 anthraquinones and 24 chalcones was enumerated. The resulting compounds were optimized to the near drug-likeness properties, and the physicochemical descriptors were calculated for all datasets including FDA, Non-FDA, and NPs from ZINC 15. UMAP and PCA were applied to compare and represent the chemical space coverage of each dataset. Subsequently, the Laplacian score and Gini coefficient were applied to delineate feature selection and selectivity among properties, respectively. Finally, we demonstrated the diversity between the datasets by employing Murcko's and the central scaffolds systems, calculating three fingerprint descriptors and analyzing their diversity by PCA and SOM. The optimized enumeration resulted in 1,610,268 compounds with NP-Likeness, and synthetic feasibility mean scores close to FDA, Non-FDA, and NPs datasets. The overlap between the chemical space of the 1.6 M database was more prominent than with the NPs dataset. A Laplacian score prioritized NP-likeness and hydrogen bond acceptor properties (1.0 and 0.923), respectively, while the Gini coefficient showed that all properties have selective effects on datasets (0.81-0.93). Scaffold and fingerprint diversity indicated that the descending order for the tested datasets was FDA, Non-FDA, NPs and 1.6 M. Virtual combinatorial libraries based on NPs can be considered as a source of the combinatorial compound with NP-likeness properties. Furthermore, measuring molecular diversity is supposed to be performed by different methods to allow for comparison and better judgment.

Hydroxyapatite Biobased Materials for Treatment and Diagnosis of Cancer

Great advances in cancer treatment have been undertaken in the last years as a consequence of the development of new antitumoral drugs able to target cancer cells with decreasing side effects and a better understanding of the behavior of neoplastic cells during invasion and metastasis. Specifically, drug delivery systems (DDS) based on the use of hydroxyapatite nanoparticles (HAp NPs) are gaining attention and merit a comprehensive review focused on their potential applications. These are derived from the intrinsic properties of HAp (e.g., biocompatibility and biodegradability), together with the easy functionalization and easy control of porosity, crystallinity and morphology of HAp NPs. The capacity to tailor the properties of DLS based on HAp NPs has well-recognized advantages for the control of both drug loading and release. Furthermore, the functionalization of NPs allows a targeted uptake in tumoral cells while their rapid elimination by the reticuloendothelial system (RES) can be avoided. Advances in HAp NPs involve not only their use as drug nanocarriers but also their employment as nanosystems for magnetic hyperthermia therapy, gene delivery systems, adjuvants for cancer immunotherapy and nanoparticles for cell imaging.

Mechanism of Huangqi Sanxian Decoction Inhibiting Osteoclast Differentiation Based on Network Pharmacology

Osteoclasts (OCs) have been the unique cell type exhibiting the bone-resorption activity in body. It is important to identify drugs to resist osteoclastogenesis to manage the bone-loss disorders. Huangqi Sanxian decoction (HQSXD) is utilized for the treatment of postmenopausal osteoporosis (PMOP) for a long history in East Asia. This work aimed to examine HQSXD’s activity in OC differentiation. Based on staining with tartrate-resistant acid phosphatase (TRAP), it was found that HQSXD suppressed OC generation under the induction of RANKL produced in the bone marrow-derived monocytes/macrophages (BMMs), with no cytotoxic effect. Later analysis like molecular exploration and network pharmacology (NP) suggested the role of HQSXD in suppressing genes associated with osteoclastogenesis via PI3K/Akt-mediated mechanism dose-dependently. This work might illustrate the molecular pharmacological mechanism involved in HQSXD’s effect on treating OC-associated disorders. Moreover, NP was found to modernize traditional Chinese medicine (TCM) research.

α-Asarone Attenuates Osteoclastogenesis and Prevents Against Oestrogen-Deficiency Induced Osteoporosis

Osteoporosis (OP) is defined as low bone mineral density which features over activated osteoclasts (OCs) and bone resorption. Targeting excessive OCs activity is thought to be an effective therapeutic approach for OP treatment. α-asarone (ASA), a compound from the traditional Chinese medicinal herb Acorus tatarinowii, has been widely used as a therapeutic agent against several diseases such as epilepsy, cough, bronchitis and asthma for many years. Recently, it was reported that ASA-derived lignins which were purified from Acorus tatarinowii root tissues effectively suppressed both RANKL-induced osteoclastogenesis and bone resorption. Besides, a classic Chinese formulation Bajitianwan (BJTW) which consisted of root and rhizome of Acorus tatarinowii Schott also showed positive effects on age-related bone loss. In the present study, we aimed to study the effects of ASA on osteoclastogenesis in vitro and in vivo. As illustrated by TRAP staining, ASA was capable of inhibiting RANKL-induced osteoclastogenesis in a dose-dependent manner, not only at an early-stage, but also in the late-stage. Besides, it also effectively suppressed bone resorption of mature OCs in a pit resorption assay. The formation of F-actin ring during osteoclastogenesis, which was important in OCs bone-resorption, was impaired as well. Subsequent mechanism experiments exposed that ASA inhibited osteoclastogenesis related genes in a time-dependent manner through AKT, p38 and NF-κB, followed by NFATc1/c-fos signaling pathway. Notably, our in vivo study uncovered that ASA was capable of improving the bone microstructure in oestrogen-deficiency induced OP models. Thus, our current work highlighted the important role of an old drug ASA in bone metabolism especially in OCs differentiation. ASA may find its potential as a lead compound to treat excessive OCs activity-induced bone loss diseases and more structure optimization is further needed.

Antifungal and insecticidal activities of rhein derivatives: synthesis, characterization and preliminary structure-activity relationship studies

There is an urgent need to replace highly polluting pesticides with environmentally friendly green pesticides of high efficiency and low toxicity, because of the growing concern for quality and safety of agricultural products. To discover new pesticides with diverse chemical structures from natural products, a series of rhein derivatives 3a-9b were designed, synthesized, and evaluated for their antifungal activity and insecticidal activity. The bioassay showed that some compounds exhibited moderate antifungal activity against Rhizoctonia solani, but lower activity against the other five pathogens. Surprisingly, most compounds displayed potent insecticidal activity against Spodoptera litura and Tetranychus cinnabarinus at a concentration of 2 μmol/mL. In particular, compounds 3a, 5a and 3 b exhibited potent insecticidal activities against S. litura at 72 h, with mortality rates of 100%, 100% and 92.1%, respectively, which were equivalent to that of the insecticide fipronil (100%). Their structure-activity relationships were also discussed. The findings of this experiment provide helpful research ideas for the development of these rhein derivatives as novel natural product-based pesticides in crop protection.

Rhein Derivatives, A Promising Pivot?

Rhein, an anthraquinone derivative, has been employed widely, especially for the treatment of intractable diseases like diabetic nephropathy, arthritis, and cancer in a unique action mechanism. In the last decades, considerable efforts have been made in structural modification of rhein. This paper reviewed patents on pharmacological activity and therapeutic application of rhein and its derivatives from 1978 to 2018. Particularly, an analysis of patents was made, with the top 10 most valuable patents presented, and the interpretation of the legal status of patents was given. Given the properties of superior pharmacological activity, rich resources, cheap price, low toxicity, and mature extraction process, it is believed that an in-depth investigation on rhein and its derivatives is worth trying.

An MSC bone-homing compound, Rab001, increases bone mass and reduces the incidence of osteonecrosis in a glucocorticoid-induced osteonecrosis mouse model

Currently, there are no effective medications to either prevent or slow the progression of atraumatic osteonecrosis (ON). The objective of this study is to determine the effects of bone-targeted delivery of mesenchymal stem cells on the prevalence of ON in a glucocorticoid (GC)-induced mouse model. Eight-week-old male BALB/c mice were randomized into groups that received placebo (PL), prednisolone (GC), or concurrent treatments with GC + mesenchymal stromal cells (MSCs), Rab001 or GC + Rab001 + MSCs. Human parathyroid hormone (hPTH) was used as a positive control for bone anabolism. Mice were killed after 30 days, and quantitative measurements of bone mass, bone strength, prevalent ON at the distal femoral epiphysis (DFE) were performed. Angiogenesis was accessed by RNA-Seq, the circulating angiogenic markers, as well as by immunohistochemical staining. We have showed that a novel agent, Rab001 that can noncovalently bind to mesenchymal stem cells (MSC) and direct them to the bone, prevents the incidence of glucocorticoid-induced osteonecrosis in the mouse. In contrast, PTH, a bone anabolic treatment, preserves bone mass but sustains higher ON incidence than Rab001+/- MSC-treated mice. The results of these experiments reveal that glucocorticoids increase the prevalence of ON, and agents that prevent loss of bone vascularity appear to prevent the development of ON. This intervention might be useful in patients with early stages of atraumatic ON.

Anti-inflammatory Effects and Mechanisms of Rhein, an Anthraquinone Compound, and Its Applications in Treating Arthritis: A Review

Inflammation is a defensive response of living tissues to damaging agents, which exists in two forms, acute inflammation and chronic inflammation, and chronic inflammation is closely related to arthritis. Currently, the commonly prescribed anti-inflammatory medications are greatly limited by high incidence of gastrointestinal erosions in the clinical applications. Rhein, a bioactive constituent of anthraquinone, exhibits excellent anti-inflammatory activities and therapeutic effects on arthritis with less gastrointestinal damages. Although there are numbers of studies on anti-inflammatory effects and mechanisms of rhein in the last few decades, to the best of our knowledge, only a few review articles pay attention to the interactive relationships of rhein on multiple inflammatory signaling pathways and cellular processes from a comprehensive perspective. Herein, we summarized anti-inflammatory effects and mechanisms of rhein and its practical applications in the treatment of arthritis, thereby providing a reference for its basic researches and clinical applications.

The extract of Trachelospermum jasminoides (Lindl.) Lem. vines inhibits osteoclast differentiation through the NF-κB, MAPK and AKT signaling pathways

Osteoclasts are the only cells in the body with a bone-resorption function. The identification of anti-osteoclastogenic agents is important in managing bone loss diseases. The dried vines of Trachelospermum jasminoides (Lindl.) Lem. have been used as a herbal medicine to treat musculoskeletal soreness in East Asia for hundreds of years. In the present study, we focused on the effect of Trachelospermum jasminoides (Lindl.) Lem. extract (TJE) on osteoclast differentiation. As indicated by tartrate-resistant acid phosphatase (TRAP) staining, TJE inhibited osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand from bone marrow-derived monocytes/macrophages without showing any cytotoxicity. In addition, TJE effectively suppressed F-actin ring formation and the bone-resorption function of osteoclasts. The subsequent studies such as network pharmacology and molecular investigation, revealed that TJE inhibited osteoclastogenesis-related genes in a dose- and time-dependent manner through NF-κB, MAPK and AKT-mediated mechanism followed by the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)/c-Fos pathway. Our study could potentially explain the underlying molecular pharmacology of TJE in osteoclast-related diseases. What's more, it suggested that network pharmacology could help the modernization of traditional Chinese medicine.

Synthesis and biological activities of drugs for the treatment of osteoporosis

Osteoporosis is an asymptomatic progressive disease. With the improvement of people's living standard and the aging of population, osteoporosis and its fracture have become one of the main diseases threatening the aging society. The serious medical and social burden caused by this has aroused wide public concern. Osteoporosis is listed as one of the three major diseases of the elderly. At present, the drugs for osteoporosis include bone resorption inhibitors and bone formation promoters. The purpose of these anti-osteoporosis drugs is to balance osteoblast bone formation and osteoclast bone resorption. With the development of anti-osteoporosis drugs, new anti osteoporosis drugs have been designed and synthesized. There are many kinds of new compounds with anti osteoporosis activity, but most of them are concentrated on the original drugs with anti osteoporosis activity, or the natural products with anti-osteoporosis activity are extracted from the natural products for structural modification to obtain the corresponding derivatives or analogues. These target compounds showed good ALP activity in vitro and in vivo, promoted osteoblast differentiation and mineralization, or had anti TRAP activity, inhibited osteoclast absorption. This work attempts to systematically review the studies on the synthesis and bioactivity of anti-osteoporosis drugs in the past 10 years. The structure-activity relationship was discussed, which provided a reasonable idea for the design and development of new anti-osteoporosis drugs.

Rhein-PEG-nHA conjugate as a bone targeted drug delivery vehicle for enhanced cancer chemoradiotherapy

Bone-targeted therapies have been the choice of treatments for cancer metastases in bone to minimize skeletal morbidity and preserve patients' quality of life. Rhein is of particular interest due to its high bone affinity. Here we reported a novel Rhein- polyethylene glycol (PEG)-nano hydroxyapatite (nHA) conjugate to deliver doxorubicin (DOX) and Phosphorus-32 (³²P) simultaneously for enhanced cancer chemo-radiotherapy. The synthetic Rhein-PEG-nHA conjugates were sphere in shape with an average diameter of ~120 nm. Their morphology, drug release and bone affinity were confirmed in vitro. The release profiles of DOX depend on pH condition, but ³²P exhibited good stability. Rhein-PEG-nHA also showed high bone affinity in vivo, and the tumor volume decreased after the DOX@Rhein-PEG-nHA and ³²P@Rhein-PEG-nHA treatments. Most importantly, the DOX/³²P@Rhein-PEG-nHA showed the strongest inhibition on the growth of bone metastases of breast cancer. We revealed the potential of Rhein-PEG-nHA in combined chemo-radiation treatment for bone metastases of breast cancer.

The effects of tranylcypromine on osteoclastogenesis in vitro and in vivo

Identification of anti-osteoclastogenic agents is important for the treatment of bone loss diseases that feature excessive osteoclast (OC) activity and bone resorption. Tranylcypromine (TCP), an irreversible inhibitor of monoamine oxidase (MAO), has been used as an antidepressant and anxiolytic agent in the clinical treatment of mood and anxiety disorders. TCP has been discovered to exert anabolic effect on osteoblasts, and MAO-A has also been verified as an important mediator in prostate cancer cells to accelerate osteoclastogenesis. In current study, we were focused on TCP and MAO-A effects on osteoclastogenesis. As illustrated by tartrate-resistant acid phosphatase staining, TCP was capable of inhibiting osteoclastogenesis induced by receptor activators of the NF-κB ligand (RANKL) in bone marrow-derived macrophage cells without any cytotoxicity. It was also shown to effectively suppress bone resorption of OCs. The subsequent study revealed that TCP inhibited osteoclastogenesis-related genes in a time-dependent manner through protein kinase B (AKT)-mediated mechanism followed by the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)-c-fos pathway. And TCP could overcome the osteoclastogenic effects of AKT activator SC79. In addition, our results indicated that the expression and catalytic activity of MAO-A were up-regulated by RANKL stimulation and down-regulated by TCP in vitro and in vivo. Furthermore, the effects of MAO-A knockdown on OC differentiation indicated that MAO-A played an important role in osteoclastogenesis in vitro and might contribute to the inhibitory effects of TCP. And AKT, NFATc1, and c-fos were involved in the MAO-A pathway. Notably, our in vivo study reflected that TCPs were capable of restoring the bone loss in LPS-induced calvaria osteolysis and estrogen deficiency-induced osteoporosis models. Thus, our current work provided a potential option for the treatment of bone loss diseases and highlighted the important role of MAO-A in osteoclastogenesis as well.-Liu, Z., Yang, K., Yan, X., Wang, T., Jiang, T., Zhou, Q., Qi, J., Qian, N., Zhou, H., Chen, B., Huang, P., Guo, L., Zhang, X., Xu, X., Jiang, M., Deng, L. The effects of tranylcypromine on osteoclastogenesis in vitro and in vivo.

Health functions and structure-activity relationships of natural anthraquinones from plants

Anthraquinone compounds with the anthraquinone ring structure are widely found in traditional Chinese medicines and they are attracting a lot of attention due to their good pharmacological activity. Diversities of anthraquinones depend on their chemical structures, such as the number of anthraquinone rings and the substituents; what's more, the difference in chemical structure determines the difference in physiological activity. Based on results of previous studies, this review summarizes several natural anthraquinones identified from Chinese herbal medicines and their physiological activities including anti-cancer, anti-pathogenic microorganisms, anti-inflammatory, anti-oxidation, anti-osteoporosis, anti-depression, and anti-constipation. The source, effect, model, and action mechanism of the active anthraquinones are described in detail, from which their structure-activity relationship is summarized. By analyzing the relationship between anthraquinone structure and function, we found that, on the whole structure, the anthraquinone ring and anthraquinone glycosides have significant anticancer activity and anti-constipation activity, while for their substituents, anthraquinones substituted by alizarin have significant antioxidant activity and the polarity of the substituents is closely related to their antibacterial activities.

Convenient Synthesis of 6,7,12,13-Tetrahydro-5H-Cyclohepta[2,1-b:3,4-b']diindole Derivatives Mediated by Hypervalent Iodine (III) Reagent

Bisindolyl alkaloids represent a large family of natural and synthetic products that display various biological activities. Among the bisindole compounds, 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b']diindoles have received little attention. Only two methods have been developed for the construction of the 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b']diindole scaffold thus far, including the classical Fischer indole synthesis conducted by reacting indole-fused cycloheptanone and hydrazines, and the condensation reaction to build the seven-membered ring. Here, we report for the first time a new route to synthesize 6,7,12,13-tetrahydro-5H-cyclohepta[2,1-b:3,4-b']diindoles through intramolecular oxidative coupling of 1,3-di(1H-indol-3-yl)propanes in the presence of PIFA, DDQ and TMSCl with moderate to excellent yields.

A Novel Rhein Derivative Modulates Bone Formation and Resorption and Ameliorates Estrogen-Dependent Bone Loss

Osteoporosis, an osteolytic disease that affects millions of people worldwide, features a bone remodeling imbalance between bone resorption by osteoclasts and bone formation by osteoblasts. Identifying dual target-directed agents that inhibit excessive bone resorption and increase bone formation is considered an efficient strategy for developing new osteoporosis treatments. Rhein, a natural anthraquinone, can be isolated from various Asian herbal medicines. Rhein and its derivatives have been reported to have various beneficial pharmacological effects, especially their bone-targeting ability and anti-osteoclastogenesis activity. Moreover, hydrogen sulfide (H₂ S) was reported to prevent ovariectomy- (OVX-) induced bone loss by enhancing bone formation, and sulfur replacement therapy has been considered a novel and plausible therapeutic option. Based on this information, we synthesized a rhein-derived thioamide (RT) and investigated its effects on bone resorption and bone formation in vitro and in vivo. It has been found that the RT-inhibited receptor activator of the nuclear factor-κB (NF-κB) ligand- (RANKL-) induced osteoclastogenesis and bone resorption in a dose-dependent manner. The expression of osteoclast marker genes was also suppressed by RT treatment. Furthermore, exploration of signal transduction pathways indicated that RT markedly blocked RANKL-induced osteoclastogenesis by attenuating MAPK pathways. However, RT treatment in an osteoblastic cell line, MC3TE-E1, indicated that RT led to an increase in the deposition of minerals and the expression of osteoblast marker genes, as demonstrated by Alizarin Red staining and alkaline phosphatase activity. Importantly, an OVX mouse model showed that RT could attenuate the bone loss in estrogen deficiency-induced osteoporosis in vivo with a smart H₂ S-releasing property and that there was a considerable improvement in the biomechanical properties of bone. Accordingly, our current work highlights the dual regulation of bone remodeling by the rhein-derived molecule RT. This may be a highly promising approach for a new type of anti-osteoporosis agent. © 2018 American Society for Bone and Mineral Research.

Small molecule nAS-E targeting cAMP response element binding protein (CREB) and CREB-binding protein interaction inhibits breast cancer bone metastasis

Bone is the most common metastatic site for breast cancer. The excessive osteoclast activity in the metastatic bone lesions often produces osteolysis. The cyclic-AMP (cAMP)-response element binding protein (CREB) serves a variety of biological functions including the transformation and immortalization of breast cancer cells. In addition, evidence has shown that CREB plays a key role in osteoclastgenesis and bone resorption. Small organic molecules with good pharmacokinetic properties and specificity, targeting CREB-CBP (CREB-binding protein) interaction to inhibit CREB-mediated gene transcription have attracted more considerations as cancer therapeutics. We recently identified naphthol AS-E (nAS-E) as a cell-permeable inhibitor of CREB-mediated gene transcription through inhibiting CREB-CBP interaction. In this study, we tested the effect of nAS-E on breast cancer cell proliferation, survival, migration as well as osteoclast formation and bone resorption in vitro for the first time. Our results demonstrated that nAS-E inhibited breast cancer cell proliferation, migration, survival and suppressed osteoclast differentiation as well as bone resorption through inhibiting CREB-CBP interaction. In addition, the in vivo effect of nAS-E in protecting against breast cancer-induced osteolysis was evaluated. Our results indicated that nAS-E could reverse bone loss induced by MDA-MB-231 tumour. These results suggest that small molecules targeting CREB-CBP interaction to inhibit CREB-mediated gene transcription might be a potential approach for the treatment of breast cancer bone metastasis.

Rubiadin-1-methyl ether from Morinda officinalis How. Inhibits osteoclastogenesis through blocking RANKL-induced NF-κB pathway

Rubiadin-1-methyl ether (RBM) is a natural anthraquinone compound isolated from the root of Morinda officinalis How. In our previous study, RBM was found to have inhibitory effects on the TRAP activity of osteoclasts, which means that RBM may be a candidate for therapy of bone diseases characterized by enhanced bone resorption. However, the further effect of RBM on osteoclasts and the underlying mechanism remain unclear. In the present study, we investigated the effects of RBM isolated from Morinda officinalis How. on osteoclasts derived from bone marrow macrophages (BMMs) and the underlying mechanism in vitro. RBM at the dose that did not affect the viability of cells significantly inhibited RANKL-induced osteoclastogenesis and actin ring formation of osteoclast, while RBM performed a stronger effect at the early stage. In addition, RBM downregulated the expression of osteoclast-related proteins, including nuclear factor of activated T cells cytoplasmic 1 (NFATc1), cellular oncogene Fos (c-Fos), matrix metallopeptidase 9 (MMP-9) and cathepsin K (CtsK) as shown by Western blot. Furthermore, RBM inhibited the phosphorylation of NF-κB p65 and the degradation of IκBα as well as decreased the nuclear translocation of p65. Collectively, the results suggest that RBM inhibit osteoclastic bone resorption through blocking NF-κB pathway and may be a promising agent for the prevention and treatment of bone diseases characterized by excessive bone resorption.

The prevention of latanoprost on osteoclastgenesis in vitro and lipopolysaccharide-induced murine calvaria osteolysis in vivo

Identification of agents that inhibit osteoclast formation and function is important for the treatment of osteolytic diseases which feature excessive osteoclast formation and bone resorption. Latanoprost (LTP), an analog of prostaglandin F2α, is a medication which works to lower pressure inside the eyes. Prostaglandin F2α was reported to regulate bone metabolism, however, the effect of LTP in osteoclastogenesis is still unknown. Here, we found that LTP suppressed RANKL-induced osteoclastogenesis in a dose-dependent manner as illustrated by TRAP activity and TRAP staining. In addition, the osteoclast function was also reduced by LTP treatment, as indicated in less osteoclastic resorption pit areas. Furthermore, LTP inhibited the mRNA expressions of osteoclast marker genes such as TRAP and cathepsin K. In order to illustrate its molecular mechanism, we examined the changing of mRNA and protein levels of NFATc1 and c-fos by LTP treatment, as well as the phosphorylation of ERK, AKT, JNK, and p38. The results suggested that LTP inhibited RANKL-induced osteoclastgenesis and function by inhibiting ERK, AKT, JNK, and p38 cascade, following by the c-fos/NFATc1 pathway. In agreement with in vitro results, using an in vivo lipopolysaccharide-induced murine calvaria osteolysis mouse model, we found that administration of LTP was able to reverse the lipopolysaccharide-induced bone loss. Together, these data demonstrated that LTP attenuated the bone loss in lipopolysaccharide-induced murine calvaria osteolysis mice through inhibiting osteoclast formation and function. Our study thus provided the evidences that LTP was a potential treatment option against osteolytic bone diseases.