20(S)-Protopanaxadiol Inhibits Titanium Particle-Induced Inflammatory Osteolysis and RANKL-Mediated Osteoclastogenesis via MAPK and NF-κB Signaling Pathways

Synthesis, Anti-Inflammatory Activities, and Molecular Docking Study of Novel Pyxinol Derivatives as Inhibitors of NF-κB Activation

Pyxinol, an active metabolite of ginsenosides in human hepatocytes, exhibits various pharmacological activities. Here, a series of C-3 modified pyxinol derivatives was designed and virtually screened by molecular docking with the key inflammation-related proteins of the nuclear factor kappa B (NF-κB) pathway. Some of the novel derivatives were synthesized to assess their effects in inhibiting the production of nitric oxide (NO) and mitochondrial reactive oxygen species (MtROS) in lipopolysaccharide-triggered RAW264.7 cells. Derivative 2c exhibited the highest NO and MtROS inhibitory activities with low cytotoxicity. Furthermore, 2c decreased the protein levels of interleukin 1β, tumor necrosis factor α, inducible nitric oxide synthase, and cyclooxygenase 2 and suppressed the activation of NF-κB signaling. Cellular thermal shift assays indicated that 2c could directly bind with p65 and p50 in situ. Molecular docking revealed that 2c's binding to the p65-p50 heterodimer and p50 homodimer was close to their DNA binding sites. In summary, pyxinol derivatives possess potential for development as NF-κB inhibitors.

Synthesis and Biological Evaluation of Heterocyclic Ring-Fused 20(S)-Protopanaxadiol Derivatives as Potent Antiosteoporosis Agents

A series of heterocyclic ring-fused derivatives of 20(S)-protopanaxadiol (PPD) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Among these compounds, 33 (SH491, IC50 = 11.8 nM) showed the highest potency with 100% inhibition at 0.1 μM and 44.4% inhibition at an even lower concentration of 0.01 μM, which was much more potent than the lead compound PPD (IC50 = 10.3 μM). Cytotoxicity tests indicated that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation was not due to their cytotoxicity. Interestingly, SH491 also exhibited a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. Mechanistic studies revealed that SH491 inhibits the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, CTSK, MMP-9, and ATPase v0d2. In vivo, SH491 could dramatically decrease the ovariectomy-induced osteoclast activity and relieve osteoporosis obviously. Thus, these PPD derivatives could be served as promising leads for the development of novel antiosteoporosis agents.

Protopanaxadiol ameliorates NAFLD by regulating hepatocyte lipid metabolism through AMPK/SIRT1 signaling pathway

Non-alcoholic fatty liver disease (NAFLD) has become one of the main chronic liver diseases worldwide. Protopanaxadiol (PPD), an active compound derived from Gynostemma pentaphyllum, has been found able to improve free fatty acid-induced lipid accumulation in hepatocytes. However, the efficacy of PPD on NAFLD and the underlying mechanism remains unknown. In this study, the mice were fed with a high-fat diet for 22 weeks to induce the NAFLD model, and then were treated with PPD by gavage for 8 weeks. Moreover, AML12 and HepG2 cells induced by free fatty acids for 24 h, were treated with different doses of PPD and/or AMPK or SIRT1 inhibitor to explore the pharmacological mechanism of PPD. The results showed that mice with PPD treatment had significantly reduced liver weight and serum aminotransferase levels, less severe hepatosteatosis, and inflammatory cell infiltration in liver tissues when compared with the model mice. PPD also reversed the down-regulated activation of AMPK and SIRT1 expression as well as the change of lipid metabolism-related molecules in the mice liver tissues. Consistently, the in vitro experiments showed the effect of PPD in ameliorating lipid accumulation in hepatocytes. The inhibitor of AMPK or SIRT1 suppressed the AMPK and SIRT1 signaling and markedly diminished the anti-steatosis effect of PPD. In conclusion, our results prove the ameliorating impact of PPD on NAFLD and also reveal the involvement of regulation of AMPK/SIRT1 signaling pathway-mediated lipid metabolism in the underlying mechanism, suggesting PPD as a potential natural compound for the treatment of NAFLD.

Fusion of Michael-acceptors enhances the anti-inflammatory activity of ginsenosides as potential modulators of the NLRP3 signaling pathway

Ginsenosides are a promising group of secondary metabolites for developing anti-inflammatory agents. In this study, Michael acceptor was fused into the aglycone A-ring of protopanoxadiol (PPD)-type ginsenosides (MAAG), the main pharmacophore of ginseng, and its liver metabolites to produce novel derivatives and assess their anti-inflammatory activity in vitro. The structure-activity relationship of MAAG derivatives was assessed based on their NO-inhibition activities. Of these, a 4-nitrobenzylidene derivative of PPD (2a) was the most effective and dose-dependently inhibited the release of proinflammatory cytokines. Further studies indicated that 2a-induced downregulation on lipopolysaccharide (LPS)-induced iNOS protein expression and cytokine release may be related to its inhibitory effect on MAPK and NF-κB signaling pathways. Importantly, 2a almost completely inhibited LPS-induced production of mitochondrial reactive oxygen species (mtROS) and LPS-induced NLRP3 upregulation. This inhibition was higher than that by hydrocortisone sodium succinate, a glucocorticoid drug. Overall, the fusion of Michael acceptors into the aglycone of ginsenosides greatly enhanced the anti-inflammatory activities of the derivatives, and 2a alleviated inflammation considerably. These findings could be attributed to the inhibition of LPS-induced mtROS to block abnormal activation of the NLRP3 pathway.

20(S)-Protopanaxatriol ameliorates MAFLD by inhibiting NLRP3 inflammasome

Metabolic associated fatty liver disease (MAFLD) is one of the most common chronic liver diseases and may develop into non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and even hepatocellular carcinoma, which has threatened human health. Although NLRP3 inflammasome is widely recognized in the pathogenesis of MAFLD, there are currently no drugs targeting NLRP3 inflammasome approved by regulatory agencies. Panax ginseng and its main saponin components have been used to regulate inflammatory and metabolic disorders. Notably, 20(S)-protopanaxatriol (PPT) is an active metabolite of protopanaxatriol saponins with prominent anti-inflammatory activity. However, the mechanism by which PPT ameliorates MAFLD has not been fully elucidated. Therefore, this study explored the efficacy and mechanism of PPT in treating MAFLD based on the inhibition of NLRP3 inflammasome activation. First, we screened potential NLRP3 inflammasome blockers from protopanaxadiol saponins in mouse primary bone marrow-derived macrophages (BMDMs) stimulated by LPS and different inflammasome inducers. Second, LPS-primed mouse BMDMs, mouse primary hepatocytes, mouse primary Kupffer cells and human peripheral blood mononuclear cells (PBMCs) stimulated by cholesterol and ATP were used to evaluate the effect of PPT in inhibiting NLRP3 inflammasome. Finally, MCD-induced mouse MAFLD were established to verify the therapeutic effect of PPT by inhibiting NLRP3 inflammasome. Our results showed that PPT of ginseng saponins significantly inhibited NLRP3 inflammasome activation in multiple primary cells, suppressed systemic inflammation, restored liver function, and attenuated liver inflammation as well as fibrosis in MCD--induced mouse MAFLD. Collectively, protopanaxatriol saponins metabolite PPT, may serve as a potent therapeutic agent for MAFLD by inhibiting NLRP3 inflammasome activation.

Design, Synthesis, and Anti-Inflammatory Activities of 12-Dehydropyxinol Derivatives

Pyxinol skeleton is a promising framework of anti-inflammatory agents formed in the human liver from 20S-protopanaxadiol, the main active aglycone of ginsenosides. In the present study, a new series of amino acid-containing derivatives were produced from 12-dehydropyxinol, a pyxinol oxidation metabolite, and its anti-inflammatory activity was assessed using an NO inhibition assay. Interestingly, the dehydrogenation at C-12 of pyxinol derivatives improved their potency greatly. Furthermore, half of the derivatives exhibited better NO inhibitory activity than hydrocortisone sodium succinate, a glucocorticoid drug. The structure-activity relationship analysis indicated that the kinds of amino acid residues and their hydrophilicity influenced the activity to a great extent, as did R/S stereochemistry at C-24. Of the various derivatives, 5c with an N-Boc-protected phenylalanine residue showed the highest NO inhibitory activity and relatively low cytotoxicity. Moreover, derivative 5c could dose-dependently suppress iNOS, IL-1β, and TNF-α via the MAPK and NF-κB pathways, but not the GR pathway. Overall, pyxinol derivatives hold potential for application as anti-inflammatory agents.

Photoluminescent carbon dots (PCDs) from sour apple: a biocompatible nanomaterial for preventing UHMWPE wear-particle induced osteolysis via modulating Chemerin/ChemR23 and SIRT1 signaling pathway and its bioimaging application

Photoluminescent nanomaterials have been widely employed in several biological applications both in vitro and in vivo. For the first time, we report a novel application of sour apple-derived photoluminescent carbon dots (PCDs) for reducing ultra-high molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis using mouse calvarial model. Generally, aseptic prosthetic loosening seems to be a significant postoperative problem for artificial joints replacement, which is mainly contributed by UHMWPE-induced osteolysis. Hence, inhibiting osteoclastic bone-resorption could minimize UHMWPE-induced osteolysis for implant loosening. Prior to osteolysis studies, the prepared sour apple-derived PCDs were employed for bioimaging application. As expected, the prepared PCDs effectively inhibited the UHMWPE particle-induced osteoclastogenesis in vitro. The PCDs treatment effectively inhibited the UHMWPE-induced osteoclast differentiation, F-actin ring pattern, and bone resorption in vitro. Also, the PCDs reduced the UHMWPE-induced ROS stress as well as the expression level of pro-inflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-8. Further, the qPCR and western blot results hypothesized that PCDs inhibited the UHMWPE wear particle-induced osteolysis through suppressing chemerin/ChemR23 signaling and NFATc1 pathway, along with upregulation of SIRT1 expression. Overall, these findings suggest that the synthesized PCDs could be a potential therapeutic material for minimizing UHMWPE particle-induced periprosthetic osteolysis to avoid postoperative complications.

Gallium Porphyrin and Gallium Nitrate Reduce the High Vancomycin Tolerance of MRSA Biofilms by Promoting Extracellular DNA-Dependent Biofilm Dispersion

Biofilms, structured communities of bacterial cells embedded in a self-produced extracellular matrix (ECM) which consists of proteins, polysaccharide intercellular adhesins (PIAs), and extracellular DNA (eDNA), play a key role in clinical infections and are associated with an increased morbidity and mortality by protecting the embedded bacteria against drug and immune response. The high levels of antibiotic tolerance render classical antibiotic therapies impractical for biofilm-related infections. Thus, novel drugs and strategies are required to reduce biofilm tolerance and eliminate biofilm-protected bacteria. Here, we showed that gallium, an iron mimetic metal, can lead to nutritional iron starvation and act as dispersal agent triggering the reconstruction and dispersion of mature methicillin-resistant Staphylococcus aureus (MRSA) biofilms in an eDNA-dependent manner. The extracellular matrix, along with the integral bacteria themselves, establishes the integrated three-dimensional structure of the mature biofilm. The structures and compositions of gallium-treated mature biofilms differed from those of natural or antibiotic-survived mature biofilms but were similar to those of immature biofilms. Similar to immature biofilms, gallium-treated biofilms had lower levels of antibiotic tolerance, and our in vitro tests showed that treatment with gallium agents reduced the antibiotic tolerance of mature MRSA biofilms. Thus, the sequential administration of gallium agents (gallium porphyrin and gallium nitrate) and relatively low concentrations of vancomycin (16 mg/L) effectively eliminated mature MRSA biofilms and eradicated biofilm-enclosed bacteria within 1 week. Our results suggested that gallium agents may represent a potential treatment for refractory biofilm-related infections, such as prosthetic joint infections (PJI) and osteomyelitis, and provide a novel basis for future biofilm treatments based on the disruption of normal biofilm-development processes.

Inhibitory effects of biochanin A on titanium particle-induced osteoclast activation and inflammatory bone resorption via NF-κB and MAPK pathways

Revision operations have become a new issue after successful artificial joint replacements, and periprosthetic osteolysis leading to prosthetic loosening is the main cause of why the overactivation of osteoclasts (OCs) plays an important role. The effect of biochanin A (BCA) has been examined in osteoporosis, but no study on the role of BCA in prosthetic loosening osteolysis has been conducted yet. In this study, we utilised enzyme-linked immunosorbent assay, computed tomography imaging, and histological analysis. Results showed that BCA downregulated the secretion levels of tumor necrosis factor-α, interleukin-1α (IL-1α), and IL-1β to suppress inflammatory responses. The secretion levels of receptor-activated nuclear factor-κB ligand, CTX-1, and osteoclast-associated receptor as well as Ti-induced osteolysis were also reduced. BCA effectively inhibited osteoclastogenesis and suppressed hydroxyapatite resorption by downregulating OC-related genes in vitro. Analysis of mechanisms indicated that BCA inhibited the signalling pathways of mitogen-activated protein kinase (P38, extracellular signal-regulated kinase, and c-JUN N-terminal kinase) and nuclear factor-κB (inhibitor κB-α and P65), thereby downregulating the expression of nuclear factor of activated T cell 1 and c-Fos. In conclusion, BCA may be an alternative choice for the prevention of prosthetic loosening caused by OCs.

Chemical composition and anti-oxidant potential on essential oils of Thymus quinquecostatus Celak. from Loess Plateau in China, regulating Nrf2/Keap1 signaling pathway in zebrafish

Chemical profile and antioxidant potency of essential oils (EOs) of Thymus quinquecostatus Celak. (thyme oils) obtained from Loess Plateau in China had been studied. 130 constituents of thyme oils were determined using gas chromatography-mass spectrometry (GC–MS) and carvacrol ethyl ether was firstly reported as a new natural product, which has been used as a synthetic flavoring substance with no safety concern. The thyme oils showed the anti-oxidant activity using 2,2 diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS), ferric reducing antioxidant power (FRAP) and thiobarbituric acid reactive substances (TBARS) and conferred protection against oxidative stress in zebrafish. In addition, a class of carvacrol analogues was found to develop as potential natural antioxidant products of thyme oils from Loess Plateau by the correlation analysis. YL-thyme oil performed the best antioxidant activity in this research, which could be recommended as preferred sources of thyme oils. Furthermore, YL-thyme oil exhibited a potent antioxidant capacity by reactive oxygen species (ROS) scavenging, enhancing the endogenous antioxidant system, inhibiting lipid peroxidation and activation of Keap1/Nrf2 pathway in zebrafish.

Dammarane-type leads panaxadiol and protopanaxadiol for drug discovery: Biological activity and structural modification

Based on the definite therapeutic benefits, such as neuroprotective, cardioprotective, anticancer, anti-diabetic and so on, the Panax genus which contains many valuable plants, including ginseng (Panax ginseng C.A. Meyer), notoginseng (Panax notoginseng) and American ginseng (Panax quinquefolius L.), attracts research focus. Actually, the biological and pharmacological effects of the Panax genus are mainly attributed to the abundant ginsenosides. However, the low membrane permeability and the gastrointestinal tract influence seriously limit the absorption and bioavailability of ginsenosides. The acid or base hydrolysates of ginsenosides, 20 (R,S)-panaxadiol and 20 (R,S)-protopanaxadiol showed improved bioavailability and diverse pharmacological activities. Moreover, relative stable skeletons and active hydroxyl group at C-3 position and other reactive sites are suitable for structural modification to improve biological activities. In this review, the pharmacological activities of panaxadiol, protopanaxadiol and their structurally modified derivatives are comprehensively summarized.

Curcumin has immunomodulatory effects on RANKL-stimulated osteoclastogenesis in vitro and titanium nanoparticle-induced bone loss in vivo

Wear particle‐stimulated inflammatory bone destruction and the consequent aseptic loosening remain the primary causes of artificial prosthesis failure and revision. Previous studies have demonstrated that curcumin has a protective effect on bone disorders and inflammatory diseases and can ameliorate polymethylmethacrylate‐induced osteolysis in vivo. However, the effect on immunomodulation and the definitive mechanism by which curcumin reduces the receptor activators of nuclear factor‐kappa B ligand (RANKL)‐stimulated osteoclast formation and prevents the activation of osteoclastic signalling pathways are unclear. In this work, the immunomodulation effect and anti‐osteoclastogenesis capacities exerted by curcumin on titanium nanoparticle‐stimulated macrophage polarization and on RANKL‐mediated osteoclast activation and differentiation in osteoclastic precursor cells in vitro were investigated. As expected, curcumin inhibited RANKL‐stimulated osteoclast maturation and formation and had an immunomodulatory effect on macrophage polarization in vitro. Furthermore, studies aimed to identify the potential molecular and cellular mechanisms revealed that this protective effect of curcumin on osteoclastogenesis occurred through the amelioration of the activation of Akt/NF‐κB/NFATc1 pathways. Additionally, an in vivo mouse calvarial bone destruction model further confirmed that curcumin ameliorated the severity of titanium nanoparticle‐stimulated bone loss and destruction. Our results conclusively indicated that curcumin, a major biologic component of Curcuma longa with anti‐inflammatory and immunomodulatory properties, may serve as a potential therapeutic agent for osteoclastic diseases.

Rictor ablation in BMSCs inhibits bone metastasis of TM40D cells by attenuating osteolytic destruction and CAF formation

The mTOR complex 2 (mTORC2) is recognized as a promising target for breast cancer treatment. As mTORC2-specific inhibitors do not yet exist, studies into the role of mTORC2 in cancer are performed by deleting Rictor or by RNAi-mediated Rictor silencing. The purpose of this study was to explore the effects of Rictor ablation in bone mesenchymal stromal cells (BMSCs) on bone metastasis of breast cancer. First, female mice with the genotype of Prx1-Cre;Rictor^f/f (hereafter RiCKO) or Rictor^f/f (as control) were injected intratibially with cells of the breast cancer cell line (TM40D) at 4 months of age. Three weeks later, osteolytic bone destruction was detected in metastatic legs by X-ray and micro-CT. We found that Rictor ablation in BMSCs inhibited TM40D-induced osteolytic bone destruction and resulted in greater bone volume maintenance in vivo. Lower CTX-I serum level, a decreased number of TRAP+ osteoclasts and lower Cathepsin-K expression observed at the tumor-bone interface indicated that osteoclastogenesis was inhibited in RiCKO mice. Additionally, co-culture experiments confirmed that Rictor deletion in BMSCs diminished osteoclast differentiation partly via down regulation of RANKL expression. Furthermore, Rictor deficiency was found to reduce the transition of BMSCs to CAFs coupled with decreased secretion of cytokines (IL-6, RANKL, TGFβ), which resulted in lower chemotaxis and less proliferation in TM40D cells. These results suggest that Rictor ablation in BMSCs plays dual roles in breast cancer bone metastasis: (1) repression of osteolytic bone destruction; (2) inhibition of tumor growth.