Zhenxi Li

Maslinic Acid Suppresses Osteoclastogenesis and Prevents Ovariectomy-Induced Bone Loss by Regulating RANKL-Mediated NF-κB and MAPK Signaling Pathways

Activation of NF‐κB and MAPK/activator protein 1 (AP‐1) signaling pathways by receptor activator NF‐κB ligand (RANKL) is essential for osteoclast activity. Targeting NF‐κB and MAPK/AP‐1 signaling to modulate osteoclast activity has been a promising strategy for osteoclast‐related diseases. In this study we examined the effects of maslinic acid (MA), a pentacyclic triterpene acid that is widely present in dietary plants, on RANKL‐induced osteoclastogenesis, osteoclast function, and signaling pathways by in vitro and in vivo assay systems. In mouse bone marrow monocytes (BMMs) and RAW264.7 cells, MA inhibited RANKL‐induced osteoclastogenesis in a dose‐dependent manner within nongrowth inhibitory concentration, and MA decreased osteoclastogenesis‐related marker gene expression, including TRACP, MMP9, c‐Src, CTR, and cathepsin K. Specifically, MA suppressed osteoclastogenesis and actin ring formation at early stage. In ovariectomized mice, administration of MA prevented ovariectomy‐induced bone loss by inhibiting osteoclast activity. At molecular levels, MA abrogated the phosphorylation of MAPKs and AP‐1 activity, inhibited the IκBα phosphorylation and degradation, blocked NF‐κB/p65 phosphorylation, nuclear translocation, and DNA‐binding activity by downregulating RANK expression and blocking RANK interaction with TRAF6. Together our data demonstrate that MA suppresses RANKL‐induced osteoclastogenesis through NF‐κB and MAPK/AP‐1 signaling pathways and that MA is a promising agent in the treatment of osteoclast‐related diseases such as osteoporosis.

Synthesis and biological evaluation of heterocyclic ring-fused betulinic acid derivatives as novel inhibitors of osteoclast differentiation and bone resorption.

A series of betulinic acid (BA) derivatives were designed and synthesized by introducing various fused heterocyclic rings at C-2 and C-3 positions. Their inhibitory effects of RANKL-induced osteoclastogenesis were evaluated by using a cell-based tartrate-resistant acid phosphatase (TRAP) activity assay. To our delight, most of these compounds exhibited a dramatic increase in inhibitory potency, compared with BA. The most potent compound, 20, showed 66.9% inhibition even at the low concentration of 0.1 μM, which was about 200-fold more potent than the lead compound BA. Whats more, the cytotoxicity assay on RAW264.7 suggested that the inhibition of 20 on osteoclast differentiation did not result from its cytotoxicity. The primary mechanistic study indicated that 20 could inhibit osteoclastogenesis-related marker gene expression levels of cathepsin K and TRAP. More importantly, 20 could attenuate bone loss of ovariectomy mouse in vivo. Therefore, these BA derivatives could be used as potential leads for the development of a new type of antiosteoporosis agent.

Nitidine Chloride inhibits breast cancer cells migration and invasion by suppressing c-Src/FAK associated signaling pathway.

Nitidine is a benzophenanthridine alkaloid, which has been shown to have anti-tumor properties. Here, we demonstrated that Nitidine Chloride (NC) could inhibit breast cancer cells migration and invasion both in vitro and in vivo. Meanwhile, the protrusion formation and partial proteolytic activity of MMP-9 and MMP-2 were attenuated by NC in a dose-dependent manner in MDA-MB-231 cells. Furthermore, addition NC to cells significantly decreases PDGF induced phosphorylation of c-Src, FAK, MAPKs, activation of RhoA, Rac1 and AP-1 transcriptional activity. Taken together, our results indicate that NC could have potential as a novel anti-metastasis drug to breast cancer.

Inhibition of Breast Cancer Metastases by a Novel Inhibitor of TGFβ Receptor 1

BACKGROUND Transforming growth factor beta (TGFβ), which is implicated in metastasis to various organs in breast cancer, is a potential target for new antitumor metastasis drugs. METHODS To identify specific inhibitors of TGFβ receptor 1 (TGFβR1) in breast cancer metastasis, a virtual library of more than 400000 different compounds was screened by molecular docking modeling and confirmed with Smad-binding element luciferase and TGFβR1 kinase assays. Affymetrix GeneChip expression analysis of mRNA levels and real-time polymerase chain reaction were performed to determine expression changes of TGFβ-mediated, metastasis-associated genes in breast cancer cells after treatment with the small-molecule inhibitor YR-290. YR-290 was also examined for its effects on breast cancer migration, invasion, and metastasis using transwell and epithelial-to-mesenchymal transition (EMT) assays in vitro and three different mouse (BALB/c and NU/NU nude) models (n = 10 per group). Kaplan-Meier analyses were used to assess survival. All statistical tests were two-sided. RESULTS YR-290 interacted with the kinase domain of TGFβR1, abrogated kinase activity (half maximal inhibitory concentration = 137nM, 95% confidence interval = 126.4 to 147.6nM) and inhibited the TGFβ-mediated downstream signaling pathway and metastasis-associated genes in breast cancer cells. YR-290 inhibited TGFβ-modulated breast cancer cell migration and invasion. In tumor metastasis mouse models, YR-290 almost completely blocked cancer metastasis. Numbers of lung tumor nodules of mice treated with 1mg/kg and 5mg/kg YR-290 were reduced by 74.93% (95% confidence interval = 61.45% to 88.41%) and 94.93% (95% confidence interval = 82.13% to 100%), respectively, compared with control mice. Treatment with YR-290 also statistically significantly prolonged the survival of tumor-bearing mice. CONCLUSIONS YR-290 is a novel inhibitor of tumor metastasis that works by blocking TGFβ signaling pathways.

GPR116, an Adhesion G-Protein Coupled Receptor, Promotes Breast Cancer Metastasis via the Gαq-p63RhoGEF-Rho GTPase Pathway

Adhesion G-protein-coupled receptors (GPCR), which contain adhesion domains in their extracellular region, have been found to play important roles in cell adhesion, motility, embryonic development, and immune response. Because most adhesion molecules with adhesion domains have vital roles in cancer metastasis, we speculated that adhesion GPCRs are potentially involved in cancer metastasis. In this study, we identified GPR116 as a novel regulator of breast cancer metastasis through expression and functional screening of the adhesion GPCR family. We found that knockdown of GPR116 in highly metastatic (MDA-MB-231) breast cancer cells suppressed cell migration and invasion. Conversely, ectopic GPR116 expression in poorly metastatic (MCF-7 and Hs578T) cells promoted cell invasion. We further showed that knockdown of GPR116 inhibited breast cancer cell metastasis in two mammary tumor metastasis mouse models. Moreover, GPR116 modulated the formation of lamellipodia and actin stress fibers in cells in a RhoA- and Rac1-dependent manner. At a molecular level, GPR116 regulated cell motility and morphology through the Gαq-p63RhoGEF-RhoA/Rac1 pathway. The biologic significance of GPR116 in breast cancer is substantiated in human patient samples, where GPR116 expression is significantly correlated with breast tumor progression, recurrence, and poor prognosis. These findings show that GPR116 is crucial for the metastasis of breast cancer and support GPR116 as a potential prognostic marker and drug target against metastatic human breast cancer.

Caffeic acid 3,4-dihydroxy-phenethyl ester suppresses receptor activator of NF-κB ligand–induced osteoclastogenesis and prevents ovariectomy-induced bone loss through inhibition of mitogen-activated protein kinase/activator protein 1 and Ca2+–nuclear factor of activated T-cells cytoplasmic 1 signaling pathways.

Receptor activator of NF‐κB ligand (RANKL) stimulation leads to the activation of mitogen‐activated protein kinase (MAPK)/AP‐1 and Ca2+–nuclear factor of activated T‐cells cytoplasmic 1 (NFATc1) signaling pathways in osteoclastogenesis. Targeting these pathways has been an encouraging strategy for bone‐related diseases, such as postmenopausal osteoporosis. In this study, we examined the effects of caffeic acid 3,4‐dihydroxy‐phenethyl ester (CADPE) on osteoclastogenesis. In mouse bone marrow monocytes (BMMs) and RAW264.7 cells, CADPE suppressed RANKL‐induced osteoclast differentiation and actin‐ring formation in a dose‐dependent manner within non–growth inhibitory concentrations at the early stage, while CADPE had no effect on macrophage colony‐stimulating factor (M‐CSF)‐induced proliferation and differentiation. At the molecular level, CADPE inhibited RANKL‐induced phosphorylation of MAPKs, including extracellular signal‐regulated kinases 1/2 (ERK1/2), p38, and c‐Jun N‐terminal kinase (JNK), without significantly affecting the NF‐κB signaling pathway. CADPE abrogated RANKL‐induced activator protein 1 (AP‐1)/FBJ murine osteosarcoma viral oncogene homolog (c‐Fos) nuclear translocation and activation. Overexpression of c‐Fos prevented the inhibition by CADPE of osteoclast differentiation. Furthermore, CADPE suppressed RANKL‐induced the tumor necrosis factor receptor associated factor 6 (TRAF6) interaction with c‐src tyrosine kinase (c‐Src), blocked RANKL‐induced the phosphorylation of protein kinase B (AKT), and inhibited RANKL‐induced Ca2+ oscillation. As a result, CADPE decreased osteoclastogenesis‐related marker gene expression, including NFATc1, TRAP, cathepsin K, and c‐Src. To test the effects of CADPE on osteoclast activity in vivo, we showed that CADPE prevented ovariectomy‐induced bone loss by inhibiting osteoclast activity. Together, our data demonstrate that CADPE suppresses osteoclastogenesis and bone loss through inhibiting RANKL‐induced MAPKs and Ca2+‐NFATc1 signaling pathways. CADPE is a novel agent in the treatment of osteoclast‐related diseases, such as osteoporosis.

Plasmon-enhanced upconversion fluorescence in NaYF4:Yb/Er/Gd nanorods coated with Au nanoparticles or nanoshells

We investigate plasmon-enhanced upconversion (UC) fluorescence in Yb3+-Er3+-Gd+3 codoped sodium yttrium fluoride (NaYF4:Yb/Er/Gd) nanorods using gold nanoparticles or nanoshells. A simple method was proposed for the preparation of core/shell NaYF4/Au structures, with dispersed Au nanoparticles or uniform Au coating on the surface of the UC nanorod. Pure hexagonal-phase NaYF4:Yb/Er/Gd nanorods were synthesized via a liquid-solid reaction in oleic acid and ethanol solvent. A one-step approach was introduced to modify the hydrophobic surfaces of the as-deposited NaYF4:Yb/Er/Gd nanorods. After this surface modification, Au nanoparticles or nanoshells were successfully attached on the surfaces of NaYF4:Yb/Er/Gd nanorods. The as-deposited UC nanorods showed a strong UC emission in green and red bands under 980 nm laser excitation. The attachment of Au nanoparticles onto NaYF4:Yb/Er/Gd nanorods resulted in a more than three-fold increase in UC emissions, whereas the formation of continuous and compact Au shells ...

REGγ deficiency promotes premature aging via the casein kinase 1 pathway

Our recent studies suggest a role for the proteasome activator REG (11S regulatory particles, 28-kDa proteasome activator)γ in the regulation of tumor protein 53 (p53). However, the molecular details and in vivo biological significance of REGγ-p53 interplay remain elusive. Here, we demonstrate that REGγ-deficient mice develop premature aging phenotypes that are associated with abnormal accumulation of casein kinase (CK) 1δ and p53. Antibody array analysis led us to identify CK1δ as a direct target of REGγ. Silencing CK1δ or inhibition of CK1δ activity prevented decay of murine double minute (Mdm)2. Interestingly, a massive increase of p53 in REGγ−/− tissues is associated with reduced Mdm2 protein levels despite that Mdm2 transcription is enhanced. Allelic p53 haplodeficiency in REGγ-deficient mice attenuated premature aging features. Furthermore, introducing exogenous Mdm2 to REGγ−/− MEFs significantly rescues the phenotype of cellular senescence, thereby establishing a REGγ-CK1-Mdm2-p53 regulatory pathway. Given the conflicting evidence regarding the “antiaging” and “proaging” effects of p53, our results indicate a key role for CK1δ-Mdm2-p53 regulation in the cellular aging process. These findings reveal a unique model that mimics acquired aging in mammals and indicates that modulating the activity of the REGγ-proteasome may be an approach for intervention in aging-associated disorders.

MiR-126-5p regulates osteoclast differentiation and bone resorption in giant cell tumor through inhibition of MMP-13

Giant cell tumor (GCT) of bone is an aggressive skeletal tumor characterized by localized bone resorption. Matrix metalloproteinase-13 (MMP-13) is the principal proteinase expressed by the stromal cells of GCT (GCTSCs) and also considered to play a crucial role in formation of the osteolytic lesion in GCT. However, the exact mechanism of the regulation of MMP-13 expression in GCTSCs was unknown. In this study, we identified miR-126-5p was significantly downregulated in GCTSCs and affect osteoclast (OC) differentiation and bone resorption by repressing MMP-13 expression at the post-transcriptional level. Thus, our studies show that miR-126-5p plays an important physiological role in multinucleated giant cell formation and osteolytic lesion in GCT.

Large-scale growth of Cu2ZnSnSe4 and Cu2ZnSnSe4/Cu2ZnSnS4 core/shell nanowires

We present a fast and simple protocol for large-scale preparation of quaternary Cu(2)ZnSnSe(4) (CZTSe), as well as CZTSe/Cu(2)ZnSnS(4) (CZTS) core/shell nanowires using CuSe nanowire bundles as self-sacrificial templates. CuSe nanowire bundles were synthesized by reacting Cu(2 - x)Se nanowire bundles with sodium citrate solution. CZTSe nanowires were prepared by reacting CuSe nanowire bundles with Zn(CH(3)COO)(2) and SnCl(2) in triethylene glycol. X-ray diffraction (XRD) and selected area electron diffraction studies show that stannite CZTSe is formed. The formed CZTSe nanowire bundles have diameters of 200-400 nm and lengths of up to hundreds of micrometers. CZTSe/CZTS nanocable bundles with similar morphologies were grown by the addition of some elemental sulfur to the reaction system for growth of CZTSe bundles. The stannite CZTSe/kesterite CZTS core/shell structure of the grown nanocables was confirmed by XRD and high-resolution transmission electron microscope investigation. The influence of S/Se molar ratio in the reaction system on the crystallographic structures and optical properties of CZTSe/CZTS nanocables was studied. The obtained CZTSe/CZTS core/shell nanocable bundles show broad and enhanced optical absorption over the visible and near-infrared region, which is promising for use in photovoltaic applications.