Differential involvement of Wnt signaling in Bmp regulation of cancellous versus periosteal bone growth

Bone morphogenetic proteins (Bmp) are well-known to induce bone formation following chondrogenesis, but the direct role of Bmp signaling in the osteoblast lineage is not completely understood. We have recently shown that deletion of the receptor Bmpr1a in the osteoblast lineage with Dmp1-Cre reduces osteoblast activity in general but stimulates proliferation of preosteoblasts specifically in the cancellous bone region, resulting in diminished periosteal bone growth juxtaposed with excessive cancellous bone formation. Because expression of sclerostin (SOST), a secreted Wnt antagonist, is notably reduced in the Bmpr1a-deficient osteocytes, we have genetically tested the hypothesis that increased Wnt signaling might mediate the increase in cancellous bone formation in response to Bmpr1a deletion. Forced expression of human SOST from a Dmp1 promoter fragment partially rescues preosteoblast hyperproliferation and cancellous bone overgrowth in the Bmpr1a mutant mice, demonstrating functional interaction between Bmp and Wnt signaling in the cancellous bone compartment. To test whether increased Wnt signaling can compensate for the defect in periosteal growth caused by Bmpr1a deletion, we have generated compound mutants harboring a hyperactive mutation (A214V) in the Wnt receptor Lrp5. However, the mutant Lrp5 does not restore periosteal bone growth in the Bmpr1a-deficient mice. Thus, Bmp signaling restricts cancellous bone accrual partly through induction of SOST that limits preosteoblast proliferation, but promotes periosteal bone growth apparently independently of Wnt activation

Cyclopentadione-aniline conjugate suppresses proliferation and induces apoptosis in liver cancer cells via up-regulation of p38 phosphorylation

Purpose: To investigate the effect of cyclopentadione-aniline conjugate (CAC) on proliferation of liver cancer cells. Methods: MTT assay and flow cytometry were used for the determination of the effect of CAC on cell proliferation and apoptosis. Western blotting was used to measure the influence of CAC on the expressions of various proteins, while Matrigel-coated Transwell assay was used for assessment of cell invasion. Results: CAC inhibited proliferation of liver cancer cells in a concentration-dependent manner. The degree of proliferation of HepG2 cells was 98, 89, 76, 66, 51, 42 or 36 %, on treatment with 0.25, 0.5, 1.0, 1.5, 2.0, 2.5 or 3.0 µM CAC, respectively. In H4TG cells, treatment with 0.25, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 µM CAC decreased proliferation of cells to 99, 91, 79, 70, 54, 46 and 40 %, respectively. Apoptosis was induced in 34.56, 37.37 and 52.98 % cells, on treatment with 2.0, 2.5 and 3.0 µM CAC, respectively. The invasive potential of HepG2 cells was significantly decreased by CAC (p < 0.05). Marked decreases were observed in Bcl-2, MMP-2, MMP-9, c-ERK1/2 and phospho-Akt levels in CACtreated HepG2 cells. CAC treatment markedly upregulated Bax and phospho ERK1/2, but significantly downregulated phospho PI3K, phospho mTOR and phospho Akt in HepG2 cells (p < 0.05). However, the level of phospho p38 was decreased in CAC-treated cells. Conclusion: These results demonstrate that CAC inhibits proliferation of liver cancer cells via apoptosis induction. Thus, CAC can potentially be used for the treatment of liver cancer in human

Overexpression of Wnt7b antagonizes the inhibitory effect of dexamethasone on osteoblastogenesis of ST2 cells

Introduction: It is well established that glucocorticoid-induced osteoporosis is highly associated with preosteoblast differentiation and function. This study is based on the premise that Wnt7b can promote bone formation through Wnt signalling pathway because it can stimulate preosteoblast differentiation and increase its activity. However, it is unknown whether Wnt7b can rescue the inhibited osteoblast differentiation and function caused by exogenous glucocorticoid. Material and methods: In this study we used Wnt7b overexpression ST2 cells to explore whether Wnt7bcan rescue the inhibited osteoblast differentiation and function, which can provide strong proof to investigate a new drug for curing the glucocorticoid induced osteoporosis. Results/Conclusion: We found that Wnt7b can rescue the suppressed osteoblast differentiation and function without cell viability caused by dexamethasone

HMGB1 can activate cartilage progenitor cells in response to cartilage injury through the CXCL12/CXCR4 pathway

Introduction: Recent studies have suggested that cartilage progenitor cells (CPCs) could be activated and differentiated into chondrocytes to produce matrix and to restore the integrity of damaged cartilage after injury. However, the mechanism involved in CPC activation upon damage is still unclear. This study aims to investigate the role of high mobility group box chromosomal protein 1 (HMGB1) in both activation and migration of CPCs during cartilage injury. Material and methods: Explants harvested from mature bovine stifle joints were used for impact injury. The proliferation and migration of CPCs were examined via confocal imaging. Gene and protein expression of Hmbg1, Cxcl12, and Cxcr4 was also examined by quantitative polymerase chain reaction (qPCR), ELISA, and western blot. Each experiment was repeated 3 times. ANOVA and Student’s t-test were performed for statistical analysis. Results: HMGB1 released from dead and damaged chondrocytes after an impact injury could activate CPCs in the superficial zone of cartilage and promote their migration and proliferation to injury sites. However, the block of HMGB1 activation with its specific binding inhibitor glycyrrhizin inhibits the proliferation and migration of CPCs. Further investigations demonstrate that HMGB1 promotes CPCs migration through the pathway of C-X-C motif chemokine 12 (CXCL12) and its receptor CXCR4. Quantitative analysis of HMGB1 in cell culture medium also indicates that CPCs may have a self-activation property after the HMGB1 released from dead cells has been exhausted. Conclusion: HMGB1 is a pivotal factor that could enhance the migration and proliferation of CPCs through the CXCL12/CXCR4 pathway after cartilage injury, which could provide useful information for cartilage repair and osteoarthritis treatment

Multiplexed neurochemical transmission emulated using a dual-excitatory synaptic transistor

Abstract The ability to emulate multiplexed neurochemical transmission is an important step toward mimicking complex brain activities. Glutamate and dopamine are neurotransmitters that regulate thinking and impulse signals independently or synergistically. However, emulation of such simultaneous neurotransmission is still challenging. Here we report design and fabrication of synaptic transistor that emulates multiplexed neurochemical transmission of glutamate and dopamine. The device can perform glutamate-induced long-term potentiation, dopamine-induced short-term potentiation, or co-release-induced depression under particular stimulus patterns. More importantly, a balanced ternary system that uses our ambipolar synaptic device backtrack input ‘true’, ‘false’ and ‘unknown’ logic signals; this process is more similar to the information processing in human brains than a traditional binary neural network. This work provides new insight for neuromorphic systems to establish new principles to reproduce the complexity of a mammalian central nervous system from simple basic units

Targeting HMGB1-mediated autophagy as a novel therapeutic strategy for osteosarcoma

Autophagy is a catabolic process critical to maintaining cellular homeostasis and responding to cytotoxic insult. Autophagy is recognized as “programmed cell survival” in contrast to apoptosis or programmed cell death. Upregulation of autophagy has been observed in many types of cancers and has been demonstrated to both promote and inhibit antitumor drug resistance depending to a large extent on the nature and duration of the treatment-induced metabolic stress as well as the tumor type. Cisplatin, doxorubicin and methotrexate are commonly used anticancer drugs in osteosarcoma, the most common form of childhood and adolescent cancer. Our recent study demonstrated that high mobility group box 1 protein (HMGB1)-mediated autophagy is a significant contributor to drug resistance in osteosarcoma cells. Inhibition of both HMGB1 and autophagy increase the drug sensitivity of osteosarcoma cells in vivo and in vitro. Furthermore, we demonstrated that the ULK1-FIP200 complex is required for the interaction between HMGB1 and BECN1, which then promotes BECN1-PtdIns3KC3 complex formation during autophagy. Thus, these findings provide a novel mechanism of osteosarcoma resistance to therapy facilitated by HMGB1-mediated autophagy and provide a new target for the control of drug-resistant osteosarcoma patients

Cladribine in combination with entinostat synergistically elicits anti-proliferative/anti-survival effects on multiple myeloma cells

<p>Cladribine (2CdA), a synthetic purine analog interfering with DNA synthesis, is a medication used to treat hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia. Entinostat, a selective class I histone deacetylase (HDAC) inhibitor, shows antitumor activity in various human cancers, including hematological malignancies. The therapeutic potential of cladribine and entinostat against multiple myeloma (MM) remains unclear. Here we investigate the combinatorial effects of cladribine and entinostat within the range of their clinical achievable concentrations on MM cells. While either agent alone inhibited MM cell proliferation in a dose-dependent manner, their combinations synergistically induced anti-proliferative/anti-survival effects on all MM cell lines (RPMI8226, U266, and MM1.R) tested. Further studies showed that the combinations of cladribine and entinostat as compared to either agent alone more potently induced mitotic catastrophe in the MM cells, and resulted in a marked increase of the cells at G1 phase associated with decrease of Cyclin D1 and E2F-1 expression and upregulation of p21^waf−1. Apoptotic ELISA and western blot analyses revealed that the combinations of cladribine and entinostat exerted a much more profound activity to induce apoptosis and DNA damage response, evidenced by enhanced phosphorylation of histone H2A.X and the DNA repair enzymes Chk1 and Chk2. Collectively, our data demonstrate that the combinations of cladribine and entinostat exhibit potent activity to induce anti-proliferative/anti-survival effects on MM cells via induction of cell cycle G1 arrest, apoptosis, and DNA damage response. Regimens consisting of cladribine and/or entinostat may offer a new treatment option for patients with MM.</p> <p><b>Abbreviations:</b> MM, multiple myeloma; HCL, hairy cell leukemia; HDAC, histone deacetylase; Ab, antibody; mAb, monoclonal Ab; FBS, fetal bovine serum; CI, combination index; PAGE, polyacrylamide gel electrophoresis; ELISA, enzyme-linked immunosorbent assay; PARP, poly(ADP-ribose) polymerase; MTS, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium,inner salt</p