The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform
Gerald J Atkins - One of the best experts on this subject based on the ideXlab platform.
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1 25 dihydroxyvitamin d3 and extraCellular calcium promote mineral deposition via npp1 activity in a mature osteoblast Cell Line mlo a5
Molecular and Cellular Endocrinology, 2015Co-Authors: Dongqing Yang, Andrew G Turner, Asiri R Wijenayaka, Paul H Anderson, Howard A Morris, Gerald J AtkinsAbstract:While vitamin D supplementation is common, the anabolic mechanisms that improve bone status are poorly understood. Under standard mineralising conditions including media ionised calcium of 1.1 mM, 1,25-dihydroxyvitamin D3 (1,25D) enhanced differentiation and mineral deposition by the mature osteoblast/pre-Osteocyte Cell Line, MLO-A5. This effect was markedly increased with a higher ionised calcium level (1.5 mM). Gene expression analyses revealed that 1,25D-induced mineral deposition was associated with induction of Enpp1 mRNA, coding for nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and NPP1 protein levels. Since MLO-A5 Cells express abundant alkaLine phosphatase that was not further modified by 1,25D treatment or exposure to increased calcium, this finding suggested that the NPP1 production of pyrophosphate (PPi) may provide alkaLine phosphatase with substrate for the generation of inorganic phosphate (Pi). Consistent with this, co-treatment with Enpp1 siRNA or a NPP1 inhibitor, PPADS, abrogated 1,25D-induced mineral deposition. These data demonstrate that 1,25D stimulates osteoblast differentiation and mineral deposition, and interacts with the extraCellular calcium concentration. 1,25D regulates Enpp1 expression, which presumably, in the context of adequate tissue non-specific alkaLine phosphatase activity, provides Pi to stimulate mineralisation. Our findings suggest a mechanism by which vitamin D with adequate dietary calcium can improve bone mineral status.
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pro inflammatory cytokines tnf related weak inducer of apoptosis tweak and tnfα induce the mitogen activated protein kinase mapk dependent expression of sclerostin in human osteoblasts
Journal of Bone and Mineral Research, 2009Co-Authors: Cristina Vincent, Asiri R Wijenayaka, David M Findlay, Katie J Welldon, Timothy S Zheng, D R Haynes, Nicola L Fazzalari, Andreas Evdokiou, Gerald J AtkinsAbstract:We have recently shown that TNF-related weak inducer of apoptosis (TWEAK) is a mediator of inflammatory bone remodeling. The aim of this study was to investigate the role of TWEAK in modulating human osteoblast activity, and how TWEAK and TNFα might interact in this context. Recombinant TWEAK and TNF were both mitogenic for human primary osteoblasts (NHBC). TWEAK dose- and time-dependently regulated the expression of the osteoblast transcription factors RUNX2 and osterix. TWEAK inhibited in vitro mineralization and downregulated the expression of osteogenesis-associated genes. Significantly, TWEAK and TWEAK/TNF induced the expression of the osteoblast differentiation inhibitor and SOST gene product, sclerostin. Sclerostin induction was mitogen-activated protein kinase (MAPK) dependent. The SOST mRNA levels induced by TWEAK were equivalent to or exceeded those seen in steady-state human bone, and the TWEAK/TNF induction of SOST mRNA was recapitulated in fresh canCellous bone explants. TWEAK-induced sclerostin expression was observed in immature osteoblastic Cells, both in cycling (Ki67+) primary NHBC and in the Cell Lines MC3T3-E1 and MG-63, as well as in human Osteocyte-like Cells and in the Osteocyte Cell Line, MLO-Y4. Treatment of NHBC with recombinant human sclerostin mimicked the effects of TWEAK to suppress RUNX2 and osteocalcin (OCN). TWEAK, TNF, and sclerostin treatment of NHBC similarly altered levels of phosphorylated and total GSK3β and active and total levels of β-catenin, implying that the Wnt signaling pathway was affected by all three stimuli. Sclerostin also rapidly activated ERK-1/2 MAPK signaling, indicating the involvement of additional signaling pathways. Together, our findings suggest that TWEAK, alone and with TNF, can regulate osteoblast function, at least in part by inducing sclerostin expression. Our results also suggest new roles and modes of action for sclerostin.
Asiri R Wijenayaka - One of the best experts on this subject based on the ideXlab platform.
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1 25 dihydroxyvitamin d3 and extraCellular calcium promote mineral deposition via npp1 activity in a mature osteoblast Cell Line mlo a5
Molecular and Cellular Endocrinology, 2015Co-Authors: Dongqing Yang, Andrew G Turner, Asiri R Wijenayaka, Paul H Anderson, Howard A Morris, Gerald J AtkinsAbstract:While vitamin D supplementation is common, the anabolic mechanisms that improve bone status are poorly understood. Under standard mineralising conditions including media ionised calcium of 1.1 mM, 1,25-dihydroxyvitamin D3 (1,25D) enhanced differentiation and mineral deposition by the mature osteoblast/pre-Osteocyte Cell Line, MLO-A5. This effect was markedly increased with a higher ionised calcium level (1.5 mM). Gene expression analyses revealed that 1,25D-induced mineral deposition was associated with induction of Enpp1 mRNA, coding for nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and NPP1 protein levels. Since MLO-A5 Cells express abundant alkaLine phosphatase that was not further modified by 1,25D treatment or exposure to increased calcium, this finding suggested that the NPP1 production of pyrophosphate (PPi) may provide alkaLine phosphatase with substrate for the generation of inorganic phosphate (Pi). Consistent with this, co-treatment with Enpp1 siRNA or a NPP1 inhibitor, PPADS, abrogated 1,25D-induced mineral deposition. These data demonstrate that 1,25D stimulates osteoblast differentiation and mineral deposition, and interacts with the extraCellular calcium concentration. 1,25D regulates Enpp1 expression, which presumably, in the context of adequate tissue non-specific alkaLine phosphatase activity, provides Pi to stimulate mineralisation. Our findings suggest a mechanism by which vitamin D with adequate dietary calcium can improve bone mineral status.
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pro inflammatory cytokines tnf related weak inducer of apoptosis tweak and tnfα induce the mitogen activated protein kinase mapk dependent expression of sclerostin in human osteoblasts
Journal of Bone and Mineral Research, 2009Co-Authors: Cristina Vincent, Asiri R Wijenayaka, David M Findlay, Katie J Welldon, Timothy S Zheng, D R Haynes, Nicola L Fazzalari, Andreas Evdokiou, Gerald J AtkinsAbstract:We have recently shown that TNF-related weak inducer of apoptosis (TWEAK) is a mediator of inflammatory bone remodeling. The aim of this study was to investigate the role of TWEAK in modulating human osteoblast activity, and how TWEAK and TNFα might interact in this context. Recombinant TWEAK and TNF were both mitogenic for human primary osteoblasts (NHBC). TWEAK dose- and time-dependently regulated the expression of the osteoblast transcription factors RUNX2 and osterix. TWEAK inhibited in vitro mineralization and downregulated the expression of osteogenesis-associated genes. Significantly, TWEAK and TWEAK/TNF induced the expression of the osteoblast differentiation inhibitor and SOST gene product, sclerostin. Sclerostin induction was mitogen-activated protein kinase (MAPK) dependent. The SOST mRNA levels induced by TWEAK were equivalent to or exceeded those seen in steady-state human bone, and the TWEAK/TNF induction of SOST mRNA was recapitulated in fresh canCellous bone explants. TWEAK-induced sclerostin expression was observed in immature osteoblastic Cells, both in cycling (Ki67+) primary NHBC and in the Cell Lines MC3T3-E1 and MG-63, as well as in human Osteocyte-like Cells and in the Osteocyte Cell Line, MLO-Y4. Treatment of NHBC with recombinant human sclerostin mimicked the effects of TWEAK to suppress RUNX2 and osteocalcin (OCN). TWEAK, TNF, and sclerostin treatment of NHBC similarly altered levels of phosphorylated and total GSK3β and active and total levels of β-catenin, implying that the Wnt signaling pathway was affected by all three stimuli. Sclerostin also rapidly activated ERK-1/2 MAPK signaling, indicating the involvement of additional signaling pathways. Together, our findings suggest that TWEAK, alone and with TNF, can regulate osteoblast function, at least in part by inducing sclerostin expression. Our results also suggest new roles and modes of action for sclerostin.
Cristina Vincent - One of the best experts on this subject based on the ideXlab platform.
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pro inflammatory cytokines tnf related weak inducer of apoptosis tweak and tnfα induce the mitogen activated protein kinase mapk dependent expression of sclerostin in human osteoblasts
Journal of Bone and Mineral Research, 2009Co-Authors: Cristina Vincent, Asiri R Wijenayaka, David M Findlay, Katie J Welldon, Timothy S Zheng, D R Haynes, Nicola L Fazzalari, Andreas Evdokiou, Gerald J AtkinsAbstract:We have recently shown that TNF-related weak inducer of apoptosis (TWEAK) is a mediator of inflammatory bone remodeling. The aim of this study was to investigate the role of TWEAK in modulating human osteoblast activity, and how TWEAK and TNFα might interact in this context. Recombinant TWEAK and TNF were both mitogenic for human primary osteoblasts (NHBC). TWEAK dose- and time-dependently regulated the expression of the osteoblast transcription factors RUNX2 and osterix. TWEAK inhibited in vitro mineralization and downregulated the expression of osteogenesis-associated genes. Significantly, TWEAK and TWEAK/TNF induced the expression of the osteoblast differentiation inhibitor and SOST gene product, sclerostin. Sclerostin induction was mitogen-activated protein kinase (MAPK) dependent. The SOST mRNA levels induced by TWEAK were equivalent to or exceeded those seen in steady-state human bone, and the TWEAK/TNF induction of SOST mRNA was recapitulated in fresh canCellous bone explants. TWEAK-induced sclerostin expression was observed in immature osteoblastic Cells, both in cycling (Ki67+) primary NHBC and in the Cell Lines MC3T3-E1 and MG-63, as well as in human Osteocyte-like Cells and in the Osteocyte Cell Line, MLO-Y4. Treatment of NHBC with recombinant human sclerostin mimicked the effects of TWEAK to suppress RUNX2 and osteocalcin (OCN). TWEAK, TNF, and sclerostin treatment of NHBC similarly altered levels of phosphorylated and total GSK3β and active and total levels of β-catenin, implying that the Wnt signaling pathway was affected by all three stimuli. Sclerostin also rapidly activated ERK-1/2 MAPK signaling, indicating the involvement of additional signaling pathways. Together, our findings suggest that TWEAK, alone and with TNF, can regulate osteoblast function, at least in part by inducing sclerostin expression. Our results also suggest new roles and modes of action for sclerostin.
Lynda F Bonewald - One of the best experts on this subject based on the ideXlab platform.
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glucocorticoid dose determines Osteocyte Cell fate
The FASEB Journal, 2011Co-Authors: Junjing Jia, Lynda F Bonewald, Wei Yao, Min Guan, Weiwei Dai, Mohammad Shahnazari, Rekha Kar, Jean X Jiang, Nancy E LaneAbstract:In response to Cellular insult, several pathways can be activated, including necrosis, apoptosis, and autophagy. Because glucocorticoids (GCs) have been shown to induce both Osteocyte apoptosis and autophagy, we sought to determine whether Osteocyte Cell fate in the presence of GCs was dose dependent by performing in vivo and in vitro studies. Male Swiss-Webster mice were treated with slow-release prednisolone pellets at 1.4, 2.8, and 5.6 mg/kg/d for 28 d. An Osteocyte Cell Line, MLO-Y4 Cells, was treated with various doses of dexamethasone. We found that GC treatments dose dependently decreased activation of antioxidant-, autophagy-, and antiapoptosis-focused RT-PCR gene pathways in mouse cortical bone. The activation of antioxidant genes was correlated with autophagy gene expression after the GC treatments. The presence of Osteocyte autophagy, as detected by immunostaining for LC3, increased ∼50% at the distal femur cortical bone region but not at trabecular bone region at the 1.4 and 2.8 mg/kg/d GC dose levels. The number of apoptotic Osteocytes was increased at the cortical bone region by ∼40% initially observed at the 2.8 mg/kg/d dose level. In addition, the presence of the Osteocyte autophagy was associated with an increased protein level of cathepsin K in vitro after the GC treatments. In summary, we found that GC treatment dose-dependently decreased antioxidant gene expression, with lower GC doses activating autophagy, whereas a higher dose increased apoptosis. These data suggest that autophagy may provide a mechanism for Osteocytes to survive the stress after GC exposure and provide further insight into how GCs alter bone Cell fate.
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establishment of an Osteocyte like Cell Line mlo y4
Journal of Bone and Mineral Research, 2010Co-Authors: Yoichi Kato, Jolene J Windle, Barbara A Koop, Gregory R Mundy, Lynda F BonewaldAbstract:Although Osteocytes are the most abundant Cells in bone, their functional role remains unclear. In part, this is due to lack of availability of Osteocyte Cell Lines which can be studied in vitro. Since others have shown that Cell Lines can be readily developed from transgenic mice in which the SV40 large T-antigen oncogene is expressed under the control of a promoter which targets the Cells of interest, we used this approach to develop an Osteocyte Cell Line. We chose as a promoter osteocalcin, whose expression is essentially limited to bone Cells and which is expressed more abundantly in Osteocytes than in osteoblasts. From these transgenic mice, we isolated Cells from the long bones using sequential collagenase digestion and maintained these Cells on collagen-coated surfaces which are optimal for Osteocyte maintenance and growth. We describe here the properties of a Cell Line cloned from these cultures, called MLO-Y4 (for murine long bone Osteocyte Y4). The properties of MLO-Y4 Cells are very similar to primary Osteocytes. Like primary Osteocytes and unlike primary osteoblasts, the Cell Line produces large amounts of osteocalcin but low amounts of alkaLine phosphatase. The Cells produce extensive, complex dendritic processes and are positive for T-antigen, for osteopontin, for the neural antigen CD44, and for connexin 43, a protein found in gap junctions. This Cell Line also produces very small amounts of type I collagen mRNA compared with primary osteoblasts. MLO-Y4 Cells lack detectable mRNA for osteoblast-specific factor 2, which appears to be a positive marker for osteoblasts but may be a negative marker for Osteocytes. This newly established Cell Line should prove useful for studying the effects of mechanical stress on Osteocyte function and for determining the means whereby Osteocytes communicate with other bone Cells such as osteoblasts and osteoclasts.
Nicola L Fazzalari - One of the best experts on this subject based on the ideXlab platform.
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pro inflammatory cytokines tnf related weak inducer of apoptosis tweak and tnfα induce the mitogen activated protein kinase mapk dependent expression of sclerostin in human osteoblasts
Journal of Bone and Mineral Research, 2009Co-Authors: Cristina Vincent, Asiri R Wijenayaka, David M Findlay, Katie J Welldon, Timothy S Zheng, D R Haynes, Nicola L Fazzalari, Andreas Evdokiou, Gerald J AtkinsAbstract:We have recently shown that TNF-related weak inducer of apoptosis (TWEAK) is a mediator of inflammatory bone remodeling. The aim of this study was to investigate the role of TWEAK in modulating human osteoblast activity, and how TWEAK and TNFα might interact in this context. Recombinant TWEAK and TNF were both mitogenic for human primary osteoblasts (NHBC). TWEAK dose- and time-dependently regulated the expression of the osteoblast transcription factors RUNX2 and osterix. TWEAK inhibited in vitro mineralization and downregulated the expression of osteogenesis-associated genes. Significantly, TWEAK and TWEAK/TNF induced the expression of the osteoblast differentiation inhibitor and SOST gene product, sclerostin. Sclerostin induction was mitogen-activated protein kinase (MAPK) dependent. The SOST mRNA levels induced by TWEAK were equivalent to or exceeded those seen in steady-state human bone, and the TWEAK/TNF induction of SOST mRNA was recapitulated in fresh canCellous bone explants. TWEAK-induced sclerostin expression was observed in immature osteoblastic Cells, both in cycling (Ki67+) primary NHBC and in the Cell Lines MC3T3-E1 and MG-63, as well as in human Osteocyte-like Cells and in the Osteocyte Cell Line, MLO-Y4. Treatment of NHBC with recombinant human sclerostin mimicked the effects of TWEAK to suppress RUNX2 and osteocalcin (OCN). TWEAK, TNF, and sclerostin treatment of NHBC similarly altered levels of phosphorylated and total GSK3β and active and total levels of β-catenin, implying that the Wnt signaling pathway was affected by all three stimuli. Sclerostin also rapidly activated ERK-1/2 MAPK signaling, indicating the involvement of additional signaling pathways. Together, our findings suggest that TWEAK, alone and with TNF, can regulate osteoblast function, at least in part by inducing sclerostin expression. Our results also suggest new roles and modes of action for sclerostin.
