Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enamel extracts induce biomineralization such as osteogenesis and cementogenesis, but the molecular component responsible for this activity remains uncertain. We fractionated enamel extracts from developing pig teeth and isolated the osteoinductive fraction. Proteins from pig enamel scrapings were extracted under alkaline conditions (pH 10.8) and fractionated with the use of a Sephadex G-100 (size exclusion) column. The ability of each fraction to enhance alkaline phosphatase (ALP) activity was assayed in ST2 cells, a mouse bone marrow stromal cell line. The osteoinductive fraction of enamel extracts (OFE) was found in fractions 44 and 45, which induced ST2 cells to express the phenotype of bone-forming osteoblasts, and to form mineralized nodules. Furthermore, the ALP activity of ST2 cells exposed to OFE was reduced by noggin, an antagonist of BMPs, and OFE reacted with BMP-2/4 antibody in dot-blot analysis. These results indicate that OFE contains BMPs that contribute to the induction of biomineralization.
 ...
PMID:Noggin blocks osteoinductive activity of porcine enamel extracts. 1209 29

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is critical for phenotype determination at early differentiation stages of mesenchymal cells. Activation of this nuclear receptor inhibits gene expression in part by antagonizing the activities of several transcription factors. In this study we examined inhibitory mechanisms of osteoblast differentiation markers by activating PPAR-gamma. Our data indicate that the PPAR-gamma natural ligand 15d-PGJ2 dose-dependently inhibits expression of alkaline phosphatase and mineral deposition by primary stromal cells and by cell lines such as ST2 and MC3T3-E1. We next show that PPAR-gamma nuclear translocation coincides with duration and doses of ligand addition, indicating that 15d-PGJ2-activated PPAR-gamma rapidly translocates to the nuclear component where it exerts its biological effects. Further examination of downstream osteogenic signaling pathways induced by beta-glycerophosphate and ascorbic acid reveals that induction of osteoblast differentiation by these agents involves activation of the transcription factors Cbfa1 and NF-kappaB. The former is critical for osteoblast differentiation. To test whether inhibition of alkaline phosphatase expression and mineral deposition by activated PPAR-gamma reflects attenuation of transcriptional activity, we performed DNA protein-binding assays for NF-kappaB and Cbfa1. Our findings indicate that 15d-PGJ2-induced PPAR-gamma abrogates beta-glycerophosphate-activated Cbfa1 and NF-kappaB. These findings were consistent in primary and stromal cell lines, ST2 and MC3T3-E1. Thus activation of PPAR-gamma by 15d-PGJ2 inhibits DNA-binding activity of the transcription factors Cbfa1 and NF-kappaB, leading to diminished expression of osteoblast/stromal differentiation markers.
 ...
PMID:Activation of peroxisome proliferator-activated receptor-gamma inhibits differentiation of preosteoblasts. 1287 83

Bone morphogenetic protein-6 (BMP-6) is a potent inducer of osteogenic differentiation and its expression is stimulated by 17beta-estradiol. The existence of a regulatory loop between sex steroids and BMP-6 is therefore reasonable to hypothesize. Here we determined whether the sex steroids 17beta-estradiol and dihydrotestosterone, and the phytoestrogen resveratrol can modulate BMP-6-induced alkaline phosphatase activity and osteocalcin expression. Mesenchymal cells of murine (osteoblastic MC3T3-E1 cells, preadipogenic ST2 cells, prechondrogenic ATDC5 cell) and human origin (osteosarcoma SaOS and HOS cells, primary bone marrow stromal cells) were cultured in the presence of recombinant BMP-6 under serum-free conditions. BMP-6 dose-, and time-dependently increased alkaline phosphatase activity in murine cell lines, but not in human cells. Osteocalcin expression was also increased upon stimulation with BMP-6. The presence of 17beta-estradiol, dihydrotestosterone, and resveratrol had no effect on BMP-6-induced alkaline phosphatase activity and osteocalcin expression. These data suggest that osteogenic differentiation in response to BMP-6 occurs independent of steroid hormones and resveratrol in mesenchymal cells that express basal receptor levels.
 ...
PMID:BMP-6-induced osteogenic differentiation of mesenchymal cell lines is not modulated by sex steroids and resveratrol. 1296 49

We investigated the direct effects of various bisphosphonates on osteoblasts. At 10(-5) M, clodronate increased alkaline phosphatase activity in cultured MC3T3-E1 (osteoblast-like line) and ST2 (pluripotent mesenchymal line) cells. Etidronate significantly increased alkaline phosphatase activity at 10(-5) M only in MC3T3-E1 cells. These effects were due to an increase in alkaline phosphatase-positive cell numbers, and the differentiation-enhanced cells were capable of mineralization (von Kossa stain). Other bisphosphonates (pamidronate, alendronate, and incadronate) did not increase alkaline phosphatase activity in either cell line. In cultured rat calvariae, clodronate stimulated the expression of genes for alkaline phosphatase and osteocalcin (osteoblast-differentiation markers), but decreased the expression of the gene for tartrate-resistant acid phosphatase (osteoclast marker). Clodronate, etidronate, and incadronate inhibited protein Tyr phosphatase and Ser/Thr phosphatase activities in MC3T3-E1 cells. These data suggest that clodronate acts directly on mesenchymal cells to enhance osteoblast differentiation, and this effect may be partly expressed through inhibition of protein Tyr phosphatase and/or Ser/Thr phosphatase activity.
 ...
PMID:Clodronate stimulates osteoblast differentiation in ST2 and MC3T3-E1 cells and rat organ cultures. 1451 92

Menin, the product of the multiple endocrine neoplasia type 1 (MEN1) gene, is required for commitment of multipotential mesenchymal stem cells to the osteoblast lineage, however, it inhibits their later differentiation (Sowa, H., Kaji, H., Canaff, L., Hendy, G.N., Tsukamoto, T., Yamaguchi, T., Miyazono, K., Sugimoto, T., and Chihara, K. (2003) J. Biol. Chem. 278, 21058-21069). Here, we have examined the mechanism of action of menin in regulating osteoblast differentiation using the mouse bone marrow stromal ST2 and osteoblast MC3T3-E1 cell lines. In ST2 cells, reduced menin expression achieved by transfection of menin antisense DNA (AS) antagonized bone morphogenetic protein (BMP)-2-induced alkaline phosphatase activity and osteocalcin and Runx2 mRNA expression. Menin was co-immunoprecipitated with Smad1/5 in ST2 and MC3T3-E1 cells, and inactivation of menin antagonized BMP-2-induced transcriptional activity of Smad1/5 in ST2 cells, but not MC3T3-E1 cells. Menin was co-immunoprecipitated with the key osteoblast regulator, Runx2, and AS antagonized Runx2 transcriptional activity and the ability of Runx2 to stimulate alkaline phosphatase activity only in ST2 cells but not in MC3T3-E1 cells. In the osteoblast MC3T3-E1 cells, transforming growth factor-beta and its signaling molecule, Smad3, negatively regulated Runx2 transcriptional activity. Menin and Smad3 were co-immunoprecipitated, and combined menin and Smad3 overexpression antagonized, whereas menin and the dominant-negative Smad3DeltaC together enhanced BMP-2-induced transcriptional activity of Smad1/5 and Runx2. Smad3 alone had no effect. Therefore, menin interacts physically and functionally with Runx2 in uncommitted mesenchymal stem cells, but not in well differentiated osteoblasts. In osteoblasts the interaction of menin and the transforming growth factor-beta/Smad3 pathway negatively regulates the BMP-2/Smad1/5- and Runx2-induced transcriptional activities leading to inhibition of late-stage differentiation.
 ...
PMID:Menin is required for bone morphogenetic protein 2- and transforming growth factor beta-regulated osteoblastic differentiation through interaction with Smads and Runx2. 1515 Feb 73

Single-wall carbon nanohorns (SWNHs) are recently discovered nanostructured spherical aggregates of graphitic tubes. The unique physicochemical properties of SWNHs, including their large surface area, suggest their possible utility as carriers in drug delivery systems. Here we investigated the in vitro binding and release of the antiinflammatory glucocorticoid dexamethasone (DEX) by as-grown SWNHs and their oxidized form, oxSWNHs. Adsorption analyses using [3H]-DEX determined the amount of DEX adsorbed by oxSWNHs to be 200 mg for each gram of oxSWNHs in 0.5 mg/mL of DEX solution, which was approximately 6 times larger than that obtained for as-grown SWNHs. Adsorption kinetics indicated that oxSWNHs had higher affinity for DEX than as-grown SWNHs. Treatment of oxSWNHs at 1200 degrees C under H2, which removed the oxygen-containing functional groups on oxSWNHs, did not diminish the high affinity for DEX, suggesting that oxygen-containing functional groups have little contribution for the affinity. DEX-oxSWNH complexes exhibited sustained release of DEX into phosphate-buffered saline (pH 7.4) at 37 degrees C and more rapid biphasic release into culture medium. The biological integrity of the released DEX form was confirmed by activation of glucocorticoid response element-driven transcription in mouse bone marrow stromal ST2 cells and induction of alkaline phosphatase in mouse osteoblastic MC3T3-E1 cells. Notably, synthesis of SWNHs does not require a metal catalyst, the toxicity of which could become problematical in clinical use, and no cytotoxicity was observed in cells cultured in the presence of oxSWNHs under our conditions. Taken together, these observations highlight the potential utility of SWNHs in drug delivery systems.
 ...
PMID:Drug-loaded carbon nanohorns: adsorption and release of dexamethasone in vitro. 1602 51

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to induce ectopic bone formation requires a carrier. Type I atelocollagen, a biomaterial with a porous structure, excellent operational features, and biocompatibility, is an effective carrier for rhBMP-2. However, the conventionally used lyophilized rhBMP-2/collagen mixture does not necessarily give adequate bone-induction effect. In the present study, we examined the effect of immobilizing rhBMP-2 to type I atelocollagen on the cellular activity of ST2 cells. The following results were obtained: (1) rhBMP-2 was effectively immobilized to succinylated type I atelocollagen, indicating the usefulness of succinylated type I atelocollagen in immobilization; (2) studies of alkaline phosphatase activity confirmed the effectiveness of rhBMP-2 immobilized on succinylated atelocollagen in augmenting cellular activity.
 ...
PMID:Effects of immobilized recombinant human bone morphogenetic protein-2/succinylated type I atelocollagen on cellular activity of ST2 cells. 1605 89

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor (TGF)-beta superfamily, and some display potent osteogenic activity both in vivo and in vitro. The BMP signaling cascade involving BMP receptors at the cell membrane and intracellular messengers (Smads) has been elucidated, but the regulatory mechanisms of BMP signaling have not been clarified. We previously found that pentoxifyline (PeTx), a nonspecific inhibitor of phosphodiesterase (PDE), and rolipram, a PDE-4-specific inhibitor, enhance BMP-4-induced osteogenic differentiation of mesenchymal cells, probably through the elevation of intracellular cyclic adenosine monophosphate (cAMP) accumulation and modulation of BMP signaling pathways as enhanced BMP-4 action was reproduced by addition of dibutylyl-cAMP (dbcAMP). However, the precise mechanisms underlying the enhancing effects of those agents on BMP signaling were not completely revealed. As already reported, BMPs utilize a specific intracellular signaling cascade to target genes via R-Smads (Smad1,5,8), Co-Smad (Smad4) and I-Smads (Smad6,7). One possibility for cAMP-mediated effects on BMP signaling might be suppression of I-Smads expression since these proteins form a negative feedback loop in BMP signaling. To examine this possibility, changes in I-Smad (Smad6) expression on addition of dbcAMP or PeTx were examined in a bone-marrow-derived osteogenic cell line (ST2). Alkaline phosphatase activity in ST2 cells was consistently induced by BMP-4 treatment (300 ng/ml), and Smad6 mRNA expression was also induced by BMP-4 treatment. Although concurrent treatment of ST2 cells with BMP-4 and dbcAMP elicited further activation of alkaline phosphatase, addition of dbcAMP reduced BMP-4-induced Smad6 expression in a dose-dependent manner. Furthermore, detection of phosphorylated Smad1/5/8 on Western blotting analysis was prolonged, suggesting prolonged kinase activity of BMP receptors through suppressed expression of Smad6. Elevated intracellular cAMP might thus enhance BMP signaling by suppressing Smad6 induction and prolonging intracellular BMP signaling.
 ...
PMID:Bone morphogenetic protein activities are enhanced by 3',5'-cyclic adenosine monophosphate through suppression of Smad6 expression in osteoprogenitor cells. 1620 97

In the present study, the fatty acid composition of bone marrow aspirates and serum phospholipids in nine patients with hematologic diseases was investigated, and the effect of fatty acids on osteoblast differentiation in ST2 cells was examined. The concentrations of oleic acid and palmitic acid were significantly higher in bone marrow aspirates than in serum phospholipids, but the concentrations of other fatty acids did not differ. The rate of alkaline phosphatase positive ST2 cells induced by BMP2 was significantly increased by oleic acid, but was unaffected by the presence or absence of palmitic acid. We conclude that the fatty acid composition of bone marrow aspirates differs from that of serum phospholipids. This difference may affect osteoblast differentiation in the bone marrow microenvironment.
 ...
PMID:Analysis of fatty acid composition in human bone marrow aspirates. 1623 77

Stromal-derived factor 1 (SDF-1) is a chemokine with important functions in development and postnatal tissue homeostasis. SDF-1 signaling via the G-protein-coupled receptor CXCR4 regulates the recruitment of stem and precursor cells to support tissue-specific repair or regeneration. In this study we examined the contribution of SDF-1 signaling to osteogenic differentiation of mesenchymal C2C12 cells induced by bone morphogenic protein 2 (BMP2). Blocking SDF-1 signaling before BMP2 stimulation by treatment with siRNA, antibodies against SDF-1 or CXCR4, or the G-protein-coupled receptor inhibitor pertussis toxin strongly suppressed BMP2 induction of osteogenic differentiation in C2C12 cells, as evidenced by an early decrease in the expression of the myogenesis inhibitor Id1, the osteogenic master regulators Runx2 and Osx, the osteoblast-associated transcription factors JunB, Plzf, Msx2, and Dlx5, and later of the bone marker proteins osteocalcin and alkaline phosphatase. Similarly, blocking SDF-1/CXCR4 signaling strongly inhibited BMP2-induced osteogenic differentiation of ST2 bone marrow stromal cells. Moreover, we found that the interaction between SDF-1 and BMP2 signaling was mediated via intracellular Smads and MAPK activation. Our data provide the first evidence for a co-requirement of the SDF-1/CXCR4 signaling axis in BMP2-induced osteogenic differentiation of C2C12 and ST2 cells and, thus, uncover a new potential target for modulation of osteogenesis.
 ...
PMID:A novel regulatory role for stromal-derived factor-1 signaling in bone morphogenic protein-2 osteogenic differentiation of mesenchymal C2C12 cells. 1743 46


<< Previous 1 2 3 4 5 Next >>