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)

Space flight-induced bone loss has been attributed to a decrease in osteoblast function, without a significant change in bone resorption. To determine the effect of microgravity (MG) on bone, we used the Rotary Cell Culture System [developed by the National Aeronautics and Space Administration (NASA)] to model MG. Cultured mouse calvariae demonstrated a 3-fold decrease in alkaline phosphatase (ALP) activity and failed to mineralize after 7 d of MG. ALP and osteocalcin gene expression were also decreased. To determine the effects of MG on osteoblastogenesis, we cultured human mesenchymal stem cells (hMSC) on plastic microcarriers, and osteogenic differentiation was induced immediately before the initiation of modeled MG. A marked suppression of hMSC differentiation into osteoblasts was observed because the cells failed to express ALP, collagen 1, and osteonectin. The expression of runt-related transcription factor 2 was also inhibited. Interestingly, we found that peroxisome proliferator-activated receptor gamma (PPARgamma2), which is known to be important for adipocyte differentiation, adipsin, leptin, and glucose transporter-4 are highly expressed in response to MG. These changes were not corrected after 35 d of readaptation to normal gravity. In addition, MG decreased ERK- and increased p38-phosphorylation. These pathways are known to regulate the activity of runt-related transcription factor 2 and PPARgamma2, respectively. Taken together, our findings indicate that modeled MG inhibits the osteoblastic differentiation of hMSC and induces the development of an adipocytic lineage phenotype. This work will increase understanding and aid in the prevention of bone loss, not only in MG but also potentially in age-and disuse-related osteoporosis.
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PMID:Modeled microgravity inhibits osteogenic differentiation of human mesenchymal stem cells and increases adipogenesis. 1474 52

Poly(epsilon-caprolactone) (PCL) and biphasic calcium phosphate (CaP) composite membranes were prepared for use in tissue regeneration by a novel solvent casting-pressing method. An antibiotic drug, tetracycline hydrochloride (TCH), was entrapped within the membranes to investigate the efficacy of the material as a drug delivery system. The CaP powders were varied in amount (0-50 wt %) and in powder characteristics by heat treating at different temperatures, and their effects on the mechanical and biological properties and drug release of the membranes were examined. With CaP addition up to 30 wt %, the elastic modulus of the membranes was enhanced much due to the rigidity of CaP. While the tensile strength and elongation rate decreased gradually with CaP addition because the CaP powders acted as a failure source. The osteoblast-like cells cultured on the CaP-PCL composite membranes exhibited significant improvements in proliferation and alkaline phosphatase (ALP) activity compared to pure PCL and culture plastic control, indicating excellent cell viability and functional activity. The TCH drugs were released from the PCL and CaP-PCL membranes in a similar fashion; an initial burst followed by a reduced release rate. The initial burst effect diminished much by the addition of CaP powders. The CaP addition increased the drug release rate after an initial period, and this was attributed to the high water uptake capacity and dissolution of the CaP containing membranes. Compared to the composite membranes containing heat-treated CaP powders, those with as-precipitated ones had higher dissolution and drug releases. These observations on mechanical properties and cellular responses as well as on drug release profiles suggested that the CaP-PCL composite membranes are potentially applicable to tissue regeneration and drug delivery system.
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PMID:Effect of biphasic calcium phosphates on drug release and biological and mechanical properties of poly(epsilon-caprolactone) composite membranes. 1529 21

Apert syndrome is an autosomal dominant disease characterized by craniosynostosis and bony syndactyly associated with point mutations (S252W and P253R) in the fibroblast growth factor receptor (FGFR) 2 that cause FGFR2 activation. Here we investigated the role of the S252W mutation of FGFR2 on osteoblastic differentiation. Osteoblastic cells derived from digital bone in two Apert patients with the S252W mutation showed more prominent alkaline phosphatase activity, osteocalcin and osteopontin mRNA expression, and mineralized nodule formation compared with the control osteoblastic cells derived from two independent non-syndromic polydactyly patients. Stable clones of the human MG63 osteosarcoma cells (MG63-Ap and MG63-IIIc) overexpressing a splice variant form of FGFR2 with or without the S252W mutation (FGFR2IIIcS252W and FGFR2IIIc) showed a higher RUNX2 mRNA expression than parental MG63 cells. Furthermore MG63-Ap exhibited a higher osteopontin mRNA expression than did MG63-IIIc. The enhanced osteoblastic marker gene expression and mineralized nodule formation of the MG63-Ap was inhibited by the conditioned medium from the COS-1 cells overexpressing the soluble FGFR2IIIcS252W. Furthermore the FGF2-induced osteogenic response in the mouse calvarial organ culture system was blocked by the soluble FGFR2IIIcS252W. These results show that the S252W mutation in the FGFR2 gene enhances the osteoblast phenotype in human osteoblasts and that a soluble FGFR2 with the S252W mutation controls osteoblast differentiation induced by the S252W mutation through a dominant negative effect on FGFR2 signaling in Apert syndrome.
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PMID:A soluble form of fibroblast growth factor receptor 2 (FGFR2) with S252W mutation acts as an efficient inhibitor for the enhanced osteoblastic differentiation caused by FGFR2 activation in Apert syndrome. 1531 Jul 57

To define the role of activated neutrophils in lung injury during bovine respiratory tract infections (BRTI) their in vitro function was investigated. As a means to achieve this goal the comparison of secretory action between neutrophils from the BRTI group and control was made on the basis of elastase, myeloperoxidase (MPO), alkaline phosphatase (ALK-P) release, and nitric oxide production. We noted that there is an interdependence between secretory response of neutrophils and clinical severity of BRTI. The release of elastase was greater in the BRTI group than in the control group (49.17+/-4.41 versus 46.43+/-4.95% of the total content). Neutrophils from infected heifers exhibited a significantly (p<0.05) higher value of MPO release than from healthy heifers and reached 39.23+/-10.18 versus 25.54+/-8.41% of the total content. ALK-P containing granules released significantly (p<0.001) more enzyme in the group with BRTI than in the control group (22.42+/-6.27 versus 13.74+/-2.01% of the total enzyme content). The level of nitrite accumulation rose in the culture of cells isolated from heifers with BRTI from 4+/-0.53 microM after 0.5h to 6.9+/-0.52 microM after 72 h. Our data suggest that during BRTI the increase of neutrophil secretory action results in augmentation of enzyme release including elastase, MPO and ALK-P, and the nitrite production. During an excessive secretory response of neutrophils all these factors contribute to lung injury and worsen the course of a disease and might be recognised as markers of lung injury. Moreover, such a destructive action of neutrophils must be taken into account during the introduction of new methods of BRTI treatment.
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PMID:Assessment of neutrophil components as markers of lung injury in the course of bovine respiratory tract infections. 1547 59

In adult animals, bone marrow is the major site of blood cell production, which is controlled by interactions between the local stroma and blood cell progenitors. The endosteal/subendosteal environment comprises bone-lining and adjacent reticular cells and sustains haemopoietic stem cell (HSC) self-renewal, proliferation and differentiation. We have questioned the specific role of each of these stroma cells in controlling HSC fate. We have isolated two distinct stroma-cell populations containing subendosteal reticulocytes (F-RET) and osteoblasts (F-OST) from periosteum-free fragments of murine femurs by a two-step collagenase-digestion procedure. Both populations produce similar extracellular matrix (collagen I, laminin, fibronectin, decorin), except for collagen IV, which is low in F-OST. They also express osteogenic markers: osteopontin, osteonectin, bone sialoprotein and alkaline phosphatase (ALP). The quantity and activity of ALP are however higher in F-OST. When co-cultured with bone marrow mononuclear cells or lineage-negative haemopoietic progenitors, F-OST stroma induces low proliferation and high maintenance of early haemopoietic progenitors, whereas F-RET stroma induces high short-term proliferation and differentiation. Analysis by reverse transcription/polymerase chain reaction has revealed higher levels of Jagged-1 expression by F-OST cells than by the F-RET population. Thus, two adjacent stroma cells (subendosteal and endosteal) play distinct roles in controlling the stem-cell capacity and fate of HSC and probably contribute distinctly to HSC niche formation.
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PMID:Bone marrow subendosteal microenvironment harbours functionally distinct haemosupportive stromal cell populations. 1557 25

Ca(2+)/calmodulin-dependent protein kinase IIalpha (alpha-CaMKII) was once thought to be exclusively expressed in neuronal tissue, but it is becoming increasingly evident that CaMKII is also expressed in various extraneural cells. CaMKII plays a critical role in regulating various signaling pathways leading to modulation of several aspects of cellular functions, including proliferation, differentiation, cytoskeletal structure, and gene expression. The purpose of this study was to examine the expression of CaMKII in osteoblast-like cells (MC4) and to elucidate its role in osteoblast differentiation. We demonstrated that CaMKII, specifically the alpha isoform, is expressed in osteoblasts both in vitro and in vivo. Inhibition of CaMKII by the calmodulin antagonist trifluoperazine or the CaMKII antagonist KN93 reduces alkaline phosphatase activity and mineralization, as well as causes 85 and 56% decreases in alkaline phosphatase and osteocalcin gene expression, respectively. CaM and CaMKII antagonists, using the newborn mouse calvaria in vivo model, cause a 50% decrease in osteoblast number (N.Ob-BS) and a 32% decrease in mineralization (BV/TV). Pharmacologic and genetic inhibition of alpha-CaMKII by using trifluoperazine, KN93, and alpha-CaMKII small interfering RNA decreases the phosphorylation of ERK and of cAMP-response element-binding protein, leading to a significant decrease in the transactivation of serum response element and cAMP-response element. Inhibition of alpha-CaMKII decreases the expression of c-fos, AP-1 transactivation, and AP-1 DNA binding activity. Our findings demonstrated that alpha-CaMKII is expressed in osteoblasts and is involved in c-fos expression via regulation of serum response element and cAMP-response element. Inhibition of alpha-CaMKII results in a decrease in c-fos expression and AP-1 activation, leading to inhibition of osteoblast differentiation.
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PMID:Calmodulin and calmodulin-dependent kinase IIalpha regulate osteoblast differentiation by controlling c-fos expression. 1559 Jun 32

Capillary supply of skeletal muscle decreases during denervation. To gain insight into the regulation of this process, we investigated capillary supply and gene expression of angiogenesis-related factors in mouse gastrocnemius muscle following denervation for 4 months. Frozen transverse sections were stained for alkaline phosphatase to detect endogenous enzyme in the capillary endothelium. The mRNA for angiogenesis-related factors, including hypoxia inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/Flk-1), fms-like tyrosine kinase (Flt-1), angiopoietin-1 and tyrosine kinase with Ig and epidermal growth factor(EGF) homology domain 2 (Tie-2), was analysed using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The fibre cross-sectional area after denervation was about 20% of the control value, and the capillary to fibre ratio was significantly lower in denervated than in control muscles. The number of capillaries around each fibre also decreased to about 40% of the control value. These observations suggest that muscle capillarity decreases in response to chronic denervation. RT-PCR analysis showed that the expression of VEGF mRNA was lower in denervated than in control muscles, while the expression of HIF-1alpha mRNA remained unchanged. The expression levels of the KDR/Flk-1 and Flt-1 genes were decreased in the denervated muscle. The expression levels of angiopoietin-1 but not Tie-2 genes were decreased in the denervated muscle. These findings indicate that reduction in the expression of mRNAs in the VEGF/KDR/Flk-1 and Flt-1 as well as angiopoietin-1/Tie-2 signal pathways might be one of the reasons for the capillary regression during chronic denervation.
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PMID:Capillary supply and gene expression of angiogenesis-related factors in murine skeletal muscle following denervation. 1570 74

An experimental model, based on Pringle's scheme of acute warm hepatic ischemia in normothermia was employed in order to study the hepatoprotective properties of prolactin (PRL). In the proposed model one liver lobe was maintained in the portal circulation and the remaining lobes were perfused with HTK solution for 2 hours. The experiment was carried out on female rabbits of the Chinchilla race. In the control group (n= 10) the liver was perfused with HTK solution. In the examined group (n=10), 3 microg of PRL per g of liver per hour was added to HTK solution. Additionally, the animals in the PRL-treated group were intravenously administered a dose of 600 microg of PRL / kg body weight. 1 h before the surgical treatment. The activities of alanine aminotransferase (ALT), alkaline phosphatase (ALP). gamma-glutamyl transferase (GGT) and the lactate concentration were determined in the eluate obtained from the perfused part of the liver. It was found that administration of prolactin during 2 h of perfusion led to a significant decrease of ALT, ALP and lactate concentrations in the eluate. In addition, increase of calcium concentration in the liver was significantly lower with the prolactin group. The observed results let us to draw the conclusion that administration of PRL shows signs of protective effects on hepatocytes in normothermic acute ischemia.
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PMID:The influence of prolactin on the chosen biochemical parameters of the rabbit liver in ischemia. 1579 42

A G protein-coupled receptor agonist, angiotensin II (AngII), induces epidermal growth factor (EGF) receptor (EGFR) transactivation possibly through metalloprotease-dependent, heparin-binding EGF (HB-EGF) shedding. Here, we have investigated signal transduction of this process by using COS7 cells expressing an AngII receptor, AT1. In these cells AngII-induced EGFR transactivation was completely inhibited by pretreatment with a selective HB-EGF inhibitor, or with a metalloprotease inhibitor. We also developed a COS7 cell line permanently expressing a HB-EGF construct tagged with alkaline phosphatase, which enabled us to measure HB-EGF shedding quantitatively. In the COS7 cell line AngII stimulated release of HB-EGF. This effect was mimicked by treatment either with a phospholipase C activator, a Ca2+ ionophore, a metalloprotease activator, or H2O2. Conversely, pretreatment with an intracellular Ca2+ antagonist or an antioxidant blocked AngII-induced HB-EGF shedding. Moreover, infection of an adenovirus encoding an inhibitor of G(q) markedly reduced EGFR transactivation and HB-EGF shedding through AT1. In this regard, AngII-stimulated HB-EGF shedding was abolished in an AT1 mutant that lacks G(q) protein coupling. However, in cells expressing AT1 mutants that retain G(q) protein coupling, AngII is still able to induce HB-EGF shedding. Finally, the AngII-induced EGFR transactivation was attenuated in COS7 cells overexpressing a catalytically inactive mutant of ADAM17. From these data we conclude that AngII stimulates a metalloprotease ADAM17-dependent HB-EGF shedding through AT1/G(q)/phospholipase C-mediated elevation of intracellular Ca2+ and reactive oxygen species production, representing a key mechanism indispensable for EGFR transactivation.
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PMID:G protein coupling and second messenger generation are indispensable for metalloprotease-dependent, heparin-binding epidermal growth factor shedding through angiotensin II type-1 receptor. 1590 75

Bone marrow stromal cells (MSC) are the major source of osteoblasts for bone remodeling and repair in postnatal animals. Rodent MSC cultured with bone morphogenetic proteins (BMPs) differentiate into osteoblasts, but most human MSC show a poor osteogenic response to BMPs. In this study we demonstrate that BMP-induced osteogenesis in poorly responsive human MSC requires modulation of ERK and phosphatidylinositol 3-kinase (PI3-K) pathways. Either treating human MSC cultures with the MAPK/ERK kinase inhibitor PD98059 or transferring them to serum-free medium with insulin or IGF-I permits BMP-dependent increases in the expression of the early osteoblast-associated genes, alkaline phosphatase and osteopontin. Increased expression of these genes in BMP-treated, serum-free cultures correlates with increased nuclear levels of activated Smads, whereas serum-free cultures of human MSC expressing constitutively active MAPK/ERK kinase show decreased expression of early osteoblast genes and decreased nuclear translocation of BMP-activated Smads. Inhibiting ERK activity in human MSC also elevates the expression of Msx2, a transcription factor that is directly regulated by Smad-binding elements in its promoter. Therefore, growth factor stimulation leading to high levels of ERK activity in human MSC results in suppressed BMP-induced transcription of several early osteoblast genes, probably because levels of BMP-activated nuclear Smads are decreased. In contrast, inhibiting the insulin/IGF-I-activated PI3-K/AKT pathway decreases BMP-induced alkaline phosphatase and osteopontin expression in serum-free cultures of human MSC, but increases BMP activation of Smads; thus, PI3-K signaling is required for BMP-induced expression of early osteoblast genes in human MSC either downstream or independent of the BMP-activated Smad signaling pathway.
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PMID:Bone morphogenetic protein regulation of early osteoblast genes in human marrow stromal cells is mediated by extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling. 1590 16


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