Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To understand the mechanisms by which glucocorticoids promote differentiation of fetal rat calvaria derived osteoblasts to produce bone-like mineralized nodules in vitro, a panel of osteoblast growth and differentiation related genes that characterize development of the osteoblast phenotype has been quantitated in glucocorticoid-treated cultures. We compared the mRNA levels of osteoblast expressed genes in control cultures of subcultivated cells where nodule formation is diminished, to cells continuously (35 days) exposed to 10(-7) M dexamethasone, a synthetic glucocorticoid, which promotes nodule formation to levels usually the extent observed in primary cultures. Tritiated thymidine labelling revealed a selective inhibition of internodule cell proliferation and promotion of proliferation and differentiation of cells forming bone nodules. Fibronectin, osteopontin, and c-fos expression were increased in the nodule forming period. Alkaline phosphatase and type I collagen expression were initially inhibited in proliferating cells, then increased after nodule formation to support further growth and mineralization of the nodule. Expression of osteocalcin was 1,000-fold elevated in glucocorticoid-differentiated cultures in relation to nodule formation. Collagenase gene expression was also greater than controls (fivefold) with the highest levels observed in mature cultures (day 35). At this time, a rise in collagen and TGF beta was also observed suggesting turnover of the matrix. Short term (48 h) effects of glucocorticoid on histone H4 (reflecting cell proliferation), alkaline phosphatase, osteopontin, and osteocalcin mRNA levels reveal both up or down regulation as a function of the developmental stage of the osteoblast phenotype. A comparison of transcriptional levels of these genes by nuclear run-on assays to mRNA levels indicates that glucocorticoids exert both transcriptional and post-transcriptional effects. Further, the presence of glucocorticoids enhances the vitamin D3 effect on gene expression. Those genes which are upregulated by 1,25(OH)2D3 are transcribed at an increased rate by dexamethasone, while those genes which are inhibited by vitamin D3 remain inhibited in the presence of dexamethasone and D3. We propose that the glucocorticoids promote changes in gene expression involved in cell-cell and cell-extracellular matrix signaling mechanisms that support the growth and differentiation of cells capable of osteoblast phenotype development and bone tissue-like organization, while inhibiting the growth of cells that cannot progress to the mature osteoblast phenotype in fetal rat calvarial cultures.
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PMID:Glucocorticoids promote development of the osteoblast phenotype by selectively modulating expression of cell growth and differentiation associated genes. 146 73

It has been established that regenerating marrow induces an osteogenic response in distant skeletal sites and that this activity is mediated by factors released into the circulation by the healing tissue. In the present study we have characterized one of these factors, a 14 amino acid peptide named osteogenic growth peptide (OGP). Synthetic OGP, identical in structure to the native molecule, stimulates the proliferation and alkaline phosphatase activity of osteoblastic cells in vitro and increases bone mass in rats when injected in vivo. Immunoreactive OGP in high abundance is present physiologically in the serum, mainly in the form of an OGP-OGP binding protein complex. A marked increase in serum bound and unbound OGP accompanies the osteogenic phase of post-ablation marrow regeneration and associated systemic osteogenic response. Authentic OGP is identical to the C-terminus of histone H4 and shares a five residue motif with a T-cell receptor beta-chain V-region and the Bacillus subtilis outB locus. Since these latter proteins have not been implicated previously in the control of cell proliferation or differentiation, OGP may belong to a novel, heretofore unrecognized family of regulatory peptides. Perhaps more importantly, OGP appears to represent a new class of molecules involved in the systemic control of osteoblast proliferation and differentiation.
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PMID:Histone H4-related osteogenic growth peptide (OGP): a novel circulating stimulator of osteoblastic activity. 158 15

We have previously shown that calcitonin (CT), an inhibitor of bone resorption, increases vertebral, but not femoral bone density in the rat. To address the physiologic responses associated with these effects on bone mineral density (BMD), we assessed mRNA transcripts reflecting activities of osteoblasts (type I collagen, osteocalcin, osteopontin, and alkaline phosphatase), osteoclasts [tartrate-resistant acid phosphatase (TRAP)], and cell proliferation (histone H4) in the spine and femur of these rats. CT increased spine BMD while increasing type I collagen and decreasing TRAP and histone mRNAs. In the femur, where CT had no effect on BMD, it decreased type I collagen and histone H4 mRNA but did not affect TRAP. CT had no effect on the gene expression of osteocalcin, osteopontin, or alkaline phosphatase at either site. The results indicate that selective alterations in gene expression, as reflected by steady state mRNA levels, are consistent with the changes observed by BMD measurement, and can more clearly define the specific contribution from osteoblast and osteoclast activity. This study demonstrates a heterogeneity in response of the axial and appendicular skeleton to CT, reflected by alterations in gene expression that provide a basis for understanding the observed BMD responses to various pharmacologic interventions.
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PMID:Responsiveness of gene expression markers of osteoblastic and osteoclastic activity to calcitonin in the appendicular and axial skeleton of the rat in vivo. 808 57

TSH-suppressive doses of thyroid hormone are associated with bone loss. We have previously reported that L-T4 decreases femoral, but not vertebral bone mineral density (BMD) in rats. As bisphosphonates are able to decrease bone resorption, especially in high bone turnover states, we investigated the potential effects of etidronate disodium (EHDP) on L-T4-induced bone loss in the rat model by assessing BMD and gene expression of osteoblast (osteocalcin, osteopontin, type I collagen, and alkaline phosphatase), osteoclast (tartrate-resistant acid phosphatase), and cell growth (histone) markers in the skeleton. L-T4 administered for 20 days decreased BMD in the femur, but had no effect on the lumbar spine. EHDP alone had no effect on femoral or vertebral BMD, but did prevent the L-T4-induced bone loss in the femur. L-T4 increased mRNA levels of alkaline phosphatase, tartrate-resistant acid phosphatase, and histone H4 in the femur, but not in the vertebrae. EHDP, which alone had no effect on gene expression in the femur or vertebrae, inhibited the effect of L-T4 on mRNA markers in the femur. The results demonstrate that EHDP can prevent the L-T4-induced decrease in femoral BMD in rats that is associated with the prevention of changes in mRNA markers of osteoclast and osteoblast function. EHDP and other bisphosphonate compounds may be useful in the prevention of thyroid hormone-induced bone loss in humans.
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PMID:Etidronate inhibits the thyroid hormone-induced bone loss in rats assessed by bone mineral density and messenger ribonucleic acid markers of osteoblast and osteoclast function. 824 71

Fibroblast growth factors (FGF) are osteoblast mitogens, but their effects on bone formation are not clearly understood. Most in vitro studies examining the effects of FGFs on osteoblasts have been performed only during the initial proliferative stage of osteoblast culture. In these studies, we examined the consequential effect of acidic FGF in cultures of rat fetal diploid osteoblasts that undergo a developmental differentiation program producing a mineralized bone-like matrix. During the initial growth period (days 1-10), addition of acidic FGF (100 micrograms/ml) to actively proliferating cells increased (P < 0.05) 3H-thymidine uptake (2,515 +/- 137, mean +/- SEM vs. 5,884 +/- 818 cpm/10(4) cells). During the second stage of maturation (days 10-15), osteoblasts form multilayered nodules of cells and accumulate matrix, followed by mineralization (stage 3, days 16-29). Addition of acidic FGF to the osteoblast cultures from days 7 to 15 completely blocked nodule formation. Furthermore, addition of acidic FGF after nodule formation (days 14-29) inhibited matrix mineralization, which was associated with a marked increase in collagenase gene expression, and resulted in a progressive change in the morphology of the nodules, with only a few remnants of nonmineralized nodules present by day 29. Histochemical and biochemical analyses revealed a decrease in alkaline phosphatase and mineral content, confirming the acidic FGF-induced inhibition of nodule and matrix formation. To identify mechanisms contributing to these changes, we examined expression of cell growth and bone phenotypic markers. Addition of acidic FGF during the proliferative phase (days 7-8) enhanced histone H4, osteopontin, type I collagen, and TGF-beta mRNA levels, which are coupled to proliferating osteoblasts, and blocked the normal developmental increase in alkaline phosphatase and osteocalcin gene expression and calcium accumulation. Addition of acidic FGF to the cultures during matrix maturation (days 14-15) reactivated H4, osteopontin, type I collagen, and TGF-beta gene expression, and decreased alkaline phosphatase and osteocalcin gene expression. In an in vivo experiment, rats were treated with up to 60 micrograms/kg/day acidic FGF intravenously for 30 days. Proliferation of osteoblasts and deposition of bone occurred in the marrow space of the diaphysis of the femur in a dose-related fashion. The metaphyseal areas were unaffected by treatment. In conclusion, our data suggest that acidic FGF is a potent mitogen for early stage osteoblasts which leads to modifications in the formation of the extracellular matrix; increases in TGF-beta and collagenase are functionally implicated in abrogating competency for nodule formation. Persistence of proliferation prevented expression of alkaline phosphatase and osteocalcin, also contributing to the block in the progression of the osteoblast developmental sequence.
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PMID:Acidic fibroblast growth factor inhibits osteoblast differentiation in vitro: altered expression of collagenase, cell growth-related, and mineralization-associated genes. 872 64

We have previously studied the expression of alkaline phosphatase (ALP) and alpha2(I) collagen (two phenotypic markers of osteoblastic cell differentiation) during development of the rat mandible, and the spatial and temporal distribution of the respective transcripts. Our current studies utilize the rat mandible and hind foot as in vivo model systems to investigate the relationship between osteoblastic differentiation and proliferation during intramembranous and endochondral bone formation. Pregnant rats, at 15.17, and 19 days of gestation were intraperitoneally injected with various doses of [3H]-thymidine, and sacrificed at various time intervals in order to label dividing embryonic osteoblastic and preosteoblastic cells. Cross sections through the mid-body of 15-day embryos showed [3H-thymidine dose-dependent labeling of a relatively high percentage of cells in the liver (49 +/- 8% at 440 muCi) and a lower percentage of cells of the developing vertebral cartilage (29 +/- 6% at 440 muCi). ALP-positive condensed mesenchyme--consisting of mandibular preosteoblast (15 days of gestation) showed a relatively high (32 +/- 5%) level of [3H]-thymidine labeling, compared to surrounding ALP-negative loose mesenchymal cells (22 +/- 1%). Similar results were observed in the developing hind foot of 19-day embryos for ALP-positive cells (15 +/- 6%) and surrounding ALP-negative cells (13 +/- 5%). In both the hind foot and the mandible an overall decrease in labeling was observed during bone development. RNA samples from these tissues show increasing amounts of ALP mRNA, and decreasing amounts of histone H4 mRNA between days 15 and 19 of gestation. These data indicate that a general inverse correlation between osteoblastic differentiation and proliferation, similar to the correlation previously described in cultured osteogenic cells, is also present in developing bones in vivo. However, these results indicate that ALP-positive preosteoblasts, committed to the osteoblastic lineage, maintain their proliferative capacity. In an attempt to elucidate underlying molecular mechanisms, we further investigated the levels of expression of m-twist in these tissues. This member of the basic helix-loop-helix family of transcription regulators has been previously implied as playing a role in osteoblast differentiation in culture. Our results demonstrate a decrease in m-twist levels during bone development in both the mandible and the hind foot.
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PMID:Endochondral and intramembranous fetal bone development: osteoblastic cell proliferation, and expression of alkaline phosphatase, m-twist, and histone H4. 877

Thyroid hormones influence growth and differentiation of bone cells. In vivo and in vitro data indicate their importance for development and maintenance of the skeleton. Triiodothyronine (T3) inhibits proliferation and accelerates differentiation of osteoblasts. We studied the regulatory effect of T3 on markers of proliferation as well as on specific markers of the osteoblastic phenotype in cultured MC3T3-E1 cells at different time points. In parallel to the inhibitory effect on proliferation, T3 down-regulated histone H4 mRNA expression. Early genes (c-fos/c-jun) are highly expressed in proliferating cells and are down-regulated when the cells switch to differentiation. When MC3T3-E1 cells are cultured under serum-free conditions, basal c-fos/c-jun expressions are nearly undetectable. Under these conditions, c-fos/c-jun mRNAs can be stimulated by EGF, the effect of which is attenuated to about 46% by T3. In addition, T3 stimulated the expression at the mRNA and protein level of osteocalcin, a marker of mature osteoblasts and alkaline phosphatase activity. All these effects were more pronounced when cells were cultured for more than 6 days. These data indicate that T3 acts as a differentiation factor in osteoblasts by influencing the expression of cell cycle-regulated, of cell growth-regulated, and of phenotypic genes.
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PMID:Triiodothyronine, a regulator of osteoblastic differentiation: depression of histone H4, attenuation of c-fos/c-jun, and induction of osteocalcin expression. 935 83

Estrogen responsiveness of bone is a fundamental regulatory mechanism operative in skeletal homeostasis. We examined the expression of estrogen receptor-alpha (ER) messenger RNA (mRNA) in cultured rat calvarial-derived osteoblasts during progressive development of the osteoblast phenotype. Levels of ER message were compared with the expression of traditional osteoblastic markers that have been mapped throughout the differentiation process of these cells. ER transcripts, measured using semiquantitative RT-PCR analysis, were expressed at low levels in early stage proliferating osteoblasts and increased at confluence upon initial expression of bone cell phenotypic genes. A 23-fold up-regulation of ER mRNA expression coincided with the initiation of alkaline phosphatase activity (day 8). ER mRNA levels progressively increased 70-fold, reaching a maximum level on days 22-25 in fully differentiated osteoblasts when osteocalcin expression peaked, but declined precipitously by day 32 in osteocytic cells. Analysis of RNA isolated directly from rat calvaria confirmed these in vitro results and demonstrated that ER message levels become more abundant postnatally as bone becomes more mineralized. We also examined the responsiveness of osteoblasts to 17beta-estradiol (17beta-E2) at two periods of maturation: the nodule-forming stage (day 14) and the late mineralization stage (day 30). Estradiol suppressed the levels of alkaline phosphatase, osteocalcin, osteonectin, and ER mRNAs on day 14, but up-regulated these messages on day 30. In contrast, 17beta-E2 treatment regulated the steady state levels of transforming growth factor-beta1 and type I procollagen mRNAs only in the late mineralization stage, whereas histone H4 message was unaffected by the steroid at either stage of differentiation. Thus, the observed developmental expression of ER mRNA correlates with progressive osteoblast differentiation and may be a contributing factor to differential regulation of bone cell gene expression by 17beta-E2.
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PMID:Estrogen receptor-alpha is developmentally regulated during osteoblast differentiation and contributes to selective responsiveness of gene expression. 952 93

Transplantation of diffusion chambers (DC) containing osteoblast-like cells to extraskeletal sites has been highly studied and proven to be a useful technique to investigate the process of osteoblast differentiation and bone formation. To investigate the molecular basis of osteogenesis in DC, we examined the temporal pattern of gene expression of the proliferation marker histone H4, immediate early response genes (IEGs), c-fos, c-jun, c-myc, osteoblast phenotype-associated genes, osteocalcin (OC), osteopontin (OP), type I collagen (COL1A1), alkaline phosphatase (ALP), parathyroid hormone receptor (PTHR) and matrix modifying enzyme, matrix metalloproteinase-9 (MMP-9). DC containing ROS 17/2.8 were implanted intraperitoneally into rat hosts and cultured in vivo for various times up to 56 days. Histological analysis of von Kossa stained sections of the DC contents showed a well-organized connective tissue and the production of mineralized matrices/nodules. In contrast, histological examination of DC containing Rat-2 fibroblast cells revealed the lack of an organized mineralized matrix. Molecular analysis of DC containing ROS 17/2.8 cells at 0, 3, 10, 28, and 56 days demonstrated a time-dependent decrease in DNA content associated with cell death. In the surviving cells, an increase in histone H4 mRNA (consistent with an increase in cell proliferation) was evident by 3-10 days and thereafter expression returned to control levels. In vitro, ROS 17/2.8 cells expressed detectable levels of c-fos, c-jun, c-myc, OC, OP, ALP, COL1A1, and PTHR but not MMP-9. In vivo, the expression of c-fos increased 2-fold in 3-28 days and by 56 days was 4-5 fold above control levels. In 3-10 days, c-jun expression increased 1.6-1.8-fold above control levels. In contrast, by day 28, c-jun expression decreased to control levels, but increased to 2.1-fold above control by 56 days. c-myc mRNA expression increased 3-fold within 3 days and then dropped to below control values by 10-56 days. After transplantation in vivo, the expression of OC and PTHR decreased to undetectable levels. Similarly, ALP mRNA decreased to </=28% of preimplantation values. In contrast, OPN mRNA levels increased up to 7-fold by day 10 and thereafter, returned to 1.7-fold above control values. COL1A1 mRNA decreased 2-fold at day 3 and increased to 3.5-, 1.6-, and 2.8-fold above control at days 10, 28, and 56, respectively. MMP-9 levels increased 5- to 10-fold by days 3-10, but fell to undetectable levels by 28-56 days. These results indicate that the formation of mineralized matrix (bone nodules) seen in the 56-day DC of ROS 17/2.8 cells was preceded by coordinate temporal expression of IEGs, matrix proteins, and matrix-modifying enzymes. Additionally, these results substantiate that measurement of molecular parameters in tissues formed by cells incubated in DC in vivo may be a useful predictor of the osteogenic process.
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PMID:Molecular characterization of gene expression changes in ROS 17/2.8 cells cultured in diffusion chambers in vivo. 1043 Jun 46

Intestinal epithelial cells participate in an acute phase response (APR) by responding to cytokines and by expressing acute phase protein genes. We hypothesized that butyrate, a fermentation product of the bacterial intestinal flora with deacetylase activity, affects the APR in intestinal epithelial cells. Sodium butyrate (NaBu) and Trichostatin A (TSA) induced alkaline phosphatase activity and histone H4 acetylation in IEC-6 rat intestinal epithelial cells treated with or without interleukin-1beta (IL-1). In contrast, both NaBu and TSA attenuated the IL-1-dependent induction of the acute phase protein gene haptoglobin, as well as C/EBPbeta and C/EBPdelta transcription factors mRNAs. Gel shift and supershift assays showed a strong decrease in the IL-1-induced C/EBPbeta and C/EBPdelta containing complexes binding to the HaptoA C/EBP DNA-binding site of the haptoglobin promoter, by NaBu and TSA. Furthermore, site-specific mutation of the HaptoA site abolished the NaBu- and TSA-dependent inhibition of haptoglobin, as determined by transient transfection assays. These results suggest that deacetylase inhibitors may regulate the IL-1 dependent induction of haptoglobin by down-regulating C/EBP isoforms, and that C/EBPs represent a target for the action of butyrate in the control of the APR of intestinal epithelial cells.
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PMID:Inhibition by deacetylase inhibitors of IL-1-dependent induction of haptoglobin involves CCAAT/Enhancer-binding protein isoforms in intestinal epithelial cells. 1102 30


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