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

---

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

Recent studies have shown that 24R,25-(OH)(2)D(3) mediates its effects on growth plate chondrocytes via membrane receptors. This study examined the roles of phospholipase A(2) (PLA(2)) and cyclooxygenase (Cox) in the mechanism of action of 24R, 25-(OH)(2)D(3) in resting zone chondrocytes in order to determine whether the activity of one or both enzymes provides a regulatory checkpoint in the signaling pathway resulting in increased protein kinase C (PKC) activity. We also determined whether constitutive or inducible Cox is involved. Cultures were incubated with 24R, 25-(OH)(2)D(3) for 90 min to measure PKC or for 24 h to measure physiological responses ([(3)H]-thymidine incorporation, alkaline phosphatase-specific activity, [(35)S]-sulfate incorporation). Based on RT-PCR and Northern blot analysis, resting zone chondrocytes express mRNAs for both Cox-1 and Cox-2. Levels of mRNA for both proteins were unchanged from control levels after a 24-h incubation with 24R,25-(OH)(2)D(3). To examine the role of Cox, the cultures were also treated with resveratrol (a specific inhibitor of Cox-1), NS-398 (a specific inhibitor of Cox-2), or indomethacin (a general Cox inhibitor). Cox-1 inhibition resulted in effects on proliferation, differentiation, and matrix production typical of 24R, 25-(OH)(2)D(3). In contrast, inhibition of Cox-2 had no effect, indicating that 24R,25-(OH)(2)D(3) exerts its effects via Cox-1. Inhibition of Cox-1 also blocked 24R,25-(OH)(2)D(3)-dependent increases in PKC. Activation of PLA(2) with melittin inhibited 24R, 25-(OH)(2)D(3)-dependent stimulation of PKC, and inhibition of PLA(2) with quinacrine stimulated PKC in response to 24R, 25-(OH)(2)D(3). Inclusion of resveratrol reduced the melittin-dependent inhibition of PLA(2) and caused an increase in quinacrine-stimulated PLA(2) activity. Metabolism of arachidonic acid to leukotrienes is not involved in the response to 24R, 25-(OH)(2)D(3) because inhibition of lipoxygenase had no effect. The effect of 24R,25-(OH)(2)D(3) was specific because 24S,25-(OH)(2)D(3), the biologically inactive stereoisomer, failed to elicit a response from the cells. These results support the hypothesis that 24R, 25-(OH)(2)D(3) exerts its effects via more than one signaling pathway and that these pathways are interrelated via the modulation of PLA(2). PKC regulation may occur at multiple stages in the signal transduction cascade.
...
PMID:24R,25-(OH)(2)D(3) mediates its membrane receptor-dependent effects on protein kinase C and alkaline phosphatase via phospholipase A(2) and cyclooxygenase-1 but not cyclooxygenase-2 in growth plate chondrocytes. 1065 6

1alpha,25-(OH)(2)D(3) mediates its effects on growth zone chondrocytes via rapid membrane-associated events as well as through traditional nuclear receptor mechanisms. The membrane-associated signaling pathways include rapid production of diacylglycerol and activation of protein kinase C (PKC), as well as activation of phospholipase A(2) (PLA(2)), increased production of arachidonic acid, and increased production of prostaglandins. This study examined the roles of PLA(2) and cyclooxygenase (Cox) in the mechanism of action of 1alpha,25-(OH)(2)D(3) in these cells to determine whether one or both enzymes catalyze the rate limiting step and whether constitutive or inducible Cox is involved. Cultures were incubated with 1alpha,25-(OH)(2)D(3) for 9 min to measure PKC or for 24 h to measure physiological responses ([(3)H]-thymidine incorporation, alkaline phosphatase specific activity, [(35)S]-sulfate incorporation). Based on RT-PCR and Northern blot analysis, growth zone chondrocytes expressed mRNAs for both Cox-1 and Cox-2 and neither Cox was modulated by 1alpha,25-(OH)(2)D(3). To examine the role of Cox, the cultures were also treated with resveratrol (a specific inhibitor of Cox-1), NS-398 (a specific inhibitor of Cox-2), or indomethacin (a general Cox inhibitor). The results showed that Cox-1 inhibition reduced the 1alpha,25-(OH)(2)D(3)-dependent effects on proliferation, differentiation, and matrix production, whereas inhibition of Cox-2 only had an effect on proliferation. The effects of Cox inhibition were not rate limiting, based on experiments in which PLA(2) was activated with melittin or inhibited with quinacrine. However, at least part of the action of 1alpha,25-(OH)(2)D(3) was regulated by metabolism of arachidonic acid to prostaglandins. This supports the hypothesis that 1alpha,25-(OH)(2)D(3) exerts its effects via more than one signaling pathway and that these pathways are interrelated via the modulation of PLA(2) as a rate-limiting step. PKC regulation may occur at multiple stages in the signal transduction cascade. J. Cell. Biochem. Suppl. 36: 32-45, 2001.
...
PMID:Effects of 1alpha,25-(OH)(2)D(3) on rat growth zone chondrocytes are mediated via cyclooxygenase-1 and phospholipase A(2). 1145 68

Membrane-mediated increases in protein kinase C (PKC) activity and PKC-dependent physiological responses of growth plate chondrocytes to vitamin D metabolites depend on the state of endochondral maturation; 1alpha,25-dihydroxyvitamin D(3) [1alpha,25-(OH)(2)D(3)] regulates growth zone (GC) cells, whereas 24R,25-(OH)(2)D(3) regulates resting zone (RC) cells. Different mechanisms, including protein kinase A signaling, mediate the effects of 1alpha,25-(OH)(2)D(3) and 24R,25-(OH)(2)D(3) on PKC, suggesting that different mechanisms may also regulate any MAPK involvement in the physiological responses. This study used confluent cultures of rat costochondral chondrocytes as a model. 1alpha,25-(OH)(2)D(3) stimulated MAPK specific activity in GC in a time- and dose-dependent manner, evident within 9 min. 24R,25-(OH)(2)D(3) stimulated MAPK in RC; increases were dose dependent, occurred after 9 min, and were greatest at 90 min. In both cells the effect was due to ERK1/2 activation (p42 > p44 in GC; p42 = p44 in RC). MAPK activation was dependent on PKC, but not protein kinase A. The effect of 1alpha,25-(OH)(2)D(3) required phospholipase C, and the effect of 24R,25-(OH)(2)D(3) required phospholipase D. Inhibition of cyclooxygenase activity reduced the effect of 1alpha,25-(OH)(2)D(3) on MAPK in GC and enhanced the effect of 24R,25-(OH)(2)D(3) in RC. Based on MAPK inhibition with PD98059, ERK1/2 MAPK mediated the effect of 24R,25-(OH)(2)D(3) on [(3)H]thymidine incorporation and [(35)S]sulfate incorporation by RC, but only partially mediated the effect of 1alpha,25-(OH)(2)D(3) on GC. ERK1/2 was not involved in the regulation of alkaline phosphatase specific activity by either metabolite. This paper supports the hypothesis that 1alpha,25-(OH)(2)D(3) regulates the physiology of GC via rapid membrane-mediated signaling pathways, and some, but not all, of the response to 1alpha,25-(OH)(2)D(3) is via the ERK family of MAPKs. In contrast, 24R,25-(OH)(2)D(3) exerts its effects on RC via PKC-dependent MAPK. Whereas 1alpha,25-(OH)(2)D(3) increases MAPK activity via phospholipase C and increased prostaglandin production, 24R,25-(OH)(2)D(3) increases MAPK via phospholipase D and decreased prostaglandin production. The cell specificity, metabolite stereospecificity, and the dependence on PKC argue for the participation of membrane receptors for 1alpha,25-(OH)(2)D(3) and 24R,25-(OH)(2)D(3) in the regulation of ERK1/2 in the growth plate.
...
PMID:1alpha,25-dihydroxyvitamin D(3) and 24R,25-dihydroxyvitamin D(3) modulate growth plate chondrocyte physiology via protein kinase C-dependent phosphorylation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase. 1207 13

Phospholipase A2 (PLA2) is pivotal in the rapid membrane-mediated actions of 1,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3]. Microarray analysis indicated that PLA2 activating protein (PLAA) mRNA is upregulated 6-fold before rat growth plate cells exhibit 1alpha,25(OH)2D3-dependent protein kinase C (PKC) increases, suggesting that it plays an important role in 1alpha,25(OH)2D3's mechanism of action. PLAA mRNA was confirmed in 1alpha,25(OH)2D3-responsive growth zone (prehypertrophic and upper hypertrophic cell zones) chondrocytes by RT-PCR and Northern blot in vitro and by in situ hybridization in vivo. PLAA protein was shown by Western blot and immunohistochemistry. PLAAs role in 1alpha,25(OH)2D3 signaling was evaluated in growth zone cell cultures using PLAA peptide. Arachidonic acid release was increased as was PLA2-specific activity in plasma membranes and matrix vesicles. PKCalpha, but not PKCbeta, PKCepsilon, or PKCzeta, was increased. PLAAs effect was comparable to that of 1alpha,25(OH)2D3 and was additive with 1alpha,25(OH)2D3. PLA2 inhibitors quinacrine and AACOCF3, and cyclooxygenase inhibitor indomethacin blocked the effect of PLAA peptide on PKC, indicating arachidonic acid and its metabolites were involved. This was confirmed using exogenous arachidonic acid. Prostaglandin acted via EP1 based on inhibition by SC19220 and not via EP2 since AH6809 had no effect. Like 1alpha,25(OH)2D3, PLAA peptide also increased activity of phospholipase C-specific activity via beta-1 and beta-3 isoforms, but not delta-1 or gamma-1; the effect of PLAA was via lysophospholipid but not via arachidonic acid. PLAA peptide decreased [3H]-thymidine incorporation to 50% of the decrease caused by 1alpha,25(OH)2D3. In contrast, PLAA peptide increased alkaline phosphatase-specific activity and proteoglycan production in a manner similar to 1alpha,25(OH)2D3. This indicates that PLAA is a specific activator of PLA2 in growth plate chondrocytes, and suggests that it mediates the membrane effect of 1alpha,25(OH)2D3, thereby modulating physiological response.
...
PMID:Phospholipase A2 activating protein (PLAA) is required for 1alpha,25(OH)2D3 signaling in growth plate chondrocytes. 1536 40

Prostaglandins are ubiquitous metabolites of arachidonic acid, and cyclooxygenase inhibitors prevent their production and secretion. Animals with loss of cyclooxygenase-2 function have reduced reparative bone formation, but the role of prostaglandins during endochondral bone formation is not defined. The role of PGE2 as a regulator of chondrocyte differentiation in chick growth plate chondrocytes (GPCs) was examined. While PGE2, PGD2, PGF2alpha, and PGJ2 all inhibited colX expression, approximately 80% at 10(-6) M, PGE2 was the most potent activator of cAMP response element (CRE)-mediated transcription. PGE2 dose-dependently inhibited the expression of the differentiation-related genes, colX, VEGF, MMP-13, and alkaline phosphatase gene, and enzyme activity with significant effects at concentrations as low as 10(-10) M. PGE2 induced cyclic AMP response element binding protein (CREB) phosphorylation and increased c-Fos protein levels by 5 min, and activated transcription at CRE-Luc, AP-1-Luc, and c-Fos promoter constructs. The protein kinase A (PKA) inhibitor, H-89, completely blocked PGE2-mediated induction of CRE-Luc and c-Fos promoter-Luc promoters, and partially inhibited induction of AP-1-Luc, while the protein kinase C (PKC) inhibitor Go-6976 partially inhibited all three promoters, demonstrating substantial cross-talk between these signaling pathways. PGE2 inhibition of colX gene expression was dependent upon both PKA and PKC signaling. These observations demonstrate potent prostaglandin regulatory effects on chondrocyte maturation and show a role for both PKA and PKC signaling in PGE2 regulatory events.
...
PMID:PGE2 inhibits chondrocyte differentiation through PKA and PKC signaling. 1538 23

The osteoporosis that occurs with aging is associated with reduced number and activity of osteoblastic cells. Aging, menopause, and osteoporosis are correlated with increased oxidative stress and reduced antioxidant defense mechanisms. We previously demonstrated that oxidative stress induced by a variety of compounds such as xanthine/xanthine oxidase (XXO) and minimally oxidized LDL (MM-LDL) inhibit the osteogenic differentiation of osteoprogenitor cells. Oxysterols are a family of products derived from cholesterol oxidation that have important biological activities. Recently, we reported that a specific oxysterol combination consisting of 22(S)- or 22(R)-hydroxycholesterol and 20(S)-hydroxycholesterol has potent osteogenic properties in vitro when applied to osteoprogenitor cells including M2-10B4 (M2) marrow stromal cells. We now demonstrate that this osteogenic combination of oxysterols prevents the adverse effects of oxidative stress on differentiation of M2 cells into mature osteoblastic cells. XXO and MM-LDL inhibited the osteogenic differentiation of M2 cells, demonstrated by the inhibition of markers of osteogenic differentiation: alkaline phosphatase activity, osteocalcin expression and mineralization. Treatment of M2 cells with osteogenic oxysterol combination 22(S)- and 20(S)-hydroxycholesterol both blocked and reversed the inhibition of osteogenic differentiation produced by XXO and MM-LDL in these cells. The protective effect of the oxysterols against oxidative stress was dependent on cyclooxygenase 1 and was associated with the osteogenic property of the oxysterols. These findings further demonstrate the ability of the osteogenic oxysterols to positively regulate osteogenic differentiation of cells, and suggests that the use of these compounds may be a novel strategy to prevent the adverse effects of oxidative stress on osteogenesis.
...
PMID:Osteogenic oxysterols inhibit the adverse effects of oxidative stress on osteogenic differentiation of marrow stromal cells. 1588 Jul 3

Previous studies have indicated that one of the causes of alveolar bone destruction with periodontitis is lipopolysaccharide (LPS) from the cell wall of gram-negative bacteria in plaque, and that prostaglandin E(2) (PGE(2)) is one of the bone resorption factors that stimulate osteoclast formation through an intercellular interaction between osteoblasts and osteoclast precursors. The present study was undertaken to determine the effect of LPS on cell growth, alkaline phosphatase (ALPase) activity, the production of PGE(2), and the expression of receptors by PGE(2), cyclooxygenase (COX)-1, and COX-2, using human osteosarcoma cell line Saos-2 as osteoblasts. The cells were cultured with 0, 1, or 10 microg mL(-1) of LPS for up to 14 days. The production of PGE(2) and the gene expression of COX-1, COX-2, and PGE(2) receptors, including Ep1, Ep2, Ep3, and Ep4, were determined using enzyme-linked immunosorbent assay (ELISA) and real-time reverse transcription-polymerase chain reaction (real-time RT-PCR), respectively. With the addition of LPS, cell growth and ALPase activity decreased by day 5 of the culture, while PGE(2) production increased in a dose-dependent manner throughout the entire 14-day culture period. LPS-reduced ALP activity and LPS-induced PGE(2) production returned to the control level by the addition simultaneously with indomethacin. The expression of COX-1, Ep1, Ep2, and Ep3 receptors decreased on day 14 of the culture, whereas the expression of COX-2 and Ep4 receptors increased significantly with the addition of LPS. These results suggest that LPS promotes PGE(2) production by increasing the expression of COX-2, and that LPS promotes the production of Ep4 receptors in osteoblasts. These results also indicate that LPS-induced PGE(2) may combine with osteoblast Ep4 receptors in autocrine or paracrine modes, and may promote the formation of osteoclasts.
...
PMID:Lipopolysaccharide stimulates the production of prostaglandin E2 and the receptor Ep4 in osteoblasts. 1628 20

Previous studies have indicated that lipopolysaccharide (LPS) from Gram-negative bacteria in plaque induces the release of prostaglandin E(2) (PGE(2)), which promotes alveolar bone resorption in periodontitis, and that tobacco smoking might be an important risk factor for the development and severity of periodontitis. We determined the effect of nicotine and LPS on alkaline phosphatase (ALPase) activity, PGE(2) production, and the expression of cyclooxygenase (COX-1, COX-2), PGE(2) receptors Ep1>4, and macrophage colony stimulating factor (M-CSF) in human osteoblastic Saos-2 cells. The cells were cultured with 10(-3) M nicotine in the presence of 0, 1, or 10 mug/ml LPS, or with LPS alone. ALPase activity decreased in cells cultured with nicotine or LPS alone, and decreased further in those cultured with both nicotine and LPS, whereas PGE(2) production significantly increased in the former and increased further in the latter. By itself, nicotine did not affect expression of COX-1, COX-2, any of the PGE(2) receptors, or M-CSF, but when both nicotine and LPS were present, expression of COX-2, Ep3, Ep4, and M-CSF increased significantly. Simultaneous addition of 10(-4) M indomethacin eliminated the effects of nicotine and LPS on ALPase activity, PGE(2) production, and M-CSF expression. Phosphorylation of protein kinase A was high in cells cultured with nicotine and LPS. These results suggest that LPS enhances the production of nicotine-induced PGE(2) by an increase in COX-2 expression in osteoblasts, that nicotine-LPS-induced PGE2 interacts with the osteoblast Ep4 receptor primarily in autocrine or paracrine mode, and that the nicotine-LPS-induced PGE(2) then decreases ALPase activity and increases M-CSF expression.
...
PMID:Lipopolysaccharide enhances the production of nicotine-induced prostaglandin E2 by an increase in cyclooxygenase-2 expression in osteoblasts. 1734 54

Selective progesterone receptor modulators (SPRMs) have been suggested as therapeutic agents for treatment of gynecological disorders. One such SPRM, asoprisnil, was recently in clinical trials for treatment of uterine fibroids and endometriosis. We present the crystal structures of progesterone receptor (PR) ligand binding domain complexed with asoprisnil and the corepressors nuclear receptor corepressor (NCoR) and SMRT. This is the first report of steroid nuclear receptor crystal structures with ligand and corepressors. These structures show PR in a different conformation than PR complexed with progesterone (P4). We profiled asoprisnil in PR-dependent assays to understand further the PR-mediated mechanism of action. We confirmed previous findings that asoprisnil demonstrated antagonism, but not agonism, in a PR-B transfection assay and the T47D breast cancer cell alkaline phosphatase activity assay. Asoprisnil, but not RU486, weakly recruited the coactivators SRC-1 and AIB1. However, asoprisnil strongly recruited the corepressor NCoR in a manner similar to RU486. Unlike RU486, NCoR binding to asoprisnil-bound PR could be displaced with equal affinity by NCoR or TIF2 peptides. We further showed that it weakly activated T47D cell gene expression of Sgk-1 and PPL and antagonized P4-induced expression of both genes. In rat leiomyoma ELT3 cells, asoprisnil demonstrated partial P4-like inhibition of cyclooxygenase (COX) enzymatic activity and COX-2 gene expression. In the rat uterotrophic assay, asoprisnil demonstrated no P4-like ability to oppose estrogen. Our data suggest that asoprisnil differentially recruits coactivators and corepressors compared to RU486 or P4, and this specific cofactor interaction profile is apparently insufficient to oppose estrogenic activity in rat uterus.
...
PMID:A structural and in vitro characterization of asoprisnil: a selective progesterone receptor modulator. 1735 70

Sandhika is a polyherbal formulation, (water soluble fraction of Commiphora mukul, Boswellia serrata, Semecarpus anacardium and Strychnos nux vomica), which has been in clinical use in India for last 20 years. Its modified formulation BHUx has shown specific inhibition of cyclooxygenase (COX)-2 and lipoxygenase (LOX)-15 and has prevented diet-induced atherosclerosis in rabbits. In order to explore the possibility of the use of Sandhika for the management of osteoporosis, we have examined its influence on MC3T3-E1 osteoblast-like cells in presence of lipopolysaccharide (1 microg/ml) in terms of calcium nodule formation and alkaline phosphatase activity. MC3T3-E1 osteoblast-like cells (80% confluence in 6-well plates) were treated with water extract of Sandhika, for 10 days, in the concentration range of 0.5 to 16 mg/ml final concentration, in presence of LPS. Media was changed on every third day and culture supernatant was collected after every change to assess the alkaline phosphatase activity and on the tenth day, cells were washed and stained with "Alizarin S" for visualization of calcium nodules by using Meta Morph software (Universal Imaging, Downingtown, PA). The results showed significant enhancement in calcium nodule formation in the dose dependent manner up to 2 mg/ml, followed by gradual decrease at higher concentrations. This change was accompanied with the increase in the alkaline phosphatase activity in these plates, indicating a potential anabolic effect of this polyherbal formulation on osteoblast-like cells under inflammatory conditions induced by LPS.
...
PMID:Role of Sandhika: a polyherbal formulation on MC3T3-E1 osteoblast-like cells. 1768 34


<< Previous 1 2 3 4 Next >>

---