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applied to the parallel synthesis of diverse prostaglandins by ..
Effects of SRT1720 on theprostaglandin E2 (PGE2)-stimulated release ofosteoprotegerin (OPG) in MC3T3-E1 cells. The cultured cells werepre-treated with various concentrations of SRT1720 for 60 min andthen stimulated with 10 μM of PGE2 (●) or the vehicle(○) for 48 h. OPG concentrations in the culture medium weredetermined by ELISA. Each value represents the mean ± SEM oftriplicate determinations from 3 independent cell preparations.
Prostacyclin (PGI2) plays an integral role in O2 mediation of pulmonary vasomotor tone in the fetus and newborn. We hypothesized that O2 modulates PGI2 synthesis in vitro in ovine fetal intrapulmonary arteries, with decreasing O2 causing attenuated synthesis. A decline in PO2 from 680 to 40 mmHg caused a 26% fall in basal PGI2 synthesis. PGI2 synthesis maximally stimulated by bradykinin, A23187, and arachidonic acid were also attenuated at low PO2, by 35%, 33%, and 35%, respectively. PGE2 synthesis was equally affected. In contrast, varying O2 did not alter PGI2 synthesis with exogenous PGH2, which is the product of cyclooxygenase and the substrate for prostacyclin synthetase. Prostaglandin-mediated effects of O2 on cAMP production were also examined. Decreasing PO2 to 40 mmHg caused complete inhibition of basal cAMP production, whereas cAMP production stimulated by exogenous PGI2 was not affected. In parallel studies of mesenteric arteries, PGI2 synthesis and cAMP production were enhanced at low O2. Thus, PGI2 synthesis in fetal intrapulmonary arteries is modulated by changes in O2, with decreasing O2 causing attenuated synthesis. This process is due to an effect on cyclooxygenase activity, it causes marked parallel alterations in cAMP production, and it is specific to the pulmonary circulation.
Parallel synthesis of prostaglandin E1 analogues
Effects of resveratrol on theprostaglandin E2 (PGE2)-stimulated release ofosteoprotegerin (OPG) in MC3T3-E1 cells. The cultured cells werepre-treated with various concentrations of resveratrol for 60 minand then stimulated with 10 μM of PGE2 (●) or thevehicle (○) for 48 h. OPG concentrations in the culture medium weredetermined by ELISA. Each value represents the mean ± SEM oftriplicate determinations from 3 independent cell preparations.*P
Clinical Context: Iloprost is a synthetic analogue of prostacyclin (prostaglandin I2 [PGI2]) that dilates systemic and pulmonary arterial vascular beds. It is approved for use in pulmonary arterial hypertension, but has been found effective for secondary Raynaud syndrome, administered either orally or intravenously.
"Inhibition of prostaglandin synthesis as a ..
It has been firmly established that PGs act asautocrine and paracrine regulators for osteoblasts and playessential roles in the regulation of bone metabolism (,).Among these, prostaglandin E (PGE) is apotent stimulator of bone resorption as it enhances osteoclastformation (). As regards theintracellular signaling of PGE in osteoblasts, we havepreviously demonstrated that PGE stimulatesinterleukin-6 (IL-6) synthesis through Ca mobilizationand cAMP production in osteoblast-like MC3T3-E1 cells (). In addition, we have previouslydemonstrated that PGE stimulates the induction of heatshock protein 27 (HSP27) through Ca mobilization andprotein kinase C (PKC)-dependent activation of both p44/p42mitogen-activated protein (MAP) kinase and p38 MAP kinase inMC3T3-E1 cells (). However,the effects of PGE on the synthesis of OPG inosteoblasts and the mechanisms involved have not yet beenelucidated.
Resveratrol, which is a natural polyphenolabundantly found in red grapes and berries, is recognized aspossessing antioxidant properties that exert various beneficialeffects on human health (). Ithas been reported that resveratrol increases the life span of lowerorganisms by activating sirtuin 1 (SIRT1), a nicotinamide adeninedinucleotide (NAD)-dependent class III deacetylase(). The various beneficialeffects of resveratrol are considered to be mediated through theactivation of SIRT1 in mammalians as well (). As regards bone cells, we haverecently reported that resveratrol suppresses the synthesis ofvascular endothelial growth factor (VEGF) stimulated by bonemorphogenetic protein-4 (BMP-4) in a SIRT1 activation-dependentmanner in osteoblast-like MC3T3-E1 cells (). However, the mechanisms underlyingthe effects of resveratrol on bone metabolism remain to beelucidated.
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of bone prostaglandin synthesis, ..
In conclusion, our results strongly suggest thatresveratrol reduces the PGE-stimulated OPG synthesisthrough the inhibition of p44/p42 MAP kinase, p38 MAP kinase andSAPK/JNK in osteoblasts, and that these suppressive effects are notmediated through the activation of SIRT1.
Method of inhibiting prostaglandin synthesis in a …
Evidence is accumulating that the beneficial effectsof resveratrol are mediated through SIRT1 activation (). On the other hand, we demonstratedthat SRT1720, a potent activator of SIRT1 (), exerted minimal effects on thePGE-stimulated release of OPG and on thephosphorylation of the three MAP kinases induced by PGEin osteoblast-like MC3T3-E1 cells. Therefore, it seems unlikelythat the inhibitory effects of resveratrol on thePGE-induced events shown in our study areSIRT1-dependent in these cells. In a previous study of ours(), we demonstrated thatresveratrol significantly suppressed the BMP-4-induced VEGFsynthesis, and that the effects were mediated at least in part bythe activation of SIRT1 in MC3T3-E1 cells. Based on our findings,it is possible that the intracellular signaling mechanismsunderlying the effects of resveratrol in osteoblasts arecharacterized according to each agonist or product. It has beenreported that resveratrol affects the cellular function ofadipocytes and regulates the number of fat cells in aSIRT1-independent manner (,). Since both osteoblasts andadipocytes originate from undifferentiated mesenchymal stem cells,the SIRT-independent effects of resveratrol observed in osteoblastsmay be due to these same stem cells.
Method of inhibiting prostaglandin synthesis ..
Taken together, our results revealed that an AMPKinhibitor decreases PGF-stimulated IL-6 synthesis viasuppression of p38 MAP kinase in osteoblasts.
The Coxibs, Selective Inhibitors of Cyclooxygenase-2 ? …
The three major MAP kinases, p44/p42 MAP kinase, p38MAP kinase and SAPK/JNK are recognized as central elements used bymammalian cells to transduce diverse messages () and play central roles in a varietyof cellular functions, including proliferation, differentiation andsurvival (). As regards theintracellular signaling of PGE in osteoblasts, we havepreviously demonstrated that PGE induces the activationof p44/p42 MAP kinase and p38 MAP kinase in osteoblast-likeMC3T3-E1 cells, and that PGE stimulates the inductionof HSP27 through the PKC-dependent activation of both p44/p42 MAPkinase and p38 MAP kinase in MC3T3-E1 cells (). In the present study, we found thatPGE stimulated the phosphorylation of SAPK/JNK in theMC3T3-E1 cells in a time-dependent manner and the most prominenteffects of PGE were observed at 20 min followingstimulation (data not shown). It is generally established that MAPkinases are activated by the phosphorylation of threonine andtyrosine residues by dual-specificity MAP kinase kinase (). Therefore, our findings suggestthat PGE stimulates the activation of SAPK/JNK inaddition to that of p44/p42 MAP kinase and p38 MAP kinase inosteoblast-like MC3T3-E1 cells. Furthermore, we demonstrated thatPD98059, a specific inhibitor of the upstream kinase activatingp44/p42 MAP kinase (),SB203580, a specific inhibitor of p38 MAP kinase () and SP600125, a specific inhibitorof SAPK/JNK () markedlyreduced the PGE-stimulated release of OPG, suggestingthat three major MAP kinases, namely the p44/p42 MAP kinase, p38MAP kinase and SAPK/JNK function as positive regulators in thePGE-stimulated OPG synthesis in these cells. Inaddition, we demonstrated that resveratrol markedly suppressed thephosphorylation of p44/p42 MAP kinase, p38 MAP kinase and SAPK/JNKinduced by PGE in the MC3T3-E1 cells. Taking ourfindings into account, it is likely that resveratrol inhibits thePGE-induced OPG synthesis in osteoblast-like cells, andthat the suppressive effects of resveratrol are exerted at a pointupstream of three MAP kinases.
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