Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Primary PSCs can be subcultured only several times because of their limited growth potential. A continuous cell line would be valuable in studying molecular mechanisms of these pancreatic disorders. The aim of this study was to establish an immortalized cell line of rat PSCs. PSCs were isolated from the pancreas of male Wistar rats, and the simian virus 40 T antigen was introduced to PSCs by retrovirus-mediated gene transfer. This procedure yielded an actively growing cell line, designated as SAM-K. This cell line has been passaged repeatedly for almost 2 years, and is thus likely immortalized. SAM-K cells retained morphological characteristics of primary PSCs, and expressed alpha-smooth muscle actin, glial fibrillary acidic protein, type I collagen, fibronectin, and prolyl hydroxylases. The level of p53 expression was very high in SAM-K cells. Proliferation of SAM-K cells was stimulated by serum and platelet-derived growth factor-BB. Interleukin-1beta (IL-1beta) activated nuclear factor-kappaB, activator protein-1, and three classes of mitogen-activated protein (MAP) kinases: extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase, and p38 MAP kinase. IL-1beta induced expression of intercellular adhesion molecule-1 and monocyte chemoattractant protein-1, both of which were abolished in the presence of pyrrolidine dithiocarbamate, a specific inhibitor of nuclear factor-kappaB activation. IL-1beta-induced monocyte chemoattractant protein-1 was partially inhibited by specific inhibitors of MAP kinase kinase (U0126) and of p38 MAP kinase (SB203580) whereas intercellular adhesion molecule-1 expression was not altered by the inhibitors. Thus, SAM-K would be useful for in vitro studies of cell biology and signal transduction of PSCs.
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PMID:Establishment and characterization of a simian virus 40-immortalized rat pancreatic stellate cell line. 1249 15

Pancreatic stellate cells (PSCs) play a key role in pancreatic fibrosis, a constant feature of chronic pancreatitis. PSC activation occurs in response to profibrogenic mediators such as cytokines and involves proliferation, transition towards a myofibroblastic phenotype and enhanced production of extracellular matrix proteins. Previously, we have shown that PSC activation correlates with the activity of the Ras-Raf-ERK (extracellular signal-regulated kinase) signalling cascade [Gut 51 (2002) 579]. Using a rat culture model of PSCs, we have now evaluated the effects of lovastatin, a hydroxymethylglutaryl coenzyme A reductase inhibitor that interferes with protein isoprenylation, on PSC viability and activation as well as on signalling through Ras proteins. Apoptotic cells were detected applying the TUNEL assay. Proliferation of PSCs was quantitated using the bromodeoxyuridine DNA incorporation assay. Expression of alpha-smooth muscle actin (an indicator of the myofibroblastic phenotype), ERK activation and membrane translocation of the Ras superfamily member RhoA were analysed by immunoblotting. Lovastatin inhibited serum- and platelet-derived growth factor-stimulated PSC proliferation in a dose-dependent manner. At drug concentrations above the level required for growth inhibition, a strong increase of apoptotic cells was observed. Furthermore, lovastatin inhibited induction of alpha-smooth muscle actin expression in the course of primary culture. Immunoblot experiments indicated that lovastatin suppressed both Ras-mediated ERK 1/2 activation and platelet-derived growth factor-induced membrane translocation of RhoA. Together, our data suggest that lovastatin, through the interruption of Ras signalling, interferes with PSC activation. The antifibrotic efficiency of statins should be tested in animal models of chronic pancreatitis.
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PMID:Inhibition of pancreatic stellate cell activation by the hydroxymethylglutaryl coenzyme A reductase inhibitor lovastatin. 1269 70

Pancreatic stellate cells (PSCs) are essentially involved in the development of pancreatic fibrosis, a constant feature of chronic pancreatitis and pancreatic cancer. Profibrogenic mediators, such as ethanol metabolites and cytokines, induce a PSC activation process that involves proliferation, enhanced production of extracellular matrix proteins and a phenotypic transition towards myofibroblasts which includes a loss of the characteristic retinoid-containing fat droplets. Here, we have analysed how exogenous all-trans retinoic acid (ATRA) affects activation of rat PSCs induced by sustained culture. Bromodeoxyuridine-incorporation assays indicated an ATRA-dependent inhibition of DNA synthesis. In contrast, ATRA did not affect expression of alpha-smooth muscle actin, a protein typical for myofibroblasts. Quantification of [3H]proline incorporation revealed a diminished collagen production in ATRA-treated PSCs. Furthermore, zymography experiments showed that supernatants of ATRA-exposed PSC cultures contained higher levels of matrix metalloproteinase-9 but not of matrix metalloproteinase-2 than untreated controls. At the level of intracellular signalling, ATRA had no effect on extracellular signal-regulated kinase activation after incubation of PSCs with the mitogen platelet-derived growth factor (PDGF). In addition, PDGF-induced DNA binding of activator protein-1 (AP-1) transcription factors was not inhibited by ATRA treatment. Luciferase reporter gene assays, however, revealed an ATRA-dependent transrepression of AP-1 in PDGF-stimulated PSCs. Together, the results indicate that exogenous ATRA displays inhibitory effects on PSC proliferation and collagen synthesis but does not block phenotypic transition towards myofibroblasts. We hypothesise that inhibition of AP-1 signalling may be involved in the mediation of biological effects of ATRA on PSCs.
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PMID:Regulation of pancreatic stellate cell function in vitro: biological and molecular effects of all-trans retinoic acid. 1290 28

In response to pancreatic injury and in cell culture, pancreatic stellate cells (PSCs) are transformed ("activated") into highly proliferative myofibroblast-like cells that express alpha-smooth muscle actin and produce extracellular matrix components. Activated PSCs are implicated in the pathogenesis of pancreatic fibrosis and inflammation. We here evaluated the effects of SP600125 (anthra[1,9-cd]pyrazole-6 (2H)-one), an inhibitor of c-Jun NH(2)-terminal kinase (JNK), on the activation of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. Activation of JNK was determined by Western blotting using anti-phosphospecific JNK and c-Jun antibodies. Activation of transcription factors was determined by electrophoretic mobility shift assay. The effects of SP600125 on the key parameters of activation (chemokine production, collagen production, and proliferation) were examined. The effect of SP600125 on the activation of freshly isolated PSCs in culture also was examined. Interleukin-1beta activated both 46- and 54-kDa JNK, whereas platelet-derived growth factor-BB activated only 46-kDa JNK. SP600125 inhibited interleukin-1beta-induced JNK activity and activator protein-1 activation, but it did not affect the activation of extracellular-regulated kinase, p38 mitogen-activated protein kinase, and nuclear factor-kappaB. SP600125 inhibited platelet-derived growth factor-induced proliferation, inducible monocyte chemoattractant protein-1 production, and serum-induced type I collagen production. Although SP600125 did not inhibit the transformation, it attenuated the proliferation of freshly isolated PSCs in culture. Collectively, our results suggest a role of JNK in the activation of PSCs, and a potential application of JNK inhibitors for the treatment of pancreatic fibrosis and inflammation.
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PMID:A c-Jun NH2-terminal kinase inhibitor SP600125 (anthra[1,9-cd]pyrazole-6 (2H)-one) blocks activation of pancreatic stellate cells. 1505 26

Pancreatic stellate cells (PSCs) play a central role in development of pancreatic fibrosis. In chronic pancreatitis, pancreatic tissue pressure is higher than that of the normal pancreas. We here evaluate the effects of pressure on the activation of rat PSCs. PSCs were isolated from the pancreas of Wistar rat using collagenase digestion and centrifugation with Nycodenz gradient. Pressure was applied to cultured rat PSCs by adding compressed helium gas into the pressure-loading apparatus to raise the internal pressure. Cell proliferation rate was assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation. MAPK protein levels and alpha-smooth muscle actin (alpha-SMA) expression were evaluated by Western blot analysis. Concentration of activated transforming growth factor-beta1 (TGF-beta1) secreted from PSCs into culture medium was determined by ELISA. Collagen type I mRNA expression and collagen secretion were assessed by quantitative PCR and Sirius red dye binding assay, respectively. Application of pressure significantly increased BrdU incorporation and alpha-SMA expression. In addition, pressure rapidly increased the phosphorylation of p44/42 and p38 MAPK. Treatment of PSCs with an MEK inhibitor and p38 MAPK inhibitor suppressed pressure-induced cell proliferation and alpha-SMA expression, respectively. Moreover, pressure significantly promoted activated TGF-beta1 secretion, collagen type I mRNA expression, and collagen secretion. Our results demonstrate that pressure itself activates rat PSCs and suggest that increased pancreatic tissue pressure may accelerate the development of pancreatic fibrosis in chronic pancreatitis.
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PMID:Pressure activates rat pancreatic stellate cells. 1531 86

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic inflammation and fibrosis. Trypsin and tryptase, which are agonists for protease-activated receptor-2 (PAR-2), are involved in the pathogenesis of pancreatitis. Here, we examined whether PSCs expressed PAR-2 and its agonists affect the cell functions of PSCs. PSCs were isolated from rat pancreas tissue. Expression of PAR-2 was examined by Western blotting and reverse transcription-polymerase chain reaction. Trypsin, activating peptide (SLIGRL-NH(2), corresponding to the PAR-2 tethered ligand), and tryptase were tested for their ability to affect proliferation, chemokine production, and collagen synthesis in culture-activated PSCs. Activation of mitogen-activated protein (MAP) kinases was assessed by Western blotting using antiphosphospecific antibodies. The effect of PAR-2 agonists on the activation of freshly isolated PSCs in culture was also examined. PAR-2 expression was observed in culture-activated PSCs, whereas it was undetectable in freshly isolated PSCs. PAR-2 agonists activated activator protein-1 and MAP kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAP kinase) but not nuclear factor kappaB. PAR-2 agonists induced proliferation of PSCs through the activation of extracellular signal-regulated kinase. PAR-2 agonists increased collagen synthesis through the activation of c-Jun N-terminal kinase and p38 MAP kinase. PAR-2 agonists did not induce the production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1 or initiate the transformation of freshly isolated PSCs in culture. Taken together, our results suggest a role of PAR-2 in the sustenance of pancreatic fibrosis through the increased proliferation and collagen production in PSCs.
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PMID:Protease-activated receptor-2-mediated proliferation and collagen production of rat pancreatic stellate cells. 1536 78

Until now, no specific therapies are available to inhibit pancreatic fibrosis, a constant pathological feature of chronic pancreatitis and pancreatic cancer. One major reason is the incomplete knowledge of the molecular principles underlying fibrogenesis in the pancreas. In the past few years, evidence has been accumulated that activated pancreatic stellate cells (PSCs) are the predominant source of extracellular matrix (ECM) proteins in the diseased organ. PSCs are vitamin A-storing, fibroblast-like cells with close morphological and biochemical similarities to hepatic stellate cells (also known as Ito-cells). In response to profibrogenic mediators such as various cytokines, PSCs undergo an activation process that involves proliferation, exhibition of a myofibroblastic phenotype and enhanced production of ECM proteins. The intracellular mediators of activation signals, and their antagonists, are only partially known so far. Recent data suggest an important role of enzymes of the mitogen-activated protein kinase family in PSC activation. On the other hand, ligands of the nuclear receptor PPARgamma (peroxisome proliferator-activated receptor gamma) stimulate maintenance of a quiescent PSC phenotype. In the future, targeting regulators of the PSC activation process might become a promising approach for the treatment of pancreatic fibrosis.
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PMID:Molecular regulation of pancreatic stellate cell function. 1546 5

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Ellagic acid is a plant-derived polyphenol found in fruits and nuts, and has anti-oxidant and anti-inflammatory properties. But, little is known about the effects of ellagic acid on PSCs as well as on the activation of signal transduction pathways. We here evaluated the effects of ellagic acid on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. Ellagic acid inhibited platelet-derived growth factor (PDGF)-BB-induced proliferation and migration, interleukin (IL)-1beta- and tumor necrosis factor (TNF)-alpha-induced monocyte chemoattractant protein-1 production, and expression of alpha-smooth muscle actin and collagen genes. Ellagic acid inhibited PDGF-BB-induced tyrosine phosphorylation of PDGF beta-receptor and the downstream activation of extracellular signal-regulated kinase and Akt. Ellagic acid inhibited IL-1beta- and TNF-alpha-induced activation of activator protein-1 and mitogen-activated protein kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase), but not of nuclear factor-kappaB. In addition, ellagic acid inhibited transformation of freshly isolated cells to an activated, myofibroblast-like phenotype. In conclusion, ellagic acid inhibited key cell functions and activation of PSCs.
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PMID:Ellagic acid blocks activation of pancreatic stellate cells. 1602 81

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Inhibition of activation and cell functions of PSCs is a potential target for the treatment of pancreatic fibrosis and inflammation. The polyphenol compound curcumin is the yellow pigment in curry, and has anti-inflammatory and anti-fibrotic properties. We here evaluated the effects of curcumin on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. The effects of curcumin on proliferation, alpha-smooth muscle actin gene expression, monocyte chemoattractant protein (MCP)-1 production, and collagen expression were examined. The effect of curcumin on the activation of freshly isolated cells in culture was also assessed. Curcumin inhibited platelet-derived growth factor (PDGF)-induced proliferation, alpha-smooth muscle actin gene expression, interleukin-1beta- and tumor necrosis factor (TNF)-alpha-induced MCP-1 production, type I collagen production, and expression of type I and type III collagen genes. Curcumin inhibited PDGF-BB-induced cyclin D1 expression and activation of extracellular signal-regulated kinase (ERK). Curcumin inhibited interleukin-1beta- and TNF-alpha-induced activation of activator protein-1 (AP-1) and mitogen-activated protein (MAP) kinases (ERK, c-Jun N-terminal kinase (JNK), and p38 MAP kinase), but not of nuclear factor-kappaB (NF-kappaB). In addition, curcumin inhibited transformation of freshly isolated cells to myofibroblast-like phenotype. In conclusion, curcumin inhibited key cell functions and activation of PSCs.
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PMID:Curcumin blocks activation of pancreatic stellate cells. 1629 27

Interleukin (IL)-6 is a proinflammatory cytokine assumed to participate in pancreatic fibrosis by activating pancreatic stellate cells (PSCs). Autocrine TGF-beta1 is to central in PSC functional regulation. In this study, we examined IL-6 secretion from culture-activated rat PSCs and its regulatory mechanism. Activated PSCs express and secrete IL-6. When anti-TGF-beta1 neutralizing antibody was added in the culture medium, IL-6 secretion from activated PSCs was inhibited, whereas exogenous TGF-beta1 added in the culture medium enhanced IL-6 expression and secretion by PSCs in a dose dependent manner. Infection of PSCs with an adenovirus expressing dominant-negative Smad2/3 attenuated basal and TGF-beta1-stimulated IL-6 expression and secretion of PSCs. We also demonstrated the reciprocal effect of PSCs-secreted IL-6 on autocrine TGF-beta1. Anti-IL-6 neutralizing antibody inhibited TGF-beta1 secretion from PSCs. Preincubation of cells with 10 nM PD98059, an extracellular signal-regulated kinase (ERK)-dependent pathway inhibitor, attenuated IL-6-enhanced TGF-beta1 expression and secretion of PSCs. In addition, IL-6 activated ERK in PSCs. These data indicate the existence of autocrine loop between IL-6 and TGF-beta1 through ERK- and Smad2/3-dependent pathways in activated PSCs.
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PMID:Existence of autocrine loop between interleukin-6 and transforming growth factor-beta1 in activated rat pancreatic stellate cells. 1659 47


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