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)

Alcohol is a major cause of both acute and chronic pancreatitis. Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic inflammation and fibrosis. Herein, we examined the effect of ethanol and acetaldehyde on the activation of transcription factors and mitogen-activated protein (MAP) kinases in PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. PSCs were treated with ethanol and acetaldehyde at clinically relevant concentrations (50 mM and 200 microM, respectively). Ethanol and acetaldehyde activated activator protein-1 but not nuclear factor-kappaB. In addition, they activated three classes of MAP kinases: extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase/stress-activated protein kinase, and p38 MAP kinase. Ethanol- and acetaldehyde-induced activation of activator protein-1 and MAP kinases was blocked by the antioxidant N-acetyl-cysteine, suggesting a role of oxidative stress in the signal transduction. Ethanol and acetaldehyde induced alpha1(I) procollagen gene expression but did not induce intercellular adhesion molecule-1 and monocyte chemoattractant protein-1. The acetaldehyde-induced increase of alpha1(I) procollagen gene expression was inhibited by the p38 MAP kinase inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole (SB203580) but not by the MAP kinase inhibitor 2'-amino-3'-methoxyflavone (PD98059). Specific activation of these signal transduction pathways may play a role in the pathogenesis of alcohol-induced pancreatic injury.
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PMID:Alcohol activates activator protein-1 and mitogen-activated protein kinases in rat pancreatic stellate cells. 1206 97

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

Matrix metalloproteinases (MMPs) are the proteases involved in the degradation of the extracellular matrix. MMP-1 is thought to be one of the key enzymes in fibrolysis, a process closely related to tissue remodeling. In the present study, we investigated MMP-1 secretion from human pancreatic periacinar myofibroblasts in response to pro-inflammatory cytokines IL-1beta and TNF-alpha. We also attempted to clarify the intracellular signaling pathways mediating the cytokine-induced MMP-1 secretion. MMP-1 secretion was measured by an enzyme-linked immunosorbent assay. MMP-1 molecules were analyzed by Western blotting. MMP-1 mRNA expression was evaluated by Northern blotting. IL-1l and TNF-alpha stimulated the MMP-1 secretion in a dose- and time-dependent manner. Ninety percent of MMP-1 was secreted as inactive form (pro-MMP-1). The effects of IL-1beta and TNF-alpha were significantly inhibited by PD98059 MEK/ERK inhibitor). In contrast, SB203580 (p38 MAPK inhibitor), GF109203X (PKC inhibitor), and PDTC (NF-kappaB inhibitor) did not alter the MMP-1 secretion induced by IL-1beta and TNF-alpha. These effects were also observed at them RNA level. In conclusion, in human pancreatic periacinar myofibroblasts, MMP-1 secretion was regulated by the pro-inflammatory cytokines via the MEK/ERK cascade. Thus, human pancreatic periacinar myofibroblasts may play an important role in the remodeling of damaged pancreatic tissue in chronic pancreatitis via MMP-1 secretion.
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PMID:Pro-inflammatory cytokine-induced matrix metalloproteinase-1 (MMP-1) secretion in human pancreatic periacinar myofibroblasts. 1452 52

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

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

Galectin-1 is a beta-galactoside-binding lectin. Previous studies have shown that galectin-1 was expressed in fibroblasts of chronic pancreatitis and of desmoplastic reaction associated with pancreatic cancer. These fibroblasts are now recognized as activated pancreatic stellate cells (PSCs). Here, we examined the role of galectin-1 in cell functions of PSCs. PSCs were isolated from rat pancreatic tissue and used in their culture-activated phenotype unless otherwise stated. Expression of galectin-1 was assessed by Western blot analysis, RT-PCR, and immunofluorescent staining. The effects of recombinant galectin-1 on chemokine production and proliferation were evaluated. Activation of transcription factors was assessed by EMSA. Activation of MAPKs was examined by Western blot analysis using anti-phosphospecific antibodies. Galectin-1 was strongly expressed in culture-activated but not freshly isolated PSCs. Recombinant galectin-1 increased proliferation and production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1. Galectin-1 activated ERK, JNK, activator protein-1, and NF-kappaB, but not p38 MAPK or Akt. Galectin-1 induced proliferation through ERK and chemokine production mainly through the activation of NF-kappaB and in part by JNK and ERK pathways. These effects of galectin-1 were abolished in the presence of thiodigalactosie, an inhibitor of beta-galactoside binding. In conclusion, our results suggest a role of galectin-1 in chemokine production and proliferation through its beta-galactoside binding activity in activated PSCs.
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PMID:Galectin-1 induces chemokine production and proliferation in pancreatic stellate cells. 1637 24

Pancreatic stellate cells (PSC) are now recognized as the key mediators of pancreatic fibrosis, a characteristic feature of chronic pancreatitis. The role of PSC in alcoholic pancreatic fibrosis has been examined in vivo (using pancreatic tissue from patients with alcohol-induced chronic pancreatitis and from animal models of experimental pancreatitis) and in vitro (using PSC in culture). These studies indicate that PSC are activated early in the course of pancreatic injury and are the predominant source of collagen in the fibrotic pancreas. The factors responsible for mediating PSC activation during chronic alcohol exposure include ethanol, its metabolite acetaldehyde, oxidant stress and cytokines (released during episodes of alcohol-induced pancreatic necroinflammation). Most recently, the intracellular signaling mechanisms regulating ethanol-induced PSC activation have been identified and include the mitogen-activated protein kinase (MAPK) pathway, phosphatidylinositol-3-kinase (PI3K) and protein kinase C (PKC), and the transcription factor activator protein-1 (AP-1).
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PMID:Battle-scarred pancreas: role of alcohol and pancreatic stellate cells in pancreatic fibrosis. 1695 84

Tyrosine kinase receptors such as members of the epidermal growth factor receptor family and their respective ligands are frequently overexpressed in pancreatic cancer as well as in chronic pancreatitis. In this study, the role of ErbB2 in the exocrine pancreas was examined by ectopic overexpression under the control of the proximal rat elastase promoter. Three independent transgenic mouse lines overexpressing ErbB2 were established by pronuclear injection. Pancreatic mRNA and protein levels were analyzed by real time PCR, immunohistochemistry and immunoblot analysis, RAS activity by using a specific immunoprecipitation assay and various kinase activities by phosphospecific antibodies. Overexpression of ErbB2 in the exocrine pancreas resulted in increased RAS activity and downstream activation of ERK1/2, but not in transgenic increased proliferation of acinar and ductal cells. At later timepoints, some mice showed focal areas of acinar cell damage with upregulated mRNA levels for Cyclin D1 and p16(INK4a). Despite the increased mRNA level, cyclin D1 protein levels were downregulated. We observed areas of focal infiltrations with inflammatory cells interspersed in the exocrine pancreas. NF-kappaB activity was induced in transgenic acinar cells compared with controls contributing to high levels of chemokine and cytokine gene expression such as CCR-1 and CCL3. These data suggest that overexpression of ErbB2 in acinar cells leads to increased RAS activity without cell cycle progression and mediates inflammation via NF-kappaB. We conclude that the biological response of ErbB2/RAS signaling depends highly on cellular context.
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PMID:Overexpression of ErbB2 in the exocrine pancreas induces an inflammatory response but not increased proliferation. 1754 89

Local tissue pressure is higher in chronic pancreatitis than in the normal pancreas. We reported recently that pressure application induces synthesis of extracellular matrix (ECM) and cytokines in pancreatic stellate cells (PSCs) and that epigallocatechin gallate (EGCG), a potent antioxidant, inhibits the transformation of PSCs from quiescent to activated phenotype and ethanol-induced synthesis of ECM and cytokines in PSCs. These results suggest that oxidative stress and reactive oxygen species (ROS) are important in PSC activation. The aim of this study was to clarify the effects of ROS on activation and functions of pressure-stimulated PSCs. We used freshly isolated rat PSCs and culture-activated PSCs. Pressure was applied on rat cultured PSCs by adding compressed helium gas into a pressure-loading apparatus. PSCs were cultured with or without antioxidants (EGCG and N-acetyl cysteine) under normal or elevated pressure. Externally applied high pressure (80 mmHg) resulted in a gradual decrease of superoxide dismutase activity in PSCs and increased intracellular ROS generation as early as 30 s, reaching a peak level at 1 h. Antioxidants significantly inhibited ROS generation. Pressure increased the expression levels of alpha-smooth muscle actin, alpha(1)(I)-procollagen, and TGF-beta1 in PSCs. EGCG suppressed these alterations, abolished pressure-induced phosphorylation of p38 MAPK, and suppressed pressure-induced PSC transformation to activated phenotype. Our results indicated that ROS is a key player in pressure-induced PSC activation and ECM synthesis. Antioxidants could be potentially effective against the development of pancreatic fibrosis in patients with chronic pancreatitis.
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PMID:Externally applied pressure activates pancreatic stellate cells through the generation of intracellular reactive oxygen species. 1776 38


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