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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent evidence shows the involvement of reactive oxygen species (ROS) in the mitogenic cascade initiated by the tyrosine kinase receptors of several growth factor peptides. We have asked whether also the vascular endothelial growth factor (VEGF) utilizes ROS as messenger intermediates downstream of the VEGF receptor-2 (VEGFR-2)/KDR receptor given that the proliferation of endothelial cells during neoangiogenesis is physiologically regulated by oxygen and likely by its derivative species. In porcine aortic endothelial cells stably expressing human KDR, receptor activation by VEGF is followed by a rapid increase in the intracellular generation of hydrogen peroxide as revealed by the peroxide-sensitive probe dichlorofluorescein diacetate. Genetic and pharmacological studies suggest that such oxidant burst requires as upstream events the activation of phosphatidylinositol 3-kinase and the small GTPase Rac-1 and is likely initiated by lipoxygenases. Interestingly, ROS generation in response to VEGF is not blocked but rather potentiated by endothelial nitric-oxide synthase inhibitors diphenyleneiodonium and N(G)methyl-l-arginine, ruling out the possibility of nitric oxide being the oxidant species here detected in VEGF-stimulated cells. Inhibition of KDR-dependent generation of ROS attenuates early signaling events including receptor autophosphorylation and binding to a phospholipase C-gamma-glutathione S-transferase fusion protein. Moreover, catalase, the lipoxygenase inhibitor nordihydroguaiaretic acid, the synthetic ROS scavenger EUK-134, and phosphatidylinositol 3-kinase inhibitor wortmannin all reduce ERK phosphorylation in response to VEGF, and antioxidants prevent VEGF-dependent mitogenesis. Finally, cell culture and stimulation in a nearly anoxic environment mimic the effect of ROS scavenger on receptor and ERK phosphorylation, reinforcing the idea that ROS are necessary components of the mitogenic signaling cascade initiated by KDR. These data identify ROS as a new class of intracellular angiogenic mediators and may represent a potential premise for new antioxidant-based antiangiogenic therapies.
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PMID:Reactive oxygen species as downstream mediators of angiogenic signaling by vascular endothelial growth factor receptor-2/KDR. 1171 8

Methylglyoxal (MG), a reactive dicarbonyl produced during glucose metabolism, is known as a preferred substrate of aldose reductase (AR; AKR1B1) that concomitantly catalyzes the reduction of glucose in the polyol pathway. MG modifies cellular proteins to form cross-links of amino groups, generating so-called advanced glycation end products. Increased rates of MG formation under hyperglycemic conditions and ensuing high serum levels of MG are reported in diabetic patients. As involvement of AR in the pathogenesis of diabetic complications has been suggested, we investigated the effects of MG on AR activity using cultured vascular smooth muscle cells (SMC) isolated from rat aorta. MG-induced a dose- and time-dependent increase in AR mRNA levels to a maximum of 4.5-fold. This increase in mRNA was accompanied by elevated enzyme activity and protein levels. Pretreatment of SMC with N-acetyl-L-cysteine significantly suppressed the MG-induced AR expression, while DL-buthionine-(S,R)-sulfoximine further augmented the MG-induced increase in AR mRNA level. Intracellular levels of reactive oxygen species determined using 2',7'-dichlorofluorescein diacetate were significantly elevated in SMC treated with MG, suggesting the involvement of oxidative stress in this process. Under oxidative stress generated by hydrogen peroxide, the major signaling pathway mediating the up-regulation of AR expression was demonstrated to be the epidermal growth factor receptor-ERK pathway. In contrast, the p38 kinase pathway appears to mediate MG-induced AR expression. The cytotoxic effect of MG was significantly enhanced in the presence of the AR inhibitor ponalrestat, indicating a protective role of AR against MG-induced cell damage.
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PMID:Up-regulation of aldose reductase by the substrate, methylglyoxal. 1260 18

Diabetic neuropathies, affecting the autonomic, sensory, and motor peripheral nervous system, are among the most frequent complications of diabetes. The symptoms of diabetic polyneuropathies are multi-faceted; the etiology and the underlying mechanisms are as yet unclear. Clinical studies established a significant correlation between the control of the patients' blood glucose level and the severity of the damage to the peripheral nervous system. Recent in vitro studies suggest that elevated glucose levels induced dysfunction and apoptosis in cultured cells of neuronal origin, possibly through the formation of reactive oxygen species (ROS). Based on these results, we hypothesized that elevated glucose levels impair neuronal survival and function via ROS dependent intracellular signaling pathways. In order to test this hypothesis, we cultured neural crest-derived PC12 pheochromocytoma cells under euglycemic (5 mM) and hyperglycemic (25 mM) conditions. Continuous exposure of undifferentiated PC12 cells for up to 72 h to elevated glucose induced the enhanced generation of ROS, as assessed from the increase in the cell-associated fluorescence of the ROS-sensitive fluorogenic indicator, 2,7-dichlorodihydrofluorescein diacetate. In cells cultured in high glucose, both basal and secretagogue-stimulated catecholamine release were enhanced. Furthermore, high glucose, reduced (by ca. 30%) the rate of cell proliferation and enhanced the occurrence of apoptosis, as assessed by DNA fragmentation, TUNEL assay and the activation of an apoptosis-specific protease, caspase CCP32. Elevated glucose levels significantly attenuated nerve growth factor (NGF)-induced neurite extension, as quantitated by computer-aided image analysis. Culturing PC12 cells in high glucose resulted in alterations in basal and NGF-stimulated mitogen-activated protein kinase (MAPK) signaling pathways, specifically in a switch from the neuronal survival/differentiation-associated MAPK ERK to that of apoptosis/stress-associated MAPK p38 and JNK. Based on our results we present a model in which the prolonged, excess formation of ROS represents a common mechanism for hyperglycemia-induced damage to neuronal cells. We propose that this simple in vitro system might serve as an appropriate model for evaluating some of the effects of elevated glucose on cultured cells of neuronal origin.
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PMID:Reactive oxygen species, apoptosis and altered NGF-induced signaling in PC12 pheochromocytoma cells cultured in elevated glucose: an in vitro cellular model for diabetic neuropathy. 1471 73

This study investigates the effects of one of the most frequently used brominated flame-retardants (BFR), tetrabromobisphenol-A (TBBPA), on formation of reactive oxygen species (ROS) and calcium levels in human neutrophil granulocytes. TBBPA enhanced ROS production in a concentration-depended manner (1-12 microM), measured as 2,7-dichlorofluorescein diacetate amplified (DCF) fluorescence. The results on ROS production by TBBPA was confirmed by lucigenin-amplified chemiluminescence. The TBBPA induced formation of ROS was due to activation of respiratory burst, as shown by the NADPH oxidase inhibitor DPI (10 microM). TBBPA induced activation of respiratory burst was also inhibited by the MEK 1/2 inhibitor U0126 (10 microM), the PKC inhibitor BIM (0.25 microM), and the tyrosine kinase inhibitor erbstatin-A (25 microM). We also found a small reduction in ROS formation in the absence of extracellular calcium and when verapamil was added. The phosphorylation of ERK 1/2 was confirmed by Western blotting. TBBPA also induced a concentration dependent increase in intracellular free calcium measured with Fura-2/AM. We suggest that exposure of human neutrophil granulocytes to the brominated flame retardant TBBPA leads to an activation of the NADPH oxidase primarily by an ERK 1/2 stimulated pathway. The data also show that PKC, calcium, and tyrosine kinases may be involved in the activation.
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PMID:The effect of a brominated flame retardant, tetrabromobisphenol-A, on free radical formation in human neutrophil granulocytes: the involvement of the MAP kinase pathway and protein kinase C. 1545 14

Matrix metalloproteinases (MMPs), aldosterone, and reactive oxygen species (ROS) are implicated in myocardial remodeling. Although ROS, cytokines, and neurohormones regulate MMP in cardiac fibroblasts, it is unknown whether aldosterone regulates MMP in cardiomyocytes. Therefore, we tested the hypothesis that aldosterone regulates MMP in cultured adult rat ventricular myocytes (ARVMs). ARVMs were treated with aldosterone for 24 hours, and MMP-2 and MMP-9 activities were measured by zymography. Aldosterone (50 nmol/L) increased MMP-2 (43+/-5%) and MMP-9 (55+/-15%; P<0.001 for both) activities. Pretreatment with spironolactone (100 nmol/L) abolished the aldosterone-induced increase in MMP activities. Aldosterone (50 nmol/L; 30 minutes) increased mitogen/extracellular signal-regulated kinase (MEK) (31+/-3%) and extracellular signal-regulated kinase 1/2 (ERK1/2; 41+/-7%; P<0.001 for both) phosphorylation. U0126 (10 micromol/L), an MEK1/2 inhibitor, abolished the aldosterone-induced increase in MMP activities. Aldosterone increased intracellular ROS as assessed by dichlorofluorescein diacetate (27+/-4%; P<0.05). This increase was inhibited by apocynin, an NADPH oxidase inhibitor. Apocynin likewise inhibited aldosterone-induced ERK1/2 phosphorylation and the increase in MMP activities. Furthermore, the antioxidants MnTMPyP and N-acetylcysteine inhibited the aldosterone-induced increase in ERK1/2 phosphorylation and MMP activities, respectively. Protein kinase C (PKC) is implicated in the nongenomic effects of aldosterone. To test the role of PKC, ARVMs were pretreated with chelerythrine, a PKC inhibitor. Chelerythrine prevented the aldosterone-induced increase in ERK1/2 phosphorylation and MMP activities. Thus, aldosterone induces MMP activity in ARVM via activation of the mineralocorticoid receptor, PKC, and ROS-dependent activation of the MEK/ERK pathway. NADPH oxidase is a likely source of ROS in this system.
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PMID:Aldosterone stimulates matrix metalloproteinases and reactive oxygen species in adult rat ventricular cardiomyocytes. 1604 62

Isothiocyanates (ITCs) are potentially important cancer chemopreventive compounds found in cruciferous vegetables. In this study, three ITCs: allyl ITC, benzyl ITC and phenylethyl ITC, induced DNA cell-cycle changes and cell death in undifferentiated Caco-2 cells and their roles in PI3K/Akt and MEK/ERK signaling pathways have been investigated. Flow cytometric analysis was used to measure cell-cycle distribution, expression of mitotic marker (phosphorylated H3 histone), mitochondrial transmembrane potential for the determination of ITC-induced apoptosis measured by Annexin V-FITC staining and metabolic conversion of fluorescein diacetate, and quantification of sub-G1 population. Cellular MAPK and phosphorylated MAPK were measured using western blot analysis. All ITCs tested induced G2/M cell-cycle arrest after 24-h treatment, a time- and concentration-dependent activation of ERK1/2, dissipation of mitochondrial transmembrane potential and apoptosis. Both PI3K/Akt and MEK/ERK inhibitors, LY294002 and PD98059, attenuated the extent of BITC-induced cell death. Pretreatment of cells with either the PD98059 or LY294002 inhibitor, caused a dose-dependent inhibition of histone H3 (p-H3) phosphorylation. Despite the LY294002 inhibitor having no effect on the proportion of ITC-induced G2/M arrested cells, a significant decrease of p-H3/(G2/M) ratio in both PD98059- and LY294002-treated cells was observed. We suggest that the decrease of mitotic cells was compensated for by an increase of cells in G2 phase. LY294002 and PD98059 affect cell transition from G2 to M phase and from S to G2 phase respectively. These results indicate that isothiocyanates can induce cell cycle-change through multiple signaling pathways and more detailed study is merited to further unravel the chemopreventive and chemotherapeutic mechanisms of ITCs.
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PMID:Effects of MEK1 and PI3K inhibitors on allyl-, benzyl- and phenylethyl-isothiocyanate-induced G2/M arrest and cell death in Caco-2 cells. 1621 Dec 42

The effect of synthetic isothiocyanate ethyl-4-isothiocyanatobutanoate (E-4IB) on survival of mismatch repair-proficient TK6 and -deficient MT1 cell lines as well as the influence of proteasomal inhibitor MG132, caspase inhibitor Z-VAD-fmk, and ATM inhibitor caffeine on E-4IB modulation of cell cycle and apoptosis was evaluated. Flow cytometric analyses of DNA double strand breaks (gamma-H2AX), mitotic fraction (phospho-histone H3), cell cycle modulation, apoptosis induction (sub-G(0) fraction and fluorescein diacetate staining), and dissipation of transmembrane mitochondrial potential (JC-1 staining) were performed. Western blotting was used for the evaluation of ERK activation, expression of p53, p21(cip1/waf1) and GADD45alpha proteins, as well as PARP fragmentation. Analysis of mitotic nuclei was performed for chromosomal aberrations assessment. MT1 cells were more resistant to E-4IB treatment then TK6 cells (IC(50) 8 muM vs. 4 muM). In both cell lines E-4IB treatment induced phosphorylation of H2AX, increase of p53 protein level, phospho-histone H3 staining, and G(2)/M arrest. The sub-G(0) fragmentation was accompanied by PARP degradation, decreased mitochondrial transmembrane potential, and diminished p21(cip1/waf1) protein expression in TK6 cells. Caspase inhibitor Z-VAD-fmk decreased E-4IB induced sub-G(0) fragmentation and extent of apoptosis in TK6 cells, while proteasome inhibitor MG132 increased number of apoptotic cells in both cell lines tested. A number of aberrant metaphases and clastogenic effect of high E-4IB concentration was observed. The synthetic isothiocyanate E-4IB induced DNA strand breaks, increased mitotic fraction and apoptosis potentiated by MG132 inhibitor in both mismatch repair-proficient and -deficient cell lines.
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PMID:Apoptotic effect of ethyl-4-isothiocyanatobutanoate is associated with DNA damage, proteasomal activity and induction of p53 and p21cip1/waf1. 1683 Feb 28

Alveolar macrophages (AM) have an important role in clearing particles from the lungs. In response to different stimuli they can release reactive oxygen species (ROS) and inflammatory mediators and promote pulmonary inflammation. We exposed rat AM to carbon black (CB) particles (0.63-20 microg/ml) and measured the eneration of ROS by using the fluorescent probe 2',7'-dichlorofluorescein diacetate. Fluorescence was elevated in a concentration dependent manner in the AM exposed to CB. Follow-up experiments using a series of enzyme inhibitors indicate that the ERK MAP kinase pathway and the p38 MAP kinase pathway may be involved in the formation of ROS.
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PMID:Carbon black particles increase reactive oxygen species formation in rat alveolar macrophages in vitro. 1711 25

Libraries of siloxane-polyurethane coatings were designed, formulated, and screened using high-throughput experimentation. Four independent variables that were analyzed were the molecular weight of poly(dimethylsiloxane) (PDMS), presence or absence of poly(epsilon-caprolactone) (PCL) blocks attached to the PDMS backbone, the length of the PCL blocks, and the siloxane polymer level in the coating formulations. In addition to the siloxane libraries (3-aminopropyl-terminated PDMS and poly(epsilon-caprolactone)-poly(dimethylsiloxane)-poly(epsilon-caprolactone) (PCL-PDMS-PCL) triblock copolymers), the coating formulation included a trifunctional isocyanate crosslinker, trifunctional poly(epsilon-caprolactone) polyol, 2,4-pentanedione (pot-life extender), dibutyltin diacetate (catalyst), and a blend of solvents. The resulting coatings were analyzed for their surface energy and pseudobarnacle adhesion both before and after aging the coatings for 30 days in water. The water and methylene iodide contact angle averages increase with increasing molecular weight of PDMS. Coatings prepared from PCL-PDMS-PCL triblock copolymers have lower surface energies than coatings prepared from 3-aminopropyl-terminated PDMS; however, lower pseudobarnacle adhesion results were obtained for the coatings prepared from 3-aminopropyl-terminated PDMS than coatings prepared from PCL-PDMS-PCL triblock copolymers. The siloxane polymer level in the coating formulations does not have a significant effect on the surface energy of the coatings, but it resulted in higher pseudobarnacle adhesion.
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PMID:Combinatorial and high-throughput screening of the effect of siloxane composition on the surface properties of crosslinked siloxane-polyurethane coatings. 1720 46

Cholesteatoma is a destructive ear condition requiring complete surgical removal. One major problem lies in the frequent occurrence of residual cholesteatoma caused by squamous epithelium remaining in the middle ear. Our aim is to develop a laser treatment that is selectively directed against residual cholesteatoma cells and can be performed after cholesteatoma surgery in the same session. In a first trial, we studied the photodynamic effect of argon (AL) and diode lasers (DL) on cholesteatoma tissue. Intraoperatively harvested monolayer-cultured cholesteatoma cells were stained in vivo with different absorption enhancers: neutral red (NR), fluorescein diacetate (FDA), and indocyanine green (ICG). In vitro, staining tests on enhanced cellular dye absorption and laser tests were followed by cytotoxicity measurements to determine the respective amount of damage. To achieve selective cell destruction, antibody-mediated staining of cholesteatoma and middle ear mucosa cells was examined in a second trial. Cell cultures (cytospin and coverglass growing) and paraffin-embedded cholesteatoma tissue sections were studied immunohistochemically to determine the binding of monoclonal mouse antibodies against human cytokeratins CK5, CK10, CK14 and the epidermal growth factor receptor EGFR. Intracellular staining with absorption enhancers increased the optical density at the wavelength corresponding to the dye. Staining and subsequent laser irradiation destroyed up to 92% of cultured cholesteatoma cells. Unstained irradiated tissue was not affected. In cytospins, the antibody against CK5/6 showed strong staining of cholesteatoma and weak staining of mucosa cells. Reactivity for CK14 and EGFR was positive in both tissues. In coverglass cultures, staining of cholesteatoma cells was positive for CK5/6, CK14 and EGFR. Mucosa cells were positive for EGFR but negative for cytokeratins. Both cell types were negative for CK10. In embedded cholesteatoma tissue, CK5/6 and CK14 were localized in the basal layers of the matrix, while CK10 was situated in the suprabasal layers, and EGFR was present in all layers of the matrix and perimatrix. As for the technical aspects of laser-assisted cholesteatoma surgery, AL and DL have proved to be suitable devices; ICG and FDA are effective nontoxic absorption enhancers. The investigated antibodies against cytokeratins and EGFR show nonselective staining and thus appear to be inappropriate for avoiding unwanted cell damage. For safe and specific intraoperative application to intact tissue, the chromophore should be coupled to a particular antibody that binds solely to an easily accessible specific antigen at the surface of cholesteatoma cells.
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PMID:Laser-assisted cholesteatoma surgery: technical aspects, in vitro implementation and challenge of selective cell destruction. 1825 41


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