Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.12.2 (MEK)
 18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, our laboratory reported that lactosylceramide (LacCer) stimulated human aortic smooth muscle cell proliferation via specific activation of p44 mitogen-activated protein kinase (MAPK) in the p21(ras)/Raf-1/MEK2 pathway and induced expression of the transcription factor c-fos downstream to the p44 MAPK signaling cascade (Bhunia A. K., Han, H., Snowden, A., and Chatterjee S. (1996) J. Biol. Chem. 271, 10660-10666). In the present study, we explored the role of free oxygen radicals in LacCer-mediated induction of cell proliferation. Superoxide levels were measured by the lucigenin chemiluminescence method, MAPK activity was measured by immunocomplex kinase assays, and Western blot analysis and c-fos expression were measured by Northern blot assay. We found that LacCer (10 microM) stimulates endogenous superoxide production (7-fold compared with control) in human aortic smooth muscle cells specifically by activating membrane-associated NADPH oxidase, but not NADH or xanthine oxidase. This process was inhibited by an inhibitor of NADPH oxidase, diphenylene iodonium (DPI), and by antioxidants, N-acetyl-L-cysteine (NAC) or pyrrolidine dithiocarbamate. NAC and DPI both abrogated individual steps in the signaling pathway leading to cell proliferation. For example, the p21(ras).GTP loading, p44 MAPK activity, and induction of transcription factor c-fos all were inhibited by NAC and DPI as well as an antioxidant pyrrolidine dithiocarbamate or reduced glutathione (GSH). In contrast, depletion of GSH by L-buthionine (S, R)-sulfoximine up-regulated the above described signaling cascade. In sum, LacCer, by virtue of activating NADPH oxidase, produces superoxide (a redox stress signaling molecule), which mediates cell proliferation via activation of the kinase cascade. Our findings may explain the potential role of LacCer in the pathogenesis of atherosclerosis involving the proliferation of aortic smooth muscle cells.
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PMID:Redox-regulated signaling by lactosylceramide in the proliferation of human aortic smooth muscle cells. 918 53

Ischemia/reperfusion (I/R) injury induces both functional and morphological changes in the kidney. Necrosis, predominantly of the proximal tubule (PT), is the hallmark of this model of renal injury, whereas cells of the distal nephron survive, apparently intact. We examined whether differences in cellular outcome of the various regions of the nephron may be due to segmental variation in the activation of the mitogen-activated protein kinases (MAPKs) in response to I/R injury. Whereas c-Jun N-terminal kinase (JNK) is activated in both the cortex and inner stripe of the outer medulla, the extracellular regulated kinase (ERK) pathway is activated only in the inner stripe in which thick ascending limb (TAL) cells predominate. These studies are consistent with the notion that ERK activation is essential for survival. To test this hypothesis directly, we studied an in vitro system in which manipulation of these pathways and their effects on cellular survival could be examined. Oxidant injury was induced in mouse PT and TAL cells in culture by the catabolism of hypoxanthine by xanthine oxidase. PT cells were found to be more sensitive than TAL cells to oxidative stress as assessed by cell counting, light microscopy, propidium iodide uptake, and fluorescence-activated cell sorting (FACS) analysis. Immunoprecipitation/kinase analysis revealed that JNK activation occurred in both cell types, whereas ERK activation occurred only in TAL cells. We then examined the effect of PD-098059, a MAP kinase kinase (MEK)-1 inhibitor of the ERK pathway, on PT and TAL survival. In TAL cells, ERK inhibition reduced cell survival nearly fourfold (P < 0.001) after oxidant exposure. In PT cells, activation of the ERK pathway by insulin-like growth factor I (IGF-I) increased survival by threefold (P < 0.001), and this IGF-I-enhanced cell survival was inhibited by PD-098059. These results indicate that cell survival in the kidney after ischemia may be dependent on ERK activation, suggesting that this pathway may be a target for therapeutic treatment in I/R injury.
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PMID:MAPK activation determines renal epithelial cell survival during oxidative injury. 1044 73

Conditioned medium from stimulated microglia and from the monocyte/macrophage cell line (RAW 264.7; MC-CM) promotes the differentiation of cholinergic neurons from undifferentiated progenitors in the septal nuclei and adjacent basal forebrain (BF). We have studied the regulation of this process by measuring the activity of choline acetyltransferase (ChAT) in cultured BF taken from embryonic day 16 rat brain. Inhibition of either xanthine oxidase with allopurinol or nitric oxide synthase with N(G)-monomethyl-l-arginine produces a small but significant improvement in the efficacy of MC-CM while inclusion of pyrrolidine dithiocarbamate, a hydroxyl radical scavenger widely used as an antioxidant, lowers MC-CM-induced ChAT activity. Addition of nerve growth factor (NGF) but not brain-derived neurotrophic factor or glial-derived neurotrophic factor together with MC-CM has a synergistic effect on both ChAT activity and ChAT mRNA, raising ChAT activity as much as 29-fold and ChAT mRNA almost 15-fold. While MC-CM raised mRNA for trkA, the effect was not synergistic with NGF. mRNA for the common neurotrophin receptor (p75NTR) showed a modest synergistic increase. Blockade of the Ras/Raf/ERK [extracellular signal-regulated kinase, also known as mitogen-activated protein [(MAP) kinase] signal transduction pathway with either PD28059 (an inhibitor of MAP kinase/ERK kinase kinase or MEK) or N-acetyl-S-farnesyl-l-cysteine (an inhibitor of Ras farnesylation and, hence, activation) inhibited the action of MC-CM. Moreover, a subpopulation of cells responded rapidly to MC-CM with an increased appearance of phosphorylated ERK. Because NGF also utilizes this pathway, synergy may occur along this signal transduction pathway.
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PMID:Macrophage cell-conditioned medium promotes cholinergic differentiation of undifferentiated progenitors and synergizes with nerve growth factor action in the developing basal forebrain. 1068 94

Acute lung injury is frequently associated with sepsis or blood loss and is characterized by a proinflammatory response and infiltration of activated neutrophils into the lungs. Hemorrhage or endotoxemia result in activation of cAMP response element-binding protein (CREB) and NF-kappa B in lung neutrophils as well as increased expression of proinflammatory cytokines, such as TNF-alpha and macrophage-inflammatory peptide-2, by these cells. Activation of the extracellular regulated kinase (ERK) pathway occurs in stress responses and is involved in CREB activation. In the present experiments, hemorrhage or endotoxemia produced increased activation of mitogen-activated protein kinase kinase (MEK)1/2 and ERK2 (p42), but not of ERK1 (p44), in lung neutrophils. ERK1, ERK2, and MEK1/2 were not activated in peripheral blood neutrophils after hemorrhage or endotoxemia. Inhibition of xanthine oxidase led to further increase in the activation of MEK1/2 and ERK2 in lung neutrophils after hemorrhage, but not after endotoxemia. Alpha-adrenergic blockade before hemorrhage resulted in increased activation in lung neutrophils of MEK1/2, ERK1, ERK2, and CREB, but decreased activation of NF-kappa B. In contrast, alpha-adrenergic blockade before endotoxemia was associated with decreased activation of MEK1/2, ERK2, and CREB, but increased activation of NF-kappa B. Beta-adrenergic blockade before hemorrhage did not alter MEK1/2 or ERK1 activation in lung neutrophils, but decreased activation of ERK2 and CREB, while increasing activation of NF-kappa B. Beta-adrenergic inhibition before endotoxemia did not affect activation of MEK1/2, ERK1, ERK2, CREB, or NF-kappa B. These data indicate that the pathways leading to lung neutrophil activation after hemorrhage are different from those induced by endotoxemia.
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PMID:Activation of extracellular signal-regulated kinases, NF-kappa B, and cyclic adenosine 5'-monophosphate response element-binding protein in lung neutrophils occurs by differing mechanisms after hemorrhage or endotoxemia. 1112 32

We recently reported that alpha(1)-adrenoceptor (alpha(1)-AR) stimulation induces hypertrophy via activation of the mitogen/extracellular signal-regulated kinase (MEK) 1/2-extracellular signal-regulated kinase (ERK) 1/2 pathway and generates reactive oxygen species (ROS) in adult rat ventricular myocytes (ARVM). Here we investigate the intracellular source of ROS in ARVM and the mechanism by which ROS activate hypertrophic signaling after alpha(1)-AR stimulation. Pretreatment of ARVM with the ROS scavenger Mn(III)terakis(1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP) completely inhibited the alpha(1)-AR-stimulated activation of Ras-MEK1/2-ERK1/2. Direct addition of H(2)O(2) or the superoxide generator menadione activated ERK1/2, which is also prevented by MnTMPyP pretreatment. We found that ARVM express gp91(phox), p22(phox), p67(phox), and p47(phox), four major components of NAD(P)H oxidase, and that alpha(1)-AR-stimulated ERK1/2 activation was blocked by four structurally unrelated inhibitors of NAD(P)H oxidase [diphenyleneiodonium, phenylarsine oxide, 4-(2-aminoethyl)benzenesulfonyl fluoride, and cadmium]. Conversely, inhibitors for other potential ROS-producing systems, including mitochondrial electron transport chain, nitric oxide synthase, xanthine oxidase, and cyclooxygenase, had no effect on alpha(1)-AR-stimulated ERK1/2 activation. Taken together, our results show that ventricular myocytes express components of an NAD(P)H oxidase that appear to be involved in alpha(1)-AR-stimulated hypertrophic signaling via ROS-mediated activation of Ras-MEK1/2-ERK1/2.
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PMID:Role of reactive oxygen species and NAD(P)H oxidase in alpha(1)-adrenoceptor signaling in adult rat cardiac myocytes. 1188 Feb 81

This study examines the effects of an increase in passive stretch in endothelium-removed bovine coronary artery on oxidant-induced changes in force generation. Increasing passive stretch on the arterial segments from 5 to 20 g for 20 minutes caused a subsequent increase (P<0.05) in force generation to 30 mmol/L KCl or 0.1 micromol/L serotonin compared with the prestretch control response. Also associated with the passive stretch were increases in superoxide detection by lucigenin and a selective increase in extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase phosphorylation measured by Western analysis. The stretch-induced increase in force generation was eliminated by inhibition of the ERK pathway by the MEK inhibitor PD98059 but not by inhibitors of the p38 MAP kinase pathway (SB202190) or c-Jun N-terminal protein kinase pathway (SP200169). Additionally, stretch-induced increases in both ERK phosphorylation and force generation were attenuated by inhibition of tyrosine kinases (genistein), src (PP2), and specific sites on the epidermal growth factor receptor (EGFR) (AG1478). Probes for oxidant signaling, including NAD(P)H oxidase inhibitors (diphenyliodonium and apocynin) or enhancement of peroxide consumption (ebselen) but not inhibition of xanthine oxidase (allopurinol), attenuated the effects of stretch on both ERK phosphorylation and force generation. Furthermore, stretch caused an increase in EGFR phosphorylation and cytosolic to membrane translocation of the p47phox NAD(P)H oxidase subunit. Hydrogen peroxide also elicited contraction through EGFR phosphorylation and ERK. In summary, stretch seems to enhance force generation via ERK signaling through an EGFR/src-dependent mechanism activated by peroxide derived from a stretch-mediated activation of the NAD(P)H oxidase, a response that may contribute to hypertensive alterations in vascular reactivity.
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PMID:Stretch enhances contraction of bovine coronary arteries via an NAD(P)H oxidase-mediated activation of the extracellular signal-regulated kinase mitogen-activated protein kinase cascade. 1252 17

Two-dimensional gel electrophoretic analysis of cell lysates from Brucella abortus 2308 and the isogenic hfq mutant Hfq3 revealed that the RNA binding protein Hfq (also known as host factor I or HF-I) is required for the optimal stationary phase production of the periplasmic Cu,Zn superoxide dismutase SodC. An isogenic sodC mutant, designated MEK2, was constructed from B. abortus 2308 by gene replacement, and the sodC mutant exhibited much greater susceptibility to killing by O(2)(-) generated by pyrogallol and the xanthine oxidase reaction than the parental 2308 strain supporting a role for SodC in protecting this bacterium from O(2)(-) of exogenous origin. The B. abortus sodC mutant was also found to be much more sensitive to killing by cultured resident peritoneal macrophages from C57BL6J mice than 2308, and the attenuation displayed by MEK2 in cultured murine macrophages was enhanced when these phagocytes were treated with gamma interferon (IFN-gamma). The attenuation displayed by the B. abortus sodC mutant in both resting and IFN-gamma-activated macrophages was alleviated, however, when these host cells were treated with the NADPH oxidase inhibitor apocynin. Consistent with its increased susceptibility to killing by cultured murine macrophages, the B. abortus sodC mutant also displayed significant attenuation in experimentally infected C57BL6J mice compared to the parental strain. These experimental findings indicate that SodC protects B. abortus 2308 from the respiratory burst of host macrophages. They also suggest that reduced SodC levels may contribute to the attenuation displayed by the B. abortus hfq mutant Hfq3 in the mouse model.
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PMID:The Brucella abortus Cu,Zn superoxide dismutase is required for optimal resistance to oxidative killing by murine macrophages and wild-type virulence in experimentally infected mice. 1584 93

Hemeoxygenase-1 (HO-1) is an oxidative stress responsive gene upregulated by various physiological and exogenous stimuli. HO-1 has cytoprotective activities and arsenite is a potent inducer of HO-1 in many cell types and tissues, including epidermal keratinocytes. We investigated the potential contributions of reactive oxygen species (ROS) generation and mitogen-activated protein kinase (MAPK) activation to arsenite-dependent regulation of HO-1 in HaCaT cells, an immortalized human keratinocyte line. Both epidermal growth factor (EGF) and arsenite stimulated ROS production was detected by dihydroethidium (DHE) staining and fluorescence microscopy. Arsenite induced HO-1 in a time- and concentration-dependent manner, while HO-1 expression in response to EGF was modest and evident at extended time points (48-72 h). Inhibition of EGF receptor, MEK I/II or Src decreased arsenite-stimulated HO-1 expression by 20-30%. In contrast, addition of a superoxide scavenger or inhibition of p38 activity decreased the arsenite-dependent response by 80-90% suggesting that ROS and p38 are required for HO-1 induction. However, ROS generation alone was insufficient for the observed arsenite-dependent response as use of a xanthine/xanthine oxidase system to generate ROS did not produce an equivalent upregulation of HO-1. Cooperation between ERK signaling and ROS generation was demonstrated by synergistic induction of HO-1 in cells co-treated with EGF and xanthine/xanthine oxidase resulting in a response nearly equivalent to that observed with arsenite. These findings suggest that the ERK/MAPK activation is necessary but not sufficient for optimal arsenite-stimulated HO-1 induction. The robust and persistent upregulation of HO-1 may have a role in cellular adaptation to chronic arsenic exposure.
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PMID:Contributions of reactive oxygen species and mitogen-activated protein kinase signaling in arsenite-stimulated hemeoxygenase-1 production. 1719 36

PD98059 and U0126 are organic compound inhibitors frequently used to block the activity of the MEK-1/2 protein kinase. In the present work, promoter activation analyses of xanthine oxidoreductase (XOR) in epithelial cells uncovered the unexpected opposite effect of these inhibitors on activation of XOR. Activation of an XOR-luciferase fusion gene was studied in stably transfected epithelial cells. The XOR reporter gene was activated by the epidermal growth factors (EGF), prolactin, and dexamethasone and by the acute phase cytokines (APC) IL-1, IL-6, and TNFalpha as previously reported for its native gene, and insulin further stimulated activation induced with acute phase cytokines or growth factors. Activation of the proximal promoter was blocked by inhibitors of the glucocorticoid receptor (GR), p38 MAP kinase, and U0126. Unexpectedly, PD98059 activated the promoter and significantly enhanced expression induced by insulin, APC, or growth factors. Analysis of the XOR upstream DNA and proximal promoter revealed primary roles for the GR and STAT3 in mediating the effects of PD98059 on XOR activation and protein complex formation with the promoter. STAT3 phosphotyrosine-705 was rapidly induced by PD98059, dexamethasone, and insulin. XOR activation by PD98059, dexamethasone, or insulin was superinduced by a constitutively active derivative of STAT3, while a dominant negative derivative of STAT3 blocked the enhancing effect of PD98059 on XOR activation. These data demonstrate a previously unrecognized effect of PD98059 on STAT3 and the GR that could have unanticipated consequences when used to infer the involvement of the MEK-1/2 protein kinase.
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PMID:PD98059 enhanced insulin, cytokine, and growth factor activation of xanthine oxidoreductase in epithelial cells involves STAT3 and the glucocorticoid receptor. 1737 Mar 12

Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis. We have previously shown that MPs from apoptotic T cells induce endothelial dysfunction, but the mechanisms implicated are not completely elucidated. In this study, we dissect the pathways involved in endothelial cells with respect to both NO and reactive oxygen species (ROS). Incubation of endothelial cells with MPs decreased NO production that was associated with overexpression and phosphorylation of endothelial NO synthase (eNOS). Also, MPs enhanced expression of caveolin-1 and decreased its phosphorylation. Microparticles enhanced ROS by a mechanism sensitive to xanthine oxidase and P-IkappaBalpha inhibitors. PI3K inhibition reduced the effects of MPs on eNOS, but not on caveolin-1, whereas it enhanced the effects of MPs on ROS production. Microparticles stimulated ERK1/2 phosphorylation via a PI3K-depedent mechanism. Inhibition of MEK reversed eNOS phosphorylation but had no effect on ROS production induced by MPs. In vivo injection of MPs in mice impaired endothelial function. In summary, MPs activate pathways related to NO and ROS productions through PI3K, xanthine oxidase, and NF-kappaB pathways. These data underscore the pleiotropic effects of MPs on NO and ROS, leading to an increase oxidative stress that may account for the deleterious effects of MPs on endothelial function.
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PMID:Phosphatidylinositol 3-kinase and xanthine oxidase regulate nitric oxide and reactive oxygen species productions by apoptotic lymphocyte microparticles in endothelial cells. 1835 28


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