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:1.6.99.6 (NADPH oxidase)
10,295 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of neutrophil oxidases, including NADPH oxidase, is Ca2+ dependent. The aim of this study was to determine the roles of intra- and extracellular Ca2+, leading to generation of the respiratory burst, as monitored by luminol-dependent chemiluminescence (CL). All results were recorded as integrals (millivolt.min) and compared by a two-tail Student's t test. Preincubation of cells with chelators of intra- or extracellular Ca2+ inhibited N-Formyl-Met-Leu-Phe (FMLP)-stimulated burst activity (p < 0.01). In contrast, stimulation by phorbol myristate acetate (PMA), while inhibited by extracellular Ca2+ chelation with EGTA (p < 0.001), was potentiated by intracellular Ca2+ chelation with BAPTA (p < 0.01). This suggests that the protein kinase C (PKC)-mediated burst may be diminished by intracellular Ca(2+)-dependent phosphatase. A selective inhibitor of tyrosine phosphatase, sodium vanadate, potentiated CL generation by both FMLP and PMA, indicating a dominant phosphatase activation with transiently increased Ca2+, masking the kinase-mediated respiratory burst. The selective inhibitors of PKC or tyrosine kinase prevented PMA and vanadate/PMA stimulation (p < 0.005). Furthermore, the putative Ca2+ channel agonists glutamate (10(-5)M) and N-methyl-D-aspartate (NMDA) (10(-5)M) alone failed to influence CL output, but produced marked potentiation following pre-treatment with vanadate. Again this indicates a dominant activation of phosphatase triggered by the glutamate-mediated Ca2+ influx, so masking the kinase-dependent NADPH oxidase activity. A competitive antagonist of NMDA, AP7, significantly decreased vanadate-mediated CL in an EGTA-sensitive manner (p < 0.001). The data confirm a requirement for intra- and extracellular Ca2+ in neutrophil respiratory burst activation via the kinase/phosphatase cycle, and an agonist effect by NMDA within the Ca2+ cascade mechanism.
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PMID:Activation of the neutrophil respiratory burst requires both intracellular and extracellular calcium. 970 67

This study reviews the putative mechanism of ethanol (ETOH)-mediated downregulation of inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) and protein and upregulation of constitutive NOS activity (ecNOS) in immunocompetent cells and endothelium, in vivo. Current evidence supports the hypothesis that ETOH inhibits the phospholipase D-tyrosine kinase pathway involved in the phosphorylation and activation of NADPH oxidase and myeloperoxidase, which upregulates the formation of reactive oxygen intermediates and mitogen-activated protein kinase cascade, including the extracellular receptor-linked kinase 1 and 2 (erk1 and erk2). This decreases reactive oxygen intermediate formation, tyrosine kinase-induced phosphorylation, and activation of transcription factors that, in turn, decreases the expression of iNOS mRNA. Also, ETOH-mediated attenuation of endotoxin-induced downregulation of nuclear protein kinase C activity appears to decrease the stability of expressed iNOS mRNA. ETOH-mediated inhibition of tyrosine kinase activity may also explain the ability of ETOH to upregulate ecNOS enzymatic activity, because tyrosine kinase activity suppresses ecNOS enzymatic activity.
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PMID:The potential mechanism of induction of inducible nitric oxide synthase mRNA in alveolar macrophages by lipopolysaccharide and its suppression by ethanol, in vivo. 972 48

Caspase-3(-like) proteases play important roles in controlling mammalian apoptosis. However, the downstream events from the caspase-3(-like) protease activation to death of cells are still unclear. Previously, we reported that hydrogen peroxide (H2O2) was generated by the activation of caspase-3(-like) proteases in the process of tyrosine kinase inhibitor-induced apoptosis in human small cell lung carcinoma Ms-1 cells. In the present study, we examined whether generation of H2O2 is a critical event for the apoptotic pathway downstream of caspase-3(-like) protease activation by various anticancer drugs. Anticancer drugs such as camptothecin, vinblastine, inostamycin, and adriamycin induced activation of caspase-3(-like) proteases and apoptosis. Generation of H2O2 was commonly detected after treatment with each of the four anticancer drugs, and scavenging of H2O2 caused cells to fail to undergo apoptosis. Moreover, anticancer drug-induced H2O2 production was inhibited not only by an inhibitor of caspase-3(-like) proteases but also by diphenyleneiodonium chloride, an inhibitor of flavonoid-containing enzymes such as NADPH oxidase. However, activation of caspase-3(-like) proteases was not inhibited by diphenyleneiodonium chloride. These findings suggest that activation of caspase-3(-like) proteases by various anticancer drugs causes generation of H2O2 presumably through the activation of NADPH oxidase, thereby inducing apoptosis. Therefore, H2O2 may function as a common mediator for apoptosis induced by various anticancer drugs.
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PMID:Requirement of caspase-3(-like) protease-mediated hydrogen peroxide production for apoptosis induced by various anticancer drugs. 975 37

Exposure of guinea-pig eosinophils to leukotriene B4 (LTB4; 1 microM) resulted in a rapid generation of H2O2 (index of NADPH oxidase activation), stimulated [3H]arachidonic acid (AA) release (index of phospholipase A2 activity), and promoted CD18-dependent homotypic aggregation. Under similar conditions, LTB4 (1 microM) induced a rapid activation of extracellular-regulated kinases-1 and 2 (ERK-1/2) but not c-jun N-terminal kinases 46 and 54 (JNK-46/54) or p38 mitogen-activated protein kinase (p38 MAP kinase). To examine the role of ERK-1/2 in the mechanism of eosinophil activation, a selective inhibitor of MAP kinase kinase-1/2 (MEK-1/2), PD098059, was employed. However, PD 098059 at concentrations that attenuated ERK-1/2 activation had no significant affect on eosinophil activation. In contrast, a role for tyrosine kinases in LTB4-induced eosinophil activation was suggested by studies with the tyrosine kinase inhibitors, herbimycin A and lavendustin A. However, the results of those experiments implied divergent pathways for the control of eosinophil responses because the inhibitors were more effective at attenuating H2O2 generation than [3H]AA release, and had little effect on homotypic aggregation.
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PMID:Role of the mitogen-activated protein kinases and tyrosine kinases during leukotriene B4-induced eosinophil activation. 976 37

Monocyte infiltration into the vessel wall, a key initial step in the process of atherosclerosis, is mediated in part by monocyte chemoattractant protein-1 (MCP-1). Hypertension, particularly in the presence of an activated renin-angiotensin system, is a major risk factor for the development of atherosclerosis. To investigate a potential molecular basis for a link between hypertension and atherosclerosis, we studied the effects of angiotensin II (Ang II) on MCP-1 gene expression in rat aortic smooth muscle cells. Rat smooth muscle cells treated with Ang II exhibited a dose-dependent increase in MCP-1 mRNA accumulation that was prevented by the AT1 receptor antagonist losartan. Ang II also activated MCP-1 gene transcription. Inhibition of NADH/NADPH oxidase, which generates superoxide and H2O2, with diphenylene iodonium or apocynin decreased Ang II-induced MCP-1 mRNA accumulation. Induction of MCP-1 gene expression by Ang II was inhibited by catalase, suggesting a second messenger role for H2O2. The tyrosine kinase inhibitor genistein and the mitogen-activated protein kinase kinase inhibitor PD098059 inhibited Ang II-induced MCP-1 gene expression, consistent with a mitogen-activated protein kinase-dependent signaling mechanism. Ang II may thus promote atherogenesis by direct activation of MCP-1 gene expression in vascular smooth muscle cells.
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PMID:Angiotensin II induces monocyte chemoattractant protein-1 gene expression in rat vascular smooth muscle cells. 979 45

We studied differences between the NADPH oxidase activation pathways triggered by pervanadate, a protein tyrosine phosphatase inhibitor, and phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, in guinea pig neutrophils. Previously, pervanadate has been shown to activate NADPH oxidase via the tyrosine kinase-dependent pathway (Yamaguchi et al. Arch. Biochem. Biophys. 323, 382-386, 1995). Both pervanadate and PMA induced superoxide anion (O-2) production, translocation of the 47-kDa protein component of the phagocyte oxidase (p47-phox) to the plasma membrane, and phosphorylation of p47-phox in the membrane. A selective protein kinase C inhibitor, GF 109203X, markedly inhibited PMA-induced O-2 production, p47-phox translocation, and p47-phox phosphorylation, but did not inhibit pervanadate-induced O-2 production and only slightly suppressed pervanadate-induced translocation and phosphorylation. These results demonstrate that pervanadate activates NADPH oxidase independently of protein kinase C. Phosphopeptide mapping of p47-phox revealed differences in the mechanism between pervanadate-induced and PMA-induced phosphorylation. Furthermore, some protein kinases which phosphorylate p47-phox-derived peptide are activated by pervanadate. These results suggest the existence of novel protein kinases responsible for the phosphorylation of p47-phox and the activation of these protein kinases by tyrosine kinase.
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PMID:Pervanadate activates NADPH oxidase via protein kinase C-independent phosphorylation of p47-phox. 988 22

Guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) induces respiratory burst (O-2 generation) in permeabilized human neutrophils. The signal pathway from GTPgammaS to the enzyme responsible for O-2 generation (NADPH oxidase) is not well defined. To elucidate the signaling pathway activated by GTPgammaS, we used selective inhibitors to test for the involvement of several enzymes, comparing the effects of these inhibitors on fMet-Leu-Phe (fMLP) activation. GTPgammaS-induced respiratory burst was not influenced by genistein, a selective inhibitor of tyrosine kinase, while fMLP-induced response was completely abolished. The respiratory burst by GTPgammaS was efficiently inhibited by the protein kinase C inhibitor GF109203X even more than fMLP activation. The mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 showed a partial inhibition of both GTPgammaS and fMLP activation. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase, completely blocked fMLP activation, but had no effect on the GTPgammaS-induced respiratory burst. Using U73122, phospholipase C is shown to be essential in GTPgammaS signaling as well as fMLP signaling. Butanol blocked fMLP signaling but not GTPgammaS signaling, indicating that only fMLP activation involves phospholipase D. These results suggest that there are several differences between GTPgammaS- and fMLP-induced activation, but both activators share a common pathway including phospholipase C, protein kinase C, and MAPK kinase.
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PMID:Guanosine 5'-O-(3-thiotriphosphate)-induced O-2 generation in permeabilized neutrophils requires protein kinase C and phospholipase C but not tyrosine kinase or phospholipase D. 988 54

The mannose receptor (MR) is involved in the phagocytosis of pathogenic microorganisms. Here we investigated its role in the bactericidal functions of human monocyte-derived macrophages (MDMs), using (i) trimannoside-bovine serum albumin (BSA)-coated latex beads and zymosan as particulate ligands of the MR, and (ii) mannan and mannose-BSA as soluble ligands. We show that phagocytosis of mannosylated latex beads did not elicit the production of O2-. Zymosan, which is composed of alpha-mannan and beta-glucan, was internalized by the MR and a beta-glucan receptor, but the production of O2- was triggered only by phagocytosis through the beta-glucan receptor. Activation and translocation of Hck, a Src family tyrosine kinase located on lysosomes, has previously been used as a marker of fusion between lysosomes and phagosomes in human neutrophils. In MDMs, Hck was activated and recruited to phagosomes containing zymosan later than LAMP-1 and CD63. Phagosomes containing mannosylated latex beads fused with LAMP-1 and CD63 vesicles but not with the Hck compartment, and the kinase was not activated. We also demonstrate that the MR was unable to distinguish between nonpathogenic and pathogenic mycobacteria, as they were internalized at similar rates by this receptor, indicating that this route of entry cannot be considered as a differential determinant of the intracellular fate of mycobacteria. In conclusion, MR-dependent phagocytosis is coupled neither to the activation of NADPH oxidase nor to the maturation of phagosomes until fusion with the Hck compartment and therefore constitutes a safe portal of entry for microorganisms.
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PMID:The mannose receptor mediates uptake of pathogenic and nonpathogenic mycobacteria and bypasses bactericidal responses in human macrophages. 991 47

In this study, the underlying mechanisms of stimulation by cyclocommunin, a natural pyranoflavonoid, of respiratory burst in rat neutrophils was investigated. Cyclocommunin evoked a concentration-dependent stimulation of superoxide anion (O2*-) generation with a slow onset and long lasting profile. The maximum response (16.4+/-2.3 nmol O2*-/10 min per 10(6) cells) was observed at 3-10 microM cyclocommunin. Cyclocommunin did not activate NADPH oxidase in a cell-free system. Cells pretreated with pertussis toxin or n-butanol did not affect the cyclocommunin-induced O2*- generation. However, a protein kinase inhibitor staurosporine and EGTA greatly reduced the O2*-generation caused by cyclocommunin. Treatment of neutrophils with phorbol 12-myristate 13-acetate (PMA), but not with formylmethionyl-leucyl-phenylalanine (fMLP), for 20 min significantly reduced the O2*- generation following the subsequent stimulation of cells with cyclocommunin. Cyclocommunin did not affect the cellular mass of phosphatidic acid (PA). Neither the tyrosine kinase inhibitor, genistein, nor the p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, affected cyclocommunin-induced O2*- generation. The enzyme activities of neutrophil cytosolic and membrane-associated protein kinase C (PKC) were both increased significantly with 100 microM cyclocommunin. The membrane-associated PKC-theta and PKC-beta were increased following the stimulation of neutrophils with 30 and 100 microM cyclocommunin, respectively. Cyclocommunin reduced the [3H]phorbol 12,13-dibutyrate ([3H]PDB) binding to cytosolic PKC in a concentration-dependent manner. Cyclocommunin (> or =3 microM) significantly evoked a slow and long lasting [Ca2+]i elevation in neutrophils, and a phospholipase C (PLC) inhibitor U73122 greatly inhibited these Ca2+ responses. Moreover, the increase in cellular inositol bis- and trisphosphate (IP2 and IP3) levels were observed in neutrophils stimulated with 30 microM cyclocommunin for 3 min. Collectively, these results indicate that the stimulation of respiratory burst by cyclocommunin is probably mediated by the synergism of PKC activation and [Ca2+]i elevation in rat neutrophils.
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PMID:Stimulation of respiratory burst by cyclocommunin in rat neutrophils is associated with the increase in cellular Ca2+ and protein kinase C activity. 1021 46

Angiotensin (A) II is a potent constrictor as well as growth stimulant of vascular smooth muscle cell caused by activation of AT1 receptor signal transduction systems. There are two major signal systems of AT1 receptor: one leads to an increase in cytosolic free calcium levels causing smooth muscle contraction which may result in high blood pressure, and the other leads to smooth muscle proliferation and inflammation which may result in atherosclerosis. AT1 receptor activation induces phosphinositide hydrolysis by phospholipase C and creates an inositol phosphate, which release calcium from cytosolic calcium pools. Cytosolic calcium can also be elevated by activation of calcium channel via a link between AT1 receptor and a G protein. Protein phosphorylation triggered by AT1 receptor is important for cell growth, in which tyrosine kinase, serine/threonine kinase and protein kinase C are involved. Free radicals are generated by NADH/NADPH oxidase in response to AT1 receptor activation, causing expression of genes leading to atherosclerosis. On the other hand, activation of AT2 receptor is shown to play a role of lowering blood pressure. Some phosphatases and NO/cyclic GMP would be involved in the mechanism. In renal vasculature, endothelium dependent epoxygenase products are synthesized by AT2 receptor stimulation causing vasorelaxation. In summary, AT1 receptor signals are vasopressive and evoke atherosclerosis, whereas AT2 receptor signals may possibly be vasodilatory.
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PMID:[Signal transduction systems of angiotensin II receptors]. 1036 37


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