Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.99.6 (NADPH oxidase)
 10,295 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

f-Met-Leu-Phe-stimulated luminol-enhanced chemiluminescence was found to be repeatedly defective in some MDS patients. This defect was not attributed to myeloperoxidase deficiency, nor to a defect in NADPH oxidase function, because PMA chemiluminescence was found to be normal in these individuals. An arbitrary value of 7 mV (half the mean control value) was chosen to subdivide the group: MDS patients with values < 7 mV had a mean f-Met-Leu-Phe chemiluminescence response of 2.5 +/- 0.5 compared to MDS patients with values > 7 mV who had a mean response of 15.6 +/- 1.6 mV, P < 0.01 (healthy controls 14 +/- 2 mV). The characteristics of the f-Met-Leu-Phe receptor and initial calcium flux results suggested that the receptor itself was normal in number and function in low f-Met-Leu-Phe responders. The rate of superoxide generation, which is calcium-dependent, was also found to be in the normal range in low f-Met-Leu-Phe responders, although total superoxide production was reduced in some of these patients. When MDS neutrophils with a low f-Met-Leu-Phe response were stimulated with PMA, chemiluminescence was normal, suggesting normal activity of the NADPH-oxidase complex. Furthermore, myeloperoxidase activity was reduced in only three out of the 11 low f-Met-Leu-Phe responders. Following priming with GM-CSF, f-Met-Leu-Phe chemiluminescence was 27 +/- 1.6 mV in low f-Met-Leu-Phe responders compared to controls (87.7 +/- 11 mV, P < 0.005). Thus, although responses were improved, they were not as marked as in control neutrophils. These data suggest that a subgroup of MDS patients have a low f-Met-Leu-Phe chemiluminescence response which is not due to a defect in the f-Met-Leu-Phe receptor or oxidase activity, and in the majority of cases MPO activity is normal. Initial patient survival data suggest that these patients may have an increased risk of infective mortality. It is proposed that defective f-Met-Leu-Phe chemiluminescence results from a putative defect in cell-signalling mechanism upstream of PKC, and GM-CSF priming only partially improves responsiveness.
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PMID:Identification of a subgroup of myelodysplastic patients with a neutrophil stimulation-signalling defect. 791 69

Secretory leukocyte protease inhibitor (SLPI) is a potent proteinase inhibitor produced in the lung. Stimulated neutrophils at sites of inflammation can inactivate SLPI by myeloperoxidase-mediated oxidation of the methionine residue in the active site of SLPI. Apocynin is a selective inhibitor of NADPH oxidase and may therefore protect SLPI against neutrophil-mediated oxidative inactivation. The aim of the present study was to determine the effect of apocynin on the efficacy of SLPI in preventing experimental emphysema. To investigate the effect of apocynin on emphysema without SLPI treatment, three groups of eight hamsters each received drinking water containing apocynin at concentrations of 2, 20, and 200 micrograms/ml, respectively. Emphysema was induced in these hamsters by intratracheal instillations of 500 micrograms of lipopolysaccharide (LPS) twice a week for 4 wk. In hamsters that received 200 micrograms/ml apocynin, the development of emphysema was reduced by 26.2% (p = 0.01). Other apocynin concentrations had no effect. The experiment was repeated, with SLPI added to the treatment. Of a total of six groups of hamsters, four groups (three with apocynin and one with solvent) received twice-weekly doses of a mixture of 500 micrograms of LPS and 1 mg SLPI in 200 microliters saline in the trachea for 4 wk. In addition, each LPS instillation was followed 24 and 48 h later by an instillation containing 1 mg of SLPI. Apocynin (20 and 200 micrograms/ml) improved the protective effect of SLPI from 37 to 64% and 79%, respectively (p < 0.01). We conclude that oral administration of apocynin can improve the efficacy of SLPI in preventing LPS-induced emphysema.
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PMID:Apocynin improves the efficacy of secretory leukocyte protease inhibitor in experimental emphysema. 795 25

In neutrophils, N-formyl-Met-Leu-Phe (FMLP) stimulates a respiratory burst with subsequent generation of superoxide anion (O2-.) by NADPH oxidase. Signal transduction involved in this process includes FMLP receptor stimulation of phosphoinositide hydrolysis with formation of inositol 1,4,5-trisphosphate and diacylglycerol and phosphatidylcholine hydrolysis with formation of phosphatidic acid. Generation of these second messengers would lead to activation of NADPH oxidase and generation of O2-.. Neutrophils from diabetic subjects and normal neutrophils exposed to glucose have diminished ability to activate the respiratory burst in response to various agonists. The mechanism of this suppression remains unknown. We report herein that treatment of neutrophils with 15 and 50 mM glucose significantly suppresses the O2-. formation in response to receptor-mediated stimulation. The decreased O2-. generation is associated with marked inhibition of phospholipase D (PLD) activity, with limited hydrolysis of phosphatidylcholine and formation of phosphatidic acid. Sorbitol (50 mM), a nonmetabolizable sugar with a similar osmotic effect, has no influence on O2-. generation or PLD activation. The 4 beta-phorbol 12-myristate 13-acetate (PMA)-induced O2-. generation as well as PLD activation are unaffected by glucose. Furthermore, the intracellular Ca2+ transient in response to FMLP is not influenced by glucose. Taken together, these data suggest that glucose differentially interferes with activation of PLD but not phospholipase C. And, the fact that PMA-induced activation of PLD is not altered by glucose further suggests that a protein kinase C independent step leading to the activation of PLD may be altered by glucose.
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PMID:Glucose suppresses superoxide generation in normal neutrophils: interference in phospholipase D activation. 838 32

Infection is a frequent complication and the major cause of death among end-stage renal patients. Polymorphonuclear phagocytes (PMNL) are important in host defense mainly because of bacterial destruction by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-related free radical production following phagocytosis. In this study, hexose monophosphate pathway glycolytic activity, delivering energy to NADPH oxidase, is evaluated in vivo and in vitro, in healthy controls and in dialyzed renal failure patients. Our results show a marked parallel and correlated inhibition in the response to three stimuli for phagocytic activity (Staphylococcus aureus, formyl-methionine-leucine-phenylalanine, phorbol myristic acid) in predialysis samples. These data point to a main suppression of metabolic pathways, possibly beyond protein kinase C. This response is further suppressed at the 15th minute of cuprophane dialysis, for all stimuli studied (-40 to -94%; p < 0.001) except PMA. PMNL response remains intact during dialysis with non-complement-activating dialyzers. In vitro experiments confirm decreased PMNL glycolytic activity after the suspension of cuprophane fragments in normal whole blood. We conclude that polymorphonuclear cell energy delivery to NADPH oxidase is impaired in patients with end-stage renal failure. The impaired response against various stimuli is different in predialysis blood samples compared to samples collected during cuprophane dialysis, and may be related to two different conditions. These events probably contribute to the acquired immune suppression of uremia and the high incidence of infection among dialysis patients.
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PMID:Depressed phagocytosis in hemodialyzed patients: in vivo and in vitro mechanisms. 845 76

The activation of human platelets by polymorphonuclear leukocytes (PMN) was investigated in human whole blood challenged with "priming" concentrations of arachidonic acid or collagen in the presence or absence of N-formyl-Met-Leu-Phe (FMLP), a selective activator of PMN. With the use of arachidonic acid or collagen alone at priming concentrations or FMLP alone, no platelet response was observed. In contrast, FMLP in combination with arachidonic acid or collagen caused irreversible platelet aggregation with thromboxane A2 production. Platelet response to FMLP-activated PMN was enhanced by superoxide dismutase and blocked by catalase or the NADPH oxidase inhibitor diphenyliodonium, suggesting a role for the O2-.-H2O2 system in this cellular interaction. This was corroborated by experiments with exogenously added H2O2, which mimicked FMLP effects in the activation of primed platelets in whole blood. The present investigation indicates that platelets primed with minute amounts of arachidonic acid or collagen can be activated, in human whole blood, by oxygen-reactive species released by PMN.
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PMID:Polymorphonuclear leukocyte-derived O2-reactive species activate primed platelets in human whole blood. 849 72

We studied the effects of antiallergic drugs, epinastine, ketotifen, oxatomide, mequitazine and cromolyn sodium on superoxide anion (O2-) generation from rat neutrophils. Epinastine, ketotifen, oxatomide and mequitazine dose-dependently prevented the N-formyl-Met-Leu-Phe- and phorbol 12-myristate 13-acetate-induced O2- generation, but cromolyn sodium did not prevent it. When membrane and cytosol fractions were incubated with each drug, epinastine, ketotifen and mequitazine prevented O2- generation. On the other hand, when only the membrane fraction was incubated with each drug, ketotifen and mequitazine prevented O2- generation, but epinastine did not. Epinastine may inhibit the NADPH oxidase system through the obstruction of NADPH oxidase-associated cytosol components.
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PMID:Inhibitory effect of epinastine on superoxide generation by rat neutrophils. 853 20

In response to formyl-Met-Leu-Phe (fMLP), human neutrophils (PMN) generate superoxide anion (O2-) by the enzyme complex NADPH oxidase. The modulation of phosphoinositide (PPI) turnover and the activation of phospholipases C (PLC) and D (PLD) have been shown to be early steps in the oxidative response of fMLP-stimulated PMN. Although the physiological nonapeptide bradykinin (BK) is involved in inflammation, its participation in PMN activation has not been properly studied. In this work, activation of signal transduction pathways that mediate the oxidative response, and the modulation of the NADPH oxidase activity by BK, are analyzed. A direct comparison between the signal transduction pathway induced by BK and fMLP is also made. BK was not able to elicit O2- production by PMN. Nevertheless, several signal transduction pathways associated with PMN activation were triggered by BK. The nonapeptide induced the phosphorylation of prelabeled membrane PPI. This phenomenon was imitated by PMA and inhibited by H7 and staurosporine, thus suggesting the participation of protein kinase c (PKC). A loss of labeled [32P]PPI was triggered by fMLP. The fact that both PMA and fMLP stimulated O2- production but modulated PPI turnover in different ways, indicates that PPI labeling does not correlate with the oxidative response. Because PKC activation seemed to be a prerequisite for BK-induced modulation of PPI turnover, PLC activation could act as an intermediate step in this mechanism. Our results show that BK activated a PIP2-PLC measured as the release of [3H]IP3. On the contrary, a PC-PLD was highly stimulated by fMLP but not by BK. The fact that BK induced PLC activity but neither that of PLD nor NADPH oxidase, whereas fMLP triggered the activation of both phospholipases and evoked the PMN respiratory burst, suggests that diacylglycerol (DAG) from PIP2 as well as PA or PA-derived DAG, synergize to trigger the PMN oxidative response. Finally, BK inhibited O2- production by fMLP-activated PMN in a time-dependent manner. Since BK did not induce NO production by PMN, the inhibitory effect on the oxidative function was not due to ONOO- formation. These data show that BK plays an important role in inflammation by modulating the PMN function.
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PMID:Bradykinin stimulates phosphoinositide turnover and phospholipase C but not phospholipase D and NADPH oxidase in human neutrophils. 861 9

Stimulation of the respiratory burst in phagocytes induces the formation of mixed disulfides between sulfhydryl groups of proteins and low-molecular-weight thiols. We hypothesized that this process (S-thiolation) might be involved in turning off the respiratory burst. However, induction of S-thiolation by pretreatment of neutrophils with diamide, a direct thiol oxidizing agent, actually primed the cells for a two- to fivefold increase in total release and fourfold increase in rate of release of 02- on stimulation by f-Met-Leu-Phe. Generation of intracellular oxidants (hydroethidine fluorescence) was increased ninefold. Priming and S-thiolation were apparent at 1 min of incubation and peaked at 5-10 min. Diamide pretreatment also reduced the lag time between addition of phorbol diester and release of 02- by a mean of 23 s (41%). Dithioerythritol, a sulfhydryl-reducing agent, abolished both the S-thiolation and priming mediated by diamide. H202 also induced priming and S-thiolation; and these were eliminated by dithioerythritol. In contrast to the effect of endotoxin, diamide priming did not affect Ca2+ homeostasis of the neutrophils. Diamide did not significantly alter NADPH oxidase activity in a cell-free system. These findings suggest that sulfhydryl groups on one or more proteins play an important role in modulating the respiratory burst.
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PMID:Diamide primes neutrophils for enhanced release of superoxide anion: relationship to S-thiolation of cellular proteins. 877 80

1. The possible mechanisms of the inhibitory effect of ethyl 2-(3-hydroxyanilino)-4-oxo-4,5-dihydrofuran-3-carboxylate (HAJ11) on the respiratory burst of rat neutrophils in vitro was investigated. 2. HAJ11 caused a reversible and a concentration-dependent inhibition of formyl-Met-Leu-Phe (fMLP)-induced superoxide anion (O2.-) generation (IC50 4.9 +/- 0.7 microM) and O2 consumption (IC50 4.9 +/- 1.5 microM). Concanavalin A (Con A)- and NaF-induced O2.- generation were also suppressed by HAJ11. However, HAL11 was a weak inhibitor of the phorbol 12-myristate 13-acetate (PMA)-induced responses. 3. HAJ11 did not scavenge the /2.- generation in the xanthine-xanthine oxidase system and dihydroxyfumaric acid (DHF) autoxidation. 4. HAJ11 showed no activity on fMLP-induced inositol phosphates formation and [Ca2+]i elevation in intact neutrophils. In addition, HAJ11 had no effect on neutrophil cytosolic phospholipase C (PLC) activity. 5. HAJ11 reduced fMLP-induced phosphatidic acid (PA) (IC50 29.1 +/- 6.5 microM) and phosphatidylethanol (PE+) (IC50 22.6 +/- 1.9 microM) formation in a concentration-dependent manner. HAJ11 also reduced protein tyrosine phosphorylation in neutrophils stimulated by fMLP. 6. HAJ11 was a weak inhibitor of neutrophil cytosolic protein kinase C (PKC) activity, and had a negligible effect on brain PKC. Cellular cyclic nucleotides levels were not altered by HAJ11. In addition, HAJ11 did not affect protein kinase A (PKA) activity. 7. HAJ11 had not effect on the O2.- generation of PMA-activated and arachidonic acid (AA)-activated NADPH oxidase preparations. 8. Taken together these results indicate that the inhibition of respiratory burst by HAJ11 probably mainly occurs through inhibition of protein tyrosine phosphorylation and phospholipase D (PLD) activity.
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PMID:Inhibition by HAJ11 of respiratory burst in neutrophils and the involvement of protein tyrosine phosphorylation and phospholipase D activation. 911 3

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


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