The superoxide-forming enzymatic system of phagocytes

Cell-free translocation of recombinant p47-phox, a component of the neutrophil NADPH oxidase: effects of guanosine 5'-O-(3-thiotriphosphate), diacylglycerol, and an anionic amphiphile

We reported previously that diacylglycerol (diC8) and GTP gamma S synergize with an anionic amphiphile such as sodium dodecyl sulfate (SDS) to produce high rates of superoxide generation in a cell-free system consisting of neutrophil plasma membrane plus cytosol [Burnham, D. N., Uhlinger, D. J., & Lambeth, J. D. (1990) J. Biol. Chem. 265, 17550-17559]. Here we investigate the effects of these activating factors on the plasma membrane association in an in vitro translated radiolabeled recombinant p47-phox protein. Apparent translocation, assayed by cosedimentation with plasma membranes, required the presence of excess cytosol and an anionic amphiphile, was enhanced by both GTP gamma S and diC8, and was inhibited by high salt, correlating qualitatively with activation; up to 70% cosedimentation was observed with the combination of activators (compared with less than 20% in their absence). Similar results were obtained using heat-inactivated cytosol, wherein another oxidase component, p67-phox, has been inactivated. Unexpectedly, from 50 to 80% of the apparent translocation occurred in the absence of membranes, indicating that protein aggregation accounted for a significant part of the observed translocation. Nevertheless, the percent translocation was increased in all cases by the presence of membranes, indicating some degree of protein-membrane interaction. While a control in vitro translated protein failed to translocate, cosedimentation of p47-phox occurred equally well when red blood cell or neutrophil plasma membranes lacking cytochrome b558 were used. Also, the peptide RGVHFIF, which is contained within the C-terminus of the large subunit of cytochrome b558, failed to inhibit translocation/aggregation of p47-phox, despite its ability to inhibit cell-free activation of the oxidase. The data are consistent with the following: (a) SDS, diC8, and GTP gamma S all act on cytosolic components to alter protein-protein and/or protein-membrane associations, and these changes are necessary (but not sufficient) for activation; (b) these altered associations are likely to function by increasing the local concentration of p47-phox and other components at the plasma membrane; (c) a high background of nonspecific associations in the cell-free activation system is likely to obscure any specific, functionally relevant associations (e.g., with cytochrome b558); and (d) the mechanism of translocation in the cell-free system differs from that seen in intact neutrophils.

Spermine down-regulates superoxide generation induced by fMet-Leu-Phe in electropermeabilized human neutrophils

Effect of spermine, a naturally occurring polyamine, was investigated on superoxide generation in intact and electropermeabilized human neutrophils. Spermine suppressed N-formyl-methionyl leucyl phenylalanine (fMLP)-induced superoxide generation in permeabilized cells by reducing the rate and shortening the duration time. The inhibition was specific for spermine comparing with its precursor amines, spermidine and putrescine. The inhibition was not observed when cells were preincubated with spermine without permeabilization. Concanavalin A-induced superoxide generation was also down-regulated by spermine in permeabilized cells, but the activation induced by non receptor-mediated agonist (dioctanoylglycerol, phorbol myristate acetate, and arachidonate) was not affected by spermine. On the other hand, GTP-gamma-S-induced activation of superoxide generation was substantially suppressed by spermine. These results indicate that spermine inhibition occurs at a step prior to protein kinase C in signal transduction or in a pathway which is independent of the kinase.

The role of superoxide radical in chromium (VI)-generated hydroxyl radical: the Cr(VI) Haber-Weiss cycle

To understand the role of the superoxide (O-2) radical in chromate-related genotoxicity, we investigated whether Cr(VI) can catalyze the Haber-Weiss cycle in vitro: O-2 + Cr(VI)----Cr(V) + O2 Cr(V) + H2O2----Cr(VI) + .OH + OH-. ESR and spin trapping techniques were utilized to monitor the O-2 (produced using xanthine/xanthine oxidase), .OH, and Cr(V) species. Superoxide dismutase as well as catalase inhibited the .OH radical radical formation, attesting to the direct involvement of O-2 and H2O2 in the process. ESR measurements also provided direct evidence for the formation of Cr(V). Kinetic measurements were consistent with the role of Cr(V) and H2O2 as intermediates in .OH formation. These results indicate that in cellular media, especially during chromate phagocytosis, the O-2 radical can become a significant source of .OH radicals and hence a significant factor in the biochemical mechanism of cellular damage due to Cr(VI) exposure.

Inactivation of NADPH oxidase from human neutrophils by affinity labeling with pyridoxal 5'-diphospho-5'-adenosine

When a particulate NADPH oxidase prepared from phorbol ester-activated human neutrophils was treated with pyridoxal 5'-diphospho-5'-adenosine (PLP-AMP), the superoxide anion-producing activity was inhibited according to affinity labeling kinetics. NADPH afforded a protection against inactivation which was competitive with respect to PLP-AMP; 2',5'-ADP and 2'-phospho-5' diphosphoadenosine (ATP ribose) appeared to be as potent as NADPH as protecting agents. NADP+ and ATP were less effective, while ADP and GTP-gamma-S did not protect significantly. These results suggest that PLP-AMP can be used, in conjunction with tritiated cyanoborohydride, to identify the elusive NADPH-dependent flavoprotein which is part of the electron transfer chain of NADPH oxidase.

Extracellular release of reactive oxygen species from human neutrophils upon interaction with Escherichia coli strains causing renal scarring

The production of reactive oxygen metabolites by neutrophils plays a key role in the host defense against invading microorganisms and in tissue damage resulting from infection. In the present study we measured the ability of different uropathogenic Escherichia coli strains to induce generation of oxygen metabolites upon interaction with human neutrophils. The strains were selected to represent two groups of patients with recurrent episodes of acute pyelonephritis: one with renal scars (12 strains) and one without renal scarring (11 strains). The majority of strains (from both groups) induced a pronounced neutrophil respiratory burst activity. When the intracellular and extracellular oxidative responses were measured separately, it was found that the response induced by nonscarring strains was primarily of intracellular (intraphagosomal) origin, whereas a proportionally larger fraction of the response induced by the scarring strains was extracellular. Since reactive oxygen products are toxic to the renal tissue, this release can be of importance in the development of renal scars.

Macrophage hydrogen peroxide production and phagocytic function are decreased following phagocytosis mediated by Fc receptors but not complement receptors

Previous in vivo and in vitro studies have shown that the phagocytosis of IgG-coated erythrocytes results in a depression of macrophage function. The present study compared the effect of phagocytosis mediated by Fc receptors with that mediated by complement receptors. The phagocytosis of IgG-coated erythrocytes by elicited peritoneal macrophages depressed their capacity to produce hydrogen peroxide as well as phagocytic function. Phagocytosis of erythrocytes coated with IgM and complement had neither of these effects. These results implicate the intracellular signaling that results from Fc receptor mediated phagocytosis in the depression of macrophage function that is caused by phagocytosis.

Melanin content and hydroperoxide metabolism in human melanoma cells

Human melanoma cells were grown to exponential and stationary phases showing melanin contents of 4.2 +/- 0.3 and 11.3 +/- 0.6 micrograms/10(6) cells, respectively. The cells were separated in four subpopulations by a Percoll gradient; the subpopulation of density 1.07 (g/ml) was the most enriched in pigmented cells and produced 28 and 58% of the cells in exponential and stationary phases, respectively. Melanoma cells had similar superoxide dismutase and glutathione peroxidase activities in exponential and stationary phases. Moreover melanoma cells exhibited a higher catalase activity in the stationary phase: whole homogenate and cytosol activities were 7.0 +/- 0.3 and 10.8 +/- 0.6 U/mg protein, whereas in exponential phase the activities were 4.9 +/- 0.1 and 7.6 +/- 0.3 U/mg protein for whole homogenate and cytosol, respectively. The intracellular H2O2 steady-state concentration was 3.3 +/- 0.2 and 2.1 +/- 0.2 microM H2O2 for exponential and stationary phases, respectively. The spontaneous chemiluminescence of the two culture phases was 169 +/- 27 cps/10(6) cells (exponential) and 78 +/- 24 cps/10(6) cells (stationary). The cytotoxicity of H2O2 generated extracellularly by glucose oxidase was determined after 60 min of exposure. IC50 values for exponential and stationary cell cultures were 0.9 and 2.4 mU/ml of glucose oxidase, respectively. The increased catalase activities in the stationary phase as compared with the exponential phase are consistent with the decreased intracellular H2O2, with the decreased spontaneous chemiluminescence, and with the increased resistance to exogenous H2O2.

Effect of pentoxifylline on superoxide anion production by human sperm

The in-vitro effect of pentoxifylline, a methylxanthine derivative, on superoxide anion generation by sperm was studied in 27 men with superoxide anion production ranging from 0.57 to 13.8 nmoles 02-. per 10(6) sperm. Superoxide anion release stimulated by phorbol myristate acetate, a potent activator of oxygen radical generation, was reduced by 29-72% following the addition of 10 mM pentoxifylline. The inhibitory effect of this millimolar concentration of the drug did not depend on the initial superoxide production in the presence of phorbol myristate acetate. These results point to a potential use for pentoxifylline in the treatment of male infertility in men with an increased superoxide anion generation capacity.

Molecular characteristics of cytochrome b558 isolated from human granulocytes, monocytes and HL60 and U937 cells differentiated into monocyte/macrophages

Enriched cytochrome b558 preparations were obtained from human mature monocytes (MN) and retinoic acid plus interferon gamma induced human myeloid leukemia cell lines HL-60 and U937, using an adaptation of the procedure described by A.W. Segal (Nature (1987) 326, 88-91) for purification of cytochrome b558 from human polymorphonuclear leukocytes (PMN). Spectral characteristics of cytochrome b558 were determined and found to be independent of cell type and specific heme b content of the preparation. To increase the sensitivity of the spectral assay, analysis in the gamma band were used and delta epsilon 427-413 was determined to be equal to 158 mM-1 cm-1. An alpha beta type heterodimeric cytochrome b558 was found for PMN and MN by the concordant elution of heme b spectral activity from heparin agarose and the detection of two polypeptide chains by SDS-PAGE. The expression of the lighter polypeptide alpha chain in the various human monocyte-like cell lines was assessed and its identity, as a component of cytochrome b, was confirmed by immunodetection using a rabbit polyclonal antibody reacting with the alpha subunit of PMN cytochrome b558. Immunoblotting studies detected the alpha subunit in monocyto-macrophagic differentiated HL-60 and U 937 cells and mature MN at 22 kDa, but not in uninduced cells which did not express the respiratory burst. Whatever the specific content or the cell origin of the cytochrome b558-enriched preparations, the heme b binding site was shown to be associated with the alpha subunit defined by a constant molecular mass of 22 kDa, as evidenced by the finding of a constant ratio between the silver stained band intensity and the corresponding heme b amount. The heavy polypeptide beta chain from MN cytochrome b was found to have a significantly higher molecular weight than the beta subunit from PMN at 94 +/- 5 kDa instead of 90 +/- 4 kDa. In contrast, in cytochrome b preparations from induced monocyto-macrophagic cells, isolated with a low heme specific content, the variability in the detection of the staining intensity of the beta band either in SDS-PAGE or immunodetection reactivities precludes accurate definition of its molecular mass and estimation of the stoichiometry between the alpha and beta subunits in the differentiated cells. However, wheat-germ agglutinin binding studies indicated the presence of N-glycosylated protein in the range of 85-110 kDa.

Respiratory burst activity in brain macrophages: a flow cytometric study on cultured rat microglia

A new flow cytometric method for the investigation of the respiratory burst of macrophages/microglia isolated from neonatal rat brain has been established. Respiratory burst activity was measured quantitatively in single viable cells by the intracellular oxidation of non-fluorescent dihydrorhodamine 123 (DHR) to fluorescent rhodamine 123. Cultured microglia exhibited high spontaneous respiratory burst activity already before stimulation. After maximal stimulation with phorbol myristate acetate, DHR oxidation rose by 40-95%. The respiratory burst activity in resident or inflammatory, i.e. thioglycolate elicited, peritoneal macrophages was significantly lower than in cultured brain macrophages suggesting a high potential of microglia for oxidative tissue destruction.

The effects of N-ethylmaleimide on extracellularly and intracellularly generated chemiluminescence in neutrophils indicate that the rate of deactivation of NADPH-oxidase is higher when the oxidase system is localized on the plasma membrane than when it is localized on the phagosomal membrane

Sustained generation of reactive oxygen metabolites following respiratory burst activation in neutrophils is a result of continued replenishment of a pool of active NADPH-oxidase. The sulphydryl-modifying reagent N-ethylmaleimide (NEM) has been shown to be without effect on the turnover of activated NADPH-oxidase but to inhibit the replenishment of active oxidase molecules (Akard et al., 1988). NEM was thus used to determine the rate of deactivation of extracellularly and intracellularly generated chemiluminescence in human neutrophils. We have shown that deactivation is more rapid when activation leads to a release of oxygen metabolites (extracellular chemiluminescence) than when the metabolites are generated intracellularly. The results indicate that the rate of deactivation of NADPH-oxidase is higher when the oxidase system is localized on the plasma membrane than when it is localized on the phagosomal membrane.

Amiloride does not influence the capability of interferon gamma to potentiate superoxide anion and hydrogen peroxide release by human mononuclear phagocytes

Since the molecular mechanisms of macrophage activation in response to interferon gamma (IFN-gamma) are still not well defined we have investigated whether amiloride, a specific inhibitor of the Na+/H+ antiporter, had any effect on the IFN-gamma-mediated potentiation of human monocyte and monocyte-derived macrophage capability to produce O2- (respiratory burst). Here, we demonstrate that amiloride neither inhibits the capability of IFN-gamma to activate the mononuclear phagocyte respiratory burst nor influences IFN-gamma induction of steady-state mRNA levels for 2 components of the superoxide anion-generating enzyme system. On the contrary, we show that IFN-gamma-enhanced expression of the HLA-DR alpha gene is significantly inhibited by amiloride These data indicate that Na+/H+ antiporter stimulation by IFN-gamma is not involved in the mechanism of activation of macrophage oxidative metabolism.

Microcirculatory disturbances and leucocyte adherence in transplanted livers after cold storage in Euro-Collins, UW and HTK solutions

Integrity of the hepatic microcirculation and maintenance of endothelial cell viability are critical components in preventing primary non-function after liver transplantation. Therefore, hepatic microcirculation and leucocyte-endothelial interaction were studied in rat livers stored for 1 h in Euro-Collins (EC), University of Wisconsin (UW), and histidine-tryptophan-ketoglutarate (HTK) solutions and subsequently transplanted. One hour after transplantation surgery, the livers were exposed under an intravital fluorescence microscope. After injection of the leucocyte marker acridine orange (1 mumol/kg), six pericentral fields were observed for 30 s and experiments were recorded continuously. The percentage of perfused sinusoids was reduced in the livers in the EC group (82.9%) in contrast to the UW (93.2%) and HTK groups (91.0%). Livers in the EC group showed a reduction in the diameters of pericentral sinusoids (7.3 +/- 0.2 microns; mean +/- SEM) compared with the UW group (9.5 +/- 0.2 microns; P less than 0.05) and HTK group (10.2 +/- 0.8 microns; P less than 0.05), indicating substantial cell swelling in livers stored in EC solution. Permanent adherence of leucocytes was most frequently observed in the EC group (33.5 +/- 1%), while this phenomenon was less pronounced in the UW group (14.5 +/- 1.1%; P less than 0.05) and HTK group (16.3 +/- 0.7%; P less than 0.05). Conversely, temporary adherence of leucocytes was reduced in the EC group (19.7 + 1.3%) compared with the UW group (30.5 + 2.1%) and the HTK group (34.4 + 0.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of an oxidase activating factor of 63 kilodaltons from bovine neutrophils

A 63-kDa protein, which behaves as an oxidase activating factor in bovine neutrophils, has been purified to electrophoretic homogeneity. The protein was isolated from the cytosol of resting bovine neutrophils after several steps, including ammonium sulfate precipitation and chromatography on AcA44, DE-52 cellulose, Mono Q, and Superose 12 in the presence of dithiothreitol. The oxidase activating potency of the protein was assayed with a cell-free system consisting of neutrophil membranes, GTP gamma S, arachidonic acid, and a complementary cytosolic fraction. The purification factor was 200 and the yield 3%. During the course of gel filtration on calibrated Superose 12, the 63-kDa protein eluted as a dimer. Its isoelectric point was 6.4 +/- 0.1. Antibodies raised in rabbits against the 63-kDa protein reacted with a protein of similar size in human neutrophils and in HL60 promyelocytic cells induced to differentiate into granulocytes. No immune reaction was observed in cytosol from undifferentiated HL60 cells, in extracts from bovine skeletal muscle, liver, and brain, or in cytosol prepared from neutrophils derived from a patient with an autosomal cytochrome b positive form of chronic granulomatous disease lacking the 67-kDa oxidase activating factor. Immunoblotting with the 63-kDa bovine protein antiserum demonstrated that activation of bovine neutrophil oxidase by phorbol myristate acetate induced the translocation of the 63-kDa protein from cytosol to the membrane.

NADPH-cytochrome c reductase from rabbit peritoneal neutrophils. Purification, properties and function in the respiratory burst

An NADPH-dependent membrane-bound flavoprotein dehydrogenase, assayed as a catalyst of electron transfer from NADPH to cytochrome c, was extracted from membranes of rabbit peritoneal neutrophils with Triton X-100 and sodium deoxycholate in the presence of diisopropylfluorophosphate as antiprotease, and purified to electrophoretic homogeneity. The purified enzyme in detergent was able to enhance the rate of formation of the superoxide anion O2- in a cell-free system, consisting of membrane and cytosolic fractions from resting neutrophils complemented with arachidonic acid, guanosine 5'-[gamma- thio]triphosphate and Mg2+. This suggested that the NADPH dehydrogenase was a component of the rabbit neutrophil oxidase complex. The purification factor of the enzyme with respect to the membrane fraction was close to 1000 and the recovery of activity was 33%. FMN and FAD were associated with the enzyme in a molar ratio close to 1. On SDS/PAGE, the enzyme migrated with a molecular mass of 77 kDa. A similar mass was determined by filtration on a molecular sieve. The isoelectric point of this enzyme was 4.7 +/- 0.1. Its activity was maximal between pH 7.5 and pH 8.5, and depended on the ionic strength of the medium, with a maximum at an ionic strength of 0.5. Reduction of cytochrome c by NADPH obeyed Michaelis-Menten kinetics with a KM value of 15 microM for cytochrome c. When NADPH was the variable substrate, a KM value of 1.9 microM for NADPH was found, but a significant deviation from Michaelis-Menten kinetics was observed at high concentrations of NADPH. Mersalyl strongly inhibited the reductase activity when added to the enzyme prior to NADPH; preincubation of the enzyme with NADPH considerably reduced the inhibitory efficiency of mersalyl. A partially proteolyzed water-soluble, active, form of enzyme with a molecular mass of 67 kDa was prepared. The proteolyzed enzyme exhibited the same specificity, and kinetic behavior with respect to NADPH, and the same dependency on the ionic strength, as the native enzyme.

Oxygen radicals, inflammation, and arthritis: pathophysiological considerations and implications for treatment

A vast amount of circumstantial evidence implicates oxygen-derived free radicals, especially superoxide and hydroxyl radical (and to lesser extent, hydrogen peroxide), as mediators of inflammation and/or tissue destruction in inflammatory and arthritic disorders. The substrates for radical generation, namely properly stimulated phagocytic cells, transition metal catalysts, and (to a limited extent) ischemia, are all amply present, although there is no particular rheumatic disease in which a consistent abnormality of radical generation has been identified. These radical species can clearly degrade hyaluronic acid, modify collagen and perhaps proteoglycan structure and/or synthesis, alter and interact with immunoglobulins, activate enzymes and inactivate their inhibitors, and possibly participate in chemotaxis. In most situations, however, there is ample scavenging ability to detoxify these radicals before they hit their target, and many rheumatic disease drugs can decrease their production and/or effects. Despite the apparent sufficiency of natural scavengers and the lack of direct evidence that oxygen radicals are pathogenetically important, substantial pharmaceutical effort is still being made to develop free radical scavengers as therapeutic agents. Although individual free radicals die out quickly, rheumatologic interest in them has been sustained for nearly two decades.

The antifolate 10-deazaaminopterin inhibits neutrophil chemotaxis and superoxide generation

The effect of the dihydrofolate reductase inhibitor 10-deazaaminopterin on several neutrophil functions was tested in vitro. At 100 uM it inhibited chemotaxis by 50% and reduced the generation of superoxide by 30%. It had no influence on phagocytosis and did not significantly change the secretion of beta-D-glucuronidase, a marker enzyme of degranulation. After preincubation of white cells with various concentrations of 10-deazaaminopterin, followed by resuspension in drug-free medium, no inhibition of chemotaxis or superoxide generation was seen. Therefore, the effects on chemotaxis and NADPH oxidase appear to be reversible and not due to metabolic transformation of the dihydrofolate reductase inhibitor.

Time-dependent cadmium-neurotoxicity in rat brain synaptosomal plasma membranes

1. The modulation of lipid dynamics and lipid protein interactions were studied in rat brain synaptosomal plasma membranes (SPM) up to 24 hr after exposure to cadmium (Cd). 2. The activity of acetylcholinesterase and adenylate cyclase showed a considerable decrease after 6 hr of Cd exposure, followed by a progressive increase up to 24 hr. 3. SPM chemiluminescence showed a maximum decrease at 12 hr, demonstrating a considerable increase in lipid peroxidation. 4. SPM of Cd-exposed animals showed a statistical significant increase in fluorescence anisotropy parameter [(r0/r) - 1]-1 at 18 and 24 hr compared to SPM of the control, indicating a decrease of membrane fluidity.

Superoxide formation and chemiluminescence of peripheral polymorphonuclear leukocytes in rapidly progressive periodontitis patients

Previous studies have indicated that in certain types of chronic inflammatory periodontal diseases, polymorphonuclear leucocytes (PMN) functions are impaired. In view of the damage oxygen free radicals may cause to the periodontal tissues, the present study focussed on superoxide (SO) formation and luminol-dependent chemiluminescence (LDCL) by peripheral PMN cells in rapidly progressive periodontitis patients (RPP). PMN cell preparations were stimulated by either opsonized bacteria or phorbol myristate acetate (PMA). The results indicate that PMN cells from RPP patients, stimulated by opsonized bacteria, have significantly enhanced SO formation and LDCL response as compared to healthy subjects. The hyperactivity was cell-associated. In the presence of PMA, no significant differences were detected between the groups. The results suggest that PMN cells from RPP patients are functionally activated, and produce elevated levels of oxygen radicals. These oxygen radicals may play a role in the pathogenesis of RPP.

The newly developed neutrophil oxidative burst antagonist apocynin inhibits joint-swelling in rat collagen arthritis

Methylated catechols like apocynin selectively inhibits neutrophil superoxide production without significant side-effects. When rats were treated orally with low doses of apocynin the severity of collagen-induced arthritis was significantly reduced, pointing at a role of oxyradicals in the induction of this disease.

Release of azurophilic granule contents in fMLP-stimulated neutrophils requires two activation signals, one of which is a rise in cytosolic free Ca2+

We have used a continuous spectrofluorimetric method to analyse the role of cytosolic free Ca2+ ([Ca2+]i) in the lysosomal enzyme release from the azurophilic granules in human neutrophils stimulated with f-Met-Leu-Phe (fMLP) in the presence of cytochalasin B. Measurements were performed with the beta-glucuronidase substrate 4-methylumbelliferyl-beta-D-glucuronide. We found that the transient rise in [Ca2+]i induced by fMLP is a necessary signal to obtain maximal degranulation. When this Ca2+ transient is prevented by the Ca2+ chelator BAPTA, degranulation can still be induced by a stimulated Ca2+ influx, albeit to a lower extent. We also studied the degranulation process in the neutrophils of a patient with a generalized chemotactic defect. Release of beta-glucuronidase from the patient's neutrophils could not be induced despite the occurrence of a normal Ca2+ response and normal degranulation of specific granules. We conclude that, besides an increase in [Ca2+]i, an additional signal is required for the fusion of azurophilic granules with the plasma membrane in human neutrophils.

Intracellular production of reactive oxygen species in human neutrophils following activation by the soluble stimuli FMLP, dioctanoylglycerol and ionomycin

The stimuli, sn-1, 2-dioctanoylglycerol; (DG8) the calcium specific ionophore, ionomycin, and the chemotactic peptide formylmethionyl-leucyl-phenylalanine (FMLP) can interact with normal human neutrophils and activate their superoxide/hydrogen peroxide generating NADPH-oxidase. In response to the peptide as well as DG8, the neutrophils produced both superoxide (O2-) and hydrogen peroxide (H2O2). Since interaction between the cells and ionomycin was not associated with any notable superoxide production and hydrogen peroxide was induced only in the presence of azide, a potent inhibitor of the hydrogen peroxide-consuming enzymes catalase and myeloperoxidase, we conclude that this stimulus can generate oxygen metabolites intracellularly. Since the DG8-induced production of hydrogen peroxide was increased in the presence of azide, whereas the FMLP-induced response was largely unaffected, we concluded that the three stimuli differ in their capacity to generate oxygen metabolites intracellularly. The use of sn-1,2-didecanoylglycerol (DG10) as stimulating agent did not result in any detectable activation of the NADPH-oxidase. However, preincubation caused an increased (primed) response during stimulation with the chemotactic peptide FMLP. The response of primed neutrophils to FMLP proceeds with a time-course different from that seen in normal cells. From the results presented on FMLP-induced activity in the presence of azide, we conclude that FMLP causes normal cells to produce oxygen radicals which are released from the cells. However, the primed cells are also capable of generating oxygen metabolites that are retained inside the cells. In fact, measurement of the intracellularly generated metabolites discloses this to be the predominant part of the response.

Superoxide generation by Kupffer cells and priming of neutrophils during reperfusion after hepatic ischemia

The objective of this study was to identify the cellular source of the vascular oxidant stress in hepatic ischemia-reperfusion injury in male Fischer rats. Nonparenchymal cells (Kupffer cells, endothelial cells) and neutrophils were isolated from postischemic liver lobes by collagenase-pronase digestion followed by centrifugal elutriation. The spontaneous and stimulated generation of superoxide by these cells were subsequently quantified in vitro. Large Kupffer cells from the postischemic lobes spontaneously generated 300% more superoxide than similar cells from control animals. No difference in spontaneous superoxide formation was found when the small Kupffer cells were compared. No other cells isolated from the postischemic lobes or control liver including neutrophils released any detectable superoxide spontaneously. In contrast, small Kupffer cells and neutrophils from the postischemic liver generated significantly more superoxide after stimulation with phorbol ester or opsonized zymosan than the controls. The considerably higher response with zymosan stimulation compared to phorbol ester indicates a particular priming for a receptor-mediated signal transduction pathway during reperfusion. These studies demonstrate that Kupffer cells are the principal source of the oxidant stress during the initial reperfusion phase after hepatic ischemia. The priming of neutrophils during this time may be an important factor for the later neutrophil-induced injury phase.

Role of oxygen free radicals in respiratory distress induced by arachidonic acid in the rat

The purpose of our present study is the possible implication of oxygen free radicals in the respiratory distress induced in rats by intravenous administration of arachidonic acid (20 mg/kg). The respiratory frequency was measured and plasma TXB2 concentration was assayed by RIA from blood withdrawn 1 min after arachidonic acid administration. The substances studied were: SOD, catalase, mannitol, DMSO, BHT, imidazole. All the drugs, except imidazole, significantly protect the rats from the respiratory distress induced by arachidonic acid. SOD, catalase, BHT and imidazole inhibit whereas mannitol and DMSO increase the plasma levels of TXB2. We suggest that oxygen free radicals generated in the respiratory burst induced by arachidonic acid are mainly responsible for the consequent respiratory distress.

Respiratory burst of rabbit peritoneal neutrophils. Transition from an NADPH diaphorase activity to an .O2(-)-generating oxidase activity

Superoxide (.O2-) production by the NADPH oxidase of a membrane fraction derived from rabbit peritoneal neutrophils activated by 4 beta-phorbol 12-myristate 13-acetate (PMA) was studied at 25 degrees C under different conditions, and measured by the superoxide dismutase inhibitable reduction of cytochrome c. Whereas PMA-activated rabbit neutrophils incubated in a glucose-supplemented medium exhibited a substantial rate of production of .O2-, the membranes prepared by sonication of the activated neutrophils were virtually unable to generate .O2- in the presence of NADPH. Instead, they exhibited an NADPH-dependent diaphorase activity, measured by the superoxide-dismutase-insensitive reduction of cytochrome c. Upon addition of arachidonic acid, which is known to elicit oxidase activation, the NADPH diaphorase activity of the rabbit neutrophil membranes vanished and was stoichiometrically replaced by an NADPH oxidase activity. The emerging oxidase activity was fully sensitive to iodonium biphenyl, a potent inhibitor of the respiratory burst, whereas the diaphorase activity was not affected. Addition of 0.1% Triton X-100 or an excess of arachidonic acid, acting as detergent, resulted in the reappearance of the diaphorase activity at the expense of the oxidase activity. These results indicate that the diaphorase-oxidase transition is reversible. When the rabbit neutrophil membranes were supplemented with rabbit neutrophil cytosol, guanosine 5'-[gamma-thio]triphosphate and Mg2+, in addition to arachidonic acid, not only the NADPH diaphorase activity disappeared, but the emerging NADPH oxidase activity was markedly enhanced (about 10 times compared to that of membranes treated with arachidonic acid alone). The diaphorase-oxidase transition was accompanied by a 10-fold increase in the Km for NADPH, suggesting a change of conformation propagated to the NADPH-binding site during the transition. The treatment of PMA-activated rabbit neutrophils with cross-linking reagents, like glutaraldehyde or 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide, prevented the loss of the PMA-elicited oxidase activity upon disruption of the cells by sonication, suggesting that the interactions between the components of the oxidase complex are stabilized by cross-linking.

Tumor necrosis factor primes neutrophils by shortening the lag period of the respiratory burst

Pretreatment of neutrophils (PMNs) with low-dose tumor necrosis factor (TNF) enhances their capacity to produce oxidant radicals after stimulation with a variety of agents ('priming'). We used a continuous cytochrome C assay to investigate the superoxide production by human PMNs primed with TNF and subsequently stimulated with phorbol myristate acetate (PMA). There was no difference in the maximum rate of superoxide production by primed and unprimed PMNs stimulated with either high (2 x 10(-6) M) or low levels of PMA (2 x 10(-8) M). Following stimulation with high levels of PMA, primed PMNs demonstrated a significantly shorter lag period than unprimed cells (103.3 +/- 14.4 vs. 142.1 +/- 21.7 seconds) and larger amounts of superoxide generated in the intervals between 100 seconds (3.1 +/- 0.5 vs. 1.7 +/- 0.3 nmol/10(6) PMNs) and 300 seconds (14.9 +/- 1.2 vs. 12.2 +/- 1.1). Primed cells stimulated with low levels of PMA (2 x 10(-8) M) displayed a significantly shorter lag period (1225.8 +/- 96.8 vs. 1573.8 +/- 74.3 seconds) and a greater production of superoxide between 1300 seconds (5.4 +/- 0.9 vs. 3.0 +/- 0.4 nmol/10(6) PMNs) and 1900 seconds (25.7 +/- 4.3 vs. 14.9 +/- 2.4) than unprimed cells. These results indicate that priming of PMNs with TNF increases superoxide production during the early phase of the respiratory burst through a shortening of the post-stimulation lag period.

Adherence of human neutrophils changes Ca2+ signaling during activation with opsonized particles

Changes in the cytosolic free Ca2+ concentration ([Ca2+]i) upon activation of human neutrophils by opsonized particles (serum-treated zymosan; STZ) were evaluated by three different methods: (i) measurement of total fluorescence changes in indo-1 loaded neutrophils activated in suspension; (ii) measurement of fluorescence changes in individual indo-1 loaded neutrophils in a flow cytometer and (iii) measurement of fluorescence changes in individual fura-2 loaded neutrophils adherent to serum-coated coverslips. Our study shows that the opsonized particle-induced change in [Ca2+]i in neutrophils is altered during adherence of the cells to a serum-coated surface. These observations might be of importance for neutrophil function in vivo, since adherence is a prerequisite for diapedesis and chemotaxis.

Isolation and characterization of a cDNA clone for a novel serine-rich neutrophil protein

A cDNA expression library from pig blood neutrophils was immunoscreened with a rabbit antiserum raised against a 32 kDa neutrophil membrane phosphoprotein. Previous work indicated this protein as a component of the superoxide-forming NADPH oxidase enzyme complex (1,2). Only one cDNA clone (B+) was highly positive. The B+ clone contained a 1109 bp insert, with an open reading frame encoding for 284 amino acids. The deduced B+ amino acid sequence contained a 72 amino acid domain with proline and glutamine repeats and two domains extremely enriched with serine residues. The isolated cDNA hybridizes with a 3.1 kb mRNA expressed in pig and human leukocytes.

Characterization of multiple active forms of the NADPH dehydrogenase component of the oxidase complex from rabbit peritoneal neutrophils by photolabeling with an arylazido derivative of NADP+

A NADPH cytochrome c oxidoreductase purified from membranes of rabbit peritoneal neutrophil was shown to behave as the NADPH dehydrogenase component of the O2- generating oxidase complex. A photoactivable derivative of NADP+, azido nitrophenyl-gamma-aminobutyryl NADP+ (NAP4-NADP+), was synthesized in its labeled [3H] form and used to photolabel the NADPH cytochrome c reductase at different stages of the purification procedure. Control assays performed in dim light indicated that the reduced form of NADP4-NADP+ generated by reduction with glucose-6-phosphate and glucose-6-phosphate dehydrogenase was oxidized at virtually the same rate as NADPH. Upon photoirradiation of the purified reductase in the presence of [3H]NAP4-NADP+ and subsequent separation of the photolabeled species by sodium dodecyl sulfate polyacrylamide gel electrophoresis, radioactivity was found to be present predominantly in a protein band with a molecular mass of 77-kDa and accessorily in bands of 67-kDa and 57-kDa. Evidence is provided that the 67-kDa and 57-kDa proteins arose from the 77-kDa protein by proteolysis. Despite removal of part of the sequence, the proteolyzed proteins were still active in catalyzing electron transport from NADPH to cytochrome c and in binding the photoactivable derivative of NADP+.

Priming effect of 2,3-dibenzylbutane-1,4-diol (mammalian lignan) on superoxide production in human neutrophils

We investigated the effect of 2,3-dibenzylbutane-1,4-diol (DBB), a mammalian lignan, on superoxide production and [Ca2+]i mobilization in human neutrophils. DBB did not generate superoxide production by itself, but enhanced the FMLP or A23187-induced superoxide production in a dose dependent manner. DBB did not influence the OAG-induced superoxide production. The priming effect of DBB was inhibited by W-7 or trifluoroperazine, but not by H-7 or staurosporine. And the priming effect of DBB was observed in the presence or absence of extracellular Ca2+. DBB enhanced the low dose FMLP-induced [Ca2+]i mobilization. These results suggest that the priming effect of DBB in human neutrophils may be caused by the activation of the calcium-calmodulin pathway but not the protein kinase pathway.

Interaction between the respiratory burst activity of neutrophil leukocytes and experimentally induced Escherichia coli mastitis in cows

The respiratory burst activity of neutrophil leukocytes from bovine peripheral blood was studied before and during an experimentally induced Escherichia coli mastitis. The competence of neutrophils to generate reactive oxygen species following stimulation with opsonized particles prior to infection was negatively correlated with severity of subsequently induced E. coli mastitis. In the presence of the soluble activator, phorbol myristate acetate, no such correlation was obtained. However, combination of blood neutrophil numbers with phorbol myristate acetate induced respiratory burst competence, called reactive oxygen species-generating capacity, displayed a negative correlation with the intensity of a subsequent inflammation of the bovine mammary gland. At the onset of mastitis, a concomitant reduction in blood neutrophil numbers, a strong shift in cell types, and a substantial decrease in production of reactive oxygen species occurred. Reestablishment and even enhancement of the respiratory burst activity coincided with the reappearance of mature neutrophils. Possible stimulatory effects on neutrophil superoxide generation are discussed. Data suggest that generation of reactive oxygen species by mature neutrophils may be of primary importance for microbial killing during the onset and recovery from mastitis.

Properties of the NADPH dehydrogenase component of the oxidase complex from rabbit peritoneal neutrophils: reconstitution of an oxidase activity with the dehydrogenase component and a membrane extract

A flavin-linked NADPH cytochrome c oxido-reductase of molecular mass 77-kDa was extracted from membranes of rabbit peritoneal neutrophils and purified in the presence of Triton X-100. The redox properties of this enzyme were examined. By some criteria including its high sensitivity to mersalyl, and its relatively high specificity for NADPH compared to NADH, the rabbit neutrophil NADPH cytochrome c reductase resembled NADPH-cytochrome P-450 reductase. Limited proteolysis generated water soluble fragments, with molecular masses of 67-kDa and 57-kDa, which were still endowed with a substantial reductase activity. When added to a lysate of neutrophil membranes in octylglucoside, in the presence of an oxidase activation medium consisting of rabbit neutrophil cytosol, GTP-gamma-S, arachidonic acid and Mg2+, the purified reductase enhanced the production of O2-., suggesting that it forms part of the O2-. generating oxidase.

Kawasaki disease and oxidative metabolism

The plasmid lipid peroxidation products: malonyldialdehyde (MDA), organic hydroperoxides (OHP) and zinc peripheral values were analysed in seven children with Kawasaki disease, in the acute phase, before and after treatment with intravenous immunoglobulins. In the acute phase, plasma levels of MDA (2.95 +/- 0.30 mumol/l, control group: 2.52 +/- 0.08 mumol/l) and OHP (235 +/- 65 mumol/l, control group: 120 +/- 10) were increased (p less than 0.05 and p less than 0.01). Moreover, plasma zinc levels were significantly decreased (10 +/- 2.15 mumol/l versus 15.6 +/- 2.5 mumol/l in control group, p less than 0.05). After treatment with immunoglobulins, MDA, OHP and plasma zinc levels returned to normal. The parallel normalisation of clinical injury draws attention to the possible role of oxygen intermediates in connective tissue degradation and in the pathogenesis of vascular abnormalities in Kawasaki disease.

Cytosolic factors in bovine neutrophil oxidase activation. Partial purification and demonstration of translocation to a membrane fraction

The O2(.-)-generating oxidase of bovine neutrophils is activated in a cell-free system consisting of a particulate fraction enriched in plasma membrane and containing the dormant oxidase, a high-speed supernatant from neutrophil homogenate (cytosol), Mg ions, GTP gamma S, and arachidonic acid [Ligeti, E., Doussiere, J., & Vignais, P.V. (1988) Biochemistry 27, 193-200]. The cytosolic components participating in the activation of the membrane-bound oxidase have been investigated. These components were resolved into several active peaks by Q Sepharose chromatography. The oxidase-activating potency of these peaks was synergistically enhanced by combining samples from separate peaks, or by supplying them with a threshold amount of crude cytosol. Partial purification of two active fractions containing a limited number of proteins of 65, 56, 53, and 45 kDa was achieved by gel filtration of cytosol on Ultrogel AcA44, followed by chromatography on hydroxylapatite and Mono Q. The specific oxidase-activating potency of these partially purified fractions (activating potency per milligram of soluble protein) was 6-8-fold higher than that of crude cytosol; it was enhanced up to 75-fold by complementation with a minute amount of crude cytosol, which per se had a limited efficiency. These data indicate that oxidase activation requires more than one cytosolic component to be activated. To check whether translocation of cytosolic proteins to the membrane occurred concomitantly with oxidase activation, use was made of radiolabeled cytosolic proteins. Cytosol was treated with phenyl[14C]isothiocyanate ([14C]PITC), such that 60% of its activation potency was still present.(ABSTRACT TRUNCATED AT 250 WORDS)

Two cytosolic components of the human neutrophil respiratory burst oxidase translocate to the plasma membrane during cell activation

The superoxide-forming respiratory burst oxidase of human neutrophils is composed of membrane-associated catalytic components and cytosolic constituents required for oxidase activation. This study concerns the hypothesis that cytosolic oxidase components translocate to a membrane fraction when neutrophils are stimulated and the oxidase is activated. A polyclonal antiserum that recognizes two discrete cytosolic oxidase components of 47 and 67 kD was used to probe transfer blots of electrophoresed membrane and cytosol fractions of resting and stimulated neutrophils. In contrast to their strictly cytosolic localization in unstimulated cells, both proteins were detected in membrane fractions of neutrophils activated by phorbol esters and other stimuli. This translocation event was a function of stimulus concentration as well as time and temperature of exposure to the stimulus. It was inhibited by concentrations of N-ethylmaleimide that blocked superoxide formation but was unaffected by 2-deoxyglucose. There was a correlation between translocation of the cytosolic proteins and activation of the oxidase as determined by superoxide formation. Quantitative analyses suggested that approximately 10% of total cellular p47 and p67 became membrane-associated during phorbol ester activation of the oxidase. Analysis of Percoll density gradient fractions indicated that the target membrane for translocation of both proteins was the plasma membrane rather than membranes of either specific or azurophilic granules. In the cell-free oxidase system arachidonate-dependent but membrane-independent precipitation of the cytosolic oxidase proteins was demonstrated. The data show that activation of the respiratory burst oxidase in stimulated human neutrophils is closely associated with translocation of the 47- and 67-kD cytosolic oxidase components to the plasma membrane. We suggest that this translocation event is important in oxidase activation.