Cytochrome b, flavins, and ubiquinone-50 in enucleated human neutrophils (polymorphonuclear leukocyte cytoplasts)

Respiratory response of phagocytes: terminal NADPH oxidase and the mechanisms of its activation

The chemical composition, properties and activation mechanism of the O2(-)-forming NADPH oxidase of phagocytes were investigated, using partially purified enzyme preparations. Highly active NADPH oxidase was extracted as an aggregate of high Mr from the membranes of neutrophils and macrophages. The enzyme complex contained phospholipids and cytochrome b-245, very little FAD and almost no quinones or NAD(P)H-dye reductase activity. The purification of a polypeptide with a relative molecular mass of 31 500 strictly paralleled the purification of NADPH oxidase, suggesting that this polypeptide is a component of the enzyme. This protein was identified as cytochrome b -245 after dissociation of the proteolipid complex and purification of the cytochrome moiety. The 31 500 Mr protein was phosphorylated in enzyme preparations from activated but not from resting cells. The results indicate that: cytochrome b-245 is a major component of NADPH oxidase; the involvement of NAD(P)H dye reductases in the O2(-)-forming activity is questionable; the cytochrome b-245: FAD ratio in the enzyme complex is much higher than that indicated in crude preparations; the Mr of pig neutrophil cytochrome b-245 is 31 500; the activation of the O-2-forming system involves a process of phosphorylation of cytochrome b-245.

The NADPH oxidase of professional phagocytes--prototype of the NOX electron transport chain systems

The NADPH oxidase is an electron transport chain in "professional" phagocytic cells that transfers electrons from NADPH in the cytoplasm, across the wall of the phagocytic vacuole, to form superoxide. The electron transporting flavocytochrome b is activated by the integrated function of four cytoplasmic proteins. The antimicrobial function of this system involves pumping K+ into the vacuole through BKCa channels, the effect of which is to elevate the vacuolar pH and activate neutral proteases. A number of homologous systems have been discovered in plants and lower animals as well as in man. Their function remains to be established.

Long-term follow-up and outcome of 39 patients with chronic granulomatous disease

OBJECTIVES

To evaluate the clinical long-term course in patients with chronic granulomatous disease (CGD) with respect to different CGD subtypes and currently used antimicrobial prophylactic measures.

STUDY DESIGN

The records of 39 patients with CGD who were monitored during a period of 22 years were reviewed. All infections, infectious complications, and clinical outcomes were documented for a total observation period of 610 patient-years and were stratified with respect to different CGD subtypes.

RESULTS

Lymphadenitis, skin abscesses, and pneumonia occurred in 87%, 72%, and 59% of the patients, respectively. In 151 microbiologic isolates Staphylococcus aureus, Aspergillus species, Candida species, Pseudomonas species, and Salmonella species were the most frequently detected microorganisms. There were 167 severe infections requiring hospitalization and intravenous antimicrobial treatment, resulting in an incidence of 3.7 severe infections per 100 patient months (SI/100 PM). Long-term antibiotic prophylaxis significantly reduced the incidence of severe bacterial infections from 4.8 SI/100 PM to 1. 6 SI/100 PM (P =.0035). In contrast, fungal infections increased under antibiotic prophylaxis from a mean incidence of 0.2 SI/100 PM to 1.9 SI/100 PM (P =.04). We found a 50% survival rate through the fourth decade of life, with a plateau after the third decade of life. Patients with a complete absence of cytochrome b(558) showed an earlier manifestation of their disease and a higher incidence of infections and had significant lower survival than patients with only diminished cytochrome b(558) or autosomal recessive CGD.

CONCLUSIONS

Infections with Aspergillus species have become the major cause of infectious complications and death in patients with CGD. Prophylactic and therapeutic measures are needed to further increase life expectancy and quality for patients with CGD.

An in-frame triplet deletion within the gp91-phox gene in an adult X-linked chronic granulomatous disease patient with residual NADPH-oxidase activity

In an adult patient suffering from X-linked chronic granulomatous disease (X-CGD) with residual activity of the NADPH-oxidase we found an unusual biochemical constellation with a defective gp91-phox gene. As shown by Western blot using a specific antibody the gp91-phox protein was normal in PMN. However, NADPH-oxidase activity was reduced and no heme spectrum was detectable. By Southern blot and RFLP analysis of genomic DNA a larger defect within the gp91-phox gene was excluded. Sequencing of the gp91-phox cDNA revealed an in-frame deletion of a TTC triplet in exon VI of the gp91-phox gene. This mutation indicates the loss of one amino acid (phenylalanine 215 or 216) in the gp91-phox protein. Sequencing of genomic DNA from the heterozygous daughter of the propositus confirmed this mutation. The absence of a functional cytochrome b558-spectrum in granulocytes of the patient suggests an involvement of the phenylalanine 216 area in heme binding by gp91 phox. This is the first mutation described in a X-CGD patient with absence of a functional cytochrome b558-spectrum but with detectable gp91-phox protein and residual NADPH-oxidase activity.

Chronic granulomatous disease in adults

BACKGROUND

Chronic granulomatous disease (CGD), an inherited disorder of granulocyte function caused by failure of intracellular superoxide production, normally presents in the first years of life with severe recurrent bacterial and fungal infections.

METHODS

From the files of two children's hospitals we identified 11 CGD patients who were remarkable for an unusually late diagnosis, at 13-43 years of age. Their clinical and laboratory features were examined.

FINDINGS

The first clinical manifestation occurred at a median age of 3.6 years but CGD was not diagnosed until a median age of 22 years. Pneumonias and abscesses caused by Staphylococcus aureus and Aspergillus species were the most frequent infections. Granulomas, often leading to chronic complications, occurred in 7 of the patients. With 1.1 severe infections in 100 patient months, the 11 patients had a lower frequency of severe infections than patients with classic CGD; however, such infections could be equally life-threatening. 8 of the patients had X-linked CGD with small but detectable quantities of cytochrome b558, normally absent in X-linked CGD; and 3 had autosomal-recessive CGD. 9 patients had residual production of reactive oxygen metabolites, a feature that could explain the low incidence of infections.

INTERPRETATION

CGD in adults may be more common than previously assumed. In view of the possibility of timely treatment, infection prophylaxis, and genetic counselling for affected families, CGD should be excluded in any patient with unexplained infections or granulomas.

The superoxide-generating oxidase of phagocytic cells. Physiological, molecular and pathological aspects

Professional phagocytes (neutrophils, eosinophils, monocytes and macrophages) possess an enzymatic complex, the NADPH oxidase, which is able to catalyze the one-electron reduction of molecular oxygen to superoxide, O2-. The NADPH oxidase is dormant in non-activated phagocytes. It is suddenly activated upon exposure of phagocytes to the appropriate stimuli and thereby contributes to the microbicidal activity of these cells. Oxidase activation in phagocytes involves the assembly, in the plasma membrane, of membrane-bound and cytosolic components of the oxidase complex, which were diassembled in the resting state. One of the membrane-bound components in resting phagocytes has been identified as a low-potential b-type cytochrome, a heterodimer composed of two subunits of 22-kDa and 91-kDa. The link between NADPH and cytochrome b is probably a flavoprotein whose subcellular localization in resting phagocytes remains to be determined. Genetic defects in the cytochrome b subunits and in the cytosolic factors have been shown to be the molecular basis of chronic granulomatous disease, a group of inherited disorders in the host defense, characterized by severe, recurrent bacterial and fungal infections in which phagocytic cells fail to generate O2- upon stimulation. The present review is focused on recent data concerning the signaling pathway which leads to oxidase activation, including specific receptors, the production of second messengers, the organization of the oxidase complex and the molecular defects responsible for granulomatous disease.

NADH oxidase of plasma membranes

NADH oxidase is a cyanide-resistant and hormone-responsive oxidase intrinsic to the plasma membrane of both plant and animal cells. The activity has many unique characteristics that distinguish it from other oxidases and oxidoreductases of both organelles and internal membranes and from other oxidoreductases of the plasma membrane. Among these are resistance to inhibition by cyanide, catalase, superoxide dismutase, and phenylchloromercuribenzoate. Activity is stimulated by hormones and growth factors and inhibited by quinone analogs such as piercidin, the flavin antagonist atebrin, and growth inhibiting gangliosides such as GM3. In marked contact to the NADH-ferricyanide oxidoreductase of the plasma membrane, the NADH oxidase is activated by lysophospholipids and fatty acids, products of phospholipase A2 action, in a time-dependent manner suggestive of stabilization of an activated form of the enzyme. The hormone-responsive NADH oxidase of the plasma membrane is not a peroxidase and may function as a terminal oxidase to link transfer of electrons from NADH to oxygen at the plasma membrane. The functional significance of the NADH oxidase of the plasma membrane is unknown but some relationship to growth or growth control is indicated. In both animal and plant plasma membranes, the oxidase is activated by growth factors and hormones to which the cells or tissues of origin have functional hormone or growth factor receptors. In addition, substances that inhibit the oxidase, the associated transmembrane reductase or both, inhibit growth. In transformed cells and tissues, the hormone and growth factor responsiveness of the NADH oxidase is reduced or absent. With human keratinocytes which exhibit an increased sensitivity to the antiproliferative action of both retinoic acid and calcitriol, the NADH oxidase of the plasma membrane is strongly inhibited by these agents and shows the same increased sensitivity. If transfer of electrons from NADH to oxygen across or within the eukaryotic plasma membrane is an important aspect of growth or growth control, then the hormone- and growth factor-responsive NADH oxidase associated with the plasma membrane could be of fundamental importance. Because of its low basal activity, stimulation by growth factors and hormones, and the inhibition of growth in direct proportion to inhibition of the oxidase, the activity is a candidate as a rate-limiting step in the growth process. Completely unknown is the mechanism whereby NADH oxidation and growth or growth control may be coupled. This, together with further characterization of the activity and the mechanism of loss of control with neoplastic transformation, represent important challenges for future investigations.

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.

The participation of coenzyme Q in free radical production and antioxidation

Published experimental data pertaining to the participation of coenzyme Q as a site of free radical formation in the mitochondrial electron transfer chain and the conditions required for free radical production have been reviewed critically. The evidence suggests that a component from each of the mitochondrial NADH-coenzyme Q, succinate-coenzyme Q, and coenzyme QH2-cytochrome c reductases (complexes I, II, and III), most likely a nonheme iron-sulfur protein of each complex, is involved in free radical formation. Although the semiquinone form of coenzyme Q may be formed during electron transport, its unpaired electron most likely serves to aid in the dismutation of superoxide radicals instead of participating in free radical formation. Results of studies with electron transfer chain inhibitors make the conclusion dubious that coenzyme Q is a major free radical generator under normal physiological conditions but may be involved in superoxide radical formation during ischemia and subsequent reperfusion. Experiments at various levels of organization including subcellular systems, intact animals, and human subjects in the clinical setting, support the view that coenzyme Q, mainly in its reduced state, may act as an antioxidant protecting a number of cellular membranes from free radical damage.

Preparation and characterization of plasma membrane vesicles from human polymorphonuclear leukocytes

It would be advantageous to prepare models of the neutrophil plasma membrane in order to examine the role of the plasma membrane in transmembrane signal transduction in the human neutrophil and to dissect ligand-receptor interactions and structural changes in the cell surface upon stimulation. A number of investigators have prepared neutrophil membrane vesicles by homogenization, sonication, or centrifugation--techniques that can result in the loss of substantial amounts of surface membrane material, disruption of lysosomes causing proteolysis of membrane proteins, and contamination of the plasma membrane fraction by internal membranes. These limitations have been overcome in the present studies by employing a modification of the method previously developed in this laboratory. Human neutrophils were suspended in a buffer simulating cytoplasmic ionic and osmotic conditions and disrupted by nitrogen cavitation. The resultant cavitate was freed of undisrupted cells and nuclei and then centrifuged through discontinuous isotonic/isoosmotic Percoll gradients, which resolved four fractions: alpha (intact azurophilic granules), beta (intact specific granules), gamma (membrane vesicles), and delta (cytosol). The gamma fraction was highly enriched in alkaline phosphatase, a marker of the plasma membrane. In addition, this fraction contained less than 5% of the amounts of lysosomes (indicated by lysozyme activity) and nuclei (indicated by DNA content) found in intact cells or in unfractionated cavitate. Furthermore, the gamma fraction contained less than 10% of the levels of endoplasmic reticulum, Golgi, mitochondrial, and lysosomal membranes in cells or cavitates, as determined by assays for glucose 6-phosphatase, galactosyl transferase, monoamine oxidase, and Mo1 (CD11b/CD18; Mac-1), respectively. Finally, 75% of the membrane vesicles were sealed, as indicated by assay of ouabain-sensitive (Na+,K+) ATPase activity, and 55% were oriented right-side-out, as determined by exposure of concanavalin A (ConA) receptors and sialic acid residues on the surfaces of the vesicles. These heterogeneous preparations could be enriched for right-side-out vesicles by their selective adherence to ConA-coated plates and subsequent detachment by rinsing the surfaces of the plates with alpha-methylmannoside. This enrichment protocol did not affect the integrity of the vesicles and resulted in populations in which greater than 85% of the vesicles were oriented right-side-out. This procedure thus permits the preparation of sealed, right-side-out membrane vesicles that may be used as valid experimental models of the neutrophil plasma membrane in a variety of functional studies.

Leukocytic oxygen activation and microbicidal oxidative toxins

Following a brief introduction of cellular response to stimulation comprising leukocyte activation, three major areas are discussed: (1) the neutrophil oxidase; (2) myeloperoxidase (MPO)-dependent oxidative microbicidal reactions; and (3) MPO-independent oxidative reactions. Topics included in section (A) are current views on the activation mechanism, redox composition, structural and topographic organization of the oxidase, and its respiratory products. In section (B), emphasis is placed on recent research on cidal mechanisms of HOCl, including the oxidative biochemistry of active chlorine compounds, identification of sites of lesions in bacteria, and attendant metabolic consequences. In section (C), we review the (bio)chemistry of H2O2 and .OH microbicidal reactions, with particular attention being given to addressing the controversial issue of probe methods to identify .OH radical and critical assessment of the recent proposal that MPO-independent killing arises from site-specific metal-catalyzed Fenton-type chemistry.

Subcellular localization and dynamics of components of the respiratory burst oxidase

Membrane and cytosolic factors cooperate to generate NADPH-oxidase. The study of the syndrome of NADPH-oxidase deficiencies, chronic granulomatous disease, has enabled the identification of two membrane factors: a flavin adenine dinucleotide flavoprotein and a b cytochrome. The nature of the cytosolic components is still unknown, but a 47-kD protein, whose phosphorylation occurs in parallel with the generation of a respiratory burst in intact cells, seems to be one of the cytosolic factors. The subcellular localization of the membrane-bound NADPH-oxidase components has been studied in neutrophils: In unstimulated cells, only a minute fraction of the NADPH-oxidase components is localized in the plasma membrane, whereas approximately 80% is localized in the membrane of the specific granules and the majority of the rest is in a newly described membrane-bound compartment, the secretory granules, identified by latent alkaline phosphatase. During stimulation, these NADPH-oxidase components are translocated to the plasma membrane as a result of fusion of granule membrane with plasma membrane. Only the NADPH-oxidase components present in the plasma membrane are incorporated in the respiratory burst oxidase generated in intact cells.

Partial correction of the phagocyte defect in patients with X-linked chronic granulomatous disease by subcutaneous interferon gamma

Chronic granulomatous disease, a disorder of host defense, is characterized by an impairment in the killing of microbes that results from a defect in the production of superoxide anion by phagocytes. We examined the efficacy of interferon gamma, a physiologic activator of phagocytic-cell function, in the treatment of the disease. Two subcutaneous injections of recombinant interferon gamma (0.1 mg per square meter of body-surface area per dose) were administered on consecutive days to four patients with the X-linked form of the disease. Treatment resulted in 5- to 10-fold increases in superoxide production by granulocytes and monocytes; the improvement was sustained for more than two weeks. Granulocyte bactericidal activity rose proportionally. In the two most responsive patients, both phagocytic functions reached the normal range of activity. In association with these functional changes, we observed an increase in cellular contents of phagocyte cytochrome b (a critical component of the superoxide-producing oxidase) and immunoreactive cytochrome b heavy chain (the product of the gene that is defective in X-linked chronic granulomatous disease). Levels of cytochrome b detected by spectrophotometry rose from near zero to 10 to 50 percent of normal values. This study demonstrates partial correction of the cellular defects in chronic granulomatous disease by interferon gamma and provides a basis for clinical trials of the agent.

Distinct patterns of granulocyte luminol-dependent chemiluminescence response to lectins WGA and RCA-I

THe chemiluminescence response was measured in human polymorphonuclear leukocytes (PMNLs) after stimulation with different concentrations of the lectins Triticum vulgaris agglutinin (wheat germ agglutinin, WGA) and Ricinus communis agglutinin I (RCA-I). The two lectins achieved distinct patterns of chemiluminescence; RCA-I evoked a dose-dependent response (0-15 micrograms/ml) with respect to the initial rate of light emission, but the peak value was reached after different lengths of time. A maximum response was obtained after about 25 min with a concentration of 2-4 micrograms/ml. By contrast, WGA caused a bimodal reaction after stimulus addition. In this case the first peak occurred after 15-20 min, and the second peak after around 60 min with maximum effect for 0.5 and 0.25-0.50 micrograms/ml WGA, respectively. The PMNL response is discussed in relation to the regulation of the production of oxygen metabolites and in relation to the pathophysiologic consequences of lectin-mediated activation of phagocytic cells in intestinal epithelium.

The superoxide-forming enzymatic system of phagocytes

The formation of oxygen-derived free radicals by the phagocytes (neutrophils, eosinophils, monocytes and macrophages) is catalysed by a membrane-bound NADPH oxidase which is dormant in resting cells and becomes activated during phagocytosis or following interaction of the cells with suitable soluble stimulants. This enzyme is under investigation in many laboratories but its molecular structure remains to be clarified. Possible components such as flavoproteins, cytochrome b558, and quinones have been proposed on the basis of enzyme purification studies, effects of inhibitors, kinetic properties and analysis of genetic defects of the oxidase. An extensive discussion of the evidence for the participation of these constituents is reported. On the basis of the available information on the structure and the catalytic properties of the NADPH oxidase, a series of possible models of the electron-transport chain from NADPH to O2 is presented. Finally, the triggering mechanism of the respiratory burst is discussed, with particular reference to the stimulus-response coupling and the final modification(s) of the oxidase (phosphorylation, assembly, change of lipid environment, etc.) which are involved in its activation.

Separation and function of neutrophil karyogranuloplasts and comparison with cytoplasts and intact cells

Since neutrophil cytoplasts lacking nucleus and granules were first prepared by centrifuging neutrophils over a discontinuous Ficoll gradient containing cytochalasin B, several functional deficits have been reported in these cytoplasts. Although these functional deficits have been considered to originate from the absence of organelles, cell damage during preparation could not be excluded. Therefore, in the following experiments the Ficoll gradient was modified to isolate both cytoplasts and karyogranuloplasts, which have a nucleus and granules and represent the cell after loss of the cytoplast. Electron microscopy and analysis of marker proteins and cell volume showed that karyogranuloplasts were distinct from neutrophils. The phorbol myristate acetate (PMA) or N-formylmethionylleucylphenylalanine (FMLP)-induced O2- release, corrected by surface area, was in the following order: neutrophils greater than cytoplasts greater than karyogranuloplasts. Both aggregation and membrane potential depolarization were maximal in neutrophils, intermediate in karyogranuloplasts, and lowest in cytoplasts when either PMA or FMLP was used as a stimulant. Extracellular release of the granule contents (degranulation) was triggered by FMLP in both neutrophils and karyogranuloplasts. Cytochalasin B pretreatment greatly enhanced FMLP-induced O2- release, degranulation, aggregation, and depolarization of membrane potential in neutrophils and karyogranuloplasts, but not in cytoplasts. The ability of cytochalasin B to potentiate FMLP-triggered cell function probably depends on granules or cell organelles which are depleted in cytoplasts. Chemokinesis and chemotaxis were impaired in both karyogranuloplasts and cytoplasts. Specific FML[3H]P binding was greater in karyogranuloplasts than in cytoplasts. Cellular actin content, measured by the DNase I inhibition assay, was abundant in cytoplasts and was extremely low in karyogranuloplasts. Karyogranuloplasts retain various neutrophil functions, except for chemotaxis, and provide an important control when studying the role of cell organelles in cytoplast function.

Flavonoid impairment of neutrophil response

Flavonoids are a class of phenolic plant pigments which impair the oxidative burst of neutrophils to an extent dependent on their hydrophobicity. The distribution of quercetin and of morin in nitrogen-cavitated neutrophils paralleled their respective hydrophobic characteristics and respiratory burst inhibition. While both flavonoids were localized primarily in the specific granule membrane of neutrophils, the amount of quercetin was considerably greater than that of morin. We here demonstrate inhibition of the initial stimulation response, depolarization of the membrane potential as monitored by fluorescence of the membrane probe diS-C3-(5), and of the respiratory burst, monitored by following the destruction of diS-C3-(5), a reaction mediated by the H2O2 produced in the burst. The flavonoids kaempferol, morin, quercetin, or fisetin were preincubated with human neutrophils at a concentration of 100 microM per 2 X 10(6) cells/ml for 2-3 min and subsequently stimulated with 1 microgram/ml of the tumor promoter phorbol myristate acetate (PMA) or with 60 micrograms/ml of immune complex. The effect of each compound differed, i.e. depolarization was enhanced by some and inhibited by others, while H2O2 generation was inhibited by each, supporting our previous findings that membrane potential depolarization and the respiratory burst are dissociable events. Concentration-response experiments, performed at flavonoid concentrations between 12.5 and 500 microM to determine the IC50 values of these compounds for depolarization and burst activation, indicated that none of the flavonoids affected the resting potential, while all perturbed the stimulus-coupled response, the direction and extent of the perturbation depending upon the stimulus, and the function assessed. These data show that the effects of flavonoids on human neutrophils are complex and suggest several sites of action depending upon the flavonoid's subcellular distribution and pathway of stimulation.

The respiratory burst of bovine neutrophils. Role of a b type cytochrome and coenzyme specificity

A new method of preparation of bovine polymorphonuclear leukocytes (PMN) is described. The subcellular distribution of cytochrome b in resting and activated bovine PMN was compared to that of the O2-.-generating oxidase (assessed as NADPH cytochrome c reductase inhibited by superoxide dismutase). In resting PMN and in PMN activated by phorbol myristate acetate (PMA), cytochrome b was located into two membrane fractions, one of which was enriched in plasma membrane and cosedimented with alkaline phosphatase, while the other consisted of a denser material cosedimenting with markers of the specific and azurophil granules, i.e. the vitamin-B12-binding protein and myeloperoxidase respectively. During activation of PMN by PMA, 15-20% cytochrome b migrated from dense granules to the plasma membrane. The distribution of the O2-. generating oxidase and cytochrome b in subcellular particles was studied during the course of phagocytosis of PMA-coated latex beads by bovine PMN. At the onset of the respiratory burst, the phagocytic vacuoles arising from internalization of the plasma membrane were enriched in oxidase and alkaline phosphatase, but their specific content of cytochrome b was limited; in contrast, cytochrome b was predominant in denser membrane fractions cosedimenting with myeloperoxidase and the vitamin-B12-binding protein. After a few minutes of phagocytosis, a fraction of light vacuoles, slightly denser than the phagocytic vacuoles, became enriched in O2-.-generating oxidase, cytochrome b, the vitamin-B12-binding protein and myeloperoxidase. These vacuoles probably arose from the fusion of the phagocytic vacuoles with dense granules. In bovine PMN supplemented with glucose and maintained in anaerobiosis, activation by PMA induced slow reduction of cytochrome b (60-70% in 15 min at 37 degrees C). Similar results were obtained with cytoplasts after activation by PMA (30% reduction in 3 min at 37 degrees C). Cytochrome b in a particulate fraction obtained by centrifugation at 100 000 X g of an homogenate of PMA-activated PMN, was slowly reduced upon addition of NADPH under anaerobiosis (less 20% in 20 min at 37 degrees C). No reduction occurred in the 100 000 X g fraction prepared from non-activated PMN. The Soret band of cytochrome b reduced by dithionite was displaced by CO only by 1-2 nm. At subsaturating concentrations, CO had no effect on the rate of O2 uptake by activated bovine PMN.(ABSTRACT TRUNCATED AT 400 WORDS)

Superoxide dismutase and glutathione peroxidase activities in neutrophils from selenium deficient and copper deficient cattle

Oxygen consumption and the activities of the selenoenzyme glutathione peroxidase, and of the hexose monophosphate shunt were lower than normal in neutrophils from Se deficient cattle. However, these activities and the activity of Cu/zinc superoxide dismutase were unaffected in neutrophils from Cu deficient cattle. These results are discussed with reference to impaired neutrophil microbicidal activity previously demonstrated to result from Se or Cu deficiency in cattle.

Spectroscopic interference of hemoglobin with neutrophil cytochrome b-245 and its elimination by carbon monoxide

A cytochrome b, designated as cytochrome b-245, exists in neutrophils and is probably involved in their stimulated oxidative burst. As a rule, its concentration is spectroscopically measured by the height of its alpha-peak at 558-559 nm (dithionite-reduced minus oxidized). Hemoglobin (Hb), which usually contaminates neutrophils isolated from blood, interferes with the spectroscopic measurement of the cytochrome. Hb contamination from less than 0.4 red blood cells per 100 neutrophils leads to over-estimation of the cytochrome by approximately 50%. This interference can be overcome by bubbling CO through neutrophil homogenates heavily contaminated by Hb, prior to the conventional spectroscopic procedure. The cytochrome B-245 concentration obtained in neutrophils by CO bubbling is 7.2 +/- 1.28 pmoles per 10(6) polymorphonuclear neutrophils.