Identification of ubiquinone-50 in human neutrophils and its role in microbicidal events

Intracellular reduction of coenzyme Q homologues with a short isoprenoid side chain induces apoptosis of HeLa cells

Coenzyme Q (CoQ) is an essential factor of the mitochondrial respiratory chain. CoQ homologues with different lengths of the isoprenoid side chain are widely distributed in nature, but little is known about the relationship between the isoprenoid side chain length and biological function; therefore, we examined the effects of CoQ homologues on HeLa cells. When CoQ homologues with a shorter isoprenoid side chain than CoQ4 were added to HeLa cells, they induced cell death, and the order of cytotoxic intensity was as follows: CoQ0 ≫ CoQ3 ≈ CoQ1 > CoQ2 ≫ CoQ4. Furthermore, we found that CoQ1, CoQ2 and CoQ3 could induce caspase-mediated apoptosis, and the order of intensity was as follows: CoQ3 > CoQ2 ≥ CoQ1. We could not identify the participation of reactive oxygen species in the apoptosis induction, but observed that an NAD(P)H dehydrogenase (quinone) 1 (NQO1) inhibitor, dicumarol, could inhibit not only the intracellular reduction of the homologues but also apoptosis. However, because dicumarol did not affect well-known apoptosis inducers, such as anti-Fas IgG, tumor necrosis factor (TNF)-α, TNF-related apoptosis-inducing ligand, UV-B and H2O2 of HeLa cells at all, we concluded that NQO1-related intracellular reduction of CoQ, or its reduced product, ubiquinol, may participate in the apoptosis induction of HeLa cells.

Prepartal Energy Intake Alters Blood Polymorphonuclear Leukocyte Transcriptome During the Peripartal Period in Holstein Cows

In the dairy industry, cow health and farmer profits depend on the balance between diet (ie, nutrient composition, daily intake) and metabolism. This is especially true during the transition period, where dramatic physiological changes foster vulnerability to immunosuppression, negative energy balance, and clinical and subclinical disorders. Using an Agilent microarray platform, this study examined changes in the transcriptome of bovine polymorphonuclear leukocytes (PMNLs) due to prepartal dietary intake. Holstein cows were fed a high-straw, control-energy diet (CON; NE_L = 1.34 Mcal/kg) or overfed a moderate-energy diet (OVE; NE_L = 1.62 Mcal/kg) during the dry period. Blood for PMNL isolation and metabolite analysis was collected at −14 and +7 days relative to parturition. At an analysis of variance false discovery rate <0.05, energy intake (OVE vs CON) influenced 1806 genes. Dynamic Impact Approach bioinformatics analysis classified treatment effects on Kyoto Encyclopedia of Genes and Genomes pathways, including activated oxidative phosphorylation and biosynthesis of unsaturated fatty acids and inhibited RNA polymerase, proteasome, and toll-like receptor signaling pathway. This analysis indicates that processes critical for energy metabolism and cellular and immune function were affected with mixed results. However, overall interpretation of the transcriptome data agreed in part with literature documenting a potentially detrimental, chronic activation of PMNL in response to overfeeding. The widespread, transcriptome-level changes captured here confirm the importance of dietary energy adjustments around calving on the immune system.

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.

Synthesis and structural characterization of silver(I), aluminium(III) and cobalt(II) complexes with 4-isopropyltropolone (hinokitiol) showing noteworthy biological activities. Action of silver(I)-oxygen bonding complexes on the antimicrobial activities

Through two unequivalent oxygen donor atoms of the hinokitiol (Hhino; C10H12O2; 4-isopropyltropolone) ligand that showed noteworthy biological activities, the dimeric, silver(I)-oxygen bonding complex [Ag(hino)]2 1, the monomeric aluminium(III) complex [Al(hino)3].0.5H2O 4 and the cobalt(II) complex "[Co(hino)2]2.H2O" 6 were synthesized and characterized with elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR and solution (1H and 13C) NMR spectroscopy. The crystal structure of 1 was determined by Rietveld analysis based on X-ray powder diffraction (XPD) data and those of [Al(hino)3].MeOH 4a and [Co(hino)2(EtOH)]2 6a, being obtained as yellow block crystals and red platelet crystals, respectively, by crystallization of 4 and 6, were determined by single-crystal X-ray analysis. The antimicrobial activities of 1, 4 and 6, evaluated with minimum inhibitory concentration (MIC; microg ml(-1)), were compared with those of other metal complexes (M=Na, Li, Cs, Ca, V, Zn) with the hino- ligand. The antimicrobial activities observed in the alkali-metal salts strongly suggested that they were attributed to the effect of the anionic hino- species. The antimicrobial activities of 1 were significantly enhanced, whereas those of other metal complexes were suppressed, compared with those of the neutral Hhino and anionic hino- molecules. The antimicrobial activities observed in 1 were comparable with those of other recently found silver(I)-oxygen bonding complexes, the ligands of which had no activity. Thus, it is proposed that the antimicrobial activities of the silver(I)-oxygen bonding complexes are due to a direct interaction or complexation of the silver(I) ion with biological ligands such as protein, enzyme and membrane, and the coordinating ligands of the silver(I) complexes play the role of a carrier of the silver(I) ion to the biological system.

Inhibitory effect of beta-thujaplicin on ultraviolet B-induced apoptosis in mouse keratinocytes

Sunburn cells are thought to represent ultraviolet B-induced apoptotic keratinocytes. It has been demonstrated that enzymatic and nonenzymatic antioxidants effectively suppress sunburn cell formation, indicating that reactive oxygen species may play a role in the progression of ultraviolet B-induced apoptosis. Metallothionein, a cytosol protein, has antioxidant activity, and overexpression of metallothionein has been reported to reduce the number of sunburn cells in mouse skin. We have also demonstrated that overexpression of metallothionein inhibits ultraviolet B-induced DNA ladder formation in mouse keratinocytes. These findings support the hypothesis that cellular metallothionein may play an important role in the inhibition of ultraviolet B-induced apoptosis in keratinocytes through its antioxidant activity. In the present study, we investigated the effects of beta-thujaplicin, an extract from the woods of Thuja plicata D. Don. and Chamaecyparis obtuse, Sieb. et Zucc., on ultraviolet B-induced apoptosis in keratinocytes and on metallothionein induction. Topical application of beta-thujaplicin decreased the number of ultraviolet B-mediated sunburn cells and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling-positive cells in mouse ear skin. Incubation with beta-thujaplicin suppressed ultraviolet B-induced DNA ladder formation in cultured mouse keratinocytes. Histochemical analysis showed that topical application of beta-thujaplicin induced metallothionein protein in mouse skin. Northern analysis and western blotting revealed significant induction of metallothionein mRNA and metallothionein protein, respectively, in beta-thujaplicin-treated cultured mouse keratinocytes. These findings indicate that beta-thujaplicin inhibits ultraviolet B-induced apoptosis in keratinocytes and strongly suggest that the inhibitory mechanism is due to the antioxidant activity of metallothionein induced by the agent.

Influences of lovastatin administration on the respiratory burst of leukocytes and the phosphorylation potential of mitochondria in guinea pigs

Lovastatin, a cholesterol-lowering drug, decreased plasma cholesterol and cardiac tissue coenzyme Q10 levels in guinea pigs given 20 mg per kg body weight twice a day. Plasma cholesterol levels were reduced 40% in animals 2 to 4 months of age and 61% in animals 2 years of age. Coenzyme Q10 values in cardiac muscle and cardiac mitochondria of the treated, older group were decreased 31% and 37%, respectively. A significant decrease was not observed in coenzyme Q10 levels of the younger animal group. The potential to phosphorylate ADP to ATP driven by pyruvate-malate and succinate oxidation was decreased 43% and 45%, respectively, for cardiac mitochondria from the treated, 2-year-old animals. A decrease in phosphorylation potential was not observed for the younger group. The respiratory burst of leukocytes isolated from the intraperitoneal cavities of the treated, older animals was decreased 67%, while leukocytes isolated directly from their blood was decreased 76% (Diebold, B., Bhagavan, N. and Guillory, R. (1991) FASEB J. 5, A1203). In contrast to the intact leukocytes, the superoxide production of the cell-free systems prepared from leukocytes isolated from treated and untreated animals did not differ significantly. These observations suggest that in vivo lovastatin may not directly affect the leukocyte superoxide generating system, but may influence it indirectly possibly by modifying the lipid content of the membrane.

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.

Coenzyme Q10 increases T4/T8 ratios of lymphocytes in ordinary subjects and relevance to patients having the AIDS related complex

Coenzyme Q10 (CoQ10) is indispensable to biochemical mechanisms of bioenergetics, and it has a non-specific role as an antioxidant. CoQ10 has shown a hematological activity for the human and has shown an influence on the host defense system. The T4/T8 ratios of lymphocytes are known to be low in patients with AIDS, ARC and malignancies. Our two patients with ARC have survived four-five years without any symptoms of adenopathy or infection on continuous treatment with CoQ10. We have newly found that 14 ordinary subjects responded to CoQ10 by increases in the T4/T8 ratios and an increase in blood levels of CoQ10; both by p less than 0.001. This knowledge and survival of two ARC patients for four-five years on CoQ10 without symptoms, and new data on increasing ratios of T4/T8 lymphocytes in the human by treatment with CoQ10 constitute a rationale for new double blind clinical trials on treating patients with AIDS, ARC and diverse malignancies with CoQ10.

Phospholipase A2, an in vivo immunomodulator

Arachidonic acid (AA) can be released from membrane phospholipids by the action of phospholipase A2 (PLA2). There is evidence that unsaturated fatty acids, particularly AA, released from membrane phospholipids are required to activate the respiratory burst of macrophages. The data reported here indicate that peritoneal macrophages harvested 30 min after i.p. injection of PLA2 can phagocytose Candida albicans more efficiently and emit more chemoluminescence (CL) than normal cells when stimulated by zymosan. PLA2 injection also enhances the CL of peritoneal cells from mice already stimulated by immunomodulators such as trehalose dimycolate (TDM), bestatin, or oncostatic drugs such as aclacinomycin (ACM). CL is not sensitive to potassium cyanide (KCN), but is inhibited by catalase, superoxide dismutase (SOD), nordihydroguaiaretic acid (NDGA) and high doses of indomethacin (10(-3) M). In vivo PLA2 treatment stimulates the synthesis of both cyclooxygenase and lipoxygenase derivatives of AA metabolism (PGE2, 6-keto, PGF1 alpha TXB2 and LTC4). Inhibitors of AA metabolism (NDGA, indomethacin) modulate the production of free oxidizing radicals in this experimental model, partly because of their effect on AA metabolism, as determined by the measuring immunoreactive products. However, this work indicates that the effects of these inhibitors, which have been extensively used in CL studies, should be interpreted with caution, since their specificity for AA metabolism is relative.

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.

The lateral organization of components of the membrane skeleton and superoxide generation in the plasma membrane of stimulated human neutrophils

Studies were performed to examine the lateral organization of the NADPH oxidase system in the plasma membrane of human neutrophils. Analysis of the subcellular fractionation of human neutrophils by isopycnic sedimentation of cavitated cell lysates suggested that there may be more than one population of plasma membrane vesicles formed upon cell disruption. One population (30-32% sucrose) contained surface accessible wheat germ agglutinin binding sites, alkaline phosphatase activity, and cytochrome b. Another population (34-36% sucrose) contained membrane-bound flavin and, when the cells were prestimulated with phorbol myristate acetate (PMA), NADPH-dependent superoxide generating activity. Approximately 25% of the neutrophil cytochrome b cosedimented with the heavy population, confirming our previous hypothesis (Parkos et al. (1985) J. Biol. Chem. 260, 6541-6547) that only a fraction of the total cellular cytochrome b is involved in superoxide production. The heavy plasma membrane fraction was also enriched in membrane associated actin and fodrin as detected by Western blot analysis. After extraction of the plasma membrane vesicles with detergent cocktails, the majority of superoxide generating activity remained associated with the detergent insoluble pellet. Western blot analysis demonstrated that the pellets were also enriched in actin. Further analysis of these pellets using rate-zonal detergent-containing sucrose density gradients indicated that the superoxide generating complex had an approximate sedimentation coefficient of 80 S, suggesting that the neutrophil superoxide generating system may form a complex on the plasma membrane which is associated with or somehow organized by the membrane skeletal matrix. This organization may be of functional relevance not only to the actual production of superoxide, but also to the targeting of microbicidal oxidants.

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.

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.

Intracellular organelle motility and membrane fusion processes in human neutrophils upon cell activation

Release and subcellular fractionation experiments indicate that fusion of a novel tertiary granule with the plasma membrane is concomitant with human neutrophil activation. Phorbol 12-myristate 13-acetate (PMA) induced a respiratory burst in human neutrophils as well as a high release of gelatinase, a marker of the tertiary granule. Preincubation of neutrophils with cytochalasin E induced a partially activated or 'primed' state, in which cells were unable to generate superoxide anion, but showed a reduced latency period for this activity. Fusion of tertiary granules with the cell surface also occurred during priming, although to a lesser extent than in PMA stimulation. The rapid tertiary granule degranulation, preceding that of specifics and azurophilics, seems to play an important role in the functionality and secretory properties of human neutrophils.

Studies on the nature and activation of O2- -forming NADPH oxidase of leukocytes. II. Relationships between phosphorylation of a component of the enzyme and oxidase activity

The activation of O2- -formation by neutrophil NADPH oxidase is associated with phosphorylation of several membrane and cytosolic proteins. In the membranes a phosphoprotein of 32 kDa belonging to the NADPH oxidase-cytochrome b-245 system (P. Bellavite et al., Free Rad. Res. Commun., 1, 11 (1985] showed the highest relative increase of 32Pi incorporation. Concomitant with the phosphorylation, a shift of the apparent molecular mass of the protein from 31 to 32 kDa occurred. The time-course, the sensitivity to trifluoperazine and the dose-dependence of phosphorylation were similar to those of O2- forming activity, except that the latter showed a longer lag-time than the former. The increase of the 32 kDa phosphoprotein was also comparable to the kinetics of cytochrome b-245 reduction by anaerobically activated neutrophils. The phosphorylation and the NADPH oxidase were triggered by various stimulants including phorbol myristate acetate, opsonized zymosan, arachidonic acid and sodium fluoride. With arachidonic acid the O2- formation was highly active but the phosphorylation was low. With fluoride the enzyme activity was reversible upon removal of the stimulant but the phosphorylation of the 32 kDa peptide was not reversible. Neutrophils treated with PMA at 17 degrees C showed phosphorylation but not activation. The results indicate that phosphorylation of a component of NADPH oxidase is a fundamental but probably not sufficient event in the activation mechanism of the enzyme.

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)

Purification and resolution of NADH diaphorase activity from NADPH diaphorase-linked: O2 oxidoreductase activity of human neutrophils

Intrinsic NADPH diaphorase activity is a component of the membrane-bound NAD(P)H:O2 oxidoreductase of human neutrophils. NADH-specific diaphorase activity is also present in membrane fractions rich in oxidoreductase activity. Studies were undertaken to determine whether the NADH diaphorase might also be intrinsic to the oxidoreductase. The latter diaphorase was freed from the membrane by detergent extraction and partially purified approximately 80-fold. Its apparent molecular weight following solubilization in deoxycholate and Tween-20 was 204 000 +/- 10 000. The specific activity of the partially purified diaphorase with ferricyanide as electron acceptor was 7.6 X 10(3) mU/mg protein, its pH optimum was 7.0, and its Km for NADH was 13 microM. It is completely devoid of NADPH diaphorase activity, lacks the capacity to reduce molecular oxygen, yet readily reduces ferricyanide, 2,6-dichlorophenolindophenol and ferricytochrome c. Whereas the NADH diaphorase was freed from the particulate fraction of cell lysates by extraction in 10 mM Tris-HCl buffer (pH 8.6) made up in 15% glycerol and 0.5% Tween-20, NADPH-dependent diaphorase and superoxide-generating activities also present in the membrane were not. These observations make it unlikely that the principal membrane-bound NADH diaphorase found in human neutrophils is a component of the NAD(P)H:O2 oxidoreductase, despite its common association in the same particulate fraction of cell lysates.

Mechanism of production of toxic oxygen radicals by granulocytes and macrophages and their function in the inflammatory process

The paper deals with 1) the features of the respiratory burst (increase of the respiration with production of O2 metabolites, O2-, H2O2, OH) of the inflammatory cells; 2) the factors responsible for its activation; 3) the methods for its measurement; 4) the molecular events which take place at the level of the plasma membrane following the interaction between the stimuli and the cell surface (the Ca++ changes, the modification of membrane potential, the activation of phospholipid turnover) and the hypothesis of the activation of the protein kinase C; 5) the nature of the NADPH oxidase whose activation is responsible for the respiratory burst and the production of O2 metabolites; 6) the defensive, toxic, proinflammatory and modulatory effects due to the reactivity of the oxygen metabolites.

Mechanisms and functions of the oxygen radicals producing respiration of phagocytes

Respiratory burst is due to the activation of a membrane bound NADPH oxidase induced by perturbation of the plasma membrane during phagocytosis or following interaction between the cell surface and a number of environmental stimuli. It refers to the increase in the non-mitochondrial O2 consumption with a concomitant production of different reactive species (superoxide anion, hydrogen peroxide, hydroxyl radical, singlet oxygen ...). The effects of the respiratory burst depend on the intensity and combination of the different actions which are defensive, toxic, activatory and modulatory of the inflammatory process.

Role of metals in oxygen radical reactions

Partially-reduced forms of dioxygen or "oxy-radicals" (superoxide, O2-/HO2; hydrogen peroxide, H2O2; hydroxyl radical X OH) and oxidants of comparable reactivity are implicated in an increasing number of physiological, toxicological, and pathological states. Transition metal catalysis is recognized as being integral to the generation and the reactions of these activated oxygen species. Factors such as pH and chelation govern the reactivity of the transition metals with dioxygen and "oxy-radicals" and therefore influence the apparent mechanisms by which oxidative damage to phospholipids, DNA, and other biomolecules is initiated. In biological systems the concentrations of redox-active transition metals capable of catalyzing these reactions appears to be relatively low. However, under certain conditions metal storage and transport proteins (ferritin, transferrin, ceruloplasmin, etc.) may furnish additional redox active metals.

Isolation from neutrophil membranes of a complex containing active NADPH oxidase and cytochrome b-245

NADPH-dependent O2- forming activity was extracted with deoxycholate from subcellular particles of guinea-pig neutrophils following stimulation with phorbol myristate acetate. The solubilized enzyme was purified by chromatography on Ultrogel AcA22, by isopycnic glycerol density gradient centrifugation and by treatment with 0.4 M NaCl. This procedure yielded a high-molecular-weight complex containing phospholipids, cytochrome b-245 and NADPH oxidase activity. Cytochrome b was found to be purified to the same extent as NADPH oxidase activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the various purification fractions showed a progressive enrichment of a band whose molecular weight is 3.2 X 10(4). The enrichment of this protein band paralleled those of NADPH oxidase activity and of cytochrome b, indicating that it is a component of the oxidase system. The possibility that this band corresponds to either cytochrome b or a flavoprotein/cytochrome b complex is considered.

NADPH-dependent reduction of ubiquinone-1 associated with the superoxide-forming oxidase of pig polymorphonuclear leucocytes

NADPH-dependent ubiquinone-1 reductase activity was present in the phagocytic vesicles of pig polymorphonuclear leucocytes. The apparent Km-value of the reductase for NADPH was 29 microM which is similar to that of the NADPH-dependent superoxide formation. Increase of the quinone-reductase activity by increasing the concentrations of ubiquinone-1 was associated with the decrease of the superoxide forming activity, the rate of the NADPH oxidation being constant independent of the quinone concentration. p-Chloromercuribenzoate inhibited both superoxide formation and reduction of the quinone, whereas low concentrations of cetyltrimethylammonium bromide which inhibit the superoxide formation did not inhibit the reduction of the quinone. The reduction of 2,6-dichlorophenolindophenol which has been shown not to be inhibited by both inhibitors. The quinone-reductase activity could be extracted with a mixture of deoxycholate and Tween 20 which extracts the superoxide forming activity. The observations indicate that a region of the superoxide-forming NADPH oxidase between a mercurial-sensitive site and a site sensitive to the cationic detergent is responsible for the reduction of ubiquinone.

Electrophoretic isolation of a membrane-bound NADPH oxidase from guinea-pig polymorphonuclear leukocytes

Electrophoretic isolation of a membrane-bound NADPH oxidase of guinea-pig polymorphonuclear leukocytes was attempted with the O2- -generating membranes of cells unstimulated or stimulated with C3b-zymosan or sodium dodecyl sulfate, and also with the phagosomes isolated from the phorbol myristate acetate-coated latex particle-phagocytosing cells. When these vesicles were subjected to discontinuous polyacrylamide gel electrophoresis in the presence of Triton X-100 and then assayed for NADPH-Nitroblue tetrazolium reducing activity, the activity was detected by the appearance of a single, blue band of the reduced dye on the gel, independent of the source of vesicles. In addition, the enzyme was able to generate O2- and its activity was significantly augmented with the homologous liver microsomal cytochrome b5. Its activity was heat-labile and inactivated by N-ethylmaleimide and p-chloromercuribenzene sulfonate. The enzyme, with an apparent molecular weight of 150 000, in the phagosomes was easily susceptible to limited proteolysis by trypsin and formed an active fragment with a molecular weight of 70 000, accompanying the loss of O2- -generating activity of the vesicles.