Oxygen-dependent microbial killing by phagocytes (second of two parts)

[Formation of cytoplasmic vacuoles of phagocytizing polymorphonuclear leukocytes in O2-and N2-atmosphere in in vitro-experiments (author's transl)]

During O2 and N2 gasification in vitro, neutrophilic granulocytes ingest killed staphylococci with equal intensity. O2-gassed neutrophilic granulocytes form significantly more cytoplasmic vacuoles than N2-gassed neutrophilic granulocytes in absolute terms an in relation to the number of ingested staphylococci. The cytoplasmic vacuoles of O2-gassed neutrophilic granulocytes occupy a larger surface in smear preparations than those of N2-gassed neutrophilic granulocytes. The results make it probable that the formation of cytoplasmic vacuoles in neutrophilic granulocytes is an O2-dependent process. This interpretation is in agreement with concepts on the peroxidation of membrane lipids and membrane destabilization. It is consistent with the process of membrane fusion and thus the formation of cytoplasmic vacuoles, which are to be regarded as phagolysosomes.

Role of cell-generated hydrogen peroxide in granulocyte-mediated killing of schistosomula of Schistosoma mansoni in vitro

Human as well as murine granulocytes have been shown to kill the larval stages of helminth parasites; the mechanism of this cell-mediated cytotoxicity is, however, poorly understood. The present study was designed to assess the role of peroxidative processes in killing of schistosomula of Schistosoma mansoni by human granulocytes in vitro. The rate of H(2)O(2) production by human neutrophils, eosinophils, and basophils was measured upon incubation with schistosomula alone or in the presence of specific antibody or complement. Opsonized parasites (antibody and/or complement) increased the rate of H(2)O(2) production by neutrophils, eosinophils, and basophils by respective percentages of 500, 500, and 371. The rate of H(2)O(2) release was directly related to the number of granulocytes and to the proportion of cells attached to the surface of the schistosomula. Increased hydrogen peroxide release occurred by 10 min of incubation and was demonstrable up to 16 h after addition of leukocytes to schistosomula. The primary source of this oxygen product was found to be the granulocytes adherent to the schistosomula and not those that remained unattached. Hydrogen peroxide production by neutrophils and eosinophils was quantitatively similar (schistosomula coated with antibody plus complement stimulated 5 x 10(6) neutrophils and eosinophils to release H(2)O(2) at respective rates of 0.35 and 0.40 nmol/min). Granulocyte-mediated parasite killing correlated with rate of H(2)O(2) generation; both processes were inhibited by catalase. To define further the role of oxidative metabolites, neutrophils and eosinophils of two subjects with chronic granulomatous disease were used; marked reduction of granulocyte-mediated parasite mortality was observed. Peroxidase was required for H(2)O(2)-mediated killing. Addition of the peroxidase inhibitors azide (1 mM), cyanide (1 mM), or aminotriazole (1 cM) to neutrophilschistosomula mixtures significantly reduced parasite cytotoxicity (P < 0.01); similar reduction was observed when eosinophils were used (P < 0.01). Fixation of halide (iodide) to trichloroacetic acid-precipitable protein (2.4-6.0 nmol/h per 10(7) neutrophils) was demonstrated in the presence of granulocytes, opsonins, and parasites; this process was completely inhibited by 1 mM azide. These data indicate that contact between the surfaces of human granulocytes and schistosomula results in release of cellular hydrogen peroxide and iodination. The generation of H(2)O(2) and its interaction with peroxidase appear to be crucial in effecting in vitro granulocyte-mediated parasite cytotoxicity.

Dimethyl sulfoxide inhibits killing of Staphylococcus aureus by polymorphonuclear leukocytes

Increasing concentrations of the highly permeable, hydroxyl radical scavenger dimethyl sulfoxide progressively decreased killing of Staphylococcus aureus 502A by human polymorphonuclear leukocytes; methane, a product of the reaction of the hydroxyl radical with dimethyl sulfoxide, was generated in the process.

Monocyte-mediated serum-independent damage to hyphal and pseudohyphal forms of Candida albicans in vitro

Human peripheral blood monocytes attached to Candida albicans hyphae in the absence of serum and damaged the hyphae without completely ingesting them. Attachment and damage was not augmented by the addition of serum. Damage to hyphae was quantitated by a previously developed metabolic assay that measured leukocyte-induced reduction in uptake of [(14)C]cytosine by the hyphae. Use of cells from patients with hereditary disorders of leukocyte function, chronic granulomatous disease, and myeloperoxidase deficiency indicated that myeloperoxidase-independent and nonoxidative mechanisms could sometimes damage hyphae where oxidative mechanisms were impaired. Damage to hyphae by normal monocytes was inhibited by concentrations of sodium azide and sodium cyanide that primarily affect myeloperoxidase activity, as well as by halide-free conditions, catalase, and putative antagonists of hypochlorous acid or singlet oxygen. Iodination of hyphae, a myeloperoxidase and hydrogen peroxide-dependent process of monocytes, was similarly inhibited by sodium azide, sodium cyanide, and catalase. Under anaerobic conditions, damage to hyphae was reduced by 64.0-68.4%. In contrast, inhibitors of potential nonoxidative antifungal mechanisms, iron salts to saturate iron chelators, and polyanionic amino acid polymers to neutralize cationic proteins did not block damage to hyphae by monocytes. Preparations rich in lysosomal granules from fractionated normal monocytes also did not damage hyphae. Overall, it appeared that oxidative mechanisms were most important for damage to hyphae by normal monocytes. Electron microscopy confirmed that Candida hyphae were damaged and probably killed by monocytes, but monocytes appeared to sustain significant damage in the process. In the absence of serum, monocyte cell membranes became closely approximated to Candida cell walls. It appeared that some Candida could escape this partial engulfment, as they were seen floating free with vesicular trilaminar membrane remnants covering hyphal surfaces. In general, monocytes appeared to be damaged by interactions with Candida hyphae more than neutrophils had been in previous studies.

Effect of calcium on superoxide production by phagocytic vesicles from rabbit alveolar macrophages

Phagocytic vesicles from rabbit lung macrophages produced superoxide in the presence of NADH or NADPH. At 37 degrees C, these vesicles generated 51+/-7.8 nmol O(2) (-)/min per mg protein in the presence of 0.5 mM NADPH. The apparent K(m) for NADPH and NADH (66 and 266 muM, respectively), the pH optimum for the reaction (6.9), and the cyanide insensitivity were similar to properties of plasma membrane-rich fractions of stimulated polymorphonuclear leukocytes studied by others. The activity of the phagocytic vesicles was trypsin sensitive. The specific superoxide-generating activity of macrophage phagocytic vesicles isolated from cells incubated up to 90 min with phagocytic particles remained constant. Calcium in micromolar concentrations inhibited the NADPH-dependent O(2) (-)-generating activity of phagocytic vesicles. In a physiological ionic medium (100 mM KCl, 2.5 mM MgCl(2), 30 mM imidazole-HCl, pH 6.9), a maximal inhibition of O(2) (-) generation by phagocytic vesicles of 80% was observed at 40 muM free Ca(2+). The half maximum inhibitory effect was at 0.7 muM Ca(2+). Variations of the calcium concentration resulted in rapid and reversible alterations in O(2) (-)-forming activity. Preincubation of phagocytic vesicles in the presence of EGTA rendered their O(2) (-) generation rate in the presence of NADPH insensitive to alterations in the free calcium concentration. This desensitization by low EGTA concentrations (</=100 muM) was reversible by the addition of excess calcium, but desensitization by high EGTA concentrations (>1 mM) was not reversible by the addition of calcium either in the presence or absence of purified rabbit lung macrophage or bovine brain calmodulins. Furthermore, trifluoperazine, a drug that inhibits calmodulin-stimulated reactions, did not alter the activity or the calcium sensitivity of the superoxide-generating system of sensitive phagocytic vesicles. Peripheral plasma membrane vesicles (podosomes) prepared by gentle sonication of macrophages possessed on O(2) (-)-generating system with similar properties to those of phagocytic vesicles. We conclude that the activated O(2) (-)-generating system of rabbit lung macrophages has its initial localization in the plasmalemma and undergoes subsequent internalization into phagocytic vesicles, where it can function for prolonged periods of time. Calcium at concentrations likely to exist in macrophage cytoplasm exerts a regulatory effect on the activated system.

Phorbol diester-induced macrophage differentiation of leukemic blasts from patients with human myelogenous leukemia

Phorbol esters, including 12-O-tetradecanoylphorbol 13-acetate (TPA), induce terminal macrophagelike differentiation of cells from human acute myelogenous leukemia lines. We report that myelogenous leukemia cells obtained from patients undergo macrophagelike differentiation after exposure to TPA. The myeloid leukemic cell cultured with TPA became adherent to charged surfaces with long filamentous pseudopodia; developed positive staining for alpha-napthyl acetate esterase, increased lysozyme secretion, reduced nitroblue tetrazolium, and acquired the ability to phagocytose candida. Cells from patients with lymphocytic leukemia did not become macrophagelike when cultured with TPA.

Potential mediator of inflammation. Phagocyte-derived oxidants suppress the elastase-inhibitory capacity of alpha 1-proteinase inhibitor in vitro

Human polymorphonuclear leukocytes, monocytes, or pulmonary alveolar macrophages, stimulated in vitro by phorbol myristate acetate (PMA), released reactive oxygen species able to suppress the elastase inhibitory capacity (EIC) of human serum. Immunoelectrophoresis using antibodies against alpha(1)-proteinase inhibitor (alpha(1)-Pi) and elastase showed that inactivation of alpha(1)-Pi was responsible for the decreased serum EIC. Treatment of phagocyte-inactivated serum with a reducing agent (dithiothreitol) resulted in significant recovery of EIC, suggesting that alpha(1)-Pi had been oxidatively inactivated. Serum EIC was partially protected by superoxide dismutase or catalase. Hydrogen peroxide alone had no effect on serum EIC. Thus, neither H(2)O(2) nor O(2) (-) alone, but a product of the two, may have oxidatively inactivated alpha(1)-Pi. In support of the foregoing, neutrophils or monocytes from a patient with chronic granulomatous disease failed to produce detectable levels of O(2) (-) after incubation with PMA. These cells also failed to suppress serum EIC. In the case of PMA-stimulated polymorphonuclear leukocytes or monocytes, extracellular myeloperoxidase may have also played a role in alpha(1)-Pi inactivation since serum EIC was partly protected by azide, cyanide, or the depletion of extracellular chloride. Indeed, in a cell-free system consisting of purified myeloperoxidase, a glucose oxidase-H(2)O(2)-generating system, and Cl(-), the EIC of human serum or purified alpha(1)-Pi could also be suppressed. Omission of any single reactant prevented this effect, as did NaN(3) or catalase, suggesting that enzymatically active myeloperoxidase and H(2)O(2) were necessary. Immunoelectrophoresis of myeloperoxidase-inactivated serum showed that, as before, inactivation of alpha(1)-Pi was responsible for the decreased EIC. Treating myeloperoxidase-inactivated serum with dithiothreitol led to significant recovery of EIC, again suggesting that oxidative inactivation of alpha(1)-Pi had occurred. Oxidative inactivation of alpha(1)-Pi in the microenvironment of inflammatory cells, at sites of acute or chronic inflammation, may allow proteases released from these cells to damage adjacent connective tissue components more readily.

Damage to Candida albicans hyphae and pseudohyphae by the myeloperoxidase system and oxidative products of neutrophil metabolism in vitro

In previous studies, we noted that Candida hyphae and pseudohyphae could be damaged and probably killed by neutrophils, primarily by oxygen-dependent nonphagocytic mechanisms. In extending these studies, amount of damage to hyphae again was measured by inhibition of [(14)C]cytosine uptake. Neutrophils from only one of four patients with chronic granulomatous disease damaged hyphae at all, and neutrophils from this single patient damaged hyphae far less efficiently than simultaneously tested neutrophils from normal control subjects. Neutrophils from neither of two subjects with hereditary myeloperoxidase deficiency damaged the hyphae. This confirmed the importance of oxidative mechanisms in general and myeloperoxidase-mediated systems in particular in damaging Candida hyphae. Several potentially fungicidal oxidative intermediates are produced by metabolic pathways of normal neutrophils, but their relative toxicity for Candida hyphae was previously unknown. To help determine this, cell-free in vitro systems were used to generate these potentially microbicidal products. Myeloperoxidase with hydrogen peroxide, iodide, and chloride resulted in 91.2% damage to hyphal inocula in 11 experiments. There was less damage when either chloride or iodide was omitted, and no damage when myeloperoxidase was omitted or inactivated by heating. Azide, cyanide, and catalase (but not heated catalase) inhibited the damage. Systems for generation of hydrogen peroxide could replace reagent hydrogen peroxide in the myeloperoxidase system. These included glucose oxidase, in the presence of glucose, and xanthine oxidase, in the presence of either hypoxanthine or acetaldehyde. In the presence of myeloperoxidase and a halide, the toxicity of the xanthine oxidase system was not inhibited by superoxide dismutase and, under some conditions, was marginally increased by this enzyme. This suggested that superoxide radical did not damage hyphae directly but served primarily as an intermediate in the production of hydrogen peroxide. The possible damage to hyphae by singlet oxygen was examined using photoactivation of rose bengal. This dye damaged hyphae in the presence of light and oxygen. The effect was almost completely inhibited by putative quenchers of singlet oxygen: histidine, tryptophan, and 1,4-diazobicyclo[2.2.2]octane. These agents also inhibited damage to hyphae by myeloperoxidase, halide, and either hydrogen peroxide or a peroxide source (xanthine oxidase plus acetaldehyde). Myeloperoxidase-mediated damage to hyphae was also inhibited by dimethyl sulfoxide, an antioxidant and scavenger of the hydroxyl radical. These data support the involvement of oxidative mechanisms and the myeloperoxidase-H(2)O(2)-halide system, in particular in damaging hyphae in vitro and perhaps in vivo as well.

Chronic granulomatous disease. Expression of the metabolic defect by in vitro culture of bone marrow progenitors

Chronic granulomatous disease (CGD), an often fatal syndrome of recurrent infections results from the inability of patients' peripheral blood phagocytic leukocytes to generate superoxide despite otherwise normal phagocytic functions such as ingestion and degranulation. Circulating granulocytes and monocytes are the progeny of bone marrow progenitor cells, colony-forming units in culture. We compared the function of cells grown in two different in vitro cuture systems from the bone marrow of a CGD patient with those from normal subjects. The cells of normal colony-forming unit in culture colonies grown in semisolid medium reduced nitroblue tetrazolium dye when stimulated by phorbol myristate acetate; none of the cells from colonies derived from CGD marrow did so. Cells grown in liquid suspension culture from normal marrow generated superoxide nearly as well as normal peripheral blood granulocytes; those from CGD marrow produced no superoxide, similarly cultured cells from both normal and CGD marrow ingested opsonized bacteria at rates equal to peripheral blood granulocytes. CGD marrow-derived cells showed increased exocytic degranulation relative to both normal marrow-derived cells and normal peripheral blood granulocytes. These studies demonstrate that the basic functional characteristics of CGD are embedded in the genetic program of granulocyte progenitors.

X-linked inheritance in females with chronic granulomatous disease

Chronic granulomatous disease in males is familial and its transmission is is usually clearly x-linked. The mode of inheritance in females with the syndrome is unknown and the carrier state difficult to identify. Defective polymorphonuclear leukocyte bactericidal activity in this disease is associated with an absence of the respiratory burst generated in stimulated phagocytes and may be detected by the chemiluminescence assay. Polymorphonuclear leukocytes from three of four females with chronic granulomatous disease had extremely low chemiluminescence production, their asymptomatic mothers had intermediate values, and their fathers were normal. Polymorphonuclear neutrophils of two affected males in these kinships generated no chemiluminescence, whereas two of seven female relatives had intermediate values, and all nonaffected males had normal values. In the three families in which leukocytes were studied by nitroblue tetrazolium reduction, two populations of neutrophils were demonstrated for the female patients and/or their mothers. The wide phenotypic variability for clinical disease, evidence of two leukocyte populations in the patients or their mothers, and low but detectable leukocyte chemiluminescence in the affected females is consistent with the Lyon hypothesis of x-chromosome inactivation in these families. The findings suggest an x-linked inheritance in these females with chronic granulomatous disease.

Gonococci-human polymorphonuclear leukocyte interactions: metabolic studies associated with attachment and ingestion

Utilizing monolayers of human polymorphonuclear leukocytes, optimal conditions for attachment and ingestion of Neisseria gonorrhoeae were determined. Both attachment and ingestion were optimal at 36 degrees C when a bacteria-leukocyte ratio of 100:1 was employed. After 30 min of incubation, log-phase viable type 2 gonococci were attached to 90% of leukocytes, whereas log-phase viable type 4 gonococci were ingested by 80 to 90% of cells. Respiratory inhibitors had no effect on attachment or ingestion, whereas glycolytic inhibitors blocked ingestion but did not affect attachment of gonocci to the leukocyte surface. Inhibition was dose dependent and partially reversible. The oxidative metabolism of leukocytes with gonococci attached or ingested was also examined. Attachment of log-phase type 2 gonococci stimulated a minimal increase in glucose oxidation and oxygen consumption by leukocytes in contrast to marked increases by leukocytes that had ingested viable type 4 or heat-killed typed 2 organisms. These results demonstrate that attachment of log-phase type 2 gonococci to the surface membrane does not stimulate significant leukocyte oxidative metabolism nor initiate the phagocytic process.

Dissociation of opsonized particle phagocytosis and respiratory burst activity in an Epstein-Barr virus-infected myeloid cell line

A continuous tissue culture cell line (Karpas line 120), derived from a patient with acute myeloblastic leukemia, not only demonstrates myeloblastic morphology and in vitro expression of several myeloid-specific biochemical markers but also contains Epstein-Barr virus (EBV) nuclear antigen. The present studies demonstrate EBV-genome-specific DNA within the total cellular DNA by molecular hybridization, thus establishing the presence of stable viral genome integration. The cells demonstrate complex coordinated myeloid functions including ingestion, degranulation, and respiratory burst activity. Line 120 cells show a respiratory burst (superoxide and hydrogen peroxide generation and hexosemonophosphate shunt activity) in response to soluble (phorbol myristate acetate) and particulate (latex beads) stimuli, as do normal granulocytes. They ingest complement-opsonized particles (lipopolysaccharide-oil droplets, zymosan, and bacteria), and degranulate in response to them. However, unlike normal granulocytes, the line 120 cells do not demonstrate respiratory burst activity in response to these complementopsonized particles. The dissociation between ingestion of complement-opsonized particles and activation of oxygen-dependent bactericidal activity severely impairs bacterial killing as compared with normal polymorphonuclear phagocytes.

Macrophages and the synthesis of connective tissue components

1. Macrophage homogenate, added to the incubation medium of granulation tissue slices, decreases the incorporation of labelled proline to collagen and other proteins, to a greater extent in the presence of certain prostaglandins and in oxygen atmosphere, but to a lesser degree if serotonin and cyclic AMP are added. 2. Rheumatoid synovial fluid, connective tissue active peptide (CTAP) of Castor and an extract from CCl4-damaged liver stimulate collagen synthesis in the presence of macrophages. 3. Preparations from non-treated macrophages stimulate the incorporation of glucosamine to acid mucopolysaccharides, mainly hyaluronate. 4. In a developing rat granuloma, the formation of collagen was stimulated by homogenized macrophages and by macrophage culture medium, but especially by whole macrophages in the presence of SiO2.

Effect of phagocytosis by human polymorphonuclear leukocytes and rabbit alveolar macrophages on 2-deoxyglucose transport

2-Deoxyglucose transport was characterized in human polymorphonuclear leukocytes (PMN) and rabbit alveolar macrophages (AM). The Km was 1 mM for human PMN and 1.6 mM for rabbit AM, and the Vmax was 0.66 x 10(-3) micromoles/45 sec/10(6) PMN and 5.09 x 10(-4) micromoles/45 sec/10(6) AM. The rate of 2-deoxyglucose transport was the same before and after phagocytosis in PMN from normal individuals and three patients with chronic granulomatous disease, as well as rabbit AM. Studies of the kinetics of 2-deoxyglucose transport and intracellular fate of 2-deoxyglucose in human PMN indicate that the nature of the membrane transport system is not altered by phagocytosis. The results support the concept that the plasma membrane is mosaic in character with geographically separate transport and phagocytic sites.

Absence of a newly described cytochrome b from neutrophils of patients with chronic granulomatous disease

A unique cytochrome b which becomes incorporated into phagocytic vacuoles has been described in human neutrophils. This cytochrome b appears to be situated in the plasma membrane of these cells, and acts as a component of the microbicidal oxidase system. Absence or gross abnormality of this cytochrome b was demonstrated in all four patients with chronic granulomatous disease who were investigated, and reduced concentrations in two mothers known to be carriers of the disease.