Human granulocyte generation of hydroxyl radical

Decreased Tocopherol Concentration of Varicose Veins is Associated with a Decrease in Antilipoperoxidant Activity without Similar Changes in Plasma

Antilipoperoxidant and antiradicalar powers were determined in human varicose saphenous veins, and correlated with tocopherol content in plasma or venous homogenates. No difference was found between plasma levels of tocopherol in samples from controls (10.25 ± 1.93 μg ml−1) and from patients with varicose veins (11.50 ± 4.05 μg ml−1), while a significant decrease in tocopherol level was observed in varicose saphenous vein (4.46 ± 1.75 μg/100 mg) as compared to normal vein homogenates (6.25 ± 1.52μg/100mg). In addition, a positive linear correlation ( r = 0.939, p < 0.001) between the antilipoperoxidant activity of venous tissues and their tocopherol content was noticed, whereas no similar relation exists with the plasma tocopherol concentrations. Moreover, a negative linear correlation ( r = 0.814, p < 0.001) between plasma and vessel-wall anti-OH properties was demonstrated, without similar correlation between anti-OH power and the tocopherol levels, neither for the plasma nor for the venous samples.

Concerning antiradicalar activities, a positive linear correlation ( r = 0.761, p < 0.001) was noticed between anti-OH power and anti-ferryl ion properties observed in venous wall homogenates.

This study provides a new valuation in man concerning the implication of tocopherol in the oxidative status of venous tissue.

Bleach etches nanosilver: HOCl-responsive drug delivery system to target leukemic cells

Hypochlorous acid-mediated dissolution of therapeutically active and ultrasmall (<5 nm) Ag NPs is exploited to develop an oxidant responsive combinatorial drug delivery system. Drug release findings and growth inhibition of myeloperoxidase positive leukemic cells support the role of oxidant in the dissolution of Ag NPs.

Using oxidant susceptibility of thiol stabilized nanoparticles to develop an inflammation triggered drug release system

Ultrasmall thiol passivated ZnS NPs are prepared using a newly developed synthetic protocol. Exposure to hydroxyl radicals results in oxidation of the thiol groups, thus destabilizing the ZnS nanolids to open drug encompassing pores for attaining an inflammation responsive drug delivery system.

Metabolic consequences of acute limb ischemia and their clinical implications

Acute limb ischemia is a common medical condition resulting from arterial embolization, in situ thrombosis, trauma, and other causes. The severity of injury is related to the duration of ischemia and the effects of reperfusion. Metabolic consequences of reperfusion injury can be variable, ranging from transient symptoms in the lower extremity to systemic inflammation with multiple organ dysfunction. This article provides an overview of some of the key mediators of reperfusion injury. Additional discussion is focused on the clinical effects of reperfusion in the extremity, as well as the pulmonary, cardiac, and renal organ systems. A better understanding of these processes may result in improved patient outcomes and decreased mortality.

The merits of in vitro versus in vivo modeling in investigation of the immune system

Immunity is vital for determining self and for the recognition and swift eradication of foreign antigens without harming the host. Innate immunity developed in metazoan, multi-cellular organisms under overwhelming selection pressure of invasive microbes and, although imperfect, has performed admirably to enable the evolution of higher eukaryotes. Adaptive immunity developed within an existing innate immune system to more effectively eradicate foreign antigens, whether from pathogens, malignant cells, or microbial toxins, such that repeated stimulations with foreign antigens are more efficiently excluded. Investigation of the immune system requires both in vivo and in vitro experimentation, not only because of the inherent complexity of immunity and the required pertinence of using higher mammals to not falsely disrupt the immune system, but also to use isolates of the specific cellular and humoral components to determine function, signal transduction, and a possible role of these constituents without the complexity and redundancy of immunity in intact animals. The hypotheses of well-designed in vitro experiments must also be tested in intact in vivo models to determine relevance and to discard artifactual findings secondary to the in vitro environment. The following review outlines the basic constituents and functions of both adaptive and innate immunity to demonstrate the importance of both in vivo and in vitro investigation of immunity in our attempt to define host defense and to decrease morbidity and mortality in humans.

Structural organization of the neutrophil NADPH oxidase: phosphorylation and translocation during priming and activation

The reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is part of the microbicidal arsenal used by human polymorphonuclear neutrophils (PMNs) to eradicate invading pathogens. The production of a superoxide anion (O2-) into the phagolysosome is the precursor for the generation of more potent products, such as hydrogen peroxide and hypochlorite. However, this production of O2- is dependent on translocation of the oxidase subunits, including gp91phox, p22phox, p47phox, p67phox, p40phox, and Rac2 from the cytosol or specific granules to the plasma membrane. In response to an external stimuli, PMNs change from a resting, nonadhesive state to a primed, adherent phenotype, which allows for margination from the vasculature into the tissue and chemotaxis to the site of infection upon activation. Depending on the stimuli, primed PMNs display altered structural organization of the NADPH oxidase, in that there is phosphorylation of the oxidase subunits and/or translocation from the cytosol to the plasma or granular membrane, but there is not the complete assembly required for O2- generation. Activation of PMNs is the complete assembly of the membrane-linked and cytosolic NADPH oxidase components on a PMN membrane, the plasma or granular membrane. This review will discuss the individual components associated with the NADPH oxidase complex and the function of each of these units in each physiologic stage of the PMN: rested, primed, and activated.

Redox regulation of pro-inflammatory cytokines and IkappaB-alpha/NF-kappaB nuclear translocation and activation

Reduction-oxidation (redox) state constitutes such a potential signaling mechanism for the regulation of an inflammatory signal associated with oxidative stress. Exposure of alveolar epithelial cells to ascending DeltapO(2) regimen+/-reactive oxygen species (ROS)-generating systems induced a dose-dependent release of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. Similarly, the Escherichia coli-derived lipopolysaccharide-endotoxin (LPS) up-regulated cytokine biosynthesis in a dose- and time-dependent manner. Irreversible inhibition of gamma-glutamylcysteine synthetase, the rate-limiting enzyme in the biosynthesis of glutathione (GSH), by L-buthionine-(S,R)-sulfoximine (BSO), induced the accumulation of ROS and augmented DeltapO(2) and LPS-mediated release of cytokines. Analysis of the molecular mechanism implicated revealed an inhibitory-kappaB (IkappaB-alpha)/nuclear factor-kappaB (NF-kappaB)-independent pathway in mediating redox-dependent regulation of inflammatory cytokines. BSO stabilized cytosolic IkappaB-alpha and down-regulated its phosphorylation, thereby blockading NF-kappaB activation, yet it augmented cytokine secretion. Glutathione depletion is associated with the augmentation of oxidative stress-mediated inflammatory state in a ROS-dependent mechanism and the IkappaB-alpha/NF-kappaB pathway is redox-sensitive but differentially involved in regulating redox-dependent regulation of cytokines.

A non-hypoxic, ROS-sensitive pathway mediates TNF-alpha-dependent regulation of HIF-1alpha

A non-hypoxic, reactive oxygen species (ROS)-sensitive pathway mediating tumor necrosis factor-alpha (TNF-alpha)-dependent regulation of hypoxia-inducible factor-1alpha (HIF-alpha) was investigated in vitro. TNF-alpha mediated the translocation of HIF-1alpha, associated with up-regulating its activity under normoxia. Analysis of the mode of action of TNF-alpha revealed the accumulation of hydrogen peroxide (H2O2), superoxide anion (O(2-.)) and hydroxyl radical (.OH). Antioxidants purported as prototypical scavengers of H2O2 and .OH, attenuated TNF-alpha-induced HIF-1alpha activation, and blockading NADPH-oxidase by scavenging O(2-.) reduced the activity of HIF-1alpha. Inhibition of the mitochondrion complex I abrogated TNF-alpha-dependent activation of HIF-1alpha. Interrupting the respiratory chain reversed the excitatory effect of TNF-alpha on HIF-1alpha. These results indicate a non-hypoxic pathway mediating cytokine-dependent regulation of HIF-1alpha in a ROS-sensitive mechanism.

Chemioxyexcitation (delta pO2/ROS)-dependent release of IL-1 beta, IL-6 and TNF-alpha: evidence of cytokines as oxygen-sensitive mediators in the alveolar epithelium

The signalling mechanisms in oxidative stress mediated by cytokines in the perinatal alveolar epithelium are not well known. In an in vitro model of fetal alveolar type II epithelial cells, we investigated the profile of cytokines in response to ascending Deltap O(2)regimen (oxyexcitation). The peak of TNF-alpha (4 h) preceded IL-1beta and IL-6 (6-9 h), indicating a positive feedback autocrine loop confirmed by exogenous rmTNF-alpha. Reactive oxygen species (ROS) induced a dose-dependent release of cytokines, an effect specifically obliterated by selective antioxidants of the hydroxyl radical (*OH) and superoxide anion (O(2)-). Actinomycin and cycloheximide blocked the induced production of cytokines, implicating transcriptional and translational control. Whilst the dismutating enzymes superoxide dismutase (SOD) and catalase were ineffective in reducing ROS-induced cytokines, MnP, a cell-permeating SOD mimetic, abrogated xanthine/xanthine oxidase-dependent cytokine release. Desferrioxamine mesylate, which inhibits the iron-catalysed generation of *OH via the Fenton reaction, exhibited a mild effect on the release of cytokines. Dynamic variation in alveolar p O(2)constitutes a potential signalling mechanism within the perinatal lung allowing upregulation of cytokines in an ROS-dependent manner.

Degradation of Japanese encephalitis virus by neutrophils

The ability of neutrophils to degrade the phagocytosed Japanese encephalitis (JE) virion, via triggering of the respiratory burst and generation of toxic radicals has been investigated. JEV or JEV-induced macrophage derived factor (MDF) induces increase in intracellular oxidative signals with generation of superoxide anion (O2-), via activation of cytosolic NADPH and subsequent formation of hydrogen peroxide, with maximum activity on day 7 post infection. The response was sensitive to anti-MDF antibody treatment. Further, the study revealed rapid degradation of phagocytosed JE viral protein and nucleic acid. The viral protein degradation was partially dependent on the generation of toxic oxygen species as it could be abrogated by pretreatment of the cells with staurosporine.

The role of erythrocytes in the inactivation of free radicals

We propose that, in addition to its function of gas exchange, the erythron provides a mechanism for the inactivation of reactive oxygen and oxide radicals in vivo. In carrying out this function, individual erythrocytes undergo changes in biochemical and structural properties, which are reflected by shape and functional alterations. The changes indicate damage to the labile components of the red cell and demonstrate the expendable nature of the individual red cell. We propose that a superoxide anion channel allows the transport of superoxide and other free radicals into the red cell, where they are deactivated by the erythrocyte antioxidant system which effectively prevents extensive oxidative damage to tissues.

Attenuation of adjuvant arthritis in rats by treatment with oxygen radical scavengers

The contribution of reactive oxygen species (ROS), in particular hydroxyl radical (OH.), to joint inflammation was examined in rats developing adjuvant arthritis (AA) by treatment with ROS scavengers dimethylthiourea (DMTU) and DMSO. Adjuvant arthritis was induced in Sprague-Dawley (SD) rats by a single intradermal (i.d.) injection of Mycobacterium tuberculosis (MT) in oil on day 0. By day 14, all rats exhibited arthritis in the hindlimbs and the majority had involvement of the forelimbs. A marked inflammatory cell influx (75% neutrophils) was present in the synovial fluid. These cells, in vitro, spontaneously produced OH. (0.96 +/- 0.28 OH. units/h per 10(5) cells). In contrast, spontaneous OH. production by normal circulating leucocytes was absent (0.07 +/- 0.03 OH. units/h per 10(5) cells). Adjuvant-injected rats were treated with DMTU (500, 250 and 100 mg/kg), DMSO (330 and 165 mg/kg) or saline (disease control) once daily on days 8, 9 and 10 and twice daily on days 11, 12 and 13 postadjuvant injection. Both DMTU and DMSO significantly reduced the clinical evidence of arthritis (clinical scores: DMTU [500 mg/kg] = 0, P < 0.0001; DMSO [3.0 mL/kg] = 0.4 +/- 0.3, P < 0.01, compared with disease control = 2.3 +/- 0.3). Synovial fluid cell accumulation was also significantly reduced (DMTU [500 mg+kg] = 0.5 +/- 0.1 x 10(5) cells/four joints, P < 0.0001; DMSO [3.0 mL/kg] 2.75 +/- 1.9 x 10(5) cells/four joints, P < 0.01 compared with disease control = 11.76 +/- 1.7 x 10(5) cells/four joints). Neither treatment inhibited cutaneous delayed type hypersensitivity (DTH) to the disease inducing antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of lactoferrin as an anti-inflammatory molecule

The formation of hydroxyl radical via the iron catalyzed Haber-Weiss reaction has been implicated in phagocyte-mediated microbicidal activity and inflammatory tissue injury. The fact that neutrophils contain lactoferrin and mononuclear phagocytes have the capacity to acquire exogenous iron has suggested that iron bound to lactoferrin may influence the nature of free radical products generated by these cells. Over the years the iron-lactoferrin complex has been heralded as both a promoter and inhibitor of hydroxyl radical formation. This manuscript is intended to provide an overview of work performed to date related to this controversy and to present results of a number of preliminary studies which shed further light on the role of lactoferrin in inflammation.

Effect of zinc on superoxide-dependent hydroxyl radical production in vitro

Trace elements play an important role in oxygen metabolism and therefore in the formation of free radicals. Whereas iron and copper are usually the main enhancers of free radical formation, other trace elements, such as zinc and selenium, protect against the harmful effects of these radicals. To investigate the different protective mechanisms of zinc on radical formation, we examined the effects of added zinc and copper on superoxide dismutase activity. We also studied the effects of copper and iron on xanthine oxidase activity and on the Haber-Weiss cycle (iron, superoxide, and hydrogen peroxide), which generates hydroxyl radicals in vitro. The hypoxanthine/xanthine oxidase radical generating system contained a variety of different physiological ligands for binding the iron. This study confirmed the inhibitory effect of copper on xanthine oxidase activity. Moreover, it demonstrated that zinc inhibited hydroxyl radical formation when this formation was catalyzed by a citrate-iron complex in the hypoxanthine/xanthine oxidase reaction. Finally, human blood plasma inhibited citrate-iron-dependent hydroxyl radical formation under the same conditions. Although trace elements seemed responsible for this antioxidant activity of plasma, it is likely that zinc played no role as a plasma antioxidant. Indeed, calcium appeared to be responsible for most of this effect under our experimental conditions.

Rapid and sensitive detection of hydroxyl radicals formed by activated neutrophils in the presence of chelated iron: hydroxylation of deoxyguanosine to 8-hydroxydeoxyguanosine

Hydroxyl radicals (OH) can react with deoxyguanosine (dG) leading to the formation of 8-hydroxydeoxyguanosine (8OHdG). In this study, this has been used to detect the hydroxyl radicals formed when human polymorphonuclear leukocytes (PMNL) are stimulated with phorbol myristate acetate (PMA) in the presence of chelated iron. Reaction mixtures containing PMNL, PMA, dG and Fe-EDTA were incubated at 37 degrees C, and the formation of 8OHdG was analysed with high-performance liquid chromatography and electrochemical detection. 8OHdG formation was detected at PMA concentrations of 2 nM or higher, and half-maximal 8OHdG formation was found at around 6 nM PMA. Stimulation of 500,000 cells with 10 nM PMA for 20 min resulted in a 500 to 1000-fold increase in 8OHdG formation as compared to unstimulated cells. The 8OHdG formation decreased after addition of hydroxyl radical scavengers (sodium benzoate, dimethylsulfoxide, and mannitol) and increased after addition of platelet-activating factor (PAF), an agent known to stimulate the generation of reactive oxygen metabolites in neutrophils. These results demonstrate that hydroxylation of dG to 8OHdG can be used to determine neutrophil-generated hydroxyl radicals in different experimental systems. Since the analysis of 8OHdG is rapid, sensitive and easy, this may have wide applications in inflammation and cancer research.

Activation of the fifth component of human complement by oxygen-derived free radicals, and by methionine oxidizing agents: a comparison

The fifth component of human complement, C5, was activated by non-enzymical, chemical treatment in either of two ways: 1) by oxidation with a hydroxyl radical (OH.) generating system consisting of H2O2, FeEDTA, and ascorbate, activation product called C5(H2O2); 2) by oxidation with chloramine T, activation product called C5(Cl-T). Evaluating earlier findings, completed by new results, both products were compared. Both products are C5-like in that they are capable of binding C6 and form the nucleus for the cytotoxic complex C5-9. Both differ from C5b, the natural activation product of C5, as they comprise the whole, uncleaved C5 protein, and do not immediately decay when not bound to C6. In both cases the treatment involves oxidation of methionine residues in the C5 protein. However, while chloramine T specifically attacks only methionine, oxidation by the OH. generating system involves other amino acid residues, in addition. This probably explains the lower yield of C5b-like activity after treatment with H2O2, and other quantitative differences between C5(H2O2) and C5(Cl-T). Whereas the generation of C5(H2O2) may be physiologically relevant, C5(Cl-T) may prove to be a suitable object for the study of changes in the C5 molecule essential for its activation.

Active oxygen species, articular inflammation and cartilage damage

Rheumatoid arthritis and osteoarthritis are age-related diseases, in which degenerative changes (arthrosis) and superimposed inflammatory reactions (arthritis) lead to progressive destruction of the joints. Active oxygen species derived from various sources play a role in this process, which may be influenced by appropriate treatment with antioxidants and free radical scavengers.

Possible role of bacterial siderophores in inflammation. Iron bound to the Pseudomonas siderophore pyochelin can function as a hydroxyl radical catalyst

Tissue injury has been linked to neutrophil associated hydroxyl radical (.OH) generation, a process that requires an exogenous transition metal catalyst such as iron. In vivo most iron is bound in a noncatalytic form. To obtain iron required for growth, many bacteria secrete iron chelators (siderophores). Since Pseudomonas aeruginosa infections are associated with considerable tissue destruction, we examined whether iron bound to the Pseudomonas siderophores pyochelin (PCH) and pyoverdin (PVD) could act as .OH catalysts. Purified PCH and PVD were iron loaded (Fe-PCH, Fe-PVD) and added to a hypoxanthine/xanthine oxidase superoxide- (.O2-) and hydrogen peroxide (H2O2)-generating system. Evidence for .OH generation was then sought using two different spin-trapping agents (5.5 dimethyl-pyrroline-1-oxide or N-t-butyl-alpha-phenylnitrone), as well as the deoxyribose oxidation assay. Regardless of methodology, .OH generation was detected in the presence of Fe-PCH but not Fe-PVD. Inhibition of the process by catalase and/or SOD suggested .OH formation with Fe-PCH occurred via the Haber-Weiss reaction. Similar results were obtained when stimulated neutrophils were used as the source of .O2- and H2O2. Addition of Fe-PCH but not Fe-PVD to stimulated neutrophils yielded .OH as detected by the above assay systems. Since PCH and PVD bind ferric (Fe3+) but not ferrous (Fe2+) iron, .OH catalysis with Fe-PCH would likely involve .O2(-)-mediated reduction of Fe3+ to Fe2+ with subsequent release of "free" Fe2+. This was confirmed by measuring formation of the Fe2(+)-ferrozine complex after exposure of Fe-PCH, but not Fe-PVD, to enzymatically generated .O2-. These data show that Fe-PCH, but not Fe-PVD, is capable of catalyzing generation of .OH. Such a process could represent as yet another mechanism of tissue injury at sites of infection with P. aeruginosa.

Superoxide enhances hypochlorous acid production by stimulated human neutrophils

Stimulated neutrophils undergo a respiratory burst discharging large quantities of superoxide and hydrogen peroxide. They also release myeloperoxidase, which catalyses the conversion of hydrogen peroxide and Cl- to hypochlorous acid. Human neutrophils stimulated with opsonized zymosan promoted the loss of monochlorodimedon. This loss was entirely due to hypochlorous acid, since it did not occur in Cl(-)-free buffer, was inhibited by azide and cyanide, and was enhanced by adding exogenous myeloperoxidase. It was not inhibited by desferal, diethylenetriaminepentaacetic acid, mannitol or dimethylsulfoxide, which excluded involvement of the hydroxyl radical. Approx. 30% of the detectable superoxide generated was converted to hypochlorous acid. As expected, formation of hypochlorous acid was completely inhibited by catalase, but it was also inhibited by up to 70% by superoxide dismutase. Superoxide dismutase also inhibited the production of hypochlorous acid by neutrophils stimulated with phorbol myristate acetate. Our results indicate that generation of superoxide by neutrophils enables these cells to enhance their production of hypochlorous acid. Furthermore, inhibition of neutrophil processes by superoxide dismutase and catalase does not necessarily implicate the hydroxyl radical. It is proposed that superoxide may potentiate oxidant damage at inflammatory sites by optimizing the myeloperoxidase-dependent production of hypochlorous acid.

Neutrophil degranulation inhibits potential hydroxyl-radical formation. Relative impact of myeloperoxidase and lactoferrin release on hydroxyl-radical production by iron-supplemented neutrophils assessed by spin-trapping techniques

Hydroxyl radical (.OH) formation by neutrophils in vitro requires exogenous iron. Two recent studies [Britigan, Rosen, Thompson, Chai & Cohen (1986) J. Biol. Chem. 261, 17026-17032; Winterbourn (1987) J. Clin. Invest. 78, 545-550] both reported that neutrophil degranulation could potentially inhibit the formation of .OH, but differed in their conclusions as to the responsible factor, myeloperoxidase (MPO) or lactoferrin (LF). By using a previously developed spin-trapping system which allows specific on-line detection of superoxide anion (O2-) and .OH production, the impact of MPO and LF release on neutrophil .OH production was compared. When iron-diethylenetriaminepenta-acetic acid-supplemented neutrophils were stimulated with phorbol myristate acetate or opsonized zymosan, .OH formation occurred, but terminated prematurely in spite of continued O2- generation. Inhibition of MPO by azide increased the magnitude, but not the duration, of .OH formation. No azide effect was noted when MPO-deficient neutrophils were used. Anti-LF antibody increased both the magnitude and duration of .OH generation. Pretreatment of neutrophils with cytochalasin B to prevent phagosome formation did not alter the relative impact of azide or anti-LF on neutrophil .OH production. An effect of azide or anti-LF on spin-trapped-adduct stability was eliminated as a confounding factor. These data indicate that neutrophils possess two mechanisms for limiting .OH production. Implications for neutrophil-derived oxidant damage are discussed.

Stimulated human neutrophils damage cardiac sarcoplasmic reticulum function by generation of oxidants

An important aspect of myocardial injury is the role of neutrophils in post-ischemic damage to the heart. Stimulated neutrophils initiate a series of reactions that produce toxic oxidizing agents. Superoxide rapidly dismutases to H2O2 and neutrophils contain myeloperoxidase which catalyzes the oxidation of Cl- by H2O2 to yield hypochlorous acid (HOCl). The highly reactive HOCl combines non-enzymatically with nitrogenous compounds to generate long-lived, non-radical oxidants, monochloramine and taurine N-monochloramine. We investigated the role of oxygen radicals and long-lived oxidants on cardiac sarcoplasmic reticulum function, which plays a major role in the regulation of intracellular Ca2+ and thereby in the generation of force. Incubation of sarcoplasmic reticulum with phorbol myristate acetate (PMA)-stimulated neutrophils (4 x 10(6) cells/ml) significantly decreased calcium uptake rate (0.85 +/- 0.11 to 0.11 +/- 0.06 mumol/min per mg) and Ca2+-ATPase activity (1.67 +/- 0.08 to 0.46 +/- 0.10 mumol/min per mg). Inclusion of myeloperoxidase inhibitors (cyanide, sodium azide and 3-amino-1,2,4-triazole), catalase, superoxide dismutase plus catalase, and alpha-tocopherol significantly protected (P less than 0.01) calcium uptake rates and Ca2+-ATPase activity of sarcoplasmic reticulum. Superoxide dismutase (10 microgram/ml) alone or deferoxamine (1 mM) had no protective effect in this system. The maximum inhibition of sarcoplasmic reticulum function was observed with (3-4) x 10(6) cells/ml in 4-6 min. HOCl and NH2Cl inhibited calcium uptake rate and Ca2+-ATPase activity of sarcoplasmic reticulum in a dose-dependent manner (2-20 microM), whereas H2O2 damaged sarcoplasmic reticulum at concentrations ranging from 5 to 25 mM. HOCl (20 microM) inhibited 80-90% of Ca2+-uptake rate and Ca2+-ATPase activity and L-methionine (0.1-1 mM) provided complete protection. We conclude that stimulated neutrophils damage cardiac sarcoplasmic function by generation of myeloperoxidase-catalyzed oxidants.

Effect of granulocyte-macrophage colony-stimulating factor on chemiluminescence of human neutrophils

We investigated the capacity of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) to enhance the function of neutrophils. Neutrophil function was measured in terms of N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced luminol-dependent chemiluminescence (LDCL). LDCL of fMLP-stimulated neutrophils was enhanced up to 4.5 fold following preincubation with rhGM-CSF. This enhancement depended on the length of preincubation, reaching an optimal level at 120 min. The dose-response relationship for fMLP-induced LDCL of neutrophils preincubated with rhGM-CSF revealed that half-maximum enhancement was achieved at an approximately 20-fold higher concentration than that of colony-forming units in culture-derived colony formation. These results suggest that differences in dose dependency may be explained by differences in the distribution of receptor(s) for GM-CSF. This may also enable GM-CSF to affect the hematopoietic system, which contains cells at various levels of differentiation, thus mediating the host-defense mechanism.

Conversion of superoxide generated by polymorphonuclear leukocytes to hydroxyl radical: a direct spectrophotometric detection system based on degradation of deoxyribose

Hydroxyl radical is produced secondarily after phagocytic cells have been stimulated to generate superoxide anion. The systems used most commonly for detection of cell-generated hydroxyl radical are often inconvenient for routine biomedical research. We have modified an assay used heretofore in cell-free systems, that is, the degradation of deoxyribose, and adapted it for use with neutrophils. The time and dose responses of the system, requirement for chelated iron, inhibition profiles with various scavengers, and correlation with superoxide production have been ascertained. The method correlated strongly with a standard but more cumbersome technique. Values for a normal population are provided. The method can readily be used to study the parameters of superoxide-hydroxyl radical conversion by cells in various disease or treatment states.

Detection of phagocyte-derived free radicals with spin trapping techniques: effect of temperature and cellular metabolism

Human neutrophils activated with either particulate or soluble stimuli generate oxygen-centered free radicals which are detected by spin trapping in conjunction with electron spin resonance (ESR) spectroscopy. We investigated the effect of temperature on ESR spectra resulting from stimulation of human neutrophils with phorbol myristate acetate (PMA) or opsonized zymosan in the presence of the spin trap, 5,5-dimethyl-1-pyrroline 1-oxide (DMPO). At 20 degrees C with either stimuli, neutrophil superoxide production was manifested predominantly as the superoxide spin-trapped adduct, 5,5-dimethyl-5-hydroperoxy-1-pyrrolidinyloxy (DMPO-OOH). In contrast, at 37 degrees C, the hydroxyl spin-trapped adduct, 2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy (DMPO-OH) was dominant. No evidence of hydroxyl radical (defined as the methyl spin-trapped adduct, 2,2,5-trimethyl-1-pyrrolidinyloxy, DMPO-CH3) was observed, suggesting that elevated temperatures increased the rate of DMPO-OOH conversion to DMPO-OH. In addition, the elevated temperature activated a neutrophil reductase which accelerated the rate of DMPO-OH reduction to its corresponding hydroxylamine, 2,2-dimethyl-5-hydroxy-1-hydroxypyrrolidine. This bioreduction was dependent upon the presence of both superoxide and a phagocyte-derived factor (possibly a thiol) released into the surrounding media.

Aspects of in vitro placental perfusion: effects of hyperoxia and phenol red

The study of a number of parameters of placental function indicated that the perfused human placental lobe maintained its structural and functional integrity when PO2 levels in buffer perfusate were near physiological values, despite low O2 consumption. High O2 content in the perfusate may reduce placental transfer either through a direct vasoconstrictor effect or in combination with the destruction of vascular cyclo-oxygenase, resulting in the reduced synthesis of the vasodilator prostacyclin. A similar mechanism may be involved in the reduction of placental transfer observed in the presence of phenol red. These studies suggest that aspects of in vitro methodologies which may relate to prostaglandin production deserve careful consideration and further study.

Monocyte-derived macrophages as helper cells in monocyte-mediated cytolysis

Human peripheral blood monocytes (M), incubated with opsonized zymosan particles (OPZ), lysed human erythrocyte (RBC) targets, as detected by a 51Cr release method. Conversely, cells derived in vitro from M (monocyte-derived macrophages, MDM) were ineffective. When added to the M-RBC system, MDM enhanced the lysis. The lysis by M and M plus MDM was prevented by catalase, azide and amino acids (alanine, taurine), consistent with the requirement for hypochlorous acid (HOCl). Moreover, MDM per se incapable of generating HOCl augmented the HOCl recovery from the M-RBC system. The results provide evidence for a previously unrecognized form of interaction between two distinct populations of mononuclear phagocytes.

Do humans neutrophils form hydroxyl radical? Evaluation of an unresolved controversy

Hydroxyl radical is a potent oxidizing agent of potential importance in human pathobiology. Since neutrophilic phagocytes make superoxide and hydrogen peroxide during phagocytosis, it has been proposed that hydroxyl radical is also formed. In this paper we review the literature which supports or refutes formation of hydroxyl radical by neutrophils and the mechanism(s) by which this radical might be formed. We conclude that there is no definitive proof for hydroxyl radical formation by neutrophils. In fact, neutrophil release of lactoferrin and myeloperoxidase appears to limit formation of this radical. Future studies are likely to determine whether superoxide released by neutrophils interacts with target substrates to allow formation of hydroxyl radical.

Effect of free radical altered IgG on allergic inflammation

The rheumatoid synovium is capable of producing large amounts of IgG which may become modified by the actions of free radicals. A rat model of synovitis was established and challenged with both normal and free radical altered IgG. IgG was prepared from homologous pooled serum by high performance liquid chromatography, and free radical damage was induced by 15 minutes ultraviolet (UV) irradiation. The results showed a worsening in gross assessments of inflammation, increases in biochemical indices of lipid peroxidation, and also a rise in the proportion of IgG which, on reisolation, showed the characteristic fluorescence associated with free radical damage. This demonstrated how the presence of free radical altered IgG might convert an inflammatory insult to a more persistent stimulus, and the capacity of an environment subjected to continuing antigenic stimulation to induce further free radical damage to IgG.

Effects of zymosan-activated plasma and phorbol myristate acetate on isolated, perfused rabbit lungs

The effects of complement activation on pulmonary vascular permeability are disputed. In rabbit lungs perfused with autologous blood, zymosan activated plasma (ZAP) induced a moderate increase in pulmonary vascular resistance (PVR), but did not detectably change the vascular permeability within 2 h. The stronger neutrophil granulocyte (PMN) activator, phorbol myristate acetate (PMA), usually gave larger PVR increases and also increased pulmonary vascular permeability. Lungs from neutropenic animals, similarly perfused and given PMA, showed unchanged PVR reactions but had no apparent increase in vascular permeability. Lungs perfused with cell-free medium and given PMA displayed modest PVR increases, and no measurable permeability change. The lung preparatory procedure itself markedly influenced leukocyte circulation. Exsanguination of lung donors decreased the concentration of circulating PMN significantly, and they virtually disappeared from the perfusate within minutes after start of lung perfusion. PMN-mediated effects must therefore have been caused by cells already sequestered in the lungs. We conclude that ZAP does not induce an increased pulmonary vascular permeability in isolated, perfused rabbit lungs, in contrast to PMA. The permeability effects of PMA appear to be PMN dependent.

Reduction of ferricytochrome C may underestimate superoxide production by monocytes

Superoxide production by stimulated phagocytes is commonly measured by reduction of ferricytochrome C, with specificity of the assay assumed if the reaction is inhibited by superoxide dismutase (SOD). Most preparations of ferricytochrome C contain a small proportion in the reduced (ferro) form, and this is also formed by the reaction of ferricytochrome C with superoxide. The generation of other reactive oxygen intermediates, such as hydrogen peroxide or hydroxyl radical, could cause oxidation of ferrocytochrome C and consequent underestimation of superoxide production. In support of this, it has been demonstrated that exogenous catalase enhanced the reduction of ferricytochrome C by phorbol myristate acetate (PMA)-stimulated human monocytes. Control experiments confirmed that this was due to enhanced detection rather than increased production of superoxide. In addition, SOD was found to promote oxidation of ferrocytochrome C by PMA-stimulated human monocytes, but this was also inhibited by catalase. These effects of catalase and SOD on ferricytochrome C reduction/ferrocytochrome C oxidation were also demonstrated when superoxide was produced independently of monocytes by a xanthine and xanthine oxidase generating system. It is concluded that the assay of superoxide, using 'SOD inhibitable' reduction of ferricytochrome C, underestimates superoxide production.

O-phenylenediamine oxidation by phorbol myristate acetate-stimulated human polymorphonuclear leukocytes: characterization of two distinct oxidative mechanisms

O-Phenylenediamine (OPD) oxidation has been extensively utilized for the measurement of peroxidase-mediated catabolism of hydrogen peroxide. However, until now this system has not been evaluated for the measurement of hydrogen peroxide produced upon activation of the hexose monophosphate shunt (HMPS) in polymorphonuclear leukocytes (PMNs). OPD oxidation by phorbol myristate acetate (PMA)-stimulated PMNs was mediated by both hydrogen peroxide and superoxide produced by the activation of the HMPS. Furthermore, OPD oxidation by an oxidative mechanism independent of the HMPS was observed by the PMA stimulation of PMNs obtained from patients with chronic granulomatous disease (CGD). This HMPS-independent OPD oxidation was inhibited by superoxide dismutase or 1 mM potassium cyanide (KCN). Superoxide dismutase, catalase, or 1 mM potassium cyanide inhibited 50% OPD oxidation obtained with PMA-stimulated normal PMNs. PMA treatment of purified human myeloperoxidase (MPO) produced OPD oxidation which is inhibited by superoxide dismutase or 1 mM KCN. These data indicate that OPD oxidation observed with CGD PMNs is mediated by a PMA-induced oxidase activity of myeloperoxidase. OPD oxidation in the presence of 1 mM KCN is a method comparable in sensitivity with ferricytochrome c reduction for the evaluation of HMPS activity. Furthermore, the OPD assay can measure myeloperoxidase oxidase activity in PMA-stimulated PMNs.

Alveolar destruction in experimental Klebsiella pneumonia

Sequential histological changes of the lungs were studied in experimental Klebsiella pneumonia, using untreated control mice, cyclophosphamide-treated mice, and carrageenan-treated mice. Cyclophosphamide was used to deplete polymorphonuclear leukocytes and monocytes, and carrageenan was used to deplete mononuclear phagocytes selectively. At 72 hours, varying degree of alveolar necrosis could be seen in untreated control mice. However, the lung lesions of cyclophosphamide- or carrageenan-treated mice were significantly different from those of the control mice. The lung lesions of cyclophosphamide-treated mice indicated that destruction of the alveolar septa was not induced by K. pneumoniae itself but by inflammatory cells, because the alveolar walls were preserved very well in spite of considerable bacterial multiplication in alveolar lumina until infiltration of inflammatory cells occurred. The lung lesions of carrageenan-treated mice showed that alveolar spaces were packed with polymorphonuclear leukocytes, but the alveolar walls were preserved very well as far as the authors could tell after examining the lung lesions by silver impregnation staining. These results suggest that macrophages rather than polymorphonuclear leukocytes and organisms play an important role in alveolar injury in experimental Klebsiella pneumonia.

Ginkgo biloba extract inhibits oxygen species production generated by phorbol myristate acetate stimulated human leukocytes

A Ginkgo biloba extract (Gbe) containing flavonoids, among other compounds, was tested for the release of activated oxygen species (O-2, H2O2, OH.) during the stimulation of human neutrophils (PMNs) by a soluble agonist. The extract slows down O2 consumption (respiratory burst) of stimulated cells by its inhibitory action on NADPH-oxidase, the enzyme responsible for the reduction of O2 to O-2. Consequently, superoxide anion (O-.2) and hydrogen peroxide (H2O2) production is significantly decreased when the PMNs stimulation is done in the presence of the extract at concentrations of 500, 250 and 125 micrograms/ml. Moreover, the hydroxyl radical generation (OH.) is very much decreased at concentrations as low as 15.6 micrograms Gbe/ml, which indicates that the extract also has free radical scavenging activity. Gbe is able at least to reduce very severely the activity of myeloperoxidase contained in neutrophils. This enzyme, secreted into the intra and extracellular medium, catalyzes the oxidation of chloride (Cl-) by H2O2 to yield strong oxidants (HOCl, chloramines) which are implicated in inflammatory processes.

Hydroxyl radical mediation of immune renal injury by desferrioxamine

The acute phase of glomerular injury in a model of antiglomerular basement membrane, antibody-induced glomerulonephritis (antiGBM-GN) in rabbits was shown to be neutrophil-dependent using nitrogen mustard depletion studies. Administration of desferrioxamine (DFX) prevented the development of proteinuria in this model of renal injury [24 hr protein excretion (mean +/- SEM): antiGBM-GN/DFX = 16.2 +/- 2.9 mg compared with antiGBM-GN control = 271.5 +/- 92.2 mg, P less than 0.01]. Antibody binding levels, glomerular filtration rates, circulating complement and neutrophil counts, glomerular C3 deposition, and neutrophil infiltration did not differ between DFX treated and antiGBM-GN groups. In vitro assay systems to assess oxygen radical production [superoxide anion (O2-) and hydroxyl radical (OH.)] by neutrophils activated via the interaction of antiGBM antibody, GBM and complement were established. In these assays, DFX inhibited OH. production by immunologically-stimulated neutrophils (ISN) [nM diphenol/hr/10(6) cells, mean +/- SEM, ISN/DFX = 8 +/- 2 compared with ISN = 191 +/- 22, P less than 0.01] while production of O2- was not affected [nM O2-/hr/10(6) cells, mean +/- SEM, ISN/DFX = 29.1 +/- 4.3 compared with ISN = 32.6 +/- 2.5, P greater than 0.05]. These studies demonstrate that the iron chelator desferrioxamine can prevent neutrophil-dependent immune renal injury by interfering with neutrophil function. Treatment with the hydroxyl radical scavenger dimethylthiourea also significantly attenuated renal injury in antiGBM-GN. Together, the in vivo and in vitro data strongly suggest that neutrophil-dependent immunological renal injury is mediated via hydroxyl radical production by activated neutrophils within glomeruli.