Relationship between intracellularly and extracellularly generated oxygen metabolites from primed polymorphonuclear leukocytes differs from that obtained from nonprimed cells

Is the neutrophil reactive oxygen species production measured by luminol and lucigenin chemiluminescence intra or extracellular? Comparison with DCFH-DA flow cytometry and cytochrome c reduction

BACKGROUND

Polymorphonuclear neutrophils (PMNs) are crucial in host defense against invading microorganisms through reactive oxygen species (ROS) production. However, generated ROS released in excess into media can damage the host tissue. It is therefore essential, when exploring oxygen species production, to discriminate between its intracellular (IC) and extracellular (EC) localization. Several methods of ROS detection are commonly used. However, the literature shows that it is not always clear whether the species detected are IC or EC, especially with the chemiluminescence technique.

METHODS

We compared PMN ROS production, determined by chemiluminescence, using two different probes (luminol and lucigenin) with that measured by 2'-7'-dichlorofluorescin diacetate (DCFH-DA) flow cytometry for IC production and by cytochrome c reduction for EC production.

RESULTS

We found that luminol-dependent chemiluminescence explored IC ROS production more specifically (r=0.77, p<0.01: correlation between luminol-amplified chemiluminescence and DCFH-DA flow cytometry). Lucigenin-amplified chemiluminescence and cytochrome c reduction were closely related (r=0.55, p<0.01).

CONCLUSION

Luminometry detection can thus afford reproducible information on intracellular ROS kinetic production using luminol and extracellular ROS detection using lucigenin, simply and at low cost.

Estimation of H2O2 gradients across biomembranes

When cells are exposed to an external source of H2O2, the rapid enzymatic consumption of H2O2 inside the cell provides the driving force for the formation of the gradient across the plasma and other subcellular membranes. By using the concepts of enzyme latency, the following gradients - formed after a few seconds following the exposure to H2O2 - were estimated in Jurkat T-cells: [H2O2](cytosol)/[H2O2](peroxisomes)=3; [H2O2](extracellular)/[H2O2](cytosol)=7. The procedure presented in this work can easily be applied to other cell lines and provides a quantitative framework to interpret the data obtained when cells are exposed to an external source of H2O2.

Beta-adrenergic modulation of FMLP- and zymosan-induced intracellular and extracellular oxidant production by polymorphonuclear leukocytes

Evaluation of catecholamine modulation of PMNL extracellular and intracellular oxidant production may reflect beneficial and harmful effects of beta-adrenergic agonists in various disease states. We investigated the kinetics and potency of adrenaline-mediated inhibition of oxidant generation in FMLP- and zymosan-stimulated PMNLs. In FMLP-stimulated cells, the short-term burst of oxidant generation was inhibited by adrenaline in a dose-dependent fashion. Intra- and extracellular chemiluminescence and extracellular superoxide anion and hydrogen peroxide generation showed similar IC50 values for adrenaline (1.3-3.0 x 10(-8) M) indicating that both extracellular and intracellular events were inhibited with the same potency. In contrast, intracellular oxidant production evoked by the phagocytosis of zymosan was only minimally affected by 3 x 10(-5) -3 x 10(-12) M adrenaline. Extracellular inhibition of oxidant production was also apparent in zymosan-stimulated cells. In conclusion, adrenaline's ability to depress extracellular generation of oxygen metabolites while retaining prolonged intracellular oxidant production for phagocytosis supports its beneficial role as selectively targeted physiological protector.

Escherichia coli-induced activation of neutrophil NADPH-oxidase: lipopolysaccharide and formylated peptides act synergistically to induce release of reactive oxygen metabolites

The prevailing view of neutrophil NADPH-oxidase activation during interaction with bacteria is that the production of toxic oxygen metabolites should be directed into the phagosome containing the engulfed prey. However, in this report we show that a common Escherichia coli strain, HB101, may induce a release of neutrophil oxygen metabolites to the extracellular milieu. This phenomenon is dependent on three factors: (i) the mobilization (upregulation) of neutrophil secretory vesicles prior to interaction with the bacteria, (ii) soluble bacterial factors binding to the formylmethionyl-leucyl-phenylalanine receptor and tentatively identified as formylated peptides, and (iii) a bacterium-associated priming factor identified as lipopolysaccharide.

Endothelin-1 does not prime polymorphonuclear leukocytes for enhanced production of reactive oxygen metabolites

The in vitro effect of endothelin-1 (ET-1) on the capacity of polymorphonuclear leukocytes (PMNLs) to generate reactive oxygen species (ROS) was investigated. Human PMNLs were separated from healthy volunteers and preincubated for 10 min. at 37 degrees C with varying concentrations (10(-7)-10(-12) M) of ET-1. After subsequent stimulation with FMLP (10(-7) M) or opsonized zymosan (0.5 mg/ml) the intra- and extracellular generation of ROS was assessed by luminol-amplified chemiluminescence, superoxide radical (.O2-) and hydrogen peroxide (H2O2) production.

RESULTS

ET-1 alone failed to stimulate ROS generation. Neither the capacity for extracellular generation of oxygen metabolites nor the production of ROS with an intracellular origin was changed after preincubation of PMNLs with ET-1. ET-1 did not cause a shift of the .O2-/H2O2 production ratio after stimulation of PMNLs with FMLP. These findings suggest that ET-1 in vitro does not prime human PMNLs for enhanced production of ROS.

Hydrogen peroxide as a potent bacteriostatic antibiotic: implications for host defense

Host defense against bacterial pathogens in higher organisms is mediated in part by the generation of reactive oxygen species (ROS) by PMN. In this study, we determined the following effects of exposure of constant concentrations of H2O2 on E. coli in a culture continuously monitored for H2O2 concentration, numbers, and viabilities of cells: (1) E. coli growth rates monitored for 1 h were profoundly affected by concentrations of H2O2, between 25-50 microM. (2) Complete bacteriostasis was observed at 100 microM. (3) Significant cell killing was not observed until the concentration of H2O2 was greater than 500 microM. (4) Bacteriostatic (25-50 microM) concentrations of H2O2 appeared not to be toxic to human skin fibroblasts for a 2-h exposure. (4) Bacteriostasis by H2O2 could not be explained by metabolic inhibition, because intracellular ATP levels were not compromised at bacteriostatic doses of H2O2. (5) Measurements of H2O2 concentrations in subcutaneous abscess fluid infected with both E. coli and S. aureus indicated prevailing concentrations of the oxidant consistent with a proposed role of H2O2 in host defense.

Neutrophil alkaline phosphatase activity increase in bacterial infections is not associated with a general increase in secretory vesicle membrane components

The content of alkaline phosphatase (ALP) was determined in neutrophils isolated from patients with acute bacterial infections by a standard enzyme assay. Compared with control cells, patient cells exhibited about a fivefold increase in ALP activity. There was no difference between the ALP Km values of control and patient cells, which indicates that the elevated activity in patient cells was due to the presence of increased amounts of the enzyme. The ALP isozyme in both cell types was determined to be the tissue-unspecific ALP. The fact that much of the ALP activity was measurable only in the presence of detergent suggested that the enzyme was localized in the secretory vesicles, a putative reservoir of plasma membrane components. The amount and subcellular distribution of two other secretory vesicle membrane proteins, i.e., cytochrome b and complement receptor 3, were not altered; hence, we conclude that there was no general increase in amounts of secretory vesicle membrane constituents in the patient cells.

Priming of oxidative response in human neutrophils by anti-CD18 monoclonal antibodies

Type I collagen, the most abundant protein in the body, after acid extraction adheres to and can induce a respiratory burst from neutrophils. It has been proposed that the effects of collagen are mediated via the CD18 subfamily of integrins. In the present study, adhesion was measured by affinity chromatography in a column containing collagen-coated microcarriers, while oxygen metabolite production was measured with luminol-dependent chemiluminescence. Neutrophil adherence to collagen was attenuated by anti-CD18 monoclonal antibodies. The respiratory burst in response to collagen was not affected by the antibodies. Incubation of neutrophils with anti-CD18 antibodies prior to stimulation with FMLP increased both the extra- and intracellular respiratory burst. Treatment with antibodies prior to PMA stimulation increased only the extracellular respiratory burst. In conclusion, the respiratory burst from neutrophils is primed by pretreatment with anti-CD18 monoclonal antibodies. The collagen-stimulated respiratory burst is probably also primed, but the effect is hidden by the simultaneous attenuation of adhesion.

Effects of five amino-amide local anaesthetic agents on human polymorphonuclear leukocytes measured by chemiluminescence

The aim of this study was to assess the influence of five amino-amide local anesthetic agents on the production of oxygen metabolites in the human polymorphonuclear leukocyte (PMNL), both intra- and extracellularly. Ropivacaine, a new long-acting amino-amide local anaesthetic agent, bupivacaine, lidocaine, mepivacaine and prilocaine in concentrations 1-5 micrograms.ml-1 up to 500-1000 micrograms.ml-1 were compared to an untreated control. PMNLs were isolated from heparinized blood (healthy adult volunteers). Cells were incubated with the various local anaesthetics (37 degrees C, 30 min), then placed in a Biolumat (luminol-amplified chemiluminescence) and stimulated by formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate (PMA) or ionomycin. Horseradish peroxidase (HRP) was added to discriminate between an intra- or extracellular response. In general, a decrease in chemiluminescence-response was seen with higher concentrations (500-1000 micrograms.ml-1) of the various local anaesthetics. Lidocaine showed a decrease even at lower concentrations. A marked increase in intracellular response for prilocaine 1000 micrograms.ml-1 (3894 mumol.l-1) accompanied by a reduction in extracellular response, using FMLP +/- HRP as a stimuli, was noted. Ropivacaine 1000 micrograms.ml-1 (3216 mumol-l-1) showed a decrease both intra- and extracellularly that was similar to, and even somewhat more pronounced than lidocaine 1000 micrograms.ml-1 (3692 mumol.l-1), when using PMA with or without HRP as the stimuli.

Increased chemiluminescence response of neutrophils from the peripheral blood of patients with senile dementia of the Alzheimer's type

The metabolic activity of circulating neutrophils from patients with senile dementia of the Alzheimer's type (SDAT) was investigated by a chemiluminescence assay and compared with that of old and young healthy controls. Neutrophils from demented patients showed a higher and faster chemiluminescence emission than those of controls when activated in vitro by autologous or heterologous sera. Granulocytes from patients with Parkinson's disease did not show an increased chemiluminescence activity. Moreover, serum from patients with SDAT depressed the chemiluminescence emission of granulocytes from young donors. Serum levels of alpha 1-antichymotrypsin (alpha 1-ACT) were also determined and were found to be higher in demented subjects than in old and young controls. These data suggest that peripheral and systemic indexes of inflammation are present in the disease and might be associated with mental deterioration.

Improved preparation of leukocytes for chemiluminescent study of human phagocytic leukocyte-generated reactive oxygen species

Leukocyte oxidative function was investigated in a more physiological milieu than currently used in the chemiluminescence (CL) technique. Heparinized blood was mixed with 6% dextran-T70 (9:1) and the leukocyte-rich plasma obtained without centrifugation was used for the CL experiments (phagocyte count was adjusted to 0.7 x 10(6)/mL with Hanks' buffer) (method A). In this medium, phagocytes responded to stimulation by opsonized zymosan, producing strong luminescence in the presence of 0.5 mumol/L MCLA. CL was inhibited by superoxide dismutase, suggesting that the luminescence reaction was attributable to O2-. Granulocytes were also prepared by the usual method involving centrifugation and were then suspended in plasma (method B). Oxidative function of phagocytes prepared by the two methods was studied together with whole blood as aliquots diluted with Hanks' buffer up to a factor of 1000. Luminescence reached a peak value at a dilution factor of 16, but at very high dilutions luminescence decreased sharply. Significantly higher luminescence values were obtained with samples from method A. Luminescence of whole blood peaked at a dilution factor of 248 but it was less than the value obtained using samples prepared by method A or B. As samples prepared by method A contain all the leukocyte populations, platelets, residual red cells and plasma proteins, the assay of leukocyte-generated reactive oxygens using CL is attained in more physiological conditions than method B in which leukocytes may be damaged owing to repeated centrifugation and hypotonic shock.

Direct and indirect effects of E. coli lipopolysaccharide on isolated human polymorphonuclear granulocytes and mixed leukocytes

Polymorphonuclear neutrophil granulocytes (PMN) may contribute to the lung injury induced by nonpulmonary infections with gram-negative bacteria. The direct effect of E. coli lipopolysaccharide (LPS) on isolated human PMN or mixed leukocytes (ML), as well as the priming effect of preincubating cells with LPS, was examined in assays measuring the maximal rate of oxygen consumption (OC), cell chemiluminescence (CHML), and aggregation (AGG). LPS, 1-10 micrograms/ml, caused no acute response in PMN or ML suspended in Fisher's-HEPES medium with BSA (FHA), but increased both CHML and AGG of cells suspended in autologous plasma. Preincubation in FHA with LPS, 1 microgram/ml, for more than 15 min increased the OC of PMN activated with zymosan-activated plasma (ZAP) or n-formyl-methionyl-leu-cyl-phenylalanine (FMLP) by more than 100%. A similar increase in the CHML of such cells was seen after FMLP, but not after ZAP. ZAP, however, primed the CHML response of the cells to subsequent activation with FMLP more than did preincubation with LPS. Previous exposure to both agents had an additive effect. Preincubation of PMN with LPS decreased the time interval from addition of phorbol myristate acetate (PMA) to peak OC response, but less so than previous activation with FMLP. Neither agent affected the maximal rate of OC after addition of PMA. LPS also increased the PMN aggregation induced by ZAP and FMLP, but not by PMA. Cells preincubated with LPS, 0.01 microgram/ml, increased their CHML in response to FMLP if suspended in Krebs-Ringer balanced salt solution, but not if suspended in FHA. Such preincubation had no effect on OC of similarly activated cells in any of the media.

Oxygen radical production and trapping in subjects with previous Yersinia infection

Previous studies indicate that oxygen radical production by 1-min activation of N-formyl-methionyl-leucyl-phenylalanine-induced chemiluminescence (CL) by whole blood is increased in subjects with previous Yersinia arthritis (YA). This finding is confirmed in the present study and extended further by demonstrating that subjects with previous YA show increased oxygen radical generation and enhanced release of myeloperoxidase from neutrophils and increased CL activity by serum, all factors that can contribute to an increase in the initial activation of CL. Initial activation was not increased in subjects who had had Yersinia enteritis without arthritis; however, intracellular oxygen radical production by purified neutrophils was significantly increased, suggesting that the cells had been primed in vivo. The water-soluble antioxidants of plasma samples tested by a peroxyl radical-trapping assay were much the same in subjects with previous YA, in subjects with previous Yersinia enteritis without arthritis, and in healthy subjects. The results suggest that aberrations in neutrophil oxygen radical production play a role in the pathogenesis of YA.

Phagocytosis by lipopolysaccharide-primed human neutrophils is associated with increased extracellular release of reactive oxygen metabolites

The effect of priming human neutrophils with lipopolysaccharide was investigated regarding the respiratory burst activity generated during phagocytosis of IgG- or C3b-opsonized yeast particles. LPS pretreatment significantly enhanced the respiratory burst activity, measured as luminol-amplified chemiluminescence, of both types of opsonized particles. In control cells most of the activity was produced intracellularly, probably in the phagosomes. In the primed cells, however, extracellular release of reactive oxygen metabolites was significantly increased during Fc- and CR3-mediated phagocytosis (P less than 0.01 and P less than 0.002, respectively). The release was most pronounced when using C3b-opsonized particles. Potent oxygen metabolites acting together with lysosomal enzymes are of importance in inflammatory-induced tissue damage. An increased extracellular release of reactive oxygen species by phagocytizing primed neutrophils can therefore lead to greater damage to the surrounding tissues.

Bovine neutrophils recruited by endotoxin to a teat cistern continuously produce oxygen radicals and show increased phagocytosis and extracellular chemiluminescence

Bovine neutrophils were harvested from a teat cistern following endotoxin infusion and were compared with blood neutrophils by measurements of chemiluminescent and phagocytic activity towards C3- and IgG-opsonized and unopsonized yeast particles. Both phagocytosis and luminol-dependent chemiluminescence elicited by all three particles were enhanced in the teat cells. The increase in the luminol-dependent chemiluminescence towards C3- and IgG-opsonized particles was due to an enhanced extracellular release of myeloperoxidase. The observed increase in phagocytosis of unopsonized yeast was shown to reflect the interaction between up-regulated CR3 receptors on the surface of the teat neutrophils and the yeast particles. A high chemiluminescent activity of the teat neutrophils in both the luminol- and lucigenin-dependent systems in the absence of a phagocytic prey indicated that the NADPH oxidase was permanently active and that myeloperoxidase was continuously released by the cells. Treatment of neutrophils with cytochalasin B showed that the chemiluminescence and phagocytosis of teat neutrophils were less sensitive to this drug than that of blood neutrophils. These results indicate that the teat neutrophils have up-regulated their receptors for IgG- and C3-opsonized and unopsonized yeast on the cell surface by the action of actin. The cells also have a permanently active NADPH oxidase dependent on the association with actin and show a higher tendency than blood neutrophils to secrete the content of their primary granules during phagocytosis.

Isolation and phagocytic properties of neutrophils and other phagocytes from nonmastitic bovine milk

A technique for the separation of neutrophils from macrophages-epithelial cells in samples of nonmastitic bovine milk with low cell counts has been developed. The procedure is based on centrifugation in a discontinuous metrizamide gradient and is rapid, taking less than 40 min. The recovery of the neutrophils is about 30% and their viability about 90%. The isolated neutrophils showed an appreciable unstimulated luminol- and lucigenin-dependent chemiluminescence, which was due to NADPH oxidase rather than to xanthine oxidase. The neutrophils had a higher rate of ingestion of C3-opsonized particles than macrophages-epithelial cells, whereas no significant differences in phagocytosis of IgG-opsonized yeast or unopsonized yeast were detected between the two cell populations. The macrophages-epithelial cells produced no luminol-dependent chemiluminescence and induced considerably lower activity in the lucigenin-dependent system than neutrophils, indicating that these cells contain no myeloperoxidase. Analyses of the activity of the neutrophils in response to C3-opsonized yeast particles showed that the luminol-dependent chemiluminescence of cells isolated from residual milk increased significantly over the lactation period. Moreover, a tendency to a higher phagocytosis and chemiluminescence of neutrophils isolated from residual milk than from stripping milk was indicated.

A new technique, requiring small amounts of cells, for the parallel study of chemiluminescence and phagocytosis via different receptors in the same cell population

An assay permitting the parallel assessment of phagocytosis and chemiluminescence in the same cell population has been developed. The method is based on the phagocytosis of fluorescein isothiocyanate-conjugated yeast particles, either unopsonized or opsonized with complement factor C3 or IgG, by purified cells in suspension in a luminometer. Only a small number of cells (2 x 10(4)-1 x 10(5)) is required, and the reproducibility is high. Moreover, the technique permits phagocytosis to be related to oxygen-dependent killing activity in the same cell population. Since phagocytosis, degranulation and oxygen radical formation as a consequence of well-defined receptor recognition mechanisms can be characterized in very small cell populations, the method is suitable for monitoring the phagocytic function of cells from extravascular sites.

Wound tissue respiratory burst and local microbial inflammation

Local and systemic chemiluminescent (CL) response was measured in 32 patients with wound infection and in 27 patients with crush syndrome complicated by severe wound infection. The level of wound CL depends upon the local microbial concentration and the dynamics of wound healing. CL response of neutrophils in circulation was higher in higher local CL response, but extremely high wound microbial concentration (greater than 10(8) CFU/g) suppressed both local and systemic responses. No metabolic reserve was observed in wound tissue. Wound healing was characterized by changes in the mode of local CL response: from a prevalence of luminol-dependent (neutrophilic) CL to a prevalence of lucigenin-independent (macrophagal) CL.

Altered O2-/H2O2 production ratio by in vitro and in vivo primed human neutrophils

Human neutrophils were primed by exudation or pretreatment with a synthetic diacylglycerol (diC10), the Ca2+ ionophore ionomycin or lipopolysaccharide (LPS). Compared to control cells, these primed cells showed a significantly decreased O2-/H2O2 ratio when stimulated with formylmethionyl-leucyl-phenylalanine (FMLP). This shift indicates a comparative (and net) increased H2O2 detection in the extracellular medium and can not be explained by a dose-dependent impairment in either O2- or H2O2 detecting capacity. An altered H2O2 degenerating capacity was not observed in the primed cells. We propose that priming enhances the capacity to divalently reduce oxygen and thereby directly produce H2O2.