Is lysosomal fusion required for the granulocyte chemiluminescence reaction?

An in vitro study of the protective effect of the flavonoid silydianin against reactive oxygen species

The inhibitory effect of silydianin, an active constituent of Silybium marianum, on the in vitro production and release of oxidative products has been examined. Polymorphonuclear neutrophils (PMNs) play a primary role in the initiation and propagation of inflammatory responses. Their apoptosis is a major mechanism associated with the resolution of inflammatory reactions. Neutrophils were assessed for caspase-3 activity, the rst step in the execution phase of apoptosis. When cells were cultured with 100 microM silydianin for 24 h, caspase-3 was activated. Induction of apoptosis by silydianin was accompanied by a decrease in luminol-enhanced chemiluminescence as well as superoxide radical (O2*-) release in freshly isolated cells and lipid peroxidation in mouse spleen microsomes. No significant effect of silydianin on PMN hydrogen peroxide production evaluated by a flow cytometric dichlorofluorescin oxidation assay was found. Such results indicate a possible antiinflammatory activity for silydianin, which regulates caspase-3 activation, affects cell membranes and acts as a free radical scavenger.

Validation of different chemilumigenic substrates for detecting extracellular generation of reactive oxygen species by phagocytes and endothelial cells

Chemiluminescence is a widely used tool to detect extracellular generation of reactive oxygen species (ROS). In the present study we tested four different chemilumigenic substrates (CLS)--luminol, isoluminol, lucigenin and pholasin-to detect extracellular CL in different cell types: polymorphonuclear leukocytes (PMN); DMSO-differentiated HL-60 cells; murine macrophages (RAW 264.7); and TNF alpha-stimulated human endothelial cells (HUVEC). Extracellular ROS production was calculated by subtracting intracellular CL response in the presence of superoxide dismutase and catalase from the overall CL response in the absence of enzymes. CL varied considerably in dependence on the CLS and the stimulus used to evoke ROS generation. Luminol (oxidized LDL and zymosan stimulation) and isoluminol (FMLP and PMA stimulation) were the most effective CLS for PMN. Using 5 micromol/L lucigenin as CLS, small but consistent CL responses could be obtained in macrophages stimulated with PMA, zymosan or oxidized LDL. FMLP-stimulated extracellular CL in H-60 cells, HUVEC and macrophages was detected with the greatest sensitivity by pholasin. Our results demonstrate that none of the investigated CLS consistently yielded the highest CL quantum, either in different cell types with one stimulating agent or by different stimulating agents in one cell type. To get the highest CL quantum in experimental studies, we recommend optimizing the CLS depending on the cell type and the ROS-generating stimulus used.

Functional states of polymorphonuclear leukocytes determined by chemiluminescent kinetic analysis

During the respiratory burst, upon stimulation with both soluble and particulate matter, polymorphonuclear leukocytes (PMN) generate reactive oxygen species (ROS) and emit chemiluminescence (CL) as a result of metabolic activation. The measurement of CL has been demonstrated to be a useful tool for in vitro assessment of the opsonophagocytic function of PMN. Using component analysis of CL kinetics, we characterized the functional state of PMN by three parameters of the respiratory burst: capacity, effectiveness and velocity (CEV space). The possibility of delimiting eight different functional states of PMN is discussed. The CL kinetics shown by blood PMN in different functional states was analysed, and revealed six out of eight functional states. We conclude that CEV-estimated functional states of PMN are relative, depending on both PMN readiness to generate ROS and conditions of the CL test.

Modulation of luminol chemiluminescence of fMet-Leu-Phe-stimulated neutrophils by affecting dephosphorylation and the metabolism of phosphatidic acid

This paper is addressed to study how PKC-mediated effects and phosphatidic acid interact together in activation of NADPH-oxidase in formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) stimulated neutrophils as detected by luminol chemiluminescence. The early luminescence response in fMet-Leu-Phe-stimulated cells (up to 5 min after stimulation) depends mainly on reactive oxygen species generated extracellularly, whereas all later events are caused by oxidation of luminol inside the cells. The two protein phosphatase inhibitors, okadaic acid and calyculin A, dramatically increased the late luminescence of cells. This enhancement was totally inhibited by the phospholipase D modulator butanol, while the protein kinase C (PKC) inhibitor bisindolylmaleimide I was insensitive. The early luminescence response of the cells was slightly inhibited by both protein phosphatase inhibitors and depended on protein kinase C as well as on phospholipase D activities. Propranolol, an inhibitor of phosphatidate phosphohydrolase, enhanced all parts of luminescence response of fMet-Leu-Phe-stimulated neutrophils at concentrations up to 2.5 x 10(-5) mol/L. While the late luminescence response of propranolol-treated cells was not inhibited by the PKC inhibitor bisindolylmaleimide I, the first response depended on protein kinase C. The inhibitor of diacylglycerol kinase R59949 enhanced the luminescence signal only during the first 4 min in fMet-Leu-Phe-stimulated cells. Only diacylglycerols derived from phospholipase C, such as 1-stearoyl-2-arachidonoyl-sn-glycerol, were able to initiate an oxidative burst in cells. Saturated diacylglycerols (e.g. 1,2-dipalmitoyl-sn-glycerol or 1,2-distearoyl-sn-glycerol) did not yield any luminol chemiluminescence, although they were incorporated into the plasma membrane, as evidenced by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Our results demonstrate that phosphatidic acid produced by phospholipase D is responsible for NADPH-oxidase activity in fMet-Leu-Phe-stimulated neutrophils over the entire measuring time, whereas PKC-mediated processes are only involved during the first 5 min.

A rise in ionized calcium activates the neutrophil NADPH-oxidase but is not sufficient to directly translocate cytosolic p47phox or p67phox to b cytochrome containing membranes

Neutrophil production of reactive oxygen species is dependent on an assembly process that involves a translocation of the cytosolic NADPH-oxidase components (p47phox; p67phox; Rac2) to a b cytochrome containing membrane. Based on the fact that an intracellular Ca2+ rise can activate the oxidase without any extracellular release of reactive oxygen species, we suggest that the oxidase can be assembled in a membrane distinct from the plasma membrane. Disintegrated cells were used to monitor Ca2+ dependent membrane binding of neutrophil cytosolic proteins. Membranes containing the b cytochrome part of the oxidase, i.e., specific granules and plasma membranes/secretory vesicles, were used in the translocation experiments. Several cytosolic proteins were found to translocate to specific granules as well as the plasma membranes/secretory vesicles, one of them being annexin I. Using antibodies in the blotting assay against the cytosolic oxidase components p47phox and p67phox, we could show that no Ca2+ dependent translocation of these cytosolic proteins occur to neither of the b cytochrome containing membranes.

A simple chemiluminescence assay for the determination of reactive oxygen species produced by human neutrophils

We show that phagocyte production of reactive oxygen species can be measured using a microtitre plate based chemiluminescence blotting technique. The production of reactive oxygen species is determined by their ability to catalyze the oxidation of luminol or isoluminol, resulting in light emission which is recorded on a photographic film. The method permits the determination of NADPH oxidase activity from as few as 9000 cells. It could be used to detect NADPH oxidase defects in neutrophils (e.g. from patients suffering from chronic granulomatous disease), and to screen pharmaceuticals with scavenging activity for reactive oxygen species.

Influence of different luminols on the characteristics of the chemiluminescence reaction in human neutrophils

In search for a luminol with very high output of light, 20 different luminol samples were tested for their ability to enhance the chemiluminescence reaction in phorbol myristate acetate activated human neutrophils. We found that the majority of luminols tested (17 samples) gave almost the same light output from neutrophils, and that the major part of the activity was from an intracellular origin. Owing to the fact that three isoluminol samples were unable to monitor respiratory burst activity taking place intracellularly, a very low level of chemiluminescence was obtained with these samples. Their light output was, however, greatly increased when horseradish peroxidase or myeloperoxidase was added, showing that the light-generating reaction with isoluminol as well as with luminol is peroxidase-dependent. The fact that isoluminol could also use myeloperoxidase as amplifying peroxidase, suggests that that the lack of measurable intracellular activity in the presence of isoluminol is somehow related to a limited or restricted diffusion of the molecule to intracellular sites. The isoluminol system constitutes a sensitive system for measuring release of oxygen metabolites from phagocytic cells.

A new approach for analysis of chemiluminescent kinetics of activated phagocytes in blood

Luminol chemiluminescence (LCL) is a simple, sensitive and time-saving tool to elucidate the oxidative activity of polymorphonuclear leukocytes (PMNL). In this study, a new approach for analysing the LCL kinetics, recorded from stimulated PMNL, and for a more accurate elucidation of their functional state, is proposed. This approach is based on the proposal that the LCL kinetics of stimulated PMNL is a result of time-probabilistic nature of the processes, leading to light emission. On this basis the LCL response was described by the parameters of a Poisson-type distribution. Relationships between these parameters and some factors influencing LCL kinetics (number of PMNL and erythrocytes, temperature, stirring) were investigated. The model descriptions of the LCL responses obtained had two components (modes). Their development in time was different. It was suggested, that the two phases of the model LCL response were connected with extracellular and intracellular LCL. The terms and the advantages of this approach for analysis of phagocyte oxidative capacity are discussed.

Effect of sulphite on the oxidative metabolism of human neutrophils: studies with lucigenin- and luminol-dependent chemiluminescence

To assess the effect of sulphite on the oxidative metabolism of human neutrophils, chemiluminescence (CL) measurements were performed using lucigenin and luminol as chemiluminigenic probes. Lucigenin-dependent CL was used for measuring superoxide anion (O2-) production, and luminol-dependent CL was used for determination of myeloperoxidase (MPO)-connected processes. With sulphite concentrations of 0.01 to 1 mmol/L, resting neutrophils showed an up to sixfold increase of lucigenin-dependent CL, but only a 1.9-fold increase of luminol-dependent CL. Subsequent stimulation of sulphite-treated neutrophils with phorbol myristate acetate (PMA) (soluble stimulant) or zymosan (particulate stimulant) resulted in an additional significant increase of lucigenin-dependent CL compared to stimulated control cells, whereas luminol-dependent CL increased slightly by 0.01 mmol/L sulphite and decreased then continuously. Sulphite concentrations above 1 mmol/L decreased both lucigenin- and luminol-dependent CL of resting and PMA- or zymosan-stimulated neutrophils. Lucigenin-dependent CL of sulphite-treated and subsequently stimulated neutrophils was strongly inhibited by extracellularly added superoxide dismutase, whereas luminol-dependent CL was markedly reduced by the MPO inhibitor azide. The intracellular activity of MPO in neutrophils stimulated with PMA in the presence of sulphite (2 mmol/L) was reduced by 55%. Sulphite (0.1 mmol/L) also inhibited strongly the activity of MPO in a cell-free system. These results indicate that micromolar concentrations of sulphite exert a stimulating effect on the O2- production of neutrophils extracellularly, but have an inhibitory effect on MPO-catalysed reactions intracellularly.

Peroxidation of egg yolk phosphatidylcholine liposomes by hypochlorous acid

The powerful neutrophil-derived oxidant hypochlorous acid HOCl/OCl- is assumed to contribute to tissue injury in a number of pathological states accompanied by massive accumulation of neutrophils. The production of malondialdehyde to indicate lipid peroxidation was studied in egg yolk phosphatidylcholine liposomes upon treatment with NaOCl as a source for hypochlorous acid. Its accumulation was inhibited by alpha-tocopherol and butylated hydroxytoluene. Singlet oxygen, hydroxyl radicals or superoxide anion radicals derived from direct reactions of hypochlorous acid seem not to be involved in initiation of lipid peroxidation because the malondialdehyde accumulation was unaffected by hydrogen peroxide, catalase, superoxide dismutase, ferrous sulphate or ferric chloride. Double bonds of fatty acid residues seem to be the primary target for NaOCl. Their number is continuously diminished in liposomes (2 mg lipids/ml) after incubation with increasing amounts of NaOCl at 37 degrees C for 40 min as detected by two independent methods (iodine bromide reduction and 1H-NMR spectroscopy). A 1:1 molar ratio between the loss of double bonds and NaOCl added was found only at low NaOCl concentrations. Then double bonds are decreased with a lower efficiency. A continuous increase of lipid peroxidation products was only observed up to 0.5-0.7 mmol/l NaOCl. The yield of lipid hydroperoxides kept constant at higher NaOCl concentrations. However, diene conjugates and malondialdehyde exhibit a maximum at 0.7-1 mmol/l or 0.5 mmol/l NaOCl, respectively, while the concentration of these products decreases at higher doses of NaOCl. The decrease of malondialdehyde was more pronounced than for diene conjugates. These results were discussed from the background that at minimum two (diene conjugates) or three (malondialdehyde) double bonds in a fatty acid residue are necessary for formation of lipid peroxidation products.

Scavenging of reactive oxygen species by silibinin dihemisuccinate

Silibinin dihemisuccinate (SDH) is a flavonoid of plant origin with hepatoprotective effects which have been partially attributed to its ability to scavenge oxygen free radicals. In the present paper the antioxidant properties of SDH were evaluated by studying the ability of this drug to react with relevant biological oxidants such as superoxide anion radical (O2-), hydrogen peroxide (H2O2), hydroxyl radical (HO.) and hypochlorous acid (HOCl). In addition, its effect on lipid peroxidation was investigated. SDH is not a good scavenger of O2- and no reaction with H2O2 was detected within the sensitivity limit of our assay. However, it reacts rapidly with HO. radicals in free solution at approximately diffusion-controlled rate (K = (1.0-1.2) x 10(10)/M/sec) and appears to be a weak iron ion chelator. SDH at concentrations in the micromolar range protected alpha 1-antiproteinase against inactivation by HOCl, showing that it is a potent scavenger of this oxidizing species. Luminol-dependent chemiluminescence induced by HOCl was also inhibited by SDH. The reaction of SDH with HOCl was monitored by the modification of the UV-visible spectrum of SDH. The studies on rat liver microsome lipid peroxidation induced by Fe(III)/ascorbate showed that SDH has an inhibitory effect, which is dependent on its concentration and the magnitude of lipid peroxidation. This work supports the reactive oxygen species scavenger action ascribed to SDH.

Increased native chemiluminescence in granulocytes isolated from synovial fluid and peripheral blood of patients with rheumatoid arthritis

Polymorphonuclear leukocytes (PMNs) isolated from peripheral blood and synovial fluid of patients with rheumatoid arthritis and from peripheral blood of volunteers were stimulated with 12-phorbol-13-myristate acetate (PMA). No significant differences in luminol-amplified chemiluminescence were found between different patients and control groups. However, two distinct patterns of native chemiluminescence were observed. Type I showed no, or only a small, increase in native chemiluminescence with integral counts over 30 min less than 3 x 10(5) cpm, and the majority of samples from volunteers were of this type. Type II was characterized by a burst of native chemiluminescence starting 8 to 15 min after cell stimulation. It was found in most PMN samples from patients with rheumatoid arthritis. Integral counts over 30 min were always higher than 10(6) cpm and as high as 10(8) cpm in some cases. A strong inhibition of the Type II native chemiluminescence was caused by desferal, catalase, thiourea, and glutathione. However, the luminol-amplified chemiluminescence remained unchanged or was only slightly decreased under the same experimental conditions. Sodium azide strongly inhibited both kinds of luminescence. Hydroxyl radicals, formed in a Fenton reaction, may be important intermediates in the Type II native chemiluminescence.

Hypochlorite oxidation causes cross-linking of Lp(a)

When purified low density lipoprotein (LDL) or lipoprotein(a) (Lp[a]) was oxidized in vitro using concentrations of hypochlorite (50-500 microM) which might be achieved by activated neutrophils in vivo, high molecular weight species were observed on SDS polyacrylamide gels. The reaction was concentration-, temperature- and time-dependent. The high molecular weight apoprotein complexes were resistant to heating in SDS and DTT, suggesting covalent, but non-disulfide bond, cross-linking. Negligible amounts of lower molecular weight degradation products were formed. Bityrosine formation, measured by fluorescence and HPLC analysis, was found to increase with the amount of hypochlorite added. However, the molar concentration of bityrosine could not account for cross-linking, even if it was assumed that every bityrosine was intermolecular. Hypochlorite-oxidized Lp(a) and LDL were both effective as ligands for loading mouse peritoneal macrophages in vitro. We conclude that hypochlorite produced in inflammatory reactions might be important in the generation of atherogenic forms of lipoproteins.

Structure-activity relationship in the ability of flavonols to inhibit chemiluminescence

Fourteen flavonoids were evaluated for their ability to inhibit chemiluminescence, either of neutrophils that had been briefly exposed to both luminol and phorbol-myristate acetate or to an enzymatic system with H2O2, luminol and horseradish peroxidase. Using chemiluminescence as the quantitative parameter, it can be concluded that the hydroxyl group in position 3 of the flavonols is vital for their inhibitory effect, and that two hydroxyl groups on the phenyl ring are optimal for such an effect. It was also noted that the C2-C3 double bond is essential for the flavonols' anti-oxidative effect. It is suggested that the ability of flavonols to suppress chemiluminescence is reciprocally correlated with their lipophilicity.

Polymorphonuclear leukocyte chemiluminescence induced by Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus in serum and saliva

The ability of different strains of Actinobacillus actinomycetemcomitans (A.a.) and Haemophilus aphrophilus (H.a.) to trigger activation of an oxidative burst in human polymorphonuclear leukocytes (PMNL) was examined by measuring the luminol-amplified light emission--chemiluminescence (CL)--from these cells. Bacterial cells were incubated with PMNL from one healthy subject, in the presence of either active serum, heat-inactivated serum, saliva, or saliva and active serum. In the presence of active serum, all five H.a. strains and two out of five A.a. strains triggered a CL response. The CL induced in the presence of heat-inactivated serum was considerably less than that achieved with fresh serum. In the presence of only saliva, all strains induced considerably weaker CL responses than those induced in the presence of saliva with active serum. In the presence of serum, intracellular reactions appeared to be the main source of CL, while addition of saliva and active serum increased the extracellular CL. The results indicate that strain-dependent differences exist among A.a. strains in their ability to trigger the oxygen-dependent bactericidal mechanisms of human PNML. In contrast, the CL patterns of H.a. strains were equivalent. Various factors in the environment, such as activated complement and salivary compounds, affect the interaction of these species with neutrophils.

Mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite

Two different mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite were found. Most substances investigated in these experiments acted by scavenging NaOCl. This mechanism was independent of the concentration of hydrogen peroxide and the incubation time between luminol and inhibitors. The most potent inhibitors were substances containing SH groups. Compounds with amino groups as a target for HOCl/OCl- to yield chloramines were much less effective inhibitors. Another mechanism of inhibition was found for catalase. It depended on the presence of hydrogen peroxide in the incubation medium and the incubation time between luminol and catalase. The enzyme inhibited the luminescence by removing H2O2 at molar concentrations much smaller than those found for all other inhibitors. Our results confirm the present models of the mechanism of generation of luminescence in luminal oxidation.

Chemiluminescence in activated human neutrophils: role of buffers and scavengers

Human neutrophils (PMNs) suspended in Hanks' balanced salt solution (HBSS), which are stimulated either by polycation-opsonized streptococci or by phorbol myristate acetate (PMA), generate nonamplified (CL), luminol-dependent (LDCL), and lucigenin-dependent chemiluminescence (LUCDCL). Treatment of activated PMNs with azide yielded a very intense CL response, but only a small LDCL or LUCDCL responses, when horse radish peroxidase (HRP) was added. Both CL and LDCL depend on the generation of superoxide and on myeloperoxidase (MPO). Treatment of PMNs with azide followed either by dimethylthiourea (DMTU), deferoxamine, EDTA, or detapac generated very little CL upon addition of HRP, suggesting that CL is the result of the interaction among H2O2, a peroxidase, and trace metals. In a cell-free system practically no CL was generated when H2O2 was mixed with HRP in distilled water (DW). On the other hand significant CL was generated when either HBSS or RPMI media was employed. In both cases CL was markedly depressed either by deferoxamine or by EDTA, suggesting that these media might be contaminated by trace metals, which catalyzed a Fenton-driven reaction. Both HEPES and Tris buffers, when added to DW, failed to support significant HRP-induced CL. Nitrilotriacetate (NTA) chelates of Mn2+, Fe2+, Cu2+, and Co2+ very markedly enhanced CL induced by mixtures of H2O2 and HRP when distilled water was the supporting medium. Both HEPES and Tris buffer when added to DW strongly quenced NTA-metal-catalyzed CL. None of the NTA-metal chelates could boost CL generation by activated PMNs, because the salts in HBSS and RPMI interfered with the activity of the added metals. CL and LDCL of activated PMNs was enhanced by aminotriazole, but strongly inhibited by diphenylene iodonium (an inhibitor of NADPH oxidase) by azide, sodium cyanide (CN), cimetidine, histidine, benzoate, DMTU and moderately by superoxide dismutase (SOD) and by deferoxamine LUCDCL was markedly inhibited only by SOD but was boosted by CN. Taken together, it is suggested that CL generated by stimulated PMNs might be the result of the interactions among, NADPH oxidase, (inhibitable by diphenylene iodonium), MPO (inhibitable by sodium azide), H2O2 probably of intracellular origin (inhibitable by DMTU but not by catalase), and trace metals that contaminate salt solutions. The nature of the salt solutions employed to measure CL in activated PMNs is critical.

Antioxidant activity of micronized diosmin on oxygen species from stimulated human neutrophils

Flavonoids are known to reduce reactive oxygen species released by polymorphonuclear neutrophils (PMNs) in vitro. We have studied the effects of S5682 (Daflon 500 mg), a purified flavonoid fraction composed of 90% diosmin and 10% hesperidin. S5682 produced a dose-dependent inhibition of the luminol chemiluminescence (CL) induced by phorbol myristate acetate on PMNs (IC50 = 5 x 10(-5) M), with no effect on superoxide anion (O2.-) formation and on cellular superoxide dismutase activity as determined by lucigenin-amplified CL. The CL results were confirmed by the hydrogen peroxide (H2O2) determination showing that S5682 reduced H2O2 formed through either PMN stimulation (IC50 = 1.6 x 10(-6) M) or an in vitro enzymatic mechanism (IC50 = 2 x 10(-6) M). S5682 inhibited luminol-dependent CL induced by H2O2 (IC50 = 5 x 10(-6) M). However, O2 was not formed from H2O2 in contact with S5682 and the UV spectrum of this compound was not modified. In contrast, S5682 inhibited luminol-dependent CL induced by H2O2 in the presence of horseradish peroxidase (IC50 = 3 x 10(-6) M), and the UV spectrum of S5682 was modified. Luminol-dependent CL induced by hypochlorite (OCl- 10(-5) M) was also inhibited by S5682 (IC50 = 7 x 10(-5) M). This inhibitory effect was similar to that of sodium azide on myeloperoxidase activity. Moreover, OCl- 5 x 10(-4) M also altered the UV spectrum of S5682 10(-4) M. These results indicate that S5682 could be active on the H2O2-OCl(-)-myeloperoxidase system.

Role of functional groups of human plasma and luminol in scavenging of NaOCl and neutrophil-derived hypochlorous acid

Hypochlorous acid HOCl/OCl- and other oxidants derived from stimulated polymorphonuclear leukocytes are involved in tissue damage during a number of pathological processes. In order to obtain more detailed information on possible reactions of HOCl/OCl- the effects of both NaOCl and PMN-derived hypochlorous acid on functional groups of amino acid solutions and human plasma are studied. In valine and lysine solutions NaOCl diminishes the number of amino groups in a molar ratio of 1:1 between NaOCl and amino groups. In cysteine and methionine samples the decrease of amino groups starts only after all sulfhydryl or thioether groups are oxidized by NaOCl. If freshly prepared human plasma is treated with increasing amounts of NaOCl all plasma SH groups are oxidized first, then probably the thioether groups and only after this the amino groups are affected. Furthermore, it was found, that the reactivity of luminol against NaOCl is similar to that of amino groups. Increasing amounts of SH groups of components of human plasma are oxidized by incubation with PMA-stimulated polymorphonuclear leukocytes dependent on the incubation time. Plasma amino groups are not affected under the same experimental conditions. The addition of plasma to FMLP-stimulated PMN in the presence of luminol decreases that part of chemiluminescence caused by extracellularly generated hypochlorous acid. Plasma samples pretreated with NaOCl cause a lower inhibition of light generation in FMLP-stimulated PMN only when more than 4.10(-8) mol NaOCl per mg protein are used to pretreat plasma. It is assumed that in the development of tissue injuries caused by infiltrated PMN the following sequence of damage occurs in accessible tissue regions. First, the sulfhydryl groups are oxidized, then the thioether groups, and only after this amino and other target groups are affected.

Effect of different inhibitors on the intracellularly and extracellularly generated chemiluminescence induced by formylmethionyl-leucyl-phenylalanine in polymorphonuclear leukocytes. Cellular response in the presence of mannitol, benzoate, taurine, indomethacin and NDGA

When polymorphonuclear leukocytes (PMNL) interact with the soluble stimulus formylmethionyl-leucyl-phenylalanine (FMLP), the cells increase their production of oxidative metabolites. This increased production can be measured as lumino-amplified light emission or chemiluminescence (CL). In the present report, experimental systems which allow a quantitation of extracellularly and intracellularly generated metabolites have been used, and the effect of mannitol, benzoate, taurine, indomethacin and nordihydroguaiaretic acid has been investigated. The presence of the hypochlorous acid scavenger taurine had no effect on the intracellular response, whereas the extracellular response was reduced with around 50%. The hydroxyl radical scavenger mannitol had only minor effects on the response, whereas benzoate, another hydroxyl radical scavenger, reduced the extracellular response with around 50% and the intracellular response with more than 90%. Indomethacin, an inhibitor of arachidonic acid metabolism, did not influence the response, whereas NDGA, also an inhibitor of the arachidonic acid metabolism, totally abolished both the extracellular and the intracellular response. The use of scavengers/inhibitors as a means of determining the mechanisms of light emission, and the origin of chemiluminescence produced by neutrophils stimulated by FMLP is discussed.

On radical production by PMA-stimulated neutrophils as monitored by luminol-amplified chemiluminescence

The means by which neutrophils within the body ward off infectious and neoplastic processes by the activation of molecular oxygen, as well as how such mechanisms dysfunction, is the subject of extensive ongoing research. Most previous studies of neutrophil activation indicate that there is a transient production of reactive oxygen species. Luminol-amplified chemiluminescence surveillance of O2-. and H2O2 supported these general findings. Yet, recent studies showed that production of reactive oxygen species by PMA-stimulated neutrophils is not transient but persistent; however, luminol-dependent methods do not corroborate such findings. The kinetics of O2-. production by human neutrophils were studied using luminol-amplified chemiluminescence (CL), spin trapping combined with electron spin resonance detection, and ferricytochrome c reduction. The effects of pH and O2 level on luminol-amplified CL were determined using hypoxanthine/xanthine oxidase to produce O2-. and H2O2 in cell-free systems. As we have found by electron spin resonance and ferricytochrome c reduction, stimulated neutrophils continued to generate O2-. for several hours, yet when luminol-amplified CL was used to continuously follow radical production, CL was shortly lost. Similar loss of CL was observed with continuous enzymatic formation of O2-. and H2O2. The failure of the CL assay to report O2-. and H2O2 formation results from some luminol reaction product which interferes with the light reaction. Our results show that the cells are operative for long periods indicating that cell exposure to prolonged O2-. fluxes does not terminate radical production, and even when pH, [O2], and reagents are optimized, the use of luminol-amplified CL is not a valid assay for continuous monitoring of O2-. and H2O2 generated by either stimulated neutrophils or in cell-free systems.

Luminol enhanced chemiluminescence of the perfused rat heart during ischemia and reperfusion

We show that the production of Luminol reactive oxygen radicals in the perfused rat heart under ischemia and reperfusion can be monitored continuously by measuring the chemiluminescence of Luminol-perfused hearts. Luminol did not affect the monitored physiological parameters of the hearts. Chemiluminescence increased during ischemia and reperfusion. Superoxide dismutase treatment of the heart before ischemia, but not catalase, abolished these increases.