Chemiluminescence as an analytical tool in cell biology and medicine

Chemiluminescent detection of carbohydrates in the tumoral breast diseases

Nowadays, there is an increase of investigations into the fibroadenoma, mainly because some studies have shown that the occurrence of fibroadenoma is linked to an increased risk of developing breast carcinoma. Currently, the chemiluminescence biomarkers are applied for validation methods and screening. Here, a lectin chemiluminescence is proposed as new histochemistry method to identify carbohydrates in mammary tumoral tissues. The lectins concanavalin A (Con A) and peanut agglutinin (PNA) conjugated to acridinium ester were used to characterize the glycocode of breast tissues: normal, fibroadenoma, and invasive duct carcinoma (IDC). The lectin chemiluminescence expressed in relative light units (RLU) was higher in fibroadenoma and IDC than in normal tissue for both lectins tested. The relationship RLU emission versus tissue area described a linear and hyperbolic curve for IDC and fibroadenoma, respectively, using Con A whereas hyperbolic curves for both transformed tissues using PNA. RLU was abolished by inhibiting the interaction between tissues and lectins using their specific carbohydrates: methyl-α-D: -mannoside (Con A) and galactose (PNA). The intrinsic fluorescence emission did not change with combination of the lectins (Con A/PNA) to the acridinium ester for hydrophobic residues. These results represent the lectin chemiluminescence as an alternative of histochemistry method for tumoral diagnosis in the breast.

Acridinium ester conjugated to lectin as chemiluminescent histochemistry marker

Cell differentiation/dedifferentiation includes changes in oligosaccharide composition and distribution in the cell surface glycoconjugates. Lectins have been used as auxiliary tools in histopathological diagnosis of mammary, uterus and brain pathologies. Acridinium ester (AE) conjugated to biomolecules has been employed in chemiluminescent analytical applications. This work aimed to use a lectin, concanavalin A (Con A), conjugated to AE as a chemiluminescent histochemistry tool. Biopsies of normal and infiltrating duct carcinoma (IDC) of mammary tissues were treated by a Con A-AE derivative. Photon emission, observed during the breakage of the chemical bound between Con A and AE, was quantified, expressed in relative light units (RLU) and correlated to the labelling of the normal and transformed tissues. The results demonstrated that RLU presented a linear relationship with the labelled tissue area in the range 0.125-1.0 cm2 (r=0.98). Furthermore, RLU was much higher for the IDC (1283.920x103+/-220.621x103) than the normal tissue (2.565x103+/-0.247x103), namely, about 500 times higher. The Con A-AE conjugation efficiency, differential staining of normal and IDC tissues, and quantification of results contribute to a decrease in the subjectivity in routine histopathological diagnoses and indicate that acrydinum ester can join other lectin marker to be used in histochemistry.

Mouse model for noninvasive imaging of HIF prolyl hydroxylase activity: assessment of an oral agent that stimulates erythropoietin production

Many human diseases are characterized by the development of tissue hypoxia. Inadequate oxygenation can cause cellular dysfunction and death. Tissues use many strategies, including induction of angiogenesis and alterations in metabolism, to survive under hypoxic conditions. The heterodimeric transcription factor hypoxia-inducible factor (HIF) is a master regulator of genes that promote adaptation to hypoxia. HIF activity is linked to oxygen availability because members of the EGLN family hydroxylate HIFalpha subunits on specific prolyl residues when oxygen is present, which marks them for ubiquitination and proteasomal degradation. We created a mouse that ubiquitously expresses a bioluminescent reporter consisting of firefly luciferase fused to a region of HIF that is sufficient for oxygen-dependent degradation. Our validation studies suggest that this mouse will be useful for monitoring hypoxic tissues and evaluating therapeutic agents that stabilize HIF. One such agent, the HIF prolyl hydroxylase inhibitor FG-4383, was active in the liver and kidney after systemic administration as determined by bioluminescence imaging, transcription profiling, and production of erythropoietin, indicating that the HIF transcriptional program can be manipulated in vivo with orally active organic small molecules.

A rapid antimicrobial susceptibility test based on chemiluminescence assay and its application to screening of genotypes in vancomycin-resistant enterococci

Minimum inhibitory concentrations (MICs) of vancomycin (VCM) and teicoplanin (TEIC) were measured using a novel susceptibility test based on the chemiluminescence assay (CA) method (Rapid-Lumi Eiken; Eiken Chemicals, Tokyo, Japan) against 33 strains in total: 7, 5, and 10 strains of which are VCM-resistant enterococci (VRE) with vanA, vanB, and vanC genes, respectively, and the other 11 strains are vancomycin-susceptible enterococci (VSE). The results were in good accordance with the values determined by the standard broth dilution method approved by the National Committee for Clinical Laboratory Standards (NCCLS): i.e., 88% (29/33) of consistency for VCM and 97% (32/33) for TEIC, respectively. In addition, genotypes in VRE strains (vanA, vanB, vanC-1, and vanC-2/3 genes) were properly estimated from the results of the CA method and the NCCLS interpretive categories, even though the incubation time was very short (2-4 h). In conclusion, it was found that the new method is reliable and rapid to detect VRE strains in clinical laboratories.

Evaluation of a novel automated chemiluminescent assay system for antimicrobial susceptibility testing

The newly developed Rapid Lumi Eiken/IS60 (RL/IS60) system automatically determines MICs by detecting chemiluminescence produced in the reaction of a chemiluminescent probe and oxygen metabolites from living microorganisms. The present study evaluated this system for accuracy in antimicrobial susceptibility testing. Chemiluminescence intensities after 4 h of cultivation of clinically important strains were plotted against various concentrations of antimicrobial agents, which resulted in curves reflecting the levels of susceptibility. Sixty-percent inhibitory concentrations based on the susceptibility curves agreed with MICs determined by the reference microdilution method. When the MICs of antimicrobial agents for four quality control (QC) strains (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa) were determined by the RL/IS60 system, most (91.1%) of them were within the QC limits proposed by the National Committee for Clinical Laboratory Standards. The system was further assessed for a total of 162 clinical isolates, including E. coli, Citrobacter freundii, Enterobacter cloacae, Klebsiella pneumoniae, Serratia marcescens, Proteus mirabilis, Morganella morganii, P. aeruginosa, Haemophilus influenzae, S. aureus, coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium, and Streptococcus pneumoniae. Overall, there was 90.6% agreement between the RL/IS60 system and the reference microdilution method. Our results suggest that the RL/IS60 system provides rapid and reliable MICs of a variety of antimicrobial agents for clinical isolates as well as QC strains.

Ca(2+)-dependent production of reactive oxygen metabolites by human neutrophils in response to fluorinated propranolol analogues

Fluorinated analogues of propranolol, namely trifluoroethyl propranolol (F3), pentafluoropropyl propranolol (F5), and heptafluorobutyl propranolol (F7), were found to induce reactive oxygen metabolite (ROM) production in human neutrophils in a dose-dependent manner. Preincubation of neutrophils with the calcium chelator BAPTA-AM or the tyrosine kinase inhibitor genistein inhibited this ROM production. Direct measurements of intracellular calcium revealed that these analogues caused a transient increase in intracellular calcium. In addition, these fluorinated analogues of propranolol caused a transient increase in actin polymerization. The effects of these compounds were found to be dependent upon the degree of fluorination of the parent compound. Propranolol, on the other hand, had no direct effect on ROM, calcium, or actin polymerization when added alone to neutrophils, although it did modify responses of cells to various stimuli. Whereas ROM production induced by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine was enhanced in a dose-dependent manner, the response to the particulate stimulus, latex beads, was abolished.

Evidence for IL-12-Activated Ca2+ and Tyrosine Signaling Pathways in Human Neutrophils

The cytokine IL-12 is proposed to play a bridging role between innate and adaptive immunity. Here we demonstrate that IL-12 binds specifically to human neutrophils. This binding leads to a transient increase in 1) intracellular free calcium due to its release from membrane-enclosed stores and its influx from extracellular medium, 2) actin polymerization, and 3) tyrosine phosphorylation. IL-12 treatment also leads to a concentration-dependent increase in reactive oxygen metabolite production. The effect of IL-12 is blocked by neutralizing Abs to IL-12. Inhibition of either calcium transient or tyrosine phosphorylation causes inhibition of reactive oxygen metabolite production. However, inhibition of actin polymerization enhances IL-12-induced oxidase activation. Our data suggest 1) a direct role for IL-12 in the activation of human neutrophils, and 2) a calcium-dependent signaling pathway for IL-12.

Influence of age on the release of reactive oxygen species by phagocytes as measured by a whole blood chemiluminescence assay

Polymorphonuclear and mononuclear phagocytes play an important role in host defense, but may also cause tissue injury through excessive inflammation. Reactive oxygen species (ROS) are not only directly ore indirectly involved in a wide variety of clinical disorders, such as atherosclerosis, reperfusion injury, pulmonary toxicity and cancer, but they are also important in the aging process. This process is associated with increasing susceptibility to infection. In this study we investigated the influence of age and sex on phagocyte activation by means of a whole blood chemiluminescence (CL) assay. Circulating phagocyte activity was measured in 55 healthy volunteers (24 females, 31 males) aged from 6 to 92 years. Using an automated luminescence system, phagocytes were stimulated by polystyrene beads and Luminol-enhanced CL was determined in terms of peak height and peak time in freshly withdrawn, peripheral venous whole blood. An extremely significant positive correlation (p < 0.0001) between the maximum of light emission after stimulation and increasing age was found. This finding is true for the total population of blood phagocytes as well as for a single cell. In contrast the time of the appearance of the maximum of light emission showed an extremely significant inverse correlation (p < 0.0003) with increasing age. The influence of sex on the CL-parameters showed no significant difference between women and men. It is concluded that the increased susceptibility of circulating phagocytes to oxidative burst in elderly subjects may be the consequence of several biological events. Senescent cells express more and also have new antigens on their surfaces that trigger an autoimmune response. Cellular senescence appears earlier in old organisms. Therefore phagocytes in aging individuals may be increasingly involved in their scavenger tasks that grow with the catabolic bias in cell turnover. Moreover, atherosclerotic alterations in the intima and endothelial lesions are physiologic concomitants of age and may lead to a stimulation of circulating phagocytes.

Effect of N-3 polyunsaturated fatty acid supplemented diet on neutrophil-mediated ileal permeability and neutrophil function in the rat

RATIONALE AND OBJECTIVE

Fish oil, rich in n-3 polyunsaturated fatty acids, can alter leukotriene production and hence neutrophil function, factors which may be important in the inflammation of Crohn's disease (CD). Therefore we studied the effect of dietary PUFA on neutrophil mediated ileal inflammation and neutrophil function in the rat.

METHODS

Animals were ad libitum-fed pellet diets containing 9.5% fish oil (menhaden oil, rich in n-3 PUFA) with 0.5% safflower oil, 10% safflower oil (rich in n-6 PUFA) or standard chow (6% fat) for 50 days prior to the study. Weight and circulating leukocyte and total neutrophil counts were identical in all three groups. Neutrophil mediated ileal inflammation induced by formyl-methionyl-leucyl-phenylalanine (fMLP) perfusion was evaluated by measuring macromolecular uptake of radiolabelled dextran (MW 70,000) and changes in mucosal neutrophil infiltration.

RESULTS

The fish oil diet group showed no difference in fMLP-induced permeability changes relative to the Chow Control group. However, the Safflower Oil supplemented diet group had a reduced permeability response (p < 0.01). Mirroring the permeability changes, there was diminished mucosal neutrophil infiltration in the Safflower Oil group following ileal perfusion with fMLP (< .005). Chemotaxis and chemiluminescence, two important neutrophil functions, were also significantly suppressed in the Safflower Oil animals (p < 0.05).

CONCLUSIONS

The failure of a n-3 PUFA enriched diet to diminish the ileal inflammatory response to a bacterial peptide and suppress neutrophil function in the rat suggests such therapy would not be expected to be highly successful in CD. However, it requires confirmation in man, especially under the more complicated inflammatory conditions found in CD. On the other hand, the decreased neutrophil mediated responses with a high linoleic acid (n-6 PUFA) diet warrant further investigation.

Relative roles of elastase and reactive oxygen species in the degradation of human glomerular basement membrane by intact human neutrophils

Glomerular basement membrane (GBM) damage and proteinuria occurring during the early phase of acute glomerulonephritis are often neutrophil (PMN) dependent. The present study sought to identify the potential roles of PMN derived elastase and reactive oxygen species (ROS) in the pathogenesis of glomerular basement damage in an homologous in vitro model of anti-GBM nephritis using intact PMN. Human PMN (5 x 10(6)), incubated with human GBM (0.5 mg) pretreated with human anti-GBM IgG, degraded 10.3 +/- 1.1% of the GBM type IV collagen in six hours (8 micrograms/hr), and underwent a two-hour respiratory burst. The same number of sonically disrupted PMN solubulized 22.4 +/- 5.1% of GBM under the same incubation conditions. The inclusion of the elastase inhibitors alpha 1 proteinase inhibitor (alpha 1Pi), and a smaller highly-specific synthetic compound (L658,758), reduced degradation by PMN homogenates by 84.8% and 85.7%, respectively, whereas they were only able to inhibit intact PMN mediated degradation by a maximum of 49.2% and 50.9%, respectively. The inclusion of EDTA (10 mM), an inhibitor of metalloproteinases, reduced GBM degradation by APMA activated and disrupted PMN by only 7.5%. Incubation of PMN with diphenylene iodonium (DPI) abolished PMN reactive oxygen species generation by > 95% but preserved elastase release. This compound did not directly affect GBM degradation. It did, however, abolish the inhibitory effect of ROS on alpha 1Pi activity and thus indirectly reduced GBM damage by up to 20%.

Quantitative analysis of enzymic digests of DNA using gel electrophoresis

Quantitative electrophoresis of enzymic digests of DNA and its applications are reviewed. Factors affecting the overall analysis such as DNA length distribution, labels for visualizing DNA, techniques for quantitation, and electrophoresis itself are studied. Methods to analyze restriction fragments and lesions in DNA by gel electrophoresis are presented.

Imaging calcium dynamics in living plants using semi-synthetic recombinant aequorins

The genetic transformation of the higher plant Nicotiana plumbaginifolia to express the protein apoaequorin has recently been used as a method to measure cytosolic free calcium ([Ca2+]i) changes within intact living plants (Knight, M. R., A. K. Campbell, S. M. Smith, and A. J. Trewavas. 1991. Nature (Lond.). 352:524-526; Knight, M. R., S. M. Smith, and A. J. Trewavas. 1992. Proc. Natl. Acad. Sci. USA. 89:4967-4971). After treatment with the luminophore coelenterazine the calcium-activated photoprotein aequorin is formed within the cytosol of the cells of the transformed plants. Aequorin emits blue light in a dose-dependent manner upon binding free calcium (Ca2+). Thus the quantification of light emission from coelenterazine-treated transgenic plant cells provides a direct measurement of [Ca2+]i. In this paper, by using a highly sensitive photon-counting camera connected to a light microscope, we have for the first time imaged changes in [Ca2+]i in response to cold-shock, touch and wounding in different tissues of transgenic Nicotiana plants. Using this approach we have been able to observe tissue-specific [Ca2+]i responses. We also demonstrate how this method can be tailored by the use of different coelenterazine analogues which endow the resultant aequorin (termed semi-synthetic recombinant aeqorin) with different properties. By using h-coelenterazine, which renders the recombinant aequorin reporter more sensitive to Ca2+, we have been able to image relatively small changes in [Ca2+]i in response to touch and wounding: changes not detectable when standard coelenterazine is used. Reconstitution of recombinant aequorin with another coelenterazine analogue (e-coelenterazine) produces a semi-synthetic recombinant aequorin with a bimodal spectrum of luminescence emission. The ratio of luminescence at two wavelengths (421 and 477 nm) provides a simpler method for quantification of [Ca2+]i in vivo than was previously available. This approach has the benefit that no information is needed on the amount of expression, reconstitution or consumption of aequorin which is normally required for calibration with aequorin.

Wind-induced plant motion immediately increases cytosolic calcium

Wind is one of the most unusual and more dramatic of the environmental signals to modify plant development. Wind-stimulated crops are also known to experience considerable reductions in growth and subsequent yield. There is at present no experimental data to suggest how wind signals are perceived and transduced by plant cells. We have genetically transformed Nicotiana plumbaginifolia to express aequorin and thus produced luminous plants that directly report cytosolic calcium by emitting blue light. With these plants we have found wind stimulation to cause immediate increases in cytosolic calcium and our evidence, based on the use of specific inhibitors, suggests that this calcium is mobilized from organelle sources. Our data further suggest that wind-induced movement of tissues, by mechanically stimulating and stressing constituent plant cells, is responsible for the immediate elevation of cytosolic calcium; increases occur only when the plant tissue is actually in motion. Repeated wind stimulation renders the cells refractory to further calcium signaling but responsiveness is rapidly recovered when stimulation is subsequently diminished. Our data suggest that mechanoperception in plant cells may possibly be transduced through intracellular calcium. Since mechanoperception and transduction are considered crucial to plant morphogenesis, our observations suggest that calcium could be central in the control and generation of plant form.

Lucigenin chemiluminescence as a probe for measuring reactive oxygen species production in Escherichia coli

Addition of oxygen to whole cells of Escherichia coli suspended in the presence of the chemiluminescent probe bis-N-methylacridinium nitrate (lucigenin) resulted in a light emission increase of 200% of control. Addition of air to cells showed a chemiluminescent response far less than the response to oxygen. The redox cycling agents paraquat and menadione, which are known to increase intracellular production of O2- and H2O2, were also found to cause a measurable increase in lucigenin chemiluminescence in E. coli cells when added at concentrations of 1 and 0.1 mM, respectively. The oxygen-induced chemiluminescent response was not suppressed by extracellularly added superoxide dismutase or catalase. Further, the lucigenin-dependent chemiluminescent response of aerobically grown E. coli to oxygen was significantly greater than that of cells grown anaerobically. Heat-killed cells showed no increase in chemiluminescence on the addition of either oxygen, paraquat, or menadione. These results show that lucigenin may be used as a chemiluminescent probe to demonstrate continuous intracellular production of reactive oxygen metabolites in E. coli.

Expression and secretion of aequorin as a chimeric antibody by means of a mammalian expression vector

A fusion protein has been expressed from the relevant genes in mammalian cells consisting of the photoprotein aequorin and an anti-4-hydroxy-3-nitrophenacetyl antibody gene. This chimeric antibody has allowed the development of a sensitive luminescent immunoassay. Initially the cDNA of the photoprotein aequorin from Aequorea victoria was cloned and expressed in Escherichia coli. The gene was expressed as apoaequorin and, by using luciferin isolated from Renilla reniformis, its activity was found essentially identical to native aequorin. The aequorin gene was subcloned into a mammalian expression vector to produce a fusion protein directing secretion of apoaequorin; the aequorin gene was fused to the 3' terminus of an immunoglobulin heavy-chain gene that directed expression of an anti-4-hydroxy-3-nitrophenacetyl antibody. The gene fusion contained the variable region, the constant region domain 1, and part of domain 2 for the IgG2b mouse immunoglobulin, followed by the aequorin gene. Transfection of the chimeric gene into a cell line expressing the complementary lambda 1 light chain, J558L, allowed recovery of a chimeric antibody with binding specificity for the 4-hydroxy-3-nitrophenacetyl group and the related 4-hydroxy-3-iodo-5-nitrophenacetyl hapten. The Ca2(+)-dependent bioluminescent activity of aequorin was also recovered.

Interactions between paraquat and ferric complexes in the microsomal generation of oxygen radicals

Transition metals may play a central role in the toxicity associated with paraquat. Studies were carried out to evaluate the interaction of paraquat with several ferric complexes in the promotion of oxygen radical generation by rat liver microsomes. In the absence of added iron, paraquat produced some increase in low level chemiluminescence by microsomes; there was a synergistic increase in light emission in the presence of paraquat plus ferric-ATP or ferric-citrate, but not paraquat plus either ferric-EDTA or ferric-diethylenetriamine pentaacetic acid (ferric-DETAPAC). Synergistic interactions could be observed at a paraquat concentration of 100 microM and a ferric-ATP concentration of 3 microM. In the absence or presence of paraquat, microsomal light emission was not affected by catalase or dimethyl sulfoxide (DMSO), indicating no significant role for hydroxyl radicals. Superoxide dismutase (SOD) did not affect chemiluminescence in the absence of paraquat but produced some inhibition in the presence of paraquat; this inhibition by SOD was most prominent in the absence of added iron and less pronounced in the presence of ferric-ATP or ferric-citrate. Although microsomal chemiluminescence is closely associated with lipid peroxidation, paraquat did not increase malondialdehyde production as reflected by production of thiobarbituric acid-reactive components. However, lipid peroxidation was sensitive to inhibition by SOD in the presence, but not in the absence, of paraquat, analogous to results with chemiluminescence. Paraquat synergistically increased microsomal hydroxyl radical production as measured by the production of ethylene from 2-keto-4-thiomethylbutyrate in the presence of ferric-EDTA or ferric-citrate. The interaction of paraquat with microsomes and ferric complexes resulted in an increase in oxygen radical generation. Various ferric complexes can increase the catalytic effectiveness of paraquat in promoting microsomal generation of oxygen radicals, although, depending on the reaction being investigated, the nature of the ferric complex is important.

Control of exogenous proteinases and their inhibitors at the macrophage cell surface

The actions and availability of human neutrophil elastase and its protein inhibitor, Eglin, when co-incubated with macrophages were investigated. Eglin did not induce radical production by mouse peritoneal macrophages; nor were specific binding sites for Eglin detected on these cells. Mouse peritoneal macrophages could inactivate both elastase and Eglin extensively, when these targets were used at concentrations appropriate to the extravascular fluids. Two methods were used for assessing such inactivation: one, as in previous literature, only took account of molecules remaining in the supernatant after interaction with the cells; the other (lacking from most previous studies) took into account all target molecules, including those associated with the cells. From an analysis of both types of experiment, it was shown that the cell-derived inactivators were stable products, whose quantity was not significantly influenced by the induction of a macrophage oxidative burst and its associated free radicals. They were probably mainly proteinases and proteinase inhibitors. Thus, mouse peritoneal macrophages restrict the activity of proteinases and inhibitors by means of stable molecules, such as proteins. Other mononuclear phagocytes may use free radicals and oxidants more extensively in this respect.

Alzheimer's disease: a pathogenic role for aluminosilicate-induced phagocytic free radicals

The occurrence of aluminosilicate deposits within the cerebral plaques in Alzheimer's senile dementia sufferers has prompted further consideration of the possible role of such materials in the aetiology and pathogenesis of the disease. We have monitored the ability of various natural and synthetic model aluminosilicate particulates of differing morphological and chemical composition to stimulate the generation of phagocyte-derived free radical reactive oxygen metabolites (ROM) using an in vitro chemiluminescent technique on purified human blood-derived polymorphonuclear leukocytes (PMN). The results indicate that an enhanced chemiluminescent response is produced by calcium-bearing fibriform particulates. It is proposed that an analogous in vivo particle-induced and phagocyte-mediated oxidative stress could provide a potential pathogenic mechanism in the development of Alzheimer's disease.

The reaction of 5-amino-salicylic acid with hypochlorite. Implications for its mode of action in inflammatory bowel disease

Although 5-amino-salicylic acid (5-ASA) provides effective treatment for inflammatory bowel disease, its mode of action is unestablished. 5-ASA inhibits luminol-dependent chemiluminescence triggered by activated neutrophils, hydrogen peroxide plus peroxidase or sodium hypochlorite. The concentrations required for 50% inhibition of the cells was approximately 3.6 microM. In the non-cellular system, the concentration of 5-ASA required for total inhibition being approximately equivalent to concentration of sodium hypochlorite. The reaction of 5-ASA with hypochlorite or activated neutrophils resulted in the production of a non-fluorescent product of 5-ASA. The production of this metabolite by cells was dependent upon the activity of the peroxidase and occurred with a time course which was coincident with oxygen consumption. It was concluded that by reacting with hypochlorite, 5-ASA would provide protection against the potentially damaging effects of activated neutrophils in the inflamed bowel.

Increased NADPH-dependent chemiluminescence by microsomes after chronic ethanol consumption

The generation of reactive oxygen intermediates by microsomes from ethanol-fed rats and pair-fed controls was determined by assaying for NADPH-dependent chemiluminescence. In the absence or presence of added ferric complexes, microsomal light emission was elevated several-fold after chronic ethanol consumption. Iron complexes such as ferric-citrate or ferric-ATP stimulated, while ferric-EDTA, inhibited microsomal chemiluminescence. Freeze-thawing the microsomes to elevate their content of lipid hydroperoxides resulted in large increases in chemiluminescence; under all conditions, the light emission remained several-fold higher with microsomes from the ethanol-fed rats. Chemiluminescence was not sensitive to superoxide dismutase, catalase, or the hydroxyl radical scavenging agent, dimethyl sulfoxide, but was inhibited by antioxidants and by glutathione. Replacing air with a mixture of 50% nitrogen-50% air or 50% carbon monoxide-50% air had no effect on chemiluminescence by microsomes from the pair-fed controls. However, the chemiluminescent response by microsomes from the ethanol-fed rats was inhibited about 50% by the nitrogen mixture, and was further inhibited (about 75% of values found with 100% air, and 50% of values found with 50% nitrogen-50% air) with the carbon monoxide mixture. The sensitivity to carbon monoxide suggests the possibility that the alcohol-inducible cytochrome P-450 isozyme may contribute, in part, to the elevated light emission produced by microsomes from the ethanol-fed rats. The increase in chemiluminescence by microsomes after chronic ethanol consumption appears to reflect an elevated level of lipid hydroperoxides as well as an increased rate of generation of reactive oxygen species.

Free-radical generation by copper ions and hydrogen peroxide. Stimulation by Hepes buffer

Hydroxyl radicals (OH.), generated by a phosphate-buffered Cu2+/H2O2 system, were detected by lucigenin-amplified chemiluminescence, deoxyribose degradation and benzoate hydroxylation. In each system the buffer, Hepes, was found to stimulate radical generation significantly. There are two main reasons for this effect: Hepes increases Cu2+ solubility in phosphate-buffered systems, and forms a complex with Cu2+ that is effective in generating OH. from H2O2. Pipes, a structurally similar buffer, and histidine, a known Cu2+ chelator, were found to have a similar effect. These data suggest that the crucial factor in such free-radical-generating systems is the availability of Cu2+, and that these actions of Hepes should be considered in the design of studies utilizing such systems.

Luminol-enhanced chemiluminescence of peripheral blood leukocytes as an early indicator of graft take after allogeneic bone marrow transplantation in patients with acute myelogenous leukaemia

The luminol-enhanced chemiluminescence (CL) of peripheral blood leukocytes was studied daily in five patients with acute myelogenous leukaemia (AML) in first remission, who were undergoing allogeneic bone marrow transplantation (BMT). The CL was measured after stimulation of leukocytes with opsonized zymosan in highly diluted whole blood. All patients had an undetectable CL level on day +7, post BMT, simultaneously with severe pancytopenia caused by the pre-conditioning for BMT. Subsequently, CL started to rise, reaching the maximum level, twice that of healthy controls, on day +11. This preceded the rise of blood leukocytes above 1.0 x 10(9) l.-1 and that of neutrophils above 0.5 x 10(9) l.-1 by 3-14 days, but coincided with the appearance of large unstained cells (LUC; a parameter given by a Technicon H 6000 blood analyzer). One of the patients later had a transient decline of CL. This preceded the fall in white blood count and platelets by 7 days, suggesting marrow suppression. We conclude that in AML the measurement of leukocyte CL is a more sensitive test for prediction of graft take than the conventional blood counts.

Formation of the Ca2+-activated photoprotein obelin from apo-obelin and mRNA inside human neutrophils

1. A method has been developed to incorporate the apoprotein of the Ca2+-activated photoprotein obelin, and mRNA purified from the hydroid Obelia, into the cytoplasm of intact human neutrophils. This was based on internal release from pH-sensitive immunoliposomes taken up initially by phagocytosis. 2. Addition of the prosthetic group of obelin, coelenterazine, to these cells containing apo-obelin or Obelia mRNA resulted in formation of active Ca2+-activated obelin. 3. The obelin formed within the neutrophils responded to the chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (1 microM) and to the membrane attack complex of complement (C5B6789n). 4. The formation of the apo-obelin from mRNA within neutrophils was inhibited by over 80% in the absence of added amino acids, and by over 90% by the protein-synthesis inhibitor puromycin (100 micrograms/ml). 5. The translation of Obelia mRNA inside cells provides a method for circumventing consumption of Ca2+-activated photoproteins during cell activation or injury, and for monitoring protein synthesis in living cells.

Hydroperoxide-mediated fragmentation of proteins

1. Chemiluminescence and benzoic acid hydroxylation were used to detect oxygen-centred free-radical production by 2.5 mM-H2O2 and 100 microM-Cu2+. Free radicals could not be detected by these methods when H2O2 was replaced with 10 mM-t-butyl hydroperoxide (TBH) or 10 mM-cumene hydroperoxide (CH). The inclusion of the thiol compound dithioerythritol (DTET; 100 microM) increased radical production by H2O2 and Cu2+ as judged by both assays. Mannitol scavenged radicals in the chemiluminescence system in a dose-dependent manner. 2. H2O2, TBH and CH, each with Cu2+, gave rise to substantial fragmentation of the protein bovine serum albumin (BSA). This fragmentation could be increased by the inclusion of DTET. Omission of Cu2+ or the addition of the chelator DETAPAC (diethylenetriaminepenta-acetic acid; 1 mM) lead to virtual abolition of fragmentation. Autoxidized lipid in the presence of Cu2+ caused protein fragmentation by reactions of lipid hydroperoxides. 3. Polyacrylamide-gel electrophoresis in the presence of SDS confirmed that production of fragments had occurred. 4. Susceptibility of BSA to enzymic hydrolysis by two different proteinases acting at pH 5 and pH 7.2 was increased after a limited exposure to hydroperoxides in the presence of Cu2+. 5. These results may have biological significance, particularly for proteins in lipid environments (e.g. membrane proteins and lipoproteins).

Threshold responses in production of reactive oxygen metabolites in individual neutrophils detected by flow cytometry and microfluorimetry

1. The fluorescent compound 2',7'-dichlorofluorescein was used as an indicator of intracellular H2O2 production by neutrophils in order to compare the response of the cell population with that observed with individual cells determined by flow cytometry and quantitative fluorescence microscopy. 2. 2',7'-Dichlorofluorescein diacetate was deacetylated by intracellular esterases to form reduced 2',7'-dichlorofluorescein. The polar non-fluorescent intermediate remained trapped within both intracellular granules and the cytoplasm. Reduced dichlorofluorescein was oxidized by H2O2, a product of the oxidative burst, to yield the highly fluorescent product dichlorofluorescein. 3. A population of neutrophils stimulated by suboptimal concentrations of fMet-Leu-Phe (N-formylmethionyl-leucyl-phenylalanine) or phorbol ester (phorbol 12-myristate 13-acetate) resulted in an oxidation of 45-50% of the cellular dichlorofluorescein (non-fluorescent) to oxidized dichlorofluorescein within 30 min. Subcellular fractionation showed that, although dichlorofluorescein (non-fluorescent) occurred both in the cytoplasm and the granules, oxidation of dichlorofluorescein (non-fluorescent) occurred predominantly in the granules of stimulated neutrophils. 4. Flow cytometry showed that unstimulated cells consisted of a single population of cells with low cellular fluorescence. Activation of neutrophils (to produce reactive oxygen metabolites) resulted in the appearance of a second population of cells, with high fluorescence. The number of cells in this new population increased with time. fMet-Leu-Phe (0.1 microM) or phorbol ester (1 ng/ml) activated 45% of the cells within 8 min and 42% within 30 min respectively. 5. Analysis of individual cells by quantitative fluorescence microscopy demonstrated that, in the presence of a suboptimal concentration of stimulus, cells either failed to respond or were activated after different time delays, 4-120 s (39 +/- 18.4 s) by fMet-Leu-Phe or 12-200 s (59 +/- 17.4 s) by phorbol ester. Furthermore the oxidative bursts were of different magnitudes. 6. It is concluded that, in order for an individual cell to cross the activation threshold for the 'end response', a critical concentration of stimulus together with the necessary changes in intracellular signals are required.

Chemiluminescence studies on the generation of oxygen radicals from the interaction of NADPH-cytochrome P-450 reductase with iron

The ability of NADPH-cytochrome P-450 reductase to interact with iron and generate oxygen radicals was evaluated by assaying for low level chemiluminescence. The basic reaction system which contained the reductase, an NADPH-generating system, ferric-EDTA as an electron acceptor, and t-butyl hydroperoxide as the oxidant acceptor, resulted in the production of chemiluminescence. Omission of any of these components resulted in a complete loss of chemiluminescence. The light emission was completely sensitive to inhibition by glutathione and butylated hydroxytoluene, partially sensitive (about 60% decrease) to catalase and hydroxyl radical scavengers, and relatively insensitive (about 20% decrease) to superoxide dismutase. The ability of other ferric chelates to replace ferric-EDTA in catalyzing the reductase-dependent chemiluminescence was evaluated. Ferric-citrate, -ADP, -ATP, and ferric-ammonium sulfate were ineffective in promoting chemiluminescence, whereas ferric-diethylenetriaminepentaacetic acid was even more effective than ferric-EDTA. Thus, the ferric chelates, which catalyze reductase-dependent chemiluminescence, are those which are efficient electron acceptors from the reductase and were previously shown to be those capable of catalyzing hydroxyl radical production by microsomes and the reductase. It is suggested that chemiluminescence results from (a) the direct interaction of the reduced iron chelate with the hydroperoxide (Fenton-type of reaction) to generate alkoxyl and peroxyl radicals, and (b) the generation of hydroxyl radicals, which subsequently react with the hydroperoxide to generate secondary radicals. The latter, but not the former, would be sensitive to inhibition by catalase and competitive hydroxyl radical scavengers, whereas both would be sensitive to antioxidants such as butylated hydroxytoluene. Chemiluminescence appears to be a versatile tool for studying the reductase-dependent generation of oxygen radicals and for the interaction of reductase with iron.

Diacylglycerol kinase inhibitor, R59022, potentiates neutrophil oxidase activation by Ca2+-dependent stimuli. Evidence for two separate but convergent pathways

An inhibitor of diacylglycerol kinase, R59022, enhanced activation of the neutrophil oxidase stimulated by the Ca2+-ionophore, A23187 (1 microM), and by N-formyl-methionyl leucyl-phenylalanine (1 microM). The enhancement was reversed by two inhibitors of c-kinase, retinal (10 microM), and gossypol (20 microM). Activation by phorbol-myristyl-acetate and unopsonised latex beads were not enhanced. It was concluded that the chemotactic peptide generated diacylglycerol, but that maximum activation of c-kinase by this route was not achievable. The role of diacylglycerol in activation by beads remained unclear.

Pholasin--a bioluminescent indicator for detecting activation of single neutrophils

Pholasin is the protein-bound luciferin from the bivalve mollusc Pholas dactylus which reacts with its luciferase and molecular oxygen to produce light. Pholasin was purified 226-fold with a yield of 58% from P. dactylus to give a preparation free from luciferase contamination. The ratio (k) of endogenous pholasin chemiluminescence to that when maximally stimulated by luciferase was 8.12 X 10(-6) +/- 0.87 X 10(-6) (mean +/- SD, n = 6), equivalent to a t 1/2 of 23.7 h at pH 9. Pholasin could detect reactive oxygen metabolite production from neutrophils stimulated by the chemotactic peptide N-formyl-Met-Leu-Phe, in the presence and absence of 2-chloroadenosine or cytochalasin B, and by latex beads in the presence and absence of cytochalasin B. Pholasin was also able to detect a longer-lived oxidative activity distinct from myeloperoxidase, and released from neutrophils activated by latex beads or chemotactic peptide; luminol could not. Under optimal conditions pholasin produced a signal some 50-100 times that of luminol in the presence of activated neutrophils. This enabled activation of a single neutrophil by chemotactic peptide (1 microM) to be detected, giving a signal of 194 +/- 21 chemiluminescent counts per second, some six times that of the background signal (mean +/- SD, n = 2). Pholasin thus provides an indicator sufficiently sensitive to establish whether neutrophil activation occurs through thresholds in individual cells.

A homogeneous assay for biotin based on chemiluminescence energy transfer

Chemiluminescence energy transfer between aminobutylethylisoluminol (ABEI)-biotin and fluorescein-avidin was investigated in order to establish a homogeneous assay for serum biotin in the physiological range. ABEI chemiluminescence was measured at pH 7.4 using microperoxidase-hydrogen peroxide and the chemiluminescence at two wavelengths (460 and 525 nm) measured simultaneously to quantify chemiluminescence energy transfer. ABEI-biotin was synthesized by a mixed anhydride reaction and purified by TLC and HPLC. Binding of ABEI-biotin to fluorescein-avidin resulted in a quenching of the chemiluminescence. Chemiluminescence energy transfer was demonstrated by a 2.5-fold decrease in the ratio of blue (460 nm) to green (525 nm) light emission compared with unbound ABEI-biotin. This energy transfer was used to establish an assay for biotin in the range 1 to 10 nM by relating the concentration of biotin to the ratio of chemiluminescence monitored at 460 and 525 nm simultaneously. The assay was capable of detecting biotin in reference sera and in patients with malabsorption syndromes and chronic alcoholism. The reference range in normal subjects was 1.2 to 4.3 nmol/liter mean +/- SD = 2.41 +/- 0.91 nmol/liter (n = 20). The quenching of the chemiluminescence of ABEI-biotin when bound to fluorescein-avidin appeared to be the result of a direct interaction between the excited state product of ABEI and fluorescein.

The recovery of human polymorphonuclear leucocytes from sublytic complement attack is mediated by changes in intracellular free calcium

Using polymorphonuclear leucocyte-erythrocyte ghost hybrids entrapping the calcium-activated photoprotein obelin, we have demonstrated that sublytic amounts of the complement membrane attack complex induce a rapid but transient increase in intracellular free calcium ion concentration ([Ca2+]i). This increase in [Ca2+]i occurs prior to, and is required for, rapid removal of membrane attack complexes from the cell surface. The increase in [Ca2+]i is not only due to increased influx from outside the cell, but also results from mobilization of intracellular stores. The possible mechanism of mobilization of calcium, and the importance of an increase in [Ca2+]i as a mediator of recovery processes in nucleated cells, are discussed.

Inhibition by adenosine of reactive oxygen metabolite production by human polymorphonuclear leucocytes

The stimulation of reactive oxygen metabolite production from human polymorphonuclear leucocytes by chemotactic peptide (fMet-Leu-Phe) was inhibited by adenosine with a K0.5 of 0.6 microM. Dipyridamole (0.1 microM), an inhibitor of adenosine uptake, did not prevent the effect of adenosine. Non-metabolizable analogues could substitute for adenosine in the potency order N-ethoxycarboxamideadenosine greater than 2-chloroadenosine greater than adenosine greater than L-N6-(phenylisopropyl)adenosine = D-N6-(phenylisopropyl)adenosine, which is characteristic of an A2 adenosine receptor. The effects of adenosine, 2-chloroadenosine and N-ethoxycarboxamideadenosine were reversed by 8-phenyltheophylline. When endocytosis was inhibited with cytochalasin B, cells were still susceptible to adenosine receptor agonists. 2-Chloroadenosine (10 microM) reduced the activation of respiration in response to chemotactic peptide from 3.3-fold to 1.4-fold. Activation of reactive oxygen metabolite production in response to latex beads was not reversed by adenosine or its analogues. It was concluded that adenosine acts at an A2 adenosine receptor to antagonize the activation of polymorphonuclear leucocytes by those stimuli, such as chemotactic peptide, which cause an increase in the intracellular free Ca2+ concentration.