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PubMed1995

Phorbol ester-induced priming of superoxide generation by phosphatidic acid-stimulated neutrophils and granule-free neutrophil cytoplasts.

This study was undertaken to examine the mechanisms involved in polymorphonuclear leukocyte superoxide release stimulated by exogenous phosphatidic acid (PA). Unlike the immediate burst of superoxide release affected by membrane-permeable dioctanoylglycerol (DiC8-DAG), dioctanoyl phosphatidic acid (DiC8-PA) induced superoxide release after a lag period of 5-20 min. This period was considerably reduced or eliminated when cells were primed by substimulatory levels of phorbol myristate acetate (PMA). Granule-depleted neutrophil cytoplasts also responded to DiC8-PA with a burst of superoxide generation. Activation of the cytoplast superoxide generating system in response to DiC8-PA was also significantly faster after cells had been preexposed to substimulatory levels of PMA, indicating that at least a portion of the priming mechanism was independent of PMA-induced degranulation. To further examine the potential mechanism of PMA priming of responses to PA, we evaluated the activity of neutrophil ecto-phosphatidic acid phosphohydrolase (ecto-PA phosphohydrolase), which generates diacylglycerol from exogenous PA. PMA priming had no discernable effect on the activity of this enzyme. In addition, propranolol, an inhibitor of PA phosphohydrolase, did not selectively inhibit PMA priming of neutrophil responses to DiC8-PA, indicating that priming did not result from acceleration of DiC8-PA hydrolysis. We therefore investigated the possibility that activation of protein kinase C was the basis of the primed response. Several semiselective protein kinase C inhibitors (calphostin C, H-7, and acylmethylglycerol) inhibited DiC8-DAG- and DiC8-PA-induced superoxide release as well as PMA-primed responses to approximately the same extent. These results are consistent with the hypothesis that neutrophil responses to phosphatidate are mediated by diglyceride generated by the action of ecto-PA phosphohydrolase. PMA priming does not result from increased catalytic activity of ecto-PA phosphohydrolase but rather seems to result from potentiation of an intermediate involved in the cells' response to multiple stimuli.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Establishment of radioimmunoassay for human neutrophil peptides and their increases in plasma and neutrophil in infection.

Neutrophil peptide, also called defensin, is an antimicrobial peptide localized in azurophil granules in neutrophils. Using a synthetic human neutrophil peptide-1 (HNP-1), we prepared an antiserum against the peptide and established a highly sensitive radioimmunoassay (RIA). This RIA equally recognized HNP-1, -2, and -3 on a molar basis. Analyses of leukocyte and blood extracts obtained from normal individuals and patients with bacterial infection by reverse-phase high-performance liquid chromatography coupled with the RIA showed that the antiserum specifically detected HNP molecules. Concentrations of HNP 1-3 in total in normal human blood and plasma are 13.2 +/- 1.4 (mean +/- SEM) ng/mu 1 and 403.8 +/- 38.9 pg/mu 1, respectively. The values increased in infection and returned to within the normal levels after the recovery of the disorder. Granulocyte colony-stimulating factor (G-CSF) increased the plasma and blood concentrations of HNP 1-3. The RIA established here provides a useful tool to elucidate the pathophysiological significance of HNP and to evaluate the neutrophil functions in infection and inflammation.

Acute Disease↗
PubMed1994

Localization of human neutrophil peptide (HNP) and its messenger RNA in neutrophil series.

Human neutrophil peptides (HNPs) 1,2 and 3, also called defensins, have high antimicrobial activity and are cytotoxic to both normal and transformed human cells. The localization of HNPs 1-3 and their mRNAs in cells of normal human bone marrow and peripheral blood was investigated. Immunoreactivity for HNPs 1-3 appeared in the promyelocyte stage and increased with the maturation of the neutrophil series. HNPs 1-3 were absent from such mononuclear phagocyte systems as peripheral monocytes, alveolar macrophages, and Kupffer cells in the liver. HNP 1-3 mRNAs were detected in bone marrow cells by Northern blot analysis and in peripheral leukocytes by the reverse transcription-polymerase chain reaction (RT-PCR). HNPs 1-3 are restricted to cells of neutrophil lineage and seem to function as microbicidal agents in the neutrophil-mediated defense system.

Adolescent↗
PubMed2001

Contribution of cytokine-induced neutrophil chemoattractant CINC-2 and CINC-3 to neutrophil recruitment in lipopolysaccharide-induced inflammation in rats.

OBJECTIVE: We have estimated the contribution of three types of cytokine-induced neutrophil chemoattractants (CINC-1, -2 and -3) and rat macrophage inflammatory protein (MIP)-1alpha to neutrophil recruitment in the air pouch/ lipopolysaccharide (LPS)-induced inflammation in rats. MATERIALS AND METHODS: Excess amounts of anti-CINC-2, CINC-3 and MIP-1alpha antibodies (Abs), together with LPS (1 microg/ml), were injected into the preformed air pouch of rats. Chemokine levels and chemotactic activity in the pouch fluid were measured using enzyme-linked immunosorbent assay and multiwell-type Boyden chambers in vitro, respectively. RESULTS: Excess amounts of the Abs significantly neutralized CINC-1 and almost completely neutralized CINC-2, CINC-3 and MIP-1 alpha in the pouch fluid, and a significant suppression (about 60% inhibition) of neutrophil infiltration by the Abs was found. In agreement with the in vivo results, in vitro neutralization experiments demonstrated that complete neutralization of CINCs and MIP-1alpha by the Abs resulted in a marked suppression (73% inhibition) of chemotactic potency of 8-h pouch fluid (exudate) from LPS-treated rats. On the other hand, treatment with anti-CINC-2, CINC-3 or MIP-1alpha Ab alone resulted in 48%, 34% or 10% inhibition, respectively, of chemotactic activity of the 8-h exudate. CONCLUSIONS: Our results suggest that CINC-2, a novel rat CXC chemokine and CINC-3 play an important role in neutrophil recruitment in the rat air pouch/LPS-induced inflammation.

Air↗
PubMed1985

Activation of NADPH oxidase in human neutrophils. Synergism between fMLP and the neutrophil products PAF and LTB4.

The induction of the respiratory burst in human neutrophils by combinations of fMLP and either PAF or LTB4 was studied. Pretreatment with PAF (0.0001 to 10 uM), which by itself did not elicit the burst, greatly enhanced the rate and extent of fMLP-induced superoxide production. A synergism of a different kind was observed with the reversed stimulus sequence: Pretreatment with fMLP made the neutrophils capable to respond to PAF with superoxide production. A moderate enhancement of the fMLP response was also obtained following pretreatment with LTB4. The response of the cells to LTB4, however, was not influenced by fMLP, and no synergism was observed between the two neutrophil products PAF and LTB4. The results of this study demonstrate a marked synergism between fMLP and PAF and suggest that PAF may function as an amplifier of the respiratory burst response of stimulated neutrophils.

Drug Synergism↗
PubMed1993

Agonist-stimulated Cl- efflux from human neutrophils. A common phenomenon during neutrophil activation.

When human peripheral blood neutrophils were stimulated with various agonists which activate and/or prime neutrophils, we found that Cl- efflux was enhanced with a dramatic (50%) loss of intracellular Cl-. Interestingly, the Cl- efflux was enhanced by both agonists which induce a rapid transient increase in intracellular Ca2+ concentration ([Ca2+]i) [class I, e.g. N-formyl-methionyl-leucyl-phenylalanine (fMLP), interleukin-8 (IL8), platelet-activating factor, leukotriene B4 and C5a] and those which do not induce such an [Ca2+]i elevation [class II, e.g. tumor necrosis factor alpha (TNF) and granulocyte-macrophage colony-stimulating factor (GM-CSF)]. The time course of agonist-stimulated Cl- efflux differed depending on the agonist. Class I agonists such as IL8 and fMLP exhibited a 1 min lag phase before the onset of Cl- efflux; class II agonists such as GM-CSF and TNF displayed a 2 and 5 min lag phase, respectively. Both IL8 (class I)- and TNF (class II)-stimulated Cl- efflux exhibited similar sensitivity to inhibition by different types of ion transport inhibitors [ethacrynic acid (EA), amiloride, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, anthracene-9-carboxylic acid, and 4-4'-diisothiocyanatostilbene-2,2'-disulfonic acid]. On the other hand, natural Cl- efflux, which is thought to be mainly mediated by Cl-/Cl- self exchange, was not inhibited by EA (0.5 mM) or amiloride (0.3 mM). These results imply that both class I and class II agonist-stimulated Cl- efflux occurs via a common Cl- transporter which is different from that reported previously in resting human neutrophils. Although all agonists which induced a Cl- efflux also induced shape change of neutrophils, there did not appear to be a causal relationship between shape change and agonist-stimulated Cl- efflux. However, a temporal correlation was found to exist between agonist-stimulated Cl- efflux and intracellular alkalinization following agonist stimulation. Agonist-stimulated Cl- efflux therefore seems to be a common phenomenon activated by several agonists which act through different signal transduction pathways.

Biological Transport↗
PubMed1980

Physical and chemical properties of platelet-activating factor obtained from human neutrophils and monocytes and rabbit neutrophils and basophils.

Platelet-activating factor secreted by stimulated human neutrophils and monocytes and rabbit neutrophils and basophils was isolated, purified and chemically and physically characterized. All four preparations had identical thin layer chromatographic behavior in a variety of solvent systems, identical solubility behavior in various organic and aqueous solvents and responded comparably to a variety of chemical and physical agents designed to reveal the presence functional groups. These findings indicate that human neutrophil and monocyte, and rabbit neutrophil and basophil derived platelet-activating factor preparations are indistinguishable, and support the conclusion that platelet-activating factor is a neutral, polar lipid molecule whose functional activity is dependent upon the presence of a carboxylic acid ester.

Animals↗
PubMed2003

The ITIM-bearing CLECSF6 (DCIR) is down-modulated in neutrophils by neutrophil activating agents.

The recently discovered CLECSF6 protein displays the features of a receptor involved in the down-modulation of leukocyte activation. Although CLECSF6 has been the focus of the interest of many researchers lately, a Western blot characterization of the protein is still lacking. This highly reduces our ability to gain full knowledge of the biological relevance of this protein in cell responses. We produced two rabbit polyclonal antisera that detected a glycosylated protein at approximately 35kDa in neutrophils. Four different CLECSF6 mRNA species have been discovered to date. When deglycosylated, the protein displayed the molecular weight expected for the longest CLECSF6 form. Neutrophil membrane fractions were strongly enriched in the protein. We showed a down-modulation of the expression of this protein in neutrophils treated with granulocyte-macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor (TNF-alpha), lipopolysaccharide (LPS), and interleukin (IL)-4. This work supports the hypothesis that CLECSF6 is involved in the control of inflammation in neutrophils.

Animals↗
PubMed2005

Effect of indole acetic acid administration on the neutrophil functions and oxidative stress from neutrophil, mesenteric lymph node and liver.

This study was done to investigate the effect of the in vivo administration of indole acetic acid (IAA) on the neutrophil function, the activities of antioxidants enzymes in neutrophils, the mesenteric lymph node and on the oxidative stress in liver and plasma. The animals received subcutaneous administration of IAA in a phosphate-buffered saline (the control group received only the phosphate-buffered saline). The other groups received IAA at concentrations of 1 mg (T1), 2 mg (T2) and 18 mg (T3) per kg of body mass per day. Administration of IAA in both treatments T2 and T3 promoted a significant rise in the phagocytic capacity of neutrophils (by 51%), in comparison with the control. Another alteration was observed in antioxidant enzyme activities of the neutrophil and lymph node. But in the liver, the treatments imposed a significant decrease in the activity of catalase of 19% and 30% for T2 and T3, respectively, in comparison with the control. A similar effect was observed in the activity of hepatic glutathione peroxidase for T3 where a significant decrease of 31%, compared with the control, was obtained. The IAA did not show another significant alteration of the activities of superoxide dismutase and glutathione reductase activities in liver. The hepatic lipid peroxidation level, available by reactive products with thiobarbituric acid, has shown a significant decrease of 27% and 29% with T1 and T3 respectively, in comparison with the control. IAA treatment did not show a significant alteration in reduced glutathione contents in comparison with the liver and plasma controls. In conclusion, the IAA administration has a good potential animal utilization for increasing the phagocytic capacity with no prooxidant effect.

Animals↗
PubMed1998

Erythrocyte membrane band 3 profile imposed by cellular aging, by activated neutrophils and by neutrophilic elastase.

The aim of this study was to evaluate in vitro the modifications in the profile of erythrocyte membrane protein band 3 (monomer, aggregates and fragments) imposed by cellular aging, by activated neutrophils (AN) and by neutrophilic elastase. The modifications imposed by cellular aging were evaluated in fractions of less dense and dense red blood cells (RBCs). To evaluate the changes imposed by AN, suspensions of RBCs and AN were used, in a ratio similar to or higher than that described elsewhere for individuals post-myocardial infarction (Santos-Silva A et al. Atherosclerosis 1995; 116:199-209). Neutrophilic elastase was used at increased concentrations. We found that the modifications imposed upon band 3 profile by AN and neutrophilic elastase were significantly correlated with AN and elastase concentration, and were similar to those presented by cellular aging. We propose band 3 profile as a useful cumulative marker of oxidative and/or proteolytic stress conditions, namely those arising from normal RBC aging or from an accelerated aging process imposed by stressful situations, such as inflammatory diseases.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1979

Abnormal neutrophil maturation in a neutrophil defect with morphologic abnormality and impaired function.

Neutrophils from a patient with recurrent pyogenic infections since infancy were found to have morphologic abnormalities and impaired functions. The neutrophils had an abnormal nuclear shape, no or few secondary granules, and no alkaline phosphatase activity. Primary granules were normal in number and structure, and were positive for peroxidase. Immature granulocytes were structurally normal. The neutrophils were impaired in chemotaxis and bactericidal capacity. The patient's marrow cells formed increased numbers of granulocytic colonies of small size in culture. Her peripheral leukocytes produced elevated levels of CSA and adherent marrow cells did not inhibit colony formation. These data indicate an intrinsic neutrophil defect which allows normal proliferation of precursor cells, but results in abnormal morphogenesis and impaired function as the cells mature.

Bone Marrow↗
PubMed1999

Glycosylation of natural human neutrophil gelatinase B and neutrophil gelatinase B-associated lipocalin.

Gelatinase B is a matrix metalloproteinase (MMP-9) involved in tissue remodeling, development, cancer, and inflammation. Neutrophils produce three major forms of (pro)gelatinase B: 92 kDa monomers, homodimers, and complexes of gelatinase B covalently bound to neutrophil gelatinase B-associated lipocalin (NGAL). In contrast to the case for other proteinases, little information about the glycosylation of any natural human MMP is available. Here, both gelatinase B and NGAL were purified from human peripheral blood neutrophils, and the entire contents of the released N- and O-glycan pools were analyzed simultaneously using recently developed high-performance liquid chromatography-based technology. The results are discussed within the context of the domain structure of gelatinase B and a molecular model of NGAL based on data from this study and the three-dimensional nuclear magnetic resonance (NMR) structure of the protein. More than 95% of the N-linked glycans attached to both gelatinase B and NGAL were partially sialylated, core-fucosylated biantennary structures with and without outer arm fucose. The O-linked glycans, which were estimated to comprise approximately 85% of the total sugars on gelatinase B, mainly consisted of type 2 cores with Galbeta1,4GlcNAc (lactosamine) extensions, with or without sialic acid or outer arm fucose. This paper also contains the first report of O-linked glycans attached to NGAL. Although both proteins were isolated from neutrophils and contained O-linked glycans mainly with type 2 cores, the glycans attached to individual serine/threonine residue(s) in NGAL were significantly smaller than those on gelatinase B. In contrast to NGAL, gelatinase B contains a region rich in Ser, Thr, and Pro typical of O-glycosylated mucin-like domains.

Acute-Phase Proteins↗
PubMed2000

Role of neutrophils in induction of acute inflammation in T-cell-mediated immune dermatosis, psoriasis: a neutrophil-associated inflammation-boosting loop.

A growing body of evidence has indicated that T-cell-mediated immunity plays an important role in triggering and maintenance of psoriatic lesions. In this review we present our own experimental results as well as those from the literature related to the pathomechanism of the development of inflammatory changes in psoriatic lesions. First of all it is important to acknowledge the fact that psoriatic lesions are not uniform as assumed by many authors but that they are actually rather heterogeneous both clinically and histologically even within the same plaques. Lymphokines produced by activated T cells in psoriatic lesions have a strong influence on the proliferation of the epidermis, whose stimulated kertinocytes released several cytokines, which in turn enhance the activation state of T cells. Thus, they form a vicious cycle, a T-cell-mediated inflammation-sustaining loop. Although the interaction between T-cell-mediated immunity and epidermal keratinocytes may well explain the maintenance of background "chronic" inflammatory changes diffusely observed throughout psoriatic lesions, it is not enough to explain the island-like, "acute" inflammatory changes observed within and at the border of the plaque lesions. Characteristic neutrophil accumulation under the stratum corneum can be observed in the highly inflamed and therapeutically recalcitrant areas of psoriatic lesions. They are chemotactically attracted and activated there by synergistic action of chemokines, IL-8 and Gro-a released by the stimulated keratinocytes, and particularly C5a/C5a des arg produced via the alternative complement pathway activation possibly on the surface of corneocytes. In this review, we emphasize that the accumulation of neurophils is not simply a passive event. We think that those stimulated neutrophils are able to influence not only the growth and differentiation of epidermal keratinocytes but also the activation-state of T cells by aberrant expression of HLA-DR on their surfaces as well as by their effects. These T cells in turn influence the transepidermal neutrophil migration through the effect of their lymphokines on the keratinocyte production of pro-inflammatory mediators including C3. Therefore, we propose a neutrophil-associated inflammation-boosting loop that may well explain the localized "acute" inflammatory changes scattered over the "chronic" psoriatic plaques as well as in the acutely inflamed lesions of pustular psoriasis.

Acute Disease↗
PubMed1999

No association between neutrophil FcgammaRIIa allelic polymorphism and anti-neutrophil cytoplasmic antibody (ANCA)-positive systemic vasculitis.

ANCA, implicated as having a pathogenic role in systemic vasculitis, can activate tumour necrosis factor-alpha (TNF-alpha)-primed neutrophils by cross-linking surface-expressed ANCA antigens with neutrophil FcgammaRIIa receptors to release reactive oxygen species. The FcgammaRIIa receptor exists as polymorphic variants, R131 and H131, which differ in their ability to ligate human IgG2 and IgG3. Neutrophils homozygous for the FcgammaRIIa-H131 allotype bind more efficiently to IgG3 than the FcgammaRIIa-R131 allotype and are the only human FcgammaR which bind IgG2. Our aim was to determine whether the homozygous FcgammaRIIa-H131 individuals are more susceptible to developing ANCA-associated systemic vasculitis and nephritis due to differential IgG binding and activation. FcgammaRIIa allotype was determined by both allele-specific polymerase chain reaction (PCR) and Southern blotting with allele-specific oligonucleotide probes end-labelled with 32P-gammaATP, after PCR amplification of genomic FcgammaRIIa DNA in 107 Caucasian patients with ANCA+ vasculitis (of whom 89 had renal disease) and 100 ethnically matched controls. Phenotyping of neutrophil FcgammaRIIa alleles was confirmed in some patients by quantitative flow cytometry using murine MoAbs 41H16 and IV.3. Of the patients with ANCA+ systemic vasculitis, 75 had ANCA with specificity for proteinase 3 and 32 with specificity for myeloperoxidase. Overall, no skewing in FcgammaRIIa allotypes was seen in patients compared with controls. No significant increase of the FcgammaRIIa-H131 allotype was found amongst patients irrespective of ANCA specificity, and no association between the FcgammaRIIa allotype and nephritis was found. Our data suggest that the FcgammaRIIa receptor allotype is not a major factor predisposing to the development of ANCA+ systemic vasculitis, or to nephritis.

Alleles↗
PubMed2002

Human neutrophil antigen-2a expression on neutrophils from healthy adults in western Japan.

BACKGROUND: Human neutrophil antigen-2a (HNA-2a)-specific MoAb, which is necessary to prepare panel neutrophils and to determine the phenotype of patients' neutrophils, has been produced in many laboratories in Japan. The frequency of the HNA-2a-positive population in western Japan is unknown. STUDY DESIGN AND METHODS: A cell line secreting an HNA-2a-specific MoAb, TAG4, was established. TAG4 was characterized by flow cytometry, and the reactivities of TAG4 and another HNA-2a-specific MoAb, 7D8, were compared in an inhibition assay and two-color flow cytometry. TAG4 was tested against granulocytes from 408 healthy adult volunteers in western Japan. RESULTS: TAG4 reacted with neutrophils, but not with the other blood cells. The reactivity of TAG4 with granulocytes treated with glycosyl-phosphatidylinositol-specific phospholipase C was markedly reduced. The reactivity of TAG4 and 7D8 was similar, but 7D8 did not prevent TAG4 from binding. A total of 406 of 408 donors were TAG4 positive. The mean percentage of HNA-2a expression of females was 70.2 percent, and that of males was 66.8 percent. CONCLUSION: TAG4 and 7D8 seem to bind to different epitopes of HNA-2a. The frequency of the HNA-2a-positive population is 99.5 percent of healthy adults in western Japan. The mean percentage of HNA-2a expression of females was greater than in males.

Adult↗
PubMed2005

Chimerical anti-TNF-alpha, infliximab, inhibits neutrophil chemotaxis and production of reactive oxygen species by blocking the priming effect of mononuclear cells on neutrophils.

Clinical experience with anti-tumor necrosis factor alpha (anti-TNF-alpha) agents implies that these agents can cause a rapid onset amelioration of the symptoms and laboratory parameters in some inflammatory diseases. Precise explanation of this fast antiinflammatory action is not known. The aim of our study is to investigate the direct and indirect effects of anti-TNF agents on the chemotaxis and reactive oxygen species (ROS) production of neutrophils. For this purpose, isolated neutrophil cultures (INCs) and mixed leukocyte cultures were prepared from the venous blood of healthy subjects. Those cultures were separated to different groups according to the presence of anti-TNF or the stimulation of phytohemagglutinin (PHA). In this study, anti-TNF treatment did not change the migration ability of neutrophils in INCs. However, we established that chimerical anti-TNF-alpha, infliximab, inhibits neutrophil chemotaxis and production of ROS by blocking the priming effect of PHA-stimulated circulating mononuclear cells. These results may explain, at least partly, the rapid onset antiinflammatory actions of these agents observed in clinical practice.

Adult↗
PubMed1999

N-formylpeptides induce two distinct concentration optima for mouse neutrophil chemotaxis by differential interaction with two N-formylpeptide receptor (FPR) subtypes. Molecular characterization of FPR2, a second mouse neutrophil FPR.

The N-formylpeptide receptor (FPR) is a G protein-coupled receptor that mediates mammalian phagocyte chemotactic responses to bacterial N-formylpeptides. Here we show that a mouse gene named Fpr-rs2 encodes a second N-formylpeptide receptor subtype selective for neutrophils which we have provisionally named FPR2. The prototype N-formylpeptide fMLF induced calcium flux and chemotaxis in human embryonic kidney (HEK) 293 cells stably transfected with FPR2. The EC(50)s, approximately 5 microM for calcium flux and chemotaxis, were approximately 100-fold greater than the corresponding values for mouse FPR-transfected HEK 293 cells. Consistent with this, fMLF induced two distinct concentration optima for chemotaxis of normal mouse neutrophils, but only the high concentration optimum for chemotaxis of neutrophils from FPR knockout mice. Based on these data, we hypothesize that high- and low-affinity N-formylpeptide receptors, FPR and FPR2, respectively, may function in vivo as a relay mediating neutrophil migration through the high and low concentration portions of N-formylpeptide gradients.

Animals↗
PubMed1997

Mechanisms of nitroso compound-induced inhibition of superoxide generation in neutrophils: fluorescence quenching of perylene by nitroso-compounds in the membrane fractions of neutrophils.

To investigate the mechanism of nitroso compound-induced inhibition of the respiratory burst in neutrophils, we studied fluorescence quenching of perylene by nitroso-compounds in the membrane fractions of neutrophils at 17, 27, and 37 degrees C and the reagent-induced inhibition of superoxide generation at 28 and 37 degrees C. With increasing temperature, the quenching of perylene fluorescence and inhibition of superoxide generation by nitrosobenzene (NB) were both diminished, while those by 2-nitrosotoluene (NT) were both enhanced. The temperature dependence of the inhibition constants and the quenching constants indicates that the binding of NB is exothermic (deltaH= -27 kJ/mol for inhibition and deltaH= -29 kJ/mol for quenching) and essentially enthalpy-driven. On the other hand, that of NT is endothermic (deltaH= +16 kJ/mol for inhibition and quenching) and essentially entropy-driven. Quenching studies of perylene fluorescence in synthetic vesicles made of endogenous polar lipids of neutrophils showed that the enthalpy changes of NB- and NT-binding with perylene in lipids were similar to each other. Moreover, their values were in good agreement with that of NT, but not of NB, in the membrane fractions, an assembly of proteins and lipids, of neutrophils. These results suggest that NB inhibits the activity by binding to proteins in the membrane, whereas inhibition by NT occurs through hydrophobic interaction with lipids and/or proteins.

Animals↗