Human Neutrophil Degranulation Research Articles

Soluble guanylyl cyclase activator YC-1 inhibits human neutrophil functions through a cGMP-independent but cAMP-dependent pathway.

3-(5'-Hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a novel type of soluble guanylyl cyclase (sGC) activator, is useful in investigating the signaling of cGMP and may provide a new approach for treating cardiovascular diseases. Herein, YC-1 was demonstrated to inhibit the generation of superoxide anion (O2-) and the release of beta-glucuronidase release, to diminish the membrane-associated p47phox and to accelerate resequestration of cytosolic calcium in formyl-l-methionyl-l-leucyl-l-phenylalanine-activated human neutrophils. YC-1 not only directly promoted sGC activity and cGMP formation but also dramatically potentiated sodium nitroprusside-induced sGC activity and cGMP formation in human neutrophils. However, the synergistic increase in the amount of cGMP was inconsistent with its cellular response. Moreover, neither an sGC inhibitor nor protein kinase G inhibitors reversed the inhibitory effect of YC-1. Interestingly, YC-1 also increased the cAMP concentration and protein kinase (PK)A activity. The inhibitory effect of YC-1 was significantly enhanced by prostaglandin (PG)E1 and isoproterenol, and almost abolished by PKA inhibitors. These results show that cAMP, but not cGMP, mediates the YC-1-induced inhibition of human neutrophils. YC-1 increased the PGE1- and forskolin-induced but not 3-isobutyl-1-methylxanthine-produced cAMP formation, suggesting inhibition of phosphodiesterase. These findings thus reveal novel mechanism-mediated anti-inflammatory properties of YC-1 in human neutrophils, which can influence the progression of cardiovascular disease. cAMP, but not cGMP, plays an important role in the regulation of respiratory burst and degranulation in human neutrophils.

Ethanol-induced inhibition of cytokine release and protein degranulation in human neutrophils

Ethanol impairs immune responses in humans and animal models, in vivo and in vitro. In particular, ethanol inhibits some key functions of human polymorphonuclear neutrophils (PMN). We investigated the impact of ethanol on cytokine production by highly purified PMN. In a time- and concentration-dependent manner, ethanol inhibited the production of interleukin (IL)-8 protein and mRNA and also hindered tumor necrosis factor alpha (TNF-alpha) release by modulating the expression of the TNF-alpha-converting enzyme involved in TNF-alpha shedding. This disruption of PMN cytokine release by ethanol may contribute to the increased risk of infection in alcoholic patients. Degranulation of hepatocyte growth factor (HGF) was also impaired by a clinically relevant ethanol concentration (0.8%), an action that may delay the repair of alcoholic liver damage. These findings suggest that ethanol may modulate three major cytokines involved in alcoholic liver diseases, IL-8, TNF-alpha, and HGF, via three different mechanisms.

Immunostimulatory DNA induces degranulation and NADPH-oxidase activation in human neutrophils while concomitantly inhibiting chemotaxis and phagocytosis.

We examined the effects of oligodeoxynucleotides (ODN) with different structures and sequences on human neutrophil function. In lymphocytes and monocytes, the CpG-mediated immunostimulation is dependent on motif content, flanking sequences and DNA backbone composition. In neutrophils, however, native phosphodiester ODN were without effect regardless of CpG content, while backbone-substituted phosphorothioate ODN (PS-ODN) modulated neutrophil function in a sequence-independent manner. The neutrophil respiratory burst and degranulation of the specific and gelatinase granules were markedly increased by PS-ODN, as was the shedding of L-selectin. In contrast, neutrophil chemotaxis and phagocytosis were inhibited by PS-ODN. In summary, PS-ODN have both stimulatory and inhibitory effects on neutrophil function. This impact of PS-ODN on neutrophil function is unique and distinct from that exerted on other immune cells, with respect to both the identity of the activating DNA molecules and the regulation of the effector functions. These findings may have implications for the development of DNA-based immunotherapy and vaccination.

Identification of Diacylated Ureas as a Novel Family of Fungus-specific Leukocyte-activating Pathogen-associated Molecules

Polymorphonuclear leukocytes represent primary components of the host's innate immune defenses against fungal infection, suggesting involvement of fungal leukocyte attractants. We have found in various fungi, but not in bacteria or host cells, unstable lipid-like leukocyte chemoattractants, which also induced adherence and degranulation in human neutrophils. Purification from bakers' yeast and structural analyses by electrospray mass spectrometry, (1)H NMR spectroscopy, and chemical synthesis revealed these inflammatory mediators as diacylated ureas, a novel class of unstable lipoids. The N,N'-dipalmitoleyl urea appeared to be the most potent innate immune responses inducing compound eliciting half-maximum neutrophil chemotactic activity at 140 nm. The all-trans isomer, N,N'-dipalmitelaidyl urea, was found to be inactive with respect to stimulation of degranulation in neutrophils, which indicates a Delta(9) cis-double bond to be essential for bioactivity of these diacyl ureas. N,N'-Dipalmitoleyl urea elicited Ca(2+) mobilization in neutrophils, which was found to be pertussis toxin-sensitive and sensitive toward a carboxylmethyltransferase inhibitor, indicating that these diacyl ureas activate leukocytes via a putative Galpha(i)-protein-coupled receptor. Their isolation exclusively from fungi suggests that these lipoids are fungus-specific pathogen-associated molecules that may alert the human innate immunity system to the presence of a fungal infection.

Effect of imidazo[1,2-a]pyrimidine derivatives on leukocyte function.

A series of six imidazo[1,2-a]pyrimidine (IP) derivatives were evaluated for their effects on leukocyte functions in vitro as well as on the inflammatory response induced by zymosan in the mouse air pouch. Human neutrophils and murine peritoneal macrophages were used for in vitro assays. Mouse air pouch was performed in Swiss mice. Test compounds were incubated with either human neutrophils or mouse peritoneal macrophages at concentrations not showing cytotoxic effects. For in vivo experiments, IPs were injected into the air pouch. Elastase and myeloperoxidase release, superoxide generation and LTB4 production were assayed in human neutrophils treated with different stimuli. Mouse peritoneal macrophages were stimulated with lipopolysaccharide (LPS), followed by determination of nitrite and PGE2 levels in supernatants. Zymosan was injected into six days-old mouse air pouches. Dunnett's t-test was employed for statistical analysis. All IPs inhibited human neutrophil degranulation with IC50 values in the microM range. IP-1, IP-2 and IP-5 also decreased superoxide generation. In LPS-stimulated macrophages, IP-4 and IP-6 inhibited nitrite production with a moderate reduction in PGE2 generation. In addition, these two compounds at 100 nmol/pouch inhibited leukocyte migration and LTB4 levels in the exudate of the mouse air pouch. Imidazo[1,2-a]pyrimidines are a class of compounds with antiinflammatory potential.

Medium-chain, triglyceride-containing lipid emulsions increase human neutrophil beta2 integrin expression, adhesion, and degranulation.

To test the hypothesis that lipid emulsions with different triglyceride structures have distinct immunomodulatory properties, we analyzed human neutrophil adhesion and degranulation after lipid incubation. Neutrophils, isolated from the blood of 10 healthy volunteers, were incubated in medium or physiologic (2.5 mmol/L) emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, or structured (SL) triglycerides. Expression of adhesion molecules and degranulation markers was evaluated by flow cytometry. Also, functional adhesion was investigated by means of a flow cytometric assay using fluorescent beads coated with the integrin ligand intercellular adhesion molecule (ICAM)-1. Although LCT and SL had no effect, LCT/MCT significantly increased expression of the beta2 integrins lymphocyte-function-associated antigen 1 (+18%), macrophage antigen 1 (+387%), p150,95 (+82%), and (alphaDbeta2 (+230%). Degranulation marker expression for azurophilic (CD63, +210%) and specific granules (CD66b, +370%) also significantly increased, whereas L-selectin (CD62L, -70%) decreased. The effects of LCT/MCT were mimicked by the MCT emulsion. ICAM-1 adhesion (% beads bound) was increased by LCT/MCT (34% +/- 4%), whereas LCT (19% +/-3%) and SL (20% +/- 2%) had no effect compared with medium (17% +/- 3%). LCT/MCT and MCT, contrary to LCT and SL emulsions, increased neutrophil beta2 integrin expression, adhesion, and degranulation. Apart from other emulsion constituents, triglyceride chain length might therefore be a key feature in the interaction of lipid emulsions and the phagocyte immune system.

Effects of 60 Hz magnetic field exposure on polymorphonuclear leukocyte activation

We have investigated the effects of a sinusoidal 60 Hz magnetic field on free radical (superoxide anion) production, degranulation (β-glucuronidase and lysozyme release) and viability in human neutrophils (PMNs). Experiments were performed blindly in very controlled conditions to examine the effects of a magnetic field in resting PMNs and in PMNs stimulated with a tumor promoter: phorbol 12-myristate 13-acetate (PMA). Exposure of unstimulated human PMNs to a 60 Hz magnetic field did not affect the functions examined. In contrast, exposure of PMNs to a 22 milliTesla (mT), 60 Hz magnetic field induced significant increases in superoxide anion (O 2 −) production (26.5%) and in β-glucuronidase release (53%) when the cells were incubated with a suboptimal stimulating dose of PMA. Release of lysozyme and lactate dehydrogenase was unchanged by the magnetic field, whether the cells were stimulated or not. A 60 Hz magnetic field did not have any effect on O 2 − generation by a cell-free system xanthine/xanthine oxidase, suggesting that a magnetic field could upregulate common cellular events (signal transduction) leading to O 2 − generation and β-glucuronidase release. In conclusion, exposure of PMNs to a 22 mT, 60 Hz magnetic field potentiates the effect of PMA on O 2 − generation and β-glucuronidase release. This effect could be the result of an alteration in the intracellular signaling.

LXA4, aspirin-triggered 15-epi-LXA4, and their analogs selectively downregulate PMN azurophilic degranulation.

The eicosanoid lipoxin A4 (LXA4) is biosynthesized in vivo by cells present at inflammatory sites and appears to be an endogenous anti-inflammatory mediator. Further, in the presence of aspirin, the 15-epimer of LXA4 (15-epi-LXA4) is biosynthesized and may mediate some of aspirin's desirable bioactions. LXA4, 15-epi-LXA4, and their stable analogs inhibit inflammation in established animal models, indicating that these compounds may be useful for treating inflammatory disease states. To investigate the cellular mechanisms by which these lipid mediators downregulate inflammation, we investigated whether these eicosanoids could influence receptor-mediated degranulation of human neutrophils, an event thought to play a major causative role in several inflammatory disease states. LXA4, 15-epi-LXA4, and their stable analogs potently (IC50 < 1 nM) and selectively downregulated neutrophil release of azurophilic granule contents but did not affect other neutrophil secretory functions. Thus the cellular basis of action of these natural off-switches to inflammation appears to involve downregulation of neutrophil azurophilic granule release.

The Role of Protein Kinase C and [Ca2+]i in Superoxide Anion Synthesis and Myeloperoxidase Degranulation of Human Neutrophils.

A chemiluminescence procedure has been developed to determine superoxide anion (O2-) generation and myeloperoxidase (MPO) release from human activated neutrophils. By using this procedure, the role of protein kinase C (PKC) and cytosolic calcium ion (Ca2+[i) for O2- generation and MPO release was examined. Activation of Fc gamma R on neutrophils with IgG-coated zymosan (IgGZ) caused a transient rise of Ca2+[i, followed by O2- generation and MPO release. A PKC inhibitor suppressed completely the O2- generation and slightly the MPO release. Direct activation of PKC by a specific PKC activator, phorbol myristate acetate (PMA), induced a remarkable O2- generation and a small MPO release, indicating that PKC may regulate entirely O2- synthesis and partially MPO degranulation. Influx of extracellular Ca2+ induced by the calcium ionophore A23187 provoked MPO release only. Complete inhibition of this MPO release with a Ca2+/calmodulin (CaM)-coupling inhibitor and a CaM inhibitor provides evidence that Ca2+[i may regulate MPO degranulation through direct activation of CaM, but not PKC. The Ca2+/CaM inhibitors significantly prevented IgGZ-induced O2- generation and MPO release, while they did not affect PMA-induced O2- generation and MPO release. These results suggest that in Fc gamma R-stimulated neutrophils, Ca2+[i activates CaM, which in turn mediates not only activation of PKC-induced O2- synthesis and MPO degranulation, but also MPO degranulation without PKC intermediate.

Lipofundin® increases in vitro adhesion molecule expression, degranulation and binding capacity of human neutrophils, contrary to Intralipid® and structured Fat Emulsion 73403®

Lipofundin® increases in vitro adhesion molecule expression, degranulation and binding capacity of human neutrophils, contrary to Intralipid® and structured Fat Emulsion 73403®

Synthesis and anti-inflammatory activity of chalcone derivatives

Chalcones and their derivatives were synthesized and evaluated for their anti-inflammatory activity. In vitro, chalcones 2, 4, 8, 10 and 13 inhibited degranulation and 5-lipoxygenase in human neutrophils, whereas 11 behaved as scavenger of superoxide. Only four compounds (4-7) inhibited cyclo-oxygenase-2 activity. The majority of these samples showed anti-inflammatory effects in the mouse air pouch model.

Intracellular Pool of Vascular Endothelial Growth Factor in Human Neutrophils

AbstractVascular endothelial growth factor (VEGF ), an endothelial cell mitogen, is a potent angiogenic factor produced by several cell types. Whether human neutrophils are potential producers of VEGF has not yet been described. The present work shows that phorbol-12-myristate 13-acetate (PMA), fMet-Leu-Phe, and tumor necrosis factor-α (TNF-α) triggered a time-dependent secretion of VEGF by human neutrophils. Cells incubated with 50 ng/mL of PMA released significant amounts of VEGF after 15 minutes. Because the extracellular content of VEGF in human neutrophils supernatants remained constant over a period of 2 to 24 hours and because PMA is a potent inducer of human neutrophil degranulation, the PMA-induced secretion of VEGF may be due to a pre-existing intracellular pool of this molecule. This hypothesis was reinforced by the absence of cycloheximide effect on the PMA-induced secretion of VEGF. The existence of an intracellular pool of VEGF was confirmed by measuring the intracellular content of VEGF in resting neutrophils. A dosedependent inhibition of PMA-induced VEGF secretion was observed when the cells were incubated in the presence of pentoxifylline, a methylxanthine known to inhibit neutrophil degranulation. To confirm the implication of neutrophil degranulation in VEGF release, the effects of two inducers of physiologic degranulation, fMet-Leu-Phe and TNF-α, were determined. Both agonists induced a release of VEGF in the absence of cytochalasin B, confirming the involvement of neutrophil degranulation and suggesting the intracellular localization of VEGF in the specific granule fraction. In addition, the kinetics of fMet-Leu-Phe– and TNF-α–induced secretion of lactoferrin were similar to those of VEGF release induced by these two both agonists. The subcellular fractionation of human neutrophils showed a granule-specific distribution of the intracellular pool of VEGF in resting neutrophils. The finding that human neutrophils contain an intracellular pool of VEGF, secreted in the extracellular space under PMA-, fMet-Leu-Phe–, and TNF-α–induced degranulation, suggests a role for human neutrophils as cellular effectors of physiologic as well as pathologic angiogenesis.

3-Morpholino-sydnonimine-induced suppression of human neutrophil degranulation is not mediated by cyclic GMP, nitric oxide or peroxynitrite: inhibition of the increase in intracellular free calcium concentration by N-morpholino-iminoacetonitrile, a metabolite of 3-morpholino-sydnonimine.

This study was designed to clarify the mechanism of the inhibitory action of a nitric oxide (NO) donor 3-morpholino-sydnonimine (SIN-1) on human neutrophil degranulation. SIN-1 (100-1000 microM) inhibited degranulation (beta-glucuronidase release) in a concentration-dependent manner and concomitantly increased the levels of cGMP in human neutrophils in suspension. However, further studies suggested that neither NO nor increase in cGMP levels were mediating the inhibitory effect of SIN-1 on human neutrophil degranulation because 1) red blood cells or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl added as NO scavengers did not inhibit the effect; 2) inhibitors of cGMP synthesis (methylene blue) or phosphodiesterases (3-isobutyl-1-methylxanthine) did not produce changes in cell function correlating with the changes in cGMP. SIN-1 releases both nitric oxide and superoxide, which together form peroxynitrite. Chemically synthesized peroxynitrite (1-100 microM) did not inhibit, but at high concentrations (1000-2350 microM), it potentiated FMLP-induced beta-glucuronidase release from neutrophils. Thus formation of peroxynitrite from SIN-1 does not explain its inhibitory effects on neutrophil degranulation. The NO-deficient metabolite of SIN-1, SIN-1C (330-1000 microM) inhibited human neutrophil degranulation in a concentration-dependent manner similar to that of SIN-1 and reduced the increase in intracellular free calcium induced by N-formyl-L-methionyl-L-leucyl-L-phenylalanine. C88-3934 (330-1000 microM), another NO-deficient sydnonimine metabolite, also inhibited human neutrophil degranulation. In conclusion, the data shows that the NO-donor SIN-1 inhibits human neutrophil degranulation in a cGMP-, NO-, and peroxynitrite-independent manner, probably because of the formation of more stable active metabolites such as SIN-1C. The results demonstrate that studies on the role of NO and/or peroxynitrite carried out with SIN-1 and other NO-donors should be carefully re-evaluated as to whether the effects found are really attributable to NO or peroxynitrite and that in future studies, it will be crucial to carry out control experiments with the NO-deficient metabolites in any studies with sydnonimine NO-donors.

Modulation of degranulation and superoxide generation in human neutrophils by unsaturated fatty acids of odd carbon numbers

Unsaturated fatty acids of odd carbons, 13:1(12), 17:1(10trans), 19:1(7) and 19:1(10) inhibited release of myeloperoxidase (MPO) from fMet-Leu-Phe-cytochalasin B-treated neutrophils. The inhibitory effect was smaller than that of aseanostatins which have been isolated as microbial-derived free fatty acids with a methyl blanch (i-14:0 and ai-15:0) (Journal of Antibiotics (1991) 44, 524–532). These unsaturated fatty acids also inhibited lactoferrin release by the same treatment. On the other hand, 13:1(12), 15;1(10) and 19:1(10) inhibited fMet-Leu-Phe-stimulated superoxide generation of neutrophils, and the fatty acids 15:1(10), 17:(10) and 19:2(10,13) induced superoxide generation in both unstimulated cells and the cell-free system. However, none of unsaturated fatty acids of odd carbons tested inhibited β-glucuronidase release, whereas 15:1(10), 17:1(10), 19:1(7), 19:1(10) and 19:2(10,13) rather enhanced an increase in β-glucuronidase activity liberated from cells at high concentrations over 35 μM, indicating cellular damages by these fatty acids. These observations suggest that unsaturated free fatty acids having odd carbons such as 13, 15, 17 and 19 may act as modulators of neutrophil functions including degranulation and superoxide generation.

PLD AUGMENTS CALCIUM INDUCED DEGRANULATION IN STREPTOLYSIN O PERMEABILIZED NEUTROPHILS. • 901

Neutrophil degranulation is characterized by the fusion of azurophil and specific granules with the plasma membrane. This process is preceded by a complex series of alterations in membrane phospholipid composition mediated, at least in part, by phospholipases C and D. The activation of phospholipase C activation initiates a rise in intracellular Ca2+, while phospholipase D (PLD) hydrolyzes membrane phosphatidylcholine (PC) to phosphatidic acid(PA). (This conversion of PC to PA converts a nonfusogenic phospholipid to a fusogenic one). Using a Streptolysin O permeabilized cell model, we examined the potential role of PLD metabolism on Ca2+-induced degranulation in human neutrophils. Neutrophils permeabilized with streptolysin O can be induced to release their granular contents in response to elevated extracellular [Ca2+]. We found that the addition of exogenous(Streptomyces chromofuscus) PLD caused a dose-dependent augmentation in the Ca2+-induced release of both specific (lactoferrin) as well as azurophil (β-glucuronidase) granular contents (Table 1). Secretion was dependent on both permeabilization as well as the preactivation of PLD with non-stimulatory [Ca2+], indicating that actual metabolism by PLD was important and that it was targeting an intracellular membrane. This work was funded by NICHD and NIAID grants HD28820 and AI20065

Effects of topical nasal steroids on human respiratory mucosa and human granulocytes in vitro.

Human respiratory mucosa and human granulocytes were exposed to topical nasal steroids in vitro. The preparations containing benzalkonium chloride and benzalkonium chloride alone destroyed the mucosa within 10 days. The same preparations also inhibited human neutrophil actin polymerization, degranulation and oxidative burst in vitro in a time and concentration dependent manner. Preparations without benzalkonium chloride, as well as the steroid compounds themselves, did not have these effects. It is concluded that benzalkonium chloride has toxic effects on human respiratory mucosa and human neutrophils in vitro.

Effects of marine 2-polyprenyl-1,4-hydroquinones on phospholipase A 2 activity and some inflammatory responses

Three 2-polyprenyl-1,4-hydroquinone derivatives (2-heptaprenyl-1,4-hydroquinone: IS1, 2-octaprenyl-1,4-hydroquinone: IS2 and 2-[24-hydroxy]-octaprenyl-1,4-hydroquinone: IS3) isolated from the Mediterranean sponge Ircinia spinosula, were evaluated for effects on phospholipase A 2 activity of different origin ( Naja naja venom, human recombinant synovial fluid and bee venom), as well as on human neutrophil function and mouse ear oedema induced by 12- O-tetradecanoylphorbol 13-acetate (TPA). IS1 interacted minimally with these responses. In contrast, IS2 and IS3 inhibited human recombinant synovial phospholipase A 2 in a concentration-dependent manner, with minor effects on the rest of the enzymes. Both compounds slightly affected superoxide generation and degranulation in human neutrophils, whereas they decreased thromboxane B 2 and leukotriene B 4 synthesis and release in a mixed suspension of human platelets and neutrophils stimulated by ionophore A23187, with IC 50 values in the μM range. IS3 was the most effective inhibitor of the synthesis of thromboxane B 2 by human platelet microsomes and of leukotriene B 4 by high speed supernatants from human neutrophils. IS2 and IS3 showed topical anti-inflammatory activity against the TPA-induced ear inflammation in mice, with similar effects on oedema and a higher inhibition of IS3 on leukocyte migration, estimated as myeloperoxidase activity in supernatants of ear homogenates. Some structure-activity relationships were established since differences in the prenylated chain attached to the hydroquinone moiety result in important modifications of these inflammatory responses.

Synthesis and pharmacological evaluation of 2'-hydroxychalcones and flavones as inhibitors of inflammatory mediators generation.

2'-Hydroxy-3,4-dimethoxy-3',4'-dimethylchalcone (3a), 2'-hydroxy-3',4',3,4-tetramethoxychalcone (3b), and their corresponding flavones, 3',4'-dimethoxy-7,8-dimethylflavone (4a) and 3',4',7,8-tetramethoxyflavone (4b), were prepared from 3,4-dimethoxycinnamic acid and the respective phenol. The four compounds inhibited enzymic lipid peroxidation and showed weak peroxyl scavenging activity. They also reduced LTB4 release from human neutrophils stimulated by A23187. The chalcone 3b was the only compound able to inhibit in a concentration-dependent way, synovial human recombinant phospholipase A2 activity, human platelet TXB2 generation, and human neutrophil degranulation. This chalcone exerted topical antiinflammatory effects in mice.

Neisserial porins inhibit human neutrophil actin polymerization, degranulation, opsonin receptor expression, and phagocytosis but prime the neutrophils to increase their oxidative burst

Porins are trimeric proteins that constitute water-filled pores that allow transmembrane diffusion of small solutes through the outer membrane layer of gram-negative bacteria. The porins are capable of inserting into the membranes of eucaryotic cells, and in the present study we have examined the in vitro effects on neutrophil functions of the following purified porins: meningococcal outer membrane protein classes 1 and 3 and gonococcal outer membrane protein 1B (P1B). The neisserial porins inhibited human neutrophil chemoattractant-induced actin polymerization and degranulation of both primary and secondary granules. The neutrophil expression of immunoglobulin G (IgG) Fc receptors II (Fc gamma RII; CDw32) and III (Fc gamma RIII; CD16), as well as the activation-dependent downregulation of Fc gamma RIII, were reduced by the meningococcal and gonococcal porins. The neisserial porins impaired the upregulation of complement receptors 1 (CD35) and 3 (CD11b) and inhibited the phagocytic capacity of neutrophils, as evaluated by the uptake of meningococci (strain 44/76) in the presence of patient serum containing known amounts of IgG against meningococcal porins. The porins also primed neutrophils to increase their intracellular hydrogen peroxide production in response to FMLP, whereas no such priming was observed if the neutrophil protein kinase C was stimulated directly with phorbol myristate acetate. The neisserial porins influenced neutrophil functions in a time- and concentration-dependent manner. The meningococcal class 1 outer membrane protein and the gonococcal P1B tended to alter neutrophil functions more than the meningococcal class 3 protein. Thus, the neisserial porins inhibited human neutrophil actin polymerization, degranulation, opsonin receptor expression, and phagocytosis but primed the neutrophils to increase their oxidative burst. It remains to be determined whether these in vitro observations reflect mechanisms that may be of importance for the interaction between neutrophils and Neisseria species in vivo.

Liposome-based studies of human neutrophil degranulation and protein-lipid interactions in membrane fusion

Liposome-based studies of human neutrophil degranulation and protein-lipid interactions in membrane fusion