Human Neutrophil Degranulation Research Articles

Effects of flavonoids isolated from licorice roots (Glycyrrhiza inflata Bat.) On degranulation in human polymorphonuclear neutrophils

AbstractThe effects of chalcones and flavanone isolated from licorice roots (Glycyrrhiza inflata Bat.) on human polymorphonuclear neutrophil (PMN) degranulation were investigated. Licochalcone A (2‐methoxy‐4,4′‐dihydroxy‐5‐α,α‐dimethylallylchalcone) and licochalcone B (2‐methoxy 3,4,4′‐trihydroxychalcone), at concentrations of 10−6M to 10−3M, inhibited calcium ionophore A 23187 (A 23187)‐, leukotriene B4 (LTB4) plus cytochalasin B (cyto B)‐, platelet activating factor (PAF) plus cyto B‐ and N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP) plus cyto B‐induced lysosomal enzyme release from human PMNs. Isoliquiritigenin, isoliquiritin, liquiritigenin and liquiritin had no effects on PMN degranulation induced by various stimuli. In addition, licochalcones A and B, at high concentrations (10−4M–10−3M), increased cyclic AMP in human PMNs. Furthermore, licochalcones A and B, at concentrations of 10−6M to 10−3M, reduced the elevation of cytosolic free calcium concentration induced by calcium ionophore ionomycine (ionomycine), fMLP, PAF and LTB4.

Association between leukotriene B 4-induced phospholipase D activation and degranulation of human neutrophils

We have explored the role of phospholipase D (PLD) activation in leukotriene B 4 (LTB 4)-induced Ca 2+ mobilization and degranulation of human neutrophils. Stimulation of [ 3H]alkyl-acylphosphatidylcholine-labeled neutrophils with LTB 4 resulted in a rapid accumulation of [ 3H]alkylphosphatidic acid (PA) as well as a somewhat slower accumulation of [ 3H]alkyl-diglyceride (DG). In the presence of ethanol, PLD catalyzed a transphosphatidylation reaction in which LTB 4 increased [ 3H]alkyl-phosphatidylethanol formation and simultaneously decreased LTB 4-induced PA and DG accumulation. This pattern of lipid metabolism is consistent with the conclusion that LTB 4 stimulates PLD activity in human neutrophils. Additional studies in which the extracellular and intracellular concentrations of Ca 2+ were varied indicated that maximal LTB 4-induced PLD activation was dependent upon Ca 2+ and potentiated by inhibitors of protein kinase C. The time-course and concentration-response curves for LTB 4-induced PLD activation were different from those for LTB 4-induced Ca 2+ mobilization, as measured by fura-2 fluorescence. On the other hand, the concentration-response curve for LTB 4-induced PLD activation was similar to that for LTB 4-induced degranulation. Preincubation of the cells with ethanol inhibited LTB 4-induced PA and DG accumulation, as well as degranulation, suggesting that one or both of these metabolites were important for this response. In contrast, ethanol had no effect on LTB 4-induced Ca 2+ mobilization. Propranolol, an inhibitor of phosphatidate phosphohydrolase, abolished DG accumulation in response to LTB 4 but had no effect on degranulation, suggesting that PA is more important than DG as a mediator of degranulation. Taken collectively, these data indicate that LTB 4-induced activation of PLD in human neutrophils is mediated by a Ca 2+-dependent mechanism, but not by protein kinase C. In addition, PLD activation in these cells may induce degranulation, but not Ca 2+ mobilization.

Regulation of human neutrophil degranulation by LY-83583 and L-arginine: role of cGMP-dependent protein kinase.

The effects of guanosine 3',5'-cyclic monophosphate (cGMP) on the secretory response of activated human neutrophils were investigated using LY-83583, an inhibitor of soluble guanylate cyclase, and L-arginine, the precursor of nitric oxide formation. A 30% release of myeloperoxidase (MPO) and lactoferrin (LF) from the primary and specific granules, respectively, was detected by enzyme-linked immunosorbent assay in adhered neutrophils stimulated with 0.1 microM N-formyl-methionyl-leucyl-phenylalanine (FMLP) or 20 microM A-23187. LY-83583 (100 microM) inhibited the release of both LF and MPO after stimulation with FMLP or A-23187. Conversely, preincubation of neutrophils with 0.5 mM L-arginine augmented the release of LF and MPO in FMLP- and A-23187-stimulated cells. Concurrent with the increase in the degranulation response was an elevation of cGMP levels in L-arginine-treated cells, while stimulated cGMP levels were reduced in LY-83583-treated cells. Furthermore, cGMP-dependent protein kinase (G-kinase) activity was reduced in LY-83583-treated cells, as determined by the delay in G-kinase translocation to intermediate filaments and the inhibition of vimentin phosphorylation. Degranulation, elevation of cGMP levels, and targeting of G-kinase were also dependent on the concentration of A-23187 or FMLP. These data suggest that activators of neutrophil degranulation mediate this response through a cGMP-dependent protein kinase mechanism.

ONO-4057, a novel, orally active leukotriene B4 antagonist: Effects on LTB 4-induced neutrophil functions

ONO-4057(5-[2-(2-Carboxyethyl)-3-{6-( 4-methoxyphenyl )-5E-hexenyl} oxyphenoxy ] valeric acid), an orally active leukotriene B 4(LTB 4) antagonist, displaced the binding of [ 3H] LTB 4 to the LTB 4 receptor in human neutrophil (Ki = 3.7±0.9 nM). ONO-4057 inhibited the LTB 4-induced rise in cytosolic free calcium (the concentration causing 50% inhibition (IC 50) = 0.7±0.3μM) and inhibited human neutrophil aggregation, chemotaxis or degranulation induced by LTB 4 (IC 50 = 3.0±0.1, 0.9±0.1 and 1.6±0.1μM) without showing any agonist activity at concentration up to 30μM. ONO-4057 did not inhibit fMLP or C5a-induced neutrophil activation at concentrations up to 30μM. In the in vivo study, ONO-4057 given orally, prevented LTB 4-induced transient neutropenia or intradermal neutrophil migration in guinea pig (the dose causing 50% efficacy (ED 50) = 25.6mg/kg or 5.3mg/kg). Furthermore, ONO-4057 given topically, suppressed phorbol-12-myristate-13-acetate (PMA)-induced neutrophil infiltration in guinea pig ear (the effective dose = 1 mg/ear). These results indicate that ONO-4057 is a selective and orally active LTB 4 antagonist and may be a potential candidate for the treatment of various inflammatory diseases.

Annexin-mediated membrane fusion of human neutrophil plasma membranes and phospholipid vesicles

Membrane fusion was studied using human neutrophil plasma membrane preparations and phospholipid vesicles approximately 0.15 μm in diameter and composed of phosphatidylserine and phosphatidylethanolamine in a ratio of 1 to 3. Liposomes were labeled with N-(7-nitrobenzo-2-oxa-1,3-diazol-4-yl (NBD) and lissamine rhodamine B derivatives of phospholipids. Apparent fusion was detected as an increase in fluorescence of the resonance energy transfer donor, NBD, after dilution of the probes into unlabeled membranes. 0.5 mM Ca 2+ alone was sufficient to cause substantial fusion of liposomes with a plasma membrane preparation but not with other liposomes. Both annexin I and des(1–9)annexin I caused a substantial increase in the rate of fusion under these conditions while annexin V inhibited fusion. Fusion mediated by des(1–9)annexin I was observed at Ca 2+ concentrations as low as aproximately 5 μM, suggesting that the truncated form of this protein may be active at physiologically low Ca 2+ concentrations. Trypsin treated plasma membranes were incapable of fusion with liposomes, suggesting that plasma membrane proteins may mediate fusion. Liposomes did not fuse with whole cells at any Ca 2+ concentration, indicating that the cytoplasmic side of the membrane is involved. These results suggest that annexin I and unidentified plasma membrane proteins may play a role in Ca 2+-dependent degranulation of human neutrophils.

Monokines Mediate Decreased Hepatic Glucocorticoid Binding in Endotoxemia

Several studies indicate that the actin filament system is not only involved in cell motility, but also in the regulation of other neutrophil functions. The aim of the present investigation was to examine the mechanisms by which actin filament formation participates in the control of the respiratory burst and degranulation in human neutrophils. The approach taken was to use both an inhibitor (cytochalasin B) and a potentiator (tetracaine) of formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe)-induced actin polymerization. The total inhibition of fMet-Leu-Phe-induced actin polymerization in cytochalasin B-treated cells was accompanied by an impressive potentiation of both oxidase activity and degranulation (azurophilic and specific granules). However, preincubation with tetracaine, which causes an enhanced accumulation of F-actin in the periphery of fMet-Leu-Phe-stimulated cells, also augmented the rate and duration of peptide-induced superoxide anion production, but inhibited degranulation (specific granules). A likely explanation for the potentiating effects of cytochalasin B and tetracaine is provided by our observation that both of these substances reduced the acid-resistant binding of fMet-Leu-Phe (interpreted as a decrease in the internalization of fMet-Leu-Phe-receptor-complexes), resulting in an enhanced formation of second messengers (diacylglycerol). The findings that tetracaine potentiated the activity of the oxidase, whereas it inhibited degranulation (specific granules), suggest that actin polymerization per se plays a role in the latter process. Consequently, this study argues against the idea of a direct inhibitory effect of F-actin on chemotactic factor-induced oxidase activation, but supports an active role of actin filaments in the translocation and release of granule components.

Tumor necrosis factor-induced degranulation in adherent human neutrophils is dependent on CD11b/CD18-integrin-triggered oscillations of cytosolic free Ca2+.

We have recently been able to correlate closely the "spontaneous" oscillatory activity of cytosolic free Ca2+ in adherent human neutrophils with the ability of tumor necrosis factor (TNF) to induce secretion of granule proteins from these cells. In the present work we show with a single-cell technique that preincubation of human neutrophils with antibodies to CD18, the common beta chain of leukocyte adhesion proteins, inhibits TNF-induced secretion of lactoferrin in a time- and concentration-dependent manner. Similar effects of CD18 antibodies were found on chemotactic factor (fMet-Leu-Phe)- but not on phorbol 12-myristate 13-acetate-induced secretion, suggesting that cell-surface-receptor-mediated secretion is dependent on integrin-associated signals. Similarly, antibodies to CD11b (alpha chain of macrophage 1) also inhibited TNF- and fMet-Leu-Phe- but not phorbol 12-myristate 13-acetate-stimulated release of lactoferrin. Antibodies to CD11a (alpha chain of lymphocyte function-associated antigen 1) or CD11c (alpha chain of p150,95) had only a minimal effect on agonist-induced secretion. Data obtained in several laboratories, including our own, made us suspect that integrin interaction with the surface is responsible for the oscillatory activity of cytosolic free Ca2+ in adherent cells. Indeed, preincubation with antibodies to either CD18 or CD11b, but not to CD11c, inhibited the oscillations of cytosolic free Ca2+ in adherent neutrophils. This inhibitory effect was evident both as a reduction of the number of responding cells and as a reduction of the oscillatory activity in the cells. In conclusion, the oscillatory activity of cytosolic free Ca2+ in adherent neutrophils is mediated through the CD18/CD11b integrins. The generation of this Ca2+ signal may explain how adherence, by way of the integrins, changes the functional properties of the cell and enables TNF to induce secretion.

Degranulation of human neutrophils after exposure to bacterial phospholipase C

Because an endogenous phospholipase C (PLC) participates in neutrophil activation and because many bacterial pathogens produce PLCs, these studies examined the effect of PLC from Bacillus cereus on the release of the granule enzyme lysozyme from human neutrophils. Bacillus cereus PLC caused dose-dependent lysozyme release, and combined stimulation of neutrophils with PLC and fluoride led to increased secretion. Stimulation of neutrophil degranulation is a potential contributing factor for tissue damage in infections caused by PLC-producing organisms.

Correlation between spontaneous oscillations of cytosolic free Ca2+ and tumor necrosis factor-induced degranulation in adherent human neutrophils.

By using a hemolytic plaque assay to detect release of lactoferrin and myeloperoxidase, tumor necrosis factor (TNF) was shown previously to induce secretion of these granule proteins from single adherent neutrophils. Secretion was inhibited by loading neutrophils with calcium chelators, indicating a crucial role of cytosolic free [Ca2+] in the signal transduction mechanism of TNF. In the present study, using a microfluorometer technique to follow changes in the cytosolic free [Ca2+] in single adherent neutrophils, we were not able to detect any TNF-induced [Ca2+] transients. However, these adherent cells exhibited spontaneous oscillations of their cytosolic free [Ca2+], as previously reported (Jaconi, M.E.E., Rivest, R.W., Schlegel, W., Wollheim, C.B., Pittet, D., and Lew, P.D. (1988) J. Biol. Chem. 263, 10557-10560). A close correlation was found between a reduced oscillatory activity of cytosolic free [Ca2+] and a reduced ability of TNF to induce degranulation, by reducing the extracellular [Ca2+] or loading the cells with a calcium chelator (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). In addition, when the cells were incubated at 37 degrees C for 3 h there was a parallel decline in the spontaneous oscillatory activity of cytosolic free [Ca2+] and TNF-induced secretion of lactoferrin. Control experiments showed that phorbol 12-myristate 13-acetate-induced secretion was not affected under the same conditions, indicating that the secretory process per se was not disturbed. We conclude that TNF by itself does not give rise to any changes of the cytosolic free [Ca2+] but that the spontaneous oscillatory activity of cytosolic free [Ca2+] in adherent neutrophils is necessary for TNF-induced degranulation.

Degranulation in human neutrophils primes the cells for subsequent responsiveness to the chemoattractant N-formylmethionylleucylphenylalanine but does not increase the sensitivity of the NADPH-oxidase to an intracellular calcium rise

Both the chemotactic peptide formylmethionylleucylphenylalanine (FMLP) and the calcium-specific ionophore ionomycin can activate the NADPH-oxidase in human neutrophils. However, since ionomycin and FMLP activity differ in their requirement for azide, a potent inhibitor of the hydrogen peroxide consuming enzymes catalase and myeloperoxidase, we propose that the two stimuli can activate different pools of the oxidase. Degranulation, induced in vitro by sn-1,2-dedecaoylglycerol or in vivo by an exudation process, resulted in a priming of the cells using FMLP as stimulating agent as well as in a reduced capacity to generate H 2O 2 in response to ionomycin. The sensitivity of the plasma membrane-bound NADPH-oxidase to an intracellular [Ca 2+] rise, induced by the ionophore was, however, not changed by the degranulation. From these results we propose that FMLP activates the plasma membrane-bound oxidase, whereas the ionophore is capable of activating a granule-bound pool of the oxidase.

Neutrophil elastase and cathepsin G stimulate secretion from cultured bovine airway gland serous cells.

To investigate the hypothesis that neutrophil proteases stimulate airway gland secretion, we studied the effect of human cathepsin G and elastase on secretion of 35S-labeled macromolecules from cultured bovine airway gland serous cells. Both proteases stimulated secretion in a concentration-dependent fashion with a threshold of greater than or equal to 10(-10) M. Elastase was more potent than cathepsin G, causing a maximal secretory response of 1,810 +/- 60% over baseline at 10(-8) M. The maximal response to cathepsin G (1,810 +/- 70% over baseline at 10(-7) M) was similar to the maximal response to elastase. These responses were greater than 10-fold larger than the response to other agonists such as histamine. Protease-induced secretion was noncytotoxic and required catalytically active enzymes. The predominant sulfated macromolecule released by proteases was chondroitin sulfate proteoglycan. Immunocytochemical staining demonstrated chondroitin sulfate in cytoplasmic granules and decreased granular staining after stimulation of cells with elastase. The neutrophil proteases also degraded the proteoglycan released from serous cells. Cathepsin G and elastase in supernatant obtained by degranulation of human peripheral neutrophils also caused a secretory response. Thus, neutrophil proteases stimulate airway gland serous cell secretion of chondroitin sulfate proteoglycan and degrade the secreted product. These findings suggest a potential role for neutrophil proteases in the pathogenesis of increased and abnormal submucosal gland secretions in diseases associated with inflammation and neutrophil infiltration of the airways.

Mechanisms involved in the bidirectional effects of protein kinase C activators on neutrophil responses to leukotriene B4.

Three protein kinase C (PKC) activators (PMA, mezerein, and a diacylglycerol) had bidirectional effects on human polymorphonuclear neutrophil (PMN) degranulation responses to leukotriene (LT) B4. Lower concentrations of the three agents enhanced, whereas higher concentrations inhibited, release of lysozyme and beta-glucuronidase stimulated by the arachidonic acid metabolite. Contrastingly, the activators inhibited but never enhanced LTB4-induced Ca2+ transients. We examined the causes for these varying effects. Each PKC activator reduced PMN specific binding of [3H]LTB4. Scatchard analyses revealed that PMA (greater than or equal to 0.16 nM) decreased the number of high affinity LTB4 receptors. The receptor losses correlated closely with inhibition of Ca2+ transients. PMN pretreated with 0.5 nM PMA for 5 min retained approximately 50% of their high affinity LTB4 receptors. These cells responded to 10 nM LTB4 with reduced but still substantial rises in cytosolic Ca2+, enhanced PKC mobilization, and increased granule enzyme release. The latter two effects appeared calcium-dependent because sequential exposure to PMA and LTB4 did not synergistically stimulate PKC mobilization or degranulation in PMN that were: 1) Ca2(+)-depleted; 2) challenged with 5 nM PMA; or 3) treated with LTB4 for 5 min before PMA. Each of the latter treatments completely interfered with the extent or timing of LTB4-induced Ca2+ transients. Accordingly, we suggest that the response-specific, bidirectional effects of PKC activators on LTB4 result from two opposing mechanisms. First, PKC activators down-regulate LTB4 high affinity receptors and thereby reduce those PMN responses that are not elicited by activated PKC (i.e., Ca2+ transients). Second, LTB4, by elevating cytosolic Ca2+, increases the amount of PKC mobilized by PKC activators and thereby promotes PKC-dependent responses (e.g., degranulation). The two mechanisms may be pertinent to the bidirectional effects of PKC activators on various other agonists. Furthermore, PKC, by down-regulating receptors, may serve as a physiologic stop signal for terminating function and producing a poststimulatory state of desensitization.

Stimulus-Specific Effects of Pentoxifylline on Neutrophil CR3 Expression, Degranulation, and Superoxide Production

The effects of pentoxifylline (Trental) on human neutrophil CR3 up-modulation, degranulation, and superoxide production were studied. We used the chemotactic peptide fMLP and the phorbol ester PMA as soluble stimuli, and beta-glucan particles as a CR3-specific solid phase stimulus of neutrophil superoxide production. Since neutrophils have adenosine A2 receptors, we compared effects of pentoxifylline to effects of adenosine, and we also looked at the effect of cytochalasin B, which breaks up actin filaments. Pentoxifylline inhibited both CR3 up-modulation and degranulation of myeloperoxidase and lysozyme. Pentoxifylline is a more potent inhibitor of fMLP- compared to PMA-induced degranulation, and is especially potent against superoxide production. While pentoxifylline is less potent than adenosine in its inhibition of fMLP-induced superoxide production, it is more potent in its inhibition of PMA- and beta-glucan particle-stimulated superoxide production. Cytochalasin B, which enhances degranulation and fMLP-stimulated superoxide production, was found to inhibit beta-glucan particle-stimulated superoxide production. These findings are consistent with the hypothesis that pentoxifylline can affect both the cytoskeletal architecture of unstimulated neutrophils and the activation and responses of neutrophils which involve actin polymerization and receptor-cytoskeletal interactions.

Inhibition of protein kinase c by H-7 potentiates the release of oleic, linoleic and arachidonic acids in A23187-stimulated human neutrophils

This present report describes the effect of H-7, a protein kinase C inhibitor, on the release of oleic, linoleic and arachidonic acids in A23187-stimulated neutrophils. Surprisingly, the inhibitor potentiated the release of all three unsaturated fatty acids in neutrophils stimulated with A23187 alone. In contrast, released oleic acid, linoleic acid and arachidonic acid in phorbol 12-myristate 13-acetate-primed neutrophils were attenuated by 35, 47 and 33%, respectively, in the presence of H-7 (300 μM). Phorbol 12-myristate 13-acetate (PMA) had no effect on A23187-stimulated release of saturated fatty acids. Both PMA and H-7 when used alone had no effect on the release of saturated or unsaturated fatty acids. We, therefore, conclude that H-7 may have effects other than inhibiting PMA-primed responses including superoxide generation, degranulation and arachidonic acid release in human neutrophils.

Fibronectin degradation products containing the cytoadhesive tetrapeptide stimulate human neutrophil degranulation.

We investigated whether adhesive glycoproteins, such as fibronectin or fibrinogen, could function to provide a nidus for neutrophil degranulation. Elastase release in recalcified plasma was normal in afibrinogenemic plasma, but 73% less in plasma depleted of fibronectin. Proteolytic digests of fibronectin, but not intact fibronectin (50-1,000 micrograms/ml), induced a concentration-dependent release of neutrophil elastase and lactoferrin. MAbs N293, which recognized the mid-molecule of fibronectin, N294, which was directed toward the 11-kD cell adhesive fragment, and N295, generated against the amino terminal of the 11-kD fragment, inhibited the release of elastase by 7, 24, and 60%, respectively. The cytoadhesive tetrapeptide portion of fibronectin, Arg-Gly-Asp-Ser (250-1,000 micrograms/ml), released 1.94 +/- 0.10 micrograms/ml of elastase from 10(7) neutrophils, in contrast to the lack of release by the control hexapeptide, Arg-Gly-Tyr-Ser-Leu-Gly. Plasmin appeared to be the enzyme responsible for fibronectin cleavage, since neutrophil elastase release in plasma that had been depleted of plasminogen was decreased and reconstitution of plasminogen-deficient plasma with purified plasminogen corrected the abnormal release. Plasmin cleaved fibronectin to multiple degradation products, each less than 200 kD. This fibronectin digest released 1.05 microgram/ml of elastase from 10(7) neutrophils. We suggest that the activation of plasminogen leads to the formation of fibronectin degradation products capable of functioning as agonists for neutrophils.

(±)-Trans-2-(3-methoxy-5-methylsulfonyl-4-propoxyphenyl)-5-(3,4,5-trimethoxyphenyl)tetrahydrofuran (L-659,989), a novel, potent PAF receptor antagonist

The title compound, L-659,989, is a highly potent, competitive, and selective antagonist of the binding of [3H]PAF to its receptors in platelet membranes from rabbits and humans. It exhibits equilibrium inhibition constants for PAF binding of 1.1 nM (rabbit) to 9.0 nM (human), values that are at least 1–2 orders of magnitude lower than those of other PAF antagonists tested. L-659,989 potently inhibits PAF-induced aggregation of rabbit platelets and degranulation of rat (ED50 4.5 nM) and human (ED50 10 nM) neutrophils. L-659,989 inhibits PAF-induced extravasation and lysosomal enzyme release in rats, and is active orally in female rats (ED50 0.2 mg/kg) with an extraordinary oral duration of action of 12 to 16 hours at 1.0 mg/kg p.o.

Stimulation of human neutrophil degranulation by mefloquine.

The effect of the antimalarial drug mefloquine on human neutrophil degranulation, chemiluminescence, superoxide production and viability was examined in vitro. Mefloquine was found to significantly stimulate the release of lysozyme, beta-glucuronidase and myeloperoxide at a concentration of 10 micrograms/ml (2.5 X 10(-5) M) without loss of cell viability. At 40 micrograms/ml mefloquine (1 X 10(-4) M) cell viability was significantly decreased. Mefloquine at 10 micrograms/ml also significantly increased the release of lysozyme and beta-glucuronidase but not myeloperoxidase when neutrophils were stimulated with opsonized zymosan. At a lower zymosan concentration myeloperoxidase release was also increased. Enzyme activity was not directly stimulated by mefloquine. Mefloquine at 10 micrograms/ml significantly increased luminol-dependent chemiluminescence but significantly inhibited lucigenin-dependent chemiluminescence when neutrophils were stimulated with opsonized zymosan. Under these conditions superoxide release, measured by cytochrome c reduction, was inhibited to a lesser degree. These results are discussed with reference to our previous report that mefloquine inhibits the neutrophil iodination reaction [Immunology 58: 125-130, 1986] and the use of mefloquine as an anti-inflammatory drug.

Effects of tumour necrosis factor alpha and interleukin-1 alpha and beta on human neutrophil migration, respiratory burst and degranulation.

Recombinant human tumour necrosis factor alpha (rHuTNF alpha) was shown to inhibit human neutrophil migration in the presence or absence of a chemotactic gradient generated with the tripeptide, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), at doses of 20-100 U/10(6) cells. In contrast, neither recombinant human interleukin-1 alpha (rHuIL-1 alpha), rHuIL-1 beta, human leucocyte-derived IL-1 alpha (1HuIL-1 alpha) nor 1HuIL-1 beta contained neutrophil migration inhibition properties. However, both the interleukins (1HuIL-1 alpha, 1HuIL-1 beta and rHuIL-1 alpha) and rHuTNF alpha stimulated a neutrophil respiratory burst and significantly elevated the neutrophil respiratory response to fMLP (measured as chemiluminescence and H2O2 production). The stimulatory effects were observed at doses of between 5 and 100 U/5 x 10(5) cells. A characteristic feature of the effects of the cytokines was the range of variation observed in neutrophil responses from different individuals. However, a concentration-related effect was observed with each experiment, delineating suboptimal, optimal and supra-optimal cytokine concentrations. Neutrophils treated with rHuTNF alpha and rHuIL-1 alpha and washed free of exogenous cytokine retained the capacity to show an enhanced response to fMLP. Pretreatment of cells with cytochalasin B enhanced their response to fMLP, and this response was further increased if the cells had also been pretreated with the cytokines. The response to phorbol myristate acetate was also enhanced by rHuTNF alpha and rHuIL-1 alpha. The effects of these cytokines on neutrophils could be abolished by boiling the preparation but not by treating it with polymixin B, suggesting that bacterial lipopolysaccharide was not responsible for the activity of these preparations. The rHuIL-1 alpha increased the release of lysozyme, beta-glucuronidase and myeloperoxidase initiated by cytochalasin B/fMLP, while rHuTNF alpha only increased lysozyme release.

Interleukin 2 inhibits migration and stimulates respiratory burst and degranulation of human neutrophils in vitro

Interleuking 2 (IL2) is a lymphocyte product recognised for its role as a T lymphocyte growth factor. Since some other lymphokines and monokines can modulate the function of granulocytes we examined the effects of natural and recombinant human IL2 on neutrophil locomotion, respiratory burst and degranulation. Purified T cell-derived IL2 inhibited both random and chemotactically-directed migration of neutrophils. IL2 induced a respiratory burst and release of lysosomal enzymes in neutrophils and increased these responses in classically stimulated neutrophils. Recombinant IL2 was also effective in altering neutrophil functions. We conclude that IL2 modulates neutrophil function.

The effect of a protein kinase C inhibitor, H-7, on human neutrophil oxidative burst and degranulation.

The role of C-kinase in the activation of human polymorphonuclear leukocytes has been examined using H-7, a recently described C-kinase inhibitor. We found that H-7 will inhibit PMN superoxide anion release in response to the tumor promotor phorbol myristate acetate and the calcium ionophore A23187. In contrast, no inhibition by H-7 was seen for PMN superoxide release stimulated by the chemotactic peptide FMLP. H-7 did not inhibit PMN NADPH oxidase activity or PMN degranulation by any stimulant, but it reversed a phorbol ester-induced inhibition of granule release by FMLP. The results show that H-7 differentially affects the PMN functional events of secretion and superoxide release and suggests that an H-7 inhibitable C-kinase is not involved in chemotactic peptide induced activation of PMN and may not regulate stimulus induced PMN degranulation.