Cytochalasin E diminishes the lag phase in the release of superoxide by human neutrophils

Neutrophil MMP-9 proenzyme, unencumbered by TIMP-1, undergoes efficient activation in vivo and catalytically induces angiogenesis via a basic fibroblast growth factor (FGF-2)/FGFR-2 pathway

The structural and catalytic requirements for neutrophil MMP-9 proenzyme (proMMP-9) to induce angiogenesis were investigated using a quantitative angiogenesis model based on grafting of collagen onplants onto the chorioallantoic membrane of chick embryos. Both physiological activation of neutrophil proMMP-9 and proteolytic activity of the generated MMP-9 enzyme were critically dependent on the tissue inhibitor of metalloproteinase (TIMP)-free status of the zymogen. The presence of an intact active site and hemopexin domain were required for full angiogenesis-inducing activity of the MMP-9 enzyme. Timed additions of TIMP-1 to the onplants containing TIMP-free neutrophil proMMP-9 indicated that in vivo activation of the zymogen occurred during the first 24 h after grafting. Within the onplant tissue, MMP-9 activation was accompanied by proteolytic modifications of fibrillar collagen and an influx of host proteins, the rate of which depended on the TIMP-free status of the zymogen. By quantifying the levels of host angiogenic factors, we demonstrated that basic fibroblast growth factor (FGF-2) was a major cytokine becoming bioavailable in the onplant tissue undergoing a neutrophil proMMP-9-mediated angiogenic switch. Inhibition of angiogenesis with specific function-blocking antibodies further indicated an involvement of a FGF-2/FGFR-2 pathway in neutrophil proMMP-9-induced angiogenesis. The enhanced angiogenesis catalyzed by neutrophil MMP-9 appears to evoke also a localized, low threshold level vascular endothelial growth factor (VEGF)/VEGFR-2 pathway, likely functioning in the formation and/or stabilization of blood vessels. That neutrophil proMMP-9, unencumbered by TIMP-1, directly mediates FGF-2-dependent angiogenesis was also demonstrated in our quantitative mouse angiogenesis model employing subcutaneous collagen implants, thus implicating the novel TIMP-free MMP-9/FGF-2/FGFR-2 pathway in proMMP-9-induced angiogenesis in a mammalian setting.

Glutamate is the chemotaxis-inducing factor in placental extracts

Human placental extracts are known to help wound healing. Rapid migration of neutrophils to the wound site is a prerequisite to the wound healing process. Gel filtration analysis of heat-treated placental extract gave the initial cue to the small nature of the migration promoting factor of the extract. HPLC analysis of the extract revealed glutamate to be the predominant free amino acid. Our studies show that glutamate at an optimum concentration of 8 muM induced phenotypic neutrophil chemotaxis, as seen in the time lapse- and transwell assays. Glutamate was also found to induce chemokinesis of the neutrophil, though the stimulation of chemotaxis was more pronounced. The glutamate induced chemotaxis was accompanied by polarization of the actin cytoskeleton, and by polymerization of F-actin. These data indicate that glutamate has a strong chemotactic functionality in the neutrophil, which could be of interest both therapeutically and in further investigation of the molecular basis of chemotaxis.

Bacillus anthracis toxins inhibit human neutrophil NADPH oxidase activity

Bacillus anthracis, the causative agent of anthrax, is a Gram-positive, spore-forming bacterium. B. anthracis virulence is ascribed mainly to a secreted tripartite AB-type toxin composed of three proteins designated protective Ag (PA), lethal factor, and edema factor. PA assembles with the enzymatic portions of the toxin, the metalloprotease lethal factor, and/or the adenylate cyclase edema factor, to generate lethal toxin (LTx) and edema toxin (ETx), respectively. These toxins enter cells through the interaction of PA with specific cell surface receptors. The anthrax toxins act to suppress innate immune responses and, given the importance of human neutrophils in innate immunity, they are likely relevant targets of the anthrax toxin. We have investigated in detail the effects of B. anthracis toxin on superoxide production by primary human neutrophils. Both LTx and ETx exhibit distinct inhibitory effects on fMLP (and C5a) receptor-mediated superoxide production, but have no effect on PMA nonreceptor-dependent superoxide production. These inhibitory effects cannot be accounted for by induction of neutrophil death, or by changes in stimulatory receptor levels. Analysis of NADPH oxidase regulation using whole cell and cell-free systems suggests that the toxins do not exert direct effects on NADPH oxidase components, but rather act via their respective effects, inhibition of MAPK signaling (LTx), and elevation of intracellular cAMP (ETx), to inhibit upstream signaling components mediating NADPH oxidase assembly and/or activation. Our results demonstrate that anthrax toxins effectively suppress human neutrophil-mediated innate immunity by inhibiting their ability to generate superoxide for bacterial killing.

Unusual polyclonal anti-gp91 peptide antibody interactions with X-linked chronic granulomatous disease-derived human neutrophils are not from compensatory expression of Nox proteins 1, 3, or 4

To obtain topological information about human phagocyte flavocytochrome b558 (Cytb), rabbit anti-peptide antibodies were raised against synthetic peptides mimicking gp91(phox) regions: 1-9 (MGN), 30-44 (YRV), 150-159 (ESY), 156-166 (ARK), 247-257 (KIS-1, KIS-2). Following affinity purification on immobilized peptide matrices, all antibodies but not prebleed controls recognized purified detergent-solubilized Cytb by enzyme-linked immunosorbent assay (ELISA). Affinity-purified antibodies recognizing KIS, ARK and ESY but not YRV, MGN or prebleed IgG specifically detected gp91(phox) in immunoblot analysis. Antibodies recognizing MGN, ESY, ARK and KIS but not YRV or the prebleed IgG fraction labeled intact normal neutrophils. Surprisingly, all antibodies, with the exception of YRV and pre-immune IgG controls, bound both normal and Cytb-negative neutrophils from the obligate heterozygous mother of a patient with X-linked chronic granulomatous disease (X-CGD) and all neutrophils from another patient lacking the gp91(phox) gene. Further immunochemical examination of membrane fractions derived from nine genetically unrelated patients with X-CGD, using an antibody that recognizes other Nox protein family members, suggests that the unusual reactivity observed does not reflect the compensatory expression of gp91(phox) homologs Nox1, 3 or 4. These results suggest that an unusual surface reactivity exists on neutrophils derived from X-linked chronic granulomatous disease patients that most likely extends to normal neutrophils as well. The study highlights the need for caution in interpreting the binding of rabbit polyclonal antipeptide antibodies to human neutrophils in general and, in the specific case of antibodies directed against Cytb, the need for Cytb-negative controls.

A Stable Aspirin-Triggered Lipoxin A4Analog Blocks Phosphorylation of Leukocyte-Specific Protein 1 in Human Neutrophils

Lipoxins and their aspirin-triggered 15-epimers are endogenous anti-inflammatory agents that block neutrophil chemotaxis in vitro and inhibit neutrophil influx in several models of acute inflammation. In this study, we examined the effects of 15-epi-16-(p-fluoro)-phenoxy-lipoxin A(4) methyl ester, an aspirin-triggered lipoxin A(4)-stable analog (ATLa), on the protein phosphorylation pattern of human neutrophils. Neutrophils stimulated with the chemoattractant fMLP were found to exhibit intense phosphorylation of a 55-kDa protein that was blocked by ATLa (10-50 nM). This 55-kDa protein was identified as leukocyte-specific protein 1, a downstream component of the p38-MAPK cascade in neutrophils, by mass spectrometry, Western blotting, and immunoprecipitation experiments. ATLa (50 nM) also reduced phosphorylation/activation of several components of the p38-MAPK pathway in these cells (MAPK kinase 3/MAPK kinase 6, p38-MAPK, MAPK-activated protein kinase-2). These results indicate that ATLa exerts its anti-inflammatory effects, at least in part, by blocking activation of the p38-MAPK cascade in neutrophils, which is known to promote chemotaxis and other proinflammatory responses by these cells.

Protein phosphorylation in neutrophils monitored with phosphospecific antibodies

Protein phosphorylation in neutrophils was monitored with two phosphospecific antibodies (pAbs) [termed pPKC(S1) Ab and pPKC(S2) Ab] that recognize products of protein kinase C (PKC) and other Arg/Lys-directed Ser/Thr protein kinases. The pPKC(S1) Ab bound preferentially to p-Ser/p-Thr residues with Arg or Lys in the -3 and -5 positions or the -2 and -3 positions, whereas the pPKC(S2) Ab bound preferentially to p-Ser with Arg or Lys in the -2 and +2 positions and with a hydrophobic residue at the +1 position. Phosphorylated pleckstrin, myristoylated alanine-rich C-kinase substrate (MARCKS), the 47-kDa subunit of the phagocyte oxidase (p47-phox) and numerous unidentified proteins that underwent phosphorylation during neutrophil stimulation were readily detected with these pAbs. Priming effects of tumor necrosis factor alpha (TNF-alpha) and the susceptibility of certain reactions in neutrophils to inhibitors of protein kinases could also be easily investigated with these reagents. Compared to the commonly used 32P-labeling/autoradiographic method, Western blotting with pAbs was found to be a faster, safer, more specific and in many cases more sensitive approach for monitoring protein phosphorylation events in neutrophils. These pAbs may facilitate the identification of several new phosphorylation reactions involved in neutrophil stimulation.

Induction of gp91-phox, a component of the phagocyte NADPH oxidase, in microglial cells during central nervous system inflammation

Gp91-phox is an integral component of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex that generates reactive oxygen species (ROS) in activated circulating phagocytes. The authors previously demonstrated that gp91-phox knockout (KO) mice show significant protection from neuronal injury after cerebral ischemia--reperfusion injury, suggesting a pivotal role for this enzyme. Moreover, results from chimeric mice suggested that elimination of gp91-phox from both circulating phagocytes and a putative central nervous system (CNS) source were required to confer neuroprotection. In the current study, the authors demonstrated gp91-phox-specific immunostaining of perivascular cells in the CNS of control rats. However, after transient cerebral ischemia, gp91-phox-positive phagocytes were observed within the core ischemic region and activated microglial cells were positive in the penumbra. Such activated microglial cells were also gp91-phox-positive in the CNS of a chimpanzee with mild meningitis. Finally, in humans, both normal adult CNS tissues and isolated fetal microglial cells expressed gp91-phox mRNA. These microglia also expressed mRNA for the five other known components that comprise the NADPH oxidase complex. These data strongly suggest that microglial cells may contain a functionally active NADPH oxidase capable of generating ROS during CNS inflammation.

Autosomal recessive chronic granulomatous disease caused by defects in NCF-1, the gene encoding the phagocyte p47-phox: mutations not arising in the NCF-1 pseudogenes

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by defects in any one of 4 genes encoding phagocyte NADPH oxidase subunits. Unlike other CGD subtypes, in which there is great heterogeneity among mutations, 97% of affected alleles in patients previously reported with A47(0) CGD carry a single mutation, a GT deletion (DeltaGT) in exon 2 of the p47-phox gene, NCF-1. This unusually high incidence results from recombination events between NCF-1 and its highly homologous pseudogenes, in which DeltaGT originates. In 50 consecutive patients with A47(0) CGD, 4 were identified who were heterozygous for DeltaGT in NCF-1, and for the first time, 2 were identified whose DNA appeared normal at this position. To avoid co-amplification of pseudogene sequence and to enable the identification of mutations in these patients, allele-specific polymerase chain reaction was used to amplify alleles not containing DeltaGT. In each of the 4 patients who were heterozygous for DeltaGT, an additional novel mutation was identified. These were 2 missense mutations, G125 --> A in exon 2 (predicting Arg42 --> Gln) and G784 --> A in exon 8 (Gly262 --> Ser), and 2 splice junction mutations at the 5' end of intron 1, gt --> at and gtg --> gtt. The first of 2 patients who appeared normal at the GT position was a compound heterozygote with the G125 --> A transition on one allele and a deletion of G811 on the other. In the second of these patients, only a single defect was detected, G574 --> A, which predicts Gly192 --> Ser but is likely to result in defective splicing because it represents the final nucleotide of exon 6.

Characterization of rac and cdc42 activation in chemoattractant-stimulated human neutrophils using a novel assay for active GTPases

A major function of Rac2 in neutrophils is the regulation of oxidant production important in bacterial killing. Rac and the related GTPase Cdc42 also regulate the dynamics of the actin cytoskeleton, necessary for leukocyte chemotaxis and phagocytosis of microorganisms. Although these GTPases appear to be critical downstream components of chemoattractant receptor signaling in human neutrophils, the pathways involved in direct control of Rac/Cdc42 activation remain to be determined. We describe an assay that measures the formation of Rac-GTP and Cdc42-GTP based on their specific binding to the p21-binding domain of p21-activated kinase 1. A p21-binding domain glutathione S-transferase fusion protein specifically binds Rac and Cdc42 in their GTP-bound forms both in vitro and in cell samples. Binding is selective for Rac and Cdc42 versus RhoA. Using this assay, we investigated Rac and Cdc42 activation in neutrophils and differentiated HL-60 cells. The chemoattractant fMet-Leu-Phe and the phorbol ester phorbol myristate acetate stimulate formation of Rac-GTP and Cdc42-GTP with distinct time courses that parallel cell activation. We also show that the signaling pathways leading to Rac and Cdc42 activation in HL-60 cells involve G proteins sensitive to pertussis toxin, as well as tyrosine kinase and phosphatidylinositol 3-kinase activities.

Interleukin-8 (IL-8), melanoma growth-stimulatory activity, and neutrophil-activating peptide selectively mediate priming of the neutrophil NADPH oxidase through the type A or type B IL-8 receptor

The capacity of neutrophils to generate superoxide (O-2) can be enhanced by prior exposure to "priming" agents such as interleukin-8 (IL-8), melanoma growth-stimulatory activity (MGSA), and neutrophil-activating peptide (ENA-78). The biological effects of these chemokines are mediated by at least two distinct receptors: type A (IL-8-RA) and type B (IL-8-RB). Using neutralizing monoclonal antibodies to IL-8-RA and IL-8-RB, we have investigated the contribution each receptor makes to the priming response. Preincubation with IL-8, MGSA, or ENA-78 enhanced the ability of neutrophils to generate O-2 following stimulation with the bacterial peptide formyl-Met-Leu-Phe. The priming effect of IL-8 was eliminated by an anti-IL-8 monoclonal antibody (mAb) that is known to bind IL-8 with high affinity and prevent receptor occupancy. Incubation of neutrophils with a neutralizing mAb specific for IL-8-RA blocked IL-8-induced priming but had no effect on priming by MGSA or ENA-78. In contrast, treatment with a neutralizing mAb specific for IL-8-RB failed to inhibit the priming effect of IL-8 but blocked both MGSA and ENA-78-induced priming. These observations indicate that the priming effect of IL-8 on the neutrophil respiratory burst is predominantly mediated via IL-8-RA, whereas priming by MGSA and ENA-78 is mediated by IL-8-RB.

Naphthalenesulphonamides block neutrophil superoxide production by intact cells and in a cell-free system: is myosin light chain kinase responsible for these effects?

Selective antagonists of myosin light chain kinase (MLCK) [e.g. ML-7; 1-(5-iodonaphthalene-1-sulphonyl)-1H-hexahydro-1,4-diazepine hydrochloride] were found to inhibit superoxide (O2-) release from stimulated neutrophils. The concentrations of ML-7 that were inhibitory were substantially lower than those reported for a selective antagonist of protein kinase C [i.e. H-7; 1-(5-isoquinolinesulphonyl)-2-methylpiperazine dihydrochloride]. ML-7 also reduced the phosphorylation of the 47 kDa subunit of the NADPH-oxidase system (p47-phox) and blocked translocation of this protein to the Triton X-100-insoluble fraction in stimulated cells. Interestingly, ML-7 also inhibited O2- production in a cell-free system derived from neutrophils at concentrations similar to those that were effective in vivo. This cell-free system does not require ATP and is insensitive to all other inhibitors of protein kinases tested, including some highly effective against MLCK (i.e. staurosporine). Thus, the data suggest that ML-7 does not block O2- release by inhibiting a protein kinase but instead may interact directly with a subunit of the oxidase. The binding site for ML-7 may provide a valuable target for inhibiting the inflammatory properties of phagocytic leucocytes by naphthalenesulphonamides designed to lack activity against protein kinases.

Solubilization of glycosyl-phosphatidylinositol-anchored proteins in quiescent and stimulated neutrophils

In human neutrophils, alkaline phosphatase (AlkPase), a low-affinity receptor for IgG (FcRIIIB), and complement decay accelerating factor (DAF) are glycosyl-phosphatidylinositol (GPI)-anchored proteins. Varying greatly in biological function these three integral membrane proteins exhibit regulated cell surface expression in neutrophils. Defined by their common membrane-linkage motif, AlkPase, FcRIIIB, and DAF can be released from the lipid bilayer by the action of phosphatidylinositol-specific phospholipase C and are relatively resistant to low temperature extraction with Triton X-100 (TX-100). In this study we show that neutrophil AlkPase, FcRIII, and DAF display differential extractibility; they are relatively insensitive to TX-100 solubilization at 4 degrees C, but are readily extracted with TX-100 at 37 degrees C or by the detergent octyl glucoside at 4 degrees C. The differential extractibility of these GPI-anchored proteins is the same in unstimulated cells, where these proteins exist primarily in an intracellular pool, and stimulated cells, where they are expressed principally at the cell surface. However, no differential extraction effect is observed with two neutrophil transmembrane proteins, complement receptor 1 (CD35, CR1) and MHC Class I in either stimulated or unstimulated cells.

A variant X-linked chronic granulomatous disease patient (X91+) with partially functional cytochrome b

Genetic analysis of a patient with the variant cytochrome b-245-positive form of chronic granulomatous disease revealed a missense mutation resulting in a Arg54-->Ser substitution in the gp91phox subunit of cytochrome b-245. As a consequence, although no O2- is made, NADPH oxidase-associated FAD accepts electrons from NADPH in the cell-free activation system and becomes reduced. The reduced flavin exhibits normal levels of iodonitrotetrazolium violet diaphorase activity, and the patient's neutrophils exhibit high levels of intracellular oxidant production and show a low level of NBT staining in the NBT slide test. Thus, this mutation appears to render the heme center of NADPH oxidase present but nonfunctional, while leaving the flavin center fully functional.

Requirement for posttranslational processing of Rac GTP-binding proteins for activation of human neutrophil NADPH oxidase

Rac1 and Rac2 are closely related, low molecular weight GTP-binding proteins that have both been implicated in regulation of phagocyte NADPH oxidase. This enzyme system is composed of multiple membrane-bound and cytosolic subunits and when activated catalyzes the one-electron reduction of oxygen to superoxide. Superoxide and its highly reactive derivatives are essential for killing microorganisms. Rac proteins undergo posttranslational processing, primarily the addition of an isoprenyl group to a carboxyl-terminal cysteine residue. We directly compared recombinant Rac1 and Rac2 in a human neutrophil cell-free NADPH oxidase system in which cytosol was replaced by purified recombinant cytosolic components (p47-phox and p67-phox). Processed Rac1 and Rac2 were both highly active in this system and supported comparable rates of superoxide production. Under different cell-free conditions, however, in which suboptimal amounts of cytosol were present in the assay mixture, processed Rac2 worked much better than Rac1 at all but the lowest concentrations. This suggests that a factor in the cytosol may suppress the activity of Rac1 but not of Rac2. Unprocessed Rac proteins were only weakly able to support superoxide generation in either system, but preloading of Rac1 or Rac2 with guanosine 5'-O-(3-thio-triphosphate) (GTP gamma S) restored activity. These results indicate that processing is required for nucleotide exchange but not for interaction with oxidase components.

Regulation of phagocyte oxygen radical production by the GTP-binding protein Rac 2

A major action of the microbicidal system of human neutrophils is the formation of superoxide anion (O2-) by a multicomponent oxidase that transfers electrons from the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) to molecular oxygen. The mechanism of assembly and activation of the oxidase from its cytosolic and membrane-bound components is unknown, but may require the activity of a guanosine 5'-triphosphate (GTP)-binding component. A cytosolic GTP-binding protein (Gox) that regulates the NADPH oxidase of neutrophils was identified. Gox was purified and shown to augment the rate of O2- production in a cell-free oxidase activation system. Sequence analysis of peptide fragments from Gox identified it as Rac 2, a member of the Ras superfamily of GTP-binding proteins. Antibody to a peptide derived from the COOH-terminus of Rac 2 inhibited O2- generation in a concentration-dependent manner. These results suggest that Rac 2 is a regulatory component of the human neutrophil NADPH oxidase, and provide new insights into the mechanism by which this oxygen radical-generating system is regulated.

Staurosporine inhibits the soluble and membrane-bound protein tyrosine kinases of human neutrophils

Superoxide production by neutrophils triggered with a chemotactic peptide or a phorbol ester is inhibited by the protein kinase antagonists staurosporine or 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). We evaluated the effects of these antagonists on the protein tyrosine kinases and protein kinase C activities of neutrophils. Staurosporine completely inhibited all of these enzymes, whereas 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine was only substantially effective against protein kinase C. Thus, if a protein tyrosine kinase is involved in superoxide production, it is likely to function with a second kinase sensitive to 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine.

A simple method for ultrastructural enzyme cytochemistry on small volumes and numbers of isolated cells

A simple technique is described for ultrastructural enzyme cytochemistry using small volumes and numbers of single cells. Small aliquots (1-5 microliters) of single cells suspended in a glutaraldehyde fixative are incubated on poly-L-lysine-coated glass coverslips. Cells in contact with the coated coverslip become immobilized to that support. All changes of solutions are accomplished without repeated centrifugation.

Functional defect in neutrophil cytosols from two patients with autosomal recessive cytochrome-positive chronic granulomatous disease

The kinetics of activation of the respiratory burst oxidase in the cell-free oxidase-activating system have been explained by a three-stage mechanism in which the membrane-associated oxidase components M: (a) take up a cytosolic factor S to form a complex M.S that is (b) slowly converted in the second stage to a precatalytic species [M.S]*, which finally (c) takes up two more (possibly identical) cytosolic components, C alpha and C beta, to successively generate [M.S]*C alpha, a low-activity (i.e., high Km) oxidase, and finally [M.S]*C alpha C beta, the ordinary (i.e., low Km) oxidase (Babior, B.M., R. Kuver, and J.T. Curnutte. 1988. J. Biol. Chem. 263:1713-1718). Studies with the cell-free oxidase-activating system from normal neutrophils and from neutrophils obtained from two patients with type II (autosomal recessive cytochrome-positive) chronic granulomatous disease (CGD) have suggested that (a) the defective element in the cytosol from patient neutrophils is S; (b) in normal neutrophil cytosol, S is limiting with respect to M; and (c) C alpha and C beta interact cooperatively with the activated precursor complex [M.S]*. It was further speculated that S might be identical to the nonphosphorylated progenitor of the phosphorylated 48-kD proteins that are missing in certain forms of CGD, and that other forms of type II CGD besides the one described in this report remain to be discovered.

Evidence that de novo protein synthesis participates in a time-dependent augmentation of the chemotactic peptide-induced respiratory burst in neutrophils. Effects of recombinant human colony stimulating factors and dihydrocytochalasin B

We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O2- production by neutrophils. We confirmed a time dependent augmentation of O2- production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O2- production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O2- -production that was first evident at 2 hours. The fall in O2- -forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O2-, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils.

Cell surface dynamics of neutrophils stimulated with phorbol esters or retinoids

Neutrophils undergo rapid morphological changes as well as metabolic perturbations when stimulated with certain phorbol esters. Stimulated cells initially exhibit pronounced projections emanating from the cell bodies, followed by rounding of the cells, reduction in granule number, and the appearance of intracellular vesicles. We show these vesicles to be derived, at least in part, from the plasmalemma. The experimental approach involved labeling stimulated and unstimulated cells with native ferritin and cationized ferritin, along with the cytochemical localization of ecto-5'-nucleotidase. The labeling patterns of the vesicles indicate that these structures are involved in both phorbol ester-stimulated adsorptive and fluid-phase endocytosis. Neutrophils stimulated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) exhibit two distinct rates of superoxide release in which the second, prolonged level is approximately 50% of the initial rate. All-trans-retinal, which we have recently shown to stimulate O2- release but not granule exocytosis or cell vesiculation, induces a single prolonged rate of maximal O2- release. Neutrophils treated with both all-trans-retinal and TPA exhibit only a single sustained rate of maximal O2- release similar to that observed with all-trans-retinal alone. Moreover, treatment of cells with all-trans-retinal blocks the vesiculation of neutrophils induced by TPA in a dose-dependent manner. This observation provides a possible explanation for the differences in the kinetics of superoxide release.

Augmentation of interleukin-2 release by cytochalasins

Augmentation of mitogen-induced release of the T cell lymphokine interleukin-2 (IL-2) occurred using several cytochalasins in coculture with a T cell lymphoma line (JM) or with purified T cells. When added concurrently with mitogen, cytochalasins had no apparent negative effect either on the ability of mitogen to signal IL-2 production or on the total amount produced. Use of cytochalasins that affect submembranous actin in peripheral lymphocytes established a link between cytoskeletal alterations and lymphokine release, although direct membrane perturbation cannot be excluded. These data indicate that an intracellular pool of IL-2 may accumulate in both T cell lines and in purified peripheral T cells and that maintenance of that pool may be affected by alterations of the cytoskeletal elements. Cytochalasins not only increased IL-2 release, but could substitute for phorbol myristic acetate (PMA) in supporting mitogen-signaled IL-2 production. We interpret these data also to indicate that cytoskeletal attachment to the surface molecules that signal IL-2 production is not needed for the activation.

Retinoids stimulate the release of superoxide by neutrophils and change their morphology

All-trans-retinal stimulated the release of superoxide by human and guinea pig neutrophils 63 +/- 14 SD and 53 +/- 5 SD nmol of O2-/min/10(7) cells, respectively. Superoxide release by unstimulated cells was negligible. All-trans-retinal also induced morphological changes (i.e., evaginations) in these cells. Other retinoids were effective in instigating these phenomena. The similarities of these effects to those instigated by cis-unsaturated fatty acids (Badwey, J.A., et al., 1984, J. Biol. Chem., 259:7870-7877) are discussed in light of possible mechanisms.

Activation of human neutrophil nicotinamide adenine dinucleotide phosphate, reduced (triphosphopyridine nucleotide, reduced) oxidase by arachidonic acid in a cell-free system

Sonicates from unstimulated human neutrophils produce no measurable superoxide since the superoxide-generating enzyme, NADPH oxidase, is inactive in these preparations. Previous attempts to activate the oxidase in disrupted cells with conventional neutrophil stimuli have been unsuccessful. This report describes a cell-free system in which arachidonic acid (82 microM) was able to activate superoxide generation that was dependent upon the presence of NADPH and the sonicate. For activation to occur, both the particulate and supernatant fractions of the sonicate must be present. Calcium ions, which are required for activation of intact neutrophils by arachidonate, were not necessary in the cell-free system. In quantitative terms, the superoxide-generating activity in the cell-free system could account for at least 20-50% of the superoxide rate observed in intact neutrophils stimulated with arachidonate. Sonicates from patients with chronic granulomatous disease (CGD) could not be activated by arachidonic acid in the cell-free system. In three patients representing both genetic forms of CGD, the defect appeared to reside in the particulate fraction. The soluble cofactor was normal in all three patients and could be used to activate normal neutrophil pellets in the presence of arachidonic acid. Thus, at least a portion of the activation mechanism in the neutrophil, that residing in the soluble phase, appeared to be normal in patients with CGD.