Receptor-mediated regulation of superoxide production in human neutrophils stimulated by phorbol myristate acetate

Selective and sensitive superoxide detection with a new diselenide-based molecular probe in living breast cancer cells

A diselenide-based BODIPY probe was prepared; it was found to be sensitive and selective for superoxide in giving [-Se(O)Se(O)-] oxidation. Probing was reversible through the use of biothiols; (77)Se NMR and other types of spectroscopy were employed. Practical medicinal utility was demonstrated in MCF-7/ADR cancer cells.

Changes in the innate immune response of Atlantic salmon, Salmo salar L., exposed to experimental infection with Neoparamoeba sp

An experiment was conducted to determine the effect of Neoparamoeba sp. infection on the innate immune responses of Atlantic salmon. Atlantic salmon were experimentally infected with Neoparamoeba sp. and serially sampled 0, 1, 4, 6, 8 and 11 days post-exposure (dpe). Histological analysis of infected fish gill arches identified the presence of characteristic amoebic gill disease lesions as early as 1 dpe with a steady increase in the number of affected gill filaments over time. Immune parameters investigated were anterior kidney phagocyte function (respiratory burst, chemotaxis and phagocytosis) and total plasma protein and lysozyme. In comparison with non-exposed control fish basal respiratory burst responses were suppressed at 8 and 11 dpe, while phorbol myristate acetate-stimulated activity was significantly suppressed at 11 dpe. Variable differences in phagocytic activity and phagocytic rate following infection were identified. There was an increase in the chemotactic response of anterior kidney macrophages isolated from exposed fish relative to control fish at 8 dpe. Total protein and lysozyme levels were not affected by Neoparamoeba sp. exposure.

Resveratrol modulates rat macrophage functions

This study investigated the effects of trans-resveratrol (trans-3,4',5-trihydroxystilbene, RESV), a natural polyphenol from grapes with known antioxidant activity, on the respiratory-burst responses and phagocytic activity of rat macrophages. RESV at concentrations of 1-10 microM significantly and dose-dependently inhibited (a) the extracellular production of reactive oxygen intermediates (ROls) by resident peritoneal macrophages stimulated with phorbol 12-myristate 13-acetate (PMA) (a potent activator of protein kinase C, PKC) and (b) intracellular production of ROIs after opsonin-independent phagocytosis of Kluyveromyces lactis cells. Over the 10-100 microM concentration ranges, RESV likewise inhibited the production of reactive nitrogen intermediates (RNIs) by macrophages stimulated with thioglycollate. RESV concentrations above 10 microM also dose-dependently inhibited the phagocytosis of K. lactis cells. The results obtained demonstrate that RESV is a potent inhibitor of the antipathogen responses of rat macrophages and, thus, suggest that this agent may have applications in the treatment of diseases involving macrophage hyperresponsiveness.

The mechanisms of serum-treated zymosan (STZ)-induced oxidative metabolism by human eosinophils and the effects of IL-5 priming

BACKGROUND

The aim of this work was to study the mechanisms of action of IL-5 on the subsequent stimulation of the oxidative metabolism of blood eosinophils by serum-treated zymosan (STZ), in terms of signal transduction characteristics, and by comparing the response of cells from healthy and allergic subjects during environmental exposure to birch pollen.

METHODS

Eosinophils from healthy controls and allergic patients were purified to over 95% by Percoll gradients and the MACS system. Oxidative metabolism was measured by a lucigenin-enhanced chemiluminescence (CL) assay. Eosinophils were primed with IL-5 and subsequently stimulated with STZ. The signal transduction mechanisms of IL-5 priming were studied with the MEK inhibitor PD 98059,the PkC inhibitors staurosporine and Ro 318220, and the PI3 kinase inhibitor wortmannin.

RESULTS

IL-5 increased the maximum radical production (P=0.0079) and reduced the t(1/2) rise (0.000018) of the CL reactions. The t(1/2) rise was PkC dependent and MEK independent, while the maximum radical production was PkC, MEK, and PI3 kinase dependent. During the pollen season, IL-5 reduced the total STZ-induced CL response in the patients' cells (P=0.016), but not in the control cells, whereas it primed the response to STZ of both cell populations in terms of the t(1/2) rise (P=0.012 and 0.00066, respectively).

CONCLUSION

STZ-induced oxidative metabolism consists of different stages. The initial stage (t(1/2) rises of the curves) is PkC dependent and MEK independent, while the end stage (maximum radical production) is PkC, MEK, and PI3 kinase dependent. IL-5 shortened the initial stage, and increased the end stage. During allergen exposure, however, the end stage was reduced by IL-5. This could be due to increased amounts of hypodense eosinophils and/or some abnormality in cell responses.

Ultracytochemical study on the localization of superoxide producing sites in stimulated rat neutrophils

Superoxide anion production in neutrophils plays an important role in the microbicidal defense system in the body. In this study, isolated rat neutrophils were stimulated experimentally and examined by electron microscopy to determine the site of superoxide production and its subsequent translocation during different cell stimulation time periods. Blood and peritoneal neutrophils were incubated for periods of 5, 10, and 15 min with phorbol 12-myristate 13-acetate (PMA), N-formyl-Met-Leu-Phe (fMLP), and combinations of PMA and cytochalasin B (CB) and fMLP and CB. Ultracytochemical detection of O(2)(-) was performed with the 3, 3'-diaminobenzidine-manganese (DAB/Mn) cytochemical method and cationized ferritin (CF) particles were added to stimulation media to monitor endocytotic events that occurred during neutrophil stimulation. Unstimulated neutrophils were devoid of O(2)(-) activity in cytoplasmic granules and at the plasma membrane surface. After 5 min stimulations with PMA, PMA + CB, or fMLP + CB, electron-dense DAB/Mn reaction product was detected in small, centrally located tubular compartments within the neutrophils. CF particles which were added to the stimulation media became internalized in endocytotic vesicles after 5 min stimulation; these vesicles were devoid of O(2)(-) activity. At 10 min stimulation with PMA, O(2)(-)-positive granules subsequently fused with each other and translocated to sub-plasma membrane regions where they either contacted the plasma membrane or fused with CF-containing endocytotic vesicles. Little reaction product was observed on the surface of the neutrophils. Spectrophotometric comparison of the stimulatory effects of PMA, fMLP, and fMLP + CB revealed different rates and yields of O(2)(-) production. Results from this study suggest that the O(2)(-)-producing sites of rat neutrophils originate intracellularly and translocate to the plasma membrane surface following stimulation with PMA, PMA + CB, and fMLP + CB, but not with fMLP or CB alone. Furthermore, these compartments appear to possess the ability to fuse with endocytotic vesicles, a process that may be linked to intracellular microbicidal activity in circulating and tissue neutrophils.

Protein kinase C mediates experimental colitis in the rat

Protein kinase C (PKC) plays an important role in the cell signal transduction of many physiological processes. In contrast to these physiological responses, increases in PKC activity have also been associated with inflammatory disease states, including ulcerative colitis. The objective of this study was to examine the role of PKC as a causative mediator in initiation of experimentally induced colitis in the rat. Colitis was induced in rats by intrarectal (0.6 ml) instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS; 75 mg/kg in 50% ethanol) or the PKC activator phorbol 12-myristate 13-acetate (PMA; 1.5-3.0 mg/kg in 20% ethanol). Gross and histological mucosal damage, mucosal neutrophil infiltration, mucosal PKC activity, and PKC protein content for PKC isoforms alpha, beta, delta, and epsilon were assessed 2 h to 14 days after an inflammatory challenge. Both PKC activity and mucosal injury increased significantly within 4 h of TNBS treatment. PKC activity was maximal at 7 days and declined at 14 days, whereas mucosal damage became maximal at 1 day and declined after 7 days. In contrast, neutrophil infiltration as assessed by myeloperoxidase activity only increased 12 h after TNBS treatment, became maximal 1 day after TNBS administration, and declined thereafter. PKCbeta, -delta, and -epsilon were increased in response to TNBS, whereas PKCalpha protein content was decreased. The PKC antagonists staurosporine and GF-109203X (25 ng/kg iv) reduced TNBS-induced changes in mucosal PKC activity and the degree of mucosal damage. In contrast, neutropenia induced by antineutrophil serum treatment did not significantly affect the degree of injury or mucosal PKC activity. Furthermore, activation of mucosal PKC activity with PMA also induced mucosal damage, which was also inhibited by pretreatment with a PKC antagonist. In conclusion, these results suggest that increases in PKC activity play a causative role in TNBS-induced colitis. The PKC-mediated response to TNBS does not appear to involve neutrophil infiltration.

Effect in vitro of gamma interferon and interleukin-10 on generation of oxidizing species by human granulocytes

We examined the effect of interleukin-10 (IL-10), gamma interferon (IFN-gamma), phorbol ester (PDB), opsonized zymosan (OZ) and aminophylline (a cAMP phosphodiesterase inhibitor) on the reducing power and oxidizing species generation by human neutrophils, using MTT dye reduction and luminol-dependent chemiluminescence assays, respectively. Gamma interferon (IFN-gamma), phorbol ester (PDB) and opsonized zymosan (OZ) were activators while interleukin-10 (IL-10) and aminophylline were inhibitors. A strong parallelism was observed between oxidizing species generation and cellular reducing power in both activation and inhibition experiments. Our results also demonstrate for the first time the effect of IL-10 on free radical generation by neutrophils. The consequence of these activating and inhibiting effects on the inflammatory process are discussed.

Dexamethasone and methylprednisolone affect rat peritoneal phagocyte chemiluminescence after administration in vivo

Production of reactive oxygen compounds by peritoneal monocytes/macrophages was studied in rats exposed to dexamethasone or methylprednisolone in the drinking water. Luminol-amplified chemiluminescence was measured in preparations of peritoneal leukocytes activated ex vivo by serum opsonized zymosan, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) or phorbol 12-myristate 13-acetate (PMA). After dexamethasone administration for 1 day (approximately 0.13 mg/kg per 24 h) a significant reduction in chemiluminescence was found in cells stimulated with serum opsonized zymosan, while responses to fMLP and PMA stimulation were significantly reduced after 2 days. The maximal inhibition obtained after 5-8 days of dexamethasone administration (plasma levels < 5 nM) was 92.0 +/- 1.2%, 87.6 +/- 0.2% and 84.5 +/- 3.1% in cells stimulated with serum opsonized zymosan, fMLP and PMA, respectively. Administration of dexamethasone or methylprednisolone for 48 h gave a dose-dependent reduction of chemiluminescence. ED50 values of dexamethasone were estimated at 0.06-0.15 mg/kg for the different stimulators (plasma concentrations 5-10 nM). Estimated ED50 values for methylprednisolone were 35-36 mg/kg. Since the percentage of mononuclear phagocytes in the peritoneal cell population did not change significantly with dose or time of dexamethasone exposure, this study indicates that glucocorticoids have a depressive effect on the monocyte/macrophage 'respiratory burst' in vivo. The results are consistent with the hypothesis that these effects are mediated by glucocorticoid receptors. Although the pathway activated by serum opsonized zymosan was more rapidly inhibited than the fMLP- and PMA-activated pathways, the responses induced by the different stimulators were similarly affected, suggesting a modulation of common components in the activation pathways, possibly protein kinase C or the NADPH-oxidase complex, after administration of low pharmacological doses of glucocorticoids in vivo.

Phorbol myristate acetate ex vivo model of enhanced colonic epithelial permeability. Reactive oxygen metabolite and protease independence

The initiating mechanisms involved in colonic injury are currently unknown. The goal of the current study was to examine the role of the inflammatory mediators reactive oxygen metabolites and proteases in an ex vivo model of selective epithelial permeability. Rats were prepared with exteriorized colonic chambers to which the protein kinase C (PKC) activator phorbol myristate acetate (PMA) was added in doses ranging from 5 to 800 micrograms. PMA caused a dose-dependent transient increase in epithelial permeability, but had no significant effect on microvascular permeability. There was no accumulation of neutrophils and no apparent histological changes. PMA acts via a PKC-dependent mechanism, as assessed using the PKC-inactive phorbol analog 4 alpha-phorbol didecanoate, and the response is tachyphylactic. The mechanism is independent of reactive oxygen metabolites and proteases, as shown by the lack of effect of the free radical scavengers superoxide dismutase and catalase and the general serine protease inhibitor soybean trypsin inhibitor. The classic inflammatory process does not appear to be involved in the PMA-induced epithelial permeability changes. This finding suggests that noninflammatory mechanisms may regulate the increased epithelial permeability induced by PMA. Further study to elucidate these mechanisms is of importance for understanding both normal gastrointestinal physiology and initiation of pathology.

Neutrophil-independence of the initiation of colonic injury. Comparison of results from three models of experimental colitis in the rat

Although the role of neutrophils in the pathogenesis of several forms of gastrointestinal injury has been well demonstrated, their role in the development of experimental colonic injury is less clear. To examine whether neutrophils play a role in the development of experimental colitides, the effects of a sustained neutropenia on multiple indices of colonic injury in rats was examined 24 hr following the initiation of colitis with the intrarectal application of acetic acid, trinitrobenzene sulfonic acid (TNBS)-ethanol, or the potent proinflammatory agent, phorbol-12-myristate-13-acetate (PMA). In comparison to animals with normal neutrophil counts and colitis induced by any of the three agents, no attenuation in macroscopic damage or histopathologic injury was observed in neutropenic animals exhibiting a greater than 95% reduction in circulating neutrophils and 85% reduction in tissue-associated myeloperoxidase activity. Although the tissue edema associated with acetic acid or PMA-induced colitis was not reduced by neutropenia, the colonic edema associated with TNBS colitis was attenuated by prior neutrophil depletion with anti-neutrophil antiserum. Despite our initial hypothesis that neutrophils played a key role in the genesis of experimental colitis (especially that induced by PMA), the results demonstrated that these cells are not essential for the development of the major pathological features of colitis induced by this agent, acetic acid, or TNBS. Although these results support the proposal that in these models of colitis, inflammation develops secondary to injury (rather than the converse), further studies will be necessary to elucidate the role of inflammatory cells other than neutrophils in the genesis of experimental colitides.

Staurosporine up-regulates the expression of phorbol dibutyrate binding sites in human platelets

Tumor-promoting phorbol esters bind to and activate protein kinase C (PKC). Staurosporine, a potent PKC inhibitor, interferes with PKC catalytic activity without altering phorbol ester binding sites in cell-free systems. We found that, unlike cell-free systems, treatment of intact platelets with staurosporine enhances the expression of phorbol 12, 13-dibutyrate (PDBu) binding sites. Incubation of platelets at 37 degrees with staurosporine (25 nM to 1 microM and 2 nM tritiated PDBu ([3H]PDBu) increased the amount of [3H]PDBu specifically bound to intact platelets by approximately 10 to 200% of control values. This effect was rapid and plateaued after 10 min of cell treatment. Scatchard analysis of the data showed that staurosporine (500 nM) significantly increased the total binding capacity Bmax from 42.9 +/- 15.4 x 10(3) to 78 +/- 7.3 x 10(3) sites per platelet and reduced the apparent dissociation constant value Kd from 30.8 +/- 8.6 nM to 9.4 +/- 3.4 nM. Enhanced PDBu binding capacity and affinity were also observed with human mononuclear and polymorphonuclear leukocytes. Fractionation of staurosporine-treated platelets showed an increased binding capacity of the particulate fraction (102%) and decreased binding capacity of the soluble fraction (60%) compared to controls, with no change in the affinity of PDBu binding to these fractions. Chelation of internal calcium with BAPTA did not significantly attenuate the staurosporine-mediated rise in PBDu binding but prevented the platelet-activating factor-induced response, indicating that cytosolic calcium does not play an important role in these staurosporine effects. These results show that, in addition to interfering with PKC protein-phosphorylating activity, staurosporine enhances PDBu binding affinity and capacity in intact platelets. This latter effect appears to be due to translocation of soluble PDBu binding sites, presumably PKC units.

Action of the 4-nitro-2-phenoximethanesulphonanilide (nimesulide) on neutrophil chemotaxis and superoxide production

4-nitro-2-phenoximethanesulphonanilide (nimesulide) is a nonsteroidal anti-inflammatory agent that has been employed in the treatment of inflammatory diseases because of its specific actions on the inflammatory response mechanisms caused by injury. The objectives of this paper were to determine the action of this agent on two notable neutrophil functions, chemotaxis and production of the superoxide anion. These two functions were studied after the neutrophils were pre-incubated with three different concentrations of 4-nitro-2-phenoximethanesulphonanilide (0.1; 0.3 and 0.5 mN). The results obtained herein demonstrated that 4-nitro-2-phenoximethanesulphonanilide-exposed peripheral blood neutrophils from healthy subjects produced significantly less superoxide when challenged by phorbolmirystate acetate (PMA at 50 ng/ml) or formy-methionil-leucyl-phenilalanine (FMLP 10-7 M) and opsonizided zymozan (1 mg/ml). Additionally, the agent was equally effective in reducing the PMN chemotoaxis when challenged by C5a factor (2% zimozan activated solution), FMLP 10-9 M and leukotrien (3.10-7 M). The results obtained suggest that in addition to its interference in the metabolism of the aracdonic acid, the 4-nitro-2-phenoximethanesulphonanilide may interfere in a more direct fashion with the neutrophil function. This specific action may contribute to its anti-inflammatory activity.

Respiratory burst reaction changes with age in rat peritoneal macrophages

The respiratory burst reaction, estimated as O2.- production, has been studied in rat peritoneal macrophages of different age (3, 12 and 24 months). To stimulate NADPH oxidase, the enzyme responsible for the respiratory burst, various stimuli that act in different ways have been used: PMA (phorbol myristate acetate), Con-A (concanavalin A) and N-FMLP (N-formyl-methionyl-leucyl-phenylalanine). All produced a decrease in response with age, with that from PMA being the greatest. The PMA-induced decrease in the O2.- production may be related to the inactivation of NADPH-producing enzymes such as glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase that we have found with age. Glutathione reductase, an enzyme that participates in the maintenance of the redox status in the cell, also showed an age-related decrease. Enzymes that participate in oxygen species scavenging, such as glutathione peroxidase and Cu/Zn superoxide dismutase, did not change with age, although an age-related decrease in catalase activity was found.

A protein kinase inhibitor, staurosporine, enhances the expression of phorbol dibutyrate binding sites in human polymorphonuclear leucocytes

Staurosporine, a potent protein kinase C (PKC) inhibitor, was studied for its effects on the binding of phorbol 12,13-dibutyrate (PDBu) to human polymorphonuclear leucocytes (PMNs). Treatment of PMNs with staurosporine concentrations in the range 50 nM-2 microM at 37 degrees C (but not at 4 degrees C) and with 1 nM [3H]PDBu at both temperatures enhanced specific PDBu binding to PMNs by approx. 10-600% relative to control values. The potentiation was rapid (detectable within 1 min) and reached a plateau after 10 min of cell treatment. Scatchard analysis of the binding showed that staurosporine increased the total number of PDBu-binding sites (Bmax) from (178 +/- 9) x 10(3) (control) to (324 +/- 15) x 10(3) sites per PMN and lowered the apparent dissociation constant (Kd) from 9.6 +/- 0.8 (control) to 3.3 +/- 0.3 nM. In Ca(2+)-depleted cells, staurosporine induced similar changes in Kd values, whereas the Bmax. increased by 60%. Treatment of PMNs with 500 nM staurosporine enhanced PDBu binding in the particulate fraction by 120 +/- 7% and decreased PDBu binding in the soluble fraction by 69 +/- 4%, whereas PKC histone-phosphorylating activity of both fractions was almost completely inhibited. Incubation of staurosporine-pretreated particulate fractions with soluble fractions enriched the particulate fraction in PDBu-binding sites at the expense of the soluble fraction, without altering the binding affinity of PDBu for either fraction. Stimulation of PMNs with chemotactic N-formyl peptides induced a transient increase in PDBu binding. This effect was potentiated by approx. 52% by staurosporine. These results show that, in addition to its interference with PKC protein-phosphorylating activity, staurosporine enhances both PDBu-binding capacity and affinity to PMNs, through a mechanism involving Ca(2+)-dependent and -independent processes. Alterations of PDBu binding to soluble and particulate fractions suggest that the enhanced binding capacity in intact PMNs may be due to translocation of PDBu receptors, presumably PKC units. This phenomenon may affect PKC-dependent cellular responses mediated by physiological stimulation.

Mechanism of hydrogen peroxide-induced inhibition of sheep airway cilia

To study the effect of the inflammatory mediator hydrogen peroxide (H2O2) on airway ciliary activity, we measured ciliary beat frequency (CBF) in cultured tracheal explants from sheep. Addition of H2O2 (10(-8) to 10(-4) M) produced a concentration-dependent mean (+/- SEM) decrease in CBF between 11.1 +/- 0.4% (P less than 0.01) and 100 +/- 0% (P less than 0.001); at each concentration, the maximal effect was reached by 20 to 25 min. Between 10(-8) and 10(-6) M H2O2, the decrease in CBF was reversible, lactate dehydrogenase (LDH) release was not significantly increased, and major morphologic lesions were not seen. At higher concentrations of H2O2, incomplete recovery of CBF (10(-5) M) or irreversible ciliostasis (10(-4) M) developed, and a significant increase in LDH and morphologic lesions were present. Catalase (2,000 U/ml) and H-7 (10(-5) M), a protein kinase inhibitor, abolished cilioinhibition produced by H2O2 at 10(-6) M and lower concentrations but not at 10(-5) M and higher concentrations. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, caused a dose-dependent (10(-11) to 10(-5) M), reversible decrease in CBF; this effect was abolished by H-7. We suggest that at nonlethal concentrations, H2O2 inhibits the beat frequency of airway epithelial cilia reversibly, through the activation of second messengers, including protein kinase C. This mechanism might contribute to the previously demonstrated impairment of mucociliary clearance in airway inflammation.

Beta-naphthylamine induces anion superoxide production in rat peritoneal macrophages

Rat peritoneal macrophages were incubated in the presence of beta-naphthylamine (beta-NA), a well known carcinogenic agent, and some parameters of respiratory burst were studied. beta-NA induced a time- and dose-dependent stimulation of superoxide anion (O-2) production, and this enhancement was suppressed by the addition of superoxide dismutase enzyme. Also, no cooperative effect between beta-NA and phorbol 12-myristate 13-acetate was observed. Other observations were as follows: (i) the simultaneous presence of polymyxin B, and staurosporine inhibitors of protein kinase C, inhibited beta-NA-dependent O-2 production; (ii) NADPH-oxidase contained in postnuclear fraction from beta-NA-incubated macrophages showed a greater activity than control fractions; (iii) the stimulation of O-2 production elicited by beta-NA was several-fold enhanced in activated macrophages compared to resident cells. These data suggest that beta-NA produces the activation of NADPH-oxidase through protein kinase C.

Toxicodynamics of tumour promoters of mouse skin. II. Binding to protein kinase C of some new diterpene esters and induction of luminol-enhanced chemoluminescence in mouse peritoneal neutrophils

In binding competition assays using a protein kinase C preparation from mouse brain (particulate fraction) 3H-labelled 12-O-tetradecanoylphorbol-13-acetate (TPA), for a series of new diterpene esters (DTE) the relative binding affinity [rba = Kia(TPA)/Kia(DTE)] in relation to TPA was determined. A wide range of values was noticed, some of the DTE binding more strongly than TPA (rba greater than 1), others binding less strongly than TPA (rba less than 1) In comparative terms, competition for specific binding sites appears to correlate better with irritant than with promoting activity of the DTE. Using mouse peritoneal neutrophils, binding of [3H]-TPA was determined by a modification of the "cold-acetone filter assay"; saturation of high-affinity sites (Kda = 0.2 nM) was obtained at concentrations less than or equal to 1 nM, but there was also evidence for specific binding at "low-affinity" sites (Kda = 26 nM). Induction of chemoluminescence in the presence of luminol in mouse peritoneal neutrophils with a set of DTE usually elecited two peaks; at concentrations greater than or equal to 10 nM DTE a short-lived, "spike-like" response lasting only from 0 to about 5 min (phase A) its followed by a "plateau" response from about 5-120 min (phase B). This latter phase of chemoluminescence stimulation with luminol correlated well with the irritant potential of the DTE used. The sequence of the two phases can be inverted partially by using first TPA at 2,5 nM followed by a quick concentration increase to 100 nM; this indicates two different concentration-dependent events. As regards the intensity of the chemoluminescent response, quantitative but not qualitative differences between DTE were observed, which show some correlation with strong and weak tumour-promoting activity. Inhibition studies suggest the involvement of the myeloperoxidase/H2O2/Cl- system in the luminogenic response; it is suggested that the release of hypochlorite or a closely related oxidant may be instrumental in tumour promotion.

TPA and resiniferatoxin-mediated activation of NADPH-oxidase. A possible role for Rx-kinase augmentation of PKC

The non-tumour promoting irritant, resiniferatoxin, was capable of activating the NADPH-oxidase respiratory burst of starch-elicited, but not resident mouse peritoneal macrophages in vitro. Unlike TPA, the response was synergised by incubation with zymosan. The Rx-stimulated NADPH-oxidase activity in a cell-free assay was selectively enhanced in the presence of exogenous Rx-kinase rather than PKC and in the absence of Ca2+. Since resiniferatoxin is a poor activator of PKC, it is probable that the Ca2(+)-independent Rx-kinase plays a role in activation of the macrophage respiratory burst following stimulation by zymosan.

Alterations in complement-induced shape change and stimulus-specific superoxide anion generation by neonatal calf neutrophils

Increased susceptibility of neonates to infection may be related to defects in newborn neutrophil (PMN) functional activities, including altered responses to complement fragments (Cf) and defective microbicidal activity. We therefore compared the kinetics of newborn and adult bovine PMN membrane shape change responses following stimulation with zymosan-activated plasma (ZAP) as a source of Cf. Measurement of PMN membrane shape change was a rapid, sensitive, and reproducible measure of Cf stimulation within a population of PMNs; a maximum of 67-85% of the PMNs exhibited easily detectable membrane ruffling, lamellipodia formation, and polarity within 2 min. Newborn PMNs exhibited significantly increased (P less than 0.01) membrane shape change at 20, 30, 60, 120, and 300 sec after Cf stimulation. A maximum of 85.8 +/- 3.2% of newborn PMNs exhibited such Cf-induced shape changes by 120 sec. which was significantly greater (P less than 0.01) than the maximum stimulation (67.7 +/- 4.3%) attained with adult PMNs. These data indicate enhanced kinetics of induced newborn PMN membrane shape change in response to Cf stimulation. We also compared stimulus-specific superoxide anion (O2-) generation as a measure of respiratory burst activity after incubation of newborn and adult PMNs with soluble (phorbol myristate acetate, PMA) and particulate (opsonized zymosan, OZ) stimuli. When PMA was used as the stimulus, newborn PMNs generated significantly less O2- (9.3 +/- 0.5 nmol O2-/10(6) PMN, P less than 0.05) than did adult PMNs (12.4 +/- 0.3 nmol O2-/10(6) PMN). This finding was reversed when OZ was used as the stimulus; newborn PMNs generated significantly more O2- (7.7 +/- 0.4 nmol O2-/10(6) PMN, P less than 0.05) than did adult PMNs (5.5 +/- 0.5 nmol O2-/10(6) PMN). These findings collectively document biochemical and morphological differences between newborn and adult PMNs as determined by stimulus-specific O2- generation and Cf-induced membrane shape change. Such differences may be important to neonatal disease susceptibility.

Inhibition of ciliary activity by phorbol esters in rabbit tracheal epithelial cells

To study the effect of protein kinase C activation on respiratory ciliary activity, we measured ciliary beat frequency (CBF) by a photoelectric technique in response to phorbol esters and cell-permeable diglyceride in cultured tracheal epithelial cells from rabbits. Phorbol 12-myristate 13-acetate (PMA) resulted in a concentration- and time-dependent inhibition of CBF (half maximum inhibitory concentration (IC50) = 3 x 10(-10) M) with the maximal decrease being 21.0 +/- 1.4% (mean +/- SE, p less than 0.001) observed at 10(-6) M. L-alpha-dioctanoylglycerol (DiC8), another known activator of protein kinase C, likewise reduced CBF in a dose-dependent fashion. In contrast, phorbol 12,13-didecanoate, a non-tumor-promoting phorbol ester that does not stimulate protein kinase C, produced no significant changes in CBF. The decrease in CBF induced by PMA was not affected by blockade of arachidonic acid metabolism with indomethacin and nordihydroguaiaretic acid, but was antagonized by pretreatment with H-7, a specific inhibitor of protein kinase C (p less than 0.01). Maximal ciliary inhibition with either PMA or DiC8 was not accompanied by a decrease in intracellular concentration of cyclic AMP. These results indicate that activation of protein kinase C has a significant depressive effect on ciliary activity, and hence the airway mucociliary transport function, presumably through a regulatory pathway that is not dependent on cyclic AMP or arachidonic acid metabolites.

Ceruloplasmin reduces the adhesion and scavenges superoxide during the interaction of activated polymorphonuclear leukocytes with endothelial cells

The plasma protein, ceruloplasmin, has been implicated as an anti-inflammatory agent, although this property has not been demonstrated unequivocally in vivo. The role of this protein in an in vitro system of cultured endothelial cells and polymorphonuclear leukocytes (PMNs) was investigated. One of the initial steps in an inflammatory response is increased adhesion between PMNs and the endothelial lining of the blood vessels. The results showed that ceruloplasmin interferes with this process and reduces the number of phorbol myristate acetate-activated leukocytes that adhere to endothelium. Preincubation of either the activated PMNs or the endothelium with ceruloplasmin did not produce the same results, suggesting that the continuous presence of ceruloplasmin is required. During attachment PMNs become activated and release a variety of substances, including toxic oxygen species such as superoxide and hydrogen peroxide. In the in vitro system used in this study no injury occurred to the endothelial cells, as measured by 51Cr release, when activated PMNs were added with ceruloplasmin. The data show that ceruloplasmin reduced, in a dose dependent manner, the levels of superoxide produced by the activated PMNs, further supporting ceruloplasmin's previously reported role as a scavenger of superoxide. Ceruloplasmin also reduced the levels of superoxide when activated PMNs were in contact with endothelial cells. Although ceruloplasmin interfered with the copper-dependent scavenger enzyme, superoxide dismutase (SOD), in a cell-free system, ceruloplasmin had no effect on SOD in intact endothelial cells. These results suggest that ceruloplasmin may act as an anti-inflammatory agent by reducing the number of PMNs attaching to endothelium and by acting as an extracellular scavenger of superoxide.

Synergism between protein kinase C activator and fatty acids in stimulating superoxide anion production in guinea pig polymorphonuclear leukocytes

Treatment of guinea pig polymorphonuclear leukocytes (PMNL) with various fatty acids elicited superoxide anion (O2-) production and an increase in intracellular Ca2+ [( Ca2+]i). Both responses, however, were seldom observed when PMNL were treated at lower concentrations. But, simultaneous addition of 1-oleoyl-2-acetylglycerol (OAG), a protein kinase C activator, caused an increase in O2- production even at the lower concentrations of fatty acids. In contrast to the synergism in O2- production, [Ca2+]i remained at almost the basal level irrespective of the presence of OAG. Among saturated fatty acids, those with carbon numbers of 14 to 18 were most effective in stimulating O2- production in combination with OAG. Unsaturated fatty acids with a carbon number of 18 were almost equally effective irrespective of the number of double bonds.

Modulation of polymorphonuclear leukocyte microbicidal activity and oxidative metabolism by fibrinogen degradation products D and E

Fibrinogen degradation products (FDP) D and E are typically present in blood of patients with disseminated intravascular coagulation and related conditions in which granulocyte (PMN) defense against bacterial infection may be compromised. This study was intended to determine whether FDP modify PMN functions critical to their bactericidal activity. Incubation of human PMN and Escherichia coli with 50-100 micrograms/ml FDP did not affect phagocytosis, but reduced by greater than 90% the cells' ability to inhibit bacterial colony growth compared with control PMN incubated with albumin or fibrinogen. FDP (10-100 micrograms/ml) inhibited PMN O2- release and chemotaxis stimulated by FMLP by 17-50% (P less than 0.005) and 41% (P less than 0.01), respectively. Fragment E3, and not fragment D1, was primarily responsible for inhibition of FMLP-induced PMN O2- release. Phorbol myristate acetate (10 ng/ml), 1-oleoyl-2-acetylglycerol (10(-6) M), AA (4.2 x 10(-5) M), and zymosan-activated serum-stimulated PMN O2- release were also decreased 37-63% by FDP compared with control protein. There are at least two mechanisms by which FDP may impair PMN responses. With respect to FMLP, FDP (16-100 micrograms/ml) inhibited specific binding to the cell surface over a ligand concentration range of 1.4-85 nM [3H]FMLP. In contrast, FDP did not effect the extent of phorbol ester binding to PMN but blocked activation of protein kinase C. These data suggest that elevated plasma FDP inhibit several PMN functions critical to the bactericidal role of these inflammatory cells.

Translocation of protein kinase C to subcellular fractions of human neutrophils

The subcellular localization of protein kinase C in unstimulated human neutrophils and neutrophils stimulated by phorbol-myristate-acetate (PMA), 1-oleoyl-2-acetyl-rac-glycerol (OAG), and ionomycin was investigated in subcellular fractions obtained by nitrogen cavitation and Percoll density gradient centrifugation. Protein kinase C was found to be localized mainly in the cytosol in unstimulated cells, whereas significant translocation to fractions containing the plasma membrane was observed after stimulation by PMA, OAG, and ionomycin. At the same time, phospholipid-insensitive protein kinase activity appeared in the cytosol and the plasma membrane fractions. To determine whether binding of protein kinase C occurred to the plasma membrane or to intracellular membranes that had translocated to the plasma membrane, we investigated the ability of isolated azurophil, specific and secretory granules, and plasma membrane vesicles to bind protein kinase C in response to addition of PMA and OAG. Only fractions containing plasma membranes and secretory granules were able to bind protein kinase C. The observation explains the selective activation of plasma membrane structures by protein kinase C.

Induction of Epstein-Barr virus early antigens by tumor promoters of the diterpene ester type in Raji cells and specific (receptor) binding as compared to irritant and promoting activities

Sixteen new diterpene esters (DTE) of the tigliane, ingenane, daphnane, and 1 alpha-alkyldaphnane types were investigated in two in vitro assays: as inhibitors of specific binding of 3H-labeled 12-O-tetradecanoylphorbol 13-acetate (TPA) to protein kinase C in a receptor preparation from mouse brain, and as inducers of Epstein-Barr virus (EBV) early antigens in Raji cells. Inhibition of binding of [3H]TPA to the receptor preparation by tigliane and ingenane DTE correlates with irritant activity in vivo, while some daphnane and 1 alpha-alkyldaphnane DTE inhibit binding of [3H]TPA in a less pronounced manner but still are very irritant. Tumor-promoting activity does not correlate consistently with the receptor-binding data. To test the hypothesis that early antigen induction in Raji cells by DTE is coupled to functional DTE receptors (protein kinase C), the latter were searched on these Raji cells by a 'cold acetone-filter assay' and shown to be present. The dependence of the early antigen induction rate on the concentration of the DTE tested was demonstrated. At a given concentration of DTE, differences in the induction rate between various DTE are seen. However, a clear quantitative correlation either between early antigen induction and receptor binding data in vitro, or early-antigen-inducing activity in vitro versus irritancy and tumor-promoting activity in vivo was not observed.

Further studies on a chemoattractant derived from Aleurites Fordii Hemsl. seed

1. Activities stimulatory to PMN superoxide generation and chemotactic function were present in two separate gel chromatographic fractions of AFH-S and were designated AFH-S1 (500 kD) and AFH-S2 (38 kD). 2. Characterization studies of these activities revealed physiologic and pharmacologic characteristics dissimilar to those of other previously studied chemoattractants such as bacterial peptide FMLP.

Albumin in monocyte function assays. Differential stimulation of superoxide or arachidonate release by calcium ionophores

Peripheral blood monocytes release superoxide (O2-) and arachidonic acid (AA) when stimulated with 12-O-tetradecanoate phorbol-13-acetate (TPA) or calcium ionophores (A23187 or ionomycin). In vitro assays of AA or O2- release performed in the presence of albumin failed to detect superoxide production when ionophore was used as the stimulating agent. Raising the concentration of ionophore or reducing the BSA concentration balanced one another in terms of detection of superoxide release. Binding of ionophore by albumin, which reduced the effective concentration of the stimulating agent, most likely accounted for this effect, but a small component could be attributed to calcium binding by albumin as well. These results indicate differing susceptibilities of monocyte functions to stimulation by increased intracellular Ca2+. Under strictly defined conditions, superoxide and arachidonate release may be assayed simultaneously. Binding of ionophores (and, by analogy, other agents) to albumin must be taken into account when determining stimulating doses for use in monocyte function assays.

Chemiluminescence in human whole blood: modulation by the cocarcinogens phorbol diester and polychlorobiphenyls

A human whole blood chemiluminescence (CL) assay was established using zymosan as cell activator. Aroclor 1254 was found to inhibit this CL response in a direct linear relation to its concentration, (50% inhibitory dose, (ID50) equal to 5 x 10(-4)M) in diluted blood samples of 10 normal human subjects. In comparison the ID50 of other inhibitors was 1.3 x 10(-3)M for ethylenediamine tetraacetic acid, 3.3 x 10(-3)M for ascorbic acid, 4 x 10(-3)M for reduced glutathione, 1.2 x 10(-1)M for ethanol, 2.5 x 10(-1)M for methanol and 3.7 x 10(-1)M for dimethyl sulfoxide. Using 12-o-tetradecanoyl-phorbol-13-acetate (TPA) as cell activator the CL response was likewise inhibited by Aroclor 1254 with an ID50 of 4.5 x 10(-4)M. However, it was found that Aroclor 1254 alone has a stimulatory CL effect on otherwise unactivated cells. To compare the mechanisms involved in the CL elicited by the three stimulants zymosan, TPA and Aroclor 1254, the CL signal was measured in the presence of cytochalasin B. Cytochalasin B inhibited zymosan-induced CL, had a smaller inhibitory effect on TPA-induced CL but it could augment the CL response initiated by Aroclor 1254. This pattern of responses implicates Aroclor 1254 in the activation of eicosanoid metabolism as it matches the differential responses reported for arachidonic acid.

Inactivation of alpha-1-proteinase inhibitor in serum by stimulated human polymorphonuclear leucocytes. Evidence for a myeloperoxidase-dependent mechanism

Triggered polymorphonuclear leucocytes (PMNL) can decrease the elastase inhibitory capacity of serum by inactivating the main inhibitor of elastase alpha-1-proteinase inhibitor (alpha-1-PI). Maximal inactivation occurs with stimuli that release myeloperoxidase from PMNL along with hydrogen peroxide. Specific protection of alpha-1-PI function is obtained with antioxidants that interfere with this system. PMNL that are activated with phorbol myristate acetate release hydrogen peroxide but not myeloperoxidase, and only inactivate alpha-1-PI in the presence of exogenously-added PMNL-derived supernatants which contain this enzyme. Cell-free inactivation requires both active enzyme and hydrogen peroxide, and is greatest at pH 6.2, the pH optimum for myeloperoxidase-catalysed inactivation of alpha-1-PI. This data supports the notion that leucocyte myeloperoxidase may act to suppress the antiprotease screen afforded by alpha-1-PI by generating hypochlorous acid in the presence of chloride and respiratory burst-derived hydrogen peroxide, and in the microenvironment of lowered pH associated with degranulation. Pulmonary emphysema seems to be associated with an imbalance between elastase and its inhibitors at the lung surface. PMNL are likely to play an important role in the pathogenesis of emphysema since they contain both elastase, which can solubilize connective tissue elastin, and the constituents of an oxidative system which can inactivate the most important antielastase, alpha-1-PI.

Role of hydroxyl radicals derived from granulocytes in lung injury induced by phorbol myristate acetate

Lung injury induced by phorbol myristate acetate (PMA) is closely associated with toxic oxidants released from activated granulocytes. But the major toxic oxidant causing lung damage is not really known. We have, therefore, conducted investigations using various oxygen radical scavengers. The intravenous administration of dimethylthiourea (DMTU), a potent hydroxyl radical scavenger, or of superoxide dismutase (SOD), a superoxide anion scavenger, plus catalase, a hydrogen peroxide scavenger, to rabbits intravenously injected with PMA prevented biochemical data and cellularity indicative of lung damage in lung lavages. Morphologically, the lungs of PMA-injected rabbits revealed mild interstitial edema, aggregates of granulocytes within the interstitial capillaries, and the increase of granulocytes in alveolar spaces. Furthermore, there was direct morphologic evidence of pulmonary endothelial cell disruption. In rabbits treated with DMTU or SOD plus catalase, there was no evidence of destructive changes in the lungs. SOD-treated rabbits did not show evidence of protection from PMA-induced lung injury. Only a little protection was provided by catalase treatment. Moreover, in the ultracytochemical study for examination of hydrogen peroxide (H2O2) generation, the number of H2O2-generated granulocytes remarkably decreased in lung lavages of catalase-treated rabbits, but destructive changes were observed in the lungs. In contrast, though the number of H2O2-generated granulocyte was not decreased in lung lavages of DMTU-treated rabbits, treatment with DMTU could afford protection from lung injury. These data indicate that the hydroxyl radical, a toxic oxidant derived from stimulated granulocytes, is deeply involved in the pathogenesis of PMA-induced lung injury.

Impaired function of numerically augmented Fc-receptors on granulocytes in a HLA B8+ patient with palmoplantar pustulosis

We examined granulocytes or polymorphonuclear leukocytes (PMN) in an HLA B8+ patient with palmoplantar pustulosis (PPP). Controls included another patient with PPP, however, lacking this antigen and a healthy, HLA B8+ person. Chemiluminescence (CL) served to monitor the respiratory burst in PMN comparing as stimuli zymosan, opsonized zymosan, phorbol myristate acetate, as well as aggregated immunoglobulin (aggIg), the latter as Fc-receptor (FcR) stimulus. FcR density on PMN was determined using 125I-IgG and expressed in the form of Scatchard plots. The effects of serum on the aggIg-induced CL were also measured. We found both control individuals to respond to stimulation by aggIg as a function of a dose-dependent increase of CL. By contrast, the HLA B8+ patient with PPP failed to respond to aggIg; only the highest concentration of aggIg induced marginal CL. Conversely, stimulation by the other agents was similar in all three individuals. The patient with the functional FcR defect expressed 2.5 times more FcR/PMN than the controls. No difference emerged in comparing autologous serum with a reference normal serum on the aggIg-induced CL, ruling out saturation by serum factors alone to be a cause for the defect. In remission, the functional FcR was absent. Our results suggest a defect of signal transduction in PMN from numerically enhanced FcR to the cytosol in the patient with PPP.

Receptor-mediated O2- release by alveolar macrophages and peripheral blood monocytes from smokers and nonsmokers. Priming and triggering effects of monomeric IgG, concanavalin A, N-formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, and cytochalasin D

Receptor-mediated superoxide (O2-) release by alveolar macrophages and peripheral blood monocytes from smokers and nonsmokers was studied in vitro. When the cells were incubated with monomeric IgG or monomeric Fc(IgG) fragment, no cell O2- release was observed. However, when cytochalasin D (Cyto D) was subsequently added to the cell suspension, we observed a markedly enhanced O2- release. Neither Cyto D alone nor the double stimulation of following Cyto D with monomeric IgG induced O2- release. Concanavalin A (Con A) also had a priming effect on O2 release in combination with Cyto D, as did monomeric IgG or monomeric Fc(IgG) fragment. On the other hand, heat-aggregated IgG, N-formyl-methionyl-leucyl-phenylalanine (FMLP), or phorbol myristate acetate (PMA) induced O2- release without the addition of Cyto D. Thus, we observed 2 different mechanisms in the receptor-mediated O2- release by alveolar macrophages and peripheral blood monocytes. Alveolar macrophages from smokers, which had a higher affinity and a larger number of monomeric IgG binding sites per cell than those from nonsmokers, were more reactive to the double stimulation of following monomeric IgG with Cyto D than to that of Con A and Cyto D, FMLP, or PMA, but for peripheral blood monocytes it was the reverse. We conclude that the binding of monomeric IgG to the Fc(IgG) receptor of alveolar macrophages or peripheral blood monocytes results in a priming effect on the cells for O2- release, and that the regulation of receptor-mediated O2- release by alveolar macrophages differs at least in part from that of peripheral blood monocytes.

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.

Functional Fc-receptor defect of polymorphonuclear leukocytes in a patient with Sjögren's syndrome

We investigated polymorphonuclear leukocyte (PMN) function in a 50-year-old woman with primary Sjögren's syndrome (SS). The respiratory burst of PMN was monitored by luminol-enhanced chemiluminescence using zymosan, opsonized zymosan, zymosan-activated serum, and phorbol-myristate-acetate, as well as serial dilutions of aggregated immunoglobulin (aggIg) as Fc-receptor (FcR) stimulus. The effects of serum on the chemiluminescent response as well as the binding of aggIg to PMN were also compared. We found the patient's PMN not to respond to stimulation by aggIg, only the highest concentration (greater than 180 micrograms/ml) induced a marginal chemiluminescent response in the patient. By contrast, incubation of the patient's PMN with other stimuli resulted in responses similar to those in a healthy control. Binding of aggIg to PMN was higher in the patient (3.6% vs 1.5% of the radioactivity added in the control). Sera of patient and control induced similar chemiluminescence on PMN as did that of another human serum. Our data indicate a selective functional FcR defect of PMN despite unimpaired binding of aggIg in a patient with SS.

High- and low-affinity receptors regulate platelet responses to phorbol diesters and teleocidin

We examined binding of 3H-phorbol dibutyrate (3H-PDBu) to gel filtered human platelets (GFP) and discovered that GFP possess two classes of receptors for phorbol diesters (PDE). High-affinity (HA) receptors, approximately 5000/GFP, bound 3H-PDBu with an apparent dissociation constant (KD) of approximately 12 nM. Low-affinity receptors were approximately 5 times more numerous (2.4 X 10(4)/GFP) and had a 10-fold lower affinity for 3H-PDBu (apparent KD = 115 nM). The potencies of phorbol myristate acetate (PMA) and PDBu paralleled their binding affinities to the PDE receptors. Teleocidin (Tel), although structurally distinct from PDE, competed with 3H-PDBu for its HA-receptors (KI Tel = 1.9 nM). Binding of PDE to HA- or LA- receptors was rapid, reversible, saturable and stereospecific. The HA- and LA-receptors modulated different platelet responses. HA-receptors regulated the secretion of beta-thromboglobulin from alpha-granules and the release of N-acetyl-beta-D-hexosaminidases from lysosomes. LA-receptors mediated both platelet aggregation and the release of serotonin from dense granules. This is the first demonstration of two physiologically active classes of PDE/Tel receptors in human platelets, and demonstrates that particular platelet responses may be directed by distinct classes of receptors for specific agonists.

Adhesion of polymorphonuclear leukocytes to endothelium enhances the efficiency of detoxification of oxygen-free radicals

Polymorphonuclear leukocytes can produce active oxygen species such as hydrogen peroxide and superoxide under various conditions. Because these substances can be toxic to cells, it is possible that the interaction between the circulating leukocytes and the blood vessel wall, either in normal circulation or during the acute inflammatory response, could damage the endothelial lining. Using an in vitro system of cultured endothelial cells and isolated polymorphonuclear leukocytes, we have measured the levels of detectable superoxide when neutrophils are attached to either endothelial monolayers or to plastic. Our results show that the levels of superoxide, on a per-cell basis, are lower when the neutrophils are attached to endothelium than when attached to plastic, even if the neutrophils are stimulated with phorbol myristate acetate. This is also reflected in data showing that no injury occurs to the endothelial cells, as measured by 51Cr release, under these same conditions. When endothelial cells are pretreated with an inhibitor of superoxide dismutase, diethyldithiocarbamate, the levels of superoxide detected are the same for neutrophils stimulated on plastic and those on the endothelial monolayer, suggesting that endothelial superoxide dismutase may remove a portion of the neutrophil-generated superoxide from the detection system. Further evidence for the role of endothelium in destroying superoxide is suggested by results that show that the level of detectable superoxide released from neutrophils attached to formalin-fixed endothelial monolayers is the same as that for neutrophils attached to plastic. It is important to note that with the inhibitor of superoxide dismutase present, the endothelial monolayers do not display enhanced 51Cr release under the conditions employed. When both endothelial catalase and glutathione reductase are inhibited, we detect increased 51Cr release from endothelial cells in response to stimulated neutrophils. Our results show that the endothelial cells are important in affecting the apparent reduction of toxic oxygen products derived from polymorphonuclear leukocytes attached to their surface.

Chemiluminescence response of human B-cell lines

Epstein-Barr virus (EBV)-transformed human B lymphoblastoid cells share certain properties with monocytes: they are capable of presenting protein antigens to antigen-specific T-lymphocytes and of releasing an Interleukin 1-like factor. It was our interest to study whether transformed B-cells resemble monocytes by generating toxic oxygen radicals. Human B-cell lines were developed from human peripheral blood lymphocytes by EBV-transformation. The induction of the respiratory burst in the B-cells was assessed by chemiluminescence (CL) in the presence of lucigenin. B-cells were stimulated with phorbol-myristate-acetate (PMA), zymosan particles, the chemotactic peptide f-met-phe, the complement split product C5a and with a recently described granulocyte activating cytokine (GRAM). Stimulation with PMA elicited a distinct CL-response in the tested B-cell lines. The CL-signal was significantly reduced by superoxide dismutase, but not by D-mannitol and catalase. No significant response to any of the other stimuli was detected. Furthermore, none of the stimuli induced a luminol-enhanced CL signal, which, in contrast to lucigenin, is dependent on the presence of peroxidase. Our results indicate that EBV infected B-cells were able to generate significant amounts of reactive oxygen species, particularly superoxide. It appears that virus transformation uncovers genetic information which is usually not expressed in non-transformed B-cells.

Impaired chemiluminescence response by neutrophils in patients with multiple myeloma

Neutrophil chemiluminescence (CL) as a measure of oxygen-dependent killing activity was evaluated in 3 groups of patients: (a) 63 patients with multiple myeloma (MM); (b) 31 subjects with monoclonal gammopathy of undetermined significance (MGUS); (c) 32 healthy controls. Neutrophil CL response was shown to be significant reduced both in patients with MM (p less than 0.001) and in subjects with MGUS (p less than 0.001). A significant difference was also observed between the results obtained in MM and those of MGUS (p less than 0.001). Treated MM patients showed a more severe impairment of neutrophil chemiluminescence response than that observed in untreated patients (p less than 0.001). It is suggested that the impairment of neutrophil CL response, possibly related to decreased killing activity, may play a role, along with other known causes, in the increased susceptibility to infection observed in MM patients.

Effects of phorbol diesters and teleocidin on normal human platelets

Teleocidins are newly described indole alkaloid tumor promoters that are structurally distinct from phorbol diesters (PDE). We compared the effects of teleocidin and selected PDE on platelet aggregation, secretion and aspects of arachidonate metabolism. Three tumor-promoting PDE (phorbol myristate acetate (PMA), phorbol dibutyrate (PDBu) and 4-beta-phorbol didecanoate (4-beta-PDD] and a non-tumor promoting PDE (4-alpha-phorbol didecanoate (4-alpha-PDD] were used. Teleocidin and tumor promoting PDE caused platelet aggregation after a delay that was inversely related to tumor promoter concentration and also triggered secretion of alpha- and dense granules and selective release of lysosomal enzymes. Aggregation and its associated 125I-fibrinogen binding to platelets were both inhibited by Na2EDTA. 4-alpha-PDD was ineffective. Analysis of platelet aggregation responses and activation kinetics revealed that PDBu was 11.7 times less potent than teleocidin PMA, or 4-beta-PDD. Neither PDE nor teleocidin stimulated 14C-arachidonate release from normal human platelets, and both aggregated aspirin-treated platelets. These results show that representatives of two structurally distinct classes of tumor promoters, phorbol diesters and indole alkaloids, are potent activators of platelet aggregation, fibrinogen binding, and granule/lysosomal secretion, by a mechanism that bypasses arachidonate release and formation of cyclooxygenase-dependent arachidonate metabolites.

Stimulation of superoxide release in neutrophils by 1-oleoyl-2-acetylglycerol incorporated into pH-sensitive liposomes

Incorporation of 1-oleoyl-2-acetylglycerol (OAG) into multilamellar liposomes composed of egg phosphatidylethanolamine (PE) and arachidonic acid (AA) resulted in a significant enhancement of superoxide release by guinea pig neutrophils when compared to free OAG. OAG incorporated into liposomes containing phosphatidylcholine and arachidonic acid were generally less effective than free OAG. The potency of the liposomes correlates well with the ability of the liposomes to undergo lipid mixing at acidic pH. The enhanced effect of liposome-associated OAG could be related to exposure to an acidic environment in the endosomes/lysosomes once liposomes are endocytosed by neutrophils.

Aggregation of human neutrophils by heparin

Commercial heparin preparations induce the aggregation of human polymorphonuclear neutrophils (PMNs). The minimum aggregating concentration (MAC) of different heparin lots was measured under standardized conditions. It was found to vary between 0.3 and 15 units/ml. Gel filtration of heparin showed that the aggregating activity eluted in a sharp peak with a pattern different from heparin. When heparin was bound to antithrombin III-Sepharose, the aggregating activity eluted totally in the high-affinity fraction. When PMNs are partially aggregated with heparin, further aggregation by N-formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate-acetate (PMA) is not affected. Pretreatment of PMNs with a low-aggregating heparin fraction, inhibits further aggregation by a high-aggregating heparin fraction. These results suggest that the PMNs have binding sites for heparin different from those for PMA and FMLP. Binding of heparin is not enough for inducing aggregation. Certain structural requirements of the heparin molecule are probably essential for aggregation.