Activity Of Human Polymorphonuclear Leukocytes Research Articles

Cystic Fibrosis Transmembrane Conductance Regulator Recruitment to Phagosomes in Neutrophils

Optimal microbicidal activity of human polymorphonuclear leukocytes (PMN) relies on the generation of toxic agents such as hypochlorous acid (HOCl) in phagosomes. HOCl formation requires H₂O₂ produced by the NADPH oxidase, myeloperoxidase derived from azurophilic granules, and chloride ion. Chloride transport from cytoplasm into phagosomes requires chloride channels which include cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel. However, the phagosomal targeting of CFTR in PMN has not been defined. Using human peripheral blood PMN, we determined that 95-99% of lysosomal-associated membrane protein 1 (LAMP-1)-positive mature phagosomes were CFTR positive, as judged by immunostaining and flow cytometric analysis. To establish a model cell system to evaluate CFTR phagosomal recruitment, we stably expressed enhanced green fluorescent protein (EGFP) alone, EGFP-wt-CFTR and EGFP-DF508-CFTR fusion proteins in promyelocytic PLB-985 cells, respectively. After differentiation into neutrophil-like cells, CFTR presentation to phagosomes was examined. EGFP-wt-CFTR was observed to associate with phagosomes and colocalize with LAMP-1. Flow cytometric analysis of the isolated phagosomes indicated that such a phagosomal targeting was determined by the CFTR portion of the fusion protein. In contrast, significantly less EGFP-DF508-CFTR was found in phagosomes, indicating a defective targeting of the molecule to the organelle. Importantly, the CFTR corrector compound VRT-325 facilitated the recruitment of DF508-CFTR to phagosomes. These data demonstrate the possibility of pharmacologic correction of impaired recruitment of mutant CFTR, thereby providing a potential means to augment chloride supply to the phagosomes of PMN in patients with cystic fibrosis to enhance their microbicidal function.

Human neutrophil alpha‐defensins induce formation of fibrinogen and thrombospondin‐1 amyloid‐like structures and activate platelets via glycoprotein IIb/IIIa

Human neutrophil α-defensins (HNPs) are important constituents of the innate immune system. Beyond their antimicrobial properties, HNPs also have pro-inflammatory features. While HNPs in plasma from healthy individuals are barely detectable, their level is strongly elevated in septic plasma and plasma from patients with acute coronary syndromes. As thrombosis and inflammation are intertwined processes and activation of human polymorphonuclear leukocytes (PMNL) and subsequent degranulation is associated with full activation of surrounding platelets, we studied the effect of HNPs on platelet function. The effect of HNPs on platelet activation parameters and apoptosis was investigated via aggregometry, flow cytometry, confocal microscopy and the ELISA technique. It was found that HNPs activate platelets in pathophysiologically relevant doses, inducing fibrinogen and thrombospondin-1 binding, aggregation, granule secretion, sCD40L shedding, and procoagulant activity. HNPs bound directly to the platelet membrane, induced membrane pore formation, microparticle formation, mitochondrial membrane depolarization and caspase-3-activity. Confocal microscopy revealed the HNP-induced formation of polymeric fibrinogen and thrombospondin-1 amyloid-like structures, which bound microorganisms. Platelets adhered to these structures and formed aggregates. Blocking of glycoprotein IIb/IIIa (GPIIb/IIIa) markedly inhibited HNP-induced platelet activation. In addition, heparin, heparinoid, serpins and α(2)-macroglobulin, which all bind to HNPs, blocked HNP-1-induced platelet activation in contrast to direct thrombin inhibitors such as hirudin. HNPs activate platelets and induce platelet apoptosis by formation of amyloid-like proteins. As these structures entrapped bacteria and fungi, they might reflect an additional function of HNPs in host defense. The described mechanism links again thrombosis and infection.

BK channels in innate immune functions of neutrophils and macrophages

AbstractOxygen-dependent antimicrobial activity of human polymorphonuclear leukocytes (PMNs) relies on the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to generate oxidants. As the oxidase transfers electrons from NADPH the membrane will depolarize and concomitantly terminate oxidase activity, unless there is charge translocation to compensate. Most experimental data implicate proton channels as the effectors of this charge compensation, although large-conductance Ca2+-activated K+ (BK) channels have been suggested to be essential for normal PMN antimicrobial activity. To test this latter notion, we directly assessed the role of BK channels in phagocyte function, including the NADPH oxidase. PMNs genetically lacking BK channels (BK−/−) had normal intracellular and extracellular NADPH oxidase activity in response to both receptor-independent and phagocytic challenges. Furthermore, NADPH oxidase activity of human PMNs and macrophages was normal after treatment with BK channel inhibitors. Although BK channel inhibitors suppressed endotoxin-mediated tumor necrosis factor-α secretion by bone marrow-derived macrophages (BMDMs), BMDMs of BK−/− and wild-type mice responded identically and exhibited the same ERK, PI3K/Akt, and nuclear factor-κB activation. Based on these data, we conclude that the BK channel is not required for NADPH oxidase activity in PMNs or macrophages or for endotoxin-triggered tumor necrosis factor-α release and signal transduction BMDMs.

Antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Human peripheral blood polymorphonuclear leucocytes (PMN) were examined in vitro for antifungal activity against yeast cells of Paracoccidioides brasiliensis. The yeast cell of this fungus was resistant to killing by PMN. However, PMN exhibited a fungistatic effect on the fungal isolates employed in a long-term (∼72 h) assay. Lysates of PMN did not show a fungistatic or fungicidal effect, indicating that live PMN are necessary for the antifungal effect. Interferon-Γ (IFN-Γ) enhanced the antifungal activity of PMN. IFN-Γ-treated PMN killed isolate Bt-4 within 2 h of coculture, and after 24 h a still greater killing effect was observed. By contrast, IFN-Γ-treated PMN did not show a significant killing effect on isolate Tatu, but did exhibit an enhanced fungistatic effect on this isolate. In contrast, tumor necrosis factor-α and interleukin 8 had no effect on the antifungal activity of PMN. Scanning electron microscopy revealed that the surface structure of the fungal cell was apparently damaged by PMN within 24 h of cocultures. Based on these novel findings, we speculate that human PMN might play a role in host resistance in early infection with this fungus due to their antifungal activity.

Interaction of amphotericin B lipid formulations and triazoles with human polymorphonuclear leucocytes for antifungal activity against Zygomycetes

The frequency of zygomycosis has increased considerably over recent years mainly in immunocompromised and diabetic patients. Little is known about the effects of host innate immunity against different Zygomycetes especially under the influence of antifungal agents. The antifungal activity of human polymorphonuclear leucocytes (PMN) in combination with liposomal amphotericin B (LAMB), amphotericin B lipid complex (ABLC), voriconazole (VRC) and posaconazole (PSC) against Rhizopus oryzae and Rhizopus microsporus, frequently isolated Zygomycetes, were studied and compared with Absidia corymbifera, a less pathogenic Zygomycete. Antifungal activity was evaluated as per cent of hyphal damage using the XTT metabolic assay. While A. corymbifera was more susceptible to PMN than the other two Zygomycetes, R. microsporus appeared to be the most susceptible to combined effects of amphotericin B formulations and VRC with PMN. LAMB exhibited synergistic activity with PMN in inducing hyphal damage to R. microsporus but not to the other fungi. In contrast, ABLC exhibited synergistic or additive activity with PMN against all three fungi. Among triazoles, only VRC exhibited additive effect with PMN against R. microsporus. Lipid formulations of amphotericin B and particularly ABLC interact with PMN predominantly in inducing augmented hyphal damage to three different species of Zygomycetes.

Oxidative activity of human polymorphonuclear leukocytes stimulated by the long-chain phosphatidic acids

It has already been suggested that phosphatidic acids (PAs) play an important role in the regulation of signaling pathways involved in the production of reactive oxygen species (ROS) by human polymorphonuclear leukocytes (PMNs). The present study was performed to elucidate the effects of extracellularly added PA-- 1,2-distearoyl- (DSPA) and 1-stearoyl-2-arachidonoyl-sn-glycero-phosphate (SAPA)--on the ROS production and on the elastase release by human PMNs. ROS production was monitored by luminol-amplified chemiluminescence and the elastase activity was measured in the supernatant of the PA-stimulated human PMNs by colorimetric assay. Obtained effects were compared with those of cells stimulated by either a chemotactic tripeptide, phorbol ester or calcium ionophore. Our results show that long-chain PAs at concentrations higher than 3 x 10(-5) mol/l stimulate the ROS production by human PMNs, whereas they were ineffective in promoting the elastase release. The chemiluminescence pattern of the SAPA-stimulated cells exhibited a biphasic curve, whereas cell stimulation with DSPA resulted in a monophasic chemiluminescence curve. Stimulation of the ROS production by PAs in dependence of the fatty acid composition required the activity of protein kinases.

Inteferon gamma and granulocyte–macrophage colony-stimulating factor augment the antifungal activity of human polymorphonuclear leukocytes againstScedosporiumspp.: comparison withAspergillusspp.

While Aspergillus spp. have been the most frequent filamentous fungi causing infections in immunocompromised patients, Scedosporium spp. are emerging as life-threatening pathogens. We studied the effects of interferon gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) alone or combined on the antifungal activities of human polymorphonuclear leukocytes (PMN) against Scedosporium apiospermum and Scedosporium prolificans. We paralleled these activities to those against Aspergillus fumigatus and Aspergillus flavus. Incubation of PMN with IFN-gamma and GM-CSF for 22 h enhanced PMN-induced hyphal damage of both Aspergillus spp. and S. prolificans (p < 0.05) but not of S. apiospermum. However, hyphae of S. apiospermum were damaged significantly more after incubation with PMN that had been treated with IFN-gamma and GM-CSF for 2 h. In addition, incubation of PMN with GM-CSF for 2 h enhanced PMN oxidative burst measured as superoxide anion (O2-) production in response to nonopsonized hyphae of A. flavus and Scedosporium spp. (p < 0.05). In contrast, after 2 h, IFN-gamma and GM-CSF alone did not enhance PMN O2- in response to opsonized hyphae of A. flavus and Scedosporium spp.; however, the combination of IFN-gamma and GM-CSF showed significant enhancement against these species. Thus, IFN-gamma and GM-CSF, particularly in combination, demonstrate a species- and time-dependent augmentation of PMN responses to Scedosporium spp.

Human phagocytic cell responses to Scedosporium apiospermum (Pseudallescheria boydii): variable susceptibility to oxidative injury.

Scedosporium apiospermum (Pseudallescheria boydii) is an emerging opportunistic filamentous fungus that causes serious infections in both immunocompetent and immunocompromised patients. To gain insight into the immunopathogenesis of infections due to S. apiospermum, the antifungal activities of human polymorphonuclear leukocytes (PMNs), mononuclear leukocytes (MNCs), and monocyte-derived macrophages (MDMs) against two clinical isolates of S. apiospermum were evaluated. Isolate SA54A was amphotericin B resistant and was the cause of a fatal disseminated infection. Isolate SA1216 (cultured from a successfully treated localized subcutaneous infection) was susceptible to amphotericin B. MDMs exhibited similar phagocytic activities against conidia of both isolates. However, PMNs and MNCs responded differently to the hyphae of these two isolates. Serum opsonization of hyphae resulted in a higher level of superoxide anion (O(2)(-)) release by PMNs in response to SA54A (amphotericin B resistant) than that seen in response to SA1216 (amphotericin B susceptible; P < 0.001). Despite this increased O(2)(-) production, PMNs and MNCs induced less hyphal damage to SA54A than to SA1216 (P < 0.001). To investigate the potential mechanisms responsible for these differences, hyphal damage was evaluated in the presence of antifungal oxidative metabolites as well as in the presence of a series of inhibitors and scavengers of antifungal PMN function. Mannose, catalase, superoxide dismutase, dimethyl sulfoxide, and heparin had no effect on PMN-induced hyphal damage to either of the two isolates. However, azide, which inhibits PMN myeloperoxidase activity, significantly reduced hyphal damage to SA1216 (P < 0.01) but not to SA54A. Hyphae of SA1216 were slightly more susceptible to oxidative pathway products, particularly HOCl, than those of SA54A. Thus, S. apiospermum is susceptible to antifungal phagocytic function to various degrees. The selective inhibitory pattern of azide with respect to hyphal damage and the parallel susceptibility to HOCl suggests an important difference in susceptibilities to myeloperoxidase products that may be related to the various levels of pathogenicity and amphotericin B resistance of S. apiospermum.

Selective inhibition of interleukin-8-induced neutrophil chemotaxis by ketoprofen isomers

Although it is commonly accepted that the anti-inflammatory effect of nonsteroidal anti-inflammatory drugs (NSAIDs) is mainly associated to their ability to inhibit the cyclooxygenase (COX) enzyme system, several results indicate that non-COX mechanisms could be important in the therapeutical effect of these drugs. The aim of this study was to define if NSAIDs could exert, at least in part, their anti-inflammatory effect by inhibiting the activities of human polymorphonuclear leukocytes (PMNs) triggered by chemotactic stimuli and, if so, to understand the relationship of this effect with COX inhibition. A unique opportunity to dissociate the inhibition of prostaglandin (PG) synthesis from other therapeutical properties of NSAIDs is constituted by ketoprofen isomers being the S-isomer 100 time more potent than R-isomer on COX inhibition. Our results show that R- and S-ketoprofen, independently of their potency as PG inhibitors, proved very efficacious in selective inhibition of interleukin-8 (IL-8) chemotaxis. Inhibition of IL-8 chemotaxis was not restricted to ketoprofen isomer as it could be observed also with drugs belonging to different classes of NSAIDs and it was obtained at drug concentration superimposable to plasma levels after therapeutic administration in patients. Reduction of IL-8 migration by ketoprofen isomers was paralleled by selective inhibition of PMN response in terms of intracellular calcium concentration ([Ca 2+] i) increase and extracellular signal regulated kinase(ERK)-2 activation, two intracellular mediators reported to be critical for PMN activities. It is concluded that inhibition of IL-8 chemotaxis could represent a new clinical target for ketoprofen isomers and, in fact, contribute to the anti-inflammatory activity of NSAIDs.

Evidence of Qi-gong energy and its biological effect on the enhancement of the phagocytic activity of human polymorphonuclear leukocytes.

In order to test for an effect of phosphate buffered saline (PBS) treated externally with Qi energy ("Qi-treated" PBS) on the phagocytic activity of human polymorphonuclear leukocytes (PMNs), rigorously controlled experiments employing masking and randomized procedures were carried out under independent monitoring. In all experiments, Qi treatment was externally applied under monitoring to newly purchased unopened 100 ml bottles of PBS, and the PMN phagocytic activity was assayed by one experimenter in masked, randomized and monitored conditions using a highly sensitive chemiluminescence method. Phagocytic activity data were obtained in triplicate for each sample and then statistically analyzed. The PBS samples Qi-treated by the Qi-gong master and by one of the Qi-gong trainees showed clear stimulation of PMN phagocytic activity which was significant statistically, and this phenomenon was highly reproducible. Out of 10 experiments by the Qi-gong master, only twice did Qi-treatment fail to influence the PBS. The activity of Qi-treated PBS decayed over days or weeks. Furthermore, it was found that Qi-treated PBS had decreased phagocytic stimulatory activity after microwave treatment, but not after autoclave treatment. We also demonstrated that microwave irradiation and infrared laser pulse irradiation have similar effects on PBS as Qi-treatment. The results obtained in this experiment provide evidence of the existence of Qi energy, its ability to influence an electrolyte solution and its biological effect. Furthermore, microwave or infrared laser pulse treatment was found to partly mimic the Qi-treatment of PBS.

16(R)-Hydroxyeicosatetraenoic Acid, a Novel Cytochrome P450 Product of Arachidonic Acid, Suppresses Activation of Human Polymorphonuclear Leukocytes and Reduces Intracranial Pressure in a Rabbit Model of Thromboembolic Stroke

16(R)-Hydroxyeicosatetraenoic Acid, a Novel Cytochrome P450 Product of Arachidonic Acid, Suppresses Activation of Human Polymorphonuclear Leukocytes and Reduces Intracranial Pressure in a Rabbit Model of Thromboembolic Stroke

16(R)-Hydroxyeicosatetraenoic Acid, a Novel Cytochrome P450 Product of Arachidonic Acid, Suppresses Activation of Human Polymorphonuclear Leukocytes and Reduces Intracranial Pressure in a Rabbit Model of Thromboembolic Stroke

Activated polymorphonuclear leukocytes (PMNs) have been suggested to contribute to the development of increased intracranial pressure (ICP). We recently demonstrated that human PMNs produce a novel cytochrome P450-derived arachidonic acid metabolite, 1 6(R)-hydroxyeicosatetraenoic acid [16(R)-HETE], that modulates their function. It was thus of interest to examine this novel mediator in an acute stroke model. 16-HETE was assessed initially in a variety of human PMN and platelet in vitro assays and subsequently in an established rabbit model of thromboembolic stroke. A total of 50 rabbits completed a randomized, blinded, four-arm study, receiving 16(R)-HETE, tissue plasminogen activator, both, or neither. Experiments were completed 7 hours after autologous clot embolization. The primary end point for efficacy was the suppression of increased ICP. In in vitro assays, 16(R)-HETE selectively inhibited human PMN adhesion and aggregation and leukotriene B4 synthesis. In the thromboembolic stroke model, animals that received 16(R)-HETE demonstrated significant suppression of increased ICP (7.7 +/- 1.2 to 13.1 +/- 2.7 mm Hg, baseline versus final 7-h time point, mean +/- standard error), compared with either the vehicle-treated group (7.7 +/- 0.9 to 15.8 +/- 2.6 mm Hg) or the tissue plasminogen activator-treated group (7.6 +/- 0.6 to 13.7 +/- 2.1 mm Hg). The group that received the combination of 16(R)-HETE plus tissue plasminogen activator demonstrated no significant change in ICP for the duration of the protocol (8.6 +/- 0.6 to 11.1 +/- 1.2 mm Hg). 16(R)-HETE suppresses the development of increased ICP in a rabbit model of thromboembolic stroke and may serve as a novel therapeutic strategy in ischemic and inflammatory pathophysiological states.

Effect of cytokines on antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Effect of cytokines on antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Cytokine-induced fungicidal activity of human polymorphonuclear leukocytes against Penicillium marneffei

We investigated the fungicidal activity of human polymorphonuclear leukocytes (PMN) against Penicillium marneffei. The yeast cells were cocultured in vitro with PMN for 24 h. Microscopic examination was also performed to examine the germination of yeast cells and their transformation to hyphal form during culture. Unstimulated PMN inhibited fungal growth when used at a higher effector/target (E/T) ratio but inhibited germination at a lower E/T ratio. We also examined the effects of various PMN-activating cytokines, including granulocyte-macrophage colony stimulating factor (GM-CSF), G-CSF, interleukin (IL)-8, interferon (IFN)-γ and tumor necrosis factor (TNF)-α on the activity of PMN. Among these, GM-CSF, G-CSF and IFN-γ enhanced PMN activity from being fungistatic to fungicidal. However, the other cytokines had little or no effect on PMN activity. In contrast, all tested cytokines enhanced PMN inhibitory effects on germination and morphological changes of P. marneffei. These antifungal activities were most strongly induced by GM-CSF. The combined use of any of the above cytokines failed to synergistically enhance antifungal PMN activity. Our results demonstrated that cytokine-activated PMN exert a significant antifungal activity, by suppressing the growth and germination of P. marneffei. Our results suggest that PMN may contribute to host resistance to infection against this fungal pathogen.

Cytokine-induced fungicidal activity of human polymorphonuclear leukocytes against Penicillium marneffei.

We investigated the fungicidal activity of human polymorphonuclear leukocytes (PMN) against Penicillium marneffei. The yeast cells were cocultured in vitro with PMN for 24 h. Microscopic examination was also performed to examine the germination of yeast cells and their transformation to hyphal form during culture. Unstimulated PMN inhibited fungal growth when used at a higher effector/target (E/T) ratio but inhibited germination at a lower E/T ratio. We also examined the effects of various PMN-activating cytokines, including granulocyte-macrophage colony stimulating factor (GM-CSF), G-CSF, interleukin (IL)-8, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha on the activity of PMN. Among these, GM-CSF, G-CSF and IFN-gamma enhanced PMN activity from being fungistatic to fungicidal. However, the other cytokines had little or no effect on PMN activity. In contrast, all tested cytokines enhanced PMN inhibitory effects on germination and morphological changes of P. marneffei. These antifungal activities were most strongly induced by GM-CSF. The combined use of any of the above cytokines failed to synergistically enhance antifungal PMN activity. Our results demonstrated that cytokine-activated PMN exert a significant antifungal activity, by suppressing the growth and germination of P. marneffei. Our results suggest that PMN may contribute to host resistance to infection against this fungal pathogen.

Antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Platelet-derived Growth Factor-specific Regulation of theJE Promoter in Rat Aortic Smooth Muscle Cells

JE is a member of the family of "immediate early" genes induced by growth factors and cytokines. JE encodes a low molecular weight secretory glycoprotein analogous to the human monocyte chemoattractant protein, MCP-1. JE and MCP-1 proteins are thought to play an important role in inflammation and in the recruitment of monocyte/macrophages to the vessel wall during the development of atherosclerosis. We have previously reported that the induction of JE in rat aortic smooth muscle cells (SMC) was specific to platelet-derived growth factor (PDGF) and was not seen with other growth agonists. Using a luciferase reporter system and transient transfection assays of rat aortic SMC, we now report the identification of a region in the proximal rat JE promoter that is responsive to PDGF but not to other growth factors (angiotensin II and alpha-thrombin) or cytokines (interleukin 1-beta and tumor necrosis factor-alpha). The full response to PDGF (approximately 6-fold) requires the cooperative activity of two potentially novel cis-acting elements, at positions -146 to -128 and -84 to -59. While each element produces a different pattern in electrophoretic mobility shift assays, they appear to bind the same PDGF-responsive species. Further analysis of these regions should provide important insights into PDGF-specific responses in vascular SMC.

Activation of human polymorphonuclear leukocytes by products derived from the peroxidation of human red blood cell membranes.

Oxidation of red blood cell (RBC) ghost preparations initiated by tert-butyl hydroperoxide (tBuOOH) was employed to explore the formation of lipid products derived from endogenous phospholipids that specifically expressed biological activity toward the human polymorphonuclear leukocyte (PMN). Common measure of lipid peroxidation, thiobarbituric acid-reactive substances (TBARS) and the increased absorbance at 235 nm consistent with the formation of conjugated dienes, was observed following a 90-min incubation of RBC ghosts with tBuOOH. Saponification of phospholipids and separation of the resultant fatty acids by RP-HPLC permitted direct mass spectrometric analysis of oxidized fatty acids. Individual HPLC fractions were assayed for their ability to increase intracellular free calcium ion concentrations in human PMN to guide structural investigations. Two fractions were found to contain biologically active components, and tandem mass spectrometric analysis of the abundant ions observed in these fractions resulted in the characterization of several oxidized polyunsaturated fatty acids derived from arachidonic and linoleic acids. The major components in these fractions included 5-hydroxyeicosatetraenoic acid (5-HETE) and 5-hydroperoxyeicosatetraenoic acid (5-HpETE). The dose-dependent increases in intracellular calcium in the neutrophil using synthetic 5(rac)-HETE, 5(rac)-HpETE, and 5-oxo-ETE were found to have EC50's of 250, 6, and 3 nM, respectively. The quantity of 5-oxygenated arachidonate components present in oxidized RBC was consistent with the observed biological response elicited by fractions A and B. This study suggests that 5-HETE and 5-HpETE are abundant products of lipid peroxidation of cellular membranes and that these racemic products possess significant biological activity. Such compounds could play important roles as mediators of the cellular response to toxicologic stimuli that generate free radical species.

Meropenem-induced alteration of the susceptibility of Escherichia coli and Staphylococcus aureus to the bactericidal activity of human polymorphonuclear leucocytes

The analysis of the interaction between antimicrobials and phagocytosis in vitro provides information additional to standard MIC and MBC estimations in predicting in-vivo efficacy. This study investigated the effects of meropenem, a newly available carbapenem, on the activities of human neutrophils against Escherichia coli and Staphylococcus aureus. The results were compared with those obtained with imipenem. Pretreatment of E. coli and S. aureus with meropenem and imipenem sensitized the bacteria to leucocytic killing. In the presence of antibiotics, opsonophagocytic killing of E. coli, but not S. aureus, was synergistically enhanced.

Palmitic Acid Anilide-Induced Respiratory Burst In Human Polymorphonuclear Leukocytes is Inhibited by a Protein Kinase C Inhibitor, Ro 31-8220

Human polymorphonuclear leukocytes (PMNL) were exposed to palmitic acid anilide, an impurity in the case oils that caused the Spanish Toxic Oil Syndrome in 1981, and to the corresponding fatty acid, palmitic acid. The effects of these compounds were studied on the production of reactive oxygen metabolites (ROM) and changes in the levels of free intracellular calcium. Palmitic acid anilide induced the production of reactive oxygen metabolites in PMNL. Interestingly, the palmitic acid anilide-induced respiratory burst was completely blocked by a protein kinase C inhibitor, Ro 31-8220. Moreover, palmitic acid anilide additively amplified the production of ROM caused by a chemotactic peptide, formyl-Methionyl-Leucyl-Phenylalanine (FMLP). In contrast, palmitic acid anilide did not have any effect on the production of ROM induced by a tumor promoter, phorbol myristate acetate (PMA). Palmitic acid, in turn, did not markedly induce the production of ROM nor did it amplify the agonist-induced respiratory burst. Neither of the compounds, alone or in combination with FMLP, affected the levels of intracellular calcium in PMNL. These results indicate that the aniline moiety in palmitic acid modifies its effects on the activation of human PMNL, and the subsequent oxidative burst. The present results also suggest that palmitic acid anilide may activate PMNL through a protein kinase C-dependent mechanism. © 1997 Elsevier Science Inc.