Cryoballoon ablation of atrial fibrillation is effectively feasible without previous imaging of pulmonary vein anatomy: insights from the 1STOP project.

BACKGROUND: Pulmonary vein isolation by cryoablation (PVI-C) is a standard therapy for the treatment of atrial fibrillation (AF); however, PVI-C can become a challenging procedure due to the anatomy of the left atrium and pulmonary veins (PVs). Importantly, the utility of imaging before the procedure is still unknown regarding the long-term clinical outcomes following PVI-C. The aim of the analysis is to evaluate the impact of imaging before PVI-C on procedural data and AF recurrence. METHODS: Patients with paroxysmal AF underwent an index PVI-C. Data were collected prospectively in the framework of 1STOP ClinicalService® project. Patients were divided into two groups according to the utilization of pre-procedural imaging of PV anatomy (via CT or MRI) or the non-usage of pre-procedural imaging. RESULTS: Out of 912 patients, 461 (50.5%) were evaluated with CT or MRI before the PVI-C and denoted as the imaging group. Accordingly, 451 (49.5%) patients had no pre-procedural imaging and were categorized as the no imaging group. Patient baseline characteristics were comparable between the two cohorts, but the ablation centers that comprised the imaging group had fewer PVI-C cases per year than the no imaging group (p < 0.001). The procedure, fluoroscopy, and left atrial dwell times were significantly shorter in the no imaging cohort (p < 0.001). The rates of complications were significantly greater in the imaging group compared to the no imaging group (6.9% vs. 2.7%; p = 0.003); this difference was attributed to differences in transient diaphragmatic paralysis. The 12-month freedom from AF was 76.2% in the imaging group and 80.0% in the no imaging group (p = 0.390). CONCLUSIONS: In our analysis, PVI-C was effective regardless of the availability of imaging data on PV anatomy.

A comparison of the metabolic response to phagocytosis in human granulocytes and monocytes.

Recent studies indicate that oxygen radicals such as superoxide or singlet oxygen may be important in the functional activity of human granulocytes. We have examined the possible importance of these radicals in the functional capacity of human blood monocytes. Monocytes, like granulocytes, generate chemiluminescence during phagocytosis. Chemiluminescence is impaired 50-90% by superoxide dismutase, an enzyme which enhances the dismutation of superoxide to hydrogen peroxide. These results indicate that superoxide is related to the chemiluminescence generated by monocytes. Superoxide dismutase in a concentration which impaired chemiluminescence also impaired the staphylococcal killing by monocytes. Hexose monophosphate shunt activity and hydrogen peroxide production by granulocytes and monocytes were also evaluated. The oxidation of [1-14C]glucose was used as a measure of hexose monophosphate shunt activity and the oxidation of [14C]formate as an estimation of hydrogen peroxide production. The oxidation of both substrates by monocytes was increased during phagocytosis but, in contrast to results in granulocytes, was not further increased by the addition of superoxide dismutase. These data indicate that superoxide may be important in bactericidal activity of human monocytes. Our results also suggest that the metabolism of oxygen radicals in monocytes and granulocytes may be different.

Mechanisms of methylene blue stimulation of the hexose monophosphate shunt in erythrocytes.

The response of the hexose monophosphate shunt in erythrocytes was studied with the ionization chamber-electrometer apparatus to measure continuously 14CO2 derived from 14C-labeled substrates. The effect of methylene blue at high (0.1 mM) and low (1 muM) concentrations was evaluated under different gas mixtures; air, carbon monoxide, and 6% carbon monoxide in air. The latter gas mixture results in nearly 100% carboxyhemoglobin but provides a physiologic partial pressure of oxygen. The extent to which pentose is recycled through the shunt in response to methylene blue stimulation was examined with radioactive glucose substrates labeled on the first, second, and third carbon positions. Generation of hydrogen peroxide after stimulation of erythrocytes with methylene blue was evaluated by the catalase-aminotriazole trapping technique, [14C]formate oxidation, and oxidation of reduced glutatione. Stimulation of the shunt with 1 muM methylene blue was markedly impaired in the absence of oxyhemoglobin, but stimulation with 0.1 mM methylene blue was only slightly impaired under the carbon monoxide-air mixture. The higher concentration of methylene blue produced evidence of hydrogen peroxide generation of all three techniques. Despite the evidence for the involvement of oxygen, oxyhemoglobin, and hydrogen peroxide in the response to methylene blue, cells containing methemoglobin induced by sodium nitrite or from a patient with congenital methemoglobinemia responded normally to methylene blue in the absence of oxygen. These experiments indicate that the reactions induced by methylene blue in erythrocytes are more complex than generally thought and that high concentrations are associated with production of peroxide.

Effects of corticosteroids on human monocyte function.

This report examined the effect of corticosteroids in vitro on human peripheral blood monocytes, essential cells in both immune and nonimmune cellular defense mechanisms. Monocyte chemotaxis in response to sera, Escherichia coli filtrate, and lymphokine chemotactic factor was markedly reduced (P < 0.01) by hydrocortisone succinate (HCS) at 16 mug/ml. Methylprednisolone succinate and unesterified hydrocortisone produced similar impairment of monocyte chemotaxis while two drugs which unmodified do not enter cells, hydrocortisone phosphate (HCP) and cortisone acetate, had no effect on chemotaxis. HCS also significantly impaired monocyte random migration at 16 mug/ml. Monocyte bactericidal activity was reduced by HCS at 16 mug/ml (P < 0.01)) but was not affected by HCP even at 120 mug/ml. In comparison, HCS did not alter granulocyte chemotaxis even at 500 mug/ml, and bactericidal activity was reduced at 16 mug/ml (P < 0.01). Monocyte phagocytosis of cryptococci was reduced only 20% (P < 0.05) at 120 mug/ml. HCS at 120 mug/ml did not alter monocyte base-line or postphagocytic hexosemonophosphate shunt activity, viability by trypan blue exclusion, adherence to tissue culture flasks, or surface binding of IgG globulin. These corticosteroid-induced defects in monocyte function may contribute to reduced cellular defense during corticosteroid therapy.

The effect of oxidant stress on diamide-treated human granulocytes.

The role of sulfhydryls in the protection of human polymorphonuclear neutrophils against extracellular oxidant attack was investigated by simultaneously exposing polymorphonuclear neutrophils to the thiol-oxidizing agent diamide and the oxidant-generating system xanthine-xanthine oxidase. Neither diamide nor the oxidants generated by the xanthine-xanthine oxidase system alone impaired the burst in chemiluminescence, hexose monophosphate shunt activity or formate oxidation normally seen during polymorphonuclear neutrophil phagocytosis. Incubation of the polymorphonuclear neutrophils simultaneously with diamide and xanthine-xanthine oxidase markedly impaired polymorphonuclear neutrophil phagocytosis, hexose monophosphate shunt activity, chemiluminescence and formate oxidation. Although the polymorphonuclear neutrophils exposed to diamide and xanthine-xanthine oxidase did not respond to a variety of phagocytizable stimuli, trypan blue exclusion was normal and hexose monophosphate shunt activity could be stimulated by diamide. The damaging effect of the diamide xanthine-xamthine oxidase system could be blocked by the addition of superoxide dismutase or catalase, but not by hydroxyl radical or singlet oxygen scavengers. We hypothesize that an unidentified population of thiols may play a role in protecting the polymorphonuclear neutrophil from endogenously derived oxidants.

A new method for the detection of hydroxyl radical production by phagocytic cells.

Benzoic acid, a specific scavenger of hydroxyl radical (OH.) is known to be oxidized as the result of a reaction with OH.. We have determined that the decarboxylation of benzoic acid can be used to detect OH. generated in cell-free systems and human granulocytes. Benzoic acid is oxidized by the xanthine-xanthine oxidase enzyme system. This system is known to generate O2-, H2O2 and OH.. This oxidation is inhibited by superoxide dismutase, catalase and mannitol. Therefore, the oxidation of benzoic acid occurs by a mechanism similar to that reported for the oxidation of methional to ethylene and involves OH.. Resting granulocytes do not oxidize benzoic acid. However, marked oxidation of this substrate occurs during the phagocytosis of opsonized zymosan particles, indicating the production of OH. by these cells. The reaction can be inhibited by superoxide dismutase, catalase, azide and mannitol. Therefore, the production of OH. in the cell may be similar to that observed in the cell-free system. The granulocytes of a patient with known chronic granulomatous disease did not oxidase benzoic acid, indicating a defect in the generation of OH. by these cells.

Glucose metabolism of hairy cells.

Hairy cell leukemia is a malignant B-cell disorder characterized by splenomegaly and pancytopenia. The malignant cell is morphologically unique and characterized by fine cytoplasmic projections. Although studies of the cell have revealed important information about its proliferative capacity, cell surface, and membrane composition, less is known about the metabolic characteristics of the cell. We have previously investigated the oxidative metabolism of the hairy cell and have suggested that hairy cells might have a unique glucose metabolism compared to normal lymphocytes. This is indicated by a high rate of [6-14C]glucose oxidation in short-term culture consistent with an active Kreb's cycle and a high ratio of [6-14C]glucose oxidation to [1-14C] glucose oxidation. In this study, we evaluated an additional group of patients with hairy cell leukemia prior to or after treatment with the experimental drug 2'-deoxycoformycin (dCF). We found that in seven of eight patients the leukemic cells had a pattern similar to that previously described and that all of these seven patients had a significant response to therapy. The cells of the eighth patient had minimal Kreb's cycle activity, and at the time of study the patient was resistant to therapy with dCF. The metabolic activity of hairy cells may distinguish them from other lymphoid populations and may be a marker for sensitivity to dCF.

Human monocyte to macrophage differentiation in vitro: characterization and mechanisms of the increased antibody-dependent cytotoxicity associated with differentiation.

Human monocyte-to-macrophage differentiation in vitro is associated with marked enhancement in the capacity to bind and lyse antibody-opsonized red blood cells (rbc). We previously demonstrated that this was due in part to an increased number of Fc receptors. The current study further characterized the mechanism of this enhanced macrophage as antibody-dependent cellular cytotoxicity (ADCC). We observed that 1) macrophages but not monocytes lysed "innocent bystander" rbc as well as opsonized rbc; 2) macrophages exhibited an increased hexose monophosphate shunt activity compared to monocytes; 3) macrophage produced H2O2 but not OH.; and 4) macrophage lyses of opsonized rbc were 80% O2 dependent. We conclude that human monocyte-to-macrophage maturation in vitro is associated with an enhanced O2-dependent cytotoxic mechanism normally present in monocytes. The enhanced H2O2 production noted in macrophages may reflect an increased generation of several other reactive oxygen species in these cells. One of these oxygen radicals may be the mediator of the enhanced macrophage cytotoxicity and of the "innocent bystander" phenomenon observed.

Activation and deactivation of guinea pig peritoneal eosinophils during chronic polymyxin B stimulation.

Eosinophils exhibit different levels of oxidative metabolism depending on their site of origin and various host factors that may influence metabolism. The present study examined the time course of eosinophil oxidative metabolism in animals undergoing chronic peritoneal stimulation. Eosinophils were purified from the peritoneal exudates of guinea pigs stimulated with weekly polymyxin B and saline peritoneal lavage. 14C-1- and 14C-6-glucose oxidation and H2O2 production were measured at week 0 and at various time points throughout 43 weeks of stimulation. Baseline oxidative metabolism of eosinophils was relatively high throughout the time course, but then declined sharply after 32 weeks. These "deactivated" cells that were recovered after 32 weeks also failed to respond to phorbol myristate acetate (PMA) or opsonized zymosan. Electron microscopy did not reveal significant differences between deactivated eosinophils and cells from earlier time points. These findings document the time course of eosinophil activation and deactivation in this model and suggest that metabolic heterogeneity of eosinophils can occur over time in response to a chronic stimulus.

Biotransformation of para-aminobenzoic acid and salicylic acid by PMN.

Para-aminobenzoic acid (PABA) is an essential cofactor for the production of folic acid in bacteria and has mild anti-inflammatory activity. We have recently reported that salicylic acid and benzoic acid are oxidized by stimulated granulocytes Polymorphonuclear Neutrophils (PMN). The oxidation of salicylate appears mediated by a potent oxygen metabolite generated during the respiratory burst which is dependent primarily on superoxide (O2-) for its production. These background studies with the salicylate group of drugs suggested that PABA might be similarly metabolized by PMN. In these studies, we demonstrate that PABA is metabolized by stimulated PMN. However, in contrast to the biochemical mechanism involved in the metabolism of salicylate, our scavenger studies indicate that PABA is metabolized primarily by the myeloperoxidase pathway. Our results may explain the mild anti-inflammatory actions of the drug and suggest that the degradation of PABA by PMN at an inflammatory site may limit the availability of PABA for bacterial growth.

Aminobenzoic acid compounds as HOCl traps for activated neutrophils.

This study was designed to develop traps for hypochlorous acid (HOCl) which could be used to detect HOCl in the microenvironment of activated neutrophils. Reagent HOCl was found to react with para-aminobenzoic acid (PABA) in aqueous solution to produce a predominant metabolite detectable by high performance liquid chromatography (HPLC). Mass spectroscopy and nuclear magnetic resonance identified this metabolite as the ring addition product 3-chloro PABA. The related compound para-aminosalicylic acid (PAS) was also metabolized by HOCl to 3-chloro PAS. The formation of the 3-chloro metabolite was specific for reactions involving HOCl, since several other oxidants in chloride buffer failed to produce the metabolite. Human blood neutrophils activated by phorbol myristate acetate or zymosan in the presence of PABA (or PAS) used their HOCl to produce large amounts of the 3-chloro metabolite. The formation of 3-chloro PABA was inhibited by azide, catalase, and taurine, which is consistent with the production of the metabolite by the neutrophil myeloperoxidase (MPO) pathway. The reaction of HOCl with PABA and PAS was relatively slow as shown by competitive reactions with endogenous antioxidants like taurine, methionine, and glutathione. This was confirmed in reactions involving PABA/PAS and reagent HOCl or HOCl generated by the MPO enzyme system. In these in vitro systems, glutathione and serum completely inhibited the formation of the 3-chloro metabolite. In contrast, activated neutrophils metabolized PABA/PAS to the 3-chloro metabolite even in the presence of 1% serum. These findings demonstrate that PABA and PAS are specific trapping agents for HOCl produced by neutrophils in complex biological conditions.

Leukemic reticuloendotheliosis. A study of the origin of the malignant cell.

A highly pure preparation of neoplastic cells from the spleen of a patient with leukemic reticuloendotheliosis was studied for function, membrane characteristics and glucose metabolism. Glass adherence and phagocytosis of small particles (latex and carbon black) were demonstrated with phase contrast microscopy. Staphylocidal activity was similar to that of normal monocytes. Immunofluorescent assays revealed nonspecific uptake of antiserums to immunoglobulins G (IgG), M (IgM), A (IgA) and kappa and kappa and lambda light chains. Rosette assays indicated the presence of receptors for IgG on the surface of all cells but no receptors for complement (C3) or sheep red blood cells. Glucose metabolic studies revealed a pattern that differed from that of normal monocytes or lymphocytes with intermediate values for glycolysis, low hexose monophosphate shunt activity and high Krebs cycle activity. Increments in tritiated (3H)-thymidine uptake and glucose metabolism in response to phytohemagglutinin stimulation were minimal (5 per cent of normal lymphocyte values) and no response was noted with pokeweed mitogen stimulation. These findings suggest that the leukemic reticuloendotheliosis cell most closely resembles cells of the monocyte-histiocyte series.

Effects of mitomycin C on metabolism in a rat liver preparation.

Quinone drugs are used extensively as anti-neoplastic agents. The mechanism of their actions and the reasons for their unfavorable side effects are not well understood. Mitomycin C (MC) is an N-heterocyclic quinone with chemotherapeutic action against solid tumors. Previous research has led to the development of a model for drug activation involving NADPH reduction of the drug via microsomal mixed-function oxidases. We tested the possibility that NADPH is provided from the hexose monophosphate shunt (HMPS). The MC did indeed increase HMPS activity aerobically, while not affecting Kreb's cycle activity. Anaerobic stimulation of the shunt is also predicted by the model. However, under hypoxic conditions no HMPS or Kreb's activity was observed in MC-treated or untreated samples. Other investigators have documented the involvement of reactive oxygen species in microsomal systems in vitro. The oxygen requirement for MC stimulation of HMPS suggests oxygen radical involvement. We carried out experiments using [14C]-formate as a scavenger for hydrogen peroxide. There was no apparent change in H2O2 production when MC was added. Catalase is known to be involved in peroxide metabolism in vivo; however, addition of the catalase inhibitor sodium azide did not alter endogenous or MC-stimulated shunt activity. The microsomal inhibitor SKF-525A (10(-3) M) prevented MC stimulation of the HMPS, which is consistent with the model implicating microsomal enzymes in MC metabolism. Overall, we have shown the oxygen dependence of endogenous and MC-stimulated shunt activity, and the results provide evidence for MC activation of oxidative metabolism by a mechanism which involves microsomes.

Metabolism of phenytoin and covalent binding of reactive intermediates in activated human neutrophils.

ontivation of neutrophils by phorbol-12-myristate-13-acetate (PMA) causes rapid production of superoxide radical (O2-), leading to the formation of additional reactive oxygen species, including hydrogen peroxide (H2O2), hypochlorous acid (HOCl), and possibly hydroxyl radical (.OH). These reactive oxygen species have been associated with the oxidation of some drugs. We investigated the metabolism of phenytoin (5,5-diphenylhydantoin) and the covalent binding of reactive intermediates to cellular macromolecules in activated neutrophils. In incubations with 100 microM phenytoin, PMA-stimulated neutrophils from six human subjects produced p-, m-, and o-isomers of 5-(hydroxyphenyl)-5-phenylhydantoin (HPPH) in a ratio of 1.0:2.1:2.8, respectively, as well as unidentified polar products. Analysis of cell pellets demonstrated that phenytoin was bioactivated to reactive intermediates that bound irreversibly to macromolecules in neutrophils. Glutathione, catalase, superoxide dismutase, azide, and indomethacin all diminished the metabolism of phenytoin and the covalent binding of its reactive intermediates. The iron-inactivating chelators desferrioxamine and diethylenetriaminepentaacetic acid had little or no effect on the metabolism of phenytoin by neutrophils, demonstrating that adventitious iron was not contributing via Fenton chemistry. In an .OH-generating system containing H2O2 and Fe2+ chelated with ADP, phenytoin was oxidized rapidly to unidentified polar products and to p-, m-, and o-HPPH (ratio 1.0:1.7:1.5, respectively). Reagent HOCl and human myeloperoxidase (MPO), in the presence of Cl- and H2O2, both formed the reactive dichlorophenytoin but no HPPH. However, no chlorinated phenytoin was detected in activated neutrophils, possibly because of its high reactivity. These findings, which demonstrated that activated neutrophils biotransform phenytoin in vitro to hydroxylated products and reactive intermediates that bind irreversibly to tissue macromolecules, are consistent with phenytoin hydroxylation by .OH generated by a transition metal-independent process, chlorination by HOCl generated by MPO, and possibly cooxidation by neutrophil hydroperoxidases. Neutrophils activated in vivo may similarly convert phenytoin to reactive intermediates, which could contribute to some of the previously unexplained adverse effects of the drug.

Hydroxylation of salicylate by activated neutrophils.

Salicylates are metabolized in vivo to hydroxylated compounds, including 2,3-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid (gentisic acid). The present study hypothesized that activated neutrophils represent one pathway for salicylate hydroxylation. Human neutrophils were incubated in medium containing 10 mM salicylate and stimulated with phorbol myristate acetate (PMA) for 1 hr. The cell-free supernatant fractions were analyzed by HPLC. Neutrophils (1 x 10(6) cells) produced 55 +/- 11 ng of gentisic acid. Neutrophils also produced smaller quantities of 2,3-dihydroxybenzoic acid. Antioxidant inhibitor experiments indicated that superoxide dismutase (SOD), heme protein inhibitors, and glutathione blocked gentisic acid formation, whereas catalase, mannitol, and deferoxamine failed to inhibit. Experiments with the reagent hypochlorous acid (HOCl) and the model myeloperoxidase (MPO) enzyme system did not support a role for the MPO pathway in gentisic acid formation. These findings demonstrate that activated neutrophils can hydroxylate salicylate by an unknown pathway. This pathway may contribute to the increased recovery of hydroxylated salicylates in patients with inflammatory disorders.

Effect of O2 partial pressure on the myeloperoxidase pathway of neutrophils.

Neutrophils recruited to different tissues undergo respiratory burst activity at widely different PO2 levels. The present study investigated the in vitro effects of PO2 on neutrophil oxidative metabolism. When neutrophils were stimulated with either zymosan or phorbol myristate acetate (PMA) under different PO2's (0-700 Torr), hexose monophosphate shunt activity, H2O2, and hydroxyl radical (OH.) production were directly related to the level of PO2. Neutrophils functioned surprisingly well at PO2's as low as 10 Torr, where metabolic burst activity was prolonged and usually exceeded 50% of maximal values. The production of neutrophil stable oxidants and hypochlorous acid (HOCl) by zymosan-stimulated neutrophils was also directly related to PO2. In contrast, the production of stable oxidants and HOCl by PMA-stimulated neutrophils was significantly higher at 10 Torr compared with 700 Torr. The decrease in stable oxidant production by PMA-stimulated neutrophils at elevated PO2's was explained by both increased destruction of stable oxidant products and by decreased availability of the precursor HOCl. Superoxide dismutase and the OH. scavenger benzoate partially prevented the fall in stable oxidants at elevated PO2's. Measurements of stable oxidants in PMA-stimulated supernates generated at 10 and 700 Torr correlated with the ability of these supernates to decrease the elastase inhibitory capacity of the serum antiprotease alpha 1-antitrypsin. These findings suggest that different PO2's alter the magnitude and pattern of neutrophil oxidative metabolism.

Effect of dimethylthiourea on the neutrophil myeloperoxidase pathway.

The sulfur-centered compound dimethylthiourea (DMTU) affords antioxidant protection in animal models of acute lung injury, an effect that has been attributed to its OH. scavenging properties. Although DMTU can also react with H2O2 in certain experimental systems, the effect of DMTU on the neutrophil myeloperoxidase (MPO) pathway has not been studied. DMTU (1-10 mM) completely blocked stable oxidants and hypochlorous acid formation by phorbol myristate acetate- and zymosan-stimulated neutrophils. DMTU also provided complete inhibition when incubated with cell-free supernatants after the formation of the MPO products. DMTU prevented the oxidative inactivation of alpha 1-antitrypsin by neutrophil-stable oxidants. Evidence that DMTU was oxidized by the MPO products was obtained by titration of oxidized DMTU with reduced glutathione. Surprisingly, supernatants from cells incubated with DMTU (10 mM) consumed two- to threefold higher amounts of reduced glutathione than supernatants from cells incubated with taurine (15 mM). Metabolic studies with stimulated neutrophils and experiments with the MPO enzyme system in a cell-free system suggested that DMTU acts by scavenging the products of the MPO pathway rather than by blocking H2O2 production in the intact cell. These findings demonstrate that DMTU blocks the neutrophil MPO pathway in addition to its known ability to scavenge other reactive O2 species. The capacity of DMTU to scavenge MPO products may explain some of its protective effects in acute lung injury.

Evidence that OH. production by human PMNs is related to prostaglandin metabolism.

Recent studies indicate that human granulocytes generate OH. during the phagocytosis of zymosan particles. Several theoretical considerations suggested to us that this OH. production might be related to prostaglandin metabolism, particularly the observation that OH. is generated by the reducation of hydroperoxides in microsomal systems. In our studies, we tested the importance of prostaglandin metabolism in the production of OH. by human granulocytes (PMNs). Indomethacin and aspirin at concentrations known to impair cyclooxygenase activity decreased OH. production by PMNs during the phagocytosis of zymosan particles. Phenol, which is known to alter prostaglandin metabolism, ablated OH. completely. None of these drugs at the concentrations used impaired the generation of O-2 or H2O2 by PMNs, as indicated by their failure to diminish significantly the generation of chemiluminescence. Thus, the decrement in OH. production by these drugs could not be attributed to a nonspecific effect on the production of O-2 or H2O2. These experiments therefore, indicate that the model for OH. production observed during prostaglandin synthesis with microsomal systems applies to human granulocytes.

Effect of diethyldithiocarbamate (DDC) on human monocyte function and metabolism.

Recent evidence indicates that phagocytic cells play a major role in tissue inflammation. The release of enzymes, lipid metabolites such as prostaglandins, and reactive oxygen species by these cells appear to mediate the inflammatory process. In this study we have evaluated the effects of diethyldithiocarbamate (DDC) on human monocyte function and metabolism. We demonstrate that DDC impairs that antibody-dependent cytoxicity (ADCC) of monocytes to red cell targets. The concentration of DDC which caused maximal suppression of ADCC also prevented the burst of oxidative metabolism in monocytes stimulated by sensitized red cells targets or phorbol myristate acetate (PMA). DDC also impairs the lipid metabolism of these cells as indicated by a decrement in malonyldialdehyde (MDA) production. These data indicate that DDC impairs the activity of two major biochemical pathways in monocytes which are related to the inflammatory process, i.e., the release of oxygen metabolites and prostaglandins.

Evaluation of the role of oxygen radicals in polymorphonuclear leukocyte aggregation.

oxygen radicals have been shown to alter granulocyte function by injury to the cell membrane or cytoskeleton. We have investigated the effect of such injury on the aggregation of granulocytes upon C5a or PMA stimulation. Granulocyte aggregation was not altered in the presence of the oxygen radical scavengers SOD, catalase, mannitol, or benzoate. To test whether oxygen radicals were required for aggregation, we evaluated three patients with chronic granulomatous disease of childhood. The response of PMNs from these patients was no different from controls. Hydrocortisone, an inhibitor of both granulocyte aggregation and oxygen radical generation, was then studied to decide whether its impairment of radical production contributed to its effect on aggregation. Five times the concentration of hydrocortisone needed to inhibit radical generation was required to impair aggregation by 50%. In addition, hydrocortisone was able to impair the aggregation of the PMNs of a patient with chronic granulomatous disease. These data suggest that oxidative injury to the cell membrane or cytoskeleton does not significantly contribute to the aggregation of granulocytes. In addition, inhibitors of aggregation, such as hydrocortisone, work through mechanisms other than by scavenging radicals.