Generation of nitrogen-chlorine oxidants by human phagocytes

Human phagocytes can be triggered to generate large quantities of long-lived nitrogen-chlorine derivatives. This class of oxidants can be detected as early as 5 min after the addition of phorbol myristate acetate or opsonized zymosan particles. Unlike all other oxygen metabolites known to be generated by phagocytes, the nitrogen-chlorine compounds can be readily detected in cell supernatants 90 min after stimulation. The generation of these oxidants is linear with neutrophil concentration, favored at alkaline pH, and inhibited by supraphysiologic concentrations of iodide or bromide. The oxidants are hydrophilic in nature and have a half-life ranging from 5 h at 37 degrees C to greater than 100 h at 4 degrees C. Gel filtration chromatography of the accumulated nitrogen-chlorine derivatives revealed that the oxidants generated by neutrophils or monocytes are a complex mixture of products whose Mr range from 150-5,000. One-half of the nitrogen chlorine derivatives migrate as a single peak with an Mr of approximately 150. Amino acid analysis of this fraction identified the beta-amino acid, taurine, as the single nitrogenous compound present. Neutrophils triggered in the presence of serum albumin accumulated increased amounts of the nitrogen-chlorine derivatives while continuing to generate their endogenous low Mr oxidants. Quantitative analysis of the 36Cl incorporation revealed that the albumin molecule was chlorinated with the formation of both nitrogen-chlorine and carbon-chlorine bonds. We conclude that human phagocytes can chlorinate both endogenous and exogenous nitrogenous compounds at inflammatory sites to generate a heterogeneous mixture of nitrogen-chlorine derivatives. The ability of phagocytes to generate this class of long-lived oxidants whose hydrophilic characteristics restrict their localization to the extracellular space suggests that these species play an important role in modulating the inflammatory response.

The effect of transition modules on new graduate adaptation

The purpose of this study was to determine the effectiveness of educational modules to aid new graduate nurses in adapting to the work environment. An experimental group of new graduates (n = 63) and their controls (n = 58) from eight hospitals were given Corwin's Role Conception Scale, Seeman's Powerlessness Scale, Benner's Clinical Skills Inventory, and Munson's Job Satisfaction Index to measure adaptation at entry to work and 6 months later. The effects of the educational modules were determined by the adaptation measures, cognitive tests, and a Nursing Service Questionnaire. After 6 months in the work setting, the experimental group had less discrepancy between their desired and existing level of clinical skill (p less than .05) and a greater orientation to bureaucratic expectations than controls (p less than .01), as well as an increase in job satisfaction (p less than .05) and a decrease in role deprivation (p less than .05). In addition, the impact on turnover saved hospitals an average of $3,178 for every 10 new graduates they hired.

Oxidative mechanisms utilized by human neutrophils to destroy Escherichia coli

Serum-opsonized bacteria are efficiently ingested and killed by neutrophils within the phagocytic vacuole, where they are exposed to an array of reactive oxygen metabolites and toxic lysosomal components. Although bacteria may be destroyed by oxygen-independent mechanisms alone, many types of bacteria are not killed effectively unless they are attacked by oxygen metabolites. However, the apparent inability of extracellular scavengers, or inhibitors, of oxygen metabolites to gain access to the phagocytic vacuole makes this system difficult to evaluate. Therefore, we investigated the ability of neutrophils triggered with phorbol myristate acetate to destroy unopsonized E. coli in a serum-free model system. Neutrophils incubated with phorbol myristate acetate at a cell-to-bacteria ratio of 1:4 caused a greater than 95% reduction in colony-forming units (CFU) of E. coli in 60 min at 37 degrees C. Destruction of E. coli by the stimulated neutrophils was dependent on neutrophil number, stimuli concentration, and the incubation period. The neutrophil-mediated bactericidal effect was stimulated by superoxide dismutase, but was inhibited by catalase, azide, or compounds known to scavenge hypochlorous acid. Although stimulated neutrophils can generate long-lived endogenous N- chloroamines , these compounds did not play a direct role in destruction of E. coli in our model system. However, in the presence of exogenous iodide, endogenous N- chloroamines exerted a powerful bactericidal effect. Finally, neutrophils triggered with opsonized zymosan could also mediate E. coli destruction by a qualitatively similar process. Thus, we have demonstrated that neutrophils have the potential to utilize the myeloperoxidase system to generate bactericidal quantities of a species with characteristics similar to, if not identical with, hypochlorous acid.

Neutrophils degrade subendothelial matrices in the presence of alpha-1-proteinase inhibitor. Cooperative use of lysosomal proteinases and oxygen metabolites

Triggered neutrophils rapidly degraded labeled matrices secreted by cultured, venous endothelial cells via a process dependent on elastase but not oxygen metabolites. In the presence of high concentrations of alpha-1-proteinase inhibitor, the ability of the stimulated neutrophil to solubilize the matrix was impaired. However, at lower concentrations of alpha-1-proteinase inhibitor the neutrophil could enhance the degradative potential of its released elastase by a H2O2-dependent process. Coincident with this increase in matrix damage, the stimulated neutrophil destroyed the elastase inhibitory activity of the alpha-1-proteinase inhibitor via a catalase-inhibitable process. The ability of the triggered neutrophil to solubilize the matrix in the presence of alpha-1-proteinase inhibitor was unaffected by superoxide dismutase or hydroxyl radical scavengers but was markedly impaired by catalase, azide, or hypochlorous acid scavengers. We conclude that neutrophils can cooperatively use an oxidant with characteristics similar, if not identical, to hypochlorous acid and the lysosomal proteinase elastase to negate the protective effects of alpha-1-proteinase inhibitor in order to attack the subendothelial matrix.

Effect of thyrotropin on iodide efflux in FRTL-5 cells mediated by Ca2+

A functioning rat thyroid cell line (FRTL-5) responds acutely to the addition of TSH, norepinephrine, and the Ca2+ ionophore A23187 by a depression in iodide (I-) uptake levels. The decrease in I- content measured at the steady state depends on the presence of external Ca2+ and can be accounted for by an effect on stimulated I- efflux. As contrasted to the prolonged time (hours and days) involved in the stimulatory effect of TSH on I- uptake, the acute response to TSH is 1) seen within 5 min and maintained for about 20 min, 2) maximum, at a 1 X 10(-7)M concentration of TSH compared with the concentration of 1 X 10(-9)M necessary for the stimulatory effect, 3) independent of whether the cells are growing in the presence or absence of TSH, and 4) not mimicked by the addition of (Bu)2cAMP. The results suggest that TSH and adrenergic stimulation lead to increased membrane permeability to I- which is mediated by an elevation in the intracellular Ca2+ concentration.

Thyrotropin-stimulated iodide transport mediated by adenosine 3',5'-monophosphate and dependent on protein synthesis

Iodide (I-) uptake by FRTL-5 cells, a functioning rat thyroid cell line, is TSH dependent. The effects of TSH withdrawal are not apparent until 1 day; 1 week is required to reduce I- uptake to a minimal level. The readdition of TSH leads to a return of the I--concentrating ability after a latency of 12-24 h. The reappearance of I- uptake induced by TSH is mimicked by (Bu)2cAMP and agents that elevate intracellular cAMP levels in these cells, such as forskolin, cholera toxin, and a Graves' disease serum. The appearance of I- uptake after TSH occurs 12 h after the appearance of TSH-induced [35S]methionine incorporation. Cycloheximide blocks both the TSH- and (Bu)2cAMP-induced increases in methionine incorporation and I- uptake to the same extent and in an identical concentration-dependent manner. TSH-induced [35S]methionine incorporation is associated with increased radiolabeling of several specific proteins, as revealed by gel electrophoresis; none, however, is radiolabeled coincident in time with the appearance of TSH-induced I- uptake. Several proteins whose apparent synthesis is induced by TSH also exhibit TSH-dependent phosphorylation.

Iodide transport in a continuous line of cultured cells from rat thyroid

The properties of TSH-dependent iodide (I-) uptake are defined for a cloned, continuously growing, functioning rat thyroid cell line (FRTL-5 cells). Since these cells grow without a lumen and are therefore restricted in their ability to iodinate thyroglobulin, the FRTL-5 cells offer the opportunity to directly study transport processes across the membrane into the cell as well as the process whereby I- moves from the cell. FRTL-5 cells concentrate I- approximately 30-fold and exhibit many of the properties of I- uptake seen in thyroid tissue slice and primary cell culture systems. In these cells, accumulation of I- is consistent with a Na+-dependent carrier model for I- uptake, and effects on the influx and efflux processes can be dissociated. Because FRTL-5 cells can be maintained in culture indefinitely and can provide large quantities of a homogeneous functional thyroid cell preparation for study, these cells offer the unique opportunity to further define the mechanism and kinetics of I- transport in a less complex system.

Quantitative and temporal characterization of the extracellular H2O2 pool generated by human neutrophils

The extracellular H2O2 concentration surrounding stimulated human neutrophils was continuously quantitated with a sensitive, H2O2-detecting electrode. Following stimulation of neutrophils with phorbol myristate acetate, opsonized zymosan particles, or N-formyl-Met-Leu-Phe, the extracellular H2O2 concentration rapidly increased and maintained steady state conditions before falling to undetectable levels in a manner that was dependent on the triggering agent used. Total extracellular H2O2 accumulation for each stimulus was quantitated as the integral of the H2O2 concentration with respect to time. H2O2 accumulation in the extracellular milieu was unaffected by the addition of superoxide dismutase, whereas exogenous catalase or myeloperoxidase completely consumed the released H2O2. Analysis of H2O2 metabolism by neutrophils revealed that stimulus-dependent differences in the size of the extracellular H2O2 pool may be partially attributable to differences in hypochlorous acid generation by the H2O2, myeloperoxidase, chloride system. Finally, both the concentration of H2O2 in the extracellular space and its utilization by myeloperoxidase could be diminished in the presence of an extracellular target cell. These data indicate that the ability of a triggering agent to stimulate the neutrophil to generate H2O2 and release myeloperoxidase, coupled with the characteristics of a target cell population, control H2O2 metabolism in effector-target cell interactions.

A cost-benefit analysis of a smoking cessation program

Smoking cessation programs are usually evaluated in terms of the percentage of participants who have stopped smoking at least 6 months after the program's completion. This paper shows how a relatively low rate of behavior change may actually result in a high ratio of benefits to costs. Cost-benefit analysis is done for a specific program but the procedures and cost estimates are generalizable to other smoking cessation programs. Benefits to the firm included reduced costs of insurance and the savings due to employee absenteeism and disability. Costs included the program costs as well as the opportunity costs of the participants. Data from the literature and from the specific program are combined to form conclusions about the effectiveness of the program.

Long-lived oxidants generated by human neutrophils: characterization and bioactivity

Human neutrophils were found to generate an unusual class of oxidants with a half-life of approximately 18 hours and with characteristics similar to, if not identical with, those of N-chloroamines. These neutrophil-derived N-chloroamines have sufficient oxidizing potential to attack sulfhydryl- or thioether-containing compounds and can react with both a methionine-containing chemotactic peptide and a plasma protease inhibitor. As judged by their stability and selective reactivity, the N-chloroamines generated by stimulated neutrophils may play an important role in the local and systemic regulation of inflammatory events in vivo.

The chlorinating potential of the human monocyte

Human monocytes incubated with phorbol myristate acetate (PMA) or opsonized zymosan particles can chlorinate the beta-amino acid taurine to its monochloramine derivative. Taurine monochloramine can then be quantitated by its ability to oxidize 5-thio-2-nitrobenzoic acid to its disulfide or by its characteristic absorption peak at 252 nm. Stimulated, but not resting, monocytes chlorinated taurine by a process dependent on time, cell concentration, and pH. The formation of taurine chloramine by stimulated monocytes could be inhibited by catalase, azide, or cyanide, was unaffected by superoxide dismutase, and was stimulated by exogenous myeloperoxidase. Thus, taurine chloramine generation by human monocytes appeared dependent on both H2O2 and myeloperoxidase. Compared to human neutrophils, the monocyte could generate similar amounts of chloramine when stimulated with phorbol myristate acetate, but far less if opsonized zymosan particles were used as the trigger. Based on the known ability of the H2O2-myeloperoxidase-Cl- system to generate free HOCl, it would seem that this oxidant is the most likely species responsible for the monocyte-mediated chlorination reactions. Thus, we have used a simple quantitative assay to demonstrate the ability of the human monocyte to generate large quantities of a highly reactive and toxic oxygen metabolite.

Role differentiation between nurse and physician: implications for nursing

The aim of this study was to determine whether a series of systematic dialogue sessions among nurses, consumers, and physicians would result in consensus regarding (a) unique areas of nursing practice as differentiated from medical practice and (b) areas of common practice shared by both professions. A stratified sample of 72 nurses, consumers, and physicians met monthly for 20 months in small multidisciplinary groups to discuss areas of health care such as health promotion and maintenance, communication in health relationships, access to medical records, illness self-care, cost considerations, and ethics. Perceived areas of role differentiation between nurse and physician were identified through analysis of (a) verbatim transcripts of the structured dialogue sessions and (b) a subsequent Likert-type inventory completed by all dialogue participants. While no unique nursing domain emerged from the respondents' data, a substantial percent of responsibilities and behaviors were viewed as overlapping areas of practice for nurses and physicians. The data suggested (a) demonstrated health-care arenas where nursings' role is formally acknowledged, (b) lack of clarity within the nursing profession regarding competencies unique to the discipline of nursing, and (c) a continuing public image of nursing as an extender of functions performed by the physician.

The Health Role Expectations Index: A measure of alignment, disparity, and change

Growing controversy over mutual role expectations of physician, nurse, and consumer underlines the need to clarify attitudes toward their responsibilities in health care. This article describes the development and testing of the Health Role Expectations Index, a measure of attitudes regarding the amount of shared responsibility which should exist in the relationships of nurse, physician, and consumer. Testing for validity through differential prediction to known groups and prediction to external measures is detailed. Internal consistency and test-retest reliability findings are also presented. While both the validity and the reliability of the Health Role Expectations Index are supported, the preliminary nature of test results and areas for further testing of the tool are emphasized. Implications for the instrument's use are then discussed.

Effects of antimycin A on receptor-activated calcium mobilization and phosphoinositide metabolism in rat parotid gland

The effects of the mitochondrial poison, antimycin A, on responses of parotid acinar cells to cholinergic stimuli were examined. Antimycin A (10 microM) partially inhibited the agonist-induced increase in 86Rb efflux. Specifically, the initial transient phase of the response, believed to arise from intracellular calcium release, was partially inhibited, while the sustained phase of the response, believed to result from calcium entering from the extracellular space, was completely blocked. The stimulation of 45Ca influx by a cholinergic agonist was also completely blocked. Antimycin A (10 microM) caused a rapid loss of [32P] polyphosphoinositides. Stimulation of [32P]phosphatidylinositol breakdown and [32P] phosphatidate synthesis by methacholine was blocked by antimycin A. Breakdown of [32P]phosphatidylinositol-4,5-bisphosphate in response to cholinergic stimulation was partially inhibited. These results indicated that the activation by cholinergic agonists of cellular calcium mobilization as well as effects on phosphoinositide metabolism are similarly inhibited by antimycin A. Furthermore, this presumably indicates a role for ATP in receptor-activated calcium mobilization and phosphoinositide turnover.

Receptor-mediated net breakdown of phosphatidylinositol 4,5-bisphosphate in parotid acinar cells

The metabolism of phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] in rat parotid acinar cells was investigated, particularly with regard to the effects of receptor-active agonists. Stimulation of cholinergic-muscarinic receptors with methacholine provoked a rapid disappearance of 40--50% of [32P]PtdIns(4,5)P2, but had no effect on PtdIns4P. Adrenaline, acting on alpha-adrenoceptors, and Substance P also stimulated net loss of PtdIns(4,5)P2. The beta-adrenoceptor agonist, isoprenaline, and the Ca2+ ionophore, ionomycin, failed to affect labelled PtdIns(4,5)P2 or PtdIns4P. By chelation of extracellular Ca2+ with excess EGTA, and by an experimental protocol that eliminates cellular Ca2+ release, it was demonstrated that the agonist-induced decrease in PtdIns(4,5)P2 is independent of both Ca2+ influx and Ca2+ release. These results may suggest that net PtdIns(4,5)P2 breakdown is an early event in the stimulus-response pathway of the parotid acinar cell and could be directly involved in the mechanism of agonist-induced Ca2+ release from the plasma membrane.

Chlorination of taurine by human neutrophils. Evidence for hypochlorous acid generation

The model hydrogen peroxide-myeloperoxidase-chloride system is capable of generating the powerful oxidant hypochlorous acid, which can be quantitated by trapping the generated species with the beta-amino acid, taurine. The resultant stable product, taurine chloramine, can be quantitated by its ability to oxidize the sulfhydryl compound, 5-thio-2-nitro-benzoic acid to the disulfide, 5,5'-dithiobis(2-nitroben-zoic acid) or to oxidize iodide to iodine. Using this system, purified myeloperoxidase in the presence of chloride and taurine converted stoichiometric quantities of hydrogen peroxide to taurine chloramine. Chloramine generation was absolutely dependent on hydrogen peroxide, myeloperoxidase, and chloride and could be inhibited by catalase, myeloperoxidase inhibitors, or chloride-free conditions. In the presence of taurine, intact human neutrophils stimulated with either phorbol myristate acetate or opsonized zymosan particles generated a stable species capable of oxidizing 5-thio-2-nitrobenzoic acid or iodide. Resting cells did not form this species. The oxidant formed by the stimulated neutrophils was identified as taurine chloramine by both ultraviolet spectrophotometry and electrophoresis. Taurine chloramine formation by the neutrophil was dependent on the taurine concentration, time, and cell number. Neutrophil-dependent chloramine generation was inhibited by catalase, the myeloperoxidase inhibitors, azide, cyanide, or aminotriazole and by chloride-free conditions, but not by superoxide dismutase or hydroxyl radical scavengers. Thus, it appears that stimulated human neutrophils can utilize the hydrogen peroxide-myeloperoxidase-chloride system to generate taurine chloramine. Based on the demonstrated ability of the myeloperoxidase system to generate free hypochlorous acid we conclude that neutrophils chlorinate taurine by producing this powerful oxidant. The biologic reactivity and cytotoxic potential of hypochlorous acid and its chloramine derivatives suggest that these oxidants play an important role in the inflammatory response and host defense.

Immune complex induced generation of oxygen metabolites by human neutrophils

Human neutrophils have been studied for their ability to respond with production of O(2) and H2O2 by human neutrophils contain a 1:2 weight ratio of antigen and antibody (molar ratio of 1.5:1). The metabolic stimulation of leukocytes is a linear function of the total amount of complex used. Complexes containing F(ab')2 are ineffective in stimulating leukocytes to produce O(2) and H2O2. The complexes that maximally stimulate production of O(2) by neutrophils differ from those complexes that are 1) most effective in complement fixation, 2) maximally taken up by neutrophils, and 3) most effective in the induction of enzyme release. These findings suggest that immune complex-induced damage in tissues may reflect the effects of a heterogeneous population of immune complexes.

Immune complex induced generation of oxygen metabolites by human neutrophils

Human neutrophils have been studied for their ability to respond with production of O(2) and H2O2 by human neutrophils contain a 1:2 weight ratio of antigen and antibody (molar ratio of 1.5:1). The metabolic stimulation of leukocytes is a linear function of the total amount of complex used. Complexes containing F(ab')2 are ineffective in stimulating leukocytes to produce O(2) and H2O2. The complexes that maximally stimulate production of O(2) by neutrophils differ from those complexes that are 1) most effective in complement fixation, 2) maximally taken up by neutrophils, and 3) most effective in the induction of enzyme release. These findings suggest that immune complex-induced damage in tissues may reflect the effects of a heterogeneous population of immune complexes.

Phagocyte-generated oxygen metabolites and cellular injury

Phagocytic leukocytes are motile cells capable of inducing damage and lysis of a wide variety of biologic targets. Recent insights into the mechanisms of phagocyte-mediated destruction have derived from the observation that these cells can consume and metabolize oxygen to generate an impressive array of reactive oxygen intermediates. The role of oxygen metabolites in antimicrobial defense mechanisms has been the subject of intensive study, but only recently has attention focused on the potential importance of oxygen in phagocyte-mammalian cell interactions. In this review we will examine evidence obtained in a variety of in vitro model systems demonstrating the ability of intact phagocytes to generate oxygen metabolites capable of destroying normal or neoplastic cells. A basic understanding of the biochemistry of phagocyte-mediated oxygen-dependent events should allow us to elucidate and potentially modulate immunologic defenses against neoplastic invasion, the destruction of normal tissue in pathogenic states, and the course of the inflammatory response. The role of phagocyte-derived oxygen metabolites in microbicidal activity will not be the subject of this report, and the reader is referred to recent comprehensive reviews.

Regulation of phosphatidate synthesis by secretagogues in parotid acinar cells

The metabolism of phosphatidate in rat parotid acinar cells was investigated, particularly with regard to the actions of agonists known to act by mobilizing Ca2+. When cells were incubated in medium containing 10 microM-[32P]Pi, phosphatidate was rapidly labelled, approaching an apparent steady-state with a half-time of approx. 20 min. Methacholine provoked a more than doubling of phosphatidate radioactivity, which was reversed by the muscarinic antagonist atropine. These results suggest that phosphatidate labels to near steady-state rapidly and that in cells prelabelled for 60 min the increase in radioactivity induced by agonists probably reflects net synthesis rather than an increase in specific radioactivity. Phosphatidate synthesis in response to methacholine was rapid and occurred, within the resolution of a few seconds, with no measurable latency. Adrenaline and substance P also stimulated phosphatidate synthesis but both agonists were less efficacious than methacholine. A Ca2+ ionophore, ionomycin, did not provoke phosphatidate synthesis. By using a protocol that eliminates the receptor-regulated Ca2+ pool, it was demonstrated that methacholine-induced phosphatidate formation does not come about as a consequence of Ca2+ influx nor of Ca2+ release. These results indicate that the phosphatidate synthesis response has characteristics compatible with its previously suggested role as a primary mediator of membrane Ca2+-gating.

Incentive processes and the peak shift

Intradimensional operant discrimination schedules were employed, which eliminated the covariation of response and reinforcement rates that are found on most operant baselines. In Phase 1, one keylight (S(1)) controlled an increase in pigeons' treadle pressing, relative to another keylight (S(2)), while being correlated with a decrease in frequency of reinforcement. In Phase 2 both treadle pressing and reinforcement increased in the presence of one keylight, relative to the second. In Phase 1 the relatively flat treadle-press generalization gradients peaked at S(1), whereas the peaks of those in Phase 2 were shifted from S(1) in a direction away from S(2). It was postulated that these positive and negative stimulus-reinforcement contingencies influence the likelihood of obtaining peak shift through the operation of a classically conditioned "central motive state." How response-reinforcement and stimulus-reinforcement contingencies might contribute to the development of inhibitory effects of S(2) is discussed. Autoshaped key pecking also was produced by these procedures. During manipulations of stimuli, the gradients obtained for autoshaped key pecking were narrow and sharply peaked at the food-correlated stimulus (S(2)) in Phase 1. This failure to obtain peak shift for an elicited response suggests a difference in discriminative processes operating in classical and instrumental learning.

Actions of ionomycin in rat parotid gland

The effects of ionomycin (SQ 23,377), a carboxylic acid Ca-ionophore, on the rat parotid acinar cell were investigated. Ionomycin stimulated 86Rb efflux from parotid slices and was substantially more potent and efficacious than the Ca-ionophore, A-23187. The release of 86Rb was dependent on the concentration of ionomycin and of Ca. Ionomycin also stimulated 22Na uptake and 3H-protein secretion, but did not stimulate the incorporation of 32PO4 into phosphatidylinositol. These observations are consistent with an action of ionomycin in increasing cytosolic Ca by acting as an ionophore and not involving endogenous receptors. Pretreatment with ionomycin inhibited the transient, Ca-independent responses to carbachol or physalaemin. When ionomycin was added to parotid cells pre-equilibrated with 45Ca, a net loss of radiocalcium was observed. These observations suggest that ionomycin can release the receptor-regulated cellular Ca pool. Morphological studies did not reveal any nonspecific deleterious effects in the cells after incubation with 2.67 microM ionomycin.

Neutrophil-mediated methemoglobin formation in the erythrocyte. The role of superoxide and hydrogen peroxide

Human neutrophils incubated with phorbol myristate acetate oxidized hemoglobin within the intact erythrocyte by a mechanism dependent on cell-cell contact but independent of phagocytosis. Spectrophotometric examination of the erythrocyte lysates revealed that the major component formed was methemoglobin along with small amounts of a species with spectral characteristics similar to choleglobin. Methemoglobin formation was directly related to the neutrophil concentration and the time of incubation. The addition of superoxide dismutase or catalase modestly inhibited the formation of methemoglobin, while a combination of the enzymes provided the most dramatic protection. Methemoglobin of hydroxyl radical or hypochlorous acid scavengers. Apparently, either O2.- or H2O2 alone was capable of mediating methemoglobin formation in the intact erythrocyte. Maintenance of the intraerythrocytic hemoglobin in its oxygenated state or its derivatization to carbon monoxyhemoglobin markedly inhibited methemoglobin formation. Blockade of the anion channels in the intact erythrocyte with sulfonated stilbenes inhibited O2.- but not H2O2 from oxidizing intracellular hemoglobin. It appears that neutrophil-derived O2.- and H2O2 can cross the erythrocyte membrane through the anion channel or diffuse directly into the intracellular space and react with oxyhemoglobin or deoxyhemoglobin to form a mixture of hemoglobin oxidation products within the intact cell.

Human neutrophils transform prostaglandins by a myeloperoxidase-dependent mechanism

Intact human neutrophils, incubated with the soluble stimulant phorbol myristate acetate, discharge lysosomal components, generate oxygen metabolites, and transform exogenous 6-keto-prostaglandin F1 alpha, prostaglandin E2, and prostaglandin F2 alpha as assessed by thin layer radiochromatography. Neutrophils alone were incapable of transforming the prostaglandins. The addition of catalase or the myeloperoxidase inhibitor, azide, protected all three prostaglandins from the phorbol-stimulated neutrophils. Neither superoxide dismutase, heat-inactivated catalase, nor albumin had any inhibitory effect in this system. A model system consisting of glucose-glucose oxidase, as a source of H2O2, purified myeloperoxidase, and chloride was also able to transform the prostaglandins in an identical fashion. Neither glucose-glucose oxidase alone nor glucose-glucose oxidase and myeloperoxidase under chloride-free conditions were able to mediate this transformation. Thus, it appears that intact human neutrophils can transform prostaglandins by a mechanism dependent on H2O2, the lysosomal enzyme myeloperoxidase, and chloride. Given the importance of prostaglandins in regulating immune function, neutrophil-dependent prostaglandin transformation could play a novel role in modulating the inflammatory response.