Localization of eosinophil cationic protein, major basic protein, and eosinophil peroxidase in human eosinophils by immunoelectron microscopic technique

An immunoelectron microscopic technique using protein A-gold as a specific marker was used for precise intracellular localization of eosinophil granule proteins. Eosinophils from healthy individuals were isolated in metrizamide gradients. Eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO) were clearly located in the matrix of the large crystalloid-containing granules. In addition, ECP was probably present in the small granules of eosinophils. Major basic protein (MBP) was present in the crystalloid structure of specific granules. This method can be applied in studies of eosinophil degranulation to trace the release of biological effector molecules.     

Isolation and partial characterization of an eosinophil chemotactic factor from metacestodes of Taenia taeniaeformis (ECF-Tt)

Eosinophil chemotactic activity associated with protein extracts of Taenia taeniaeformis metacestodes was investigated. Chemotactic activity was associated with the nonbound protein after QAE cellulose chromatography of a 3 M KCl extract of homogenized larvae. When this material was precipitated with ammonium sulfate, activity was present in the 40 to 80% precipitate. Upon rechromatography on QAE cellulose equilibrated in a low ionic strength buffer, eosinophil chemotactic activity was retained by the gel and eluted after application of the NaCl gradient. Gel filtration of Sephacryl S-300 yielded an estimated m.w. of 91,000. Chromatofocusing revealed a broad peak of activity with a pI of 4.5 to 5.0. SDS-PAGE showed the active fraction migrated as a protein with a m.w. of 10,400. ECF-Tt had chemotactic and chemokinetic activity for equine eosinophils and murine eosinophils, but not for equine and murine neutrophils.     

Extracellular release of rat eosinophil peroxidase (EPO) I. Role of anaphylactic immunoglobulins

The release of intracellular peroxidase (EPO) was investigated in order to evaluate rat eosinophil activation by various immunoglobulin (Ig) isotypes. After successive incubations with purified rat IgG1, IgG2a, IgG2b, IgG2c, IgE, or IgM and their respective anti-Ig antisera, eosinophils released significant amounts of EPO (up to 26% of the intracellular content) only in the case of Ig with anaphylactic activities (IgG2a and IgE). Other classes and subclasses were unable to induce EPO exocytosis. Selective depletion and reconstitution experiments suggested that mast cells were not required in this process. Similar levels of EPO could be released after interaction of eosinophils with antigen-antibody complexes (IgG2a monoclonal antibody and Schistosoma mansoni antigen) immobilized on nonphagocytosable surfaces. These results indicate that EPO exocytosis can be obtained after cell activation with specific antibodies, and that this mechanism is independent of phagocytosis. A kinetic study of eosinophils from S. mansoni-infected rats revealed that IgG2a and IgE cytophilic antibodies induced EPO release after incubation with either specific antisera or specific antigen, which suggests the in vivo relevance of such findings. The present work underlines the parallelism of interaction of anaphylactic-type Ig with eosinophils and with mast cells. Moreover, EPO release seems to represent an interesting marker of eosinophil activation, because close relationships were established between the present findings and previous work on the effector function of rat eosinophils.     

Post-translational tyrosine nitration of eosinophil granule toxins mediated by eosinophil peroxidase

Nitration of tyrosine residues has been observed during various acute and chronic inflammatory diseases. However, the mechanism of tyrosine nitration and the nature of the proteins that become tyrosine nitrated during inflammation remain unclear. Here we show that eosinophils but not other cell types including neutrophils contain nitrotyrosine-positive proteins in specific granules. Furthermore, we demonstrate that the human eosinophil toxins, eosinophil peroxidase (EPO), major basic protein, eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP), and the respective murine toxins, are post-translationally modified by nitration at tyrosine residues during cell maturation. High resolution affinity-mass spectrometry identified specific single nitration sites at Tyr349 in EPO and Tyr33 in both ECP and EDN. ECP and EDN crystal structures revealed and EPO structure modeling suggested that the nitrated tyrosine residues in the toxins are surface exposed. Studies in EPO(-/-), gp91phox(-/-), and NOS(-/-) mice revealed that tyrosine nitration of these toxins is mediated by EPO in the presence of hydrogen peroxide and minute amounts of NOx. Tyrosine nitration of eosinophil granule toxins occurs during maturation of eosinophils, independent of inflammation. These results provide evidence that post-translational tyrosine nitration is unique to eosinophils.     

Monoclonal antibody to rat uterine peroxidase and its use in identification of the peroxidase as being of eosinophil origin

Peroxidase was purified from uteri of estrogen-treated rats by calcium chloride extraction, affinity chromatography on concanavalin A-Sepharose and hydrophobic interaction chromatography on phenyl-Sepharose. An overall purification of greater than 1700-fold was achieved with a final recovery of 27%. Monoclonal antibodies to peroxidase were subsequently prepared by immunization of male C57BL/10J mice with the highly purified peroxidase from rat uterus. Spleen and lymph node cells from the mice were fused with Sp2/0-Ag 14 mouse myeloma cells. The resultant hybrid cells were screened for production of antibody using a solid-phase, double antibody radioimmunoassay. The mature rat spleen, shown previously to be abundant in eosinophils, contains high peroxidase activity. Spleen peroxidase purified by the same procedure as the uterine enzyme cross-reacted with a monoclonal antibody, designated IgG-107B, used in all subsequent studies. Peroxidase extracted from isolated rat eosinophils also cross-reacted with the antibody and yielded identical titers as the spleen and uterine peroxidases. Spleen, uterine and horse eosinophil peroxidase had the same apparent molecular weight, 57000, as determined by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis. Following electrophoretic transfer to nitrocellulose, spleen, uterine and eosinophil peroxidase reacted with monoclonal antibody, using an immunoblotting technique. These results provide biochemical and immunological evidence that the majority of the calcium chloride-extractable peroxidase activity from the uteri of estrogen-treated rats is derived from infiltrating eosinophils.     

Low molecular weight eosinophil chemotactic factor in granulomatous liver of murine schistosomiasis.

An acidic peptide, preferentially chemotactic for eosinophils, was extracted from livers of mice infected with Schistosoma mansoni. Sephadex G-25 column chromatography showed that the majority of the eosinophil chemotactic activity was detected in the fractions just after elution of the molecular marker vitamin B12 (m.w. 1355.4). This activity began to appear in the livers of some mice 5 weeks after infection. Peak activity was detected at 8 to 12 weeks after infection and persisted at least until 16 weeks. It was sensitive to carboxypeptidase-A. By Dowex-1 anion exchange chromatography, the activity eluted as a narrow peak at pH 3.1 TO 2.6 as shown for eosinophil chemotactic factor of anaphylaxis (ECF-A). The activity was also detected in a broad peak at pH 6.3 to 3.7. Unlike ECF-A, the activity was stable to boiling in both acid and alkali. These findings suggest that granulomatous liver of murine schistosomiasis-derived eosinophil chemotactic factor (ECF-G) may play a specific role in eosinophil accumulation in this chronic inflammation.     

Monoclonal antibody to rat uterine peroxidase and its use in identification of the peroxidase as being of eosinophil origin

Peroxidase was purified from uteri of estrogen-treated rats by calcium chloride extraction, affinity chromatography on concanavalin A-Sepharose and hydrophobic interaction chromatography on phenyl-Sepharose. An overall purification of greater than 1700-fold was achieved with a final recovery of 27%. Monoclonal antibodies to peroxidase were subsequently prepared by immunization of male C57BL/10J mice with the highly purified peroxidase from rat uterus. Spleen and lymph node cells from the mice were fused with Sp2/0-Ag 14 mouse myeloma cells. The resultant hybrid cells were screened for production of antibody using a solid-phase, double antibody radioimmunoassay. The mature rat spleen, shown previously to be abundant in eosinophils, contains high peroxidase activity. Spleen peroxidase purified by the same procedure as the uterine enzyme cross-reacted with a monoclonal antibody, designated IgG-107B, used in all subsequent studies. Peroxidase extracted from isolated rat eosinophils also cross-reacted with the antibody and yielded identical titers as the spleen and uterine peroxidases. Spleen, uterine and horse eosinophil peroxidase had the same apparent molecular weight, 57 000, as determined by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis. Following electrophoretic transfer to nitrocellulose, spleen, uterine and eosinophil peroxidase reacted with monoclonal antibody, using an immunoblotting technique. These results provide biochemical and immunological evidence that the majority of the calcium chloride-extractable peroxidase activity from the uteri of estrogen-treated rats is derived from infiltrating eosinophils.     

Electron cytochemistry of developing and mature eosinophils in the bone marrow of the fowl and the duck

Synopsis Enzyme cytochemical studies have been carried out on eosinophils in the fowl and the duck. Peroxidase was found in all regions of the Golgi apparatus, the rough endoplasmic reticulum and the perinuclear cisternae of the early cells. In fowl eosinophil granules irregular deposits of peroxidase and arylsulphatase final reaction product were found, but the acid phosphatase deposits were even. In the duck in contrast, peroxidase was demonstrated in the external part of the granule only. Acid phosphatase and arylsulphatase were found in both the interna and the externa of the duck eosinophil granules. An ammoniacal silver nitrate reaction for the presence of the histone arginine was also studied. Silver deposits were found occupying all regions of the granules of eosinophils from both species of bird.The presence of the hydrolytic enzymes acid phosphatase and arylsulphatase in avian eosinophil granules supports the theory that these structures are lysosomal in nature and that they correspond with mammalian eosinophils in this respect.     

Distinctive cationic proteins of the human eosinophil granule: major basic protein, eosinophil cationic protein, and eosinophil-derived neurotoxin

The human eosinophil granule contains a number of cationic proteins that have been identified and purified to homogeneity, including the major basic protein (MBP), the eosinophil cationic protein (ECP), and the eosinophil-derived neurotoxin (EDN). Because of confusion in the literature regarding the distinctiveness of MBP and ECP, we investigated the immunochemical and physicochemical properties of these purified proteins by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels (SDS-PAGE), by specific double antibody radioimmunoassays (RIA) for MBP and ECP, and by fractionation of acid-solubilized eosinophil granules on Sephadex G-50 columns. Analysis of a mixture of the three purified proteins by SDS-PAGE showed that they migrated as three distinct bands with differing m.w. Comparison by specific RIA for MBP and ECP did not demonstrate any appreciable immunochemical cross-reactivities among the three proteins. Sephadex G-50 column fractions of acid-solubilized eosinophil granules were analyzed by RIA and by SDS-PAGE analysis of individual column fractions. MBP, ECP, and EDN eluted at different volumes from Sephadex G-50 columns as determined by RIA and SDS-PAGE. Soluble extracts of eosinophil granules from patients with the hypereosinophilic syndrome contained between six and 64 times more MBP than ECP on a weight basis. These observations demonstrate that MBP, ECP, and EDN are distinctive cationic proteins of the human eosinophil granule and that eosinophil granules from patients with eosinophilia contain considerably greater quantities of MBP than ECP.     

Role of specific IgE antibodies in peroxidase (EPO) release from human eosinophils

After the demonstration of cytophilic IgE immunoglobulins (Ig) on human blood and lung eosinophils, their role in cell activation was studied by eosinophil peroxidase (EPO) assay. Hypodense human eosinophils from filariasis-infected patients were activated by anti-human Ig or various antigens. A selective release of EPO occurred after incubation with anti-human IgE, but not with anti-human IgG. The activation by antigens showed a strict antibody specificity of cytophilic IgE antibodies. The direct involvement of IgE antibodies in activation by the specific antigen was evidenced by inhibition experiments with aggregated human IgE myeloma protein. Circulating IgE antibodies exhibiting the same specificity and able to induce EPO release were detected in the sera from filariasis patients by a passive sensitization assay. Only the hypodense eosinophils were able to release EPO after IgE-dependent activation both in the direct assay and in the passive sensitization test, confirming the functional heterogeneity of human eosinophils. These results suggest that the interaction between IgE antibodies and human eosinophils can play a role both in protective immunity and pathology by releasing active pharmacologic mediators.     

Differentiation stages of eosinophils characterized by hyaluronic acid binding via CD44 and responsiveness to stimuli

To characterize interleukin (IL)-5-induced eosinophils, we examined the expression of CD44, very late antigen (VLA)-4, and the IL-5 receptor alpha chain, as well as the levels of eosinophil peroxidase and the generation of superoxide. Eosinophils were prepared from IL-5-transgenic mice, then characterized using electron microscopy to determine their responses to stimuli. Whereas CD44 densities remained almost constant, the level of VLA-4 increased in parallel with eosinophil maturation. Although a subset of IL-5-induced eosinophils with high side scatter recovered from bone marrow and rare ones found in blood recognized hyaluronic acid (HA), most did not have this property. Bone marrow eosinophils with high side scatter and lower density contained eosinophil peroxidase, not only in granules, but also in membranous structures for 30% of this population. This population developed HA-binding ability in response to IL-3, IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein (MIP)-2, monocyte chemotactic protein (MCP)-1, eotaxin, nerve growth factor (NGF), and opsonized zymosan (OZ). Peripheral blood eosinophils acquired HA-binding ability in response to the same stimuli, but their responses were less than those of bone marrow eosinophils with high levels of side scatter. However, splenic eosinophils did not respond to these stimuli. Although peripheral blood eosinophils did not proliferate when stimulated by IL-5, these were the only cells that released eosinophil peroxidase in response to IL-4, MIP-2, MCP-1, eotaxin, NGF, and OZ. With the exception of a subset of bone marrow eosinophils, the ability to acquire HA binding, but not the ability to generate superoxide, correlated with eosinophil peroxidase activity and major basic protein accumulation in the granules of maturing cells.     

Properties of glutathione peroxidase isolated from human plasma

Human plasma glutathione peroxidase (GPx) was purified to homogeneity by ammonium sulfate fractionation, gel filtration on Sephadex G-150, chromatography on DEAE Sephacel, chromatofocusing with polybuffer, and gel filtration with Sephadex G-75. This isolation resulted in about 5,400-fold purification of the enzyme with a 32% yield in enzyme activity. The final preparation had a specific activity of about 28 units (mmoles NADPH oxidized) per milligram of protein. Determination of selenium on the purified enzyme revealed a content of 3.8 g atoms per mole GPx. Gel electrophoresis using SDS with standard proteins revealed a molecular weight of about 23,000 for the subunits, which would indicate a molecular weight of about 92,000 for the native enzyme. Amino acid analyses of the purified GPx indicated aspartate, glutamate, proline, glycine, alanine, and leucine as the predominant amino acids and cysteine, methionine, tryptophan, and histidine as the minor amino acids.     

Purification and characterization of an abscisic acid-inducible anionic peroxidase associated with suberization in potato (Solanum tuberosum)

An anionic peroxidase (EC 1.11.1.7), thought to be involved in suberization, was purified 110-fold from wound-healing slices of Solanum tuberosum by a combination of ammonium sulfate fractionation, Sephadex G-100 gel filtration, isoelectric focusing, and phenyl-Sepharose CL-4B chromatography in 24% yield. The purified enzyme was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and horizontal thin-layer polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 47,000 by both Sephadex G-100 gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This peroxidase was found to be a glycoprotein containing about 17% carbohydrate, approximately one-quarter of which was shown to be glucosamine residues. It was found to have an isoelectric point of 3.15. An anionic peroxidase was also isolated from abscisic acid-treated callus tissue culture of S. tuberosum by the above purification procedure. The two enzymes were shown to be immunologically similar, if not identical, based on their cross-reactivity with rabbit antibody prepared against the peroxidase from wound-healing slices, whereas the major cationic peroxidase from wound-healing slices did not cross-react with this antibody. The anionic enzyme from both sources showed very similar specific activities when assayed with a range of substrates, whereas the specific activities found for the cationic isozyme isolated from wound-healing slices were quite different.     

Induction of myeloperoxidase and nitrotyrosine formation in a human eosinophilic leukemia cell line, EoL-1

The human eosinophilic leukemia cell line, EoL-1, differentiated with butyrate as an eosinophilic cellular model was evaluated for peroxidase-dependent tyrosine nitration. Butyrate suppressed cell growth and induced eosinophilic granules in EoL-1 cells after 9 days of culture. Peroxidase activity was detected biochemically and histochemically from 3-day cultures and it increased in a time dependent manner. This peroxidase activity was inhibited by cyanide. Nitrotyrosine formation catalysed by peroxidase using hydrogen peroxide and nitrite was detected at a high level similar to that of mature eosinophils. However, no expression of eosinophil peroxidase (EPO) was detected by RT-PCR or immunocytochemistry. In contrast, the induction of myeloperoxidase (MPO) by butyrate was clearly detected by RT-PCR, Northern blot, and immunocytochemical staining. These results suggest that butyrate induces MPO rather than EPO in EoL-1 cells and that the formation of nitrotyrosine in butyrate-induced cells is dependent on MPO.     

Purification and some physicochemical properties of staphylococcal enterotoxin D.

A method was developed for the isolation of staphylococcal enterotoxin D in highly purified form from cultures of Staphylococcus aureus strain 1151m. The method involves removal of the toxin from the culture supernatant fluid with the ion-exchange resin CG-50 followed by chromatography on carboxymethylcellulose (twice) and by gel filtration on Sephadex G-75 (twice). The purified toxin is homogeneous by polyacrylamide gel and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and double gel diffusion tests. It is a simple, colorless, antigenic protein with an isoelectric point of 7.4 as determined by isoelectric focusing. Its molecular weight was determined to be 27 300 +/- 700 by molecular sieve chromatography on Sephadex G-100 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its serological activity is stable over a wide range of pH values (1.2--10.7). The enterotoxin consists of 236 amino acid residues and contains no free sulfhydryl groups. End-group analysis showed serine to be the NH2-terminal amino acid and lysine to be the COOH-terminal amino acid.     

Extensive eosinophil degranulation and peroxidase-mediated oxidation of airway proteins do not occur in a mouse ovalbumin-challenge model of pulmonary inflammation

Paradigms of eosinophil effector function in the lungs of asthma patients invariably depend on activities mediated by cationic proteins released from secondary granules during a process collectively referred to as degranulation. In this study, we generated knockout mice deficient for eosinophil peroxidase (EPO) to assess the role(s) of this abundant secondary granule protein in an OVA-challenge model. The loss of EPO had no effect on the development of OVA-induced pathologies in the mouse. The absence of phenotypic consequences in these knockout animals extended beyond pulmonary histopathologies and airway changes, as EPO-deficient animals also displayed OVA-induced airway hyperresponsiveness after provocation with methacholine. In addition, EPO-mediated oxidative damage of proteins (e.g., bromination of tyrosine residues) recovered in bronchoalveolar lavage from OVA-treated wild-type mice was <10% of the levels observed in bronchoalveolar lavage recovered from asthma patients. These data demonstrate that EPO activities are inconsequential to the development of allergic pulmonary pathologies in the mouse and suggest that degranulation of eosinophils recruited to the lung in this model does not occur at levels comparable to those observed in humans with asthma.     

Further characterization of human eosinophil peroxidase.

The large and the small subunits (Mr 50 000 and 10 500 respectively) of human eosinophil peroxidase were isolated by gel filtration under reducing conditions. The subunits were very strongly associated but not apparently cross-linked by disulphide bridges. During storage, the large subunit tended to form aggregates, which required reduction to dissociate them. Amino acid analysis of the performic acid-treated large subunit showed the presence of 19 cysteic acid residues. The small subunit of eosinophil peroxidase had the same Mr value as the small subunit of myeloperoxidase. However, although these subunits have very similar amino acid compositions, they showed different patterns of peptide fragmentation after CNBr treatment. The carbohydrate of eosinophil peroxidase seemed associated exclusively with the large subunit and comprised mannose (4.5%, w/w) and N-acetylglucosamine (0.8%, w/w). The far-u.v.c.d. spectrum of the enzyme indicated the presence of relatively little ordered secondary structure.     

Purification and characterization of a high molecular weight eosinophil chemotactic factor from Schistosoma japonicum eggs

A high m.w. eosinophil chemotactic factor (ECF-SjE) was isolated and purified from a soluble egg antigen preparation (SEA) of Schistosoma japonicum by gel filtration on Sephacryl S-200, anion-exchange chromatography on DE52, and isoelectric focusing. ECF-SjE had a m.w. of more than 900,000 and an isoelectric point of 4.1. It contained 40% (w/w) sugar residues and bound to concanavalin A (Con A). The chemotactic activity of ECF-SjE was heat stable (100 degrees C, 60 min) and resistant to pronase digestion, but was destroyed by periodate oxidation. IgG antibody to ECF-SjE was detected in the serum of a rabbit infected with S. japonicum, demonstrating the antigenic nature of ECF-SjE. The antigenicity of ECF-SjE was also sensitive to periodate oxidation. Thus, ECF-SjE is a glycoprotein or proteoglycan from the eggs of S. japonicum, and the sugar chain is important for the expression of chemotactic and antigenic activities. However ECF-SjE differs from the major allergenic components of S. japonicum (JEAL) in m.w. and isoelectric point. A low m.w. eosinophil chemotactic factor was also detected in SEA. Together they are proposed to have a role in the direct accumulation of eosinophils in the egg-induced granulomas in S. japonicum infection.     

Purification and characterization of a toxin inhibiting protein synthesis from Croton mongue, a Madagascar Euphorbiaceae

Monguine, a thermostable toxic protein was extracted from the seeds of Croton mongue (Euphorbiaceae) and purified by ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephadex G-25 and G-15. Polyacrylamide gel electrophoresis of purified monguine in the presence of sodium dodecyl sulfate and after treatment with 2-mercaptoethanol showed one band corresponding to a molecular weight of 9000. The same molecular weight was determined by analytical centrifugation. Amino acid analysis revealed a high content in both aspartic and glutamic acids (or the corresponding amides). The LD50 (24 h) is 12 mg/kg of mouse body weight. Monguine inhibits protein synthesis in hepatoma tissue culture cells and globin synthesis in a rabbit reticulocyte lysate.     

Purification and characterization of chymodenin. A hormone-like peptide from porcine duodenum

Chymodenin, a hormone-like duodenal peptide which rapidly alters the proportions of secreted pancreatic digestive enzymes to a mixture relatively richer in chymotrypsinogen than that found in basal secretion, has been purified to homogeneity. The starting material was an acidic methanol-soluble, neutral pH-insoluble fraction of an acetic acid extract of porcine duodenum; the purification consisted of cation-exchange chromatography on SP-Sephadex and CM-Sephadex in ammonium bicarbonate gradients, and gel filtration on Sephadex G-75 in dilute acetic acid. The yield of material was followed by radioimmunoassay. Homogeneity was determined from chymodenin's behavior in disc gel electrophoresis in an acidic counter-migration-of-dye system, sodium dodecyl sulfate-urea gels, gel filtration, dansyl-Edman reaction, reversed-phase high pressure liquid chromatography, isotachophoresis, and sedimentation equilibrium ultracentrifugation. The electrophoretic mobility, the molecular weight of 9,000-10,000, and the biological activity differed from those of other gastrointestinal peptide hormones. The amino acid composition was unique. Chymodenin is the first purified hormone-like substance reported capable of altering the composition of the mixture of secreted digestive enzymes, independent of the stimulation of massive pancreatic protein output.