Comparative studies on oestrogen-induced rat uterus peroxidase and rat eosinophil peroxidase.
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ABSTRACT:
SUBMITTER: Olsen RL
PROVIDER: S-EPMC1153907 | biostudies-other | 1982 Dec
REPOSITORIES: biostudies-other
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Project description:1. The visible absorption spectrum of peroxidase II, isolated from the uterine tissue of oestradiol-treated rats, and some of its derivatives were recorded. The spectral properties of this enzyme are very similar to eosinophile peroxidase and lactoperoxidase, suggesting that these enzymes may have a similar form of haem as prosthetic group. 2. The uterine peroxidase is modified upon interaction with H2O2 and the difference spectrum of this modified enzyme is similar to that of complex II of lactoperoxidase. The modified enzyme was found to revert spontaneously to the native enzyme at rates which depended on the concentration of free enzyme and H2O2.
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Project description:The distribution of oestrogen-induced peroxidase in the resuspended 8000g pellet of rat uterine homogenates was examined by centrifugation in a sucrose density gradient. Within 10h of treatment with oestradiol, peroxidase activity was found in a region devoid of catalase or urate oxidase (peroxisomal markers) which did not overlap the fractions containing succinate dehydrogenase (mitochondrial marker) or acid phosphatase (lysosomal marker). The induced uterine enzyme was localized in reticular membrane-bound vesicles with isopycnic density of 1.28g/ml from which it could be released by treatment with detergent.
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Project description:1. An enzyme that can be induced in rat uteri by oestrogens and that catalyses the oxidation of guaiacol and the metabolism and binding of [4-14C]oestradiol to protein in the presence of H2O2 was partially purified by (NH4)2SO4 fractionation and polyacrylamide-gel chromatography. 2. The molecular weight of this uterine peroxidase was estimated to be about 40 000 and thus shown to differ from that of eosinophil peroxidase. 3. Cycloheximide, which blocks the increase in peroxidase activity brought about by oestrogen, was used to determine the half-life (about 4h) of the induced uterine enzyme.
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Project description: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.
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Project description:1. Both the post-partum involution of the rat uterus and the rapid breakdown of collagen that accompanies it are extensively inhibited by oestrogenic hormones. In the normal rat, 85% of the uterine collagen is degraded within 4 days after parturition; in rats treated with 100mug. of 17beta-oestradiol/day, only 35% of uterine collagen is broken down in the same period. 2. Similar effects are produced by diethylstilboestrol if the dose is increased tenfold. 3. Collagen breakdown is inhibited to a greater extent than is the loss of wet weight by oestradiol but not by diethylstilboestrol. 4. The oestrogens appear to act by blocking the breakdown of collagen. There is a greatly decreased concentration of free hydroxyproline in the uterus of treated animals. 5. Acid hydrolase concentrations (beta-glucuronidase, beta-galactosidase, cathepsin D and acid phosphatase) in the uterus are decreased by oestrogen treatment compared with controls, but the total amounts of these enzymes in the uterus are somewhat elevated. Oestrogens do not appear to inhibit collagen breakdown by altering the concentration and total amount of acid hydrolases.
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Project description:Eosinophil peroxidase (EPX) is a major constituent of the large cytoplasmic granules of both human and mouse eosinophilic leukocytes. Human EPX deficiency is a rare, autosomal-recessive disorder limited to the eosinophil lineage. Our intent was to explore the impact of EPX gene deletion on eosinophil content, structure, and function. In response to repetitive intranasal challenge with a filtrate of the allergen, Alternaria alternata, we found significantly fewer eosinophils peripherally and in the respiratory tracts of EPX-/- mice compared to wild-type controls; furthermore, both the major population (Gr1-/lo ) and the smaller population of Gr1hi eosinophils from EPX-/- mice displayed lower median fluorescence intensities (MFIs) for Siglec F. Quantitative evaluation of transmission electron micrographs of lung eosinophils confirmed the relative reduction in granule outer matrix volume in cells from the EPX-/- mice, a finding analogous to that observed in human EPX deficiency. Despite the reduced size of the granule matrix, the cytokine content of eosinophils isolated from allergen-challenged EPX-/ - and wild-type mice were largely comparable to one another, although the EPX-/- eosinophils contained reduced concentrations of IL-3. Other distinguishing features of lung eosinophils from allergen-challenged EPX-/- mice included a reduced fraction of surface TLR4+ cells and reduced MFI for NOD1. Interestingly, the EPX gene deletion had no impact on eosinophil-mediated clearance of gram-negative Haemophilus influenzae from the airways. As such, although no clinical findings have been associated with human EPX deficiency, our findings suggest that further evaluation for alterations in eosinophil structure and function may be warranted.
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Project description:Eosinophil peroxidase has been implicated in promoting oxidative tissue damage in a variety of inflammatory conditions, including asthma. It uses H(2)O(2) to oxidize chloride, bromide and thiocyanate to their respective hypohalous acids. The aim of this study was to establish which oxidants eosinophil peroxidase produces under physiological conditions. By measuring rates of H(2)O(2) utilization by the enzyme at neutral pH, we determined the catalytic rate constants for bromide and thiocyanate as 248 and 223 s(-1) and the Michaelis constants as 0.5 and 0.15 mM respectively. On the basis of these values thiocyanate is preferred 2.8-fold over bromide as a substrate for eosinophil peroxidase. Eosinophil peroxidase catalysed substantive oxidation of chloride only below pH 6.5. We found that when eosinophil peroxidase or myeloperoxidase oxidized thiocyanate, another product besides hypothiocyanite was formed; it also converted methionine into methionine sulphoxide. During the oxidation of thiocyanate, the peroxidases were present as their compound II forms. Compound II did not form when GSH was included to scavenge hypothiocyanite. We propose that the unidentified oxidant was derived from a radical species produced by the one-electron oxidation of hypothiocyanite. We conclude that at plasma concentrations of bromide (20-120 microM) and thiocyanate (20-100 microM), hypobromous acid and oxidation products of thiocyanate are produced by eosinophil peroxidase. Hypochlorous acid is likely to be produced only when substrates preferred over chloride are depleted. Thiocyanate should be considered to augment peroxidase-mediated toxicity because these enzymes can convert relatively benign hypothiocyanite into a stronger oxidant.
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Project description: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.
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Project description:Eosinophil peroxidase (EPO) is one of the major oxidant-producing enzymes during inflammatory states in the human lung. The degradation of single-walled carbon nanotubes (SWCNTs) upon incubation with human EPO and H?O? is reported. Biodegradation of SWCNTs is higher in the presence of NaBr, but neither EPO alone nor H?O? alone caused the degradation of nanotubes. Molecular modeling reveals two binding sites for SWCNTs on EPO, one located at the proximal side (same side as the catalytic site) and the other on the distal side of EPO. The oxidized groups on SWCNTs in both cases are stabilized by electrostatic interactions with positively charged residues. Biodegradation of SWCNTs can also be executed in an ex vivo culture system using primary murine eosinophils stimulated to undergo degranulation. Biodegradation is proven by a range of methods including transmission electron microscopy, UV-visible-NIR spectroscopy, Raman spectroscopy, and confocal Raman imaging. Thus, human EPO (in vitro) and ex vivo activated eosinophils mediate biodegradation of SWCNTs: an observation that is relevant to pulmonary responses to these materials.
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Project description:1. An enzyme that catalyses the metabolism and binding of [4-(14)C]oestradiol to protein and to other high-molecular-weight substances in the presence of H(2)O(2) was shown to be absent from the uteri of immature rats and to be induced by physiological doses of oestrogen or pregnant-mare-serum gonadotrophin. 2. The pH optimum, stability to heat and other characteristics of the uterine enzyme system as well as its subcellular distribution were determined. 3. The increase in the ability of uterine preparations to convert [4-(14)C]oestradiol into water-soluble products as a result of oestrogen treatment was accompanied by an increase in peroxidase and NADH oxidase activities and was inhibited by actinomycin D and cycloheximide. 4. The results support the proposal that the increase in peroxidase activity after oestrogen treatment might be part of an adaptive response of the uterus permitting it to bind and inactivate oestrogens and thus limit the duration of their effect upon this target tissue.
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