Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The SOS chromotest is a simple short-term genotoxicity assay measuring the induction of gene sfiA in Escherichia coli K-12. The recent availability of SOS tester strains with additional mutations in DNA repair or protection systems allows testing of DNA damaging compounds for genotoxic specificity. E. coli PQ300 differs from the standard SOS tester strain PQ37 in that it contains an additional mutation in gene oxyR that renders it more sensitive to oxidative genotoxins. The generation of reactive oxygen intermediates (ROI) by hydroperoxides (H2O2, t-butyl hydroperoxide, cumene hydroperoxide), gamma-radiation, glucose oxidase, and xanthine oxidase resulted in a more vigorous SOS response in strain PQ300 compared to strain PQ37. PQ300 was also more sensitive than PQ37 for the detection of reducing agents such as ascorbic acid, cysteine, and glutathione, which also alter the redox status of the bacterial cells. However, intercalating agents (adriamycin, bleomycin, and mitomycin C) and the UV- and radiomimetic compound 4-nitroquinoline-1-oxide whose DNA damaging potential are known also to involve ROI did not show significant differences between strains PQ37 and PQ300. It is concluded that the oxyR-deficient strain PQ300 is useful for detecting certain classes of genotoxins that change the oxidative/antioxidative balance of tester bacteria in the SOS chromotest.
Environ Mol Mutagen 1992
PMID:Assessment of oxidative DNA damage in the oxyR-deficient SOS chromotest strain Escherichia coli PQ300. 142 9

The chemical targets and mechanisms of iron-catalyzed oxidative injury in myocardium are poorly understood. Oxygen metabolites, in the presence of iron, can initiate free-radical chain reactions in unsaturated membrane lipids, generating lipid peroxides and causing membrane injury. We examined whether exposure to iron-catalyzed oxidative injury would increase myocardial lipid peroxide levels as injury evolved in the intact heart. Isolated, buffer perfused rabbit hearts were exposed for 30 min to 100 uM Fe2+/500 uM ADP and 10 uM H2O2 (IRON group, n = 5), saline vehicle (CON group, n = 6) or 500 uM ADP and 10 uM H2O2 without iron (ADP, n = 5). Lipid peroxides were measured in cytosol and membrane fractions by a new method, using the lipid peroxide-induced oxidation of exogenous GSH to GSSG, catalyzed by the enzyme glutathione peroxidase. The results indicated that iron-catalyzed lipid peroxidation occurs in the intact heart during chemically-mediated oxidative injury.
J Mol Cell Cardiol 1992 Sep
PMID:Iron-catalyzed reactions cause lipid peroxidation in the intact heart. 143 19

An underinvestigated aspect of the mitogenic and cell regulatory actions of vanadium is the regulation of gene expression. Among the fifteen cellular genes studied in cultured mouse C127 cells, vanadium (as 10 microM sodium vanadate) increased levels of mRNA of the actin and c-Ha-ras to four times control values. These increases represented de novo synthesis of mRNA, since they were inhibited by actinomycin D. Vanadate did not increase mRNA corresponding to c-src, c-mos, c-myc, p53, HSP70, pODC or RB genes, and expression of c-erb A, c-erb B, c-sis and c-fes genes was undetectable whether vanadium was present or not. Expression of a third gene affected by vanadium, c-jun, was augmented by addition of a reductant or oxidant together with the vanadate. Addition of NADH (marginally effective on its own) or H2O2 (effective alone) dramatically enhanced the effect of vanadate on c-jun gene expression. Catalase inhibited the effect of NADH partly. The vanadate-stimulated expression of actin and c-Ha-ras mRNA were unaffected by oxidants, reductants, metal chelators, or anti-oxidant enzymes. Evidently vanadate acts by two separate mechanisms on these two categories of genes. The alternate hypothesis that the actions of vanadate on actin and c-Ha-ras were mediated by a protein kinase cascade was inconsistent with the following observations. Neither insulin nor epidermal growth factor increased mRNA levels of c-Ha-ras or actin gene. Neither genistein (a tyrosine kinase inhibitor) nor pretreatment with 12-O-tetradecanoylphorbol-13-acetate blocked the actions of vanadate on these genes. Clearly the biological actions of vanadium depend in part on altered expression of genes. Since two of the genes are proto-oncogenes, this mechanism is potentially relevant to the mitogenic responses of cells to vanadium.
Mol Cell Biochem 1992 Sep 22
PMID:Vanadate-induced gene expression in mouse C127 cells: roles of oxygen derived active species. 143 69

To test the hypothesis that reactive species in the oxygen cascade are responsible for spontaneous mutation, we examined the spectra of oxygen and hydrogen peroxide-induced mutations at the hprt locus in a human B-lymphoblastoid cell line. We compared these spectra with the spontaneous mutational spectrum. Large gene alterations were studied by Southern analysis of individual TGR clones. A combination of high fidelity polymerase chain reaction, denaturing gradient gel electrophoresis and direct DNA sequencing were used to detect and identify point mutations in exon 3 of hprt. With regard to spontaneous mutations, a previous study showed that 39% of the spontaneous TGR clones had large gene alterations. In the present study, the analysis of spontaneous point mutations within exon 3 revealed two hotspots. A one base-pair deletion (-A) at base-pair 256 or 257 and a two base-pair deletion (-GG) at base-pair 237 and 238, were detected in triplicate cultures. Each of the hotspots comprised about 1% of the TGR mutants. The analysis of individual oxygen-induced TGR clones (48 h, 910 microM-O2) showed 43% had large gene alterations similar to the spontaneous TGR clones. However, none of the spontaneous point mutation hotspots was found among triplicate oxygen-treated cultures. Two point mutations in common with H2O2-treated cultures were found in one of the three oxygen-treated cultures. Hydrogen peroxide-induced mutations (1 h, 20 microM) also differed from spontaneous mutations. Only 24% of the hydrogen peroxide-induced TGR clones had large gene alterations. The analysis of point mutations showed three hotspots within exon 3 of hprt. An AT to TA transversion at base-pair 259 had an average frequency of 3% of all TGR mutants (present in all of 3 H2O2-treated cultures). Two GC to CG transversions at base-pairs 243 and 202 were present at a frequency of 0.6% and 0.4%, respectively. A five base-pair deletion (base-pair 274 to 278) was present at an average frequency of 0.3%. The latter three mutations were detected in two of three H2O2-treated cultures. Thus, the point mutation spectra of both oxygen and hydrogen peroxide were significantly different from the spontaneous spectrum. The oxygen and hydrogen peroxide-induced spectra shared some features, suggesting that oxygen and hydrogen peroxide share some but not all pathways for induction of mutations within the DNA sequence studied here.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1992 Dec 05
PMID:Mutational spectra in human B-cells. Spontaneous, oxygen and hydrogen peroxide-induced mutations at the hprt gene. 146 15

Two of the major cell types in bone marrow stroma, macrophages and fibroblasts, have been shown to be important regulators of both myelopoiesis and lymphopoiesis. The enzymology relating to cell-specific metabolism of phenolic metabolites of benzene in isolated mouse bone marrow stromal cells was examined. Fibroblastoid stromal cells had elevated glutathione-S-transferase (4.5-fold) and DT-diaphorase (4-fold) activity relative to macrophages, whereas macrophages demonstrated increased UDP-glucuronosyltransferase (UDP-GT, 7.5-fold) and peroxidase activity relative to stromal fibroblasts. UDP-GT and glutathione-S-transferase activities in macrophages and fibroblasts, respectively, were significantly greater than those in unpurified white marrow. Aryl sulfotransferase activity could not be detected in either bone marrow-derived macrophages or fibroblasts, and there were no significant differences in GSH content between the two cell types. Because UDP-GT activity is high in macrophages, these data suggest that DT-diaphorase levels would be rate limiting in the detoxification of benzene-derived quinones in bone marrow macrophages. The peroxidase responsible for bioactivation of benzene-derived phenolic metabolites in bone marrow macrophages is unknown but has been suggested to be prostaglandin H synthase (PGS). Hydrogen peroxide, but not arachidonic acid, supported metabolism of hydroquinone to reactive species in bone marrow-derived macrophage lysates. These data do not support a major role for PGS in peroxidase-mediated bioactivation of hydroquinone in bone marrow-derived macrophages, although PGS mRNA could be detected in these cells. Similarly, hydrogen peroxide, but not arachidonic acid, supported metabolism of hydroquinone in a human bone marrow homogenate. Peroxidase-mediated interactions between phenolic metabolites of benzene occurred in bone marrow-derived macrophages. Bioactivation of hydroquinone to species that would bind to acid-insoluble cellular macromolecules was increased by phenol and was markedly stimulated by catechol. Bioactivation of catechol was also stimulated by phenol but was inhibited by hydroquinone. These data define the enzymology and the cell-specific metabolism of benzene metabolites in bone marrow stroma and demonstrate that interactions between phenolic metabolites may contribute to the toxicity of benzene in this critical bone marrow compartment.
Mol Pharmacol 1992 Dec
PMID:Cell-specific metabolism in mouse bone marrow stroma: studies of activation and detoxification of benzene metabolites. 148 Jan 34

The effect of peroxidation on 5'-nucleotidase activity as well as on membrane microviscosity has been investigated in liver plasma membranes from Wistar rats. The peroxidation was performed with 100 microM H2O2 and 200 microM FeSO4 and/or with 5 mM t-butylhydroperoxide. Treatment of the membranes with these oxidizing agents resulted in an elevation of the transition temperatures of the polarization of the lipid fluorescent probes 1,6 diphenyl-1,3,5 hexatriene (DPH), 3-p-(6-phenyl) 1,3,5 hexatriene phenylpropionic acid (PA-DPH) as well as of the fluorescent thiol reagent N-(1-pyrene) maleimide (1-PM). The peroxidation resulted in a decrease of the activity of 5'nucleotidase. Our data support that the increase of membrane microviscosity of the lipid domain regulates the activity of 5'-nucleotidase.
Cell Mol Biol 1992 Jul
PMID:Lipid peroxidation causes an increase of lipid order and a decrease of 5'-nucleotidase activity in the liver plasma membrane. 149 43

Trypanosoma cruzi epimastigotes permeabilized with digitonin (65 micrograms (mg protein)-1) to measure mitochondrial respiration were exposed to different substrates. Although none of the NADH-dependent substrates stimulated respiration, succinate supported not only oxygen consumption but also oxidative phosphorylation (respiratory control ratio of 1.9 +/- 0.3) indicating that the mitochondria were coupled. The rate of NADH-dependent oxygen consumption by membrane fractions (9.4 +/- 0.7 nmol min-1 (mg protein)-1) was reduced by 50% upon addition of catalase indicating that the electrons from NADH oxidation reduced oxygen to H2O2. NADH-dependent H2O2 production (16 +/- 1 nmol min-1 (mg protein)-1) was confirmed using cytochrome c peroxidase. This activity was inhibited by fumarate by 70%, suggesting a competition between fumarate and oxygen for the electrons from NADH, probably at the fumarate reductase level. The respiratory chain inhibitor antimycin blocked both respiration by intact cells and succinate-dependent cytochrome c by isolated membranes. No inhibition by antimycin was observed when NADH replaced succinate as an electron donor, indicating that the electrons from NADH oxidation reduced cytochrome c through a different route. Malonate blocked not only succinate-cytochrome c reductase and fumarate reductase, but also intact cell motility. These results suggest that succinate has a central role in the intermediate metabolism of i. cruzi, as it may be used for respiration or excreted to the extracellular space under anaerobic conditions. In addition, 2 potential sources of H2O2 were tentatively identified as: (a) the enzyme fumarate reductase; and (b) a succinate-dependent site, which may be the semiquinone form of Coenzyme Q9, as in mammalian mitochondria.
Mol Biochem Parasitol 1992 Aug
PMID:Succinate-dependent metabolism in Trypanosoma cruzi epimastigotes. 151 31

Reactive oxygen species stimulate metabolism of arachidonic acid (AA) to eicosanoids in a variety of cells and tissues, yet the pathway(s) by which oxidants increase the availability of AA for oxidative metabolism are not known. Thus, we explored the effects of hydrogen peroxide (H2O2) on deacylation and reacylation of AA to determine the enzymatic mechanism(s) by which this oxidant increases levels of free, unesterified AA, and thereby its oxidative metabolism to eicosanoids, in the rat alveolar macrophage (AM). Over the range from 0.1 to 0.5 mM, H2O2 caused marked time- and dose-dependent inhibition of incorporation of [3H]AA into macrophage phospholipids, whereas calcium ionophore A23187 and zymosan particles did not cause such inhibition. Within this concentration range, there was an almost exact reciprocal correlation between inhibition of [3H]AA acylation and H2O2-stimulated accumulation of free [3H]AA in prelabeled AM cultures. Thimerosal, which blocks AA reacylation but spares deacylation via phospholipase A2 (PLA2), did not affect accumulation of free [3H]AA in prelabeled cells stimulated with H2O2, while markedly augmenting [3H]AA release in response to A23187 and to zymosan. Despite its ability to block AA acylation almost completely, H2O2 did not directly inhibit arachidonoyl CoA synthetase or arachidonoyl CoA:lysophosphatide acyltransferase, which catalyze AA incorporation into phospholipids. However, H2O2 (0.1 to 0.5 mM) markedly depleted AMs of ATP, required for synthesis of the acylation intermediate arachidonoyl CoA, suggesting that this was the means by which H2O2 inhibited acylation. Notably, H2O2 (0.03 to 3 mM) failed to stimulate macrophage PLA2 activity. We conclude that H2O2, in contrast to A23187 and zymosan, inhibits incorporation of AA into phospholipids, and that this represents the major mechanism by which the oxidant increases the availability of free AA for oxidative metabolism in the AM. This may be an important basis for release of eicosanoids in oxidant-induced inflammation and injury of the lung.
Am J Respir Cell Mol Biol 1992 Sep
PMID:Hydrogen peroxide increases the availability of arachidonic acid for oxidative metabolism by inhibiting acylation into phospholipids in the alveolar macrophage. 152 Apr 93

Endogenous hydrogen peroxide (H2O2) release from aortic endothelial cells was studied in the presence of antioxidant enzyme inhibitors, mitochondrial inhibitors, a microsomal cytochrome P-450 inhibitor, and after oxidative stress induced with H2O2 or menadione. Extracellular H2O2 generation was determined spectrofluorometrically using 3-methoxy-4-hydroxy phenylacetic acid, and intracellular H2O2 production (in or near peroxisomes) was measured indirectly using aminotriazole, which inactivates catalase in the presence of H2O2. Extracellular H2O2 release was 0.079 +/- 0.005 nmol/min/mg protein in Hanks' balanced salt solution, was constant during a 120-min incubation period, and was not affected by the cell passage number. The half-life for catalase inactivation with aminotriazole was 23 min. Inhibition of catalase, glutathione reductase, or gamma-glutamylcysteine synthetase did not change the rate of extracellular release of H2O2. Furthermore, inhibition of the mitochondrial respiratory chain (rotenone, antimycin A) or microsomal cytochrome P-450 (8-methoxypsoralen) did not change extracellular H2O2 release or intracellular H2O2 production (at peroxisomes) by endothelial cells or cells in which glutathione reductase was inactivated. When the cells were exposed to exogenous H2O2 (30 microM), extracellular H2O2 was scavenged primarily by the glutathione redox pathway. Exogenously added H2O2 (100 microM) changed intracellular H2O2 production (in or near peroxisomes) only when the glutathione redox cycle was inactivated. Menadione (20 microM), which undergoes intracellular redox cycling, increased extracellular H2O2 release almost 4-fold to 0.3 nmol/min/mg protein. Furthermore, menadione increased peroxisomal H2O2 levels and decreased the half-life for catalase inactivation in the presence of aminotriazole to 13 min. Catalase inhibition increased extracellular H2O2 release during menadione treatment, indicating that H2O2 can diffuse across the plasma membrane during oxidant stress.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1992 Feb
PMID:Regulation of hydrogen peroxide generation in cultured endothelial cells. 154 Mar 80

To study the effect of the inflammatory mediator hydrogen peroxide (H2O2) on airway ciliary activity, we measured ciliary beat frequency (CBF) in cultured tracheal explants from sheep. Addition of H2O2 (10(-8) to 10(-4) M) produced a concentration-dependent mean (+/- SEM) decrease in CBF between 11.1 +/- 0.4% (P less than 0.01) and 100 +/- 0% (P less than 0.001); at each concentration, the maximal effect was reached by 20 to 25 min. Between 10(-8) and 10(-6) M H2O2, the decrease in CBF was reversible, lactate dehydrogenase (LDH) release was not significantly increased, and major morphologic lesions were not seen. At higher concentrations of H2O2, incomplete recovery of CBF (10(-5) M) or irreversible ciliostasis (10(-4) M) developed, and a significant increase in LDH and morphologic lesions were present. Catalase (2,000 U/ml) and H-7 (10(-5) M), a protein kinase inhibitor, abolished cilioinhibition produced by H2O2 at 10(-6) M and lower concentrations but not at 10(-5) M and higher concentrations. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, caused a dose-dependent (10(-11) to 10(-5) M), reversible decrease in CBF; this effect was abolished by H-7. We suggest that at nonlethal concentrations, H2O2 inhibits the beat frequency of airway epithelial cilia reversibly, through the activation of second messengers, including protein kinase C. This mechanism might contribute to the previously demonstrated impairment of mucociliary clearance in airway inflammation.
Am J Respir Cell Mol Biol 1992 Jun
PMID:Mechanism of hydrogen peroxide-induced inhibition of sheep airway cilia. 159 Oct 15


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