Elimination of hydrogen peroxide by Haemophilus somnus, a catalase-negative pathogen of cattle.
(9/34)
Haemophilus somnus is a catalase-negative, gram-negative pathogen of cattle which is refractory to killing by bovine neutrophils. In this report, we showed that H. somnus rapidly inhibited Luminol-dependent chemiluminescence of bovine neutrophils costimulated with opsonized zymosan or phorbol myristate acetate. We have postulated that this inhibition resulted in part from H. somnus preventing the accumulation of hydrogen peroxide (H2O2) during the oxidative burst. In support of this hypothesis, we have demonstrated that when stimulated with viable H. somnus, bovine neutrophils accumulate lower levels of H2O2 than did neutrophils stimulated with heat-killed H. somnus or opsonized zymosan. We have presented evidence that four separate strains of H. somnus, despite being catalase negative by conventional criteria, removed H2O2 from solution. Viable cells of H. somnus were required for the removal of H2O2 from solution; little or no activity was observed when suspensions of heat-killed, formalin-killed, or sonicated cells of H. somnus were incubated with H2O2. In addition, the elimination of H2O2 occurred only in the presence of carbon sources that could be utilized by H. somnus, indicating that elimination of H2O2 was an energy-dependent process. The amount of H2O2 that could be eliminated by 10(7) cells of H. somnus was greater than 10 nmol, an amount comparable to that produced by a similar number of stimulated bovine neutrophils. Thus, we suggest that the ability of H. somnus to remove H2O2 from solution may be an important virulence mechanism that contributes to the survival of the organism following ingestion by bovine neutrophils. (+info)
Characterization of acatalasemic erythrocytes treated with low and high dose hydrogen peroxide. Hemolysis and aggregation.
(10/34)
The effects of hydrogen peroxide on normal and acatalasemic erythrocytes were examined. Severe hemolysis of acatalasemic erythrocytes and a small tyrosine radical signal (g = 2.005) associated with the formation of ferryl hemoglobin were observed upon the addition of less than 0.25 mM hydrogen peroxide. However, when the concentration of hydrogen peroxide was increased to 0.5 mM, acatalasemic erythrocytes became insoluble in water and increased the tyrosine radical signal. Polymerization of hemoglobin and aggregation of the erythrocytes were observed. On the other hand, normal erythrocytes exhibited only mild hemolysis by the addition of hydrogen peroxide under similar conditions. From these results, the scavenging of hydrogen peroxide by hemoglobin generates the ferryl hemoglobin species (H-Hb-Fe(IV)=O) plus protein-based radicals (*Hb-Fe(IV)=O). These species induce hemolysis of erythrocytes, polymerization of hemoglobin, and aggregation of the acatalasemic erythrocytes. A mechanism for the onset of Takarara disease is proposed. (+info)
Effect of covalent attachment of polyethylene glycol on immunogenicity and circulating life of bovine liver catalase.
(11/34)
Methoxypolyethylene glycols of 1900 daltons (PEG-1900) or 5000 daltons (PEG-5000) were covalently attached to bovine liver catalase using 2,4,6-trichloro-s-triazine as the coupling agent. Rabbits were immunized by the intravenous and intramuscular routes with catalase modified by covalent attachment of PEG-1900 to 43% of the amino groups (PEG-1900-catalase). The intravenous antiserum did not yield detectable antibodies against PEG-1900-catalase or native catalase, as determined by Ouchterlony and complement fixation methods, whereas the intramuscular antiserum contained antibodies to both PEG-1900-catalase and catalase. PEG-1900 did not react with either antiserum. Catalase was prepared in which PEG-5000 was attached to 40% of the amino groups (PEG-5000-catalase). This catalase preparation did not react with either antiserum. PEG-1900-catalase retained 93% of its enzymatic activity; PEG-5000-catalase retained 95%. PEG-5000-catalase resisted digestion by trypsin, chymotrypsin, and a protease from Streptomyces griseus. PEG-1900-catalase and PEG-5000-catalase exhibited enhanced circulating lives in the blood of acatalasemic mice during repetitive intravenous injections. No evidence was seen of an immune response to injections of the modified enzymes. Mice injected repetitively with PEG-5000-catalase remained immune competent for unmodieied catalase, and no evidence of tissue or organ damage was seen. (+info)
Peroxisomes and aging.
(12/34)
Peroxisomes are indispensable for proper functioning of human cells. They efficiently compartmentalize enzymes responsible for a number of metabolic processes, including the absolutely essential beta-oxidation of specific fatty acid chains. These and other oxidative reactions produce hydrogen peroxide, which is, in most instances, immediately processed in situ to water and oxygen. The responsible peroxidase is the heme-containing tetrameric enzyme, catalase. What has emerged in recent years is that there are circumstances in which the tightly regulated balance of hydrogen peroxide producing and degrading activities in peroxisomes is upset-leading to the net production and accumulation of hydrogen peroxide and downstream reactive oxygen species. The factor most essentially involved is catalase, which is missorted in aging, missing or present at reduced levels in certain disease states, and inactivated in response to exposure to specific xenobiotics. The overall goal of this review is to summarize the molecular events associated with the development and advancement of peroxisomal hypocatalasemia and to describe its effects on cells. In addition, results of recent efforts to increase levels of peroxisomal catalase and restore oxidative balance in cells will be discussed. (+info)
Hepatocellular carcinomas in acatalasemic mice treated with nafenopin, a hypolipidemic peroxisome proliferator.
(13/34)
The effects of long-term administration of nafenopin, a potent hypolipidemic drug with marked hepatomegalic and peroxisome-proliferative properties, were studied in wild-type (Csa strain) and acatalasemic (Csb strain) mice. Nafenopin was administered in the diet at a concentration of 0.1% during the first 12 months and then at 0.05% until the termination of the experiment at 20 months. By 56 weeks, 100% mortality occurred in both male and female wild-type mice, whereas the mortality rate in acatalasemic mice was approximately 50%. Between 18 and 20 months of the experiment, 9 of 9 male and 12 of 12 female acatalasemic mice that survived chronic nafenopin treatment developed hepatocellular carcinomas, some of which metastasized to the lungs. None of the 15 male and 15 female acatalasemic controls developed liver cancers. Numerous peroxisomes were seen in the lung metastases of these hepatocellular carcinomas on electron microscopic examination; in contrast the number of peroxisomes in primary liver tumor cells varied considerably. The hepatocarcinogenicity of nafenopin strongly suggests the need for long-term studies with other hypolipidemic drugs that cause hepatomegaly and peroxisome proliferation to clarify the role, if any, of peroxisome proliferation in liver carcinogenesis. (+info)
Mammalian acatalasemia: the perspectives of bioinformatics and genetic toxicology.
(14/34)
The molecular defects in the catalase gene, levels of m-RNA and properties of the residual catalase studied by scientists are reviewed in human (Japanese, Swiss and Hungarian) and non-human (mouse and beagle dog) acatalasemia with reference to the bioinformatics. Japanese acatalasemia-I, the G to A transition at the fifth position of intron 4 of the catalase gene, limited the correct splicing of the mRNA and synthesized trace catalase with normal properties. Hungarian acatalasemia type C showed a splicing mutation. In the Japanese acatalasemia II and the type A and B of Hungarian acatalasemia, the deletion or insertion of nucleotides was observed in the coding regions, and the frame shift altered downstream amino acid sequences and formed truncated proteins. In the Hungarian acatalasemia D, the substitution of a nucleotide in the exon was found. In mouse and beagle dog acatalasemia, the substitution of nucleotides in the coding regions was also observed. Studies of residual catalase in Swiss, mouse and beagle dog acatalasemia showed that aberrant catalase protein degrades more quickly than normal catalase in cells. The experimental research in genetic toxicology concerning the effect of oxidative stressors (nitrogen monoxide, nitrogen dioxide and so on) on Japanese acatalasemic blood and acatalasemic mice is described. The clinical features of Japanese and Hungarian acatalasemic subjects are also described. (+info)
Antiinflammatory effects of hydrogen peroxide in neutrophil activation and acute lung injury.
(15/34)