Superoxide dismutase and glutathione peroxidase in polymorphonuclear leucocytes

Glutathione redox pathway and reperfusion injury. Effect of N-acetylcysteine on infarct size and ventricular function

Glutathione peroxidase is an important enzyme in the degradative cascade of reactive oxygen free radicals. N-Acetylcysteine (NAC) is a low molecular weight compound that has been used clinically to replenish glutathione. To assess the role of the glutathione redox pathway on reperfusion injury, 23 animals underwent 90 minutes of proximal left anterior descending coronary artery occlusion followed by 24 hours of reperfusion with the administration of NAC (n = 11) or saline (n = 12) beginning 30 minutes into occlusion and continuing for 3 hours after reperfusion. Regional ventricular function was measured with contrast ventriculography, and regional myocardial blood flow was determined with microspheres. At 24 hours, the area at risk was defined in vivo with Monastral Blue, and the area of necrosis was defined by incubation in triphenyltetrazolium. Biopsies were taken from the ischemic and nonischemic zones to determine levels of total glutathione, superoxide dismutase and glutathione peroxidase activity, and reactivity to thiobarbituric acid, an index of lipid peroxidation. The rate-pressure product and myocardial blood flow were similar in the two groups throughout the study. No significant differences were noted in infarct size expressed as a percentage of the area at risk (28.6 +/- 5.3% vs. 36.6 +/- 6.0%) and of the total left ventricle (14.4 +/- 3.2% vs. 16.5 +/- 3.1%), and no differences were noted between the two groups on examination of the ischemic subendocardium by light and electron microscopy. Both groups exhibited similar degrees of dyskinesis during occlusion; however, treated animals showed significant improvement in regional radial shortening at 3 hours (3.4 +/- 2.4% vs. -2.4 +/- 2.1%, p less than 0.02) and 24 hours (9.2 +/- 2.2% vs. -2.5 +/- 6.3%, p less than 0.001) after reperfusion. No differences were present in total glutathione, thiobarbituric acid reactivity, or superoxide dismutase and glutathione peroxidase activity in the ischemic zones of the two groups. This study suggests that N-acetylcysteine treatment before reperfusion may reduce myocardial stunning but does not limit myocyte death after reperfusion.

Diminished neutrophil function in Crohn's disease and ulcerative colitis identified by decreased oxidative metabolism and low superoxide dismutase content

Features of the neutrophil oxidative metabolism and enzyme activity in peripheral blood neutrophils were studied in 43 patients with Crohn's disease, 13 with ulcerative colitis and 33 healthy controls. The production of superoxide anion (O2-.) by phorbol-myristate-acetate stimulated neutrophils from patients with Crohn's disease and ulcerative colitis was significantly diminished compared with controls mean (SE) = 47.1 (3.6) and 38.0 (3.8) v 67.4 (7.5) nmol/10(7) cells/min, p less than or equal to 0.02, respectively, while the production of hydrogen peroxide was normal. The neutrophil content of superoxide dismutase (SOD), a cytoprotective enzyme, was also markedly diminished in Crohn's disease mean (SE) = 7.11 (0.23) ng SOD/micrograms DNA, p less than 0.05, and ulcerative colitis mean (SE) = 5.74 (0.42) compared with controls 7.84 (0.27), p less than 0.001. In contrast, the concentration of neutrophil elastase, a neutral protease, was found to be normal when compared with neutrophils from controls. The neutrophil O2-. production and the SOD concentrations were significantly and negatively correlated with the disease activity in Crohn's disease and ulcerative colitis. The results indicate diminished neutrophil function in peripheral blood of patients with Crohn's disease and ulcerative colitis as illustrated by a diminished oxidative system, which correlates with the disease activity.

Superoxide dependent iron release from ferritin in inflammatory diseases

Convincing evidence is presented that oxygen free radicals are involved in the pathogenesis of rheumatoid arthritis (RA). Superoxide is produced by polymorphonuclear leucocytes (PMN) in synovial fluid and by macrophages in the synovial membrane. Tissue damage typical for free radical attack is detected in RA. No absolute deficiency of protective factors is found in RA compared to controls, but the available protection is insufficient to cope with all radicals formed. The toxicity of superoxide is increased by iron. It is doubtful whether a low molecular weight iron pool is present. Superoxide is able to release iron from ferritin, providing a suitable source of iron, for the formation of hydroxyl radicals. This new pathogenetic mechanism stimulates to the application of iron chelators in the treatment of RA. Preliminary results with desferrioxamine were disappointing because of serious side-effects. Hopefully in the future intra-articular injection of iron chelators with better pharmacodynamics will be possible. The interaction of free radicals and ferritin is probably also involved in the pathogenesis of other inflammatory diseases such as systemic lupus erythematosus, hepatitis, and haemochromatosus.

Aspects of the structure, function, and applications of superoxide dismutase

The current status of superoxide dismutase (SOD) is that it is an enzyme with diverse ramifications. This review attempts an understanding of SOD as a structural, functional, and biological entity. Accordingly, the review is in three parts. The first part discusses SOD in terms of protein structure, proceeding from primary to secondary and three-dimensional structure for the three forms of SOD: copper/zinc SOD, manganese SOD, and iron SOD. This is the order of structural knowledge of the enzyme. Iron SOD is an enzyme of prokaryotes and some higher plants. Manganese SOD is an enzyme of prokaryotes and eukaryotes. Copper/zinc SOD is an enzyme of eukaryotes and certain prokaryotes. The evolutionary relationships of the three forms of SOD, the status of the copper/zinc SOD gene in prokaryotes, and the cloning and sequencing of SOD genes are discussed. The second part of the review deals with the catalytic mechanism of SOD in the three forms of the enzyme. Structural and mechanistic conclusions from various spectroscopic studies are critically considered. A detailed picture is given of the active site of copper/zinc SOD. The third part is a review of SOD in the general context of oxygen toxicity. After consideration of the question of superoxide toxicity and superoxide pathology, several areas in which SOD has been investigated or used as a tool in a biochemical, pharmacological, or clinical context are discussed, including population genetics; trisomy 21; development and senescence; the nutritional copper, zinc, and manganese status; hemolysis and anemia; oxygen toxicity in the lung and nervous system; inflammation, autoimmune disease and chromosome breakage, ischemia and degenerative changes; radiation damage; and malignancy. A comprehensive picture is given of measurements of SOD activity in disease states, and the question of superoxide-related disease is considered at several points.

Effects of 1,2-dibromoethane on glutathione metabolism in rat liver and kidney

There are few reports of the effects of glutathione-depleting agents administered for periods longer than 24 hr on the turnover of glutathione (GSH) in mammalian tissues. Studies of such effects are important in relation to the protection of tissues from damage from, for example, reactive metabolites derived from xenobiotics. In the investigation described here, 1,2-dibromoethane dibromide)-a widely used insecticide, nematocide, fungicide and petrol additive, which is hepato- and nephrotoxic-was administered to rats and the effects on non-protein thiol contents and GSH-related enzyme activities were determined in liver and kidney. The classical GSH-depleter diethylmaleate was used in parallel studies for comparative purposes.

Protective factors against oxygen free radicals and hydrogen peroxide in rheumatoid arthritis synovial fluid

Oxygen free radicals are probably involved in the pathogenesis of rheumatoid arthritis (RA). The enzymes involved in protection against oxygen free radicals and H2O2 (superoxide dismutase, catalase, and glutathione peroxidase) were measured. Superoxide dismutase was not increased, glutathione peroxidase was slightly and catalase was strongly elevated in RA synovial fluid (SF) compared with control SF. Although these enzymes are present in SF, the activities are insufficient to protect against oxygen free radicals and H2O2. In contrast to transferrin, ferritin was increased in RA synovial fluid. Ceruloplasmin was also elevated. When rat liver microsomes were used as a target for oxygen free radicals, serum and SF were both protective. Gel filtration experiments showed that the fraction pattern in which there was maximal protective potential against lipid peroxidation corresponded closely to the level of ceruloplasmin. After removal of ceruloplasmin from serum or SF, about 70% of the protective capacity disappeared. It is concluded that ceruloplasmin is an important protector against oxygen free radicals.

Can dietary selenium reduce leukotriene production?

The leukotrienes, prominent mediators of immediate hypersensitivity and inflammation, are derived from the major product of leukocyte lipoxygenase activity, 5-HPETE. An alternative pathway for 5-HPETE metabolism is reduction to 5-HETE. I hypothesize that, in analogy to its established role in platelet lipoxygenase metabolism, the selenium-dependent glutathione peroxidase mediates this reduction. If so, supplementary selenium may decrease leukotriene production, and thus have value as a nutritional adjuvant in the management of asthma and various other inflammatory disorders.

[Superoxide-dismutase and superoxide-radical-release in rheumatoid arthritis (author's transl)]

Polymorphonuclear leukocytes (PMNs) release superoxide anion (O-2) when they are exposed to a phagocytic stimulus. Intracellularly the copper-containing enzyme superoxide dismutase (SOD) protects against the toxic effects of O-2. To investigate the role of O-2 and SOD in the inflammatory process we determined the O-2 release and SOD content in PMNs. In PMNs of children with rheumatoid arthritis the SOD activity was diminished compared to healthy controls. Upon stimulation with opsonized zymosan PMNs obtained from children with rheumatoid arthritis generated greater amounts of superoxide anion than control cells. The "SOD deficiency" in PMNs of children with rheumatoid arthritis may promote this extreme release of the toxic superoxide radical inducing the damage of the connective tissue. The involvement of superoxide dismutase and superoxide anion in inflammatory process may induce further studies, leading hopefully to an appropriate understanding or even to new principles in the treatment of the rheumatoid arthritis.

Concanavalin A capping in polymorphonuclear leukocytes

Various polymorphonuclear leukocyte (PMN) functions are dependent on an intact intracellular cytoskeleton consisting of the microtubules and the microfilaments. To investigate the microtublule system in PMNs we observed the spontaneous, Colchicine and Diamide induced cap-formation by fluorescence microscopy ion PMNs obtained from children with bacterial and viral infections demonstrated with 47 +/- 1% a significantly increased number of spontaneous capped PMNs compared to 22 +/- 1% capped cells obtained from controls. Furthermore, 52 +/- 2% PMNs of patients on immunosuppressive therapy exhibited spontaneous surface capping. There was no significant elevation in the number of capped PMNs (30 +/- 2%) obtained from children with viral infections. Colchicine and Diamide increased the number of capped cells in control PMNs as well as in PMNs from patients to 69 +/- 1% and 67 +/- 1%, respectively. Since the increased spontaneous cap formation in PMNs is associated with a defect of microtubule assembly, the various leukocyte function defects described in patients with bacterial infections, bronchial asthma or on immunosuppressive therapy may have to be considered the consequence of an altered microtubule system.

[Phagocytosis mechanisms of alveolar macrophages and granulocytes (author's transl)]

Alveolar macrophages and granulocytes protect the organism against invaded microorganisms under various conditions. To investigate whether the environmental difference may influence the various phagocytic functions the adherence, chemotaxis, ingestion rate, degranulation as well as the bactericidal activity were determined in alveolar macrophages and granulocytes obtained from guinea pigs. In addition, the cytoskeleton was examined by observing the fluorescence of Concanavalin A receptors. Various functional differences between both cell types have been demonstrated. Both cell types exhibited the same adherence. In contrast, granulocytes demonstrated a greater chemotactic activity and ingestion rate than alveolar macrophages. Following the exposure to opsonized zymosan alveolar macrogphages secreted almost totally the lysosomal enzyme beta-glucuronidase during the degranulation. Nevertheless, alveolar macrophages exhibited a lower bactericidal activity than granulocytes. This functional differences were not caused by an alteration of the cytoskeleton. A random fluorescence distribution of FITC-Concanavalin A receptors was observed in 72% alveolar macrophages and 73% granulocytes, demonstrating polymerisation of the microtubuli. Only 12% alveolar macrophages and 11% granulocytes showed a capped FITC-Concanavalin A fluorescence which is associated with an alteration of the microtubulin. This study demonstrates that the difference in adherence, chemotaxis, ingestion rate, as well as the bactericidal activity of alveolar macrophages and granulocytes is a specific cell-type property.