Role of catalase in in vitro acetaldehyde formation by human colonic contents

Ingested ethanol is transported to the colon via blood circulation, and intracolonic ethanol levels are equal to those of the blood ethanol levels. In the large intestine, ethanol is oxidized by colonic bacteria, and this can lead to extraordinarily high acetaldehyde levels that might be responsible, in part, for ethanol-associated carcinogenicity and gastrointestinal symptoms. It is believed that bacterial acetaldehyde formation is mediated via microbial alcohol dehydrogenases (ADHs). However, almost all cytochrome-containing aerobic and facultative anaerobic bacteria possess catalase activity, and catalase can, in the presence of hydrogen peroxide (H2O2), use several alcohols (e.g., ethanol) as substrates and convert them to their corresponding aldehydes. In this study we demonstrate acetaldehyde production from ethanol in vitro by colonic contents in a reaction catalyzed by both bacterial ADH and catalase. The amount of acetaldehyde produced by the human colonic contents was proportional to the ethanol concentration, the amount of colonic contents, and the length of incubation time, even in the absence of added nicotinamide adenine dinucleotide or H2O2. The catalase inhibitors sodium azide and 3-amino-1,2,4-triazole (3-AT) markedly reduced the amount of acetaldehyde produced from 22 mM ethanol in a concentration dependent manner compared with the control samples (0.1 mM sodium azide to 73% and 10 mM 3-AT to 67% of control). H2O2 generating system [beta-D(+)-glucose + glucose oxidase] and nicotinamide adenine dinucleotide induced acetaldehyde formation up to 6- and 5-fold, respectively, and together these increased acetaldehyde formation up to 11-fold. The mean supernatant catalase activity was 0.53+/-0.1 micromol/min/mg protein after the addition of 10 mM H2O2, and there was a significant (p < 0.05) correlation between catalase activity and acetaldehyde production after the addition of the hydrogen peroxide generating system. Our results demonstrate that colonic contents possess catalase activity, which probably is of bacterial origin, and indicate that in addition to ADH, part of the acetaldehyde produced in the large intestine during ethanol metabolism can be catalase dependent.

Free radicals and antioxidant status following pylorus ligation induced gastric mucosal injury in rats

The present investigation was undertaken to suggest the involvement of free radicals in the pathogenesis of pyloric ligation induced ulcers in rats. Lipid peroxidation product (MDA), antioxidant contents and secretory activity have been studied in the rat stomach at different time intervals after pylorus ligation induced ulcers. A time-dependent increase in the peptic activity, free and total acid content in the gastric juice was observed. MDA level, myeloperoxidase (a neutrophil maker) and catalase activity in the rat stomach homogenate were augmented 2, 4 and 19 h after pylorus ligation. While a significant and time-dependent decrease in the glutathione content, superoxide dismutase and glutathione peroxidase activity was observed after pyloric ligation. An increase in the acid and pepsin content in the gastric juice in N-ethyl maleamide (GSH depletor) or aminotriazole (catalase inhibitor) pretreated animals, further suggests that depletion in the antioxidant levels enhance ulceration. Thus the results obtained have shown alterations in the antioxidant status following ulceration, indicating that free radicals seems to be associated with the pylorus ligation induced ulceration in rats.

Erythrocyte defenses against hydrogen peroxide: the role of ascorbic acid

Ascorbate has been reported to increase intracellular hydrogen peroxide (H2O2) generation in human erythrocytes. In the present work, the basis for this prooxidant effect of the vitamin was investigated in the context of erythrocyte defenses against H2O2. Ascorbate added to erythrocytes caused a dose-dependent increase in intracellular H2O2, which was measured as inactivation of endogenous catalase in the presence of 3-amino-1,2,4-triazole (aminotriazole). Ascorbate-induced catalase inactivation was not observed when only the intracellular ascorbate concentration was increased, when cells were incubated with ascorbate in plasma, or when extracellular Fe3+ was chelated. Together, these results suggest that the observed ascorbate-induced H2O2 generation is due to Fe3+-catalyzed oxidation of extracellular, as opposed to intracellular, ascorbate by molecular oxygen. Rather than generate an oxidant stress in erythrocytes, ascorbate was one of the most sensitive intracellular antioxidants to H2O2 coming from outside the cells. On the other hand, intracellular ascorbate contributed little to the detoxification of H2O2, which was found to be mediated by both catalase and by the GSH system.

Cloning and sequencing of a Candida albicans catalase gene and effects of disruption of this gene

Catalase plays a key role as an antioxidant, protecting aerobic organisms from the toxic effects of hydrogen peroxide, and in some cases has been postulated to be a virulence factor. To help elucidate the function of catalase in Candida albicans, a single C. albicans-derived catalase gene, designated CAT1, was isolated and cloned. Degenerate PCR primers based on highly conserved areas of other fungal catalase genes were used to amplify a 411-bp product from genomic DNA of C. albicans ATCC 10261. By using this product as a probe, catalase clones were isolated from genomic libraries of C. albicans. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 487 amino acid residues. Construction of a CAT1-deficient mutant was achieved by using the Ura-blaster technique for sequential disruption of multiple alleles by integrative transformation using URA3 as a selectable marker. Resulting mutants exhibited normal morphology and comparable growth rates of both yeast and mycelial forms. Enzymatic analysis revealed an abundance of catalase in the wild-type strain but decreasing catalase activity in heterozygous mutants and no detectable catalase in a homozygous null mutant. In vitro assays showed the mutant strains to be more sensitive to damage by both neutrophils and concentrations of exogenous peroxide that were sublethal for the parental strain. Compared to the parental strain, the homozygous null mutant strain was far less virulent for mice in an intravenous infection model of disseminated candidiasis. Definitive linkage of CAT1 with virulence would require restoration of activity by reintroduction of the gene into mutants. However, initial results in mice, taken together with the enhanced susceptibility of catalase-deficient hyphae to damage by human neutrophils, suggest that catalase may enhance the pathogenicity of C. albicans.

Antioxidant defense mechanisms in the lung toxicity of tri-n-butyl phosphate

Pneumotoxic effects of the tri-n-butyl phosphate (TBP) are investigated on rats using biological markers in bronchoalveolar lavage fluid (BALF) and studying key antioxidant enzymes in lung homogenate. Each animal from the experimental group received intratracheally 5 microliters TBP (20% v/v in n-dodecane). Six rats from the control and treated groups are sacrificed on post-treatment days 1, 3, 7, 14, and 28. The lactate dehydrogenase activity, the total protein content and the total cell number in BALF are increased mainly on day 1 after the treatment. The activities of superoxide dismutase and catalase are decreased to day 7 and those of glutathione peroxidase and glutathione reductase on day 1 only. The malondialdehyde content is elevated to day 14. It is concluded that TBP causes moderate toxic injury of the lung parenchyma. The depression of the key antioxidant enzymes and the elevated lipid peroxidation are probably important mechanisms of the lung damage.

Repression of hypoxia-reoxygenation injury in the catalase-overexpressing heart of transgenic mice

Hypoxia-reoxygenation injury results at least in part from reactive oxygen free radicals. Catalase is a major enzyme involved in detoxification of hydrogen peroxide. The activity of catalase per gram of tissue in the heart is very low, being only about 2% that of liver in rodents and humans, which may be responsible for the high sensitivity of the heart to hypoxia-reoxygenation injury. The present study was undertaken to determine whether elevation of catalase specifically in the heart of transgenic mice could provide protection against hypoxia-reoxygenation injury. Transgenic mice with elevated cardiac catalase 60-fold higher than normal were selected, and the effects of catalase elevation on hypoxia-reoxygenation induced functional and morphological changes in isolated atria were determined. Catalase overexpression ameliorated reductions in contractile force and heart rate caused by hypoxia-reoxygenation, and eliminated reoxygenation-induced arrhythmia. The catalase-overexpressing transgenic atria were also highly resistant to hypoxia-reoxygenation-induced morphological alterations, as examined by electron microscopy. Use of cardiac catalase-overexpressing transgenic mice thus demonstrates that hydrogen peroxide is involved in hypoxia-reoxygenation cardiotoxicity, and that this mouse model provides a useful tool for study of free radical mechanism in the heart damage.

Decreased antioxidant defense mechanisms in rat liver after methanol intoxication

The primary metabolic fate of methanol is oxidation to formaldehyde and then to formate by enzymes of the liver. Cytochrome P-450 and a role for the hydroxyl radical have been implicated in this process. The aim of the paper was to study the liver antioxidant defense system in methanol intoxication, in doses of 1.5, 3.0 and 6.0 g/kg b.w., after methanol administration to rats. In liver homogenates, the activities of Cu,Zn-superoxide dismutase and catalase were significantly increased after 6 h following methanol ingestion in doses of 3.0 and 6.0 g/kg b.w. and persisted up to 2-5 days, accompanied by significant decrease of glutathione reductase and glutathione peroxidase activities. The content of GSH was significantly decreased during 6 hours to 5 days. The liver ascorbate level was significantly diminished, too, while MDA levels were considerably increased after 1.5, 3.0 and 6.0 g/kg b.w. methanol intoxication. Changes due to methanol ingestion may indicate impaired antioxidant defense mechanisms in the liver tissue.

The role of gastrointestinal factors in alcohol metabolism

Although the liver is the major organ responsible for ethanol metabolism, such metabolism also occurs in the gastrointestinal (GI) tract. However, compared to the liver, GI metabolism of ethanol is quantitatively much lower. Various enzyme systems have been characterized in GI mucosal cells including various isozymes of alcohol dehydrogenase (ADH), cytochrome P450 2E1 (CYP 2E1) and catalase. Gastric ADH activity is one factor by which first pass metabolism (FPM) is influenced and its activity is modulated by genetics, gender, age, drugs and gastric morphology. Another important factor in FPM of ethanol is the speed of gastric emptying. In addition to mucosal ethanol metabolism, ethanol can also be oxidized by many bacterial species in the upper GI tract including oropharynx and stomach as well as in the large intestine. GI metabolism of ethanol may influence systemic bioavailability of ethanol and may lead to local toxicity most likely mediated by acetaldehyde. Such toxicity could be of importance in ethanol-associated carcinogenesis.

Catalase mediates acetaldehyde formation from ethanol in fetal and neonatal rat brain

Fetal ethanol (E) exposure has well documented deleterious effects on brain development, yet it is uncertain if the neurotoxicity of maternal E consumption is generated by E itself, by its primary metabolite acetaldehyde (AcHO), or both. The current studies present evidence that homogenates of immature rat brains can generate AcHO via a catalase (CAT)-mediated reaction and that AcHO may be produced in vivo by this system. Homogenates of day 19 fetal rat brain were incubated with E (50 mM). When incubated with CAT inhibitors (sodium azide or 3-aminotriazole), AcHO formation was blocked, whereas neither the alcohol dehydrogenase inhibitor, 4-methylpyrazole, nor P-450 inhibitors decreased AcHO production. Three hours after one oral dose of E (4 g/kg) to a pregnant dam (gestation day 19), AcHO levels in fetal brain increased to 14.28 +/- 1.82 nM/g tissue. Baseline CAT activity in day 19 fetal brains was 4.5 times adult values (p < 0.05). Western blot analysis determined that CAT protein level in the day 19 fetal brain exceeded that in adult brain by 2.5 times. One hour after a single dose of E, CAT activity in day 19 fetal brain increased by 8.2 units/mg protein. In 5-day-old neonatal brains during the "third trimester" brain growth spurt, baseline CAT activity was twice the adult values (p < 0.05) and a 2-day in vivo E regimen increased AcHO levels to four times the control values, with a concomitant 1.7-fold increase in CAT activity. This was prevented by administration of a CAT inhibitor (3-amino-1,2,4-triazole). Immunohistochemical staining of neonatal brains exposed to E illustrated the presence of acetaldehyde-protein adducts. We conclude that AcHO is likely produced in rat fetal and neonatal brain via CAT-mediated oxidation of E. This phenomenon may be an important factor in the neurotoxic effects of in utero E exposure.

Inhibition of astrocyte glutamate uptake by reactive oxygen species: role of antioxidant enzymes

BACKGROUND

The recent literature suggests that free radicals and reactive oxygen species may account for many pathologies, including those of the nervous system.

MATERIALS AND METHODS

The influence of various reactive oxygen species on the rate of glutamate uptake by astrocytes was investigated on monolayers of primary cultures of mouse cortical astrocytes.

RESULTS

Hydrogen peroxide and peroxynitrite inhibited glutamate uptake in a concentration-dependent manner. Addition of copper ions and ascorbate increased the potency and the efficacy of the hydrogen peroxide effect, supporting the potential neurotoxicity of the hydroxyl radical. The free radical scavenger dimethylthiourea effectively eliminated the inhibitory potential of a mixture containing hydrogen peroxide, copper sulphate, and ascorbate on the rate of glutamate transport into astrocytes. The inhibitory effect of hydrogen peroxide on glutamate uptake was not altered by the inhibition of glutathione peroxidase, whereas the inhibition of catalase by sodium azide clearly potentiated this effect. Superoxide and nitric oxide had no effect by themselves on the rate of glutamate uptake by astrocytes. The absence of an effect of nitric oxide is not due to an inability of astrocytes to respond to this substance, since the same cultures did respond to nitric oxide with a sustained increase in cytoplasmic free calcium.

CONCLUSION

These results confirm that reactive oxygen species have a potential neurotoxicity by means of impairing glutamate transport into astrocytes, and they suggest that preventing the accumulation of hydrogen peroxide in the extracellular space of the brain, especially during conditions that favor hydroxyl radical formation, could be therapeutic.

Changes in free radical scavengers and lipid peroxide in thyroid glands of various thyroid disorders

To clarify whether the changes of free radicals and its scavengers are induced by thyroid disorders, we measured levels of free radical scavengers and checked O2 radical generating systems in the human thyroid gland. Thyroid specimens from patients with Graves' disease, follicular adenoma, and papillary and follicular carcinomas contained significantly higher concentrations of xanthine oxidase (XOD) and gluthathione peroxidase (GSH-PX), compared to those in the normal thyroid tissue. Catalase concentration was significantly lower in thyroid specimens from patients with Graves' disease and significantly lower in thyroid specimens from patients with follicular adenoma, compared to those in the normal thyroid tissue. Cu/Zn superoxide dismutase (Cu/Zn SOD) concentration was significantly lower in the specimens from follicular adenoma and papillary carcinoma and Mn SOD concentration was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue. The lipid peroxide concentration, expressed as malondialdehyde (MDA) concentration, was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue. These findings suggest that the levels of free radicals are increased and are scavenged and catalyzed in the thyroid of Graves' disease, whereas free radicals and lipid peroxide are not completely scavenged in papillary carcinoma tissues, suggesting that these substances affect some role in cell function of thyroid tumors.

Mice deficient in cellular glutathione peroxidase develop normally and show no increased sensitivity to hyperoxia

Glutathione peroxidase, a selenium-containing enzyme, is believed to protect cells from the toxicity of hydroperoxides. The physiological role of this enzyme has previously been implicated mainly using animals fed with a selenium-deficient diet. Although selenium deficiency also affects the activity of several other cellular selenium-containing enzymes, a dramatic decrease of glutathione peroxidase activity has been postulated to play a role in the pathogenesis of a number of diseases, particularly those whose progression is associated with an overproduction of reactive oxygen species, found in selenium-deficient animals. To further clarify the physiological relevance of this enzyme, a model of mice deficient in cellular glutathione peroxidase (GSHPx-1), the major isoform of glutathione peroxidase ubiquitously expressed in all types of cells, was generated by gene-targeting technology. Mice deficient in this enzyme were apparently healthy and fertile and showed no increased sensitivity to hyperoxia. Their tissues exhibited neither a retarded rate in consuming extracellular hydrogen peroxide nor an increased content of protein carbonyl groups and lipid peroxidation compared with those of wild-type mice. However, platelets from GSHPx-1-deficient mice incubated with arachidonic acid generated less 12-hydroxyeicosatetraenoic acid and more polar products relative to control platelets at a higher concentration of arachidonic acid, presumably reflecting a decreased ability to reduce the 12-hydroperoxyeicosatetraenoic acid intermediate. These results suggest that the contribution of GSHPx-1 to the cellular antioxidant mechanism under normal animal development and physiological conditions and to the pulmonary defense against hyperoxic insult is very limited. Nevertheless, the potential antioxidant role of this enzyme in protecting cells and animals against the pathogenic effect of reactive oxygen species in other disorders remains to be defined. The knockout mouse model described in this report will also provide a new tool for future study to distinguish the physiological role of this enzyme from other selenium-containing proteins in mammals under normal and disease states.

Hydrogen peroxide-induced impairment of reactivity in rat isolated aorta: potentiation by 3-amino-1,2,4-triazole

1. In this study the impairment induced by hydrogen peroxide of vascular reactivity and the role of endogenous catalase in protection against this impairment was assessed in isolated rings of rat aorta. 2. Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout depressed, in a time-dependent manner, the subsequent ability of endothelium-containing and endothelium-denuded rings to contract to phenylephrine. 3. Incubation with 3-amino-1,2,4-triazole (50 mM, 90 min, followed by washout) to inhibit endogenous catalase had no effect by itself on subsequent phenylephrine-induced contraction. However, pretreatment with 3-amino-1,2,4-triazole did lead to a profound enhancement of the ability of hydrogen peroxide (1 mM, present for the final 30 min of the 90 min incubation, followed by washout) to depress phenylephrine-induced contraction in both endothelium-containing and endothelium-denuded rings. 4. Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout inhibited, in a time-dependent manner, the subsequent ability of acetylcholine (10 nM-3 microM) to induce endothelium-dependent relaxation. Furthermore, incubation with hydrogen peroxide 1 mM (30 min, followed by washout) also inhibited relaxation induced by glyceryl trinitrate (1-100 nM) or isoprenaline (10 nM-3 microM) in endothelium-denuded rings. 5. Incubation with 3-amino-1,2,4-triazole (50 mM, 90 min, followed by washout) had no effect by itself on relaxation induced by acetylcholine, glyceryl trinitrate or isoprenaline. In contrast, pretreatment with 3-amino-1,2,4-triazole led to profound enhancement of the ability of hydrogen peroxide (1 mM, present for final 30 min of the 90 min incubation) to block relaxation to acetylcholine, glyceryl trinitrate or isoprenaline. 6. On the basis of the actions of 3-amino-1,2,4-triazole, it is likely that endogenous catalase plays an important role in the protection of vascular reactivity of rat aorta against oxidant damage by high (1 mM) but not lower (0.1 mM) concentrations of hydrogen peroxide. The data are consistent with the promotion of non-selective damage to the vascular smooth muscle cells by hydrogen peroxide, but endothelial damage may also be sustained.

Endothelial cells protect vascular smooth muscle cells from H2O2 attack

Endothelial-dependent vascular responses are altered in ischemic acute renal failure. Oxidants formed during reperfusion of ischemic kidneys injure the renal microvasculature and prevent recovery of renal function. To determine whether endothelial cells (EC) modulate oxidant attack on vascular smooth muscle cells (VSMC), rat mesenteric artery VSMC were grown on coverslips and then coincubated with bovine pulmonary artery EC grown in wells. In the absence of EC, H2O2 caused time- and concentration-dependent increases in VSMC injury as indicated by release of [3H]adenine. In contrast, addition of EC reduced H2O2-mediated (5 mM, 1 h) VSMC adenine release from 63.8 +/- 4.5% to 28.6 +/- 2.9% (P < 0.001). The protective effect of EC did not occur when H2O2 was added to the surface of VSMC unopposed to EC and was partially reversed when EC were treated with aminotriazole to inactivate catalase (41.7 +/- 2.7%). To determine whether EC nitric oxide (NO) modified H2O2 attack on VSMC, EC were treated with N omega-nitro-L-arginine (L-NNA). The protective effect of EC was partially abrogated with L-NNA (53.8 +/- 4.3%). Treatment of EC with interleukin-1 beta (IL-1 beta) for 24 h prior to coincubation with VSMC enhanced the protective effect of EC. IL-1 beta-induced protection was reversed with L-NNA. No protection was observed when VSMC were treated with 8-bromoguanosine 3',5'-cyclic monophosphate, forskolin, or phorbol 12-myristate 13-acetate. Our conclusions are as follows. VSMC are protected by EC from luminal but not contraluminal oxidant attack. The protective effect of EC is mediated by catalase- and NO-dependent inactivation of oxidants. EC dysfunction could account for renal injury caused by oxidants formed during reperfusion of ischemic kidneys.

The role of antioxidant enzymes in the control of opossum sphincter of Oddi motility

Superoxide rapidly oxidizes nitric oxide (NO) to form peroxynitrite, thus terminating the biological activity of NO. The aims of our study were to determine if superoxide alters the motor function of the sphincter of Oddi and to localize the antioxidant enzymes in the sphincter of Oddi. Immunostaining was performed and enzyme activities were measured in the sphincter of Oddi. In physiological experiments, force-displacement transducers recorded tension in the spontaneously contracting sphincter of Oddi and after electrical field stimulation (EFS) of precontracted sphincter of Oddi. Superoxide was generated by the addition of xanthine with xanthine oxidase, superoxide radicals were scavenged by the addition of superoxide dismutase (SOD), and catalase or SOD was inhibited by diethyldithiocarbamic acid. Immunostaining demonstrated SOD and catalase immunoreactivity in ganglia situated at the serosal surface of the circular muscle. Total SOD activity was 202 +/- 12 U/mg. Generation of superoxide or inhibition of SOD increased the contractile frequency and decreased relaxation after EFS. We conclude that superoxide alters sphincter of Oddi motor function, and the presence of superoxide scavenging enzymes in enteric plexuses suggests that they may regulate sphincter of Oddi neuromuscular function by clearing endogenous superoxide.

Two divergent catalase genes are differentially regulated during Aspergillus nidulans development and oxidative stress

Catalases are ubiquitous hydrogen peroxide-detoxifying enzymes that are central to the cellular antioxidant response. Of two catalase activities detected in the fungus Aspergillus nidulans, the catA gene encodes the spore-specific catalase A (CatA). Here we characterize a second catalase gene, identified after probing a genomic library with catA, and demonstrate that it encodes catalase B. This gene, designated catB, predicts a 721-amino-acid polypeptide (CatB) showing 78% identity to an Aspergillus fumigatus catalase and 61% identity to Aspergillus niger CatR. Notably, similar levels of identity are found when comparing CatB to Escherichia coli catalase HPII (43%), A. nidulans CatA (40%), and the predicted peptide of a presumed catA homolog from A. fumigatus (38%). In contrast, the last two peptides share a 79% identity. The catalase B activity was barely detectable in asexual spores (conidia), disappeared after germination, and started to accumulate 10 h after spore inoculation, throughout growth and conidiation. The catB mRNA was absent from conidia, and its accumulation correlated with catalase activity, suggesting that catB expression is regulated at the transcription level. In contrast, the high CatA activity found in spores was lost gradually during germination and growth. In addition to its developmental regulation, CatB was induced by H2O2, heat shock, paraquat, or uric acid catabolism but not by osmotic stress. This pattern of regulation and the protective role against H2O2 offered by CatA and CatB, at different stages of the A. nidulans life cycle, suggest that catalase gene redundancy performs the function of satisfying catalase demand at the two different stages of metabolic and genetic regulation represented by growing hyphae versus spores. Alternative H2O2 detoxification pathways in A. nidulans were indicated by the fact that catA/catB double mutants were able to grow in substrates whose catabolism generates H2O2.

Effects of antioxidant enzyme modulations on interleukin-1-induced nuclear factor kappa B activation

Nuclear factor kappa B (NF-kappa B) is a potent and pleiotropic transcription factor that can be activated by a wide variety of inducers, including interleukin-1 (IL-1). Although the detailed activation mechanism of NF-kappa B is still under investigation, it requires both phosphorylation and degradation of its inhibitory subunit I kappa B and the presence of an oxidative environment. In this study, we systematically evaluated the influence of glutathione peroxidase, glutathione reductase and catalase on IL-1-induced NF-kappa B activation by analysing the effect of specific inhibitors of these enzymes. For the three antioxidant enzymes mentioned, their inhibition correlated with an overactivation of NF-kappa B, particularly for glutathione peroxidase. Inversely, we tested the response of glutathione peroxidase-transfected cells on NF-kappa B activation, which was lower as compared with the parental cells. Furthermore, interleukin-6 production also correlated perfectly with the reduced level of NF-kappa B activation is these experiments. The results clearly show that NF-kappa B activation is, strongly dependent on the antioxidant potential of the cells, especially on the activity of reduced glutathione-dependent enzymes such as glutathione peroxidase. The results support the hypothesis that the level of the oxidised glutathione:reduced glutathione ratio and the activity of intracellular antioxidant enzymes play a major role in NF-kappa B tine tuning.

Nutritional metabolic diseases of poultry and disorders of the biological antioxidant defence system

Deficiencies or disturbances of nutrition cause a variety of diseases and can arise in different ways. The amount of a particular nutrient in the diet may be insufficient to meet the requirements, the diet may contain substances that inactivate the nutrient or inhibit its absorption/utilisation, or metabolism may be upset by the interaction of dietary and environmental factors. Peroxidation of lipids or oxygen free radical generation in general is a physiological process important for cell metabolism, division and differentiation and also for the biosynthesis of hormones and prostaglandins. Free radicals generated through these processes are effectively scavenged by the antioxidant defence system. Uncontrolled lipid oxidation caused by disturbances of that system may play a crucial role in some important poultry diseases and toxicoses. The first route of lipid peroxide loading of the organism is via the feed, such as through oxidised lipids. Oxidised fatty acids are absorbed from the intestine mainly in the form of unsaturated keto compounds and initiate lipid peroxidation in the tissues. The second problem is the insufficient amount of antioxidants in the feed, e.g. vitamin E deficiency. Nutritional encephalomalacia is a problem in poultry production which depends both on the actual vitamin E supply and the dietary amount of polyunsaturated fatty acids. In young birds the primary target of vitamin E deficiency is the brain because it contains low amounts of vitamin E, and the vitamin E content of the liver acting as store decreases rapidly during the first week of life. Besides vitamin E, other components of the antioxidant system, e.g. the antioxidant enzymes (catalase and glutathione peroxidase) also have low activity in the brain as compared to other major tissues. The brain is highly susceptible to oxidative stress because of the accumulation of polyunsaturated fatty acids. The third source of free radical generation is the toxic level of different feed ingredients, e.g. toxicoses caused by vitamin A, selenium, and ionophore antibiotics. Other important aspects of antioxidants (e.g. vitamin E and selenium) in poultry are stimulation of the immune response (e.g. in the case of vaccination) and reduction of the risks of free radical formation as a result of macrophage function.

Possible involvement of catalase in the protective effect of interleukin-6 against 6-hydroxydopamine toxicity in PC12 cells

We examined the effects of various neurotrophic factors and cytokines on 6-hydroxydopamine (6-OHDA)-induced toxicity in PC12 cells. Exposure of PC12 cells to 6-OHDA resulted in a concentration- and time-dependent cell death, as evidenced by the release of lactate dehydrogenase into the culture medium. Addition of catalase, but not superoxide dismutase, to the culture medium protected PC12 cells from the 6-OHDA-induced toxicity. Interleukin (IL)-6 provided a dose-dependent protection against the 6-OHDA toxicity, as did nerve growth factor (NGF). In addition, basic fibroblast growth factor and dibutyryl cyclic AMP partially protected PC12 cells from 6-OHDA toxicity. Neither IL-1alpha, IL-2, IL-4, transforming growth factor-beta, nor leukemia inhibitory factor had any effect. The protective effect of IL-6 was attenuated by 3-amino-1,2,4-triazole, an inhibitor of catalase. These results suggest that IL-6 may protect PC12 cells against the 6-OHDA toxicity by activating free radical detoxifying mechanisms, such as catalase activity.

EUK-134, a synthetic superoxide dismutase and catalase mimetic, protects rat kidneys from ischemia-reperfusion-induced damage

The effect of a new synthetic superoxide dismutase and catalase mimetic was investigated on renal ischemia-reperfusion syndrome in rats. Synthetic salen-manganese complexes have characteristics that might facilitate their potential usefulness as therapeutic agents: (1) unlike proteinaceous antioxidant enzymes, synthetic complexes, due to their low molecular weight, have a better stability and bioavailability; (2) they have a catalytic activity enhancing their efficiency over noncatalytic reactive oxygen metabolite scavengers; and finally, (3) exhibiting combined superoxide dismutase and catalase activity, they destroy both superoxide anions and hydrogen peroxides, thereby enhancing their protective effect on ischemically injured tissues. One such compound, EUK-134, was tested in uninephrectomized rats that underwent a left renal artery clamping. After a 75-min left renal artery clamping, a single intravenous injection of EUK-134 at 0.2 mg/kg, just before unclamping, provided significantly better renal function recovery during the week after the ischemic insult compared with recovery of untreated animals. Two hours after several periods of renal ischemia (30, 45, 60, and 75 min of left renal artery clamping), EUK-134 given at a similar dose significantly improved the glomerular filtration rate after an acute ischemia of 30 and 45 min, as assessed by EDTA 51Cr. Overall, these results show that synthetic superoxide dismutase-catalase mimetics such as EUK-134 can protect ischemically injured rat kidneys from ischemia-reperfusion syndrome when administered just before reperfusion.

Role of catalase in rat gastric mucosal ethanol metabolism in vitro

To evaluate the possible role of catalase in gastric ethanol metabolism in rats, we studied acetaldehyde formation from ethanol by gastric mucosal homogenate under various in vitro conditions. Homogenized rat gastric mucosa produced significant amounts of acetaldehyde in a time and ethanol concentration-dependent manner, even in the absence of added NAD. Both acetaldehyde formation and catalase activity peaked around the physiological pH, whereas alcohol dehydrogenase (ADH) activity was in that pH range low and reached peak values only at a higher pH of 9 to 10. Catalase inhibitors sodium azide (SA) and 3-amino-1,2,4-triazole (3-AT) had little effect on ADH activity but markedly decreased catalase activity and acetaldehyde formation (1 mM of SA to 56 +/- 13% of control, 5 mM of 3-AT to 67 +/- 3% of control; mean +/- SE). 4-Methylpyrazole decreased ADH activity significantly, but did not affect acetaldehyde formation. Heating of the homogenate at 60 degrees C for 5 min decreased ADH activity only slightly, but totally abolished catalase activity and reduced acetaldehyde formation to 39 +/- 3% of control. Addition of a H2O2 generating system (beta-D(+)-glucose + glucose oxidase] increased acetaldehyde formation in a concentration-dependent manner up to 8-fold of the control value. Our results strongly suggest that, in addition to ADH, catalase may play a significant role in gastric ethanol metabolism in rats.

Active involvement of catalase during hemolytic crises of favism

The endemic occurrence of favism in certain Mediterranean regions provided an investigative opportunity for testing in vivo the validity of claims as to the role of catalase in protecting human erythrocytes against peroxidative injury. Reduced activity of catalase was found in the erythrocytes of six boys who were deficient in erythrocytic glucose-6-phosphate dehydrogenase (G6PD) and who were studied while suffering hemolysis after ingesting fava beans. Activity of catalase was further reduced when their red blood cells were incubated with aminotriazole. In contrast, minimal reduction of catalase activity was found, both with and without incubation with aminotriazole, in erythrocytes of a G6PD-deficient boy who had ingested fava beans 7 days earlier and in erythrocytes of seven G6PD-deficient men with a past history of favism. These results confirmed earlier studies in vitro indicating that catalase is a major disposer of hydrogen peroxide in human erythrocytes and, like the glutathione peroxidase/reductase pathway, is dependent on the availability of reduced nicotinamide adenine dinucleotide phosphate (NADPH). The effect of divicine on purified catalase and on the catalase of intact G6PD-deficient erythrocytes was similar to the previously demonstrated effect on catalase of a known system for generating hydrogen peroxide. This effect of divicine strengthens earlier arguments that divicine is the toxic peroxidative component of fava beans.

Hydrogen peroxide induces leukocyte rolling: modulation by endogenous antioxidant mechanisms including NO

In this study, intravital microscopy was used to examine the mechanisms that regulate H2O2-induced leukocyte rolling within rat mesenteric venules in vivo. H2O2 elicited leukocyte rolling within a narrow response window between 10 and 500 microM H2O2. Continuous superfusion with 100 microM H2O2 induced a large but transient increase in the flux of rolling leukocytes, whereas a short 5-min pulse elicited a sustained increase in rolling flux. Both treatments caused increases in leukocyte adhesion. H2O2-induced increases in leukocyte flux and adhesion could be prevented with an anti-P-selectin antibody. Inhibition of endogenous catalase (aminotriazole), glutathione (diethyl maleate), or nitric oxide (NG-nitro-L-arginine methyl ester) shifted the effective concentration of H2O2; continuous superfusion with 10 microM H2O2 now elicited large and sustained increases in leukocyte rolling flux, whereas 100 microM H2O2 elicited less than optimal responses. Dual antioxidant inhibition further reduced the effective H2O2 concentration to 1 microM H2O2. A nitric oxide donor prevented the increased rolling flux induced by 100 microM H2O2. These findings suggest that endogenous antioxidants are important regulators of H2O2-induced, P-selectin-dependent leukocyte rolling in vivo.