Expression of manganese superoxide dismutase is not altered in transgenic mice with elevated level of copper-zinc superoxide dismutase

In evaluating the relative expression of copper-zinc and manganese superoxide dismutase (CuZnSOD and MnSOD) in vivo in states like Down syndrome in which one dismutase is present at increased levels, we measured activities of both enzymes, in tissues of control and transgenic mice constitutively expressing increased levels of CuZnSOD, during exposure to normal and elevated oxygen tensions. Using SOD gel electrophoresis assay, CuZnSOD and MnSOD activities of brain, lung, heart, kidney, and liver from mice exposed to either normal (21%) or elevated (>99% oxygen, 630 torr) oxygen tensions for 120 h were compared. Whereas CuZnSOD activity was elevated in tissues of transgenic relative to control mice under both normoxic or hyperoxic conditions, MnSOD activities in organs of transgenic mice were remarkably similar to those of controls under both conditions. To confirm the accuracy of this method in quantitating MnSOD relative to CuZnSOD expression, two other methods were utilized. In lung, which is the organ exposed to the highest oxygen tension during ambient hyperoxia, a sensitive, specific ELISA for MnSOD was used. Again, MnSOD protein was not different in transgenic relative to control mice during exposure to air or hyperoxia. In addition, lung MnSOD protein was not changed significantly by exposure to hyperoxia in either group. In kidney, a mitochondrion-rich organ, SOD assay, before and after inactivation of CuZnSOD with diethyldithiocarbamate, was used. MnSOD activity was not different in organs from air-exposed transgenic relative to control mice. The data indicated that expression of MnSOD in vivo was not affected by overexpression of the CuZnSOD and, therefore, the two enzymes are probably regulated independently.     

Effects of continuous and episodic hyperoxia on stress and hepatic glutathione levels in one-summer-old rainbow trout (Oncorhynchus mykiss)

One-summer-old rainbow trout ( Oncorhynchus mykiss ) were exposed to continuous hyperoxia (173 ± 24%) and three hyperoxic/normoxic treatments for 14 days. Hepatic glutathione status as the indicator of oxidative stress, as well as classical stress indicators such as hemoglobin, hematocrit and plasma cortisol levels, were measured during normoxic, constantly hyperoxic and the following episodically hyperoxic oxygen treatment regimes: 12 h hyperoxia:12 h normoxia (12 HYP:12 NOR), 24 HYP:24 NOR and 48 HYP:24 NOR. Constant hyperoxia tended to shrink erythrocytes, but the 12 HYP:12 NOR treatment increased the number of erythrocytes and thus enhanced the oxygen carrying capacity of blood. Similarly, a trend toward an elevation in plasma cortisol concentrations was detected in 12 HYP:12 NOR treatment group. The finding that elevated hepatic glutathione (GSH) levels (P < 0.01), indicative of enhanced potential of the liver tissue to resist oxidative stress, coincided with elevated cortisol levels might suggest that in the 12 HYP:12 NOR treatment physiological processes were recruited to increase oxygen carrying capacity in blood and to elevate protection against oxyradicals. However, none of the episodic hyperoxia treatments or continuous hyperoxia caused mortality or resulted in better growth. These data indicate that continuous hyperoxia (173 ± 24%) and hyperoxic-normoxic treatments may be applied in intensive culture of rainbow trout provided that fish have at least 24 h in normoxia prior to the next bout of hyperoxia. Shorter recovery periods, like in a 12 HYP:12 NOR treatment, may result in the increased need of oxygen in tissues followed by an activation of glutathione dependent defence system against an increased oxygen load.     

Gene expression of apoptosis-related genes,stress protein and antioxidant enzymes in hemocytes of white shrimp Litopenaeus vannamei under nitrite stress

Apoptotic cell ratio and mRNA expression of caspase-3, cathepsin B (CTSB), heat shock protein 70 (HSP70), manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx) and thioredoxin (TRx) in hemocytes of white shrimp Litopenaeus vannamei exposed to nitrite-N (20 mg/L) was investigated at different stress time (0, 4, 8, 12, 24, 48 and 72 h). The apoptotic cell ratio and mRNA expression level of CTSB were significantly increased in shrimp exposed to nitrite-N for 48 and 72 h. Caspase-3 mRNA expression level significantly increased by 766.50% and 1811.16% for 24 and 48 h exposure, respectively. HSP70 expression level significantly increased at 8 and 72 h exposure. MnSOD mRNA expression in hemocytes up-regulated at 8 and 48 h, while CAT mRNA expression level increased at 24 and 48 h. GPx expression showed a trend that increased first and then decreased. Significant increases of GPx expression were observed at 8 and 12 h exposure. Expression level of TRx reached its highest level after 48 h exposure. These results suggest that nitrite exposure induces expression of apoptosis-related genes in hemocytes, and subsequently caused hemocyte apoptosis. Meanwhile, expression levels of HSP70 and antioxidant enzymes up-regulated to protect the hemocyte against nitrite stress.     

Altered Composition of Cerebral Microvessel Membrane Phosphoglycerides from Senescent Mouse

Abstract— Phosphoglyceride and fatty acid composition was determined in the cellular membranes of isolated cerebral microvessels and brain parenchymal cells (neurons and glia) taken from 10-, 20-, and 27–30-month-old C57BL6/NNIA mice. Lipids were extracted from each fraction and the fatty acid profiles of ethanolamine, cho-line, serine, and inositol phosphoglycerides analyzed by gas chromatography. The results suggest that membrane phosphoglycerides from cerebral microvessels are significantly more affected by the aging process than are those of the brain parenchyma. Relative percentage for fatty acids in cerebral microvessels indicate an overall decline in membrane unsaturation with a concomitant elevation in the level of saturation. The decline in unsaturation is reflected primarily in the loss of precursor fatty acids for arachidonic (18:2n-6 and 20:3n-6) and docosahexaenoic (20:5n-3 and 22:5n-3) acids. Levels of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids in each phos-phoglyceride remained unchanged with age; however, mol% for ethanolamine plasmalogen, a major source of these fatty acids, was significantly reduced in 27–30-month-old mice. Conversely, mol% for choline phospho-glyceride increased with age. The age-related changes in fatty acid profile for microvessel membrane phosphoglycerides are reflected by increased saturation/unsaturation ratios and decreased unsaturation indices. These parameters were not affected by aging in parenchymal membranes.     

Responses of type II pneumocyte antioxidant enzymes to normoxic and hyperoxic culture

Summary Cultured type II pneumocyte responses to in vitro normoxia (95% air: 5% CO₂) or hyperoxia (95% O₂:5% CO₂) were quantified. Normoxic culture (0 to 96 h) of rabbit type II cells resulted in enhanced cell-monolayer protein and DNA content. During this same time, cellular activities of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GSH Px) decreased. Compared to cultures maintained in normoxia, hyperoxic exposure of cultures resulted in decreased cell-associated protein and DNA content. Exposure to hyperoxia also resulted in cytotoxicity as demonstrated by elevated cellular release of DNA, lactate dehydrogenase (LDH), and preincorporated 8-[¹⁴C]adenine. Cellular catalase and GSH Px activities in hyperoxic cells decreased similarly to normoxic controls. In contrast, cellular SOD activity in hyperoxic cells decreased less than in normoxic cultures. Cellular SOD activity in hyperoxic cultures, when normalized for cellular protein, but not DNA, was greater than normoxic values after 24 to 96 h of exposure. Unlike the decrease in cellular antioxidant enzymes during normoxic and hyperoxic culture, cellular LDH activity increased during both these exposures. Cellular LDH activity in 24 to 96 h hyperoxia-exposed cells increased to a lesser extent than normoxic controls. The extent of depression in LDH activity was dependent on whether the activity was normalized for cellular protein or DNA. Type II pneumocytes, which normally undergo hyperplasia and hypertrophy during hyperoxia in vivo, exhibited oxygen sensitivity in vitro. Exposure of type II cells to hyperoxia in vitro resulted in alterations in cellular SOD and LDH activities, but recognition of such changes were dependent on whether enzymatic activities were normalized for cellular DNA or protein. This work was supported by a grant from the Health Effects Institute, grant HL40458 from the National Institutes of Health, Bethesda, MD, and a grant from the American Lung Association, New York, NY.     

Hyperoxia results in transient oxidative stress and an adaptive response by antioxidant enzymes in goldfish tissues

The effects of hyperoxia on the status of antioxidant defenses and markers of oxidative damage were evaluated in goldfish tissues. The levels of lipid peroxides, thiobarbituric acid reactive substances, carbonyl proteins and the activities of some antioxidant enzymes were measured in brain, liver, kidney and skeletal muscle of goldfish, Carassius auratus L., over a time course of 3-12 h of hyperoxia exposure followed by 12 or 36 h of normoxic recovery. Exposure to high oxygen resulted in an accumulation of protein carbonyls in tissues throughout hyperoxia and recovery whereas lipid peroxides and thiobarbituric acid reactive substances accumulated transiently under short-term hyperoxia stress (3-6 h) but were then strongly reduced. This suggests that hyperoxia stimulated an enhancement of defenses against lipid peroxidation or mechanisms for enhancing the catabolism of peroxidation products. The activities of principal antioxidant enzymes, superoxide dismutase and catalase, were not altered under hyperoxia but catalase increased during normoxic recovery; activities may rise in anticipation of further hyperoxic excursions. In most tissues, the activities of glutathione-utilizing enzymes (glutathione peroxidase, glutathione-S-transferase, glutathione reductase) as well as glucose-6-phosphate dehydrogenase, were not affected under hyperoxia but increased sharply during normoxic recovery. Correlations between some enzyme activities and oxidative stress markers were found, for example, an inverse correlation was seen between levels of thiobarbituric acid reactive substances and glutathione-S-transferase activity in liver and catalase and glucose-6-phosphate dehydrogenase in kidney. The results suggest that liver glutathione-S-transferase plays an important role in detoxifying end products of lipid peroxidation accumulated under hyperoxia stress.     

Hyperoxia damages phagocytic defenses of neonatal rabbit lung

The effect of hyperoxia on phagocytic defenses of neonatal rabbit lung was ascertained by exposure to a fractional inspired O2 concentration of 0.95 + or 0.21 for 48, 96, or 168 h. Intrapulmonary clearance of inhaled staphylococci was reduced by 67 and 74% after 96 and 168 h in hyperoxia (P less than 0.05). Impaired phagocytic killing was not due to diminished bacterial ingestion. Alveolar macrophages (AM) lavaged from pups reared in normoxia had a progressive ability to release superoxide (O-2) and showed increasing cyanide-sensitive O2 consumption during the 1st wk of life. Conversely, AM recovered from litters housed in hyperoxia for 48 h produced 190% more O-2 than normoxic controls (P less than 0.005), but this capacity to generate O-2 fell by 43% after 96 h of exposure (P less than 0.05). After 96 h of hyperoxia, AM had a significant shift toward cyanide-insensitive metabolism compared with normoxic cells (P less than 0.05). Polymorphonuclear leukocytes (PMN) entered the alveoli after 96 h of hyperoxia, and mortality rose abruptly in animals exposed for 168 h (16%) vs. 96 h (3%). Our findings indicate neonatal hyperoxia induces metabolic and bactericidal dysfunction in the primary pulmonary phagocyte, the AM, and this injury is followed by additional lung insult during PMN migration into the airways.     

Deletion of Thioredoxin Interacting Protein (TXNIP) Augments Hyperoxia-Induced Vaso-Obliteration in a Mouse Model of Oxygen Induced-Retinopathy

We have recently shown that thioredoxin interacting protein (TXNIP) is required for VEGF-mediated VEGFR2 receptor activation and angiogenic signal. Retinas from TXNIP knockout mice (TKO) exhibited higher cellular antioxidant defense compared to wild type (WT). This study aimed to examine the impact of TXNIP deletion on hyperoxia-induced vaso-obliteration in ischemic retinopathy. TKO and WT pups were subjected to oxygen-induced retinopathy model. Retinal central capillary dropout was measured at p12. Retinal redox and nitrative state were assessed by reduced-glutathione (GSH), thioredoxin reductase activity and nitrotyrosine formation. Western blot and QT-PCR were used to assess VEGF, VEGFR-2, Akt, iNOS and eNOS, thioredoxin expression, ASK-1 activation and downstream cleaved caspase-3 and PARP in retinal lysates. Retinas from TKO mice exposed to hyperoxia showed significant increases (1.5-fold) in vaso-obliteration as indicated by central capillary drop out area compared to WT. Retinas from TKO showed minimal nitrotyrosine levels (10% of WT) with no change in eNOS or iNOS mRNA expression. There was no change in levels of VEGF or activation of VEGFR2 and its downstream Akt in retinas from TKO and WT. In comparison to WT, retinas from TKO showed significantly higher level of GSH and thioredoxin reductase activity in normoxia but comparable levels under hyperoxia. Exposure of TKO to hyperoxia significantly decreased the anti-apoptotic thioredoxin protein (∼50%) level compared with WT. This effect was associated with a significant increase in activation of the apoptotic ASK-1, PARP and caspase-3 pathway. Our results showed that despite comparable VEGF level and signal in TKO, exposure to hyperoxia significantly decreased Trx expression compared to WT. This effect resulted in liberation and activation of the apoptotic ASK-1 signal. These findings suggest that TXNIP is required for endothelial cell survival and homeostasis especially under stress conditions including hyperoxia.     

Enhanced expression of mitochondrial superoxide dismutase leads to prolonged in vivo cell cycle progression and up-regulation of mitochondrial thioredoxin

Mn superoxide dismutase (MnSOD) is an important mitochondrial antioxidant enzyme, and elevated MnSOD levels have been shown to reduce tumor growth in part by suppressing cell proliferation. Studies with fibroblasts have shown that increased MnSOD expression prolongs cell cycle transition time in G1/S and favors entrance into the quiescent state. To determine if the same effect occurs during tissue regeneration in vivo, we used a transgenic mouse system with liver-specific MnSOD expression and a partial hepatectomy paradigm to induce synchronized in vivo cell proliferation during liver regeneration. We show in this experimental system that a 2.6-fold increase in MnSOD activity leads to delayed entry into S phase, as measured by reduction in bromodeoxyuridine (BrdU) incorporation and decreased expression of proliferative cell nuclear antigen (PCNA). Thus, compared to control mice with baseline MnSOD levels, transgenic mice with increased MnSOD expression in the liver have 23% fewer BrdU-positive cells and a marked attenuation of PCNA expression. The increase in MnSOD activity also leads to an increase in the mitochondrial form of thioredoxin (thioredoxin 2), but not in several other peroxidases examined, suggesting the importance of thioredoxin 2 in maintaining redox balance in mitochondria with elevated levels of MnSOD.     

N-acetylcysteine treatment prevents the up-regulation of MnSOD in chronically hypoxic rat hearts

Chronic intermittent hypoxia (CIH) is associated with increased production of reactive oxygen species that contributes to the adaptive mechanism underlying the improved myocardial ischemic tolerance. The aim was to find out whether the antioxidative enzyme manganese superoxide dismutase (MnSOD) can play a role in CIH-induced cardioprotection. Adult male Wistar rats were exposed to intermittent hypobaric hypoxia (7000 m, 8 h/day, 25 exposures) (n=14) or kept at normoxia (n=14). Half of the animals from each group received N-acetylcysteine (NAC, 100 mg/kg) daily before the hypoxic exposure. The activity and expression of MnSOD were increased by 66 % and 23 %, respectively, in the mitochondrial fraction of CIH hearts as compared with the normoxic group; these effects were suppressed by NAC treatment. The negative correlation between MnSOD activity and myocardial infarct size suggests that MnSOD can contribute to the improved ischemic tolerance of CIH hearts.     

Effects of intermittent hypoxia on oxidative stress-induced myocardial damage in mice.

Obstructive sleep apnea is associated with increased risk for cardiovascular diseases. As obstructive sleep apnea is characterized by episodic cycles of hypoxia and normoxia during sleep, we investigated effects of intermittent hypoxia (IH) on ischemia-reperfusion-induced myocardial injury. C57BL/6 mice were subjected to IH (2 min 6% O(2) and 2 min 21% O(2)) for 8 h/day for 1, 2, or 4 wk; isolated hearts were then subjected to ischemia-reperfusion. IH for 1 or 2 wk significantly enhanced ischemia-reperfusion-induced myocardial injury. However, enhanced cardiac damage was not seen in mice treated with 4 wk of IH, suggesting that the heart has adapted to chronic IH. Ischemia-reperfusion-induced lipid peroxidation and protein carbonylation were enhanced with 2 wk of IH, while, with 4 wk, oxidative stress was normalized to levels in animals without IH. H(2)O(2) scavenging activity in adapted hearts was higher after ischemia-reperfusion, suggesting the increased antioxidant capacity. This might be due to the involvement of thioredoxin, as the expression level of this protein was increased, while levels of other antioxidant enzymes were unchanged. In the heart from mice treated with 2 wk of IH, ischemia-reperfusion was found to decrease thioredoxin. Ischemia-reperfusion injury can also be enhanced when thioredoxin reductase was inhibited in control hearts. These results demonstrate that IH changes the susceptibility of the heart to oxidative stress in part via alteration of thioredoxin.     

Prolonged exposure to hyperoxia increases perivascular mast cells in rat lungs.

Prolonged hyperoxia, as may be used to treat patients with severe hypoxemia, can lead to lung injury, respiratory failure, and death. Resident mast cells play important roles in regulating the lung response to changing environmental conditions, as evidenced by their roles in asthma and airway hyperresponsiveness. In this study we evaluated the effect of prolonged hyperoxia on the number and distribution of mast cells in the rat lung. In rats maintained in normoxia, mast cells were distributed primarily in the loose connective tissue surrounding large bronchioles and vessels of the lung. In rats exposed to normobaric hyperoxia for 72 hr, mast cell number in lung sections increased significantly, and mast cells were found preferentially accumulated around vessels throughout the lung. Notably, mast cells around smaller vessels were abundant in hyperoxic lungs but rare in normoxic lungs. Also, mast cells were increased in the pleura of lungs exposed to hyperoxia. These changes in mast cell number and distribution in response to hyperoxia were evident in aged (22-month-old) rats as well as young (3-month-old) rats. As mast cell-derived mediators have many effects, e.g., on vascular leak and vascular tone, positioning of increased mast cell numbers throughout the lung vasculature may be an important contributor to changes in lung function subsequent to persistent hyperoxia.     

β-cell death and proliferation after intermittent hypoxia: Role of oxidative stress

Intermittent hypoxia (IH), such as occurs in sleep apnea, induces increased oxidative stress and is associated with altered glucose homeostasis. Because pancreatic β cells are very sensitive to oxidative stress we tested whether they could be affected by IH. The effects of IH exposure (24 h/day, 5.7 and 21% O₂ alternation) in mice on β-cell proliferation and β-cell death were tested using Ki67 staining and TUNEL staining, respectively. To assess the role of oxidative stress in these processes, transgenic mice with β-cell-specific overexpression of the antioxidant protein MnSOD were exposed to IH. After 4 days of IH exposure, β-cell proliferation was increased almost fourfold. Coinciding with the increase in proliferation, the subcellular localization of the cell cycle regulator cyclin D2 was increased in the nucleus. In addition, β-cell death was increased approximately fourfold. MnSOD transgene did not alter the effects of IH on β-cell proliferation, but completely abrogated the IH effects on cell death. Thus, IH exposure that mimics sleep apnea can lead to increased β-cell proliferation and cell death. Furthermore, the cell death response seems to be due to oxidative stress.     

Increased sensitivity of homozygous Sod2 mutant mice to oxygen toxicity.

Induction or overexpression of pulmonary manganese superoxide dismutase (MnSOD) has been shown to protect against oxygen (O2) toxicity. Genetic inactivation of MnSOD (Sod2) results in multiple organ failure and early neonatal death. However, lungs or O2-tolerance of Sod2 knockout mice have not been investigated. We evaluated survival, lung histopathology, and other pulmonary antioxidants (glutathione cycle) of homozygous (-/-) and heterozygous (+/-) Sod2 mutant mice compared with wild-type controls (Sod2+/+) following 48 h exposure to either room air or to O2. The ability of antioxidant N-acetylcysteine to compensate for the loss of MnSOD was explored. Mortality of Sod2-/- mice increased from 0% in room air to 18 and 83% in 50 and 80% O2, respectively. N-acetylcysteine did not alter mortality of Sod2-/- mice. Histopathological analysis revealed abnormalities in saccules of Sod2-/- mice exposed either to room air or to 50% O2 suggestive of delayed postnatal lung development. In 50% O2, activities of glutamate-cysteine ligase (GCL) (previously known as gamma-glutamylcysteine synthetase, gamma-GCS) and glutathione peroxidase increased in Sod2-/- (35 and 70%, respectively) and Sod2+/- (12 and 70%, respectively) mice, but glutathione levels remained unaltered. We conclude that MnSOD is required for normal O2 tolerance and that in the absence of MnSOD there is a compensatory increase in pulmonary glutathione-dependent antioxidant defense in hyperoxia.     

Aerosolized human extracellular superoxide dismutase prevents hyperoxia-induced lung injury

An important issue in critical care medicine is the identification of ways to protect the lungs from oxygen toxicity and reduce systemic oxidative stress in conditions requiring mechanical ventilation and high levels of oxygen. One way to prevent oxygen toxicity is to augment antioxidant enzyme activity in the respiratory system. The current study investigated the ability of aerosolized extracellular superoxide dismutase (EC-SOD) to protect the lungs from hyperoxic injury. Recombinant human EC-SOD (rhEC-SOD) was produced from a synthetic cassette constructed in the methylotrophic yeast Pichia pastoris. Female CD-1 mice were exposed in hyperoxia (FiO2>95%) to induce lung injury. The therapeutic effects of EC-SOD and copper-zinc SOD (CuZn-SOD) via an aerosol delivery system for lung injury and systemic oxidative stress at 24, 48, 72 and 96 h of hyperoxia were measured by bronchoalveolar lavage, wet/dry ratio, lung histology, and 8-oxo-2'-deoxyguanosine (8-oxo-dG) in lung and liver tissues. After exposure to hyperoxia, the wet/dry weight ratio remained stable before day 2 but increased significantly after day 3. The levels of oxidative biomarker 8-oxo-dG in the lung and liver were significantly decreased on day 2 (P<0.01) but the marker in the liver increased abruptly after day 3 of hyperoxia when the mortality increased. Treatment with aerosolized rhEC-SOD increased the survival rate at day 3 under hyperoxia to 95.8%, which was significantly higher than that of the control group (57.1%), albumin treated group (33.3%), and CuZn-SOD treated group (75%). The protective effects of EC-SOD against hyperoxia were further confirmed by reduced lung edema and systemic oxidative stress. Aerosolized EC-SOD protected mice against oxygen toxicity and reduced mortality in a hyperoxic model. The results encourage the use of an aerosol therapy with EC-SOD in intensive care units to reduce oxidative injury in patients with severe hypoxemic respiratory failure, including acute respiratory distress syndrome (ARDS).     

Mechanisms of interaction between oxygen and granulocytes in hyperoxic lung injury

Hyperoxia and infused granulocytes act synergistically in producing a nonhydrostatic high-permeability lung edema in the isolated perfused rabbit lung within 4 h, which is substantially greater than that seen with hyperoxia alone. We hypothesized that the interaction between hyperoxia and granulocytes was principally due to a direct effect of hyperoxia on the lung itself. Isolated perfused rabbit lungs that were preexposed to 2 h of hyperoxia (95% O2-5% CO2) prior to the infusion of unstimulated granulocytes (under normoxic conditions) developed significant nonhydrostatic lung edema (P = 0.008) within 2 h when compared with lungs that were preexposed to normoxia (15% O2-5% CO2) prior to granulocyte perfusion. The edema in the hyperoxic-preexposed lungs was accompanied by significant increases in bronchoalveolar lavage (BAL) protein, BAL granulocytes, BAL thromboxane and prostacyclin levels, perfusate chemotactic activity, and lung lipid peroxidation. These findings suggest that the synergistic interaction between hyperoxia and granulocytes in producing acute lung injury involves a primary effect of hyperoxia on the lung itself.     

Increased expression of stress proteins in the surf clam Donax variabilis following hydrogen sulfide exposure

Endogenous free radical production and resulting oxidative damage may result from exposure to hypoxia, hyperoxia, or hydrogen sulfide. Previous investigations of sulfide-induced oxidative damage have produced conflicting results, perhaps because these studies utilized species presumably adapted to sulfide. We examined the effects of sulfide, hypoxia and hyperoxia on the surf clam Donax variabilis to test whether these stressors induce a cellular response to oxidative stress. These clams inhabit high-energy sandy beaches and are unlikely to have specific adaptations to these stressors. In duplicate flow-through experiments performed in fall and spring, clams were exposed to normoxia (22 kPa P(O(2))), hypoxia (10 kPa), hyperoxia (37 kPa), or sulfide with normoxia ( approximately 100 mumol L(-1), 22 kPa respectively) for 24 h. We quantified whole-animal expression of three antioxidants (Cu/Zn and Mn superoxide dismutases, glutathione peroxidase), a lipid peroxidation marker (4-hydroxy-2E-nonenol-adducted protein), a DNA repair enzyme (OGG1-m), four heat shock proteins (small Hsp, Hsp60, Hsp70, and mitochondrial Hsp70), ubiquitin, and actin. Clams exposed to sulfide showed upregulation of the greatest number of stress proteins and the pattern was consistent with a cellular response to oxidative stress. Furthermore, there was a marked seasonality, with greater stress protein expression in clams from the spring.     

Physiological significance of catalase and glutathione peroxidases,and in vivo peroxidation,in selected tissues of the toadDiscoglossus pictus (Amphibia) during acclimation to normobaric hyperoxia

1. Various parameters related to oxidative stress were measured in adult Discoglossus pictus acclimated for 15 days to either normoxia or hyperoxia (PO2 = 710 mmHg). 2. Total weight of the toads and total and relative wet weight of liver, kidneys, lungs and heart were not changed by hyperoxic acclimation. 3. In vivo tissue peroxidation increased in lung, decreased in skeletal muscle, and was not changed in liver, kidney, heart and skin after hyperoxic exposure. 4. Hyperoxic acclimation increased catalase activities in the lung, liver, kidney and heart but not in skeletal muscle and skin. 5. Liver showed higher GSH-peroxidase activity with cumene-OOH than with H2O2 as substrate, whereas lung, skeletal muscle and skin presented similar GSH-peroxidase activities with both substrates. 6. GSH-peroxidase activities did not change between hyperoxic and normoxic animals in liver, lung, skeletal muscle and skin. 7. These results show that catalase, not GSH-peroxidase, is the principal H2O2 detoxifying enzyme involved in the adaptation of D. pictus to hyperoxia.     

Catalase is needed to avoid tissue peroxidation in Rana perezi in normoxia

1. In order to clarify the relative role of catalase (CAT) and glutathione peroxidases (GSH-Px) at normal and high O2 tensions, Rana perezi frogs were chronically treated with aminotriazole (AT), hyperoxia, or both. 2. A 100% survival was observed with both treatments. Hyperoxia increased liver catalase and kidney TBA-RS and decreased GSH-Px. 3. AT caused quantitatively higher alterations than hyperoxia in both organs: CAT was depleted, TBA-RS increased (114% in kidney) and GSH-Px decreased. 4. It is concluded that in Rana perezi (a) CAT, in spite of its much higher KM and Vmax in relation to GSH-Px, is needed to avoid oxidative stress even in normoxia; (b) normoxic tissues have significative amounts of H2O2; (c) GSH-Px does not compensate the lack of CAT.