Alterations In Antioxidant Enzyme Activities Research Articles

Spontaneous hypomorphic mutations in antioxidant enzymes of mice

An antioxidant enzymatic system is pivotal for aerobic animals to minimize the damage induced by reactive oxygen species. Spontaneous mutant animals with altered antioxidant enzyme activity should be useful for the study of the function of these enzymes in vivo. We examined the nucleotide sequences of the genes for the major antioxidant enzymes, including catalase ( Cat), superoxide dismutase ( Sod1, Sod2, Sod3), glutathione peroxidase ( Gpx1, Gpx2, Gpx3, Gpx4, Gpx5), and glutathione reductase ( Gsr) in 10 inbred mouse strains. Nonsynonymous nucleotide polymorphisms were identified in all genes, except for Gpx1, Gpx3, and Gpx4. Notably, the SJL/J mouse strain possessed unique nucleotide substitutions in the Gsr and Sod2 genes, which led to Asp39Ala and Val138Met amino acid substitutions in GSR and SOD2, respectively. The specific activity of GSR of SJL/J mice was reduced to 65% of that of NZB/N mice. In vivo activity, however, was higher in SJL/J, due to upregulated expression of the enzyme. The SOD2 activity in SJL/J mice was reduced to half that of other mouse strains. Consistent with this reduction, oxidative damage in the mitochondria was increased as demonstrated by a decrease of total glutathione and an increase in the levels of protein oxidation. These spontaneous hypomorphic alleles would be valuable in the study of free radical biology.

Sex hormone-induced alterations in the activities of antioxidant enzymes and lipid peroxidation status in the prostate of Noble rats.

Oxidative stress has been implicated in prostate carcinogenesis. In the Noble rat model, treatment of rats with testosterone (T) plus 17beta-estradiol (E(2)) induced dysplasia and adenocarcinoma. Previous reports from us and other have indicated a linkage between steroid hormones and oxidative status in prostate cells in vivo and in vitro. Here, we provide further evidence that androgens and estrogens could induce a lobe-specific shift of prooxidant-antioxidant balance and alterations in antioxidant enzyme activities, leading to oxidative stress in the rat prostate gland in vivo. Male Noble rats were subjected to single (T, E(2), or diethylstilbestrol [DES] alone) or combined (T + E(2) or T + DES) hormone treatments. Lipid peroxidation status and antioxidant enzyme activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD) were assayed spectrophotometrically. Treatment of rats with T did not alter lipid peroxidation in either the ventral prostate (VP) or the dorsolateral prostate (DLP). In contrast, exposure of rats to DES or E(2) modestly elevated lipid peroxidation in rat VP or DLP, respectively. Of importance, T + DES and T + E(2) treatments of rats induced marked increases in lipid peroxidation in the VP and the DLP, respectively. Antioxidant enzyme activities in the VP and DLP exhibited differential responses to sex hormone challenges. The activities of catalase, GPx, GR, and G6PD were mostly suppressed in either single or dual hormone-treated DLP, whereas there is a general increase of GR and G6PD activities in the VP after hormonal exposures. The changes in T + DES-treated VP were most dramatic with a marked activation of GPx (by one-fold), GR (by one-fold), and G6PD (by five-fold). The lobe-specific differential responses of hormone-induced oxidative stress and modulations of antioxidant enzymatic defenses in the rat prostate suggest that reactive oxygen species may play a role in hormone-induced prostate carcinogenesis.

The changes in the antioxidant status of heart during experimental hypomagnesemia in balb/c mice.

The present experiment was performed to assess if hypomagnesemia can influence antioxidant status in mice heart. The results could explain possibly a free radical theory of heart damage in magnesium deficiency. We used a rodent model of hypomagnesemia. The magnesium sufficient group received a standard diet whereas a magnesium deficient group received the diet containing a trace amount of magnesium. The activities of the most important antioxidant enzymes--catalase, glutathione peroxidase and superoxide dismutase were assessed in mice heart and liver in a time dependent manner, on the 10th and the 20th day of experiment. The level of magnesium in plasma of animals receiving the magnesium deficient diet dropped twice after the 8th day and four times after the 13th day and then reached a plateau value. The activity of catalase in heart in the magnesium deficient group increased gradually and was significantly (P < 0.05) elevated by 27% on the 20th day of experiment whereas the superoxide dismutase activity was significantly decreased by 17% on the 20th day. Glutathione peroxidase activity was insignificantly elevated. The alterations of antioxidant enzyme activities in the heart indicate cardiomyocytes's exposure to oxidative stress, which can be responsible for the cardiac lesions observed during hypomagnesemia.

Mitochondrial dysfunction and oxidative stress in aging and neurodegenerative disease.

A major risk factor for neurodegenerative diseases such as Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and progressive supranuclear palsy (PSP) is aging. Two processes that have been implicated in aging are free radical-induced oxidative damage and mitochondrial dysfunction. A progressive impairment of mitochondrial function and/or increased oxidative damage has been suggested to play critical roles in the pathogenesis of these neurodegenerative diseases. For example, decreased complex I activity, increased oxidative damage and altered activities of antioxidant defense enzymes have been demonstrated in PD. In AD, decrements in complex IV activity and increased oxidative damage have been reported. Reductions in complex II activity, increased cortical lactate levels and oxidative damage have been described in HD. Some familial ALS cases are associated with mutations in the gene for Cu,Zn superoxide dismutase (SOD1) while increased oxidative damage is observed in sporadic ALS. Studies in PSP have demonstrated regionally specific reductions in brain and muscle mitochondrial function, hypofrontality and increased oxidative damage. Altogether, the age-dependent onset and progressive course of these neurodegenerative diseases may ultimately highlight an association between aging, mitochondrial impairment and oxidative stress.

Antioxidant status in anorexia nervosa.

The study of the antioxidant status in female adolescents (N = 82) with anorexia nervosa, by the measurement of erythrocyte tocopherol concentration, and the determination of activities of the main antioxidant enzymes: superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. Tocopherol was measured by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection, and antioxidant enzyme activities by spectrometric methods using a Cobas Fara automated centrifugal analyzer. Tocopherol was significantly decreased in the anorexic patients compared to reference values (p < .02). In 21% of patients, tocopherol levels were below the reference interval. Superoxide dismutase activity was significantly decreased (p < .0001), while catalase activity was increased (p < .0001). The activity of the glutathione system enzymes did not show significant differences between patients and controls. The deficient concentration of erythrocyte tocopherol together with the altered antioxidant enzyme activities suggest a certain degree of oxidative damage in anorexia nervosa owing to both factors deficient micronutrient intake and oxidative stress.

Glucocorticoids Increase the Accumulation of Reactive Oxygen Species and Enhance Adriamycin-Induced Toxicity in Neuronal Culture

Glucocorticoids (GCs), the adrenal steroids secreted during stress, are known to affect diverse processes involving reactive oxygen species, from exacerbation of ischemic damage to alteration of antioxidant enzyme activities. To determine whether GCs have a direct effect on oxidative processes, we constructed a dose–response curve using adriamycin, an oxygen radical generator, in primary neuronal cultures. In cultures derived from the hippocampus, which has the greatest concentration of corticosteroid receptors in the brain, higher levels of GCs significantly increased adriamycin toxicity, while not being toxic themselves. In cortical cultures, which contain lesser amounts of corticosteroid receptors, GCs had no effect on the adriamycin dose–response. Surprisingly, when tested with dichlorofluorescein for levels of reactive oxygen species (ROS), GCs increased ROS by approximately 10% basally and at all adriamycin doses in both hippocampal and cortical cultures. Thus, greater generation of ROS does not account for the increased susceptibility of the hippocampus to oxidative damage.

Effect of MPTP and l‐Deprenyl on Antioxidant Enzymes and Lipid Peroxidation Levels in Mouse Brain

Excessive free radical formation or antioxidant enzyme deficiency can result in oxidative stress, a mechanism proposed in the toxicity of MPTP and in the etiology of Parkinson's disease (PD). However, it is unclear if altered antioxidant enzyme activity is sufficient to increase lipid peroxidation in PD. We therefore investigated if MPTP can alter the activity of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) and the level of lipid peroxidation. L-Deprenyl, prior to MPTP administration, is used to inhibit MPP+ formation and its subsequent effect on antioxidant enzymes. MPTP induced a threefold increase in SOD activity in the striatum of C57BL/6 mice. No parallel increase in GSH-PX or CAT activities was observed, while striatal lipid peroxidation decreased. At the level of the substantia nigra (SN), even though increases in CAT activity and reduction in SOD and GSH-PX activities were detected, lipid peroxidation was not altered. Interestingly, L-deprenyl induced similar changes in antioxidant enzymes and lipid peroxidation levels, as did MPTP. Taken together, these results suggest that an alteration in SOD activity, without compensatory increases in CAT or GSH-PX activities, is not sufficient to induce lipid peroxidation.

Effect of exercise training on antioxidant system in brain regions of rat

The purpose of this investigation was to determine whether any alterations in antioxidant enzyme activities and levels of glutathione (GSH) in brain regions occurred following exercise training. Sprague-Dawley rats were given exercise training on a treadmill for 7.5 weeks and sacrificed 18 h after the last exercise along with the sedentary control rats. Different brain regions—cerebral cortex (CC), brainstem (BS), corpus striatum (CS), and hippocampus (H)—were isolated; GSH, oxidized glutathione (GSSG), Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were determined. The exercise training increased SOD activity significantly (130% of sedentary control) in BS and in CS. SOD activity in H was the lowest of all four brain regions. Different brain regions showed GSH-Px activity in decreasing order for CS < BS < CC < H. GSH levels were 43% less in BS than CC and CS. The ratio of GSH/ GSSG significantly increased from 6.8 to 8.3 in CC, and from 9.4 to 13.5 in BS as a result of exercise training. Different brain regions contained different activities of antioxidant enzymes, as well as GSH and GSSG levels, which were preferentially altered as a result of exercise training to cope with oxidative stress.

Variation in Antioxidant Enzyme Activities in Anatomic Subcompartments within Rat and Rhesus Monkey Lung

Antioxidant enzymes including catalase, superoxide dismutase, glutathione peroxidase, and glutathione S-transferases are thought to be the primary cellular defense against reactive oxygen species. Since pulmonary injury produced by oxidant air pollutants like ozone is highly focal, involving primarily the trachea and centriacinar areas of the lung, measurements of alterations in antioxidant enzyme activities in whole lung may substantially underestimate changes occurring in target areas of the respiratory tract. We have applied a technique for preparation of lung specimens from well-defined anatomic locations to determine whether the focal injury associated with ozone exposure is related to an uneven distribution of antioxidant enzyme activity in the respiratory tract. Our study compared enzyme activities in rat and monkey, species which differ considerably in sensitivity to ozone-induced injury (monkey > rat). The activities of glutathione S-transferase varied less than twofold between different airway subcompartments for both the rat and monkey. Pulmonary veins had approximately 50% of the activity of airways in both species. Glutathione peroxidase activity was slightly higher in proximal compared to distal airways of the rat but was evenly distributed at all airway levels in the monkey. In both species, activity in pulmonary veins was lower than that in airways. The activity of superoxide dismutase was similar in rat and monkey and marked differences were not observed in the various subcompartments studied. Similarly, catalase activity was relatively evenly distributed in rat airways but, in the monkey, the distal bronchiole and lobar bronchus had marginally higher activity than the trachea. We conclude that: (1) measurement of antioxidant enzyme activities in anatomic subcompartments within the lung is feasible using microdissected specimens, (2) antioxidant enzyme activity can vary in different subcompartments of the lung of the same species. (3) the pattern of variation in enzyme activity differs by the enzyme and by species, and (4) species and subcompartment differences in ozone injury are not due primarily to differences in the distribution of antioxidant enzyme activity.

Metabolic consequences of dietary 2,3- dichloro-1,4-naphthoquinone (CNQ) in the rat: Alteration in anti-oxidant enzyme activities

Dietary exposure of rats to a high concentration of 2,3-dichloro-1,4-naphthoquinone (CNQ) (2 g/kg diet) for 60 days altered cardiac mitochondrial function and activities of anti-oxidant enzymes in hepatic and cardiac tissue. CNQ moderately depressed the cardiac mitochondrial respiratory control ratio (RCR) to 85% of control; this was exacerbated to 60% of control in animals fed α-tocopheroldeficient diets. Dietary CNQ increased hepatic Superoxide dismutase (SOD) and catalase activities and increased cardiac SOD activity, but depressed cardiac glutathione reductase and hepatic glutathione peroxidase activities. These effects are consistent with previous in vitro findings that CNQ induces oxidative stress. No significant differences in heart weight or body weight were observed in rats fed CNQ as compared to untreated controls.