Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:APRD00369 (ROS)
 19,271 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bleomycin-induced, 6-thioguanine-resistant, "non deletion" mutants pretreated with or without either TRIEN (triethylenetetramine), a superoxide dismutase (SOD) inhibitor, or TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a SOD mimic, were analyzed by polymerase chain reaction (PCR)-directed DNA sequencing in a Chinese hamster ovary (CHO) cell derivative, AS52. Among the 23 bleomycin-induced mutants, six have 3-bp 5'-TGA-3' deletions in the region of 366-371, five have single-base deletions, seven have base substitutions, three have insertions, and two have possible translocations. Among the 16 bleomycin-induced mutants pretreated with TRIEN, six have the 5'-TGA-3' deletion (366-371), two have single-base deletions, one has a 13-bp deletion, four have single-base substitutions, one has a double-base substitution, and two have insertions. Among the 17 bleomycin-induced mutants pretreated with TEMPOL, six have the same TGA deletions, two have single-base deletions, two have single-base insertions, four have single-base substitutions, one mutant has a 12-bp deletion, one has a 13-bp deletion, and one mutant shows no detectable change in its coding region in the DNA sequence. A possible shift from a ROS-mediated mutational spectrum to a spontaneous mutational spectrum by TRIEN further indicates that reactive oxygen species play an important role in bleomycin mutagenesis in mammalian cells.
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PMID:Polymerase chain reaction-directed DNA sequencing of bleomycin-induced "nondeletion"-type, 6-thioguanine-resistant mutants in Chinese hamster ovary cell derivative AS52: effects of an inhibitor and a mimic of superoxide dismutase. 751 29

We are constantly exposed, throughout life, to a wide variety of extrinsic and intrinsic agents which have the potential to damage cellular biomolecules, including DNA. Imperfections in cellular defence systems which protect against the fixation of DNA damage can lead to an accumulation of mutations which on their own, or in combination with other age-related changes, may contribute to ageing and the development of age-related pathologies. We have previously reported an increase in frequency of mutation with age in human lymphocytes taken from healthy males in the age groups, 35-39, 50-54 and 65-69 years. In this article we report on the findings of a recent study which was designed to assess whether the age-related increase in frequency of mutation was due to a decreased efficacy of the defence systems against ROS-induced DNA damage, namely antioxidant status and DNA repair processes, in the same study subjects. In vivo antioxidant status was assessed in each of the study subjects by measuring blood levels of; superoxide dismutase (SOD; EC 1.15.1.1), glutathione peroxidase (GPx; EC 1.11.1.9), catalase (EC 1.11.1.6), caeruloplasmin (CPL), uric acid and bilirubin. We did not find any statistically significant differences in the mean levels of these antioxidants between the three different age groups. To investigate the efficacy of DNA repair processes against ROS-induced DNA damage, an ELISA was used to quantitate DNA damage (as % single-stranded DNA; %SS-DNA) at various times following treatment of peripheral blood lymphocytes with hydrogen peroxide (H2O2). The results of this part of the study showed that in untreated lymphocytes, basal levels of %SS-DNA were significantly higher in individuals from the 65-69 years age group compared to the 35-39 years age group (p = 0.039, 0.0013; at 5% level of significance). No significant differences were found in H2O2 susceptibility with age immediately following treatment (p = 0.71, 1.00; at 5% level of significance) but a consistent and significant increase was observed in %SS-DNA remaining 90 min post-treatment in lymphocytes from subjects in the 65-69 years age group, compared to %SS-DNA present in lymphocytes from the 35-39 years age group (p = 0.013, 0.024; at 5% level of significance). The results of this study suggest that the age-related increase in frequency of mutations is not contributed to by alterations of in vivo antioxidant status with age but is by a decreased efficacy of the repair of ROS-induced DNA damage with age. The biological implications of somatic mutations in the ageing process are discussed.
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PMID:An investigation of antioxidant status, DNA repair capacity and mutation as a function of age in humans. 756 67

The most important electron acceptor in the biosphere is molecular oxygen which, by virtue of its bi-radical nature, readily accepts unpaired electrons to give rise to a series of partially reduced species collectively known as reduced (or 'reactive') oxygen species (ROS). These include superoxide (O.2-), hydrogen peroxide (H2O2), hydroxyl radical (HO.) and peroxyl (ROO.) and alkoxyl (RO.) radicals which may be involved in the initiation and propagation of free radical chain reactions and which are potentially highly damaging to cells. Mechanisms have evolved to restrict and control such processes, partly by compartmentation, and partly by antioxidant defences such as chain-breaking antioxidant compounds capable forming stable free radicals (e.g. ascorbate, alpha-tocopherol) and the evolution of enzyme systems (e.g. superoxide dismutase, catalase, peroxidases) that diminish the intracellular concentration of the ROS. Although some ROS perform useful functions, the production of ROS exceeding the ability of the organism to mount an antioxidant defence results in oxidative stress and the ensuing tissue damage may be involved in certain disease processes. Evidence that ROS are involved in primary pathological mechanisms is a feature mainly of extraneous physical or chemical perturbations of which radiation is perhaps the major contributor. One of the important radiation-induced free-radical species is the hydroxyl radical which indiscriminately attacks neighbouring molecules often at near diffusion-controlled rates. Hydroxyl radicals are generated by ionizing radiation either directly by oxidation of water, or indirectly by the formation of secondary partially ROS. These may be subsequently converted to hydroxyl radicals by further reduction ('activation') by metabolic processes in the cell. Secondary radiation injury is therefore influenced by the cellular antioxidant status and the amount and availability of activating mechanisms. The biological response to radiation may be modulated by alterations in factors affecting these secondary mechanisms of cellular injury.
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PMID:Free radicals in biology: oxidative stress and the effects of ionizing radiation. 790 6

Human mtDNA is a naked circular double-stranded DNA, which is continually exposed to the matrix that contains high levels of ROS and free radicals. High oxidative stress and a lack of proofreading during mtDNA replication and efficient DNA repair mechanisms in the mitochondria have rendered mtDNA extremely vulnerable to oxidative damage. More than one dozen large-scale deletions in mtDNA have been identified in various tissues of old humans. The 4,977-bp and 7,436-bp deletions are the most prevalent and abundant ones. The onset age of various mtDNA deletions varies greatly with tissues of each individual and type of deletion. In this and previous studies, we have demonstrated with PCR techniques that the frequency of occurrence and the proportion of the 4,977-bp and 7,436-bp deleted mtDNAs are significantly increased with the age of the human. The mtDNA deletions are not detectable in any tissues from young healthy subjects or blood cells from normal individuals of any age, which indicates that the deletions are generated and accumulated only in postmitotic cells upon aging. Moreover, we found that these mtDNA deletions occur more frequently and abundantly in tissues with high energy demand (e.g., muscle) as compared to those with low energy demand. On the other hand, we found that the amount of lipid peroxides measured as malondialdehyde and the activity of manganese-superoxide dismutase in the mitochondria exhibit an age-dependent increase in various human tissues. The lipid peroxide level in muscle was significantly higher than that in the other tissues. Moreover, we found a positive correlation between the proportion of the 4,977-bp deleted mtDNA and lipid peroxide content in the mitochondria of human tissues during aging. Muscle the tissue of high energy demand, was found to be more vulnerable to oxidative damage that lead to most abundant mtDNA deletions and lipid peroxidation among all the tissues examined. Taking these results together, we suggest that the enhanced generation of reactive oxygen species and lipid peroxides in the mitochondria during the aging process occur simultaneously with large-scale deletions and the other types of mutations in mtDNA, which are early molecular events and major contributory factors of human aging.
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PMID:Simultaneous increase of mitochondrial DNA deletions and lipid peroxidation in human aging. 868 24

This study has investigated the antioxidant capacity of human seminal plasma due to the presence of both high and low molecular weight antioxidant factors. Methods for the measurement of superoxide dismutase-like activity (SOD-like) and total antioxidant status (TAS) were automated, and had a within-run coefficient of variation of 7.3% for SOD-like activity and 4.8% for TAS. In 69 semen samples from unselected infertile men, SOD-like activity in seminal plasma ranged from 2 to 16 U/ml, with a mean of 6.9 +/- 2.8 U/ml. As SOD-like activity was correlated positively with levels of citric acid (p < 0.0001), zinc (p < 0.0002) and acid phosphatase activity (p < 0.0005), and there was no correlation with fructose levels, our results suggest that prostatic secretions are an important source of superoxide anion scavengers. Evaluation of SOD-like activity in infertile men with accessory sex gland infections (n = 12) showed significantly lower activity (p < 0.003) compared to values found in 12 infertile men without signs of infection. The values obtained for total antioxidant status (equivalent to the antioxidant capacity of alpha-tocopherol analogue) ranged from 1.7 to 2.3 mmol/L, with a mean of 2.1 +/- 0.1 (n = 40), reflecting the protective activity of ascorbate, urate and albumin, and to a very low extent of glutathione and taurine. The data obtained by TAS assay correlated with fructose, a major marker of vesicular secretion (p < 0.005), suggesting that low molecular weight components with antioxidant capacity derive partly from the seminal vesicles. The results indicate that the relative contribution of antioxidant defence systems capable of counteracting the deleterious action of superoxide anions, depends on the secretory activity of accessory sex glands and is independent of excessive ROS production due to increased oxidative stress.
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PMID:Superoxide anion scavenging capacity of human seminal plasma. 873 38

Human spermatozoa exhibit a capacity to generate ROS and initiate peroxidation of the unsaturated fatty acids in the sperm plasma membrane, which plays a key role in the etiology of male infertility. The short half-life and limited diffusion of these molecules is consistent with their physiologic role in key biological events such as acrosome reaction and hyperactivation. The intrinsic reactivity of these metabolites in peroxidative damage induced by ROS, particularly H2O2 and the superoxide anion, has been proposed as a major cause of defective sperm function in cases of male infertility. The number of antioxidants known to attack different stages of peroxidative damage is growing, and it will be of interest to compare alpha-tocopherol and ascorbic acid with these for their therapeutic potential in vitro and in vivo. Both spermatozoa and leukocytes generate ROS, although leukocytes produce much higher levels. The clinical significance of leukocyte presence in semen is controversial. Seminal plasma confers some protection against ROS damage because it contains enzymes that scavenge ROS, such as catalase and superoxide dismutase. A variety of defense mechanisms comprising a number of anti-oxidants can be employed to reduce or overcome oxidative stress caused by excessive ROS. Determination of male infertility etiology is important, as it will help us develop effective therapies to overcome excessive ROS generation. ROS can have both beneficial and detrimental effects on the spermatozoa and the balancing between the amounts of ROS produced and the amounts scavenged at any moment will determine whether a given sperm function will be promoted or jeopardized. Accurate assessment of ROS levels and, subsequently, OS is vital, as this will help clinicians both elucidate the fertility status and identify the subgroups of patients that respond or do not respond to these therapeutic strategies. The overt commercial claims of antioxidant benefits and supplements for fertility purposes must be cautiously looked into, until proper multicentered clinical trials are studied. From the current data it appears that no single adjuvant will be able to enhance the fertilizing capacity of sperm in infertile men, and a combination of the possible strategies that are not toxic at the dosage used would be a feasible approach.
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PMID:Role of reactive oxygen species in male infertility. 897 65

Although free radical species (ROS; i.e., .O2-. .OH.H2O2) among other mediators, may be involved in altering the blood-brain barrier (BBB), little is known about the endogenous ability of cerebromicrovascular endothelium to generate ROS. This study examines the capacity of rat endothelial cells (RBEC) to produce ROS in normoxia and hypoxia/reoxygenation. Cultured RBEC were exposed to an oxygen-depleted atmosphere (containing 95% N2 and 5% CO2) for 4 hr at 37 degrees C and air (10 min) at room temperature to simulate "ischemia/reperfusion". Nitroblue tetrazolium (NBT) reduction [formation of nitroblue formazan (NBF)] served as a marker for the production of ROS. The release of lactate dehydrogenase (LDH) and [3H]arachidonic acid (AA) was used to assess cellular integrity. RBEC exposed to hypoxia/reoxygenation produced up to 59% greater NBF formation than controls without affecting the LDH or AA release. The production of ROS was calcium-dependent and not affected by AA or its metabolites. The findings indicate that the RBEC can produce superoxide dismutase (SOD)-inhibitable ROS which are augmented by hypoxia/reoxygenation. It is suggested that in vivo cerebromicrovascular endothelium may contribute to the formation of ROS and play a role in ischemic brain edema.
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PMID:Hypoxia modulates free radical formation in brain microvascular endothelium. 941 63

In vitro models based on primary cultured human chondrocytes could be useful to study the ROS-mediated inflammatory processes that seem to involve chondrocytes in vivo. In this work, we studied the enzymatic antioxidative capability of human chondrocytes removed from vertebral plates during micro-discectomy and cultured 18 days, measuring total superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) activities. We also evaluated in the same cells the amount of malondialdehyde (MDA) in order to verify the effect of the variation of the cellular enzymatic antioxidative capability on the degree of membrane lipid peroxidation. Total SOD activity increased, even if not significantly, between the 12th and the 18th day. A significant variation of GSHPx (P<0.01) and of catalase (P<0.001) activity was observed between the 3rd and the 6th day with no further variation until the 18th day. A significant increase (P<0.001) of lipid peroxidation from the 3rd to the 18th day was also observed. These results seem to indicate that only fresh human cultured chondrocytes are suitable to study, through in vitro models, the in vivo behavior of the antioxidative status of these cells.
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PMID:Antioxidant enzymatic activities and lipid peroxidation in cultured human chondrocytes from vertebral plate cartilage. 970 92

The effect of methotrexate (MTX) and leucovorin (LCV) on pentose cycle enzymes and the activity of enzymes involved in enzyme defence mechanisms against ROS in HeLa cells, were studied. The effect of MTX was also investigated on the cellular levels of glutathione. MTX inhibited the activity of glucose-6-phosphate and 6-phosphogluconate dehydrogenases. The activities of glutathione reductase and gamma-glutamylcysteine synthetase were also inhibited by the drug. No effect was observed on the activities of catalase, superoxide dismutase or transketolase. LCV had no effect on any of the enzymes studied. MTX decreased the cellular levels of glutathione (70 per cent), while the presence of LCV and glutamine did not interfere with the effect of MTX. The net results appear to show that the biological situation resulting from treatment with MTX leads to a reduction of effectiveness of the antioxidant enzyme defence system.
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PMID:Methotrexate: pentose cycle and oxidative stress. 985 91

Mitochondrial DNA (mtDNA) mutations and impaired respiratory function have been demonstrated in various tissues of aged individuals. We hypothesized that age-dependent increase of ROS and free radicals production in mitochondria is associated with the accumulation of large-scale mtDNA deletions. In this study, we first confirmed that the proportion of mtDNA with the 4977 bp deletion in human skin tissues increases with age. We then investigated the 8-hydroxy-2'-deoxyguanosine (8-OH-dG) content in skin tissues and lipid peroxides content of the skin fibroblasts from subjects of different ages. The results showed an age-dependent increase of 8-OH-dG level in the total DNA of skin tissues of the subjects above the age of 60 years. The specific content of malondialdehyde, an end product of lipid peroxidation, was also found to increase with age. On the other hand, we examined the enzyme activities of Cu, Zn-superoxide dismutase (Cu,Zn-SOD), Mn-superoxide dismutase (Mn-SOD), catalase, and glutathione peroxidase (GPx) in the skin fibroblasts. The activities of Cu,Zn-SOD, catalase and glutathione peroxidase were found to decrease with age. However, the activity of Mn-SOD was increased with age before 60 years but was decreased thereafter. Moreover, the activity ratios of Mn-SOD/catalase and Mn-SOD/GPx exhibited the same pattern of change with age. This indicates that free radical scavenging enzymes can effectively dispose of ROS and free radicals before 60 years of age. However, elevated oxidative stress caused by an imbalance between the production and removal of ROS and free radicals occurred in skin fibroblasts after 60 years of age. Taken together, we suggest that the functional decline of free radical scavenging enzymes and the elevation of oxidative stress may play an important role in eliciting oxidative damage and mutation of mtDNA during the human aging process.
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PMID:Oxidative damage elicited by imbalance of free radical scavenging enzymes is associated with large-scale mtDNA deletions in aging human skin. 1002 67


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