Effect of copper deficiency on oxidative DNA damage in Jurkat T-lymphocytes

The micronutrient copper is a catalytic cofactor for copper, zinc superoxide dismutase and ceruloplasmin, which are two important antioxidant enzymes. As such, a lack of copper may promote oxidative stress and damage. The purpose of this study was to determine the effect of copper deficiency on oxidative damage to DNA in Jurkat T-lymphocytes. To induce copper deficiency, cells were incubated for 48 h with 5-20 microM 2,3,2-tetraamine (2,3,2-tet), a high affinity copper chelator. Such treatment did not affect cell proliferation/viability, as assessed by measuring mitochondrial reduction of WST-1 reagent (4-[3-(4-Iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-ben zen e disulfonate). Furthermore, the induction of copper deficiency did not promote oxidative DNA damage as evaluated by the comet assay. Comet scores were 15 +/- 0 and 16 +/- 1 for control and copper-deficient cells, respectively. However, the copper-deficient cells sustained greater oxidative DNA damage than the control cells (comet scores of 175 +/- 15 and 50 +/- 10, respectively) when both were oxidatively challenged with 50 microM hydrogen peroxide (H(2)O(2)). Supplemental copper but not zinc or iron prevented the potentiation of the H(2)O(2)-induced oxidative DNA damage caused by 2,3,2-tet. These data suggest that copper deficiency compromises the antioxidant defense system of cells, thereby increasing their susceptibility to oxidative DNA damage.     

Lymphocyte DNA damage and oxidative stress in patients with iron deficiency anemia

Oxidant stress has been shown to play an important role in the pathogenesis of iron deficiency anemia. The aim of this study was to investigate the association between lymphocyte DNA damage, total antioxidant capacity and the degree of anemia in patients with iron deficiency anemia. Twenty-two female with iron deficiency anemia and 22 healthy females were enrolled in the study. Peripheral DNA damage was assessed using alkaline comet assay and plasma total antioxidant capacity was determined using an automated measurement method. Lymphocyte DNA damage of patients with iron deficiency anemia was significantly higher than controls (p<0.05), while total antioxidant capacity was significantly lower (p<0.001). While there was a positive correlation between total antioxidant capacity and hemoglobin levels (r=0.706, p<0.001), both total antioxidant capacity and hemoglobin levels were negatively correlated with DNA damage (r=-0.330, p<0.05 and r=-0.323, p<0.05, respectively). In conclusion, both oxidative stress and DNA damage are increased in IDA patients. Increased oxidative stress seems as an important factor that inducing DNA damage in those IDA patients. The relationships of oxidative stress and DNA damage with the severity of anemia suggest that both oxidative stress and DNA damage may, in part, have a role in the pathogenesis of IDA.     

Magnesium deficiency increases oxidative stress in rats

Magnesium deficiency has been implicated in the development of atherosclerosis and late diabetic complications, diseases often associated with increased oxidative stress. Present study was carried out to examine the effect of magnesium deficiency on oxidative stress and total radical trapping antioxidant parameter (calculated) in rats and correlate it with the development of free radical mediated diseases. Male Wistar rats were divided into two groups and pair fed for six weeks with low magnesium diet (70 mg/kg) and control diet (990 mg/kg) prepared synthetically. Deionized water was given ad libitum. Low magnesium diet caused a significant decrease in plasma and red blood cell magnesium levels. A marked increase in plasma malondialdehyde and corresponding decrease in total radical trapping antioxidant parameters (calculated) were observed in the low magnesium diet group than control group. The level of plasma glucose increased moderately in the low magnesium diet group. Hypertriglyceridemia and significantly decreased plasma HDL (high density lipoprotein)-cholesterol levels were observed in the low magnesium diet group. The results clearly demonstrate that magnesium deficiency is associated with increased oxidative stress through reduction in plasma antioxidants and increased lipid peroxidation suggesting that the increased oxidative stress may be due to increased susceptibility of body organs to free radical injury.     

The oxidative stress of zinc deficiency

Zinc is an essential catalytic and structural cofactor for many enzymes and other proteins. While Zn2+ is not redox active under physiological conditions, it has been known for many years that zinc deficiency causes increased oxidative stress and, consequently, increased oxidative damage to DNA, proteins, and lipids. These results have indicated that zinc plays an indirect antioxidant role and that dietary inadequacy may contribute to human diseases such as cancer. Recent studies are helping to identify the primary sources of oxidative stress in low zinc. In addition, through studies of the model eukaryotic cell, Saccharomyces cerevisiae, we are now beginning to understand the strategies cells use to limit this stress and reduce its damage.     

DNA damage responses in the prostate

Comment on: Zhewei Z, et al. Cell Cycle 2011; 10:3545-53.     

Absent effect of zinc deficiency on the oxidative stress of erythrocytes in chronic uremic rats

Both anemia and zinc deficiency are commonly observed in patients with chronic uremia. Oxidative stress of red blood cells (RBC) has been suggested to participate in the development of anemia in these patients with chronic uremia due to reduced life span of RBC. Whether zinc deficiency aggravates the effect of oxidative stress on RBC of chronic uremia is still not understood. We thus performed the study to determine the influence of zinc deficiency on the oxidative stress of RBC in uremic rats. Zinc deficiency was induced by long-term dietary zinc deficiency. Five-sixth nephrectomy (5/6 Nx) was used to produce chronic uremia. Experiment was carried out in the following five groups: normal control (NL), chronic uremia (Nx), chronic uremia + dietary zinc deficiency (Nx-D), Nx-D + zinc supplement (Nx-DZ) and Chronic uremia + pair-fed (Nx-PF). Osmotic fragility and lipid peroxidation of RBC were used to evaluate the oxidative stress of RBC. Five weeks after 5/6 nephrectomy (Nx), 5/6 Nx rats present a syndrome of uremia to elevate the levels of plasma creatinine and urea, and reduce the level of plasma zinc (1.12 +/- 0.08 vs 1.35 +/- 0.05 ug/ml). But they does not find to produce anemia and to increase osmotic fragility and lipid peroxidation in RBC. Dietary zinc deficiency in Nx-D group produced severe anorexia and reduced plasma zinc and selenium levels and the activity of RBC-GPX. Yet in Nx-D rats, osmotic fragility and susceptibility of lipid peroxidation in red cells did not increase, because of the increase of plasma copper level (1.85 +/- 0.3 vs 1.41 +/- 0.05 microg/ml) and RBC-SOD activity (1.95 +/- 0.27 vs 0.78 +/- 0.05 unit/g Hb). Zinc supplement in Nx-D rats (Nx-DZ group) recovered the appetite and normalized the levels of plasma zinc, copper and selenium. Food restriction in 5/6 Nx rats (Nx-PF group) decreased plasma copper level and increased osmotic fragility of RBC and elevated the susceptibility of lipid peroxidation after stressing RBC with H2O2 Because Nx-PF rats presented a lower RBC-SOD activity (0.44 +/- 0.11 vs 0.78 +/- 0.05 unit/g Hb) and a lower plasma copper level. We further found a positive relationship (r=0. 802,p<0.01) between plasma copper level and RBC-SOD activity in normal and uremic rats. This study suggests that RBC-SOD activity may play an important role in preventing RBC oxidative stress. Plasma copper level may be a marker of RBC-SOD activity. We conclude, in chronic uremia, zinc deficiency doses not result in RBC oxidative stress as plasma copper level is normal, but may affect the absorption of intestinal nutrition.     

DNA repair BER pathway inhibition increases cell death caused by oxidative DNA damage in Trypanosoma cruzi

Trypanosoma cruzi, a parasitic protozoan, is the etiological agent of Chagas disease, an endemic and neglected pathology in Latin America. It presents a life cycle that involves a hematophagous insect and man as well as domestic and wild mammals. The parasitic infection is not eliminated by the immune system of mammals; thus, the vertebrate host serves as a parasite reservoir. Additionally, chronic processes leading to dysfunction of the cardiac and digestive systems are observed. To establish a chronic infection some parasites should resist the oxidative damage to its DNA exerted by oxygen and nitrogen free radicals (ROS/RNS) generated in host cells. Till date there are no reports directly showing oxidative DNA damage and repair in T. cruzi. We establish that ROS/RNS generate nuclear and kinetoplastid DNA damage in T. cruzi that may be partially repaired by the parasite. Furthermore, we determined that both oxidative agents diminish T. cruzi cell viability. This effect is significantly augmented in parasites subsequently incubated with methoxyamine, a DNA base excision repair (BER) pathway inhibitor, strongly suggesting that the maintenance of T. cruzi viability is a consequence of DNA repair mechanisms.     

Acute hypoxia and hypoxic exercise induce DNA strand breaks and oxidative DNA damage in humans.

The present study investigated the effect of a single bout of exhaustive exercise on the generation of DNA strand breaks and oxidative DNA damage under normal conditions and at high-altitude hypoxia (4559 meters for 3 days). Twelve healthy subjects performed a maximal bicycle exercise test; lymphocytes were isolated for analysis of DNA strand breaks and oxidatively altered nucleotides, detected by endonuclease III and formamidipyridine glycosylase (FPG) enzymes. Urine was collected for 24 h periods for analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a marker of oxidative DNA damage. Urinary excretion of 8-oxodG increased during the first day in altitude hypoxia, and there were more endonuclease III-sensitive sites on day 3 at high altitude. The subjects had more DNA strand breaks in altitude hypoxia than at sea level. The level of DNA strand breaks further increased immediately after exercise in altitude hypoxia. Exercise-induced generation of DNA strand breaks was not seen at sea level. In both environments, the level of FPG and endonuclease III-sensitive sites remained unchanged immediately after exercise. DNA strand breaks and oxidative DNA damage are probably produced by reactive oxygen species, generated by leakage of the mitochondrial respiration or during a hypoxia-induced inflammation. Furthermore, the presence of DNA strand breaks may play an important role in maintaining hypoxia-induced inflammation processes. Hypoxia seems to deplete the antioxidant system of its capacity to withstand oxidative stress produced by exhaustive exercise.     

Marginal zinc deficiency increased the susceptibility to acute lipopolysaccharide-induced liver injury in rats

Lipopolysaccharide (LPS) triggers a global activation of inflammatory responses leading to liver injury in humans. Zinc pretreatment has been shown to prevent LPS-induced hepatic necrosis. In North America, suboptimal zinc status is more common than once realized. However, the effect of inadequate zinc nutrition on the host's susceptibility to LPS-induced liver injury is not known. The objective of this study was to determine whether marginal zinc deficiency would render rats more susceptible to LPS-induced liver injury. Weanling Sprague-Dawley rats were assigned to one of three dietary treatment groups: marginally low zinc ad libitum (Z3; 3 mg zinc/kg diet), adequate zinc ad libitum (Z30; 30 mg zinc/kg diet), or adequate zinc pair-fed (Z30P) group. After 6 weeks, each dietary treatment group was further divided into LPS-control (saline) groups (C-Z3, C-Z30P, C-Z30) and LPS-treatment (1 mg/kg body weight, intraperitoneal, 8 hrs) groups (LPS-Z3, LPS-Z30P, LPS-Z30). LPS reduced the serum zinc concentration and increased the liver zinc concentration regardless of dietary zinc intake. Serum alanine aminotransferase level was higher in the LPS-Z3 rats than in the LPS-Z30P and LPS-Z30 rats. LPS also induced hepatocyte necrosis and neutrophil infiltration into the liver sinusoids. This LPS-induced liver damage was more severe in the LPS-Z3 rats than in the LPS-Z30P and LPS-Z30 rats. Together these findings have demonstrated that marginal zinc deficiency increased the susceptibility to LPS-induced liver injury in rats. These results indicate that patients with sepsis who have suboptimal zinc nutrition status may be at higher risk of developing greater liver damage.     

Repair of oxidative DNA damage

Cellular genomes suffer extensive damage from exogenous agents and reactive oxygen species formed during normal metabolism. The MutT homologs (MutT/MTH) remove oxidized nucleotide precursors so that they cannot be incorporated into DNA during replication. Among many repair pathways, the base excision repair (BER) pathway is the most important cellular protection mechanism responding to oxidative DNA damage. The 8-oxoG glycosylases (Fpg or MutM/OGG) and the MutY homologs (MutY/MYH) glycosylases along with MutT/MTH protect cells from the mutagenic effects of 8-oxoG, the most stable and deleterious product known caused by oxidative damage to DNA. The key enzymes in the BER process are DNA glycosylases, which remove different damaged bases by cleavage of the N-glycosylic bonds between the bases and the deoxyribose moieties of the nucleotide residues. Biochemical and structural studies have demonstrated the substrate recognition and reaction mechanism of BER enzymes. Cocrystal structures of strated the substrate recognition and reaction mechanism of BER enzymes. Cocrystal structures of several glycosylases show that the substrate base flips out of the sharply bent DNA helix and the minor groove is widened to be accessed by the glycosylases. To complete the repair after glycosylase action, the apurinic/apyrimidinic (AP) site is further processed by an incision step, DNA synthesis, an excision step, and DNA ligation through two alternative pathways. The short-patch BER (1-nucleotide patch size) and long-patch BER (2–6-nucleotide patch size) pathways need AP endonuclease to generate a 3′ hydroxyl group but require different sets of enzymes for DNA synthesis and ligation. Protein-protein interactions have been reported among the enzymes involved in BER. It is possible that the successive players in the repair pathway are assembled in a complex to perform concerted actions. The BER pathways are proposed to protect cells and organisms from mutagenesis and carcinogenesis.     

Hepatic oxidative DNA damage correlates with iron overload in chronic hepatitis C patients

Hepatic oxidative stress occurs in chronic hepatitis C (CH-C), but little is known about its producing mechanisms and precise role in the pathogenesis of the disease. To determine the relevance of hepatic oxidatively generated DNA damage in CH-C, 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts were quantified in liver biopsy specimens by immunohistochemical staining, and its relationship with clinical, biochemical, and histological parameters, and treatment response was assessed in 40 CH-C patients. Hepatic 8-OHdG counts were significantly correlated with serum transaminase levels (r=0.560, p=0.0005) and histological grading activity (p=0.0013). Remarkably, 8-OHdG levels were also significantly related to body and hepatic iron storage markers (vs serum ferritin, r=0.565, p=0.0004; vs hepatic total iron score, r=0.403, p=0.0119; vs hepatic hepcidin messenger RNA, r=0.516, p=0.0013). Baseline hepatic oxidative stress was more prominent in nonsustained virological responder (non-SVR) than in SVR to interferon (IFN)/ribavirin treatment (50.8 vs 32.7 cells/10(5) microm2, p=0.0086). After phlebotomy, hepatic 8-OHdG levels were significantly reduced from 53.4 to 21.1 cells/10(5) microm2 (p=0.0125) with concomitant reductions of serum transaminase and iron-related markers in CH-C patients. In conclusion, this study showed that hepatic oxidatively generated DNA damage frequently occurs and is strongly associated with increased iron deposition and hepatic inflammation in CH-C patients, suggesting that iron overload is an important mediator of hepatic oxidative stress and disease progression in chronic HCV infection.     

Age-dependent increases in oxidative damage to DNA,lipids, and proteins in human skeletal muscle

A role for oxidative damage in normal aging is supported by studies in experimental animals, but there is limited evidence in man. We examined markers of oxidative damage to DNA, lipids, and proteins in 66 muscle biopsy specimens from humans aged 25 to 93 years. There were age-dependent increases in 8-hydroxy-2-deoxyguanosine (OH⁸dG), a marker of oxidative damage to DNA, in malondialdehyde (MDA), a marker of lipid peroxidation, and to a lesser extent in protein carbonyl groups, a marker of protein oxidation. The increases in OH⁸dG were significantly correlated with increases in MDA. These results provide evidence for a role of oxidative damage in human aging which may contribute to age-dependent losses of muscle strength and stamina.     

Mouse heat shock transcription factor 1 deficiency alters cardiac redox homeostasis and increases mitochondrial oxidative damage

In this study, using heat shock factor 1 (Hsf1) knockout mice as a model, we tested the hypothesis that HSF1-dependent regulation of heat shock proteins (Hsps) is required to maintain redox state and attenuate oxidative damage in the normal heart. Here we report that, in mice, HSF1 deficiency reduces cardiac expression of Hsp25, alphaB-crystallin and Hsp70, but not Hsp60 and Hsp90. Consistent with the downregulation of Hsp25, for example, a significantly lower glutathione (GSH)/glutathione disulfate (GSSG) ratio was associated with the decreased activity, but not protein content, of glucose 6-phosphate dehydrogenase. Con sequently, superoxide was generated at a higher rate, and several mitochondrial proteins, including adenine nucleotide translocase 1 (ANT1), were more oxidized by HSF1 deficiency in vivo. Oxidative damage to ANT1 protein, a structural component of the mitochondrial permeability transition pore (MPTP), decreases its catalytic activity and increases MPTP opening, respectively. Taken together, our results indicate for the first time that constitutive expression of HSP chaperones requires HSF1 activity, and that such HSF1-dependent requirements are directly and functionally linked to maintain redox homeostasis and antioxidative defenses at normal (37 degrees C) temperature.     

Induction of oxidative DNA damage in the peri-infarct region after permanent focal cerebral ischemia

To address the role of oxidative DNA damage in focal cerebral ischemia lacking reperfusion, we investigated DNA base and strand damage in a rat model of permanent middle cerebral artery occlusion (MCAO). Contents of 8-hydroxyl-2'-deoxyguanosine (8-OHdG) and apurinic/apyrimidinic abasic sites (AP sites), hallmarks of oxidative DNA damage, were quantitatively measured in nuclear DNA extracts from brains obtained 4-72 h after MCAO. DNA single- and double-strand breaks were detected on coronal brain sections using in situ DNA polymerase I-mediated biotin-dATP nick-translation (PANT) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), respectively. Levels of 8-OHdG and AP sites were markedly elevated 16-72 h following MCAO in the frontal cortex, representing the peri-infarct region, but levels did not significantly change within the ischemic core regions of the caudateputamen and parietal cortex. PANT- and TUNEL-positive cells began to be detectable 4-8 h following MCAO in the caudate-putamen and parietal cortex and reached maximal levels at 72 h. PANT- and TUNEL-positive cells were also detected 16-72 h after MCAO in the lateral frontal cortex within the infarct border, where many cells also showed colocalization of DNA single-strand breaks and DNA fragmentation. In contrast, levels of PANT-positive cells alone were transiently increased (16 h after MCAO) in the medial frontal cortex, an area distant from the infarct zone. These data suggest that within peri-infarct brain regions, oxidative injury to nuclear DNA in the form of base and strand damage may be a significant and contributory cause of secondary expansion of brain damage following permanent focal ischemia.     

Basal damage and oxidative DNA damage in children with chronic kidney disease measured by use of the comet assay

One consequence of chronic kidney disease (CKD) is an elevated risk for cancer. There is sufficient evidence to conclude that there is an increased incidence of at least some cancers in kidney-dialysis patients. Cancer risk after kidney transplantation has mainly been attributed to immunosuppressive therapy. There are no data evaluating DNA damage in children with CKD, in dialysis patients, or following kidney transplantation. In this study, the comet assay and the enzyme-modified comet assay - with the use of endonuclease III (Endo III) and formamidopyrimidine glycosylase (FPG) enzymes - were conducted to investigate the basal damage and the oxidative DNA damage as a result of treatment in peripheral blood lymphocytes of children. Children at various stages of treatment for kidney disease, including pre-dialysis patients (PreD) (n=17), regular hemodialysis patients (HD) (n=15), and those that received kidney transplants (Tx) (n=17), comprised the study group. They were compared with age- and gender-matched healthy children (n=20) as a control group. Our results show that the %DNA intensity, a measure of basal damage, was significantly increased in children with CKD (mean ± SD) (5.22 ± 1.57) and also in each of the PreD, HD, and Tx groups [(4.92 ± 1.23), (4.91 ± 1.35), and (5.79 ± 1.94), respectively, vs the healthy children (2.74 ± 2.91) (p<0.001). Significant increases in oxidative DNA damage were only found in the FPG-sensitive sites for the PreD and Tx groups, compared with control and HD groups (p<0.05), suggesting that basal DNA damage was more evident for the PreD, HD, and Tx groups. The findings of the present study indicate a critical need for further research on genomic damage with different endpoints and also for preventive measures and improvements in treatment of pediatric patients, in order to improve their life expectancy.     

Low doses of selenium specifically stimulate the repair of oxidative DNA damage in LNCaP prostate cancer cells

Epidemiological studies have demonstrated an inverse relationship between selenium (Se) intake and cancer incidence and/or mortality. However, the molecular mechanisms underlying the cancer chemopreventive activity of Se compounds remain largely unknown. The objective of this study was to investigate the effect of low doses of Se on the stimulation of DNA repair systems in response to four different qualities of DNA damage. P53-proficient LNCaP human prostate adenocarcinoma cells were grown either untreated or in the presence of low concentrations of two Se compounds (30° nM sodium selenite, or 10 μM selenomethionine) and exposed to UVA, H2O2, methylmethane sulfonate (MMS) or UVC. Cell viability as well as DNA damage induction and repair were evaluated by the alkaline Comet assay. Overall, Se was shown to be a very potent protector against cell toxicity and genotoxicity induced by oxidative stress (UVA or H2O2) but not from the agents that induce other types of deleterious lesions (MMS or UVC). Furthermore, Se-treated cells exhibited increased oxidative DNA repair activity, indicating a novel mechanism of Se action. Therefore, the benefits of Se could be explained by a combination of antioxidant activity, the reduction in DNA damage and the enhancement of oxidative DNA repair capacity.     

Induction of oxidative DNA damage in anaerobes

We compared oxidative DNA damage in strictly anaerobic Prevotella melaninogenica, aerotolerant anaerobic Bacteroides fragilis, and facultative anaerobic Salmonella typhimurium after exposure to O2 or H2O2. Using HPLC with electrochemical detection, we measured 8-hydroxydeoxyguanosine (8OHdG) as a damage marker. O2 induced 8OHdG in P. melaninogenica but not in B. fragilis, which shows catalase activity, or in S. typhimurium. In P. melaninogenica, with catalase, O2 induced less 8OHdG; superoxide dismutase had no effect; with glucose and glucose oxidase, O2 induced more 8OHdG. H2O2 also markedly increased 8OHdG. O2 was suggested to induce 8OHdG through H2O2. O2 or H2O2 decreased survival only in P. melaninogenica. Highly sensitive to oxidative stress, P. melaninogenica could prove useful for investigating oxidative DNA damage.     

Mitochondrial DNA mutations and oxidative damage in skeletal muscle of patients with chronic uremia

Abundant evidence has been gathered to suggest that mitochondrial DNA (mtDNA) sustains many more mutations and greater oxidative damage than does nuclear DNA in human tissues. Uremic patients are subject to a state of enhanced oxidative stress due to excess production of oxidants and a defective antioxidant defense system. This study was conducted to investigate mtDNA mutations and oxidative damage in skeletal muscle of patients with chronic uremia. Results showed that large-scale deletions between nucleotide position (np) 7,900 and 16,300 of mtDNA occurred at a high frequency in muscle of uremic patients. Among them, the 4,977-bp deletion (mtDNA⁴⁹⁷⁷) was the most frequent and most abundant large-scale mtDNA deletion in uremic skeletal muscle. The proportion of mtDNA⁴⁹⁷⁷ was found to correlate positively with the level of 8-hydroxy 2-deoxyguanosine (8-OHdG) in the total DNA of skeletal muscle (r=0.62, p<0.05). Using long-range PCR and DNA sequencing, we identified and characterized multiple deletions of mtDNA in skeletal muscle of 16 of 19 uremic patients examined. The 8,041-bp deletion, which occurred between np 8035 and 16,075, was flanked by a 5-bp direct repeat of 5-CCCAT-3. Some of the deletions were found in more than 1 patient. On the other hand, we found that the mean 8-OHdG/10⁵ dG ratio in the total cellular DNA of muscle of uremic patients was significantly higher than that of the controls (182.7 ± 63.6 vs. 50.9 ± 21.5, p=0.05). In addition, the mean 8-OHdG/10⁵ dG ratio in muscle mtDNA of uremic patients was significantly higher than that in nuclear DNA (344.0 ± 56.9 vs. 146.3 ± 95.8, p=0.001). Moreover, we found that the average content of lipid peroxides in mitochondrial membranes of skeletal muscle of uremic patients was significantly higher than that of age-matched healthy subjects (23.76 ± 6.06 vs. 7.67 ± 0.95 nmol/mg protein; p<0.05). The average content of protein carbonyls in the mitochondrial membranes prepared from uremic skeletal muscles was significantly higher than that in normal controls (24.90 ± 4.00 vs. 14.48 ± 1.13 nmol/mg protein; p<0.05). Taken together, these findings suggest that chronic uremia leads to mtDNA mutations together with enhanced oxidative damage to DNA, lipids, and proteins of mitochondria in skeletal muscle, which may contribute to the impairment of mitochondrial bioenergetic function and to skeletal myopathy commonly seen in uremic patients.     

Progress in the analysis of urinary oxidative DNA damage

Oxidative DNA damage has been implicated to be important in the pathogenesis of many diseases, including cancer and heart disease. The assessment of damage in various biological matrices, such as DNA, serum, and urine, is vital to understanding this role and subsequently devising intervention strategies. Despite the numerous techniques to measure oxidative DNA damage products in urine, it remains unclear what these measurements truly represent. Sources of urinary lesions may include the diet, cell death, and, of most interest, DNA repair. Were it possible to exclude the two former contributions, a noninvasive assay for DNA repair would be invaluable in the study of DNA damage and disease. This review highlights that, although progress has been made, significant work remains. Diet, cell death, and repair need continued examination to further elucidate the kinetics of lesion formation and clearance in vivo. Studies from our laboratory and others are making appreciable progress towards the interpretation of urinary lesion measurements along with the development of urinary assays to evaluate DNA repair. Upon establishment of these details, urinary oxidative DNA damage measurements may become more than a reflection of generalized oxidative stress.