Antioxidant and redox status after maximal aerobic exercise at high altitude in acclimatized lowlanders and native highlanders

Exercise-induced increase in oxygen consumption leads to oxidative stress. On the contrary, hypoxia triggers oxidative stress despite decreased oxygen flux. Therefore, exercise under hypoxia may aggravate oxidative damage. Highlanders are expected to have better antioxidant capacity than lowlanders as a result of adaptation to hypoxia. The present study was undertaken to investigate the effect of exercise on antioxidant system in lowlanders and highlanders at high altitudes (HA). This study was conducted on active male volunteers, randomly selected and categorized into three groups, i.e., lowlanders tested at sea level (LL-SL, n = 35), lowlanders tested at altitude of 4560 m (LL-HA, n = 35) and native highlanders tested (HAN, n = 20) at the same height. Volunteers performed maximal exercise until exhaustion. Blood samples were collected before and after exercise. Both LL-SL and HAN had shown similar VO_2max, which was significantly higher than LL-HA. GSH/GSSG ratio significantly increased in LL-SL and decreased in HAN after exercise. With exercise there were a decrease in superoxide dismutase and increase in glutathione peroxidase and catalase activities in HAN. Therefore, the results have suggested that HAN are more susceptible to oxidative stress when subjected to high-intensity exercise than lowlanders. The cumulative effect of higher VO_2max and longer duration of exercise in hypoxia may be the reason of higher level of oxidative insult among HAN. Comparatively better management of antioxidant system observed in lowlanders at HA may be explained by the lower VO_2max and shorter duration of exercise in hypoxia.     

Effects of long-term acclimatization in lowlanders migrating to high altitude: comparison with high altitude residents

The physiological response to submaximal and maximal exercise was assessed in lowlanders and Tibetans at low (500 m above sea level) and high altitude (HA, 3 680 m). The times spent at HA by the lowland migrators was 8 days (n = 60), 7 months (n = 60, same group), 15 months (n = 29) and 27 months (n = 29). After the 15-month stay at HA, the maximal oxygen uptake ( O_2max) and maximal heart rate of the lowland migrators almost reached those of the HA native residents (Tibetans, n = 57), but their total work capacity and the gross efficiency () of mechanical work remained lower than those of the Tibetans. The rate of O_2max achieved at 90 W by the Tibetans was lower than that of the lowland migrators. It was concluded that, at HA, the lowlanders regained much of the aerobic capacity which they had lost initially. However, they did not attain the same gross mechanical efficiency as the Tibetans, who seemed to be at an advantage in respect of work at HA.     

Longer apnea duration at low altitude in Tibetan and Han highlanders compared with Han lowlanders: A retrospective study

Prolonged duration of obstructive apnea (OA) has been observed in highlanders after descending to low altitude. It is proposed that due to adaptation to a hypoxic high‐altitude environment, Tibetan highlanders (TH) and Han highlanders (HH) would manifest different OA durations at low altitude as compared to Han lowlanders (HL). Data collection on consecutive obstructive sleep apnea patients (167 TH, 210 HH and 233 HL) was performed over a period of 8 years in Chengdu (altitude 500 m). The analyses were performed with non‐matched groups and with body mass index and apnea–hypopnea index‐matched groups. Significance rankings for mean duration of OA (s) in non‐matched groups and matched groups were TH (27.7; 28.6) = HH (25.7; 26.0) > HL (21.7; 21.3), respectively. For the longest OA duration, the significance rankings across three groups with regard to the percentage of patients having a duration longer than 2 min (%) and mean values (s) were TH (26.9; 82) > HH (10.0; 67) > HL (1.3; 50). In terms of nadir and mean oxygen saturation, significant differences were found between TH and HH or HL. In addition, longest and mean OA duration were positively correlated with blood pressure and heart rate, whereas nadir and mean oxygen saturation were negatively correlated with these measures in both non‐matched and matched groups, and the correlation was more robust in TH. These findings raise important clinical questions regarding whether such significant prolongation of OA duration and a more severe hypoxic burden among highlanders, especially in TH, may lead to adverse clinical consequences when at low altitude.     

Exercise‐induced lipid peroxidation: Implications for deoxyribonucleic acid damage and systemic free radical generation

Exercise‐induced deoxyribonucleic acid (DNA) damage is often associated with an increase in free radicals; however, there is a lack of evidence examining the two in parallel. This study tested the hypothesis that high‐intensity exercise has the ability to produce free radicals that may be capable of causing DNA damage. Twelve apparently healthy male subjects (age: 23 ± 4 years; stature: 181 ± 8 cm; body mass: 80 ± 9 kg; and VO_2max: 49 ± 5 ml/kg/min) performed three 5 min consecutive and incremental stages (40, 70, and 100% of VO_2max) of aerobic exercise with a 15‐min period separating each stage. Blood was drawn after each bout of exercise for the determination of ex vivo free radicals, DNA damage, protein carbonyls, lipid hydroperoxide (LOOH) concentration, and a range of lipid‐soluble antioxidants. Lipid‐derived oxygen‐centered free radicals (hyperfine coupling constants a_Nitrogen = 13.7 Gauss (G) and aβ_Hydrogen = 1.8 G) increased as a result of acute moderate and high‐intensity exercise (P < 0.05), while DNA damage was also increased (P < 0.05). Systemic changes were observed in LOOH and for lipid‐soluble antioxidants throughout exercise (P < 0.05); however, there was no observed change in protein carbonyl concentration (P > 0.05). These findings identify lipid‐derived free radical species as possible contributors to peripheral mononuclear cell DNA damage in the human exercising model. This damage occurs in the presence of lipid oxidation but in the absence of any change to protein carbonyl concentration. The significance of these findings may have relevance in terms of immune function, the aging process, and the pathology of carcinogenesis. Environ. Mol. Mutagen. 52:35–42, 2011. © 2010 Wiley‐Liss, Inc.     

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced lipid peroxidation and DNA damage in mouse bone marrow and blood

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin that induces Parkinsonism in humans, monkeys, and mice and oxidative stress in mammalian cells and tissues. In the present study, the relationship between the generation of lipid peroxidation products and DNA damage was studied in mice treated with MPTP. The frequency of micronucleated polychromatic erythrocytes (MN-PCE) and the concentrations of malonaldehyde and 4-hydroxyalkenals were determined in the bone marrow and peripheral blood of mice 0, 24, 48, 72, and 96 hr after treatment with MPTP, cyclophosphamide as a positive control, or diluent. Both MN-PCE and the lipid peroxidation products increased in MPTP-treated mice, with significant levels being detected in bone marrow starting at 24 hr after treatment and in blood starting at 48 hr after treatment. These results suggest that the generation of oxidative products is related to the DNA damage produced by MPTP in mice.     

急性高原病患者支气管肺泡灌洗前后肺功能及血气的改变

目的:探讨急性高原反应(HAAR)及高原肺水肿(HAPE)的发病机理。方法:对10例HAAR患者及6例HAPE患者灌洗前和灌洗后进行肺功能和动脉血气检测, 并与10例高原健康者进行对比。结果:HAAR患者及HAPE患者灌洗前动脉血氧分压明显低于对照组, HAAR同HAPE均存在弥散功能障碍;HAPE肺弥散功能(DLCO%)由灌洗前的(76.01±6.29)%, 上升到灌洗后的(103.31±9.23)%;气体转化因子(DLCO/VA%)由灌洗前的(150.30±15.20)%, 上升到灌洗后的(176.04±16.10)%;动脉血氧分压(PaO₂)由(31.73±3.01)mmHg上升到(45.31±3.56)mmHg。而HAAR及对照组灌洗后上述指标差异不显著。结论:HAPE患者肺泡内大量的液体渗出是HAPE病情恶化的主要原因之一。HAAR属HAPE发展的初级阶段, 存在着间质性肺水肿。     

Synergistic DNA damage and lipid peroxidation in cultured human white blood cells exposed to 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone and ultraviolet A

4-(Methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is an important carcinogen in cigarette smoke, while ultraviolet (UV) irradiation from sunlight is a major factor for causing skin aging and skin cancer. However, little is known about the effects of the interaction between NNK and UV light on the induction of DNA damage and oxidative stress. In this study, we incubated human white blood cells (WBCs) with NNK, followed by irradiating the cells with ultraviolet A (UVA) (320-380 nm), and we measured DNA strand breaks (by the Comet or single-cell gel electrophoresis assay), lipid peroxidation (as thiobarbituric acid-reactive substances, TABRS), and the levels of intracellular reactive oxygen species (ROS). We found that preincubation with 1.0 mM NNK, followed by UVA irradiation (7.6 kJ/m2) synergistically increased DNA damage, lipid peroxidation, and the level of intracellular ROS in WBCs, while NNK or UVA alone had little or no effect. Electron spin resonance spectroscopic analyses showed that NNK plus UVA enhanced the UVA-induced generation of singlet oxygen but not hydroxyl radicals. In addition to ROS, bioactivation of NNK by cytochromes P450 (CYP) to form reactive NNK intermediates may also be involved in the synergistic damage to WBCs by NNK plus UVA. This is evidenced by the synergistic increase in N7-methylguanine (7-mGua), a major DNA adduct produced by NNK. Overall, the present study demonstrates that exposure of WBCs to both NNK and UVA synergistically increases DNA damage and lipid peroxidation and that such effects involve enhanced generation of ROS, especially singlet oxygen, and activation of NNK to 7-mGua by CYP. The results imply that NNK is a phototoxic agent.     

Effect of antitheines with different effects on memory on cAMP phosphodiesterase,lipid peroxidation,and RNA synthesis in rat brain neurons

Academician S. V. Anichkov Department of Pharmacology, Research institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR A. N. Klimov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 5, pp. 483–485, May, 1991.     

The impact of DNA damage, genetic mutation and cellular responses on cancer prevention, longevity and aging: observations in humans and mice

Over the past 5 years, data collected from the mouse suggest that pathways important for either preventing or resolving DNA damage are longevity assurance mechanisms whose critical overall function is somatic cell maintenance, a necessary part of cancer prevention. These pathways include those that reduce DNA damage levels caused by exogenous sources, replication errors and by-products of cellular respiration. Unresolved DNA damage leads to permanent mutations in the genetic code that may be oncogenic. Therefore, pathways that resolve DNA damage are important anti-cancer mechanisms. As an important line of defense, there are a variety of pathways that repair DNA damage. In addition, there are anti-cancer pathways that respond to DNA damage by either preventing cellular replication or inducing cell death. Genes in these pathways, termed longevity assurance genes (LAG), code for proteins that reduce cancer incidence and as a result assures a sufficiently long health span needed for reproduction. Data from mouse models, many that were originally designed to study cancer, are showing that a potential consequence of DNA damage and responses to DNA damage is aging; these models support the hypothesis that at least some aspects of normal aging are the consequence of anticancer mechanisms designed to deal with damaged DNA.     

Influence of oxygen tension, pro-oxidants and antioxidants on the formation of lipid peroxidation products (lipofuscin) in individual cultivated human glial cells

Cultivated human glial cells, kept in a state of density-dependent inhibition of growth, accumulate age pigment (lipofuscin) within their lysosomal vacuomes which has the same characteristics as the age pigment observed in vivo. The rate of formation and accumulation of lipofuscin is greatly accelerated under the conditions of routine cell culture in comparison to the in vivo event. Lipofuscin is generally considered to be composed of products of lipid peroxidation and thus it would be reasonable to suggest that factors which influence lipid peroxidation would also alter the rate of lipofuscin formation and accumulation. Human glial cells were grown in the presence of various oxygen concentrations (5%, 10%, 20%, 40%) or exposed to pro-oxidants (vitamin C/Fe) or antioxidants (vitamin E/Se, dimethylsulfoxide, reduced glutathione) treatments in the presence of normal oxygen concentration (20%). It was found that these factors can modulate (accelerate or decrease) the rate of formation of lipofuscin. This study thus provides: (1) important supportive evidence for the lipid peroxidation origin of lipofuscin, (2) a useful model system for studying the effect of lipofuscin accumulation on lysosomal function and cell growth kinetics, (3) evidence that our culture conditions are far from ideal: oxygen concentration may drastically alter rates of lipofuscin formation and accumulation. Cell culture technique, as we know it today, may benefit from more closely controlled oxygen tensions, i.e. by reducing oxygen to levels that more closely approximate conditions in vivo.     

Alkaline comet assay study with breast cancer patients: evaluation of baseline and chemotherapy-induced DNA damage in non-target cells

Abstract The sensitivity of the alkaline comet assay for the evaluation of baseline and treatment-induced DNA damage in white blood cells of breast cancer patients receiving adjuvant chemotherapy according to three conventional anthracycline- and cyclophosphamide-containing protocols was investigated. Additionally, baseline DNA damage in cancer patients was compared with the levels of DNA damage recorded in healthy women. Altogether 30 patients with diagnosed breast cancer and 30 female blood donors with no known familial history of breast cancer participated in the study. Alkaline comet assay was performed according to standard protocol and DNA migration in peripheral blood leukocytes was measured by a computer-based image analysis system. For each subject the frequency of “damaged” cells, i.e., long-tailed nuclei (LTN) with tail length exceeding 95th percentile for the considered parameter among controls, is also reported. Breast cancer patients had significantly increased background levels of DNA damage in their peripheral blood leukocytes as compared to healthy women. Prior to the chemotherapy, a majority of patients showed a statistically significant increase in the number of LTN compared to healthy blood donors. Marked interindividual variations in baseline DNA damage among patients were recorded, some of them related to the disease stage and status. The present study confirmed the alkaline comet assay as a sensitive technique able to detect significantly elevated DNA migration in blood cells of patients already one hour after completion of the first cycle of chemotherapy. Administration of antineoplastic drugs in three chemotherapy protocols studied induced a similar increase of primary DNA damage in nontarget cells. The evaluation of the LTN frequencies indicates the best response to the protocol containing cyclophosphamide, methotrexate and 5-fluorouracil (CMF). Our results point to the significance of simultaneous evaluation of DNA migration and frequency of LTN in the same subject and approved the use of alkaline comet assay as a suitable method for the routine detection of critical DNA lesions produced after administration of antineoplastic drugs in the clinical settings.     

Intestinal oxidative damage in inflammatory bowel disease: semi-quantification,localization, and association with mucosal antioxidants

Intestinal inflammation is accompanied by excessive production of reactive oxygen and nitrogen metabolites. In order to counteract their harmful effects, the intestinal mucosa contains an extensive system of antioxidants. It has previously been shown that the levels of and the balance between the most important antioxidants are seriously impaired within the intestinal mucosa from inflammatory bowel disease (IBD) patients compared with normal mucosa. The present study investigated the consequences of this antioxidative imbalance by evaluating parameters of oxidative stress-related mucosal damage in the same tissue samples. The extent of apoptosis, peroxynitrite-mediated protein nitration (3-NT), and lipid peroxidation were assessed in relation to the expression of nitric oxide synthase (NOS) and the superoxide-producing enzyme xanthine oxidase (XO). In addition, bi- and multi-variate regression analyses were performed to associate these parameters with the levels of the antioxidants assessed previously. Apoptotic cell death was visualized by TUNEL staining in luminal epithelium of normal controls, and in IBD additionally in the inflammatory infiltrate and in deeper parts of the crypts, but its frequency was unrelated to the severity of inflammation. In Crohn's disease (CD), epithelial apoptosis levels were strongly associated with the expression of XO, implying a role for this enzyme in the regulation of epithelial cell homeostasis, although its levels were unaffected by intestinal inflammation and were comparable to those in normal control mucosa. 3-NT immunoreactivity was substantially increased in luminal crypt cells, neutrophils, and mononuclear cells in the inflamed mucosa of ulcerative colitis (UC) patients. The inflamed IBD luminal epithelium, but not the inflammatory cells, also contained increased amounts of NOS. The immunoreactivity of both 3-NT and NOS was significantly higher in UC than in CD. Unexpectedly, the increased 3-NT expression in UC was associated with neutrophilic myeloperoxidase and not with NOS, which suggests that 3-NT is formed in areas with a dense neutrophilic infiltrate via a peroxynitrite-independent oxidation pathway. Lipid peroxidation, as estimated by the malondialdehyde (MDA) concentration, was elevated in both the inflamed CD and the inflamed UC mucosa, and was identified in the luminal epithelium using a histochemical technique. In CD, lipid peroxidation was independently associated with the concentration of metallothionein and with Mn-superoxide dismutase activity, suggesting the involvement of hydroxyl radicals and superoxide anions. In UC, however, the amount of MDA was associated with epithelial catalase expression and neutrophilic myeloperoxidase activity, suggesting a hydrogen peroxide- and/or hypochlorous acid-mediated mechanism. The present study underlines the importance of oxidative stress in the pathogenesis of IBD and provides clues regarding the (anti)oxidants involved which indicate that this process evolves through diverging pathways in CD and UC.     

Renal failure in high altitude: renal functions, renal pathology and bone mineralization in rats with ablation nephropathy at 1200 m altitude

The effect of altitude on renal failure and bone mineralization is not well known. This topic is studied in a 5/6 nephrectomy rat model. After hemoglobin, creatinine clearance and proteinuria were determined in 28 Wistar rats. Two 5/6 nephrectomy (Nx1-Nx2, n=7 each) and two sham (Sh1-Sh2, n=7 each) groups were formed. The Nx1-Sh1 and Nx2-Sh2 groups were kept at sea level and at 1200 m altitude, respectively. The same analyses were performed after 3 months just before sacrifices in order to harvest kidneys and femurs for histopathologic examination. Hemoglobin, creatinine clearance, and proteinuria were similar in all groups at the onset. Final hemoglobin was higher in Nx2-Sh2, but only Sh2 vs. Sh1 was significant (p=0.001). Creatinine clearance decreased (p=0.001 for Nx1) and proteinuria increased (p=0.002 for Nx1 and p=0.005 for Nx2) after 5/6 nephrectomy, but Nx1 vs. Nx2 was similar. Histopathological changes in the remnant kidneys were prominent, but Nx1 vs. Nx2 was not different. Although the relative osteoid volume increased in Nx groups, only Nx1 vs. Sh1 was different (p=0.006). In conclusion, exposure to 1200 m altitude, compared to the sea level, preserved the creatinine clearance better in 5/6 nephrectomized rats. No change was observed in proteinuria, renal histopathology, and bone mineralization.     

DNA damage and acute toxicity caused by the urban air pollutant 3-nitrobenzanthrone in rats: characterization of DNA adducts in eight different tissues and organs with synthesized standards

3-Nitrobenzanthrone (3-NBA) is an urban air pollutant and rat lung carcinogen that is among the most potent mutagens yet tested in the Salmonella reversion assay. In the present study, 1 mg 3-NBA was administered orally to female F344 rats and DNA adduct formation was examined in liver, lung, kidney and five sections of the gastrointestinal (GI) tract at 6 hr, and 1, 2, 3, 5, and 10 days after administration. The DNA adduct patterns, analyzed by (32)P-postlabelling followed by HPLC separation, were similar in all tissues and organs. Five of the adduct peaks cochromatographed with synthesized DNA adduct standards. Three of these unequivocally determined standards, dGp-C8-N-ABA, dGp-N2-C2-ABA, and dAp-N6-C2-ABA, were of the nonacetylated type, suggesting that at least part of the pathway for activation of 3-NBA proceeds through O-acetylation of the hydroxylamine intermediate. The two other DNA adduct standards, dGp-C8-C2-N-Ac-ABA, and dGp-N2-C2-N-Ac-ABA, were of the acetylated type, but there was some ambiguity in the characterization of these DNA adducts, since they varied inconsistently between samples and they also aligned with peaks found in controls. At 6 hr after treatment, the level of DNA adducts was highest in glandular stomach (relative adduct labeling (RAL), approximately 70 adducts/10(8) normal nucleotides (NN)); adduct levels in this organ decreased at 24 hr, but increased afterwards. DNA adduct levels in the majority of organs were characterized by an early increase (from 6 hr to 3 days), which was followed by a decrease at 5 days and a maximum level 10 days after administration (RAL approximately 120 adducts/10(8) NN for the lung, kidney and glandular stomach, approximately 80 adducts/10(8) NN for the forestomach and ceacum, and approximately 40 adducts/10(8) NN for the liver, small intestine, and colon). This pattern was consistent with pathological observations during autopsy showing high levels of tissue damage in the GI tract; the tissue damage included hemorrhages, loss of villous surface structure in the small intestine, as well as intestine fragility and oedema of the adipose tissue around the GI-tract. Tissue damage decreased and DNA adduct levels increased at 10 days after administration. These observations suggest that 3-NBA not only exerts acute toxic effects, but that the bioavailability is affected by storage in tissues and later becomes available, resulting in the increased DNA adduct levels at the later time points of collection.