Protective effect of melatonin and pinoline on nitric oxide-induced lipid and protein peroxidation in rat brain homogenates

Nitric oxide (NO) is a physiological neurotransmitter, a mediator of the excitatory neurotransmitter glutamate pathways that regulates several neuroendocrine functions, but excessive NO is toxic by itself and it interacts with superoxide radical (O(2)(-)) to form the peroxynitrite anion (ONOO(-)). Using rat brain homogenates, we investigated the effects of melatonin and pinoline in preventing the level of lipid peroxidation (LPO) and carbonyl contents in proteins induced by nitric oxide (NO) which was released by the addition of sodium nitroprusside (SNP). Lipid and protein peroxidation were estimated by quantifying malondialdehyde (MDA) and 4-hydroxyalkenal (4-HDA) concentrations and carbonyl contents, respectively. SNP increased MDA+4-HDA and carbonyl contents production in brain homogenates in a time and concentration dependent manner. Both, melatonin and pinoline reduced NO-induced LPO and carbonyl contents in a dose-dependent manner in concentrations from 0.03 to 3 mM and 1 to 300 microM, respectively. Under the in vitro conditions of this experiment, both antioxidants were more efficient in limiting SNP protein oxidation than lipid damage.     

Melatonin and vitamin E limit nitric oxide-induced lipid peroxidation in rat brain homogenates

We have investigated the level of lipid peroxidation (LPO) in rat brain homogenates in the presence of nitric oxide (NO) which was released by the addition of sodium nitroprusside (SNP) and compared it with that induced by H₂O₂. We also examined the effect of melatonin and vitamin E on the NO-induced LPO. The concentration of malonaldehyde (MDA) plus 4-hydroxyalkenals (4-HDA) was used as an index of LPO. While both H₂O₂ and SNP increased MDA+4-HDA production in brain homogenates in a concentration-dependent manner, SNP was more potent than H₂O₂ at all concentrations tested. Both melatonin or vitamin E reduced NO-induced LPO in a dose-dependent manner in concentrations ranging from 10 μM to 10 mM. Under the in vitro conditions of this experiment, vitamin E was more efficient than melatonin in limiting NO-induced LPO in rat brain homogenates.     

Oxidative Stress in Bacterial Meningitis

Fifty years after the advent of antibiotics for clinical use, the rates of morbidity and mortality associated with bacterial meningitis remain high. The unfavourable clinical outcome is often due to intracranial complications including cerebrovascular insults, raised intracranial pressure, hydrocephalus, and brain edema. Reactive oxygen species (ROS) are known effector molecules in the antimicrobial armature of polymorphonuclear and mononuclear phagocytes. However, over the last decade, there has been a substantial body of work implicating a central role of ROS in the development of intracranial complications and brain damage in bacterial meningitis. Recently, it also became evident that reactive nitrogen species (RNS), especially nitric oxide, are important mediators of meningitis-associated pathophysiological changes, at least during the early phase of the disease. There is now substantial evidence that much of the oxidative injury associated by simultaneous production of superoxide and nitric oxide is mediated by the strong oxidant peroxynitrite. ROS and peroxynitrite can be cytotoxic via a number of independent mechanisms. Their cytotoxic effects include initiation of lipid peroxidation and induction of DNA single strand breakage. Damaged DNA activates poly(ADP-ribose) polymerase (PARP). Recent experimental data propose a role of lipid peroxidation and PARP activation in the development of meningitis-associated intracranial complications and brain injury. Agents which interfere with the production of ROS and peroxynitrite, as well as with PARP activation and lipid peroxidation may represent novel, therapeutic strategies to limit meningitis-associated brain damage, and, thus, to improve the outcome of this serious disease.     

Effect of diet and vitamin C on DNA strand breakage in freshly-isolated human white blood cells

We have measured DNa strand breaks induced by ionising radiation in nucleated cells from freshly isolated whole blood from normal human subjects. Samples werer taken after subjects had fasted overnight and again 1 h after they had eaten breakfast in combination with approximately 35 mg/kg vitamin C. Damage was measured by single cell gel electrophoresis (the ‘comet’ assay), in which DNA single strand breaks generate a comet tail streaming from the nucleus. In repeat experiments on 6 subjects a reduction in DNA damage, as indicated by a highly significant decrease in overall comet length, was observed following vitamin C ingestion, both in the unirradiated control blood samples and in the dose response to ionising radiation damage. In addition, consistent differences in dose response between individual subjects were found. The peak effect was 4 h after intake of food and vitamin C. An effect was also seen with vitamin C alone and after breakfast without additional vitamin C. Protection against strand breakage was also seen in Ficoll-separated mononucleasr cells but evidence was not obtained from protection of separated, mitogen stimulated T-lymphocytes either against ionising radiation cell killing in a clonal assay, or against clastogenicity assessed by micronucleus formation following one cell division. Exposure of separated lymphocytes in vitro to vitamin C, at doses greater than 200 μM, did not offer protection but induced strand breakage. Our results raise the possibility in normal diet may not only affect susceptibility to endogenous oxidative damage, but may affect some responses of the individual to radiation.     

Antioxidant, anticlastogenic and radioprotective effect of Coleus aromaticus on Chinese hamster fibroblast cells (V79) exposed to gamma radiation

Coleus aromaticus (Benth, Family: Laminaceae), Indian Oregano native to India and Mediterranean, is well known for its medicinal properties. A preliminary study was undertaken to elucidate in vitro free radical scavenging potential and inhibition of lipid peroxidation by C.aromaticus hydroalcoholic extract (CAE). Anti-clastogenic and radioprotective potential of CAE were studied using micronucleus assay after irradiating Chinese hamster fibroblast (V79) cells. CAE at 10, 20, 40, 60, 80, 100 and 120 mug/ml resulted in a dose-dependent increase in radical scavenging ability against various free radicals viz., 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), superoxide anion (O(2)(*-)), hydroxyl (OH(*)) and nitric oxide (NO(*)) generated in vitro. A maximum scavenging potential was noticed at 100 mug/ml and a saturation point was reached thereafter with the increasing doses of CAE. The free radical scavenging potential of the extract was in the order of DPPH > ABTS > Superoxide > Hydroxyl > Nitric oxide. CAE also exhibited a moderate inhibition of lipid peroxidation in vitro, with a maximum inhibition at 60 mug/ml (33%), attaining saturation at higher doses. The extract also rendered protection against radiation induced DNA damage, as evidenced by the significant (P < 0.05) decrease in the percentage of radiation-induced micronucleated cells (MN) and frequency of micronuclei (total). A maximum anticlastogneic effect/ radioprotection was noticed at a very low concentration i.e., 5 mug/ml of CAE, treated 1 h prior to 2 Gy of gamma radiation. A significant (P < 0.0001) anticlastogenic/radioprotective effect was also observed when the cells were treated with an optimum dose of CAE (5 mug/ml) 1 h prior to 0.5, 1, 2 and 4 Gy of gamma radiation compared with the respective radiation control groups. Overall, our results established an efficient antioxidant, anticlastogenic and radioprotective potential of CAE, which may be of great pharmacological importance.     

The role of glutathione in DNA damage by potassium bromate in vitro

We have investigated the role of reduced glutathione (GSH) in the genetic toxicity of the rodent renal carcinogen potassium bromate (KBrO(3)). A statistically significant increase in the concentration of 8-oxodeoxyguanosine (8-oxodG) relative to deoxyguanosine was measured following incubation of calf thymus DNA with KBrO(3) and GSH or N-acetylcysteine (NACys). This was dependent on these thiols and was associated with the loss of GSH and production of oxidized glutathione. A short-lived (<6 min) intermediate was apparent which did not react with the spin trap dimethylpyrroline N-oxide. DNA oxidation was not evident when potassium chlorate (KClO(3)) or potassium iodate (KIO(3)) were used instead of KBrO(3), though GSH depletion also occurred with KIO(3), but not with KClO(3). Other reductants and thiols in combination with KBrO(3) did not cause a significant increase in DNA oxidation. DNA strand breakage was also induced by KBrO(3) in human white blood cells (5 mM) and rat kidney epithelial cells (NRK-52E, 1.5 mM). This was associated with an apparent small depletion of thiols in NRK-52E cells at 15 min and with an elevation of 8-oxodG at a delayed time of 24 h. Depletion of intra-cellular GSH by diethylmaleate in human lymphocytes decreased the amount of strand breakage induced by KBrO(3). Extracellular GSH, however, protected against DNA strand breakage by KBrO(3), possibly due to the inability of the reactive product to enter the cell. In contrast, membrane-permeant NACys enhanced KBrO(3)-induced DNA strand breakage in these cells. DNA damage by KBrO(3) is therefore largely dependent on access to intracellular GSH.     

Acute exposure of uranyl nitrate causes lipid peroxidation and histopathological damage in brain and bone of Wistar rat.

Although the kidneys are the main target organs for uranium (U) toxicity, recent studies have shown that U can cross the blood-brain barrier to accumulate in the brain. Uranyl nitrate (U-238)induced oxidative damage was investigated in brain and bone of Wistar rats after intraperitoneal injection of uranyl nitrate at acute doses either nephrotoxic (576 microg of U/kg body weight) or subnephrotoxic (144 microg U/kg body weight). The health effects of U administration at 576 microg of U/kg body weight were seen in terms of decrease in food intake and no gain in body weight compared to respective controls. These alterations were correlated with increased lipid peroxidation as measured by thiobarbituric acid reactive substances in rat brain and bone. However, at lower dosage of U (144 microg U/kg body weight), no significant lipid peroxidation was observed in brain and bone. Histological examination of U-treated (576 microg of U/kg body weight) rat brain tissues showed marked and diffuse cystic degeneration and a similar pattern in histological alterations was observed in kidneys in treated animals; whereas no significant histological change was observed in rat brains and kidney treated with a lower dose of U (144 microg U/kg body weight). It is concluded that administration of U at an acute nephrotoxic dose caused oxidative stress in brain and bone manifested as lipid peroxidation and histopathological damage.     

Post treatment effect of Grewia asiatica against radiation-induced biochemical alterations in Swiss albino mice

The increasing use of nuclear radiation for human welfare necessitates the search for new, safe, and cost-effective radioprotectors not only for the personnel charged with the responsibility of testing or working with radiation in laboratories, but also for the general public. With this view, the present study has been undertaken to find out the possible radioprotective potential of the Grewia asiatica fruit pulp extract (GAE). It is reported to have a high content of antioxidants such as vitamin C, anthocyanin, folate carotenoids, etc. that may play a possible role in radioprotection. In the present investigation, healthy Swiss albino mice were selected from an inbred colony and divided into four groups: (i) control (vehicle treated), (ii) only GAE treated (700 mg/Kg. body wt./day for 15 consecutive days), (iii) irradiated (5 Gy), and (iv) irradiated + GAE treated. Mice were sacrificed at different autopsy intervals posttreatment, viz., 1-30 days. Blood was collected and liver was removed for various biochemical estimations, viz., glutathione (GSH) and lipid peroxidation. The results indicated that GAE posttreatment protects liver and blood against radiation-induced damage by inhibiting glutathione depletion and ameliorating lipid peroxidation levels that attended normal levels by day 30 posttreatment. Moreover, the magnitude of recovery from oxidative damage in terms of TBARS and GSH content was significantly higher (p<0.001) in the irradiated + GAE-treated group.     

活性氧清除剂对缺氧所致大鼠大脑皮层细胞产生脂质过氧化物的影响

对缺氧所致的大鼠大脑皮层细胞选用不同的活性氧清除剂观察其对脂质过氧化物的影响。苯甲酸钠可抑制脑细胞脂质过氧化，使脂质过氧化物生成减少；超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶对细胞脂质过氧化亦有不同程度的抑制作用，其中超氧化物歧化酶作用较强，谷胱甘肽过氧化物酶次之，过氧化氢酶作用较弱。结果提示缺氧可引起脑细胞活性氧生成增加。拮抗ＯＨ·或清除Ｏ和Ｈ＿（２）Ｏ＿（２），减弱ＯＨ·的效应均可降低细胞脂质过氧化物的生成。     

Copper impairs biliary epithelial cells and induces protein oxidation and oxidative DNA damage in the isolated perfused rat liver

Copper is one of the major metals causing environmental contamination. Previous studies showed that copper induced toxic effects in isolated perfused rat liver models and these effects were associated with lipid peroxidation. Here we investigated whether effects of copper (at concentrations of 0.01, 0.03, and 0.1 mM of Cu(2+) in Krebs-Henseleit buffer perfusing the isolated rat liver for 60 min), were associated with biliary epithelial cell injury, as well as protein oxidation and oxidative DNA damage. The highest concentration of copper in perfusate (0.1 mM) did not allow complete evaluation of all parameters because it blocked portal flow within 30 min of perfusion, indicating severe microcirculatory disturbances. Further, copper decreased secretion of bile and it increased lactate dehydrogenase, aspartate transaminase, and alanine transaminase leakage into perfusate as well as liver weight in a dose-dependent manner. Biliary gamma-glutamyltransferase, an index of biliary epithelial cell integrity increased similarly at 0.01 and 0.03 mM copper concentrations in perfusate. Compared to controls, 0.01 and 0.03 mM concentrations of copper increased the amount of thiobarbituric acid reacting substances, a marker of lipid peroxidation, tissue protein carbonyl groups, an index of protein oxidation, and 8-oxo-7,8-dihydro-2'-deoxyguanosine, a marker of oxidative DNA damage. The results suggest that toxic effects of copper in the isolated perfused rat liver may involve biliary epithelial cells and they are associated with lipid peroxidation, protein oxidation, and oxidative DNA damage.     

Superoxide dismutase derivative prevents oxidative damage in liver and kidney of rats induced by exhausting exercise

To prevent oxidative tissue damage induced by strenuous exercise in the liver and kidney superoxide dismutase derivative (SM-SOD), which circulated bound to albumin with a half-life of 6 h, was injected intraperitoneally into rats. Exhausting treadmill running caused a significant increase in the activities of xanthine oxidase (XO), and glutathione peroxidase (GPX) in addition to concentrations of thiobarbituric acid-reactive substances (TBARS) in hepatic tissue immediately after running. There was a definite increase in the immunoreactive content of mitochondrial superoxide dismutase (Mn-SOD) 1 day after the running. Meanwhile, the TBARS concentration in the kidney was markedly elevated 3 days after running. The activities of GPX, and catalase in the kidney increased significantly immediately and on days 1 and 3 following the test. The immunoreactive content of Mn-SOD also increased 1 day after running. The exercise induced no significant changes in immunoreactive Cu, Zn-SOD content in either tissue. The administration of SM-SOD provided effective protection against lipid peroxidation, and significantly attenuated the alterations in XO and all the anti-oxidant enzymes, measured. In summary, the present data would suggest that exhausting exercise may induce XO-derived oxidative damage in the liver, while the increase in lipid peroxidation in the kidney might be the result of washout-dependent accumulation of peroxidised metabolites. We found that the administration of SM-SOD provided excellent protection against exercise-induced oxidative stress in both liver and kidney.     

Pinealectomy causes hippocampal CA1 and CA3 cell loss: reversal by melatonin supplementation

This experiment determined if the loss of endogenous melatonin via pinealectomy affected rat CA1 and CA3 pyramidal neuron numbers over a 20-month span. Since pinealectomy eliminates many neurohormones, some rats received daily melatonin supplementation to determine if this would reverse its effects. CA1 pyramidal cells were significantly reduced between 2 and 4 months after pinealectomy. CA3 loss was evident at 2 months post-pinealectomy. Melatonin replacement in the drinking water prevented these effects and seemingly promoted the genesis of CA1 cells. Analyses of hippocampal thiobarbituric acid reactive substances (TBARS) levels at 3 and 20 months post-surgery, revealed no significant group differences in lipid peroxidation. However, hippocampal TBARS were higher at 20 than at 3 months in all groups. Pinealectomized rats exhibited a significantly higher ratio of reduced to oxidized glutathione at 3 months but not 20 months, when compared to the sham and melatonin-supplemented rats. This suggests that pinealectomy caused oxidative stress and a subsequent compensatory change in the glutathione system. These results indicate that endogenous melatonin is neuroprotective.     

褪黑素对衰老小鼠脑组织NO和氧自由基生成的作用

观察褪黑素对D 半乳糖衰老模型小鼠NO生成和氧自由基的作用以探讨其抗衰老机制。D 半乳糖诱导昆明小鼠衰老同时每日腹腔注射外源性褪黑素 (5mg kg)连续 8周 ,测定小鼠不同脑区NO、NOS、SOD、MDA、脂褐素的变化。模型组NO、NOS、MDA 脂褐素水平明显升高 (P <0 0 1;P <0 0 1;P <0 0 1;P <0 0 5 ) ,SOD活性明显减弱 (P <0 0 1) ,给药 (D +MT)组则上述变化逆转。褪黑素抑制NO的过度生成及减轻脂质过氧化损伤是其抗衰老机制之一     

Protection of ionizing radiation-induced cytogenetic damage by hydroalcoholic extract of Cynodon dactylon in Chinese hamster lung fibroblast cells and human peripheral blood lymphocytes.

The radiomodulatory potential of hydroalcoholic extract of a medicinal plant Cynodon dactylon (family: Poaceae) against radiation-induced cytogenetic damage was analyzed using Chinese hamster lung fibroblast (V79) cells and human peripheral blood lymphocytes (HPBLs) growing in vitro. Induction of micronuclei was used as an index of cytogenetic damage, evaluated in cytokinesis blocked binucleate cells. The hydroalcoholic Cynodon dactylon extract (CDE) rendered protection against the radiation-induced DNA damage, as evidenced by the significant (p<0.001) reduction in micronucleated binucleate cells (MNBNC%) after various doses of CDE treatment in V79 cells and HPBLs. The optimum dose of CDE (40 and 50 microg/ml in HPBLs and V79 cells, respectively) with the greatest reduction in micronuclei was further used in combination with various doses of gamma radiation (0.5, 1, 2, 3, and 4 Gy) exposed 1 h after CDE treatment. A linear dose-dependent MNBNC% increase in radiation alone group was observed, while 40/50 microg/ml CDE significantly resulted in the reduction of MNBNC%, compared to the respective radiation alone groups. CDE resulted in a dose-dependent increase in free radical scavenging ability against various free radicals, viz., 2, 2-diphenyl-2-picryl-hydrazyl (DPPH); 2, 2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS); superoxide anion (O2*-); hydroxyl radical (OH*) and nitric oxide radical (NO*) generated in vitro. Also, an excellent (70%) inhibition of lipid peroxidation in vitro was observed at a dose of 300 microg/ml CDE, attaining the saturation point at higher doses. The present findings demonstrated the radioprotective effect of CDE, also rendering protection against radiation-induced genomic instability and DNA damage. The observed radioprotective effect may be partly attributed to the free radical scavenging and antilipid peroxidative potential of CDE.     

Effects of magnetic fields on the accumulation of thiobarbituric acid reactive substances induced by iron salt and H2O2 in mouse brain homogenates or phosphotidylcholine

In this study, we examined the effects of magnetic fields (MFs) on the generation of thiobarbituric acid reactive substances (TBARS) in the mouse brain homogenates or phosphotidylcholine (PC) solution, incubated with FeCl₃ and/or H₂O₂. Active oxygen species were generated and lipid peroxidation was induced in mouse brain homogenates by incubation with iron ions, resulting in the accumulation of TBARS. Lipid peroxidation was induced in PC by incubation with iron ions and H₂O₂. Exposure to sinusoidal MFs (60 Hz, 0.2–1.2 mT), symmetric sawtooth-waveform MFs (50 Hz, 25–600 mT/s), rectangular MFs (1/0.4–1/16 Hz, 3.3 mT) and static MFs (1, 5–300 mT) had no effect on the accumulation of TBARS in brain homogenates induced by FeCl₃. In contrast, when the homogenates were incubated with FeCl₃ in static MFs (2–4 mT), the accumulation of TBARS was decreased. However, this inhibitory effect disappeared when EDTA was added to the homogenate and incubated with H₂O₂. The accumulation of TBARS in PC solution incubated with FeCl₃ and H₂O₂ was also inhibited by the static MF. These results indicate that only static MFs had an inhibitory effect on iron-induced lipid peroxidation and the effectiveness of this magnetic field on iron ion-induced active oxygen species generation is restricted to a so called ‘window’ of field intensity of 2–4 mT.     

Excitotoxic brain damage involves early peroxynitrite formation in a model of Huntington's disease in rats: protective role of iron porphyrinate 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III)

Oxidative/nitrosative stress is involved in NMDA receptor-mediated excitotoxic brain damage produced by the glutamate analog quinolinic acid. The purpose of this work was to study a possible role of peroxynitrite, a reactive oxygen/nitrogen species, in the course of excitotoxic events evoked by quinolinic acid in the brain. The effects of Fe(TPPS) (5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III)), an iron porphyrinate and putative peroxynitrite decomposition catalyst, were tested on lipid peroxidation and mitochondrial function in brain synaptic vesicles exposed to quinolinic acid, as well as on peroxynitrite formation, nitric oxide synthase and superoxide dismutase activities, lipid peroxidation, caspase-3-like activation, DNA fragmentation, and GABA levels in striatal tissue from rats lesioned by quinolinic acid. Circling behavior was also evaluated. Increasing concentrations of Fe(TPPS) reduced lipid peroxidation and mitochondrial dysfunction induced by quinolinic acid (100 microM) in synaptic vesicles in a concentration-dependent manner (10-800 microM). In addition, Fe(TPPS) (10 mg/kg, i.p.) administered 2 h before the striatal lesions, prevented the formation of peroxynitrite, the increased nitric oxide synthase activity, the decreased superoxide dismutase activity and the increased lipid peroxidation induced by quinolinic acid (240 nmol/microl) 120 min after the toxin infusion. Enhanced caspase-3-like activity and DNA fragmentation were also reduced by the porphyrinate 24 h after the injection of the excitotoxin. Circling behavior from quinolinic acid-treated rats was abolished by Fe(TPPS) six days after quinolinic acid injection, while the striatal levels of GABA, measured one day later, were partially recovered. The protective effects that Fe(TPPS) exerted on quinolinic acid-induced lipid peroxidation and mitochondrial dysfunction in synaptic vesicles suggest a primary action of the porphyrinate as an antioxidant molecule. In vivo findings suggest that the early production of peroxynitrite, altogether with the enhanced risk of superoxide anion (O2*-) and nitric oxide formation (its precursors) induced by quinolinic acid in the striatum, are attenuated by Fe(TPPS) through a recovery in the basal activities of nitric oxide synthase and superoxide dismutase. The porphyrinate-mediated reduction in DNA fragmentation simultaneous to the decrease in caspase-3-like activation from quinolinic acid-lesioned rats suggests a prevention in the risk of peroxynitrite-mediated apoptotic events during the course of excitotoxic damage in the striatum. In summary, the protective effects that Fe(TPPS) exhibited both under in vitro and in vivo conditions support an active role of peroxynitrite and its precursors in the pattern of brain damage elicited by excitotoxic events in the experimental model of Huntington's disease. The neuroprotective mechanisms of Fe(TPPS) are discussed.     

Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate.

To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.     

电离辐射氧化应激致轻度认知功能障碍及其综合干预的研究

电离辐射氧化应激致机体细胞内水分子水解产生活性氧和自由基或直接损伤DNA等靶分子,脑组织细胞凋亡致海马体积缩小,并在脑膜、大脑皮层和海马的血管壁内可见β淀粉样蛋白沉积,神经组织的病理损伤,引起脑部认知功能障碍.神经功能发生改变轻度认知功能障碍成为当今研究的热点,本文系统阐述了电离辐射氧化应激致机体轻度认知功能障碍(MCI)的发生机制、临床表现与临床诊断,讨论了生物学标志物检测、影像学检查、综合干预对MCI的诊断和预防价值.     

Comparison of the effect of a mitochondrial uncoupler, 2,4-dinitrophenol and adrenaline on oxygen radical production in the isolated perfused rat liver

Using the isolated perfused rat liver, we examined the effect of stimulation of mitochondrial respiration by 2,4-dinitrophenol (2,4-DNP) and adrenaline on reactive oxygen species (ROS) production, liver damage and lipid peroxidation. ROS production was monitored by luminol- and lucigenin-enhanced chemiluminescence and oxygen uptake was measured simultaneously. Liver damage and lipid peroxidation were evaluated by measuring hepatic lactate dehydrogenase (LDH) and thiobarbituric acid reacting substances (TBARS) release. Tissue ROS level decreased and oxygen uptake increased soon after 2,4-DNP infusion. On termination of 2,4-DNP infusion, there was a sharp increase in lucigenin-enhanced chemiluminescence, which declined slowly, but luminol-enhanced chemiluminescence did not change prominently. Hepatic LDH and TBARS release increased gradually during 2,4-DNP infusion and were manifested by termination of the infusion. Allopurinol did not affect ROS production and TBARS release, but delayed increases in LDH release after termination of 2,4-DNP infusion. Adrenaline, which stimulates mitochondrial respiration without uncoupling caused similar but smaller ROS changes observed in 2,4-DNP. LDH and TBARS release were not affected significantly by adrenaline infusion. These results indicate that uncoupling of oxidative phosphorylation decreases ROS production and restoration of oxidative phosphorylation enhances ROS production and liver damage. Xanthine oxidase is unlikely to contribute to enhanced ROS production after termination of 2,4-DNP but has some protective effect during uncoupling.     

Comparison of the effect of a mitochondrial uncoupler, 2,4-dinitrophenol and adrenaline on oxygen radical production in the isolated perfused rat liver.

Using the isolated perfused rat liver, we examined the effect of stimulation of mitochondrial respiration by 2,4-dinitrophenol (2,4-DNP) and adrenaline on reactive oxygen species (ROS) production, liver damage and lipid peroxidation. ROS production was monitored by luminol- and lucigenin-enhanced chemiluminescence and oxygen uptake was measured simultaneously. Liver damage and lipid peroxidation were evaluated by measuring hepatic lactate dehydrogenase (LDH) and thiobarbituric acid reacting substances (TBARS) release. Tissue ROS level decreased and oxygen uptake increased soon after 2,4-DNP infusion. On termination of 2,4-DNP infusion, there was a sharp increase in lucigenin-enhanced chemiluminescence, which declined slowly, but luminol-enhanced chemiluminescence did not change prominently. Hepatic LDH and TBARS release increased gradually during 2,4-DNP infusion and were manifested by termination of the infusion. Allopurinol did not affect ROS production and TBARS release, but delayed increases in LDH release after termination of 2,4-DNP infusion. Adrenaline, which stimulates mitochondrial respiration without uncoupling caused similar but smaller ROS changes observed in 2,4-DNP. LDH and TBARS release were not affected significantly by adrenaline infusion. These results indicate that uncoupling of oxidative phosphorylation decreases ROS production and restoration of oxidative phosphorylation enhances ROS production and liver damage. Xanthine oxidase is unlikely to contribute to enhanced ROS production after termination of 2,4-DNP but has some protective effect during uncoupling.