Changes in free radicals,trace elements,and neurophysiological function in rats with liver damage induced byD-galactosamine

The changes in trace elements, free radicals, and neurophysiological function were investigated in rats with liver damage induced byd-galactosamine (GalN). The elevated results showed that all the parameters related to free radical metabolism changed after administration of GalN. Relative free radical concentration, malonaldehyde (MDA), and oxidized glutathione (GSSG) elevated, but reduced glutathione (GSH) decreased. Concurrently, zinc, copper, manganese, and selenium contents in liver were significantly reduced, whereas iron was elevated. In rats with hepatic encephalopathy (HE) owing to fulminant hepatic failure (FHF) induced by a high dosage of GalN, the latencies of VEPs were delayed. Moreover, there is a correlation between Zn content of brain and the latencies of VEPs. The results of this study suggested that lipid peroxidation by free radicals might be responsible for GalN-induced liver damage in which trace elements were involved, and that change in brain Zn might play a role in the neural inhibition of HE owing to FHF.     

Oxygen free radical producing activity of polymorphonuclear leukocytes in patients with Parkinson's disease

Oxygen free radicals (OFRs) have been suggested in the pathogenesis of Parkinson's disease (PD). These free radicals exert their cytotoxic effect by peroxidation of lipid membrane resulting in the formation of malondialdehyde (MDA). Polymorphonuclear (PMN) leukocyte is one of the major sources of OFR. However, the oxygen free radical producing activity of PMN leukocytes in patients with PD is not known. We therefore studied the oxygen free radical producing activity of polymorphonuclear leukocytes and MDA levels in the serum of healthy subjects and in patients with Parkinson's disease. The oxygen free radical producing activity of PMN leukocytes in blood and the MDA content in serum were significantly higher in patients with Parkinson's disease than in healthy subjects. These results indicate a possible role of oxygen free radicals in the pathogenesis of Parkinson's disease.     

Free radical activity, antioxidant enzyme, and glutathione changes with muscle stretch injury in rabbits.

The present study investigated changes in rate of free radical production, antioxidant enzyme activity, and glutathione status immediately after and 24 h after acute muscle stretch injury in 18 male New Zealand White rabbits. There was no change in free radical production in injured muscles, compared with noninjured controls, immediately after injury (time 0; P = 0.782). However, at 24 h postinjury, there was a 25% increase in free radical production in the injured muscles. Overall, there was an interaction (time and treatment) effect (P = 0.005) for free radical production. Antioxidant enzyme activity demonstrated a treatment (injured vs. control) and interaction effect for both glutathione peroxidase (P = 0.015) and glutathione reductase (P = 0.041). There was no evidence of lipid peroxidation damage, as measured by muscle malondialdehyde content. An interaction effect occurred for both reduced glutathione (P = 0.008) and total glutathione (P = 0.015). Morphological analysis (hematoxylin and eosin staining) showed significant polymorphonuclear cell infiltration of the damaged region at 24 h postinjury. We conclude that acute mechanical muscle stretch injury results in increased free radical production within 24 h after injury. Antioxidant enzyme and glutathione systems also appear to be affected during this early postinjury period.     

Nickel-mediated inhibition in the glutathione-dependent protection against lipid peroxidation

Glutathione protects liver microsomes against the rapid onset of lipid peroxidation via a sulfhydryl dependent heat labile factor known as free radical reductase. The administration of nickel to mice resulted in an inhibition in the activity of free radical reductase, and enhanced lipid peroxidation and the activity of glutathione S-transferase in a dose dependent manner. The pretreatment of cyclam, a known specific chelator of nickel restored free radical reductase and glutathione S-transferase activities and alleviated nickel mediated enhancement of lipid peroxidation. Our results indicate that nickel-mediated inhibition in free radical reductase activity and activation of glutathione S-transferase may be due to the interaction of nickel with sensitive-SH groups located on these proteins.     

Micromethods in single muscle fibers. 2. Determination of glutathione reductase and glutathione peroxidase

This paper extends the previous study for systems which control intracellular oxidative events in muscle and describes procedures suitable to assay glutathione peroxidase (GSHPx), glutathione reductase (GR), and total glutathione (GSH + GSSG) after fiber typing of individual muscle fibers. In human skeletal muscle, both GR and GSHPx activities were relatively low when compared to those of other tissue. No difference was found among fiber types (I, IIA, and IIB) with regard to GR activity, but in contrast GSHPx activity was significantly lower in type IIB fibers than in the other types. These results suggest that type IIB fibers may have a reduced ability to cope with hydroperoxides generated during oxidative stress, which, in turn, could lead to increased damage to membrane structures by lipid peroxidation or oxidation of sensitive intracellular thiol (-SH) enzymes by hydrogen peroxide. The Km of skeletal muscle GR for GSSG was 27 microM and for NADPH was 22 microM. If one assumes approximately 95% of total glutathione is present in the reduced state, then GSSG concentration would be of the order of 0.3 mmol/kg and under these conditions skeletal muscle GR would be efficient in all muscle fiber types.     

Seasonal modulation of free radical metabolism in estivating land snails Helix aspersa

We investigated the regulation of free radical metabolism in Helix aspersa snails during a cycle of 20-day estivation and 24-h arousal in summer in comparison with estivation/arousal in winter-snails. In winter-snails (J. Exp. Biol. 206, 675-685, 2003), we had already observed an increase in the selenium-dependent glutathione-peroxidase (Se-GPX) activity in foot muscle and hepatopancreas and in the contents of hepatopancreas GSH-equivalents (GSH-eq=GSH+2 GSSG) during estivation compared with 24-h aroused snails. Summer-estivation prompted a 3.6-fold increase in Se-GPX activity in hepatopancreas, though not in foot muscle. Total-superoxide dismutase and catalase activities in hepatopancreas decreased (by 30-40%) during summer-estivation; however, no changes occurred in the activities of glutathione reductase, glutathione S-transferase and glucose-6-phosphate dehydrogenase in the two organs. GSH-eq levels were increased (by 54%) in foot muscle during estivation, but were unchanged in hepatopancreas. In contrast with winter-snails, oxidative stress markers (lipid peroxidation, carbonyl protein, and the GSSG/GSH-eq ratio) were unaltered during estivation/arousal in summer. These results demonstrate that seasonality modulates not only the absolute activities/levels of antioxidants (enzymes and GSH-eq) in H. aspersa, but also the regulatory process that controls the snail's antioxidant capacity during estivation/arousal. These results suggest that H. aspersa has an "internal clock" controlling the regulation of free radical metabolism in the different seasons.     

Free radical oxidation and antiradical protection of the rat brain during adaptation to intense physical loading

The cerebral free radical oxidation processes on 40 Wistar rats-males were studied by evaluation of thiobarbituric-active products of lipid peroxidation level, superoxide dismutase and glutathione peroxidase activity in sensomotor cortex, hypothalamus and brain stem. Was found that differential stability of rats to motor activities during single intensive physical loading is due by reactivity of free radicals oxidation, associated with decrease of cerebral antioxidant enzymes activity. Long term intensive physical loading may accompanied by reducing of reserve possibilities of antioxidant enzymes an cerebral structures, what possible play potential role in pathogenetic mechanisms of osteoarthritis.     

灵芝抗氧化清除自由基作用的研究

文中综述了灵芝的抗氧化清除自由基作用。灵芝对各种因素引起的脑、心脏、胰腺、肝脏、胃肠道、肾脏和其他重要脏器的脂质过氧化损伤具有明显的保护作用。灵芝可显著减少脂质过氧化产物丙二醛(MDA)的含量,增强抗氧化酶如超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)以及其他抗氧化酶的活性。稹灵芝对体外培养的巨噬细胞(小鼠)、胰岛细胞(小鼠)、大脑皮层细胞(大鼠)、嗜铬细胞瘤细胞(大鼠)、血管内皮细胞(大鼠、人)和皮肤角质细胞(人)的氧化损伤具有明显保护作用。灵芝在体内外对不同动物模型和细胞模型的抗氧化清除自由基作用可能与其免疫调节、抗肿瘤、降血压、降血糖、保肝、心血管保护和抗衰老作用的机制有关。     

Protection mechanisms against excess light in the resurrection plants Craterostigma wilmsii and Xerophyta viscosa

Mechanisms of avoidance and protection against light damage were studied in the resurrection plants Craterostigma wilmsii and Xerophyta viscosa.In C. wilmsii, a combination of both physical and chemical changes appeared to afford protection against free radical damage. During dehydration leaves curled inwards, and the abaxial surface became exposed to light. The tissue became purple/brown in colour, this coinciding with a three-fold increase in anthocyanin content and a 30% decline in chlorophyll content. Thus light-chlorophyll interactions are progressively reduced as chlorophyll became masked by anthocyanins in abaxial layers and shaded in the adaxial layers. Ascorbate peroxidase (AP) activity increased during this process but declined when the leaf was desiccated (5% RWC). During rehydration leaves uncurled and the potential for normal light-chlorophyll interaction was possible before full hydration had occurred. Superoxide dismutase (SOD) and glutathione reductase (GR) activities increased markedly during this stage, possibly affording free radical protection until full hydration and metabolic recovery had occurred.In contrast, the leaves of X. viscosa did not curl, but light-chlorophyll interactions were minimised by the loss of chlorophyll and dismantling of thylakoid membranes. During dehydration, free radical protection was afforded by a four-fold increase in anthocyanin content and increased activities of AP, GR and SOD. These declined during rehydration. It is suggested that potential free radical damage may be avoided by the persistence of anthocyanins during the period of thylakoid membrane re-assembly and full chlorophyll restitution which only occurred once the leaves were fully rehydrated.     

Nitric oxide counteracts the senescence of rice leaves induced by abscisic acid

In the present study, we evaluate the protective effect of nitric oxide (NO) against senescence of rice leaves promoted by ABA. Senescence of rice leaves was determined by the decrease of protein content. ABA treatment resulted in (1) induction of leaf senescence, (2) increase in H2O2 and malondialdehyde (MDA) contents, (3) decrease in reduced form glutathione (GSH) and ascorbic acid (AsA) contents, and (4) increase in antioxidative enzyme activities (superoxide dismutase, ascorbate peroxidase, glutathione reductase, and catalase). All these ABA effects were reduced by free radical scavengers such as sodium benzoate and GSH. NO donors [N-tert-butyl-alpha-phenylnitrone (PBN), sodium nitroprusside, 3-morpholinosydonimine, and AsA + NaNO2] were effective in reducing ABA-induced leaf senescence. PBN prevented ABA-induced increase in the contents of H2O2 and MDA, decrease in the contents of GSH and AsA, and increase in the activities of antioxidative enzymes. The protective effect of PBN on ABA-promoted senescence, ABA-increased H2O2 content and lipid peroxidation, ABA-decreased GSH and AsA, and ABA-increased antioxidative enzyme activities was reversed by 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a NO-specific scavenger, suggesting that the protective effect of PBN is attributable to NO released. Reduction of ABA-induced senescence by NO in rice leaves is most likely mediated through its ability to scavenge active oxygen species including H2O2.     

Possible neuroprotective effects of lecithin and alpha-tocopherol alone or in combination against ischemia/reperfusion insult in rat brain

A close correlation exists between ischemia/reperfusion (I/R)-induced insult and the release of free radicals. Lecithin is a polyunsaturated phosphatidylcholine that corresponds to the phosphatidylcholine molecule. Phosphatidylcholines are high-energy functional and structural elements of all biologic membranes. alpha-Tocopherol is the major lipid-soluble chain-breaking antioxidant in the body tissues and effectively protects against neuronal damage. Therefore, we studied the effect of lecithin (300 mg/kg, p.o., 14 days) and alpha-tocopherol (200 mg/kg, p.o., 14 days), alone or in combination, on the brain redox state during I/R. Adult male Wistar rats were subjected to global ischemia by the occlusion of the two carotid arteries 24 h after the last dose of drug administration. Reperfusion was carried out 1 h after induction of ischemia and lasted for another hour. Brain lipid peroxides (MDA) and glutathione (GSH) contents, as well as superoxide dismutase (SOD) and catalase (CAT) activities were assessed. The results showed that I/R elevated brain lipid peroxides content which was accompanied by a reduction in both antioxidant enzyme activities, however, brain GSH level remained unaltered. Lecithin, alpha-tocopherol and their combination restored MDA content, as well as CAT activity with a slight tendency to normalize SOD activity. We conclude that lecithin has a possible neuroprotective effect partly through its antioxidant action which is comparable to that of alpha-tocopherol.     

Effect of thyroidectomy and adrenalectomy on changes in liver glutathione and malonaldehyde levels after acute ethanol injection

At low concentrations ethanol is metabolized largely by alcohol dehydrogenase to acetaldehyde, while at higher concentrations a microsomal ethanol oxidising system (MEOS) is involved, namely cytochrome P450 IIE1, which also probably generates free radical species. In hyperthyroidism hepatic glutathione stores are depleted and net superoxide anion production occurs. In contrast, in hypothyroidism hepatic glutathione may be increased and thus renders the liver less sensitive to alcohol generated free radical production. Steroid hormones inhibit lipid peroxidation. Sixty male Wistar rats either underwent thyroidectomy, adrenalectomy, or sham procedures. Twenty control animals were pair fed with thyroidectomized animals, whilst another twenty fed ad libitum. An intraperitoneal injection of alcohol (75 mmol/kg) was given 2.5 h prior to sacrifice to half the animals in each group, the remainder receiving saline. The total hepatic glutathione contents of the pair fed and the ad libitum groups were not different, but were significantly increased by thyroidectomy (p = <0.001). This effect was significantly reduced by alcohol (p < 0.01). The sham procedures and dietary restrictions had no effect. The ethanol alone reduced total hepatic glutathione, but this only reached statistical significance in the thyroidectomized and sham-adrenalectomized groups. Hepatic malonaldehyde (MDA) levels were significantly reduced in the thyroidectomy group but alcohol had no effect on them. We conclude that hypothyroidism increased hepatic glutathione status, presumably by reducing radical production by enzyme systems, which would otherwise consume this important scavenger. Long term exposure to ethanol with induction of MEOS is probably required for it to generate toxic levels of free radical species.     

An aqueous extract of Rubus chingii fruits protects primary rat hepatocytes against tert-butyl hydroperoxide induced oxidative stress

Different in vitro free radical generating systems were used to assess the antioxidative activity of aqueous extracts of the five herbal components of Wu-zi-yan-zong-wan, a traditional Chinese medicinal formula with a long history of use for tonic effects. Fructus Rubi [Rubus chingii (Rosaceae) fruits] was found to be the most potent. It was further investigated using the primary rat hepatocyte system. tert-Butyl hydroperoxide (t-BHP) was used to induce oxidative stress. Being a short chain analog of lipid hydroperoxide, t-BHP is metabolized into free radical intermediates by the cytochrome P450 system in hepatocytes, which in turn, initiate lipid peroxidation, glutathione depletion and cell damage. Pre-treatment of hepatocytes with Fructus Rubi extract (50 microg/ml to 200 microg/ml) for 24 h significantly reversed t-BHP-induced cell viability loss, lactate dehydrogenase leakage and the associated glutathione depletion and lipid peroxidation. The amount of reactive oxygen species formed was also decreased as visualized by the fluorescence probe 2',7'-dichlorofluorescin diacetate. These results suggested that Fructus Rubi was useful in protecting against t-BHP-induced oxidative damage and may also be capable of attenuating cytotoxicity of other oxidants.     

Hesperidin, an antioxidant flavonoid, prevents acrylonitrile-induced oxidative stress in rat brain

Acrylonitrile (ACN) is a volatile, toxic liquid used as a monomer in the manufacture of synthetic rubber, styrene plastics, acrylic fiber, and adhesives. ACN is a potent neurotoxin. A role for free radical mediated lipid peroxidation in the toxicity of ACN has been suggested. We examined the ability of hesperidin, an antioxidant flavonoid, to attenuate ACN-induced alterations in lipid peroxidation in rat brains. The daily oral administration of ACN to male albino rats in a dose of 50 mg/kg bwt for a period of 28 days produced a significant elevation in brain lipid peroxides measured as malondialdehyde (MDA) amounting to 107%, accompanied by a marked decrease in brain-reduced glutathione (GSH) content reaching 63%. In addition, ACN administration resulted in significant reductions in the enzymatic antioxidant parameters of brain; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione-S-transferase (GST) recording 43%, 64%, 52%, and 43%, respectively. On the other hand, pretreatment with hesperidin and its coadministration with ACN once daily in a dose of 200 mg/kg bwt i.p. for 28 days ameliorated ACN-induced alterations in brain lipid peroxidation. These results suggest that hesperidin may have a beneficial role against ACN-induced oxidative stress in the brain; an effect that is mainly attributed to the antioxidant property of hesperidin.     

Role of Oxidative Damage in Friedreich's Ataxia

Plasma malondialdehyde (MDA) levels were raised in Friedreich's ataxia (FRDA) patients. These levels correlated with increasing age and disease duration, suggesting lipid peroxidation increased with disease progression. Using fibroblasts from FRDA patients we observed that GSH levels and aconitase activities were normal, suggesting their antioxidant status was unchanged. When exposed to various agents to increase free radical generation we observed that intracellular superoxide generation induced by paraquat caused enhanced oxidative damage. This correlated with the size of the GAA1 expansion, suggesting decreased frataxin levels may render the cells more vulnerable to mild oxidative stress. More severe oxidative stress induced by hydrogen peroxide caused increased cell death in FRDA fibroblasts but was not significantly different from control cells. We propose that abnormal respiratory chain function and iron accumulation may lead to a progressive increase in oxidative damage, but increased sensitivity to free radicals may not require detectable respiratory chain dysfunction.     

Free radicals in exhaustive physical exercise: mechanism of production, and protection by antioxidants

Moderate exercise is a healthy practice. However, exhaustive exercise generates free radicals. This can be evidenced by increases in lipid peroxidation, glutathione oxidation, and oxidative protein damage. It is well known that activity of cytosolic enzymes in blood plasma is increased after exhaustive exercise. This may be taken as a sign of damage to muscle cells. The degree of oxidative stress and of muscle damage does not depend on the absolute intensity of exercise but on the degree of exhaustion of the person who performs exercise. Training partially prevents free radical-formation in exhaustive exercise. Treatment with antioxidants such as vitamins C or E protects in part against free radical-mediated damage in exercise. Xanthine oxidase is involved in free-radical formation in exercise in humans and inhibition of this enzyme with allopurinol decreases oxidative stress and muscle damage associated with exhaustive exercise. Knowledge of the mechanism of free-radical formation in exercise is important because it will be useful to prevent oxidative stress and damage associated with exhaustive physical activity.     

高温胁迫下外源褪黑素对黄瓜幼苗活性氧代谢的影响

以黄瓜品种‘津春4号’为试材,用叶面喷施的方法,研究了高温胁迫条件下外源褪黑素(melatonin,MT)对黄瓜幼苗活性氧（ROS）代谢的影响.结果表明：外源MT能显著降低高温胁迫下黄瓜叶片超氧阴离子自由基（O₂^-.）产生速率、过氧化氢（H₂O₂）含量、电解质漏渗率（relative electric conductivity, REC）及丙二醛(MDA)含量,增强黄瓜幼苗叶片中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性,提高抗坏血酸（AsA）、谷胱甘肽（GSH）及可溶性蛋白质含量.说明MT预处理能抑制高温胁迫条件下黄瓜幼苗体内ROS的产生,提高抗氧化酶系的活性及抗氧化物质的含量,降低膜质过氧化水平,保护脂膜的完整性,减少电解质的外渗,减轻高温胁迫对幼苗造成的伤害,提高幼苗抗高温胁迫的能力.     

Effect of nodules on dehydration response in alfalfa (Medicago sativa L.)

Drought is a key abiotic stress that negatively affects growth and development as well as symbiotic nitrogen fixation in alfalfa (Medicago sativa L.). To understand whether nodulation would affect drought stress response in alfalfa, we analyzed the lipid peroxidation, activities of antioxidant enzymes including superoxide dismutase (SOD), and catalase (CAT), contents of superoxide anion radical, non-enzymatic antioxidants including reduced glutathione (GSH) and proline, total protein, and soluble sugar in dehydration-stressed alfalfa. Three-month-old alfalfa plants without nodule, with active nodules, or with inactive nodules were dehydrated for 0, 1, 2, 4, 6, 8, and 10 h. We found that roots and leaves from plants with nodules, especially with active nodules, showed less lipid peroxidation which was associated with higher CAT activities and higher levels of GSH. Roots and leaves with active nodules also accumulated less free proline and soluble sugar compared to plants without nodules, suggesting that proline and soluble sugar may have a limited role in osmotic adjustment in these plants. The results suggested that active nodules may have a positive effect on drought stress tolerance in alfalfa.     

Free radical activity following contraction-induced injury to the extensor digitorum longus muscles of rats.

The purpose of the study was to investigate the role of free radicals in the injury induced by a protocol of repeated pliometric (lengthening) contractions to the extensor digitorum longus (EDL) muscle in situ in rats. Previous data have indicated that prior treatment with the antioxidant polyethylene glycol-superoxide dismutase reduced the damage that was apparent at 3 days following this type of exercise. Three hours and 3 days following the protocol, the magnitude of the semiquinone-derived free radical signal observed by electron spin resonance spectroscopy (ESR) was not different for exercised and non-exercised skeletal muscles. A reduction in the protein thiol content of muscle was evident at 3 h, and was still apparent at 3 days. Three hours after the protocol, the total muscle glutathione content and the percentage in the oxidized form were unchanged, but by 3 days the percentage of muscle glutathione present in the oxidized form was elevated. The susceptibility of muscle to lipid peroxidation in vitro was reduced 3 days after the pliometric contractions. These data indicate that oxidation of protein thiols and glutathione may be involved in the secondary damage following pliometric contractions, but provide no evidence that the species involved were derived from mitochondrial semiquinone radicals.     

Lipid peroxidation and benzo[a]pyrene activation to mutagenic metabolites: in vivo influence of vitamins A, E and C and glutathione in both dietary vitamin A sufficiency and deficiency

Rats fed with either a sufficient-vitamin A or a vitamin A-free diet were pretreated with 750 mg/kg body weight of retinyl palmitate, alpha-tocopherol acetate, ascorbic acid or glutathione. Benzo[a]pyrene (BaP) metabolism and BaP-induced mutagenesis in Salmonella typhimurium TA98 were investigated and related to lipid peroxidation activities in postmitochondrial (S9) liver fraction. The microsomal mixed-function oxidase activities were decreased by vitamin A deficiency and weakly affected by scavenger treatment. The rate of lipid peroxidation of microsomal membranes was unaffected by vitamin A deficiency because of decreased polyunsaturated fatty acids and increased vitamin E contents. However, lipid peroxidation was decreased by pretreatment with fat-soluble vitamins (chiefly vitamin E) and increased by ascorbic acid. Within each experimental group both BaP metabolism and BaP mutagenic activity were closely correlated with the rate of lipid peroxidation. In vitamin A deficiency, the increased BaP metabolism and mutagenicity could be related to a decrease in cytosolic contents of scavengers (vitamin A and glutathione). In Ames test conditions, the free radical pathway became a route for BaP metabolism and thus the BaP activation to mutagenic metabolites is related to the cellular status in free radical scavengers.