饲料硒和维生素E对大鼠机体抗氧化能力的影响

 用克山病病区粮配成基础低硒饲料,补充硒和/或维生素E组成四种不同水平的饲料,饲喂雄性断乳大鼠,观察其对机体抗氧化能力的影响。评价指标是用抗坏血酸诱发的红细胞溶血率、被O~-_2(超氧阴离子)氧化的血红蛋白量和组织中的TBA值。动物饲养13周后,自尾静脉取血,测定溶血率和血红蛋白被氧化的百分率,和全血SeGSHPx(含硒谷胱甘肽过氧化物酶)活力。15周后将动物断头杀死,立即取出心脏和肝脏测定SeGSHPx活力和TBA值。结果表明在克山病病区粮的饲料中补充硒或维生素E,或者二者同时补充均明显提高组织中的SeGSHPx活力和降低组织中的TBA值。不论在硒缺乏时或硒充足时,饲料中补充维生素E显著降低抗坏血酸诱发的红细胞溶血率,对O~-_2氧化血红蛋白无保护作用。在维生素E缺乏时,仅补充硒对溶血无作用。不论饲料中维生素E缺乏或者充足,补充硒对O~-_1氧化血红蛋白均有显著保护作用。     

Effect of metal ion catalyzed oxidation of rifamycin SV on cell viability and metabolic performance of isolated rat hepatocytes

The effect of rifamycin SV on metabolic performance and cell viability was studied using isolated hepatocytes from fed, starved and glutathione (GSH) depleted rats. The relationships between GSH depletion, nutritional status of the cells, glucose metabolism, lactate dehydrogenase (LDH) leakage and malondialdehyde (MDA) production in the presence of rifamycin SV and transition metal ions was investigated. Glucose metabolism was impaired in isolated hepatocytes from both fed and starved animals, the effect is dependent on the rifamycin SV concentration and is enhanced by copper (II). Oxygen consumption by isolated hepatocytes from starved rats was also increased by copper (II) and a partial inhibition due to catalase was observed. Cellular GSH levels which decrease with increasing the rifamycin SV concentration were almost depleted in the presence of copper (II). A correlation between GSH depletion and LDH leakage was observed in fed and starved cells. Catalase induced a slight inhibition of the impairment of gluconeogenesis, GSH depletion and LDH leakage in starved hepatocytes incubated with rifamycin SV, iron (II) and copper (II) salts. Lipid peroxidation measured as MDA production by isolated hepatocytes was also augmented by rifamycin SV and copper (II), especially in hepatic cells isolated from starved and GSH depleted rats. Higher cytotoxicity was observed in isolated hepatocytes from fasted animals when compared with fed or GSH depleted animals. It seems likely that in addition to GSH level, there are other factors which may have an influence on the susceptibility of hepatic cells towards xenobiotic induced cytotoxicity.     

The mechanism for the effect of selenium supplementation on immunity

Lipid peroxide (LPO) in lymphocytes from mice was evaluated by measuring substances reactive to thiobarbituric acid (TBA). The product resulting from the reaction of TBA with lymphocytes was extracted with n-butyl and fluorescence intensity was determined. The degree of lipid peroxidation, expressed as fluorescence intensity f547, was assessed for stimulation of lymphocytes with concanavalin A (Con A), and was related to lymphocyte proliferation in response to Con A if Se was administered. The lymphocyte proliferation was determined by [³H]thymidine incorporation, expressed as cpm. The effect of superoxide dismutase (SOD), added to cell culture on lymphocyte proliferation was also evaluated. It was found that LPO in lymphocytes before Con A stimulation was significantly less than that after stimulation (p<0.001), and that SOD promoted lymphocyte proliferation dose dependently. The addition of Na₂SeO₃ to lymphocyte culture or supplementation in drinking water to mice decreased the produced LPO in lymphocyte in response to Con A. In the presence of Se, there is an inverse correlation between the levels of LPO in lymphocyte and the stimulated proliferation (r=−0.8902,r=−0.9439). In conclusion, active oxygen species scavenging was proposed as one of the mechanisms for Se to promote immunity.     

Inhibition of lipid peroxidation by a novel compound (CV-2619) in brain mitochondria and mode of action of the inhibition

Lipid peroxidation in rat brain mitochondria was induced by NADH in the presence of ADP and FeCl3. CV-2619 inhibited the lipid peroxidation in a concentration-dependent manner; the concentration giving 50% inhibition (IC50) was 84 microM. In addition, the inhibitory effect of CV-2619 was strongly enhanced by adding substrates of mitochondrial respiration; when succinate, glutamate, or succinate plus glutamate was added, the IC50 of CV-2619 was changed to 1.1, 10, or 0.5 microM, respectively. Metabolites of CV-2619 also inhibited the lipid peroxidation. The inhibitory effect of CV-2619 on mitochondrial lipid peroxidation disappeared when TTFA, an inhibitor of complex II in mitochondrial respiratory chain, was added. The results indicate that in mitochondria CV-2619 is changed to its reduced form which inhibits lipid peroxidation.     

The flanking sequence contributes to the immobilisation of spermine at the G-quadruplex in the NHE (nuclease hypersensitivity element) III1 of the c-Myc promoter

Defining the molecular basis of the DNA sequence selectivity of polyamine binding is central to understanding polyamine-dependent gene expression. We have studied, by selective NMR experiments, the variation of spermine mobility and conformation in the presence of G-quadruplexes formed by sequences of the purine-rich strand of the c-Myc promoter, nuclease hypersensitivity element III₁ (NHE III₁). All the NHE quadruplexes restrict spermine mobility and induce a spermine conformational change but the most effective immobilisation occurs when all five G-tracts of the NHE III₁ are present. This suggests structure within the nucleotides flanking the G-quadruplex has a role in immobilising spermine.     

Possible mechanisms underlying copper-induced damage in biological membranes leading to cellular toxicity

It is generally accepted that copper toxicity is a consequence of the generation of reactive oxygen species (ROS) by copper ions via Fenton or Haber-Weiss reactions. Copper ions display high affinity for thiol and amino groups occurring in proteins. Thus, specialized proteins containing clusters of these groups transport and store copper ions, hampering their potential toxicity. This mechanism, however, may be overwhelmed under copper overloading conditions, in which copper ions may bind to thiol groups occurring in proteins non-related to copper metabolism. In this study, we propose that indiscriminate copper binding may lead to damaging consequences to protein structure, modifying their biological functions. Therefore, we treated liver subcellular membrane fractions, including microsomes, with Cu²⁺ ions either alone or in the presence of ascorbate (Cu²⁺/ascorbate); we then assayed both copper-binding to membranes, and microsomal cytochrome P450 oxidative system and GSH-transferase activities. All assayed sub-cellular membrane fractions treated with Cu²⁺ alone displayed Cu²⁺-binding, which was significantly increased in the presence of Zn²⁺, Hg²⁺, Cd²⁺, Ag⁺¹ and As³⁺. Treatment of microsomes with Cu²⁺ in the μM range decreased the microsomal thiol content; in the presence of ascorbate, Cu²⁺ added in the nM concentrations range induced a significant microsomal lipoperoxidation; noteworthy, increasing Cu²⁺ concentration to ≥50 μM led to non-detectable lipoperoxidation levels. On the other hand, μM Cu²⁺ led to the inhibition of the enzymatic activities tested to the same extent in either presence or absence of ascorbate. We discuss the possible significance of indiscriminate copper binding to thiol proteins as a possible mechanism underlying copper-induced toxicity.     

Preparation of low-molecular-weight and high-sulfate-content chitosans under microwave radiation and their potential antioxidant activity in vitro

In the present paper microwave radiation has been used to introduce N-sulfo and O-sulfo groups into chitosan with a high degree of substitution and low-molecular weight. The sulfation of chitosan was performed in microwave ovens. It was found that microwave heating is a convenient way to obtain a wide range of products of different degrees of substitution and molecular weight only by changing reaction time or/and radiation power. Moreover, microwave radiation accelerated the degradation of sulfated chitosan, and the molecular weight of sulfated chitosan was considerably lower than that obtained by traditional heating. There are no differences in the chemical structure of sulfated chitosan obtained by microwave and by conventional technology. FTIR and 13C NMR spectral analyses demonstrated that a significantly shorter time is required to obtain a satisfactory degree of substitution and molecular weight by microwave radiation than by conventional technology. In this present paper, we also determined antioxidant activity of low-molecular-weight and high-sulfate-content chitosans (LCTS). The results showed LCTS could scavenge superoxide and hydroxyl radical. Its IC50 is 0.025 and 1.32 mg/mL, respectively. It is a potential antioxidant in vitro.     

Combined effect of vanadium(V) and chromium(III) on lipid peroxidation in liver and kidney of rats

Since chromium(III) was demonstrated to have antioxidative action, we have decided to study the effect of this element on V-induced LPO in liver and kidney of rats. Outbred 2-month-old, albino male Wistar rats received daily, for a period of 12 weeks: group I (control), deionized water to drink; group II, sodium metavanadate (SMV) solution at a concentration of 0.100mgV/mL; group III, chromium chloride (CC) solution at a concentration of 0.004mgCr/mL and group IV, SMV-CC solution at a concentration of 0.100mgV and 0.004mgCr/mL. The particular experimental groups took up with drinking water about 8.6mgV/kg b.w./24h (group II), 0.4mgCr/kg b.w./24h (group III), 9mgV and 0.36mgCr/kg b.w./24h (group IV). The V- or Cr-treated groups had higher concentrations of these two elements in liver and kidney compared to the controls. The administration of vanadium alone caused a significant decrease in fluid intake and in body weight gain compared to the controls. In liver supernatants obtained from all tested rats a statistically significant increase in MDA concentration was demonstrated in spontaneous LPO in comparison with the control rats. Moreover, in rats intoxicated with vanadium alone a statistically significant increase in liver MDA level was observed in the presence of 100microM NaVO(3). Instead, in supernatants of liver received from rats treated with chromium alone, a statistically significant increase in MDA concentration in comparison with the controls was found in the presence of 400microM NaVO(3). In kidney supernatants obtained from rats treated with chromium alone, a statistically significant increase in lipid peroxidation was shown in the presence of 30microM FeSO(4) and 400microM NaVO(3). These results show that the tested doses of vanadium(V) and chromium(III) ingested by rats with their drinking water caused significant alterations in internal organs, especially in liver. Under the conditions of our experiment, Cr(III) did not demonstrate antioxidant action, it rather had an oxidant effect.     

Synergistic effect of conjugated linolenic acid isomers against induced oxidative stress,inflammation and erythrocyte membrane disintegrity in rat model

Background

α-Eleostearic acid and punicic acid, two typical conjugated linolenic acid (CLnA) isomers present in bitter gourd and snake gourd oil respectively, exhibit contrasting cis-trans configuration which made them biologically important.

Methods

Rats were divided into six groups. Group 1 was control and group 2 was treated control. Rats in the groups 3 and 4 were treated with mixture of α-eleostearic acid and punicic acid (1:1) (0.5% and 1.0% respectively) while rats in the groups 5 and 6 were treated with 0.5% of α-eleostearic acid and 0.5% of punicic acid respectively along with sodium arsenite by oral gavage once per day.

Results

Results showed that increase in nitric oxide synthase (NOS) activity, inflammatory markers expression, platelet aggregation, lipid peroxidation, protein oxidation, DNA damage and altered expression of liver X receptor-α (LXR-α) after arsenite treatment were restored with the supplementation of oils containing CLnA isomers. Altered activities of different antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and ferric reducing ability of plasma (FRAP) also restored after oil supplementation. Altered morphology and fluidity of erythrocyte membrane studied by atomic force and scanning electron microscopy, after stress induction were significantly improved due to amelioration in cholesterol/phospholipid ratio and fatty acid profile of membrane. Oils treatment also improved morphology of liver and fatty acid composition of hepatic lipid.

Conclusions

Overall two isomers showed synergistic antioxidant and anti-inflammatory effect against induced perturbations and membrane disintegrity.

General significance

Synergistic antioxidant and anti-inflammatory role of these CLnA isomers were established by this study.