Characterization of the antioxidant effects of melatonin and related indoleamines in vitro

Abstract: The antioxidant and possible pro-oxidant effects of melatonin and related indoleamines (tryptophan, serotonin, N-acetylserotonin, and 5-methoxytryptamine) were studied in vitro. In two model membrane systems, i.e., phospholipid liposomes and rat erythrocytes, lipid peroxidation induced by Fe²⁺ and H₂O₂, respectively, were reduced by the tested indoleamines except for tryptophan. The 5-hydroxy-indoleamines, serotonin, and N-acetylserotonin exhibited pro-oxidant actions in the bleomycin assay by reducing Fe³⁺ to Fe²⁺, which leads to DNA damage. The 5-methoxy-indoleamines, melatonin and 5-methoxytryptamine, were devoid of any pro-oxidant actions in this assay. Serotonin, but not N-acetylserotonin, scavenged the superoxide anion. None of the indoleamines tested had any reactivity towards H₂O₂. All the indoleamines, including tryptophan, were, however, shown to react with hypochlorous acid. These findings support an antiperoxidative and antioxidant action of melatonin which is devoid of pro-oxidant effect on non-lipid substrates.     

Randomized,controlled trial of antioxidant vitamins and cardioprotective diet on hyperlipidemia,oxidative stress,and development of experimental atherosclerosis: The diet and antioxidant trial on atherosclerosis (DATA)

Summary The effects of administration of guava and papaya fruit (100 g/day), vegetables, and mustard oil (5 g/day) (group A); antioxidant vitamins C (50 mg/day) and E (30 mg/day) plus betacarotene (10 mg/day) (group B); a high-fat (5–10 g/day) (group C); or a low-fat (4–5 g/day) diet (group D) were compared over 24 diet weeks in a randomized fashion, while all groups of rabbits (five in each of four groups) received a hydrogenated fat diet (5–10 g/day) for a period of 36 weeks. After 12 weeks on the high-fat diet, each group of rabbits had an increase in blood lipoproteins. The fruit and vegetable-enriched prudent diet (group A) caused a significant decline in blood lipids at 24 and 36 weeks, whereas the lipid levels increased significantly in groups C and D. Group A also had a significant rise in vitamin E (2.1 Umol/l), C (10.5 Umol/l), A (0.66 Umol/l), and carotene (0.08 Umol/l) and a decrease in lipid peroxides (0.34 nmol/ml at 36 weeks, whereas the levels were unchanged in groups C and D. Group B rabbits had a significant and greater increase than group A in plasma vitamins E, C, A, and carotene; a rise in HDL cholesterol; and a greater decrease in lipid peroxides after 24 and 36 weeks of treatment. After stimulation of lipid peroxidation in all rabbits, 3 of 5 group C and 2 of 5 group D rabbits died due to coronary thrombosis, whereas in groups A and B there were no deaths, indicating that antioxidant therapy can provide protection against lipid peroxidation and free radical generation. Aortic lipids and sudanophilia, indicating atherosclerosis, were significantly higher in groups C and D than in groups A and B. Fatty streaks and atheromatous and fibrous plaques were noted in all the rabbits in groups C and D. Intimal fibrosis and medial degeneration were also present in the group C rabbits. While group A (36.4±4.4 µm) and group B (37.1±4.2 µm) rabbits had minimal coronary artery plaque sizes, group C (75.4±10.6 µm) and group D rabbits (69.5±6.2 µm) had significantly greater plaque sizes. Aortic plaque sizes were also greater in groups C and D than in groups A and B. It is possible that combined therapy with antioxidant vitamins C, E, and carotene, and a diet rich in antioxidants, could independently inhibit free radical generation and the development of atherosclerosis.     

Effects of antioxidant therapy in experimentally induced heart infarcts

Summary Experiments were performed on dog hearts following coronary ligation and treatment with synthetic antioxidant of dihydroquinoline type. Experimental groups were: (i) control dogs, (ii) dogs with ligation of descendens anterior coronary branch, (iii) coronary ligated dogs with antioxidant pretreatment and (iv) dogs with coronary ligation and simultaneous antioxidant infusion therapy. The heart infarctionper se is accompanied by the disintegration of membrane polyunsaturated fatty acids expressed by increase of malondialdehyde (MDA) concentration and the impairment of natural scavenging characterized by the decrease of superoxide dismutase (SOD) and reduced glutathione (GSH) content. The oral pretreatment with antioxidant for 8 days prevented or decreased the unfavourable pathobiochemical responses. The acute infusion therapy exerted no immediate protection, nonetheless, it could decrease the severity of pathological signs.     

Phytochemical composition and in vitro antioxidant activity of aqueous extract of Aerva lanata (L.) Juss. ex Schult. Stem (Amaranthaceae)

ObjectiveTo analyze the phytochemical composition and in vitro antioxidant properties of aqueous extract of Aerva lanata (A. lanata) stem.MethodsDuring the preliminary phytochemical analysis, the aqueous extract of A. lanata was screened for the presence of carbohydrates, proteins, phenolic compounds, oil and fats, saponins, flavonoids, alkaloids, tannins and phytosterols. Antioxidant activity of the extract was determined by 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity, metal chelating activity, reducing power activity and DNA damage inhibition activity. Analysis of phenolic compounds was performed by Folin-Ciocalteau reagent method and gradient high performance liquid chromatography technique.ResultsPreliminary phytochemical analysis exhibited the presence of phenolic compounds, saponins, flavonoids, tannins and phytosterols as major phytochemical groups. The extract exhibited high 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity (IC₅₀= 110.74 μg/mL), metal chelating activity (IC₅₀= 758.17 μg/mL), reducing power activity and DNA damage inhibition efficiency. The extract was reported to possess a high amount of total phenolic content and some of them were identified as gallic acid (3,4,5-OH), apigenin-7-O-glucoside (apigetrin), quercetin-3-O-rutinoside (rutin) and myricetin (3,5,7,3,4,5-OH) by high performance liquid chromatography analysis. The extract was found non toxic towards human erythrocytes in the hemolytic assay (IC₅₀ = 24.89 mg/mL).ConclusionsThese results conclud that A. lanata stem possesses high antioxidant activity and can be used for the development of natural and safe antioxidant compounds.     

Phytochemical,antioxidant and antibacterial potential of Elaeagnus kologa (Schlecht.) leaf

ObjectiveTo screen different solvent extracts of Elaeagnus kologa (E. kologa) leaf to determine the phytochemicals, potent antioxidant and antibacterial activity to find out the possible source of applied pharmaceutical formulations.MethodsSolvent extracts of leaf material were prepared using the Soxhlet apparatus. A study was performed on antioxidant activity of methanolic extract of leaf by 1-1-diphenyl-2-picrylhydrazyl method. The phenolic and flavonoid content of all the fractions were determined using high performance liquid chromatography. Leaves were also subjected to protein and carbohydrate test.ResultsThe total phenols, flavonoids were found to be high in petroleum ether as compare to other solvent fraction. The IC₅₀ value of methanolic extract of the sample was 62.20 μg/mL which showed significant antibacterial activity against Bacillus subtilis (Gram-positive).ConclusionsThe present study suggests that the methanolic extract of E. kologa leaf possesses antioxidant and antibacterial properties. Such properties may be of great use in mitigating the detrimental effects of oxidative stress and reducing susceptibility to bacterial infection. Notably, extracts of E. kologa leaf also contain proteins and carbohydrates which add to its nutritional value.     

Expression of oxidative stress-related molecules in circulating leukocytes and urine in patients with chronic viral hepatitis.

AIMS: Oxidative stress plays a role in pathogenesis of chronic viral hepatitis. Expression of oxidative stress-related molecules remains to be clarified. METHODS: 4-hydroxy-2-nonenal (4-HNE), 4-hydroxy-2-hexenal (4-HHE), catalase, superoxide dismutase-1 (SOD-1), glutathione peroxidase-1, thioredoxin (TRX) in leukocytes and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) were examined in 164 persons, including 130 chronic viral hepatitis patients and 34 normal individuals, by Western blot analysis and enzyme-linked immunosorbent assay, respectively. Hepatic expression of these proteins was immunohistochemically examined in 12 patients with chronic viral hepatitis, compared with three persons without liver damage. RESULTS: The 4-HNE/beta-actin ratios in chronic viral hepatitis were significantly higher than those in normal individuals (P<0.01), and were significantly correlated with asparate aminotransferase (AST) and alanine aminotransferase (ALT) (P<0.01, each). The catalase/beta-actin and SOD-1/beta-actin ratios in chronic viral hepatitis were higher than those in normal individuals, and were significantly correlated with 4-HNE/beta-actin ratios (P<0.01, each). Hepatic expression of 4-HNE, 4-HHE, catalase, SOD-1 and TRX in chronic viral hepatitis was higher than that without liver damage. Urinary excretion of 8-OHdG was not changed in chronic viral hepatitis. CONCLUSIONS: The results of the present study suggest that expression of oxidative stress-related molecules in leukocytes is upregulated in relation to serum aminotransferase levels.     

Evaluation of phytochemical and antioxidant activities of the different fractions of Hybanthus enneaspermus (Linn.) F. Muell. (Violaceae)

ObjectiveTo investigate the naturally occurring antioxidant for the first time from the different solvent fractions of Hybanthus enneaspermus (H. enneaspermus) Linn F. Muell. family (Violaceae).MethodsDifferent fractions of H. enneaspermus were tested for total phenolic content, and in vitro antioxidant activity was measured by total antioxidant assay, DPPH assay, reducing power, nitric oxide (NO), hydrogen peroxide (H₂O₂) scavenging assays.ResultsThe ethyl acetate (EA) fraction was found to have high levels of phenolic content [(212.15±0.79) mg GAE/g]. The EA fraction exhibited higher total antioxidant capacity, higher percentage of DPPH radical scavenging activity [(127.07±2.29) μg/mL], nitric oxide [(245.16±1.44) μg/mL], hydrogen peroxide [(227.38±7.18) μg/mL], deoxyribose [(270.61±8.72) μg/mL] and higher reducing power. There was a significant correlation between total phenolic content and total antioxidant activity (r²=0.972).ConclusionsThese results reveal that EA fraction of H. enneaspermus has strong antioxidant potential compared with other fractions. Our further study has been extended to the isolation of the possible compound that is responsible for having antioxidant property.     

Phytochemical,antioxidant and hepatoprotective effects of different fractions of Moringa oleifera leaves methanol extract against liver injury in animal model

Objective: To evaluate the potential antioxidant and hepatoprotective effects of n-hexane, dichloromethane(DCM), ethyl acetate(EtOAc), n-butanol and aqueous fractions of Moringa oleifera(M. oleifera) leaves methanol extract against carbon tetrachloride(CCl_4)-induced liver injury in rats. Methods: These fractions were prepared from the M. oleifera leaves methanol extract by solubilization in water and partitioning in n-hexane, EtOAc, DCM and n-butanol. Their phyto-components were identified by GC-MS analysis. The in vitro antioxidant effect of these fractions was carried out by assessment of 1,1-diphenyl-2-picrylhydrazyl scavenging activity. A total of 40 Sprague Dawley rats were allocated into 8 equal groups: group 1 given olive oil(1 m L/kg b.wt.), group 2 injected with CCl_4, group 3 to 7 administered with n-hexane, DCM, EtOAc, n-butanol and aqueous fractions, respectively after CCl_4, group 8 administered with silymarin after CCl_4. The activities of aspartate aminotransferase, alanine aminotransferase, and the levels of total cholesterol, triglycerides, glucose, total proteins and albumin in serum were determined spectrophotometrically. Glutathione reduced, lipid peroxide by-products levels, glutathione-s-transferase and catalase enzyme activities in the liver homogenate were determined by spectrophotometer. Liver specimens were also examined for histopathological alterations under light microscope. Results: The GCMS analysis of different fractions of the M. oleifera leaves methanol extract revealed that n-hexane, DCM, EtOAc, n-butanol, and aqueous fractions contained 17, 22, 23, 19 and 32 compounds, respectively. The percent and the molecular structure of each component in each fraction were identified. The n-butanol and EtOAc fractions exhibited the strongest in vitro antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl. CCl_4 significantly decreased glutathione reduced and total proteins concentration and glutathione-s-transferase and catalase activities but increased lipid peroxide by-products and total cholesterol levels. The n-hexane followed by aqueous and DCM fractions were the most potent to regulate serum enzyme activities and lipid peroxide by-products levels in the liver homogenate. Conclusions: n-hexane, DCM, and aqueous fractions have the highest effectiveness against CCl_4-induced hepatotoxicity. Isolation and purification of the active constituents require further experiments.     

δ-Aminolevulinic acid-induced lipid peroxidation in rat kidney and liver is attenuated by melatonin: An in vitro and in vivo study

Abstract: Acute intermittent porphyria (AIP) is a genetically inherited disease characterized by a partial block in liver heme biosynthesis and by increased urinary excretion of the δ-aminolevulinic acid (ALA). Recently, it has been proposed that the toxic effects of ALA are related to the generation of free radicals. In the present study the in vitro and in vivo effect of melatonin, a recently described antioxidative agent, on ALA-induced lipid peroxidation in rat liver and kidney was determined. The concentration of malonaldehyde (MDA) and 4-hydroxyalkenals (4-HDA) was assayed as an index of induced membrane oxidative damage. In vitro melatonin protected, in a concentration-dependent manner, against ALA-induced lipid peroxidation in liver and kidney homogenates. In in vivo experiments as well, it was demonstrated that ALA (40 mg/kg)-induced lipid peroxidation in liver and kidney was reduced by acute melatonin (10 m/g) treatment. The results support the involvement of free radicals in ALA toxicity and show that in vitro and in vivo melatonin confers protection against this toxicity, likely due to the antioxidative capability of the indole.     

In vitro antioxidant activity and total phenolic content of endophytic fungi isolated from Eugenia jambolana Lam.

ObjectiveTo elucidate the antioxidant activity and total phenolic content (TPC) of ethyl acetate extracts of endophytic fungi isolated from Eugenia jambolana by three different antioxidant assays.MethodsTwenty one different endophytic fungal extracts were screened for presence of various phytochemicals, TPC and in vitro antioxidant activity. TPC was tested by Folin-Ciocalteau reagent based assay. DPPH free radical scavenging, hydrogen peroxide scavenging and reducing power assays were used to evaluate the antioxidant activity.ResultsAlkaloids, phenols, flavonoids, saponins, and terpenes were the main phytochemicals presents in all 21 endophytes. A significant positive correlation was found between antioxidant activity and TPC in fungal extracts. There is 36% endophytic extracts having high phenolic content exhibited potent antioxidant activity. Chaetomium sp., Aspergillus sp., Aspergillus peyronelii and Aspergillus niger strain showed the highest antioxidant activity ranging from 50% to 80% having 58 mg/g to 60 mg/g GAE total phenolics. Ascorbic acid used as a standard showed 90% reducing potential.ConclusionsThe results reveal that metabolites produced by endophytic fungi isolated from Eugenia jambolana can be a potential source of novel natural antioxidant compounds.     

Indole-based analogs of melatonin: in vitro antioxidant and cytoprotective activities

The known neuroprotective actions of melatonin could be due to its antioxidant or radical scavenging activity, or they could be due to specific interactions of the indole with its receptors. A study of structure-activity relationships may provide useful information when a validated macromolecular target has not been (or is not) identified. A set of indole derivatives, with changes in the 5-methoxy and acylamino groups, the side chain position and the lipophilic/hydrophilic balance, were selected and tested for their in vitro antioxidant potency in the ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid disodium salt) and thiobarbituric acid reactive substances (TBARS) assays and for their cytoprotective activity against kainate excitotoxicity on cerebellar cell cultures. No quantitative model was able to relate the potencies obtained in the two antioxidant assays, probably because they are related to different physico-chemical properties. However, the lipophilicity of the compounds and the antioxidant potency in the TBARS assay were linearly correlated. This may be due to improved access to the lipidic substrate, where the antioxidant action occurs. In the cytoprotection assay, most compounds showed potencies comparable with or lower than melatonin. An exception was N-[2-(5-methoxy-1H-indol-2-yl)ethyl]acetamide (12), yielding, at 50 microM, percentages of cell vitality higher than 75%, while melatonin EC50 was 333 microM. No correlation was observed between cytoprotective and antioxidant potencies, nor with MT1 or MT(2) receptor affinity. Compound 12 is a low-affinity antagonist at melatonin membrane receptors, and one of the most potent compounds in the antioxidant assays; its cytoprotective potency and the absence of agonist activity at melatonin membrane receptors make it a valid candidate for further investigations.     

Melatonin protects against pressure ulcer-induced oxidative injury of the skin and remote organs in rats

Pressure ulcers (PU) cause morphological and functional alterations in the skin and visceral organs; the damage is believed to be due to ischemia/reperfusion (I/R) injury. In this study, we examined the role of oxidative damage in PU and the beneficial effect of treatment with the antioxidant melatonin. PU were induced by applying magnets over steel plates that were implanted under the skin of rats; this compressed the skin and caused ischemia. Within a 12-hr period, rats were subjected to five cycles of I/R (2 and 0.5 hr respectively), followed by an additional 12 hr of ischemia (to simulate the period at sleep at night). This protocol was repeated for 3 days. In treatment groups, twice a day during reperfusion periods, melatonin (5 mg per rat) was either applied locally as an ointment on skin, or administered i.p. (10 mg/kg). At the end of the experimental period, blood and tissue (skin, liver, kidney, lung, stomach, and ileum) samples were taken for determination of biochemical parameters and for histological evaluation. Local treatment with melatonin inhibited the increase in malondialdehyde levels; an index of lipid peroxidation, myeloperoxidase activity; an indicator of tissue neutrophil infiltration, and the decrease in glutathione; a key antioxidant, in the skin induced by PU, but was less efficient in preventing the damage in visceral organs. However, systemic treatment prevented the damage in the visceral organs. Significant increases in creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and collagen levels in animals with PU were prevented by melatonin treatment. The light microscopic examination exhibited significant degenerative changes in dermis and epidermis in the PU rats. Tissue injury was decreased especially in the locally treated group. Findings of the present study suggest that local and/or systemic melatonin treatment may prove beneficial in the treatment of PU.     

The role of lipid peroxidation in pathogenesis of ischemic damage and the antioxidant protection of the heart

Summary A working hypothesis on pathogenesis of ischemic heart damage has been proposed. According to this hypothesis, a crucial role in conversion of reversible damage into irreversible damage is played by cardiomyocyte membrane destruction caused by the so-called lipid triad. The latter comprises activation of lipid peroxidation, activation of phospholipases, and the degergentlike action of excessive amounts of free fatty acids and lysophospholipids. Marked activation of lipid peroxidation in experimental myocardial infarction, as well as reoxygenation following transitory ischemia, have been demonstrated. The proposed hypothesis and experimental data underly successful application of synthetic free radical scavengers (antioxidants) for heart protection against experimental myocardial infarction, transitory ischemia, and emotional, painful stress.

---

Zusammenfassung In der vorliegenden Studie wird eine Arbeitshypothese zur Pathogenese der ischämischen Herzschädigung aufgestellt. Nach dieser Hypothese ist ein entscheidender Faktor für den Übergang von der reversiblen zur irreversiblen Schädigung eine Membrandestruktion der Herzmuskelzellen, welche durch sog. Lipid-Triaden verursacht wird. Letztere beinhaltet eine Aktivierung der Lipid-Peroxidation und der Phospholipase sowie eine Detergenz-ähnliche Wirkung exzessiver Mengen von freien Fettsäuren und Lysophospholipiden. Eine ausgepräge Aktivierung der Lipid-Peroxidation beim experimentellen Herzinfarkt sowie eine Reoxigenierung nach vorübergehender Ischämie wurden demonstriert. Die vorgelegte Hypothese und die experimentellen Daten legen eine Anwendung von Radialfängern (Antioxidantien) nahe für die Protektion des Herzens gegen experimentellen Myokardinfarkt, vorübergehende Ischämie und emotionalen Streß bei Schmerzsituationen.

     

Effect of α-tocopherol on lipid peroxidation and total antioxidant status in spontaneously hypertensive rats

The aim of this study was to determine the effects of α-tocopherol on lipid peroxidation and total antioxidant status of spontaneously hypertensive rats (SHR), comparing them with normal Wistar-Kyoto (WKY) rats. SHR were divided into three groups and treated with different doses of α-tocopherol (α₁, 17 mg/kg diet; α₂, 34 mg/kg diet; and α₃, 170 mg/kg diet). Normal WKY and untreated SHR were used as normal (N) and hypertensive control (HC). Blood pressures were recorded every 10 days for 3 months. At the end of the trial, animals were killed and measurement of plasma total antioxidant status, plasma superoxide dismutase (SOD) activity, and lipid peroxide levels in plasma and blood vessels was carried out following well-established methods.From our study it was found that lipid peroxides in thoracic aorta (N, 0.47 ± 0.17; H, 0.96 ± 0.37; P < .0001) and plasma (N, 0.06 ± 0.01; H, 0.13 ± 0.01) were significantly higher in hypertensives than in normal rats. SOD activity was significantly lower in hypertensive than normal rats (N, 172.93 ± 46.91; H, 110.08 ± 14.38; P < .005). Total antioxidant status was significantly higher in normal than hypertensive rats (N, 0.88 ± 0.05; H, 0.83 ± 0.02; P < .05). After the antioxidant trial, it was found that in the treated groups rise of blood pressure was prevented significantly (P < .001) and lipid peroxides in blood vessels were significantly reduced more than in the controls (P < .001). For plasma lipid peroxide it was only significant for groups α₂ (P < .001) and α₃ (P < .05). Although all three treated groups showed improved total antioxidant status, only groups α₂ (0.87 ± 0.04, P < .005) and α₃ (1.20 ± 0.18, P < .001) were statistically significant. All the three groups showed significant increases in their SOD activity (P < .001).Correlation studies showed that total antioxidant status and SOD were significantly negatively correlated with blood pressure in normal rats (P = .007; P = .008). Lipid peroxides in both blood vessel and plasma showed a positive correlation. In the treated groups, lipid peroxides in blood vessels maintained a significant positive correlation with blood pressure in all groups (α₁, P = .021; α₂, P = .019; α₃, P = .002), whereas for plasma lipid peroxides the correlation was in groups α₁ (P = .005) and α₂ (P = .009). For SOD activity, significant negative correlations were found with blood pressure in the α₂ (P = .017) and α₃ (P = .025) groups. Total antioxidant status maintained a significant negative correlation with blood pressure in all three groups (α₁, P = .012; α₂, P = .044; α₃, P = .014).In conclusion it was found that supplement of α-tocopherol may prevent development of increased blood pressure, reduce lipid peroxides in plasma and blood vessels, and enhance the total antioxidant status, including SOD activity.     

Quantification of the water/lipid affinity of melatonin and a pinoline derivative in lipid models

This study assessed the location of melatonin (N-acetyl-5-methoxytryptamine) and of a pinoline derivative (GWC22) [6-ethyl-1-(3-methoxyphenyl)-2-propyl-1,2,3,4-tetrahydro-beta-carboline], when present in lipid assemblies such as linoleate micelles, phosphatidylcholine liposomes or low density lipoproteins (LDL). The efficiency of radical scavenging by these compounds is highly dependent on their partitioning between the lipidic and aqueous phases. We determined the proportion of melatonin or GWC22 in the aqueous and lipid phases of each system (concentrations of the antioxidants ranging between 3 x 10(-5) and 10(-4) m) by assaying melatonin or GWC22 by HPLC/UV detection, or by fluorescence for melatonin in micelles. Our results show that melatonin and GWC22 were preferentially located in the aqueous phase of micelles (68.4% and 59.0%, respectively), whereas only 30.5% of melatonin and 39.0% of GWC22 were found in the lipid phase. By contrast, in phosphatidylcholine liposomes, both compounds were essentially present in the lipid phase (73.5% for melatonin and 79.1% for GWC22, versus 25.9% and 19.5% in the aqueous phase, respectively). In the case of LDL, 99.9% of the melatonin added was found in the methanol/water extracting phase containing phospholipids, unesterified cholesterol and apolipoprotein B100. The partitioning of melatonin and GWC22 in linoleate micelles gave new insights on the marked protective effect of GWC22 towards radiation-induced lipid peroxidation and allowed us to determine more accurately the lower limit values of the reaction rate constants of the two molecules studied with lipid peroxyl radicals, i.e. k(LOO.+melatonin)) >or= 9.0 x 10(4)m(-1)s(-1) and k(LOO.+GWC22) >or= 3.5 x 10(5)m(-1)s(-1).     

Cadmium-induced changes of antioxidant and metabolic status in red blood cells of rats: in vivo effects

Abstract: Chronic exposure of adult rats to dietary untake of cadmium (15 mg CdCl₂/day/kg for 30 days) leads to development of anemia and thrombocytosis. Anemia is characterized by significant reticulocytosis (13.1 ± 1.0%), anysocytosis, poikilocytosis, iron deficiency and marked alterations of antioxidant and metabolic status of red blood cells. Activities of SOD, catalase, GPx and GR were significantly increased in red blood cells of cadmium-treated rats. In treated animals cadmium induced an increase of red cell reduced and oxidized glutathione with no changes of GSSG/GSH ratio. However, significant reduction of lipid peroxidation was found. Plasma levels of tocopherol and ascorbate, as well as activity of glutathione-S-transferase, were all significantly increased in cadmium-treated rats. The energy metabolism of red blood cells was deeply altered in cadmium-treated rats. The levels of ATP, ADP, AMP and TAN were significantly increased while ATP/ADP ratio and adenylate energy charge (AEC) were significantly reduced. The level of 2,3-BPG was somewhat lower, but 2,3-BPG/Hb ratio was considerably higher, in red blood cells of cadmium-treated rats.     

Cardiac lipids and antioxidant status in high fructose rats and the effect of alpha-lipoic acid

BACKGROUND AND AIMS: The development of insulin resistance has been shown to be an early step in the development of cardiovascular diseases in diabetic patients. Oxidative stress may be important in the development of coronary artery disease. Fructose loaded rats, which show the characteristic features of insulin resistance, also display an imbalance between the peroxidation process and the antioxidant system. Alpha-lipoic acid (LA)--a co-enzyme--is known for its potent antioxidant effects. The present study examined whether LA mitigates fructose-induced oxidative stress in heart tissue. METHODS AND RESULTS: Male Wistar rats with a body weight of 150-170g were divided into 4 groups of 6 rats each. Control rats received a control diet containing starch and water ad libitum. Fructose rats received a fructose-enriched diet (>60% of total calories). Fructose + LA rats received a fructose diet and alpha-lipoic acid (35mg/kg b.w i.p.). Control + LA rats received control diet and alpha-lipoic acid. After the 20-day treatment period, we assessed the insulin sensitivity index in terms of HOMA. The levels of lipid peroxidation markers and the enzymatic and non-enzymatic antioxidant status in the heart tissue were measured. Plasma and heart tissue lipids were also analysed. Fructose rats showed decreased insulin sensitivity as reflected by high values of HOMA, increased peroxidation, impaired antioxidant status and lipid abnormalities in the cardiac tissue. These abnormalities were attenuated and the antioxidant levels were enhanced by LA. The reduction in HOMA values suggests LA improves insulin sensitivity. CONCLUSIONS: Improvement of insulin sensitivity and enhancement of cardiac antioxidant status suggest that LA may be useful as a cardioprotective agent in insulin-resistant states.     

Influence of alpha-lipoic acid on lipid peroxidation and antioxidant defence system in blood of insulin-resistant rats

Background: High fructose feeding induces insulin resistance and hyperinsulinaemia in rats. A role for oxidative stress in the occurrence of insulin resistance has been suggested by several workers. Aim: The aim of this study was to investigate the effect of α‐lipoic acid (LA) on oxidant–antioxidant balance in rats fed on a high‐fructose diet that showed characteristic features of insulin resistance. Methods: Male Wistar rats weighing 150–170 g were divided into seven groups. The control group received the control diet containing starch. The fructose group was given a high‐fructose diet (>60% of total calories). The third and fourth groups were given fructose diet and were administered two different doses of LA at a low dose (35 mg/kg body weight) and high dose (70 mg/kg body weight) using olive oil as vehicle. The fifth group received fructose diet and olive oil. The sixth group received control diet and was administered LA (70 mg/kg body weight). And, the seventh group received the control diet and olive oil. Products of lipid peroxidation and activities of enzymic antioxidants, namely superoxide dismutase, catalase, glutathione peroxidase, glutathione‐S‐transferase and glutathione reductase, in red blood cells were assayed. Levels of non‐enzymic antioxidants α‐tocopherol, ascorbic acid and reduced glutathione were determined in plasma. Results: The levels of lipid peroxides, diene conjugates and thiobarbituric acid‐reactive substances were significantly higher in fructose‐fed rats. Inadequate antioxidant system was observed in high‐fructose‐fed rats. Treatment of fructose rats mitigated the imbalance between peroxidation and antioxidant defence system at both the doses tested. Increases in glucose, triglycerides, free fatty acids, insulin and insulin resistance were observed in fructose‐fed rats. LA administration prevented these alterations and improved insulin sensitivity. Significant positive correlations were obtained between insulin resistance and lipid peroxidation indices. Conclusions: Increased lipid peroxidation and deficient antioxidant system are observed in high‐fructose‐fed rats. LA administration preserves the antioxidant system and lowers lipid peroxidation. The findings suggest an interrelationship between lipid peroxidation and insulin resistance.