Melatonin reduces lipid and protein oxidative damage in synaptosomes due to aluminium

Prolonged exposure to excessive aluminium (Al) concentrations is involved in the ethiopathology of certain dementias and neurological disorders. Melatonin is a well-known antioxidant that efficiently reduces lipid peroxidation due to oxidative stress. Herein, we investigated in synaptosomal membranes the effect of melatonin in preventing Al promotion of lipid and protein oxidation when the metal was combined with FeCl₃ and ascorbic acid. Lipid peroxidation was estimated by quantifying malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations in the membrane suspension and protein carbonyls were measured in the synaptosomes as an index of oxidative damage. Under our experimental conditions, the addition of Al (0.0001–1 mmol/L) enhanced MDA+4-HDA formation in the synaptosomes. In addition, Al (1 mmol/L) raised protein carbonyl contents. Melatonin reduced, in a concentration-dependent manner, lipid and protein oxidation due to Al, FeCl₃ and ascorbic acid in the synaptosomal membranes. These results show that melatonin confers protection against Al-induced oxidative damage in synaptosomes and suggest that this indoleamine may be considered as a neuroprotective agent in Al toxicity because of its antioxidant activity.     

Melatonin protects against taurolithocholic‐induced oxidative stress in rat liver

Cholestasis, encountered in a variety of clinical disorders, is characterized by intracellular accumulation of toxic bile acids in the liver. Furthermore, oxidative stress plays an important role in the pathogenesis of bile acids. Taurolithocholic acid (TLC) was revealed in previous studies as the most pro‐oxidative bile acid. Melatonin, a well‐known antioxidant, is a safe and widely used therapeutic agent. Herein, we investigated the hepatoprotective role of melatonin on lipid and protein oxidation induced by TLC alone and in combination with FeCl₃ and ascorbic acid in rat liver homogenates and hepatic membranes. The lipid peroxidation products, malondialdehyde and 4‐hydroxyalkenals (MDA + 4‐HDA), and carbonyl levels were quantified as indices of oxidative damage to hepatic lipids and proteins, respectively. In the current study, the rise in MDA + 4‐HDA levels induced by TLC was inhibited by melatonin in a concentration‐dependent manner in both liver homogenates and in hepatic membranes. Melatonin also had protective effects against structural damage to proteins induced by TLC in membranes. These results suggest that the indoleamine melatonin may potentially act as a protective agent in the therapy of those diseases that involve bile acid toxicity. J. Cell. Biochem. 110: 1219–1225, 2010. Published 2010 Wiley‐Liss, Inc.     

Melatonin reduces Fenton reaction-induced lipid peroxidation in porcine thyroid tissue

Free radicals and reactive oxygen species (ROS) participate in physiological and pathological processes in the thyroid gland. Bivalent iron cation (ferrous, Fe(2+)), which initiates the Fenton reaction (Fe(2+) + H2O2 --> Fe(3+) + *OH + OH(-)) is frequently used to experimentally induce oxidative damage, including that caused by lipid peroxidation. Lipid peroxidation is involved in DNA damage, thus indirectly participating in the early steps of carcinogenesis. In turn, melatonin is a well-known antioxidant and free radical scavenger. The aim of the study was to estimate the effect of melatonin on basal and iron-induced lipid peroxidation in homogenates of the porcine thyroid gland. In order to determine the effect of melatonin on the auto-oxidation of lipids, thyroid homogenates were incubated in the presence of that indoleamine in concentrations of 0.0, 0.00001, 0.0001, 0.001, 0.01, 0.1, 0.25, 0.5, 1.0, 2.5, or 5.0 mM. To study melatonin effects on iron-induced lipid peroxidation, the homogenates were incubated in the presence of FeSO(4) (40 microM) plus H2O2 (0.5 mM), and, additionally, in the presence of melatonin in the same concentrations as above. The degree of lipid peroxidation was expressed as the concentration of malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) per mg protein. Melatonin, in a concentration-dependent manner, decreased lipid peroxidation induced by Fenton reaction, without affecting the basal MDA + 4-HDA levels. In conclusion, melatonin protects against iron + H2O2-induced peroxidation of lipids in the porcine thyroid. Thus, the indoleamine would be expected to prevent pathological processes related to oxidative damage in the thyroid, cancer initiation included.     

Vanillin as an antioxidant in rat liver mitochondria: Inhibition of protein oxidation and lipid peroxidation induced by photosensitization

Using rat liver mitochondria, as model systems, we have examined the ability of the natural compound and the food-flavoring agent, vanillin to protect membranes against oxidative damage induced by photosensitization at concentrations normally used in food preparations. Vanillin, at a concentration of 2.5 mmol/L, has afforded significant protection against protein oxidation and lipid peroxidation in hepatic mitochondria induced by photosensitization with methylene blue plus light. The effect observed was both time- and concentration-dependent. The inhibitory effect is similar to ascorbic acid and the singlet oxygen quencher, diazabicyclo[2.2.2]octane (DABCO) but less effective than sodium azide and glutathione. Examination of possible mechanisms responsible for the observed protection, showed that vanillin has a significant ability to quench singlet oxygen (¹O₂), a reactive species responsible for damage induced during photosensitization by Type II mechanism. Hence, this flavoring compound, due to its antioxidant ability, may have potential to prevent oxidative damage to membranes in mammalian tissues and thereby the ensuing diseased states.     

Evaluation of malondialdehyde as an index of lead damage in rat brain homogenates

Lipid peroxidation in vitro homogenates of brain was examined as sequela of lead toxicity. The levels of malondialdehyde (MDA) in homogenates of rat brain (1 ml, 5% w/v) treated with lead (50 g) alone or in combination with ascorbic acid (100 g), alphatocopherol (100 g) or hydroquinone (100 g) were evaluated. The levels of MDA were consistently evoked by lead in a dose-related manner. The toxicity of lead was further advanced by the action of the pro-oxidant drug ascorbic acid on the brain. However, the anti-oxidant drugs alphatocopherol and hydroquinone decreased the toxic effect of lead on the brain. These results clearly show that the enhanced lipid peroxidation may provide a basis of lead-induced neurotoxicity.     

Walker-256 tumor growth causes oxidative stress in rat brain

The elevated rate of oxygen consumption and high amount of polyunsaturated fatty acids make the central nervous system vulnerable to oxidative stress. The effect of Walker-256 tumor growth on oxi-reduction indexes in the hypothalamus (HT), cortex (CT), hippocampus (HC) and cerebellum (CB) of male Wistar rats was investigated. The presence of the tumor caused an increase in thiobarbituric acid reactant substances (TBARs) in the HT, CB and HC. Due to tumor growth, the activity of glucose-6-phosphate dehydrogenase increased in the HT and CB, whereas citrate synthase activity was reduced in the HT, CT and CB. Therefore, the potential for generation of reducing power is increased in the cytosol and decreased in the mitochondria of various brain regions of Walker-256 tumor-bearing rats. These changes occurred concomitantly with an unbalance in the brain enzymatic antioxidant system. The tumor decreased the activities of catalase in the HT and CB and of glutathione peroxidase in the HT, CB and HC, and raised the CuZn-superoxide dismutase activity in the HT, CB and HC. These combined findings indicate that Walker-256 tumor growth causes oxidative stress in the brain.     

Galangin,a natural flavonoid reduces mitochondrial oxidative damage in streptozotocin-induced diabetic rats

Objective: We designed this study to observe the effect of galangin on damaged mitochondria in the liver of diabetic rats.

Methods: Male albino Wistar rats were made diabetic by injecting streptozotocin (STZ) intraperitoneally (40?mg?kg^?1 body weight (BW)). Galangin (8?mg?kg^?1 BW) or glibenclamide (600?µg?kg^?1 BW) was given orally daily once for 45 days to both healthy and diabetic rats.

Results: Diabetic rats showed significant (P?P?P?P?P?Conclusion: From the results, we conclude that galangin could maintain liver mitochondrial function in diabetic rats.     

Brain oxidative stress and selective behaviour of aluminium in specific areas of rat brain: potential effects in a 6-OHDA-induced model of Parkinson's disease

The ability of aluminium to affect the oxidant status of specific areas of the brain (cerebellum, ventral midbrain, cortex, hippocampus, striatum) was investigated in rats intraperitoneally treated with aluminium chloride (10 mg Al³⁺/kg/day) for 10 days. The potential of aluminium to act as an etiological factor in Parkinson's disease (PD) was assessed by studying its ability to increase oxidative stress in ventral midbrain and striatum and the striatal dopaminergic neurodegeneration induced by 6-hydroxydopamine in an experimental model of PD. The results showed that aluminium caused an increase in oxidative stress (TBARS, protein carbonyl content, and protein thiol content) for most of the brain regions studied, which was accompanied by a decrease in the activity of some antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase). However, studies in vitro confirmed the inability of aluminium to affect the activity of those enzymes. The reported effects exhibited a regional-selective behaviour for all the cerebral structures studied. Aluminium also enhanced the ability of 6-hydroxydopamine to cause oxidative stress and neurodegeneration in the dopaminergic system, which confirms its potential as a risk factor in the development of PD.     

Melatonin prevents oxidative kidney damage in a rat model of thermal injury

Animal models of thermal trauma implicate oxygen radicals as causative agents in local wound response and distant organ injury following burn. This study was designed to determine the effect of melatonin treatment on levels of glutathione (GSH), malondialdehyde (MDA), protein oxidation (PO) and myeloperoxidase (MPO) activity in the kidney tissues of rats with thermal injury. Under ether anaesthesia, shaved dorsum of the rats was exposed to 90 degrees C bath for 10 s to induce burn injury. Rats were decapitated either 3 h or 24 h after burn injury. Melatonin was administered i.p. immediately after burn injury. In the 24-h burn group melatonin injections were repeated for two more occasions. In the sham group the same protocol was applied except that the dorsum was dipped in a 25 degrees C water bath for 10 s. Severe skin scald injury (30% of total body surface area) caused a significant decrease in GSH level, and significant increases in MDA and PO levels, and MPO activity at post-burn 3 and 24 hours. Treatment of rats with melatonin (10 mg/kg) significantly elevated the reduced GSH levels while it decreased MDA and PO levels as well as MPO activity.     

Resistance training lowers exercise-induced oxidative stress and homocysteine levels in overweight and obese older adults

Objective: To compare exercise‐induced oxidative stress and levels of homocysteine and cholesterol in normal‐weight and overweight older adults after resistance exercise (RX). Research Methods and Procedures: This interventional study was conducted at a wellness center. Forty‐nine older adults (age range, 60 to 72 years) were stratified by BMI (<25 kg/m² normal weight, ≥25 kg/m² overweight/obese) and then randomly assigned to either a control non‐exercise group or an RX group. The RX group completed a 6‐month training program. Exercise‐induced lipid hydroperoxides (PEROXs) and thiobarbituric‐reactive acid substances, homocysteine, lipoprotein a, cholesterol, and high‐density lipoprotein cholesterol were measured before and after the 6‐month RX program. Results: PEROXs and thiobarbituric‐reactive acid substances were lower in both the overweight/obese and normal‐weight RX‐trained groups compared with control groups (p < 0.05). Homocysteine levels were lower in both overweight/obese and normal‐weight RX groups compared with control groups (p < 0.05). Lipoprotein a, total cholesterol, and high‐density lipoprotein cholesterol were not different in normal‐weight and overweight/obese groups before or after RX. The change in muscle strength was correlated with homocysteine at 6 months (r = ?0.452, p < 0.05), whereas the change in PEROXs was correlated with the change in body fat (r = ?0.329). Discussion: To our knowledge, these data are the first to show that RX reduces exercise‐induced oxidative stress and homocysteine regardless of adiposity, indicating that this protection can be afforded in an older, overweight/obese population as effectively as in healthy older adults. These data suggest that RX may afford some protection against emerging cardiovascular risk factors using a mode of exercise that supports body weight.     

Cadmium induced lipid peroxidation in rat testes and protection by selenium

The main goal of this study was to investigate the role of cadmium in the promotion of lipid peroxidation in the homogenates of rat testes and the effect of selenium on lipid peroxidation in testes of rats after cadmium injection. Treatment of rats with cadmium resulted in a time- and dose-related accumulation of the metal ions in testes. The concentrations of cadmium, copper, zinc, selenium and iron in the tissues were determined by an atomic absorption spectrophotometer and lipid peroxidation in testes was measured by a spectrophotometer. Cadmium produced enhanced lipid peroxidation in testes. These cadmium-induced changes were accompanied by a significant increase of iron and copper, and a decrease of zinc in testes. Concurrent treatment with selenium and cadmium reduced the cadmium-induced alterations in lipid peroxidation and essential metal levels. Data suggest that lipid peroxidation was associated with cadmium toxicity in testes and that the addition of selenium was found to be effective in attenuation of this effect.     

A model of aluminum exposure associated with lipid peroxidation in rat brain

We have developed a rat model to investigate the relationship between aluminum exposure and aluminum accumulation, and with oxidative damage in brain tissues. Intraperitoneal injections of aluminum lactate for 7 wk (the total aluminum dosage per rat was approx 100 mg) significantly increased aluminum levels in the brain. The concentration of lipid peroxidation products (thiobarbituric acid-reactive substances [TBARS]) also increased in the brain following aluminum lactate injections. No significant correlations between the concentrations of aluminum and of TBARS were found in the whole brain. Subcellular analysis revealed that aluminum lactate injections led to a significant increase in the concentration of aluminum in the mitochondrial fraction but had no significant effect on the concentration of peroxides in any subcellular fraction. These results suggest that aluminum accumulation induced by the aluminum lactate administration associates with the acceleration of lipid peroxidation in rat brain. Furthermore, these data indicate that the pro-oxidant effect of aluminum may be indirect and concentration independent. The experimental conditions used here provide an animal model of aluminum accumulation in the brain that should prove useful for further investigations of the mechanisms of aluminum neurotoxicity.     

Medium-chain fatty acids accumulating in MCAD deficiency elicit lipid and protein oxidative damage and decrease non-enzymatic antioxidant defenses in rat brain

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most frequent disorder of fatty acid oxidation with a similar prevalence to that of phenylketonuria. Affected patients present tissue accumulation of the medium-chain fatty acids octanoate (OA), decanoate (DA) and cis-4-decenoate. Clinical presentation is characterized by neurological symptoms, such as convulsions and lethargy that may develop into coma and sudden death. The aim of the present work was to investigate the in vitro effect of OA and DA, the metabolites that predominantly accumulate in MCADD, on oxidative stress parameters in rat cerebral cortex homogenates. It was first verified that both DA and OA significantly increased chemiluminescence and thiobarbituric acid-reactive species levels (lipoperoxidation) and decreased the non-enzymatic antioxidant defenses, measured by the decreased total antioxidant capacity. DA also enhanced carbonyl content and oxidation of sulfhydryl groups (protein damage) and decreased reduced glutathione (GSH) levels. We also verified that DA-induced GSH decrease and sulfhydryl oxidation were not observed when cytosolic preparations (membrane-free supernatants) were used, suggesting a mitochondrial mechanism for these actions. Our present data show that the medium-chain fatty acids DA and OA that most accumulate in MCADD cause oxidative stress in rat brain. It is therefore presumed that this pathomechanism may be involved in the pathophysiology of the neurologic symptoms manifested by patients affected by MCADD.     

Silicon increases boron tolerance and reduces oxidative damage of wheat grown in soil with excess boron

The effect of silicon on the growth, boron concentrations, malondialdehyde (MDA) content, lipoxygenase (LOX) activity, proline (PRO) and H₂O₂ accumulation, and the activities of major antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] and non-enzymatic antioxidants (AA) of wheat grown in soil originally with toxic B concentrations were investigated. Applied of 5.0 and 10.0 mM Si to the B toxic soil significantly increased Si concentration of the wheat and counteracted the deleterious effects of B on shoot growth. The contents of PRO, H₂O₂, MDA, and LOX activity of wheat grown in B toxic soil were significantly reduced by Si treatments. Compared with control plants, the activities of SOD, CAT, APX and content of AA were decreased by applied Si. Based on the present work, it can be concluded that Si alleviates B toxicity of wheat by preventing oxidative membrane damage and also translocation of B from root to shoot and/or soil to plant.     

Antioxidant properties of dehydrozingerone and curcumin in rat brain homogenates

The present study investigates the inhibition of lipid peroxidation by dehydrozingerone and curcumin in rat brain homogenates. Both the test compounds inhibited the formation of conjugated dienes and spontaneous lipid peroxidation. These compounds also inhibited lipid peroxidation induced by ferrous ions, ferric-ascorbate and ferric-ADP-ascorbate. In all these cases, curcumin was more active than dehydrozingerone and dl--tocopherol.     

Region specific increase in the antioxidant enzymes and lipid peroxidation products in the brain of rats exposed to lead

The objective of this study is to determine the effect of lead (pb) on antioxidant enzymes and lipid peroxidation products in different regions of rat brain. Wistar male rats were treated with lead acetate (500 ppm) through drinking water for a period of 8 weeks. Control animals were maintained on sodium acetate. Treated and control rats were sacrificed at intervals of 1st, 4th and 8th week and the whole brains were dissected on ice into four regions namely the cerebellum, the hippocampus, the frontal cortex and the brain stem. Antioxidant enzymes namely catalase and superoxide dismutase in all the four regions of brain were determined. In addition, lipid peroxidation products were also estimated. The results indicated a gradual increase in the activity of antioxidant enzymes in different regions of the brain and this response was time-dependent. However, the increase was more in the cerebellum and the hippocampus compared to other regions of the brain. The lipid peroxidation products also showed a similar trend suggesting increased effect of lead in these two regions of the brain. The data indicated a region-specific oxidative stress in the brain exposed to lead.     

Effect of melatonin on oxidative status of rat brain, liver and kidney tissues under constant light exposure

An enormous amount of data has been published in recent years demonstrating melatonin's defensive role against toxic free radicals. In the present study, we examined the role of melatonin as an antioxidant against the effect of continuous light exposure. Rats were divided into three groups. Control rats (group A) were kept under natural conditions whereas other group of rats (group B and C) were exposed to constant light for inhibition of melatonin secretion by the pineal gland. Group C rats also received melatonin via s.c. injection (1 mg x kg(- 1) body weight x day(- 1)). At the end of experiment, all animals were sacrificied by decapitation, serum and tissue samples were removed for determination of malondialdehyde (MDA), a product of lipid peroxidation, conjugated dienes levels and glutathione peroxidase (GSH-Px) activity levels. It was found that lipid peroxidation was increased in the rats which were exposed to constant light. Melatonin injection caused a decrease in lipid peroxidation, especially in the brain. In addition, melatonin application resulted in increased GSH-Px activity, which has an antioxidant effect. Thus, melatonin is not only a direct scavenger of toxic radicals, but also stimulates the antioxidative enzyme GSH-Px activity to detoxify hydroxyl radical produced by constant light exposure.     

Effects of proteasome inhibitor, MG132, on proteasome activity and oxidative status of rat liver

In vivo effects of N-benzyloxycarbonyl (Cbz)-Leu-Leu-leucinal (MG132) on chymotryptic-like (ChT-L), tryptic-like, and post-glutamyl peptide hydrolytic-like proteasome activities, protein oxidation, lipid peroxidation (LP), glutathione (GSH) level, as well as on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione-reductase) in the rat liver were studied. The possibility of MG132 provoking the formation of free oxygen radicals was also assayed in primary hepatocytes. The following results were obtained: (1) In vivo, MG132 did not change the spontaneous LP, but increased Fe-induced LP and the amount of oxidized proteins; it decreased the GSH level in liver. From the proteasome activities studied in liver cytosol only ChT-L activity was significantly decreased after MG132 administration. Furthermore, MG132 increased antioxidant enzyme activities of SOD, CAT, and GSH-Px. (2) In vitro, MG132 increased free radical oxygen species in hepatocytes; this effect disappeared in the presence of CAT or mannitol. In conclusion, since nowadays proteasome inhibitors are entering into the swing of laboratory and clinical practice, the present data could provide useful information for MG132 action. Consequently, future in vivo experiments with MG132 could highlight the possibility of its use at different pathological conditions.     

Effects of acute manganese chloride exposure on lipid peroxidation and alteration of trace metals in rat brain

Although manganese (Mn) is an essential element, exposure to excessive levels of Mn and its accumulation in the brain can cause neurotoxicity and extrapyramidal syndrome. We have investigated the differences in the accumulated levels of Mn, the degree of lipid peroxidation, and its effects on the levels of trace elements (Fe, Cu, and Zn) in various regions in the brain of rats having undergone acute Mn exposure. The rats in the dose—effect group were injected intraperitoneally (ip) with MnCl₂ (25, 50, or 100 mg MnCl₂/kg) once a day for 24 h. The Mn significantly accumulated (p<0.05) in the frontal cortex, corpus callosum, hippocampus, striatum, hypothalamus medulla, cerebellum, and spinal cord in each case. The rats in the timecourse group were ip injected with MnCl₂ (50 mg MnCl₂/kg) and then monitored 12, 24, 48, and 72 h after exposure. The Mn accumulated in the frontal cortex, corpus callosum, hippocampus, striatum hypothalamus, medulla, cerebellum, and spinal cord after these periods of time, In both the dose—effect and time-course studies, we observed that the concentration of malondialdehyde, an end product of lipid peroxidation, increased significantly in the frontal cortex, hippocampus, striatum, hypothalamus, medulla, and cerebellum. However, no relationship between the concentrations of Mn in the brain and the extent of lipid peroxidation was observed. In addition, we found that there was a significant increase (p<0.05) in the level of Fe in the hippocampus, striatum, hypothalamus, medulla, and cerebellum, but the Cu and Zn levels had not changed significantly. These findings indicated that Mn induces an increase in the iron level, which provides direct evidence for Fe-mediated lipid peroxidation in the rats' brains; these phenomena might play important roles in the mechanisms of Mn-induced neurotoxicology.