Effects of exogenous metallothionein on acute cadmium toxicity in rats

The present study was carried out to evaluate the effect of exogenously administered metallothionein (MT) to rats exposed to high cadmium levels. A total of 72 rats were used in the study. The animals were divided into three groups: controls, Cd administered, and Cd+MT. Cadmium was administered by subcutaneous injection of cadmium(II) chloride at a dose of 3.5 mg/kg for 7 d. In addition to CdCl₂, 30 μmol/kg MT was administered to the second group of rats (group II). Control rats received 0.5 mL physiologic serum via subcutaneous injection. Eight rats from each group were sacrificed on the 1st, 3rd, 5th, and 7th day after administration of the compounds. Liver, kidney, and blood samples were harvested. Levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px), serum ALT, AST, BUN, ALP, creatinine, and urea were measured. MDA levels in group I were observed to increase starting from d 1 compared to group II (p<0.05). Although MDA levels in group II were higher than controls (p<0.05), they were lower, especially in liver and blood, compared to group II. Erythrocyte GSH-Px activity levels were determined to decrease starting from d 1 in both groups (p<0.05). Decreases in GSH-Px activity levels in group II were less than group I. Serum creatinine levels in both groups were increased significantly compared to controls (p<0.05); the increase in group I was higher than group II. Serum ALT, AST, and ALP levels in group I increased to very high levels compared to controls, whereas increases in group II were at moderate levels (p<0.05). Although serum BUN levels were determined to be reduced, there was no significant change among the groups. Serum urea levels in both groups were higher than controls. Based on our results, it is possible to postulate that exogenous MT can act as antioxidant against Cd toxicity and lipid peroxidation.     

Myocardial oxidative stress and toxicity induced by acute ethanol exposure in mice

Alcoholic cardiomyopathy has been known for a long time, but there is little mechanistic insight into this important clinical problem. The present study was undertaken using a mouse model to test the hypothesis that alcohol exposure induces cardiac injury through induction of oxidative stress. Adult female Friend Virius B-type (FVB) mice were treated with ethanol by gavage at a dose of 5 g/kg. Six hours after the treatment, ethanol-induced myocardial injury was observed, as indicated by a significant increase in serum creatine phosphokinase activity, a common biomarker of myocardial injury, and myocardial ultrastructural alterations, predominantly mitochondrial swelling and cristae disarray and reduction in numbers. The myocardial injury was associated with a significant increase in the myocardial lipid peroxidation, determined by measuring thiobarbituric acid reactive substances (TBARS), and a significant increase in protein oxidation as measured by a protein carbonyl content assay. Acute alcohol exposure decreased glutathione (GSH) content in the heart, more so in the mitochondria than in the cytosol. These alcohol-induced myocardial injuries and oxidative stresses were all significantly inhibited by supplementation with N-acetyl-L-cysteine (NAC) prior to alcohol exposure. However, NAC did not affect the rise in blood alcohol concentrations following alcohol exposure. This study thus demonstrates that acute alcohol administration causes myocardial injury through, at least in part, the induction of oxidative stress. A rapid decrease in mitochondrial GSH content may be partially responsible for the observed mitochondrial damage.     

Phosphine-induced oxidative damage in rats: attenuation by melatonin

Phosphine (PH(3)), from hydrolysis of aluminum, magnesium and zinc phosphide, is an insecticide and rodenticide. Earlier observations on PH(3)-poisoned insects, mammals and a mammalian cell line led to the proposed involvement of oxidative damage in the toxic mechanism. This investigation focused on PH(3)-induced oxidative damage in rats and antioxidants as candidate protective agents. Male Wistar rats were treated ip with PH(3) at 2 mg/kg. Thirty min later the brain, liver, and lung were analyzed for glutathione (GSH) levels and lipid peroxidation (as malondialdehyde and 4-hydroxyalkenals) and brain and lung for 8-hydroxydeoxyguanosine (8-OH-dGuo) in DNA. PH(3) caused a significant decrease in GSH concentration and elevation in lipid peroxidation in brain (36-42%), lung (32-38%) and liver (19-25%) and significant increase of 8-OH-dGuo in DNA of brain (70%) and liver (39%). Antioxidants administered ip 30 min before PH(3) were melatonin, vitamin C, and beta-carotene at 10, 30, and 6 mg/kg, respectively. The PH(3)-induced changes were significantly or completely blocked by melatonin while vitamin C and beta-carotene were less effective or inactive. These findings establish that PH(3) induces and melatonin protects against oxidative damage in the brain, lung and liver of rats and suggest the involvement of reactive oxygen species in the genotoxicity of PH(3).     

The oxidative stress: endoplasmic reticulum stress axis in cadmium toxicity

Cadmium preferentially accumulates in the kidney, the major target for cadmium-related toxicity. Several underlying mechanisms are postulated, and reactive oxygen species (ROS) have been considered as crucial mediators for tissue injuries. In addition to oxidative stress, we recently disclosed that endoplasmic reticulum (ER) stress also plays a critical role. Cadmium causes ER stress in vitro and in vivo and mediates induction of apoptosis in target tissues. In this article, we describe a role for ER stress and involvement of particular branches of the unfolded protein response (UPR) in cadmium-triggered tissue injury, especially nephrotoxicity. We also discuss relationship between oxidative stress and ER stress, and involvement of selective ROS in the induction of pro-apoptotic branches of the UPR.     

Specific induction of metallothionein synthesis by mitochondrial oxidative stress.

Metallothionein (MT), a sulfhydryl-rich protein, may be increased by administration of a variety of agents, including metals, cytokines and oxidative stress agents. Mitochondria are a major source of reactive oxygen species, but antioxidant systems against mitochondrial free radicals are not fully understood. In this study, we examined the induction of MT synthesis by administration of mitochondrial-specific reactive oxygen generators such as antimycin A (AA), an electron transfer inhibitor, and 2,4-dinitrophenol (DNP), an uncoupling agent. Subcutaneous administration of AA to mice significantly increased the hepatic MT concentration in a dose- and time-dependent manner. AA slightly elevated glutathione peroxidase (GSHPx) activity, but the rate of increase in GSHPx (1.3-fold) was smaller than that in MT (11.8-fold). Other antioxidants such as catalase, manganese-superoxide dismutase (Mn-SOD), copper/zinc-superoxide dismutase (Cu/Zn-SOD) and GSHPx were not activated by AA treatment. Moreover, administration of DNP induced the synthesis of MT in the liver. Although DNP slightly elevated Mn-SOD activity, the rate of increase in Mn-SOD (1.3-fold) was smaller than that in MT (3.7-fold). Other antioxidants such as catalase, Cu/Zn-SOD and GSHPx were not activated by DNP treatment. These data suggest that MT plays a major role in protection against oxidative stress induced in mitochondria.     

Curcumin ameliorates oxidative stress during nicotine-induced lung toxicity in Wistar rats

Nicotine, a major toxic component of cigarette smoke has been identified as a major risk factor for lung related diseases. In the present study, we evaluated the protective effects of curcumin on lipid peroxidation and antioxidants status in bronchoalveolar lavage fluid (BALF) and bronchoalveolar lavage (BAL) of nicotine treated Wistar rats. Lung toxicity was induced by subcutaneous injection of nicotine at a dose of 2.5 mg/kg body weight (5 days a week, for 22 weeks) and curcumin (80 mg/kg body weight) was given simultaneously by intragastric intubation for 22 weeks. Measurement of biochemical marker enzymes: alkaline phosphatase, lactate dehydrogenase, lipid peroxidation and antioxidants were used to monitor the antiperoxidative effects of curcumin. The increased biochemical marker enzymes as well as lipid peroxides in BALF and BAL of nicotine treated rats was accompanied by a significant decrease in the levels of glutathione, glutathione peroxidase, superoxide dismutase and catalase. Administration of curcumin significantly lowered the biochemical marker enzymes, lipid peroxidation and enhanced the antioxidant status. The results of the present study suggest that curcumin exert its protective effect against nicotine-induced lung toxicity by modulating the biochemical marker enzymes, lipid peroxidation and augmenting antioxidant defense system.     

Intracerebroventricular injection of streptozotocin in rats produces both oxidative stress in the brain and cognitive impairment

Recent reports suggest the involvement of free radicals in the pathophysiology of Alzheimer's disease [AD]. Streptozotocin [STZ] injection in the brain is known to cause cognitive impairment in rats and is likened to sporadic AD in humans. Though STZ is known to cause impairment in glucose and energy metabolism, it is not known whether this is associated with free radical generation. The present study was designed to investigate if the changes in learning and memory by intracerebroventricular administration of STZ are associated with changes in the markers of oxidative stress. Adult male Wistar rats [330-340 g] were injected with intracerebroventricular STZ [3 mg/kg] bilaterally stereotaxically under ketamine anesthesia [70 mg/kg]. The rats were treated with STZ twice, on day 1 and on day 3. The learning and memory behavior was analyzed using passive avoidance paradigms, elevated plus maze and the closed field activity test while the parameters of oxidative stress assessed were malondialdehyde [MDA] and glutathione. The behavioral tests were performed on day 17, 18 and 19. The rats developed significant deficits in learning, memory and cognitive behavior, indicated by deficits in passive avoidance paradigm and elevated plus maze as compared to sham rats. On day 21, the rats were sacrificed under ether anesthesia and the brains were analyzed for biochemical studies. There was a development of oxidative stress in the brain as indicated by significant elevations in malondialdehyde [MDA] levels and decreased levels of glutathione. The study demonstrates that intracerebroventricular STZ may be appropriate model for investigations of antioxidants as potential treatment in Alzheimer's dementia.     

Comparison of Prussian blue and apple-pectin efficacy on 137Cs decorporation in rats

Cesium-137 (137Cs) is one of the most important nuclear fission elements that contaminated the environment after the explosion of the Chernobyl nuclear power plant in Ukraine (1986). The aim of the study was to compare the efficacy of two chelating agent, Prussian blue and apple-pectin on 137cesium decorporation in rats. Rats were intravenously injected with a solution of 137cesium (5 kBq per rat). Chelating agents, Prussian blue or apple-pectin were given immediately after Cs contamination and during 11 days by addition of each chelating agent in drinking water at a concentration corresponding to 400 mg kg(-1) day(-1). Efficiency was evaluated 11 days after contamination (at the end of treatment) through their ability to promote Cs excretion and to reduce the radionuclide accumulation in some retention compartments (blood, liver, kidneys, spleen, skeleton and in the remaining carcass). In these conditions after treatment with Prussian blue a fivefold increase in fecal excretion of Cs was observed and was associated with a reduction in the radionuclide retention in the main organs measured. In contrast, no significant differences were observed between untreated rats and rats treated with apple-pectin. These observations were discussed in terms of ability of pectins to bind Cs and compared to recently published results obtained after treatment of Cs-contaminated children with this chelate.     

Interrelations between oxidative stress and calcineurin in the attenuation of cardiac apoptosis by eugenol

In view of the known involvement of oxidative stress and calcineurin (Ca²⁺-calmodulin dependent protein phosphatase) in β-Adrenergic stimulated events, we examined the influence of eugenol (an antioxidant generally regarded as safe by the Food and Agricultural Organization of the United Nations) on isoproterenol-induced apoptosis in neonatal cardiomyocytes. In comparison to unstimulated controls, cardiomyocytes stimulated with 50 μM isoproterenol for 48 h demonstrated (a) increased intracellular Ca²⁺ levels (b) oxidative stress involving enhanced reactive oxygen species, decreased GSH/GSSG ratio, enhanced lipid peroxidation, increased activities of superoxide dismutase and glutathione peroxidase (c) apoptosis, evidenced by increased number of annexin V/TUNEL positive cells, enhanced membrane fluidity, decreased mitochondrial membrane potential, increased activities of caspase 3 and 9 along with (d) increased calcineurin activity. Pre-incubation of cardiomyocytes with 100 μM eugenol for 1 h, followed by isoproterenol treatment for 48 h, led to reversal of enhanced intracellular Ca²⁺ levels, oxidative stress, calcineurin activation and apoptosis caused by isoproterenol. In addition, similar treatment of cardiomyocytes with 10 nM FK506, a calcineurin inhibitor, could also attenuate isoproterenol-induced apoptosis. These results indicate the beneficial effects of eugenol in preventing cardiomyocyte apoptosis.     

Creatine supplementation reduces oxidative stress biomarkers after acute exercise in rats

The objective of this study was to evaluate the effect of creatine supplementation on muscle and plasma markers of oxidative stress after acute aerobic exercise. A total of 64 Wistar rats were divided into two groups: control group (n = 32) and creatine-supplemented group (n = 32). Creatine supplementation consisted of the addition of 2% creatine monohydrate to the diet. After 28 days, the rats performed an acute moderate aerobic exercise bout (1-h swimming with 4% of total body weight load). The animals were killed before (pre) and at 0, 2 and 6 h (n = 8) after acute exercise. As expected, plasma and total muscle creatine concentrations were significantly higher (P < 0.05) in the creatine-supplemented group compared to control. Acute exercise increased plasma thiobarbituric acid reactive species (TBARS) and total lipid hydroperoxide. The same was observed in the soleus and gastrocnemius muscles. Creatine supplementation decreased these markers in plasma (TBARS: pre 6%, 0 h 25%, 2 h 27% and 6 h 20%; plasma total lipid hydroperoxide: pre 38%, 0 h 24%, 2 h 12% and 6 h 20%, % decrease). Also, acute exercise decreased the GSH/GSSG ratio in soleus muscle, which was prevented by creatine supplementation (soleus: pre 8%, 0 h 29%, 2 h 30% and 6 h 44%, % prevention). The results show that creatine supplementation inhibits increased oxidative stress markers in plasma and muscle induced by acute exercise.     

The effects of 6-hydroxydopamine and oxidative stress on the level of brain metallothionein

Oxidative stress, resulting either from excess generation or reduced scavenging of free radicals, has been proposed to play a role in damaging striatal neurons in Parkinson's disease. Since metallothionein is able to regulate the intracellular redox potential, we have undertaken a group of experiments to see whether or not 6-hydroxydopamine, which generates free radicals and is toxic to dopaminergic neurons, could alter the level of zinc and metallothionein. 6-Hydroxydopamine (8 μg in 4 μl 0.02% ascorbic acid) reduced the level of zinc and metallothionein in the striatum but not other brain regions tested. Dopamine plus selegiline increased the synthesis of metallothionein in Chang cells as judged by enhanced incorporation of [³⁵S]cysteine into metallothionein. The effect of dopamine was selective, in that dopamine could not stimulate the synthesis of metallothionein in neuroblastoma IMR-32 cells, which are devoid of dopaminergic receptors. The effect of dopamine in stimulating the synthesis of metallothionein was similar to that of zinc, known to generate the synthesis of metallothionein, and to that of H₂O₂ and FeS0₄, known to generate free radicals. The results of these experiments provide additional evidence that zinc or zinc metallothionein are altered in conditions where oxidative stress has taken place.     

The role of oxidative stress in developmental and reproductive toxicity of tamoxifen

The antiestrogen tamoxifen (TAM) is widely used as a drug against breast cancer and is currently being tested as a chemopreventive agent. However, a number of studies showed genotoxic and carcinogenic effects of TAM. These effects are thought to be related to oxygen radical overproduction which occurs during TAM metabolic activation. There is no evidence, thus far, on TAM toxicity to embryos and gametes. The present study was designed to elucidate the mechanisms of TAM-induced developmental, reproductive and cytogenetic toxicity towards sea urchin (SU) embryos with regard to the possibility of TAM-initiated oxidative stress. Embryo cultures from SU were subjected to long-term (throughout embryogenesis) or short-term (two hours) incubation with TAM at concentrations from 10(-8) to 10(-5) M. The experiments on TAM-induced toxicity to gametes were carried out with SU sperm, or unfertilized eggs, suspended in TAM (10(-8) to 10(-6) M). To assess the effects of TAM to embryos or to gametes, developmental defects, embryonic mortality, fertilization success, and cytogenetic abnormalities were scored. Oxidative damage to DNA and lipids was detected by measurements of 8OHdG levels and lipid peroxidation, respectively. Reactive oxygen species (ROS) production by eggs and embryos was recorded by luminol-dependent chemiluminescence (LDCL) and cytochrome c reduction methods. The changes in activities of SU superoxide dismutase (SOD) and catalase were also evaluated. TAM exerted: a) early embryonic mortality to exposed embryos and to the offspring of exposed eggs; b) developmental defects to the offspring of exposed sperm; c) decrease in sperm fertilization success, and d) cytogenetic effects in the offspring of exposed sperm or eggs. These morphological effects corresponded to the state of oxidative stress in SU embryos (increased oxidative damage to DNA and lipids and induction of antioxidant enzymes). Since TAM did increase significantly ROS production by embryos, it is suggested that TAM may be metabolically activated by SU embryonic oxidases and peroxidases, which in turn could be induced by TAM. The present study provides further support to the utilization of the SU system as a useful model to help elucidate mechanisms of chemical teratogenesis and carcinogenesis.     

Mechanism of nitrofurantoin toxicity and oxidative stress in mitochondria

5-Nitrofuran derivatives change the inner mitochondrial membrane permeability as indicated by the transmembrane potential, the rate of spontaneous K+ efflux and the basal respiratory rate: (a) at low concentrations nitrofurantoin prevents the increase of inner membrane permeability due to hydroperoxides or to diamide; (b) at higher concentrations or after longer times of incubation, nitrofurantoin enhances the membrane damage due to hydroperoxides or to diamide; the damage due Ca2+ plus Pi is enhanced by nitrofurantoin at all concentrations; (c) higher nitrofurantoin concentrations cause membrane damage independently of the presence of hydroperoxides or of diamide. The effect of nitrofurantoin is cancelled by the addition of free-radical scavengers. The above effects of nitrofurantoin are compatible with the observations of Mason and colleagues that nitrofurantoin is reduced by a NADPH nitroreductase to a nitro anion radical which can then undergo subsequent reactions, among which are (a) initiation of a free-radical reaction chain and (b) reduction of hydroperoxides and diamide.     

A protective effect of curcumin on cardiovascular oxidative stress indicators in systemic inflammation induced by lipopolysaccharide in rats

ObjectiveInflammation has been considered as an important factor in cardiovascular diseases (CVD). Curcumin has been well known for its anti-inflammatory effects. In current research, protective effect of curcumin on cardiovascular oxidative stress indicators in systemic inflammation induced by lipopolysaccharide (LPS) was investigated in rats.Material and methodsThe animals were divided into five groups and received the treatments during two weeks [1]: Control in which vehicle was administered instead of curcumin and saline was injected instead of LPS [2], LPS group in which vehicle of curcumin plus LPS (1 mg/kg) was administered [3-5], curcumin groups in them three doses of curcumin (5, 10 and 15 mg/kg) before LPS were administered.ResultsAdministration of LPS was followed by an inflammation status presented by an increased level of white blood cells (WBC) (p < 0.001). An oxidative stress status was also occurred after LPS injection which was presented by an increased level of malondialdehyde (MDA) while, a decrease in thiols, superoxide dismutase (SOD) and catalase(CAT) in all heart, aorta and serum (p < 0.001). The results also showed that curcumin decreased WBC (doses: 10 and 15 mg/kg) (p < 0.001) accompanying with a decrease in MDA (P < 0.01 and P < 0.001). Curcumin also improved the thiols and the activities of SOD and catalase (P < 0.05, P < 0.01 and P < 0.001).ConclusionBased on our findings, curcumin can ameliorates oxidative stress and inflammation induced by LPS in rats to protect the cardiovascular system.     

Effects of melatonin on oxidative stress and spatial memory impairment induced by acute ethanol treatment in rats

Melatonin has recently been suggested as an antioxidant that may protect neurons from oxidative stress. Acute ethanol administration produces both lipid peroxidation as an indicator of oxidative stress in the brain and impairs water-maze performance in spatial learning and memory tasks. The present study investigated the effect of melatonin against ethanol-induced oxidative stress and spatial memory impairment. The Morris water maze was used to evaluate the cognitive functions of rats. Thiobarbituric acid reactive substances (TBARS), which are the indicators of lipid peroxidation, and the activities of antioxidative enzymes (glutathione peroxidase and superoxide dismutase) were measured in the rat hippocampus and prefrontal cortex which form interconnected neural circuits for spatial memory. Acute administration of ethanol significantly increased TBARS levels in the hippocampus. Combined melatonin-ethanol treatment caused a significant increase in glutathione peroxidase activities and a significant decrease of TBARS in the rat hippocampus. In the prefrontal cortex, there was only a significant decrease of TBARS levels in the combined melatonin-ethanol receiving group as compared to the ethanol-treated group. Melatonin did not affect the impairment of spatial memory due to acute ethanol exposure, but melatonin alone had a positive effect on water maze performances. Our study demonstrated that melatonin decreased ethanol-induced lipid peroxidation and increased glutathione peroxidase activity in the rat hippocampus.     

Attenuation of the acute adriamycin-induced cardiac and hepatic oxidative toxicity by N-(2-mercaptopropionyl) glycine in rats

The protective effect of the synthetic aminothiol, N-(2-mercaptopropionyl) glycine (MPG) on adriamycin (ADR) induced acute cardiac and hepatic oxidative toxicity was evaluated in rats. ADR toxicity, induced by a single intraperitoneal injection (15 mg/kg), was indicated by an elevation in the level of serum glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), creatine kinase isoenzyme (CK-MB), and lactic dehydrogenase (LDH). ADR produced significant elevation in thiobarbituric acid reactive substances (TBARS), indicating lipid peroxidation, and significantly inhibited the activity of superoxide dismutase (SOD) in heart and liver tissues. In contrast, a single injection of ADR did not affect the cardiac or hepatic glutathione (GSH) content and cardiac catalase (CAT) activity but elevated hepatic CAT. Pretreatment with MPG, (2.5 mg/kg) intragastrically, significantly reduced TBARS concentration in both heart and liver and ameliorated the inhibition of cardiac and hepatic SOD activity. In addition, MPG significantly decreased the serum level of GOT, GPT, CK-MB, and LDH of ADR treated rats. These results suggest that MPG exhibited antioxidative potentials that may protect heart and liver against ADR-induced acute oxidative toxicity. This protective effect might be mediated, at least in part, by the high redox potential of sulfhydryl groups that limit the activity of free radicals generated by ADR.     

Reduction of diabetes-induced oxidative stress by phosphodiesterase inhibitors in rats

Increased oxidative stress has been suggested to be involved in the pathogenesis and progression of diabetic tissue damage. The aim of this study was to investigate the effect of different phosphodiesterase inhibitors on lipid peroxidation and total antioxidant capacity (TAC) of plasma in streptozotocin-induced diabetic rats (Rattus norvegicus). Rats became diabetic by a single administration of streptozotocin (STZ, 45 mg/kg). The effects of 15-days treatment by milrinone, sildenafil, and theophylline as cyclic-AMP and -GMP phosphodiesterase inhibitors (PDEIs) on diabetes-induced oxidative stress were studied. The levels of glucose, malonedialdehyde (MDA) the by product of lipid peroxides, and TAC (FRAP test) were estimated in plasma of control and experimental groups of rats. A significant increase in the levels of plasma glucose, and MDA and a concomitant decrease in the levels of TAC were observed in diabetic rats. These alterations were reverted back to near normal level after the treatment with PDEIs. Treatment of diabetic rats by PDEIs reduced MDA levels and increased TAC in the order of milrinone>sildenafil>theophylline. In conclusion, the present investigation show that PDIS possesses antioxidant activities, which may be attributed to their enhancing effect on cellular cyclic nucleotides contributing to the protection against oxidative stress in streptozotocin-induced diabetes. Exact mechanism of protective actions of cAMP- and cGMP-phosphodiesterase remains to be elucidated by further studies. This finding may suggest a place for PDEIs in maintaining health in diabetes.     

Sex differences in oxidative stress induced by benzene in rats

Role of sex differences on oxidative stress induced by benzene has been studied in liver, kidney and lungs of rat. It was observed that benzene administration enhanced lipid peroxidation in liver, kidney and lungs of rat, nevertheless, significant variations were recorded in male and female rats. Decrease of GSH and CYTP(450)2E1 was higher in female rats than male rats except lungs. The results suggest that oxidative stress induced by benzene is higher in female rats.