Cadmium-induced lipid peroxidation and the antioxidant system in rat erythrocytes: the role of antioxidants

Stress responses in captive Crocodylus moreletii associated with metal exposure

Environmental pollution by metals has repercussions on wildlife health. It is known that some metals can have an influence on the neuroendocrine stress response, and at the same time, metals have pro-oxidant effects that can overwhelm the antioxidant system and cause oxidative stress. This study evaluates the association of metals with neuroendocrine stress activity and biomarkers of oxidative stress in 42 captive female Morelet's crocodiles (Crocodylus moreletii). We measured five metals of ecotoxicological importance (Hg, Cd, Pb, Cu and Zn), and three biomarkers of the oxidative stress response in the liver: glutathione (GSH) and glutathione disulfide (GSSG) as markers for antioxidant system and thiobarbituric acid reactive substances (TBARS) for oxidative damage. We also measured one biomarker of the neuroendocrine response to stress: corticosterone (B) in blood plasma. The mean ± SD concentrations of metals in the liver expressed in μg/g (dw) were: Cd: 0.004 ± 0.003, Hg: 0.014 ± 0.019, Cu: 0.017 ± 0.013, Zn: 0.043 ± 0.035, Pb: 0.16 ± 0.256. The mean ± SD of GSH was 0.42 ± 0.35 nmol/mg protein, the mean ± SD of GSSG was 0.24 ± 0.20 nmol/mg protein, the mean ± SD concentrations of TBARS were 0.36 ± 0.21 nmol/mg protein, and the mean ± SD of B was 393.57 ± 405.14 pg/mL. Hg presented a significant negative relationship with corticosterone. Cd had a negative relationship with both GSH and GSSG; meanwhile, Zn showed a negative relationship with TBARS levels, could be a protective element against hepatic oxidative damage. Finally, B had negative relationship with oxidative damage. The connection found between Hg and the neuroendocrine stress response, as well as the correlations of Cd and Zn with oxidative damage and antioxidant activity should be studied further, given their toxicological importance and implications for the conservation of C. moreletii and other crocodilians.

Environmental Co-Exposure to Potassium Perchlorate and Cd Caused Toxicity and Thyroid Endocrine Disruption in Zebrafish Embryos and Larvae (Danio rerio)

The increasing pollution of aquatic habitats with anthropogenic compounds has led to various test strategies to detect hazardous chemicals. However, information on the effects of pollutants on the thyroid system in fish, which is essential for growth, development, and parts of reproduction, is still scarce. Modified early life-stage tests were carried out with zebrafish exposed to the known thyroid inhibitor potassium perchlorate (0.1, 1, 1.5, 2, 2.5, and 5 mM) to identify adverse effects on embryo development. The endogenous antioxidant defense mechanism is one of the key functions of the thyroid gland; in this regard, we examined the co-exposure to potassium perchlorate (KClO₄), which could disrupt thyroid function, with cadmium (Cd), a known pro-oxidant compound. Zebrafish embryos were exposed to control KClO₄ 1 mM and Cd 0.5 μM for 96 h after fertilization (hpf) individually and in combination. The morphological alteration, body length, and messenger RNA (mRNA) expression related to thyroid function and oxidative stress, thyroid hormone levels, and malondialdehyde were measured. Significant down-regulation of mRNAs related to thyroid function (thyroid hormone receptor-alpha (THRα), thyroid hormone receptor-beta (THRβ), haematopoietically expressed homeobox (hhex)) and decreased thyroxin (T4) levels were observed after co-exposure to KClO₄ and Cd, but this was not observed in the individually treated groups. These results suggest that co-exposure to KClO₄ and Cd could affect antioxidant defense mechanisms and potentially normally increase Cd toxicity on mRNA expression, altering the thyroid functions important in zebrafish embryonic developmental stages.

Neuroprotective effect of grape seed extract against cadmium toxicity in male albino rats

Cadmium toxicity can disturb brain chemistry leading to depression, anxiety, and weakened immunity. Cadmium disturbs the neurotransmitter dopamine, resulting in low energy, lack of motivation, and depression, which are predisposing factors for violence. The purpose of this study was to evaluate the ameliorative effect of grape seed extract (GSE) on the brain of 40 male albino rats after exposure to cadmium chloride (Cd) toxicity. The rats were separated into either the control group, the Cd group, the GSE group, or the GSE and Cd mixture (treated) group. The cerebrum showed evidence of degeneration of some nerve fibers and cells. Fibrosis, vacuolations, and congestion in the blood vessels were demonstrated. Satelletosis was located in the capsular cells. Immunohistochemical expression of Bax was strongly positive in the Cd group and decreased in the treated group. These histopathological changes were decreased in the brain tissue of the treated group, but a few blood vessels still had evidence of congestion. Cadmium administration increased the level of MDA and decreased MAO-A, acetylcholinesterase, and glutathione reductase (GR), while the treatment with GSE affected the alterations in these parameters. In addition, cadmium downregulated the mRNA expression levels of GST and GPx, while GSE treatment normalized the transcript levels. The expression of both dopamine and 5-hydroxytryptamine transporter was downregulated in the rats administered cadmium and the addition of GSE normalized the expression of these aggression associated genes.

Autophagy in Neurodegenerative Diseases and Metal Neurotoxicity

Autophagy generally refers to cell catabolic and recycling process in which cytoplasmic components are delivered to lysosomes for degradation. During the last two decades, autophagy research has experienced a recent boom because of a newfound connection between this process and many human diseases. Autophagy plays a significant role in maintaining cellular homeostasis and protects cells from varying insults, including misfolded and aggregated proteins and damaged organelles, which is particularly crucial in neuronal survival. Mounting evidence has implicated autophagic dysfunction in the pathogenesis of several major neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease and Huntington's disease, where deficient elimination of abnormal and toxic protein aggregates promotes cellular stress, failure and death. In addition, autophagy has also been found to affect neurotoxicity induced by exposure to essential metals, such as manganese, copper, and iron, and other heavy metals, such as cadmium, lead, and methylmercury. This review examines current literature on the role of autophagy in the mechanisms of disease pathogenesis amongst common neurodegenerative disorders and of metal-induced neurotoxicity.

Protective effects of selenium on cadmium-induced brain damage in chickens

Selenium (Se) is an important dietary micronutrient with antioxidative roles. Cadmium (Cd), a ubiquitous environmental pollutant, is known to cause brain lesion in rats and humans. However, little is reported about the deleterious effects of subchronic Cd exposure on the brain of poultry and the protective roles on the brain by Se against Cd. The aim of this study was to investigate the protective effects of Se on Cd-induced brain damage in chickens. One hundred twenty 100-day-old chickens were randomly assigned to four groups and were fed a basal diet, or Se (as 10 mg Na2SeO3/kg dry weight of feed), Cd (as 150 mg CdCl2/kg dry weight of feed), or Cd + Se in their basic diets for 60 days. Then, concentrations of Cd and Se, production of nitric oxide (NO), messenger RNA (mRNA) level and activity of inducible NO synthase (iNOS), level of oxidative stress, and histological and ultrastructural changes of the cerebrum and cerebellum were examined. The results showed that Cd exposure significantly increased Cd accumulation, NO production, iNOS activities, iNOS mRNA level, and MDA content in the cerebrum and cerebellum. Cd treatment obviously decreased Se content and antioxidase activities and caused histopathological changes in the cerebrum and cerebellum. Se supplementation during dietary Cd obviously reduced Cd accumulation, NO production, mRNA level and activity of iNOS, oxidative stress, and histopathological damage in the cerebrum and cerebellum of chickens. It indicated that Se ameliorates Cd-induced brain damage in chickens by regulating iNOS-NO system changes, and oxidative stress induced by Cd and Se can serve as a potential therapeutic for Cd-induced brain lesion of chickens.

Protective role of catechin and quercetin in sodium benzoate-induced lipid peroxidation and the antioxidant system in human erythrocytes in vitro

The aim of this study was to evaluate the protective effect of catechin and quercetin in sodium benzoate- (SB-) induced oxidative stress in human erythrocytes in vitro. For this, the effects of SB (6.25, 12.5, 25, 50, and 100 μg/mL), catechin (10 μM), and quercetin (10 μM) on lipid peroxidation (LPO) and the activities of SOD, CAT, GPx, and GST were studied. Significantly higher LPO and lower activities of antioxidant enzymes were observed with the increasing concentrations of SB. Catechin or quercetin protected the erythrocytes against SB-induced toxicity only at low concentrations of SB. The presence of catechin or quercetin at 10 μM have no effect on SB-induced toxicity at high concentrations of SB (50 and 100 μg/mL). In conclusion, SB may cause oxidative stress as food additive in human erythrocytes in vitro. So, it appears that our findings provide evidence for the protection of erythrocytes from SB that could be considered for further studies.

Histopathology and cytotoxicity as biomarkers in treated rats with cadmium and some therapeutic agents

The present study aimed to investigate the protective role of ascorbic acid (vitamin C) and zinc (Zn) against cadmium (Cd) induced histopathological changes in tissues of liver, kidney, lung and testis of rats as well as chromosomal aberrations. For this purpose, 60 male albino rats were divided into six groups; each group contained 10 animals. The first group served as control and was given only distilled water. The second and third groups received distilled water supplemented with 2 g ascorbic acid/l and 500 mg Zn/l, respectively. The fourth group received a daily oral dose containing 3 mg Cd/kg b.w. (1/30 LD50). The fifth group received Cd + ascorbic acid (3 mg Cd/kg b.w. + 2 g ascorbic acid/l), while the sixth group received Cd + Zn (3 mg Cd/kg b.w. +500 mg Zn/l). The treatment in all groups lasted for 90 consecutive days. Rats exposed to cadmium showed severe histopathological changes in the liver, kidney, lung and testicular tissues as well as chromosomal aberrations such as: break, ring, centromeric separation and polyploidy. Co-treatment with zinc partially improved the histopathological changes and chromosomal aberrations while co-treatment with vitamin C exhibited a more protective role and markedly reduced tissues damage induced by Cd.

Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review

Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.

Calcium signaling is involved in cadmium-induced neuronal apoptosis via induction of reactive oxygen species and activation of MAPK/mTOR network

Cadmium (Cd), a toxic environmental contaminant, induces oxidative stress, leading to neurodegenerative disorders. Recently we have demonstrated that Cd induces neuronal apoptosis in part by activation of the mitogen-activated protein kineses (MAPK) and mammalian target of rapamycin (mTOR) pathways. However, the underlying mechanism remains elusive. Here we show that Cd elevated intracellular calcium ion ([Ca²+](i)) level in PC12, SH-SY5Y cells and primary murine neurons. BAPTA/AM, an intracellular Ca²+ chelator, abolished Cd-induced [Ca²+](i) elevation, and blocked Cd activation of MAKPs including extracellular signal-regulated kinase 1/2 (Erk1/2), c-Jun N-terminal kinase (JNK) and p38, and mTOR-mediated signaling pathways, as well as cell death. Pretreatment with the extracellular Ca²+ chelator EGTA also prevented Cd-induced [Ca²+](i) elevation, MAPK/mTOR activation, as well as cell death, suggesting that Cd-induced extracellular Ca²+ influx plays a critical role in contributing to neuronal apoptosis. In addition, calmodulin (CaM) antagonist trifluoperazine (TFP) or silencing CaM attenuated the effects of Cd on MAPK/mTOR activation and cell death. Furthermore, Cd-induced [Ca²+](i) elevation or CaM activation resulted in induction of reactive oxygen species (ROS). Pretreatment with BAPTA/AM, EGTA or TFP attenuated Cd-induced ROS and cleavage of caspase-3 in the neuronal cells. Our findings indicate that Cd elevates [Ca²+](i), which induces ROS and activates MAPK and mTOR pathways, leading to neuronal apoptosis. The results suggest that regulation of Cd-disrupted [Ca²+](i) homeostasis may be a new strategy for prevention of Cd-induced neurodegenerative diseases.

Perfluorooctane sulfonic acid exposure increases cadmium toxicity in early life stage of zebrafish, Danio rerio

Exposure to perfluorooctane sulfonic acid (PFOS) is known to induce thyroid-related adverse effects in aquatic organisms. Because an antioxidant defense mechanism is one of the key functions of the thyroid gland, we examined whether preexposure to PFOS could disrupt thyroid function and enhance cadmium (Cd)-induced oxidative stress in fish. Zebrafish embryos were exposed to control or 0.5 mg/L PFOS for 7 d after fertilization and subsequently exposed to 0.038 mg/L of Cd(2+) or a mixture of the PFOS and Cd for an additional 3 d until 10 d postfertilization (dpf). Survival rates, body length, messenger RNA (mRNA) expressions related to thyroid function and oxidative stress, the levels of thyroid hormones, and malondialdehyde and antioxidant enzyme activities were measured. Significant down-regulation of mRNAs related to thyroid function (thyroid hormone receptor-alpha [THRα], thyroid hormone receptor-beta [THRβ], hematopoietically expressed homeobox [hhex], and paired box gene 8 [pax8]) and decrease of throxine (T4) levels were observed in the PFOS preexposure group, suggesting that PFOS preexposure would influence the performance of thyroid gland in the later stages of life. Certain genes relative to oxidative stress, such as superoxide dismutase 1 (sod1) and heat shock protein 70 (hsp70), in the PFOS preexposure group were significantly up-regulated when the larvae were subsequently exposed to Cd or to the mixture of PFOS and Cd. Glutathione S-transferase activity and malondialdehyde levels of the PFOS-preexposed group were increased significantly by Cd exposure. Significant decrease of the survival rates and body length of fish were observed at 10 dpf among the larvae that were previously exposed to PFOS. These results suggest that preexposure to PFOS could affect antioxidant defense mechanisms and potentially increase the toxicity of Cd on mRNA expression and enzyme activity level responses, as well as on survival or growth of individuals.

Effects of cadmium on some haematological and biochemical characteristics of Oreochromis niloticus (Linnaeus, 1758) dietary supplemented with tomato paste and vitamin E

The present study investigates the potential protective effects of tomato paste (9 mg/kg-lycopene) in comparison with vitamin E (50 mg/kg) against the impacts of cadmium (Cd) toxicity (4.64 mg/l: ¼ of 96 h LC50) on fishes Cd exposed for 15 and 30 days. Cd impacts were evaluated in terms of biological, haematological and biochemical characteristics. Cd significantly induced free radicals in serum and liver. The activities of aspartate aminotransferase and alanine aminotransferase in serum were significantly increased due to Cd. Treatment with Cd caused a significant increase in Lipid peroxidation and DNA fragmentation in liver tissue and serum glucose and total lipid. On the other hand, Cd significantly led to decline in serum total protein, blood haemoglobin, red blood cell count, haematocrit value, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Dietary supplementation with vitamin E and/or tomato paste to Cd-exposed fish declined significantly the increased lipid peroxidation and DNA fragmentation in liver tissue and the increased aspartate aminotransferase, alanine aminotransferase, glucose and total lipid in serum to the normal condition. This supplementation also significantly increased the declined serum total protein, blood haemoglobin, red blood cell count, haematocrit value, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration to the normal state. Cd impacts and tomato paste/or vitamin E supplementations did not reflected on the condition factor of the fish. These findings demonstrated the beneficial diet supplementation of tomato paste phytonutrients and vitamin E in counteracting the harmful effects of Cd on the characters investigated.

Cadmium ions promote monocytic differentiation of human leukemia HL-60 cells treated with 1α,25-dihydroxyvitamin D3

Cadmium exposure has multiple effects on the immune system. These can be stimulating, leading to improved clearance of infections, or inhibiting, increasing susceptibility toward infectious agents. Onein vivoobservation in cadmium-exposed individuals is increased monocyte numbers. Therefore, the objective of this study is to investigate the impact of cadmium on monocyte differentiation in the HL-60 model cell line. Administered alone, cadmium had no effect. However, cadmium amplified the expression of monocyte surface markers CD11b and CD14 when differentiation was induced by 1α,25-dihydroxyvitamin D3 (VD3). Furthermore, differentiation with VD3 in the presence of cadmium augmented key monocyte functions: the capacities to perform phagocytosis and generate an oxidative burst. One important signaling pathway required for monocyte differentiation involves extracellular signal-regulated kinase (ERK)1/2. Notably, cadmium induced ERK1/2 phosphorylation in HL-60 cells. Furthermore, U0126, which inhibits ERK1/2 phosphorylation by upstream MAPK/ERK kinases (MEK)1/2, reduced VD3-mediated differentiation and abrogated the effects of cadmium. In conclusion, cadmium can augment monocytic differentiation by activating ERK1/2 signaling, leading to increased generation of functional monocytes. These increased monocyte numbers could contribute to the impact of cadmium on the immune system owing to their role in the production of pro-inflammatory cytokines and activation of T-cells by antigen presentation.

Effect of 3-(1H-Pyrrol-2-yl)-1H-indazole on the antioxidant status of rats

The influence of injection periods of 3-(1H-pyrrol-2-yl)-1H-indazole regarding vitamins A, E, C, selenium (Se), malondialdehyde (MDA) levels, and glutathione peroxidase (GSH-Px) activity in rats has been investigated. The substance was given by subcutaneous injection at 20 mg/kg every other day for a total of 15 injections. At the end of the treatment, Se levels in serum were determined by fluorimetry, and those of vitamins A, E, C, and malondialdehyde in serum, liver, and kidney were determined by high-performance liquid chromatography. GSH-Px activities in erythrocytes were determined spectrophotometrically. Vitamins A, E, C, and Se levels were generally lower than in the controls, while GSH-Px activity at the third injection period was maximally increased, with the activities after the other injection periods being higher than in the control group. In addition, vitamins A, E, and C levels were generally lower than the control groups, while serum, liver, and kidney MDA levels gradually increased depending on injection periods. On the other hand, GSH-Px activity was higher than in the control group. Thus, the results show that while vitamins A, E, C, and Se levels decreased, MDA levels and GSH-Px activities increased after administration of 3-(1H-pyrrol-2-yl)-1H-indazole to the rats. These findings might be related to the increased amount of free radicals caused by 3-(1H-pyrrol-2-yl)-1H-indazole injection.

Cerium caused life span shortening and oxidative stress resistance in Drosophila melanogaster

To investigate the effects of the rare earth element cerium (Ce) on the life span and biomarkers of oxidative stress in the fruit fly (Drosophila melanogaster). Fruit flies were fed on media with different dose of ceric sulfate (1, 4, 16, 64, 256, 1024mg/L, corresponding to cerium concentrations of 0.45, 1.65, 6.91, 26.3, 104, and 429microg/g culture medium). Mean life span, maximum life span, and fertility were calculated. There was a significant decrease in mean life span and maximum life span with increasing doses of cerium. At some concentrations, there was a decrease in reproductive output, especially concentrations >6.91microg/g. We also measured superoxide dismutase (SOD) activity, catalase (CAT) activity, and lipid peroxidation product levels (malondialdehyde (MDA) content). Cerium caused a significant increase in MDA content and decrease in SOD and CAT activities at concentrations >6.91microg/g. These results suggest that cerium may result in oxidative toxicity to D. melanogaster.

Determination of acute and chronic effects of cadmium on the cardiovascular system of rats

In this study, the systemic hemodynamics induced by acute and chronic cadmium (Cd+2) intoxication in the cardiovascular system of rats using thoracic electrical bioimpedance were examined and the acute and chronic effects of Cd+2 intoxication on the activities of antioxidant enzymes and malondialdehyde (MDA) were compared. Also, in this study, ultrastructural changes in the heart and aorta of rats were evaluated. Thirty-eight male Wistar albino rats were randomly divided into control, acute, and chronic groups. Chronic group was administered by oral gavage an aqueous solution of CdCl2 for 60 days, at dose of 15 mg Cd+2/kg/day. Acute group was administered by oral gavage an aqueous solution of CdCl2 with a single dose of 15 mg Cd+2/kg. Cadmium increased the stroke volume and cardiac output of rats in the chronic group, but did not change the heart rate significantly. Antioxidant enzymes activities and MDA level significantly increased in the chronic group. In ultrastructural examination, there were widespread degenerative changes in heart muscle cells of the chronic group but endothelial cells and smooth muscle cells in the aorta tissue samples had normal morphological features in all groups. All of the findings indicate that Cd+2 toxication can cause deformation in heart muscle cells due to an increase in free radicals and lipid peroxidation. Also, this study has confirmed that a long-term-Cd+2 exposure increased stroke volume (SV) and cardiac output (CO), but did not change the heart rate (HR).

Protective effects of selenium, zinc, or their combination on cadmium-induced oxidative stress in rat kidney

The present study was conducted to investigate whether the combined treatment with Se and Zn offers more beneficial effects than that provided by either of them alone in reversing Cd-induced oxidative stress in the kidney of rat. For this purpose, 30 adult male Wistar albino rats, equally divided into control and four treated groups, received either 200 ppm Cd (as CdCl(2)), 200 ppm Cd + 500 ppm Zn (as ZnCl(2)), 200 ppm Cd + 0.1 ppm Se (as Na(2)SeO(3)), or 200 ppm Cd + 500 ppm Zn + 0.1 ppm Se in their drinking water for 35 days. The results showed that Cd treatment decreased significantly the catalase (CAT) and glutathione peroxidase (GSH-Px) activities, whereas the superoxide dismutase (SOD) activity and the renal levels of lipid peroxidation (as malondialdehyde, MDA) were increased compared to control rats. The treatment of Cd-exposed rats with Se alone had no significant effect on the Cd-induced increase in the MDA concentrations but increased significantly the CAT activities and reversed Cd-induced increase in SOD activity. It also partially prevented Cd-induced decrease in GSH-Px activity. The treatment of Cd-exposed animals with Zn alone increased significantly the CAT activity and partially protected against Cd-induced increase in the MDA concentrations, whereas it had no significant effect on the Cd-induced increase in SOD activity and decrease in GSH-Px activity. The combined treatment of Cd-exposed animals with Se and Zn was more effective than that with either of them alone in reversing Cd-induced decrease in CAT and GSH-Px activities and Cd-induced increase in MDA concentrations. Results demonstrated beneficial effects of combined Se and Zn treatment in Cd-induced oxidative stress in kidney and suggest that Se and Zn can have a synergistic role against Cd toxicity.

Cadmium-induced neurological disorders: prophylactic role of taurine

The present study was conducted to investigate whether the conditionally essential amino acid taurine could play any protective role against the potent neurotoxin cadmium (Cd)-induced oxidative impairment in mice brain. Cd administration in the form of CdCl(2 )(at a dose of 4 mg kg(-1) body weight for 3 days, orally) increased the intracellular accumulation of metallic Cd, reactive oxygen species and super oxide radicals. The toxin also augmented the extent of lipid peroxidation, protein carbonylation and the levels of glutathione disulfide. Activities of the antioxidant enzymes and the levels of reduced glutathione as well as total thiols have been significantly decreased due to Cd exposure. In addition, the toxin also caused significant DNA degradation (as evidenced from DNA smearing and diphenylamine reaction). Oral administration of taurine (at a dose of 100 mg kg(-1) body weight for 5 days) was found to be very effective in the prevention of Cd-induced oxidative impairment in the brain tissue of experimental mice. In addition, taurine treatment could also prevent the reduction in the in vivo antioxidant power linearly up to a dose of 100 mg kg(-1) body weight. The preventive role of taurine against Cd-induced cerebral oxidative damage was supported by the observation under scanning electron microscope as well as histological examination of brain segments. To validate the experimental results, a well-known water soluble antioxidant, vitamin C, was used as the positive control in the study. In all, the results suggest that taurine plays a beneficial role against Cd-induced cerebral oxidative stress.

Cadmium activates the mitogen-activated protein kinase (MAPK) pathway via induction of reactive oxygen species and inhibition of protein phosphatases 2A and 5

Cadmium (Cd), a highly toxic environmental pollutant, induces neurodegenerative diseases. Recently we have demonstrated that Cd may induce neuronal apoptosis in part through activation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (Erk1/2) pathways. However, the underlying mechanism remains enigmatic. Here we show that Cd induced generation of reactive oxygen species (ROS), leading to apoptosis of PC12 and SH-SY5Y cells. Pretreatment with N-acetyl-L-cysteine (NAC) scavenged Cd-induced ROS, and prevented cell death, suggesting that Cd-induced apoptosis is attributed to its induction of ROS. Furthermore, we found that Cd-induced ROS inhibited serine/threonine protein phosphatases 2A (PP2A) and 5 (PP5), leading to activation of Erk1/2 and JNK, which was abrogated by NAC. Overexpression of PP2A or PP5 partially prevented Cd-induced activation of Erk1/2 and JNK, as well as cell death. Cd-induced ROS was also linked to the activation of caspase-3. Pretreatment with inhibitors of JNK (SP600125) and Erk1/2 (U0126) partially blocked Cd-induced cleavage of caspase-3 and prevented cell death. However, zVAD-fmk, a pan caspase inhibitor, only partially prevented Cd-induced apoptosis. The results indicate that Cd induction of ROS inhibits PP2A and PP5, leading to activation of JNK and Erk1/2 pathways, and consequently resulting in caspase-dependent and -independent apoptosis of neuronal cells. The findings strongly suggest that the inhibitors of JNK, Erk1/2, or antioxidants may be exploited for prevention of Cd-induced neurodegenerative diseases.

Ebselen attenuates cadmium-induced testicular damage in mice

This study was designed to examine if ebselen, an organoselenium compound with antioxidant and glutathione peroxidase-mimetic properties, attenuates testicular injury caused by intraperitoneal administration of CdCl(2). A number of toxicological parameters were evaluated in the testes of mice, such as delta-aminolevulinic acid dehydratase (delta-ALA-D) activity, lipid peroxidation, ascorbic acid levels and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Ebselen attenuated lipid peroxidation levels altered by CdCl(2). delta-ALA-D activity inhibited by the highest dose of CdCl(2) was attenuated by ebselen. A significant negative correlation between lipid peroxidation levels and delta-ALA-D activity was observed. Ebselen restored ascorbic acid levels reduced by CdCl(2). A significant negative correlation between ascorbic acid levels and delta-ALA-D activity reinforces the idea that ebselen attenuated the damage induced by CdCl(2) via its antioxidant property. The significant correlation between ALT and delta-ALA-D activity supports the assumption that ebselen prevented damage caused by CdCl(2). The results show that ebselen attenuated oxidative stress, a process important for CdCl(2) toxicity.

Investigation of oxidative status of the 2-furan-2-yl-1H-benzimidazole in rats

We investigated the influence of 2-furan-2-yl-1H-benzimidazole regarding vitamins A, E, C, selenium (Se), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) levels on rats. 2-Furan-2-yl-1H-benzimidazole was given to rats by subcutaneous injection every other day for a total of 22 injections. At the end of the experiment, Se levels were determined by using a fluorimetric method. Serum levels of vitamins A, E, C, and malondialdehyde (MDA) were determined by high-performance liquid chromatography. Glutathione peroxidase (GSH-Px) levels of erythrocytes were spectrophotometrically determined. Our experimental results showed that vitamins A, E, C, and Se levels were found generally lower than the control groups, while serum MDA level and GSH-Px activity flexibly increased, which is dependent on injection days. The observed decreases in vitamins A, E, C, and Se levels in the blood might be causally related to the increased amount of free radicals that are generated with 2-furan-2-yl-1H-benzimidazole injection. However, further investigations are needed to clarify the significance of this observation in respect with the 2-furan-2-yl-1H-benzimidazole injection.

Relation between lipid peroxidation and iron concentration in mouse liver after acute and subacute cadmium intoxication

In this study the effect of acute and subacute cadmium (Cd) intoxication on iron (Fe) concentration and lipid peroxidation (LPO) was investigated in the livers of Swiss mice. Animals were divided into two groups: the Cd group--mice intoxicated with Cd and controls. In acute time-response studies, Fe and malondialdehyde (MDA) levels were determined at 4, 6, 12, 24 and 48 h after a single oral dose of Cd (20 mg Cd/kg b.w.). In the subacute experiment, mice were given 10 mg Cd/kg b.w. orally every day for 14 days; Fe and MDA contents were determined in liver after 1 and 2 weeks. Acute Cd intoxication induced a significantly increased hepatic Fe content after 4 and 6h, and a statistically significant increase in MDA 6, 12 and 24h after Cd administration, although a significantly decreased MDA level was observed after 48 h. The results suggest development of early oxidative stress in livers of mice after acute intoxication with Cd. The decreased MDA observed after 48 h occurred presumably due to the adaptive response of the organism. Subacute Cd intoxication induced a significant decrease of hepatic Fe and MDA levels at both investigated time intervals compared with control. These results indicate a positive correlation between hepatic Fe and MDA content and suggest that prolonged Cd intoxication decreases hepatic LPO indirectly, by reducing the Fe content of mouse liver.

Comparison of lycopene and tomato effects on biomarkers of oxidative stress in vitamin E deficient rats

BACKGROUND

Cohort studies suggested that individuals with higher intake of tomatoes and tomato products have a lower risk of degenerative diseases. Lycopene, an antioxidant and antiproliferative carotenoid, has been hypothesized to be responsible for the health benefits of tomatoes. However, studies demonstrated a higher potential of tomatoes compared to lycopene to reduce oxidative stress or carcinogenesis.

AIM OF THE STUDY

Our study aimed at distinguishing lycopene effect from that of tomato on oxidative stress, by using yellow tomato, a tomato variety devoid of lycopene.

METHODS

Effects of feeding with none (control), 16% freeze-dried yellow tomato (YT), 16% freeze-dried red tomato (RT) or 0.05% lycopene beadlets (LB) were compared in a rat model with mild oxidative stress induced by low vitamin E diet (LVED). Four groups of 10 rats were fed ad libitum for 6 weeks. Physiological parameters such as ingesta, body, spleen and liver weights, cholesterol and triglycerides (TG) levels were assessed. Lycopene and vitamin E concentrations and oxidative stress biomarkers were measured in the plasma and/or liver and/or heart tissue of the rats.

RESULTS

RT, YT, and LB had no effect on rats' ingesta, body and spleen weights. RT, YT and LB had no effect on plasma cholesterol concentration. RT decreased TG level compared to control, YT and LB (P < 0.05). Rats fed RT or LB accumulated lycopene in plasma in contrast with rats fed YT. Heart level of thiobarbituric reactive species (TBARS) in rats fed RT or YT was lower than that in the control and the LB fed rats (P < 0.05). Despite similar concentrations of lycopene in plasma and liver, rats fed LB showed a significantly higher heart level of TBARS than rats fed tomatoes. RT increased erythrocyte superoxide dismutase (eSOD) activity compared with LB and nitric oxide (NO) level compared with control and LB. LB decreased ferric reducing ability of plasma (FRAP) level compared with control, RT and LB (P < 0.05).

CONCLUSION

Our study showed for the first time that tomatoes, containing or not containing lycopene, have a higher potential than lycopene to attenuate and or to reverse oxidative stress-related parameters in a mild oxidative stress context.

Oral administration of lycopene reverses cadmium-suppressed body weight loss and lipid peroxidation in rats

Cadmium (Cd) exposure has been recognized to result in a wide variety of cellular responses, including oxidative stress and body weight loss. The aim of the present study was to examine the effect of lycopene supplementation on the antioxidant defense system, lipid peroxidation (LPO) level, nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha) production, and body weight in Cd-exposed rats. Animals were divided into four groups (n = 7): control, Cd-treated, Cd plus lycopene-treated, and lycopene-treated. Cadmium (as CdCl2) was administrated orally for 20 days (6.6 mg kg(-1) day(-1)), and lycopene (10 mg kg(-1) day(-1)) was similarly administered. Lycopene administration significantly suppressed Cd-induced LPO in plasma and kidney homogenates. Lycopene also reversed Cd-decreased body weight compared to the control. Cadmium treatment had diverse effects on the antioxidant enzyme activities. Although antioxidant superoxide dismutase activity was unchanged, glutathione peroxidase activity was decreased, and catalase activity was elevated in kidney homogenates of Cd-administrated group. However, lycopene treatment reversed Cd-changed enzyme activities to the control level. Xanthine oxidase activity and TNF-alpha concentration were not altered by Cd administration, indicating that superoxide anion production and inflammation were not stimulated. Cadmium did not change NO levels in kidney homogenates but decreased those in plasma, and this effect was not prevented by lycopene supplementation. The result suggests that consumption of adequate levels of lycopene may be useful to prevent heavy-metal-induced LPO and body weight loss.

Effects of selenium and vitamin E, in addition to melatonin, against oxidative stress caused by cadmium in rats

The present study was carried to evaluate the protective effects of melatonin alone and vitamin E with selenium combination against high dose cadmium-induced oxidative stress in rats. The control group received subcutaneous physiological saline. The first study group administered cadmium chloride (CdCl2) by subcutaneous injection of dose of 1 mg/kg. The second study group administered cadmium plus vitamin E with selenium (1 mg/kg sodium selenite with 60 mg/kg vitamin E); the third study group administered cadmium plus 10 mg/kg melatonin (MLT); the fourth study group administered CdCl2 plus a combination of melatonin in addition to vitamin E and selenium for a month. Determination levels of plasma malondialdehyde (MDA), glutathione peroxidase (GSH-Px), blood superoxide dismutase (SOD), creatinine alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), blood urea nitrogen (BUN), and urea were measured in serum. In only CdCl2 administered group, the MDA, creatinine, ALT, AST, ALP, and urea levels in the serum were significantly higher than the control group (p < 0.05). Whereas in all other groups, this values were significantly lower than the only CdCl2 administered group (p < 0.05). Erythrocytes GSH-Px, serum SOD activities of only CdCl2 received group were significantly lower than the control group (p < 0.05). In conclusion, vitamin E + Se, melatonin and vitamin E, and Se, in addition to MLT combinations, had protective effects against high dose cadmium-induced oxidative damage.

Protective role of selenium against renal toxicity induced by cadmium in rats

Cadmium is an environmental toxic metal implicated in human diseases. The mechanism of its toxicity is not fully understood. Therefore, the role of cadmium in renal toxicity, and the protective role of selenium against this toxicity were investigated. Forty-five male rats were used through out the study and divided into three groups of 15. The first group received saline solution daily for 10 days. The second group, received cadmium chloride (CdCl2) (2 mg/kg body weight) intraperitoneally daily for a period of 10 days. The third group, received sodium selenite (1 mg/kg body weight, twice in 10 days) and cadmium chloride (CdCl2) once a day [corrected] The results showed that cadmium treatment increased renal lipid peroxidation (measured as malondialdehyde, MDA) which was associated with a significant decrease in the antioxidant systems such as reduced glutathione levels and the activities of glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). On the other hand, pretreatment of rats with selenium and cadmium led to a significant decrease in MDA concentration, and increased levels of GSH and the activities of GPx and TrxR when compared with those of cadmium-treated group. The total levels of phospholipid, triglyceride, and cholesterolester classes were decreased, while free fatty acids levels were markedly increased after cadmium treatment. In addition, the total levels of both mono- and poly-unsaturated fatty acids of different lipid classes were significantly decreased, while the total saturated fatty acids was significantly increased by cadmium treatment. Pretreatment of rats with selenium, was found to protect kidney tissues of rats against the biochemical changes resulting from cadmium administration. These results suggest that cadmium causes renal toxicity by inducing lipid peroxidation, decreasing antioxidant systems, and also by altering lipid metabolism. In addition, selenium treatment could protect the kidney tissues against the toxicity of cadmium since it reduced MDA levels and increased the activities of antioxidant enzymes in these tissues. These results could be important for the further understanding of the complex mechanisms of cadmium toxicity in kidney tissues and in the development of better treatments for people and/or animals exposed to the heavy metal.

Attenuation of cadmium chloride induced cytotoxicity in murine hepatocytes by a protein isolated from the leaves of the herb Cajanus indicus L

Cadmium has been recognized as a strong environmental pollutant. Exposure to this heavy metal occurs through the intake of foodstuffs, drinking water and also via the inhalation of air. Present study was conducted to evaluate the protective effect of a 43 kDa protein, isolated from the leaves of the herb Cajanus indicus, against cadmium-induced cytotoxicity in hepatocytes. For this study, cadmium chloride (CdCl(2)) has been used as the source of cadmium. Treatment of hepatocytes with 800 microM CdCl(2) for 3 h caused significant reduction in cell viability in association with the increased levels of glutamate pyruvate transaminase (GPT) and alkaline phosphatase (ALP) leakage. The activities of the antioxidant enzymes, superoxide dismutase, catalase (CAT), glutathione-S-transferase and glutathione reductase, and the levels of cellular metabolites, reduced glutathione (GSH) as well as total thiols have also been decreased under the same treatment. In addition, the toxin enhanced the levels of the lipid peroxidation end products and oxidized glutathione (GSSG). Incubation of hepatocytes with the protein at a dose of 0.1 mg/ml for 3 h prior to the toxin treatment (at a dose of 800 microM for 3 h) restored the activities of all the antioxidant enzymes, the levels of GSH, total thiols, cell viability and also attenuated the increased levels of GPT, ALP, lipid peroxidation and GSSG. In addition, the protein resisted CdCl(2) induced alterations of all the parameters when applied in combination with CdCl(2). Effects of a known antioxidant, vitamin E, and a non-relevant protein, bovine serum albumin against CdCl(2) induced cytotoxicity have also been included in the study. Combining all, we would like to say that the protein possessed protective activity against CdCl(2) induced cytotoxicity in mouse hepatocytes probably via its antioxidant property.

[Anemia induced by cadmium intoxication]

Anemia is commonly induced by chronic cadmium (Cd) intoxication. Three main factors are involved in the development of Cd-induced anemia: hemolytic, iron-deficiency, and renal. Intravascular hemolysis can occur at the early stage of Cd exposure owing to the direct damaging effect on erythrocytes. In addition, Cd that accumulates in erythrocytes affects membrane cytoskeletons and decreases cell deformability, and these cells are then trapped and destroyed in the spleen. Iron deficiency can be detected in animals after an oral exposure to Cd, which competes with iron for absorption in the intestines, leading to anemia. However, an increase in body iron content along with anemia is often observed in cases of parenteral exposure or itai-itai disease. Therefore, it is estimated that Cd disrupts the efficient usage of iron in hemoglobin synthesis in the body. Renal anemia is observed during the very last phase of chronic, severe Cd intoxication, such as itai-itai disease, showing a decrease in the production of erythropoietin from renal tubular cells. Because the renal anemia is based on the same pathophysiology as Cd-induced osteomalacia, which is derived from the disturbance of mineral metabolism due to renal tubular dysfunction, it is reasonable to include renal anemia in the criteria for the diagnosis of itai-itai disease. Hemodilution could also contribute to the development of Cd-induced anemia. Bone marrow hypoplasia or the inhibition of heme synthesis might only be involved in Cd-induced anemia in severe cases of Cd intoxication.

Induction of oxidative stress in erythrocytes of male rats subchronically exposed to a mixture of eight metals found as groundwater contaminants in different parts of India

Exposure of animals and humans to different metal components through contaminated drinking water can result in a wide range of adverse clinical conditions. Toxicological consequences arising from the concurrent repeated exposure to multiple metal contaminants are not known. The purpose of the present study was to evaluate the oxidative stress-inducing potential of a mixture of eight metals (arsenic, cadmium, lead, mercury, chromium, nickel, manganese, iron), representative of groundwater contamination in different areas of India, in erythrocytes of male rats subchronically exposed to environmentally relevant doses via drinking water. The selection of these metals, as determined by literature survey of groundwater contamination in India, was primarily based on the frequency of their occurrence and contamination level above World Health Organization maximum permissible limit (MPL) in drinking water. Male albino Wistar rats were exposed to the metal mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals in drinking water for 90 days. In addition, one group of rats was also exposed to the mixture at a concentration equal to the MPL of individual components. The oxidative stress in erythrocytes was evaluated by assessing the magnitude of malondialdehyde production and reduced glutathione (GSH) content and the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and glutathione reductase (GR) after 30, 60, and 90 days of exposure. MPL and 1x dose levels did not cause any changes. The mixture at 10x and 100x doses caused dose- and time-dependent effects. After 30 days, the 10x dose did not cause any changes except increase in SOD activity. The 100x dose increased the activities of SOD, catalase and GR and the GSH level, but caused no alterations in lipid peroxidation (LPO) and GPx activity. After 60 days, the 10x dose did not cause any changes. The 100x dose increased LPO and decreased all the antioxidant parameters, except GSH. After 90 days, both 10x and 100x levels elevated LPO. The 10x dose decreased GSH level and activities of SOD and catalase, but not of GPx and GR, whereas the 100x dose decreased all the antioxidative systems. Overall, the present study demonstrates that the subchronic exposure of male rats to the mixture of metals via drinking water results in induction of oxidative stress and concomitant reduction in antioxidative defense system in erythrocytes at 10 and 100 times the mode concentrations of the individual metals in contaminated groundwater.

Protective effect of zinc supplementation on blood antioxidant defense system in rats exposed to cadmium

The aim of this study was to assess the effects of subchronic exposure to cadmium (Cd) on the antioxidant defense system of red blood cells (RBCs) and lipid peroxide concentration in the plasma, as well as the possible protective role of zinc (Zn). For this purpose, 60 male Wistar rats (8 weeks old) were divided into three groups: the first group was exposed to Cd in the form of CdCl(2), administered in five doses (each of 0.4mg Cd/kg BW) on days 5, 10, 15, 20 and 25, giving a total dose of 2mg Cd/kg BW, i.p.; the second group was simultaneously exposed to Zn and Cd with the same timeline and the same doses of Cd as the first group but with, in addition, injections of Zn in the form of ZnCl(2), administered in doses of 0.8mg Zn/kg BW, giving a total dose of 4mg Zn/kg BW, i.p.; a control group received 0.5mL of physiological saline in an identical manner. It was shown that exposure to Cd induced a significant decrease (p<0.05) in superoxide dismutase (Zn/Cu SOD) and catalase (CAT) activities in RBCs. Increased lipid peroxide concentration, measured by thiobarbituric acid reactive substances (TBARS), was also observed in the plasma of cadmium-exposed rats. Cd had no effect on glutathione peroxidase (GSH-Px) activity. Zn administration had a beneficial effect on the Cd-induced decrease in Zn/Cu SOD activity (p<0.05) but not on CAT activity. Animals receiving Cd and Zn simultaneously had significantly (p<0.05) lower concentrations of lipid peroxides than rats exposed to Cd alone. Our results indicate that Cd causes oxidative stress and that Zn supply in conditions of exposure to Cd can partially protect against Cd-induced oxidative stress.

Cadmium induces reactive oxygen species generation and lipid peroxidation in cortical neurons in culture

Cadmium is a toxic agent that it is also an environmental contaminant. Cadmium exposure may be implicated in some humans disorders related to hyperactivity and increased aggressiveness. This study presents data indicating that cadmium induces cellular death in cortical neurons in culture. This death could be mediated by an apoptotic and a necrotic mechanism. The apoptotic death may be mediated by oxidative stress with reactive oxygen species (ROS) formation which could be induced by mitochondrial membrane dysfunction since this cation produces: (a) depletion of mitochondrial membrane potential and (b) diminution of ATP levels with ATP release. Necrotic death could be mediated by lipid peroxidation induced by cadmium through an indirect mechanism (ROS formation). On the other hand, 40% of the cells survive cadmium action. This survival seems to be mediated by the ability of these cells to activate antioxidant defense systems, since cadmium reduced the intracellular glutathione levels and induced catalase and SOD activation in these cells.

Investigation of antioxidant vitamins (A, E, C) and lipid peroxidation levels in rats injected N-(1,3-benzothiazol-2-yl)-N-(4,5-dihydro-1H-imidazol-2-yl) amine

The present study examined the influence of synthetic N-(1,3-benzothiazol-2-yl)-N-(4,5-dihydro-1H-imidazol-2-yl) amine (2-Amdz) on levels of vitamins A, E and C and malondialdehyde (MDA) in rats. A total of 30 rats, divided into two groups, were used in the study. The control group was given only a subcutaneous injection of 250 µL 75% ethanol, every other day. The other group of rats was administered a subcutaneous injection of 2-Amdz (25 mg kg^-1, dissolved in 250 µL of 75% ethanol). Injections were continued for 16 days. After the application of 2-Amdz for 16 days, the serum levels of vitamins A, E and C and malondialdehyde (MDA) were determined by HPLC. The serum vitamin A, E, and C levels decreased significantly compared to controls (p<0.05) whereas serum MDA levels were higher than control levels (p<0.005). As a result, it can be suggested that 2-Amdz induced a severe stress and more importantly, increased the amount of free radicals and significantly decreased the levels of serum antioxidant vitamins.

Hazardous effect of organophosphate compound, dichlorvos in transgenic Drosophila melanogaster (hsp70-lacZ): Induction of hsp70, anti-oxidant enzymes and inhibition of acetylcholinesterase

We tested a working hypothesis that stress genes and anti-oxidant enzyme machinery are induced by the organophosphate compound dichlorvos in a non-target organism. Third instar larvae of Drosophila melanogaster transgenic for hsp70 were exposed to 0.1 to 100.0 ppb dichlorvos and 5.0 mM CuSO(4) (an inducer of oxidative stress and stress genes) and hsp70, and activities of acetylcholinesterase (AchE), superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) product were measured. The study was further extended to examine tissue damage, if any, under such conditions. A concentration- and time-dependent increase in hsp70 and anti-oxidant enzymes was observed in the exposed organism as compared to control. A comparison of stress gene expression with SOD, CAT activities and LPO product under similar experimental conditions revealed that induction of hsp70 precedes the anti-oxidant enzyme activities in the exposed organism. Further, concomitant with a significant inhibition of AChE activity, significant induction of hsp70 was observed following chemical exposure. Mild tissue damage was observed in the larvae exposed to 10.0 ppb dichlorvos for 48 h when hsp70 expression reaches plateau. Dichlorvos at 0.1 ppb dietary concentration did not evoke significant hsp70 expression, anti-oxidant enzymes and LPO and AchE inhibition in the exposed organism, and thereby, was found to be non-hazardous to D. melanogaster. Conversely, 1.0 ppb of the test chemical stimulated a significant induction of hsp70 and anti-oxidant enzymes and significant inhibition of AchE; hence this concentration of test chemical was hazardous to the organism. The present study suggests that (a) both stress genes and anti-oxidant enzymes are stimulated as indices of cellular defense against xenobiotic hazard in D. melanogaster with hsp70 being proposed as first-tier bio-indicator of cellular hazard, (b) 0.1 ppb of the test chemical may be regarded as No Observed Adverse Effect Level (NOAEL), and 1.0 ppb dichlorvos as Low Observed Adverse Effect Level (LOAEL).

Cadmium-induced changes in lipid peroxidation, blood hematology, biochemical parameters and semen quality of male rats: protective role of vitamin E and β-carotene

Cadmium is a well-known human carcinogen and a potent nephrotoxin. Lipid peroxidation is involved in cadmium-related toxicity. Vitamin E and beta-carotene are effective antioxidants and free radical scavengers. Therefore, the present study was carried out to investigate the potential protective effects of vitamin E and beta-carotene alone or in combination against cadmium (Cd) toxicity. Cadmium chloride (CdCl2, 5 mg/kg BW, 1/15 LD50), vitamin E (100 mg/kg BW), beta-carotene (10 mg/kg BW), and vitamin E with beta-carotene (100 + 10 mg/kg BW, respectively) were orally administered by gavage alone or in combination. The tested doses were given to rats every other day (15 times). Results obtained showed that CdCl2 significantly (P < 0.05) induced free radicals in plasma, liver and brain. The activities of glutathione S-transferase (GST) (plasma and liver), alkaline phosphatase (AlP) (plasma and liver), aspartate aminotransferase (AST), alanine aminotransferase (ALT) (liver) and acetylcholinesterase (AChE) (plasma and brain) were significantly (P < 0.05) decreased due to CdCl2 administration, whereas, the activities of AST and ALT were increased in plasma. Treatment with CdCl2 caused a significant (P < 0.05) increase in glucose, urea, creatinine and bilirubin in plasma. On the other hand, results showed that CdCl2 significantly (P < 0.05) decreased plasma total protein (TP), albumin (A), blood hemoglobin (Hb), total erythrocytic count (TEC) and packed cell volume (PCV), while total leukocyte count (TLC) increased. Treatment with CdCl2 caused a significant (P < 0.05) decrease in sperm concentration, motility (%), weight of testes and epididymis, and increase in dead and abnormal sperm. Results demonstrated the beneficial influences of vitamin E, -carotene alone and/or in combination in reducing the harmful effects of CdCl2.

Molecular inhibitory mechanisms of antioxidant enzymes in rat liver and kidney by cadmium

Catalase, Mn-superoxide dismutase (MnSOD) and Cu,Zn-superoxide dismutase (CuZnSOD) activities were studied in rat liver and kidney 6-48 h after CdCl(2) intraperitoneal administration or 10-30 days daily oral CdCl(2) intake in drinking water. This approach provided some indications as to the sensitivity of each enzyme to cadmium toxicity. These experiments showed that the formation of thiobarbituric acid reactive substance (TBARS) did not strictly depend on how well the antioxidant enzyme worked. From in vitro experiments it appeared that TBARS removal by vitamin E did not restore the three enzyme activities at all. As for cadmium's inhibitory mechanism on catalase activity, our data, obtained in the pH range 6.0-8.0, are a preliminary indication that the negative effect of this metal is probably due to imidazole residue binding of His-74 which is essential in the decomposition of hydrogen peroxide. Cadmium inhibition of liver mitochondrial MnSOD activity was completely removed by Mn(2+) ions, suggesting that the reducing effect on this enzyme is probably due to the substitution of cadmium for manganese. We also observed the antioxidant capacity of Mn(2+) ions, since they were able to normalize the increased TBARS levels occurring when liver mitochondria were exposed to cadmium. The reduced activity of CuZnSOD does not seem to be due to the replacement of Zn by Cd, nor to the peroxides formed. As this enzyme activity was almost completely recovered after 48 h, we hypothesize that the momentary inhibition is imputable to a cadmium/enzyme interaction. This causes some perturbation in the enzyme topography which is critical for its catalytic activity. The pathological implications linked to antioxidant enzyme disorders induced by cadmium toxicity are discussed.

Cadmium-dependent enzyme activity alteration is not imputable to lipid peroxidation

The effect of cadmium on the liver-specific activities of NADPH-cytochrome P450 reductase (CPR), malic dehydrogenase (MDH), glyceraldehyde-3-phosphate dehydrogenase (GADPH), and sorbitol dehydrogenase (SDH) was assessed 6, 24, and 48 h after administration of the metal to rats (2.5 mg/kg of body weight, as CdCl2, single ip injection). CPR specific activity increased after 6 h and afterward decreased significantly, while MDH specific activity increased up to 24 h and then remained unchanged. Both SDH and GADPH specific activities reduced after 6 h, the former only a little but the latter much more, and after 24 and 48 h were strongly inhibited. In vitro experiments, by incubating rat liver microsomes, mitochondria, or cytosol with CdCl2 in the pH range 6.0-8.0, excluded cadmium-induced lipid peroxidation as the cause of the reduction in enzyme activity. In addition, from these experiments, we obtained indications on the type of interactions between cadmium and the enzymes studied. In the case of CPR, the inhibitory effect is probably due to Cd2+ binding to the histidine residue of the apoenzyme, which, at physiological pH, acts as a nucleophilic group. In vitro, mitochondrial MDH was not significantly affected by cadmium at any pH, indicating that this enzyme is probably not involved in the decrease in mitochondrial respiration caused by this metal. As for GADPH specific activity, its inhibition at pH 7.4 and above is imputable to the binding of cadmium to the SH groups present in the enzyme active site, since in the presence of dithiothreitol this inhibition was removed. SDH was subjected to a dual effect when cytosol was exposed to cadmium. At pH 6.0 and 6.5, its activity was strongly stimulated up to 75 microM CdCl2 while at higher metal concentrations it was reduced. At pH 7.4 and 8.0, a stimulation up to 50 microM CdCl2 occurred but above this concentration, a reduction was found. These data seem to indicate that cadmium can bind to different enzyme sites. One, at low cadmium concentration, stimulates the SDH activity while the other, at higher metal concentrations, substitutes for zinc, thus causing inhibition. This last possibility seems to occur in vivo essentially at least 24 h after intoxication. The cadmium-induced alterations of the investigated enzymes are discussed in terms of the metabolic disorders produced which are responsible for several pathological conditions.

Restorative effects of zinc and selenium on nitrergic relaxations impaired by cadmium in the mouse corpus cavernosum

We investigated whether Cd2+ intake (in drinking water, 15 ppm) for 30 days can affect the nitrergic relaxations of the mouse corpus cavernosum (CC) and whether Zn2+ (25 mg kg(-1) via a stomach tube at 48-h intervals) or sodium selenate (8 microg kg(-1) day(-1) intraperitoneally) has a restorative action on the impairment in the response. Relaxant responses of the CC obtained from Cd2+-treated mice to electrical field stimulation (neurogenic) or acetylcholine (endothelium dependent) were significantly inhibited. A partial restoration was observed in the nitrergic relaxation of the CC obtained from Zn2+- or sodium selenate-co-treated animals. Neither agent exhibited any significant action on the responses of the tissue from control mice. There was no significant difference between Cd2+-treated and control mice in respect of the relaxation amplitude induced by sodium nitroprusside or papaverine. These results suggest that Cd2+ intake may impair the nitrergic relaxation of the mouse CC, and, co-treatment with Zn2+ or sodium selenate may partially improve the nitrergic mechanisms in the tissue.