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

Ameliorative effects of morel mushroom (Morchella esculenta) against Cadmium-induced reproductive toxicity in adult male rats

Cadmium (Cd) is one of the major toxicants, which affects human health through occupational and environmental exposure. In the current study, we evaluated the protective effects of morel mushrooms against Cd-induced reproductive damages in rats. For this purpose, 30 male rats were divided into 6 groups (n=5/group), the first group served as the control group, second group was treated with an intraperitoneal (i.p) injection of 1 mg/kg/day of Cd. Third and fourth groups were co-treated with 1 mg/kg/day of Cd (i.p) and 10 and 20 mg/kg/day of morel mushroom extract (orally) respectively. The final 2 groups received oral gavage of 10 and 20 mg/kg/day of morel mushroom extract alone. After treatment for 17 days, the animals were euthanized, and testes and epididymis were dissected out. One testis and epididymis of each animal were processed for histology, while the other testis and epididymis were used for daily sperm production (DSP) and comet assay. Our results showed that Cd and morel mushrooms have no effect on animal weight, but Cd significantly decreases the DSP count and damages the heritable DNA which is reversed in co-treatment groups. Similarly, the histopathological results of testes and epididymis show that morel mushrooms control the damage to these tissues. Whereas the morel mushroom extract alone could enhance the production of testosterone. These results conclude that morel mushrooms not only control the damage done by Cd, but it could also be used as a protection mechanism for heritable DNA damage.

Altered Expression of DAAM1 and PREP Induced by Cadmium Toxicity Is Counteracted by Melatonin in the Rat Testis

Cadmium (Cd) is one of the most toxic pollutants for health due to its accumulation in several tissues, including testis. This report confirms that Cd increased oxidative stress and apoptosis of germ and somatic cells and provoked testicular injury, as documented by biomolecular and histological alterations, i.e., CAT and SOD activity, the protein level of steroidogenic enzymes (StAR and 3β-HSD), and morphometric parameters. Additionally, it further documents the melatonin (MLT) coadministration produces affects in mitigating Cd-induced toxicity on adult rat testis, as demonstrated by the reduction of oxidative stress and apoptosis, with reversal of the observed histological changes; moreover, a role of MLT in partially restoring steroidogenic enzymes expression was evidenced. Importantly, the cytoarchitecture of testicular cells was perturbed by Cd exposure, as highlighted by impairment of the expression and localization of two cytoskeleton-associated proteins DAAM1 and PREP, which are involved in the germ cells' differentiation into spermatozoa, altering the normal spermatogenesis. Here, for the first time, we found that the co-treatment with MLT attenuated the Cd-induced toxicity on the testicular DAAM1 and PREP expression. The combined findings provide additional clues about a protective effect of MLT against Cd-induced testicular toxicity by acting on DAAM1 and PREP expression, encouraging further studies to prove its effectiveness in human health.

First evidence of the protective role of melatonin in counteracting cadmium toxicity in the rat ovary via the mTOR pathway

Herein, the first evidence of the ability of melatonin (MLT) to counteract cadmium (Cd) toxic effects on the rat ovary is reported. Cd treatment, enhancing oxidative stress, provoked clear morphological, histological and biomolecular alterations, i.e. in the estrous cycle duration, in the ovarian and serum E2 concentration other than in the steroidogenic and folliculogenic genes expression. Results demonstrated that the use of MLT, in combination with Cd, avoided the changes, strongly suggesting that it is an efficient antioxidant for preventing oxidative stress in the rat ovary. Moreover, to explore the underlying mechanism involved, at molecular level, in the effects of Cd-MLT interaction, the study focused on the mTOR and ERK1/2 pathways. Interestingly, data showed that Cd influenced the phosphorylation status of mTOR, of its downstream effectors and of ERK1/2, inducing autophagy and apoptosis, while cotreatment with MLT nullified these changes. This work highlights the beneficial role exerted by MLT in preventing Cd-induced toxicity in the rat ovary, encouraging further studies to confirm its action on human ovarian health with the aim to use this indolamine to ameliorate oocyte quality in women with fertility disorders.

Effects of Selenium and Cadmium on Breast Muscle Fatty-Acid Composition and Gene Expression of Liver Antioxidant Proteins in Broilers

The present work was part of a project intended to evaluate whether organic selenium (Se) has the potential to protect against toxic effects exerted by cadmium (Cd). For this reason, 300 as-hatched, one-day-old broiler chickens were randomly allocated in four dietary treatments with five replicate pens per treatment. Chickens in T1 treatment, were offered a diet supplemented with 0.3 ppm Se (as Se-yeast), without added Cd; in T2 treatment, they were offered a diet with 0.3 ppm Se and 10 ppm Cd; in T3 treatment, they were offered a diet with 0.3 ppm Se and 100 ppm Cd; in T4 treatment, chickens were offered a diet supplemented with 3 ppm Se and 100 ppm Cd. Cadmium was added to the diets in T2, T3, and T4 as CdCl₂. On the fourth and sixth weeks, liver and breast samples were obtained from two broilers per replicate pen. Relative gene expression levels of catalase (CAT), superoxide dismutase 1 (SOD1) and 2 (SOD2), methionine sulfoxide reductase A (MSRA) and B3 (MSRB3), iodothyronine deiodinase 1 (DIO1), 2 (DIO2), and 3 (DIO3), glutathione peroxidase 1 (GPX1) and 4 (GPX4), thioredoxin reductase 1 (TXNRD1) and 3 (TXNRD3), and metallothionein 3 (MT3) were analyzed by real-time quantitative PCR in liver, whereas the fatty-acid (FA) profile of breast muscle was determined by gas chromatography. Broilers supplemented with 0.3 ppm Se could tolerate low levels of Cd present in the diets, as there were no significant changes in the breast muscle FA profile, whereas excess Cd led to decreased polyunsaturated fatty acids (PUFAs), and in particular n-6 PUFA. Furthermore, treatments mainly affected the messenger RNA (mRNA) expression of SOD2, TXNRD3, and MT3, while age affected CAT, MSRB3, DIO2, DIO3, GPX4, TXNRD1, and MT3. In conclusion, dietary Se may help against the negative effects of Cd, but cannot be effective when Cd is present at excessive amounts in the diet.

Cadmium-mediated morphological, biochemical and physiological tuning in three different Anabaena species

Cyanobacteria are a natural inhabitant of paddy field and enhance the crop productivity in an eco-friendly manner. Cadmium (Cd) is a perilous trace metal element which not only limits the crop productivity but also inhibits the growth and nitrogen-fixing ability of these diazotrophs as well as the biodiversity of rice field semiaquatic agroecosystems. However, the impact of Cd toxicity in diazotrophic cyanobacteria is yet not adequately addressed. Therefore, in the present study, three diazotrophic cyanobacterial species, i.e., Anabaena sp. PCC7120, Anabaena L31, and Anabaena doliolum were subjected to their LC₅₀ doses of Cd, and their physiological (PSII, Psi, respiration, energy status and nitrogen fixation rate), biochemical variables (such as antioxidant contents and antioxidant enzymes) together with morphological parameters were evaluated. The results of physiological variables suggested that the Cd exposure adversely affects the photosynthesis, respiration, and biological nitrogen fixation ability across three Anabaena species. The results of biochemical variables in terms of accumulation of antioxidants (glutathione, thiol, phytochelatin and proline) content as well as antioxidant enzymes such as glutathione S-transferase (GST), glutathione reductase (GR), catalase-peroxidase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) revealed that their inter-species stress tolerance behavior may be attributed to the differential accumulation of antioxidants as well as differential antioxidant enzyme activity in three species. Furthermore, the enhanced antioxidant enzymes activity such as GST, GR, CAT, and SOD in Anabaena L31 advocated significantly higher as compared to Anabaena PCC7120 and Anabaena doliolum. In conclusion, Cd-toxicity assessment regarding physiological, biochemical and morphological aspects across three species identified Anabaena L31 as Cd-resistant species than the other two tested species, i.e., Anabaena PCC7120 and Anabaena doliolum.

Effects of cadmium on oxidative stress activities in plasma of freshwater turtle Chinemys reevesii

Cadmium (Cd) has been recently found in high concentrations in the aquatic environment. This study was designed to examine the effects of Cd on the oxidative stress activities in plasma of freshwater turtle Chinemys reevesii. Experimental turtles were exposed to Cd at the concentration of 15 mg/kg by intraperitoneal injection, and redox status was investigated. Compared to the controls, superoxide dismutase (SOD) and catalase activities in plasma of the treated animals significantly decreased in week 1, week 2, and week 4. However, SOD activities gradually increased from week 4 to week 8. The treated animals had higher content of MDA and lower content of GSH in plasma over the observation period. In conclusion, our results showed that Cd decreased the antioxidant capacity and increased the level of oxidative damage product in plasma, which suggest that Cd causes oxidative stress and damage in the animal under the experimental conditions.

Possible antioxidant effect of Lycium barbarum polysaccharides on hepatic cadmium-induced oxidative stress in rats

The aim of this study was to investigate the potential protective effect of Lycium barbarum polysaccharides (LBP) pretreatment against cadmium (Cd)-induced hepatotoxicity in rats. Wistar rats were divided into control group, LBP group (300 mg/kg orally, once a day, for 30 days), Cd group (CdCl₂ 4 mg/kg i.p. once), and LBP + Cd group (LBP 300 mg/kg orally, once a day, for 30 days + CdCl₂ 4 mg/kg i.p. 24 h after the last treatment). Cd liver injury was examined by morphological/histological changes, transaminases, total protein concentration, and oxidative stress evaluated by MDA, 3NT, GSH, SOD, and TEAC activities. Cd intoxication caused gross morphological changes with hyperemia of the parenchyma, increased volume, and disappearance of the anatomical limits of the lobes associated with an increase of ALT, GSH, and TEAC in plasma and a decrease of MDA, GSH, and TEAC in liver, SOD, and total proteins in plasma. LBP pretreatment caused a slight improvement in the histological architecture and in the 3NT amount together with a significant improvement of hematic parameters. On the basis of the obtained results, we can affirm that LBP pretreatment can ameliorate liver conditions, but further studies are needed to better evaluate the protective antioxidant effects of LBP against Cd-induced toxicity.

Possible antioxidant effect of Lycium barbarum polysaccharides on hepatic cadmium-induced oxidative stress in rats

The aim of this study was to investigate the potential protective effect of Lycium barbarum polysaccharides (LBP) pretreatment against cadmium (Cd)-induced hepatotoxicity in rats. Wistar rats were divided into control group, LBP group (300 mg/kg orally, once a day, for 30 days), Cd group (CdCl₂ 4 mg/kg i.p. once), and LBP + Cd group (LBP 300 mg/kg orally, once a day, for 30 days + CdCl₂ 4 mg/kg i.p. 24 h after the last treatment). Cd liver injury was examined by morphological/histological changes, transaminases, total protein concentration, and oxidative stress evaluated by MDA, 3NT, GSH, SOD, and TEAC activities. Cd intoxication caused gross morphological changes with hyperemia of the parenchyma, increased volume, and disappearance of the anatomical limits of the lobes associated with an increase of ALT, GSH, and TEAC in plasma and a decrease of MDA, GSH, and TEAC in liver, SOD, and total proteins in plasma. LBP pretreatment caused a slight improvement in the histological architecture and in the 3NT amount together with a significant improvement of hematic parameters. On the basis of the obtained results, we can affirm that LBP pretreatment can ameliorate liver conditions, but further studies are needed to better evaluate the protective antioxidant effects of LBP against Cd-induced toxicity.

Effects of diallyl tetrasulfide on cadmium-induced oxidative damage in the liver of rats

The protective efficacy of diallyl tetrasulfide (DTS) from garlic on liver injury induced by cadmium (Cd) was investigated. In this study, Cd (3 mg/kg body weight) was administered subcutaneously for 3 weeks to induce toxicity. DTS was administered orally (10, 20 and 40 mg/kg body weight) for 3 weeks with subcutaneous (sc) injection of Cd. Cd-induced liver damage was evidenced from increased activities of serum hepatic enzymes, namely aspartate transaminase, alanine transaminase, alkaline phosphatase and lactate dehydrogenase, with significant elevation of lipid peroxidation indices (thiobarbituric acid reactive substances and hydroperoxides) and protein carbonyl groups in the liver. Rats subjected to Cd toxicity also showed a decline in the levels of total thiols, reduced glutathione (GSH), vitamin C and vitamin E, accompanied by an increased accumulation of Cd, and significantly decreased activities of superoxide dismutase, catalase (CAT), glutathione peroxidase, glutathione-S-transferase (GST), glutathione reductase, and glucose-6-phosphate dehydrogenase in the liver. Administration of DTS at 40 mg/kg body weight significantly normalised the activities of hepatic marker enzymes, compared to other doses of DTS (10 and 20 mg/kg body weight). In addition, DTS (40 mg/kg body weight) significantly reduced the accumulation of Cd and the level of lipid peroxidation, and restored the level of antioxidant defense in the liver. Histological studies also showed that administration of DTS to Cd-treated rats resulted in a marked improvement of hepatocytes morphology with mild portal inflammation. Our results suggest that DTS might play a vital role in protecting Cd-induced oxidative damage in the liver. Human & Experimental Toxicology(2007) 26, 527—534

Oxidative stress, bioelements and androgen status in testes of rats subacutely exposed to cadmium

The objective of our study was to examine testicular toxicity of cadmium (Cd), focusing on oxidative stress (OS), essential metals and androgenic status and morphological changes. Male Wistar rats [controls and four Cd-subgroups (n = 6) organized according to the exposure (1, 3, 10 and 21 days)] were intraperitoneally (i.p.) treated with 1 mg CdCl2/kg/day. Testicular Cd deposition was noticed from the 1st day. After 10 and 21 days, copper (Cu) and iron (Fe) increased by 60-109% and 43-67%, respectively, while zinc (Zn) decreased by 24-33%. During 1-21 days of the exposure, decrease in testicular total superoxide dismutase (SOD) and total glutathione-s-transferase (GST) activities occurred gradually by 30-78% and 15-84%, respectively, while superoxide anion radical (O2(-)) increased gradually by 114-271%. After 10-21 days, decrease in testicular catalase (CAT) activity appeared by 13-31%. After 21 days, malondialdehyde (MDA) decreased by 44% and the ratio of oxidized glutathione/reduced glutathione (GSSG/GSH) increased by 130% in testes of the rats exposed to Cd. Additionally, decreased testicular testosterone level and the relative testes mass, along with induced microscopic and macroscopic changes were occured, what can be explained as the consequence of instantly developed OS, impaired essential metals status and Cd testicular deposition.

Nephroprotection of plantamajoside in rats treated with cadmium

Cadmium (Cd), an environmental and industrial pollutant, generates free radicals responsible for oxidative stress. Cd can also lead to various renal toxic damage such as the proximal tubules and glomerulus dysfunction. Plantamajoside (PMS), a major compound of Plantago asiatica (PA), was reported to have the antioxidant effects. In this study, we investigated the protective effects of PMS on Cd-induced renal damage in the NRK-52E cell and rat kidney tissue. Cd exposure increased the ROS generation, lipid peroxidation, serum biochemical values of renal damage, and mRNA and protein expressions of KIM-1 in vitro and in vivo. The significant reduction in glutathione (GSH)/glutathione disulfide (GSSG) ratio and activities of antioxidant enzymes were also observed in the rats treated with Cd. PMS significantly decreased the ROS generation and lipid peroxidation, thus enhancing GSH/GSSG ratio, antioxidant enzyme activities in the cells and rats, and improved histochemical appearances, indicating that PMS has protective activities against Cd-induced renal injury.

Transcriptomic response of the hydrothermal mussel Bathymodiolus azoricus in experimental exposure to heavy metals is modulated by the Pgm genotype and symbiont content

Hydrothermal vent mussels belonging to the genus Bathymodiolus dominate communities at hydrothermal sites of the Mid-Atlantic Ridge. The mussel Bathymodiolus azoricus harbors thiotrophic and methanotrophic symbiotic bacteria in its gills and evolves in naturally highly metal contaminated environments. In the context of investigations on metal tolerance/effect in B. azoricus, we focused our work on the short-term adaptive response (15days) of mussels to different metals exposure at a molecular level using metal concentrations chosen to mimic natural situations at three vents sites. The expression of a set of 38 genes involved in different steps of the metal uptake, detoxication and various metabolisms was analysed by qPCR. Mussels were also genotyped at 10 enzyme loci to explore the relationships among natural genetic variation and gene expression. Relation between symbiont content (both sulfur-oxidizing and methanogen bacteria) and gene expression was also analysed. Our study demonstrated the influence of metal cocktail composition and time exposure on the transcriptome regulation with a specific pattern of regulation observed for the three metal cocktail tested. We also evidenced the significant influence of some specific Pgm genotype on the global gene expression in our experimental populations and a general trend of a higher gene expression in individuals carrying a high symbiont content.

Mechanisms of kidney toxicity for chromium- and arsenic-based preservatives: potential involvement of a pro-oxidative pathway

Metals have been extensively used for the preservation of wood. Among metallic conservatives, mixtures of chromated copper arsenate (CCA) were thoroughly used. However, the release and consequent mobilization of such compounds by biota, may culminate in the exertion of toxic chemical effects. The present study intended to show the toxicological effects caused by arsenic (7.2 mg/kg body weight), chromium (10.2 mg/kg Cr body weight) and the commercial mixture CCA (7.2 mg/kg As body weight and 10.2 mg/kg Cr body weight) in mice, namely the oxidative stress response (catalase - CAT, glutathione peroxidase - GPx, and glutathione-S-transferases - GSTs), in kidney tissues. The determination of the tested parameters was performed after exposure; organisms were exposed, and then sacrificed at two distinct periods, namely 14 and 96 h after the administration of toxicants. Exposure to chromium and arsenic induced significant modifications in the redox state of the test organisms, evidenced by significant alterations in GSTs and GPx activities. No alterations were found concerning the activity of catalase. These findings showed that the chemical mixture used as household product may exert significant toxicological outcomes in exposed animals, such as rodents, conditioning their redox homeostasis and antioxidant response.

Cadmium induced pathophysiology: prophylactic role of edible jute (Corchorus olitorius) leaves with special emphasis on oxidative stress and mitochondrial involvement

The present study was undertaken to evaluate the protective effect of aqueous extract of Corchorus olitorius leaves (AECO) against CdCl₂ intoxication. In vitro bioassay on isolated mice hepatocytes confirmed dose dependent cytoprotective effect of AECO. The CdCl₂ (30 μM) exhibited a significantly increased levels of lipid peroxidation, protein carbonylation along with the reduction of antioxidant enzymes and reduced glutathione levels in hepatocytes. AECO (200 and 400 μg/ml) + CdCl₂ (30 μM) could significantly restore the aforementioned oxidation parameters in hepatocytes. Beside this, AECO could significantly reduce Cd-induced increase in Bad/Bcl-2 ratio and the over-expression of NF-κB, caspase 3 and caspase 9. In in vivo assay, CdCl₂ (4 mg/kg body weight, for 6 days) treated rats exhibited a significantly increased intracellular Cd accumulation, oxidative stress and DNA fragmentation in the organs. In addition, the haematological parameters were significantly altered in the CdCl₂ treated rats. Simultaneous administration of AECO (50 and 100 mg/kg body weight), could significantly restore the biochemical, antioxidant and haematological parameters near to the normal status. Histological studies of the organs supported the protective role of jute leaves. Presence of substantial quantity of phenolic compounds and flavonoids in extract may be responsible for overall protective effect.

Adaptive alterations in the fatty acids composition under induced oxidative stress in heavy metal-tolerant filamentous fungus Paecilomyces marquandii cultured in ascorbic acid presence

The ability of the heavy metal-tolerant fungus Paecilomyces marquandii to modulate whole cells fatty acid composition and saturation in response to IC50 of Cd, Pb, Zn, Ni, and Cu was studied. Cadmium and nickel caused the most significant growth reduction. In the mycelia cultured with all tested metals, with the exception of nickel, a rise in the fatty acid unsaturation was noted. The fungus exposure to Pb, Cu, and Ni led to significantly higher lipid peroxidation. P. marquandii incubated in the presence of the tested metals responded with an increase in the level of linoleic acid and escalation of electrolyte leakage. The highest efflux of electrolytes was caused by lead. In these conditions, the fungus was able to bind up to 100 mg g(-1) of lead, whereas the content of the other metals in the mycelium was significantly lower and reached from 3.18 mg g(-1) (Cu) to 15.21 mg g(-1) (Zn). Additionally, it was shown that ascorbic acid at the concentration of 1 mM protected fungal growth and prevented the changes in the fatty acid composition and saturation but did not alleviate lipid peroxidation or affect the increased permeability of membranes after lead exposure. Pro-oxidant properties of ascorbic acid in the copper-stressed cells manifested strong growth inhibition and enhanced metal accumulation as a result of membrane damage. Toxic metals action caused cellular modulations, which might contributed to P. marquandii tolerance to the studied metals. Moreover, these changes can enhance metal removal from contaminated environment.

Effect of acute cadmium exposure on metal accumulation and oxidative stress biomarkers of Sparus aurata

Cadmium (Cd) is a non-essential metal which could be toxic in traces for aquatic species. Increasing Cd concentrations in sea water is mainly related to waste waters provided from growing industrial and agricultural activities. The present study investigated the accumulation of Cd (0.5mg/L) in different tissues of Sparus aurata under a short term exposure (2, 4 and 24h) using the atomic absorption. This work investigated also the impact of the metal on oxidative stress biomarkers and acetyl cholinesterase activity (AchE). Our results showed that Cd accumulation in different tissues depends largely on the length of the exposure period to the metal. Indeed, the highest concentrations were obtained after 24h. Cd accumulation in tissues was in the following order: intestines > liver > gills > dorsal muscle. Cadmium administration increased significantly catalase activity (CAT), glutathione level (GSH) and malondialdehyde production (MDA) after 24h of exposure. In contrast, AchE activity was decreased after the same period of exposure to the metal. There were no significant changes in oxidative stress biomarkers after 2 and 4h of exposure, except for superoxide dismutase (SOD) activity which attained the highest level after 4h. These results suggest that short-term exposure of Sparus aurata to Cd (0.5mg/L) induced an important metal accumulation in intestine and a notable oxidative stress response.

Rutin- and Selenium-attenuated cadmium-induced testicular pathophysiology in rats

Cadmium (Cd) is known to cause oxidative damage in the testes of rats. The aim of this study was to investigate the protective role of rutin (RUT, 30 mg/kg) and selenium (Se, 0.15 ppm) alone or in combination against Cd (200 ppm)-induced lipid peroxidation, steroidogenesis and changes in antioxidant defence system in the rat testes. The obtained results showed that Cd increased lipid peroxidation and abnormal sperm count and decreased plasma testosterone, lactate dehydrogenase, acid phosphatase, alkaline phosphatase and testicular steroidogenic enzymes: 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD activities as well as epididymal sperm counts and motility, while RUT and Se treatment reversed this change to control values. Acute intoxication with Cd was also followed by significantly decreased activity of the antioxidant defence system (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione (GSH), and glutathione-S-transferase (GST)). Treatment with RUT and Se reversed Cd-induced alterations of antioxidant defence system and significantly prevented Cd-induced testes damage and depletion of plasma and testicular Se levels. RUT and Se appear not to have more profound effects than their separate effects against Cd-induced testicular toxicity, although Se was more potent than RUT in the recovery of testosterone levels. These results suggest that both RUT and Se do not have synergistic role against Cd-induced testicular injury.

Influence of cadmium exposure on growth and fecundity of freshwater mosquitofish Gambusia affinis: in situ and in vivo studies

This study aims to investigate the effect of cadmium (Cd) exposure on growth and fecundity of mosquitofish Gambusia affinis. For this purpose, two natural populations of pregnant females of G. affinis captured from two sites were differently contaminated with Cd (S1 present Cd levels 5-fold higher than S2) and a sublethal exposure to 0.4 mg CdCl(2)/L (10% of LC(50)) during 56 days was conducted in vivo. The length-weight regression revealed a significant difference in the growth between these two populations. A significant difference in fecundity was also noted between the two populations. Indeed, the embryo numbers in pregnant females captured from S1 are significantly higher than those noted in pregnant females from S2 (21.17±5 and 7.97±2.12, respectively; p<0.05). Following Cd exposure, we noted a growth perturbation resulting in lower values of both indices BWG and SGR following 7 and 21 days (-5.21 and -1.18 for BWG, and -2.09 and -0.46 for SGR, respectively) and a recuperation of growing weight at 42 and 56 days (1.32 and 1.71 for BWG, and 0.45 and 0.54 for SGR, respectively). For CF index, we observed a significant difference (p<0.05) between control and Cd groups at 7 and 21 days of exposure, and at 21 and 56 days respectively for HSI and GSI indices. Furthermore, Cd contents in both tissues (liver and yolk sac) and fractions (cytosolic and membrane) are significantly different between groups during experimentation. In addition, the Cd contents noticed in the liver membrane fraction are significantly higher than those noted in the yolk sac tissue. The MTs levels revealed a significant difference between the control and Cd groups. In liver tissue, a significant difference was noted, in MTs levels, during the Cd exposure (7, 21, 42, and 56 days) while in the yolk sac tissue the difference was noted at 42 days of exposure. Taken together, these results imply the potential negative effect of Cd on physiological status of G. affinis as evidenced by decreasing growth and fecundity rate.

Proteasome and antioxidant responses in Cottus gobio during a combined exposure to heat stress and cadmium

Temperature and trace metals are common environmental stressors, and their importance is increasing due to global climate change and anthropogenic pollution. Oxidative damage and antioxidant properties have been studied in liver and gills of the European bullhead (Cottus gobio) subjected to cadmium (CdCl(2) at nominal concentrations of 0.01 and 1mg/L) for 4 days at either 15°C or 21°C. First, exposure to 1mg Cd/L induced a high mortality rate (67%) in fish held at 21°C. Regarding the antioxidant enzymes, exposure to 0.01 mg Cd/L significantly increased the activity of superoxide dismutase (SOD) and decreased the activity of glutathione reductase (GR) in liver, independently of heat stress. In gills, exposure to 21°C resulted in a significantly increased activity of glutathione peroxidase (GPx), whereas the activity of glutathione S-transferase (GST) was significantly reduced as compared to fish exposed to 15°C. Furthermore, regardless of Cd stress, exposure to elevated temperature resulted in a significant decrease of lipid peroxidation (LPO) level in liver and in a significant increase in the activity of chymotrypsin-like 20S proteasome in both studied tissues of C. gobio. Overall, the present results indicated that elevated temperature and cadmium exposure independently influenced the antioxidant defense system in bullhead with clear tissue-specific and stress-specific antioxidant responses. Further, elevated temperature affected the hepatic lipid peroxidation and the activity of 20S proteasome in both tissues.

The late and persistent pathogenic effects of cadmium at very low levels on the kidney of rats

Cadmium (Cd) is an important nephrotoxic pollutant. To examine late effects on the kidney of individuals previously exposed to chronic Cd at very low levels, male Wistar rats were given 20 nmol/kg i.p. injections of Cd every other day for 4 weeks. At the 20(th), 28(th), 36(th), 44(th) and 52(nd) week of the study, renal metal accumulation, morphology and function were examined. Immunochemical staining was performed to detect renal 3-nitrotyrosine (3-NT) accumulation, metallothionein (MT) expression, cell proliferation and global DNA methylation. Results showed that renal Cd concentration and MT expression along with 3-NT accumulation were significantly higher in the Cd group than that in the control. Histopathologically renal tubule damage at the early stage and hyperplasia at the late stage were observed in the Cd group. Renal fibrosis in glomeruli was evident in the Cd group, particularly at the late stage of the study. Immunoreactivity of global DNA methylation was markedly diminished in the Cd group at both 20(th) and 52(nd) weeks. These results suggest that previous exposure to chronic Cd at very low level induced persistent damaging effects on the kidney along with increases in cell proliferation and global DNA hypomethylation.

Hesperetin, a citrus flavonone, protects potentially cadmium induced oxidative testicular dysfunction in rats

The present study was aimed to evaluate the protective effect of hesperetin (Hp) on cadmium (Cd) induced oxidative testicular toxicity in rats. Subcutaneous administration of Cd (3mg/kg body weight) for 21 days significantly elevated the levels of oxidative stress markers, Cd concentration in testis and lowered the levels of enzymatic, non-enzymatic antioxidants and membrane bound enzymes in the testicular tissue. Hp administrated orally along with Cd injection for 21 days, significantly revert back the status of oxidative stress markers, Cd concentration in testis, improved status of antioxidant markers and membrane bound enzymes in the testis to near normal level. The histopathological studies in the testis of rats also supported that Hp (40 mg/kg) markedly reduced the toxicity of Cd and preserved the normal histoarchitecture pattern of the testis. Thus, the results suggest that Hp acts as a potent antioxidative agent against Cd induced testicular toxicity in rats.

Reactive oxygen species formation and cell death in catalase-deficient tobacco leaf disks exposed to cadmium

The physiological responses of tobacco (Nicotiana tabacum L.) to oxidative stress induced by cadmium were examined with respect to reactive oxygen species (ROS) formation, antioxidant enzymes activities, and cell death appearance in wild-type SR1 and catalase-deficient CAT1AS plants. Leaf disks treated with 100 or 500 microM CdCl(2) increased Evans blue staining and leakage of electrolytes in SR1 or CAT1AS plants, more pronouncedly in the transgenic cultivar, but without evidence of lipid peroxidation in any of the cultivars compared to controls. Cadmium significantly reduced the NADPH oxidase-dependent O (2)(-) formation in a dose dependent manner in SR1 very strongly at 500 microM (to 5% of the activity in the nontreated SR1 leaf disks). In CAT1AS, the NADPH oxidase activity was constitutively reduced at 50% with respect to that of SR1, but the magnitude of the decay was less prominent in this cultivar, reaching an average of 64% of the C at 21 h, for both Cd concentrations. Hydrogen peroxide formation was only slightly increased in SR1 or CAT1AS leaf disks at 21 h of exposure compared to the respective controls. Cd increased superoxide dismutase activity more than six times at 21 h in CAT1AS, but not in SR1 and reduced catalase activity by 59% at 21 h of treatment only in SR1 plants. Despite that catalase expression was constitutively lower in CATAS1 compared to SR1 nontreated leaf disks, 500 microM CdCl(2) almost doubled it only in CAT1AS at 21 h. The mechanisms underlying Cd-induced cell death were possibly not related exclusively to ROS formation or detoxification in tobacco SR1 or CAT1AS plants.

Inhibition of purified bovine liver glutathione reductase with some metal ions

Glutathione reductase (GR; E.C. 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). In this study we tested the effects of Al3+, Ba2+, Ca2+, Li+, Mn2+, Mo6+, Cd2+, Ni2+, and Zn2+ on purified bovine liver GR. In a range of 10 microM-10 mM concentrations, Al3+, Ba2+, Li+, Mn2+, and Mo6+, and Ca2+ at 5 microM-1.25 mM, had no effect on bovine liver GR. Cadmium (Cd2+), nickel (Ni2+), and zinc (Zn2+) showed inhibitory effects on this enzyme. The obtained IC50 values of Cd2+, Ni2+, and Zn2+ were 0.08, 0.8, and 1 mM, respectively. Cd2+ inhibition was non-competitive with respect to both GSSG (Ki(GSSG) 0.221 +/- 0.02 mM) and NADPH (Ki(NADPH) 0.113 +/- 0.008 mM). Ni2+ inhibition was non-competitive with respect to GSSG (Ki(GSSG) 0.313 +/- 0.01 mM) and uncompetitive with respect to NADPH (Ki(NADPH) 0.932 +/- 0.03 mM). The effect of Zn2+ on GR activity was consistent with a non-competitive inhibition pattern when the varied substrates were GSSG (Ki(GSSG) 0.320 +/- 0.018 mM) and NADPH (Ki(NADPH) 0.761 +/- 0.04 mM), respectively.

Cadmium and mitochondria

The heavy metal cadmium (Cd) a pollutant associated with several modern industrial processes, is absorbed in significant quantities from cigarette smoke, water, food and air contaminations. It is known to have numerous undesirable effects on health in both experimental animals and humans, targeting kidney, liver and vascular system. The molecular mechanism accounting for most of the biological effects of Cd are not well-understood and the toxicity targets are largely unidentified. The present review focuses on important recent advances about the effects of cadmium on mitochondria of mammalian cells. Mitochondria are the proverbial powerhouses of the cell, running the fundamental biochemical processes that produce energy from nutrients using oxygen. They are among the key intracellular targets for different stressors including Cd. This review provides new additional informations on the cellular and molecular aspects of the interaction between Cd and cells, emphasizing alterations of mitochondria as important events in Cd cytotoxicity, thus representing an important basis for understanding the mechanisms of cadmium effect on the cells.

Taurine plays a beneficial role against cadmium-induced oxidative renal dysfunction

The present study has been carried out to investigate the role of taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, in ameliorating cadmium-induced renal dysfunctions in mice. Cadmium chloride (CdCl(2)) has been selected as the source of cadmium. Intraperitoneal administration of CdCl(2 )(at a dose of 4 mg/kg body weight for 3 days) caused significant accumulation of cadmium in renal tissues and lessened kidney weight to body weight ratio. Cadmium administration reduced intracellular ferric reducing/antioxidant power (FRAP) of renal tissues. Levels of serum marker enzymes related to renal damage, creatinine and urea nitrogen (UN) have been elevated due to cadmium toxicity. Cadmium exposure diminished the activities of enzymatic antioxidants, superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx) and glucose-6-phosphate dehydrogenase (G6PD) as well as non-enzymatic antioxidant, reduced glutathione (GSH) and total thiols. On the other hand, the levels of oxidized glutathione (GSSG), lipid peroxidation, protein carbonylation, DNA fragmentation, concentration of superoxide radicals and activities of cytochrome P450 enzymes (CYP P450s) have been found to increase due to cadmium intoxication. Treatment with taurine (at a dose of 100 mg/kg body weight for 5 days) before cadmium intoxication prevented the toxin-induced oxidative impairments in renal tissues. The beneficial role of taurine against cadmium-induced renal damage was supported from histological examination of renal segments. Vitamin C, a well-established antioxidant was used as the positive control in the study. Experimental evidence suggests that both taurine and vitamin C provide antioxidant defense against cadmium-induced renal oxidative injury. Combining all, results suggest that taurine protects murine kidneys against cadmium-induced oxidative impairments, probably via its antioxidative property.

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 accumulation and biochemical responses in Sparus aurata following sub-lethal Cd exposure

Cadmium (Cd), a heavy metal with limited biological function, is widely distributed in the aquatic environment as a result of natural and anthropogenic activities. The effect of 4 and 11 days exposure of gilthead sea bream Sparus aurata to sub-lethal concentrations of Cd was evaluated as levels of Cd content and Cd-metallothionein (MT) presence in different organs. The possible genotoxic effect was also evaluated in erythrocytes by using the "comet assay", a promising tool for estimating DNA damage at the single-cell level. The results obtained show that in the controls, Cd content was significantly higher in gills compared to in liver, but the treatment of fish with 0.1mg/l Cd induced a stronger accumulation of metal in liver depending on the length of the exposure period. Cd traces were found in plasma, muscle and kidney. Cd forms complexes in the cytosol with MT only in the liver but Cd-MT content significantly increased after 11 days of exposure to the metal, while after 4 days of treatment the protein level was similar to the control. The "comet assay" performed on S. aurata eryhtrocytes isolated from fish treated for 4 and 11 days with 0.1mg/l Cd, showed that there was no DNA damage at both exposure periods.

Naringenin protects against cadmium-induced oxidative renal dysfunction in rats

Cadmium (Cd) is an environmental and industrial pollutant that affects various organs in human and experimental animals. Naringenin is a naturally occurring plant bioflavonoid found in citrus fruits, which has been reported to have a wide range of pharmacological properties. A body of evidence has accumulated implicating the free radical generation with subsequent oxidative stress in the biochemical and molecular mechanisms of cadmium toxicity. Since kidney is the critical target organ of chronic Cd toxicity, we carried out this study to investigate the effects of naringenin on Cd-induced toxicity in the kidney of rats. In experimental rats, oral administration of cadmium chloride (5mg/(kgday)) for 4 weeks significantly induced the renal damage which was evident from the increased levels of serum urea, uric acid, creatinine with a significant (p<0.05) decrease in creatinine clearance. Cadmium also significantly decreased the levels of urea, uric acid and creatinine in urine. A markedly increased levels of lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) and protein carbonyl contents with significant (p<0.05) decrease in non-enzymatic antioxidants (total sulfhydryl groups, reduced glutathione, vitamin C and vitamin E) and enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST)) as well as glutathione metabolizing enzymes (glutathione reductase (GR) and glutathione-6-phosphate dehydrogenase (G6PD)) were also observed in cadmium-treated rats. Co-administration of naringenin (25 and 50mg/(kgday)) along with Cd resulted in a reversal of Cd-induced biochemical changes in kidney accompanied by a significant decrease in lipid peroxidation and an increase in the level of renal antioxidant defense system. The histopathological studies in the kidney of rats also showed that naringenin (50mg/(kgday)) markedly reduced the toxicity of Cd and preserved the normal histological architecture of the renal tissue. The present study suggest that the nephroprotective potential of naringenin in Cd toxicity might be due to its antioxidant and metal chelating properties, which could be useful for achieving optimum effects in Cd-induced renal damage.

Effects of subchronic digestive exposure to organic or inorganic cadmium on biomarkers in rat tissues

In an experimental food chain, Wistar rats were fed cadmium (Cd) in an inorganic (CdCl(2)) or organic (mainly associated with metallothionein from Helix aspersa snail viscera) form. After 1 month of exposure to 100 microg inorganic Cd g(-1) in food, an induction of metallothionein was observed in all target tissues. In liver, glutathione peroxidase (GSH-Px) activity decreased and alanine aminotransferase (ALAT) activity increased, suggesting that Cd causes hepatotoxicity. However, lipid peroxidation as well as catalase and caspase 3 (a marker of apoptosis) activities were not modified. At a rather low exposure (2.5 microg Cd g(-1)), metallothionein level in the kidney was found to be the most sensitive biomarker of exposure for both Cd forms. In the small intestine of rats ingesting inorganic Cd, metallothionein expression was significantly higher than that observed for rats fed organic Cd. Present results allowed proposing a simple design to assess the effect of a chemical in a trophic transfer approach.

Cytoprotective and antioxidant role of diallyl tetrasulfide on cadmium induced renal injury: An in vivo and in vitro study

Cadmium (Cd) is an environmental and industrial pollutant that affects various organs in humans and animals. A body of evidence has accumulated implicating the free radical generation with subsequent oxidative stress in the biochemical and molecular mechanisms of Cd toxicity. Since kidney is the critical target of Cd toxicity, we carried out this study to investigate the effects of diallyl tetrasulfide (DTS), an organosulfur compound derived from garlic on Cd induced toxicity in the kidney of rats and also in the kidney cell line (vero cells). In experimental rats, subcutaneous administration of Cd (3 mg/kg bw/day) for 3 weeks induced renal damage, which was evident from significantly increased levels of serum urea and creatinine with significant decrease in creatinine clearance. A markedly increased levels of lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) and protein carbonyl contents with significant decrease in nonenzymic antioxidants (total sulphydryl groups, reduced glutathione, vitamin C and vitamin E) and enzymic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase) as well as glutathione metabolizing enzymes (glutathione reductase, and glucose-6-phosphate dehydrogenase) were also observed in Cd intoxicated rats. Coadministration of DTS (40 mg/kg bw/day) and Cd resulted in the reversal of the kidney function accompanied by a significant decrease in lipid peroxidation and increase in the antioxidant defense system. In vitro studies with vero cells showed that incubation of DTS (5-50 microg/ml) with Cd (10 microM) significantly reduced the cell death induced by Cd. DTS at 40 microg/ml effectively blocked the cell death and lipid peroxidation induced by Cd (10 microM) indicating its cytoprotective property. Further, the flow cytometric assessment on the level of intracellular reactive oxygen species using a fluorescent probe 2', 7'-dichlorofluorescein diacetate (DCF-DA) confirmed the Cd induced intracellular oxidative stress in vero cells, which was significantly suppressed by DTS (40 microg/ml). The histopathological studies in the kidney of rats also showed that DTS (40 mg/kg bw/day) markedly reduced the toxicity of Cd and preserved the architecture of renal tissue. The present study suggests that the cytoprotective potential of DTS in Cd toxicity might be due to its antioxidant and metal chelating properties, which could be useful for achieving optimum effects in Cd induced renal damage.

Effect of mercury, cadmium, nickel, chromium and zinc on kinetic properties of NADPH-cytochrome P450 reductase purified from leaping mullet (Liza saliens)

Information on the mechanism of metal ion inhibition of NADPH-cytochrome P450 reductase is limited. The purpose of the present paper was to elucidate in vitro effect of Hg(+2), Cd(+2), Ni(+2), Cr(+3) and Zn(+2) ions on the purified mullet NADPH-cytochrome P450 reductase. NADPH-cytochrome P450 reductase was purified from detergent-solubilized liver microsomes from leaping mullet (Liza saliens). All of the metal ions caused inhibition of the enzyme activity except Zn(+2). At 50 microM metal concentration, Hg(+2) inhibited the cytochrome P450 reductase activity completely (100%), while, at the same concentrations, Cd(+2), Cr(+3) and Ni(+2) caused 66%, 65% and 37% inhibition, respectively. At 50 microM metal concentration, Zn(+2) had no apparent effect on cytochrome P450 reductase activity. The IC(50) values of HgCl(2), CrCl(3), CdCl(2) and NiCl(2) were estimated to be 0.07 microM, 24 microM, 33 microM and 143 microM, respectively. Of the metal ions tested, Hg(+2) exhibited much higher inhibitory effect at lower concentrations, so it was evidently a more potent inhibitor than the others. All four metal ions displayed noncompetitive type of inhibition mechanism for the purified reductase as analyzed by Dixon plot. K(i) values of Hg(+2), Cr(+3), Cd(+2), and Ni(+2) were calculated from Dixon plots as 0.048 microM, 18 microM, 73 microM and 329 microM, respectively.

Acute effect of single-dose cadmium treatment on lipid peroxidation and antioxidant enzymes in ovariectomized rats

We investigated the acute effect of single-dose cadmium (Cd) treatment on lipid peroxidation and antioxidant enzymes in liver and kidney of rats following an ovariectomy operation. Twenty-eight female Wistar albino rats were used and were divided into four groups: I, control (n=7); II, cadmium (Cd, n=7); III, ovariectomized (Ovx, n=7); and IV, ovariectomized+cadmium (Ovx-Cd, n=7). Fourteen of the rats were ovariectomized. Twelve weeks later, cadmium chloride (CdCl(2), 5 mg/kg) was administered i.p. as a single dose to the Cd and Ovx-Cd groups. Twenty-four hours after the injection, all rats were sacrificed and had their liver and kidney tissues removed for the measurement of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) levels. SOD activity showed a significant decrease (P<0.001) in both organs of Ovx and Cd rats in comparison to controls. CAT activity was significantly decreased (P<0.01) in the liver of Ovx and Cd groups but not in the kidneys of both groups compared to control values. MDA concentrations were higher (P<0.05) in both organs of Ovx and Cd rats than those values observed in the control group. Similar patterns of changes were observed in the Ovx-Cd rats, but the increase in the MDA levels and the decrease in the antioxidant enzymes for the Ovx-Cd group were higher than those of the Ovx and Cd groups. Based on the data, it can be stated that cadmium increases the effect of ovariectomy on lipid peroxidation, impairs the antioxidant defense system, and induces oxidative stress.

High sucrose consumption potentiates the sub-acute cadmium effect on Na+/K+-ATPase but not on δ-aminolevulinate dehydratase in mice

High sucrose consumption and sub-acute cadmium effects on delta-ALA-D activity, Na+/K+ -ATPase activity, and lipid peroxidation were studied in different tissues of mice. Experimental groups were control, high sucrose (200 g/L), cadmium (5 mg/kg/day, subcutaneously, two consecutive doses in different days in each week, during 4 weeks), and sucrose plus cadmium. There was a significant increase in TBARS levels for spleen and liver in cadmium and sucrose plus cadmium groups. Testicular delta-ALA-D activity of cadmium and sucrose plus cadmium-treated animals was significantly inhibited, whereas the enzyme activity increased in blood (cadmium and sucrose plus cadmium groups) and spleen (sucrose plus cadmium group). Na+/K+ -ATPase activity was significantly decreased in brain and kidney of sucrose plus cadmium-treated animals. Our data indicate that sub-acute cadmium treatment inhibits significantly testicular delta-ALA-D activity, demonstrating the prevalent cadmium effect in vivo on reproductive systems. Furthermore, high sucrose consumption and sub-acute cadmium treatment have interactive effects on cerebral and renal Na+/K+ -ATPase, showing that a short-term intake of high quantity of sucrose can aggravate the toxicity of Cd2+.

A proposed sequence of events for cadmium-induced mitochondrial impairment

Cadmium is a very important environmental toxicant, the cytotoxicity mechanism of which is likely to involve mitochondria as a target. In the present study we addressed the cause/effect relationship between the multiple cadmium-induced responses involving the mitochondrial energetic and oxidative status. Assays were performed with succinate-energized rat liver mitochondria incubated with 5 microM CdCl(2) for 0-25 min, in the absence or presence, respectively, of N-ethylmaleimide (NEM), butylhydroxytoluene (BHT), ruthenium red (RR), and cyclosporine A+ADP. A sequence of events accounting for cadmium-induced mitochondrial impairment is proposed, beginning with an apparent interaction of Cd(2+) with specific protein thiols in the mitochondrial membrane, which stimulates the cation's uptake via the Ca(2+) uniporter, and is followed by the onset of mitochondrial permeability transition (MPT); both effects dissipate the transmembrane electrical potential (Deltapsi), causing uncoupling, followed by an early depression of mitochondrial ATP levels. The respiratory chain subsequently undergoes inhibition, generating reactive oxygen species which together with iron mobilized by the cation, cause late, gradual mitochondrial membrane lipid peroxidation.

Mechanism of primary Cd2+-induced rat liver mitochondria dysfunction: discrete modes of Cd2+ action on calcium and thiol-dependent domains

We attempted to discern discrete sites of Cd2+ deleterious action on rat liver mitochondrial function. In particular, EGTA, ADP, and cyclosporin A (potent mitochondrial permeability transition antagonists) affected mainly Cd2+-induced changes in resting state respiration, eliminating its stimulation in KCl medium, while dithiothreitol (DTT, a dithiol reductant) produced its effect both on Cd2+ activation of the basal respiration and Cd2+ depression of uncoupler-stimulated respiration, evoking its restoration. Substantial differences in DTT influence on mitochondrial respiration at low and high [Cd2+] were revealed, namely, an enhanced mitochondrial permeabilization in the presence of saturated [DTT] at high [Cd2+] took place. Besides, DTT only partially reversed Cd2+-induced swelling in NH4NO3 medium when glutamate plus malate or succinate without rotenone was used. Contrarily, DTT produced complete reversal of the swelling of succinate-energized mitochondria when rotenone was present in the medium. In addition, in the presence of rotenone both Cd2+-produced activation of the resting state respiration in KCl medium and Cd2+-induced swelling in sucrose medium of succinate-energized mitochondria were more sensitive to cyclosporin A than the same Cd2+ effects obtained on mitochondria oxidizing succinate (without rotenone) or glutamate plus malate. We have concluded that Cd2+, producing primary mitochondrial dysfunction, acts both as a thiol and Me2+ binding site reagent. Suppositions about possible localization of separate sites of direct Cd2+ effects on mitochondrial function were made.

Impairment of metabolic capacities in copper and calcium contaminated wild yellow perch (Perca flavescens)

This study examined variations in resting oxygen consumption rate (ROCR), post-exercise oxygen consumption rate, relative scope for activity (RSA), liver and muscle aerobic and anaerobic capacities (using citrate synthase (CS) and lactate dehydrogenase, respectively, as indicators), and tissue biosynthetic capacities (using nucleoside diphosphate kinase (NDPK) as an indicator), in wild yellow perch from four lakes varying in copper (Cu) and cadmium (Cd) contamination. Liver Cu and Cd concentrations largely reflected environmental contamination and were positively correlated with liver protein concentrations and NDPK activities. Our results suggest that metal contamination leads to an upregulation of liver protein metabolism, presumably at least in part for the purpose of metal detoxification. In contrast, muscle NDPK activities decreased with increasing liver Cd concentrations and NDPK activities. There was a 25% decrease in ROCR for a doubling of liver Cu concentrations and a 42% decrease in RSA for a doubling of liver Cd concentrations in the range studied. Cu contamination was also associated with lower muscle CS activities. Our results support previous findings of impaired aerobic capacities in the muscle of metal-contaminated fish, and demonstrate that this impairment is also reflected in aerobic capacities of whole fish. The evidence presented suggests that mitochondria may be primary targets for inhibition by Cu, and that Cd may reduce gill respiratory capacity. Muscle aerobic and anaerobic capacities were inversely related. This work indicates that metal exposure of wild yellow perch leads to a wide range of disturbances in metabolic capacities.

In vitro effect of metal ions on the activity of two amphibian glyceraldehyde-3-phosphate dehydrogenases: potential metal binding sites

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) was purified from two amphibian species, Xenopus laevis and Pleurodeles waltl. Comparative studies revealed that the two proteins differ by their subunit molecular masses, pI values and V8 digested peptide maps. The effect of zinc, cadmium and copper ions on GAPDH enzymatic activity has been examined in vitro. A time, metal concentration and metal type dependent inhibition was observed for both enzymes. X. laevis and P. waltl GAPDHs exhibit a much greater sensitivity to copper than to cadmium or zinc ions. Different half-lives and differential sensitivity to various metals was observed between the two enzymes with P. waltl GAPDH being remarkably tolerant to cadmium ions compared to the X. laevis enzyme. In order to understand the differential sensitivity of the two enzymes to metals, we produced 3D models of both X. laevis and P. waltl GAPDH structures based upon known 3D structures of GAPDHs from other species. This necessitated, in a first step, to clone a 900 bp cDNA fragment encoding the nearly full-length P. waltl GAPDH. Spatial motif searches on the homology models indicated potential metal binding sites involving cysteine and histidine residues outside the catalytic sites, existing only in either the X. laevis or the P. waltl GAPDH sequences.

Antioxidant effect of hydroxytyrosol (DPE) and Mn2+ in liver of cadmium-intoxicated rats

Liver TBARS formation in cadmium-intoxicated rats was completely reduced by administering a low amount of MnCl(2) (2 mg/kg b.w.) 1 h before intoxication. A similar antioxidant effect was first shown by hydroxytyrosol (2-(3,4-dihydroxyphenyl)ethanol, (DPE), a phenolic compound present in olive oil, given twice to rats (9 mg/kg b.w.) after cadmium administration. The antioxidant properties shown in vivo by both Mn(2+) and DPE were also active in vitro when rat liver microsomes were subjected to lipid peroxidation by cadmium or other prooxidant systems. The increase in liver glutathione concentrations occurring in cadmium-intoxicated rats, was also found, for the first time, 24 h after MnCl(2) administration. Unlike cadmium intoxication, which caused a higher formation of both glutathione and TBARS, Mn(2+) induced glutathione synthesis without any TBARS formation. The same situation was also observed when cadmium plus Mn(2+) or cadmium plus DPE was given to rats. Our data show that: (a). both DPE and low Mn(2+) concentrations may have an antioxidant effect in the livers of cadmium-intoxicated rats and (b). Mn(2+), like cadmium, induces liver glutathione synthesis and this effect is probably independent of TBARS formation.

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.

Cyclosporin A-sensitive permeability transition pore is involved in Cd(2+)-induced dysfunction of isolated rat liver mitochondria: doubts no more

There is dose-dependent Cd(2+)-evoked swelling of isolated rat liver mitochondria energized by complex I, II, or IV respiratory substrates in sucrose medium in the absence of added Ca(2+) and P(i), which is prevented by Sr(2+). Permeability transition effectors (ADP, CsA, EGTA, RR, DTT, ATR, P(i), and Ca(2+)) affect in a corresponding way Cd(2+)-promoted membrane permeabilization in NH(4)NO(3), KCl, and sucrose media. Maximal depression of Cd(2+)-induced swelling is achieved by simultaneous addition of ADP, Mg(2+), and CsA that produces either synergistic (NH(4)NO(3)) or additive (KCl and sucrose media) action. Sustained activation by low [Cd(2+)] of mitochondrial basal respiration in KCl medium is observed both in the absence and in the presence of rotenone and/or oligomycin but only in the latter case (rotenone+oligomycin) CsA inhibits completely Cd(2+) activation of St 4 respiration and partially reverses DNP-uncoupled respiration depressed by cadmium. Cd(2+) effects are discussed in terms of comparison with those of Zn(2+) and PhAsO.