Long-term cadmium exposure accelerates age-related mitochondrial changes in renal epithelial cells

Experimental study for inorganic and organic profiling of toy makeup products: Estimating the potential threat to child health

Inorganic elements are added to toys as impurities to give desired stability, brightness, flexibility, and color; however, these elements may cause numerous health issues after acute or chronic exposure. In this study, the inorganic profile of 14 elements (Al, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Se, Sb, Pb, and Zn) in 63 toy makeup products was identified by inductively coupled plasma-mass spectrometry after microwave acid digestion method. Additionally, organic allergen fragrance was investigated by gas chromatography-mass spectrometry. The systemic exposure dosage (SED), margin of safety (MoS), lifetime cancer risk (LCR), hazard quotient (HQ), and hazard indices were used to assess the safety evaluation. Then, 57 out of 63 samples (90.48%) exceeded the limits at least for one toxic element with descending order Ni > Cr > Co > Pb > Sb > Cd > As > Hg. The SED values were compared with tolerable daily intake values and remarkably differences were found for Al and Pb. The MoS values for 57.15% of samples exceeded the limit value for Al, As, Cd, Co, Hg, Mn, Sb, and Zn elements. The LCR values were observed at 100% (n = 63), 79.37% (n = 50), 85.71% (n = 54), 77.78% (n = 49), and 18.87% (n = 10) for Cr, Ni, As, Pb, and Cd, respectively. Also, the skin sensitization risks were obtained for Cr and Ni at 26.980% (n = 17) and 9.52% (n = 6), respectively. The HQ values for 80% of samples were found to be ≥ 1 at least for one parameter. The investigation of fragrance allergens in samples did not show any significant ingredients. As a result, toy makeup products marketed in local stores were found to be predominantly unsafe. Children should be protected from harmful chemicals by regular monitoring and strict measures.

Defective autophagic flux aggravates cadmium-induced Sertoli cell apoptosis

The male reproductive dysfunction accounts for 50% of infertile couples in the world. Cadmium (Cd) is one of the most harmful heavy metals to both the environment and inhabitants. Accumulating data suggest that Cd could cause male infertility. Sertoli cell (SC) is a somatic cell of testis and a key regulator of spermatogenesis by providing physical and nutritional support for developing sperm. Many studies showed that Cd induced dysfunction of SCs was directly related to male reproductive damage. However, the mechanism of SCs injury caused by Cd remains to be clarified. We found that Cd treatment caused a significant increase of apoptosis in SCs cells, accompanied by a marked increase in the production of ROS. These results were associated with the formation of mitochondria-containing autophagosomes and increased expression of LC3-II in vitro. Interestingly, our results showed that Cd did not promote but inhibited the fusion of mitochondria-containing autophagosomes with lysosomes by reducing the function of lysosomes. Together, this study provides insight into the negative effects of Cd, which interferes with autophagic flux and induces the apoptosis of SCs.

PINK1/Parkin-mediated mitophagy modulates cadmium-induced apoptosis in rat cerebral cortical neurons

Cadmium is a persistent environmental pollutant whose neurotoxicity is of serious concern. Mitochondrial dysfunction and its mediated mitophagy and apoptosis are considered key events in Cd-induced neurological pathologies, but the exact molecular mechanism has not been fully elucidated. The aim of this study was to investigate the relationship between Cd-induced mitophagy and apoptosis and their role in Cd-induced neuronal death. Using the mitophagy inhibitor cyclosporine A (CsA), we found that the extent of mitophagy mediated by the PTEN-induced putative kinase protein 1 (PINK1)/E3 ubiquitin ligase (Parkin) pathway decreased, whereas the level of apoptosis and cell death increased in rat cerebral cortical neurons in vitro. Consistent with this, the knockdown of PINK1 also exacerbated Cd-induced apoptosis and neuronal death. Furthermore, the results of the in vivo experiments showed that Cd simultaneously activated both mitophagy and apoptosis and that the suppression of mitophagy by CsA aggravated Cd-induced apoptosis. In summary, our results indicate that PINK1/Parkin-mediated mitophagy exerts an important neuroprotective effect by inhibiting Cd-mediated apoptosis in rat cerebral cortical neurons both in vitro and in vivo. This work may allow the development of new therapeutic strategies for Cd-induced central nervous system disorders.

Puerarin alleviates cadmium-induced mitochondrial mass decrease by inhibiting PINK1-Parkin and Nix-mediated mitophagy in rat cortical neurons

Cadmium (Cd) has well-known central nervous system toxicity, and mitochondria are direct targets of Cd-induced neuronal toxicity. However, how Cd induces mitochondrial mass decrease in terms of its neurotoxic effects remains unknown. Puerarin, an isoflavone extracted from kudzu root, can cross the blood-brain barrier and exert protective effects in nervous system disease. The purpose of the study was to determine the mechanism of Cd-induced mitochondrial mass decrease and the protective role of puerarin in rat cortical neurons. The results indicated that Cd induced mitochondrial mass decrease by activating mitophagy mediated by the PTEN-induced putative kinase protein 1 (PINK1)-E3 ubiquitin ligase (Parkin) and Nip3-like protein X (Nix) pathways in rat cortical neurons. Puerarin improved the Cd-induced decrease in mitochondrial membrane potential (MMP) in vitro, and blocked PINK1-Parkin and Nix-mediated mitophagy, inhibiting Cd-induced mitochondrial mass decrease in rat cortical neurons in vitro and in vivo. In summary, our data clearly indicated that puerarin protects rat cortical neurons against Cd-induced neurotoxicity by ameliorating mitochondrial damage, inhibiting mitophagy-mediated mitochondrial mass decrease. Puerarin appears to have great potential as a neuroprotective agent.

Potential mechanisms of some selected heavy metals in the induction of inflammation and autoimmunity

Inflammation is a physiological event that protects tissues from infection and injury. Chronic inflammation causes immune cell over activation and sustained release of inflammatory cytokines and chemokines cause pathologic conditions including autoimmune diseases. Heavy metals exposure affects innate and adaptive immune systems through triggering inflammatory responses. It seems that extended inflammatory responses could accelerate heavy metal-induced autoimmunity. In the present review we discuss the exposure route and toxicity of Cadmium (Cd), Lead (Pb), Mercury (Hg), Vanadium (V) and Platinum (Pt) and their effects on inflammatory responses by innate and adaptive immune system and autoimmunity.

Mitochondrial DNA Mutagenesis: Feature of and Biomarker for Environmental Exposures and Aging

PURPOSE OF REVIEW

Mitochondrial dysfunction is a hallmark of aging. Mitochondrial genome (mtDNA) instability contributes to mitochondrial dysfunction, and mtDNA mutagenesis may contribute to aging. However, the origin of mtDNA mutations remains somewhat controversial. The goals of this review are to introduce and review recent literature on mtDNA mutagenesis and aging, address recent animal and epidemiological evidence for the effects of chemicals on mtDNA damage and mutagenesis, propose hypotheses regarding the contribution of environmental toxicant exposure to mtDNA mutagenesis in the context of aging, and suggest future directions and approaches for environmental health researchers.

RECENT FINDINGS

Stressors such as pollutants, pharmaceuticals, and ultraviolet radiation can damage the mitochondrial genome or disrupt mtDNA replication, repair, and organelle homeostatic processes, potentially influencing the rate of accumulation of mtDNA mutations. Accelerated mtDNA mutagenesis could contribute to aging, diseases of aging, and sensitize individuals with pathogenic mtDNA variants to stressors. We propose three potential mechanisms of toxicant-induced effects on mtDNA mutagenesis over lifespan: (1) increased de novo mtDNA mutations, (2) altered frequencies of mtDNA mutations, or (3) both. There are remarkably few studies that have investigated the impact of environmental chemical exposures on mtDNA instability and mutagenesis, and even fewer in the context of aging. More studies are warranted because people are exposed to tens of thousands of chemicals, and are living longer. Finally, we suggest that toxicant-induced mtDNA damage and mutational signatures may be a sensitive biomarker for some exposures.

Cadmium-Induced Cytotoxicity: Effects on Mitochondrial Electron Transport Chain

Cadmium (Cd) is a well-known heavy metal and environmental toxicant and pollutant worldwide, being largely present in every kind of item such as plastic (toys), battery, paints, ceramics, contaminated water, air, soil, food, fertilizers, and cigarette smoke. Nowadays, it represents an important research area for the scientific community mainly for its effects on public health. Due to a half-life ranging between 15 and 30 years, Cd owns the ability to accumulate in organs and tissues, exerting deleterious effects. Thus, even at low doses, a Cd prolonged exposure may cause a multiorgan toxicity. Mitochondria are key intracellular targets for Cd-induced cytotoxicity, but the underlying mechanisms are not fully elucidated. The present review is aimed to clarify the effects of Cd on mitochondria and, particularly, on the mitochondrial electron transport chain.

Ameliorative effects of resveratrol against cadmium-induced nephrotoxicity via modulating nuclear xenobiotic receptor response and PINK1/Parkin-mediated Mitophagy

Cadmium (Cd) is a toxic pollutant with high nephrotoxicity in the agricultural environment. Resveratrol has been found to have a renoprotective effect but the underlying mechanisms of this have not yet been fully elucidated. The aim of this study is to illustrate the antagonism of resveratrol against Cd-induced nephrotoxicity. A total of 80 birds were divided randomly into 4 groups and treated via diet for 90 days as follows: control group (Con); 400 mg kg-1 resveratrol group (Resv); 140 mg kg-1 Cd group (Cd 140); and 140 mg kg-1 Cd + 400 mg kg-1 resveratrol group (Cd + Resv). It was observed that resveratrol treatment dramatically alleviated Cd-induced histopathological lesions of the kidney. Simultaneously, resveratrol mitigated Cd-induced oxidative stress by reducing MDA and H2O2 production, alleviating GSH depletion and restoring the activity of antioxidant enzymes (T-SOD, Cu-Zn SOD, CAT, GST and GSH-Px). Resveratrol activated NXRs (CAR/PXR/AHR/Nrf2) signaling pathways and exerted antidotal roles by enhancing the phase I and II detoxification systems to relieve oxidative damage. Moreover, resveratrol ameliorated Cd-induced ultrastructural abnormality and mitochondria dysfunction by recovering mitochondrial function-related factors VDAC1, Cyt C and Sirt3 upregulation and Sirt1, PGC-1α, Nrf1 and TFAM transcription restrictions. Resveratrol attenuated Cd-induced excessive mitochondrial fission and promoted mitochondrial fusion, which reversed PINK1/Parkin-mediated mitophagy initiation. Collectively, our findings explicate the potential protection against Cd-induced nephrotoxicity and mitochondria damage.

Cell organelles as targets of mammalian cadmium toxicity

Ever increasing environmental presence of cadmium as a consequence of industrial activities is considered a health hazard and is closely linked to deteriorating global health status. General animal and human cadmium exposure ranges from ingestion of foodstuffs sourced from heavily polluted hotspots and cigarette smoke to widespread contamination of air and water, including cadmium-containing microplastics found in household water. Cadmium is promiscuous in its effects and exerts numerous cellular perturbations based on direct interactions with macromolecules and its capacity to mimic or displace essential physiological ions, such as iron and zinc. Cell organelles use lipid membranes to form complex tightly-regulated, compartmentalized networks with specialized functions, which are fundamental to life. Interorganellar communication is crucial for orchestrating correct cell behavior, such as adaptive stress responses, and can be mediated by the release of signaling molecules, exchange of organelle contents, mechanical force generated through organelle shape changes or direct membrane contact sites. In this review, cadmium effects on organellar structure and function will be critically discussed with particular consideration to disruption of organelle physiology in vertebrates.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

Cadmium-induced toxicity is rescued by curcumin: A review

Cadmium (Cd) is one of the most common environmental and occupational heavy metals with extended distribution. Exposure to Cd may be associated with several deleterious consequences on the liver, bones, kidneys, lungs, testes, brain, immunological, and cardiovascular systems. Overproduction of reactive oxygen species (ROS) as the main mechanism behind its toxicity causes oxidative stress and subsequent damages to lipids, proteins, and DNA. Therefore, antioxidants along with chelating agents have shown promising outcomes against Cd-induced toxicity. Curcumin with various beneficial effects and medical efficacy has been evaluated for its inhibitory activities against biological impairments caused by Cd. Thus, this article is intended to address the effectiveness of curcumin against toxicity following Cd entry. Curcumin can afford to attenuate lipid peroxidation, glutathione depletion, alterations in antioxidant enzyme, and so forth through scavenging and chelating activities or Nrf2/Keap1/ARE pathway induction. © 2017 BioFactors, 43(5):645-661, 2017.

Tyrosine phosphorylation of dihydrolipoamide dehydrogenase as a potential cadmium target and its inhibitory role in regulating mouse sperm motility

Cadmium (Cd) is reported to reduce sperm motility and functions. However, the molecular mechanisms of Cd-induced toxicity remain largely unknown, presenting a major knowledge gap in research on reproductive toxicology. In the present study, we identified a candidate protein, dihydrolipoamide dehydrogenase (DLD), which is a post-pyruvate metabolic enzyme, exhibiting tyrosine phosphorylation in mouse sperm exposed to Cd both in vivo and in vitro. Immunoprecipitation assay demonstrated DLD was phosphorylated in tyrosine residues without altered expression after Cd treatment, which further confirmed our identified result. However, the tyrosine phosphorylation of DLD did not participate in mouse sperm capacitation and Bovine Serum Albumin (BSA) effectively prevented the tyrosine phosphorylation of DLD. Moreover, Cd-induced tyrosine phosphorylation of DLD lowered its dehydrogenase activity and meanwhile, Nicotinamide Adenine Dinucleotide Hydrogen (NADH) content, Adenosine Triphosphate (ATP) production and sperm motility were all inhibited by Cd. Interestingly, when the tyrosine phosphorylation of DLD was blocked by BSA, the decrease of DLD activity, NADH and ATP content as well as sperm motility was also suppressed simultaneously. These results suggested that Cd-induced tyrosine phosphorylation of DLD inhibited its activity and thus suppressed the tricarboxylic acid (TCA) cycle, which resulted in the reduction of NADH and hence the ATP production generated through oxidative phosphorylation (OPHOXS). Taken together, our results revealed that Cd induced DLD tyrosine phosphorylation, in response to regulate TCA metabolic pathway, which reduced ATP levels and these negative effects led to decreased sperm motility. This study provided new understanding of the mechanisms contributing to the harmful effects of Cd on the motility and function of spermatozoa.

Protective effect of curcumin against heavy metals-induced liver damage

Occupational or environmental exposures to heavy metals produce several adverse health effects. The common mechanism determining their toxicity and carcinogenicity is the generation of oxidative stress that leads to hepatic damage. In addition, oxidative stress induced by metal exposure leads to the activation of the nuclear factor (erythroid-derived 2)-like 2/Kelch-like ECH-associated protein 1/antioxidant response elements (Nrf2/Keap1/ARE) pathway. Since antioxidant and chelating agents are generally used for the treatment of heavy metals poisoning, this review is focused on the protective role of curcumin against liver injury induced by heavy metals. Curcumin has shown, in clinical and preclinical studies, numerous biological activities including therapeutic efficacy against various human diseases and anti-hepatotoxic effects against environmental or occupational toxins. Curcumin reduces the hepatotoxicity induced by arsenic, cadmium, chromium, copper, lead and mercury, prevents histological injury, lipid peroxidation and glutathione (GSH) depletion, maintains the liver antioxidant enzyme status and protects against mitochondrial dysfunction. The preventive effect of curcumin on the noxious effects induced by heavy metals has been attributed to its scavenging and chelating properties, and/or to the ability to induce the Nrf2/Keap1/ARE pathway. However, additional research is needed in order to propose curcumin as a potential protective agent against liver damage induced by heavy metals.

Damaging effects of water-borne cadmium chloride on DNA of lung cells of immature mice

We investigated the effects of cadmium on lung cell DNA in immature mice. The mice were randomly divided into four groups: control group, low-dose group (1/100 LD(50)), middle-dose group (1/50 LD(50)), and high-dose group (1/25 LD(50)); they were supplied with cadmium chloride or control water for 40 days. Lung cells collected from sacrificed mice were used to evaluate the extent of DNA damage by comet assay. The ratio of tailing cells, DNA tail length, DNA comet length, DNA tail moment, DNA olive tail moment, and percentage of DNA in the comet tail were measured. The rate of tailing lung cells exposed to cadmium increased significantly; the low-concentration group had significantly (P < 0.05) higher rates, and the middle- and high-concentration groups had higher (P < 0.01) rates compared to the control. DNA tail length, DNA comet length, DNA tail moment, and DNA olive tail moment all increased with the increase in cadmium doses, but compared with those of the control group, no significant differences in low-dose group were found (P > 0.05), and the differences in middle- and high-dose groups were all highly significant (P < 0.01). The degree of DNA damage also increased with the increase of the cadmium concentrations. We conclude that cadmium significantly increases DNA damage in lung cells of immature mice in a dose-dependent manner.

Cadmium accumulation and antioxidant responses in Sparus aurata exposed to waterborne cadmium

Cadmium (Cd), a nonessential trace element, is rapidly accumulated by most living organisms and subsequently exerts its toxicity at different molecular levels. This study exposed gilthead sea bream (Sparus aurata) to waterborne 0.1 mg/l Cd for 11 days and investigated the Cd accumulation pattern, lipid oxidation, and response of antioxidant defences. At the end of the experiment, mean Cd concentrations in gills and liver, the organs most prone to metal accumulation, were 209.4 and 371.7 ng/g ww, respectively. Muscle did not show any Cd retention during the 11 days of exposure. In liver, the cytosolic fraction of the metal was chelated into the nontoxic form by metallothionein (MT), a specific Cd-inducible protein. Zn and Cu concentrations were not influenced by Cd exposure. Glutathione (GSH) concentrations and the antioxidant enzyme activities of GSH reductase and GSH peroxidase showed an overall decreasing trend. In addition, lipid and aqueous hydroperoxide levels did not show any significant variation. Oxidative stress indirectly generated by Cd seems to be compensated for by the different biochemical systems tailored to decrease cellular damage. In particular, the negative effects of Cd accumulation in tissues were probably counteracted by the induction of MT.

Internal distribution of uranium and associated genotoxic damages in the chronically exposed bivalve Corbicula fluminea

Uranium (U) internal distribution and involved effects in the bivalve Corbicula fluminea have been studied after direct chronic exposure (90 d, 10 μg.L-1). U distribution was assessed at the subcellular level (Metal Rich Granules -MRG-, pellets and cytosol fractions) in two main organs of the bivalve (gills and visceral mass). Micro-localisation was investigated by TEM-EDX analysis in the gills epithelium. DNA damage in gill and hemolymph samples was measured by the Comet assay. The 90-d exposure period led to a significant increase of U concentration in gills over time (× 5) and a large U quantity in subcellular granules in gills. Finally, a significant increase (× 2) in DNA damage was noted in exposed gills and haemocytes. This study shows that the accumulation levels and consequently the potential toxicity cannot be successfully predicted only on the basis of concentration in water or in tissues and subcellular fractions after chronic exposure.

Metabolic profiling of cadmium-induced effects in one pioneer intertidal halophyte Suaeda salsa by NMR-based metabolomics

Cadmium is a non-essential element to living organisms and has become the severe contaminant in both seawater and sediment in the intertidal zones of the Bohai Sea. The halophyte, Suaeda salsa is the pioneer plant in the intertidal zones of Bohai Sea and has been widely applied in environmental sciences. In this study, the dose- and time-dependent effects induced by environmentally relevant concentrations (2, 10 and 50 μg l(-1)) of cadmium were characterized in S. salsa using NMR-based metabolomics. The levels of amino acids (valine, leucine, glutamate, tyrosine, etc.), carbohydrates (glucose, sucrose and fructose), intermediates of tricarboxylic acid cycle (succinate, citrate, etc.) and osmolyte (betaine) were altered in the S. salsa samples after cadmium exposures. These metabolic biomarkers indicated the elevated protein degradation and disturbances in the osmotic regulation and energy metabolism caused by cadmium in S. salsa. Overall, our results demonstrated the applicability of NMR-based metabolomics for the detection of metabolic biomarkers that could be used for the interpretation of toxicological effects induced by contaminants in the pioneer plant S. salsa in the intertidal zones. In addition, the metabolic biomarkers could be potentially useful for the bio-monitoring of contaminants in the intertidal zones.

NMR-based metabolomic studies on the toxicological effects of cadmium and copper on green mussels Perna viridis

Traditional toxicology studies have focused on selected biomarkers to characterize the biological stress induced by metals in marine organisms. In this study, a system biology tool, metabolomics, was applied to the marine mussel Perna viridis to investigate changes in the metabolic profiles of soft tissue as a response to copper (Cu) and cadmium (Cd), both as single metal and as a mixture. The major metabolite changes corresponding to metal exposure are related to amino acids, osmolytes, and energy metabolites. Following metal exposure for 1 week, there was a significant increase in the levels of branched chain amino acids, histidine, glutamate, glutamine, hypotaurine, dimethylglycine, arginine and ATP/ADP. For the Cu+Cd co-exposed mussels, the levels of lactate, branched chain amino acid, succinate, and NAD increased, whereas the levels of glucose, glycogen, and ATP/ADP decreased, indicating a different metabolic profile for the single metal exposure groups. After 2 weeks of exposure, the mussels showed acclimatization to Cd exposure based on the recovery of some metabolites. However, the metabolic profile induced by the metal mixture was very similar to that from Cu exposure, suggesting that Cu dominantly induced the metabolic disturbances. Both Cu and Cd may lead to neurotoxicity, disturbances in energy metabolism, and osmoregulation changes. These results demonstrate the high applicability and reliability of NMR-based metabolomics in interpreting the toxicological mechanisms of metals using global metabolic biomarkers.

Fibroblast growth factor 23 mediates the phosphaturic actions of cadmium

Phosphaturia has been documented following cadmium (Cd) exposure in both humans and experimental animals. The fibroblast growth factor 23 (FGF23)/klotho axis serves as an essential phosphate homeostasis pathway in the bone-kidney axis. In the present study, we investigated the effects of Cd on phosphate (Pi) homeostasis in mice. Following Cd injection into WT mice, plasma FGF23 concentration was significantly increased. Urinary Pi excretion levels were significantly higher in Cd-injected WT mice than in control group. Plasma Pi concentration decreased only slightly compared with control group. No change was observed in plasma parathyroid hormone and 1,25-dihydroxy vitamin D(3) in both group of mice. We observed a decrease in phosphate transport activity and also decrease in expression of renal phosphate transporter SLC34A3 [NaPi-IIc/NPT2c], but not SLC34A1 [NaPi-IIa/NPT2a]. Furthermore, we examined the effect of Cd on Npt2c in Npt2a-knockout (KO) mice which expresses Npt2c as a major NaPi co-transporter. Injecting Cd to Npt2aKO mice induced significant increase in plasma FGF23 concentration and urinary Pi excretion levels. Furthermore, we observed a decrease in phosphate transport activity and renal Npt2c expression in Cd-injected Npt2a KO mice. The present study suggests that hypophosphatemia induced by Cd may be closely associated with the FGF23/klotho axis.

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.

Proteomic changes in response to acute cadmium toxicity in gill tissue of Paralichthys olivaceus

In the present study, we developed a two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) technique for examining the response of the proteome from gill tissue of Paralichthys olivaceus (POGT) to acute cadmium (AC) toxicity. Approximately 700 protein spots were detected from the gill sample when applying a 600μg protein 2D-PAGE gel in the pH range 5.0-8.0, and approximately 400 of these were identified by peptide mass fingerprinting (PMF) and database search. Compared to a control sample, significant changes were visualized in 18 protein spots exposed to seawater cadmium acute toxicity at 10.0ppm for 24h. Among these spots, two were up-regulated, one was down-regulated, seven showed low expression, and eight showed high expression. The collected spots were further identified by PMF and database search. Ten of the 18 proteins identified on the 2D-PAGE gel, including heat shock protein 70 and calcium-binding protein, demonstrated a synchronous response to AC, and we suggest that the variable levels and trends of these spots on the gel might be utilized as biomarker profiles to investigate cadmium contamination levels in seawater and to evaluate the degree of risk of human fatalities. The experimental results emphasize that the application of multiple biomarkers has an advantage over single biomarkers for monitoring levels of heavy metal contamination in seawater.

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.

Heavy metal and mineral concentrations and their relationship to histopathological findings in the bowhead whale (Balaena mysticetus)

The bowhead whale (Balaena mysticetus) is a species endangered over much of its range that is of great cultural significance and subsistence value to the Inuit of Northern Alaska. This species occupies subarctic and arctic regions presently undergoing significant ecological change and hydrocarbon development. Thus, understanding the health status of the Bering-Chukchi-Beaufort Sea (BCBS) stock of bowhead whales is of importance. In this study, we evaluated the concentrations of six essential and non-essential elements (Zn, tHg, Ag, Se, Cu and Cd) in liver and kidney of bowhead whales (n=64). These tissues were collected from the Inuit subsistence hunt in Barrow, Wainwright and Kaktovik, Alaska between 1983 and 2001. Reference ranges of these elements (including previously reported data from 1983-1997) were developed for this species as part of a health assessment effort, and interpreted using improved aging techniques (aspartic acid racemization and baleen isotopic (13)C methods) to evaluate trends over time with increased statistical power. Interactions between element concentrations and age, sex and harvest season were assessed. Age was found to be of highest significance. Sex and harvest season did not effect the concentrations of these elements, with the exception of renal Se levels, which were significantly higher in fall seasons. In addition, histological evaluation of tissues from whales collected between 1998-2001 was performed. Associations between concentrations of Cd in kidney and liver and scored histopathological changes were evaluated. Liver Cd concentration was strongly associated with the degree of lung fibromuscular hyperplasia (P=0.001) and moderately associated with the degree of renal fibrosis (P=0.03). Renal Cd concentration influenced the degree of lung fibromuscular hyperplasia and renal fibrosis (P=0.01). A significant age effect was found for both pulmonary fibromuscular hyperplasia and renal fibrosis, indicating age may be a causative factor. Improvements in aging techniques and the addition of histological indices help clarify the relationships between elements and the influence of life history parameters on concentrations of these elements and potential impacts on health. These data provide essential baseline input useful for monitoring the effects of arctic ecosystem change as it relates to global climate change and industrial development, as well as help inform epidemiological studies examining the public health implications of heavy metals in subsistence foods.

Single and Combination Toxic Metal Exposures Induce Apoptosis in Cultured Murine Podocytes Exclusively via the Extrinsic Caspase 8 Pathway

Arsenite, cadmium, and mercury are among the most abundant toxic metals (TM) in the environment. Although the most common renal manifestation of TM toxicity is proximal tubular dysfunction, significant glomerular injury can also occur. We hypothesized that glomerular injury following TM exposure results from TM-induced apoptosis of podocytes. To test this hypothesis we examined the extent of apoptosis and the apoptotic pathways induced in cultured murine podocytes incubated for three days with arsenite, cadmium, or mercury, and with equimolar combinations of all three metals. Apoptosis was detected by DNA laddering, and the number of apoptotic nuclei determined by Tunel assay. Treatment for three days with each TM resulted in DNA laddering and induced a dose-dependent increase in apoptotic nuclei. In contrast, treatment with equimolar combinations of TM induced significantly fewer apoptotic nuclei than individual TM treatments. Apoptosis induced by each TM was associated with a significant (approximately 400%) increase in caspase 8 activity, but no change in caspase 9 activity, and Western analyses revealed a marked up-regulation of Fas (approximately 500%) and FADD (approximately 300%) with no change in expression of Bax, Bcl-2, or Bcl-xL. Similar to the apoptotic response, combinations of TM induced less caspase 8 activity and Fas/FADD expression than individual TM treatments. Collectively, these results demonstrate that (1) TM induced apoptosis in cultured murine podocytes via the extrinsic Fas-FADD caspase 8 pathway, rather than the mitochondrial apoptotic pathway, and (2) combination TM exposure induced less apoptosis than individual TM, indicating an antagonistic rather than an additive or synergistic toxicity.

Effect of low-level lifetime exposure to cadmium on calciotropic hormones in aged female rats

The effect of low-level lifetime exposure to cadmium (Cd) on calciotropic hormones and the possible association between the Cd-induced disorders in bone metabolism and these hormones were investigated on a female rat model of human environmental exposure in areas unpolluted by this metal. For this purpose, the concentrations of 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D (1,25(OH)(2)D), calcitonin (CT) and parathormone (PTH) were measured in the serum of control and Cd-exposed (1 mg Cd/l in drinking water for 24 months) female rats. Calcium (Ca) and inorganic phosphorus (P(i)) serum concentrations, renal tubular reabsorption of Ca (TRCa) and phosphate (TRP) and the glomerular filtration rate (GFR) were estimated as well. Moreover, 1,25(OH)(2)D, metallothionein (MT) and Cd were determined in the kidney. The exposure to Cd led to a decrease in the serum concentrations of 25OHD and 1,25(OH)(2)D (by 50 and 31%, respectively) and the concentration of 1,25(OH)(2)D in the kidney mitochondrial fraction (by 55%). The serum concentrations of CT and PTH increased (5.2-fold and by 29%, respectively) and those of Ca and P(i) were unchanged, whereas the TRCa, TRP and GFR decreased due to the exposure to Cd. The results give evidence that the low lifetime exposure to Cd disturbs the metabolism of calciotropic hormones and damages the reabsorptive and filtrative function of the kidney in aged female rats. Numerous correlations noted between calciotropic hormones and the indices of kidney function, and indices of bone turnover and bone mineral status (bone mineral content and density) of these females indicate a relationship between these hormones and the kidney functional status and bone metabolism. The results of the present study together with our previous findings on the bone status in the experimental model allow for the conclusion that the low lifetime exposure to Cd by affecting the metabolism and proper function of calciotropic hormones may contribute to the advancement of bone damage at the elderly.