Bioaccumulation of thallium and other trace metals in Biscutella laevigata nearby a decommissioned zinc-lead mine (Northeastern Italian Alps)

The mineral body exploited in Salafossa (Eastern Dolomites) was one of the largest lead/zinc-containing mineral deposits in Europe. Both metals were mainly present as sulphides (sphalerite, ZnS and galena, PbS). Mining activity started around 1550, but it was only around 1960 that the richest veins of the minerals were discovered. The mine closed in 1985, and concentrations of several trace metals, such as thallium (Tl), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn), were detected in the soils and plant samples (Biscutella laevigata L.) that were collected from eighteen sites selected outside the mine. B. laevigata is a pseudometallophyta species, and it often grows near mining areas where the soil's metal concentrations are significantly higher than those of soil with a natural geochemical background. The total metal concentrations in the plant tissue (roots and leaves of Biscutella laevigata) and in the soil samples - both bulk-soil and the B. laevigata root system (rhizo-soil) - were determined through Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The metal extractability and leachability of the soil samples were estimated using soil extractions with DTPA (Diethylenetriaminepentaacetic acid). In addition, metal mobility caused by rainwater runoff was estimated by using a leaching test with a dilute solution of H₂SO₄ and HNO₃. The results showed that metals were present in a chemical form available for uptake by the plants' roots. In fact, high concentrations of the metals were also found in the plant tissue (roots and leaves) of B. laevigata, and these concentrations were higher than those whose soils present natural geochemical background levels in the corresponding rhizo-soil. Thus, B. laevigata has shown a marked ability to bioaccumulate trace metals, especially Tl and, to a lesser extent, Zn, Pb, Fe and Mn, and it can influence metal mobility in the rhizo-soil. To assess the uptake and translocation processes of the trace metals, resulting in their bioaccumulation, two different indices were calculated: the enrichment factor in roots (EFr), as the ratio between the metal concentration in belowground biomass and in the respective rhizo-soil, and the translocation factor (TF), as the ratio between the metal concentration in the leaves and the corresponding roots. For both indices, values > 1 denoted enrichment of the metal in the roots or its translocation to the upper tissues. The results showed that EFr and TF were considerably high only for Tl, reaching a maximum value of 60 for EFr and 11.6 for TF. Conversely, the other investigated metals did not show significant bioaccumulation (EFr < 1), and they showed TF > 1 only at a few sites.

Development and validation of a metal mixture bioavailability model (MMBM) to predict chronic toxicity of Ni-Zn-Pb mixtures to Ceriodaphnia dubia

Recently, several bioavailability-based models have been shown to predict acute metal mixture toxicity with reasonable accuracy. However, the application of such models to chronic mixture toxicity is less well established. Therefore, we developed in the present study a chronic metal mixture bioavailability model (MMBM) by combining the existing chronic daphnid bioavailability models for Ni, Zn, and Pb with the independent action (IA) model, assuming strict non-interaction between the metals for binding at the metal-specific biotic ligand sites. To evaluate the predictive capacity of the MMBM, chronic (7d) reproductive toxicity of Ni-Zn-Pb mixtures to Ceriodaphnia dubia was investigated in four different natural waters (pH range: 7-8; Ca range: 1-2 mM; Dissolved Organic Carbon range: 5-12 mg/L). In each water, mixture toxicity was investigated at equitoxic metal concentration ratios as well as at environmental (i.e. realistic) metal concentration ratios. Statistical analysis of mixture effects revealed that observed interactive effects depended on the metal concentration ratio investigated when evaluated relative to the concentration addition (CA) model, but not when evaluated relative to the IA model. This indicates that interactive effects observed in an equitoxic experimental design cannot always be simply extrapolated to environmentally realistic exposure situations. Generally, the IA model predicted Ni-Zn-Pb mixture toxicity more accurately than the CA model. Overall, the MMBM predicted Ni-Zn-Pb mixture toxicity (expressed as % reproductive inhibition relative to a control) in 85% of the treatments with less than 20% error. Moreover, the MMBM predicted chronic toxicity of the ternary Ni-Zn-Pb mixture at least equally accurately as the toxicity of the individual metal treatments (RMSE_Mix = 16; RMSE_{Zn only} = 18; RMSE_{Ni only} = 17; RMSE_{Pb only} = 23). Based on the present study, we believe MMBMs can be a promising tool to account for the effects of water chemistry on metal mixture toxicity during chronic exposure and could be used in metal risk assessment frameworks.

Dietary manganese source does not affect Mn, Zn and Cu tissue deposition and the activity of manganese-containing enzymes in lambs

Manganese (Mn) is a trace element required for normal physiological processes in animals and humans. Organic forms of trace elements are expected to have higher bioavailability in comparison with inorganic sources. The effect of feeding a diet supplemented with different sources of manganese to lambs was studied in a 112-d feeding trial. The aim of this study was to investigate the deposition of Mn in relation to activities of superoxide dismutase (SOD), manganese superoxide dismutase (MnSOD) and arginase in the tissues of lambs fed the diet supplemented with an inorganic or an organic source of manganese up to the maximum total Mn content allowed in the European Union (150mg Mn/kg). A total of eighteen female lambs of the improved Valachian breed were randomly allocated to three dietary treatments and fed an unsupplemented basal diet (Control, 31mg Mn/kg) or the identical diet supplemented with manganese sulphate (MnSO₄) or manganese chelate of glycine hydrate (Mn-Gly) with a total Mn content up to 150mg/kg. Regardless of the source, feed supplementation with manganese increased Mn concentrations in plasma (P˂0.05) and the liver (P˂0.001) as well as the activity of liver MnSOD (P˂0.05) and arginase (P˂0.001) compared with the control lambs. In the kidney cortex, the concentration of Mn was greatest in lambs fed the diet supplemented with the chelated Mn source compared with animals receiving the inorganic Mn source (P˂0.05) and the unsupplemented diet (P˂0.001). The 112-d intake of feed enriched with manganese did not result in any change in Mn levels, SOD or MnSOD activity in pancreas and kidney tissues. Plasma Cu concentration was depressed in both supplemented treatments. No analyzed tissue showed a change in zinc and copper levels, except the greater Cu concentration in the liver of lambs fed the diet with Mn-Gly. The presented results did not indicate any differences between dietary Mn sources either in Mn tissue deposition or activity of SOD, MnSOD and arginase in lamb tissues; however, it seems that manganese intake of up to 150mg/kg in feed may decrease plasma Cu concentration in lambs.

Silicon addition to soybean (Glycine max L.) plants alleviate zinc deficiency

It is well established the beneficial role of silicon (Si) in alleviating abiotic stress. However, it remains poorly understood the mechanisms of the Si-mediated protection against metal deficiency, especially the zinc (Zn) one. Recently, it has been proposed that Si may act by an interaction with this biometal in the root apoplast contributing to its movement through the plant, as in the case of Fe deficiency. In the present work, the effect of initial or continuous Si doses in soybean Zn deficient plants has been studied. For that purpose, plants grown in hydroponic culture were treated with different Si doses (0.0, 0.5 and 1.0 mM) under Zn limiting conditions. SPAD index in leaves, several growth parameters, mineral content in the whole plant and the formation of Zn pools in roots were determined. An initial addition of 0.5 mM of Si to the nutrient solution led to an enhancement of plants growth, Zn and Si content in leaves, and a higher storage of Zn in the root apoplast. The results suggest that this treatment enhanced Zn accumulation on roots and its movement to shoots when needed, mitigating Zn deficiency symptoms.

Different Zinc Sources Have Diverse Impacts on Gene Expression of Zinc Absorption Related Transporters in Intestinal Porcine Epithelial Cells

This study was conducted to investigate the effects of zinc sources on gene expression of zinc-related transporters in intestinal porcine epithelial cells (IPEC-1). IPEC-1 cells were treated with zinc glycine chelate (Zn-Gly), zinc methionine (Zn-Met), and zinc sulfate (ZnSO4), respectively, for measurement of cell viability. Then, the relative expression of zinc-related transporters in IPEC-1 in response to different zinc sources (50 μmol/L zinc) was measured. Zinc transporter SLC39A4 (ZIP4) expression was selectively silenced to assess the function of ZIP4 in inorganic and organic zinc absorption. The result showed that Zn-Gly and Zn-Met had lower cell damage compared with ZnSO4 on the same zinc levels. Different zinc sources improved the expression of metallothionein1 (MT1) and zinc transporter SLC30A1 (ZnT1) messenger RNA (mRNA) compared with the control (P < 0.05), while ZIP4 decreased (P < 0.05) in response to zinc addition. MT1 and ZnT1 mRNA expressions in Zn-Gly and Zn-Met were higher than those in ZnSO4, and ZIP4 mRNA expression in Zn-Met was the lowest among three kinds of zinc sources (P < 0.05). Expression of divalent metal transporter 1 (DMT1) mRNA in control was significantly higher (P < 0.05) than added different zinc sources groups. Silencing of ZIP4 significantly decreased MT1 mRNA expression in ZnSO4 and Zn-Gly treatments, reduced zinc absorption rate, and increased DMT1 mRNA expression in ZnSO4 compared with negative control. In summary, different zinc sources could improve zinc status on IPEC-1 cells and organic zinc had lower cell damage compared with ZnSO4. Moreover, Zn-Gly and Zn-Met are more efficient on zinc absorption according to the expression of various zinc-related transporters MT1, ZIP4, ZnT1, and DMT1. ZIP4 played a direct role in inorganic zinc uptake, and the absorption of zinc in Zn-Gly depends on ZIP4 partly, while absorption of Zn-Met is less dependent on ZIP4.

Effects of Dietary Zinc Pectin Oligosaccharides Chelate Supplementation on Growth Performance, Nutrient Digestibility and Tissue Zinc Concentrations of Broilers

The experiment was conducted to investigate the effects of zinc pectin oligosaccharides (Zn-POS) chelate on growth performance, nutrient digestibility, and tissue zinc concentrations of Arbor Acre broilers aged from 1 to 42 days. A total of 576 1-day-old broilers were randomly assigned into 4 groups with 9 replicates per group and 16 chicks per replicate. Chicks were fed either a basal diet (control) or basal diet supplemented with Zn-POS at 300 (Zn-POS-300), 600 (Zn-POS-600), or 900 mg/kg (Zn-POS-900), respectively, for 42 days. A 3-day metabolism trial was conducted during the last week of the experiment feeding. The average daily gain and the average daily feed intake of Zn-POS-600 were significantly higher (P < 0.05) than those of either the control, Zn-POS-300, or Zn-POS-900. Zn-POS-600 had the highest apparent digestibility of dry matter, crude protein, and metabolic energy among all groups. The control group had the lowest apparent digestibility of dry matter (P < 0.05), whereas the apparent digestibility of dry matter in Zn-POS-600 was higher (P < 0.05) than that of Zn-POS-300. The apparent digestibility of crude protein in Zn-POS-600 or Zn-POS-900 was higher (P < 0.05) compared to Zn-POS-300 or the control. The apparent digestibility of metabolic energy in Zn-POS-600 or Zn-POS-900 was higher (P < 0.05) than that of Zn-POS-300. Zn-POS-600 had the highest liver zinc concentrations (P < 0.05), while Zn-POS-900 had the highest pancreatic zinc concentrations (P < 0.05). Our data suggest that the supplementation of 600 mg/kg Zn-POS is optimal in improving the average daily gain and the average daily feed intake, utilization of dietary dry matter and crude protein, and increasing tissue zinc concentrations in liver and pancreas of broilers.

Role of Zinc Supplementation in Testicular and Epididymal Damages in Diabetic Rat: Involvement of Nrf2, SOD1, and GPX5

Zinc (Zn) is one of the most important trace elements required for several biological processes. Diabetes negatively affects many organs, and diabetic patients are often hypozincemic. The present study aims to investigate the role of Zn supplementation in the testes, epididymis, and sperms of streptozotocin (STZ)-induced diabetic rat. Serum, testicular, and sperm Zn contents were found to be altered in diabetic rat. Biochemical, histopathological, and protein expression profiles were determined to decipher the role of Zn in protecting the cellular perturbations. Further, histopathological analyses of testes and epididymis showed deranged architecture along with other noted abnormalities. Diabetic testes showed decreased Nrf2, HO-1, SOD1, PCNA, and Bcl-2 expressions whereas increased COX-2, NF-κB, MT, IL-6, and p-ERK levels. SOD1 and GPX5 were decreased in the epididymis of diabetic rat, whereas Zn supplementation attenuated these changes. The present results demonstrate the beneficial role of Zn supplementation in diabetes-associated testicular alterations of rat.

Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn

Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10mM solutions of two metals or a 5mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence Pb<Cd<Cu<Zn<Ni for the lowest metal doses, and Pb<Cu<Zn<Cd<Ni for the highest ones. The bi-metal batch experiments indicated that Cu and Pb suffered the highest retention, with high capacity to displace Cd, Ni and Zn from adsorption sites on pine bark. The transport experiments produced comparable results to those obtained in the batch experiments, with pine bark retention capacity following the sequence Pb>Cu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste.

Effects of heavy metals and chelants on phytoremediation capacity and on rhizobacterial communities of maize

Heavy metals (HMs) are one of the major ecological problem related to human activities. Phytoremediation is a promising "green technology" for soil and water reclamation, and it can be improved by means of the use of chelants. In the past particular attention was paid on the effects of HMs and/or chelants on plant health, but much less on their effects on rhizosphere communities. To shed light on the interaction among plant-HM-chelant-rhizobacterial community a pot experiment was set up. Maize plants were grown on uncontaminated, multi-metal (copper and zinc) contaminated and chelants artificially amended soils. A high concentration of HMs was detected in the different maize organs; chelants improved the accumulation capacity of the maize plants. The rhizosphere bacterial community isolated from control plants showed the largest biodiversity in terms of bacterial genera. However, the addition of HMs reduced the number of taxa to three: Bacillus, Lysinibacillus and Pseudomonas. The effects of HM treatment were counteracted by the addition of chelants in terms of the genetic biodiversity. Furthermore, several bacterial strains particularly resistant to HMs and chelants were isolated and selected. Our study suggests that the combined use of resistant bacteria and chelants could improve the phytoremediation capacity of maize.

Bioavailability of Cu, Zn and Mn from Mineral Chelates or Blends of Inorganic Salts in Growing Turkeys Fed with Supplemental Riboflavin and/or Pyridoxine

An 84-day feeding trial was conducted in growing turkeys to measure the bioavailability of Cu, Zn and Mn from a commercial mineral chelate and corresponding inorganic salts in composite feeds containing supplemental riboflavin (B2) and/or pyridoxine (B6). A total of 320, 28-day-old British United Turkeys (BUT) were assigned to eight dietary treatments in a 2 × 4 factorial arrangement comprising two trace mineral sources: chelated trace mineral blend (CTMB) and its corresponding inorganic trace minerals blend (ITMB) fed solely or with supplements of vitamin B2 (8 ppm) or B6 (7 ppm) or 8 ppm B2 + 7 ppm B6. Each treatment was replicated four times with 10 turkeys each. It was observed that turkeys fed with diets supplemented solely with ITMB elicited higher (P < 0.05) Zn excretion than their counterparts fed with diets containing ITMB with supplements of vitamins B2 and/or B6. Manganese retention was lower (P < 0.05) in turkeys fed with diets supplemented solely with ITMB than those fed with diets containing vitamins B2 and/or B6 additives. Combination of CTMB or ITMB with B6 improved (P < 0.05) the concentration of Mn in the liver and Cu in the bone. It was concluded that the minerals in CTMB were more available to the animals than ITMB. Furthermore, vitamins B2 and/or B6 supplementation improved the bioavailability of the inorganic Cu, Zn and Mn in growing turkeys and tended to reduce the concentration of these trace elements in birds' excreta.

Effects of Lumbriculus variegatus (Annelida, Oligochaete) bioturbation on zinc sediment chemistry and toxicity to the epi-benthic invertebrate Chironomus tepperi (Diptera: Chironomidae)

Classical laboratory-based single-species sediment bioassays do not account for modifications to toxicity from bioturbation by benthic organisms which may impact predictions of contaminated sediment risk to biota in the field. This study aims to determine the effects of bioturbation on the toxicity of zinc measured in a standard laboratory bioassay conducted with chironomid larvae (Chironomus tepperi). The epi-benthic chironomid larvae were exposed to two different levels of sediment contamination (1600 and 1980 mg/kg of dry weight zinc) in the presence or absence of annelid worms (Lumbriculus variegatus) which are known to be tolerant to metal and to have a large impact on sediment properties through bioturbation. Chironomids had 5-6x higher survival in the presence of L. variegatus which shows that bioturbation had a beneficial effect on the chironomid larvae. Chemical analyses showed that bioturbation induced a flux of zinc from the pore water into the water column, thereby reducing the bioavailability of zinc in pore water to the chironomid larvae. This also suggested that pore water was the major exposure path for the chironomids to metals in sediment. During the study, annelid worms (Oligochaetes) produced a thin layer of faecal pellets at the sediment surface, a process known to: (i) create additional adsorption sites for zinc, thus reducing its availability, (ii) increase the microbial abundance that in turn could represent an additional food source for opportunistic C. tepperi larvae, and (iii) modify the microbial community's structure and alter the biogeochemical processes it governs thus indirectly impact zinc toxicity. This study represents a contribution in recognising bioturbating organisms as "ecological engineers" as they directly and indirectly influence metal bioavailability and impact other sediment-inhabiting species. This is significant and should be considered in risk assessment of zinc levels (and other metals) in contaminated sediment when extrapolating from laboratory studies to the field.

Effect of waterborne zinc exposure on lipid deposition and metabolism in hepatopancreas and muscle of grass carp Ctenopharyngodon idella

The aim of the present study was to explore the effect of waterborne zinc (control, 0.85, 2.20, 3.10 mg/l, respectively) exposure on lipid deposition and metabolism in the hepatopancreas and muscle of grass carp Ctenopharyngodon idella. The lipid content, Zn accumulation, and the activities and expression levels of several enzymes involved in lipid metabolism were determined in hepatopancreas and muscle. Waterborne Zn exposure reduced growth performance and increased Zn accumulation in both tested tissues. In hepatopancreas, Zn exposure increased lipid content, the activities of lipogenic enzymes, such as 6PGD, G6PD, ME, ICDH and FAS, as well as the mRNA expression level of G6PD, 6PGD, ICDH, FAS and SREBP-1. But the activity of CPT I and the mRNA expression of HSL, CPT Iα1a, CPT Iα2a and PPARα were down-regulated by Zn exposure. In contrast, in muscle, waterborne Zn exposure decreased lipid deposition, activities of 6GPD, ICDH and ME, as well as the mRNA expression level of G6PD, ICDH, ME, FAS and SREBP-1. However, the activity of CPT I as well as the mRNA expression level of PPARα, HSL, CPT Iα2a, CPT Iα1b and CPT Iβ were up-regulated by Zn exposure. Our results indicate that waterborne Zn increases lipid content by up-regulating lipogenesis and down-regulating lipolysis in hepatopancreas. But, in muscle, waterborne Zn reduces lipid accumulation by up-regulating lipolysis and down-regulating lipogenesis. Differential patterns of lipid deposition, enzymatic activities and genes' expression indicate the tissue-specific regulatory mechanism in fish.

Assessment of metal toxicity and bioavailability in metallophyte leaf litters and metalliferous soils using Eisenia fetida in a microcosm study

The leaf litters of tree species, Acacia pycnantha (Ap) and Eucalyptus camaldulensis (Ec), predominantly growing at an abandoned copper (Cu) mine and mine soils including controls, were assessed for determining the metal toxicity and bioavailability using earthworm species Eisenia fetida, in a microcosm. Significant reduction in body weight as well as mortality were observed when the worms were introduced into mine soil or its combination with mine Ap litter. Virtually, there were no juveniles when the worms were fed on substratum that contained mine soil or mine leaf litter. The extent of bioaccumulation was dependent on water-soluble fraction of a metal in soil. The accumulation of cadmium, lead and copper in worm tissue was significantly more in treatments that received mine soil with or without mine leaf litter. However, the tissue concentration of zinc did not differ much in earthworms irrespective of its exposure to control or contaminated samples. Mine leaf litter from Ec, a known Cu hyperaccumulator, was more hospitable to earthworm survival and juvenile than that of Ap litter. Validation of the data on bioaccumulation of metals indicated that the mine leaf litter significantly contributed to metal bioavailability. However, it was primarily the metal concentration in mine soil that was responsible for earthworm toxicity and bioavailability. Our data also indicate that detrivores like earthworm is greatly responsible for heavy metal transfer from mines into the ecosystem.

ATSDR evaluation of the health effects of zinc and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites, which have the greatest public health impact. These profiles comprehensively summarise toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Zinc. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of zinc. It contains descriptions and evaluations of toxicological studies and epidemiological investigations, and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. Toxicology and Industrial Health 2006; 22: 423-493.

Local adaptation is associated with zinc tolerance in Pseudomonas endophytes of the metal-hyperaccumulator plant Noccaea caerulescens

Metal-hyperaccumulating plants, which are hypothesized to use metals for defence against pests and pathogens, provide a unique context in which to study plant-pathogen coevolution. Previously, we demonstrated that the high concentrations of zinc found in leaves of the hyperaccumulator Noccaea caerulescens provide protection against bacterial pathogens, with a potential trade-off between metal-based and pathogen-induced defences. We speculated that an evolutionary arms race between zinc-based defences in N. caerulescens and zinc tolerance in pathogens might have driven the development of the hyperaccumulation phenotype. Here, we investigate the possibility of local adaptation by bacteria to the zinc-rich environment of N. caerulescens leaves and show that leaves sampled from the contaminated surroundings of a former mine site harboured endophytes with greater zinc tolerance than those within plants of an artificially created hyperaccumulating population. Experimental manipulation of zinc concentrations in plants of this artificial population influenced the zinc tolerance of recovered endophytes. In laboratory experiments, only endophytic bacteria isolated from plants of the natural population were able to grow to high population densities in any N. caerulescens plants. These findings suggest that long-term coexistence with zinc-hyperaccumulating plants leads to local adaptation by endophytic bacteria to the environment within their leaves.

Oral treatment with a zinc complex of acetylsalicylic acid prevents diabetic cardiomyopathy in a rat model of type-2 diabetes: activation of the Akt pathway

BACKGROUND

Type-2 diabetics have an increased risk of cardiomyopathy, and heart failure is a major cause of death among these patients. Growing evidence indicates that proinflammatory cytokines may induce the development of insulin resistance, and that anti-inflammatory medications may reverse this process. We investigated the effects of the oral administration of zinc and acetylsalicylic acid, in the form of bis(aspirinato)zinc(II)-complex Zn(ASA)2, on different aspects of cardiac damage in Zucker diabetic fatty (ZDF) rats, an experimental model of type-2 diabetic cardiomyopathy.

METHODS

Nondiabetic control (ZL) and ZDF rats were treated orally with vehicle or Zn(ASA)2 for 24 days. At the age of 29-30 weeks, the electrical activities, left-ventricular functional parameters and left-ventricular wall thicknesses were assessed. Nitrotyrosine immunohistochemistry, TUNEL-assay, and hematoxylin-eosin staining were performed. The protein expression of the insulin-receptor and PI3K/AKT pathway were quantified by Western blot.

RESULTS

Zn(ASA)2-treatment significantly decreased plasma glucose concentration in ZDF rats (39.0 ± 3.6 vs 49.4 ± 2.8 mM, P < 0.05) while serum insulin-levels were similar among the groups. Data from cardiac catheterization showed that Zn(ASA)2 normalized the increased left-ventricular diastolic stiffness (end-diastolic pressure-volume relationship: 0.064 ± 0.008 vs 0.084 ± 0.014 mmHg/µl; end-diastolic pressure: 6.5 ± 0.6 vs 7.9 ± 0.7 mmHg, P < 0.05). Furthermore, ECG-recordings revealed a restoration of prolonged QT-intervals (63 ± 3 vs 83 ± 4 ms, P < 0.05) with Zn(ASA)2. Left-ventricular wall thickness, assessed by echocardiography, did not differ among the groups. However histological examination revealed an increase in the cardiomyocytes' transverse cross-section area in ZDF compared to the ZL rats, which was significantly decreased after Zn(ASA)2-treatment. Additionally, a significant fibrotic remodeling was observed in the diabetic rats compared to ZL rats, and Zn(ASA)2-administered ZDF rats showed a similar collagen content as ZL animals. In diabetic hearts Zn(ASA)2 significantly decreased DNA-fragmentation, and nitro-oxidative stress, and up-regulated myocardial phosphorylated-AKT/AKT protein expression. Zn(ASA)2 reduced cardiomyocyte death in a cellular model of oxidative stress. Zn(ASA)2 had no effects on altered myocardial CD36, GLUT-4, and PI3K protein expression.

CONCLUSIONS

We demonstrated that treatment of type-2 diabetic rats with Zn(ASA)2 reduced plasma glucose-levels and prevented diabetic cardiomyopathy. The increased myocardial AKT activation could, in part, help to explain the cardioprotective effects of Zn(ASA)2. The oral administration of Zn(ASA)2 may have therapeutic potential, aiming to prevent/treat cardiac complications in type-2 diabetic patients.

Uptake and toxicity of nano-ZnO in the plant-feeding nematode, Xiphinema vuittenezi: the role of dissolved zinc and nanoparticle-specific effects

Nanoparticulate ZnO is one of the most commonly applied nanomaterials. As ZnO is more soluble than many other oxide nanoparticles, its toxicity beyond the nanoparticle-specific effects can be attributed to the dissolved ionic zinc. The investigation of uptake and toxicity of nano-ZnO in the plant-feeding nematode, Xiphinema vuittenezi, which was used in previous studies as a biological model organism, was aimed. The establishment of the role of dissolved zinc and nanoparticle-specific effects in the toxicity was also the objective of our study. Zn uptake was found to be significantly higher for bulk and nano-ZnO than for ZnSO4 solution; however, treatments caused loss of potassium in the worms in a dissolved-zinc-dependent manner. The toxicity was the lowest for bulk ZnO, and it was very similar for nano-ZnO and ZnSO4 solution. Accordingly, the toxicity of ZnO nanoparticles is a combination of dissolved-zinc-caused toxicity and nanoparticle-specific effects.

Application of ZnSO4 or Zn-EDTA fertilizer to a calcareous soil: Zn diffusion in soil and its uptake by wheat plants

BACKGROUND

The objective of this study was to compare the efficiency of two Zn sources and two application methods on (i) Zn diffusion from fertilized soil to unfertilized soil, (ii) grain Zn concentration and (iii) grain Zn bio-accessibility to humans. In the laboratory experiment, 20 mg ZnSO4 or 4 mg Zn-EDTA were applied to a 5 mm and 1 mm-wide space in the soil in the half-cell technique. In the greenhouse experiment, Zn-ZnSO4 or Zn-ethylenediaminetetraacetic acid (Zn-EDTA) was mixed or banded with the soil at a rate of 20 or 4 mg Zn kg(-1) , respectively.

RESULTS

The results from the diffusion experiment showed that both the extractability and the diffusion coefficient of Zn were higher when Zn fertilizer was applied to a 1 mm-wide space than when it was applied to a 5 mm-wide space. Zn-EDTA had a greater diffusion distance than ZnSO4 . The greenhouse experiment showed that the mixed ZnSO4 application and the Zn-EDTA application (both mixed and banded) treatments significantly increased grain Zn concentration and bio-accessibility. The positive effect of Zn-EDTA on grain Zn concentrations and bio-accessibility was greater than that of ZnSO4 . The banded application reduced the effectiveness of ZnSO4 but not of Zn-EDTA.

CONCLUSION

It was concluded that Zn-EDTA was a better Zn source than ZnSO4 for increasing grain Zn content in a potentially Zn-deficient calcareous soil.

Evaluation of iron and zinc bioavailability of beans targeted for biofortification using in vitro and in vivo models and their effect on the nutritional status of preschool children

BACKGROUND

Biofortified beans have been produced with higher nutrient concentrations. The objective was to evaluate the in vitro and in vivo iron and zinc bioavailability of common beans Pontal (PO), targeted for biofortification, compared with conventional Perola (PE) and their effects on the iron and zinc nutritional status of preschool children.

RESULTS

In Caco-2 cells, PO and PE beans did not show differences in ferritin (PO, 13.1 ± 1.4; PE, 13.6 ± 1.4 ng mg(-1) protein) or zinc uptake (PO, 15.9 ± 1.5; PE, 15.5 ± 3.5 µmol mg(-1) protein). In the rat, PO and PE beans presented high iron bioavailability (PO, 109.6 ± 29.5; PE, 110.7 ± 13.9%). In preschool children, no changes were observed in iron and zinc nutritional status comparing before and after PO consumption (ferritin, 41.2 ± 23.2 and 28.9 ± 40.4 µg L(-1) ; hemoglobin, 13.7 ± 2.2 and 13.1 ± 3.2 g dL(-1) ; plasma zinc, 119.2 ± 24.5 and 133.9 ± 57.7 µg dL(-1) ; erythrocyte zinc, 53.5 ± 13.8 and 59.4 ± 17.1 µg g(-1) hemoglobin).

CONCLUSION

Iron and zinc bioavailability in PO and PE beans was not statistically different using either cell culture, animal or human models. Efforts should focus on increasing mineral bioavailability of beans targeted for biofortification.

Assessing the Effects of Bioturbation on Metal Bioavailability in Contaminated Sediments by Diffusive Gradients in Thin Films (DGT)

The burrowing and feeding activities of benthic organisms can alter metal speciation in sediments and affect an organisms' exposure to metals. Recently, the performance of the in situ technique of diffusive gradients in thin films (DGT) for predicting metal bioavailability has been investigated in response to the increasing demand of considering contaminant bioavailability in sediment quality assessments. In this study, we test the ability of the DGT technique for predicting the metal bioavailability in clean and contaminated sediments that are being subjected to varying degrees of sediments disturbance: low bioturbation (bivalve Tellina deltoidalis alone) and high bioturbation (bivalve and actively burrowing amphipod, Victoriopisa australiensis). Significant release of DGT-labile Cd, Ni, Pb, and Zn, but lower Cu and Fe, occurred in the pore and overlying waters of sediments exposed to high bioturbation conditions, resulting in higher bioaccumulation of zinc in bivalves. Strong relationships were found between bioaccumulation of Pb and Zn and time-integrated DGT-metal fluxes, whereas poor relationships were obtained using total or dilute-acid extractable metal concentrations. This results demonstrate that DGT is a useful tool for assessing metal bioavailability in sediments and can provide useful predictions of metal bioavailable to benthic organisms in dynamic sediment environments.

Arbuscular mycorrhizae alleviate negative effects of zinc oxide nanoparticle and zinc accumulation in maize plants--A soil microcosm experiment

ZnO nanoparticles (NPs) are considered an emerging contaminant when in high concentration, and their effects on crops and soil microorganisms pose new concerns and challenges. Arbuscular mycorrhizal (AM) fungi (AMF) form mutualistic symbioses with most vascular plants, and putatively contribute to reducing nanotoxicity in plants. Here, we studied the interactions between ZnO NPs and maize plants inoculated with or without AMF in ZnO NPs-spiked soil. ZnO NPs had no significant adverse effects at 400 mg/kg, but inhibited both maize growth and AM colonization at concentrations at and above 800 mg/kg. Sufficient addition of ZnO NPs decreased plant mineral nutrient acquisition, photosynthetic pigment concentrations, and root activity. Furthermore, ZnO NPs caused Zn concentrations in plants to increase in a dose-dependent pattern. As the ZnO NPs dose increased, we also found a positive correlation with soil diethylenetriaminepentaacetic acid (DTPA)-extractable Zn. However, AM inoculation significantly alleviated the negative effects induced by ZnO NPs: inoculated-plants experienced increased growth, nutrient uptake, photosynthetic pigment content, and SOD activity in leaves. Mycorrhizal plants also exhibited decreased ROS accumulation, Zn concentrations and bioconcentration factor (BCF), and lower soil DTPA-extractable Zn concentrations at high ZnO NPs doses. Our results demonstrate that, at high contamination levels, ZnO NPs cause toxicity to AM symbiosis, but AMF help alleviate ZnO NPs-induced phytotoxicity by decreasing Zn bioavailability and accumulation, Zn partitioning to shoots, and ROS production, and by increasing mineral nutrients and antioxidant capacity. AMF may play beneficial roles in alleviating the negative effects and environmental risks posed by ZnO NPs in agroecosystems.

Relative Penetration of Zinc Oxide and Zinc Ions into Human Skin after Application of Different Zinc Oxide Formulations

Zinc oxide (ZnO) is frequently used in commercial sunscreen formulations to deliver their broad range of UV protection properties. Concern has been raised about the extent to which these ZnO particles (both micronized and nanoparticulate) penetrate the skin and their resultant toxicity. This work has explored the human epidermal skin penetration of zinc oxide and its labile zinc ion dissolution product that may potentially be formed after application of ZnO nanoparticles to human epidermis. Three ZnO nanoparticle formulations were used: a suspension in the oil, capric caprylic triglycerides (CCT), the base formulation commonly used in commercially available sunscreen products; an aqueous ZnO suspension at pH 6, similar to the natural skin surface pH; and an aqueous ZnO suspension at pH 9, a pH at which ZnO is stable and there is minimal pH-induced impairment of epidermal integrity. In each case, the ZnO in the formulations did not penetrate into the intact viable epidermis for any of the formulations but was associated with an enhanced increase in zinc ion fluorescence signal in both the stratum corneum and the viable epidermis. The highest labile zinc fluorescence was found for the ZnO suspension at pH 6. It is concluded that, while topically applied ZnO does not penetrate into the viable epidermis, these applications are associated with hydrolysis of ZnO on the skin surface, leading to an increase in zinc ion levels in the stratum corneum, thence in the viable epidermis and subsequently in the systemic circulation and the urine.

Interactions and Toxicity of Cu-Zn mixtures to Hordeum vulgare in Different Soils Can Be Rationalized with Bioavailability-Based Prediction Models

Soil contamination with copper (Cu) is often associated with zinc (Zn), and the biological response to such mixed contamination is complex. Here, we investigated Cu and Zn mixture toxicity to Hordeum vulgare in three different soils, the premise being that the observed interactions are mainly due to effects on bioavailability. The toxic effect of Cu and Zn mixtures on seedling root elongation was more than additive (i.e., synergism) in soils with high and medium cation-exchange capacity (CEC) but less than additive (antagonism) in a low-CEC soil. This was found when we expressed the dose as the conventional total soil concentration. In contrast, antagonism was found in all soils when we expressed the dose as free-ion activities in soil solution, indicating that there is metal-ion competition for binding to the plant roots. Neither a concentration addition nor an independent action model explained mixture effects, irrespective of the dose expressions. In contrast, a multimetal BLM model and a WHAM-Ftox model successfully explained the mixture effects across all soils and showed that bioavailability factors mainly explain the interactions in soils. The WHAM-Ftox model is a promising tool for the risk assessment of mixed-metal contamination in soils.

Evaluation of single and joint toxicity of perfluorooctane sulfonate and zinc to Limnodrilus hoffmeisteri: Acute toxicity, bioaccumulation and oxidative stress

Perfluorooctane sulfonate (PFOS) and zinc have been detected in aquatic environment widely. In order to study the combined effects of PFOS and Zn, a series of experiments was conducted to explore the acute mortality, bioaccumulation and antioxidant status of Limnodrilus hoffmeisteri. The acute toxicity was evaluated by calculating 24h-EC50 values, and it was observed that 24h-EC50 values in single and joint treatments decreased with decreasing pH value or increasing exposure concentration. Toxic unit analysis suggested that the combined effects of the PFOS+Zn binary mixture were mostly simple addition, with 8 groups showing synergism and only one group showing antagonism. The analysis of internal Zn and PFOS concentration showed that the possible interaction between Zn and PFOS can affect the bioaccumulation of the two chemicals in L. hoffmeisteri. In addition, oxidative stress status was assessed by measuring oxidation-related biochemical parameters such as superoxide dismutase, glutathione peroxidase and malondialdehyde, and the integrated biomarker response index was estimated to rank the toxicity order. Exposures to Zn and PFOS were found to evoke some changes in the antioxidant defense system, and a strong self-adaptive ability was noticed for L. hoffmeisteri after 10 d exposure.

Earthworm Uptake Routes and Rates of Ionic Zn and ZnO Nanoparticles at Realistic Concentrations, Traced Using Stable Isotope Labeling

The environmental behavior of ZnO nanoparticles (NPs), their availability to, uptake pathways by, and biokinetics in the earthworm Lumbricus rubellus were investigated using stable isotope labeling. Zinc isotopically enriched to 99.5% in (68)Zn ((68)Zn-E) was used to prepare (68)ZnO NPs and a dissolved phase of (68)Zn for comparison. These materials enabled tracing of environmentally relevant (below background) NP additions to soil of only 5 mg (68)Zn-E kg(-1). Uptake routes were isolated by introducing earthworms with sealed and unsealed mouthparts into test soils for up to 72 h. The Zn isotope compositions of the soils, pore waters and earthworms were then determined using multiple collector inductively coupled plasma mass spectrometry. Detection and quantification of (68)Zn-E in earthworm tissue was possible after only 4 h of dermal exposure, when the uptake of (68)Zn-E had increased the total Zn tissue concentration by 0.03‰. The results demonstrate that at these realistic exposure concentrations there is no distinguishable difference between the uptake of the two forms of Zn by the earthworm L. rubellus, with the dietary pathway accounting for ∼95% of total uptake. This stands in contrast to comparable studies where high dosing levels were used and dermal uptake is dominant.