Toxicological assessment of arsenic-containing phosphatidylcholines in HepG2 cells

Arsenolipids include a wide range of organic arsenic species that occur naturally in seafood and thereby contribute to human arsenic exposure. Recently arsenic-containing phosphatidylcholines (AsPCs) were identified in caviar, fish, and algae. In this first toxicological assessment of AsPCs, we investigated the stability of both the oxo- and thioxo-form of an AsPC under experimental conditions, and analyzed cell viability, indicators of genotoxicity and biotransformation in human liver cancer cells (HepG2). Precise toxicity data could not be obtained owing to the low solubility in the cell culture medium of the thioxo-form, and the ease of hydrolysis of the oxo-form, and to a lesser degree the thioxo-form. Hydrolysis resulted amongst others in the respective constituent arsenic-containing fatty acid (AsFA). Incubation of the cells with oxo-AsPC resulted in a toxicity similar to that determined for the hydrolysis product oxo-AsFA alone, and there were no indices for genotoxicity. Furthermore, the oxo-AsPC was readily taken up by the cells resulting in high cellular arsenic concentrations (50 μM incubation: 1112 ± 146 μM As cellular), whereas the thioxo-AsPC was substantially less bioavailable (50 μM incubation: 293 ± 115 μM As cellular). Speciation analysis revealed biotransformation of the AsPCs to a series of AsFAs in the culture medium, and, in the case of the oxo-AsPC, to as yet unidentified arsenic species in cell pellets. The results reveal the difficulty of toxicity studies of AsPCs in vitro, indicate that their toxicity might be largely governed by their arsenic fatty acid content and suggest a multifaceted human metabolism of food derived complex arsenolipids.

Effects of a Cumulative, Suboptimal Supply of Multiple Trace Elements in Mice: Trace Element Status, Genomic Stability, Inflammation, and Epigenetics

SCOPE

Trace element (TE) deficiencies often occur accumulated, as nutritional intake is inadequate for several TEs, concurrently. Therefore, the impact of a suboptimal supply of iron, zinc, copper, iodine, and selenium on the TE status, health parameters, epigenetics, and genomic stability in mice are studied.

METHODS AND RESULTS

Male mice receive reduced or adequate amounts of TEs for 9 weeks. The TE status is analyzed mass-spectrometrically in serum and different tissues. Furthermore, gene and protein expression of TE biomarkers are assessed with focus on liver. Iron concentrations are most sensitive toward a reduced supply indicated by increased serum transferrin levels and altered hepatic expression of iron-related genes. Reduced TE supply results in smaller weight gain but higher spleen and heart weights. Additionally, inflammatory mediators in serum and liver are increased together with hepatic genomic instability. However, global DNA (hydroxy)methylation is unaffected by the TE modulation.

CONCLUSION

Despite homeostatic regulation of most TEs in response to a low intake, this condition still has substantial effects on health parameters. It appears that the liver and immune system react particularly sensitive toward changes in TE intake. The reduced Fe status might be the primary driver for the observed effects.

Evaluation of calcium lignosulfonate as a acceptable previous cargo for edible fats and oils

Shipping of edible fats and oils into Europe is permitted in bulk tanks, provided that the previous cargo is included in a positive list. The European Commission requested EFSA to evaluate the acceptability of calcium lignosulfonate as previous cargo for fats and oils. The evaluation was based on the same criteria as those used for the evaluation of the substances currently on the list in the Annex to Commission Directive 96/3/EC as a acceptable previous cargoes for edible fats and oils. In 2017, the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) concluded that calcium lignosulfonate did not meet the acceptability criteria, due to uncertainties as regards the composition and toxicity of its low‐molecular weight fraction (LMWF) below 1,000 Da. In the current evaluation, new information, showing lack of genotoxicity of the LMWF isolated from a technical grade of calcium lignosulfonate was provided. Due to uncertainties regarding the presence of lignosulfonate components below 200 Da in this LMWF tested for genotoxicity, the CONTAM Panel concluded that the information provided was insufficient to assess the acceptability of calcium lignosulfonate as previous cargo. The Panel recommends a better analysis of the LMWF and a new genotoxicity test using this LMWF, including components < 200 Da, and evidence that the tested material is representative of the LMWF in products intended to be shipped as previous cargo for edible fat and oils.

Aging affects sex- and organ-specific trace element profiles in mice

A decline of immune responses and dynamic modulation of the redox status are observed during aging and are influenced by trace elements such as copper, iodine, iron, manganese, selenium, and zinc. So far, analytical studies have focused mainly on single trace elements. Therefore, we aimed to characterize age-specific profiles of several trace elements simultaneously in serum and organs of adult and old mice. This allows for correlating multiple trace element levels and to identify potential patterns of age-dependent alterations. In serum, copper and iodine concentrations were increased and zinc concentration was decreased in old as compared to adult mice. In parallel, decreased copper and elevated iron concentrations were observed in liver. The age-related reduction of hepatic copper levels was associated with reduced expression of copper transporters, whereas the increased hepatic iron concentrations correlated positively with proinflammatory mediators and Nrf2-induced ferritin H levels. Interestingly, the age-dependent inverse regulation of copper and iron was unique for the liver and not observed in any other organ. The physiological importance of alterations in the iron/copper ratio for liver function and the aging process needs to be addressed in further studies.

GPx3 dysregulation impacts adipose tissue insulin receptor expression and sensitivity

Insulin receptor signaling is crucial for white adipose tissue (WAT) function. Consequently, lack of insulin receptor (IR) in WAT results in a diabetes-like phenotype. Yet, causes for IR downregulation in WAT of patients with diabetes are not well understood. By using multiple mouse models of obesity and insulin resistance, we identify a common downregulation of IR with a reduction of mRNA expression of selenoproteins Txnrd3, Sephs2, and Gpx3 in gonadal adipose tissue. Consistently, GPX3 is also decreased in adipose tissue of insulin-resistant and obese patients. Inducing Gpx3 expression via selenite treatment enhances IR expression via activation of the transcription factor Sp1 in 3T3-L1 preadipocytes and improves adipocyte differentiation and function. Feeding mice a selenium-enriched high-fat diet alleviates diet-induced insulin resistance with increased insulin sensitivity, decreased tissue inflammation, and elevated IR expression in WAT. Again, IR expression correlated positively with Gpx3 expression, a phenotype that is also conserved in humans. Consequently, decreasing GPx3 using siRNA technique reduced IR expression and insulin sensitivity in 3T3-L1 preadipocytes. Overall, our data identify GPx3 as a potentially novel regulator of IR expression and insulin sensitivity in adipose tissue.

Cellular toxicological characterization of a thioxolated arsenic-containing hydrocarbon

Arsenolipids, especially arsenic-containing hydrocarbons (AsHC), are an emerging class of seafood originating contaminants. Here we toxicologically characterize a recently identified oxo-AsHC 332 metabolite, thioxo-AsHC 348 in cultured human liver (HepG2) cells. Compared to results of previous studies of the parent compound oxo-AsHC 332, thioxo-AsHC 348 substantially affected cell viability in the same concentration range but exerted about 10-fold lower cellular bioavailability. Similar to oxo-AsHC 332, thioxo-AsHC 348 did not substantially induce oxidative stress nor DNA damage. Moreover, in contrast to oxo-AsHC 332 mitochondria seem not to be a primary subcellular toxicity target for thioxo-AsHC 348. This study indicates that thioxo-AsHC 348 is at least as toxic as its parent compound oxo-AsHC 332 but very likely acts via a different mode of toxic action, which still needs to be identified.

Risk assessment of ochratoxin A in food

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 μg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 μg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Development and Validation of a QuEChERS-Based Liquid Chromatography Tandem Mass Spectrometry Multi-Method for the Determination of 38 Native and Modified Mycotoxins in Cereals

Here, a reliable and sensitive method for the determination of 38 (modified) mycotoxins was developed. Using a QuEChERS-based extraction method [acetonitrile/water/formic acid (75:20:5, v/v/v)], followed by two runs of high performance liquid chromatography tandem mass spectrometry with different conditions, relevant mycotoxins in cereals were analyzed. The method was validated according to the performance criteria defined by the European Commission (EC) in Commission Decision no. 657/2002. Limits of quantification ranged from 0.05 to 150 μg/kg. Good linearity (R² > 0.99), recovery (61-120%), repeatability (RSDr < 15%), and reproducibility (RSDR < 20%) were obtained for most mycotoxins. However, validation results for Alternaria toxins and fumonisins were unsatisfying. Matrix effects (-69 to +59%) were compensated for using standard addition. Application on reference materials gave correct results while analysis of samples from local retailers revealed contamination, especially with deoxynivalenol, deoxynivalenol-3-glucoside, fumonisins, and zearalenone, in concentrations up to 369, 58, 1002, and 21 μg/kg, respectively.

Therapeutic Efficacy of the N,N' Bis-(2-Mercaptoethyl) Isophthalamide Chelator for Methylmercury Intoxication in Caenorhabditis elegans

Methylmercury (MeHg) is a global pollutant and potent neurotoxin. In humans, MeHg damages the central nervous system (CNS), causing irreversible neuronal shrinkage, and neuronal loss. Most chelators for clinical mercury detoxification are thiol-containing agents. N,N 'bis-(2-mercaptoethyl) isophthalamide (NBMI) is a lipophilic thiol agent synthesized from natural chemicals. NBMI has high affinity for mercury, cadmium and lead, and can decrease their concentrations in polluted water. However, the efficacy of NBMI for MeHg toxicity has yet to be evaluated in intact animals. Here we used the nematode Caenorhabditis elegans (C. elegans) to test the efficacy of NBMI in attenuating MeHg toxicity in vivo in the whole organism. The results showed that NBMI reduced both the acute toxicity (125 μM MeHg, 1 h) and chronic (5 μM MeHg, 24 h) MeHg toxicity. Co-treatment with NBMI achieved maximal efficacy against MeHg toxicity, however delayed treatment 6 days after initiation of exposure was also effective at reducing neurotoxicity. Co-treatment of NBMI reduced the worms' death rate, structural damage in DAergic neurons, and restored antioxidant response levels. While this study provides proof of principle for the therapeutic value of NBMI in MeHg toxicity, future studies are needed to address the cellular and molecular mechanisms and translatability of these effects to humans and other animals.

Subcellular Localization of Copper-Cellular Bioimaging with Focus on Neurological Disorders

As an essential trace element, copper plays a pivotal role in physiological body functions. In fact, dysregulated copper homeostasis has been clearly linked to neurological disorders including Wilson and Alzheimer’s disease. Such neurodegenerative diseases are associated with progressive loss of neurons and thus impaired brain functions. However, the underlying mechanisms are not fully understood. Characterization of the element species and their subcellular localization is of great importance to uncover cellular mechanisms. Recent research activities focus on the question of how copper contributes to the pathological findings. Cellular bioimaging of copper is an essential key to accomplish this objective. Besides information on the spatial distribution and chemical properties of copper, other essential trace elements can be localized in parallel. Highly sensitive and high spatial resolution techniques such as LA-ICP-MS, TEM-EDS, S-XRF and NanoSIMS are required for elemental mapping on subcellular level. This review summarizes state-of-the-art techniques in the field of bioimaging. Their strengths and limitations will be discussed with particular focus on potential applications for the elucidation of copper-related diseases. Based on such investigations, further information on cellular processes and mechanisms can be derived under physiological and pathological conditions. Bioimaging studies might enable the clarification of the role of copper in the context of neurodegenerative diseases and provide an important basis to develop therapeutic strategies for reduction or even prevention of copper-related disorders and their pathological consequences.

Functional Biomarkers for the Selenium Status in a Human Nutritional Intervention Study

Soils in Germany are commonly low in selenium; consequently, a sufficient dietary supply is not always ensured. The extent of such provision adequacy is estimated by the optimal effect range of biomarkers, which often reflects the physiological requirement. Preceding epidemiological studies indicate that low selenium serum concentrations could be related to cardiovascular diseases. Inter alia, risk factors for cardiovascular diseases are physical inactivity, overweight, as well as disadvantageous eating habits. In order to assess whether these risk factors can be modulated, a cardio-protective diet comprising fixed menu plans combined with physical exercise was applied in the German MoKaRi (modulation of cardiovascular risk factors) intervention study. We analyzed serum samples of the MoKaRi cohort (51 participants) for total selenium, GPx activity, and selenoprotein P at different timepoints of the study (0, 10, 20, 40 weeks) to explore the suitability of these selenium-associated markers as indicators of selenium status. Overall, the time-dependent fluctuations in serum selenium concentration suggest a successful change in nutritional and lifestyle behavior. Compared to baseline, a pronounced increase in GPx activity and selenoprotein P was observed, while serum selenium decreased in participants with initially adequate serum selenium content. SELENOP concentration showed a moderate positive monotonic correlation (r = 0.467, p < 0.0001) to total Se concentration, while only a weak linear relationship was observed for GPx activity versus total Se concentration (r = 0.186, p = 0.021). Evidently, other factors apart from the available Se pool must have an impact on the GPx activity, leading to the conclusion that, without having identified these factors, GPx activity should not be used as a status marker for Se.

Cross-sectional analysis of trace element status in thyroid disease

BACKGROUND

The synthesis of thyroid hormone depends on a set of trace elements, most importantly selenium and iodine. The dietary supply with certain micronutrients is limited in many areas of the world, including central Europe and large parts of Asia and Africa. Moreover, both thyroid disease risk and therapy effects are modulated by trace element supply and status.

OBJECTIVE

Assessment of trace element status in thyroid patients in a European metropolis.

MATERIAL AND METHODS

Adult patients visiting a medical praxis in Berlin, Germany, were enrolled into a cross-sectional analysis, and serum samples were obtained from thyroid patients (n = 323) with different conditions including goitre, hypothyroidism, malignancy or autoimmune thyroid disease. Trace elements (iodine, selenium, copper and zinc) were assessed by ICP-MS/MS or total reflection X-ray analysis, along with two protein biomarkers of selenium status (selenoprotein P, glutathione peroxidase), and compared to the clinical phenotype.

RESULTS

The patients displayed relatively low serum zinc and selenium concentrations as compared to a set (n = 200) of healthy subjects (zinc; 1025+/-233 vs. 1068+/-230 μg/L, p < 0.01, selenium; 76.9+/18.8 vs. 85.1+/-17.4 μg/L, p < 0.0001). A high fraction of patients (37.5%) was classified as selenium-deficient (serum selenium concentrations <70 μg/L), in particular the patients with thyroid malignancy (59%). Serum copper was not different between the groups, and total serum iodine concentrations were unrelated to thyroid disease. Explorative statistical analyses yielded no significant interactions between the trace elements and disease parameters, except for free thyroxine inversely correlating to the copper/selenium ratio.

CONCLUSIONS

In adult thyroid patients, there is no relation of circulating copper, iodine, selenium or zinc concentrations to thyroid hormone. However, a large fraction of German thyroid patients displays a considerable selenium deficit, known to constitute a disease risk potentially impairing convalescence and aggravating autoimmune disease processes. It appears advisable to testing thyroid patients for selenium deficiency, and once diagnosed, an increased supply via dietary counselling or active supplementation should be considered.

Risk assessment of aflatoxins in food

EFSA was asked to deliver a scientific opinion on the risks to public health related to the presence of aflatoxins in food. The risk assessment was confined to aflatoxin B1 (AFB1), AFB2, AFG1, AFG2 and AFM1. More than 200,000 analytical results on the occurrence of aflatoxins were used in the evaluation. Grains and grain-based products made the largest contribution to the mean chronic dietary exposure to AFB1 in all age classes, while 'liquid milk' and 'fermented milk products' were the main contributors to the AFM1 mean exposure. Aflatoxins are genotoxic and AFB1 can cause hepatocellular carcinomas (HCCs) in humans. The CONTAM Panel selected a benchmark dose lower confidence limit (BMDL) for a benchmark response of 10% of 0.4 μg/kg body weight (bw) per day for the incidence of HCC in male rats following AFB1 exposure to be used in a margin of exposure (MOE) approach. The calculation of a BMDL from the human data was not appropriate; instead, the cancer potencies estimated by the Joint FAO/WHO Expert Committee on Food Additives in 2016 were used. For AFM1, a potency factor of 0.1 relative to AFB1 was used. For AFG1, AFB2 and AFG2, the in vivo data are not sufficient to derive potency factors and equal potency to AFB1 was assumed as in previous assessments. MOE values for AFB1 exposure ranged from 5,000 to 29 and for AFM1 from 100,000 to 508. The calculated MOEs are below 10,000 for AFB1 and also for AFM1 where some surveys, particularly for the younger age groups, have an MOE below 10,000. This raises a health concern. The estimated cancer risks in humans following exposure to AFB1 and AFM1 are in-line with the conclusion drawn from the MOEs. The conclusions also apply to the combined exposure to all five aflatoxins.

Risk assessment of chlorinated paraffins in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of chlorinated paraffins in feed and food. The data for experimental animals were reviewed and the CONTAM Panel identified the liver, kidney and thyroid as the target organs for the SCCP and MCCP mixtures tested in repeated dose toxicity studies. Decreased pup survival and subcutaneous haematoma/haemorrhage were also identified as critical effects for an MCCP mixture. For the LCCP mixtures tested, the liver was identified as the target organ. The Panel selected as reference points a BMDL 10 of 2.3 mg/kg bw per day for increased incidence of nephritis in male rats, and of 36 mg/kg bw per day for increased relative kidney weights in male and female rats for SCCPs and MCCPs, respectively. For LCCPs, a reference point relevant for humans could not be identified. Due to the limitations in the toxicokinetic and toxicological database, the Panel concluded that derivation of a health-based guidance value was not appropriate. Only limited data on the occurrence of SCCPs and MCCPs in some fish species were submitted to EFSA. No data were submitted for LCCPs. Thus, a robust exposure assessment and consequently a complete risk characterisation could not be performed. A preliminary risk characterisation based only on the consumption of fish was performed, and the calculated margins of exposure suggested no health concern for this limited scenario. The Panel noted that dietary exposure will be higher due to the contribution of CPs from other foods. The Panel was not able to identify reference points for farm animals, horses and companion animals. No occurrence data for feed were submitted to EFSA. Therefore, no risk characterisation could be performed for any of these animal species.

The Interaction of Sodium and Zinc in the Priming of T Cell Subpopulations Regarding Th17 and Treg Cells

SCOPE

Nutrition is a critical determinant of a functional immune system. The aim of this study is to investigate the molecular mechanisms by which immune cells are influenced by zinc and sodium.

METHODS AND RESULTS

Mixed lymphocyte cultures and Jurkat cells are generated and incubated with zinc, sodium, or a combination of both for further tests. Zinc induces the number of regulatory T cells (Treg) and decreases T helper 17 cells (Th17), and sodium has the opposite effect. The transforming growth factor beta receptor signaling pathway is also enhanced by zinc and reduced by sodium as indicated by contrary phosphoSmad 2/3 induction. Antagonistic effects can also be seen on zinc transporter and metallothionein-1 (MT-1) mRNA expression: zinc declines Zip10 mRNA expression while sodium induces it, whereas MT-1 mRNA expression is induced by zinc while it is reduced by sodium.

CONCLUSION

This data indicate that zinc and sodium display opposite effects regarding Treg and Th17 induction in MLC, respectively, resulting in a contrary effect on the immune system. Additionally, it reveals a direct interaction of zinc and sodium in the priming of T cell subpopulations and shows that Zip10 and MT-1 play a significant role in those differentiation pathways.

The role of poly(ADP-ribose) polymerases in manganese exposed Caenorhabditis elegans

BACKGROUND AND AIM

When exceeding the homeostatic range, manganese (Mn) might cause neurotoxicity, characteristic of the pathophysiology of several neurological diseases. Although the underlying mechanism of its neurotoxicity remains unclear, Mn-induced oxidative stress contributes to disease etiology. DNA damage caused by oxidative stress may further trigger dysregulation of DNA-damage-induced poly(ADP-ribosyl)ation (PARylation), which is of central importance especially for neuronal homeostasis. Accordingly, this study was designed to assess in the genetically traceable in vivo model Caenorhabditis elegans the role of PARylation as well as the consequences of loss of pme-1 or pme-2 (orthologues of PARP1 and PARP2) in Mn-induced toxicity.

METHODS

A specific and sensitive isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to quantify PARylation in worms. Next to monitoring the PAR level, pme-1 and pme-2 gene expression as well as Mn-induced oxidative stress was studied in wildtype worms and the pme deletion mutants.

RESULTS AND CONCLUSION

While Mn failed to induce PARylation in wildtype worms, toxic doses of Mn led to PAR-induction in pme-1-deficient worms, due to an increased gene expression of pme-2 in the pme-1 deletion mutants. However, this effect could not be observed at sub-toxic Mn doses as well as upon longer incubation times. Regarding Mn-induced oxidative stress, the deletion mutants did not show hypersensitivity. Taken together, this study characterizes worms to model PAR inhibition and addresses the consequences for Mn-induced oxidative stress in genetically manipulated worms.

Toxicity of three types of arsenolipids: species-specific effects inCaenorhabditis elegans

AsHCs and AsTAG are highly bioavailable toC. elegans., AsHCs are metabolized byC. elegans., AsHCs but not AsTAG and AsFA affect survival and development inC. elegans.

Changes of trace element status during aging: results of the EPIC-Potsdam cohort study

Purpose

We aimed to evaluate age-dependent changes of six trace elements (TE) [manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), iodine (I), and selenium (Se)] over a 20-year period.

Methods

TE concentrations were determined using repeated serum samples taken at baseline and after 20 years of follow-up from 219 healthy participants of the EPIC-Potsdam study, using inductively coupled plasma tandem mass spectrometry. For each TE, absolute and relative differences were calculated between the two time points, as well as the proportion of individuals within normal reference ranges. Interdependence between age-related TE differences was investigated using principal component analysis (PCA). Relationships between selected factors (lifestyle, sociodemographic, anthropometric factors, and hypertension) and corresponding TE longitudinal variability were examined using multivariable linear regression models.

Results

Median age of our study sample was 58.32 years (4.42) at baseline and 40% were females. Median Mn, Zn, Se concentrations and Se to Cu ratio significantly decreased during aging while median Fe, Cu, I concentrations and Cu to Zn ratio significantly increased. A substantial percentage of the participants, at both time points, had Zn concentrations below the reference range. The first PCA-extracted factor reflected the correlated decline in both Mn and Zn over time while the second factor reflected the observed (on average) increase in both Cu and I over time. Overall, none of the investigated factors were strong determinants of TE longitudinal variability, except possibly dietary supplement use, and alcohol use for Fe.

Conclusions

In conclusion, in this population-based study of healthy elderly, decrease in Mn, Zn, and Se concentrations and increase in Fe, Cu, and I concentrations were observed over 20 years of follow-up. Further research is required to investigate dietary determinants and markers of TE status as well as the relationships between TE profiles and the risk of age-related diseases.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02143-w) contains supplementary material, which is available to authorized users.

Scientific opinion on the risks for animal and human health related to the presence of quinolizidine alkaloids in feed and food, in particular in lupins and lupin-derived products

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of quinolizidine alkaloids (QAs) in feed and food. This risk assessment is limited to QAs occurring in Lupinus species/varieties relevant for animal and human consumption in Europe (i.e. Lupinus albus L., Lupinus angustifolius L., Lupinus luteus L. and Lupinus mutabilis Sweet). Information on the toxicity of QAs in animals and humans is limited. Following acute exposure to sparteine (reference compound), anticholinergic effects and changes in cardiac electric conductivity are considered to be critical for human hazard characterisation. The CONTAM Panel used a margin of exposure (MOE) approach identifying a lowest single oral effective dose of 0.16 mg sparteine/kg body weight as reference point to characterise the risk following acute exposure. No reference point could be identified to characterise the risk of chronic exposure. Because of similar modes of action for QAs, the CONTAM Panel used a group approach assuming dose additivity. For food, the highest mean concentration of Total QAs (TotQAs) (i.e. the 6 most abundant QAs) was found in lupin seed samples classified as 'Lupins (dry) and similar-'. Due to the limited data on occurrence and consumption, dietary exposure was calculated for some specific scenarios and no full human health risk characterisation was possible. The calculated margin of exposures (MOEs) may indicate a risk for some consumers. For example, when lupin seeds are consumed without a debittering step, or as debittered lupin seeds high in QA content and when 'lupin-based meat imitates' are consumed. For horses, companion and farm animals, other than salmonids, the available database on adverse effects was too limited to identify no-observed-adverse-effect levels and/or lowest-observed-adverse-effect levels and no risk characterisation was possible. For salmonids, the CONTAM Panel considers the risk for adverse effects to be low.

Crosstalk of Nrf2 with the Trace Elements Selenium, Iron, Zinc, and Copper

Trace elements, like Cu, Zn, Fe, or Se, are important for the proper functioning of antioxidant enzymes. However, in excessive amounts, they can also act as pro-oxidants. Accordingly, trace elements influence redox-modulated signaling pathways, such as the Nrf2 pathway. Vice versa, Nrf2 target genes belong to the group of transport and metal binding proteins. In order to investigate whether Nrf2 directly regulates the systemic trace element status, we used mice to study the effect of a constitutive, whole-body Nrf2 knockout on the systemic status of Cu, Zn, Fe, and Se. As the loss of selenoproteins under Se-deprived conditions has been described to further enhance Nrf2 activity, we additionally analyzed the combination of Nrf2 knockout with feeding diets that provide either suboptimal, adequate, or supplemented amounts of Se. Experiments revealed that the Nrf2 knockout partially affected the trace element concentrations of Cu, Zn, Fe, or Se in the intestine, liver, and/or plasma. However, aside from Fe, the other three trace elements were only marginally modulated in an Nrf2-dependent manner. Selenium deficiency mainly resulted in increased plasma Zn levels. One putative mediator could be the metal regulatory transcription factor 1, which was up-regulated with an increasing Se supply and downregulated in Se-supplemented Nrf2 knockout mice.

Zn homeostasis in genetic models of Parkinson's disease in Caenorhabditis elegans

While the underlying mechanisms of Parkinson's disease (PD) are still insufficiently studied, a complex interaction between genetic and environmental factors is emphasized. Nevertheless, the role of the essential trace element zinc (Zn) in this regard remains controversial. In this study we altered Zn balance within PD models of the versatile model organism Caenorhabditis elegans (C. elegans) in order to examine whether a genetic predisposition in selected genes with relevance for PD affects Zn homeostasis. Protein-bound and labile Zn species act in various areas, such as enzymatic catalysis, protein stabilization pathways and cell signaling. Therefore, total Zn and labile Zn were quantitatively determined in living nematodes as individual biomarkers of Zn uptake and bioavailability with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) or a multi-well method using the fluorescent probe ZinPyr-1. Young and middle-aged deletion mutants of catp-6 and pdr-1, which are orthologues of mammalian ATP13A2 (PARK9) and parkin (PARK2), showed altered Zn homeostasis following Zn exposure compared to wildtype worms. Furthermore, age-specific differences in Zn uptake were observed in wildtype worms for total as well as labile Zn species. These data emphasize the importance of differentiation between Zn species as meaningful biomarkers of Zn uptake as well as the need for further studies investigating the role of dysregulated Zn homeostasis in the etiology of PD.

Reprotoxicity of glyphosate-based formulation in Caenorhabditis elegans is not due to the active ingredient only

Pesticides guarantee us high productivity in agriculture, but the long-term costs have proved too high. Acute and chronic intoxication of humans and animals, contamination of soil, water and food are the consequences of the current demand and sales of these products. In addition, pesticides such as glyphosate are sold in commercial formulations which have inert ingredients, substances with unknown composition and proportion. Facing this scenario, toxicological studies that investigate the interaction between the active principle and the inert ingredients are necessary. The following work proposed comparative toxicology studies between glyphosate and its commercial formulation using the alternative model Caenorhabditis elegans. Worms were exposed to different concentrations of the active ingredient (glyphosate in monoisopropylamine salt) and its commercial formulation. Reproductive capacity was evaluated through brood size, morphological analysis of oocytes and through the MD701 strain (bcIs39), which allows the visualization of germ cells in apoptosis. In addition, the metal composition in the commercial formulation was analyzed by ICP-MS. Only the commercial formulation of glyphosate showed significant negative effects on brood size, body length, oocyte size, and the number of apoptotic cells. Metal analysis showed the presence of Hg, Fe, Mn, Cu, Zn, As, Cd and Pb in the commercial formulation, which did not cause reprotoxicity at the concentrations found. However, metals can bioaccumulate in soil and water and cause environmental impacts. Finally, we demonstrated that the addition of inert ingredients increased the toxic profile of the active ingredient glyphosate in C. elegans, which reinforces the need of components description in the product labels.

Selenoneine ameliorates peroxide-induced oxidative stress in C. elegans

SCOPE

Selenoneine (2-selenyl-N_α, N_α, N_α-trimethyl-L-histidine), the selenium (Se) analogue of the ubiquitous thiol compound and putative antioxidant ergothioneine, is the major organic selenium species in several marine fish species. Although its antioxidant efficacy has been proposed, selenoneine has been poorly characterized, preventing conclusions on its possible beneficial health effects.

METHODS AND RESULTS

Treatment of Caenorhabditis elegans (C. elegans) with selenoneine for 18 h attenuated the induction of reactive oxygen and nitrogen species (RONS). However, the effect was not immediate, occurring 48 h post-treatment. Total Se and Se speciation analysis revealed that selenoneine was efficiently taken up and present in its original form directly after treatment, with no metabolic transformations observed. 48 h post-treatment, total Se in worms was slightly higher compared to controls and no selenoneine could be detected.

CONCLUSION

The protective effect of selenoneine may not be attributed to the presence of the compound itself, but rather to the activation of molecular mechanisms with consequences at more protracted time points.

The impact of apical and basolateral albumin on intestinal zinc resorption in the Caco-2/HT-29-MTX co-culture model

The molecular mechanisms of intestinal zinc resorption and its regulation are still topics of ongoing research. To this end, the application of suitable in vitro intestinal models, optimized with regard to their cellular composition and medium constituents, is of crucial importance. As one vital aspect, the impact of cell culture media or buffer compounds, respectively, on the speciation and cellular availability of zinc has to be considered when investigating zinc resorption. Thus, the present study aims to investigate the impact of serum, and in particular its main constituent serum albumin, on zinc uptake and toxicity in the intestinal cell line Caco-2. Furthermore, the impact of serum albumin on zinc resorption is analyzed using a co-culture of Caco-2 cells and the mucin-producing goblet cell line HT-29-MTX. Apically added albumin significantly impaired zinc uptake into enterocytes and buffered its cytotoxicity. Yet, undigested albumin does not occur in the intestinal lumen in vivo and impairment of zinc uptake was abrogated by digestion of albumin. Interestingly, zinc uptake, as well as gene expression studies of mt1a and selected intestinal zinc transporters after zinc incubation for 24 h, did not show significant differences between 0 and 10% serum. Importantly, the basolateral application of serum in a transport study significantly enhanced fractional apical zinc resorption, suggesting that the occurrence of a zinc acceptor in the plasma considerably affects intestinal zinc resorption. This study demonstrates that the apical and basolateral medium composition is crucial when investigating zinc, particularly its intestinal resorption, using in vitro cell culture.

Prediction of Transformation Products of Monensin by Electrochemistry Compared to Microsomal Assay and Hydrolysis

The knowledge of transformation pathways and identification of transformation products (TPs) of veterinary drugs is important for animal health, food, and environmental matters. The active agent Monensin (MON) belongs to the ionophore antibiotics and is widely used as a veterinary drug against coccidiosis in broiler farming. However, no electrochemically (EC) generated TPs of MON have been described so far. In this study, the online coupling of EC and mass spectrometry (MS) was used for the generation of oxidative TPs. EC-conditions were optimized with respect to working electrode material, solvent, modifier, and potential polarity. Subsequent LC/HRMS (liquid chromatography/high resolution mass spectrometry) and MS/MS experiments were performed to identify the structures of derived TPs by a suspected target analysis. The obtained EC-results were compared to TPs observed in metabolism tests with microsomes and hydrolysis experiments of MON. Five previously undescribed TPs of MON were identified in our EC/MS based study and one TP, which was already known from literature and found by a microsomal assay, could be confirmed. Two and three further TPs were found as products in microsomal tests and following hydrolysis, respectively. We found decarboxylation, O-demethylation and acid-catalyzed ring-opening reactions to be the major mechanisms of MON transformation.