Infant total diet study in France: Exposure to substances migrating from food contact materials

A total diet study (TDS) was conducted in France to assess the health risks related to the chemicals in food of non-breastfed children under three years of age (Infant TDS). For the first time, substances coming from food contact materials, such as bisphenol A (BPA), bisphenol A diglycidyl ether (BADGE) and its derivatives, some phthalates, and some ink photoinitiators, were targeted because of growing interest in these substances. Food samples were collected to be representative of the whole diet of non-breastfed children aged 1-36 months, and prepared as consumed prior to analysis. Dietary exposure was assessed for 705 representative children under three years of age. Generally, the substances from food contact materials were detected in few samples: 38% for BPA, 0% for BADGE and its derivatives, 0-35% for phthalates, 1.9% for benzophenone, and 0% for the other ink photoinitiators. Regarding exposure levels, the situation was deemed tolerable for BADGE and its hydrolysis products, di-isodecyl phthalate, dibutyl phthalate, butyl benzyl phthalate, bis(2-ethylhexyl) phthalate, and di-isononyl phthalate, benzophenone, and 4-methylbenzophenone. Only for BPA, the exposure levels of some children exceeded the lowest toxicological value established by the French Agency for Food, Environmental and Occupational Health & Safety at 0.083 µg.kg bw^-1.d^-1. The temporary tolerable daily intake of the European Food Safety Authority (EFSA), set at 4 µg.kg bw^-1.d^-1, was never exceeded. However, actual exposure to BPA was probably overestimated, as well as the associated risk, because the foods were sampled prior to the recent regulations banning BPA in food packaging. This study is the first worldwide to provide an estimate of infant food contamination levels and exposures of children under 3 years of age, based on a TDS approach. It therefore provides key data on the exposure of this particularly sensitive population to substances released from food contact materials, and presents useful data for studies evaluating exposure to mixtures or aggregated exposure.

Optimized Simultaneous Determination of Several Elements in Human Intestinal Caco-2 TC7 Cells by Inductively Coupled Plasma-Mass Spectrometry after Closed Vessel Microwave Digestion

A rapid procedure, based on closed vessels microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS), was evaluated to ascertain the effect of chronic exposure to cadmium on intracellular accumulation of minor and essential trace elements in cultured epithelial cells (Caco-2 TC7). For all measurements, the method of external calibration was used and 3 elements (Be, Sc, In) were selected as internal standards. Optimization procedures are discussed and results are presented for the total determination of 9 key analytes (Na, Mg, Ca, Cr, Mn, Cu, Zn, Mo, and Cd) in certified reference materials (CRMs) and 20 samples of Caco-2 TC7 cells long-term exposed to Cd. The performance characteristics of the analytical system were evaluated by calibration and linearity, limits of detection and quantitation, accuracy with spiking, trueness and repeatability with available CRMs. As a complement to the ICP-MS determinations, both available CRMs and cell samples were analyzed either by electro thermal-or flame atomic absorption spectrometry. The results were in good agreement with the ICP-MS results.

Safety assessment of the substance, titanium dioxide surface treated with fluoride-modified alumina, for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP Panel) is a safety assessment of the additive titanium dioxide surface treated with fluoride‐modified alumina, a defined mixture of particles of which ■■■■■% in number have a diameter in the range of 1–100 nm. It is intended to be used as filler and colourant up to 25% w/w in potentially all polymer types. Materials and articles containing the additive are intended to be in contact with all food types for any time and temperature conditions. The data provided demonstrate that the additive particles stay embedded even in swollen polar polymers such as polyamide, and do not migrate. Moreover, the additive particles resisted release by abrasion and did not transfer into a simulant for solid/dry foods. Thus, the additive particles do not give rise to exposure via food and to toxicological concern. Migration of solubilised ionic fluoride and aluminium occurs from the surface of the additive particles and particularly from swollen plastic. The Panel concluded that the substance does not raise safety concern for the consumer if used as an additive up to 25% w/w in polymers in contact with all food types for any time and temperature conditions. However, uses in polar polymers swelling in contact with foodstuffs simulated by 3% acetic acid should be limited to conditions simulated by contact up to 4 h at 100°C. This is due to the fact that when used at 25%, and contact was followed by 10 days at 60°C, the migration of aluminium and fluoride largely exceeded the specific migration limit (SML) of 1 and 0.15 mg/kg food, respectively. The Panel emphasises that the existing SMLs for aluminium and fluoride should not be exceeded in any case.

Safety assessment of the substance, montmorillonite clay modified with hexadecyltrimethylammonium bromide, for use in food contact materials

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of montmorillonite clay modified with hexadecyltrimethylammonium bromide (HDTA) when used as an additive at up to ■■■■■ in polylactic acid (PLA) bottles intended for contact with water for long‐term storage at ambient temperature or below. The modified clay, which 90% w/w of the particles have a dimension of 33.1 μm or less and the average size is 9 μm, has a layered structure with layers of a thickness below 100 nm. When incorporated in PLA, nanosized layers can be dispersed in the matrix, but are not expected to migrate. Thermal degradation is not expected at the maximum manufacturing temperature. No loss of integrity of the PLA surface due to interaction with bottled water was observed. The overall migration was very low. No migration of HDTA was detected at the limit of detection ■■■■■. Migration of aluminium was below or at the limit of detection ■■■■■, which would conservatively correspond to approximately ■■■■■. Comparative analysis of bottled water with and without the modified clay did not reveal additional peaks corresponding to impurities identified in the modifier and/or in the modified clay. Moreover, ■■■■■, and the modifier HDTA have been evaluated and authorised. Therefore, the CEP Panel concluded that the substance montmorillonite clay modified with HDTA bromide is not of safety concern for the consumer if the substance is used as an additive at up to ■■■■■ in PLA plastic bottles and other containers intended for long‐term storage of water at ambient temperature or below, as requested by the applicant.

Safety assessment of the active substance polyacrylic acid, sodium salt, cross-linked, for use in active food contact materials

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of polyacrylic acid, sodium salt, cross‐linked, FCM substance No 1015, which is intended to be used as a liquid absorber in the packaging of fresh or frozen foods such as meat, poultry and seafood as well as fresh fruits and vegetables. Specific migration tests were not performed due to the high absorption of liquids by the substance. The Panel noted that if polyacrylic acid, sodium salt, cross‐linked is used not in direct contact with food and placed in a pad under conditions where its absorption capacity is not exceeded, then no migration is to be expected and therefore no exposure from the consumption of the packed food is expected. The Panel also considered that the non‐cross‐linked polymer and the cross‐linkers do not raise a concern for genotoxicity. The CEP Panel concluded that the use of this polyacrylic acid, sodium salt, cross‐linked, does not raise a safety concern when used in absorbent pads in the packaging of fresh or frozen foods. The absorbent pads must be used only under conditions in which the absorption capacity of the active substance is not exceeded and direct contact with food is excluded.

Safety assessment of the substance Ln 1,4-benzene dicarboxylic acid (with Ln = La, Eu, Gd, Tb) for use in food contact materials

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP Panel) assessed the safety of the additive Ln 1,4‐benzene dicarboxylic acid (with Ln = La, Eu, Gd, Tb) for use in food contact materials. It is a family of mixtures combining the four lanthanides lanthanum (La), europium (Eu), gadolinium (Gd) and/or terbium (Tb) in different proportions as their 1,4‐benzene dicarboxylate complexes, used as a taggant in plastics for authentication and traceability purposes. The powdered additive, not in nano form, is intended to be used at up to 100 mg/kg in polyethylene, polypropylene and polybutene. Materials and articles made of these plastics are intended for contact with all foods types at up to 4 h/100°C or for long‐term storage at ambient temperature. In tests with food simulants, migration of each Ln was below 5 μg/kg. The Panel considered that irrespective of the composition of the lanthanides, these would dissociate completely from the terephthalic acid salt under aqueous conditions. Evaluation of the genotoxicity studies provided on the individual complexes (La, Eu, Gd and Tb) and on their mixture, taken together with data available in the scientific literature, allows ruling out concern for genotoxicity. Consequently, the CEP Panel concluded that the substance Ln 1,4‐benzene dicarboxylic acid (with Ln = La, Eu, Gd, Tb) does not raise a safety concern for the consumer under the proposed conditions of use and if the migration of the sum of the four lanthanides in ionic form does not exceed 50 μg/kg food.

Regulatory identification of BPA as an endocrine disruptor: Context and methodology

BPA is one of the most investigated substances for its endocrine disruptor (ED) properties and it is at the same time in the center of many ED-related controversies. The analysis on how BPA fits to the regulatory identification as an ED is a challenge in terms of methodology. It is also a great opportunity to test the regulatory framework with a uniquely data-rich substance and learn valuable lessons for future cases. From this extensive database, it was considered important to engage in a detailed analysis so as to provide specific and strong evidences of ED while reflecting accurately the complexity of the response as well the multiplicity of adverse effects. An appropriate delineation of the scope of the analysis was therefore critical. Four effects namely, alterations of estrous cyclicity, mammary gland development, brain development and memory function, and metabolism, were considered to provide solid evidence of ED-mediated effects of BPA.

Alteration of mammary gland development by bisphenol a and evidence of a mode of action mediated through endocrine disruption

The development and function of the mammary gland are endocrine-dependent processes, depending on the stage of development. Foetal and/or postnatal exposure to low doses of BPA alters tissue organisation through epithelial proliferation and stroma-epithelial interactions. BPA also alters the expression of E2-dependent epithelial and stroma transcriptomes. Several signalling pathways are consistent with the observed phenotype: proliferation and apoptosis, a focal adhesion pathway indicating changes in biomechanical properties of the extracellular matrix, and immune function. Some of BPA's effects are reversed by oestrogen and/or GPER inhibitors. BPA also alters the expression of epigenetic marks (EZH2, HOTAIR), which would explain the delayed effect of foetal BPA exposure. In conclusion, experimental evidence shows that pre- or postnatal BPA exposure consistently causes endocrine modifications in the mammary tissue of different animal species, disrupting stromal-epithelial interactions and ultimately increasing its susceptibility to carcinogens. An interspecies comparison highlights why and how these effects apply to humans.

FELASA accreditation of education and training courses in laboratory animal science according to the Directive 2010/63/EU

This document describes how the Federation of European Laboratory Animal Science Associations (FELASA) accreditation addresses both the Directive 2010/63/EU and the related European Commission guidance document.

Safety assessment of the active substance selenium nanoparticles, for use in active food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) deals with the safety assessment of selenium nanoparticles, FCM substance No 1070, which is intended to be used as an antioxidant. Selenium nanoparticles are incorporated into the adhesive middle layer of multilayer laminates with an outside polyethylene terephthalate (PET) layer and an inner polyolefin (food contact) layer. The final materials are intended to be used for contact with all food types that are susceptible to oxidation. The specific migration of total selenium was tested using multilayer pouches containing selenium nanoparticles at 0.002 mg/dm2 and filled with 3% acetic acid and 20%, 50% or 95% ethanol for 10 days at 60°C. In all tests, migration of selenium was not detectable. Taking into account current knowledge on the diffusional properties of nanoparticles in polymers, the CEF Panel concluded that there is no safety concern for the consumer if selenium nanoparticles are used in multilayer films and separated from the food by a polyolefin food contact layer for any type of food and under any food contact conditions.

Safety assessment of the substance isobutane, for use in food contact materials

The substance isobutane is intended to be used as a foaming agent at max 4.5% to produce expanded polystyrene (EPS) to be used for packaging foods, such as fruits, vegetables, meat, fish and cheese, at room temperature or lower. Isobutane is approved in Europe as a food additive (E 943b) to be used quantum satis as a gas propellant only in vegetable oil pan spray (for professional use only) and water-based emulsion spray according to Regulation (EC) No 1333/2008. The purity requirements for the use of isobutane as a food additive are described in Commission Regulation (EU) No 231/2012. The substance is a gas at room temperature. It is a saturated hydrocarbon, obtained with a high level of purity, and is not expected to react under the processing conditions used to make foamed polystyrene materials and articles. Data on migration of isobutane from trays at 20°C for 10 days ranged from 0.2 to 0.4 mg/kg food. Considering the intended applications, estimated exposure is extremely low based on migration data. In the absence of genotoxicity alerts and given the very low toxicity following repeated exposure with no observed adverse effect concentration (NOAEC) of several thousands of mg/m3 by inhalation, it was considered that the use of isobutane as a foaming agent, at the expected exposure from food, does not raise a safety concern.

Safety assessment of the substance [3-(2,3-epoxypropoxy)propyl]trimethoxy silane, for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) deals with the safety evaluation of [3-(2,3-epoxypropoxy)propyl]trimethoxy silane as a component for sizing glass fibres used for manufacturing glass-fibre-reinforced plastics. The substance is typically applied at up to around 0.2% related to the final plastic. The resulting food contact materials are intended for various scenarios of use, i.e. long-term contact at ambient temperature (e.g. storage tanks) or short-term contact at elevated temperatures (e.g. kitchen utensils). In extracts of treated fibres, neither the substance was detectable at 10 μg/kg fibre nor its hydrolysis product and oligomers at 60 μg/kg fibre. Based on the detection limits, modelling for the plastics and scenarios of intended use resulted in maximum migrations of 0.05 μg/kg food for the substance and 0.15 μg/kg food for the sum of the reaction products. The Panel concludes that the substance has a genotoxic potential. This may also apply to some of its reaction products which contain the epoxy function. However, due to the very low exposure, if any, [3-(2,3-epoxypropoxy)propyl]trimethoxy silane does not raise safety concern if used as a component of sizing agents to treat glass fibres imbedded into low diffusivity plastics (polyethylene terephthalate, polycarbonate, polybutylene terephthalate, thermoset polyesters and epoxy bisphenol vinylester) in contact with all foodstuffs. In addition, the residues in the treated glass fibres must not be detectable at 10 μg/kg for the substance and 60 μg/kg for each of the reaction products (hydrolysed monomers and epoxy-containing cyclic dimer, trimer and tetramer).

Intestinal toxicity of the type B trichothecene mycotoxin fusarenon-X: whole transcriptome profiling reveals new signaling pathways

The few data available on fusarenon-X (FX) do not support the derivation of health-based guidance values, although preliminary results suggest higher toxicity than other regulated trichothecenes. Using histo-morphological analysis and whole transcriptome profiling, this study was designed to obtain a global view of the intestinal alterations induced by FX. Deoxynivalenol (DON) served as a benchmark. FX induced more severe histological alterations than DON. Inflammation was the hallmark of the molecular toxicity of both mycotoxins. The benchmark doses for the up-regulation of key inflammatory genes by FX were 4- to 45-fold higher than the previously reported values for DON. The transcriptome analysis revealed that both mycotoxins down-regulated the peroxisome proliferator-activated receptor (PPAR) and liver X receptor - retinoid X receptor (LXR-RXR) signaling pathways that control lipid metabolism. Interestingly, several pathways, including VDR/RXR activation, ephrin receptor signaling, and GNRH signaling, were specific to FX and thus discriminated the transcriptomic fingerprints of the two mycotoxins. These results demonstrate that FX induces more potent intestinal inflammation than DON. Moreover, although the mechanisms of toxicity of both mycotoxins are similar in many ways, this study emphasize specific pathways targeted by each mycotoxin, highlighting the need for specific mechanism-based risk assessments of Fusarium mycotoxins.

Safety assessment of the substance dimethyl carbonate for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) deals with the safety assessment of dimethyl carbonate used as monomer for making a polycarbonate prepolymer with 1,6-hexanediol and then reacted with 4,4'-methylenediphenyldiisocyanate (MDI) and diols, such as polypropylene glycol and 1,4-butanediol, to form a thermoplastic polyurethane containing 29% of the polycarbonate prepolymer. This polymer is intended for repeated use articles with short-term contact (≤ 30 min) at room temperature for types of food, simulated by 10% ethanol and 3% acetic acid. In the third migration test performed at 40°C during 30 min, overall migration was below 2 mg/dm2. Complete migration of the residual dimethyl carbonate would have amounted to less than 1.5 μg/kg food. The migration of two cyclic hexanediol carbonate oligomers was below 50 μg/kg food when determined by the third migration test; that of all others was below 1 μg/kg food. Three in vitro genotoxicity studies performed in accordance with OECD Guidelines and covering the three endpoints gene mutation, structural and numerical aberrations were provided and were considered negative by the CEF Panel. The oligomers detected by the migration tests are formed from dimethyl carbonate and 1,6-hexanediol (FCM ref No 1067) do not give rise to concern for genotoxicity. The CEF Panel concluded that the use of dimethyl carbonate does not raise safety concern in the application described above. It is aware that dimethyl carbonate may be used for other polycarbonates and/or under other conditions. These are likely to result in different migrates which need to be evaluated by the business operators. In such cases, the migration of dimethyl carbonate and the total polycarbonate oligomers below 1,000 Da is of no safety concern, if each of them does not exceed 0.05 mg/kg food.

Safety assessment of the substance phosphorous acid, mixed 2,4-bis(1,1-dimethylpropyl)phenyl and 4-(1,1-dimethylpropyl)phenyl triesters for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) deals with the safety assessment of the substance phosphorous acid, mixed 2,4-bis(1,1-dimethylpropyl)phenyl and 4-(1,1-dimethylpropyl)phenyl triesters. The substance was evaluated by the CEF Panel in 2011 and 2,4-di-tert-amylphenol, an impurity and hydrolysis product was re-evaluated by the CEF Panel in 2015. In this application, the applicant requested an increase of the specific migration limit of the substance, currently established at 5 mg/kg food, to 10 mg/kg food, and provided new toxicological studies. Findings from three new in vitro mutagenicity assays on the oxidation products support the conclusion from 2011 that the substance and its oxidation products are not genotoxic. A new toxicokinetic study on the substance supports the consideration from the evaluation in 2011 that the substance does not raise concern for accumulation. The outcome of a new delayed neurotoxicity study on a structurally related substance, phosphorous acid, tris (2,4-di-tert-butylphenyl) ester, which was considered not to cause neurotoxicity in hens, strengthens the conclusion of the Panel in 2011 that the substance does not represent a concern for neurotoxicity. From a new two-generation reproduction toxicity study and a prenatal developmental toxicity study on the substance, a new subchronic toxicity study on its oxidation products that completes the one submitted in 2011 on the substance itself, and a 2-year oral toxicity study on the structurally related substance, the lowest NOAEL was 58-147 mg/kg bw per day (from the 2-year oral toxicity study). Compared to the requested increase of the migration limit, this gives an acceptable margin of safety of 348. Therefore, the CEF Panel concluded that an increase of the specific migration limit of the substance from 5 to 10 mg/kg food is not a safety concern for the consumer.

Safety assessment of the substance 1,2,3,4-tetrahydronaphthalene-2,6-dicarboxylic acid, dimethyl ester for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing aids (CEF Panel) deals with the safety assessment of 1,2,3,4-tetrahydronaphthalene-2,6-dicarboxylic acid, dimethyl ester (TDCM) for use as a co-monomer to manufacture polyester layers. The polyester layer is not intended to be in direct contact with food. The finished multilayer articles are intended for packaging aqueous, acidic and low alcoholic foodstuffs. Contact conditions include sterilisation followed by long-term storage at room temperature. No thermal degradation of TDCM is expected during the manufacture of the middle polyester layer and of the multilayer articles. Total mass transfer of the substance from a polyester monolayer was calculated to be up to 0.032 mg/kg food. Based on three in vitro genotoxicity tests, the CEF Panel considered that the substance does not raise concern for genotoxicity. When tested behind a polypropylene layer, migrating TDCM-related oligomers, their oxidation products and other related reaction products were identified. The major components were TDCM dimers. When tested behind a cyclo-olefin polymer layer, none of the TDCM-related substances were found to migrate. Based on the lack of genotoxicity of the co-monomer, the ester nature of the oligomers and on (quantitative) structure-activity relationship ((Q)SAR) analysis, the CEF Panel considered that there is no indication of genotoxicity for the oligomers, their oxidation products and other TDCM-related reaction products. The CEF Panel concluded that the substance is not of safety concern for the consumer if used as a co-monomer for the manufacture of a polyester layer intended to be used as an inner (non-food contact) layer of a multilayer material for contact with foods simulated by simulants A, B, C, D1 (as set in Regulation (EU) 10/2011). The migration of the sum of the substance and the dimers (cyclic and open chain) should not exceed 0.05 mg/kg food.

Safety assessment of the mixture of methyl-branched and linear C14-C18 alkanamides, derived from fatty acids, for use in food contact materials

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) deals with the safety assessment of the mixture of methyl-branched and linear C14-C18 alkanamides, derived from fatty acids, for use in food contact materials as a slip or release agent at up to 1% w/w in polyolefins. The final materials are intended for contact with foodstuffs other than fatty foods for long-term storage at room temperature including short heating. No thermal degradation of the substance is expected under manufacturing process conditions of polyolefins. Specific migration from low-density polyethylene (LDPE) made with 0.37% of the substance into 3% acetic acid and 10% ethanol was up to 0.68 mg/kg. Based on negative results in a bacterial mutation test and in an in vivo micronucleus test, there was no evidence of a genotoxic potential of the substance. Impurities were determined and the main ones were tested in a bacterial mutation test giving negative results. Along with the negative results from the in vivo micronucleus test on the substance containing the impurities, there was no evidence of a genotoxic potential of the impurities. Based on a 28-day study on the substance, the Panel noted that there is sufficient margin of safety between the no observed adverse effect level (NOAEL) and the maximum exposure of consumers that could occur at a migration level of 5 mg/kg food, to cover uncertainties about toxic effects due to potential accumulation of slowly hydrolysed branched amide species of the substance during chronic exposure. The CEF Panel concluded that the substance is not of safety concern for consumers if it is used in the manufacture of polyolefin articles intended for contact with all foodstuffs other than fatty foods and the migration does not exceed 5 mg/kg food. The 5 mg/kg food migration should not apply to n-stearamide.

Safety assessment of the substance 'Tungsten Oxide' for use in food contact materials

This scientific opinion of EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) deals with the risk assessment of the additive tungsten oxide, CAS No 39318‐18‐8 and FCM No 1064, for use in food contact materials as a reheat agent in polyethylene terephthalate (PET) at a maximum use level of 75 ppm (75 mg/kg PET). The substance is a mixture of tungsten oxides with tungsten at different oxidative levels. The average oxidation level of tungsten in the oxides is 2.86 corresponding to 19.93% oxygen content. Detailed information on impurities is provided as confidential. Specific migration from PET plaques with the substance at 150 mg/kg (double the maximum intended use level of 75 mg/kg) was determined into 95% ethanol, as a worst‐case simulant for PET due to its swelling effect. Under these test conditions, the specific migration, measured as tungsten using ICP‐MS, was at the level of 1 μg/kg. The Panel considered that due to the insolubility of the substance, this low migration will be typical for any foreseeable use as a reheat additive in PET. Two in vitro genotoxicity studies, a bacterial gene mutation test and an in vitro micronucleus assay, performed in accordance with the OECD Guidelines and in compliance with GLP, were provided by the applicant for the substance tungsten oxide and were considered negative by the CEF Panel. According to a scientific opinion on strategy for genotoxicity testing (EFSA, 2011), the three genotoxic endpoints, gene mutation, chromosomal and numerical aberrations, are covered by these two tests. The CEF Panel concluded that the substance tungsten oxide is not of safety concern for the consumer if the additive is used as a reheat agent in PET. For other technical functions or for use in other polymers, the migration should not exceed 50 μg/kg (expressed as tungsten).

Nivalenol has a greater impact than deoxynivalenol on pig jejunum mucosa in vitro on explants and in vivo on intestinal loops

The mycotoxins deoxynivalenol (DON) and nivalenol (NIV), worldwide cereal contaminants, raise concerns for animal and human gut health, following contaminated food or feed ingestion. The impact of DON and NIV on intestinal mucosa was investigated after acute exposure, in vitro and in vivo. The histological changes induced by DON and NIV were analyzed after four-hour exposure on pig jejunum explants and loops, two alternative models. On explants, dose-dependent increases in the histological changes were induced by DON and NIV, with a two-fold increase in lesion severity at 10 µM NIV. On loops, NIV had a greater impact on the mucosa than DON. The overall proliferative cells showed 30% and 13% decrease after NIV and DON exposure, respectively, and NIV increased the proliferative index of crypt enterocytes. NIV also increased apoptosis at the top of villi and reduced by almost half the proliferative/apoptotic cell ratio. Lamina propria cells (mainly immune cells) were more sensitive than enterocytes (epithelial cells) to apoptosis induced by NIV. Our results demonstrate a greater impact of NIV than DON on the intestinal mucosa, both in vitro and in vivo, and highlight the need of a specific hazard characterization for NIV risk assessment.

New insights into the organ-specific adverse effects of fumonisin B1: comparison between lung and liver

Fumonisin B1 (FB1) is a well-known inhibitor of de novo sphingolipid biosynthesis, due to its ability to inhibit ceramide synthases (CerS) activity. In mammals, this toxin triggers broad clinical symptoms with multi-organ dysfunction such as hepatotoxicity or pulmonary edema. The molecular mechanism of CerS inhibition by FB1 remains unknown. Due to the existence of six mammalian CerS isoforms with a tissue-specific expression pattern, we postulated that the organ-specific adverse effects of FB1 might be due to different CerS isoforms. The sphingolipid contents of lung and liver were compared in normal and FB1-exposed piglets (gavage with 1.5 mg FB1/kg body weight daily for 9 days). The effect of the toxin on each CerS was deduced from the analysis of its effects on individual ceramide (Cer) and sphingomyelin (SM) species. As expected, the total Cer content decreased by half in the lungs of FB1-exposed piglets, while in contrast, total Cer increased 3.5-fold in the livers of FB1-exposed animals. Our data also indicated that FB1 is more prone to bind to CerS4 and CerS2 to deplete lung and to enrich liver in d18:1/C20:0 and d18:1/C22:0 ceramides. It also interact with CerS1 to enrich liver in d18:1/C18:0 ceramides. Cer levels were counterbalanced by those of SM. In conclusion, these results demonstrate that the specificity of the effects of FB1 on tissues and organs is due to the effects of the toxin on CerS4, CerS2, and CerS1.

The food contaminant deoxynivalenol activates the mitogen activated protein kinases in the intestine: interest of ex vivo models as an alternative to in vivo experiments

Trichothecenes induce changes in the intestinal barrier function through decreased expression of cell junction proteins and apoptosis of enterocytes. The mitogen activated protein kinases (MAPK) play an important role in the signaling pathways of cell turnover and differentiation. Using ex vivo and in vivo approaches, the purpose of this study was to investigate the ability of low doses of DON to induce histological changes in the intestine and to activate the MAPK ERK 1/2, p38 and JNK. Twelve weaning piglets received during four weeks a control diet or a DON-contaminated diet (2.3 mg DON/kg feed). Six weaning piglets were used to prepare jejunal explants (ex vivo model). Explants were exposed during 4 h to vehicle, 5 or 10 μM DON. Intestinal changes were graded using a histological score. Pigs fed a DON-diet and explants exposed to DON showed a significant decrease in the jejunal score. In both models, the toxin significantly enhanced phosphorylation of ERK 1/2 and p38, whereas the increased phosphorylation of JNK was non significant. Taken together these results indicate that in vivo or ex vivo exposure of intestinal tissue to DON lead to similar intestinal lesions and activation of MAPK. These effects could impair the homeostasis of intestinal tissue in the aspects of barrier function and immune protection. The similarity of the in vivo and ex vivo results provides also strong evidence that the jejunal explant model is a good alternative for toxicological studies in intestinal tissue.

Toxicity of deoxynivalenol and its acetylated derivatives on the intestine: differential effects on morphology, barrier function, tight junction proteins, and mitogen-activated protein kinases

The intestinal epithelium is the first barrier against food contaminants and is highly sensitive to mycotoxins, especially de oxynivalenol (DON). Consumption of DON-contaminated food is associated with outbreaks of gastroenteritis. In cereals and their byproducts, DON is present together with two acetylated derivatives, 3-ADON and 15-ADON. The aim of this study was to compare the intestinal toxicity of DON and A-DONs, using noncytotoxic doses. The toxicity was assessed using in vitro (intestinal epithelial cell line), ex vivo (intestinal explants), and in vivo (animals exposed to mycotoxin-contaminated diets) models. The effects were studied on cell proliferation, barrier function, and intestinal structure. The mechanism of toxicity was investigated by measuring the expression of the tight junction proteins and of phosphorylated ERK1/2, p38, and JNK, which are effectors of signaling pathway involved in cellular programs including embryogenesis, proliferation, differentiation, and apoptosis. On proliferating cells, 3-ADON was less toxic than DON, which was less toxic than 15-ADON. On differentiated cells, 15-ADON impaired the barrier function, whereas DON and 3-ADON did not have a significant effect. Similarly, ex vivo and in vivo, 15-ADON caused more histological lesions than DON or 3-ADON. At the molecular level, the 15-ADON activated the mitogen-activated protein kinases (MAPK) ERK1/2, p38, and JNK in the intestinal cell line, explants, and the jejunum from exposed animals at lower dose than DON and 3-ADON. Our results show that the higher toxicity of 15-DON is due to its ability to activate the MAPK. Given that cereal-based foods are contaminated with DON and acetylated-DON, the higher toxicity of 15-ADON should be taken into account.

The low intestinal and hepatic toxicity of hydrolyzed fumonisin B₁ correlates with its inability to alter the metabolism of sphingolipids

Fumonisins are mycotoxins frequently found as natural contaminants in maize, where they are produced by the plant pathogen Fusarium verticillioides. They are toxic to animals and exert their effects through mechanisms involving disruption of sphingolipid metabolism. Fumonisin B₁ (FB₁) is the predominant fumonisin in this family. FB₁ is converted to its hydrolyzed analogs HFB₁, by alkaline cooking (nixtamalization) or through enzymatic degradation. The toxicity of HFB₁ is poorly documented especially at the intestinal level. The objectives of this study were to compare the toxicity of HFB₁ and FB₁ and to assess the ability of these toxins to disrupt sphingolipids biosynthesis. HFB₁ was obtained by a deesterification of FB₁ with a carboxylesterase. Piglets, animals highly sensitive to FB₁, were exposed by gavage for 2 weeks to 2.8 μmol FB₁ or HFB₁/kg body weight/day. FB₁ induced hepatotoxicity as indicated by the lesion score, the level of several biochemical analytes and the expression of inflammatory cytokines. Similarly, FB₁ impaired the morphology of the different segments of the small intestine, reduced villi height and modified intestinal cytokine expression. By contrast, HFB₁ did not trigger hepatotoxicity, did not impair intestinal morphology and slightly modified the intestinal immune response. This low toxicity of HFB₁ correlates with a weak alteration of the sphinganine/sphingosine ratio in the liver and in the plasma. Taken together, these data demonstrate that HFB₁ does not cause intestinal or hepatic toxicity in the sensitive pig model and only slightly disrupts sphingolipids metabolism. This finding suggests that conversion to HFB₁ could be a good strategy to reduce FB₁ exposure.

Development of a pig jejunal explant culture for studying the gastrointestinal toxicity of the mycotoxin deoxynivalenol: histopathological analysis

The digestive tract is a target for the mycotoxin deoxynivalenol (DON), a major cereals grain contaminant of public health concern in Europe and North America. Pig, the most sensitive species to DON toxicity, can be regarded as the most relevant animal model for studying the intestinal effects of DON. A pig jejunal explants culture was developed to assess short-term effects of DON. In a first step, jejunal explants from 9-13 week-old and from 4-5 week-old pigs were cultured in vitro for up to 8h. Explants from younger animals were better preserved after 8h, as assessed by morphological scores and by villi lengths. In a second step, DON dose-related alterations of the jejunal tissue were observed, including shortened and coalescent villi, lysis of enterocytes, oedema. After 4h of DON exposure of explants from 4-5 week-old pigs, a no-effect concentration level of 1 microM was estimated (corresponding to diet contaminated with 0.3mg DON/kg) based on morphological scores, and of 0.2 microM based on villi lengths. In conclusion, our data indicate that pig intestinal explants represent a relevant and sensitive model to investigate the effects of food contaminants.

Variations in zearalenone activation in avian food species

Zearalenone (ZEA), a widely distributed oestrogenic fusariotoxin, constitutes a potential risk for human and animal health. ZEA is metabolised to the main metabolites identified in vitro and in vivo: alpha-zearalenol (alpha-ZOL) and beta-zearalenol (beta-ZOL). The efficiency to produce alpha-reduced metabolites appears of particular interest in risk assessment as alpha-reduced metabolites constitute activated forms whereas beta-reduced metabolites are less oestrogenic than ZEA. In this study ZEA activation was compared in avian food species. ZEA and its reduced metabolites were quantified in subcellular fractions of six avian species and rat livers. The alpha-ZOL/beta-ZOL ratio in rats was 19. The various avian food species cannot be considered to be equivalent in terms of ZEA reduction (P<0.001). Quails represented high "beta reducers", with alpha-ZOL/beta-ZOL ratio less than two. Weak "beta reducers" included on one part ducks and chickens showing alpha-ZOL/beta-ZOL ratio greater than 3 and up to 5.6 and on a second part geese, showing a lower production of alpha-ZOL than other poultry. Comparisons of enzyme kinetics in ducks and in quails show that these variations can be explained by the action of various isoforms of dehydrogenases. These results are relevant to food safety, in the context of frequently inevitable contamination of animal feed.

Cadmium accumulation and interactions with zinc, copper, and manganese, analysed by ICP-MS in a long-term Caco-2 TC7 cell model

The influence of long-term exposure to cadmium (Cd) on essential minerals was investigated using a Caco-2 TC7 cells and a multi-analytical tool: microwave digestion and inductively coupled plasma mass spectrometry. Intracellular levels, effects on cadmium accumulation, distribution, and reference concentration ranges of the following elements were determined: Na, Mg, Ca, Cr, Fe, Mn, Co, Ni, Cu, Zn, Mo, and Cd. Results showed that Caco-2 TC7 cells incubated long-term with cadmium concentrations ranging from 0 to 10 micromol Cd/l for 5 weeks exhibited a significant increase in cadmium accumulation. Furthermore, this accumulation was more marked in cells exposed long-term to cadmium compared with controls, and that this exposure resulted in a significant accumulation of copper and zinc but not of the other elements measured. Interactions of Cd with three elements: zinc, copper, and manganese were particularly studied. Exposed to 30 micromol/l of the element, manganese showed the highest inhibition and copper the lowest on cadmium intracellular accumulation but Zn, Cu, and Mn behave differently in terms of their mutual competition with Cd. Indeed, increasing cadmium in the culture medium resulted in a gradual and significant increase in the accumulation of zinc. There was a significant decrease in manganese from 5 micromol Cd/l exposure, and no variation was observed with copper.

Increased functional expression of P-glycoprotein in Caco-2 TC7 cells exposed long-term to cadmium

The objective of this study was to investigate whether P-glycoprotein (P-gp) functional expression in intestinal cells is modified after long-term exposure to the food contaminant cadmium (Cd). The Caco-2 cell line, clone TC7, was first validated as a cellular model for long-term exposure to cadmium. Cytotoxicity tests after acute exposure of 24 h showed a significant concentration-dependent decrease in cellular viability at cadmium levels higher than 10 microM and led us to select the cadmium ranges for long-term exposure: 1, 5, and 10 microM. Intestinal cells were exposed to these cadmium concentrations for four consecutive weeks without inducing DNA condensation or fragmentation. In the second part of this work, we studied the functional expression of the drug efflux pump multidrug resistance P-glycoprotein after long-term exposure to cadmium by immunoblotting with the monoclonal antibody F4 and measurement of calcein-AM+/-the P-gp inhibitor verapamil. Western blot analysis with the F4 antibody detected a single band of 170 to 180 kDa which is the size previously reported for P-gp. Calcein-AM assay showed that four weeks exposure of intestinal cells to 1, 5, and 10 microM Cd increased P-gp functional expression in proportion to the Cd concentration.

Subchronic dietary exposure of rats to cadmium alters the metabolism of metals essential to bone health

Cadmium (Cd) was recently identified as a risk factor for osteoporosis. Skeletal damage may be the critical effect of low-level long-term exposure to Cd in the general population exposed via food, but the mechanisms behind this are not clearly understood. We investigated the effect of dietary Cd exposure on metals involved in bone turnover. Female rats received a Cd-supplemented diet (0, 10, 50, or 200 CdCl2 mg/kg diet) for 13 weeks. Cd and essential metals stored in the liver were measured by ICP-MS multianalysis. Mineral content of the livers was modified according to Cd level: iron, magnesium and selenium decreased while copper, zinc and manganese increased with increasing Cd levels. Iron was the most strikingly affected metal, falling to one-fifth of control values at high dietary Cd exposure. In this dosage group, selenium decreased to 36% of mean control concentrations while zinc increased to 168%. This mineral imbalance, especially depleted iron stores, can contribute, at least in part, to the Cd-associated risk of osteoporosis. The association between iron metabolism and Cd exposure should be investigated in humans, as Cd and low iron stores could act synergistically as risk factors for osteoporosis.

Optimized simultaneous determination of several elements in human intestinal Caco-2 TC7 cells by inductively coupled plasma-mass spectrometry after closed vessel microwave digestion

A rapid procedure, based on closed vessels microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS), was evaluated to ascertain the effect of chronic exposure to cadmium on intracellular accumulation of minor and essential trace elements in cultured epithelial cells (Caco-2 TC7). For all measurements, the method of external calibration was used and 3 elements (Be, Sc, In) were selected as internal standards. Optimization procedures are discussed and results are presented for the total determination of 9 key analytes (Na, Mg, Ca, Cr, Mn, Cu, Zn, Mo, and Cd) in certified reference materials (CRMs) and 20 samples of Caco-2 TC7 cells long-term exposed to Cd. The performance characteristics of the analytical system were evaluated by calibration and linearity, limits of detection and quantitation, accuracy with spiking, trueness and repeatability with available CRMs. As a complement to the ICP-MS determinations, both available CRMs and cell samples were analyzed either by electro thermal- or flame atomic absorption spectrometry. The results were in good agreement with the ICP-MS results.

Implication of distinct proteins in cadmium uptake and transport by intestinal cells HT-29

The mechanisms of intestinal absorption have not been clearly elucidated for cadmium, a toxic metal. In this work, we show the implication of distinct proteins in cadmium transport, and the transport step where these proteins are involved. We first validated the HT-29 model by evaluating nontoxic doses of cadmium (ranging from 1 to 20 micromol/L), and by quantifying metal uptake and transepithelial transport. The time-course of 1 micromol/L cadmium uptake at pH 7.5 showed three steps: a rapid one during the first 4 min, probably due to cadmium binding to the membrane; a slower one, characterized by Km of 1.65+/-0.54 micromol/L and Vmax of 3.9+/-0.3 micromol/min per mg protein; and a third, corresponding to slow accumulation that was not equilibrated even after 48 h of cadmium exposure. Intracellular metallothionein content following 1 or 5 micromol/L cadmium exposure showed a significant increase after 6 h of exposure, and was not equilibrated even after 72 h, allowing cadmium accumulation. After 24 h of exposure, metallothionein content was 5-fold, 14-fold, 26-fold, and 50-fold, respectively, for cells grown in the presence of 1, 5, 10, and 20 micromol/L cadmium, compared to control cells. The second step of uptake, characterized by carrier-mediated transport, was markedly increased at pH 5.5, compared to pH 7.5, and strongly inhibited by the metabolic inhibitor dinitrophenol. Moreover Nramp2 transporter cDNA was present in HT-29 cells. These data suggest the involvement of a proton-coupled transporter, which may be the divalent cation transporter Nramp2 (natural resistance-associated macrophage protein 2). Cadmium uptake was also inhibited by copper, zinc, and para-chloromercuribenzenesulfonate (pCMBS), but not by verapamil or ouabain. Taken together, our results indicate that cadmium could enter HT-29 cell by Nramp2 proton-coupled active transport and by diffusion, and accumulates in the cell as long as it binds to metallothionein. Cadmium toxicity could depend partly on the activity of Nramp2, and partly on metallothionein content.

Acetyl- and pseudo-cholinesterase activities of plasma, erythrocytes, and whole blood in male beagle dogs using Ellman's assay

Organophosphate and carbamate ester insecticides, main causes of pesticide poisoning, inhibit cholinesterase (ChE) enzymes. The aim of this study was to measure and compare baseline values for pseudocholinesterase and acetylcholinesterase (AChE) enzyme activities of different blood fractions in the dog to aid in diagnosis of anticholinesterase poisoning. After collecting blood samples from 23 6-24-mo-old male beagle dogs, Ellman's colorimetric assay was run on plasma, red blood cells (RBC), and whole blood fractions prepared in triplicate. The procedure described in a commercially available kit was applied to plasma and RBC. Hemolyzed whole blood fractions (final dilution 1:8) avoided the time-consuming and laborious separation of plasma and RBC. In addition to the kit substrate acetylthiocholine (ASCh), we used butyrylthiocholine (BSCh) as substrate. Whatever the substrate, ChE activity was lower in RBC than in other blood preparations. It was higher when using ASCh rather than BSCh as substrate (mean IU/L+/-SD): 563+/-144 and 303+/-45 respectively, in contrast to plasma (1640+/-310 and 2510+/-450). Whole blood enzyme activity did not differ significantly according to substrate: ASCh, 1590+/-190; BSCh, 1620+/-250) with a 2 to 3% within-day coefficient of variation. Enzyme activity was significantly lower in dogs <1-y old. This study confirms the low ChE activity in dog RBC compared to other species and other blood fractions. It shows that using whole blood instead of separating RBC from plasma minimizes the variability of ChE activity in the hemoglobin-rich fraction.

Absence of ventral cell populations in the developing brain in a rat model of the Smith-Lemli-Opitz syndrome

The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive condition involving craniofacial and central nervous system malformations with occasional holoprosencephaly (HPE). It is caused by a defect in the 7-dehydrocholesterol (7-DHC) reductase, the enzyme catalyzing the last step of cholesterol biosynthesis. Treatment of pregnant rats with inhibitors of 7-DHC reductase, either AY9944 or BM15.766, has provided a valuable model to study the pathogenesis in SLOS. Recently, cholesterol has been shown to be involved in the post-translational activation of the signaling protein Sonic Hedgehog. To identify the early defects associated with HPE in a rat model of SLOS, and to compare the phenotype of the treated embryos with that of the Shh(-/-) mutants, we examined brain morphology and expression of three developmental genes (Shh, Otx2, and Pax6 ) in 23-somite stage embryos from AY9944-treated dams. We report clearly abnormal morphology of the developing brain, concerning primarily the ventral aspect of the neural tube. We observed a reduced or absent expression of Shh and Otx2 in their ventral domain associated with extended ventral expression of Pax6. The results suggest an absence of the midline ventral cell type at all levels of the cranial neural tube. They provide further evidence that cholesterol-deficiency-induced HPE originates from impaired Shh signaling activity in the ventral neural tube.

Cadmium uptake and transepithelial transport in control and long-term exposed Caco-2 cells: the role of metallothionein

Exposure of humans to cadmium, a common environmental pollutant, is mainly through food intake. However, the mechanisms of intestinal absorption have not been clearly elucidated for this toxic metal ion. In order to investigate the effects of long-term exposure to this metal and the role of metallothioneins in cadmium absorption, we used human-derived Caco-2 cells cultured on porous membrane filters. We first validated this model by quantifying metal uptake and transepithelial transport on control cells and cells adapted to grow for 2 to 5 weeks in the presence of low doses of cadmium in the culture medium. The nontoxic doses of cadmium (0.1, 1.0, and 5 microM), in which Caco-2 cells could be cultured for many passages without deleterious effects, were determined by evaluating transepithelial resistance of the cells and lactate dehydrogenase leakage. After 24 h of 1 microM Cd exposure, intracellular cadmium levels were 3- and 6-fold higher for cells exposed for extended periods to 1 and 5 microM cadmium, respectively, compared to control cells. In control and long-term exposed cells, this accumulation was inhibited by zinc, copper, and pCMBS, but not by verapamil or ouabain. Intracellular metallothionein content was increased 1.5-, 5-, and 12-fold for the cells grown in the presence of 0.1, 1.0, and 5 microM cadmium, respectively, in the culture medium. The amount of metallothionein synthesized and released by the cells was highly correlated with cadmium accumulation and transport. Our results suggest that Caco-2 cell monolayers are a good predictive model for the study of cadmium intestinal absorption following exposure to repeated low doses of cadmium, and confirm the essential role of metallothionein in the regulation of cadmium intestinal absorption.

Comparative study of cadmium transfer in ewe and cow milks during rennet and lactic curds preparation

Cadmium transfer from whole milk to cream, rennet, or lactic curds was studied before and following a repeated oral cadmium administration to three lactating ewes and one cow. Before cadmium administration, the cadmium levels in milk were around 0.4 microg/L in ewes and less than 0.2 microg/L in cow. Throughout cadmium administration the mean cadmium levels in milk were 3.3+/-1.4 microg/L in ewes and 2.5+/-1 microg/L in cow. During cadmium administration, 86% of cadmium in ewe milk was dispersed in the skimmed milk and 17% in the cream, whereas only 72% was dispersed in the cow skimmed milk and 27% in the cow cream. Most of milk cadmium was associated with casein fractions. About 70% of milk cadmium was transferred to the rennet or lactic curds of ewe. The remaining cadmium present in whole milk, about 9%, was transferred to the rennet or lactic curd whey. In cow, the proportion of cadmium associated with rennet or lactic curds, rennet curd whey, and lactic curd whey was, respectively, 60%, 56%, 14% and 12% of total milk cadmium. The fraction of total cadmium transferred from milk to its milk products, whatever the species, ranged from 94% to 103%. The factor of concentration of cadmium from whole milk to milk products ranged from three to six. We suggest that the excretion of cadmium into milk is mainly achieved via the milk casein secretion. This is, to our knowledge, the first in vivo study where the cadmium transfer from milk to its milk products after repeated cadmium oral administration to ewe and cow has been studied.

Abnormal cholesterol biosynthesis as in Smith-Lemli-Opitz syndrome disrupts normal skeletal development in the rat

Smith-Lemli-Opitz syndrome (SLOS) in human infants is a common autosomal recessive malformation syndrome (estimated incidence, 1:20,000). It is characterized clinically by congenital anomalies, especially craniofacial and limb defects, and biochemically by a defect in 7-dehydrocholesterol-delta7-reductase activity (7DHC-reductase), the final enzyme in cholesterol biosynthesis. In previous studies, early administration of the 7DHC-reductase inhibitor AY9944 to pregnant rats resulted in a high frequency of holoprosencephaly, relevant to craniofacial anomalies of SLOS. In order to test the effect of AY9944 on limb development, we treated dams on gestation day 7 (GD7), which delays the biochemical defect to about GD13 to GD14. Sera were sampled on GD12, GD14, and GD21 and cholesterol and dehydrocholesterols (7DHC and 8DHC) were measured by gas-chromatography-mass spectrometry (GC-MS), as for the diagnosis of SLOS. GD21 fetuses were examined for gross malformations and skeletal development. In treated dams, the SLOS biochemical marker 7DHC accounted for one fourth and one third of total sterols, respectively, on GD12 and GD14, and cholesterolemia on these two gestation days was reduced by 50% and 43%, respectively, as compared with control values. This maternal metabolic defect was associated with decrease in fetal weight and delayed ossification. In addition, scapular malformations were observed in four fetuses from three litters. The malformations could have been caused by the same mechanism as holoprosencephaly after early treatment with AY9944. These cholesterol-deficiency-based malformations could have a common cause in the abnormal expression of Hedgehog or other developmental gene proteins, and may thus explain various congenital polymalformative syndromes in humans, including SLOS.

Cholesterol biosynthesis inhibited by BM15.766 induces holoprosencephaly in the rat

To confirm that blocking 7-dehydrocholesterol delta 7 reductase (7DHC reductase), as observed in Smith-Lemli-Opitz syndrome (SLOS), induces craniofacial defects, we tested BM15.766, which blocks 7DHC reductase but is chemically unrelated to the holoprosencephaly-inducing teratogen AY9944. Rats were given BM15.766 either in methylcellulose from days (D) 1 through D11 (3 treated groups: protocol A) or in olive oil from D4 through D7 (300 mg/kg/d: protocol B). The sera were sampled on D0, D3, and D5 or D6, D10, D14, and D21 to measure cholesterol and dehydrocholesterols in all groups and steroid hormones in protocol B. D21 fetuses showed the holoprosencephaly spectrum of malformations and the treated dams low cholesterol and accumulation of 7DHC, 8DHC, and trienols, as in SLOS-affected children. In the 3 dosage groups the malformations were dose-related and enzymatic cholesterol decreased to a plateau. The DHC reached 25-44% of the total sterols in the dams. In protocol B, one-third of the BM15.766-treated fetuses presented facial malformations and almost two-thirds pituitary agenesis. On D10, cholesterol reached a minimum and the DHC a maximum while estradiol 17 beta and progesterone were lowered, the latter decreasing in correlation with cholesterolemia. A sterol profile similar to that previously observed after AY9944 associated with a similarly high incidence of pituitary agenesis confirmed that time-limited inhibition of 7DHC reductase induces holoprosencephaly and that pituitary agenesis is the minor form of holoprosencephaly.

Inhibition of 7-dehydrocholesterol reductase by the teratogen AY9944: a rat model for Smith-Lemli-Opitz syndrome

Our aim is to verify the validity of a rat model proposed for Smith-Lemli-Opitz (SLO) syndrome, a developmental disorder characterized by a defect in 7-dehydrocholesterol-delta 7 (7DHC)-reductase and by facial dysmorphism close to the holoprosencephaly caused by the teratogen AY9944. We investigated the sterol profile in rats treated with AY9944 blocking 7DHC-reductase. AY9944 was given orally to rats on gestation day 3 (D3). The sera were sampled for kinetic data on D3, D6, D9, D12, and D21. Cholesterol was measured in parallel by the routine enzymatic method and by the gas chromatography/mass spectrometry (GC-MS) procedure used in SLO diagnosis. In addition to sterols, we dosed steroid hormones punctually on D4 and on D10, and examined D21 fetuses in other animals. The enzymatic method was not specific for cholesterol, and measured 70% pure 7DHC added to a normal serum. On D21, 77% live fetuses showed pituitary agenesis. Cholesterol was rapidly reduced by more than 50% on D6 involving an accumulation of 7DHC, 8DHC, and trienols, as identified in SLO-affected children. The most abundant 7DHC reached a maximum from D9 to D12, equaling cholesterol on D9 (11 mg/dl). On D10, the magnitudes of hypocholesterolemic and of 7DHC accumulation were found to be dose-dependent. Progesterone was reduced as early as 24 hr after treatment and dropped to 40% of the levels in the controls on D10, correlating to the decrease in cholesterolemia. This rat model reproduces the same biochemical perturbations as seen in SLO, strongly suggesting that aberrant sterols (7DHC, 8DHC, or nortrienol) may contribute to the developmental defects.

Changes in serum sterols of rats treated with 7-dehydrocholesterol-delta 7-reductase inhibitors: comparison to levels in humans with Smith-Lemli-Opitz syndrome

The impaired conversion of 7-dehydrocholesterol to cholesterol, as a result of a permanent inhibition of the activity of 7-dehydrocholesterol-delta 7-reductase, has been reported in the Smith-Lemli-Opitz (SLO) syndrome (1, 2). For the purpose of experimental teratology, an animal disease model consisting of the offspring of pregnant rats treated with AY 9944 or BM 15766, inhibitors of 7-dehydrocholesterol-delta 7-reductase, was established. The present study compares the profiles of sterols in rat serum, obtained after transient treatment with inhibitors, with profiles of sterols obtained from patients with the permanent enzyme defect. AY 9944 (single dose of 50, 75, or 100 mg/kg) or BM 15766 (60, 75, or 90 mg/kg per day for 11 days) induces hypocholesterolemia and accumulation of 7-dehydrocholesterol and aberrant sterols in rat serum. The aberrant sterols in the treated rats are similar to those detected in human SLO patients by gas chromatography coupled to mass spectrometry (1, 3, 4) and were identified as 7- and 8-dehydrocholesterol, two trienols (I and II), and 19-nor-5,7,9(10)-cholestatrien-3 beta-ol. The time- and dose-dependences of the biochemical alterations are compared to the teratogenic abnormalities induced by inhibitors. The dietary cholesterol supplementation that suppresses embryo malformations induced by AY 9944 prevents severe hypocholesterolemia and decreases the aberrant sterol levels. As a function of time after intoxication, the 8-dehydrocholesterol to 7-dehydrocholesterol ratio increases, suggested that 8-dehydrocholesterol is derived from the gradual conversion of the accumulated 7-dehydrocholesterol. The ratio of 8-dehydrocholesterol to 7-dehydrocholesterol is higher in human SLO than in the animal disease model. This may be explained by a permanent block in 7-dehydrocholesterol-delta 7-reductase in SLO compared to a transient inhibition of this enzyme in the animal model.

Effects of fluoride on secretory and postsecretory phases of enamel formation in sheep molars

Effect of fluoride was assessed on molars during and after mineralization. Two groups of 7 sheep each were dosed orally with 3.5 mg of fluoride/kg of body weight daily for 4 months (from 5 to 9 months after birth). Sheep of the first group were slaughtered immediately after fluoride administration; those of the second group were slaughtered 4 months later at the age of 13 months. Three control groups of 7 sheep each were slaughtered at 5 months (to determine the state of the teeth at the beginning of fluoride administration), and at 9 and 13 months. During fluoride administration, plasma fluoride concentration rapidly increased to about 0.50 microgram/ml; after fluoride administration, it stabilized at 0.20 microgram/ml in treated sheep, whereas controls had concentration of 0.10 micrograms/ml (P less than 0.01). Parts of the molars that were in the process of mineralization during fluoride administration (mainly second molars) had thinning enamel, with pits, mainly close to the apex, marked decrease in hardness throughout the layer (less than 100 Vickers U, compared with 240 Vickers U), and fluoride accumulation twice as high as that in controls (1,000 to 2,500 mg/kg [dry weight]). Fluoride accumulation was higher in dentine (2,700 to 4,200 mg/kg), but hardness was less affected. On parts of the molars that were already mineralized (mostly, the first molar), changes in the appearance of enamel and cementum, decreased hardness (less important than in teeth during mineralization) affecting outer enamel more than inner enamel, high fluoride concentration (4,000 to 5,500 mg/kg [dry weight]) in outer enamel extending over 200 microns were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoride pharmacokinetics in the ewe: a linear pharmacokinetics model

The kinetics of fluoride was studied in a group of 3 adult ewes given sodium fluoride solutions at 3 dose levels (0.15, 0.375 and 0.75 mg/kg bw). Data were analysed using both compartmental and noncompartmental approaches. A 3-compartment open model was selected to describe the data. Comparison of the different parameters indicated an absence of change with dose level, suggesting that fluoride behaved linearly at the doses under study. The half-life of elimination was 2.57 +/- 1.28 h, the steady-state volume of distribution was 0.26 +/- 0.5 L/kg and the body clearance was 0.105 +/- 0.26 L/kg/h. It was concluded that a single intravascular fluoride administration (bolus) may be used to evaluate oral bioavailability of fluoride in sheep in toxicity studies.