Utility of in vivo metabolomics to support read-across for UVCB substances under REACH.

Structure-based grouping of chemicals for targeted testing and read-across is an efficient way to reduce resources and animal usage. For substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs), structure-based grouping is virtually impossible. Biology-based approaches such as metabolomics could provide a solution. Here, 15 steam-cracked distillates, registered in the EU through the Lower Olefins Aromatics Reach Consortium (LOA), as well as six of the major substance constituents, were tested in a 14-day rat oral gavage study, in line with the fundamental elements of the OECD 407 guideline, in combination with plasma metabolomics. Beyond signs of clinical toxicity, reduced body weight (gain), and food consumption, pathological investigations demonstrated the liver, thyroid, kidneys (males only), and hematological system to be the target organs. These targets were confirmed by metabolome pattern recognition, with no additional targets being identified. While classical toxicological parameters did not allow for a clear distinction between the substances, univariate and multivariate statistical analysis of the respective metabolomes allowed for the identification of several subclusters of biologically most similar substances. These groups were partly associated with the dominant (> 50%) constituents of these UVCBs, i.e., indene and dicyclopentadiene. Despite minor differences in clustering results based on the two statistical analyses, a proposal can be made for the grouping of these UVCBs. Both analyses correctly clustered the chemically most similar compounds, increasing the confidence that this biological approach may provide a solution for the grouping of UVCBs.

Demonstrating the reliability of in vivo metabolomics based chemical grouping: towards best practice.

While grouping/read-across is widely used to fill data gaps, chemical registration dossiers are often rejected due to weak category justifications based on structural similarity only. Metabolomics provides a route to robust chemical categories via evidence of shared molecular effects across source and target substances. To gain international acceptance, this approach must demonstrate high reliability, and best-practice guidance is required. The MetAbolomics ring Trial for CHemical groupING (MATCHING), comprising six industrial, government and academic ring-trial partners, evaluated inter-laboratory reproducibility and worked towards best-practice. An independent team selected eight substances (WY-14643, 4-chloro-3-nitroaniline, 17α-methyl-testosterone, trenbolone, aniline, dichlorprop-p, 2-chloroaniline, fenofibrate); ring-trial partners were blinded to their identities and modes-of-action. Plasma samples were derived from 28-day rat tests (two doses per substance), aliquoted, and distributed to partners. Each partner applied their preferred liquid chromatography-mass spectrometry (LC-MS) metabolomics workflows to acquire, process, quality assess, statistically analyze and report their grouping results to the European Chemicals Agency, to ensure the blinding conditions of the ring trial. Five of six partners, whose metabolomics datasets passed quality control, correctly identified the grouping of eight test substances into three categories, for both male and female rats. Strikingly, this was achieved even though a range of metabolomics approaches were used. Through assessing intrastudy quality-control samples, the sixth partner observed high technical variation and was unable to group the substances. By comparing workflows, we conclude that some heterogeneity in metabolomics methods is not detrimental to consistent grouping, and that assessing data quality prior to grouping is essential. We recommend development of international guidance for quality-control acceptance criteria. This study demonstrates the reliability of metabolomics for chemical grouping and works towards best-practice.

The threshold of toxicological concern for prenatal developmental toxicity in rabbits and a comparison to TTC values in rats.

The Threshold Toxicological Concern (TTC) is based on the concept that reasonable assurance of safety can be given if exposure is sufficiently low. We report on the evaluation of BASF's data for oral developmental toxicity studies in rabbits with 48 NOAEL values for maternal and developmental toxicity. The 5th percentile of the NOAEL distributions was calculated to be 5mg/kgbw/d for both maternal and developmental toxicity. From literature 56 compounds tested in rabbits were taken and combined with values from BASF's studies. The 5th percentile value for developmental toxicity of these 104 studies (mostly active ingredients) was 2mg/kgbw/d. Thus, a TTC value of 4µg/kgbw/d was calculated using a safety factor of 500 to account for relatively small database. This value is in the same range as the TTC value for developmental toxicity in rats of 8µg/kgbw/d. The lower value may serve as guidance to determine whether further evaluation is needed or whether to rely on a TTC value for industrial chemicals or low concentration (environmental) contaminants if exposure is sufficiently low. A comparison of 30 compounds tested at BASF in both species, suggests that rabbits are not more sensitive than rats. We encourage others to publish data on rabbit developmental toxicity.

Whole embryo culture: an important tool in developmental toxicology today.

The number of candidate chemicals or drugs for registration and authorization is increasing at a fast rate and only few of the existing substances have been tested for teratogenicity to date. Therefore, there is high pressure on authorities to accept models like the whole embryo culture as a screening system for safety evaluation procedures. In view of this background the gradual development of the whole embryo culture into a standardized, scientifically validated tool for developmental toxicology during the last 70 years is summarized. The methodological development of the culture technique is described with the completion, improvement and refinement of the basic culture method as main intention. Special attention was paid to different culture techniques, culture media, gassing schedules, and evaluation strategies. Furthermore the importance of taking "in vitro pharmacokinetics" into consideration when a comparison of in vitro/in vivo results from embryotoxicity testing is intended, is stressed. Additionally, the demonstration of the broad spectrum of useful scientific applications when using this culture system in combination with sophisticated analytical techniques is demonstrated. Finally, an overview on different strategies for the validation of this culture system as an in vitro embryo toxicity test is provided and the officially accepted formal validation process for this application is summarized. The successful validation makes the whole embryo culture a complex in vitro embryotoxicity test with high accuracy and predictability. This robust in vitro system modelling the main phase of rodent organogenesis with a high reproducibility is valuable enough to attract special attention in related scientific fields.

In utero exposure to low doses of bisphenol A lead to long-term deleterious effects in the vagina.

The origins of the "endocrine disrupter hypothesis" may be traced to reports on adolescent daughters born to women who had taken the highly potent synthetic estrogen, diethylstilbestrol, while pregnant, and who developed a rare form of vaginal cancer and adenocarcinoma. Bisphenol A (BPA) is an estrogenic chemical that is highly employed in the manufacture of a wide range of consumer products. Some observational studies have suggested that the amounts of BPA to which we are exposed could alter the reproductive organs of developing rodents. We examined the influence of BPA at low doses to address the questions of (a) whether in utero exposure affects the vagina of the offspring and (b) which mechanisms cause the toxic effects. Gravid Sprague-Dawley dams were administered either 0.1 (low dose) or 50 mg/kg per day BPA, the no observed effect level, or 0.2 mg/kg per day 17 alpha-ethinyl estradiol by gavage. Striking morphological changes were observed in the vagina of postpubertal offspring leading us to examine vaginal estrogen receptor (ER) expression because BPA binds to the ER alpha, which is important for growth of the vaginal epithelium. We show that the full-length ER alpha is not expressed during estrus in the vagina of female offspring exposed to either dose of BPA when compared to the control group, whereas ER alpha expression does not differ from the control group during the diestrus stage. ER alpha downregulation seems to be responsible for the observed altered vaginal morphology.

A randomized trial comparing cyclosporine with antilymphoblast-globulin-azathioprine for renal allograft recipients. Results at 2 1/2-6 years.

Between September 1980 and June 1984, 246 splenectomized, transfused renal allograft recipients were stratified according to presence of diabetes and donor source, and randomized to treatment with either cyclosporine (CsA)-prednisone (pred) or antilymphoblast-globulin (ALG--azathioprine (AZA)--prednisone. As of August 1986, mean follow-up is 47 months. Over all, actuarial patient survival is 84% and 83%, respectively at 4 years. Corresponding graft survival is 70% and 63% for CsA-treated and ALG-AZA-treated patients (NS). Within the subgroup of diabetic recipients of cadaver grafts, graft survival is 70% for CsA-treated and 53% for ALG-AZA-treated recipients (P = .035). In the CsA group, 71% required either a significant reduction in CsA dosage with the addition of azathioprine or a complete switch to azathioprine, mainly because of CsA-associated nephrotoxicity. Of those CsA patients switched at a mean time of 21.3 +/- 16.4 months posttransplant with mean serum creatinine of 2.40 +/- .67, current serum creatinine is 1.79 +/- .63. Current mean serum creatinine values are significantly greater for patients randomized to CsA-pred (1.73 +/- .60) vs. ALG-AZA-pred (1.49 +/- .59), P = .014, even though most CsA-treated patients were eventually switched. The causes of graft loss are not different between CsA and ALG-AZA randomized patients. In nondiabetics, rejection is the most common cause of graft loss (17/33), whereas in diabetics loss due to complications from overimmunosuppression or death from cardiovascular events is significantly more common (27/44) than corresponding losses in nondiabetics (6/33, P less than .05). Switching does not seem to influence the incidence or cause of graft loss. Since most patients started on CsA-prednisone are ultimately switched to triple drug therapy, the latter is now the preferred initial treatment modality.

A portable microsystem-based telemetric pressure and temperature measurement unit.

This article shows how a fully implantable stand-by device for measuring intracorporal pressure and temperature under normal conditions can be implemented, consisting of a sensor element combined with a transcutaneous telemetric interface. One further point of interest is automatic event recognition in order to capture special signal components in an emergency situation. Therefore, signal processing and waveform analysis are exigent, first to observe the measured signal in realtime on a portable unit, and second to process the data offline on a stationary unit.

Effects of MDMA (ecstasy) and two of its metabolites on rat embryos in vitro.

MDMA consumers are young people of childbearing age. Consequently, developmental exposure to this drug is a potential public health concern. Several studies have addressed MDMA neurotoxicity in adults; however, knowledge of the effects of MDMA on developing embryos is limited. After administration, MDMA is metabolized species specifically via two main pathways. One leads to the formation of MDA and the other to the formation of HHMA. Here we evaluated the embryotoxic effects of MDMA, and also those of MDA, a main metabolite of MDMA in rats, and HHMA, a main metabolite in humans. For this purpose, we used the whole embryo culture (WEC). Our results show a concentration-dependent embryotoxic effect of MDMA, MDA and HHMA at a concentration range of 25-50µg/ml. The embryotoxic potential of the parent compound and the two metabolites was comparable in vitro.