Limits of the regulatory evaluation of resorcinol as a thyroid disruptor: When limited experimental data challenge established effects in humans.

Severe hypothyroidism has been reported in humans during resorcinol therapeutic use. However, available data highlight differences in the severity of resorcinol-induced thyroid effects between humans and rodents, leading to a debate on the relevance of human data for its classification as a thyroid disruptor. The aim of this review is to illustrate some of the limitations of the evaluation framework for thyroid disrupters using resorcinol as a case study of a chemical with clear thyroid-disrupting properties in humans that could not have been identified solely from regulatory studies on animals. The reliability of human data has been called into question due to the specific exposure patterns in humans and the paucity of robust toxicokinetic data. In humans, therapeutic use of resorcinol induces severe hypothyroidism, but in rodents, thyroid disruption is limited to decreased thyroxine concentrations and histological changes in the thyroid. The adverse effects of thyroid disruption, such as impaired neurodevelopment, have not been sufficiently investigated, and experimental neurobehavioral data for resorcinol remain scarce and inconclusive. Although regulatory toxicological evaluations have not included in-depth investigations of thyroid regulation and related adverse effects, they have been used to challenge the relevance of human data. Resorcinol is an emblematic example of how the framework for regulatory evaluations of thyroid disruptors relies almost exclusively on animal studies which may not be suitable for assessing thyroid disruption. This review highlights the need to revise regulatory guidelines and to adopt strategies based on up-to-date, scientifically sound approaches to identify thyroid disruptors. The limits of the current regulatory framework for identifying thyroid disruptors can lead to opposing positions between regulatory bodies. The French Agency for Food, Environmental and Occupational Health & Safety (ANSES)'proposal to identify resorcinol as a "substance of very high concern" due to its ED properties has not been adopted by the European instances.

Impact of solvents on the in vitro genotoxicity of TMPTA in human HepG2 cells.

Small hydrophobic chemical compounds require solvents to produce suitable solutions for toxicological studies. However, some solvents can modify the biological properties of substances and therefore their toxicity. This specific issue has been raised for PEG-400 as an anti-inflammatory and anti-oxidative compound. Recently, in the context of the REACH Regulation, PEG-400 was used to test the in vivo genotoxicity of trimethylolpropane triacrylate (TMPTA) in the comet assay. TMPTA failed to increase DNA damage whereas it induces genotoxicity in vitro in DMSO. Therefore, we questioned whether PEG-400 could modify the genotoxicity of TMPTA. The aim of this study was to determine the potential impact of PEG-400 on the in vitro genotoxicity of TMPTA, compared to DMSO. TMPTA was dissolved in either PEG-400 or DMSO, and the induction of γH2AX and Caspase-3 was analyzed in HepG2 cells. TMPTA induced γH2AX and Caspase-3 with both PEG-400 and DMSO. However, TMPTA induced effects at 4-fold lower concentrations when PEG-400 is used as the solvent compared to DMSO. While genotoxic effects are observed at much lower concentrations with PEG-400, it does not modify the in vitro genotoxicity of TMPTA. However, further in vitro studies with small hydrophobic compounds should be done to clarify the effect of PEG-400. Moreover, in vivo studies should be performed to confirm that PEG-400 remains suitable for in vivo genotoxicity tests.

Impairment of learning and memory performances induced by BPA: Evidences from the literature of a MoA mediated through an ED.

Many rodent studies and a few non-human primate data report impairments of spatial and non-spatial memory induced by exposure to bisphenol A (BPA), which are associated with neural modifications, particularly in processes involved in synaptic plasticity. BPA-induced alterations involve disruption of the estrogenic pathway as established by reversal of BPA-induced effects with estrogenic receptor antagonist or by interference of BPA with administered estradiol in ovariectomized animals. Sex differences in hormonal impregnation during critical periods of development and their influence on maturation of learning and memory processes may explain the sexual dimorphism observed in BPA-induced effects in some studies. Altogether, these data highly support the plausibility that alteration of learning and memory and synaptic plasticity by BPA is essentially mediated by disturbance of the estrogenic pathways. As memory function in humans involves similar signaling pathways, this mode of action of BPA has the potential to alter human cognitive abilities.

Evidence-based adverse outcome pathway approach for the identification of BPA as en endocrine disruptor in relation to its effect on the estrous cycle.

Proper cyclicity is essential to reach successful optimal fertility. In rats and mice, BPA exposure is repeatedly and reliably reported to show an adverse effect on the estrous cycle after exposures at different life stages. In humans, a possible association between modifications of menstrual cycle characteristics (e.g. length of the cycle, duration of menstrual bleeding) and sub-fecundity or spontaneous abortion has been observed. Alterations of ovarian cyclicity can therefore be definitely considered as an adverse health outcome. As a prerequisite for the EU REACH regulation to identify a substance as an endocrine disruptor and a SVHC,1 the proof has to be established that the substance can have deleterious health effects resulting from an endocrine mode of action. This review provides an overview of the currently available data allowing to conclude that the adverse effects of BPA exposure on ovarian cyclicity is mediated by an endocrine mode of action.

Concerns related to ED-mediated effects of Bisphenol A and their regulatory consideration.

The extensive database on BPA provides strong evidence of its adverse effects on reproductive, neurobehavioural, metabolic functions and mammary gland. Disruption of estrogenic pathway is central in the mediation of these effects although other modes of action may be involved. BPA has a weak affinity for ERα/ß but interaction with extranuclearly located pathways activated by estrogens such as ERRγ and GPER reveals how BPA can act at low doses. The effects are observed later in life after developmental exposure and are associated with pathologies of major societal concern in terms of severity, incidence, impact on quality of life, burden on public health system. The complexity of the dose response raise uncertainties on the possibility to establish safe levels and the scope of ED-mediated effects of BPA may be wider. These concerns fulfill the requirements for ED identification under REACH regulation.

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.

Temperature-sensitive resolution of cis- and trans-fatty acid isomers of partially hydrogenated vegetable oils on SP-2560 and CP-Sil 88 capillary columns.

This study examines the effect of the column operating temperature of 100 m SP-2560 and CP-Sil 88 capillary gas chromatographic (GC) columns on the separation of cis- and trans-octadecenoic (18:1) isomers in partially hydrogenated vegetable oils. The overlapping GC peaks were measured at column isothermal temperatures of 170, 175, 180, 185, and 190 degrees C. With both columns, isothermal operation at 180 degrees C produced the fewest overlapping peaks of the cis and trans isomers. At this temperature, all trans-18:1 isomers, except 13t-18:1 (t = trans), 14t-18:1, and 15t-18:1 isomers were resolved from the cis-18:1 isomers. The peaks of the 13t-18:1 and 14t-18:1 isomer pair, which always elute together, overlapped peaks of the 6c-18:1 (c = cis), 7c-18:1, and 8c-18:1 isomers; the peak of the 15t-18:1 isomer overlapped the major cis-18:1 peak, which was mainly due to 9c-18:1. Isothermal operations above or below 180 degrees C produced some additional overlapping problems. At 185 and 190 degrees C, the peaks of the 16t-18:1 and 13c-18:1 isomers overlapped. At 175 and 170 degrees C, the 16t-18:1 peak overlapped the 14c-18:1 peak, and the peaks of the 13t + 14t-18:1 isomer pair partially overlapped the major cis-18:1 peak. The separation of 11c-20:1 and alpha-linolenic acid and its geometric isomers was also affected by the column operating temperature. Isothermal operation of the SP-2560 column at 180 degrees C produced a baseline separation of 11c-20:1 and alpha-linolenic acid and its geometric isomers, whereas with the CP-Sil 88 column the best resolution was obtained at 170 degrees C. The results of this study show that the SP-2560 capillary column has a slight advantage over the CP-Sil 88 column for the simultaneous resolution of all the fatty acids generally found in partially hydrogenated vegetable oils.

Abietoid seed fatty acid compositions--a review of the genera Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga and preliminary inferences on the taxonomy of Pinaceae.

The seed fatty acid (FA) compositions of Abietoids (Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga) are reviewed in the present study in conclusion to our survey of Pinaceae seed FA compositions. Many unpublished data are given. Abietoids and Pinoids (Pinus, Larix, Picea, and Pseudotsuga)-constituting the family Pinaceae-are united by the presence of several delta5-olefinic acids, taxoleic (5,9-18:2), pinolenic (5,9,12-18:3), coniferonic (5,9,12,15-1 8:4), keteleeronic (5,11-20:2), and sciadonic (5,11,14-20:3) acids, and of 14-methyl hexadecanoic (anteiso-17:0) acid. These acids seldom occur in angiosperm seeds. The proportions of individual delta5-olefinic acids, however, differ between Pinoids and Abietoids. In the first group, pinolenic acid is much greater than taxoleic acid, whereas in the second group, pinolenic acid is greater than or equal to taxoleic acid. Moreover, taxoleic acid in Abietoids is much greater than taxoleic acid in Pinoids, an apparent limit between the two subfamilies being about 4.5% of that acid relative to total FA. Tsuga spp. appear to be a major exception, as their seed FA compositions are much like those of species from the Pinoid group. In this respect, Hesperopeuce mertensiana, also known as Tsuga mertensiana, has little in common with Abietoids and fits the general FA pattern of Pinoids well. Tsuga spp. and H. mertensiana, from their seed FA compositions, should perhaps be separated from the Abietoid group and their taxonomic position revised. It is suggested that a "Tsugoid" subfamily be created, with seed FA in compliance with the Pinoid pattern and other botanical and immunological criteria of the Abietoid type. All Pinaceae genera, with the exception of Pinus, are quite homogeneous when considering their overall seed FA compositions, including delta5-olefinic acids. In all cases but one (Pinus), variations from one species to another inside a given genus are of small amplitude. Pinus spp., on the other hand, have highly variable levels of delta5-olefinic acids in their FA compositions, particularly when sections (e.g., Cembroides vs. Pinus sections) or subsections (e.g., Flexiles and Cembrae subsections from the section Strobus) are compared, although they show qualitatively the same FA patterns characteristic of Pinoids. Multicomponent analysis of Abietoid seed FA allowed grouping of individual species into genera that coincide with the same genera otherwise characterized by more classical botanical criteria. Our studies exemplify how seed FA compositions, particularly owing to the presence of delta5-olefinic acids, may be useful in sustaining and adding some precision to existing taxonomy of the major family of gymnosperms, Pinaceae.