Supplementary file 3 from Costs of molecular adaptation to the chemical exposome: a focus on xenobiotic metabolism pathways

Organisms adapt to their environment through different pathways. In vertebrates, xenobiotics are detected, metabolized and eliminated through the inducible xenobiotic-metabolizing pathways (XMP) which can also generate reactive toxic intermediates. In this review, we will discuss the impacts of the chemical exposome complexity on the balance between detoxication and side effects. There is a large discrepancy between the limited number of proteins involved in these pathways (few dozens) and the diversity and complexity of the chemical exposome (tens of thousands of chemicals). Several XMP proteins have a low specificity which allows them to bind and/or metabolize a large number of chemicals. This leads to undesired consequences, such as cross-inhibition, inefficient metabolism, release of toxic intermediates, etc. Furthermore, several XMP proteins have endogenous functions that may be disrupted upon exposure to exogenous chemicals. The gut microbiome produces a very large number of metabolites that enter the body and are part of the chemical exposome. It can metabolize xenobiotics and either eliminate them or lead to toxic derivatives. The complex interactions between chemicals of different origins will be illustrated by the diverse roles of the Aryl hydrocarbon receptor which binds and transduces the signals of a large number of xenobiotics, microbiome metabolites, dietary chemicals and endogenous compounds.This article is part of the theme issue ‘Endocrine responses to environmental variation: conceptual approaches and recent developments’

Electroretinograms are normal in AhR−/− mice.

<p>(A) Representative scotopic ERG at different light intensities (from −2 to −0.49 log cd.s/m²) in both AhR+/+ and AhR−/− mice. Quantifications of a-Wave and b-Wave amplitudes are represented in the lower panel. (B) Representative photopic ERG. The photopic response is obtained using a flash intensity to −0.49 log cd.s/m² on light-adapted mice and measured for both mice. There are no significant differences between both genotypes in scotopic and photopic ERG. Blue lines correspond to the AhR+/+ mice, and red lines correspond to the AhR−/− mice.</p

The AhR is expressed in the eyes during the development of AhR+/+ mice.

<p><i>In situ</i> hybridization is performed on coronal sections of the mice eyes at two embryonic stages (E12 and E14) with digoxigenin-labeled riboprobes for AhR. (A & C) E12 coronal section of AhR+/+ (A) and AhR−/− mice (C); no expression of AhR is detected at this stage. (B & D) E14 coronal section of AhR+/+ (B) and AhR−/− mice (D); the black arrow (in B) indicates the expression of AhR in the retinal ganglion cells. Scale bar represent 250 µm.</p

AhR−/− mice retinal cells are functional despite scattered bipolar to RCG connections.

<p>Immunohistochemistry experiments were performed in retina sections of adult AhR+/+ and AhR−/− mice. AhR+/+ and AhR−/− retina at P56 is represented. Retinal ganglion cells (RGC) are labeled with antibodies against ßIII-tubulin; bipolar cells are labeled with antibodies against PKCα (Protein Kinase Cα), nucleus is labeled with DAPI; amacrine and displaced amacrine cells are labeled with both antibodies against calbindin (CaBP)-D28k and calretinin. Horizontal cells are stained with antibodies against calbindin. The density of RGC, bipolar, amacrine and displaced amacrine, and horizontal cells are not significant different between AhR+/+ and AhR−/− mice (see quantifications at the bottom of the figure). The thickness of the ONL is the same between both genotypes. The white arrows in the bottom panel of the PKCa staining indicate a disorganization of the synapses between the bipolar cells and the RGCs in some AhR−/− mice. Scale bar  = 25 µm. ONL: Outer Nuclear Layer, INL: Inner Nuclear Layer, GCL: Ganglion Cells Layer, OPL: Outer Plexiform Layer, IPL: Inner Plexiform Layer.</p

AhR−/−mice have a horizontal pendular nystagmus.

<p>(A) Positions of the eyes of the AhR+/+ mice in both horizontal (EHp) and vertical (EVp) plans in the absence of head movements in the dark. (B) Positions of the eyes of 2 different AhR−/− mice showing spontaneous nystagmus at low frequency in light (upper) and at high frequency in dark (bottom). The AhR−/− mice have an ocular instability exclusively in the horizontal plan whereas the eyes of AhR+/+ mice and AhR+/− mice are stable. (C) Frequencies of the nystagmus in light and dark conditions for each AhR−/− mouse (n = 12). The linear regression is represented by the dotted line in grey. EHp: Eye Horizontal position; EVp: Eye vertical position. In this and all following figures, eye movements to the right are presented upward.</p

Enrichment analysis using Ingenuity Pathway Analysis on the lists of mRNA probes differentially expressed after exposition to the three bisphenols A, F and S at 10 nM and 10 μM.

<p>Enrichment analysis using Ingenuity Pathway Analysis on the lists of mRNA probes differentially expressed after exposition to the three bisphenols A, F and S at 10 nM and 10 μM.</p

Experimental design and analysis workflow.

<p>BPA, BPS, BPF and DMSO: respectively Bisphenol A, S and F and dimethyl sulfoxide.</p

List of differentially expressed probes deregulated for the three bisphenols A, F and S at 10 nM.

<p>List of differentially expressed probes deregulated for the three bisphenols A, F and S at 10 nM.</p

Cerebellar morphology and function are not affected by the AhR invalidation.

<p>(A) The morphology of the cerebellum in both AhR+/+ (<i>left</i>) and AhR−/−mice (<i>right</i>) is similar. <i>Top:</i> The size of the cerebellum and its foliation are normal in AhR−/−, as shown on sagittal sections labeled with anti-calbindin antibodies and counterstained with DAPI. <i>Bottom:</i> Climbing fibers (stained by VGLUT2) properly innervate the dendritic arborization of Purkinje cells (CaBP). Scale bars represent 250 µm (<i>top</i>) and 25 µm (<i>bottom</i>). (B–C) Normalized gain (C) and phase (D) during the visuo-vestibular conflict at 0.5 Hz. The AhR−/− and AhR+/+ mice are capable of adaptation during and after the vestibulo-ocular conflict. Blue lines correspond to the AhR+/+ mice, and red lines correspond to the AhR−/− mice. Asterisk indicates statistical difference between the VOR gain before and after the conflict with <i>p</i><0.001, # represent the statistical difference between the VOR phase during all the adaptation protocol with p<0.001.</p

Number of differentially down and up-regulated miRNA probes amongst the 483 probes after the exposition of the pre-adipocytes to 10 nM or 10 μM of bisphenol (A, F and S) during differentiation shared between BPA and BPS or BPF.

<p>Number of differentially down and up-regulated miRNA probes amongst the 483 probes after the exposition of the pre-adipocytes to 10 nM or 10 μM of bisphenol (A, F and S) during differentiation shared between BPA and BPS or BPF.</p