Oral exposure and gut-targeted toxicity of PFOA and its precursor 8:2 FTOH under chronic stress: when high-resolution chemical imaging bridges food toxicology – FLUO-GUT

Les objectifs de FLUO-GUT sont sous-tendus par deux axes à l'interface biologie/physique/chimie : (i) évaluer le devenir et la toxicité du PFOA sur des modèles à la fois in vitro et in vivo avec un large éventail de paramètres ciblant l'intestin et le foie (viabilité cellulaire, génotoxicité, perméabilité intestinale, expression de protéines de jonction serrées, sécrétion de mucus, marqueurs inflammatoires, composition et activité métabolique du microbiote intestinal, activités des enzymes intestinales et hépatiques du métabolisme des xénobiotiques) ; (ii) compléter ces connaissances « biologiques » par des approches d'imagerie chimique aux échelles cellulaire et sub-cellulaire, en développant notamment les corrélations entre la microscopie électronique (morphologie des échantillons biologiques) et la spectrométrie de masse d'ions secondaires (informations analytiques).

Le premier résultat marquant de FLUO-GUT est la visualisation de la distribution du PFOA dans des cellules de l'épithélium intestinal humain, grâce à l’imagerie chimique haute résolution et en parfaite en cohérence avec le profil obtenu avec le PFOA radiomarqué sur le même modèle cellulaire.

Le développement et la valeur ajoutée de méthodes uniques d'imagerie, associés au transfert de savoir-faire entre les partenaires du projet, vont ouvrir de nouvelles perspectives dans les secteurs de la toxicologie alimentaire et des sciences de la vie en général. Les développements prévus, à la fois cognitifs et méthodologiques, pourront être mis à profit pour évaluer, chez l’Homme contemporain et les populations « sensibilisées », les risques liés à l’exposition orale au PFOA, et plus largement aux PFAS, et ainsi contribuer au maintien d’une alimentation saine et durable.

Un résumé a été soumis à EUROTOX2020 (reporté en 2021 pour cause de crise sanitaire) et porte sur le devenir et la toxicité du PFOA in vitro sur un modèle cellulaire mimant l'épithélium intestinal humain.

Perfluoroalkylated substances (PFASs) are a subset of the large anthropogenic group of perfluorinated compounds manufactured for over 60 years. Due to their unique physico-chemical characteristics, PFASs have been widely used for many industrial purposes and consumer-related applications. Because of their long half-life in human body (e.g. 3.8 years for perfluorooctanoic acid PFOA), health risks assessment of PFASs is actually a concern of paramount importance. PFOA, one of their most prominent representatives, displays a large set of adverse effects in humans and animal models, especially hepatotoxicity, genotoxicity, immunotoxicity and neurotoxicity. Dietary exposure has been suggested as the main exposure route to PFOA in the human population. In fact, the presence of PFOA has been reported in food, with fish and other seafood the most contaminated commodities. Food can also be contaminated by accumulation from the environment or by contact with packaging materials and cookware containing PFASs. Another, yet poorly explored, route of PFOA exposure includes the intake of its precursor 8:2 fluorotelomer alcohol (8:2 FTOH). This volatile pollutant is widely used in the manufacture of food items, industrial and consumer products. Even though restriction of PFOA use is extensively discussed within the European Union, its persistence in the environment, associated to its potential to accumulate in organisms and to biomagnificate in the food chain, will undoubtedly require an extended period for elevated internal exposures reaching background levels after abatement of the conspicuous external sources. The probable contribution of 8:2 FTOH precursor also deserves attention.

The gastrointestinal tract is the first physical and biological barrier against ingested PFOA and 8:2 FTOH, and meanwhile their first target. Surprisingly, their effect on the intestinal wall is largely unknown. Hence, there is a need to expand research within the field of gut toxicity of PFOA and 8:2 FTOH. Furthermore, a major environmental factor, omnipresent in modern-days society but rarely considered in toxicity studies, is chronic psychological stress. This component of the exposome can affect the gut barrier function. The objective of the FLUO-GUT proposal, which associates three academic partners (2 French laboratories: ToxAlim-Toulouse and IPREM-Pau; one from Luxembourg: LIST), is to investigate, in vitro and in vivo, and based on state-of the-art imaging developments, the consequences of PFOA and 8:2 FTOH exposure on an intact vs. stress-impaired intestinal barrier to reveal any cumulative effects. Intestinal barrier will be analysed at its luminal side through the epithelium/mucus/microbiota triad, the interactions of which have been poorly explored, in particular when facing chemical stress. The consequences on the gut/liver axis will then be assessed. Also based on the development and added-value of unique nano-imaging methods and know-how transfer from Luxembourg to France, the originality of FLUO-GUT is to address these challenging questions and to anticipate key outcomes for better environmental health risk assessment and management. Beyond PFASs, FLUO-GUT will serve as a blueprint for deciphering gut- and gut/liver axis-targeted toxicity of other environmental pollutants in “sensitized” human populations. FLUO-GUT will thus provide an important foundation for safe and sustainable food in modern-day society.