Transcriptomic Insights into PFAS Toxicity: Midgut RNA-seq Analysis in Male Poecilia reticulata

Per- and Polyfluoroalkyl Substances (PFAS) are a large group of amphiphilic compounds. They are widely produced via anthropogenic processes for industrial and commercial use. They have been used across different applications, such as food packaging, shampoos, and cosmetics, to improve service life and durability. Consequently, they have resulted in widespread environmental contamination over the years and increased human and wildlife exposure to PFAS. PFAS are extremely resistant to degradation because of their strong carbon-fluorine bond, making them known as “forever chemicals”. Their bioaccumulation and high environmental persistence not only affect ecosystems and organisms living within them, but also pose significant risks to human health. Under the One Health framework, this persistence links human, animal, and environmental health as these substances bioaccumulate through food chains across water, soil, and air worldwide. In response to growing concerns about the toxicity of these compounds, alternative PFAS have been developed by industries as potentially safer substitutes. However, some of these alternatives have been demonstrated to pose ecological and toxicological risks. The gastrointestinal tract might be a critical target organ in PFAS exposure, as it is the first biological barrier exposed to contaminated food and water. In aquatic organisms, exposure occurs continuously and directly through both the surrounding environment and feed; gut tissue is therefore an important target tissue for investigation. In this thesis, male guppies (Poecilia reticulata) were chronically exposed (90 days) to 1 g/L of the legacy compound PFOA (perfluorooctanoic acid) or to GenX (hexafluoropropylene oxide dimer acid), a commercially adopted alternative PFAS. The intestinal toxicogenomic responses were investigated using RNA sequencing (RNA-seq). RNA-seq identified a set of differentially expressed genes. Functional analyses were then conducted to detect the affected biological pathways under PFAS exposure conditions, focusing on pathways related to metabolism, immune responses, stress signaling, and intestinal homeostasis. Overall, this study provides new insights into the intestinal transcriptomic responses of male guppies following chronic exposure to PFOA and GenX and contributes to the evaluation of the toxicity of alternative PFAS.

Per- and Polyfluoroalkyl Substances (PFAS) are a large group of compounds that, due to their chemical and structural properties, are hydrophobic and hydrophilic at the same time; therefore, they are widely produced via anthropogenic processes for industrial and commercial use. Although they have been used across different applications, such as food packaging, shampoos, and cosmetics, to improve service life and durability, they have resulted in widespread environmental contamination over the years and increased human and wildlife exposure to PFAS. PFAS are extremely resistant to degradation because of their strong carbon-fluorine bond, making them known as “forever chemicals”. Their bioaccumulation and high environmental persistence not only affect ecosystems and organisms living within them, but also pose significant risks to human health. Under the One Health framework, this persistence links human, animal, and environmental health as these substances bioaccumulate through food chains across water, soil, and air worldwide. In response to growing concerns about the toxicity of these compounds, alternative PFAS have been developed by the industrial companies as potentially safer substitutes. However, some of these alternatives have been demonstrated to pose ecological and toxicological risks. The gastrointestinal tract might be a critical target organ in PFAS exposure, as it is the first biological barrier exposed to contaminated food and water. In aquatic organisms, exposure occurs continuously and directly through both the surrounding environment and feed; gut tissue is therefore an important target tissue for investigation. In this thesis, male guppies (Poecilia reticulata) were chronically exposed (90 days) to 1 g/L of PFOA (perfluorooctanoic acid), a legacy PFAS, or its alternative GenX (hexafluoropropylene oxide dimer acid), deemed to be safer. The intestinal toxicogenomic responses were investigated using RNA sequencing (RNA-seq). RNA-seq enabled the identification of a set of differentially expressed genes. Functional analyses were then conducted to detect the affected biological pathways under PFAS exposure conditions, focusing on pathways related to metabolism, immune responses, stress signaling, and intestinal homeostasis. Overall, this study helped us to improve our understanding of the molecular mechanisms underlying PFAS-induced toxicity.