Julia Pinheiro de Souza Cruz Serra Lima1,2, Thais Braga Gomes Araújo 1,2, Sidney Fernandes Sales Júnior1,2, Gabriel de Farias Araujo2, Lorena Lopes Soares1,2, Brenda Rodrigues Mota Ikehara3, Natália Reis de Almeida3, Frederico Garcia Pinto3, Fábio Veríssimo Correia 4, Enrico Mendes Saggioro1,2
Introduction: Per- and polyfluoroalkyl substances (PFAS), such as perfluorooctanoic acid (PFOA), are emerging contaminants of high toxicity, environmental persistence, and bioaccumulation potential. Classified as a Group 1 carcinogen by the International Agency for Research on Cancer, PFOA is ubiquitous in the environment, inducing oxidative stress, genetic and enzymatic alterations, hepatotoxicity, neurobehavioral toxicity, and metabolic disorders in aquatic organisms. In this context, the present study investigated metabolic alterations in brain and liver tissues of Danio rerio exposed to PFOA, applying metabolomics to identify altered metabolites and to elucidate mechanisms underlying PFOA-induced toxic effects.
Materials and methods: Danio rerio specimens (2 cm ± 1 cm) were exposed to PFOA (0.01, 10.0, 100.0, and 1000.0 µg L⁻¹) for 21 days in 36 L aquaria (14 fish per aquarium; n = 70 including controls), in accordance with CEUA/IOC approval (035/2022). Euthanasia was performed by immersion in an ice bath (4 ± 2 °C), and brain and liver tissues (pooled, n = 15 per sample) were collected. Metabolites were extracted and analyzed by gas chromatography–mass spectrometry (GC–MS), using the NIST Mass Spectral Library 2017 (similarity > 85%), with metabolic pathways mapped via MetaboAnalyst.
Results and discussion: In brain tissues, exposure to PFOA (10, 100, and 1000 µg L⁻¹) altered unsaturated fatty acid (UFA) biosynthesis, carbohydrate metabolism (galactose, starch, and sucrose), and branched-chain amino acids (valine, leucine, and isoleucine), as well as glycine, serine, and threonine metabolism (at 1000 µg L⁻¹). In the liver, similar alterations were observed at all concentrations, along with changes in aminoglycoside metabolism (neomycin, kanamycin, and gentamicin), compounds typically associated with bacteria. These findings suggest disturbances in cellular energy metabolism, reflected by reduced ATP production and dysregulation of the tricarboxylic acid (TCA) cycle. Increased galactose metabolism may lead to reactive oxygen species generation, damaging membranes, proteins, and DNA. Alterations in branched-chain amino acids support the hypothesis of oxidative stress and mitochondrial dysfunction, impairing antioxidant defenses and protein synthesis. Disturbances in UFAs, such as linoleic acid, indicate effects on key physiological processes, including cell signaling, energy balance, and immune/inflammatory responses mediated by eicosanoids. The detection of characteristic bacterial metabolites suggests that PFOA exposure disrupted gut microbiota, potentially affecting its metabolic pathways.
Conclusion: PFOA exposure induced metabolic imbalances, including impaired energy supply through altered carbohydrate metabolism and TCA cycle disruption; increased oxidative stress, linked to galactose and branched-chain amino acid pathways; and adverse effects on cellular communication and aminoglycoside-related mechanisms. These results enhance understanding of the mechanisms underlying PFOA-associated neurotoxicity, hepatotoxicity, and metabolic disorders.
Funding agencies: CAPES, FAPERJ, and CNPq.
Agradecimentos: The authors express their gratitude to Dr. Renata Jurema Medeiros and her team for providing the facilities for animal experimentation at the National Institute for Quality Control in Health (INCQS) of the Oswaldo Cruz Foundation (FIOCRUZ).