Sara Pacchini

Fish exposed to chemical contamination must continually reallocate metabolic resources to survive, diverting energy from growth and reproduction to detoxify xenobiotics and control oxidative stress. Among emerging threats to freshwater ecosystems, per- and polyfluoroalkyl substances (PFAS) became emblematic due to their persistence, bioaccumulation, and long-range transport. This study investigated energetic and redox responses to chronic PFAS exposure in the liver of Squalius cephalus from rivers with varying degrees of pollution in the Veneto region (Italy), mechanistically linking mitochondrial bioenergetics to oxidative damage pathways and revealing energy–redox trade-offs in wild fish populations. Results revealed a metabolic shift characterised by enhanced electron transport system (ETS) activity and depletion of glycogen (GLY) reserves, indicating increased mitochondrial respiration and energy mobilisation to sustain detoxification and antioxidant defences. Biotransformation responses showed activation of phase II glutathione S-transferases (GSTs), followed by inhibition of phase I carboxylesterases (CbEs), suggesting an imbalance in detoxification. Antioxidant defences were activated, particularly total antioxidant capacity (TAC), consistent with a non-enzymatic response to elevated reactive oxygen species (ROS). Nevertheless, this was insufficient to prevent macromolecular damage at the highest PFAS level, as evidenced by the accumulation of advanced oxidation protein products (AOPP) but not protein carbonyls (ProC). Superoxide dismutase (SOD) activity was reduced, suggesting impairment of part of the enzymatic antioxidant system. In contrast, the reduction in lipid peroxidation (LPO) reflects effective protection of lipids through the combined action of enzymatic and non-enzymatic scavengers. Overall, these findings demonstrate that chronic PFAS exposure imposes substantial energetic costs and oxidative stress on S. cephalus, primarily targeting mitochondrial metabolism and structural proteins, with potential long-term implications for fish health and ecosystem resilience. These results provide mechanistic evidence that PFAS-driven metabolic reprogramming prioritises survival over long-term fitness, reinforcing their ecological risk even at environmentally relevant concentrations.

Cadmium is a common contaminant of both saline and freshwater environments. It has no biological function but readily penetrates tissues, causing significant oxidative stress and consequent damage throughout the organism. In this work, we examined the effects of this metal on the nauplii of Artemia salina, a model for testing toxicity in larval zooplanktonic species, and to evaluate the impact of contaminants on natural populations. An environmentally realistic concentration (15 µg/L) and two higher concentrations (150 and 1500 µg/L) were used. The presence of metals in culture media and nauplii was verified by atomic absorption spectroscopy, while oxidative stress levels were assessed by measuring hydroperoxides, carbonyl groups, ROS, and total antioxidant capacity. Mortality and growth rates were the conventional toxicity endpoints analysed. In parallel, morphological alterations were assessed in toto and in section. Attention was directed to the gut, the primary site of metal uptake and reabsorption, and to effects on protein patterns. The results demonstrated significant dose-independent Cd uptake by the nauplii and dose-dependent oxidative stress. Consequent alterations in brush border organisation and yolk and lipid resorption were assessed. Modest teratogenic effects were detected in naupliar eye pigmentation and paired-eye organisation. Oxidative stress and the marked changes in protein pattern justify the alterations observed, while the upregulation of the hsp26 and hsp60 genes indicates naupliar attempts to mitigate damage. In conclusion, this study confirms the effects of Cd toxicity on the development of Artemia salina nauplii and demonstrates interference with reserve resorption. This evidence indicates that this heavy metal can have a profound impact on zooplanktonic communities, which are essential to the stability of the entire aquatic food web.

Living in extreme environments, marine organisms face constant exposure to a range of stressors, such as high radiation levels, fluctuations in temperature, and oxidative stress. Understanding extremophile fishes is crucial because it gives us valuable insights into the biochemical, physiological, and developmental processes that govern life, by observing how they operate under natural stressors. Among the most fascinating adaptations is the existence of specialised enzymes and compounds that function as potent antioxidants, successfully counteracting reactive oxygen species’ deleterious effects. In this review, we analysed the findings from several studies on Antarctic and deep-sea fish species, while highlighting the environmental stressors effects toward the antioxidant system. The antioxidant defences of the considered extremophile fishes have been extensively studied, but there is still much to learn to fully understand this complex system, while the relative research is still ongoing. Consequently, we are properly anticipating further advancements over the next few years about our understanding of crucial physiological processes that support cell survival.

Living in extreme environments, marine organisms face constant exposure to a range of stressors, such as high radiation levels, fluctuations in temperature, and oxidative stress. Understanding extremophile fishes is crucial because it gives us valuable insights into the biochemical, physiological, and developmental processes that govern life, by observing how they operate under natural stressors. Among the most fascinating adaptations is the existence of specialised enzymes and compounds that function as potent antioxidants, successfully counteracting reactive oxygen species' deleterious effects. In this review, we analysed the findings from several studies on Antarctic and deep-sea fish species, while highlighting the environmental stressors effects toward the antioxidant system. The antioxidant defences of the considered extremophile fishes have been extensively studied, but there is still much to learn to fully understand this complex system, while the relative research is still ongoing. Consequently, we are properly anticipating further advancements over the next few years about our understanding of crucial physiological processes that support cell survival.

Antarctica is the continent with the lowest local human impact; however, it is susceptible to pollution from external sources. Emerging pollutants such as perfluoroalkyl substances pose an increasing threat to this environment and therefore require more in-depth investigations to understand their environmental fate and biological impacts. The present study focuses on expression analysis at the transcriptional level of genes coding for four antioxidant enzymes (sod1, sod2, gpx1, and gpx4) in the liver and kidney of an Antarctic fish species, Trematomus newnesi (Boulenger, 1902). mRNA levels were also assessed in fish exposed to 1.5 μg/L of perfluoro-octanoic acid for 10 days. The kidney showed a higher level of expression than the liver in wildlife specimens. In the liver, the treatment induced an increase in gene expression for all the considered enzymes, whereas in the kidney, it induced a general decrease. The obtained results advance the scientific community’s understanding of how the potential future presence of anthropogenic contaminants in the Southern Ocean can affect the antioxidant system of Antarctic fishes. The presence of pollutants belonging to the perfluoroalkyl substances in the Southern Ocean needs to be continuously monitored in parallel with this type of research.