Contaminant-induced oxidative stress underlies biochemical, molecular and fatty acid profile changes, in gilthead seabream (Sparus aurata L.)

Fatty Acid Profiles Linked to Organohalogen Exposure in Cetaceans from the Northern South China Sea

Increasing evidence suggests that organohalogen contaminants (OHCs) could disrupt lipid metabolism in organisms, prompting consideration of fatty acids (FAs) as biological tools for assessing chemical stress in biological systems. This study examined 87 OHCs and 32 FAs in two sentinel cetacean species─Indo-Pacific humpback dolphins (n = 128) and Indo-Pacific finless porpoises (n = 26)─from the northern South China Sea (NSCS), a global hotspot for OHCs. Our results revealed higher OHC levels in these cetaceans than global averages. We identified 347 significant correlations between 79 OHCs and 32 FAs, including 32 associations with long-chain n-3 polyunsaturated fatty acids, which are critical for cetacean health. Furthermore, 45 significant correlations were found between OHC levels and desaturated enzyme activities/lipogenic indexes, suggesting that OHCs may disrupt lipid metabolism in these cetaceans. Polybrominated diphenyl ethers as legacy flame retardants were major contributors to the OHC-FA relationships. Moreover, alternative halogenated flame retardants, as PBDE substitutes, may similarly impact FA metabolism, raising concerns regarding their safety. Our findings support the potential use of FAs as bioindicators for evaluating OHC exposure risks in cetaceans. Future research is needed to elucidate the mechanisms and consequences of these OHC exposure-associated lipid-disrupting effects occurring in the NSCS cetaceans.

Effects of Mixtures of Emerging Pollutants and Drugs on Modulation of Biomarkers Related to Toxicity, Oxidative Stress, and Cancer

Background/Objectives: Over time, the scientific community has developed a growing interest in the effects of mixtures of different compounds, for which there is currently no established evidence or knowledge, in relation to certain categories of xenobiotics. It is well known that exposure to pollutants causes oxidative stress, resulting in the overproduction of reactive oxygen species (ROS), which can affect signaling pathways that regulate the cell cycle, apoptosis, energy balance, and cellular metabolism. The aim of this study was to investigate the effects of sub-lethal concentrations of mixtures of emerging pollutants and pharmaceuticals on the modulation of biomarkers related to toxicity, oxidative stress, and cancer. Methods: In this study, the hepatoma cell line HepG2 was exposed to increasing concentrations of polybrominated diphenyl ether 47 (BDE-47), cadmium chloride (CdCl2), and carbamazepine (CBZ), both individually and in mixtures, for 72 h to assess cytotoxicity using the MTT assay. The subsequent step, following the identification of the sub-lethal concentration, was to investigate the effects of exposure at the gene expression level, through the evaluation of molecular markers related to cell cycle and apoptosis (p53), oxidative stress (NRF2), conjugation and detoxification of xenobiotics (CYP2C9 and GST), DNA damage (RAD51 and γH2AFX), and SUMOylation processes (SUMO1 and UBC9) in order to identify any potential alterations in pathways that are normally activated at the cellular level. Results: The results showed that contaminants tend to affect the enzymatic detoxification and antioxidant system, influencing DNA repair defense mechanisms involved in resistance to oxidative stress. The combined effect of the compounds at sub-lethal doses results in a greater activation of these pathways compared to exposure to each compound alone, thereby exacerbating their cytotoxicity. Conclusions: The biomarkers analyzed could contribute to the definition of early warning markers useful for environmental monitoring, while simultaneously providing insight into the toxicity and hazard levels of these substances in the environment and associated health risks.

Differential Cellular Response to Mercury in Non-Farmed Fish Species Based on Mitochondrial DNA Copy Number Variation Analysis

Mercury (Hg) pro-oxidant role on biological systems and its biogeochemical cycle represent a serious threat due to its persistence in marine environment. As the mitochondrial genome is exposed to reactive oxygen species (ROS), the aim of the present study is the validation of the variation in the number of mitochondrial DNA copies (mtDNAcn) as biomarker of oxidative stress in aquatic environment. During summer 2021, three selected fish species (Mullus barbatus, Diplodus annularis and Pagellus erythrinus) were collected in Augusta Bay, one of the most Mediterranean contaminated areas remarkable by past Hg inputs, and in a control area, both in the south-east of Sicily. The relative mtDNAcn was evaluated by qPCR on specimens of each species from both sites, characterized respectively by higher and lower Hg bioaccumulation. M. barbatus and P. erythrinus collected in Augusta showed a dramatic mtDNAcn reduction compared to their control groups while D. annularis showed an incredible mtDNAcn rising suggesting a higher resilience of this species. These results align with the mitochondrial dynamics of fission and fusion triggered by environmental toxicants. In conclusion, we suggest the implementation of the mtDNAcn variation as a valid tool for the early warning stress-related impacts in aquatic system.

Impact of chronic fluoxetine exposure on zebrafish: From fatty acid profile to behavior

The consumption of antidepressants, such as fluoxetine, has increased over the years and, as a result, they are increasingly found in aquatic systems. Given the increasing use of zebrafish as an animal model in toxicological studies, this work proposed to evaluate the effects of chronic exposure, for 21 days, to fluoxetine at environmentally relevant concentrations (1, 10, 100, and 1000 ng/L). The behavioral tests performed did not reveal significant effects of fluoxetine. However, oxidative stress and changes in energy metabolism were detected after exposure to the highest concentrations of fluoxetine tested, namely a decrease in glutathione S-transferase (GST) activity (decrease of ca. 31%), increase in catalase (CAT) activity (increase of ca. 71%), and decrease in lactate dehydrogenase (LDH) activity (decrease of ca. 53%). Analysis of the fatty acid profile (FA) revealed a decrease in the omega-3 FA, docosahexaenoic acid (DHA), C22:6 (decrease in relative abundance between 6% and 8% for both the head and body), an increase in omega-6 FA, linoleic acid (LA), C18:2, (increased relative abundance between 8% and 11% in the head and between 5% and 9% in the body), which may suggest changes in the inflammatory state of these organisms. The integrated analysis adopted proved to be useful in detecting subindividual effects of fluoxetine and modes of action in fish.

Microalgae as a Sustainable Source of Antioxidants in Animal Nutrition, Health and Livestock Development

Microalgae are a renewable and sustainable source of bioactive compounds, such as essential amino acids, polyunsaturated fatty acids, and antioxidant compounds, that have been documented to have beneficial effects on nutrition and health. Among these natural products, the demand for natural antioxidants, as an alternative to synthetic antioxidants, has increased. The antioxidant activity of microalgae significantly varies between species and depends on growth conditions. In the last decade, microalgae have been explored in livestock animals as feed additives with the aim of improving both animals' health and performance as well as product quality and the environmental impact of livestock. These findings are highly dependent on the composition of microalgae strain and their amount in the diet. The use of carbohydrate-active enzymes can increase nutrient bioavailability as a consequence of recalcitrant microalgae cell wall degradation, making it a promising strategy for monogastric nutrition for improving livestock productivity. The use of microalgae as an alternative to conventional feedstuffs is becoming increasingly important due to food-feed competition, land degradation, water deprivation, and climate change. However, the cost-effective production and use of microalgae is a major challenge in the near future, and their cultivation technology should be improved by reducing production costs, thus increasing profitability.