Metabolism and mechanistic toxicity of environmental pollutants in fish models : integrating in vitro and in vivo systems for ecotoxicological studies.

The presence of legacy and emerging contaminants in the aquatic environment represents a significant threat to aquatic biota, often leading to significant declines of biodiversity. This issue is further aggravated by the influence of abiotic environmental factors, such as climate change, which could potentially modify organisms’ exposure and responses to pollution. Historically, ecotoxicological studies have relied on the use of live animals and endpoints such as mortality, growth, and reproduction to determine whether exposed organisms and populations are at risk. However, these approaches are often hindered by cost, ethic, and scientific limitations, making them unable to provide a thorough representation of exposure conditions and resulting adverse effects. Recently, significant research efforts have highlighted the need to understand pollutant-driven alterations at different levels of biological organization. In this context, new approach methodologies (NAMs), such as in vitro systems, have emerged as robust bioanalytical tools to mechanistically describe chemical-organism interactions, predict potential adverse effects from exposure, and support comprehensive assessments of risk, while reducing animal use. The scope of this dissertation relies on the applicability of NAMs, specifically cell-based bioassays, and their integration with more traditional approaches (e.g. in vivo systems) to address research gaps associated with the biotransformation of legacy compounds by fish populations with different exposure history, the endocrine disruption potential of wastewater effluents, and the description of mechanistic toxicity of natural and anthropogenic pollutants, while considering the influence of different environmental stressors. This work demonstrated that descriptions of adverse effects from exposure to pollutants are significantly facilitated by in vitro systems, but that overall characteristics of the species and areas of interest must be accounted for when selecting appropriate cell-based models, as their improper selection could significantly mislead observations and subsequent environmental management strategies. The integration of cell-based and whole-animal approaches showed that the sensitivity and specificity of in vitro systems are significant limitations for their implementation, and that their value in ecotoxicological studies relies on their integration with more complex experimentation through weight of evidence (WoE) approaches