Effects of bisphenol A on freshwater mussels: Insights into the protective mechanisms of selenium

Bisphenol A (BPA), a widespread environmental pollutant, is known for its endocrine-disrupting and pro-oxidant effects, posing serious risks to aquatic organisms. This study evaluated the impact of BPA on biochemical markers in the digestive gland of the freshwater mussel Unio ravoisieri, and assessed the potential protective role of selenium (Se), a trace element with antioxidant properties. Under laboratory conditions, mussels were exposed for 14 days to two BPA concentrations (C₁ = 10 μg/L and C₂ = 100 μg/L), either alone or combined with 100 μg/L Se. The enzymatic activity of acetylcholinesterase (AChE), catalase (CAT), and glutathione S-transferase (GST), along with the levels of malondialdehyde (MDA), reduced glutathione (GSH), and hydrogen peroxide (H₂O₂), were quantified as indicators of neurotoxicity and oxidative stress. BPA exposure led to a significant dose-dependent inhibition of AChE activity, indicating neurotoxicity, while GST activity increased, suggesting an upregulated detoxification response. An increase in CAT activity was observed at the lower BPA dose, while inhibition occurred at the higher dose. Importantly, BPA significantly GSH levels, indicating oxidative stress and impaired antioxidant and detoxification defenses. Additionally, BPA exposure at both 10 μg/L and 100 μg/L significantly elevated MDA and H₂O₂ levels, with a more pronounced increase observed at the higher dose (100 μg/L), confirming enhanced lipid peroxidation and reactive oxygen species (ROS). Notably, Se co-treatment mitigated these adverse effects by partially restoring AChE and CAT activities, normalizing GST responses, preserving GSH content, and reducing oxidative damage. These findings demonstrate the intertwined oxidative and detoxification responses of U. ravoisieri to BPA exposure and underscore the protective role of Se in counteracting BPA-induced toxicity. This study reinforces the utility of biochemical biomarkers in environmental monitoring and supports the potential use of Se in pollution mitigation strategies.