Oxidative stress and antioxidant biomarker responses in fish exposed to heavy metals: a review

Heavy metal pollution represents a serious threat to aquatic environments and human health. In aquatic ecosystems, heavy metals can lead to toxicity in fish by inducing oxidative stress, which disrupts the balance between reactive oxygen species and the body's antioxidant defense system. This review summarizes how heavy metal exposure triggers oxidative stress in fish and highlights the role of key antioxidant enzymes. Many members of the antioxidant defense system, including metallothionein, superoxide dismutase, catalase, glutathione, glutathione transferase, glutathione reductase, and glutathione peroxidase, work together to mitigate the harmful effects of heavy metal exposure on fish health. Additionally, this review systematically synthesizes and analyzes the literature published over the past 16 years regarding the levels of eight crucial antioxidant biomarkers in various fish tissues. Through a critical examination of the accumulated data, this study elucidates the temporal patterns and dose-response relationships of antioxidant responses in fish populations exposed to environmentally relevant concentrations of heavy metals. While responses may vary depending on factors such as exposure duration, metal type, and fish species, antioxidant levels generally increase in response to both acute and chronic exposure. Understanding how fish respond to heavy metal contamination, as well as the patterns of variation in antioxidant indices within their bodies, provide a foundation on which fish can be used as biological indicators to assess the ecological status of heavy metal contaminants.