Reactive Oxygen Species and Redox Stress
The purpose of Chapter 4 is to describe a particular set of phenomena that collectively comprise an important mechanism of chemical toxicity and cellular defense. These phenomena, referred to as redox stress, encompass oxidative and reductive stress and apply to a diverse array of chemicals, ultimately resulting in a diverse array of health outcomes. The study of redox stress broadly includes biological phenomena associated with the generation of reactive oxygen species (ROS), molecular systems designed to protect cells from ROS (i.e., antioxidant defense systems), and the active vs. passive deleterious impacts of ROS. As in many areas of mechanistic toxicology, understanding of redox stress in fishes has lagged behind understanding in mammals and, indeed, has depended to a large degree on studies in other biological systems for the development of methodologies and concepts; however, the study of redox stress in fishes is currently a vibrant area of investigation that is revealing a number of important similarities and differences with other organisms. Moreover, the multitude of chemicals entering freshwater and marine systems that can contribute to redox stress underlies the need for information on this phenomenon in fishes. In this chapter, we describe fundamental aspects of ROS chemistry and generation, antioxidant defense systems, cellular and organismal impacts, and specific mechanisms by which pollutants play roles in these processes. We also describe the current state of understanding of redox stress in fishes, technological advances, and potential future directions for the field.
