The Role of Superoxide Dismutase in Reptiles under Toxicity Contexts

Abstract

Reptiles are important models in evolutionary history and several species are of great ecological, sociological and commercial importance. They are transcendental in natural ecosystems, as prey, predators, herbivores, seed dispersers and as bioindicators of environmental health. In recentdecades, the role of environmental pollution as a possible reason for the decline of reptile populations has prompted researchers to evaluate the effects of pesticides on these vertebrate groups. Given the expansion of agricultural frontiers, many reptile populations live now in habitat subjected to high pollution pressure, and due to their biological characteristics, they may be exposed to pollutants at all stages of their lives. As a consequence, they appear worldwide as excellent model species of environmental contamination by different xenobiotics. Environmental pollutants are known to induce oxidative damage to biomolecules, such as proteins, lipids, and nucleic acids, due to the production of reactive oxygen species (ROS). ROS are highly reactiveand potentially deleterious to biological systems. To minimize the effects that ROS can generate, aerobic organisms have developed enzymatic and non-enzymatic antioxidant defenses. Enzymatic defenses, such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase(GPx), protect the organism by directly eliminating superoxide radicals and hydrogen peroxide, converting them into less reactive species. Oxidative stress occurs as a result of an imbalance between ROS and antioxidant mechanisms, leading to a variety of physiological and biochemical changes that cause cell deterioration and death. This occurs due to an excessive accumulation of ROS, decrease in antioxidant enzymes, or both. Specifically, SOD is the first line of defense and themost powerful antioxidant in the cell. It catalyzes the dismutation of superoxide anion (O2?-) into hydrogen peroxide (H2O2) and oxygen (O2), making potentially harmful O2?- less dangerous. Four isoforms of SOD enzyme have been described, according to their metallic cofactor; Fe- SOD, Mn-SOD, Ni-SOD and Cu/Zn-SOD, which have distinct subcellular locations. SOD has demonstrated to be sensible to environmental contamination and several studies carried out in reptiles have shown that exposure to xenobiotics produces inhibition or overproduction of SOD or altered sod gene expression in different tissues. Considering the importance of reptiles in the ecosystem and theaction of SOD against environmental pollutants, the aim of this chapter is to present the current knowledge into the structure-activity relationship and mechanism of action of SOD in a reptile species, and its importance as a biomarker for environmental contamination in sentinel species.