Suppression of reactive oxygen species production enhances neuronal survival in vitro and in vivo in the anoxia‐tolerant turtle Trachemys scripta

Hypoxia‐ischemia with reperfusion is known to cause reactive oxygen species‐related damage in mammalian systems, yet, the anoxia tolerant freshwater turtle is able to survive repeated bouts of anoxia/reoxygenation without apparent damage. Although the physiology of anoxia tolerance has been much studied, the adaptations that permit survival of reoxygenation stress have been largely ignored. In this study, we examine ROS production in the turtle striatum and in primary neuronal cultures, and examine the effects of adenosine (AD) on cell survival and ROS. Hydroxyl radical formation was measured by the conversion of salicylate to 2,3‐dihydroxybenzoic acid (2,3‐DHBA) using microdialysis; reoxygenation after 1 or 4 h anoxia did not result in increased ROS production compared with basal normoxic levels, nor did H2O2 increase after anoxia/reoxygenation in neuronally enriched cell cultures. Blockade of AD receptors increased both ROS production and cell death in vitro, while AD agonists decreased cell death and ROS. As turtle neurons proved surprisingly susceptible to externally imposed ROS stress (H2O2), we propose that the suppression of ROS formation, coupled to high antioxidant levels, is necessary for reoxygenation survival. As an evolutionarily selected adaptation, the ability to suppress ROS formation could prove an interesting path to investigate new therapeutic targets in mammals.