Neuronal injury during acute hypoxia, ischemia, and following reperfusion are partially attributable to oxidative damage caused by deleterious fluctuations of reactive oxygen species (ROS). In particular, mitochondrial superoxide (O₂•-) production is believed to upsurge during lowoxygen conditions and also following reperfusion, before being dismutated to H₂O₂ and released into the cell. However, disruptions of redox homeostasis may be beneficially attenuated in the brain of hypoxia-tolerant species, such as the naked mole-rat (NMR, Heterocephalus glaber). As such, we hypothesized that ROS homeostasis is better maintained in the brain of NMRs during severe hypoxic/ ischemic insults and following reperfusion. We predicted that NMR brain would not exhibit substantial fluctuations in ROS during hypoxia or reoxygenation, unlike previous reports from hypoxiaintolerant mouse brain. To test this hypothesis, we measured cortical ROS flux using corrected total cell fluorescence measurements from live brain slices loaded with the MitoSOX red superoxide (O₂•-) indicator or chloromethyl 2',7'-dichlorodihydrofluorescein diacetate (CM-H₂-DCFDA; which fluoresces with whole-cell hydrogen peroxide (H₂O₂) production) during various low-oxygen treatments, exogenous oxidative stress, and reperfusion. We found that NMR cortex maintained ROS homeostasis during low-oxygen conditions, while mouse cortex exhibited a ~40% increase and a ~30% decrease in mitochondrial O₂•- and cellular H₂O₂ production, respectively. Mitochondrial ROS homeostasis in NMRs was only disrupted following sodium cyanide application, which was similarly observed in mice. Our results suggest that NMRs have evolved strategies to maintain ROS homeostasis during acute bouts of hypoxia and reoxygenation, potentially as an adaptation to life in an intermittently hypoxic environment.

Maria Roy

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