Cellular and electrophysiological investigations of nitric oxide protection against a model of oxidative stress

Since the discovery of nitric oxide (NO) during the 1980’s, there has been great interest in the molecule’s mechanism of action. The main function of NO is thought to be as a second messenger in cell signalling pathways; however it has also been identified as a toxin, pro-oxidant and possible antioxidant in an array of physiological and pathological scenarios. The contradictory roles of NO in cellular and tissue injury are controversial, with evidence that NO can be both deleterious and protective against damage, depending upon the concentration and duration of NO exposure. A well-established mechanism that causes injury is through the generation of reactive oxygen species (ROS), in the presence of molecular oxygen (O2). Under these conditions NO has been considered to act as a toxin via the generation of reactive nitrogen species (RNS), and as an antioxidant, through its ability to mediate cellular processes and attenuate oxidative damage. Oxidative damage is particularly important in the brain, which is highly vulnerable to damage via oxidative stress due to its high metabolic rate and reduced capability to recover following injury. Consequently, oxidative stress has been associated with several neurodegenerative disorders including, Parkinson’s disease, Alzheimer’s disease, epilepsy and ischemic stroke. This study aimed to investigate the protective effects of prolonged NO release against oxidative damage in cell culture and acutely in hippocampal brain slices. A model of oxidative stress was established using the mitochondrial redox cycling agent menadione, which produced cytotoxicity via the generation of superoxide. Administration of a novel NO donor, tertiary-dodecane S-nitrosothiol (tDodSNO), demonstrated a protective effect at high concentrations (>50 µM) in both cell culture and in hippocampal brain slices. In cell culture this effect was associated with a reduction in the expression of p53 and changes in the concentration of zinc and iron within the cell. These findings highlight the importance of understanding the role that NO plays under conditions of oxidative stress, as this would be therapeutically beneficial for the development of novel NO donor drugs as an antioxidant to improve the treatment of neurodegenerative disorders