Protective effect of a synthetic anti‐oxidant on neuronal cell apoptosis resulting from experimental hypoxia re‐oxygenation injury

Abstract

Oxidative stress is associated with the pathology of acute and chronic neurodegenerative disease. Cultured neuronal cells exposed to hypoxia-reoxygenation (H/R) injury, as a model for stroke, yield a burst of reactive oxygen species (ROS) as measured with electron paramagnetic resonance (EPR) spectroscopy in combination with spin trapping. Added superoxide dismutase inhibited spin-adduct formation verifying that superoxide radical anion was formed in neuronal cells following H/R injury. The intracellular ADP/ATP ratio increased rapidly over the first 5 h following injury and this was due primarily to the decreased cellular pools of ATP, consistent with the notion that H/R promotes mitochondrial dysfunction leading to decreased ATP reserve and increased ROS formation. As an early response to the enhanced oxidative stress, genes encoding for hypoxia-inducible factor 1-alpha (HIF1-alpha), inducible haemoxygenase-1 (HO-1), and the oxygen-sensor neuroglobin increased significantly. Up-regulation of the HO-1 gene was paralleled by increased HO protein expression and activity. Despite this cellular response, apoptosis increased significantly following H/R injury indicating that the endogenous anti-oxidant defenses were unable to protect the cells. In contrast, addition of a phenolic anti-oxidant, bisphenol (BP), prior to H/R injury, inhibited ROS production and gene regulation and significantly decreased neuronal cell apoptosis. Added BP was converted stoichiometrically to the corresponding diphenoquinone indicating the synthetic anti-oxidant effectively decreased oxidative stress through a radical scavenging mechanism. Together, these data indicate that BP has the potential to act as a neuro-protective drug.