Cellular and subcellular oxidative stress parameters following severe spinal cord injury

The present study undertook a comprehensive assessment of the acute biochemical oxidative stress parameters in both cellular and, notably, mitochondrial isolates following severe upper lumbar contusion spinal cord injury (SCI) in adult female Sprague Dawley rats. At 24h post-injury, spinal cord tissue homogenate and mitochondrial fractions were isolated concurrently and assessed for glutathione (GSH) content and production of nitric oxide (NO^•), in addition to the presence of oxidative stress markers 3-nitrotyrosine (3-NT), protein carbonyl (PC), 4-hydroxynonenal (4-HNE) and lipid peroxidation (LPO). Moreover, we assessed production of superoxide (O2•-) and hydrogen peroxide (H₂O₂) in mitochondrial fractions. Quantitative biochemical analyses showed that compared to sham, SCI significantly lowered GSH content accompanied by increased NO^• production in both cellular and mitochondrial fractions. SCI also resulted in increased O2•- and H₂O₂ levels in mitochondrial fractions. Western blot analysis further showed that reactive oxygen/nitrogen species (ROS/RNS) mediated PC and 3-NT production were significantly higher in both fractions after SCI. Conversely, neither 4-HNE levels nor LPO formation were increased at 24h after injury in either tissue homogenate or mitochondrial fractions. These results indicate that by 24h post-injury ROS-induced protein oxidation is more prominent compared to lipid oxidation, indicating a critical temporal distinction in secondary pathophysiology that is critical in designing therapeutic approaches to mitigate consequences of oxidative stress.