Proteomic Identification of Oxidized Mitochondrial Proteins following Experimental Traumatic Brain Injury

Abstract

Experimental traumatic brain injury (TBI) results in a significant loss of cortical tissue at the site of injury, and in the ensuing hours and days a secondary injury exacerbates this primary injury, resulting in significant neurological dysfunction. The mechanism of the secondary injury is not well understood, but evidence implicates a critical role for mitochondria in this cascade. This mitochondrial dysfunction is believed to involve excitotoxicity, disruption of Ca(2+) homeostasis, production of reactive oxygen species (ROS), ATP depletion, oxidative damage of mitochondrial proteins, and an overall breakdown of mitochondrial bioenergetics. Although oxidative damage occurs following TBI, the identities of proteins undergoing oxidative modification after TBI have not been investigated. In the present study, we utilized the 3-h post-injury controlled cortical impact model of experimental TBI in 20 young adult male Sprague-Dawley rats, coupled with proteomics to identify specific mitochondrial fraction proteins from the cortex and hippocampus that were oxidatively modified after TBI. We identified, from the cortex, pyruvate dehydrogenase, voltage-dependent anion channel, fumarate hydratase 1, ATP synthase, and prohibitin. From the hippocampus, we identified cytochrome C oxidase Va, isovaleryl coenzyme A dehydrogenase, enolase-1, and glyceraldehyde-3-phosphate dehydrogenase as proteins that had undergone oxidative modification following TBI. In addition, we have also shown that, following TBI, there is a reduction in the activities of pyruvate dehydrogenase (PDH), complex I, and complex IV. These findings demonstrate that, following TBI, several proteins involved in mitochondrial bioenergetics are highly oxidatively modified, which may possibly underlie the massive breakdown of mitochondrial energetics and eventual cell death known to occur in this model. The identification of these proteins provides new insights into the mechanisms that take place following TBI and may provide avenues for possible therapeutic interventions after TBI.

Lactate Storm Marks Cerebral Metabolism following Brain Trauma

“…Significant activation of astrocytes (glial fibrillary acidic protein), neuronal injury/inflammation with the presence of dark neurons (H&E), and tauopathy (Tau immunohistology) support the observation of neuronal and glial pathology, which in turn would explain perturbed metabolism of the cell population as shown by the MR spectroscopy data. Severe head trauma results in oxidative stress reflected by the rapid accumulation of oxidative stress markers with a decrease in antioxidant defense enzymes (52)(53)(54). Oxidative stress is known to induce the formation of hyperphosphorylated Tau, consistent with the results reported here (55,56).…”

Early and Sustained Alterations in Cerebral Metabolism after Traumatic Brain Injury in Immature Rats

“…Increased lactate can result from several potential mechanisms, such as post-injury increases in glycolysis (Kawamata et al, 1995;Yoshino et al, 1991) and reduced oxidative metabolism, with oxidative injury to key metabolic enzymes (Bogaert et al, 2000;Kochanek et al, 2006;Martin et al, 2005;Opii et al, 2007;Richards et al, 2006;Robertson et al, 2007). Another source of lactate after TBI is from infiltration of inflammatory cells, such as macrophages (Lopez-Villegas et al, 1995;Schuhmann et al, 2003;Petroff et al, 1992).…”

Essential Roles of Neutral Ceramidase and Sphingosine in Mitochondrial Dysfunction Due to Traumatic Brain Injury

“…Although a few studies have provided evidence for reduced respiratory chain activity at 7 days post-TBI, which can persist for up to 14 days postinjury (6,7), there is a gap in our knowledge as to what biochemical mechanisms underlie chronic brain dysfunction after TBI. Likewise, an impairment of the mitochondrial respiratory chain enzyme COX has been implicated in secondary brain damage following TBI, but the mechanisms remain unresolved (8).…”