“TBI infants and children remains a significant cause of death and morbidity. This study will identify oxidized mitochondrial phospholipids functioning as signaling molecules in neuronal death after TBI using state of the art oxidative lipidomics approaches. We will test novel mitochondria targeted antioxidants and other compounds in experiments to prevent neuronal death after traumatic brain injury. The ability to selectively modulate this pathway could lead to targeted therapies for TBI and ultimately improve outcome for children.”

- Hülya Bayir, MD   bayihx@ccm.upmc.edu
Assistant Professor, Department of Critical Care Medicine
Principal Investigator, “Oxidative Lipidomics in Pediatric Traumatic Brain Injury”

Summary of Study

Background: Trauma in infants and children remains a significant cause of morbidity and mortality. Severe traumatic brain injury (TBI) is an important participant in this mortality and associated morbidity. Apoptosis contributes to neuronal death after TBI. The release of Cytochrome c (cyt c) from inner mitochondrial space of the mitochondria is a critical early event in mitochondrially mediated apoptotic cell death. Upon extrusion into the cytosol, cyt c activates initiator and effector caspase cascades responsible for apoptosis.

Preliminary work: Recently we have shown novel redox catalytic properties of cyt c realized though its interactions with CL in mitochondria and PS in plasma membrane resulting in their selective oxidation. The resulting products, CL and PS hydroperoxides act as important signals in two apoptotic pathways – regulation of release of apoptotic factors from mitochondria into cytosol, and externalization of PS marking apoptotic cells for phagocytosis.

Hypothesis: Our hypothesis is that TBI initiates excessive production of ROS and selective early oxidation of phospholipids with accumulation of oxidized CL triggering release of pro-apoptotic factors from mitochondria. As a consequence, we predict that TBI induced CL oxidation and apoptosis can be prevented by antioxidant strategies and treatments decreasing susceptibility of CL to oxidation by dietary manipulation of its fatty acid residues.

Approach + Specific Aims: We will utilize a comprehensive approach from in vitro (stretch injury of neurons) and in vivo models (controlled cortical impact (CCI) model in post-natal day (PND) 17 rats) to clinical pediatric TBI to address the following specific aims:

1) Determine the degree, spatial and temporal pattern of ROS production, antioxidant depletion and CL oxidation in immature brain after CCI

2)  Investigate whether gender influences ROS production, antioxidant depletion and CL oxidation in immature brain after TBI and in neurons after stretch-injury and glutamate exposure.

3) Determine the potential of antioxidants and dietary manipulation to inhibit mitochondrial CL oxidation and protect against apoptosis in immature brain after TBI and in neurons after stretch injury and glutamate exposure glutamate exposure

4) Design and investigate mechanism of action and neuroprotective efficacy of novel mitochondria-targeted compounds acting via different pathways to regulate CL/cyt c peroxidase activity.

5) Link bench to bedside confirming these important mechanisms and providing a means for monitoring the clinical effect of antioxidants and other therapies that may influence CL/cyt c peroxidase activity after severe TBI in infants and children.

Scope + Impact: These studies will employ the newly developing technology of oxidative lipidomics to provide important mechanistic information on the role of cyt c -CL interactions in neuronal apoptosis after pediatric TBI.  These specific aims will fill a major gap in knowledge since in vivo studies linking overall CL oxidation with cyt c release and apoptosis have been lacking.  The release of cyt c from mitochondria is a critical early event in the mechanism of apoptosis. The ability to selectively modulate Cyt c release could lead to targeted therapies for TBI and ultimately improve outcome for children.