1. ¹Department of Critical Care Medicine, The Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
2. ²Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
3. ³The Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
4. ⁴Department of Neurological Surgery, The Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
5. ⁵Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
6. ⁶Department of Neurology, and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
7. ⁷Geriatric Research Educational and Clinical Center, VA Pittsburgh Health System, Pittsburgh, Pennsylvania, USA

Correspondence: Dr Robert SB Clark, Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, 3434 Fifth Avenue, Pittsburgh, PA 15260, USA. E-mail: clarkrs@ccm.upmc.edu

Received 1 February 2006; Revised 10 April 2006; Accepted 11 April 2006; Published online 17 May 2006.

Abstract

The pathobiology of traumatic brain injury (TBI) includes activation of multiple caspases followed by cell death with a spectrum of apoptotic phenotypes. There are initiator (e.g. caspase-2, -8, and -9) and effector (e.g. caspase-3 and -7) caspases. Recently, caspase-2 and -8 have been shown to regulate cell death via provoking cytochrome c release from the mitochondria upstream of caspase-9. Here, we show that an intracerebral injection of the pan-caspase inhibitor boc-Aspartyl(OMe)-fluoromethylketone (BAF; 1 mol) 1 min after TBI in rats reduces caspase-3-like activity, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and tissue damage, and cytochrome c release in ipsilateral cortex at 24 h versus vehicle. To investigate whether either caspase-2 and/or caspase-8 activation may contribute to cytochrome release, the effect of BAF treatment on caspase-2 and caspase-8 proteolysis was also examined. boc-aspartyl(OMe)-fluoromethylketone treatment inhibited proteolysis of caspase-2 but not caspase-8 24 h after TBI in rats versus vehicle. However, BAF with or without nerve growth factor (12.5 ng/h 14 days intracerebrally via osmotic pump) did not result in differences in motor function, Morris water maze performance, hippocampal neuron survival, nor contusion volume at 14 days. These data suggest that BAF treatment reduces acute cell death after TBI by inhibiting mitochondrial release of cytochrome c, possibly via a mechanism involving initiator caspases; however, BAF appears to delay cell death, rather than result in permanent protection.