boc-Aspartyl(OMe)-fluoromethylketone attenuates mitochondrial release of cytochrome c and delays brain tissue loss after traumatic brain injury in rats.
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 micromol) 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 x 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.
Clark
Robert S B
RS
Department of Critical Care Medicine, The Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA. clarkrs@ccm.upmc.edu
Nathaniel
Paula D
PD
Zhang
Xiaopeng
X
Dixon
C Edward
CE
Alber
Sean M
SM
Watkins
Simon C
SC
Melick
John A
JA
Kochanek
Patrick M
PM
Graham
Steven H
SH
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology / Q000473:pathology*; D001930:Brain Injuries / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D053143:Caspase 2 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D008297:Male; D018782:Maze Learning / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D020932:Nerve Growth Factor / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D018696:Neuroprotective Agents; D051381:Rats; D017207:Rats, Sprague-Dawley
D000590:Amino Acid Chloromethyl Ketones; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; C103192:butyloxycarbonyl-O-methyl-aspartyl-fluoromethyl ketone; D045304:Cytochromes c; D020932:Nerve Growth Factor; D053143:Caspase 2; D053148:Caspase 3; D053181:Caspase 8