Activation of CPP32-Like Caspases Contributes to Neuronal Apoptosis and Neurological Dysfunction after Traumatic Brain Injury

Abstract

We examined the temporal profile of apoptosis after fluid percussion-induced traumatic brain injury (TBI) in rats and investigated the potential pathophysiological role of caspase-3-like proteases in this process. DNA fragmentation was observed in samples from injured cortex and hippocampus, but not from contralateral tissue, beginning 4 hr after TBI and continuing for at least 3 d. Double labeling of brain with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and an antibody directed to neuronal nuclear protein identified apoptotic neurons with high frequency in both traumatized rat cortex and hippocampus. Cytosolic extracts from injured cortex and hippocampus, but not from contralateral or control tissue, induced internucleosomal DNA fragmentation in isolated nuclei with temporal profiles consistent with those of DNA fragmentation observed in vivo. Caspase-3 mRNA levels, estimated by semiquantitative RT-PCR, were elevated fivefold in ipsilateral cortex and twofold in hippocampus by 24 hr after TBI. Caspase-1 mRNA content also was increased after trauma, but to a lesser extent in cortex. Increased caspase-3-like, but not caspase-1-like, enzymatic activity was found in cytosolic extracts from injured cortex. Intracerebroventricular administration of z-DEVD-fmk-a specific tetrapeptide inhibitor of caspase-3-before and after injury markedly reduced post-traumatic apoptosis, as demonstrated by DNA electrophoresis and TUNEL staining, and significantly improved neurological recovery. Together, these results implicate caspase-3-like proteases in neuronal apoptosis induced by TBI and suggest that the blockade of such caspases can reduce post-traumatic apoptosis and associated neurological dysfunction.

boc-Aspartyl(OMe)-Fluoromethylketone Attenuates Mitochondrial Release of Cytochrome c and Delays Brain Tissue Loss after Traumatic Brain Injury in Rats

“…Released cytochrome c engages with caspase-9 and apoptotic proteaseactivating factor-1 (Apaf-1) to form an 'apoptosome' that activates caspase-3 and results in cellular changes producing apoptotic cell death (Li et al, 1997;Zou et al, 1997). Several relatively selective caspase-3 inhibitors such as DEVD have been reported to be neuroprotective after experimental TBI, used primarily to target events downstream from cytochrome c release (Clark et al, 2000;Knoblach et al, 2004;Yakovlev et al, 1997). Fewer studies have tested the effects of less selective caspase inhibitors after TBI, which could be expected to have effects both upstream and downstream from cytochrome c release.…”

Caspase-independent death of meiotic and postmeiotic cells overexpressing p53: calpain involvement

“…Upregulation of caspase-3 mRNAs is reported in various in vivo models of apoptosis of the nervous system: brain injury and Huntingtin transgenic mice. 20,21 In addition to ubiquitous transcription factors, (i) caspase (3, 7, 8 and 9) gene transcription is directly regulated by E2F1 in proliferating cells (and probably by other E2F family members 22 ), (ii) in differentiating keratinocytes, Notch can also upregulate caspase-3 promoter activity. 23 In addition to the well-known posttransductional regulation of caspases, caspase gene transcription also seems tightly controlled during differentiation commitment and stress responses.…”

Post-traumatic inflammation following spinal cord injury

“…16,41,80,82 In particular, downstream caspase-3 has been shown to be important to neuronal development and injury by inducing fragmentation of nuclear DNA in vitro and in vivo. 83,114 Additional control of cell death/survival is provided by the mammalian antiapoptotic proteins Bcl-X L and Bcl-2. The latter was shown to be upregulated in injured white matter axons following SCI.…”