Caspase 7: increased expression and activation after traumatic brain injury in rats

Abstract

Caspases, a cysteine proteinase family, are required for the initiation and execution phases of apoptosis. It has been suggested that caspase 7, an apoptosis executioner implicated in cell death proteolysis, is redundant to the main executioner caspase 3 and it is generally believed that it is not present in the brain or present in only minute amounts with highly restricted activity. Here we report evidence that caspase 7 is up-regulated and activated after traumatic brain injury (TBI) in rats. TBI disrupts homeostasis resulting in pathological apoptotic activation. After controlled cortical impact TBI of adult male rats we observed, by semiquantitative real-time PCR, increased mRNA levels within the traumatized cortex and hippocampus peaking in the former about 5 days post-injury and in the latter within 6-24 h of trauma. The activation of caspase 7 protein after TBI, demonstrated by immunoblot by the increase of the active form of caspase 7 peaking 5 days post-injury in the cortex and hippocampus, was found to be up-regulated in both neurons and astrocytes by immunohistochemistry. These findings, the first to document the up-regulation of caspase 7 in the brain after acute brain injury in rats, suggest that caspase 7 activation could contribute to neuronal cell death on a scale not previously recognized.

Neuroproteomics in neurotrauma

“…The latter promotes pyknosis of the mitochondrial membrane and the release of cytochrome C into the cytosol to combine with Apaf-1 and ATP to form the apoptosome that catalyzes caspase-9 activation. Caspase-9, in turn, activates the executioner caspases-3, -6, and -7, of which caspase-3 is well known to be, and -7 was just shown to be, active after TBI (Larner et al, 2005). Alternatively, the extrinsic pathway is mitigated by binding of the death ligands Fas or TNF to their respective cell receptors.…”

Nedd4-WW Domain-Binding Protein 5 (Ndfip1) Is Associated with Neuronal Survival after Acute Cortical Brain Injury

“…factor 1) and caspases 2, 3,7,8, and 12, all of which are known to be highly regulated in TBI (O'Dell et al, 2000;Beer et al, 2001;Yakovlev et al, 2001;Larner et al, 2004Larner et al, , 2005. Finally, ubiquitination is known to be pivotal for regulating a whole range of synaptic processes, including development, pruning, plasticity, and protein turnover in synaptic membranes (DiAntonio and Hicke, 2004).…”

Validation of reference genes for normalization of real‐time quantitative RT‐PCR data in traumatic brain injury

“…Despite the increasing evidence that normalizing real-time RT-PCR data to a single reference gene may be inappropriate, many authors continue to do so without proper validation (Bustin and Benes, 2005). Indeed, the majority of papers in our area of interest (traumatic brain injury; TBI) describe the use of a single reference gene, such as GAPDH, cyclophilin, b-actin, or 18S ribosomal RNA (Li et al, 2004;Larner et al, 2005;Pascale et al, 2006;Shein et al, 2007;Sifringer et al, 2007;Yao et al, 2007;Brown et al, 2008), usually without including a reference gene validation protocol. Because the expression of these reference genes has been shown to vary across different experimental situations (Zhong and Simons, 1999;Schmittgen and Zakrajsek, 2000), it is uncertain whether these studies have measured a true change in the mRNA of interest or whether data analysis has been influenced by the variability of the reference gene.…”