PROCASPASE-3 AND APAF-1: INCREASED EXPRESSION OF PROTEINS AFTER STATUS EPILEPTICUS IN RATS
Abstract number :
2.073
Submission category :
Year :
2003
Submission ID :
2507
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Giuseppe Conti, Karen Gale, Alexei Kondratyev Department of Pediatrics, Georgetown University Medical Center, Washington, DC; Department of Pharmacology, Georgetown University Medical Center, Washington, DC
Cell death induced by status epilepticus (SE) in selected populations of neurons in hippocampus and rhinal cortex involves caspase-3-dependent mechanisms. In the intrinsic pathway of caspase-3 activation, apoptotic protease-activating factor-1 (APAF-1) is required to activate caspase-3, which is generated from a procaspase-3, a protein that is normally expressed at extremely low levels in the adult brain. Recently, we have reported increased expression of mRNA for procaspase-3 and APAF-1 after SE. In this study, we determined whether this increase in mRNA affected protein levels of procaspase-3 and APAF-1 following SE.
SE was induced in adult male Sprague-Dawley rats by kainic acid (12 mg/kg ip) and terminated after a 2 hr duration with diazepam (30 mg/kg ip). Protein levels of procaspase-3 and APAF-1 in the rhinal and piriform cortices and the hippocampus were analyzed by immunohistochemistry using specific antibodies at 2, 4, 8, 24, and 48 hr after termination of SE.
A significant increase in procaspase-3 protein was found at 8 after SE termination as compared with control animals in the piriform cortex and the CA3 hippocampal subfield. In the rhinal cortex, caspase-3 protein was significantly upregulated at 48 hr after SE. APAF-1 protein levels were also significantly elevated, with maximum at 8 hr post-SE in the rhinal and piriform cortices and in the hippocampus (CA1, CA3, CA4, and dentate gyrus).The increases in procaspase-3 and APAF-1 proteins at 8 hr were transient and their expression returned to the control level by 24 hr after SE termination.
These results demonstrate that prolonged injurious seizure activity induces both APAF-1 and procaspase-3 proteins, allowing for the initiation of a caspase-dependent apoptotic cascade. The transient nature of the increases suggests increased utilization of these proteins following SE. Interestingly, these genes are highly downregulated in the adult brain, as compared with the immature brain (prior to postnatal day 7 in rat). Our data are in agreement with the increases in caspase-3 and APAF-1 levels of mRNA after SE observed previously. These results support the possibility that SE-induced injury reengages the cellular machinery characteristic of programmed cell death during development.
[Supported by: NIH grants NS 20576, MH 02040, and by the Epilepsy Foundation.]