[The expression of Smac and XIAP in rat hippocampus following limbic seizure induced by kainic acid injection into amygdaloid nucleus].
To determine whether Smac/DIABLO (second mitochondrial activator of caspases/direct inhibitor of apoptosis protein-binding protein of low isoelectric point [PI]) and XIAP (X-chromosome-linked inhibitor of apoptosis protein) serve to regulate neuronal apoptosis following seizures, we investigated seizure-induced changes in caspase-9, Smac/DIABLO and XIAP protein expression and the in vivo effect of caspase-9 inhibition. Animals received unilateral intra-amygdaloid injection of kainic acid (0.5 microg) to induce seizures for 1 h. The seizures were then terminated by diazepam (30 mg/kg). Animals were killed 0, 2, 4, 8, 24 or 72 h following diazepam administration. The apoptotic and surviving neurons in hippocampus were observed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and cresyl violet staining, the expression of Smac/DIABLO, XIAP and caspase-9 was detected with immunofluorescence and western blot. The results showed that the levels of XIAP and the 46-kDa proenzyme form of caspase-9 were unaffected by the seizures. The expression of Smac increased at 2 h and the 37-kD cleaved fragment of caspase-9 was detected at 4 h, TUNEL-positive neurons appeared at 8 h and reached maximal at 24 h following seizure cessation within the ipsilateral (the same side as the intra-amygdaloid injection of kainic acid) CA3 subfield of the hippocampus. Intracerebroventricular infusion of caspase-9 inhibitor z-LEHD-fluoromethyl ketone (z-LEHD-fmk) significantly decreased TUNEL-positive neurons and increased the number of surviving cells. Caspase-9 immunoreactivity increased and Smac/DIABLO, XIAP immunoreactivity became extensive within the ipsilateral CA3 neurons. TUNEL-positive neurons and the alterations of the expression of Smac/DIABLO and XIAP within the ipsilateral CA3 were not detected within the contralateral hippocampus. These results suggest that seizures lead the translocation of Smac/DIABLO into the cytosol, the activation of caspase-9 and the change of subcellular locoalization of XIAP. These changes may play a role in the brain damage induced by seizures. Caspase-9 is possibly a potential therapeutic target in the treatment of brain injury associated with seizures.
Li
Tian-Fu
TF
Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China.
Luo
Yu-Min
YM
Lu
Chuan-Zhen
CZ
D000679:Amygdala / Q000502:physiology*; D000818:Animals; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D006624:Hippocampus / Q000378:metabolism*; D007608:Kainic Acid; D008032:Limbic System; D008297:Male; D008845:Microinjections; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein
D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; D011506:Proteins; C047610:SC5b-9 protein complex; D051636:X-Linked Inhibitor of Apoptosis Protein; D003165:Complement System Proteins; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases; D007608:Kainic Acid