[Role of the FOXO3a transcription factor in neuronal apoptosis in neonatal rats with hypoxic-ischemic brain damage].
OBJECTIVE
To explore the role and mechanisms of FOXO3a nuclear translocation in neuronal apoptosis after hypoxia-ischemia (HI).


METHODS
One hundred and sixty 10-day-old Sprague-Dawly rats were randomly divided into two groups: HI and sham-operated. The right common carotid artery was ligated followed by hypoxia exposure for 2.5 hours in the HI group. The sham-operated group rats were not subjected to carotid artery ligation or hypoxia treatment. Rat cerebral cortex was collected at 0.5, 2, 4, 8 and 24 hours after hypoxia. Western blot was used to detect expression of total FOXO3a protein, pnuclear and cytoplasmic FOXO3a and Bim. TUNEL staining was used to detect apoptotic cells.


RESULTS
The nuclear protein of FOXO3a obviously increased from 0.5 to 24 hours after HI in a time-dependent manner compared with the sham-operated group (P<0.01). On the contrary, cytoplasmic protein evidently decreased from 0.5 to 24 hours in the HI group compared with the sham-operated group (P<0.01). Bim protein increased from 0.5 hour, peaked at 2 hours, started to decline at 4 hours (P<0.01), and returned to baseline level at 8 and 24 hours after HI in the HI group compared with the sham-operated group. TUNEL positive cells started to express at 4 hours, and peaked at 24 hours after HI (P<0.01). However, TUNEL positive cells were rarely found in the sham-operated group.


CONCLUSIONS
HI induces FOXO3a translocation from cytoplasm to nucleus, and enhances protein expression of its target gene Bim in the neonatal rat brain. The upregulation of Bim expression might be related to neuronal apoptosis.
Department of Pediatrics, West China Second Hospital, Sichuan University, Chengdu 610041, China. quyi712002@yahoo.com.cn.
De-Yuan
DY
Li
Yi
Y
Qu
Jin-Hui
JH
Li
Li
L
Zhang
Tao
T
Xiong
De-Zhi
DZ
Mu
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000032:analysis; D000072224:Bcl-2-Like Protein 11; D005260:Female; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000502:physiology*; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D008297:Male; D008565:Membrane Proteins / Q000032:analysis; D009474:Neurons / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606778:Bcl2l11 protein, rat; C499515:FOXO3 protein, rat; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins