Effect Of GM1 On The Apoptotic Death Of Cerebral Cells After Hypoxic-Ischemic Injury In Neonatal Rats

OBJECTIVES: We studied the apoptotic process of cerebral cells in neonatal rats after hypoxic-ischemic insult,observed the effect of GM1 on the process and on the expression of Bax and Bcl-2,two genes related to apoptosis. MEHTODS: The HIE model was produced on 7-day-old SD rats with right carotid artery ligation followed by an hypoxic(8% oxygen) eposide of 2.5 hours durition,so,the right cerebral hemisphere was damaged by hypoxia-ischemia,and the left by hypoxia. Apoptosis,one of the patterns of which cerebral cells die after HI injury,was examined by Hematoxylin and Eosin staining, terminal deoxynuclieotidyl transferase mediated dUTP-biotin nick end labelling(TUNEL) staining and election-microcope.The numbers of apoptotic cells were examined at different time points,tissue sections were analyzed for presense of TUNEL.At the time point of peak apoptosis,we observed the effect of GM1 on apoptotic death of cerebral cells(three groups of rats: treated group,HI rats were injected intraperitoneally with GMI; HI control group,HJ rats were inj ected intraperitoneally with physiological saline ;normal control group) ,and on the expression of genes Bax and Bcl-2 with the method of SABC. ERESULTS: Apoptotic death existed in cerebral cells of the neonatal rats after HI injury. After HI,a few of TUNEL-positive cells could be observed at 0.5 hour.An increase in TUNEL-positive cells was seen in the lesioned cerebral tissue beginning at 6h.At 48-72h after HJ,the number of TUNEL-positive cells is very large. At 7-l4day,there were still several TUNEL-positive cells.The appearance of TUNEL labeled cells in two cerebral hemispheres followed the similar time courses, but the number of TUNEL-positive cells is larger in the right cerebral hemiphere.TUNEL-possitive cells could be seen occasionally in the normal neonatal brain. After HI, the number of TUNEL-positive cells in treated rats was smaller than in control rats. In normal control rats,both Bax and Bel-2 expressed (+?.And in HI control rats, Bcl-2 weakly expressed(+) and Bax strongly expressed(+++).In treated HI rats, Bel-2 and Bax normally expressed(?). CONCLUSIONS: .Not long after HI,cerebral cells commited apoptotic death.The number of apoptotic cells came to peak between 48-72 hour and apoptotic death could last a considerably long time in brain after HI injury.That the number of apoptotic cells is larger in the HI cerebral hemisphere than in the hypoxic cerebral hemisphere at the same time point suggested that apoptotic death be related to the degree of damage.Treated with GMI promptly after HI injury,the neonatal rats could suffer less apoptotic death.Bax and Bcl-2,two genes related to apoptosis,expressed in normal control rats, they may have important significance to the development of normal rats.That Bax highly expressed(+) and Bcl-2 lowly e~pressed (+)in I-lI control rats implied that apoptotic death of cerebral cells be related to the unbalance of two genes.GM1 could partly inhibit the expression of Bax and promote the expression of Bcl-2,It implied GM1 reduce apoptosis by affecting the expression of them.