Changes Of Heme Oxygenase-1 And Apoptosis As Well As The Relationgship Between Them Following Hypoxic-ischemic Brain Damage In Neonatal Rat

Objective Home oxygenase-1 (HO-1) catalyzes the rate-limiting step in heme degradation releasing iron, carbon monoxide (CO), and biliverdin. We investigated the changes in expression of heme oxygenase-1mRNA and protein in rat hippocampus after hypoxic-ischemic brain damage(HIBD) as well as the relationship between heme oxygenase-1 and brain cell apoptosis. Methods Experimental animals which were seven days old SD rats were randomly divided into hypoxic-ischemic brain damage group(HIBD) and sham control group with 36 pieces each. The animals in HIBD were ligated the right common carotid artery by double threads. After the operation, the rats had a rest for two hours, and then kept in a hypoxia cabin (8()ml/l oxygen) for 2 hours. Animals in sham control group were only being dissociated of the right common carotid artery without ligation.After establishment of the models in every group, the brain were taken rapidly after (0 4 12 24 48 72hours,and fixed by 4%paraformaldehyde with 0.1%DEPC,then 6. m crown shape wax brain slices were prepared. The expression of HO-1 protein and HO-1mRNA as well asapoptosis cells in brain after HIBD in the neonatal rat were determined by immunohistochemistry and in situs hybridizaion as well as terminal deoxynucleotidy transferase mediated UTP-biotin nick end labcling(TUNEL).Positive cell number of HO-1 protein and HO-1mRNA and apoptosis neuron were counted under high ken(OMx400). All data were expressed by Means +SD and SPSS 10.0-t analysis was employed.Result compared with control group , the expression of HO-1 protein ,HO-1mRNA and apoptosis of neuron have changed significantly at different time .(1) The expression of HO-1 mRNA in the right hippocampus.HO-lmRNA in hippocampus was distributed in cytosol ,pre-HO-l mRNA was also observed in the nucleus .Compared with control group, HO-1 mRNA positive cells of control groups had no difference at different times; But the HO-1 mRNA of HIBD group positive cells were sharply increased at 4h (P<0.05) after hypoxic-ischemic brain damage ,reached the peak at 12h to 24h and then decreased gradually at 48h, which was still higher than that in the control group at 72h(P<0.01).(2) Localization of the HO-1 protein appeared prevalently localized inthe cytosol and in the perinuclear region. And HO-1 was present also in the nucleus, and in the nucleoli. The level of HO-1 protein observed increase was parallel with the increase in HO-lmRNA levels.(3) In the right hippocampus, apoptosis cells could hardly be observedin control groups, but apoptosis cells were obviously observed at 24h after HIBD and then decreased at 72h, which was stillhigher than that in the sham control group (P<0.05). Conclusion(1) The expression of heme oxygenase-1 in rat hippocampus showedincreased after hypoxic-ischemia brain damage.(2) the number of apoptosis of neuron showed increased afterhypoxic-ischemia brain damage.(3) which strongly suggested that HO-1 is associated with themechanisms of hypoxic-ischemia brain damage ,and HO-1 is candidate for neuronal apoptosis.