| Background and Objective:Hypoxic-ischemic encephalopathy (HIE) of neonate is an injury disease which leads to deathof neonate and neurological deficits. Mitochondrial ATP-dependent K+ channels (mitoKATP) arelocated in the inner mitochondrial membrane .On the research of neural ischemic reperfusioninjury, mitoKATP channels have become a new therapeutical target of neuroprotection. A newdirection that the selective activation of mitoKATP Channels as a means of protecting neuronsfrom hypoxia-ischemia and other stimuli has been supported by more and moreexperiments. However , mechanism of the neuroprotective effect of the selective opener ofmitoKATP channels has not yet been clearly identified. Based upon this information, we set outto observe the changes of the percentage of brain water content, energy metabolism,mitochondrial ultrastructure, membrane fluidity of cerebral cortex and characterize theconsequences of different strategies with mitoKATP channel opener (diazoxide)and (or)mitoKATP channel inhibitor (5-HD) in a rat model of HIBD, so as to investigate theneuroprotective effect of KCO.Materials and Methods:A total of one hundred and ten SD newborn rats were randomly divided into five groups: Cgroup, HI group, KCO 1 group, KCO 2 group and KCI group. Sham operation rats serving ascontrol (n=22). Rats of the other four groups were subjected to hypoxic-ischemic brain damage,which was induced by permanent left carotid artery ligation followed by 8％O2 exposure for 2.5hours n=88). Diazoxide was administrated i.p. daily (3 times×3.8mg/kg) before surgery or aftersurgery .The percentage of brain water content, mitochondrial membrane fluidity, pathologicchanges and ATP, ADP and AMP concentration were measured at 72h after hypoxic-ischemicbrain damage.Results:The percentage of brain water content:The percentage of brain water content in each group: C group (left: 87.52±0.19; right: 87.52±0.30); HI group (left: 88.96±0.71; right: 87.72±0.50); KCO1 group (lett: 87.96±0.31; right: 87.65±0.24); KCO2 group (left: 88.89±0.46; right: 87.70±0.28); KCI group (left:88.39±0.70; right: 87.66±0.33). The percentage of brain water content was significantly higherafter HIBD compared with the C group .The brain water content in KCO1 group was higher thanthat in control group but lower than that in HI group. There were no significantly differencesbetween the KCO2 group, KCI group and HI group.The pathological changes:HE staining:Cells of cerebral cortex in the C group were in good order, and the construction of the cellswas complete. Brain edema and glial cell cann't be observed almost. In HI group the cells ofcerebral cortex had obviously decreased, some of which are necrotic. There was visibleinterstitial edema. Glial cells proliferated and large quantities of inflammatory cells infiltrated. InKCO1 group the quantity of cerebral cortex cells had not reduced obviously .The construction ofthe cells are complete. Only a few ischemic changes of the tissue could be seen. The KCO2group and KCI group had no significant changes compared with the HI group.Ultrastructure changes of mitochondria:In the control group the membrane of the mitochondria were complete and the cristae wereclear. In HI group the mitochondria had swelled and the cristae were disrupted, dissolved ordisappeared. In KCO1 group pretreated with diazoxide there was a recovery of injury caused byHIBD in neonatal rats. The KCO2 group and KCI group had no significant changes comparedwith the HI group.Mitochondrial membrane fluidity:After HIBD the microviscosity increased and the membrane fluidity of mitochondriadecreased. The membrane fluidity of the other four groups with HIBD decreased compared withthe C group (P＜0.01). The membrane fluidity of the KCO1 group increased compared with theHI group, KCI group and KCO2 group (P＜0.01). The KCO2 group and KCI group had nosignificant changes compared with the HI group (P＞0.05).Cerebral energy metabolism:After HIBD the ATP concentration of cerebral cortex in HI group, KCO1 group, KCO2group and KCI group decreased significantly compared with the C group (P＜0.01).There wereno significant difference in ATP concentration between the experimental group including HI group, KCO2 group and KCI group. In the KCO1 group pretreated with diazoxide, there was asignificant recovery of ATP concentration compared with that of HI group, KCO2 group andKCI group.The ADP concentration of cerebral cortex in HI group and KCI group decreased significantlycompared with the C group (P＜0.05). The ADP concentration in KCO1 group increasedsignificantly compared with the HI group, KCO2 group and KCI group. But there were nosignificant difference between C group and KCO1 group.Compared with the C group, there were a significant increase of AMP concentration in HIgroup and KCI group.The ECP decreased significantly in HI group, KCI group and KCO1 group compared with theC group. Compared with HI group, KCO2 group and KCI group, the ECP in KCO1 groupincreased significantly((P＜0.01).Conclusions:1. Pretreatment with KCO (diazoxide) improve the ischemic pathological changes of cerebralcortex and lighten brain edema after HIBD.2. Pretreatment with diazoxide improve the mitochondrial membrane fluidity, structuralintegrity and energy metabolism of cerebral cortex after HIBD.3. The protective effects of diazoxide were prevented by co-treatment with5-hydroxydecanoate, a mitoKATP channel antagonist, which indicates diazoxide affordedprotection via selective opening of mitoKATP channels.In a word, pretreatment with diazoxide has proved to be neuroprotective in a rat model ofHIBD, the mechanism of which may realized by protecting the structure and function ofmitochondrial. |
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