Effects Of Intro-ventricle Hypothermia On Neurons Apoptosis And P53 Gene Expression In Rabbit Model Of Cerebral Ischemia

ObjectiveBrain ischemia is commonly found in arterial vasospasm secondary to subarachnoid hemorrhage,by brain injury and during temporary occlusion of arteries during neurovascular procedures.Despite attempts of using many strategies/the results of treatment for cerebral stroke are not ever satisfactory. The severity of brain lesion depends on the duration of ischemia,on the vessel occluded and on collateral circulation. Several studies aiming better understanding of the ischemia/reperfusion pathophysiology and the improvement of brain protection in these phenomena have been done.In human being,these studies are generally clinical evaluations and image examinations that not allow detection of early cellular phenomena secondary to ischemia/reperfusion.Ex-perimental models have the advantage of better control of biological variable and allow the use of more accurate methods for measure and evaluation of results. The main disadvantage is the difficult to transfer the findings from the laboratory to human beings.Among the maneuvers used for brain protection,hypothermia is outstanding. Its mechanism of action is not completely understood,but it should be multifactorial.The effect of deep hypothermia was demonstrated in experimental studies,nevertheless,it is associated with severe side effects.Mild to moderated hypothermia has been demonstrated to have neuroprotective effect, without severe side effects.Presently,mild sub-hypothermia is widely used in antiapoptosis treatments.The mechanisms of the cerebral protection effects of sub-hypotherm ia including: 1 .reducing cerebral metabolisms,maintaining cerebral blood supply and the energy balance of brain;2.protecting blood-brain barrier, reducing vasogenic cerebral edema;3. restraining the releasing of neurotransmitters;4.reducing intracellular accumulation of Ca²⁺, weaking the linkage between free radicals and lipid oxidation;6.reducing the destruction of cerebral protein,promoting the recovery of both structure and function of brain;7.reducing other endogenous toxic products.Some researchers revealed that sub-hypothermia might alleviate cerebral edema in acute cerebral ischemia patients, depressing intracranial pressure and protecting neurons from apoptosis.IVH(intro—ventricle hypothermia) is a new technique to obtain hypothermia. As a technique of SBC(selective brain cooling), IVH is a easy to operate and it has little complications.As it has not been reported before,in our study, IVH is applying to rabbit model of acute cerebral ischemia to investigate the effect of IVH in rabbit model of ACI(acute cerebral ischemia) by observing the animals' behaviors and the cell apoptosis and the expression level of p53 in the region surrounding the cerebral artery obstruction.The rabbit is an adequate model for the study of temporary focal ischemia similar to situations finding in the human being. We did not find studies demonstrating the possible neuroprotective effect of the hypothermia on focal ischemia in rabbits.MethodsTotal 24 adult male rabbits(2.9±0.3kg,age of 4～6 months) are divided into two groups randomly.Animals(fasted for 12 hours,no water deprivations) were generally anesthetized with urethane and half dose were given in anesthesia maintenance. The rabbit model of middle cerebral artery obstruction is made by intraluminal thread approach for 24 hours. Then a double cavities ventricle tube was punctured into the left lateral ventricle,20℃physiological brine was dropped into the lateral ventricle in IVH group and 38℃in normothermic group.2 hours later,removed the tube and suture the skin.24 hours later,the animals' behaviors were observed,and then,the brains were removed and fixed in 4% paraformaldehyde.TTC staining,TUNEL staining and p53 testing were pursued 72 hours later. The numbers of positive cells of TUNEL staining and p53 testing were counted from at least five random fields(×400) within the region adjacent to the ischemic core for each animal. The data were analyzed by using SPSS 12.0 software. T test was used in comparing different groups with the same index and P<0.05 indicates statistical difference.ResultsThe animals in intro-ventricle hypothermia group have higher performance score(8 in the normal temperature group have complete paralysis of right limb,3 can crawl and 1 can jump.7 in the hypothermia group can crawl, 3 can jump and 2 have complete paralysis of right limb. ),smaller infarction volume,fewer apoptosis cells around the ischemic core and lower p53 gene expression compared with those of normal temperature group.ConclusionThe neuroprotective mechanisms of hypothermia include p53 gene expression and intro-ventricle hypothermia approach is a novel method of treating acute cerebral ischemia,which merits further investigation.