摘要
Abstract
BACKGROUND:At present, there are a number of reports about preconditioning inducing cerebral ischemia tolerance and itspossible mechanism,such as ischemic pretreatment, inhalation of oxygen, acupuncture and isoflurane preconditioning.Someoverseas studies have confirmed that tumor necrosis factor-α(TNF-α) can induce cerebral ischemic tolerance, but its exact mechanism has not been elucidated. So far, the effect of TNF-α pretreatment on cerebral ischemia-reperfusion injury in rats and its mechanism remain unclear .OBJECTIVE: To probe into the effect of TNF-α pretreatment on cerebral ischemia-reperfusion injury in rats and its possible mechanism.DESIGN: A completely randomised and case-controlled study.SETTING and MATERIALS : Our experiment was conducted in the Animal Experiment Center of the Second Affiliated Hospital, Harbin Medical University. Materials: Sixty healthy male Wistar rats, weighing 200 g to 300 g,wererandomly divided into 4 groups, namely, TNF-α 0. 05 μg group, 0. 5 μg group, 1.0μg group and control group, with 15 in each group. The experimental animals were supplied by the Animal Experiment Center of the Second Hospital of Harbin Medical University; microsurgical appliances, 25 Μl syringe and arteriole clampspurchased from Yixin Medical Appliances Co.Shanghai; fishing thread made in Japan(0. 17mm in diameter); thermostat;digital camera; computer-assisted image analyzing system made by Beijing Aeronautic and Space University; PBS; recombined rat TNF-α(purchased from Sigma, the U. S.), CD54 and GFAP kit, their second antibody, and DAB immunohistochemical kit bought from Wuhan Boster Biological Engineering Co., Ltd; 10 g/L triphenyltetrazolium chloride saline solution (TTC), and other materials for routine laboratory use.INTERVENTIONS: Rat focal brain ischemia model(occluding middle cerebral artery of the rats) was made by using modified inserting thread method. Different doses of TNF-α(0.05 μg, 0.5 μg and 1.0 μg) or PBS (control group) was injected intracisternally 48 hours before ischemia. After 2-hour ischemia followed by 22-hour reperfusion, the rats were killed.MAIN OUTCOME MEASURES: The percentage of cerebral infarction volume was measured, pathological change was observed,glial fibrillary acidic protein (GFAP)and intercellular adhesion molecule-1(ICAM-1)expressions were inspected by immunohistochemistry.RESULTS: Compared with control group, TNF-α 0. 05 μg group displayed no difference( P > 0.05, percentage of cerebral infarction volume t = 1.52,ischemic hemisphere GFAP t = 0.93, ICAM-1 t = 0.82), TNF-α 0. 5 μg and 1.0 μg groups showed reduced volume of lesion( P <0. 001, t = 18.76for 0. 5 μg group and t = 13.44 for1. 0 μg group), lessened degeneration and necrosis of the cerebral tissues, less GFAP(both P <0. 001, t =5.82for 0.5 μg group and t =6. 84 for 1.0 μg group) and ICAM-1 expression (both P < 0.001, t=6.80 for 0.5 μg group and t=7.08 for 1.0 μg group) in the ischemic hemisphere.CONCLUSION: TNF-α can induce cerebral ischemic tolerance and the effect is not related to repair of astrocytes, but related to the down-regulation of ICAM-1 expression and lessened inflammation after reperfusion. Moreover, this effect is dose-dependent.关键词
脑缺血/再灌注损伤/肿瘤坏死因子分类
医药卫生
