Ghrelin对脑缺血再灌注大鼠脑水肿和水通道蛋白4表达的影响

 目的： 探讨ghrelin对脑缺血再灌注大鼠脑水肿、血脑屏障通透性及水通道蛋白4（AQP4）表达的影响。方法： 成年SD雄性大鼠随机分为3组:sham组、大脑中动脉阻塞（MCAO）组和ghrelin处理组。采用线栓法复制MCAO模型（缺血2 h,再灌注22 h）。Ghrelin组大鼠于再灌开始时经股静脉注射ghrelin 10 nmol/kg。TTC染色观察脑梗死体积，神经功能评分判断脑功能障碍程度，分别以体积计算和干湿重法检测脑肿胀程度和脑含水量的变化，收集脑血管外伊文思蓝(EB)来评估血脑屏障的破坏程度，免疫组化和Western blotting检测AQP4的表达变化。结果： 与MCAO组比较，ghrelin处理组的脑梗死体积较小（P<0.01），神经功能评分较低（P<0.01），脑组织中的EB渗出量较少（P<0.01）。Ghrelin处理组大鼠的脑肿胀体积、脑含水量和AQP4表达明显低于MCAO组（P<0.05）。结论： Ghrelin减轻大鼠脑缺血/再灌注损伤，减轻脑水肿和血脑屏障的破坏，抑制脑组织中AQP4的表达。AQP4在ghrelin的脑保护机制中可能发挥重要作用。

Effects of ghrelin on the brain edema and expression of aquaporin 4 after cerebral ischemia /reperfusion in rat

ABSTRACT] AIM: To explore the effects of ghrelin on the brain edema, permeability of blood-brain barrier(BBB)and expression of water channel aquaporin-4 (AQP4) after cerebral ischemia /reperfusion in rat. METHODS: Adult male Sprague–Dawley rats were randomly divided into three groups,ie.,sham operation group, middle cerebral artery occlusion(MCAO)group and ghrelin treatment group. The MCAO was made with nylon thread for 2h occlusion following 22h reperfusion. Ghrelin(10 nmol/kg) was injected from femoral vein at the beginning of the reperfusion. The cerebral infarct volume were detected by 2,3,5-Triphenyltetrazolium chloride (TTC) staining. Brain functional deficits were evaluated by neurological scores. The changes of brain swelling and water content were measured through volume calculations and dry- wet weight methods. The permeability of blood-brain barrier (BBB) was detected by collecting extravascular Evans Blue (EB) in the brain cortex. The AQP4 expression changes were assessed by immunohistochemistry and Western blotting method. RESULTS: Comparing with the MCAO group, ghrelin treatment group had smaller brain infarct volume（P<0.01）, lower EB exudation content（P<0.01）and neurological scores（P<0.01）. The percentage of brain swelling , water content and AQP4 expression were decreased in ghrelin treatment group than MCAO group（P<0.05）. CONCLUSION: Ghrelin induced the injury of cerebral ischemia / reperfusion, and lightened the brain edema and damage of the blood brain barrier in rat. Ghrelin also inhibited the expression of AQP4 in brain tissue. We speculate that the AQP4 may exert an important role in the neuroprotective mechanism of ghrelin.