Ali Ahmer, Konakondla Sanjay, Zwagerman Nathan T, Peng Changya, Schafer Steven, Ding Jamie Y, Dornbos David, Sikharam Chaitanya, Geng Xiaokun, Guthikonda Murali, Kreipke Christian W, Rafols José A, Ding Yuchuan
Wayne State University, School of Medicine, Detroit, MI 48201, USA.
Neurol Res. 2012 Jun;34(5):462-8. doi: 10.1179/1743132812Y.0000000014. Epub 2012 Mar 20.
Traumatic brain injury (TBI) induces brain edema via water and glycerol transport channels, called aquaporins (AQPs). The passage of glycerol across brain cellular compartments has been shown during edema. Using a modified impact/head acceleration rodent model of diffuse TBI, we assessed the role of hypoxia inducible factor (HIF)-1alpha in regulating AQP9 expression and glycerol accumulation during the edema formation. Adult (400-425 g) male Sprague-Dawley rats received a closed head injury with a weight drop (450 g, 2-m height) and were allowed to survive up to 48 hours. Some rat groups were administered 2-methoxyestradiol (2ME2, a HIF-1alpha inhibitor) 30 minutes after injury and were euthanized at 4 and 24 hours after injury. Brain edema was measured directly by water content, and glycerol concentration was determined by the Cayman Glycerol Assay. HIF-1alpha and AQP9 protein levels were assessed by Western immunoblotting. This study demonstrated a significant (P<0·05) increase in brain water content at 4-48 hours following impact. Cerebral glycerol was significantly (P<0.05) up-regulated at as early as 1 hour and remained at high levels for up to 48 hours. Similarly, significant (P<0.05) increases in HIF-1alpha and AQP9 protein levels were found at 1 hour and up to 48 hours after injury. Compared to untreated but injured rats, inhibition of HIF-1alpha by 2ME2 significantly (P<0.05) reduced the TBI-induced AQP9 up-regulation. This reduction was temporally associated with significant (P<0.05) decreases in both edema and glycerol accumulation. The data suggested an associated induction of HIF-1alpha, AQP9, and extracellular glycerol accumulation in edema formation following diffuse TBI. The implication of HIF-1alpha and AQP9 underlying TBI-induced edema formation offers possibilities for novel TBI therapies.
创伤性脑损伤（TBI）通过水通道蛋白（AQPs）这种水和甘油转运通道诱发脑水肿。在脑水肿期间，甘油已被证明可穿过脑的细胞区室。我们使用改良的弥漫性TBI撞击/头部加速啮齿动物模型，评估了缺氧诱导因子（HIF）-1α在脑水肿形成过程中调节水通道蛋白9（AQP9）表达和甘油蓄积的作用。成年（400 - 425克）雄性Sprague-Dawley大鼠接受重物下落（450克，2米高度）所致的闭合性颅脑损伤，并使其存活长达48小时。一些大鼠组在受伤后30分钟给予2-甲氧基雌二醇（2ME2，一种HIF-1α抑制剂），并在受伤后4小时和24小时实施安乐死。通过含水量直接测量脑水肿，并通过开曼甘油测定法测定甘油浓度。通过蛋白质免疫印迹法评估HIF-1α和AQP9蛋白水平。本研究表明，撞击后4 - 48小时脑含水量显著（P<0.05）增加。早在1小时时脑甘油就显著（P<0.05）上调，并在长达48小时内保持在高水平。同样，在受伤后1小时至48小时发现HIF-1α和AQP9蛋白水平显著（P<0.05）增加。与未治疗但受伤的大鼠相比，2ME2对HIF-1α的抑制显著（P<0.05）降低了TBI诱导的AQP9上调。这种降低在时间上与水肿和甘油蓄积的显著（P<0.05）减少相关。数据表明，弥漫性TBI后水肿形成过程中HIF-1α、AQP9和细胞外甘油蓄积存在关联诱导。HIF-1α和AQP9在TBI诱导的水肿形成中的作用为新型TBI治疗提供了可能性。
