The roles of aquaporin-4 in brain edema following neonatal hypoxia ischemia and reoxygenation in a cultured rat astrocyte model
The roles of aquaporin-4 in brain edema following neonatal hypoxia ischemia and reoxygenation in a cultured rat astrocyte model
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作者：
Fu, Xuemei;Li, Qiuping;Mu, Dezhi
水通道蛋白4（AQP 4）是一种水通道蛋白，在星形胶质细胞中大量表达，在脑水肿的发生发展中起关键作用。然而，目前尚不清楚AQP 4是否有助于缺氧缺血（HI）星形胶质细胞肿胀。为了研究AQP 4在HI和复氧过程中星形胶质细胞肿胀中的作用，我们测定了培养的大鼠星形胶质细胞在HI和复氧后AQP 4的表达和星形胶质细胞体积。RNA干扰用于敲低AQP 4表达（AQP 4（-/-））。实时荧光定量PCR和Western blot检测AQP 4的抑制效率。我们发现，与野生型AQP 4（AQP 4（+/+））表达相比，AQP 4 siRNA转染（AQP 4（-/-））后星形胶质细胞中AQP 4 mRNA和蛋白的最大抑制分别为-77%和85%。与常氧培养的星形胶质细胞相比，缺氧缺血时AQP 4-/-和AQP 4 +/+星形胶质细胞的体积均显著增加（P < 0.05）。而AQP 4-/-星形胶质细胞HI时的细胞体积明显小于AQP 4 +/+星形胶质细胞（P < 0.05）。复氧后，AQP 4-/-星形胶质细胞的细胞体积在第7天逐渐降低至对照水平，但AQP 4 +/+星形胶质细胞在第5天逐渐降低至对照水平。AQP 4在HI和复氧过程中的不同作用表明，AQP 4敲低可能在HI过程中防止星形胶质细胞肿胀形成中的水流入，也可能在复氧过程中延迟星形胶质细胞肿胀消退中的水清除。总之，AQP 4介导HI和复氧过程中水在星形胶质细胞中的双向运输。在新生儿缺氧缺血性脑水肿的不同阶段，AQP 4的调控可能成为一种新的治疗策略。(C)2007 Wiley-Liss，Inc.
Aquaporin-4 (AQP4), a water channel protein, is abundantly expressed in astrocytes and plays a key role in the development of brain edema. However, it is not clear whether AQP4 contributes to astrocytic swelling in hypoxia-ischemia (HI). To investigate the roles of AQP4 in astrocytic swelling during HI and reoxygenation, we measured AQP4 expression and astrocytic cellular volume in cultured rat astrocytes following HI and reoxygenation. RNA interference was used to knockdown AQP4 expression (AQP4(-/-)). Real-time polymerase chain reaction and Western blot analysis were used to detect the inhibitory efficiency of AQP4. We found that the maximal inhibition of AQP4 mRNA and protein in astrocytes after AQP4 siRNA transfection (AQP4(-/-)) was -77 and 85%, respectively, compared to wild-type AQP4 (AQP4(+/+)) expression. Cellular volume in both AQP4-/- and AQP4+/+ astrocytes was significantly increased during HI compared to cells cultured in normoxia (P < 0.05). However, cellular volume during HI in AQP4-/- astrocytes was significantly less than that in AQP4+/+ astrocytes (P < 0.05). After reoxygenation, the cellular volume gradually decreased to control levels at 7 days in AQP4-/- but at 5 days in AQP4+/+ astrocytes. The different roles of AQP4 during HI and reoxygenation suggest that AQP4 knockdown may protect against water influx in the formation of astrocyte swelling during HI, and may also delay water clearance in the resolution of astrocyte swelling during reoxygenation. In conclusion, AQP4 mediates bidirectional transport of water across astrocytes during HI and reoxygenation. AQP4 manipulation may serve as a novel therapeutic strategy during different periods of hypoxic-ischemic brain edema in neonates. (C) 2007 Wiley-Liss, Inc.