K-ATP channel openers facilitate glutamate uptake by GluTs in rat primary cultured Astrocytes

Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel openers(KCOs) have been proposed as potential neuroprotectants. Our previous studies demonstrated that K-ATP channels could regulate glutamate uptake activity in PC12 cells as well as in synaptosomes of rats. Since glutamate transporters(GluTs) of astrocytes play crucial roles in glutamate uptake and KATP channels are also expressed in astrocytes, the present study showed whether and how KATP channels regulated the function of GluTs in primary cultured astrocytes. The results showed that nonselective KCO pinacidil, selective mitochondrial KCO diazoxide, novel, and blood-brain barrier permeable KCO iptakalim could enhance glutamate uptake, except for the sarcolemmal KCO P1075. Moreover pinacidil, diazoxide, and iptakalim reversed the inhibition of glutamate uptake induced by 1-methyl-4-phenylpyridinium(MPP+). These potentiated effects were completely abolished by mitochondrial K-ATP blocker 5-hydroxydecanoate. Furthermore, either diazoxide or iptakalim could inhibit MPP+-induced elevation of reactive oxygen species (ROS) and phosphorylation of protein kinases C(PKC). These findings are the first to demonstrate that activation of K-ATP channel, especially mitochondrial K-ATP channel, improves the function of GluTs in astrocytes due to reducing ROS production and downregulating PKC phosphorylation. Therefore, the present study not only reveals a novel pharmacological profile of KCOs as regulators of GluTs, but also provides a new strategy for neuroprotection.     

红景天苷对体外培养大鼠海马神经元化学缺氧损伤ATP敏感性钾通道亚基表达的影响

目的研究红景天苷对大鼠海马神经元化学缺氧损伤的保护作用及机制。方法体外原代培养新生SD大鼠海马神经元并鉴定。以二氮嗪为阳性对照药,通过苏木精-伊红染色观察各实验组神经元形态,通过实时定量聚合酶链反应检测各实验组内向整流性钾通道受体6.2(Kir 6.2)、磺酰脲类受体1(SUR1)mRNA的表达差异,免疫细胞化学染色法检测各实验组Kir 6.2、SUR1蛋白质的表达差异。结果化学缺氧1 h,红景天苷各剂量组均可提高缺氧神经元存活率。与模型组比较,红景天苷各剂量组神经元Kir 6.2与SUR1 mRNA的表达量显著升高(P<0.01或P<0.05),Kir 6.2与SUR1蛋白表达也显著升高(P<0.01或P<0.05)。结论红景天苷通过上调化学缺氧神经元ATP敏感性钾通道亚基Kir 6.2、SUR1的表达对神经元起保护作用。