Hyperglycemia reduces functional expression of astrocytic Kir4.1 channels and glial glutamate uptake.
Hyperglycemia reduces functional expression of astrocytic Kir4.1 channels and glial glutamate uptake.
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DOI：
10.1016/j.neuroscience.2015.09.044
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发表时间：
2015-12-03
期刊：
影响因子：
3.3
通讯作者：
Eaton MJ
中科院分区：
文献类型：
--
作者：
Rivera-Aponte DE;Méndez-González MP;Rivera-Pagán AF;Kucheryavykh YV;Kucheryavykh LY;Skatchkov SN;Eaton MJ
糖尿病患者有许多严重的健康并发症的风险，包括癫痫的发病率增加和缺血性中风后恢复较差。星形胶质细胞通过谷氨酸摄取和钾缓冲来维持细胞外稳态和防止神经毒性，在保护神经元中起关键作用。星形胶质细胞膜中钾通道（例如Kir4.1内向整流钾通道）的存在有助于这些功能。本研究的目的是确定高血糖是否改变星形胶质细胞Kir4.1钾通道的表达和稳态功能。我们使用q-PCR，蛋白质印迹，膜片钳电生理学研究电压和钾阶跃响应和比色谷氨酸清除试验，以评估Kir4.1通道水平和稳态功能的星形胶质细胞生长在正常和高糖条件。我们发现，星形胶质细胞生长在高葡萄糖（25 mM）有一个约50%的减少Kir4.1 mRNA和蛋白质的表达相比，生长在正常的葡萄糖（5 mM）。这些降低发生在暴露于高血糖的4至7天内，而逆转发生在恢复正常葡萄糖后的7至14天。使用钡阻断Kir通道证实了星形胶质细胞膜中功能性Kir通道的减少。在存在100 μm钡的情况下，从星形胶质细胞记录的响应于电压阶跃的电流减少了45%。此外，在高葡萄糖中生长的星形胶质细胞中，通过将细胞外[K+]o从3 mM增加到10 mM（反映钾的摄取）诱导的内向电流减少了50%。此外，在高葡萄糖条件下生长的星形胶质细胞对谷氨酸的清除能力明显受损。总之，我们的研究结果表明，下调星形胶质细胞Kir4.1通道的葡萄糖升高可能有助于糖尿病诱导的中枢神经系统疾病的基础病理生理学，并有助于中风后的不良预后。
Diabetics are at risk for a number of serious health complications including an increased incidence of epilepsy and poorer recovery after ischemic stroke. Astrocytes play a critical role in protecting neurons by maintaining extracellular homeostasis and preventing neurotoxicity through glutamate uptake and potassium buffering. These functions are aided by the presence of potassium channels, such as Kir4.1 inwardly rectifying potassium channels, in the membranes of astrocytic glial cells. The purpose of the present study was to determine if hyperglycemia alters Kir4.1 potassium channel expression and homeostatic functions of astrocytes. We used q-PCR, Western blot, patch-clamp electrophysiology studying voltage and potassium step responses and a colorimetric glutamate clearance assay to assess Kir4.1 channel levels and homeostatic functions of astrocytes grown in normal and high glucose conditions. We found that astrocytes grown in high glucose (25 mM) had an approximately 50% reduction in Kir4.1 mRNA and protein expression as compared with those grown in normal glucose (5 mM). These reductions occurred within 4 to 7 days of exposure to hyperglycemia, whereas reversal occurred between 7 to 14 days after return to normal glucose. The decrease in functional Kir channels in the astrocytic membrane was confirmed using barium to block Kir channels. In the presence of 100 μm barium, the currents recorded from astrocytes in response to voltage steps were reduced by 45%. Furthermore, inward currents induced by stepping extracellular [K+]o from 3 to 10 mM (reflecting potassium uptake) were 50% reduced in astrocytes grown in high glucose. In addition, glutamate clearance by astrocytes grown in high glucose was significantly impaired. Taken together, our results suggest that down-regulation of astrocytic Kir4.1 channels by elevated glucose may contribute to the underlying pathophysiology of diabetes-induced CNS disorders and contribute to the poor prognosis after stroke.