Castro Maite A, Pozo Miguel, Cortés Christian, García María de Los Angeles, Concha Ilona I, Nualart Francisco
Instituto de Bioquímica, Facultad de Ciencias Biológicas, Universidad Austral de Chile, Valdivia, Chile.
J Neurochem. 2007 Aug;102(3):773-82. doi: 10.1111/j.1471-4159.2007.04631.x.
It has been demonstrated that glutamatergic activity induces ascorbic acid (AA) depletion in astrocytes. Additionally, different data indicate that AA may inhibit glucose accumulation in primary cultures of rat hippocampal neurons. Thus, our hypothesis postulates that AA released from the astrocytes during glutamatergic synaptic activity may inhibit glucose uptake by neurons. We observed that cultured neurons express the sodium-vitamin C cotransporter 2 and the facilitative glucose transporters (GLUT) 1 and 3, however, in hippocampal brain slices GLUT3 was the main transporter detected. Functional activity of GLUTs was confirmed by means of kinetic analysis using 2-deoxy-d-glucose. Therefore, we showed that AA, once accumulated inside the cell, inhibits glucose transport in both cortical and hippocampal neurons in culture. Additionally, we showed that astrocytes are not affected by AA. Using hippocampal slices, we observed that upon blockade of monocarboxylate utilization by alpha-cyano-4-hydroxycinnamate and after glucose deprivation, glucose could rescue neuronal response to electrical stimulation only if AA uptake is prevented. Finally, using a transwell system of separated neuronal and astrocytic cultures, we observed that glutamate can reduce glucose transport in neurons only in presence of AA-loaded astrocytes, suggesting the essential role of astrocyte-released AA in this effect.
已经证明，谷氨酸能活性会导致星形胶质细胞中的抗坏血酸（AA）消耗。此外，不同的数据表明，AA可能会抑制大鼠海马神经元原代培养物中的葡萄糖积累。因此，我们的假设推测，在谷氨酸能突触活动期间从星形胶质细胞释放的AA可能会抑制神经元对葡萄糖的摄取。我们观察到，培养的神经元表达钠-维生素C共转运体2以及易化性葡萄糖转运体（GLUT）1和3，然而，在海马脑片中，检测到的主要转运体是GLUT3。通过使用2-脱氧-D-葡萄糖的动力学分析证实了GLUTs的功能活性。因此，我们表明，AA一旦在细胞内积累，就会抑制培养的皮质和海马神经元中的葡萄糖转运。此外，我们表明星形胶质细胞不受AA的影响。使用海马脑片，我们观察到，在用α-氰基-4-羟基肉桂酸阻断单羧酸利用后以及在葡萄糖剥夺后，只有在防止AA摄取的情况下，葡萄糖才能挽救神经元对电刺激的反应。最后，使用分离的神经元和星形胶质细胞培养物的Transwell系统，我们观察到，只有在存在负载AA的星形胶质细胞的情况下，谷氨酸才能降低神经元中的葡萄糖转运，这表明星形胶质细胞释放的AA在这种效应中起着至关重要的作用。
