Centre of Ophthalmology and Vision Sciences, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
Neuroscience. 2012 Sep 6;219:23-32. doi: 10.1016/j.neuroscience.2012.05.056. Epub 2012 May 29.
Diabetic retinopathy and diabetic encephalopathy are two common complications of diabetes mellitus. The impairment of glutamatergic neurotransmission in the retina and hippocampus has been suggested to be involved in the pathogenesis of these diabetic complications. In this study, we investigated the effect of elevated glucose concentration and diabetes on the protein content and surface expression of AMPA receptor subunits in the rat retina and hippocampus. We have used two models, cultured retinal and hippocampal cells exposed to elevated glucose concentration and an animal model of streptozotocin-induced type 1 diabetes. The immunoreactivity of GluA1, GluA2 and GluA4 was evaluated by Western blot and immunocytochemistry. The levels of these subunits at the plasma membrane were evaluated by biotinylation and purification of plasma membrane-associated proteins. Elevated glucose concentration increased the total levels of GluA2 subunit of AMPA receptors in retinal neural cells, but not of the subunits GluA1 or GluA4. However, at the plasma membrane, elevated glucose concentration induced an increase of all AMPA receptor subunits. In cultured hippocampal neurons, elevated glucose concentration did not induce significant alterations in the levels of AMPA receptor subunits. In the retinas of diabetic rats there were no persistent changes in the levels of AMPA receptor subunits comparing to aged-matched control retinas. Also, no consistent changes were detected in the levels of GluA1, GluA2 or GluA4 in the hippocampus of diabetic rats. We demonstrate that elevated glucose concentration induces early changes in AMPA receptor subunits, mainly in GluA2 subunit, in retinal neural cells. Conversely, hippocampal neurons seem to remain unaffected by elevated glucose concentration, concerning the expression of AMPA receptors, suggesting that AMPA receptors are more susceptible to the stress caused by elevated glucose concentration in retinal cells than in hippocampal neurons.
糖尿病性视网膜病变和糖尿病性脑病是糖尿病的两种常见并发症。谷氨酸能神经递质传递在视网膜和海马中的损伤被认为参与了这些糖尿病并发症的发病机制。在这项研究中，我们研究了高血糖浓度和糖尿病对大鼠视网膜和海马中 AMPA 受体亚基的蛋白含量和表面表达的影响。我们使用了两种模型，即暴露于高血糖浓度的培养的视网膜和海马细胞以及链脲佐菌素诱导的 1 型糖尿病动物模型。通过 Western blot 和免疫细胞化学评估 GluA1、GluA2 和 GluA4 的免疫反应性。通过生物素化和质膜相关蛋白的纯化评估这些亚基在质膜上的水平。高血糖浓度增加了视网膜神经细胞中 AMPA 受体的 GluA2 亚基的总水平，但不增加 GluA1 或 GluA4 亚基。然而，在质膜上，高血糖浓度诱导所有 AMPA 受体亚基的增加。在培养的海马神经元中，高血糖浓度没有引起 AMPA 受体亚基水平的显著变化。与年龄匹配的对照视网膜相比，糖尿病大鼠的视网膜中 AMPA 受体亚基的水平没有持续变化。此外，在糖尿病大鼠的海马中也没有检测到 GluA1、GluA2 或 GluA4 水平的一致变化。我们证明，高血糖浓度主要在 GluA2 亚基中诱导视网膜神经细胞中 AMPA 受体亚基的早期变化。相反，海马神经元似乎不受高血糖浓度表达 AMPA 受体的影响，这表明 AMPA 受体对视网膜细胞中高血糖浓度引起的应激比海马神经元更敏感。
