Lobner D, Choi D W
Department of Neurology, Washington University School of Medicine, St Louis, Mo. 63110.
Stroke. 1994 Oct;25(10):2085-9; discussion 2089-90. doi: 10.1161/01.str.25.10.2085.
Adenosine transport inhibitors attenuate ischemic central neuronal damage in vivo, but the locus of this protective action is presently unknown. To help address the question of whether adenosine transport inhibitors have a protective effect directly on brain parenchyma, we tested the effect of the adenosine transport inhibitor dipyridamole on neuronal loss induced by oxygen-glucose deprivation in vitro.
Murine cortical cultures were exposed to combined oxygen and glucose deprivation, N-methyl-D-aspartate, or kainate. The extracellular concentrations of glutamate and adenosine were measured by high-performance liquid chromatography; neuronal cell death was assessed by morphological examination and measurement of lactate dehydrogenase release.
Cultures exposed to oxygen-glucose deprivation for 30 to 75 minutes exhibited an insult-dependent increase in extracellular adenosine, followed shortly by an increase in extracellular glutamate and 24 hours later by neuronal death. Addition of the A1 receptor antagonist 8-cyclopentyltheophylline during oxygen-glucose deprivation enhanced both glutamate release and neuronal damage. Addition of 10 mumol/L dipyridamole decreased extracellular adenosine and also enhanced extracellular glutamate and neuronal death. In contrast, dipyridamole increased the levels of extracellular adenosine stimulated by N-methyl-D-aspartate or kainate.
These results are consistent with the idea that endogenous adenosine has a neuroprotective effect directly on cortical cells exposed to oxygen-glucose deprivation. However, inhibition of adenosine transport with dipyridamole was surprisingly not an effective strategy for enhancing this protective effect. The beneficial effects of adenosine transport inhibitors observed in vivo may be mediated indirectly--for example, by effects on the vasculature.
腺苷转运抑制剂可减轻体内缺血性中枢神经元损伤，但目前这种保护作用的位点尚不清楚。为了探讨腺苷转运抑制剂是否对脑实质具有直接保护作用，我们在体外测试了腺苷转运抑制剂双嘧达莫对氧 - 葡萄糖剥夺诱导的神经元损失的影响。
将小鼠皮质培养物暴露于联合氧和葡萄糖剥夺、N - 甲基 - D - 天冬氨酸或谷氨酸钾中。通过高效液相色谱法测量细胞外谷氨酸和腺苷的浓度；通过形态学检查和乳酸脱氢酶释放量的测量评估神经元细胞死亡情况。
暴露于氧 - 葡萄糖剥夺30至75分钟的培养物中，细胞外腺苷随损伤程度增加，随后细胞外谷氨酸短暂增加，24小时后出现神经元死亡。在氧 - 葡萄糖剥夺期间添加A1受体拮抗剂8 - 环戊基茶碱可增强谷氨酸释放和神经元损伤。添加10μmol/L双嘧达莫可降低细胞外腺苷水平，但也会增强细胞外谷氨酸水平和神经元死亡。相反，双嘧达莫可增加由N - 甲基 - D - 天冬氨酸或谷氨酸钾刺激引起的细胞外腺苷水平。
这些结果与内源性腺苷对暴露于氧 - 葡萄糖剥夺的皮质细胞具有直接神经保护作用的观点一致。然而，令人惊讶的是，用双嘧达莫抑制腺苷转运并非增强这种保护作用的有效策略。在体内观察到的腺苷转运抑制剂的有益作用可能是间接介导的——例如，通过对脉管系统的作用。
