Chu Stephanie, Xiong Wei, Parkinson Fiona E
Department of Pharmacology and Therapeutics, University of Manitoba, A203-753 McDermot Avenue, Winnipeg, MB, R3E 0T6, Canada.
Purinergic Signal. 2014 Dec;10(4):603-9. doi: 10.1007/s11302-014-9421-8. Epub 2014 Aug 17.
ATP is a gliotransmitter released from astrocytes. Extracellularly, ATP is metabolized by a series of enzymes, including ecto-5'-nucleotidase (eN; also known as CD73) which is encoded by the gene 5NTE and functions to form adenosine (ADO) from adenosine monophosphate (AMP). Under ischemic conditions, ADO levels in brain increase up to 100-fold. We used astrocytes cultured from 5NTE (+/+) or 5NTE (-/-) mice to evaluate the role of eN expressed by astrocytes in the production of ADO and inosine (INO) in response to glucose deprivation (GD) or oxygen-glucose deprivation (OGD). We also used co-cultures of these astrocytes with wild-type neurons to evaluate the role of eN expressed by astrocytes in the production of ADO and INO in response to GD, OGD, or N-methyl-D-aspartate (NMDA) treatment. As expected, astrocytes from 5NTE (+/+) mice produced adenosine from AMP; the eN inhibitor α,β-methylene ADP (AOPCP) decreased ADO formation. In contrast, little ADO was formed by astrocytes from 5NTE (-/-) mice and AOPCP had no significant effect. GD and OGD treatment of 5NTE (+/+) astrocytes and 5NTE (+/+) astrocyte-neuron co-cultures produced extracellular ADO levels that were inhibited by AOPCP. In contrast, these conditions did not evoke ADO production in cultures containing 5NTE (-/-) astrocytes. NMDA treatment produced similar increases in ADO in both 5NTE (+/+) and 5NTE (-/-) astrocyte-neuron co-cultures; dipyridamole (DPR) but not AOPCP inhibited ADO production. These results indicate that eN is prominent in the formation of ADO from astrocytes but in astrocyte-neuron co-cultures, other enzymes or pathways contribute to rising ADO levels in ischemia-like conditions.
三磷酸腺苷（ATP）是一种从星形胶质细胞释放的神经胶质递质。在细胞外，ATP被一系列酶代谢，包括外切5'-核苷酸酶（eN；也称为CD73），其由基因5NTE编码，功能是从单磷酸腺苷（AMP）形成腺苷（ADO）。在缺血条件下，脑内的ADO水平可增加至100倍。我们使用从5NTE（+/+）或5NTE（-/-）小鼠培养的星形胶质细胞来评估星形胶质细胞表达的eN在响应葡萄糖剥夺（GD）或氧-葡萄糖剥夺（OGD）时对ADO和肌苷（INO）产生的作用。我们还使用这些星形胶质细胞与野生型神经元的共培养物来评估星形胶质细胞表达的eN在响应GD、OGD或N-甲基-D-天冬氨酸（NMDA）处理时对ADO和INO产生的作用。正如预期的那样，5NTE（+/+）小鼠的星形胶质细胞从AMP产生腺苷；eN抑制剂α,β-亚甲基二磷酸腺苷（AOPCP）减少了ADO的形成。相比之下，5NTE（-/-）小鼠的星形胶质细胞几乎不形成ADO，且AOPCP没有显著影响。对5NTE（+/+）星形胶质细胞和5NTE（+/+）星形胶质细胞-神经元共培养物进行GD和OGD处理后产生的细胞外ADO水平受到AOPCP的抑制。相比之下，这些条件在含有5NTE（-/-）星形胶质细胞的培养物中并未引起ADO的产生。NMDA处理在5NTE（+/+）和5NTE（-/-）星形胶质细胞-神经元共培养物中均使ADO产生类似的增加；双嘧达莫（DPR）而非AOPCP抑制了ADO的产生。这些结果表明，eN在星形胶质细胞形成ADO的过程中起主要作用，但在星形胶质细胞-神经元共培养物中，其他酶或途径在类似缺血的条件下导致ADO水平升高。
