Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, 812-8582, Japan.
Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan.
Sci Rep. 2017 Jul 26;7(1):6528. doi: 10.1038/s41598-017-06636-8.
2-Oxoadenosine (2-oxo-Ado), an oxidized form of adenosine, is cytotoxic and induces growth arrest and cell death, which has potential as an anti-cancer drug. However, it is not well understood how 2-oxo-Ado exerts its cytotoxicity. We examined the effects of 2-oxo-Ado on non-tumour cells, namely immortalized mouse embryonic fibroblast lines, and investigated mechanisms by which 2-oxo-Ado exerts its cytotoxicity. We found that cell death induced by 2-oxo-Ado is classical caspase-dependent apoptosis, and requires its sequential intracellular phosphorylation catalysed by adenosine kinase (ADK) and adenylate kinase 2, resulting in intracellular accumulation of 2-oxo-ATP accompanied by accumulation of 2-oxo-Ado in RNA and depletion of ATP. Moreover, we showed that overexpression of MTH1, an oxidized purine nucleoside triphosphatase, prevents 2-oxo-Ado-induced cytotoxicity accompanied by suppression of accumulation of both intracellular 2-oxo-ATP and 2-oxo-Ado in RNA and recovery of ATP levels. We also found that 2-oxo-Ado activates the p38 MAPK pathway. However, siRNAs against Mkk3 and Mkk6, or treatment with several p38 MAPK inhibitors, except SB203580, did not prevent the cytotoxicity. SB203580 prevented intracellular phosphorylation of 2-oxo-Ado to 2-oxo-AMP, and an in vitro ADK assay revealed that SB203580 directly inhibits ADK activity, suggesting that some of the effects of SB203580 may depend on ADK inhibition.
2-氧代腺苷（2-氧代-Ado）是一种腺苷的氧化形式，具有细胞毒性，可诱导细胞生长停滞和死亡，有望成为一种抗癌药物。然而，2-氧代-Ado 如何发挥其细胞毒性作用还不太清楚。我们研究了 2-氧代-Ado 对非肿瘤细胞（即永生化的小鼠胚胎成纤维细胞系）的影响，并探讨了 2-氧代-Ado 发挥其细胞毒性的机制。我们发现，2-氧代-Ado 诱导的细胞死亡是经典的半胱天冬酶依赖性细胞凋亡，需要其顺序在细胞内被腺苷激酶（ADK）和腺苷酸激酶 2 磷酸化，导致 2-氧代-ATP 在细胞内积累，同时伴随着 RNA 中 2-氧代-Ado 的积累和 ATP 的耗竭。此外，我们表明，氧化嘌呤核苷三磷酸酶 MTH1 的过表达可防止 2-氧代-Ado 诱导的细胞毒性，同时抑制 RNA 中细胞内 2-氧代-ATP 和 2-氧代-Ado 的积累，并恢复 ATP 水平。我们还发现，2-氧代-Ado 激活 p38 MAPK 通路。然而，针对 Mkk3 和 Mkk6 的 siRNA，或用几种 p38 MAPK 抑制剂（除了 SB203580）处理，均不能防止细胞毒性。SB203580 可防止 2-氧代-Ado 在细胞内磷酸化为 2-氧代-AMP，体外 ADK 测定表明 SB203580 直接抑制 ADK 活性，表明 SB203580 的一些作用可能依赖于 ADK 抑制。
