NITRIC-OXIDE GENERATION DURING CELLULAR METABOLIZATION OF THE DIABETOGENIC N-METHYL-N-NITROSO-UREA STREPTOZOTOZIN CONTRIBUTES TO ISLET-CELL DNA-DAMAGE
NITRIC-OXIDE GENERATION DURING CELLULAR METABOLIZATION OF THE DIABETOGENIC N-METHYL-N-NITROSO-UREA STREPTOZOTOZIN CONTRIBUTES TO ISLET-CELL DNA-DAMAGE
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DOI：
10.1515/bchm3.1995.376.3.179
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发表时间：
1995-03-01
期刊：
影响因子：
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通讯作者：
KOLBBACHOFEN, V
中科院分区：
文献类型：
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作者：
KRONCKE, KD;FEHSEL, K;KOLBBACHOFEN, V
N-甲基-N-亚硝基-尿素链脲是一种具有糖尿病、致癌和抗肿瘤活性的抗生素，被认为是通过DNA和蛋白质的烷基化作用而发挥作用的。有证据表明，链脲佐菌素释放出生物活性的一氧化氮(NO)是该药物的另一种细胞毒活性。在这里，我们的EPR波谱表明，NO不是在链脲佐菌素的自发衰变过程中产生的，但它在大鼠肝细胞和胰岛细胞中的代谢产生了NO。这种一氧化氮的生成不是由于一氧化氮合酶的活性，因为在链脲佐菌素存在的情况下，肝细胞中的一氧化氮的生成不会被一氧化氮合酶抑制剂N-G-甲基-L-精氨酸所阻断。在链脲佐菌素处理的细胞中，通过iNOS特异性RT-PCR未获得特异性m RNA的阳性信号，证明iNOS活性在细胞分离过程中不被诱导，也不是NO释放的原因，此外，在细胞内NO清除剂的存在下，SZ和NO供体硝普钠诱导的早期DNA链断裂都显著减少。相反，与纯粹的烷化剂甲烷磺酸孵育后发现的DNA损伤并不被NO陷阱所抑制，这些结果证明了NO在细胞内降解SZ的过程中发生在细胞内。这种NO似乎在链脲佐菌素诱导的细胞毒性中起着重要作用。
The N-methyl-N-nitroso-urea streptozotocin is an antibiotic with diabetogenic, carcinogenic and antitumor activity thought to act via alkylation of DNA and proteins. Evidence points to a release of bioactive nitric oxide (NO) from streptozotocin as an additional cytotoxic activity of this drug. Here we show by EPR spectroscopy, that NO is not generated during spontaneous decay of streptozotocin but that its metabolization in rat hepatocytes and pancreatic islet cells yields NO. This NO formation is not due to a NO synthase (NOS) activity since NO formation in hepatocytes in the presence of streptozotocin is not blocked by the NOS inhibitor N-G-methyl-L-arginine. By iNOS-specific RT-PCR no positive signal for specific m RNA presence was obtained in streptozotocin-treated cells, proving that iNOS activity was not induced during cell isolation procedures and did not account for the NO release, Furthermore, early DNA-strand breaks induced either by SZ or by the NO donor nitroprusside were both significantly reduced in the presence of an intracellular NO scavenger. In contrast, DNA damage found after incubation with the purely alkylating agent methyl-methanesulfonate was not inhibited by the NO trap, These results prove that intracellular formation of NO occurs during degradation of SZ within cells. This NO appears to contribute significantly to streptozotocin-induced cytotoxicity.