The Potent and Novel Thiosemicarbazone Chelators Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone and 2-Benzoylpyridine-4,4-dimethyl-3-thiosemicarbazone Affect Crucial Thiol Systems Required for Ribonucleotide Reductase Activity
The Potent and Novel Thiosemicarbazone Chelators Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone and 2-Benzoylpyridine-4,4-dimethyl-3-thiosemicarbazone Affect Crucial Thiol Systems Required for Ribonucleotide Reductase Activity
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DOI：
10.1124/mol.111.071324
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发表时间：
2011-06-01
影响因子：
3.6
通讯作者：
Richardson, Des R.
中科院分区：
文献类型：
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作者：
Yu, Yu;Rahmanto, Yohan Suryo;Richardson, Des R.
二-2-吡啶酮-4，4-二甲基-3-缩氨基硫脲具有较强的选择性抗肿瘤活性。其细胞毒性归因于铁螯合作用，导致抑制含铁酶核糖核苷酸还原酶（RR）。缩氨基硫脲铁配合物已被证明是氧化还原活性，但其对细胞抗氧化系统的影响尚不清楚。使用各种抗氧化剂，我们发现，只有N-乙酰半胱氨酸显着抑制缩氨基硫脲诱导的抗增殖活性。因此，我们研究了缩氨基硫脲对主要含巯基系统的影响，考虑到它们在为RR提供还原当量方面的关键参与。缩氨基硫脲显著（p < 0.001）将氧化的三聚体硫氧还蛋白水平升高至对照的213 +/-5%（n = 3）。这很可能是由于硫氧还蛋白还原酶活性显著（p < 0.01）降低至对照的65 +/-6%（n = 4）。我们惊讶地发现，非氧化还原活性螯合剂去铁胺在较低程度上增加硫氧还蛋白氧化（152 +/- 9%; n = 3）并抑制硫氧还蛋白还原酶活性（62 +/- 5%; n = 4），但浓度比缩氨基硫脲高10倍。相比之下，只有缩氨基硫脲显著（p < 0.05）降低谷胱甘肽/氧化谷胱甘肽的比例和需要谷胱甘肽作为还原剂的谷氧还蛋白的活性。所有螯合剂显着降低RR活性，而NADPH/NADP总比率没有减少。这一点很重要，因为硫醇还原需要NADPH。因此，缩氨基硫脲可能通过其对主要含巯基系统的影响而具有额外的RR抑制机制。
Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone possesses potent and selective antitumor activity. Its cytotoxicity has been attributed to iron chelation leading to inhibition of the iron-containing enzyme ribonucleotide reductase (RR). Thiosemicarbazone iron complexes have been shown to be redox-active, although their effect on cellular antioxidant systems is unclear. Using a variety of antioxidants, we found that only N-acetylcysteine significantly inhibited thiosemicarbazone-induced antiproliferative activity. Thus, we examined the effects of thiosemicarbazones on major thiol-containing systems considering their key involvement in providing reducing equivalents for RR. Thiosemicarbazones significantly (p < 0.001) elevated oxidized trimeric thioredoxin levels to 213 +/- 5% (n = 3) of the control. This was most likely due to a significant (p < 0.01) decrease in thioredoxin reductase activity to 65 +/- 6% (n = 4) of the control. We were surprised to find that the non-redox-active chelator desferrioxamine increased thioredoxin oxidation to a lower extent (152 +/- 9%; n = 3) and inhibited thioredoxin reductase activity (62 +/- 5%; n = 4), but at a 10-fold higher concentration than thiosemicarbazones. In contrast, only the thiosemicarbazones significantly (p < 0.05) reduced the glutathione/oxidized-glutathione ratio and the activity of glutaredoxin that requires glutathione as a reductant. All chelators significantly decreased RR activity, whereas the NADPH/NADP total ratio was not reduced. This was important to consider because NADPH is required for thiol reduction. Thus, thiosemicarbazones could have an additional mechanism of RR inhibition via their effects on major thiol-containing systems.