Karaca Özden, Scalcon Valeria, Meier-Menches Samuel M, Bonsignore Riccardo, Brouwer Jurriaan M J L, Tonolo Federica, Folda Alessandra, Rigobello Maria Pia, Kühn Fritz E, Casini Angela
Molecular Catalysis, Department of Chemistry, Catalysis Research Center, Technische Universität München , Lichtenbergstraße 4, 85747 Garching bei München, Germany.
School of Chemistry, Cardiff University , Park Place, CF103AT Cardiff, U.K.
Inorg Chem. 2017 Nov 20;56(22):14237-14250. doi: 10.1021/acs.inorgchem.7b02345. Epub 2017 Nov 2.
We report here on the synthesis of a series of mono- and dinuclear gold(I) complexes exhibiting sulfonated bis(NHC) ligands and novel hydroxylated mono(NHC) Au(I) compounds, which were also examined for their biological activities. Initial cell viability assays show strong antiproliferative activities of the hydroxylated mono(NHC) gold compounds (8 > 9 > 10) against 2008 human ovarian cancer cells even after 1 h incubation. In order to gain insight into the mechanism of biological action of the gold compounds, their effect on the pivotal cellular target seleno-enzyme thioredoxin reductase (TrxR), involved in the maintenance of intracellular redox balance, was investigated in depth. The compounds' inhibitory effects on TrxR and glutathione reductase (GR) were studied comparatively, using either the pure proteins or cancer cell extracts. The results show a strong and selective inhibitory effect of TrxR, specifically for the hydroxyl-functionalized NHC gold(I) complexes (8-10). Valuable information on the gold compounds' molecular reactivity with TrxR was gained using the BIAM (biotin-conjugated iodoacetamide) assay and performing competition experiments by mass spectrometry (MS). In good agreement, both techniques suggest the binding affinity of the mono(NHC) Au(I) complexes toward selenols and thiols. Notably, for the first time, bis-carbene formation from mono-carbenes in buffered solution could be observed by MS, which may provide new insights into the speciation mechanisms of bioactive Au(I) NHC complexes. Furthermore, the compounds' interactions with another relevant in cellulo target, namely telomeric G-quadruplex DNA-a higher-order DNA structure playing key roles in telomere function-was investigated by means of FRET melting assays. The lack of interactions with this type of nucleic acid secondary structure support the idea of selective targeting of the hydrophilic Au(I) NHC compounds toward proteins such as TrxR.
我们在此报告了一系列具有磺化双（NHC）配体的单核和双核金（I）配合物以及新型羟基化单（NHC）金（I）化合物的合成，并对它们的生物活性进行了研究。初步细胞活力测定表明，即使在孵育1小时后，羟基化单（NHC）金化合物（8 > 9 > 10）对2008人卵巢癌细胞仍具有很强的抗增殖活性。为了深入了解金化合物的生物作用机制，我们深入研究了它们对关键细胞靶点硒酶硫氧还蛋白还原酶（TrxR）的影响，该酶参与维持细胞内氧化还原平衡。使用纯蛋白或癌细胞提取物对化合物对TrxR和谷胱甘肽还原酶（GR）的抑制作用进行了比较研究。结果表明，TrxR具有很强的选择性抑制作用，特别是对于羟基官能化的NHC金（I）配合物（8 - 10）。通过BIAM（生物素共轭碘乙酰胺）测定并进行质谱（MS）竞争实验，获得了有关金化合物与TrxR分子反应性的宝贵信息。两者技术均表明单（NHC）金（I）配合物对硒醇和硫醇具有结合亲和力，这与实验结果高度一致。值得注意的是，首次通过质谱观察到缓冲溶液中单卡宾形成双卡宾的现象，这可能为生物活性金（I）NHC配合物的物种形成机制提供新的见解。此外，通过FRET熔解测定法研究了化合物与另一个相关的细胞内靶点，即端粒G-四链体DNA（一种在端粒功能中起关键作用的高阶DNA结构）的相互作用。与这种类型的核酸二级结构缺乏相互作用支持了亲水性金（I）NHC化合物选择性靶向TrxR等蛋白质的观点。
