Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
J Am Chem Soc. 2021 Nov 17;143(45):19043-19057. doi: 10.1021/jacs.1c08254. Epub 2021 Nov 3.
Herein we demonstrate that copper(II)-diacetyl-bis(-methylthiosemicarbazone)(CuATSM), clinical candidate for the treatment of ALS and Parkinson's disease, is a highly potent radical-trapping antioxidant (RTA) and inhibitor of (phospho)lipid peroxidation. In THF autoxidations, CuATSM reacts with THF-derived peroxyl radicals with = 2.2 × 10 M s─roughly 10-fold greater than α-tocopherol (α-TOH), Nature's best RTA. Mechanistic studies reveal no H/D kinetic isotope effects and a lack of rate-suppressing effects from H-bonding interactions, implying a different mechanism from α-TOH and other canonical RTAs, which react by H-atom transfer (HAT). Similar reactivity was observed for the corresponding Ni complex and complexes of both Cu and Ni with other bis(thiosemicarbazone) ligands. Computations corroborate the experimental finding that rate-limiting HAT cannot account for the observed RTA activity and instead suggest that the reversible addition of a peroxyl radical to the bis(thiosemicarbazone) ligand is responsible. Subsequent HAT or combination with another peroxyl radical drives the reaction forward, such that a maximum of four radicals are trapped per molecule of CuATSM. This sequence is supported by spectroscopic and mass spectrometric experiments on isolated intermediates. Importantly, the RTA activity of CuATSM (and its analogues) translates from organic solution to phospholipid bilayers, thereby accounting for its (their) ability to inhibit ferroptosis. Experiments in mouse embryonic fibroblasts and hippocampal cells reveal that lipophilicity as well as inherent RTA activity contribute to the potency of ferroptosis rescue, and that one compound (CuATSP) is almost 20-fold more potent than CuATSM and among the most potent ferroptosis inhibitors reported to date.
在此，我们证明了铜（II）-二乙酰双（β-甲基硫代半卡巴腙）（CuATSM），作为治疗肌萎缩侧索硬化症和帕金森病的临床候选药物，是一种高效的自由基捕获抗氧化剂（RTA）和（磷酸）脂质过氧化抑制剂。在四氢呋喃自氧化中，CuATSM 与四氢呋喃衍生的过氧自由基反应， = 2.2 × 10 M s─比 α-生育酚（α-TOH）快约 10 倍，α-TOH 是自然界最好的 RTA。机理研究表明没有 H/D 动力学同位素效应，并且氢键相互作用没有抑制速率的影响，这意味着与 α-TOH 和其他典型 RTA 不同的反应机制，它们通过氢原子转移（HAT）反应。对于相应的 Ni 配合物以及 Cu 和 Ni 与其他双（硫代半卡巴腙）配体的配合物也观察到类似的反应性。计算结果证实了实验发现，限速 HAT 不能解释观察到的 RTA 活性，而是表明过氧自由基可逆加成到双（硫代半卡巴腙）配体是负责的。随后的 HAT 或与另一个过氧自由基结合推动反应向前进行，使得每个 CuATSM 分子最多可以捕获四个自由基。这一序列得到了分离中间体的光谱和质谱实验的支持。重要的是，CuATSM（及其类似物）的 RTA 活性从有机溶剂转移到磷脂双层，从而解释了其（它们）抑制铁死亡的能力。在小鼠胚胎成纤维细胞和海马细胞中的实验表明，亲脂性以及固有 RTA 活性有助于铁死亡挽救的效力，并且一种化合物（CuATSP）比 CuATSM 强约 20 倍，是迄今为止报道的最有效的铁死亡抑制剂之一。
