Dihydropyrimidine-Thiones and Clioquinol Synergize To Target β‑Amyloid Cellular Pathologies through a Metal-Dependent Mechanism

The
lack of therapies for neurodegenerative diseases arises from
our incomplete understanding of their underlying cellular toxicities
and the limited number of predictive model systems. It is critical
that we develop approaches to identify novel targets and lead compounds.
Here, a phenotypic screen of yeast proteinopathy models identified
dihydropyrimidine-thiones (DHPM-thiones) that selectively rescued
the toxicity caused by β-amyloid (Aβ), the peptide implicated
in Alzheimer’s disease. Rescue of Aβ toxicity by DHPM-thiones
occurred through a metal-dependent mechanism of action. The bioactivity
was distinct, however, from that of the 8-hydroxyquinoline clioquinol
(CQ). These structurally dissimilar compounds strongly synergized
at concentrations otherwise not competent to reduce toxicity. Cotreatment
ameliorated Aβ toxicity by reducing Aβ levels and restoring
functional vesicle trafficking. Notably, these low doses significantly
reduced deleterious off-target effects caused by CQ on mitochondria
at higher concentrations. Both single and combinatorial treatments
also reduced death of neurons expressing Aβ in a nematode, indicating
that DHPM-thiones target a conserved protective mechanism. Furthermore,
this conserved activity suggests that expression of the Aβ peptide
causes similar cellular pathologies from yeast to neurons. Our identification
of a new cytoprotective scaffold that requires metal-binding underscores
the critical role of metal phenomenology in mediating Aβ toxicity.
Additionally, our findings demonstrate the valuable potential of synergistic
compounds to enhance on-target activities, while mitigating deleterious
off-target effects. The identification and prosecution of synergistic
compounds could prove useful for developing AD therapeutics where
combination therapies may be required to antagonize diverse pathologies.

神经退行性疾病治疗手段匮乏的根源，在于我们对其潜在细胞毒性的认知尚不完整，且可用的预测模型系统数量有限。开发能够识别全新靶点与先导化合物的方法至关重要。本研究通过对酵母蛋白质病模型开展表型筛选，鉴定出二氢嘧啶硫酮类（dihydropyrimidine-thiones, DHPM-thiones）化合物，其可选择性逆转β淀粉样蛋白（β-amyloid, Aβ）引发的毒性——Aβ是与阿尔茨海默病（Alzheimer’s disease）相关的致病多肽。DHPM-thiones通过金属依赖的作用机制逆转Aβ毒性，但其生物活性与8-羟基喹啉类化合物氯喹碘方（clioquinol, CQ）截然不同。这两种结构差异显著的化合物在原本无法降低毒性的浓度下，展现出极强的协同效应。联合给药通过减少Aβ水平、恢复功能性囊泡运输，缓解了Aβ毒性。值得注意的是，低剂量联合用药可显著减轻高剂量CQ对线粒体造成的有害脱靶效应。单次给药与联合给药均能减少线虫体内表达Aβ的神经元死亡，表明DHPM-thiones靶向的是一套保守的保护机制。此外，这种保守的活性特性提示，从酵母到神经元，Aβ多肽的表达会引发相似的细胞病理变化。本研究鉴定出一种全新的、依赖金属结合的细胞保护性支架，这突显了金属现象学在介导Aβ毒性中的关键作用。同时，研究结果证实了协同化合物的应用潜力：其可增强靶向活性，同时减轻有害的脱靶效应。鉴定并开发协同化合物，或可为阿尔茨海默病治疗药物的研发提供新思路——这类疾病可能需要联合疗法来拮抗多种病理进程。