Abstract：
Iron is an essential element for life owing to its ability to participate in a diverse array of oxidation-reduction reactions. However, misregulation of iron-dependent redox cycling can also produce oxidative stress, contributing to cell growth, proliferation, and death pathways underlying aging, cancer, neurodegeneration, and metabolic diseases. Fluorescent probes that selectively monitor loosely bound Fe(II) ions, termed the labile iron pool, are potentially powerful tools for studies of this metal nutrient; however, the dynamic spatiotemporal nature and potent fluorescence quenching capacity of these bioavailable metal stores pose challenges for their detection. Here, we report a tandem activity-based sensing and labeling strategy that enables imaging of labile iron pools in live cells through enhancement in cellular retention. Iron green-1 fluoromethyl (IG1-FM) reacts selectively with Fe(II) using an endoperoxide trigger to release a quinone methide dye for subsequent attachment to proximal biological nucleophiles, providing a permanent fluorescent stain at sites of elevated labile iron. IG1-FM imaging reveals that degradation of the major iron storage protein ferritin through ferritinophagy expands the labile iron pool, while activation of nuclear factor-erythroid 2-related factor 2 (NRF2) antioxidant response elements (AREs) depletes it. We further show that lung cancer cells with heightened NRF2 activation, and thus lower basal labile iron, have reduced viability when treated with an iron chelator. By connecting labile iron pools and NRF2-ARE activity to a druggable metal-dependent vulnerability in cancer, this work provides a starting point for broader investigations into the roles of transition metal and antioxidant signaling pathways in health and disease.
摘要：
铁是生命的基本要素，因为它能够参与各种氧化还原反应。然而,铁依赖性氧化还原循环的失调也会产生氧化应激，有助于细胞生长，扩散,和衰老背后的死亡途径，癌症,神经变性,和代谢性疾病。选择性监测松散结合的Fe（II）离子的荧光探针，被称为不稳定的铁池，是研究这种金属营养素的潜在强大工具；然而，这些生物可利用的金属库的动态时空性质和有效的荧光猝灭能力对其检测提出了挑战。这里,我们报告了一种串联的基于活动的传感和标记策略,该策略通过增强细胞滞留,能够对活细胞中不稳定的铁池进行成像.铁绿-1氟甲基（IG1-FM）使用内过氧化物触发剂与Fe（II）选择性反应，释放醌甲基化染料，随后附着于近端生物亲核试剂，在升高的不稳定铁的部位提供永久性荧光染色。IG1-FM成像显示，主要的铁储存蛋白铁蛋白通过铁吞噬的降解扩大了不稳定的铁库，而核因子-红系2相关因子2（NRF2）抗氧化反应元件（AREs）的激活会耗尽它。我们进一步表明，肺癌细胞具有增强的NRF2激活，从而降低了基础不稳定铁，当用铁螯合剂处理时具有降低的活力。通过将不稳定的铁池和NRF2-ARE活动与癌症中依赖金属的药物脆弱性联系起来，这项工作为更广泛地研究过渡金属和抗氧化剂信号通路在健康和疾病中的作用提供了起点.
