Molecular Imaging of Labile Iron(II) Pools in Living Cells with a Turn-On Fluorescent Probe

Au‐Yeung, Ho Yu; Chan, Jefferson; Chantarojsiri, Teera; Chang, Christopher J.

doi:10.1021/ja4072964

Cited by 161 publications

(117 citation statements)

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“…To create a Cu + -responsive luciferin probe, we exploited a Cu + -dependent oxidative cleavage reaction mediated by the tetradentate ligand TPA (Fig. 1), inspired by the use of this pendant to develop a Cu + -selective fluorescent probe (51) as well as work from our laboratory on related metal-dependent oxidations for fluorescence detection of Co 2+ and Fe 2+ in living cells (52,53). The synthesis of CCL-1 based on this design strategy is depicted in Scheme 1 and offers a general and versatile platform for appending other potential ligands to tune metal specificity and reactivity.…”

Section: Resultsmentioning

confidence: 99%

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

Heffern

Park

Au‐Yeung

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Copper is a required metal nutrient for life, but global or local alterations in its homeostasis are linked to diseases spanning genetic and metabolic disorders to cancer and neurodegeneration. Technologies that enable longitudinal in vivo monitoring of dynamic copper pools can help meet the need to study the complex interplay between copper status, health, and disease in the same living organism over time. Here, we present the synthesis, characterization, and in vivo imaging applications of Copper-Caged Luciferin-1 (CCL-1), a bioluminescent reporter for tissue-specific copper visualization in living animals. CCL-1 uses a selective copper(I)-dependent oxidative cleavage reaction to release d-luciferin for subsequent bioluminescent reaction with firefly luciferase. The probe can detect physiological changes in labile Cu+ levels in live cells and mice under situations of copper deficiency or overload. Application of CCL-1 to mice with liver-specific luciferase expression in a diet-induced model of nonalcoholic fatty liver disease reveals onset of hepatic copper deficiency and altered expression levels of central copper trafficking proteins that accompany symptoms of glucose intolerance and weight gain. The data connect copper dysregulation to metabolic liver disease and provide a starting point for expanding the toolbox of reactivity-based chemical reporters for cell- and tissue-specific in vivo imaging.

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Section: Resultsmentioning

confidence: 99%

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

Heffern

Park

Au‐Yeung

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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161

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“…This contributes to a labile Fe pool that has been detected only indirectly using fluorescent probes. 6,7 …”

Section: Introductionmentioning

confidence: 99%

Speciation of iron in mouse liver during development, iron deficiency, IRP2 deletion and inflammatory hepatitis

et al. 2015

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The iron content of livers from 57Fe-enriched C57BL/6 mice of different ages were investigated using Mössbauer spectroscopy, electron paramagnetic resonance (EPR), electronic absorption spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). About 80% of the Fe in an adult liver was due to blood; thus removal of blood by flushing with buffer was essential to observe endogenous liver Fe. Even after exhaustive flushing, ca. 20% of the Fe in anaerobically dissected livers was typical of deoxy-hemoglobin. The concentration of Fe in newborn livers was the highest of any developmental stage (~ 1.2 mM). Most was stored as ferritin, with little mitochondrial Fe (consisting primarily of Fe/S clusters and haems) evident. Within the first few weeks of life, about half of ferritin Fe was mobilized and exported, illustrating the importance of Fe release as well as Fe storage in liver function. Additional ferritin Fe was used to generate mitochondrial Fe centres. From ca. 4 weeks of age to the end of the mouse’s natural lifespan, the concentration of mitochondrial Fe in liver was essentially invariant. A minor contribution from nonhaem high-spin FeII was observed in most liver samples and was also invariant with age. Some portion of these species may constitute the labile iron pool. Livers from mice raised on an Fe-deficient diet were highly Fe depleted; they were devoid of ferritin and contained 1/3 as much mitochondrial Fe as found in Fe-sufficient livers. In contrast, brains of the same Fe-deficient mice retained normal levels of mitochondrial Fe. Livers from mice with inflammatory hepatitis and from IRP2(−/−) mice hyper-accumulated Fe. These livers had high ferritin levels but low levels of mitochondrial Fe.

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“…In this regard, detection of iron with both metal and oxidation state specificity is of central importance, because while iron is stored primarily in the ferric oxidation state, a ferrous iron pool loosely bound to cellular ligands, defined as the labile iron pool (LIP), exists at the center of highly regulated networks that control iron acquisition, trafficking, and excretion. Indeed, as a weak binder on the Irving-Williams stability series (13), Fe 2+ provides a challenge for detection by traditional recognition-based approaches (14), and as such we (15)(16)(17) and others (18)(19)(20) have pursued activity-based sensing approaches to detect labile Fe 2+ stores in cells (21)(22)(23)(24)(25). These tools have already provided insights into iron biology, as illustrated by the direct identification of elevations in LIPs during ferroptosis (26,27), an emerging form of cell death, using the ratiometric iron indicator FIP-1 (15).…”

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confidence: 99%

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection

Aron

Heffern

Lonergan

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Iron is an essential metal for all organisms, yet disruption of its homeostasis, particularly in labile forms that can contribute to oxidative stress, is connected to diseases ranging from infection to cancer to neurodegeneration. Iron deficiency is also among the most common nutritional deficiencies worldwide. To advance studies of iron in healthy and disease states, we now report the synthesis and characterization of iron-caged luciferin-1 (ICL-1), a bioluminescent probe that enables longitudinal monitoring of labile iron pools (LIPs) in living animals. ICL-1 utilizes a bioinspired endoperoxide trigger to release D-aminoluciferin for selective reactivity-based detection of Fe 2+ with metal and oxidation state specificity. The probe can detect physiological changes in labile Fe 2+ levels in live cells and mice experiencing iron deficiency or overload. Application of ICL-1 in a model of systemic bacterial infection reveals increased iron accumulation in infected tissues that accompany transcriptional changes consistent with elevations in both iron acquisition and retention. The ability to assess iron status in living animals provides a powerful technology for studying the contributions of iron metabolism to physiology and pathology.labile iron | molecular imaging | luciferin | metal homeostasis | infectious disease I ron is an essential mineral for nearly every form of life, owing in large part to its ability to cycle between different oxidation states for processes such as nucleotide synthesis, oxygen transport, and respiration (1, 2). At the same time, the potent redox activity of iron is potentially toxic, particularly in unregulated labile forms that can trigger aberrant production of reactive oxygen species via Fenton chemistry (3). Indeed, iron deficiency remains one of the most common nutritional deficiencies in the world (4), and aberrant iron levels have been linked to various ailments, including cancer (5-7), cardiovascular (8), and neurodegenerative (9) disorders, as well as aging (10). The situation is especially complex in infectious diseases, where the requirement for iron by both host organism and invading pathogen leads to an intricate chemical tug-of-war for this metal nutrient during various stages of the immune response (11,12).The foregoing examples provide motivation for developing technologies to monitor biological iron status, with particular interest in methods to achieve in vivo iron imaging in live animal models that go beyond current state-of-the-art assays that are limited primarily to cell culture specimens. In this regard, detection of iron with both metal and oxidation state specificity is of central importance, because while iron is stored primarily in the ferric oxidation state, a ferrous iron pool loosely bound to cellular ligands, defined as the labile iron pool (LIP), exists at the center of highly regulated networks that control iron acquisition, trafficking, and excretion. Indeed, as a weak binder on the Irving-Williams stability series (13), Fe 2+ provides a challenge for d...

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Molecular Imaging of Labile Iron(II) Pools in Living Cells with a Turn-On Fluorescent Probe

Cited by 161 publications

References 71 publications

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

Speciation of iron in mouse liver during development, iron deficiency, IRP2 deletion and inflammatory hepatitis

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection

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