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MacRenaris KW, Ma Z, Krueger RL, Carney CE, Meade TJ. Cell-Permeable Esterase-Activated Ca(II)-Sensitive MRI Contrast Agent. Bioconjug Chem 2016; 27:465-73. [PMID: 26689452 DOI: 10.1021/acs.bioconjchem.5b00561] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Calcium [Ca(II)] is a fundamental transducer of electrical activity in the central nervous system (CNS). Influx of Ca(II) into the cytosol is responsible for action potential initiation and propagation, and initiates interneuronal communication via release of neurotransmitters and activation of gene expression. Despite the importance of Ca(II) in physiology, it remains a challenge to visualize Ca(II) flux in the central nervous system (CNS) in vivo. To address these challenges, we have developed a new generation, Ca(II)-activated MRI contrast agent that utilizes ethyl esters to increase cell labeling and prevent extracellular divalent Ca(II) binding. Following labeling, the ethyl esters can be cleaved, thus allowing the agent to bind Ca(II), increasing relaxivity and resulting in enhanced positive MR image contrast. The ability of this probe to discriminate between extra- and intracellular Ca(II) may allow for spatiotemporal in vivo imaging of Ca(II) flux during seizures or ischemia where large Ca(II) fluxes (1-10 μM) can result in cell death.
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Affiliation(s)
- Keith W MacRenaris
- Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, Northwestern University , Evanston, Illinois 60208 , United States
| | - Zhidong Ma
- Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, Northwestern University , Evanston, Illinois 60208 , United States
| | - Ruby L Krueger
- Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, Northwestern University , Evanston, Illinois 60208 , United States
| | - Christiane E Carney
- Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, Northwestern University , Evanston, Illinois 60208 , United States
| | - Thomas J Meade
- Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, Northwestern University , Evanston, Illinois 60208 , United States
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Cakić N, Gündüz S, Rengarasu R, Angelovski G. Synthetic strategies for preparation of cyclen-based MRI contrast agents. Tetrahedron Lett 2015. [DOI: 10.1016/j.tetlet.2014.12.087] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Angelovski G, Gottschalk S, Milošević M, Engelmann J, Hagberg GE, Kadjane P, Andjus P, Logothetis NK. Investigation of a calcium-responsive contrast agent in cellular model systems: feasibility for use as a smart molecular probe in functional MRI. ACS Chem Neurosci 2014; 5:360-9. [PMID: 24712900 DOI: 10.1021/cn500049n] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Responsive or smart contrast agents (SCAs) represent a promising direction for development of novel functional MRI (fMRI) methods for the eventual noninvasive assessment of brain function. In particular, SCAs that respond to Ca(2+) may allow tracking neuronal activity independent of brain vasculature, thus avoiding the characteristic limitations of current fMRI techniques. Here we report an in vitro proof-of-principle study with a Ca(2+)-sensitive, Gd(3+)-based SCA in an attempt to validate its potential use as a functional in vivo marker. First, we quantified its relaxometric response in a complex 3D cell culture model. Subsequently, we examined potential changes in the functionality of primary glial cells following administration of this SCA. Monitoring intracellular Ca(2+) showed that, despite a reduction in the Ca(2+) level, transport of Ca(2+) through the plasma membrane remained unaffected, while stimulation with ATP induced Ca(2+)-transients suggested normal cellular signaling in the presence of low millimolar SCA concentrations. SCAs merely lowered the intracellular Ca(2+) level. Finally, we estimated the longitudinal relaxation times (T1) for an idealized in vivo fMRI experiment with SCA, for extracellular Ca(2+) concentration level changes expected during intense neuronal activity which takes place upon repetitive stimulation. The values we obtained indicate changes in T1 of around 1-6%, sufficient to be robustly detectable using modern MRI methods in high field scanners. Our results encourage further attempts to develop even more potent SCAs and appropriate fMRI protocols. This would result in novel methods that allow monitoring of essential physiological processes at the cellular and molecular level.
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Affiliation(s)
| | | | - Milena Milošević
- Institute
for Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Beograd 11000, Serbia
| | | | - Gisela E. Hagberg
- Biomedical
Magnetic Resonance, Department of Radiology, Tübingen University Hospital, 72076 Tübingen, Germany
| | | | - Pavle Andjus
- Institute
for Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Beograd 11000, Serbia
| | - Nikos K. Logothetis
- Division
of Imaging Science and Biomedical Engineering, University of Manchester, Manchester M13 9PL, United Kingdom
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Kadjane P, Platas-Iglesias C, Boehm-Sturm P, Truffault V, Hagberg GE, Hoehn M, Logothetis NK, Angelovski G. Dual-frequency calcium-responsive MRI agents. Chemistry 2014; 20:7351-62. [PMID: 24796323 DOI: 10.1002/chem.201400159] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Indexed: 01/10/2023]
Abstract
Responsive or smart magnetic resonance imaging (MRI) contrast agents are molecular sensors that alter the MRI signal upon changes in a particular parameter in their microenvironment. Consequently, they could be exploited for visualization of various biochemical events that take place at molecular and cellular levels. In this study, a set of dual-frequency calcium-responsive MRI agents are reported. These are paramagnetic, fluorine-containing complexes that produce remarkably high MRI signal changes at the (1)H and (19)F frequencies at varying Ca(2+) concentrations. The nature of the processes triggered by Ca(2+) was revealed, allowing a better understanding of these complex systems and their further improvement. The findings indicate that these double-frequency tracers hold great promise for development of novel functional MRI methods.
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Affiliation(s)
- Pascal Kadjane
- Department for Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076 Tübingen (Germany)
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Szíjjártó C, Pershagen E, Ilchenko NO, Borbas KE. A versatile long-wavelength-absorbing scaffold for Eu-based responsive probes. Chemistry 2013; 19:3099-109. [PMID: 23307197 DOI: 10.1002/chem.201203957] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Indexed: 12/27/2022]
Abstract
Coumarin-sensitized, long-wavelength-absorbing luminescent Eu(III)-complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen-based chelating framework that is attached through a short linker to a 7-hydroxycoumarin, a 7-B(OH)(2)-coumarin, a 7-O-(4-pinacolatoboronbenzyl)-coumarin or a 7-O-(4-methoxybenzyl)-coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high-yielding steps. The sensitivity of coumarin photophysics to the 7-substituent enables modulation of the antenna-absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate-based functionalities (cages) with H(2)O(2) yielded the corresponding 7-hydroxycoumarin species. The same species was produced with peroxynitrite in a ×10(6)-10(7)-fold faster reaction. Both reactions resulted in the emergence of a strong ≈407 nm excitation band, with concomitant decrease of the 366 nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu-complex was quenched by ONOO(-). We have shown that preliminary screening of simple coumarin-based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in Eu(III)-excitation profile in the fully elaborated complex. Taken together, our results show that the 7-hydroxycoumarin antenna is a viable scaffold for the construction of turn-on and ratiometric luminescent probes.
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Affiliation(s)
- Csongor Szíjjártó
- Department of Chemistry, BMC, Uppsala University, Box 576, 75123 Uppsala, Sweden
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