Single-cell imaging tools for brain energy metabolism: a review

Martín, Alejandro San; Sotelo-Hitschfeld, Tamara; Lerchundi, Rodrigo; Fernández‐Moncada, Ignacio; Ceballo, Sebastián; Valdebenito, Rocío; Baeza-Lehnert, Felipe; Alegría, Karin; Contreras-Baeza, Yasna; Garrido-Gerter, Pamela; Romero-Gómez, Ignacio; Barros, L. Felipe

doi:10.1117/1.nph.1.1.011004

Cited by 52 publications

(47 citation statements)

References 133 publications

(73 reference statements)

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“…In vivo imaging of energy metabolism with cellular resolution has become possible only recently, thanks to the development of genetically-encoded fluorescent indicators that are sensitive to the intracellular concentrations of various energy metabolites34. Both glucose and lactate can act as neuronal energy sources, but in either case the energy-producing pathways converge to yield pyruvate, the input energy substrate for oxidative phosphorylation in mitochondria.…”

Section: Resultsmentioning

confidence: 99%

Upregulated energy metabolism in the Drosophila mushroom body is the trigger for long-term memory

et al. 2017

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Efficient energy use has constrained the evolution of nervous systems. However, it is unresolved whether energy metabolism may resultantly regulate major brain functions. Our observation that Drosophila flies double their sucrose intake at an early stage of long-term memory formation initiated the investigation of how energy metabolism intervenes in this process. Cellular-resolution imaging of energy metabolism reveals a concurrent elevation of energy consumption in neurons of the mushroom body, the fly's major memory centre. Strikingly, upregulation of mushroom body energy flux is both necessary and sufficient to drive long-term memory formation. This effect is triggered by a specific pair of dopaminergic neurons afferent to the mushroom bodies, via the D5-like DAMB dopamine receptor. Hence, dopamine signalling mediates an energy switch in the mushroom body that controls long-term memory encoding. Our data thus point to an instructional role for energy flux in the execution of demanding higher brain functions.

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Section: Resultsmentioning

confidence: 99%

Upregulated energy metabolism in the Drosophila mushroom body is the trigger for long-term memory

et al. 2017

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“…Detailed protocols for the use of the fluorescent sensors are available (59)(60)(61)(62). Cells and slices were imaged with an upright Olympus FV1000 confocal microscope and a 440-nm solid-state laser.…”

Section: Methodsmentioning

confidence: 99%

NH4+ triggers the release of astrocytic lactate via mitochondrial pyruvate shunting

Lerchundi

Fernández‐Moncada

Contreras-Baeza

et al. 2015

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

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Neural activity is accompanied by a transient mismatch between local glucose and oxygen metabolism, a phenomenon of physiological and pathophysiological importance termed aerobic glycolysis. Previous studies have proposed glutamate and K + as the neuronal signals that trigger aerobic glycolysis in astrocytes. Here we used a panel of genetically encoded FRET sensors in vitro and in vivo to investigate the participation of NH + 4 , a by-product of catabolism that is also released by active neurons. Astrocytes in mixed cortical cultures responded to physiological levels of NH + 4 with an acute rise in cytosolic lactate followed by lactate release into the extracellular space, as detected by a lactate-sniffer. An acute increase in astrocytic lactate was also observed in acute hippocampal slices exposed to NH + 4 and in the somatosensory cortex of anesthetized mice in response to i.v. NH + 4 . Unexpectedly, NH + 4 had no effect on astrocytic glucose consumption. Parallel measurements showed simultaneous cytosolic pyruvate accumulation and NADH depletion, suggesting the involvement of mitochondria. An inhibitor-stop technique confirmed a strong inhibition of mitochondrial pyruvate uptake that can be explained by mitochondrial matrix acidification. These results show that physiological NH + 4 diverts the flux of pyruvate from mitochondria to lactate production and release. Considering that NH + 4 is produced stoichiometrically with glutamate during excitatory neurotransmission, we propose that NH + 4 behaves as an intercellular signal and that pyruvate shunting contributes to aerobic lactate production by astrocytes.B rain tissue is almost exclusively energized by the oxidation of glucose. However, during neuronal activation, there is a larger increase in local glucose consumption relative to oxygen consumption (1). As this mismatch occurs in the presence of normal or augmented oxygen levels, it has been termed aerobic glycolysis, paralleling the signal detected by functional magnetic resonance imaging (2). Aerobic glycolysis and its associated lactate surge are causally linked to diverse functions of the brain in health and disease (3-10). Two signals are known to trigger aerobic glycolysis in brain tissue: glutamate and K + , which are released by active neurons and stimulate glycolysis in astrocytes (11,12).Neurons produce as much NH + 4 as they produce glutamate, both molecules being stoichiometrically linked in the glutamateglutamine cycle (13). Brain tissue NH + 4 increases within seconds of neural activation (14-16) and is quickly released to the interstitium (17, 18) to be captured by astrocytes through K + channels and transporters (19). It is well established that chronic exposure to pathological levels of NH + 4 such as those observed during liver failure has a major impact on brain metabolism, but it is not known whether this molecule may affect energy metabolism at physiological levels, particularly within the time scale of synaptic transmission. A previous study showed a reversible rise in brain tissue la...

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“…This is partly due to the lack of appropriate tools in the past, circumventing a dynamic determination of activity-related changes in energy metabolites in brain tissue with (sub-) cellular resolution . The recent development of suitable genetically encoded fluorescence sensors for metabolites such as ATP, glucose, lactate, or pyruvate (San Martin et al, 2014;Tantama, Hung, & Yellen, 2012) has provided first exciting new insights into cellular metabolism in cells in primary culture (Bittner et al, 2011;Tantama, Martinez-Francois, Mongeon, & Yellen, 2013;Winkler et al, 2017), in isolated white matter tracts (Trevisiol et al 2017), brain tissue slices (Fernandez-Moncada et al, 2018;Köhler et al, 2018), as well as in vivo (Mächler et al, 2016).…”

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confidence: 99%

FRET‐based imaging of intracellular ATP in organotypic brain slices

Lerchundi

Kafitz

Winkler

et al. 2018

J of Neuroscience Research

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Active neurons require a substantial amount of adenosine triphosphate (ATP) to re‐establish ion gradients degraded by ion flux across their plasma membranes. Despite this fact, neurons, in contrast to astrocytes, do not contain any significant stores of energy substrates. Recent work has provided evidence for a neuro‐metabolic coupling between both cell types, in which increased glycolysis and lactate production in astrocytes support neuronal metabolism. Here, we established the cell type‐specific expression of the Förster resonance energy transfer (FRET) based nanosensor ATeam1.03YEMK (“Ateam”) for dynamic measurement of changes in intracellular ATP levels in organotypic brain tissue slices. To this end, adeno‐associated viral vectors coding for Ateam, driven by either the synapsin‐ or glial fibrillary acidic protein (GFAP) promoter were employed for specific transduction of neurons or astrocytes, respectively. Chemical ischemia, induced by perfusion of tissue slices with metabolic inhibitors of cellular glycolysis and mitochondrial respiration, resulted in a rapid decrease in the cellular Ateam signal to a new, low level, indicating nominal depletion of intracellular ATP. Increasing the extracellular potassium concentration to 8 mM, thereby mimicking the release of potassium from active neurons, did not alter ATP levels in neurons. It, however, caused in an increase in ATP levels in astrocytes, a result which was confirmed in acutely isolated tissue slices. In summary, our results demonstrate that organotypic cultured slices are a reliable tool for FRET‐based dynamic imaging of ATP in neurons and astrocytes. They moreover provide evidence for an increased ATP synthesis in astrocytes, but not neurons, during periods of elevated extracellular potassium concentrations.

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Single-cell imaging tools for brain energy metabolism: a review

Cited by 52 publications

References 133 publications

Upregulated energy metabolism in the Drosophila mushroom body is the trigger for long-term memory

Upregulated energy metabolism in the Drosophila mushroom body is the trigger for long-term memory

NH4+ triggers the release of astrocytic lactate via mitochondrial pyruvate shunting

FRET‐based imaging of intracellular ATP in organotypic brain slices

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