Consequences of a Metabolic Glucose-Depletion on the Survival and the Metabolism of Cultured Rat Astrocytes

Arend, Christian; Ehrke, Eric; Dringen, Ralf

doi:10.1007/s11064-019-02752-1

Cited by 15 publications

(25 citation statements)

References 87 publications

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“…Substantial amounts of extracellular lactate and alanine were determined in glucose-deprived and pyruvate-treated astrocytes. Part of the extracellular lactate and alanine may be derived from residual free glucose, glycolysis intermediates and/or glycogen that is mobilized after glucose deprivation [ 19 , 65 , 66 ]. However, even after correction of the values obtained from pyruvate-treated astrocytes for the respective data from pyruvate-free control incubations, the amounts of lactate and alanine determined accounted to around 60% and 10%, respectively, of the total amount of pyruvate consumed by the cells.…”

Section: Discussionmentioning

confidence: 99%

“…After a given incubation period, cultured astrocytes were stained with tetramethylrhodamine ethyl ester (TMRE) to visualize the mitochondrial membrane potential [ 19 ]. The cells were incubated for 90 min in IB containing 0.5 mM pyruvate plus 40 nM TMRE in the absence or presence of 10 µM antimycin A or 1 µM BAM15.…”

Section: Methodsmentioning

confidence: 99%

“…End product of aerobic glycolysis is pyruvate, a 3-carbon α-keto acid that is a highly important metabolic intermediate which serves as substrate for various enzymes and metabolic pathways. For astrocytes it is known that intracellular pyruvate can be efficiently reduced to lactate by lactate dehydrogenase [ 18 , 19 ], oxidatively decarboxylated by mitochondrial pyruvate dehydrogenase to acetyl-CoA [ 7 , 20 ] or carboxylated by mitochondrial pyruvate carboxylase to oxaloacetate [ 6 , 7 ]. In addition, pyruvate can be transaminated to alanine by glutamate-pyruvate transaminases as astrocytes express both the cytosolic GPT1 and mitochondrial GPT2 isoenzymes [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

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Consumption and Metabolism of Extracellular Pyruvate by Cultured Rat Brain Astrocytes

et al. 2022

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Brain astrocytes are considered as glycolytic cell type, but these cells also produce ATP via mitochondrial oxidative phosphorylation. Exposure of cultured primary astrocytes in a glucose-free medium to extracellular substrates that are known to be metabolised by mitochondrial pathways, including pyruvate, lactate, beta-hydroxybutyrate, alanine and acetate, revealed that among the substrates investigated extracellular pyruvate was most efficiently consumed by astrocytes. Extracellular pyruvate was consumed by the cells almost proportional to time over hours in a concentration-dependent manner with apparent Michaelis–Menten kinetics [Km = 0.6 ± 0.1 mM, Vmax = 5.1 ± 0.8 nmol/(min × mg protein)]. The astrocytic consumption of pyruvate was strongly impaired in the presence of the monocarboxylate transporter 1 (MCT1) inhibitor AR-C155858 or by application of a 10-times excess of the MCT1 substrates lactate or beta-hydroxybutyrate. Pyruvate consumption by viable astrocytes was inhibited in the presence of UK5099, an inhibitor of the mitochondrial pyruvate carrier, or after application of the respiratory chain inhibitor antimycin A. In contrast, the mitochondrial uncoupler BAM15 strongly accelerated cellular pyruvate consumption. Lactate and alanine accounted after 3 h of incubation with pyruvate for around 60% and 10%, respectively, of the pyruvate consumed by the cells. These results demonstrate that consumption of extracellular pyruvate by astrocytes involves uptake via MCT1 and that the velocity of pyruvate consumption is strongly modified by substances that affect the entry of pyruvate into mitochondria or the activity of mitochondrial respiration.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Consumption and Metabolism of Extracellular Pyruvate by Cultured Rat Brain Astrocytes

et al. 2022

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“…Minocycline affects microglia cells [ 65 , 66 ], thereby inhibiting their cross-talk with astrocytes during neuroinflammation as a whole. Additionally, MCC950 inhibits NLRP3 inflammasome assembly and affects the maturation and secretion of the pro-inflammatory cytokine, IL-1β [ 67 , 68 ]. Our results demonstrated that these inhibitors reversed the augmentations in glucose uptake and lactate levels that were induced by LPS.…”

Section: Discussionmentioning

confidence: 99%

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway

Vizuete

Fróes

Seady

et al. 2022

J Neuroinflammation

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Neuroinflammation is a common feature during the development of neurological disorders and neurodegenerative diseases, where glial cells, such as microglia and astrocytes, play key roles in the activation and maintenance of inflammatory responses in the central nervous system. Neuroinflammation is now known to involve a neurometabolic shift, in addition to an increase in energy consumption. We used two approaches (in vivo and ex vivo) to evaluate the effects of lipopolysaccharide (LPS)-induced neuroinflammation on neurometabolic reprogramming, and on the modulation of the glycolytic pathway during the neuroinflammatory response. For this, we investigated inflammatory cytokines and receptors in the rat hippocampus, as well as markers of glial reactivity. Mitochondrial respirometry and the glycolytic pathway were evaluated by multiple parameters, including enzymatic activity, gene expression and regulation by protein kinases. Metabolic (e.g., metformin, 3PO, oxamic acid, fluorocitrate) and inflammatory (e.g., minocycline, MCC950, arundic acid) inhibitors were used in ex vivo hippocampal slices. The induction of early inflammatory changes by LPS (both in vivo and ex vivo) enhanced glycolytic parameters, such as glucose uptake, PFK1 activity and lactate release. This increased glucose consumption was independent of the energy expenditure for glutamate uptake, which was in fact diverted for the maintenance of the immune response. Accordingly, inhibitors of the glycolytic pathway and Krebs cycle reverted neuroinflammation (reducing IL-1β and S100B) and the changes in glycolytic parameters induced by LPS in acute hippocampal slices. Moreover, the inhibition of S100B, a protein predominantly synthesized and secreted by astrocytes, inhibition of microglia activation and abrogation of NLRP3 inflammasome assembly confirmed the role of neuroinflammation in the upregulation of glycolysis in the hippocampus. Our data indicate a neurometabolic glycolytic shift, induced by inflammatory activation, as well as a central and integrative role of astrocytes, and suggest that interference in the control of neurometabolism may be a promising strategy for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

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“…Assuming that the consumption of NADPH is lowered by dicoumarol-mediated inhibition of cytosolic NQO1, less glucose-6-phosphate would be needed as substrate for NADPH regeneration by the PPP [ 56 ] and more glucose-6-phosphate could be used for glycolytic lactate production. However, we can also not exclude a potential direct action of dicoumarol on mitochondrial processes which may lower mitochondrial ATP production and as a consequence increase glycolytic flux as previously shown for several compounds [ 57 , 58 ].…”

Section: Discussionmentioning

confidence: 81%

β-Lapachone Induces Acute Oxidative Stress in Rat Primary Astrocyte Cultures that is Terminated by the NQO1-Inhibitor Dicoumarol

et al. 2020

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β-lapachone (β-lap) is reduced in tumor cells by the enzyme NAD(P)H: quinone acceptor oxidoreductase 1 (NQO1) to a labile hydroquinone which spontaneously reoxidises to β-lap, thereby generating reactive oxygen species (ROS) and oxidative stress. To test for the consequences of an acute exposure of brain cells to β-lap, cultured primary rat astrocytes were incubated with β-lap for up to 4 h. The presence of β-lap in concentrations of up to 10 µM had no detectable adverse consequences, while higher concentrations of β-lap compromised the cell viability and the metabolism of astrocytes in a concentration- and time-dependent manner with half-maximal effects observed for around 15 µM β-lap after a 4 h incubation. Exposure of astrocytes to β-lap caused already within 5 min a severe increase in the cellular production of ROS as well as a rapid oxidation of glutathione (GSH) to glutathione disulfide (GSSG). The transient cellular accumulation of GSSG was followed by GSSG export. The β-lap-induced ROS production and GSSG accumulation were completely prevented in the presence of the NQO1 inhibitor dicoumarol. In addition, application of dicoumarol to β-lap-exposed astrocytes caused rapid regeneration of the normal high cellular GSH to GSSG ratio. These results demonstrate that application of β-lap to cultured astrocytes causes acute oxidative stress that depends on the activity of NQO1. The sequential application of β-lap and dicoumarol to rapidly induce and terminate oxidative stress, respectively, is a suitable experimental paradigm to study consequences of a defined period of acute oxidative stress in NQO1-expressing cells.

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Consequences of a Metabolic Glucose-Depletion on the Survival and the Metabolism of Cultured Rat Astrocytes

Cited by 15 publications

References 87 publications

Consumption and Metabolism of Extracellular Pyruvate by Cultured Rat Brain Astrocytes

Consumption and Metabolism of Extracellular Pyruvate by Cultured Rat Brain Astrocytes

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway

β-Lapachone Induces Acute Oxidative Stress in Rat Primary Astrocyte Cultures that is Terminated by the NQO1-Inhibitor Dicoumarol

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