The protective effects of hydrogen sulphide (H
S) to limit oxidative injury and preserve mitochondrial function during sepsis, ischemia/reperfusion, and neurodegenerative diseases have prompted the ...development of soluble H
S-releasing compounds such as GYY4137. Yet, the effects of GYY4137 on the mitochondrial function of endothelial cells remain unclear, while this cell type comprises the first target cell after parenteral administration. Here, we specifically assessed whether human endothelial cells possess a functional sulfide:quinone oxidoreductase (SQOR), to oxidise GYY4137-released H
S within the mitochondria for electron donation to the electron transport chain. We demonstrate that H
S administration increases oxygen consumption by human umbilical vein endothelial cells (HUVECs), which does not occur in the SQOR-deficient cell line SH-SY5Y. GYY4137 releases H
S in HUVECs in a dose- and time-dependent fashion as quantified by oxygen consumption and confirmed by lead acetate assay, as well as AzMC fluorescence. Scavenging of intracellular H
S using zinc confirmed intracellular and intramitochondrial sulfur, which resulted in mitotoxic zinc sulfide (ZnS) precipitates. Together, GYY4137 increases intramitochondrial H
S and boosts oxygen consumption of endothelial cells, which is likely governed via the oxidation of H
S by SQOR. This mechanism in endothelial cells may be instrumental in regulating H
S levels in blood and organs but can also be exploited to quantify H
S release by soluble donors such as GYY4137 in living systems.
New Biologically Active Hydrogen Sulfide Donors Roger, Thomas; Raynaud, Francoise; Bouillaud, Frédéric ...
Chembiochem : a European journal of chemical biology,
November 25, 2013, Letnik:
14, Številka:
17
Journal Article
Recenzirano
Generous donors: The dithioperoxyanhydrides (CH3COS)2, (PhCOS)2, CH3COSSCO2Me and PhCOSSCO2Me act as thiol‐activated hydrogen sulfide donors in aqueous buffer solution. The most efficient donor ...(CH3COS)2 can induce a biological response in cells, and advantageously replace hydrogen sulfide in ex vivo vascular studies.
Sulfide (H2S in the gas form) is the third gaseous transmitter found in mammals. However, in contrast to nitric oxide (NO) or carbon monoxide (CO), sulfide is oxidized by a sulfide quinone reductase ...and generates electrons that enter the mitochondrial respiratory chain arriving ultimately at cytochrome oxidase, where they combine with oxygen to generate water. In addition, sulfide is also a strong inhibitor of cytochrome oxidase, similar to NO, CO and cyanide. The balance between the electron donor and the inhibitory role of sulfide is likely controlled by sulfide and oxygen availability. The present study aimed to evaluate if and how sulfide release and oxidation impacts on the cellular affinity for oxygen. Results: i) when sulfide delivery approaches the maximal sulfide oxidation rate cells become exquisitely dependent on oxygen; ii) a positive feedback makes the balance between sulfide-releasing and -oxidizing rates the relevant parameter rather than the absolute values of these rates, and; iii) this altered dependence on oxygen is detected with sulfide concentrations that remain in the low micromolar range. Conclusions: i) within the context of continuous release of sulfide stemming from cellular metabolism, alterations in the activity of the sulfide oxidation pathway fine-tunes the cell's affinity for oxygen, and; ii) a decrease in the expression of the sulfide oxidation pathway greatly enhances the cell's dependence on oxygen concentration.
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•Sulfide decreases apparent cellular affinity for oxygen.•Not absolute rates but the ratio sulfide release/elimination is determinant.•Increasing the sulfide oxidation activity preserves cellular affinity for oxygen.
Deleterious consequences of heterozygous OPA1 mutations responsible for autosomal dominant optic atrophy remain a matter of debate. Primary skin fibroblasts derived from patients have shown diverse ...mitochondrial alterations that were however difficult to resolve in a unifying scheme. To address the potential use of these cells as disease model, we undertook parallel and quantitative analyses of the diverse reported alterations in four fibroblast lines harboring different OPA1 mutations, nonsense or missense, in the guanosine triphosphatase or the C-terminal coiled-coil domains. We tackled several factors potentially underlying discordant reports and showed that fibroblasts with heterozygous OPA1 mutations present with several mitochondrial alterations. These included defective mitochondrial fusion during pharmacological challenge with the protonophore carbonyl cyanide m‐chlorophenyl hydrazone, significant mitochondrial elongation with decreased OPA1 and DRP1 proteins, and abnormal mitochondrial fragmentation during glycolysis shortage or exogenous oxidative stress. Respiratory complex IV activity and subunits steady-state were decreased without alteration of the mitochondrial deoxyribonucleic acid size, amount or transcription. Physical link between OPA1 protein and oxidative phosphorylation was shown by reciprocal immunoprecipitation. Altered cristae structure coexisted with normal response to pro-apoptotic stimuli and expression of Bax or Bcl2 proteins. Skin fibroblasts with heterozygous OPA1 mutations thus share significant mitochondrial remodeling, and may therefore be useful for analyzing disease pathophysiology. Identifying whether the observed alterations are also present in ganglion retinal cells, and which of them underlies their degeneration process remains however an essential goal for therapeutic strategy.
► Heterozygous OPA1 mutations are associated with defective mitochondrial fusion. ► Mitochondrial morphology may be elongated despite defective mitochondrial fusion. ► Mutant OPA1 cells have altered mitochondrial dynamic response to nutritional stress. ► Mitochondrial activities are significantly altered in mutant OPA1 cells. ► Physical link between OPA1 and OXPHOS proteins is widespread.
Summary
Theileria annulata infects predominantly macrophages, and to a lesser extent B cells, and causes a widespread disease of cattle called tropical theileriosis. Disease‐causing infected ...macrophages are aggressively invasive, but this virulence trait can be attenuated by long‐term culture. Attenuated macrophages are used as live vaccines against tropical theileriosis and via their characterization one gains insights into what host cell trait is altered concomitant with loss of virulence. We established that sporozoite infection of monocytes rapidly induces hif1‐α transcription and that constitutive induction of HIF‐1α in transformed leukocytes is parasite‐dependent. In both infectedmacrophages and B cells induction of HIF‐1α activates transcription of its target genes that drive host cells to perform Warburg‐like glycolysis. We propose that Theileria‐infected leukocytes maintain a HIF‐1α‐driven transcriptional programme typical of Warburg glycolysis in order to reduce as much as possible host cell H2O2 type oxidative stress. However, in attenuated macrophages H2O2 production increases and HIF‐1α levels consequently remained high, even though adhesion and aggressive invasiveness diminished. This indicates that Theileria infection generates a host leukocytes hypoxic response that if not properly controlled leads to loss of virulence.
Rod-derived cone viability factor (RdCVF) is an inactive thioredoxin secreted by rod photoreceptors that protects cones from degeneration. Because the secondary loss of cones in retinitis pigmentosa ...(RP) leads to blindness, the administration of RdCVF is a promising therapy for this untreatable neurodegenerative disease. Here, we investigated the mechanism underlying the protective role of RdCVF in RP. We show that RdCVF acts through binding to Basigin-1 (BSG1), a transmembrane protein expressed specifically by photoreceptors. BSG1 binds to the glucose transporter GLUT1, resulting in increased glucose entry into cones. Increased glucose promotes cone survival by stimulation of aerobic glycolysis. Moreover, a missense mutation of RdCVF results in its inability to bind to BSG1, stimulate glucose uptake, and prevent secondary cone death in a model of RP. Our data uncover an entirely novel mechanism of neuroprotection through the stimulation of glucose metabolism.
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•Basigin-1 is the cell-surface receptor for RdCVF•RdCVF stimulates glucose uptake by cones•RdCVF-mediated glucose uptake stimulates aerobic glycolysis and cone survival
The rod-derived cone viability factor RdCVF promotes retinal cone survival by accelerating the entry of glucose into photoreceptors and enhancing aerobic glycolysis. RdCVF acts by binding to the cell-surface complex BSG1/GLUT1, a pathway also used by fast dividing cancer cells.
Uncoupling protein 2 (UCP2) is involved in various physiological and pathological processes such as insulin secretion, stem cell differentiation, cancer, and aging. However, its biochemical and ...physiological function is still under debate. Here we show that UCP2 is a metabolite transporter that regulates substrate oxidation in mitochondria. To shed light on its biochemical role, we first studied the effects of its silencing on the mitochondrial oxidation of glucose and glutamine. Compared with wild-type, UCP2-silenced human hepatocellular carcinoma (HepG2) cells, grown in the presence of glucose, showed a higher inner mitochondrial membrane potential and ATP:ADP ratio associated with a lower lactate release. Opposite results were obtained in the presence of glutamine instead of glucose. UCP2 reconstituted in lipid vesicles catalyzed the exchange of malate, oxaloacetate, and aspartate for phosphate plus a proton from opposite sides of the membrane. The higher levels of citric acid cycle intermediates found in the mitochondria of siUCP2-HepG2 cells compared with those found in wild-type cells in addition to the transport data indicate that, by exporting C4 compounds out of mitochondria, UCP2 limits the oxidation of acetyl-CoA–producing substrates such as glucose and enhances glutaminolysis, preventing the mitochondrial accumulation of C4 metabolites derived from glutamine. Our work reveals a unique regulatory mechanism in cell bioenergetics and provokes a substantial reconsideration of the physiological and pathological functions ascribed to UCP2 based on its purported uncoupling properties.
From electrons to cancer : Redox shift as a driving force of tumorigenesis Attal, Romain; Bakkar, Ashraf; Bouillaud, Frédéric ...
Advances in redox research : an official journal of the Society for Redox Biology and Medicine and the Society for Free Radical Research-Europe,
April 2024, 2024-04-00, 2024-04-01, Letnik:
10
Journal Article
Recenzirano
Odprti dostop
•In many cancer cells, glucose and glutamine uptake and substrate level phosphorylation are abnormally high.•Mitochondrial dysfunction lowers oxidative phosphorylation and induces an accumulation of ...reduced cofactors (NADH, NADPH and FADH2).•The core metabolism is represented as an electronic network in which the Krebs cycle pumps electrons to feed the mitochondrial respiratory chain.•In cancer cells, reduced cofactors form electronic short-circuits from catabolic processes to anabolic processes. Cancer is an electronic disease.•Methylene blue and chlorine dioxide drain electrons away from anabolic processes, lower the redox shift and can slow down the progression of cancer.
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Cancer cells are very diverse but mostly share a common metabolic property: they are strongly glycolytic even though oxygen is available. Herein, the metabolic abnormalities of cancer cells are interpreted as modifications of the electric currents in redox reactions. A lower current in the electron transport chain, an increase of the concentration of reduced cofactors and a partial reversal of the tricarboxylic acid cycle are physical characteristics of several forms of cancer. The existence of electric short-circuits between oxidative branches and reductive branches of the metabolic network argue in favor of an electronic approach of cancer in the nanoscopic scale. These changes of electron flows induce a pseudo-hypoxia and the Warburg effect through succinate production and divert electrons from oxygen to biosynthetic pathways. This new look at cancer may have potential therapeutic applications.
OBJECTIVE:To report that homoplasmic deleterious mutations in the mitochondrial DNA MT-ATP6/8 genes may be responsible for acute episodes of limb weakness mimicking periodic paralysis due to ...channelopathies and dramatically responding to acetazolamide.
METHODS:Mitochondrial DNA sequencing and restriction PCR, oxidative phosphorylation functional assays, reactive oxygen species metabolism, and patch-clamp technique in cultured skin fibroblasts.
RESULTS:Occurrence of a typical MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) syndrome in a single member of a large pedigree with episodic weakness associated with a later-onset distal motor neuropathy led to the disclosure of 2 deleterious mitochondrial DNA mutations. The MT-ATP6 m.9185T>C p.Leu220Pro mutation, previously associated with Leigh syndrome, was present in all family members, while the MT-TL1 m.3271T>C mutation, a known cause of MELAS syndrome, was observed in the sole patient with MELAS presentation. Significant defect of complexes V and I as well as oxidative stress were observed in both primary fibroblasts and cybrid cells with 100% m.9185T>C mutation. Permanent plasma membrane depolarization and altered permeability to K in fibroblasts provided a link with the paralysis episodes. Screening of 9 patients, based on their clinical phenotype, identified 4 patients with similar deleterious MT-ATP6 mutations (twice m.9185T>C and once m.9176T>C or m.8893T>C). A fifth patient presented with an original potentially deleterious MT-ATP8 mutation (m.8403T>C). All mutations were associated with almost-normal complex V activity but significant oxidative stress and permanent plasma membrane depolarization.
CONCLUSION:Homoplasmic mutations in the MT-ATP6/8 genes may cause episodic weakness responding to acetazolamide treatment.
Uncoupling protein 2 (UCP2) belongs to the mitochondrial anion carrier family and partially uncouples respiration from ATP synthesis when expressed in recombinant yeast mitochondria. We generated a ...highly sensitive polyclonal antibody against human UCP2. Its reactivity toward mitochondrial proteins was compared between wild type and ucp2(−/−) mice, leading to non-ambiguous identification of UCP2. We detected UCP2 in spleen, lung, stomach, and white adipose tissue. No UCP2 was detected in heart, skeletal muscle, liver, and brown adipose tissue. The level of UCP2 in spleen mitochondria is less than 1% of the level of UCP1 in brown adipose tissue mitochondria. Starvation and LPS treatments increase UCP2 level up to 12 times in lung and stomach, which supports the hypothesis that UCP2 responds to oxidative stress situations. Stimulation of the UCP2 expression occurs without any change in UCP2 mRNA levels. This is explained by translational regulation of the UCP2 mRNA. We have shown that an upstream open reading frame located in exon two of theucp2 gene strongly inhibits the expression of the protein. This further level of regulation of the ucp2 gene provides a mechanism by which expression can be strongly and rapidly induced under stress conditions.
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