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Jabůrek M, Klöppel E, Průchová P, Mozheitova O, Tauber J, Engstová H, Ježek P. Mitochondria to plasma membrane redox signaling is essential for fatty acid β-oxidation-driven insulin secretion. Redox Biol 2024; 75:103283. [PMID: 39067330 PMCID: PMC11332078 DOI: 10.1016/j.redox.2024.103283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2024] [Revised: 07/22/2024] [Accepted: 07/22/2024] [Indexed: 07/30/2024] Open
Abstract
We asked whether acute redox signaling from mitochondria exists concomitantly to fatty acid- (FA-) stimulated insulin secretion (FASIS) at low glucose by pancreatic β-cells. We show that FA β-oxidation produces superoxide/H2O2, providing: i) mitochondria-to-plasma-membrane redox signaling, closing KATP-channels synergically with elevated ATP (substituting NADPH-oxidase-4-mediated H2O2-signaling upon glucose-stimulated insulin secretion); ii) activation of redox-sensitive phospholipase iPLA2γ/PNPLA8, cleaving mitochondrial FAs, enabling metabotropic GPR40 receptors to amplify insulin secretion (IS). At fasting glucose, palmitic acid stimulated IS in wt mice; palmitic, stearic, lauric, oleic, linoleic, and hexanoic acids also in perifused pancreatic islets (PIs), with suppressed 1st phases in iPLA2γ/PNPLA8-knockout mice/PIs. Extracellular/cytosolic H2O2-monitoring indicated knockout-independent redox signals, blocked by mitochondrial antioxidant SkQ1, etomoxir, CPT1 silencing, and catalase overexpression, all inhibiting FASIS, keeping ATP-sensitive K+-channels open, and diminishing cytosolic [Ca2+]-oscillations. FASIS in mice was a postprandially delayed physiological event. Redox signals of FA β-oxidation are thus documented, reaching the plasma membrane, essentially co-stimulating IS.
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Affiliation(s)
- Martin Jabůrek
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Eduardo Klöppel
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Pavla Průchová
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Oleksandra Mozheitova
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Jan Tauber
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Hana Engstová
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology, No.75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, Prague, 14220, Czech Republic.
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Ježek P, Dlasková A, Engstová H, Špačková J, Tauber J, Průchová P, Kloppel E, Mozheitova O, Jabůrek M. Mitochondrial Physiology of Cellular Redox Regulations. Physiol Res 2024; 73:S217-S242. [PMID: 38647168 PMCID: PMC11412358 DOI: 10.33549/physiolres.935269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024] Open
Abstract
Mitochondria (mt) represent the vital hub of the molecular physiology of the cell, being decision-makers in cell life/death and information signaling, including major redox regulations and redox signaling. Now we review recent advances in understanding mitochondrial redox homeostasis, including superoxide sources and H2O2 consumers, i.e., antioxidant mechanisms, as well as exemplar situations of physiological redox signaling, including the intramitochondrial one and mt-to-cytosol redox signals, which may be classified as acute and long-term signals. This review exemplifies the acute redox signals in hypoxic cell adaptation and upon insulin secretion in pancreatic beta-cells. We also show how metabolic changes under these circumstances are linked to mitochondrial cristae narrowing at higher intensity of ATP synthesis. Also, we will discuss major redox buffers, namely the peroxiredoxin system, which may also promote redox signaling. We will point out that pathological thresholds exist, specific for each cell type, above which the superoxide sources exceed regular antioxidant capacity and the concomitant harmful processes of oxidative stress subsequently initiate etiology of numerous diseases. The redox signaling may be impaired when sunk in such excessive pro-oxidative state.
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Affiliation(s)
- P Ježek
- Laboratory of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.
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3
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Caggiano EG, Taniguchi CM. UCP2 and pancreatic cancer: conscious uncoupling for therapeutic effect. Cancer Metastasis Rev 2024; 43:777-794. [PMID: 38194152 PMCID: PMC11156755 DOI: 10.1007/s10555-023-10157-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 11/13/2023] [Indexed: 01/10/2024]
Abstract
Pancreatic cancer has an exaggerated dependence on mitochondrial metabolism, but methods to specifically target the mitochondria without off target effects in normal tissues that rely on these organelles is a significant challenge. The mitochondrial uncoupling protein 2 (UCP2) has potential as a cancer-specific drug target, and thus, we will review the known biology of UCP2 and discuss its potential role in the pathobiology and future therapy of pancreatic cancer.
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Affiliation(s)
- Emily G Caggiano
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- The University of Texas MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Cullen M Taniguchi
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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4
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Ježek P, Jabůrek M, Holendová B, Engstová H, Dlasková A. Mitochondrial Cristae Morphology Reflecting Metabolism, Superoxide Formation, Redox Homeostasis, and Pathology. Antioxid Redox Signal 2023; 39:635-683. [PMID: 36793196 PMCID: PMC10615093 DOI: 10.1089/ars.2022.0173] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 02/08/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023]
Abstract
Significance: Mitochondrial (mt) reticulum network in the cell possesses amazing ultramorphology of parallel lamellar cristae, formed by the invaginated inner mitochondrial membrane. Its non-invaginated part, the inner boundary membrane (IBM) forms a cylindrical sandwich with the outer mitochondrial membrane (OMM). Crista membranes (CMs) meet IBM at crista junctions (CJs) of mt cristae organizing system (MICOS) complexes connected to OMM sorting and assembly machinery (SAM). Cristae dimensions, shape, and CJs have characteristic patterns for different metabolic regimes, physiological and pathological situations. Recent Advances: Cristae-shaping proteins were characterized, namely rows of ATP-synthase dimers forming the crista lamella edges, MICOS subunits, optic atrophy 1 (OPA1) isoforms and mitochondrial genome maintenance 1 (MGM1) filaments, prohibitins, and others. Detailed cristae ultramorphology changes were imaged by focused-ion beam/scanning electron microscopy. Dynamics of crista lamellae and mobile CJs were demonstrated by nanoscopy in living cells. With tBID-induced apoptosis a single entirely fused cristae reticulum was observed in a mitochondrial spheroid. Critical Issues: The mobility and composition of MICOS, OPA1, and ATP-synthase dimeric rows regulated by post-translational modifications might be exclusively responsible for cristae morphology changes, but ion fluxes across CM and resulting osmotic forces might be also involved. Inevitably, cristae ultramorphology should reflect also mitochondrial redox homeostasis, but details are unknown. Disordered cristae typically reflect higher superoxide formation. Future Directions: To link redox homeostasis to cristae ultramorphology and define markers, recent progress will help in uncovering mechanisms involved in proton-coupled electron transfer via the respiratory chain and in regulation of cristae architecture, leading to structural determination of superoxide formation sites and cristae ultramorphology changes in diseases. Antioxid. Redox Signal. 39, 635-683.
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Affiliation(s)
- Petr Ježek
- Department No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Jabůrek
- Department No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Blanka Holendová
- Department No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Hana Engstová
- Department No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Andrea Dlasková
- Department No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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5
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Ježek P. Pitfalls of Mitochondrial Redox Signaling Research. Antioxidants (Basel) 2023; 12:1696. [PMID: 37759999 PMCID: PMC10525995 DOI: 10.3390/antiox12091696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 08/27/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
Redox signaling from mitochondria (mt) to the cytosol and plasma membrane (PM) has been scarcely reported, such as in the case of hypoxic cell adaptation or (2-oxo-) 2-keto-isocaproate (KIC) β-like-oxidation stimulating insulin secretion in pancreatic β-cells. Mutual redox state influence between mitochondrial major compartments, the matrix and the intracristal space, and the cytosol is therefore derived theoretically in this article to predict possible conditions, when mt-to-cytosol and mt-to-PM signals may occur, as well as conditions in which the cytosolic redox signaling is not overwhelmed by the mitochondrial antioxidant capacity. Possible peroxiredoxin 3 participation in mt-to-cytosol redox signaling is discussed, as well as another specific case, whereby mitochondrial superoxide release is diminished, whereas the matrix MnSOD is activated. As a result, the enhanced conversion to H2O2 allows H2O2 diffusion into the cytosol, where it could be a predominant component of the H2O2 release. In both of these ways, mt-to-cytosol and mt-to-PM signals may be realized. Finally, the use of redox-sensitive probes is discussed, which disturb redox equilibria, and hence add a surplus redox-buffering to the compartment, where they are localized. Specifically, when attempts to quantify net H2O2 fluxes are to be made, this should be taken into account.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, 14220 Prague, Czech Republic
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6
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Cardozo G, Mastrogiovanni M, Zeida A, Viera N, Radi R, Reyes AM, Trujillo M. Mitochondrial Peroxiredoxin 3 Is Rapidly Oxidized and Hyperoxidized by Fatty Acid Hydroperoxides. Antioxidants (Basel) 2023; 12:antiox12020408. [PMID: 36829967 PMCID: PMC9952270 DOI: 10.3390/antiox12020408] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 01/19/2023] [Accepted: 01/28/2023] [Indexed: 02/11/2023] Open
Abstract
Human peroxiredoxin 3 (HsPrx3) is a thiol-based peroxidase responsible for the reduction of most hydrogen peroxide and peroxynitrite formed in mitochondria. Mitochondrial disfunction can lead to membrane lipoperoxidation, resulting in the formation of lipid-bound fatty acid hydroperoxides (LFA-OOHs) which can be released to become free fatty acid hydroperoxides (fFA-OOHs). Herein, we report that HsPrx3 is oxidized and hyperoxidized by fFA-OOHs including those derived from arachidonic acid and eicosapentaenoic acid peroxidation at position 15 with remarkably high rate constants of oxidation (>3.5 × 107 M-1s-1) and hyperoxidation (~2 × 107 M-1s-1). The endoperoxide-hydroperoxide PGG2, an intermediate in prostanoid synthesis, oxidized HsPrx3 with a similar rate constant, but was less effective in causing hyperoxidation. Biophysical methodologies suggest that HsPrx3 can bind hydrophobic structures. Indeed, molecular dynamic simulations allowed the identification of a hydrophobic patch near the enzyme active site that can allocate the hydroperoxide group of fFA-OOHs in close proximity to the thiolate in the peroxidatic cysteine. Simulations performed using available and herein reported kinetic data indicate that HsPrx3 should be considered a main target for mitochondrial fFA-OOHs. Finally, kinetic simulation analysis support that mitochondrial fFA-OOHs formation fluxes in the range of nM/s are expected to contribute to HsPrx3 hyperoxidation, a modification that has been detected in vivo under physiological and pathological conditions.
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Affiliation(s)
- Giuliana Cardozo
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
| | - Mauricio Mastrogiovanni
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
| | - Ari Zeida
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
| | - Nicolás Viera
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
| | - Rafael Radi
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
| | - Aníbal M. Reyes
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
- Correspondence: (A.M.R.); (M.T.)
| | - Madia Trujillo
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
- Centro de Investigaciones Biomédicas, Universidad de la República, Montevideo 11800, Uruguay
- Correspondence: (A.M.R.); (M.T.)
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Biondi G, Marrano N, Borrelli A, Rella M, Palma G, Calderoni I, Siciliano E, Lops P, Giorgino F, Natalicchio A. Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes. Int J Mol Sci 2022; 23:ijms23105522. [PMID: 35628332 PMCID: PMC9143684 DOI: 10.3390/ijms23105522] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 12/10/2022] Open
Abstract
The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.
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Ježek P, Holendová B, Jabůrek M, Dlasková A, Plecitá-Hlavatá L. Contribution of Mitochondria to Insulin Secretion by Various Secretagogues. Antioxid Redox Signal 2022; 36:920-952. [PMID: 34180254 PMCID: PMC9125579 DOI: 10.1089/ars.2021.0113] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significance: Mitochondria determine glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells by elevating ATP synthesis. As the metabolic and redox hub, mitochondria provide numerous links to the plasma membrane channels, insulin granule vesicles (IGVs), cell redox, NADH, NADPH, and Ca2+ homeostasis, all affecting insulin secretion. Recent Advances: Mitochondrial redox signaling was implicated in several modes of insulin secretion (branched-chain ketoacid [BCKA]-, fatty acid [FA]-stimulated). Mitochondrial Ca2+ influx was found to enhance GSIS, reflecting cytosolic Ca2+ oscillations induced by action potential spikes (intermittent opening of voltage-dependent Ca2+ and K+ channels) or the superimposed Ca2+ release from the endoplasmic reticulum (ER). The ATPase inhibitory factor 1 (IF1) was reported to tune the glucose sensitivity range for GSIS. Mitochondrial protein kinase A was implicated in preventing the IF1-mediated inhibition of the ATP synthase. Critical Issues: It is unknown how the redox signal spreads up to the plasma membrane and what its targets are, what the differences in metabolic, redox, NADH/NADPH, and Ca2+ signaling, and homeostasis are between the first and second GSIS phase, and whether mitochondria can replace ER in the amplification of IGV exocytosis. Future Directions: Metabolomics studies performed to distinguish between the mitochondrial matrix and cytosolic metabolites will elucidate further details. Identifying the targets of cell signaling into mitochondria and of mitochondrial retrograde metabolic and redox signals to the cell will uncover further molecular mechanisms for insulin secretion stimulated by glucose, BCKAs, and FAs, and the amplification of secretion by glucagon-like peptide (GLP-1) and metabotropic receptors. They will identify the distinction between the hub β-cells and their followers in intact and diabetic states. Antioxid. Redox Signal. 36, 920-952.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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9
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Antioxidant Role and Cardiolipin Remodeling by Redox-Activated Mitochondrial Ca 2+-Independent Phospholipase A 2γ in the Brain. Antioxidants (Basel) 2022; 11:antiox11020198. [PMID: 35204081 PMCID: PMC8868467 DOI: 10.3390/antiox11020198] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/14/2022] [Accepted: 01/18/2022] [Indexed: 02/01/2023] Open
Abstract
Mitochondrial Ca2+-independent phospholipase A2γ (iPLA2γ/PNPLA8) was previously shown to be directly activated by H2O2 and release free fatty acids (FAs) for FA-dependent H+ transport mediated by the adenine nucleotide translocase (ANT) or uncoupling protein 2 (UCP2). The resulting mild mitochondrial uncoupling and consequent partial attenuation of mitochondrial superoxide production lead to an antioxidant effect. However, the antioxidant role of iPLA2γ in the brain is not completely understood. Here, using wild-type and iPLA2γ-KO mice, we demonstrate the ability of tert-butylhydroperoxide (TBHP) to activate iPLA2γ in isolated brain mitochondria, with consequent liberation of FAs and lysophospholipids. The liberated FA caused an increase in respiratory rate, which was fully inhibited by carboxyatractyloside (CATR), a specific inhibitor of ANT. Employing detailed lipidomic analysis, we also demonstrate a typical cleavage pattern for TBHP-activated iPLA2γ, reflecting cleavage of glycerophospholipids from both sn-1 and sn-2 positions releasing saturated FAs, monoenoic FAs, and predominant polyunsaturated FAs. The acute antioxidant role of iPLA2γ-released FAs is supported by monitoring both intramitochondrial superoxide and extramitochondrial H2O2 release. We also show that iPLA2γ-KO mice were more sensitive to stimulation by pro-inflammatory lipopolysaccharide, as reflected by the concomitant increase in protein carbonyls in the brain and pro-inflammatory IL-6 release in the serum. These data support the antioxidant and anti-inflammatory role of iPLA2γ in vivo. Our data also reveal a substantial decrease of several high molecular weight cardiolipin (CL) species and accumulation of low molecular weight CL species in brain mitochondria of iPLA2γ-KO mice. Collectively, our results support a key role of iPLA2γ in the remodeling of lower molecular weight immature cardiolipins with predominantly saturated acyl chains to high molecular weight mature cardiolipins with highly unsaturated PUFA acyl chains, typical for the brain.
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10
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Römer A, Rawat D, Linn T, Petry SF. Preparation of fatty acid solutions exerts significant impact on experimental outcomes in cell culture models of lipotoxicity. Biol Methods Protoc 2022; 7:bpab023. [PMID: 35036572 PMCID: PMC8754478 DOI: 10.1093/biomethods/bpab023] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 11/25/2021] [Accepted: 11/30/2021] [Indexed: 11/14/2022] Open
Abstract
Free fatty acids are essentially involved in the pathogenesis of chronic diseases such as diabetes mellitus, non-alcoholic fatty liver disease, and cardiovascular disease. They promote mitochondrial dysfunction, oxidative stress, respiratory chain uncoupling, and endoplasmic reticulum stress and modulate stress-sensitive pathways. These detrimental biological effects summarized as lipotoxicity mainly depend on fatty acid carbon chain length, degree of unsaturation, concentration, and treatment time. Preparation of fatty acid solutions involves dissolving and complexing. Solvent toxicity and concentration, amount of bovine serum albumin (BSA), and ratio of albumin to fatty acids can vary significantly between equal concentrations, mediating considerable harmful effects and/or interference with certain assays such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Herein, we studied the impact of commonly used solvents ethanol and dimethyl sulfoxide and varying concentrations of BSA directly and in solution with oleic acid on MTT to formazan conversion, adenosine triphosphate level, and insulin content and secretion of murine β-cell line MIN6 employing different treatment duration. Our data show that experimental outcomes and assay readouts can be significantly affected by mere preparation of fatty acid solutions and should thus be carefully considered and described in detail to ensure comparability and distinct evaluation of data.
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Affiliation(s)
- Axel Römer
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Divya Rawat
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Thomas Linn
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Sebastian F Petry
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University Giessen, 35392 Giessen, Germany
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11
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Jabůrek M, Průchová P, Holendová B, Galkin A, Ježek P. Antioxidant Synergy of Mitochondrial Phospholipase PNPLA8/iPLA2γ with Fatty Acid-Conducting SLC25 Gene Family Transporters. Antioxidants (Basel) 2021; 10:antiox10050678. [PMID: 33926059 PMCID: PMC8146845 DOI: 10.3390/antiox10050678] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/13/2021] [Accepted: 04/22/2021] [Indexed: 02/07/2023] Open
Abstract
Patatin-like phospholipase domain-containing protein PNPLA8, also termed Ca2+-independent phospholipase A2γ (iPLA2γ), is addressed to the mitochondrial matrix (or peroxisomes), where it may manifest its unique activity to cleave phospholipid side-chains from both sn-1 and sn-2 positions, consequently releasing either saturated or unsaturated fatty acids (FAs), including oxidized FAs. Moreover, iPLA2γ is directly stimulated by H2O2 and, hence, is activated by redox signaling or oxidative stress. This redox activation permits the antioxidant synergy with mitochondrial uncoupling proteins (UCPs) or other SLC25 mitochondrial carrier family members by FA-mediated protonophoretic activity, termed mild uncoupling, that leads to diminishing of mitochondrial superoxide formation. This mechanism allows for the maintenance of the steady-state redox status of the cell. Besides the antioxidant role, we review the relations of iPLA2γ to lipid peroxidation since iPLA2γ is alternatively activated by cardiolipin hydroperoxides and hypothetically by structural alterations of lipid bilayer due to lipid peroxidation. Other iPLA2γ roles include the remodeling of mitochondrial (or peroxisomal) membranes and the generation of specific lipid second messengers. Thus, for example, during FA β-oxidation in pancreatic β-cells, H2O2-activated iPLA2γ supplies the GPR40 metabotropic FA receptor to amplify FA-stimulated insulin secretion. Cytoprotective roles of iPLA2γ in the heart and brain are also discussed.
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Affiliation(s)
- Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1084, 14220 Prague, Czech Republic; (P.P.); (B.H.); (P.J.)
- Correspondence: ; Tel.: +420-296442789
| | - Pavla Průchová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1084, 14220 Prague, Czech Republic; (P.P.); (B.H.); (P.J.)
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1084, 14220 Prague, Czech Republic; (P.P.); (B.H.); (P.J.)
| | - Alexander Galkin
- Department of Pediatrics, Division of Neonatology, Columbia University William Black Building, New York, NY 10032, USA;
| | - Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1084, 14220 Prague, Czech Republic; (P.P.); (B.H.); (P.J.)
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12
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Benáková Š, Holendová B, Plecitá-Hlavatá L. Redox Homeostasis in Pancreatic β-Cells: From Development to Failure. Antioxidants (Basel) 2021; 10:antiox10040526. [PMID: 33801681 PMCID: PMC8065646 DOI: 10.3390/antiox10040526] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 12/16/2022] Open
Abstract
Redox status is a key determinant in the fate of β-cell. These cells are not primarily detoxifying and thus do not possess extensive antioxidant defense machinery. However, they show a wide range of redox regulating proteins, such as peroxiredoxins, thioredoxins or thioredoxin reductases, etc., being functionally compartmentalized within the cells. They keep fragile redox homeostasis and serve as messengers and amplifiers of redox signaling. β-cells require proper redox signaling already in cell ontogenesis during the development of mature β-cells from their progenitors. We bring details about redox-regulated signaling pathways and transcription factors being essential for proper differentiation and maturation of functional β-cells and their proliferation and insulin expression/maturation. We briefly highlight the targets of redox signaling in the insulin secretory pathway and focus more on possible targets of extracellular redox signaling through secreted thioredoxin1 and thioredoxin reductase1. Tuned redox homeostasis can switch upon chronic pathological insults towards the dysfunction of β-cells and to glucose intolerance. These are characteristics of type 2 diabetes, which is often linked to chronic nutritional overload being nowadays a pandemic feature of lifestyle. Overcharged β-cell metabolism causes pressure on proteostasis in the endoplasmic reticulum, mainly due to increased demand on insulin synthesis, which establishes unfolded protein response and insulin misfolding along with excessive hydrogen peroxide production. This together with redox dysbalance in cytoplasm and mitochondria due to enhanced nutritional pressure impact β-cell redox homeostasis and establish prooxidative metabolism. This can further affect β-cell communication in pancreatic islets through gap junctions. In parallel, peripheral tissues losing insulin sensitivity and overall impairment of glucose tolerance and gut microbiota establish local proinflammatory signaling and later systemic metainflammation, i.e., low chronic inflammation prooxidative properties, which target β-cells leading to their dedifferentiation, dysfunction and eventually cell death.
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Affiliation(s)
- Štěpánka Benáková
- Department of Mitochondrial Physiology, Institute of Physiology, Czech Academy of Sciences, 142 20 Prague 4, Czech Republic; (Š.B.); (B.H.)
- First Faculty of Medicine, Charles University, Katerinska 1660/32, 121 08 Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology, Czech Academy of Sciences, 142 20 Prague 4, Czech Republic; (Š.B.); (B.H.)
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology, Czech Academy of Sciences, 142 20 Prague 4, Czech Republic; (Š.B.); (B.H.)
- Department of Mitochondrial Physiology, Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic
- Correspondence: ; Tel.: +420-296-442-285
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Scholtes C, Giguère V. Transcriptional Regulation of ROS Homeostasis by the ERR Subfamily of Nuclear Receptors. Antioxidants (Basel) 2021; 10:antiox10030437. [PMID: 33809291 PMCID: PMC7999130 DOI: 10.3390/antiox10030437] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/09/2021] [Accepted: 03/10/2021] [Indexed: 01/08/2023] Open
Abstract
Reactive oxygen species (ROS) such as superoxide anion (O2•-) and hydrogen peroxide (H2O2) are generated endogenously by processes such as mitochondrial oxidative phosphorylation, or they may arise from exogenous sources like bacterial invasion. ROS can be beneficial (oxidative eustress) as signaling molecules but also harmful (oxidative distress) to cells when ROS levels become unregulated in response to physiological, pathological or pharmacological insults. Indeed, abnormal ROS levels have been shown to contribute to the etiology of a wide variety of diseases. Transcriptional control of metabolic genes is a crucial mechanism to coordinate ROS homeostasis. Therefore, a better understanding of how ROS metabolism is regulated by specific transcription factors can contribute to uncovering new therapeutic strategies. A large body of work has positioned the estrogen-related receptors (ERRs), transcription factors belonging to the nuclear receptor superfamily, as not only master regulators of cellular energy metabolism but, most recently, of ROS metabolism. Herein, we will review the role played by the ERRs as transcriptional regulators of ROS generation and antioxidant mechanisms and also as ROS sensors. We will assess how the control of ROS homeostasis by the ERRs can be linked to physiology and disease and the possible contribution of manipulating ERR activity in redox medicine.
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Affiliation(s)
- Charlotte Scholtes
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada;
| | - Vincent Giguère
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada;
- Department of Biochemistry, McGill University, Montréal, QC H3G 1Y6, Canada
- Correspondence:
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Lipotoxic Impairment of Mitochondrial Function in β-Cells: A Review. Antioxidants (Basel) 2021; 10:antiox10020293. [PMID: 33672062 PMCID: PMC7919463 DOI: 10.3390/antiox10020293] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 02/06/2021] [Accepted: 02/11/2021] [Indexed: 02/08/2023] Open
Abstract
Lipotoxicity is a major contributor to type 2 diabetes mainly promoting mitochondrial dysfunction. Lipotoxic stress is mediated by elevated levels of free fatty acids through various mechanisms and pathways. Impaired peroxisome proliferator-activated receptor (PPAR) signaling, enhanced oxidative stress levels, and uncoupling of the respiratory chain result in ATP deficiency, while β-cell viability can be severely impaired by lipotoxic modulation of PI3K/Akt and mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) pathways. However, fatty acids are physiologically required for an unimpaired β-cell function. Thus, preparation, concentration, and treatment duration determine whether the outcome is beneficial or detrimental when fatty acids are employed in experimental setups. Further, ageing is a crucial contributor to β-cell decay. Cellular senescence is connected to loss of function in β-cells and can further be promoted by lipotoxicity. The potential benefit of nutrients has been broadly investigated, and particularly polyphenols were shown to be protective against both lipotoxicity and cellular senescence, maintaining the physiology of β-cells. Positive effects on blood glucose regulation, mitigation of oxidative stress by radical scavenging properties or regulation of antioxidative enzymes, and modulation of apoptotic factors were reported. This review summarizes the significance of lipotoxicity and cellular senescence for mitochondrial dysfunction in the pancreatic β-cell and outlines potential beneficial effects of plant-based nutrients by the example of polyphenols.
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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Mitochondria exert age-divergent effects on recovery from spinal cord injury. Exp Neurol 2021; 337:113597. [PMID: 33422552 PMCID: PMC7870583 DOI: 10.1016/j.expneurol.2021.113597] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/15/2020] [Accepted: 01/05/2021] [Indexed: 02/07/2023]
Abstract
The extent that age-dependent mitochondrial dysfunction drives neurodegeneration is not well understood. This study tested the hypothesis that mitochondria contribute to spinal cord injury (SCI)-induced neurodegeneration in an age-dependent manner by using 2,4-dinitrophenol (DNP) to uncouple electron transport, thereby increasing cellular respiration and reducing reactive oxygen species (ROS) production. We directly compared the effects of graded DNP doses in 4- and 14-month-old (MO) SCI-mice and found DNP to have increased efficacy in mitochondria isolated from 14-MO animals. In vivo, all DNP doses significantly exacerbated 4-MO SCI neurodegeneration coincident with worsened recovery. In contrast, low DNP doses (1.0-mg/kg/day) improved tissue sparing, reduced ROS-associated 3-nitrotyrosine (3-NT) accumulation, and improved anatomical and functional recovery in 14-MO SCI-mice. By directly comparing the effects of DNP between ages we demonstrate that mitochondrial contributions to neurodegeneration diverge with age after SCI. Collectively, our data indicate an essential role of mitochondria in age-associated neurodegeneration.
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Plecitá-Hlavatá L, Engstová H, Holendová B, Tauber J, Špaček T, Petrásková L, Křen V, Špačková J, Gotvaldová K, Ježek J, Dlasková A, Smolková K, Ježek P. Mitochondrial Superoxide Production Decreases on Glucose-Stimulated Insulin Secretion in Pancreatic β Cells Due to Decreasing Mitochondrial Matrix NADH/NAD + Ratio. Antioxid Redox Signal 2020; 33:789-815. [PMID: 32517485 PMCID: PMC7482716 DOI: 10.1089/ars.2019.7800] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/03/2020] [Accepted: 06/08/2020] [Indexed: 12/19/2022]
Abstract
Aims: Glucose-stimulated insulin secretion (GSIS) in pancreatic β cells was expected to enhance mitochondrial superoxide formation. Hence, we elucidated relevant redox equilibria. Results: Unexpectedly, INS-1E cells at transitions from 3 (11 mM; pancreatic islets from 5 mM) to 25 mM glucose decreased matrix superoxide release rates (MitoSOX Red monitoring validated by MitoB) and H2O2 (mitoHyPer, subtracting mitoSypHer emission). Novel double-channel fluorescence lifetime imaging, approximating free mitochondrial matrix NADHF, indicated its ∼20% decrease. Matrix NAD+F increased on GSIS, indicated by the FAD-emission lifetime decrease, reflecting higher quenching of FAD by NAD+F. The participation of pyruvate/malate and pyruvate/citrate redox shuttles, elevating cytosolic NADPHF (iNAP1 fluorescence monitoring) at the expense of matrix NADHF, was indicated, using citrate (2-oxoglutarate) carrier inhibitors and cytosolic malic enzyme silencing: All changes vanished on these manipulations. 13C-incorporation from 13C-L-glutamine into 13C-citrate reflected the pyruvate/isocitrate shuttle. Matrix NADPHF (iNAP3 monitored) decreased. With decreasing glucose, the suppressor of Complex III site Q electron leak (S3QEL) suppressor caused a higher Complex I IF site contribution, but a lower superoxide fraction ascribed to the Complex III site IIIQo. Thus, the diminished matrix NADHF/NAD+F decreased Complex I flavin site IF superoxide formation on GSIS. Innovation: Mutually validated methods showed decreasing superoxide release into the mitochondrial matrix in pancreatic β cells on GSIS, due to the decreasing matrix NADHF/NAD+F (NADPHF/NADP+F) at increasing cytosolic NADPHF levels. The developed innovative methods enable real-time NADH/NAD+ and NADPH/NADP+ monitoring in any distinct cell compartment. Conclusion: The export of reducing equivalents from mitochondria adjusts lower mitochondrial superoxide production on GSIS, but it does not prevent oxidative stress in pancreatic β cells.
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Affiliation(s)
- Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Hana Engstová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Tauber
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tomáš Špaček
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lucie Petrásková
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Vladimír Křen
- Laboratory of Biotransformation, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jitka Špačková
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Klára Gotvaldová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Katarína Smolková
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Leguina-Ruzzi A, Vodičková A, Holendová B, Pavluch V, Tauber J, Engstová H, Dlasková A, Ježek P. Glucose-Induced Expression of DAPIT in Pancreatic β-Cells. Biomolecules 2020; 10:biom10071026. [PMID: 32664368 PMCID: PMC7408392 DOI: 10.3390/biom10071026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 07/07/2020] [Accepted: 07/08/2020] [Indexed: 12/14/2022] Open
Abstract
Transcript levels for selected ATP synthase membrane FO-subunits-including DAPIT-in INS-1E cells were found to be sensitive to lowering glucose down from 11 mM, in which these cells are routinely cultured. Depending on conditions, the diminished mRNA levels recovered when glucose was restored to 11 mM; or were elevated during further 120 min incubations with 20-mM glucose. Asking whether DAPIT expression may be elevated by hyperglycemia in vivo, we studied mice with hyaluronic acid implants delivering glucose for up to 14 days. Such continuous two-week glucose stimulations in mice increased DAPIT mRNA by >5-fold in isolated pancreatic islets (ATP synthase F1α mRNA by 1.5-fold). In INS-1E cells, the glucose-induced ATP increment vanished with DAPIT silencing (6% of ATP rise), likewise a portion of the mtDNA-copy number increment. With 20 and 11-mM glucose the phosphorylating/non-phosphorylating respiration rate ratio diminished to ~70% and 96%, respectively, upon DAPIT silencing, whereas net GSIS rates accounted for 80% and 90% in USMG5/DAPIT-deficient cells. Consequently, the sufficient DAPIT expression and complete ATP synthase assembly is required for maximum ATP synthesis and mitochondrial biogenesis, but not for insulin secretion as such. Elevated DAPIT expression at high glucose further increases the ATP synthesis efficiency.
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Plecitá-Hlavatá L, Jabůrek M, Holendová B, Tauber J, Pavluch V, Berková Z, Cahová M, Schröder K, Brandes RP, Siemen D, Ježek P. Glucose-Stimulated Insulin Secretion Fundamentally Requires H 2O 2 Signaling by NADPH Oxidase 4. Diabetes 2020; 69:1341-1354. [PMID: 32245800 DOI: 10.2337/db19-1130] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 03/30/2020] [Indexed: 11/13/2022]
Abstract
NADPH facilitates glucose-stimulated insulin secretion (GSIS) in pancreatic islets (PIs) of β-cells through an as yet unknown mechanism. We found NADPH oxidase isoform 4 (NOX4) to be the main producer of cytosolic H2O2, which is essential for GSIS; an increase in ATP alone was insufficient for GSIS. The fast GSIS phase was absent from PIs from NOX4-null, β-cell-specific knockout mice (NOX4βKO) (though not from NOX2 knockout mice) and from NOX4-silenced or catalase-overexpressing INS-1E cells. Lentiviral NOX4 overexpression or H2O2 rescued GSIS in PIs from NOX4βKO mice. NOX4 silencing suppressed Ca2+ oscillations, and the patch-clamped KATP channel opened more frequently when glucose was high. Mitochondrial H2O2, decreasing upon GSIS, provided alternative redox signaling when 2-oxo-isocaproate or fatty acid oxidation formed superoxides through electron-transfer flavoprotein:Q-oxidoreductase. Unlike GSIS, such insulin secretion was blocked with mitochondrial antioxidant SkQ1. Both NOX4 knockout and NOX4βKO mice exhibited impaired glucose tolerance and peripheral insulin resistance. Thus, the redox signaling previously suggested to cause β-cells to self-check hypothetically induces insulin resistance when it is absent. In conclusion, increases in ATP and H2O2 constitute an essential signal that switches on insulin exocytosis for glucose and branched-chain oxoacids as secretagogues (it does so partially for fatty acids). Redox signaling could be impaired by cytosolic antioxidants; hence, those targeting mitochondria should be preferred for clinical applications to treat (pre)diabetes at any stage.
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Affiliation(s)
- Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Tauber
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Vojtěch Pavluch
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Zuzana Berková
- Institute of Clinical and Experimental Medicine, Prague, Czech Republic
| | - Monika Cahová
- Institute of Clinical and Experimental Medicine, Prague, Czech Republic
| | - Katrin Schröder
- Institut für Kardiovaskuläre Physiologie, Goethe-Universität, Frankfurt, Germany
| | - Ralf P Brandes
- Institut für Kardiovaskuläre Physiologie, Goethe-Universität, Frankfurt, Germany
| | - Detlef Siemen
- Klinik für Neurologie, Universität Magdeburg, Magdeburg, Germany
| | - Petr Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Natarajan V, Chawla R, Mah T, Vivekanandan R, Tan SY, Sato PY, Mallilankaraman K. Mitochondrial Dysfunction in Age-Related Metabolic Disorders. Proteomics 2020; 20:e1800404. [PMID: 32131138 DOI: 10.1002/pmic.201800404] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 02/07/2020] [Indexed: 12/16/2022]
Abstract
Aging is a natural biological process in living organisms characterized by receding bioenergetics. Mitochondria are crucial for cellular bioenergetics and thus an important contributor to age-related energetics deterioration. In addition, mitochondria play a major role in calcium signaling, redox homeostasis, and thermogenesis making this organelle a major cellular component that dictates the fate of a cell. To maintain its quantity and quality, mitochondria undergo multiple processes such as fission, fusion, and mitophagy to eliminate or replace damaged mitochondria. While this bioenergetics machinery is properly protected, the functional decline associated with age and age-related metabolic diseases is mostly a result of failure in such protective mechanisms. In addition, metabolic by-products like reactive oxygen species also aid in this destructive pathway. Mitochondrial dysfunction has always been thought to be associated with diseases. Moreover, studies in recent years have pointed out that aging contributes to the decay of mitochondrial health by promoting imbalances in key mitochondrial-regulated pathways. Hence, it is crucial to understand the nexus of mitochondrial dysfunction in age-related diseases. This review focuses on various aspects of basic mitochondrial biology and its status in aging and age-related metabolic diseases.
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Affiliation(s)
- Venkateswaran Natarajan
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Ritu Chawla
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Tania Mah
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Rajesh Vivekanandan
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Shu Yi Tan
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Priscila Y Sato
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, 19102-1902, USA
| | - Karthik Mallilankaraman
- Mitochondrial Physiology and Metabolism Lab, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore.,Center for Healthy Longevity, National University Health System, Singapore, 119228, Singapore
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Kahancová A, Sklenář F, Ježek P, Dlasková A. Overexpression of native IF1 downregulates glucose-stimulated insulin secretion by pancreatic INS-1E cells. Sci Rep 2020; 10:1551. [PMID: 32005857 PMCID: PMC6994519 DOI: 10.1038/s41598-020-58411-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/15/2020] [Indexed: 01/08/2023] Open
Abstract
We have previously reported that transient knock-down of ATPase inhibitory factor 1 (IF1) by siRNA upregulates ATP levels and subsequently augments insulin secretion in model pancreatic β-cells INS-1E. Here we investigated how long-term IF1-overexpression impacts pancreatic β-cell bioenergetics and insulin secretion. We generated INS-1E cell line stably overexpressing native IF1. We revealed that IF1 overexpression leads to a substantial decrease in ATP levels and reduced glucose-stimulated insulin secretion. A decrease in total cellular ATP content was also reflected in decreased free ATP cytosolic and mitochondrial levels, as monitored with ATeam biosensor. Consistently, cellular respiration of IF1-overexpressing cells was decreased. 3D structured illumination microscopy (SIM) revealed a higher amount of insulin granules with higher volume in IF1-overexpressing cells. Similar effects occurred when cells were incubated at low glucose concentrations. Noteworthy, activation of PKA by dibutyryl cAMP entirely abolished the inhibitory effect of IF1 overexpression on ATP production and insulin secretion. Mitochondrial network morphology and cristae ultrastructure in INS-1E overexpressing IF1 remained mostly unchanged. Finally, we show that INS-1E cells decrease their IF1 protein levels relative to ATP synthase α-subunit in response to increased glucose. In conclusion, IF1 actively downregulates INS-1E cellular metabolism and reduces their ability to secrete insulin.
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Affiliation(s)
- Anežka Kahancová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Filip Sklenář
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic.
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Redox Signaling from Mitochondria: Signal Propagation and Its Targets. Biomolecules 2020; 10:biom10010093. [PMID: 31935965 PMCID: PMC7023504 DOI: 10.3390/biom10010093] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/02/2020] [Accepted: 01/02/2020] [Indexed: 02/07/2023] Open
Abstract
Progress in mass spectroscopy of posttranslational oxidative modifications has enabled researchers to experimentally verify the concept of redox signaling. We focus here on redox signaling originating from mitochondria under physiological situations, discussing mechanisms of transient redox burst in mitochondria, as well as the possible ways to transfer such redox signals to specific extramitochondrial targets. A role of peroxiredoxins is described which enables redox relay to other targets. Examples of mitochondrial redox signaling are discussed: initiation of hypoxia-inducible factor (HIF) responses; retrograde redox signaling to PGC1α during exercise in skeletal muscle; redox signaling in innate immune cells; redox stimulation of insulin secretion, and other physiological situations.
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Ježek P, Jabůrek M, Plecitá-Hlavatá L. Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes. Antioxid Redox Signal 2019; 31:722-751. [PMID: 30450940 PMCID: PMC6708273 DOI: 10.1089/ars.2018.7656] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 11/05/2018] [Indexed: 12/14/2022]
Abstract
Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Jezek J, Chang K, Joshi AM, Strich R. Mitochondrial translocation of cyclin C stimulates intrinsic apoptosis through Bax recruitment. EMBO Rep 2019; 20:e47425. [PMID: 31385392 PMCID: PMC6726902 DOI: 10.15252/embr.201847425] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 06/25/2019] [Accepted: 07/03/2019] [Indexed: 11/09/2022] Open
Abstract
Intrinsic apoptosis requires mitochondrial outer membrane disruption triggered by recruitment, activation, and oligomerization of the Bcl-2 homology protein Bax. Following oxidative stress, we demonstrated that the transcriptional regulator cyclin C is released into the cytosol where it directs mitochondrial fragmentation and efficient apoptotic induction. This study reveals that cytoplasmic cyclin C is required for both normal Bax activation and its efficient mitochondrial localization. This activity appears direct as cyclin C co-immunoprecipitates with active Bax in stressed cells and binds recombinant Bax in vitro. In addition, stable cyclin C-Bax association requires the fission complex. Pharmacologically stimulating cyclin C nuclear release is sufficient for Bax association and their mitochondrial localization in the absence of any stress signals. However, these cells do not undergo cell death as Bax fails to oligomerize. These data support a model that cyclin C association defines an initial step in Bax mitochondrial recruitment and provides a physical connection between the fission and apoptotic factors. This strategy allows the cell to discriminate stress-induced fission able to recruit Bax from other types of mitochondrial divisions.
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Affiliation(s)
- Jan Jezek
- Graduate School of Biomedical SciencesTwo Medical Center DriveRowan University School of Osteopathic MedicineStratfordNJUSA
| | - Kai‐Ti Chang
- Graduate School of Biomedical SciencesTwo Medical Center DriveRowan University School of Osteopathic MedicineStratfordNJUSA
| | - Amogh M Joshi
- School of Osteopathic MedicineOne Medical Center DriveRowan UniversityStratfordNJUSA
| | - Randy Strich
- Graduate School of Biomedical SciencesTwo Medical Center DriveRowan University School of Osteopathic MedicineStratfordNJUSA
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Potential of Mitochondria-Targeted Antioxidants to Prevent Oxidative Stress in Pancreatic β-cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:1826303. [PMID: 31249641 PMCID: PMC6556329 DOI: 10.1155/2019/1826303] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 04/02/2019] [Accepted: 04/10/2019] [Indexed: 12/12/2022]
Abstract
Pancreatic β-cells are vulnerable to oxidative stress due to their low content of redox buffers, such as glutathione, but possess a rich content of thioredoxin, peroxiredoxin, and other proteins capable of redox relay, transferring redox signaling. Consequently, it may be predicted that cytosolic antioxidants could interfere with the cytosolic redox signaling and should not be recommended for any potential therapy. In contrast, mitochondrial matrix-targeted antioxidants could prevent the primary oxidative stress arising from the primary superoxide sources within the mitochondrial matrix, such as at the flavin (IF) and ubiquinone (IQ) sites of superoxide formation within respiratory chain complex I and the outer ubiquinone site (IIIQ) of complex III. Therefore, using time-resolved confocal fluorescence monitoring with MitoSOX Red, we investigated various effects of mitochondria-targeted antioxidants in model pancreatic β-cells (insulinoma INS-1E cells) and pancreatic islets. Both SkQ1 (a mitochondria-targeted plastoquinone) and a suppressor of complex III site Q electron leak (S3QEL) prevented superoxide production released to the mitochondrial matrix in INS-1E cells with stimulatory glucose, where SkQ1 also exhibited an antioxidant role for UCP2-silenced cells. SkQ1 acted similarly at nonstimulatory glucose but not in UCP2-silenced cells. Thus, UCP2 can facilitate the antioxidant mechanism based on SkQ1+ fatty acid anion− pairing. The elevated superoxide formation induced by antimycin A was largely prevented by S3QEL, and that induced by rotenone was decreased by SkQ1 and S3QEL and slightly by S1QEL, acting at complex I site Q. Similar results were obtained with the MitoB probe, for the LC-MS-based assessment of the 4 hr accumulation of reactive oxygen species within the mitochondrial matrix but for isolated pancreatic islets. For 2 hr INS-1E incubations, some samples were influenced by the cell death during the experiment. Due to the frequent dependency of antioxidant effects on metabolic modes, we suggest a potential use of mitochondria-targeted antioxidants for the treatment of prediabetic states after cautious nutrition-controlled tests. Their targeted delivery might eventually attenuate the vicious spiral leading to type 2 diabetes.
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Pohl EE, Rupprecht A, Macher G, Hilse KE. Important Trends in UCP3 Investigation. Front Physiol 2019; 10:470. [PMID: 31133866 PMCID: PMC6524716 DOI: 10.3389/fphys.2019.00470] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Accepted: 04/04/2019] [Indexed: 11/13/2022] Open
Abstract
Membrane uncoupling protein 3 (UCP3), a member of the mitochondrial uncoupling protein family, was discovered in 1997. UCP3's properties, such as its high homology to other mitochondrial carriers, especially to UCP2, its short lifetime and low specificity of UCP3 antibodies, have hindered progress in understanding its biological function and transport mechanism over decades. The abundance of UCP3 is highest in murine brown adipose tissue (BAT, 15.0 pmol/mg protein), compared to heart (2.7 pmol/mg protein) and the gastrocnemius muscle (1.7 pmol/mg protein), but it is still 400-fold lower than the abundance of UCP1, a biomarker for BAT. Investigation of UCP3 reconstituted in planar bilayer membranes revealed that it transports protons only when activated by fatty acids (FA). Although purine nucleotides (PN) inhibit UCP3-mediated transport, the molecular mechanism differs from that of UCP1. It remains a conundrum that two homologous proton-transporting proteins exist within the same tissue. Recently, we proposed that UCP3 abundance directly correlates with the degree of FA β-oxidation in cell metabolism. Further development in this field implies that UCP3 may have dual function in transporting substrates, which have yet to be identified, alongside protons. Evaluation of the literature with respect to UCP3 is a complex task because (i) UCP3 features are often extrapolated from its "twin" UCP2 without additional proof, and (ii) the specificity of antibodies against UCP3 used in studies is rarely evaluated. In this review, we primarily focus on recent findings obtained for UCP3 in biological and biomimetic systems.
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Affiliation(s)
- Elena E. Pohl
- Institute of Physiology, Pathophysiology and Biophysics, University of Veterinary Medicine, Vienna, Austria
| | - Anne Rupprecht
- Institute of Physiology, Pathophysiology and Biophysics, University of Veterinary Medicine, Vienna, Austria
- Institute of Pharmacology and Toxicology, Rostock University Medical Center, Rostock, Germany
| | - Gabriel Macher
- Institute of Physiology, Pathophysiology and Biophysics, University of Veterinary Medicine, Vienna, Austria
| | - Karolina E. Hilse
- Institute of Physiology, Pathophysiology and Biophysics, University of Veterinary Medicine, Vienna, Austria
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Ježek P, Jabůrek M, Porter RK. Uncoupling mechanism and redox regulation of mitochondrial uncoupling protein 1 (UCP1). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:259-269. [DOI: 10.1016/j.bbabio.2018.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 10/15/2018] [Accepted: 11/07/2018] [Indexed: 01/11/2023]
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28
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Wu H, Gao H, Gao S, Lei Z, Dai L, Wang X, Han Y, Wang Z, Han L. A Chinese 4-herb formula, Yiqi-Huoxue granule, alleviates H 2O 2-induced apoptosis by upregulating uncoupling protein 2 in H9c2 cells. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2019; 53:171-181. [PMID: 30668396 DOI: 10.1016/j.phymed.2018.09.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/17/2018] [Accepted: 09/03/2018] [Indexed: 06/09/2023]
Abstract
BACKGROUND Although the protective effects of Yiqi-Huoxue granule (YQHX), a Chinese 4-herb formula, on patients with ischemic heart diseases are related to the attenuation of oxidative stress injury, the mechanism(s) underlying these actions remains poorly understood. PURPOSE Our aim was to investigate the potential protective effects of YQHX treatment against oxidative stress induced by hydrogen peroxide (H2O2) in rat H9c2 cells. METHODS H9c2 cells were treated with YQHX for 16 h before exposed to 200 μM H2O2 for 6 h. The apoptosis induced by H2O2 was measured using hoechst 33,342 staining and Annexin-V FITC/PI assay. The expression of uncoupling protein 2 (UCP2), Bcl-2, Bax, and caspase-3 were observed using western blot. The effects of UCP2 knockdown on cell apoptosis and intracellular ROS production were also investigated. RESULTS H2O2 exposure led to significant activation of oxidative stress followed by increased apoptosis and ROS production, as well as decreased UCP2 expression in H9c2 cells. YQHX treatment at the concentration of 0.75 and 1.5 mg/ml remarkably reduced the expression of Bax and caspase-3, whereas increased the protein expression of Bcl-2 and UCP2. These changes were attenuated by transgenic knockdown of UCP2 with Lenti-shUCP2 vector. CONCLUSIONS Taken together, our study demonstrated that YQHX attenuates H2O2-induced apoptosis by upregulating UCP2 expression in H9c2 Cells, suggesting that YQHX is a promising therapeutic approach for the treatment of I/R injury-mediated apoptosis.
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Affiliation(s)
- Hong Wu
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China; Institute of Cardiovascular Disease, Henan University of Chinese Medicine, Zhengzhou, 450002, China.
| | - Haixia Gao
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China
| | - Shuibo Gao
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China
| | - Zhen Lei
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China
| | - Liping Dai
- School of Pharmacy, Henan University of Chinese Medicine, Zhengzhou, 450046, China
| | - Xinzhou Wang
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China
| | - Yongjun Han
- Laboratory of Cell Imaging, Henan University of Chinese Medicine, 6 Dongfeng Rd, Zhengzhou, Henan 450002, China
| | - Zhentao Wang
- Institute of Cardiovascular Disease, Henan University of Chinese Medicine, Zhengzhou, 450002, China
| | - Lihua Han
- Institute of Cardiovascular Disease, Henan University of Chinese Medicine, Zhengzhou, 450002, China
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Ježek P, Holendová B, Garlid KD, Jabůrek M. Mitochondrial Uncoupling Proteins: Subtle Regulators of Cellular Redox Signaling. Antioxid Redox Signal 2018; 29:667-714. [PMID: 29351723 PMCID: PMC6071544 DOI: 10.1089/ars.2017.7225] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SIGNIFICANCE Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology state are integrated by the protonmotive force Δp or its potential component, ΔΨ, which are attenuated by proton backflux into the matrix, termed uncoupling. The mitochondrial uncoupling proteins (UCP1-5) play an eminent role in the regulation of each of the mentioned aspects, being involved in numerous physiological events including redox signaling. Recent Advances: UCP2 structure, including purine nucleotide and fatty acid (FA) binding sites, strongly support the FA cycling mechanism: UCP2 expels FA anions, whereas uncoupling is achieved by the membrane backflux of protonated FA. Nascent FAs, cleaved by phospholipases, are preferential. The resulting Δp dissipation decreases superoxide formation dependent on Δp. UCP-mediated antioxidant protection and its impairment are expected to play a major role in cell physiology and pathology. Moreover, UCP2-mediated aspartate, oxaloacetate, and malate antiport with phosphate is expected to alter metabolism of cancer cells. CRITICAL ISSUES A wide range of UCP antioxidant effects and participations in redox signaling have been reported; however, mechanisms of UCP activation are still debated. Switching off/on the UCP2 protonophoretic function might serve as redox signaling either by employing/releasing the extra capacity of cell antioxidant systems or by directly increasing/decreasing mitochondrial superoxide sources. Rapid UCP2 degradation, FA levels, elevation of purine nucleotides, decreased Mg2+, or increased pyruvate accumulation may initiate UCP-mediated redox signaling. FUTURE DIRECTIONS Issues such as UCP2 participation in glucose sensing, neuronal (synaptic) function, and immune cell activation should be elucidated. Antioxid. Redox Signal. 29, 667-714.
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Affiliation(s)
- Petr Ježek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Blanka Holendová
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Keith D Garlid
- 2 UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA , Los Angeles, California
| | - Martin Jabůrek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
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Fatty Acid-Stimulated Insulin Secretion vs. Lipotoxicity. Molecules 2018; 23:molecules23061483. [PMID: 29921789 PMCID: PMC6100479 DOI: 10.3390/molecules23061483] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 06/13/2018] [Accepted: 06/15/2018] [Indexed: 12/29/2022] Open
Abstract
Fatty acid (FA)-stimulated insulin secretion (FASIS) is reviewed here in contrast to type 2 diabetes etiology, resulting from FA overload, oxidative stress, intermediate hyperinsulinemia, and inflammation, all converging into insulin resistance. Focusing on pancreatic islet β-cells, we compare the physiological FA roles with the pathological ones. Considering FAs not as mere amplifiers of glucose-stimulated insulin secretion (GSIS), but as parallel insulin granule exocytosis inductors, partly independent of the KATP channel closure, we describe the FA initiating roles in the prediabetic state that is induced by retardations in the glycerol-3-phosphate (glucose)-promoted glycerol/FA cycle and by the impaired GPR40/FFA1 (free FA1) receptor pathway, specifically in its amplification by the redox-activated mitochondrial phospholipase, iPLA2γ. Also, excessive dietary FAs stimulate intestine enterocyte incretin secretion, further elevating GSIS, even at low glucose levels, thus contributing to diabetic hyperinsulinemia. With overnutrition and obesity, the FA overload causes impaired GSIS by metabolic dysbalance, paralleled by oxidative and metabolic stress, endoplasmic reticulum stress and numerous pro-apoptotic signaling, all leading to decreased β-cell survival. Lipotoxicity is exerted by saturated FAs, whereas ω-3 polyunsaturated FAs frequently exert antilipotoxic effects. FA-facilitated inflammation upon the recruitment of excess M1 macrophages into islets (over resolving M2 type), amplified by cytokine and chemokine secretion by β-cells, leads to an inevitable failure of pancreatic β-cells.
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31
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Jabůrek M, Ježek J, Ježek P. Cytoprotective activity of mitochondrial uncoupling protein-2 in lung and spleen. FEBS Open Bio 2018; 8:692-701. [PMID: 29632821 PMCID: PMC5881546 DOI: 10.1002/2211-5463.12410] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 02/06/2018] [Accepted: 02/12/2018] [Indexed: 01/14/2023] Open
Abstract
Mitochondrial uncoupling protein‐2 (UCP2) mediates free fatty acid (FA)‐dependent H+ translocation across the inner mitochondrial membrane (IMM), which leads to acceleration of respiration and suppression of mitochondrial superoxide formation. Redox‐activated mitochondrial phospholipase A2 (mt‐iPLA2γ) cleaves FAs from the IMM and has been shown to acts in synergy with UCP2. Here, we tested the mechanism of mt‐iPLA2γ‐dependent UCP2‐mediated antioxidant protection using lipopolysaccharide (LPS)‐induced pro‐inflammatory and pro‐oxidative responses and their acute influence on the overall oxidative stress reflected by protein carbonylation in murine lung and spleen mitochondria and tissue homogenates. We provided challenges either by blocking the mt‐iPLA2γ function by the selective inhibitor R‐bromoenol lactone (R‐BEL) or by removing UCP2 by genetic ablation. We found that the basal levels of protein carbonyls in lung and spleen tissues and isolated mitochondria were higher in UCP2‐knockout mice relative to the wild‐type (wt) controls. The administration of R‐BEL increased protein carbonyl levels in wt but not in UCP2‐knockout (UCP2‐KO) mice. LPS further increased the protein carbonyl levels in UCP2‐KO mice, which correlated with protein carbonyl levels determined in wt mice treated with R‐BEL. These results are consistent with the UCP2/mt‐iPLA2γ antioxidant mechanisms in these tissues and support the existence of UCP2‐synergic mt‐iPLA2γ‐dependent cytoprotective mechanism in vivo.
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Affiliation(s)
- Martin Jabůrek
- Department of Mitochondrial Physiology Institute of Physiology Academy of Sciences Prague Czech Republic
| | - Jan Ježek
- Department of Mitochondrial Physiology Institute of Physiology Academy of Sciences Prague Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology Institute of Physiology Academy of Sciences Prague Czech Republic
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32
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Kahancová A, Sklenář F, Ježek P, Dlasková A. Regulation of glucose-stimulated insulin secretion by ATPase Inhibitory Factor 1 (IF1). FEBS Lett 2018; 592:999-1009. [PMID: 29380352 DOI: 10.1002/1873-3468.12991] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 01/16/2018] [Accepted: 01/22/2018] [Indexed: 12/13/2022]
Abstract
ATPase Inhibitory factor 1 (IF1) is an endogenous regulator of mitochondrial ATP synthase, which is involved in cellular metabolism. Although great progress has been made, biological roles of IF1 and molecular mechanisms of its action are still to be elucidated. Here, we show that IF1 is present in pancreatic β-cells, bound to the ATP synthase also under normal physiological conditions. IF1 silencing in model pancreatic β-cells (INS-1E) increases insulin secretion over a range of glucose concentrations. The left-shifted dose-response curve reveals excessive insulin secretion even under low glucose, corresponding to fasting conditions. A parallel increase in cellular respiration and ATP levels is observed. To conclude, our results indicate that IF1 is a negative regulator of insulin secretion involved in pancreatic β-cell glucose sensing.
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Affiliation(s)
- Anežka Kahancová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Filip Sklenář
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Kener KB, Munk DJ, Hancock CR, Tessem JS. High-resolution Respirometry to Measure Mitochondrial Function of Intact Beta Cells in the Presence of Natural Compounds. J Vis Exp 2018. [PMID: 29443067 DOI: 10.3791/57053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
High-resolution respirometry allows for the measurement of oxygen consumption of isolated mitochondria, cells and tissues. Beta cells play a critical role in the body by controlling blood glucose levels through insulin secretion in response to elevated glucose concentrations. Insulin secretion is controlled by glucose metabolism and mitochondrial respiration. Therefore, measuring intact beta cell respiration is essential to be able to improve beta cell function as a treatment for diabetes. Using intact 832/13 INS-1 derived beta cells we can measure the effect of increasing glucose concentration on cellular respiration. This protocol allows us to measure beta cell respiration in the presence or absence of various compounds, allowing one to determine the effect of given compounds on intact cell respiration. Here we demonstrate the effect of two naturally occurring compounds, monomeric epicatechin and curcumin, on beta cell respiration under the presence of low (2.5 mM) or high glucose (16.7 mM) conditions. This technique can be used to determine the effect of various compounds on intact beta cell respiration in the presence of differing glucose concentrations.
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Affiliation(s)
- Kyle B Kener
- Nutrition, Dietetics and Food Science Department, Brigham Young University
| | - Devin J Munk
- Nutrition, Dietetics and Food Science Department, Brigham Young University
| | - Chad R Hancock
- Nutrition, Dietetics and Food Science Department, Brigham Young University
| | - Jeffery S Tessem
- Nutrition, Dietetics and Food Science Department, Brigham Young University;
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Ježek J, Cooper KF, Strich R. Reactive Oxygen Species and Mitochondrial Dynamics: The Yin and Yang of Mitochondrial Dysfunction and Cancer Progression. Antioxidants (Basel) 2018; 7:E13. [PMID: 29337889 PMCID: PMC5789323 DOI: 10.3390/antiox7010013] [Citation(s) in RCA: 295] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/02/2018] [Accepted: 01/09/2018] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are organelles with a highly dynamic ultrastructure maintained by a delicate equilibrium between its fission and fusion rates. Understanding the factors influencing this balance is important as perturbations to mitochondrial dynamics can result in pathological states. As a terminal site of nutrient oxidation for the cell, mitochondrial powerhouses harness energy in the form of ATP in a process driven by the electron transport chain. Contemporaneously, electrons translocated within the electron transport chain undergo spontaneous side reactions with oxygen, giving rise to superoxide and a variety of other downstream reactive oxygen species (ROS). Mitochondrially-derived ROS can mediate redox signaling or, in excess, cause cell injury and even cell death. Recent evidence suggests that mitochondrial ultrastructure is tightly coupled to ROS generation depending on the physiological status of the cell. Yet, the mechanism by which changes in mitochondrial shape modulate mitochondrial function and redox homeostasis is less clear. Aberrant mitochondrial morphology may lead to enhanced ROS formation, which, in turn, may deteriorate mitochondrial health and further exacerbate oxidative stress in a self-perpetuating vicious cycle. Here, we review the latest findings on the intricate relationship between mitochondrial dynamics and ROS production, focusing mainly on its role in malignant disease.
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Affiliation(s)
- Jan Ježek
- Department of Molecular Biology, Rowan University Graduate School of Biomedical Sciences, Stratford, NJ 08084, USA.
| | - Katrina F Cooper
- Department of Molecular Biology, Rowan University Graduate School of Biomedical Sciences, Stratford, NJ 08084, USA.
| | - Randy Strich
- Department of Molecular Biology, Rowan University Graduate School of Biomedical Sciences, Stratford, NJ 08084, USA.
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35
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Ježek J, Engstová H, Ježek P. Antioxidant mechanism of mitochondria-targeted plastoquinone SkQ1 is suppressed in aglycemic HepG2 cells dependent on oxidative phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:750-762. [PMID: 28554565 DOI: 10.1016/j.bbabio.2017.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/17/2017] [Accepted: 05/24/2017] [Indexed: 12/19/2022]
Abstract
Previously suggested antioxidant mechanisms for mitochondria-targeted plastoquinone SkQ1 included: i) ion-pairing of cationic SkQ1+ with free fatty acid anions resulting in uncoupling; ii) SkQ1H2 ability to interact with lipoperoxyl radical; iii) interference with electron flow at the inner ubiquinone (Q) binding site of Complex III (Qi), involving the reduction of SkQ1 to SkQ1H2 by ubiquinol. We elucidated SkQ1 antioxidant properties by confocal fluorescence semi-quantification of mitochondrial superoxide (Jm) and cytosolic H2O2 (Jc) release rates in HepG2 cells. Only in glycolytic cells, SkQ1 prevented the rotenone-induced enhancement of Jm and Jc but not basal releases without rotenone. The effect ceased in glutaminolytic aglycemic cells, in which the redox parameter NAD(P)H/FAD increased after rotenone in contrast to its decrease in glycolytic cells. Autofluorescence decay indicated decreased NADPH/NADH ratios with rotenone in both metabolic modes. SkQ1 did not increase cell respiration and diminished Jm established high by antimycin or myxothiazol but not by stigmatellin. The revealed SkQ1 antioxidant modes reflect its reduction to SkQ1H2 at Complex I IQ or Complex III Qi site. Both reductions diminish electron diversions to oxygen thus attenuating superoxide formation. Resulting SkQ1H2 oxidizes back to SkQ1at the second (flavin) Complex I site, previously indicated for MitoQ10. Regeneration proceeds only at lower NAD(P)H/FAD in glycolytic cells. In contrast, cyclic SkQ1 reduction/SkQ1H2 oxidation does not substantiate antioxidant activity in intact cells in the absence of oxidative stress (neither pro-oxidant activity, representing a great advantage). A targeted delivery to oxidative-stressed tissues is suggested for the effective antioxidant therapy based on SkQ1.
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Affiliation(s)
- Jan Ježek
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic.
| | - Hana Engstová
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic
| | - Petr Ježek
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic.
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Acaz-Fonseca E, Ortiz-Rodriguez A, Lopez-Rodriguez AB, Garcia-Segura LM, Astiz M. Developmental Sex Differences in the Metabolism of Cardiolipin in Mouse Cerebral Cortex Mitochondria. Sci Rep 2017; 7:43878. [PMID: 28262723 PMCID: PMC5338321 DOI: 10.1038/srep43878] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/25/2017] [Indexed: 01/15/2023] Open
Abstract
Cardiolipin (CL) is a mitochondrial-specific phospholipid. CL content and acyl chain composition are crucial for energy production. Given that estradiol induces CL synthesis in neurons, we aimed to assess CL metabolism in the cerebral cortex (CC) of male and female mice during early postnatal life, when sex steroids induce sex-dimorphic maturation of the brain. Despite the fact that total amount of CL was similar, its fatty acid composition differed between males and females at birth. In males, CL was more mature (lower saturation ratio) and the expression of the enzymes involved in synthetic and remodeling pathways was higher, compared to females. Importantly, the sex differences found in CL metabolism were due to the testosterone peak that male mice experience perinatally. These changes were associated with a higher expression of UCP-2 and its activators in the CC of males. Overall, our results suggest that the perinatal testosterone surge in male mice regulates CL biosynthesis and remodeling in the CC, inducing a sex-dimorphic fatty acid composition. In male's CC, CL is more susceptible to peroxidation, likely explaining the testosterone-dependent induction of neuroprotective molecules such as UCP-2. These differences may account for the sex-dependent mitochondrial susceptibility after perinatal hypoxia/ischemia.
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Affiliation(s)
| | | | | | | | - Mariana Astiz
- Instituto Cajal-CSIC. Avenida Doctor Arce 37, 28002 Madrid, Spain
- Biochemistry Research Institute of La Plata (INIBIOLP), CONICET. 60 and 120, 1900, La Plata, Argentina
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Gur S, Rezk BM, Abd Elmageed ZY, Kadowitz PJ, Sikka SC, Hellstrom WJG. Characterisation of pomegranate juice effects on human corpus cavernosum. Andrologia 2016; 49. [PMID: 27785815 DOI: 10.1111/and.12712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2016] [Indexed: 01/26/2023] Open
Abstract
Pomegranate (POM) juice may benefit the erectile process, but the scientific evidence is lacking. This study evaluates the molecular characterisation and confirmation of POM's action on human corpus cavernosum (HCC) obtained from patients (n = 16) undergoing penile prosthesis implantation. After phenylephrine contraction, the relaxant effects of POM with various inhibitors in the presence and absence of palmitic acid (PA)-induced acute oxidative stress were investigated. Electrical field stimulation (EFS)- and acetylcholine (ACh)-induced relaxation were performed using organ bath preparation. Expression of neuronal nitric oxide synthase (nNOS), endothelial (eNOS), phosphodiesterase (PDE)-5A and cGMP levels were assessed in cells from ex vivo organ cultures of HCC, using RT-PCR, ELISA and immunohistochemistry techniques. POM induced marked relaxation of HCC (maximum response: 97.0 ± 3.1%) and reversed the PA-induced decrease of EFS (20 Hz). nNOS transcription was increased by 7-fold in POM-treated cells without influencing eNOS and PDE5A expressions. We conclude that POM induced marked relaxation of HCC via: (i) nNOS stimulation, and (ii) downstream relaxation stimulated by nNOS and cGMP and bypassing the NO and PDE5. This action provides a rationale for the therapeutic or preventative use of POM in men with erectile dysfunction who do not respond well to PDE5 inhibitors.
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Affiliation(s)
- S Gur
- Department of Pharmacology, School of Pharmacy, Ankara University, Ankara, Turkey.,Departments of Urology and Pharmacology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - B M Rezk
- Biology Units, Southern University at New Orleans, New Orleans, LA, USA
| | - Z Y Abd Elmageed
- Departments of Urology and Pharmacology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - P J Kadowitz
- Departments of Urology and Pharmacology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - S C Sikka
- Departments of Urology and Pharmacology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - W J G Hellstrom
- Departments of Urology and Pharmacology, Tulane University Health Sciences Center, New Orleans, LA, USA
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Plecitá-Hlavatá L, Ježek P. Integration of superoxide formation and cristae morphology for mitochondrial redox signaling. Int J Biochem Cell Biol 2016; 80:31-50. [PMID: 27640755 DOI: 10.1016/j.biocel.2016.09.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/09/2016] [Accepted: 09/12/2016] [Indexed: 12/16/2022]
Abstract
The mitochondrial network provides the central cell's energetic and regulatory unit, which besides ATP and metabolite production participates in cellular signaling through regulated reactive oxygen species (ROS) production and various protein/ion fluxes. The inner membrane forms extensive folds, called cristae, i.e. cavities enfolded from and situated perpendicularly to its inner boundary membrane portion, which encompasses an inner cylinder within the outer membrane tubule. Mitochondrial cristae ultramorphology reflects various metabolic, physiological or pathological states. Since the mitochondrion is typically a predominant superoxide source and generated ROS also serve for the creation of information redox signals, we review known relationships between ROS generation within the respiratory chain complexes of cristae and cristae morphology. Notably, it is emphasized that cristae shape is governed by ATP-synthase dimers, MICOS complexes, OPA1 isoforms and the umbrella of their regulation, and also dependent on local protonmotive force (electrical potential component) in cristae. Cristae are also affected by redox-sensitive kinases/phosphatases or p66SHC. ATP-synthase dimers decrease in the inflated intracristal space, diminishing pH and hypothetically having minimal superoxide formation. Matrix-released signaling superoxide/H2O2 is predominantly integrated along mitochondrial tubules, whereas the diffusion of intracristal signaling ROS species is controlled by crista junctions, the widening of which enables specific retrograde redox signaling such as during hypoxic cell adaptation. Other physiological cases of H2O2 release from the mitochondrion include the modulation of insulin release in pancreatic β-cells, enhancement of insulin signaling in peripheral tissues, signaling by T-cell receptors, retrograde signaling during the cell cycle and cell differentiation, specifically that of adipocytes.
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Affiliation(s)
- Lydie Plecitá-Hlavatá
- Department of Membrane Transport Biophysics, No.75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Petr Ježek
- Department of Membrane Transport Biophysics, No.75, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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