1
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Kerr M, Dennis KMJH, Carr CA, Fuller W, Berridge G, Rohling S, Aitken CL, Lopez C, Fischer R, Miller JJ, Clarke K, Tyler DJ, Heather LC. Diabetic mitochondria are resistant to palmitoyl CoA inhibition of respiration, which is detrimental during ischemia. FASEB J 2021; 35:e21765. [PMID: 34318967 PMCID: PMC8662312 DOI: 10.1096/fj.202100394r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/24/2021] [Accepted: 06/14/2021] [Indexed: 01/07/2023]
Abstract
The bioactive lipid intermediate palmitoyl CoA (PCoA) can inhibit mitochondrial ADP/ATP transport, though the physiological relevance of this regulation remains unclear. We questioned whether myocardial ischemia provides a pathological setting in which PCoA regulation of ADP/ATP transport would be beneficial, and secondly, whether the chronically elevated lipid content within the diabetic heart could make mitochondria less sensitive to the effects of PCoA. PCoA acutely decreased ADP‐stimulated state 3 respiration and increased the apparent Km for ADP twofold. The half maximal inhibitory concentration (IC50) of PCoA in control mitochondria was 22 µM. This inhibitory effect of PCoA on respiration was blunted in diabetic mitochondria, with no significant difference in the Km for ADP in the presence of PCoA, and an increase in the IC50 to 32 µM PCoA. The competitive inhibition by PCoA was localised to the phosphorylation apparatus, particularly the ADP/ATP carrier (AAC). During ischemia, the AAC imports ATP into the mitochondria, where it is hydrolysed by reversal of the ATP synthase, regenerating the membrane potential. Addition of PCoA dose‐dependently prevented this wasteful ATP hydrolysis for membrane repolarisation during ischemia, however, this beneficial effect was blunted in diabetic mitochondria. Finally, using 31P‐magnetic resonance spectroscopy we demonstrated that diabetic hearts lose ATP more rapidly during ischemia, with a threefold higher ATP decay rate compared with control hearts. In conclusion, PCoA plays a role in protecting mitochondrial energetics during ischemia, by preventing wasteful ATP hydrolysis. However, this beneficial effect is blunted in diabetes, contributing to the impaired energy metabolism seen during myocardial ischemia in the diabetic heart.
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Affiliation(s)
- M Kerr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - K M J H Dennis
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - C A Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - W Fuller
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
| | - G Berridge
- Target Discovery Institute, University of Oxford, Oxford, UK
| | - S Rohling
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - C L Aitken
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - C Lopez
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - R Fischer
- Target Discovery Institute, University of Oxford, Oxford, UK
| | - J J Miller
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.,Department of Physics, University of Oxford, Oxford, UK.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - K Clarke
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - D J Tyler
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.,Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - L C Heather
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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2
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Mironova GD, Pavlov EV. Mitochondrial Cyclosporine A-Independent Palmitate/Ca 2+-Induced Permeability Transition Pore (PA-mPT Pore) and Its Role in Mitochondrial Function and Protection against Calcium Overload and Glutamate Toxicity. Cells 2021; 10:cells10010125. [PMID: 33440765 PMCID: PMC7827677 DOI: 10.3390/cells10010125] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/29/2020] [Accepted: 12/30/2020] [Indexed: 11/16/2022] Open
Abstract
A sharp increase in the permeability of the mitochondrial inner membrane known as mitochondrial permeability transition (or mPT) occurs in mitochondria under the conditions of Ca2+ and ROS stress. Permeability transition can proceed through several mechanisms. The most common mechanism of mPT is based on the opening of a cyclosporine A (CSA)-sensitive protein channel in the inner membrane. In addition to the CSA-sensitive pathway, mPT can occur through the transient opening of lipid pores, emerging in the process of formation of palmitate/Ca2+ complexes. This pathway is independent of CSA and likely plays a protective role against Ca2+ and ROS toxicity. The review considers molecular mechanisms of formation and regulation of the palmitate/Ca2+-induced pores, which we designate as PA-mPT to distinguish it from the classical CSA-sensitive mPT. In the paper, we discuss conditions of its opening in the biological membranes, as well as its role in the physiological and pathophysiological processes. Additionally, we summarize data that indicate the involvement of PA-mPT in the protection of mitochondria against calcium overload and glutamate-induced degradation in neurons.
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Affiliation(s)
- Galina D. Mironova
- Institute of Theoretical and Experimental Biophysics, RAS, Pushchino, 142290 Moscow, Russia
- Correspondence:
| | - Evgeny V. Pavlov
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA;
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3
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Amaral AU, Wajner M. Recent Advances in the Pathophysiology of Fatty Acid Oxidation Defects: Secondary Alterations of Bioenergetics and Mitochondrial Calcium Homeostasis Caused by the Accumulating Fatty Acids. Front Genet 2020; 11:598976. [PMID: 33329744 PMCID: PMC7729159 DOI: 10.3389/fgene.2020.598976] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/03/2020] [Indexed: 12/18/2022] Open
Abstract
Deficiencies of medium-chain acyl-CoA dehydrogenase, mitochondrial trifunctional protein, isolated long-chain 3-hydroxyacyl-CoA dehydrogenase, and very long-chain acyl-CoA dehydrogenase activities are considered the most frequent fatty acid oxidation defects (FAOD). They are biochemically characterized by the accumulation of medium-chain, long-chain hydroxyl, and long-chain fatty acids and derivatives, respectively, in tissues and biological fluids of the affected patients. Clinical manifestations commonly include hypoglycemia, cardiomyopathy, and recurrent rhabdomyolysis. Although the pathogenesis of these diseases is still poorly understood, energy deprivation secondary to blockage of fatty acid degradation seems to play an important role. However, recent evidence indicates that the predominant fatty acids accumulating in these disorders disrupt mitochondrial functions and are involved in their pathophysiology, possibly explaining the lactic acidosis, mitochondrial morphological alterations, and altered mitochondrial biochemical parameters found in tissues and cultured fibroblasts from some affected patients and also in animal models of these diseases. In this review, we will update the present knowledge on disturbances of mitochondrial bioenergetics, calcium homeostasis, uncoupling of oxidative phosphorylation, and mitochondrial permeability transition induction provoked by the major fatty acids accumulating in prevalent FAOD. It is emphasized that further in vivo studies carried out in tissues from affected patients and from animal genetic models of these disorders are necessary to confirm the present evidence mostly achieved from in vitro experiments.
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Affiliation(s)
- Alexandre Umpierrez Amaral
- Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Erechim, Brazil
| | - Moacir Wajner
- Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
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4
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Aitken-Buck HM, Krause J, Zeller T, Jones PP, Lamberts RR. Long-Chain Acylcarnitines and Cardiac Excitation-Contraction Coupling: Links to Arrhythmias. Front Physiol 2020; 11:577856. [PMID: 33041874 PMCID: PMC7518131 DOI: 10.3389/fphys.2020.577856] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 08/25/2020] [Indexed: 12/31/2022] Open
Abstract
A growing number of metabolomic studies have associated high circulating levels of the amphiphilic fatty acid metabolites, long-chain acylcarnitines (LCACs), with cardiovascular disease (CVD) risk. These studies show that plasma LCAC levels can be correlated with the stage and severity of CVD and with indices of cardiac hypertrophy and ventricular function. Complementing these recent clinical associations is an extensive body of basic research that stems mostly from the twentieth century. These works, performed in cardiomyocyte and multicellular preparations from animal and cell models, highlight stereotypical derangements in cardiac electrophysiology induced by exogenous LCAC treatment that promote arrhythmic muscle behavior. In many cases, this is coupled with acute inotropic modulation; however, whether LCACs increase or decrease contractility is inconclusive. Linked to the electromechanical alterations induced by LCAC exposure is an array of effects on cardiac excitation-contraction coupling mechanisms that overload the cardiomyocyte cytosol with Na+ and Ca2+ ions. The aim of this review is to revisit this age-old literature and collate it with recent findings to provide a pathophysiological context for the growing body of metabolomic association studies that link circulating LCACs with CVD.
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Affiliation(s)
- Hamish M Aitken-Buck
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Julia Krause
- University Heart and Vascular Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Hamburg, Hamburg, Germany
| | - Tanja Zeller
- University Heart and Vascular Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Hamburg, Hamburg, Germany
| | - Peter P Jones
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Regis R Lamberts
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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5
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Sen P, Wu WC, Chandra P, Vinekar A, Manchegowda PT, Bhende P. Retinopathy of prematurity treatment: Asian perspectives. Eye (Lond) 2020; 34:632-642. [PMID: 31664193 PMCID: PMC7093470 DOI: 10.1038/s41433-019-0643-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 07/05/2019] [Indexed: 01/04/2023] Open
Abstract
Retinopathy of prematurity (ROP) is a vasoproliferative disease of developing retinal vessels that affects premature infants and can lead to severe and irreversible visual loss if left untreated. India and some other Asian countries are in the middle of a 'third ROP epidemic'. Blindness due to ROP is largely preventable if appropriate, adequate and accessible screening programmes are available. Screening of the premature babies is the first step in ROP management. With the increase in use of tele-screening techniques, more premature babies have been brought under the screening network both from urban and rural regions. Laser photocoagulation to the avascular retina using indirect ophthalmoscopy delivery system is the gold standard for ROP treatment and is usually done under topical anaesthesia in the Asian region in contrast to the western world. Use of intravitreal anti-vascular endothelial growth factors (VEGF) although controversial in management of ROP has been found to be effective in various Asian studies as well. ROP surgery in India and other middle-income Asian countries is largely performed only in few tertiary eye care centres. Poor visual prognosis, late presentation with advanced retinal detachments, lack of adequate number of trained paediatric retinal surgeons and paediatric anaesthetists also contribute to this problem. This current paper summarizes the Asian experience of ROP management.
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Affiliation(s)
- Parveen Sen
- Shri Bhagwan Mahavir Vitreoretinal Services, Sankara Nethralaya, Chennai, India
| | - Wei-Chi Wu
- Chang Gung Memorial Hospital Taoyuan, Taoyuan, Taiwan
| | - Parijat Chandra
- Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Anand Vinekar
- Paediatric Retina Department, Narayana Nethralaya, Bangalore, India
| | | | - Pramod Bhende
- Shri Bhagwan Mahavir Vitreoretinal Services, Sankara Nethralaya, Chennai, India.
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6
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Abstract
Perturbations in metabolic pathways can cause substantial increases in plasma and tissue concentrations of long-chain acylcarnitines (LCACs). For example, the levels of LCACs and other acylcarnitines rise in the blood and muscle during exercise, as changes in tissue pools of acyl-coenzyme A reflect accelerated fuel flux that is incompletely coupled to mitochondrial energy demand and capacity of the tricarboxylic acid cycle. This natural ebb and flow of acylcarnitine generation and accumulation contrasts with that of inherited fatty acid oxidation disorders (FAODs), cardiac ischaemia or type 2 diabetes mellitus. These conditions are characterized by very high (FAODs, ischaemia) or modestly increased (type 2 diabetes mellitus) tissue and blood levels of LCACs. Although specific plasma concentrations of LCACs and chain-lengths are widely used as diagnostic markers of FAODs, research into the potential effects of excessive LCAC accumulation or the roles of acylcarnitines as physiological modulators of cell metabolism is lacking. Nevertheless, a growing body of evidence has highlighted possible effects of LCACs on disparate aspects of pathophysiology, such as cardiac ischaemia outcomes, insulin sensitivity and inflammation. This Review, therefore, aims to provide a theoretical framework for the potential consequences of tissue build-up of LCACs among individuals with metabolic disorders.
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Affiliation(s)
- Colin S McCoin
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Trina A Knotts
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Sean H Adams
- Arkansas Children's Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, 15 Children's Way, Little Rock, AR 72202, USA
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7
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Mironova GD, Belosludtsev KN, Belosludtseva NV, Gritsenko EN, Khodorov BI, Saris NEL. Mitochondrial Ca2+ cycle mediated by the palmitate-activated cyclosporin a-insensitive pore. J Bioenerg Biomembr 2007; 39:167-74. [PMID: 17530392 DOI: 10.1007/s10863-007-9079-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 03/12/2007] [Indexed: 10/23/2022]
Abstract
Earlier we found that in isolated rat liver mitochondria the reversible opening of the mitochondrial cyclosporin A-insensitive pore induced by low concentrations of palmitic acid (Pal) plus Ca(2+) results in the brief loss of Deltapsi [Mironova et al., J Bioenerg Biomembr (2004), 36:171-178]. Now we report that Pal and Ca(2+), increased to 30 and 70 nmol/mg protein respectively, induce a stable and prolonged (10 min) partial depolarization of the mitochondrial membrane, the release of Ca(2+) and the swelling of mitochondria. Inhibitors of the Ca(2+) uniporter, ruthenium red and La(3+), as well as EGTA added in 10 min after the Pal/Ca(2+)-activated pore opening, prevent the release of Ca(2+) and repolarize the membrane to initial level. Similar effects can be observed in the absence of exogeneous Pal, upon mitochondria accumulating high [Sr(2+)], which leads to the activation of phospholipase A(2) and appearance of endogenous fatty acids. The paper proposes a new model of the mitochondrial Ca(2+) cycle, in which Ca(2+) uptake is mediated by the Ca(2+) uniporter and Ca(2+) efflux occurs via a short-living Pal/Ca(2+)-activated pore.
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Affiliation(s)
- Galina D Mironova
- Institute of Theoretical and Experimental Biophysics RAS, Pushchino, Moscow Region 142290, Russia.
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8
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Zimmerman AW, Veerkamp JH. Fatty-acid-binding proteins do not protect against induced cytotoxicity in a kidney cell model. Biochem J 2001; 360:159-65. [PMID: 11696003 PMCID: PMC1222213 DOI: 10.1042/0264-6021:3600159] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Intracellular accumulation of fatty acids (FAs) is a well-described consequence of renal ischaemia and may lead to lethal cell injury. Fatty-acid-binding proteins (FABPs) are small cytosolic proteins with high affinity for FAs. They may protect vital cellular functions by binding to and promoting the metabolism of FAs, thereby reducing their intracellular concentration. In this study we investigated the putative cytoprotective role of FABPs in a Madin-Darby canine kidney (MDCK) cell model for renal damage. We studied the effects of transfection with cDNA encoding heart FABP, adipocyte FABP or liver FABP on cytotoxicity induced by chemical anoxia or FAs. Transfection of MDCK type II cells with these cDNA types caused a 5-20-fold increase in FABP content, but did not change the rate or extent of palmitate uptake. After 1 h of incubation with KCN, all cell types showed reduced viability and cellular ATP content and an intracellular accumulation of non-esterified FAs. High extracellular concentrations of oleate, but not palmitate, caused a markedly decreased cell viability and cellular ATP content. Oleate accumulated in non-esterified form in these cells. Simultaneous addition of glucose ameliorated the damaging effects of KCN or oleate, indicating that glycolytic ATP could substitute for uncoupled oxidative phosphorylation. No significant differences in the effects of chemical anoxia or oleate were observed between non-transfected, mock-transfected and FABP-cDNA-transfected cells. Non-esterified FA accumulation was not reduced in any of the FABP-cDNA-transfected cell lines. In conclusion, our data do not provide evidence for a cytoprotective role of FABP in this kidney cell model.
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Affiliation(s)
- A W Zimmerman
- Department of Biochemistry, University Medical Center Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
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9
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Affiliation(s)
- M Zoratti
- CNR Unit for the Physiology of Mitochondria, Department of Biomedical Sciences, Padova, Italy
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10
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van de Water B, Zoetewey JP, de Bont HJ, Mulder GJ, Nagelkerke JF. The relationship between intracellular Ca2+ and the mitochondrial membrane potential in isolated proximal tubular cells from rat kidney exposed to the nephrotoxin 1,2-dichlorovinyl-cysteine. Biochem Pharmacol 1993; 45:2259-67. [PMID: 8517866 DOI: 10.1016/0006-2952(93)90197-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effects of 1,2-dichlorovinyl-cysteine (DCVC) on the intracellular free calcium concentration ([Ca2+]i) and the mitochondrial membrane potential (delta phi) were investigated in freshly isolated rat kidney proximal tubular cells (PTC). Prior to cell death, DCVC induced a rise in [Ca2+]i and a decrease in the delta phi. Omission of extracellular calcium still resulted in a DCVC-induced increase of [Ca2+]i, indicating that calcium was released from intracellular stores. The beta-lyase inhibitor amino-oxyacetic acid completely protected against mitochondrial damage and cell death, indicating that the DCVC effects are dependent on beta-lyase metabolism. Incubation of the PTC with DCVC together with the intracellular-calcium complexing agents EDTA/acetoxy-methyl (AM), EGTA/AM or Quin-2/AM delayed (but did not prevent) the decrease of the delta phi and cell death, which indicates a relationship between [Ca2+]i and the decrease of delta phi. In individual cells four different responses induced by DCVC were observed; an increase of [Ca2+]i without an effect on delta phi, a decrease of delta phi and an increase of [Ca2+]i occurring simultaneously; an increase of [Ca2+]i preceded by a decrease of delta phi and a decrease of delta phi without any increase of [Ca2+]i. This indicates that DCVC-induced effects on [Ca2+]i and delta phi can appear independently. The data show that mitochondrial damage is potentiated by an elevation of [Ca2+]i, thereby creating a situation which rapidly leads to cell death.
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Affiliation(s)
- B van de Water
- Division of Toxicology, University of Leiden, The Netherlands
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11
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Generation of the mitochondrial permeability transition does not involve inhibition of lysophospholipid acylation. Acyl-coenzyme A:1-acyllysophospholipid acyltransferase activity is not found in rat liver mitochondria. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54765-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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12
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Mokhova E, Arrigoni-Martelli E, Bellei M, Dedukhova V, Muscatello U, Starkov A, Bobyleva V. The protecting effect of L-carnitine on Ca(2+)-loaded rat liver mitochondria. FEBS Lett 1991; 289:187-9. [PMID: 1915847 DOI: 10.1016/0014-5793(91)81066-h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
It is shown that L-carnitine strongly increases the ability of rat liver mitochondria to respond to the train of Ca2+ additions by a transient stimulation of the State-4 respiration rate. Such an effect requires ATP and the L-carnitine efficiency strongly decreases when ATP is omitted. Oleate influences the mitochondria in a fashion opposite to that of L-carnitine. The oleate effect is strongly diminished by L-carnitine. Again, the L-carnitine effect requires ATP, and D-carnitine fails to substitute for L-carnitine. It is suggested that L-carnitine removes, in an ATP-dependent manner, endogenous or added fatty acids, which are involved in oxidative damage of Ca(2+)-loaded mitochondria.
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Affiliation(s)
- E Mokhova
- Institute of General Pathology, Modena, Italy
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13
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Duan JM, Karmazyn M. Reduction of phosphate-induced dysfunction in rat heart mitochondria by carnitine. Eur J Pharmacol 1990; 189:163-74. [PMID: 2253701 DOI: 10.1016/0922-4106(90)90020-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The direct effects of varying concentrations (5-40 mM) of D,L-carnitine were studied in two populations, subsarcolemmal and interfibrillar, of cardiac mitochondria exposed to inorganic phosphate (Pi). After 5 min preincubation 20 mM Pi significantly depressed oxidative phosphorylation rate and ADP/ATP translocase activity, in both populations. Inclusion of D,L-carnitine during preincubation significantly prevented the Pi-induced depression in oxidative phosphorylation without affecting the ADP/ATP translocate system. The Pi-induced inhibition in mitochondrial oxygen consumption rate was seen with either pyruvate-malate, glutamate-malate or succinate as respiratory substrates and was also observed in uncoupled mitochondria treated with 2,4-dinitrophenol. Mitochondrial swelling and shrinkage studies revealed Pi-induced inner membrane instability, a phenomenon prevented by D,L-carnitine in a dose-dependent manner. The effect of Pi was also observed at a concentration of 5 mM which was also prevented by carnitine. Mepacrine, a phospholipase A2 inhibitor, failed to prevent any of the effects of Pi. The results therefore suggest that Pi can produce a depression in mitochondrial oxidative phosphorylation through a mechanism possibly associated with disturbed inner membrane structure and function but apparently unrelated to phospholipase A2 activation. The salutary actions of carnitine may partly explain its protective effects in the ischemic and reperfused heart, a phenomenon associated with enhanced intracellular Pi accumulation.
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Affiliation(s)
- J M Duan
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
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14
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Gunter TE, Pfeiffer DR. Mechanisms by which mitochondria transport calcium. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 258:C755-86. [PMID: 2185657 DOI: 10.1152/ajpcell.1990.258.5.c755] [Citation(s) in RCA: 1265] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
It has been firmly established that the rapid uptake of Ca2+ by mitochondria from a wide range of sources is mediated by a uniporter which permits transport of the ion down its electrochemical gradient. Several mechanisms of Ca2+ efflux from mitochondria have also been extensively discussed in the literature. Energized mitochondria must expend a significant amount of energy to transport Ca2+ against its electrochemical gradient from the matrix space to the external space. Two separate mechanisms have been found to mediate this outward transport: a Ca2+/nNa+ exchanger and a Na(+)-independent efflux mechanism. These efflux mechanisms are considered from the perspective of available energy. In addition, a reversible Ca2(+)-induced increase in inner membrane permeability can also occur. The induction of this permeability transition is characterized by swelling of the mitochondria, leakiness to small ions such as K+, Mg2+, and Ca2+, and loss of the mitochondrial membrane potential. It has been suggested that the permeability transition and its reversal may also function as a mitochondrial Ca2+ efflux mechanism under some conditions. The characteristics of each of these mechanisms are discussed, as well as their possible physiological functions.
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Affiliation(s)
- T E Gunter
- Department of Biophysics, University of Rochester, New York 14642
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15
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Khan S, Irfan M, Rahimtula AD. The hepatotoxic potential of a Prudhoe Bay crude oil: effect on mouse liver weight and composition. Toxicology 1987; 46:95-105. [PMID: 2444021 DOI: 10.1016/0300-483x(87)90141-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The hepatotoxic properties of a Prudhoe Bay Crude Oil (PBCO) were evaluated in mice. Administration of PBCO (5.0 ml/kg body wt, daily for 2 days) to mice resulted in an increase in (i) liver wet and dry weight, (ii) hepatic total proteins, RNA, glycogen and total lipids, and (iii) individual lipids such as cholesterol, triglycerides and phospholipids. Hepatic protein biosynthesis, determined in vivo by administration of L-[14C]leucine was increased in PBCO exposed mice. The rate of 3H incorporation from 3H2O was significantly enhanced in liver fatty acids, cholesterol, triglycerides and thus ultimately in total lipids. Also, an increase in 3H incorporation was noticed in hepatic glycogen after PBCO administration. The results suggest that PBCO may induce hepatotoxicity by altering the intermediary metabolism of biochemical constituents.
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Affiliation(s)
- S Khan
- Biochemistry Department, Memorial University of Newfoundland, St. John's, Canada
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