51
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Asare GA, Anang Y, Afriyie DK, Amoah BY, Asiedu B, Doku D, Ocansey HS, Odei Danso NY, Tekpor P, Osam S. Endogenous Sphingolipid Signaling Pathway Implicated in the Action of Croton membranaceus on the Prostate Gland in BPH Patients. MEDICINES 2017; 4:medicines4040084. [PMID: 29156544 PMCID: PMC5750608 DOI: 10.3390/medicines4040084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/13/2017] [Accepted: 11/15/2017] [Indexed: 11/16/2022]
Abstract
Background: Croton membranaceus extract has apoptotic effects on BPH-1 cells. This study determined if the apoptotic effects were created through the ceramide pathway. Methods: The study was a follow-up to a previous observational study of 30 histologically confirmed patients with benign prostatic hyperplasia (BPH) who were on C. membranaceus ethanolic extract at 20 mg t.i.d orally for 3 mo. Thereafter, total and free prostate-specific antigen (PSA), lipid profile plus Apo lipoprotein A and B, ceramide/Sphingophospho-kinase 1 (SphK1) and 2 (SphK2), sphingosine lyase (SPL), the cytotoxic adducts of oxidative stress 4-hydroxy-2-nonenal (4HNE) and malondialdehyde (MDA), were determined. Results: Total and free PSA were significantly (p < 0.05) different after treatment. Apo lipoprotein A was significantly different (p = 0.024). The SphK1/SphK2 ratio reduced significantly (p = 0.049). Furthermore, SPL, ceramide, and MDA increased significantly after treatment (p = 0.05, p = 0.004, and p = 0.007, respectively). A weak positive correlation was found between high-density lipoprotein (HDL) cholesterol and SphK1, and HDL and ceramide before treatment (p = 0.036, r = 0.3826; p = 0.018, r = 0.4286, respectively. Conclusions:C. membranaceus uses the ceramide pathway by modulating the SphK1/SphK2 ratio and increasing SPL to generate oxidative stress and consequently apoptosis.
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Affiliation(s)
- George Awuku Asare
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Yvonne Anang
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Daniel K Afriyie
- Department of Pharmacy, Ghana Police Hospital, Cantonments, Accra, Ghana.
| | - Brodrick Yeboah Amoah
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Bernice Asiedu
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Derek Doku
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Hannah Serwah Ocansey
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Nana Yaw Odei Danso
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Prince Tekpor
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
| | - Sarah Osam
- Chemical Pathology Unit, Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P.O. Box KB 143, Korle-bu, Accra, Ghana.
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52
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Inhibition of Caspase-8 does not protect from alcohol-induced liver apoptosis but alleviates alcoholic hepatic steatosis in mice. Cell Death Dis 2017; 8:e3152. [PMID: 29072704 PMCID: PMC5680911 DOI: 10.1038/cddis.2017.532] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 08/11/2017] [Accepted: 09/13/2017] [Indexed: 12/15/2022]
Abstract
Hepatic apoptosis is involved in the progression of alcoholic liver disease (ALD). Caspase-8, the apical initiator in death receptor-mediated apoptosis, has been implicated in acute liver injury and in non-alcoholic steatohepatitis. However, the relevance of Caspase-8 in the pathogenesis of ALD remains unclear. In the present study, we investigated the impact of Caspase-8 in human and murine alcohol-induced apoptosis and in ALD. We investigated human samples from ALD patients, primary mouse hepatocytes, and hepatocyte-specific Caspase-8 knockout (Casp8Δhepa) mice in acute and chronic models of ethanol (EtOH) administration. Caspase-8 activation was detected in liver biopsies from ALD patients, as well as in livers of wild-type (WT) mice after chronic ethanol feeding for 8 weeks using the Lieber-DeCarli model. Lack of Caspase-8 expression in Casp8Δhepa animals failed to prevent alcohol-induced liver damage and apoptosis. Instead, inhibition of Caspase-8 shifted the ethanol-induced death signals towards pronounced activation of the intrinsic, mitochondria-dependent apoptosis pathway in Casp8Δhepa livers involving enhanced release of cytochrome c, stronger Caspase-9 activation and specific morphological changes of mitochondria. In vitro and in vivo intervention using a pan-caspase inhibitor markedly attenuated alcohol-induced hepatocyte damage in a Caspase-8-independent manner. Surprisingly, EtOH-fed Casp8Δhepa mice displayed significantly attenuated steatosis and reduced hepatic triglyceride and free fatty acids content. Caspase-8 is dispensable for alcohol-induced apoptosis, but plays an unexpected role for alcohol-dependent fat metabolism. We provide evidence that simultaneous inhibition of extrinsic and intrinsic apoptosis signaling using pan-caspase inhibitors in vivo might be an optimal approach to treat alcohol-induced liver injury.
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53
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Li JJ, Zhang JJ, Wang X, Sun ZM. Effects of 17-DMAG on diffuse large B-cell lymphoma cell apoptosis. Exp Ther Med 2017; 14:3727-3731. [PMID: 29042970 PMCID: PMC5639270 DOI: 10.3892/etm.2017.4995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/20/2017] [Indexed: 12/26/2022] Open
Abstract
17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) is a water soluble, semisynthetic derivative of endotoxin that has anticancer effects. The aim of the present study was to determine whether 17-DMAG enhances the apoptosis of lymphoma cells in diffuse large B-cell lymphoma. Apoptosis was induced in SU-DHL-4 diffuse large B-cell lymphoma cells treated with 17-DMAG, as evaluated by MTT assay and flow cytometry analysis. Apoptosis-associated protein levels were assessed using western blotting, and the results indicated that B-cell lymphoma 2 (Bcl-2)-associated protein X (Bax) was upregulated, whereas heat shock protein family A member 5 (HSPA5) and Bcl-2 were downregulated. Additionally, staining with 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide revealed that treatment with 17-DMAG decreased mitochondrial membrane potential in SU-DHL-4 diffuse large B-cell lymphoma cells. These results suggested that 17-DMAG is able to inhibit proliferation in diffuse large B-cell lymphoma cells in a concentration-dependent manner. The underlying mechanism may be that 17-DMAG induces oxidative stress, which inhibits the expression of HSPA5 and Bcl-2 and promotes the expression of Bax, leading to the apoptosis of SU-DHL-4 cells. Taken together, these results indicated that 17-DMAG may be an effective novel agent for the treatment of diffuse large B-cell lymphoma.
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Affiliation(s)
- Jia-Jia Li
- Department of Hematology, Affiliated Provincial Hospital of Anhui Medical University, Hefei, Anhui 230001, P.R. China
| | - Jing-Jing Zhang
- Department of Hematology, Affiliated Provincial Hospital of Anhui Medical University, Hefei, Anhui 230001, P.R. China
| | - Xiu Wang
- Department of Hematology, Affiliated Provincial Hospital of Anhui Medical University, Hefei, Anhui 230001, P.R. China
| | - Zi-Min Sun
- Department of Hematology, Affiliated Provincial Hospital of Anhui Medical University, Hefei, Anhui 230001, P.R. China
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54
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Øverbye A, Holsæter AM, Markus F, Škalko-Basnet N, Iversen TG, Torgersen ML, Sønstevold T, Engebraaten O, Flatmark K, Mælandsmo GM, Skotland T, Sandvig K. Ceramide-containing liposomes with doxorubicin: time and cell-dependent effect of C6 and C12 ceramide. Oncotarget 2017; 8:76921-76934. [PMID: 29100358 PMCID: PMC5652752 DOI: 10.18632/oncotarget.20217] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 06/17/2017] [Indexed: 12/14/2022] Open
Abstract
Doxorubicin, a widely used chemotherapeutic drug, has several potential high-risk side effects including cardiomyopathy. Furthermore, cellular resistance to this drug develops with time. By using liposomes as carrier vesicles both the side effects and drug resistance might be avoided. In this study we have investigated the cytotoxic effect of doxorubicin encapsulated in liposomes with and without ceramides containing 6 or 12 carbon atoms in the N-amidated fatty acyl chains. The short-chain ceramide species were included in the liposomal compositions due to their pro-apoptotic properties, which might cause a synergistic anticancer effect. We demonstrate that the ceramide species enhance the liposomal doxorubicin toxicity in a cell-specific manner. The C6-ceramide effect is most pronounced in cervical cancer cells (HeLa) and colon cancer cells (HCT116), whereas the C12-ceramide effect is strongest in breast cancer cells (MDA-MB-231). Moreover, the study reveals the importance of investigating cell toxicity at several time points and in different cell-lines, to assess drug-and formulation-induced cytotoxic effects in vitro. Furthermore, our data show that the cytotoxicity obtained with the nanocarriers in vitro, does not necessarily reflect their ability to inhibit tumor growth in vivo. We speculate that the larger effect of Caelyx® than our liposomes in vivo is due to a greater in vivo stability of Caelyx®.
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Affiliation(s)
- Anders Øverbye
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Ann Mari Holsæter
- Drug Transport and Delivery Research Group, Department of Pharmacy, Faculty of Health Sciences, University of Tromsø - The Arctic University of Norway, Tromsø, Norway
| | - Fusser Markus
- Department of Tumour Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Nataša Škalko-Basnet
- Drug Transport and Delivery Research Group, Department of Pharmacy, Faculty of Health Sciences, University of Tromsø - The Arctic University of Norway, Tromsø, Norway
| | - Tore-Geir Iversen
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Maria Lyngaas Torgersen
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Tonje Sønstevold
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Olav Engebraaten
- Department of Tumour Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Kjersti Flatmark
- Department of Tumour Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Gunhild Mari Mælandsmo
- Drug Transport and Delivery Research Group, Department of Pharmacy, Faculty of Health Sciences, University of Tromsø - The Arctic University of Norway, Tromsø, Norway.,Department of Tumour Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
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55
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Prudent J, McBride HM. The mitochondria–endoplasmic reticulum contact sites: a signalling platform for cell death. Curr Opin Cell Biol 2017; 47:52-63. [DOI: 10.1016/j.ceb.2017.03.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 01/23/2023]
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56
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Engin A. Non-Alcoholic Fatty Liver Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 960:443-467. [DOI: 10.1007/978-3-319-48382-5_19] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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57
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Rostovtseva TK, Hoogerheide DP, Rovini A, Bezrukov SM. Lipids in Regulation of the Mitochondrial Outer Membrane Permeability, Bioenergetics, and Metabolism. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-55539-3_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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58
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Abstract
The sphingolipid family of lipids modulate several cellular processes, including proliferation, cell cycle regulation, inflammatory signaling pathways, and cell death. Several members of the sphingolipid pathway have opposing functions and thus imbalances in sphingolipid metabolism result in deregulated cellular processes, which cause or contribute to diseases and disorders in humans. A key cellular process regulated by sphingolipids is apoptosis, or programmed cell death. Sphingolipids play an important role in both extrinsic and intrinsic apoptotic pathways depending on the stimuli, cell type and cellular response to the stress. During mitochondrial-mediated apoptosis, multiple pathways converge on mitochondria and induce mitochondrial outer membrane permeabilization (MOMP). MOMP results in the release of intermembrane space proteins such as cytochrome c and Apaf1 into the cytosol where they activate the caspases and DNases that execute cell death. The precise molecular components of the pore(s) responsible for MOMP are unknown, but sphingolipids are thought to play a role. Here, we review evidence for a role of sphingolipids in the induction of mitochondrial-mediated apoptosis with a focus on potential underlying molecular mechanisms by which altered sphingolipid metabolism indirectly or directly induce MOMP. Data available on these mechanisms is reviewed, and the focus and limitations of previous and current studies are discussed to present important unanswered questions and potential future directions.
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Affiliation(s)
- Gauri A Patwardhan
- Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY, 40202, USA
| | - Levi J Beverly
- Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY, 40202, USA.,Department of Medicine, University of Louisville, Louisville, KY, 40202, USA.,James Graham Brown Cancer Center, University of Louisville, 505 South Hancock Street, Clinical and Translational Research Building, Room 203, Louisville, KY, 40202, USA
| | - Leah J Siskind
- Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY, 40202, USA. .,James Graham Brown Cancer Center, University of Louisville, 505 South Hancock Street, Clinical and Translational Research Building, Room 203, Louisville, KY, 40202, USA.
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59
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Signoretto E, Zierle J, Bhuyan AAM, Castagna M, Lang F. Ceranib-2-induced suicidal erythrocyte death. Cell Biochem Funct 2016; 34:359-66. [PMID: 27291470 DOI: 10.1002/cbf.3196] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/12/2016] [Accepted: 05/16/2016] [Indexed: 12/30/2022]
Abstract
Ceramide is known to trigger apoptosis of nucleated cells and eryptosis of erythrocytes. Eryptosis is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Besides ceramide, stimulators of eryptosis include increase of cytosolic Ca(2+) -activity ([Ca(2+) ]i ) and oxidative stress. Ceramide is degraded by acid ceramidase and inhibition of the enzyme similarly triggers apoptosis. The present study explored, whether ceramidase inhibitor Ceranib-2 induces eryptosis. Flow cytometry was employed to quantify phosphatidylserine-exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca(2+) ]i from Fluo3-fluorescence, reactive oxygen species (ROS) from DCF dependent fluorescence, and ceramide abundance utilizing specific antibodies. Hemolysis was estimated from hemoglobin concentration in the supernatant. A 48 h exposure of human erythrocytes to Ceranib-2 significantly increased the percentage of annexin-V-binding cells (≥50 μM) and the percentage of hemolytic cells (≥10 μM) without significantly modifying forward scatter. Ceranib-2 significantly increased Fluo3-fluorescence, DCF fluorescence and ceramide abundance. The effect of Ceranib-2 on annexin-V-binding was not significantly blunted by removal of extracellular Ca(2+) . Ceranib-2 triggers phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to increase of ceramide abundance and induction of oxidative stress, but not dependent on Ca(2+) entry. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Elena Signoretto
- Departments of Physiology and Cardiology & Cardiovascular Medicine, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany.,Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | - Jens Zierle
- Departments of Physiology and Cardiology & Cardiovascular Medicine, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany
| | - Abdulla Al Mamun Bhuyan
- Departments of Physiology and Cardiology & Cardiovascular Medicine, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany
| | - Michela Castagna
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | - Florian Lang
- Departments of Physiology and Cardiology & Cardiovascular Medicine, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany
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60
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Renault TT, Dejean LM, Manon S. A brewing understanding of the regulation of Bax function by Bcl-xL and Bcl-2. Mech Ageing Dev 2016; 161:201-210. [PMID: 27112371 DOI: 10.1016/j.mad.2016.04.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 04/19/2016] [Accepted: 04/22/2016] [Indexed: 12/17/2022]
Abstract
Bcl-2 family members form a network of protein-protein interactions that regulate apoptosis through permeabilization of the mitochondrial outer membrane. Deciphering this intricate network requires streamlined experimental models, including the heterologous expression in yeast. This approach had previously enabled researchers to identify domains and residues that underlie the conformational changes driving the translocation, the insertion and the oligomerization of the pro-apoptotic protein Bax at the level of the mitochondrial outer membrane. Recent studies that combine experiments in yeast and in mammalian cells have shown the unexpected effect of the anti-apoptotic protein Bcl-xL on the priming of Bax. As demonstrated with the BH3-mimetic molecule ABT-737, this property of Bcl-xL, and of Bcl-2, is crucial to elaborate about how apoptosis could be reactivated in tumoral cells.
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Affiliation(s)
- Thibaud T Renault
- Helmholtz Center for Infection Research, Junior Research Group Infection Biology of Salmonella, Inhoffenstraße 7, 38124 Braunschweig, Germany; Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
| | - Laurent M Dejean
- California State University of Fresno, Department of Chemistry, 2555 E. San Ramon Ave M/S SB70, Fresno, CA 93740-8034, USA
| | - Stéphen Manon
- CNRS, UMR5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France; Université de Bordeaux, 146 Rue Léo Saignat, 33076 Bordeaux, France.
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61
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Prudent J, Zunino R, Sugiura A, Mattie S, Shore GC, McBride HM. MAPL SUMOylation of Drp1 Stabilizes an ER/Mitochondrial Platform Required for Cell Death. Mol Cell 2015; 59:941-55. [PMID: 26384664 DOI: 10.1016/j.molcel.2015.08.001] [Citation(s) in RCA: 234] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/11/2015] [Accepted: 08/04/2015] [Indexed: 01/01/2023]
Abstract
There has been evidence that mitochondrial fragmentation is required for apoptosis, but the molecular links between the machinery regulating dynamics and cell death have been controversial. Indeed, activated BAX and BAK can form functional channels in liposomes, bringing into question the contribution of mitochondrial dynamics in apoptosis. We now demonstrate that the activation of apoptosis triggers MAPL/MUL1-dependent SUMOylation of the fission GTPase Drp1, a process requisite for cytochrome c release. SUMOylated Drp1 functionally stabilizes ER/mitochondrial contact sites that act as hotspots for mitochondrial constriction, calcium flux, cristae remodeling, and cytochrome c release. The loss of MAPL does not alter the activation and assembly of BAX/BAK oligomers, indicating that MAPL is activated downstream of BAX/BAK. This work demonstrates how interorganellar contacts are dynamically regulated through active SUMOylation during apoptosis, creating a stabilized platform that signals cytochrome c release.
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Affiliation(s)
- Julien Prudent
- Montreal Neurological Institute, McGill University, 3801 University Ave, Montreal, QC H3A 2B4, Canada
| | - Rodolfo Zunino
- Montreal Neurological Institute, McGill University, 3801 University Ave, Montreal, QC H3A 2B4, Canada
| | - Ayumu Sugiura
- Montreal Neurological Institute, McGill University, 3801 University Ave, Montreal, QC H3A 2B4, Canada
| | - Sevan Mattie
- Montreal Neurological Institute, McGill University, 3801 University Ave, Montreal, QC H3A 2B4, Canada
| | - Gordon C Shore
- McIntyre Medical Sciences Building, Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Heidi M McBride
- Montreal Neurological Institute, McGill University, 3801 University Ave, Montreal, QC H3A 2B4, Canada.
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62
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Lu J, Zeng H, Liang Z, Chen L, Zhang L, Zhang H, Liu H, Jiang H, Shen B, Huang M, Geng M, Spiegel S, Luo C. Network modelling reveals the mechanism underlying colitis-associated colon cancer and identifies novel combinatorial anti-cancer targets. Sci Rep 2015; 5:14739. [PMID: 26446703 PMCID: PMC4597205 DOI: 10.1038/srep14739] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 09/07/2015] [Indexed: 01/05/2023] Open
Abstract
The connection between inflammation and tumourigenesis has been well established. However, the detailed molecular mechanism underlying inflammation-associated tumourigenesis remains unknown because this process involves a complex interplay between immune microenvironments and epithelial cells. To obtain a more systematic understanding of inflammation-associated tumourigenesis as well as to identify novel therapeutic approaches, we constructed a knowledge-based network describing the development of colitis-associated colon cancer (CAC) by integrating the extracellular microenvironment and intracellular signalling pathways. Dynamic simulations of the CAC network revealed a core network module, including P53, MDM2, and AKT, that may govern the malignant transformation of colon epithelial cells in a pro-tumor inflammatory microenvironment. Furthermore, in silico mutation studies and experimental validations led to a novel finding that concurrently targeting ceramide and PI3K/AKT pathway by chemical probes or marketed drugs achieves synergistic anti-cancer effects. Overall, our network model can guide further mechanistic studies on CAC and provide new insights into the design of combinatorial cancer therapies in a rational manner.
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Affiliation(s)
- Junyan Lu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hanlin Zeng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Zhongjie Liang
- Soochow University, Center for Systems Biology, Jiangsu, China
| | - Limin Chen
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Liyi Zhang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hao Zhang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hong Liu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hualiang Jiang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Bairong Shen
- Soochow University, Center for Systems Biology, Jiangsu, China
| | - Ming Huang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Meiyu Geng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Sarah Spiegel
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Cheng Luo
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,Soochow University, Center for Systems Biology, Jiangsu, China
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63
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Saito K, Uebanso T, Maekawa K, Ishikawa M, Taguchi R, Nammo T, Nishimaki-Mogami T, Udagawa H, Fujii M, Shibazaki Y, Yoneyama H, Yasuda K, Saito Y. Characterization of hepatic lipid profiles in a mouse model with nonalcoholic steatohepatitis and subsequent fibrosis. Sci Rep 2015; 5:12466. [PMID: 26289793 PMCID: PMC4542161 DOI: 10.1038/srep12466] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 06/18/2015] [Indexed: 12/25/2022] Open
Abstract
Nonalcoholic steatohepatitis (NASH) is a major health problem since it often leads to hepatocellular carcinoma. However, the underlying mechanisms of NASH development and subsequent fibrosis have yet to be clarified. We compared comprehensive lipidomic profiles between mice with high fat diet (HFD)-induced steatosis and STAM mice with NASH and subsequent fibrosis. The STAM mouse is a model that demonstrates NASH progression resembling the disease in humans: STAM mice manifest NASH at 8 weeks, which progresses to fibrosis at 12 weeks, and finally develop hepatocellular carcinoma. Overall, 250 lipid molecules were detected in the liver using liquid chromatography-mass spectrometry. We found that STAM mice with NASH presented a significantly higher abundance of sphingolipids and lower levels of triacylglycerols than the HFD-fed control mice. The abundance of certain fatty acids in phospholipid side chains was also significantly different between STAM and control mice, although global levels of phosphatidylcholines and phosphatidylethanolamines were comparable. Finally, increase in levels of acylcarnitines and some diacylglycerols was observed in STAM mice toward the fibrosis stage, but not in age-matched control mice. Our study provides insights into the lipid status of the steatotic, NASH, and fibrotic liver that would help elucidate the molecular pathophysiology of NASH progression.
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Affiliation(s)
- Kosuke Saito
- Division of Medical Safety Science, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
| | - Takashi Uebanso
- Department of Metabolic Disorder, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan
| | - Keiko Maekawa
- Division of Medical Safety Science, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
| | - Masaki Ishikawa
- Division of Medical Safety Science, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
| | - Ryo Taguchi
- Division of Medical Safety Science, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
| | - Takao Nammo
- Department of Metabolic Disorder, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan
| | - Tomoko Nishimaki-Mogami
- Division of Biochemistry, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
| | - Haruhide Udagawa
- Department of Metabolic Disorder, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan
| | - Masato Fujii
- Stelic Institute &Co., Inc., 1-9-15 Higashi Azabu, Minato, Tokyo 106-0044, Japan
| | - Yuichiro Shibazaki
- Stelic Institute &Co., Inc., 1-9-15 Higashi Azabu, Minato, Tokyo 106-0044, Japan
| | - Hiroyuki Yoneyama
- Stelic Institute &Co., Inc., 1-9-15 Higashi Azabu, Minato, Tokyo 106-0044, Japan
| | - Kazuki Yasuda
- Department of Metabolic Disorder, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan
| | - Yoshiro Saito
- Division of Medical Safety Science, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
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Ceramides in Alzheimer's Disease: Key Mediators of Neuronal Apoptosis Induced by Oxidative Stress and Aβ Accumulation. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:346783. [PMID: 26090071 PMCID: PMC4458271 DOI: 10.1155/2015/346783] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 11/17/2022]
Abstract
Alzheimer's disease (AD), the most common chronic and progressive neurodegenerative disorder, is characterized by extracellular deposits of amyloid β-peptides (Aβ) and intracellular deposits of hyperphosphorylated tau (phospho-tau) protein. Ceramides, the major molecules of sphingolipid metabolism and lipid second messengers, have been associated with AD progression and pathology via Aβ generation. Enhanced levels of ceramides directly increase Aβ through stabilization of β-secretase, the key enzyme in the amyloidogenic processing of Aβ precursor protein (APP). As a positive feedback loop, the generated oligomeric and fibrillar Aβ induces a further increase in ceramide levels by activating sphingomyelinases that catalyze the catabolic breakdown of sphingomyelin to ceramide. Evidence also supports important role of ceramides in neuronal apoptosis. Ceramides may initiate a cascade of biochemical alterations, which ultimately leads to neuronal death by diverse mechanisms, including depolarization and permeabilization of mitochondria, increased production of reactive oxygen species (ROS), cytochrome c release, Bcl-2 depletion, and caspase-3 activation, mainly by modulating intracellular signalling, particularly along the pathways related to Akt/PKB kinase and mitogen-activated protein kinases (MAPKs). This review summarizes recent findings related to the role of ceramides in oxidative stress-driven neuronal apoptosis and interplay with Aβ in the cascade of events ending in neuronal degeneration.
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Siddique MM, Li Y, Chaurasia B, Kaddai VA, Summers SA. Dihydroceramides: From Bit Players to Lead Actors. J Biol Chem 2015; 290:15371-15379. [PMID: 25947377 DOI: 10.1074/jbc.r115.653204] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sphingolipid synthesis involves a highly conserved biosynthetic pathway that produces fundamental precursors of complex sphingolipids. The final reaction involves the insertion of a double bond into dihydroceramides to generate the more abundant ceramides, which are converted to sphingomyelins and glucosylceramides/gangliosides by the addition of polar head groups. Although ceramides have long been known to mediate cellular stress responses, the dihydroceramides that are transiently produced during de novo sphingolipid synthesis were deemed inert. Evidence published in the last few years suggests that these dihydroceramides accumulate to a far greater extent in tissues than previously thought. Moreover, they have biological functions that are distinct and non-overlapping with those of the more prevalent ceramides. Roles are being uncovered in autophagy, hypoxia, and cellular proliferation, and the lipids are now implicated in the etiology, treatment, and/or diagnosis of diabetes, cancer, ischemia/reperfusion injury, and neurodegenerative diseases. This minireview summarizes recent findings on this emerging class of bioactive lipids.
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Affiliation(s)
| | - Ying Li
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria 3004, Australia
| | | | - Vincent A Kaddai
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria 3004, Australia
| | - Scott A Summers
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria 3004, Australia.
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Regulation of ceramide channel formation and disassembly: Insights on the initiation of apoptosis. Saudi J Biol Sci 2015; 22:760-72. [PMID: 26587005 PMCID: PMC4625378 DOI: 10.1016/j.sjbs.2015.03.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/12/2015] [Accepted: 03/15/2015] [Indexed: 01/04/2023] Open
Abstract
Sphingolipid research has surged in the past two decades and has produced a wide variety of evidence supporting the role of this class of molecules in mediating cellular growth, differentiation, senescence, and apoptosis. Ceramides are a subgroup of sphingolipids (SLs) that are directly involved in the process of initiation of apoptosis. We, and others, have recently shown that ceramides are capable of the formation of protein-permeable channels in mitochondrial outer membranes under physiological conditions. These pores are indeed good candidates for the pathway of release of pro-apoptotic proteins from the mitochondrial intermembrane space (IMS) into the cytosol to initiate intrinsic apoptosis. Here, we review recent findings on the regulation of ceramide channel formation and disassembly, highlighting possible implications on the initiation of the intrinsic apoptotic pathway.
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Key Words
- Apoptosis
- Assembly and disassembly
- Bcl-2 family proteins
- Bcl-2, B cell CLL/lymphoma-2
- Cer, ceramide
- CerS, ceramide synthase
- Ceramide channels
- Chain length
- DES, dihydroceramide desaturase
- DHCer, dihydroceramide
- ER, endoplasmic reticulum
- IMS, intermembrane space
- KSR, 3-ketosphinganine reductase
- MOMP, mitochondrial outer membrane permeability
- Mitochondria
- SLs, sphingolipids
- SM, sphingomyelin
- SPT, serine palmitoyl transferase
- So, sphingosine
- Sphingolipids
- de novo synthesis
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67
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Ueda N. Ceramide-induced apoptosis in renal tubular cells: a role of mitochondria and sphingosine-1-phoshate. Int J Mol Sci 2015; 16:5076-124. [PMID: 25751724 PMCID: PMC4394466 DOI: 10.3390/ijms16035076] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 02/09/2015] [Accepted: 02/12/2015] [Indexed: 12/16/2022] Open
Abstract
Ceramide is synthesized upon stimuli, and induces apoptosis in renal tubular cells (RTCs). Sphingosine-1 phosphate (S1P) functions as a survival factor. Thus, the balance of ceramide/S1P determines ceramide-induced apoptosis. Mitochondria play a key role for ceramide-induced apoptosis by altered mitochondrial outer membrane permeability (MOMP). Ceramide enhances oligomerization of pro-apoptotic Bcl-2 family proteins, ceramide channel, and reduces anti-apoptotic Bcl-2 proteins in the MOM. This process alters MOMP, resulting in generation of reactive oxygen species (ROS), cytochrome C release into the cytosol, caspase activation, and apoptosis. Ceramide regulates apoptosis through mitogen-activated protein kinases (MAPKs)-dependent and -independent pathways. Conversely, MAPKs alter ceramide generation by regulating the enzymes involving ceramide metabolism, affecting ceramide-induced apoptosis. Crosstalk between Bcl-2 family proteins, ROS, and many signaling pathways regulates ceramide-induced apoptosis. Growth factors rescue ceramide-induced apoptosis by regulating the enzymes involving ceramide metabolism, S1P, and signaling pathways including MAPKs. This article reviews evidence supporting a role of ceramide for apoptosis and discusses a role of mitochondria, including MOMP, Bcl-2 family proteins, ROS, and signaling pathways, and crosstalk between these factors in the regulation of ceramide-induced apoptosis of RTCs. A balancing role between ceramide and S1P and the strategy for preventing ceramide-induced apoptosis by growth factors are also discussed.
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Affiliation(s)
- Norishi Ueda
- Department of Pediatrics, Public Central Hospital of Matto Ishikawa, 3-8 Kuramitsu, Hakusan, Ishikawa 924-8588, Japan.
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68
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Stiban J, Perera M. Very long chain ceramides interfere with C16-ceramide-induced channel formation: A plausible mechanism for regulating the initiation of intrinsic apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:561-7. [PMID: 25462172 DOI: 10.1016/j.bbamem.2014.11.018] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 11/13/2014] [Accepted: 11/17/2014] [Indexed: 12/29/2022]
Abstract
Mitochondria mediate both cell survival and death. The intrinsic apoptotic pathway is initiated by the permeabilization of the mitochondrial outer membrane to pro-apoptotic inter-membrane space (IMS) proteins. Many pathways cause the egress of IMS proteins. Of particular interest is the ability of ceramide to self-assemble into dynamic water-filled channels. The formation of ceramide channels is regulated extensively by Bcl-2 family proteins and dihydroceramide. Here, we show that the chain length of biologically active ceramides serves as an important regulatory factor. Ceramides are synthesized by a family of six mammalian ceramide synthases (CerS) each of which produces a subset of ceramides that differ in their fatty acyl chain length. Various ceramides permeabilize mitochondria differentially. Interestingly, the presence of very long chain ceramides reduces the potency of C16-mediated mitochondrial permeabilization indicating that the intercalation of the lipids in the dynamic channel has a destabilizing effect, reminiscent of dihydroceramide inhibition of ceramide channel formation (Stiban et al., 2006). Moreover, mitochondria isolated from cells overexpressing the ceramide synthase responsible for the production of C16-ceramide (CerS5) are permeabilized faster upon the exogenous addition of C16-ceramide whereas they are resistant to permeabilization with added C24-ceramide. On the other hand mitochondria isolated from CerS2-overexpressing cells show the opposite pattern, indicating that the product of CerS2 inhibits C16-channel formation ex vivo and vice versa. This interplay between different ceramide metabolic enzymes and their products adds a new dimension to the complexity of mitochondrial-mediated apoptosis, and emphasizes its role as a key regulatory step that commits cells to life or death.
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Affiliation(s)
- Johnny Stiban
- Department of Biology and Biochemistry, Birzeit University, P.O. Box 14, West Bank 627, Palestine.
| | - Meenu Perera
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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69
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Affiliation(s)
- Katherine Labbé
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
| | - Andrew Murley
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
| | - Jodi Nunnari
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
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70
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Chi X, Kale J, Leber B, Andrews DW. Regulating cell death at, on, and in membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2100-13. [PMID: 24927885 DOI: 10.1016/j.bbamcr.2014.06.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 05/29/2014] [Accepted: 06/03/2014] [Indexed: 11/17/2022]
Abstract
Bcl-2 family proteins are central regulators of apoptosis. Various family members are located in the cytoplasm, endoplasmic reticulum, and mitochondrial outer membrane in healthy cells. However during apoptosis most of the interactions between family members that determine the fate of the cell occur at the membranes of intracellular organelles. It has become evident that interactions with membranes play an active role in the regulation of Bcl-2 family protein interactions. Here we provide an overview of various models proposed to explain how the Bcl-2 family regulates apoptosis and discuss how membrane binding affects the structure and function of each of the three categories of Bcl-2 proteins (pro-apoptotic, pore-forming, and anti-apoptotic). We also examine how the Bcl-2 family regulates other aspects of mitochondrial and ER physiology relevant to cell death.
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Affiliation(s)
- Xiaoke Chi
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Justin Kale
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Brian Leber
- Department of Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - David W Andrews
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Biological Sciences, Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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71
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Cosentino K, García-Sáez AJ. Mitochondrial alterations in apoptosis. Chem Phys Lipids 2014; 181:62-75. [PMID: 24732580 DOI: 10.1016/j.chemphyslip.2014.04.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 03/20/2014] [Accepted: 04/02/2014] [Indexed: 12/31/2022]
Abstract
Besides their conventional role as energy suppliers for the cell, mitochondria in vertebrates are active regulators of apoptosis. They release apoptotic factors from the intermembrane space into the cytosol through a mechanism that involves the Bcl-2 protein family, mediating permeabilization of the outer mitochondrial membrane. Associated with this event, a number of additional changes affect mitochondria during apoptosis. They include loss of important mitochondrial functions, such as the ability to maintain calcium homeostasis and to generate ATP, as well as mitochondrial fragmentation and cristae remodeling. Moreover, the lipidic component of mitochondrial membranes undergoes important alterations in composition and distribution, which have turned out to be relevant regulatory events for the proteins involved in apoptotic mitochondrial damage.
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Affiliation(s)
- Katia Cosentino
- German Cancer Research Center, Heidelberg, Germany; Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Ana J García-Sáez
- German Cancer Research Center, Heidelberg, Germany; Max-Planck Institute for Intelligent Systems, Stuttgart, Germany; Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.
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72
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Liu Y, Samuel BS, Breen PC, Ruvkun G. Caenorhabditis elegans pathways that surveil and defend mitochondria. Nature 2014; 508:406-10. [PMID: 24695221 PMCID: PMC4102179 DOI: 10.1038/nature13204] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 03/04/2014] [Indexed: 01/11/2023]
Abstract
Mitochondrial function is challenged by toxic by-products of metabolism as well as by pathogen attack. Caenorhabditis elegans normally responds to mitochondrial dysfunction with activation of mitochondrial-repair, drug-detoxification and pathogen-response pathways. Here, from a genome-wide RNA interference (RNAi) screen, we identified 45 C. elegans genes that are required to upregulate detoxification, pathogen-response and mitochondrial-repair pathways after inhibition of mitochondrial function by drug-induced or genetic disruption. Animals defective in ceramide biosynthesis are deficient in mitochondrial surveillance, and addition of particular ceramides can rescue the surveillance defects. Ceramide can also rescue the mitochondrial surveillance defects of other gene inactivations, mapping these gene activities upstream of ceramide. Inhibition of the mevalonate pathway, either by RNAi or statin drugs, also disrupts mitochondrial surveillance. Growth of C. elegans with a significant fraction of bacterial species from their natural habitat causes mitochondrial dysfunction. Other bacterial species inhibit C. elegans defence responses to a mitochondrial toxin, revealing bacterial countermeasures to animal defence.
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Affiliation(s)
- Ying Liu
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA [3] State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Buck S Samuel
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Peter C Breen
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Gary Ruvkun
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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73
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Castro BM, Prieto M, Silva LC. Ceramide: a simple sphingolipid with unique biophysical properties. Prog Lipid Res 2014; 54:53-67. [PMID: 24513486 DOI: 10.1016/j.plipres.2014.01.004] [Citation(s) in RCA: 266] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 01/29/2014] [Accepted: 01/29/2014] [Indexed: 02/06/2023]
Abstract
Ceramides are involved in a variety of cellular processes and in disease. Their biological functions are thought to depend on ceramides' unique biophysical properties, which promote strong alterations of cell membrane properties and consequent triggering of signaling events. Over the last decades, efforts were made to understand the impact of ceramide on membrane biophysical features. Several studies, performed in a multitude of membrane models, address ceramides' specific interactions, the effect of their acyl chain structure and the influence of membrane lipid composition and properties on ceramide biophysical outcome. In this review, a rationale for the multiple and complex changes promoted by ceramide is provided, highlighting, on a comprehensive and critical manner, the interactions between ceramides and specific lipids and/or lipid phases. Focus is also given to the interplay between ceramide and cholesterol, particularly in lipid raft-mimicking mixtures, an issue of intense debate due to the urgent need to understand the biophysical impact of ceramide formation in models resembling the cell membrane. The implications of ceramide-induced biophysical changes on lipid-protein interactions and cell signaling are also discussed, together with the emerging evidence for the existence of ceramide-gel like domains in cellular membranes.
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Affiliation(s)
- Bruno M Castro
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Complexo I, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Manuel Prieto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Complexo I, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Liana C Silva
- iMed.UL - Research Institute for Medicines and Pharmaceutical Sciences, Faculdade de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal.
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74
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Non-alcoholic steatohepatitis and hepatocellular carcinoma: implications for lycopene intervention. Nutrients 2013; 6:124-62. [PMID: 24379011 PMCID: PMC3916853 DOI: 10.3390/nu6010124] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 12/09/2013] [Accepted: 12/11/2013] [Indexed: 02/06/2023] Open
Abstract
Increased prevalence of non-alcoholic fatty liver disease (NAFLD) is one of the consequences of the current obesity epidemic. NAFLD is a major form of chronic liver disease that is highly prevalent in obese and overweight adults and children. Nonalcoholic steatohepatitis (NASH) is the severe form of NAFLD, and uncontrolled inflammation as displayed in NASH has been identified as one of the key events in enhancing hepatic carcinogenesis. Lycopene is a non-provitamin A carotenoid and the pigment principally responsible for the characteristic deep-red color of ripe tomato and tomato products, as well as some fruits and vegetables. Lycopene's innate antioxidant and anti-inflammatory properties have generated research interests on its capacity to protect against human diseases that are associated with oxidative stress and inflammation. In addition, differential mechanisms of lycopene metabolism including endogenous cleavage by carotenoid cleavage oxygenases (BCOs), generate lycopene metabolites that may also have significant impact on human disease development. However, it remains to be elucidated as to whether lycopene or its metabolites apolycopenoids have protective effects against obesity-related complications including inflammation and tumorigenesis. This article summarizes the in vivo experiments that elucidated molecular mechanisms associated with obesity-related hepatic inflammation and carcinogenesis. This review also provides an overview of lycopene metabolism, and the molecular pathways involved in the potential beneficial properties of lycopene and apolycopenoids. More research is clearly needed to fully unravel the importance of BCOs in tomato carotenoid metabolism and the consequence on human health and diseases.
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75
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Emerging roles of lipids in BCL-2 family-regulated apoptosis. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1542-54. [DOI: 10.1016/j.bbalip.2013.03.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 02/28/2013] [Accepted: 03/02/2013] [Indexed: 01/06/2023]
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76
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Gérecová G, Kopanicová J, Jaká P, Běhalová L, Juhásová B, Bhatia-Kiššová I, Forte M, Polčic P, Mentel M. BH3-only proteins Noxa, Bik, Bmf, and Bid activate Bax and Bak indirectly when studied in yeast model. FEMS Yeast Res 2013; 13:747-54. [DOI: 10.1111/1567-1364.12074] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/27/2013] [Accepted: 08/27/2013] [Indexed: 11/30/2022] Open
Affiliation(s)
- Gabriela Gérecová
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Jana Kopanicová
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Petra Jaká
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Lucia Běhalová
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Barbora Juhásová
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Ingrid Bhatia-Kiššová
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Michael Forte
- Vollum Institute; Oregon Health & Science University; Portland OR USA
| | - Peter Polčic
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Marek Mentel
- Department of Biochemistry; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
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77
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Kogot-Levin A, Saada A. Ceramide and the mitochondrial respiratory chain. Biochimie 2013; 100:88-94. [PMID: 23933096 DOI: 10.1016/j.biochi.2013.07.027] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 07/26/2013] [Indexed: 01/01/2023]
Abstract
Ceramide is a group of sphingolipids found in cell membranes, composed of a sphingoid base linked to a fatty acid of varying chain length. Initially regarded as purely structural components, this group of molecules is now recognized as a key signaling and regulatory elements in cell biology. Ceramide species differing in acyl chain length, with distinct biophysical properties, execute distinct functions and effects. Some of these modulate mitochondrial function and oxidative phosphorylation (OXPHOS). Certain ceramides were associated with decreased mitochondrial respiratory chain (MRC) activity, increased reactive oxygen species (ROS) production and oxidative stress, mitochondrial outer membrane permeabilization (MOMP), reduced mitochondrial membrane potential, mitophagy and apoptosis. In this review we aim to summarize the most relevant findings linking ceramide to mitochondria. The physiological significance of synthetic short and naturally occurring long chain ceramides in modulating mitochondrial function with emphasis on the MRC will be discussed.
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Affiliation(s)
- Aviram Kogot-Levin
- Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ann Saada
- Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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78
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BAK activation is necessary and sufficient to drive ceramide synthase-dependent ceramide accumulation following inhibition of BCL2-like proteins. Biochem J 2013; 452:111-9. [PMID: 23480852 DOI: 10.1042/bj20130147] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Determining mechanistic details about how drugs kill cancer cells is critical for predicting which cancers will respond to given therapeutic regimens and for identifying effective combinations of drugs that more potently kill cancer cells while sparing normal cells. The BCL2 family of proteins and bioactive sphingolipids are intricately linked during apoptotic cell death. In fact, many chemotherapeutic drugs are known to cause accumulation of the pro-apoptotic sphingolipid ceramide; however, the mechanism by which this occurs is not completely understood. In the present study we demonstrate that direct inhibition of anti-apoptotic BCL2 proteins with ABT-263 is sufficient to induce C(16)-ceramide synthesis in multiple cell lines, including human leukaemia and myeloma cells. ABT-263 activates CerS (ceramide synthase) activity only in cells expressing BAK or in cells capable of activating BAK. Importantly, recombinant BAK is sufficient to increase in vitro CerS activity in microsomes purified from Bak-KO (knockout) cells and activated BAK more potently activates CerS than inactive BAK. Likewise, ABT-263 addition to wild-type, but not Bak-deficient, microsomes increases CerS in vitro activity. Furthermore, we present a feed-forward model by which BAK activation of CerS by chemotherapeutic drugs leads to elevated ceramide levels that result in synergistic channel formation by ceramide (or one of its metabolites) and BAX/BAK.
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79
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Abstract
Synthetic lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory of capacitors. To this end, we recorded channel traces and current histograms in patch-experiments on lipid membranes. We derived a theoretical current-voltage relationship for pores in lipid membranes that describes the experimental data very well when assuming an asymmetric membrane. We determined the equilibrium constant between closed and open state and the open probability as a function of voltage. The voltage-dependence of the lipid pores is found comparable to that of protein channels. Lifetime distributions of open and closed events indicate that the channel open distribution does not follow exponential statistics but rather power law behavior for long open times.
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Affiliation(s)
- Andreas Blicher
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Heimburg
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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Sukumaran P, Lönnfors M, Långvik O, Pulli I, Törnquist K, Slotte JP. Complexation of c6-ceramide with cholesteryl phosphocholine - a potent solvent-free ceramide delivery formulation for cells in culture. PLoS One 2013; 8:e61290. [PMID: 23620740 PMCID: PMC3631171 DOI: 10.1371/journal.pone.0061290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 03/06/2013] [Indexed: 12/15/2022] Open
Abstract
Ceramides are potent bioactive molecules in cells. However, they are very hydrophobic molecules, and difficult to deliver efficiently to cells. We have made fluid bilayers from a short-chain D-erythro-ceramide (C6-Cer) and cholesteryl phosphocholine (CholPC), and have used this as a formulation to deliver ceramide to cells. C6-Cer complexed with CholPC led to much larger biological effects in cultured cells (rat thyroid FRTL-5 and human HeLa cells in culture) compared to C6-Cer dissolved in dimethyl sulfoxide (DMSO). Inhibition of cell proliferation and induction of apoptosis was significantly more efficient by C6-Cer/CholPC compared to C6-Cer dissolved in DMSO. C6-Cer/CholPC also permeated cell membranes and caused mitochondrial Ca2+ influx more efficiently than C6-Cer in DMSO. Even though CholPC was taken up by cells to some extent (from C6-Cer/CholPC bilayers), and was partially hydrolyzed to free cholesterol (about 9%), none of the antiproliferative effects were due to CholPC or excess cholesterol. The ceramide effect was not limited to D-erythro-C6-Cer, since L-erythro-C6-Cer and D-erythro-C6-dihydroCer also inhibited cell priolifereation and affected Ca2+ homeostasis. We conclude that C6-Cer complexed to CholPC increased the bioavailability of the short-chain ceramide for cells, and potentiated its effects in comparison to solvent-dissolved C6-Cer. This new ceramide formulation appears to be superior to previous solvent delivery approaches, and may even be useful with longer-chain ceramides.
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Affiliation(s)
| | - Max Lönnfors
- Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Otto Långvik
- Laboratory of Organic Chemistry, Department of Natural Sciences, Åbo Akademi University, Turku, Finland
| | - Ilari Pulli
- Cell Biology, Åbo Akademi University, Turku, Finland
| | - Kid Törnquist
- Cell Biology, Åbo Akademi University, Turku, Finland
- Minerva Foundation Institute of Medical Research, Biomedicum Helsinki, Helsinki, Finland
- * E-mail: (KT); (JPS)
| | - J. Peter Slotte
- Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
- * E-mail: (KT); (JPS)
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81
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Funke C, Schneider SA, Berg D, Kell DB. Genetics and iron in the systems biology of Parkinson’s disease and some related disorders. Neurochem Int 2013; 62:637-52. [DOI: 10.1016/j.neuint.2012.11.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 11/19/2012] [Accepted: 11/28/2012] [Indexed: 12/21/2022]
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82
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Hage-Sleiman R, Esmerian MO, Kobeissy H, Dbaibo G. p53 and Ceramide as Collaborators in the Stress Response. Int J Mol Sci 2013; 14:4982-5012. [PMID: 23455468 PMCID: PMC3634419 DOI: 10.3390/ijms14034982] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 01/22/2013] [Accepted: 02/01/2013] [Indexed: 02/08/2023] Open
Abstract
The sphingolipid ceramide mediates various cellular processes in response to several extracellular stimuli. Some genotoxic stresses are able to induce p53-dependent ceramide accumulation leading to cell death. However, in other cases, in the absence of the tumor suppressor protein p53, apoptosis proceeds partly due to the activity of this "tumor suppressor lipid", ceramide. In the current review, we describe ceramide and its roles in signaling pathways such as cell cycle arrest, hypoxia, hyperoxia, cell death, and cancer. In a specific manner, we are elaborating on the role of ceramide in mitochondrial apoptotic cell death signaling. Furthermore, after highlighting the role and mechanism of action of p53 in apoptosis, we review the association of ceramide and p53 with respect to apoptosis. Strikingly, the hypothesis for a direct interaction between ceramide and p53 is less favored. Recent data suggest that ceramide can act either upstream or downstream of p53 protein through posttranscriptional regulation or through many potential mediators, respectively.
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Affiliation(s)
- Rouba Hage-Sleiman
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Infectious Diseases, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mails: (M.O.E.); (G.D.)
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +961-1-350-000 (ext. 4883)
| | - Maria O. Esmerian
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Infectious Diseases, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mails: (M.O.E.); (G.D.)
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mail:
| | - Hadile Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mail:
| | - Ghassan Dbaibo
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Infectious Diseases, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mails: (M.O.E.); (G.D.)
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Riad El Solh, 1107 2020 Beirut, Lebanon; E-Mail:
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83
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Andersen JL, Kornbluth S. The tangled circuitry of metabolism and apoptosis. Mol Cell 2013; 49:399-410. [PMID: 23395270 PMCID: PMC3801185 DOI: 10.1016/j.molcel.2012.12.026] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 12/11/2012] [Accepted: 12/26/2012] [Indexed: 12/15/2022]
Abstract
For single-cell organisms, nutrient uptake and metabolism are central to the fundamental decision of whether to grow or divide. In metazoans, cell fate decisions are more complex: organismal homeostasis must be strictly maintained by balancing cell proliferation and death. Despite this increased complexity, cell fate within multicellular organisms is also influenced by metabolism; recent studies, triggered in part by an interest in tumor metabolism, are beginning to illuminate the mechanisms through which proliferation, death, and metabolism are intertwined. In particular, work on Bcl-2 family proteins suggests that the signaling pathways governing metabolism and apoptosis are inextricably linked. Here we review the crosstalk between these pathways, emphasizing recent work that illustrates the emerging dual nature of several core apoptotic proteins in regulating both metabolism and cell death.
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Affiliation(s)
- Joshua L Andersen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA
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84
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Siemen D, Ziemer M. What is the nature of the mitochondrial permeability transition poreand What is it Not? IUBMB Life 2013; 65:255-62. [DOI: 10.1002/iub.1130] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 12/07/2012] [Indexed: 12/23/2022]
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85
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Inhibition of ceramide metabolism sensitizes human leukemia cells to inhibition of BCL2-like proteins. PLoS One 2013; 8:e54525. [PMID: 23342165 PMCID: PMC3546986 DOI: 10.1371/journal.pone.0054525] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 12/12/2012] [Indexed: 01/29/2023] Open
Abstract
The identification of novel combinations of effective cancer drugs is required for the successful treatment of cancer patients for a number of reasons. First, many “cancer specific” therapeutics display detrimental patient side-effects and second, there are almost no examples of single agent therapeutics that lead to cures. One strategy to decrease both the effective dose of individual drugs and the potential for therapeutic resistance is to combine drugs that regulate independent pathways that converge on cell death. BCL2-like family members are key proteins that regulate apoptosis. We conducted a screen to identify drugs that could be combined with an inhibitor of anti-apoptotic BCL2-like proteins, ABT-263, to kill human leukemia cells lines. We found that the combination of D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) hydrochloride, an inhibitor of glucosylceramide synthase, potently synergized with ABT-263 in the killing of multiple human leukemia cell lines. Treatment of cells with PDMP and ABT-263 led to dramatic elevation of two pro-apoptotic sphingolipids, namely ceramide and sphingosine. Furthermore, treatment of cells with the sphingosine kinase inhibitor, SKi-II, also dramatically synergized with ABT-263 to kill leukemia cells and similarly increased ceramides and sphingosine. Data suggest that synergism with ABT-263 requires accumulation of ceramides and sphingosine, as AMP-deoxynojirimycin, (an inhibitor of the glycosphingolipid pathway) did not elevate ceramides or sphingosine and importantly did not sensitize cells to ABT-263 treatment. Taken together, our data suggest that combining inhibitors of anti-apoptotic BCL2-like proteins with drugs that alter the balance of bioactive sphingolipids will be a powerful combination for the treatment of human cancers.
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86
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Abstract
The sphingolipid, ceramide, forms channels in the mitochondrial outer membrane and in lipid membranes composed of only phospholipid/cholesterol, using lipids typically found in the natural membrane. These channels are large, allowing proteins to cross membranes. Experimental results are consistent with ceramide forming barrel-stave channels that are rigid and highly organized. Bcl-2 family proteins control these channels in a manner expected from their physiological function: anti-apoptotic proteins destabilize the channels whereas pro-apoptotic proteins act synergistically with ceramide to increase membrane permeability. The use of ceramide analogs has allowed one to gain insight into the features of the molecule that are most important for channel formation. These analogs have also been useful in identifying the sites of interaction between ceramide and both Bax and Bcl-xL. The pores formed in phospholipid membranes by ceramide were visualized by electron microscopy. The most common pore size was 10 nm in diameter, consistent with results obtained from electrophysiological recordings. All indications point to a role for ceramide channels in the release of proteins from mitochondria, a key decision-making step in the apoptotic process.
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Affiliation(s)
- Marco Colombini
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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87
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Abstract
There is growing evidence that cell membranes can contain domains with different lipid and protein compositions and with different physical properties. Furthermore, it is increasingly appreciated that sphingolipids play a crucial role in the formation and properties of ordered lipid domains (rafts) in cell membranes. This review describes recent advances in our understanding of ordered membrane domains in both cells and model membranes. In addition, how the structure of sphingolipids influences their ability to participate in the formation of ordered domains, as well as how sphingolipid structure alters ordered domain properties, is described. The diversity of sphingolipid structure is likely to play an important role in modulating the biologically relevant properties of "rafts" in cell membranes.
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88
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Nunn A, Guy G, Bell JD. Endocannabinoids in neuroendopsychology: multiphasic control of mitochondrial function. Philos Trans R Soc Lond B Biol Sci 2012; 367:3342-52. [PMID: 23108551 PMCID: PMC3481535 DOI: 10.1098/rstb.2011.0393] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The endocannabinoid system (ECS) is a construct based on the discovery of receptors that are modulated by the plant compound tetrahydrocannabinol and the subsequent identification of a family of nascent ligands, the 'endocannabinoids'. The function of the ECS is thus defined by modulation of these receptors-in particular, by two of the best-described ligands (2-arachidonyl glycerol and anandamide), and by their metabolic pathways. Endocannabinoids are released by cell stress, and promote both cell survival and death according to concentration. The ECS appears to shift the immune system towards a type 2 response, while maintaining a positive energy balance and reducing anxiety. It may therefore be important in resolution of injury and inflammation. Data suggest that the ECS could potentially modulate mitochondrial function by several different pathways; this may help explain its actions in the central nervous system. Dose-related control of mitochondrial function could therefore provide an insight into its role in health and disease, and why it might have its own pathology, and possibly, new therapeutic directions.
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Affiliation(s)
- Alistair Nunn
- Metabolic and Molecular Imaging Group, MRC Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, London W12 0NN, UK.
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89
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Kajiwara K, Muneoka T, Watanabe Y, Karashima T, Kitagaki H, Funato K. Perturbation of sphingolipid metabolism induces endoplasmic reticulum stress-mediated mitochondrial apoptosis in budding yeast. Mol Microbiol 2012; 86:1246-61. [PMID: 23062268 DOI: 10.1111/mmi.12056] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/25/2012] [Indexed: 12/26/2022]
Abstract
Sphingolipids are a class of membrane lipids conserved from yeast to mammals which determine whether a cell dies or survives. Perturbations in sphingolipid metabolism cause apoptotic cell death. Recent studies indicate that reduced sphingolipid levels trigger the cell death, but little is known about the mechanisms. In the budding yeast Saccharomyces cerevisiae, we show that reduction in complex sphingolipid levels causes loss of viability, most likely due to the induction of mitochondria-dependent apoptotic cell death pathway, accompanied by changes in mitochondrial and endoplasmic reticulum morphology and endoplasmic reticulum stress. Elevated cytosolic free calcium is required for the loss of viability. These results indicate that complex sphingolipids are essential for maintaining endoplasmic reticulum homeostasis and suggest that perturbation in complex sphingolipid levels activates an endoplasmic reticulum stress-mediated and calcium-dependent pathway to propagate apoptotic signals to the mitochondria.
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Affiliation(s)
- Kentaro Kajiwara
- Department of Bioresource Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8528, Japan
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90
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Gopalan A, Yu W, Jiang Q, Jang Y, Sanders BG, Kline K. Involvement of de novo ceramide synthesis in gamma-tocopherol and gamma-tocotrienol-induced apoptosis in human breast cancer cells. Mol Nutr Food Res 2012; 56:1803-11. [PMID: 23065795 DOI: 10.1002/mnfr.201200350] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 08/11/2012] [Accepted: 08/24/2012] [Indexed: 11/11/2022]
Abstract
SCOPE This study further examines mechanisms involved in the pro-apoptotic action of gamma-tocopherol (γT) and gamma-tocotrienol (γT3) in human breast cancer cell lines. METHODS AND RESULTS γT upregulates phospho-JNK (pJNK), CCAAT/enhancer-binding protein homologous protein (CHOP), and death receptor-5 (DR5) protein expression as detected by Western blot assays. siRNA knockdown of JNK, CHOP, or DR5 shows that γT-induced apoptosis is JNK/CHOP/DR5 signaling dependent, which is similar to γT3-mediated apoptotic signaling. Furthermore, both γT and γT3 induce increased levels of cellular ceramides and dihydroceramides as determined by LC-MS/MS analyses. Inhibition of de novo ceramide synthesis using chemical inhibitors blocked the ability of γT and γT3 to induce apoptosis as detected by Annexin V-FITC/PI assay and to activate JNK/CHOP/DR5 pro-apoptotic signaling thereby demonstrating the involvement of de novo ceramide synthesis in γT- and γT3-induced apoptosis. CONCLUSION Taken together, data show that both γT and γT3 induce apoptosis via de novo ceramide synthesis dependent activation of JNK/CHOP/DR5 pro-apoptotic signaling.
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Affiliation(s)
- Archana Gopalan
- Department of Nutritional Sciences, University of Texas at Austin, Austin, TX 78712, USA
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91
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Shao C, Sun B, DeVoe DL, Colombini M. Dynamics of ceramide channels detected using a microfluidic system. PLoS One 2012; 7:e43513. [PMID: 22984432 PMCID: PMC3440423 DOI: 10.1371/journal.pone.0043513] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 07/25/2012] [Indexed: 01/15/2023] Open
Abstract
Ceramide, a proapoptotic sphingolipid, has been shown to form channels, in mitochondrial outer membranes, large enough to translocate proteins. In phospholipid membranes, electrophysiological studies and electron microscopic visualization both report that these channels form in a range of sizes with a modal value of 10 nm in diameter. A hydrogen bonded barrel-like structure consisting of hundreds of ceramide molecules has been proposed for the structure of the channel and this is supported by electrophysiological studies and molecular dynamic simulations. To our knowledge, the mechanical strength and deformability of such a large diameter but extremely thin cylindrical structure has never been reported. Here we present evidence for a reversible mechanical distortion of the cylinder following the addition of La3+. A microfluidic system was used to repeatedly lower and then restore the conductance by alternatively perfusing La3+ and EDTA. Although aspects of the kinetics of conductance drop and recovery are consistent with a disassembly/diffusion/reassembly model, others are inconsistent with the expected time scale of lateral diffusion of disassembled channel fragments in the membrane. The presence of a residual conductance following La3+ treatment and the relationship between the residual conductance and the initial conductance were both indicative of a distortion/recovery process in analogy with a pressure-induced distortion of a flexible cylinder.
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Affiliation(s)
- Chenren Shao
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland, United States of America
| | - Bing Sun
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Don L. DeVoe
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland, United States of America
| | - Marco Colombini
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
- * E-mail:
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92
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Morad SAF, Levin JC, Shanmugavelandy SS, Kester M, Fabrias G, Bedia C, Cabot MC. Ceramide--antiestrogen nanoliposomal combinations--novel impact of hormonal therapy in hormone-insensitive breast cancer. Mol Cancer Ther 2012; 11:2352-61. [PMID: 22962326 DOI: 10.1158/1535-7163.mct-12-0594] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Although the sphingolipid ceramide exhibits potent tumor suppressor effects, efforts to harness this have been hampered by poor solubility, uptake, bioavailability, and metabolic conversion. Therefore, identification of avenues to improve efficacy is necessary for development of ceramide-based therapies. In this study, we used mutant p53, triple-negative breast cancer (TNBC) cells, a type of breast cancer highly refractory to treatment, and cell-permeable nanoliposomal C6-ceramide in conjunction with the antiestrogen tamoxifen, which has been shown to be an effective modulator of ceramide metabolism. We show for the first time that nanoliposomal tamoxifen enhances nanoliposomal C6-ceramide cytotoxicity in cultured TNBC cells, a response that was accompanied by induction of cell-cycle arrest at G(1) and G(2), caspase-dependent induction of DNA fragmentation, and enhanced mitochondrial and lysosomal membrane permeability at 18 and 2 hours, respectively. Tamoxifen metabolites were also effective. Only tamoxifen promoted lysosomal membrane permeability. In addition, we show for the first time that tamoxifen inhibits acid ceramidase, as measured in intact cell assays; this effect was irreversible. Together, our findings show that tamoxifen magnifies the antiproliferative effects of C6-ceramide via combined targeting of cell-cycle traverse and lysosomal and mitochondrial integrity. We adduce that C6-ceramide-induced apoptosis is amplified by tamoxifen's impact on lysosomes and perhaps accompanying inhibition of acid ceramidase, which could result in decreased levels of sphingosine 1-phosphate. This drug regimen could serve as a promising therapy for chemoresistant and triple-negative types of breast cancer, and thus represents an indication for tamoxifen, irrespective of estrogen receptor status.
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Affiliation(s)
- Samy A F Morad
- Department of Experimental Therapeutics, John Wayne Cancer Institute, 2200 Santa Monica Blvd, Santa Monica, CA 90404, USA
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93
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Pagadala M, Kasumov T, McCullough AJ, Zein NN, Kirwan JP. Role of ceramides in nonalcoholic fatty liver disease. Trends Endocrinol Metab 2012; 23:365-71. [PMID: 22609053 PMCID: PMC3408814 DOI: 10.1016/j.tem.2012.04.005] [Citation(s) in RCA: 236] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 04/11/2012] [Accepted: 04/13/2012] [Indexed: 12/17/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is a chronic disease with a histological spectrum ranging from steatosis alone, to nonalcoholic steatohepatitis (NASH). The latter is associated with an increased risk for progression to cirrhosis. Ceramides are a lipid species that exert biological effects through cellular proliferation, differentiation, and cell death, and interact with several pathways involved in insulin resistance, oxidative stress, inflammation, and apoptosis, all of which are linked to NAFLD. We propose a mechanism through which ceramides contribute to the development of NAFLD and progression to NASH, due in part to second messenger effects via tumor necrosis factor (TNF)-α. A better understanding of the role of ceramides in steatohepatitis has both diagnostic and therapeutic implications for the treatment of fatty liver disease.
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Affiliation(s)
- Mangesh Pagadala
- Department of Gastroenterology/Hepatology, Cleveland Clinic, Cleveland, OH, 44195
| | - Takhar Kasumov
- Department of Gastroenterology/Hepatology, Cleveland Clinic, Cleveland, OH, 44195
| | - Arthur J. McCullough
- Department of Gastroenterology/Hepatology, Cleveland Clinic, Cleveland, OH, 44195
| | - Nizar N. Zein
- Department of Gastroenterology/Hepatology, Cleveland Clinic, Cleveland, OH, 44195
| | - John P. Kirwan
- Department of Gastroenterology/Hepatology, Cleveland Clinic, Cleveland, OH, 44195
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195
- Department of Nutrition, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106
- Metabolic Translational Research Center, Endocrinology and Metabolism Institute, Cleveland Clinic, OH, 44195
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94
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Lee YJ, Huang X, Kropat J, Henras A, Merchant SS, Dickson RC, Chanfreau GF. Sphingolipid signaling mediates iron toxicity. Cell Metab 2012; 16:90-6. [PMID: 22768841 PMCID: PMC3653578 DOI: 10.1016/j.cmet.2012.06.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 03/04/2012] [Accepted: 06/14/2012] [Indexed: 01/24/2023]
Abstract
Iron constitutes a major source of toxicity due to its ability to generate reactive oxygen species that can damage cellular macromolecules. However, the precise mechanism by which exposure to high iron concentrations results in cellular toxicity remains unknown. Here we identify sphingolipid synthesis and signaling as a major mediator of iron toxicity in S. cerevisiae. Inhibition of sphingolipid synthesis by myriocin treatment or after overexpression of the negative regulator Orm2p confers resistance to high iron. High iron conditions upregulate sphingolipid synthesis, and increasing sphingolipid levels by inactivating Orm2p exacerbates sensitivity to iron. Toxicity is mediated by sphingolipid signaling, as inactivation of the sphingolipid-activated protein kinases Pkh1p and Ypk1p and of the transcription factor Smp1p also enhances resistance to high iron conditions. These results demonstrate an unexpected connection between sphingolipid flux and iron toxicity and show that activation of a signal transduction cascade contributes to iron-mediated cellular toxicity.
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Affiliation(s)
- Yueh-Jung Lee
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA
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95
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George KS, Wu S. Lipid raft: A floating island of death or survival. Toxicol Appl Pharmacol 2012; 259:311-9. [PMID: 22289360 PMCID: PMC3299927 DOI: 10.1016/j.taap.2012.01.007] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 01/07/2012] [Accepted: 01/09/2012] [Indexed: 12/31/2022]
Abstract
Lipid rafts are microdomains of the plasma membrane enriched in cholesterol and sphingolipids, and play an important role in the initiation of many pharmacological agent-induced signaling pathways and toxicological effects. The structure of lipid rafts is dynamic, resulting in an ever-changing content of both lipids and proteins. Cholesterol, as a major component of lipid rafts, is critical for the formation and configuration of lipid raft microdomains, which provide signaling platforms capable of activating both pro-apoptotic and anti-apoptotic signaling pathways. A change of cholesterol level can result in lipid raft disruption and activate or deactivate raft-associated proteins, such as death receptor proteins, protein kinases, and calcium channels. Several anti-cancer drugs are able to suppress growth and induce apoptosis of tumor cells through alteration of lipid raft contents via disrupting lipid raft integrity.
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Affiliation(s)
- Kimberly S. George
- Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, USA
- Department of Chemistry, Marietta College, Marietta, OH 45750, USA
| | - Shiyong Wu
- Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, USA
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96
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Abstract
Sphingolipid metabolism in metazoan cells consists of a complex interconnected web of numerous enzymes, metabolites and modes of regulation. At the centre of sphingolipid metabolism reside CerSs (ceramide synthases), a group of enzymes that catalyse the formation of ceramides from sphingoid base and acyl-CoA substrates. From a metabolic perspective, these enzymes occupy a unique niche in that they simultaneously regulate de novo sphingolipid synthesis and the recycling of free sphingosine produced from the degradation of pre-formed sphingolipids (salvage pathway). Six mammalian CerSs (CerS1-CerS6) have been identified. Unique characteristics have been described for each of these enzymes, but perhaps the most notable is the ability of individual CerS isoforms to produce ceramides with characteristic acyl-chain distributions. Through this control of acyl-chain length and perhaps in a compartment-specific manner, CerSs appear to regulate multiple aspects of sphingolipid-mediated cell and organismal biology. In the present review, we discuss the function of CerSs as critical regulators of sphingolipid metabolism, highlight their unique characteristics and explore the emerging roles of CerSs in regulating programmed cell death, cancer and many other aspects of biology.
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97
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Shupik MA, Vanin AF, Alessenko AV. Interaction of the nitric oxide signaling system with the sphingomyelin cycle and peroxidation on transmission of toxic signal of tumor necrosis factor-α in ischemia-reperfusion. BIOCHEMISTRY (MOSCOW) 2012; 76:1197-209. [PMID: 22117546 DOI: 10.1134/s0006297911110010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
This review discusses the functional role of nitric oxide in ischemia-reperfusion injury and mechanisms of signal transduction of apoptosis, which accompanies ischemic damage to organs and tissues. On induction of apoptosis an interaction is observed of the nitric oxide signaling system with the sphingomyelin cycle, which is a source of a proapoptotic agent ceramide. Evidence is presented of an interaction of the sphingomyelin cycle enzymes and ceramide with nitric oxide and enzymes synthesizing nitric oxide. The role of a proinflammatory cytokine TNF-α in apoptosis and ischemia-reperfusion and mechanisms of its cytotoxic action, which involve nitric oxide, the sphingomyelin cycle, and lipid peroxidation are discussed. A comprehensive study of these signaling systems provides insight into the molecular mechanism of apoptosis during ischemia and allows us to consider new approaches for treatment of diseases associated with the activation of apoptosis.
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Affiliation(s)
- M A Shupik
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
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98
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Laub KR, Witschas K, Blicher A, Madsen SB, Lückhoff A, Heimburg T. Comparing ion conductance recordings of synthetic lipid bilayers with cell membranes containing TRP channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1123-34. [PMID: 22305677 DOI: 10.1016/j.bbamem.2012.01.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 12/23/2011] [Accepted: 01/17/2012] [Indexed: 10/14/2022]
Abstract
In this article we compare electrical conductance events from single channel recordings of three TRP channel proteins (TRPA1, TRPM2 and TRPM8) expressed in human embryonic kidney cells with channel events recorded on synthetic lipid membranes close to melting transitions. Ion channels from the TRP family are involved in a variety of sensory processes including thermo- and mechano-reception. Synthetic lipid membranes close to phase transitions display channel-like events that respond to stimuli related to changes in intensive thermodynamic variables such as pressure and temperature. TRP channel activity is characterized by typical patterns of current events dependent on the type of protein expressed. Synthetic lipid bilayers show a wide spectrum of electrical phenomena that are considered typical for the activity of protein ion channels. We find unitary currents, burst behavior, flickering, multistep-conductances, and spikes behavior in both preparations. Moreover, we report conductances and lifetimes for lipid channels as described for protein channels. Non-linear and asymmetric current-voltage relationships are seen in both systems. Without further knowledge of the recording conditions, no easy decision can be made whether short current traces originate from a channel protein or from a pure lipid membrane.
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Affiliation(s)
- Katrine R Laub
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Denmark
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99
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Grimm S. The ER-mitochondria interface: the social network of cell death. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:327-34. [PMID: 22182703 DOI: 10.1016/j.bbamcr.2011.11.018] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/20/2011] [Accepted: 11/21/2011] [Indexed: 12/23/2022]
Abstract
When cellular organelles communicate bad things can happen. Recent findings uncovered that the junction between the endoplasmic reticulum (ER) and the mitochondria holds a crucial role for cell death regulation. Not only does this locale connect the two best-known organelles in apoptosis, numerous regulators of cell death are concentrated at this spot, providing a terrain for intense signal transfers. Ca2+ is the most prominent signalling factor that is released from the ER and, at high concentration, mediates the transfer of an apoptosis signal to mitochondria as the executioner organelle for cell death. An elaborate array of checks and balances is fine-tuning this process including Bcl-2 family members. Moreover, MAMs, "mitochondria-associated membranes", are distinct membrane sections at the ER that are in close contact with mitochondria and have been found to exchange lipids and lipid-derived molecules such as ceramide for apoptosis induction. Recent work has also described a reverse transfer of apoptosis signals, from mitochondria to the ER, via cytochrome c release and prolonged IP3R opening or through the mitochondrial fission factor Fis1 and Bap31 at the ER, which form the ARCosome, a novel caspase-activation complex.
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100
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Lipina C, Hundal HS. Sphingolipids: agents provocateurs in the pathogenesis of insulin resistance. Diabetologia 2011; 54:1596-607. [PMID: 21468641 DOI: 10.1007/s00125-011-2127-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 02/18/2011] [Indexed: 12/16/2022]
Abstract
Obesity is a major risk factor for a variety of chronic diseases, including diabetes mellitus, and comorbidities such as cardiovascular disorders. Despite recommended alterations in lifestyle, including physical activity and energy restriction, being the foundation of any anti-obesity therapy, this approach has so far proved to be of little success in tackling this major public health concern. Because of this, alternative means of tackling this problem are currently being investigated, including pharmacotherapeutic intervention. Consequently, much attention has been directed towards elucidating the molecular mechanisms underlying the development of insulin resistance. This review discusses some of these potential mechanisms, with particular focus on the involvement of the sphingolipid ceramide. Various factors associated with obesity, such as saturated fatty acids and inflammatory cytokines, promote the synthesis of ceramide and other intermediates. Furthermore, studies performed in cultured cells and in vivo associate these sphingolipids with impaired insulin action. In light of this, we provide an account of the research investigating how pharmacological inhibition or genetic manipulation of enzymes involved in regulating sphingolipid synthesis can attenuate the insulin-desensitising effects of these obesity-related factors. By doing so, we outline potential therapeutic targets that may prove useful in the treatment of metabolic disorders.
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Affiliation(s)
- C Lipina
- Division of Cell Signalling and Immunology, Sir James Black Centre, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, UK
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