1
|
Drug instrumentalization. Behav Brain Res 2020; 390:112672. [PMID: 32442549 DOI: 10.1016/j.bbr.2020.112672] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/20/2020] [Accepted: 04/21/2020] [Indexed: 12/19/2022]
Abstract
Psychoactive drugs with addiction potential are widely used by people of virtually all cultures in a non-addictive way. In order to understand this behaviour, its population penetrance, and its persistence, drug instrumentalization was suggested as a driving force for this consumption. Drug instrumentalization theory holds that psychoactive drugs are consumed in a very systematic way in order to make other, non-drug-related behaviours more efficient. Here, we review the evolutionary origin of this behaviour and its psychological mechanisms and explore the neurobiological and neuropharmacological mechanisms underlying them. Instrumentalization goals are discussed, for which an environmentally selective and mental state-dependent consumption of psychoactive drugs can be learned and maintained in a non-addictive way. A small percentage of people who regularly instrumentalize psychoactive drugs make a transition to addiction, which often starts with qualitative and quantitative changes in the instrumentalization goals. As such, addiction is proposed to develop from previously established long-term drug instrumentalization. Thus, preventing and treating drug addiction in an individualized medicine approach may essentially require understanding and supporting personal instrumentalization goals.
Collapse
Affiliation(s)
- Christian P Müller
- Department of Psychiatry and Psychotherapy, University Hospital, Friedrich-Alexander-University Erlangen-Nürnberg, Schwabachanlage 6, 91054 Erlangen, Germany.
| |
Collapse
|
2
|
Non-pharmacological factors that determine drug use and addiction. Neurosci Biobehav Rev 2020; 110:3-27. [PMID: 30179633 PMCID: PMC6395570 DOI: 10.1016/j.neubiorev.2018.08.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/26/2018] [Accepted: 08/28/2018] [Indexed: 12/26/2022]
Abstract
Based on their pharmacological properties, psychoactive drugs are supposed to take control of the natural reward system to finally drive compulsory drug seeking and consumption. However, psychoactive drugs are not used in an arbitrary way as pure pharmacological reinforcement would suggest, but rather in a highly specific manner depending on non-pharmacological factors. While pharmacological effects of psychoactive drugs are well studied, neurobiological mechanisms of non-pharmacological factors are less well understood. Here we review the emerging neurobiological mechanisms beyond pharmacological reinforcement which determine drug effects and use frequency. Important progress was made on the understanding of how the character of an environment and social stress determine drug self-administration. This is expanded by new evidence on how behavioral alternatives and opportunities for drug instrumentalization generate different patterns of drug choice. Emerging evidence suggests that the neurobiology of non-pharmacological factors strongly determines pharmacological and behavioral drug action and may, thus, give rise for an expanded system's approach of psychoactive drug use and addiction.
Collapse
Affiliation(s)
- Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - Aldo Badiani
- Department of Physiology and Pharmacology, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; Sussex Addiction Research and Intervention Centre (SARIC), School of Psychology, University of Sussex, BN1 9RH Brighton, UK
| | - Klaus A Miczek
- Psychology Department, Tufts University, Bacon Hall, 530 Boston Avenue, Medford, MA 02155, USA; Department of Neuroscience, Sackler School of Graduate Biomedical Sciences, Boston, MA 02111, USA
| | - Christian P Müller
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany.
| |
Collapse
|
3
|
Molecular Targets of Epigallocatechin-Gallate (EGCG): A Special Focus on Signal Transduction and Cancer. Nutrients 2018; 10:nu10121936. [PMID: 30563268 PMCID: PMC6315581 DOI: 10.3390/nu10121936] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 11/30/2018] [Accepted: 12/04/2018] [Indexed: 12/15/2022] Open
Abstract
Green tea is a beverage that is widely consumed worldwide and is believed to exert effects on different diseases, including cancer. The major components of green tea are catechins, a family of polyphenols. Among them, epigallocatechin-gallate (EGCG) is the most abundant and biologically active. EGCG is widely studied for its anti-cancer properties. However, the cellular and molecular mechanisms explaining its action have not been completely understood, yet. EGCG is effective in vivo at micromolar concentrations, suggesting that its action is mediated by interaction with specific targets that are involved in the regulation of crucial steps of cell proliferation, survival, and metastatic spread. Recently, several proteins have been identified as EGCG direct interactors. Among them, the trans-membrane receptor 67LR has been identified as a high affinity EGCG receptor. 67LR is a master regulator of many pathways affecting cell proliferation or apoptosis, also regulating cancer stem cells (CSCs) activity. EGCG was also found to be interacting directly with Pin1, TGFR-II, and metalloproteinases (MMPs) (mainly MMP2 and MMP9), which respectively regulate EGCG-dependent inhibition of NF-kB, epithelial-mesenchimal transaction (EMT) and cellular invasion. EGCG interacts with DNA methyltransferases (DNMTs) and histone deacetylases (HDACs), which modulates epigenetic changes. The bulk of this novel knowledge provides information about the mechanisms of action of EGCG and may explain its onco-suppressive function. The identification of crucial signalling pathways that are related to cancer onset and progression whose master regulators interacts with EGCG may disclose intriguing pharmacological targets, and eventually lead to novel combined treatments in which EGCG acts synergistically with known drugs.
Collapse
|
4
|
Sphingolipids and lipid rafts: Novel concepts and methods of analysis. Chem Phys Lipids 2018; 216:114-131. [PMID: 30194926 PMCID: PMC6196108 DOI: 10.1016/j.chemphyslip.2018.08.003] [Citation(s) in RCA: 130] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/20/2018] [Accepted: 08/25/2018] [Indexed: 12/12/2022]
Abstract
About twenty years ago, the functional lipid raft model of the plasma membrane was published. It took into account decades of research showing that cellular membranes are not just homogenous mixtures of lipids and proteins. Lateral anisotropy leads to assembly of membrane domains with specific lipid and protein composition regulating vesicular traffic, cell polarity, and cell signaling pathways in a plethora of biological processes. However, what appeared to be a clearly defined entity of clustered raft lipids and proteins became increasingly fluid over the years, and many of the fundamental questions about biogenesis and structure of lipid rafts remained unanswered. Experimental obstacles in visualizing lipids and their interactions hampered progress in understanding just how big rafts are, where and when they are formed, and with which proteins raft lipids interact. In recent years, we have begun to answer some of these questions and sphingolipids may take center stage in re-defining the meaning and functional significance of lipid rafts. In addition to the archetypical cholesterol-sphingomyelin raft with liquid ordered (Lo) phase and the liquid-disordered (Ld) non-raft regions of cellular membranes, a third type of microdomains termed ceramide-rich platforms (CRPs) with gel-like structure has been identified. CRPs are "ceramide rafts" that may offer some fresh view on the membrane mesostructure and answer several critical questions for our understanding of lipid rafts.
Collapse
Affiliation(s)
- Erhard Bieberich
- Department of Physiology at the University of Kentucky, Lexington, KY, United States.
| |
Collapse
|
5
|
Reactive oxygen species mediates 50-Hz magnetic field-induced EGF receptor clustering via acid sphingomyelinase activation. Int J Radiat Biol 2018; 94:678-684. [PMID: 29659325 DOI: 10.1080/09553002.2018.1466208] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE Exposure to extremely low frequency electromagnetic fields (ELF-EMFs) could elicit biological effects including carcinogenesis. However, the detailed mechanisms by which these ELF-EMFs interact with biological system are currently unclear. Previously, we found that a 50-Hz magnetic field (MF) exposure could induce epidermal growth factor receptor (EGFR) clustering and phosphorylation on cell membranes. In the present experiment, the possible roles of reactive oxygen species (ROS) in MF-induced EGFR clustering were investigated. MATERIALS AND METHODS Human amnion epithelial (FL) cells were exposed to a 50-Hz MF with or without N-acetyl-l-cysteine (NAC) or pyrrolidine dithiocarbamate (PDTC). EGFR clustering on cellular membrane surface was analyzed using confocal microscopy after indirect immunofluorescence staining. The intracellular ROS level and acid sphingomyelinase (ASMase) activity were detected using an ROS assay kit and an Amplex® Red Sphingomyelinase Assay Kit, respectively. RESULTS Results showed that exposure of FL cells to a 50-Hz MF at 0.4 mT for 15 min significantly enhanced the ROS level, induced EGFR clustering and increased ASMase activity. However, pretreatment with NAC or PDTC, the scavenger of ROS, not only counteracted the effects of a 50-Hz MF on ROS level and AMS activity, but also inhibited the EGFR clustering induced by MF exposure. CONCLUSIONS The present and previous data suggest that ROS mediates the MF-induced EGFR clustering via ASMase activation.
Collapse
Affiliation(s)
- Liyuan Sun
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China.,b The Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Liangjing Chen
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China
| | - Lina Bai
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China
| | - Yongpeng Xia
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China
| | - Xiaobo Yang
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China
| | - Wei Jiang
- c Institute of Environmental Medicine, Zhejiang University School of Medicine , Hangzhou , China
| | - Wenjun Sun
- a Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine , Hangzhou , China.,c Institute of Environmental Medicine, Zhejiang University School of Medicine , Hangzhou , China
| |
Collapse
|
6
|
Lipids in psychiatric disorders and preventive medicine. Neurosci Biobehav Rev 2017; 76:336-362. [DOI: 10.1016/j.neubiorev.2016.06.002] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 05/06/2016] [Accepted: 06/06/2016] [Indexed: 01/12/2023]
|
7
|
Role of caspases in CD95-induced biphasic activation of acid sphingomyelinase. Oncotarget 2017; 8:20067-20085. [PMID: 28223543 PMCID: PMC5386744 DOI: 10.18632/oncotarget.15379] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 01/24/2017] [Indexed: 12/04/2022] Open
Abstract
Acid sphingomyelinase (A-SMase) plays an important role in the initiation of CD95 signaling by forming ceramide-enriched membrane domains that enable clustering and activation of the death receptors. In TNF-R1 and TRAIL-R1/R2 signaling, A-SMase also contributes to the lysosomal apoptosis pathway triggered by receptor internalization. Here, we investigated the molecular mechanism of CD95-mediated A-SMase activation, demonstrating that A-SMase is located in internalized CD95-receptosomes and is activated by the CD95/CD95L complex in a biphasic manner.Since several caspases have been described to be involved in the activation of A-SMase, we evaluated expression levels of caspase-8, caspase-7 and caspase-3 in CD95-receptosomes. The occurrence of cleaved caspase-8 correlated with the first peak of A-SMase activity and translocation of the A-SMase to the cell surface which could be blocked by the caspase-8 inhibitor IETD.Inhibition of CD95-internalization selectively reduced the second phase of A-SMase activity, suggesting a fusion between internalized CD95-receptosomes and an intracellular vesicular pool of A-SMase. Further analysis demonstrated that caspase-7 activity correlates with the second phase of the A-SMase activity, whereas active caspase-3 is present at early and late internalization time points. Blocking caspases-7/ -3 by DEVD reduced the second phase of A-SMase activation in CD95-receptosomes suggesting the potential role of caspase-7 or -3 for late A-SMase activation.In summary, we describe a biphasic A-SMase activation in CD95-receptosomes indicating (I.) a caspase-8 dependent translocation of A-SMase to plasma membrane and (II.) a caspase-7 and/or -3 dependent fusion of internalized CD95-receptosomes with intracellular A-SMase-containing vesicles.
Collapse
Affiliation(s)
- Mario Stephan
- Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Bärbel Edelmann
- Department of Hematology and Oncology, University Hospital Magdeburg, Magdeburg, Germany
| | | | - Ottmar Janssen
- Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Uwe Bertsch
- Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Cristiana Perrotta
- Department of Biomedical and Clinical Sciences “Luigi Sacco” (DIBIC), Università degli Studi di Milano, Milano, Italy
| | - Stefan Schütze
- Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Jürgen Fritsch
- Institute of Immunology, Christian-Albrechts-University of Kiel, Kiel, Germany
| |
Collapse
|
8
|
Acid sphingomyelinase deficiency in Western diet-fed mice protects against adipocyte hypertrophy and diet-induced liver steatosis. Mol Metab 2017; 6:416-427. [PMID: 28462076 PMCID: PMC5404101 DOI: 10.1016/j.molmet.2017.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 03/02/2017] [Accepted: 03/07/2017] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE Alterations in sphingolipid and ceramide metabolism have been associated with various diseases, including nonalcoholic fatty liver disease (NAFLD). Acid sphingomyelinase (ASM) converts the membrane lipid sphingomyelin to ceramide, thereby affecting membrane composition and domain formation. We investigated the ways in which the Asm knockout (Smpd1-/-) genotype affects diet-induced NAFLD. METHODS Smpd1-/- mice and wild type controls were fed either a standard or Western diet (WD) for 6 weeks. Liver and adipose tissue morphology and mRNA expression were assessed. Quantitative proteome analysis of liver tissue was performed. Expression of selected genes was quantified in adipose and liver tissue of obese NAFLD patients. RESULTS Although Smpd1-/- mice exhibited basal steatosis with normal chow, no aggravation of NAFLD-type injury was observed with a Western diet. This protective effect was associated with the absence of adipocyte hypertrophy and the increased expression of genes associated with brown adipocyte differentiation. In white adipose tissue from obese patients with NAFLD, no expression of these genes was detectable. To further elucidate which pathways in liver tissue may be affected by Smpd1-/-, we performed an unbiased proteome analysis. Protein expression in WD-fed Smpd1-/- mice indicated a reduction in Rictor (mTORC2) activity; this reduction was confirmed by diminished Akt phosphorylation and altered mRNA expression of Rictor target genes. CONCLUSION These findings indicate that the protective effect of Asm deficiency on diet-induced steatosis is conferred by alterations in adipocyte morphology and lipid metabolism and by reductions in Rictor activation.
Collapse
Affiliation(s)
- Svenja Sydor
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Jan-Peter Sowa
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Dominik A Megger
- Medizinisches Proteom-Center, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany; Institute of Virology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Martin Schlattjan
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Sami Jafoui
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Lena Wingerter
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Alexander Carpinteiro
- Department of Molecular Biology, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Hideo A Baba
- Institute of Pathology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Lars P Bechmann
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Barbara Sitek
- Medizinisches Proteom-Center, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany.
| | - Guido Gerken
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Erich Gulbins
- Department of Molecular Biology, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany.
| | - Ali Canbay
- Department of Gastroenterology and Hepatology, University Hospital, University Duisburg-Essen, Hufelandstr. 55, 45120 Essen, Germany; Department of Gastroenterology, Hepatology and Infectious Diseases, Otto-von-Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany.
| |
Collapse
|
9
|
Acid sphingomyelinase mediates 50-Hz magnetic field-induced EGF receptor clustering on lipid raft. J Recept Signal Transduct Res 2016; 36:593-600. [DOI: 10.3109/10799893.2016.1147583] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Yong Wang
- Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
| | - Xingwen Li
- Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
- Cixi Sanitary Supervision Station, Cixi, People’s Republic of China,
| | - Liyuan Sun
- Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
- The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
| | - Baihuan Feng
- Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
| | - Wenjun Sun
- Bioelectromagnetics Key Laboratory, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China,
- Institute of Environmental Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China
| |
Collapse
|
10
|
Combination therapy with anti-DR5 antibody and tamoxifen for triple negative breast cancer. Cancer Biol Ther 2015; 15:1053-60. [PMID: 25084100 DOI: 10.4161/cbt.29183] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
TRA-8, a monoclonal antibody targeting death receptor, has demonstrated high therapeutic effect for triple negative breast cancer (TNBC) in preclinical models. Tamoxifen, the standard of care for ERα-positive breast cancer, induces apoptosis via ERβ, which commonly presents in TNBC cells. The current study investigates the combination effects of TRA-8 and tamoxifen for TNBC. In vitro assays were implemented with two ERβ-positive TNBC cell lines, SUM159 and 2LMP, and in vivo therapy studies were followed using orthotopic breast tumor mouse models. IC50 of tamoxifen for SUM159 and 2LMP were 29 μM and 38 μM, respectively. Synergy between TRA-8 (0-1000 ng/mL) and tamoxifen (20 μM) was observed for both the cell lines. Tamoxifen (400 mg/kg diet) markedly suppressed the growth of SUM159 tumors for 6 weeks after therapy initiation, but it did not induce antitumor effect for 2LMP tumors. TRA-8 (0.1 mg, weekly, i.p.) successfully arrested the growth of both SUM159 and 2LMP tumors during therapy, but an antagonistic effect was observed when tamoxifen was combined. TRA-8 uptake into tumors was not changed by tamoxifen treatment. Histological analysis confirmed that caspase-3 activation induced by TRA-8 was significantly decreased when tamoxifen was used in combination. In conclusion, our findings suggest that the combined use of TRA-8 and tamoxifen may cause antagonistic effects for TNBC patients.
Collapse
Affiliation(s)
- Hyunki Kim
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA; Department of Biomedical Engineering; University of Alabama at Birmingham; Birmingham, AL USA; Comprehensive Cancer Center; University of Alabama at Birmingham; Birmingham, AL USA
| | - Sharon L Samuel
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Guihua Zhai
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Samir Rana
- Department of Biomedical Sciences; University of Alabama at Birmingham; Birmingham, AL USA
| | - Marie Taylor
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Heidi R Umphrey
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA; Comprehensive Cancer Center; University of Alabama at Birmingham; Birmingham, AL USA
| | - Denise K Oelschlager
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Donald J Buchsbaum
- Comprehensive Cancer Center; University of Alabama at Birmingham; Birmingham, AL USA; Department of Radiation Oncology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Kurt R Zinn
- Department of Radiology; University of Alabama at Birmingham; Birmingham, AL USA; Comprehensive Cancer Center; University of Alabama at Birmingham; Birmingham, AL USA
| |
Collapse
|
11
|
Abstract
![]()
Adaptor
protein Grb2 binds phosphotyrosines in the epidermal growth
factor (EGF) receptor (EGFR) and thereby links receptor activation
to intracellular signaling cascades. Here, we investigated how recruitment
of Grb2 to EGFR is affected by the spatial organization and quaternary
state of activated EGFR. We used the techniques of image correlation
spectroscopy (ICS) and lifetime-detected Förster resonance
energy transfer (also known as FLIM-based FRET or FLIM–FRET)
to measure ligand-induced receptor clustering and Grb2 binding to
activated EGFR in BaF/3 cells. BaF/3 cells were stably transfected
with fluorescently labeled forms of Grb2 (Grb2–mRFP) and EGFR
(EGFR–eGFP). Following stimulation of the cells with EGF, we
detected nanometer-scale association of Grb2–mRFP with EGFR–eGFP
clusters, which contained, on average, 4 ± 1 copies of EGFR–eGFP
per cluster. In contrast, the pool of EGFR–eGFP without Grb2–mRFP
had an average cluster size of 1 ± 0.3 EGFR molecules per punctum.
In the absence of EGF, there was no association between EGFR–eGFP
and Grb2–mRFP. To interpret these data, we extended our recently
developed model for EGFR activation, which considers EGFR oligomerization
up to tetramers, to include recruitment of Grb2 to phosphorylated
EGFR. The extended model, with adjustment of one new parameter (the
ratio of the Grb2 and EGFR copy numbers), is consistent with a cluster
size distribution where 2% of EGFR monomers, 5% of EGFR dimers, <1%
of EGFR trimers, and 94% of EGFR tetramers are associated with Grb2.
Together, our experimental and modeling results further implicate
tetrameric EGFR as the key signaling unit and call into question the
widely held view that dimeric EGFR is the predominant signaling unit.
Collapse
Affiliation(s)
- Noga Kozer
- Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology , Hawthorn, Victoria 3122, Australia
| | | | | | | | | | | | | |
Collapse
|
12
|
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: 260] [Impact Index Per Article: 26.0] [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.
Collapse
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.
| |
Collapse
|
13
|
Tunable nucleation time of functional sphingomyelinase--lipid features studied by membrane array statistic tool. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:13008-17. [PMID: 24059643 DOI: 10.1021/la401826b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Aggregation or assembly of lipids and proteins could significantly change the proteins' function. A peripheral membrane enzyme, sphingomyelinase (SMase), has been reported to be able to assemble to a functional feature with its lipid substrate, sphingomyelin (SM), and its lipid product, ceramide (Cer). SMase seems to processes its substrate more effectively in this feature. Here, we report that the functional feature has a tunable formation time. The peculiar behavior is that the feature formation has a time lag depending on the membrane composition. We hypothesized that the time lag is due to the significant nucleation energy barrier when the feature phase forms in its metastable parent phase in the 2-D lipid membrane. To study the stochastic nucleation of the feature, we built a corralled lipid membrane platform with numerous isolated membrane systems in parallel to capture the nucleation statistics. Using the high-throughput approach and the appropriate experimental design to circumvent the interplay of the complicated phase segregation in membranes induced by SMase, we found that the nucleation rate of the feature can be tuned by the supersaturation of the enzyme, the lipid substrate, and the lipid product, in the fluid phase of the membrane. The correlation between the supersaturation and the nucleation rate can be well described by the classical nucleation theory equation, suggesting that the feature formation follows the nucleation process with a certain component ratio specified in the equation. The certain relative component ratio suggests that the feature may have certain organization instead of being random aggregation. In addition, our finding suggests that nucleation could serve as a time lag control mechanism in this enzymatic system, and ways to reduce nucleation energy barrier could be used to shorten the aggregation time lag and vice versa.
Collapse
Affiliation(s)
- Charng-Yu Lin
- Department of Chemical Engineering, National Taiwan University , Taipei 106, Taiwan
| | | |
Collapse
|
14
|
Cilastatin protects against cisplatin-induced nephrotoxicity without compromising its anticancer efficiency in rats. Kidney Int 2012; 82:652-63. [PMID: 22718191 DOI: 10.1038/ki.2012.199] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cisplatin is an anticancer agent marred by nephrotoxicity; however, limiting this adverse effect may allow the use of higher doses to improve its efficacy. Cilastatin, a small molecule inhibitor of renal dehydropeptidase I, prevents proximal tubular cells from undergoing cisplatin-induced apoptosis in vitro. Here, we explored the in vivo relevance of these findings and the specificity of protection for kidney cells in cisplatin-treated rats. Cisplatin increased serum blood urea nitrogen and creatinine levels, and the fractional excretion of sodium. Cisplatin decreased the glomerular filtration rate, promoted histological renal injury and the expression of many pro-apoptotic proteins in the renal cortex, increased the Bax/Bcl2 ratio, and oxidative stress in kidney tissue and urine. All these features were decreased by cilastatin, which preserved renal function but did not modify the pharmacokinetics of cisplatin area under the curve. The cisplatin-induced death of cervical, colon, breast, and bladder-derived cancer cell lines was not prevented by cilastatin. Thus, cilastatin has the potential to prevent cisplatin nephrotoxicity without compromising its anticancer efficacy.
Collapse
|
15
|
Abstract
The goal of the study was to assess the efficacy of combined extracellular matrix metalloprotease inducer (EMMPRIN)- and death receptor 5 (DR5)-targeted therapy for pancreatic adenocarcinoma in orthotopic mouse models with multimodal imaging. Cytotoxicity of anti-EMMPRIN antibody and anti-DR5 antibody (TRA-8) in MIA PaCa-2 and PANC-1 cell lines was measured by ATPlite assay in vitro. The distributions of Cy5.5-labeled TRA-8 and Cy3-labeled anti-EMMPRIN antibody in the 2 cell lines were analyzed by fluorescence imaging in vitro. Groups 1 to 12 of severe combined immunodeficient mice bearing orthotopic MIA PaCa-2 (groups 1-8) or PANC-1 (groups 9-12) tumors were used for in vivo studies. Dynamic contrast-enhanced-MRI was applied in group 1 (untreated) or group 2 (anti-EMMPRIN antibody). The tumor uptake of Tc-99m-labeled TRA-8 was measured in group 3 (untreated) and group 4 (anti-EMMPRIN antibody). Positron emission tomography/computed tomography imaging with (18)F-FDG was applied in groups 5 to 12. Groups 5 to 8 (or groups 9 to 12) were untreated or treated with anti-EMMPRIN antibody, TRA-8, and combination, respectively. TRA-8 showed high killing efficacy for both MIA PaCa-2 and PANC-1 cells in vitro, but additional anti-EMMPRIN treatment did not improve the cytotoxicity. Cy5.5-TRA-8 formed cellular caps in both the cell lines, whereas the maximum signal intensity was correlated with TRA-8 cytotoxicity. Anti-EMMPRIN therapy significantly enhanced the tumor delivery of the MR contrast agent, but not Tc-99m-TRA-8. Tumor growth was significantly suppressed by the combination therapy, and the additive effect of the combination was shown in both MIA PaCa-2 and PANC-1 tumor models.
Collapse
Affiliation(s)
- Hyunki Kim
- Department of Radiology, University of Alabama at Birmingham, 1670 University Blvd, Birmingham, AL 35294, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Compartmentalization of TNF-receptor 1 signaling: TNF-R1-associated caspase-8 mediates activation of acid sphingomyelinase in late endosomes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 691:605-16. [PMID: 21153367 DOI: 10.1007/978-1-4419-6612-4_64] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
17
|
Abstract
INTRODUCTION The CD95 pathway is a potent inducer of apoptosis in nucleated cells and this death receptor is important for proper blood cell development. Although it is expressed in red blood cells, its functional role in erythrocytes is not well documented. These anucleated cells can undergo cell death via eryptosis, a process showing similarities to apoptosis of nucleated cells. This mode of cell death is mainly triggered by oxidative stress or energy depletion. METHODS CH11 was added to the purified human erythrocytes for induction of phosphatidylserine (PS) exposure. AnnexinV-FITC was used as a probe for PS detection. RESULTS No significantly enhanced PS-positive cell fraction could be observed after erythrocytes were treated with CH11. CONCLUSION Based on some key features for an activated CD95 system, this death receptor has been considered to induce PS exposure. However, we give evidence, that CD95 is not functional in red blood cells and that activation of this death receptor does not lead to the exposure of phosphatidylserine.
Collapse
Affiliation(s)
- D Sagan
- Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, Thailand
| | | | | |
Collapse
|
18
|
Caspase-8 and caspase-7 sequentially mediate proteolytic activation of acid sphingomyelinase in TNF-R1 receptosomes. EMBO J 2010; 30:379-94. [PMID: 21157428 DOI: 10.1038/emboj.2010.326] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 11/16/2010] [Indexed: 01/02/2023] Open
Abstract
We previously demonstrated that tumour necrosis factor (TNF)-induced ceramide production by endosomal acid sphingomyelinase (A-SMase) couples to apoptosis signalling via activation of cathepsin D and cleavage of Bid, resulting in caspase-9 and caspase-3 activation. The mechanism of TNF-mediated A-SMase activation within the endolysosomal compartment is poorly defined. Here, we show that TNF-induced A-SMase activation depends on functional caspase-8 and caspase-7 expression. The active forms of all three enzymes, caspase-8, caspase-7 and A-SMase, but not caspase-3, colocalize in internalized TNF receptosomes. While caspase-8 and caspase-3 are unable to induce activation of purified pro-A-SMase, we found that caspase-7 mediates A-SMase activation by direct interaction resulting in proteolytic cleavage of the 72-kDa pro-A-SMase zymogen at the non-canonical cleavage site after aspartate 253, generating an active 57 kDa A-SMase molecule. Caspase-7 down modulation revealed the functional link between caspase-7 and A-SMase, confirming proteolytic cleavage as one further mode of A-SMase activation. Our data suggest a signalling cascade within TNF receptosomes involving sequential activation of caspase-8 and caspase-7 for induction of A-SMase activation by proteolytic cleavage of pro-A-SMase.
Collapse
|
19
|
Dual function of cysteine rich domain (CRD) 1 of TNF receptor type 1: Conformational stabilization of CRD2 and control of receptor responsiveness. Cell Signal 2010; 22:404-14. [DOI: 10.1016/j.cellsig.2009.10.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 10/21/2009] [Indexed: 11/26/2022]
|
20
|
Ceramide-rich platforms in transmembrane signaling. FEBS Lett 2010; 584:1728-40. [PMID: 20178791 DOI: 10.1016/j.febslet.2010.02.026] [Citation(s) in RCA: 209] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 02/10/2010] [Accepted: 02/10/2010] [Indexed: 01/08/2023]
Abstract
Recent evidence suggests that ceramide regulates stress signaling via reorganization of the plasma membrane. The focus of this review will be to discuss the mechanism by which acid sphingomyelinase (ASMase)-generated ceramide initiates transmembrane signaling in the plasma membrane exoplasmic leaflet. In particular, we review the unique biophysical properties of ceramide that render it proficient in formation of signaling domains termed ceramide-rich platforms (CRPs), and the role of CRPs in the pathophysiology of various diseases. The biomedical significance of CRPs makes these structures an attractive therapeutic target.
Collapse
Affiliation(s)
- Branka Stancevic
- Laboratory of Signal Transduction, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
| | | |
Collapse
|
21
|
Sphingomyelinase-induced phase transformations: causing morphology switches and multiple-time-domain ceramide generation in model raft membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:344-56. [PMID: 19863058 DOI: 10.1021/la902084u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Sphingomyelinase (SMase) has been shown to be involved in a variety of cell regulation processes by reorganizing the cell membrane morphology. Here we report that SMase can induce a reaction-induced and a solvent-mediated phase transformation, causing switches of three stationary membrane morphologies and multiple-time-domain ceramide generation in model raft membranes. The reaction-induced phase transformation, triggered by the addition of SMase, transforms a pre-existing morphology to a long-lasting intermediate morphology with coexisting ceramide-enriched (Cer-enriched) and sphingomyelin-enriched (SM-enriched) domains. Solvent-mediated phase transformation ultimately transforms all of the SM-enriched domains of the intermediate morphology into Cer-enriched domains. Labeled SMase experiments suggest that the intermediate morphology results from physical trapping of SM in the SM-enriched domains, which are found to be relatively inaccessible to SMase. The characterization results from confocal fluorescence imaging show that the trigger of the solvent-mediated phase transformation is the formation of a 3-D feature rich in SMase, sphingomyelin, and ceramide. This 3-D feature is hypothesized as a slowly nucleating SMase-enriched phase, where SMase processes sphingomyelin more efficiently. The disparate time-scales of the formation of these SMase-features and the SM-enriched domains allow for the development of a significant duration of the middle intermediate morphology between the two transformations. The results show that SMase can be actively involved in the lipid membrane phase changes. The multistage morphology evolution is not only due to membrane-compositional changes caused by SMase, but also due to the selective binding of SMase, and the SMase's special phase behavior during the solvent-mediated phase transformation.
Collapse
Affiliation(s)
- Ling Chao
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | | | | | | |
Collapse
|
22
|
Phase behavior of aqueous dispersions of mixtures of N-palmitoyl ceramide and cholesterol: a lipid system with ceramide-cholesterol crystalline lamellar phases. J Phys Chem B 2009; 113:1367-75. [PMID: 19133760 DOI: 10.1021/jp803331k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ceramides are particularly abundant in the stratum corneum lipid matrix, where they determine its unusual mesostructure, are involved in the lateral segregation of lipid domains in biological cell membranes, and are also known to act as signaling agents in cells. The importance attributed to ceramides in several biological processes has heightened in recent years, demanding a better understanding of their interaction with other membrane components, namely, cholesterol. Structural data concerning pure ceramides in water are relatively scarce, and this is even more the case for mixtures of ceramides with other lipids commonly associated with them in biological systems. We have derived the thermotropic binary phase diagram of mixtures of N-palmitoyl- D-erythro-sphingosine, C16:0-ceramide, and cholesterol in excess water, using differential scanning calorimetry and small- and wide-angle X-ray diffraction. These mixtures are self-organized in lamellar mesostructures that, between other particularities, show two ceramide to cholesterol crystalline phases with molar proportions that approach 2:3 and 1:3. The 2:3 phase crystallizes in a tetragonal arrangement with a lamellar repeat distance of 3.50 nm, which indicates an unusual lipid stacking, probably unilamellar. The uncommon mesostructures formed by ceramides with cholesterol should be considered in the rationalization of their singular structural role in biological systems.
Collapse
Affiliation(s)
- Sofia L Souza
- Instituto de Tecnologia Química e Biológica-UNL, Oeiras, Portugal
| | | | | | | | | | | |
Collapse
|
23
|
Exploiting the tumor microenvironment in the development of targeted cancer gene therapy. Cancer Gene Ther 2008; 16:279-90. [PMID: 18818709 DOI: 10.1038/cgt.2008.72] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The future success of cancer gene therapy is critically dependent upon the development of safe, practical and effective targeting strategies. In this study, we describe a novel and broadly applicable targeting approach in which the induction of apoptotic tumor cell death is linked to the differential expression within the tumor microenvironment of elevated levels of the pro-angiogenic cytokine vascular endothelial growth factor (VEGF). As VEGF is generally absent or produced at only low levels in most normal tissues, undesirable toxicity will not result even if the therapeutic gene in question is inadvertently expressed in non-targeted tissue sites. The basic approach makes use of a chimeric cell-surface protein in which the membrane-spanning and cytoplasmic 'death domain' of the pro-apoptotic protein Fas are fused in frame to the extracellular ligand-binding domain of the VEGF receptor Flk-1/KDR/VEGFR2 (Flk-1/Fas). The resultant chimeric Flk-1/Fas receptor was found to be stable and capable of inducing a rapid apoptotic response when expressed in tumor cells that produce endogenous VEGF. Importantly, in the absence of VEGF, transduced tumor cells remain viable although they can be triggered to die by the addition of recombinant VEGF. Given the key role played by VEGF in tumor development and progression, it is proposed that the Flk-1/Fas chimera may have great potential in the context of tumor cell-targeted cancer gene therapy.
Collapse
|
24
|
Ceramide-enriched membrane domains--structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:178-83. [PMID: 18786504 DOI: 10.1016/j.bbamem.2008.07.030] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 07/28/2008] [Accepted: 07/29/2008] [Indexed: 12/28/2022]
Abstract
Membrane lipids seem to be organized and not randomly distributed in the cell membrane. In particular, sphingolipids seem to interact with cholesterol in the outer leaflet of the cell membrane resulting in the formation of distinct membrane domains, i.e. rafts. The generation of ceramide within rafts alters their biophysical properties and results in the formation of large ceramide-enriched membrane platforms. These platforms serve to cluster receptor molecules and to organize intracellular signalling molecules to facilitate signal transduction via a receptor upon stimulation. Thus, ceramide-enriched membrane domains amplify not only receptor-, but also stress-mediated signalling events. Although many receptors cluster, the molecular mechanisms mediating this important and general event in signal transduction need to be identified.
Collapse
Affiliation(s)
- Yang Zhang
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
| | | | | | | |
Collapse
|
25
|
Ceramide-induced cell death in malignant cells. Cancer Lett 2008; 264:1-10. [DOI: 10.1016/j.canlet.2008.02.020] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 01/28/2008] [Accepted: 02/03/2008] [Indexed: 01/18/2023]
|
26
|
Acid sphingomyelinase involvement in tumor necrosis factor alpha-regulated vascular and steroid disruption during luteolysis in vivo. Proc Natl Acad Sci U S A 2008; 105:7670-5. [PMID: 18505843 DOI: 10.1073/pnas.0712260105] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
TNF is well known for its role in inflammation, including direct effects on the vasculature. TNF also is implicated in the regulation of reproduction by its actions to affect ovarian steroidogenic cells and to induce apoptosis of corpus luteum (CL)-derived endothelial cells in vitro. We hypothesized that the disruption of TNF signaling would postpone the regression of the highly vascularized CL in vivo, and this effect could be replicated in mutant mouse models lacking TNF receptor (TNFRI(-/-)) and/or a critical enzyme of TNF signaling, acid sphingomyelinase (ASMase(-/-)). In the current study, the treatment of pseudopregnant mice with the luteolytic mediator prostaglandin F2-alpha (PGF) significantly increased TNF in the ovaries when compared with saline-treated controls. Treatment with PGF also reduced serum progesterone (P4) concentrations and caused involution of the CL. However, pretreatment of pseudopregnant mice with Etanercept (ETA), a TNF-neutralizing antibody, inhibited the PGF-induced decrease in P4 and delayed luteal regression. A similar outcome was evident in pseudopregnant TNFRI(-/-) animals. Treatment of luteal microvascular endothelial cells (MVECs) with TNF provoked a significant increase in ASMase activity when compared with the corresponding controls. Furthermore, TNF-induced MVEC death was inhibited in the ASMase(-/-) mice. The ASMase(-/-) mice displayed no obvious evidence of luteal regression 24 h after treatment with PGF and were resistant to the PGF-induced decrease in P4. Together these data provide evidence that TNF plays an active role in luteolysis. Further studies are required to determine the deleterious effects of anti-inflammatory agents on basic ovarian processes.
Collapse
|
27
|
Role of ceramide in membrane protein organization investigated by combined AFM and FCS. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1356-64. [PMID: 18346453 DOI: 10.1016/j.bbamem.2008.02.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 01/29/2008] [Accepted: 02/13/2008] [Indexed: 12/31/2022]
Abstract
Ceramide-induced alterations in the lateral organization of membrane proteins can be involved in several biological contexts, ranging from apoptosis to viral infections. In order to investigate such alterations in a simple model, we used a combined approach of atomic force microscopy, scanning fluorescence correlation spectroscopy and confocal fluorescence imaging to study the partitioning of different membrane components in sphingomyelin/dioleoyl-phosphatidylcholine/cholesterol/ceramide supported bilayers. Such model membranes exhibit coexistence of liquid-disordered, liquid-ordered (raft-like) and ceramide-rich lipid phases. Our results show that components with poor affinity toward the liquid-ordered phase, such as several fluorescent lipid analogues or the synaptic protein Synaptobrevin 2, are excluded from ceramide-rich domains. Conversely, we show for the first time that the raft-associated protein placental alkaline phosphatase (GPI-PLAP) and the ganglioside GM1 are enriched in such domains, while exhibiting a strong decrease in lateral diffusion. Analogue modulation of the local concentration and dynamics of membrane proteins/receptors by ceramide can be of crucial importance for the biological functions of cell membranes.
Collapse
|
28
|
High-resolution single-photon emission computed tomography and X-ray computed tomography imaging of Tc-99m-labeled anti-DR5 antibody in breast tumor xenografts. Mol Cancer Ther 2007; 6:866-75. [PMID: 17363481 DOI: 10.1158/1535-7163.mct-06-0230] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A murine, apoptosis-inducing monoclonal antibody (mTRA-8) targeting human DR5 was radiolabeled with Tc-99m. The binding affinity (K(d)) and the number of DR5 receptors were measured in MD MBA-231-derived 2LMP cell lines that were "sensitive" or "resistant" to mTRA-8 killing. Single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) evaluated the Tc-99m-mTRA-8 retention and distribution within xenograft tumors; biodistribution analyses confirmed the levels. Scatchard assays showed specific and high binding affinity of Tc-99m-mTRA-8 to DR5; the killing efficacy of mTRA-8 was unchanged by Tc-99m labeling. There was no significant difference between sensitive and resistant 2LMP cells for K(d) values (1.5 +/- 0.3 nmol/L = acid labile), or DR5 receptors (mean/cell = 11,000). SPECT/CT imaging analyses at 6 h after injection of Tc-99m-mTRA-8 revealed the second 1.5 mm shell from the surface of the mammary fat pad tumors (n = 5; 5,627 mm(3)) retained 12.7 +/- 1.4%ID/g, higher than the other shells, with no difference between the sensitive and resistant 2LMP tumors. Binding of Tc-99m-labeled mTRA-8 in tumor was specific; excess unlabeled mTRA-8 blocked Tc-99m-mTRA-8 retention in tumor by 45%. Retention of Tc-99m-labeled isotype antibody in tumor was consistent with the blocking study, and 30% lower. These studies show that SPECT/CT imaging provided detailed distribution information of Tc-99m-labeled mTRA-8 within breast tumor xenografts. Imaging could provide a mechanism to assess DR5 modulation when DR5 therapy is combined with chemotherapy and radiation, and thereby aid in optimizing the dosing schedule.
Collapse
Affiliation(s)
- Hyunki Kim
- Department of Radiology, Comprehensive Cancer Center, University of Alabama at Birmingham, 1808 7th Avenue South, Birmingham, AL 35294-0012, USA
| | | | | | | | | |
Collapse
|
29
|
Abstract
Previous studies indicated that signalling via CD95 and DR5 is greatly enhanced by the formation of ceramide-enriched membrane platforms. Here, we employed this concept to convert doses of subtherapeutic TRAIL that were unable to release ceramide and kill leukemic B-cells or ex vivo T lymphocytes, into a very effective apoptotic stimulus. Ceramide production was induced by application of sub-toxic doses of doxorubicin that resulted in an activation of the acid sphingomyelinase (ASM), release of ceramide and formation of ceramide-enriched membrane platforms. The latter served DR5 to cluster after application of very low doses of TRAIL in combination with doxorubicin. Genetic deficiency of the ASM abrogated doxorubicin-induced ceramide release, as well as clustering of DR5 and apoptosis induced by the combined treatment of doxorubicin and TRAIL. These data show that local release of ceramide potentiates very low, otherwise inactive doses of TRAIL that may represent a novel therapeutic concept to treat tumors.
Collapse
Affiliation(s)
- Claudia Alexandra Dumitru
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | | | | | | | | |
Collapse
|
30
|
Syndecan-2 expression increases serum-withdrawal-induced apoptosis, mediated by re-distribution of Fas into lipid rafts, in stably transfected Swiss 3T3 cells. Apoptosis 2006; 11:2065-75. [PMID: 17041758 DOI: 10.1007/s10495-006-0193-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
To examine the function of syndecan-2, one of the most abundant heparan sulfate proteoglycans in fibroblasts, we obtained stably transfected Swiss 3T3 clones. We examined the effects of stable syndecan-2 overexpression on programmed cell death, finding that syndecan-2 transfected cells were more sensitive to apoptosis induced by serum-withdrawal than control cells. In addition, overexpression of syndecan-2 correlates with increased membrane levels of the Fas/CD95 receptor, suggesting that the increased serum-withdrawal apoptosis observed in Swiss 3T3 cells might be Fas receptor-dependent. Differences in Fas membrane levels between both control and syndecan-2 transfected cells result from a redistribution of the Fas receptor. Our data clearly demonstrate that increased Fas levels are primarily related to lipid rafts and that this increase is a key factor in Fas/CD95-mediated apoptosis. Moreover, disruption of lipid rafts with methyl-beta-cyclodextrin or filipin significantly reduced apoptosis in response to serum withdrawal. The differences in Fas/CD95 membrane distribution could explain why syndecan-2 transfected cells have a higher susceptibility to serum-withdrawal-induced apoptosis.
Collapse
Affiliation(s)
- Joan Villena
- Department of Cellular Biology, Faculty of Biology, University of Barcelona, Diagonal 645, 08028, Barcelona, Spain.
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Membrane rafts in host-pathogen interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:2139-47. [PMID: 17094939 DOI: 10.1016/j.bbamem.2006.07.017] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 06/13/2006] [Accepted: 07/18/2006] [Indexed: 02/09/2023]
Abstract
Central elements in the infection of mammalian cells with viral, bacterial and parasitic pathogens include the adhesion of the pathogen to surface receptors of the cell, recruitment of additional receptor proteins to the infection-site, a re-organization of the membrane and, in particular, the intracellular signalosome. Internalization of the pathogen results in the formation of a phagosome that is supposed to fuse with lysosomes to form phagolysosomes, which serve the degradation of the pathogen, an event actively prevented by some pathogens. In summary, these changes in the infected cell permit pathogens to trigger apoptosis (for instance of macrophages paralysing the initial immune response), to invade the cell and/or to survive in the cell, but they also serve the mammalian cell to defeat the infection, for instance by activation of transcription factors and the release of cytokines. Distinct membrane domains in the plasma membrane and intracellular vesicles that are mainly composed of sphingolipids and cholesterol or enriched with the sphingolipid ceramide, are critically involved in all of these events occurring during the infection. These membrane structures are therefore very attractive targets for novel drugs to interfere with bacterial, viral and parasitic infections.
Collapse
Affiliation(s)
- Joachim Riethmüller
- Children's Hospital, University of Tuebingen, Hoppe-Seyler Str. 1, 72076 Tuebingen, Germany
| | | | | | | |
Collapse
|
32
|
Abstract
Ultraviolet light (UV) induces aggregation of Fas-receptor through a Fas-ligand-independent pathway. However, the mechanism of ultraviolet light-induced Fas-receptor aggregation is not known. In this report, we show that lipid rafts mediate ultraviolet light-induced aggregation of Fas. Our data show that UV induces a redistribution of Fas-receptor in a 25-5% Optiprep continuous gradient. The amount of Fas-receptorS is significantly increased in a gradient fraction that contain lipid rafts and is associated with an increase of FADD and caspase-8. Our data also show that the active dimeric form of caspase-8 (p44/p41) is increased in the lipid raft fraction. In addition, our data show that cholesterol, a major component of lipid rafts, is significantly reduced in only the lipid raft fractions after UV-irradiation. However, ceramide, another major lipid raft component, is increased evenly in all gradient fractions after UV-irradiation. These results suggest that UV alters the composition of major lipid raft components, which leads to the recruitment of Fas-receptor and FADD, with subsequent activation of caspase-8. Based on our results, we propose a novel mechanism by which UV induces apoptosis through a membrane lipid raft-mediated signaling pathway.
Collapse
Affiliation(s)
- Walid Elyassaki
- The Department of Chemistry and Biochemistry and Edison Biotechnology Institute, Ohio University, Athens, USA
| | | |
Collapse
|
33
|
TRAIL activates acid sphingomyelinase via a redox mechanism and releases ceramide to trigger apoptosis. Oncogene 2006; 25:5612-25. [PMID: 16636669 DOI: 10.1038/sj.onc.1209568] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have previously shown that activation of the acid sphingomyelinase (ASM), the release of ceramide and the formation of ceramide-enriched membrane domains are central for the induction of apoptosis by CD95. Here, we demonstrate that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95 activate the ASM via a redox mechanism resulting in release of ceramide and formation of ceramide-enriched membrane platforms. Ceramide-enriched membrane platforms serve to cluster DR5 upon stimulation. Antioxidants prevent TRAIL-mediated stimulation of ASM, the release of ceramide, the formation of ceramide-enriched membrane platforms and the induction of apoptosis by TRAIL. Further, ASM-deficient splenocytes fail to cluster DR5 in ceramide-enriched membrane domains upon TRAIL stimulation and resist TRAIL-induced apoptosis, events that were restored by addition of natural C(16)-ceramide. A dose-response analysis indicates that ceramide-enriched membrane platforms greatly sensitized tumor cells to TRAIL-induced apoptosis. Our data indicate that ceramide-enriched membrane platforms are required for the signaling of TRAIL-DR5 complexes under physiological conditions.
Collapse
Affiliation(s)
- C A Dumitru
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
| | | |
Collapse
|
34
|
Death or survival: Membrane ceramide controls the fate and activation of antigen-specific T-cells depending on signal strength and duration. Cell Signal 2006; 18:294-306. [PMID: 16099142 DOI: 10.1016/j.cellsig.2005.05.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Accepted: 05/04/2005] [Indexed: 01/17/2023]
Abstract
Sphingomyelinase (SMase)-mediated release of ceramide in the plasma membrane of T-lymphocytes induced by different stimuli such as ligation of Fas/CD95, irradiation, stress, inflammation or anticancer drugs primarily involves mitochondrial apoptosis signaling, but under specific conditions non-apoptotic Fas-signaling was also reported. Here we investigated, using a quantitative simulation model with exogenous C2-ceramide (and SMase), the dependence of activation and fate of T-cells on the strength and duration of ceramide accumulation. A murine, influenza virus hemagglutinin-specific T-helper cell (IP12-7) alone or together with interacting antigen presenting B-cells (APC) was used. C2-ceramide induced apoptosis of TH cells above a 'threshold' stimulus (>25 microM in 'strength' or >30 min in duration), while below the threshold C2-ceramide was non-apoptotic, as confirmed by early and late apoptotic markers (PS-translocation, mitochondrial depolarization, caspase-3 activation, DNA-fragmentation). The modest ceramide stimuli strongly suppressed the calcium response and inhibited several downstream signal events (e.g. ERK1/2-, JNK-phosphorylation, CD69 expression or IL-2 production) in TH cells during both anti-CD3 induced and APC-triggered activation. Ceramide moderately affected the Ca2+ -release from internal stores upon antigen-specific engagement of TCR in immunological synapses, while the influx phase was remarkably reduced in both amplitude and rate, suggesting that the major target(s) of ceramide-effects are membrane-proximal. Ceramide inhibited Kv1.3 potassium channels, store operated Ca2+ -entry (SOC) and depolarized the plasma membrane to which contribution of spontaneously formed ceramide channels is possible. The impaired function of these transporters may be coupled to the quantitative, membrane raft-remodeling effect of ceramide and responsible, in a concerted action, for the suppressed activation. Our results suggest that non-apoptotic Fas stimuli, received from previously activated, FasL+ interacting lymphocytes in the lymph nodes, may negatively regulate subsequent antigen-specific T-cell activation and thus modulate the antigen-specific T-cell response.
Collapse
Affiliation(s)
- Cynthia Detre
- Department of Immunology, Eötvös Lorand University, Pázmány P. sétány 1/C, 1117, Budapest, Hungary
| | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Abstract
Activation of cells by receptor- and nonreceptor-mediated stimuli not only requires a change in the activity of signaling proteins but also requires a reorganization of the topology of the signalosom in the cell. The cell membrane contains distinct domains, rafts that serve the spatial organization of signaling molecules in the cell. Many receptors or stress stimuli transform rafts by the generation of ceramide. These stimuli activate the acid sphingomyelinase and induce a translocation of this enzyme onto the extracellular leaflet of the cell membrane. Surface acid sphingomyelinase generates ceramide that serves to fuse small rafts and to form large ceramide-enriched membrane platforms. These platforms cluster receptor molecules, recruit intracellular signaling molecules to aggregated receptors, and seem to exclude inhibitory signaling factors. Thus ceramide-enriched membrane platforms do not seem to be part of a specific signaling pathway but may facilitate and amplify the specific signaling elicited by the cognate stimulus. This general function may enable these membrane domains to be critically involved in the induction of apoptosis by death receptors and stress stimuli, bacterial and viral infections of mammalian cells, and the regulation of cardiovascular functions.
Collapse
Affiliation(s)
- Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany.
| | | |
Collapse
|
36
|
Hyperoxia-induced apoptosis and Fas/FasL expression in lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 2005; 289:L647-59. [PMID: 16148053 DOI: 10.1152/ajplung.00445.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Alveolar epithelial apoptosis is an important feature of hyperoxia-induced lung injury in vivo and has been described in the early stages of bronchopulmonary dysplasia (chronic lung disease of preterm newborn). Molecular regulation of hyperoxia-induced alveolar epithelial cell death remains incompletely understood. In view of functional involvement of Fas/FasL system in physiological postcanalicular type II cell apoptosis, we speculated this system may also be a critical regulator of hyperoxia-induced apoptosis. The aim of this study was to investigate the effects of hyperoxia on apoptosis and apoptotic gene expression in alveolar epithelial cells. Apoptosis was studied by TUNEL, electron microscopy, DNA size analysis, and caspase assays. Fas/FasL expression was determined by Western blot analysis and RPA. We determined that in MLE-12 cells exposed to hyperoxia, caspase-mediated apoptosis was the first morphologically and biochemically recognizable mode of cell death, followed by necrosis of residual adherent cells. The apoptotic stage was associated with a threefold upregulation of Fas mRNA and protein expression and increased susceptibility to direct Fas receptor activation, concomitant with a threefold increase of FasL protein levels. Fas gene silencing by siRNAs significantly reduced hyperoxia-induced apoptosis. In murine fetal type II cells, hyperoxia similarly induced markedly increased Fas/FasL protein expression, confirming validity of results obtained in transformed MLE-12 cells. Our findings implicate the Fas/FasL system as an important regulator of hyperoxia-induced type II cell apoptosis. Elucidation of regulation of hyperoxia-induced lung apoptosis may lead to alternative therapeutic strategies for perinatal or adult pulmonary diseases characterized by dysregulated type II cell apoptosis.
Collapse
Affiliation(s)
- Monique E De Paepe
- Dept. of Pathology, Women and Infants Hospital, Brown Medical School, Providence, RI 02905, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Ceramide-enriched membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:284-94. [PMID: 16226325 DOI: 10.1016/j.bbamcr.2005.09.001] [Citation(s) in RCA: 256] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 09/05/2005] [Accepted: 09/06/2005] [Indexed: 01/05/2023]
Abstract
Cellular activation involves the re-organization of receptor molecules and the intracellular signalosom in the cell membrane. Recent studies indicate that specialized domains of the cell membrane, termed rafts, are central for the spatial organization of receptors and signaling molecules. Rafts are converted into larger membrane platforms by activity of the acid sphingomyelinase, which hydrolyses raft-sphingomyelin to ceramide. Ceramide molecules spontaneously associate to form ceramide-enriched microdomains, which fuse to large ceramide-enriched membrane platforms. The acid sphingomyelinase is activated by multiple stimuli including CD95, CD40, DR5/TRAIL, CD20, FcgammaRII, CD5, LFA-1, CD28, TNF, the Interleukin-1 receptor, the PAF-receptor, CD14, infection with P. aeruginosa, S. aureus, N. gonorrhoeae, Sindbis-Virus, Rhinovirus, treatment with gamma-irradiation, UV-light, doxorubicin, cisplatin, disruption of integrin-signaling and under some conditions of developmental death. Ceramide-enriched membrane platforms serve the clustering of receptors, the recruitment of intracellular signaling molecules and the exclusion of inhibitory signaling factors and, thus, facilitate signal transduction initiated by the specific stimulus.
Collapse
Affiliation(s)
- Claudia R Bollinger
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
| | | | | |
Collapse
|
38
|
Direct Binding to Ceramide Activates Protein Kinase Cζ before the Formation of a Pro-apoptotic Complex with PAR-4 in Differentiating Stem Cells. J Biol Chem 2005; 280:26415-24. [PMID: 15901738 DOI: 10.1074/jbc.m501492200] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have reported that ceramide mediates binding of atypical protein kinase C (PKC) zeta to its inhibitor protein, PAR-4 (prostate apoptosis response-4), thereby inducing apoptosis in differentiating embryonic stem cells. Using a novel method of lipid vesicle-mediated affinity chromatography, we showed here that endogenous ceramide binds directly to the PKCzeta.PAR-4 complex. Ceramide and its analogs activated PKCzeta prior to binding to PAR-4, as determined by increased levels of phosphorylated PKCzeta and glycogen synthase kinase-3beta and emergence of a PAR-4-to-phosphorylated PKCzeta fluorescence resonance energy transfer signal that co-localizes with ceramide. Elevated expression and activation of PKCzeta increased cell survival, whereas expression of PAR-4 promoted apoptosis. This suggests that PKCzeta counteracts apoptosis, unless its ceramide-induced activation is compromised by binding to PAR-4. A luciferase reporter assay showed that ceramide analogs activate nuclear factor (NF)-kappaB unless PAR-4-dependent inhibition of PKCzeta suppresses NF-kappaB activation. Taken together, our results show that direct physical association with ceramide and PAR-4 regulates the activity of PKCzeta. They also indicate that this interaction regulates the activity of glycogen synthase kinase-3beta and NF-kappaB.
Collapse
Affiliation(s)
- Guanghu Wang
- Institute of Molecular Medicine and Genetics, School of Medicine, Medical College of Georgia, Augusta 30912, USA
| | | | | | | | | | | |
Collapse
|
39
|
Abstract
Recent evidence suggests clustering of plasma membrane rafts into ceramide-enriched platforms serves as a transmembrane signaling mechanism for a subset of cell surface receptors and environmental stresses (Grassme, H., Jekle, A., Riehle, A., Schwarz, H., Berger, J., Sandhoff, K., Kolesnick, R., and Gulbins, E. (2001) J. Biol. Chem. 276, 20589-20596; Cremesti, A., Paris, F., Grassme, H., Holler, N., Tschopp, J., Fuks, Z., Gulbins, E., and Kolesnick, R. (2001) J. Biol. Chem. 276, 23954-23961). Translocation of the secretory form of acid sphingomyelinase (ASMase) into microscopic rafts generates therein the ceramide that drives raft coalescence. This process serves to feed forward Fas activation, with approximately 2% of full caspase 8 activation sufficient for maximal ASMase translocation, leading to death-inducing signaling complex formation within ceramide-rich platforms, and apoptosis. Here we report that treatment of Jurkat T cells with UV-C also induces ASMase translocation into rafts within 1 min, catalyzing sphingomyelin hydrolysis to ceramide and raft clustering. In contrast to Fas, UV-induced ASMase translocation and activation were caspase-independent. Nonetheless, ceramide-rich platforms promoted UV-C-induced death signaling, because ASMase inhibition or raft disruption inhibited apoptosis, improving clonogenic cell survival. These studies thus define two distinct mechanisms for biologically relevant ASMase activation within rafts; a Fas-mediated mechanism dependent upon caspase 8 and FADD, and a UV-induced mechanism independent of caspase activation. Consistent with this notion, genetic depletion or pharmacologic inhibition of caspase 8 or FADD, which render Jurkat cells incapable of sphingolipid signaling and apoptosis upon Fas ligation, did not impair these events upon UV-C stimulation.
Collapse
Affiliation(s)
- Jimmy A Rotolo
- Laboratory of Signal Transduction and Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA
| | | | | | | | | | | |
Collapse
|
40
|
Abstract
AbstractNeutrophils are abundant, short-lived leukocytes, and their death by apoptosis is central to hemostasis and the resolution of inflammation, yet the trigger for their entry into apoptosis is unknown. We show here that death receptor signaling, including CD95 death-inducing signaling complex (DISC) formation and caspase 8 activation, occurred early in neutrophil apoptosis. However, death receptor ligation was not required for apoptosis, suggesting a novel mechanism for caspase 8 activation. We detected ceramide generation and clustering of CD95 in lipid rafts early in neutrophil apoptosis, and neutrophil apoptosis and ceramide generation were both significantly inhibited in acid sphingomyelinase knockout (ASM–/–) mice compared to wild-type littermates. Further studies revealed that ceramide generation, CD95 clustering, and neutrophil apoptosis were dependent on reactive oxygen species (ROSs) and were preceded by a fall in reduced glutathione levels. We propose that accumulation of ROSs, as a consequence of altered redox status, initiates ligand-independent death receptor signaling via activation of ASM and clustering of preformed DISC components in lipid rafts and is therefore a primary factor limiting neutrophil life span.
Collapse
Affiliation(s)
- Dagmar Scheel-Toellner
- MRC Centre for Immune Regulation, Division of Immunity and Infection, The Medical School, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Abstract
We have shown previously that the death receptor CD95 could contribute to anticancer drug-induced apoptosis of colon cancer cells. In addition, anticancer drugs cooperate with CD95 cognate ligand or agonistic antibodies to trigger cancer cell apoptosis. In the present study, we show that the anticancer drug cisplatin induces clustering of CD95 at the surface of the human colon cancer cell line HT29, an event inhibited by the inhibitor of acid sphingomyelinase (aSMase) imipramine. The cholesterol sequestering agent nystatin also prevents cisplatin-induced CD95 clustering and decreases HT29 cell sensitivity to cisplatin-induced apoptosis and the synergy between cisplatin and anti-CD95 agonistic antibodies. CD95, together with the adaptor molecule Fas-associated death domain and procaspase-8, is redistributed into cholesterol- and sphingolipid-enriched cell fractions after cisplatin treatment, suggesting plasma membrane raft involvement. Interestingly, nystatin prevents the translocation of the aSMase to the extracellular surface of plasma membrane and the production of ceramide, suggesting that these early events require raft integrity. In addition, nystatin prevents cisplatin-induced transient increase in plasma membrane fluidity that could be required for CD95 translocation. Together, these results demonstrate that cisplatin activates aSMase and induces ceramide production, which triggers the redistribution of CD95 into the plasma membrane rafts. Such redistribution contributes to cell death and sensitizes tumor cells to CD95-mediated apoptosis.
Collapse
Affiliation(s)
- Sandrine Lacour
- Institut National de la Santé et de la Recherche Médicale U517, Dijon, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Acid sphingomyelinase and inhibition by phosphate ion: role of inhibition by phosphatidyl-myo-inositol 3,4,5-triphosphate in oligodendrocyte cell signaling. J Neurochem 2004; 89:636-44. [PMID: 15086520 DOI: 10.1046/j.1471-4159.2004.02374.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
There is ample evidence that both acid (ASMase) and neutral (NSMase) sphingomyelinases play a role in cell death so inhibitors of either enzyme could have significant value as protectors against neurodegeneration. We used a fluorogenic sphingomyelinase substrate, 6-hexadecanoylamino-4-methylumbelliferyl-phosphorylcholine, and a [(14)C]choline-labeled sphingomyelin substrate to screen large numbers of phosphocompounds for inhibition of ASMase in extracts of human oligodendroglioma cells (HOG) and neonatal rat oligodendrocytes. Non-competitive inhibition was observed with inorganic phosphate and AMP, which was a more potent inhibitor of ASMase than cyclic AMP, ADP or ATP. However, other nucleotide phosphates, sugar phosphates, nucleotide sugars and glycerol phosphate did not inhibit ASMase. Our key finding was that phosphatidyl-myo-inositol 3,4,5-triphosphate [PtdIns (3,4,5)P(3)] was a much more potent inhibitor of ASMase than lysophosphatidic acid or phosphatidyl-myo-inositol 4,5-diphosphate [PtdIns(4,5)P(2)]. When PtdIns(3,4,5)P(3) was added to cultured cells we observed 50% inhibition of ASMase but no inhibition of other lysosomal hydrolases. After transfection of HOG cells with the tumor supressor phosphatase and tensin homolog protein (PTEN), which hydrolyses PtdIns(3,4,5)P(3) to PtdIns(4,5)P(2), we observed a two-fold increase in ASMase activity. Furthermore, the phosphatidylinositol-3-kinase inhibitor wortmannin (which reduces PtdIns(3,4,5)P(3) levels) also resulted in activation of ASMase. We propose that the small amount of ASMase activity associated with detergent-resistant cell membranes (Rafts) is regulated by PtdIns(3,4,5)P(3) and is most likely involved in receptor clustering and capping.
Collapse
Affiliation(s)
- F D Testai
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA
| | | | | | | | | |
Collapse
|
43
|
Neutral sphingomyelinase inhibitor scyphostatin prevents and ceramide mimics mechanotransduction in vascular endothelium. Am J Physiol Heart Circ Physiol 2004; 287:H1344-52. [PMID: 15142848 DOI: 10.1152/ajpheart.00222.2004] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recently, we showed that neutral sphingomyelinase (N-SMase) is concentrated at the endothelial cell surface in caveolae and is activated to produce ceramide in an acute and transient manner by increase in flow rate and pressure in rat lung vasculature (Czarny M, Liu J, Oh P, and Schnitzer JE, J Biol Chem 278: 4424-4430, 2003). Here, we report further on our investigations of this new acute mechanotransduction pathway. We employed three experimental models to explore the role of N-SMase and ceramides in mechanosignaling: 1) a cell-free, in vitro model using isolated luminal plasma membranes of rat lung endothelium; 2) a fluid shear stress model using monolayers of intact bovine aorta endothelial cell in culture; and 3) an in situ model using controlled perfusion of the rat lung vasculature. Scyphostatin, which specifically inhibited N-SMase but not acid SMase activity, prevented mechanoactivation of N-SMase as well as downstream tyrosine and mitogen-activated protein kinases. Cell-permeable ceramide analogs (N-acetylsphingosine, C2-ceramide, and N-hexanoylsphingosine, C6-ceramide) but not the inactive dihydroderivatives D2-ceramide and D6-ceramide (N-acetylsphinganine and N-hexanoylsphinganine, respectively) mimic rapid mechano-induced tyrosine phosphorylation of cell surface proteins as well as mechanoactivation of Src-like kinases and the extracellular regulated kinase pathway. The responses common to ceramide and mechanical stress were inhibited by genistein, herbamycin A, and PP2, but not PP3, which suggests an obligate role of Src-like kinases in ceramide-mediated mechanotransduction. Ceramides also induced serine/threonine phosphorylation to activate the Akt/endothelial nitric oxide synthase pathway. Thus N-SMase at the plasma membrane in caveolae may be an upstream initiating mechanosensor, which acutely triggers mechanotransduction by generation of the lipid second messenger ceramide.
Collapse
Affiliation(s)
- Malgorzata Czarny
- Division of Vascular Biology and Angiogenesis, Sidney Kimmel Cancer Center, San Diego, California 92121, USA
| | | |
Collapse
|
44
|
Abstract
Ion channels have been demonstrated to be a central element in the induction and the execution of apoptosis. In particular, mitochondrial ion channels, including not only the permeability transition pore but also a mitochondrial, ATP-sensitive (mKATP) channel as well as a mitochondrial calcium-activated potassium channel are involved critically in apoptotic changes in mitochondria. Ion channels in the cell membrane that are altered by induction of apoptosis include potassium, chloride and calcium channels. The Kv1.3 potassium channel belongs to the best-characterized ion channels involved in apoptosis and a genetic model of cells deficient for Kv1.3 has indicated a critical role for Kv1.3, at least in some forms of apoptosis. The mechanisms regulating ion channels during apoptosis are, however, still poorly defined. Recent studies have suggested a function for distinct membrane domains, termed rafts, in the cell membrane for the regulation of ion channels during apoptosis. Small sphingolipid- and cholesterol-enriched membrane domains are modified by many apoptotic stimuli to form large ceramide-enriched membrane platforms. These platforms serve to cluster receptor molecules, to re-organize intracellular signalling molecules including ion channels, to bring ion channels into close contact with their regulators and/or to separate proteins from a specific ion channel. Finally, the lipid composition of the cell membrane might be involved directly in ion channel regulation.
Collapse
Affiliation(s)
- I Szabò
- Department of Biology, University of Padua, Via Colombo 6, 35121 Padua, Italy
| | | | | |
Collapse
|
45
|
Deoxycholic acid activates the c-Jun N-terminal kinase pathway via FAS receptor activation in primary hepatocytes. Role of acidic sphingomyelinase-mediated ceramide generation in FAS receptor activation. J Biol Chem 2003; 279:5821-8. [PMID: 14660582 DOI: 10.1074/jbc.m310979200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We have shown previously that bile acids can activate the JNK pathway and down-regulate cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in the neutral pathway of bile acid biosynthesis. In this study, the mechanism(s) by which deoxycholic acid (DCA) activates the JNK pathway were examined. FAS receptor (FAS-R) and acidic sphingomyelinase (ASM)-deficient hepatocytes were resistant to DCA-induced activation of the JNK pathway. Activation of the JNK pathway (2-3-fold) in response to tumor necrosis factor-alpha was similar in both wild-type and FAS-R(-/-) hepatocytes. In wild-type and FAS-R(-/-) hepatocytes, ceramide elevation was detected as early as 2 min and peaked at 10 min after DCA treatment. In contrast, ASM(-/-) hepatocytes were defective in DCA-induced ceramide generation. Treatment with DCA resulted in movement of FAS-R to the cell surface, which was blocked upon treatment with brefeldin A. However, brefeldin A failed to block DCA-mediated JNK activation in wild-type hepatocytes. DCA-induced JNK activation was independent of either the epidermal growth factor receptor activation or free radical generation. Addition of ASM to rat hepatocytes activated JNK and down-regulated CYP7A1 mRNA levels. In conclusion, these results show that DCA activates JNK and represses CYP7A1 mRNA levels in primary hepatocytes via an ASM/FAS-R-dependent mechanism that is independent of either the epidermal growth factor receptor or free radical generation.
Collapse
Affiliation(s)
- Seema Gupta
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
Ceramide, generated by the action of acid sphingomyelinase (ASM), has emerged as a biochemical mediator of stimuli as diverse as ionizing radiation, chemotherapy, UVA light, heat, CD95, reperfusion injury, as well as infection with some pathogenic bacteria and viruses. ASM activity is also crucial for developmental programmed cell death of oocytes by apoptosis. Recently, we proposed a comprehensive model that might explain these diverse functions of ceramide: Upon contacting the relevant stimuli, ASM translocates into and generates ceramide within distinct plasma membrane sphingolipid-enriched microdomains termed rafts. Ceramide, which manifests a unique biophysical property, the capability to self-associate through hydrogen bonding, provides the driving force that results in the coalescence of microscopic rafts into large-membrane macrodomains. These structures serve as platforms for protein concentration and oligomerization, transmitting signals across the plasma membrane. Preliminary data suggest that manipulation of ceramide metabolism and/or the function of ceramide-enriched membrane platforms may present novel therapeutic opportunities for the treatment of cancer, degenerative disorders, pathogenic infections or cardiovascular diseases.
Collapse
Affiliation(s)
- Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, Essen 45122, Germany.
| | | |
Collapse
|