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Antollini SS, Barrantes FJ. Carlos Gutiérrez-Merino: Synergy of Theory and Experimentation in Biological Membrane Research. Molecules 2024; 29:820. [PMID: 38398572 PMCID: PMC10893188 DOI: 10.3390/molecules29040820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/06/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
Professor Carlos Gutiérrez-Merino, a prominent scientist working in the complex realm of biological membranes, has made significant theoretical and experimental contributions to the field. Contemporaneous with the development of the fluid-mosaic model of Singer and Nicolson, the Förster resonance energy transfer (FRET) approach has become an invaluable tool for studying molecular interactions in membranes, providing structural insights on a scale of 1-10 nm and remaining important alongside evolving perspectives on membrane structures. In the last few decades, Gutiérrez-Merino's work has covered multiple facets in the field of FRET, with his contributions producing significant advances in quantitative membrane biology. His more recent experimental work expanded the ground concepts of FRET to high-resolution cell imaging. Commencing in the late 1980s, a series of collaborations between Gutiérrez-Merino and the authors involved research visits and joint investigations focused on the nicotinic acetylcholine receptor and its relation to membrane lipids, fostering a lasting friendship.
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Affiliation(s)
- Silvia S. Antollini
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Instituto de Investigaciones Bioquímicas de Bahía Blanca (CONICET-UNS), Bahía Blanca 8000, Argentina;
| | - Francisco J. Barrantes
- Laboratory of Molecular Neurobiology, BIOMED UCA-CONICET, Buenos Aires C1107AAZ, Argentina
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Battaini F, Pascale A, Ancona DM, Cagiano R, Cuomo V, Govoni S. Moderate Alcohol Intake: Behavioral and Neurochemical Correlates in Rats. Nutr Neurosci 2016; 1:151-9. [DOI: 10.1080/1028415x.1998.11747224] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Ray S, Kassan A, Busija AR, Rangamani P, Patel HH. The plasma membrane as a capacitor for energy and metabolism. Am J Physiol Cell Physiol 2015; 310:C181-92. [PMID: 26771520 DOI: 10.1152/ajpcell.00087.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
When considering which components of the cell are the most critical to function and physiology, we naturally focus on the nucleus, the mitochondria that regulate energy and apoptotic signaling, or other organelles such as the endoplasmic reticulum, Golgi, ribosomes, etc. Few people will suggest that the membrane is the most critical element of a cell in terms of function and physiology. Those that consider the membrane critical will point to its obvious barrier function regulated by the lipid bilayer and numerous ion channels that regulate homeostatic gradients. What becomes evident upon closer inspection is that not all membranes are created equal and that there are lipid-rich microdomains that serve as platforms of signaling and a means of communication with the intracellular environment. In this review, we explore the evolution of membranes, focus on lipid-rich microdomains, and advance the novel concept that membranes serve as "capacitors for energy and metabolism." Within this framework, the membrane then is the primary and critical regulator of stress and disease adaptation of the cell.
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Affiliation(s)
- Supriyo Ray
- Department of Veterans Affairs San Diego Healthcare System, San Diego, California; Department of Anesthesiology, University of California, San Diego, La Jolla, California; and
| | - Adam Kassan
- Department of Veterans Affairs San Diego Healthcare System, San Diego, California; Department of Anesthesiology, University of California, San Diego, La Jolla, California; and
| | - Anna R Busija
- Department of Veterans Affairs San Diego Healthcare System, San Diego, California; Department of Anesthesiology, University of California, San Diego, La Jolla, California; and
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California
| | - Hemal H Patel
- Department of Veterans Affairs San Diego Healthcare System, San Diego, California; Department of Anesthesiology, University of California, San Diego, La Jolla, California; and
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Wood WG, Li L, Müller WE, Eckert GP. Cholesterol as a causative factor in Alzheimer's disease: a debatable hypothesis. J Neurochem 2014; 129:559-72. [PMID: 24329875 PMCID: PMC3999290 DOI: 10.1111/jnc.12637] [Citation(s) in RCA: 136] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/24/2013] [Accepted: 12/09/2013] [Indexed: 12/17/2022]
Abstract
High serum/plasma cholesterol levels have been suggested as a risk factor for Alzheimer's disease (AD). Some reports, mostly retrospective epidemiological studies, have observed a decreased prevalence of AD in patients taking the cholesterol lowering drugs, statins. The strongest evidence causally linking cholesterol to AD is provided by experimental studies showing that adding/reducing cholesterol alters amyloid precursor protein (APP) and amyloid beta-protein (Ab) levels. However, there are problems with the cholesterol-AD hypothesis. Cholesterol levels in serum/plasma and brain of AD patients do not support cholesterol as a causative factor in AD.Prospective studies on statins and AD have largely failed to show efficacy. Even the experimental data are open to interpretation given that it is well-established that modification of cholesterol levels has effects on multiple proteins, not only amyloid precursor protein and Ab. The purpose of this review, therefore, was to examine the above-mentioned issues, discuss the pros and cons of the cholesterol-AD hypothesis, involvement of other lipids in the mevalonate pathway, and consider that AD may impact cholesterol homeostasis.
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Affiliation(s)
- W. Gibson Wood
- Geriatric Research, Education and Clinical Center, VAMC, Department of Pharmacology, University of Minnesota School of Medicine, Minneapolis, MN 55455 USA
| | - Ling Li
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN 55455 USA
| | - Walter E. Müller
- Department of Pharmacology, Biocenter Niederursel, Goethe University, Max-von-Laue-St. 9, 60438 Frankfurt, Germany
| | - Gunter P. Eckert
- Department of Pharmacology, Biocenter Niederursel, Goethe University, Max-von-Laue-St. 9, 60438 Frankfurt, Germany
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Park JS, Jung TS, Noh YH, Kim WS, Park WI, Kim YS, Chung IK, Sohn UD, Bae SK, Bae MK, Jang HO, Yun I. The Effect of Lidocaine · HCl on the Fluidity of Native and Model Membrane Lipid Bilayers. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2012; 16:413-22. [PMID: 23269904 PMCID: PMC3526746 DOI: 10.4196/kjpp.2012.16.6.413] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 10/02/2012] [Accepted: 10/10/2012] [Indexed: 12/31/2022]
Abstract
The purpose of this study is to investigated the mechanism of pharmacological action of local anesthetic and provide the basic information about the development of new effective local anesthetics. Fluorescent probe techniques were used to evaluate the effect of lidocaine·HCl on the physical properties (transbilayer asymmetric lateral and rotational mobility, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex, and liposomes of total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. An experimental procedure was used based on selective quenching of 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer from the tryptophans of membrane proteins to Py-3-Py. Lidocaine·HCl increased the bulk lateral and rotational mobility of neuronal and model membrane lipid bilayes, and had a greater fluidizing effect on the inner monolayer than the outer monolayer. Lidocaine·HCl increased annular lipid fluidity in SPMV lipid bilayers. It also caused membrane proteins to cluster. The most important finding of this study is that there is far greater increase in annular lipid fluidity than that in lateral and rotational mobilities by lidocaine·HCl. Lidocaine·HCl alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that lidocaine, in addition to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membrane lipid.
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Affiliation(s)
- Jun-Seop Park
- Department of Dental Pharmacology and Biophysics, College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
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Joo HJ, Ahn SH, Lee HR, Jung SW, Choi CW, Kim MS, Bae MK, Chung IK, Bae SK, Jang HO, Yun I. The effect of methanol on the structural parameters of neuronal membrane lipid bilayers. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2012; 16:255-64. [PMID: 22915991 PMCID: PMC3419761 DOI: 10.4196/kjpp.2012.16.4.255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 07/13/2012] [Accepted: 07/19/2012] [Indexed: 11/15/2022]
Abstract
The structures of the intact synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortexs, and the outer and the inner monolayer separately, were evaluated with 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,3-di(1-pyrenyl)propane (Py-3-Py) as fluorescent reporters and trinitrophenyl groups as quenching agents. The methanol increased bulk rotational and lateral mobilities of SPMVs lipid bilayers. The methanol increased the rotational and lateral mobilities of the outer monolayers more than of the inner monolayers. n-(9-Anthroyloxy)stearic acid (n-AS) were used to evaluate the effect of the methanol on the rotational mobility at the 16, 12, 9, 6, and 2 position of aliphatic chains present in phospholipids of the SPMVs outer monolayers. The methanol decreased the anisotropy of the 16-(9-anthroyloxy)palmitic acid (16-AP), 12-(9-anthroyloxy)stearic acid (12-AS), 9-(9-anthroyloxy)stearic acid (9-AS), and 6-(9-anthroyloxy)stearic acid (6-AS) in the SPMVs outer monolayer but it increased the anisotropy of 2-(9-anthroyloxy)stearic acid (2-AS) in the monolayers. The magnitude of the increased rotational mobility by the methanol was in the order at the position of 16, 12, 9, and 6 of aliphatic chains in phospholipids of the outer monolayers. Furthermore, the methanol increased annular lipid fluidity and also caused membrane proteins to cluster. The important finding is that was far greater increase by methanol in annular lipid fluidity than increase in lateral and rotational mobilities by the methanol. Methanol alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that methanol, in additions to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membranes lipids.
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Affiliation(s)
- Hyung-Jin Joo
- Department of Dental Pharmacology and Biophysics, School of Dentistry and Research Institute for Oral Biotechnology, Yangsan Campus of Pusan National University, Yangsan 626-870, Korea
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7
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Abstract
Lipids are essential for the structural and functional integrity of membranes. Membrane lipids are not randomly distributed but are localized in different domains. A common characteristic of these membrane domains is their association with cholesterol. Lipid rafts and caveolae are examples of cholesterol enriched domains, which have attracted keen interest. However, two other important cholesterol domains are the exofacial and cytofacial leaflets of the plasma membrane. The two leaflets that make up the bilayer differ in their fluidity, electrical charge, lipid distribution, and active sites of certain proteins. The synaptic plasma membrane (SPM) cytofacial leaflet contains over 85% of the total SPM cholesterol as compared with the exofacial leaflet. This asymmetric distribution of cholesterol is not fixed or immobile but can be modified by different conditions in vivo: (i) chronic ethanol consumption; (ii) statins; (iii) aging; and (iv) apoE isoform. Several potential candidates have been proposed as mechanisms involved in regulation of SPM cholesterol asymmetry: apoE, low-density lipoprotein receptor, sterol carrier protein-2, fatty acid binding proteins, polyunsaturated fatty acids, P-glycoprotein and caveolin-1. This review examines cholesterol asymmetry in SPM, potential mechanisms of regulation and impact on membrane structure and function.
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Affiliation(s)
- W Gibson Wood
- Department of Pharmacology, University of Minnesota, School of Medicine, Minneapolis, MN 55455, USA.
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Burns MP, Rebeck GW. Intracellular cholesterol homeostasis and amyloid precursor protein processing. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1801:853-9. [PMID: 20304094 DOI: 10.1016/j.bbalip.2010.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 01/11/2023]
Abstract
Many preclinical and clinical studies have implied a role for cholesterol in the pathogenesis of Alzheimer's disease (AD). In this review we will discuss the movement of intracellular cholesterol and how normal distribution, transport, and export of cholesterol are vital for regulation of the AD related protein, Abeta. We focus on cholesterol distribution in the plasma membrane, transport through the endosomal/lysosomal system, control of cholesterol intracellular signaling at the endoplasmic reticulum and Golgi, the HMG-CoA reductase pathway and finally export of cholesterol from the cell.
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Affiliation(s)
- Mark P Burns
- Georgetown University Medical Center, Department of Neuroscience, Washington, DC 20057, USA.
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McIntosh AL, Atshaves BP, Huang H, Gallegos AM, Kier AB, Schroeder F. Fluorescence techniques using dehydroergosterol to study cholesterol trafficking. Lipids 2008; 43:1185-208. [PMID: 18536950 PMCID: PMC2606672 DOI: 10.1007/s11745-008-3194-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Accepted: 05/09/2008] [Indexed: 12/22/2022]
Abstract
Cholesterol itself has very few structural/chemical features suitable for real-time imaging in living cells. Thus, the advent of dehydroergosterol [ergosta-5,7,9(11),22-tetraen-3beta-ol, DHE] the fluorescent sterol most structurally and functionally similar to cholesterol to date, has proven to be a major asset for real-time probing/elucidating the sterol environment and intracellular sterol trafficking in living organisms. DHE is a naturally occurring, fluorescent sterol analog that faithfully mimics many of the properties of cholesterol. Because these properties are very sensitive to sterol structure and degradation, such studies require the use of extremely pure (>98%) quantities of fluorescent sterol. DHE is readily bound by cholesterol-binding proteins, is incorporated into lipoproteins (from the diet of animals or by exchange in vitro), and for real-time imaging studies is easily incorporated into cultured cells where it co-distributes with endogenous sterol. Incorporation from an ethanolic stock solution to cell culture media is effective, but this process forms an aqueous dispersion of DHE crystals which can result in endocytic cellular uptake and distribution into lysosomes which is problematic in imaging DHE at the plasma membrane of living cells. In contrast, monomeric DHE can be incorporated from unilamellar vesicles by exchange/fusion with the plasma membrane or from DHE-methyl-beta-cyclodextrin (DHE-MbetaCD) complexes by exchange with the plasma membrane. Both of the latter techniques can deliver large quantities of monomeric DHE with significant distribution into the plasma membrane. The properties and behavior of DHE in protein-binding, lipoproteins, model membranes, biological membranes, lipid rafts/caveolae, and real-time imaging in living cells indicate that this naturally occurring fluorescent sterol is a useful mimic for probing the properties of cholesterol in these systems.
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Affiliation(s)
- Avery L. McIntosh
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Barbara P. Atshaves
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Huan Huang
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Adalberto M. Gallegos
- Department of Pathobiology Texas A&M University, TVMC College Station, TX 77843-4467
| | - Ann B. Kier
- Department of Pathobiology Texas A&M University, TVMC College Station, TX 77843-4467
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
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Koo KI, Bae JH, Lee CH, Yoon CD, Pyun JH, Shin SH, Jeon YC, Bae MK, Jang HO, Wood WG, Yun I. The effect of bupivacaine.HCl on the physical properties of neuronal membranes. PROTOPLASMA 2008; 234:3-12. [PMID: 18797982 DOI: 10.1007/s00709-008-0017-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 08/25/2008] [Indexed: 05/26/2023]
Abstract
Fluorescent probe techniques were used to evaluate the effect of bupivacaine.HCl on the physical properties (transbilayer asymmetric lateral and rotational mobilities, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortex. An experimental procedure was used based on selective quenching of both 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer (RET) from the tryptophans of membrane proteins to Py-3-Py. Bupivacaine.HCl increased the bulk lateral and rotational mobilities, and annular lipid fluidity in SPMVs lipid bilayers, and had a greater fluidizing effect on the inner monolayer than that of the outer monolayer. The magnitude of increasing effect on annular lipid fluidity in SPMVs lipid bilayer induced by bupivacaine.HCl was significantly far greater than magnitude of increasing effect of the drug on the lateral and rotational mobilities of bulk SPMVs lipid bilayer. It also caused membrane proteins to cluster. These effects of bupivacaine.HCl on neuronal membranes may be responsible for some, though not all, of the local anesthetic actions of bupivacaine.HCl.
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Affiliation(s)
- K I Koo
- Department of Dental Pharmacology and Biophysics, Pusan National University, Busan, 602-739, South Korea
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Lee JH, Kim DI, Mun H, Lee SK, Park JS, Kim JH, Lee JH, Park YH, Jeon YC, Yoon UC, Bae MK, Jang HO, Wood WG, Yun I. The effect of propoxycaine·HCl on the physical properties of neuronal membranes. Chem Phys Lipids 2008; 154:19-25. [DOI: 10.1016/j.chemphyslip.2008.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2007] [Revised: 01/30/2008] [Accepted: 03/13/2008] [Indexed: 11/30/2022]
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Norkina O, Dolganiuc A, Shapiro T, Kodys K, Mandrekar P, Szabo G. Acute alcohol activates STAT3, AP-1, and Sp-1 transcription factors via the family of Src kinases to promote IL-10 production in human monocytes. J Leukoc Biol 2007; 82:752-62. [PMID: 17575268 DOI: 10.1189/jlb.0207099] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Alcohol consumption is associated with an imbalance in pro- and anti-inflammatory cytokines and immunosuppression, partially as a result of enhanced IL-10 production. The mechanisms of IL-10 induction by alcohol remain poorly understood. We identified that increased IL-10 production in human monocytes after acute in vivo alcohol consumption or in vitro alcohol treatment was associated with increased STAT3 activation. Alcohol alone induced and in combination with LPS augmented STAT3 phosphorylation at tyrosine 705 (tyr705) and serine 727 (ser727) residues and increased STAT3 binding to DNA. Upstream, alcohol activated the Src kinases, as indicated by an increase in phosphorylated and a decrease in nonphosphorylated Src proteins. STAT3 activation by Src kinases occurred directly at the tyr705 residue and indirectly at the ser727 residue via JNK MAPKs. Using specific Src (PP2), JNK1/2 (SB600125), or p38 (SB203580) inhibitors, we determined that alcohol treatment alone induced and together with LPS, augmented the DNA-binding capacity of the specificity protein-1 (Sp-1) and AP-1 transcription factors involved in IL-10 production via Src-mediated activation of p38 MAPK and JNK, respectively. Our data suggest that acute alcohol activates Src/STAT3 and Src/MAPK/STAT3, AP-1, and Sp-1 pathways as important mechanisms for IL-10-mediated immunomodulation after acute alcohol use.
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Affiliation(s)
- Oxana Norkina
- University of Massachusetts Medical School, Department of Medicine, LRB 215, 364 Plantation Street, Worcester, MA 01605, USA
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Dai Q, Zhang J, Pruett SB. Ethanol alters cellular activation and CD14 partitioning in lipid rafts. Biochem Biophys Res Commun 2005; 332:37-42. [PMID: 15896296 DOI: 10.1016/j.bbrc.2005.04.088] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Accepted: 04/18/2005] [Indexed: 12/11/2022]
Abstract
Alcohol consumption interferes with innate immunity. In vivo EtOH administration suppresses cytokine responses induced through Toll-like receptor 4 (TLR4) and inhibits TLR4 signaling. Actually, EtOH exhibits a generalized suppressive effect on signaling and cytokine responses induced by through most TLRs. However, the underlying mechanism remains unknown. RAW264.7 cells were treated with LPS or co-treated with EtOH or with lipid raft-disrupting drugs. TNF-alpha production, IRAK-1 activation, and CD14 partition were evaluated. EtOH or nystatin, a lipid raft-disrupting drug, suppressed LPS-induced production of TNF-alpha. The suppressive effect of EtOH on LPS-induced TNF-alpha production was additive with that of methyl-beta-cyclodextrin (MCD), another lipid raft-disrupting drug. EtOH interfered with IRAK-1 activation, an early TLR4 intracellular signaling event. Cell fractionation analyses show that acute EtOH altered LPS-related partition of CD14, a critical component of the LPS receptor complex. These results suggest a novel mechanism of EtOH action that involves interference with lipid raft clustering induced by LPS. This membrane action of EtOH might be one of the mechanisms by which EtOH acts as a generalized suppressor for TLR signaling.
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Affiliation(s)
- Qun Dai
- Department of Cellular Biology and Anatomy, Louisiana State University Health Science Center, 1501 Kings Highway, Shreveport, LA 71130, USA
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Knott TK, Dopico AM, Dayanithi G, Lemos J, Treistman SN. Integrated channel plasticity contributes to alcohol tolerance in neurohypophysial terminals. Mol Pharmacol 2002; 62:135-42. [PMID: 12065764 DOI: 10.1124/mol.62.1.135] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Short-term ethanol challenge results in the reduction of peptide hormone release from the rat neurohypophysis. However, rats that have been maintained on an ethanol-containing diet for 3 to 4 weeks exhibit tolerance to this effect. Mechanistic underpinnings of this tolerance were probed by examining four ion channel conductances critical for neurohormone release. The voltage-gated L-type calcium channel and the functionally linked calcium-activated BK channel represent a functional dyad. Although these channels show opposite drug responses in the naive terminal (i.e., the L-type Ca2+ channel is inhibited whereas the BK channel is potentiated), the effect of long-term alcohol exposure is to decrease sensitivity to the short-term administration of drug in both instances. In addition to the shift in sensitivity, current density increased for the L-type Ca2+ current and decreased for the BK current, consistent with a compensatory change. Sensitivity to alcohol was also altered for two other channel types studied. Inhibition of the voltage-gated transient Ca2+ current was lessened after long-term treatment. I(A,) which is not sensitive to the drug at clinically relevant concentrations in terminals from the naive rat, acquires sensitivity after long-term exposure, representing a potentially novel type of tolerance. However, neither the transient Ca2+ current nor I(A) shows a change in current density, demonstrating the selectivity of this aspect of tolerance. Overall, these results demonstrate that channel plasticity can explain at least a portion of the behavioral tolerance resulting from changes in sensitivity of peptide hormone release. Furthermore, they suggest that an understanding of tolerance requires the examination of dynamically coupled channel populations.
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Affiliation(s)
- Thomas K Knott
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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15
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Daragan VA, Voloshin AM, Chochina SV, Khazanovich TN, Wood WG, Avdulov NA, Mayo KH. Specific binding of ethanol to cholesterol in organic solvents. Biophys J 2000; 79:406-15. [PMID: 10866966 PMCID: PMC1300944 DOI: 10.1016/s0006-3495(00)76302-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although ethanol has been reported to affect cholesterol homeostasis in biological membranes, the molecular mechanism of action is unknown. Here, nuclear magnetic resonance (NMR) spectroscopic techniques have been used to investigate possible direct interactions between ethanol and cholesterol in various low dielectric solvents (acetone, methanol, isopropanol, DMF, DMSO, chloroform, and CCl(4)). Measurement of (13)C chemical shifts, spin-lattice and multiplet relaxation times, as well as self-diffusion coefficients, indicates that ethanol interacts weakly, yet specifically, with the HC-OH moiety and the two flanking methylenes in the cyclohexanol ring of cholesterol. This interaction is most strong in the least polar-solvent carbon tetrachloride where the ethanol-cholesterol equilibrium dissociation constant is estimated to be 2 x 10(-3) M. (13)C-NMR spin-lattice relaxation studies allow insight into the geometry of this complex, which is best modeled with the methyl group of ethanol sandwiched between the two methylenes in the cyclohexanol ring and the hydroxyl group of ethanol hydrogen bonded to the hydroxyl group of cholesterol.
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Affiliation(s)
- V A Daragan
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Health Sciences Center, Minneapolis, Minnesota 55455, USA
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16
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Mason RP, Jacob RF, Walter MF, Mason PE, Avdulov NA, Chochina SV, Igbavboa U, Wood WG. Distribution and fluidizing action of soluble and aggregated amyloid beta-peptide in rat synaptic plasma membranes. J Biol Chem 1999; 274:18801-7. [PMID: 10373497 DOI: 10.1074/jbc.274.26.18801] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effects of soluble and aggregated amyloid beta-peptide (Abeta) on cortical synaptic plasma membrane (SPM) structure were examined using small angle x-ray diffraction and fluorescence spectroscopy approaches. Electron density profiles generated from the x-ray diffraction data demonstrated that soluble and aggregated Abeta1-40 peptides associated with distinct regions of the SPM. The width of the SPM samples, including surface hydration, was 84 A at 10 degrees C. Following addition of soluble Abeta1-40, there was a broad increase in electron density in the SPM hydrocarbon core +/-0-15 A from the membrane center, and a reduction in hydrocarbon core width by 6 A. By contrast, aggregated Abeta1-40 contributed electron density to the phospholipid headgroup/hydrated surface of the SPM +/-24-37 A from the membrane center, concomitant with an increase in molecular volume in the hydrocarbon core. The SPM interactions observed for Abeta1-40 were reproduced in a brain lipid membrane system. In contrast to Abeta1-40, aggregated Abeta1-42 intercalated into the lipid bilayer hydrocarbon core +/-0-12 A from the membrane center. Fluorescence experiments showed that both soluble and aggregated Abeta1-40 significantly increased SPM bulk and protein annular fluidity. Physico-chemical interactions of Abeta with the neuronal membrane may contribute to mechanisms of neurotoxicity, independent of specific receptor binding.
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Affiliation(s)
- R P Mason
- Membrane Biophysics Laboratory, Departments of Medicine and Biochemistry, MCP Hahnemann University School of Medicine, Allegheny Campus, Pittsburgh, Pennsylvania 15212-4772, USA
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17
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Wood WG, Schroeder F, Avdulov NA, Chochina SV, Igbavboa U. Recent advances in brain cholesterol dynamics: transport, domains, and Alzheimer's disease. Lipids 1999; 34:225-34. [PMID: 10230715 DOI: 10.1007/s11745-999-0357-9] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Major advances in understanding cholesterol dynamics and the role that cholesterol plays in vascular disease have recently been made. The brain is an organ that is highly enriched in cholesterol, but progress toward understanding brain cholesterol dynamics has been relatively limited. This review examines recent contributions to the understanding of brain cholesterol dynamics, focusing on extracellular and intracellular lipid carrier proteins, membrane cholesterol domains, and emerging evidence linking an association between cholesterol dynamics and Alzheimer's disease.
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Affiliation(s)
- W G Wood
- Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center and the Department of Pharmacology, University of Minnesota School of Medicine, Minneapolis 55417, USA
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18
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Avdulov NA, Chochina SV, Igbavboa U, Warden CS, Schroeder F, Wood WG. Lipid binding to sterol carrier protein-2 is inhibited by ethanol. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1437:37-45. [PMID: 9931423 DOI: 10.1016/s0005-2760(98)00178-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sterol carrier protein-2 (SCP-2) is an intracellular lipid carrier protein that binds cholesterol, phospholipids, fatty acids and other ligands. It has been reported that expression of SCP-2 was increased in brain nerve endings or synaptosomes of chronic ethanol-treated mice and it was shown that cholesterol homeostasis was altered in brain membranes of chronic ethanol-treated animals. Ethanol may interfere with the capacity of SCP-2 to bind cholesterol as well as other lipids. This hypothesis was tested using recombinant SCP-2 and fluorescent-labeled cholesterol, phosphatidylcholine (PC), and stearic acid. The association constants (Ka) of the ligand-SCP-2 complex were in the following order: NBD-cholesterol>NBD-PC>NBD-stearic acid. Ethanol, beginning at a concentration of 25 mM, significantly reduced the affinity of NBD-cholesterol and NBD-PC for SCP-2. Effects of ethanol on the Ka of NBD-stearic acid was significant only at the highest concentration that was examined (200 mM). Ethanol significantly increased the Bmax of NBD-cholesterol for SCP-2 but did not have a significant effect on the Bmax of NBD-PC. Similar results were found for effects of ethanol on the Kas and Bmaxs using pyrene-labeled cholesterol and PC. In conclusion, ethanol beginning at a physiological concentration of 25 mM inhibited binding of cholesterol and PC to SCP-2. However, effects of ethanol on lipid binding to SCP-2 were dependent on the type of lipid. Ethanol in vivo may interfere with lipid binding to SCP-2 and disrupt lipid trafficking within cells.
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Affiliation(s)
- N A Avdulov
- Geriatric Research, Education and Clinical Center, VA Medical Center and Department of Pharmacology, University of Minnesota School of Medicine, 11G, One Veterans Drive, Minneapolis, MN 55417, USA
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19
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Harikumar KG, Chattopadhyay A. Modulation of agonist and antagonist interactions in serotonin 1A receptors by alcohols. FEBS Lett 1998; 438:96-100. [PMID: 9821966 DOI: 10.1016/s0014-5793(98)01284-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The serotonin type IA (5-HT1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to GTP binding regulatory proteins (G-proteins). Serotonergic signalling has been shown to play an important role in alcohol tolerance and dependence. We have studied the effects of alcohols on ligand (agonist and antagonist) binding to bovine hippocampal 5-HT1A receptor in native as well as solubilized membranes. Our results show that alcohols inhibit the specific binding of the agonist OH-DPAT and the antagonist p-MPPF to 5-HT1A receptors in a concentration-dependent manner.
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Affiliation(s)
- K G Harikumar
- Centre for Cellular and Molecular Biology, Hyderabad, India
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20
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Chu B, Dopico AM, Lemos JR, Treistman SN. Ethanol potentiation of calcium-activated potassium channels reconstituted into planar lipid bilayers. Mol Pharmacol 1998; 54:397-406. [PMID: 9687582 DOI: 10.1124/mol.54.2.397] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the actions of ethanol on the single channel properties of large conductance Ca2+-activated K+ (BK) channels isolated from skeletal muscle T-tubule membranes and incorporated into planar lipid bilayer membranes. We have taken advantage of this preparation, because it lacks most elements of cellular complexity, including cytoplasmic constituents and complex membrane lipid composition and architecture, to examine the minimum requirements for the effects of alcohol. Clinically relevant concentrations (25-200 mM) of ethanol increased the activity of BK channels incorporated into bilayers composed of phosphatidylethanolamine (PE) alone or PE and phosphatidylserine. The potentiation of channel activity by ethanol was attributable predominantly to a decrease in the average amount of time spent in closed states. Ethanol did not significantly affect the current amplitude-voltage relationship for BK channels, indicating that channel conductance for K+ was unaffected by the drug. Although base-line characteristics of BK channels incorporated into bilayers composed only of PE differed from those of channels in PE/ phosphatidylserine in a manner expected from the change in bilayer charges, the actions of ethanol on channel activity were qualitatively similar in the different lipid environments. The effects of ethanol on single channel properties of BK channels in the planar bilayer are very similar to those reported for the action of ethanol on neurohypophysial BK channels studied in native membrane, and for cloned BK channels expressed in Xenopus laevis oocytes, which suggests that ethanol's site and mechanism of action are preserved in this greatly simplified preparation.
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Affiliation(s)
- B Chu
- Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical Center, Worcester, Massachusetts 01655, USA
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21
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Pascale A, Battaini F, Govoni S, Persichella M, De Salvia MA, Cuomo V. Chronic low doses of ethanol affect brain protein kinase C and ultrasonic calls in rats. Alcohol 1997; 14:557-61. [PMID: 9401670 DOI: 10.1016/s0741-8329(97)00047-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Few studies have investigated neurobehavioral and neurochemical consequences of chronic consumption of low doses of ethanol. The present study shows that in rats exposure to 3% ethanol (v/v in drinking water) for 2 months decreased both calcium-dependent and -independent protein kinase C (PKC) activities in the cortex and in the hippocampus. This treatment also reduced ultrasonic calls (UCs), an index of emotional and motivational states of the animal. In addition, at cortical level of ethanol-treated rats, we observed a correlation between calcium-dependent activities and UCs. These results suggest that nonaddicting doses of ethanol affect brain PKC activities and that this enzyme may be involved in the ethanol modulation of emotional and motivational behaviors.
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Affiliation(s)
- A Pascale
- Institute of Pharmacological Sciences, University of Milano, Italy.
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22
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Kang JS, Choi CM, Yun I. Effects of ethanol on lateral and rotational mobility of plasma membrane vesicles isolated from cultured mouse myeloma cell line Sp2/0-Ag14. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1281:157-63. [PMID: 8664314 DOI: 10.1016/0005-2736(95)00301-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Intramolecular excimerization of Py-3-Py and fluorescence polarization of DPH were used to evaluate effects of ethanol on the rate and range of the lateral mobility and the range of the rotational mobility of bulk bilayer structures of the Sp2/0-PMV. In a concentration-dependent manner, ethanol increased the rate and range of the lateral mobility and the range of the rotational mobility of bulk bilayer structures of Sp2/0-PMV. Selective quenching of DPH by trinitrophenyl groups was utilized to examine the range of transbilayer asymmetric rotational mobility of the Sp2/0-PVM. The anisotropy (r), limiting anisotropy (r(infinity)) and order parameter (S) of DPH in the inner monolayer were 0.022, 0.029 and 0.063, respectively, greater than calculated for the outer monolayer of the Sp2/0-PMV. Selective quenching of DPH by trinitrophenyl groups was also used to examine the transbilayer asymmetric effects of ethanol on the range of the rotational mobility of the Sp2/0-PMV. Ethanol had a greater increasing effect on the range of the rotational mobility of the outer monolayer as compared to the inner monolayer of the Sp2/0-PMV. It has been proven that ethanol exhibits a selective rather than nonselective fluidizing effect within the transbilayer domains of the Sp2/0-PMV.
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Affiliation(s)
- J S Kang
- Department of Oral Biochemistry and Molecular Biology, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, South Korea
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23
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Mauceri HJ, Becker KB, Conway S. The influence of ethanol exposure on insulin-like growth factor (IGF) type II receptors in fetal rat tissues. Life Sci 1996; 59:51-60. [PMID: 8684271 DOI: 10.1016/0024-3205(96)00257-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The effect of ethanol (ETOH) exposure on the IGF type II receptor concentration was examined in 18 and 20 day fetal rat tissues. Pregnant dams were fed an ETOH (36% of calories derived from ETOH; 6.6% v/v) liquid diet. Control fetuses were offspring of dams either pair-fed a control liquid diet or ad libitum-fed a standard pelleted lab chow. Fetal brain, heart, kidney, liver, lung and skeletal muscle were removed and whole homogenates from individual animals were analyzed. Results of immunoquantification of IGF type II receptors in whole tissue homogenates show that there is a trend towards increased receptor concentration between 18 and 20 days in all tissue and this trend is significant for lung, liver and muscle. There were no significant differences in receptor concentration between treatment groups. These studies suggest that during the later stages of fetal development, there is an increase in total IGF type II receptors and this increase is undisturbed by ETOH exposure.
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Affiliation(s)
- H J Mauceri
- Department of Biological Sciences, Northern Illinois University, DeKalb 60115, USA
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24
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Meehan E, Beaugé F, Choquart D, Leonard BE. Influence of an n-6 polyunsaturated fatty acid-enriched diet on the development of tolerance during chronic ethanol administration in rats. Alcohol Clin Exp Res 1995; 19:1441-6. [PMID: 8749808 DOI: 10.1111/j.1530-0277.1995.tb01005.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This study investigates the effects of n-6 polyunsaturated fatty acids (PUFAs), in the form of dietary Evening Primrose Oil (EPO) and safflower oil, on the development of tolerance to ethanol. The degree of fluorescence polarization of the fluoroprobes DPH, PROP-DPH, and TMA-DPH in isolated cortical synaptosomal membranes was measured. In addition, the development of tolerance, as shown by changes in synaptosomal membrane fluidity after an acute in vitro ethanol challenge, was also determined after 20 weeks of ethanol administration, either alone or together with a PUFA-enriched diet. Although the administration of EPO-enriched diet did not significantly render the inner core of the cortical synaptosomal membrane tolerant to the acute ethanol challenge, concomitant administration of ethanol and EPO was found to increase further the rigidity and tolerance to the acute ethanol challenge in the inner core. Chronic administration of safflower oil, which lacks gamma-linolenic acid (18:3, n-6) but like EPO contains linoleic acid, either alone or together with chronic ethanol had no effect on synaptosomal membrane fluidity after an acute ethanol challenge. The results suggest that gamma-linolenic acid or its metabolites may have an important role to play in the development of tolerance to chronic ethanol.
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Affiliation(s)
- E Meehan
- Department of Pharmacology, University College, Galway, Ireland
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25
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Omodeo-Salé F, Pitto M, Masserini M, Palestini P. Effects of chronic ethanol exposure on cultured cerebellar granule cells. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1995; 26:159-69. [PMID: 8573241 DOI: 10.1007/bf02815010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The aim of this study was to investigate the lipid content and composition of rat cerebellar granule cells grown in the presence of ethanol (40, 55, or 80 mM) during in vitro differentiation. Quantitative analyses showed no effects of 40 mM ethanol, whereas a significant increase of total cholesterol was observed at 55 mM. Cells exposed to the highest ethanol dose (80 mM) were characterized by a higher sialidase activity, and by the modification of the ganglioside pattern and phospholipid fatty acid composition. The observed modifications were accompanied by changes of membrane anisotropy fluorescence assessed by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene.
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Affiliation(s)
- F Omodeo-Salé
- Institute of General Physiology and Biochemistry, Faculty of Pharmacy, University of Milan, Italy
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26
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Avdulov NA, Chochina SV, Draski LJ, Deitrich RA, Wood WG. Chronic ethanol consumption alters effects of ethanol in vitro on brain membrane structure of high alcohol sensitivity and low alcohol sensitivity rats. Alcohol Clin Exp Res 1995; 19:886-91. [PMID: 7485835 DOI: 10.1111/j.1530-0277.1995.tb00963.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In this study, we examined if differences in initial membrane sensitivity to ethanol were associated with development of membrane tolerance to ethanol. High Alcohol Sensitivity (HAS) and Low Alcohol Sensitivity (LAS) rats were administered a 15% ethanol solution in water as the sole source of fluid for 30 days. The amount of ethanol consumed per day did not significantly differ between the HAS and LAS rats. Development of membrane tolerance to in vitro effects of ethanol has been previously reported for bulk membrane fluidity and protein-lipid interaction. Our data expands the understanding of "membrane tolerance" phenomenon to protein distribution and bilayer interdigitation. We also introduce genotype-dependent and genotype-independent properties of the membrane tolerance to ethanol. ethanol treatment produced genotype-dependent and genotype-independent membrane tolerance to ethanol. The in vitro effects of ethanol on synaptic plasma membrane (SPM) protein distribution and lipid bilayer interdigitation were abolished or decreased in the SPM of chronic ethanol-treated HAS rats, as compared with the SPM of HAS control rats (genotype-dependent tolerance). Protein distribution and bilayer interdigitation were not affected by ethanol in vitro in either chronic ethanol-treated or control LAS rats. Genotype-independent tolerance to ethanol in vitro was observed for SPM annular and bulk bilayer fluidity in chronic ethanol-treated HAS and LAS rats. It is concluded that initial sensitivity to ethanol contributes to the development of membrane tolerance to ethanol in HAS and LAS rats.
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Affiliation(s)
- N A Avdulov
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA
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27
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Wood WG, Igbavboa U, Rao AM, Schroeder F, Avdulov NA. Cholesterol oxidation reduces Ca(2+)+MG (2+)-ATPase activity, interdigitation, and increases fluidity of brain synaptic plasma membranes. Brain Res 1995; 683:36-42. [PMID: 7552342 DOI: 10.1016/0006-8993(95)00347-s] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
These experiments examined effects of cholesterol oxidation on Ca(2+)+Mg(2+)-ATPase activity, Na(+)+K(+)-ATPase activity, and membrane structure of brain synaptic plasma membranes (SPM). Cholesterol oxidase [E.C.1.1.3.6 from Brevibacterium sp.] was used to oxidize cholesterol. Two cholesterol pools were identified in synaptosomal membranes based on their accessibility to cholesterol oxidase. A rapidly oxidized cholesterol pool was observed with a 1t1/2 of 1.19 +/- 0.09 min and a second pool with a 2t1/2 of 38.30 +/- 4.16 min. Activity of Ca(2+)+Mg(2+)-ATPase was inhibited by low levels of cholesterol oxidation. Ten percent cholesterol oxidation, for example, resulted in approximately 35% percent inhibition of Ca(2+)+Mg(2+)-ATPase activity. After 13% cholesterol oxidation, further inhibition of Ca(2+)+Mg(2+)-ATPase activity was not observed. Activity of Na(+)+K(+)-ATPase was not affected by different levels of cholesterol oxidation (5%-40%). SPM interdigitation was significantly reduced and fluidity was significantly increased by cholesterol oxidation. The relationship observed between SPM interdigitation and Ca(2+)+Mg(2+)-ATPase activity was consistent with studies using model membranes [7]. Brain SPM function and structure were altered by relatively low levels of cholesterol oxidation and is a new approach to understanding cholesterol dynamics and neuronal function. The sensitivity of brain SPM to cholesterol oxidation may be important with respect to the proposed association between oxygen free radicals and certain neurodegenerative diseases.
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Affiliation(s)
- W G Wood
- Geriatric Research, Education and Clinical Center, VA Medical Center, Minneapolis, MN 55417, USA
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28
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Schroeder F, Woodford JK, Kavecansky J, Wood WG, Joiner C. Cholesterol domains in biological membranes. Mol Membr Biol 1995; 12:113-9. [PMID: 7767369 DOI: 10.3109/09687689509038505] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Membrane cholesterol is distributed asymmetrically both within the cell or within cellular membranes. Elaboration of intracellular cholesterol trafficking, targeting and intramembrane distribution has been spurred by both molecular and structural approaches. The expression of recombinant sterol carrier proteins in L-cell fibroblasts has been especially useful in demonstrating for the first time that such proteins actually elicit intracellular and intraplasma membrane redistribution of sterol. Additional advances in the use of native fluorescent sterols allowed resolution of transbilayer and lateral cholesterol domains in plasma membranes from cultured fibroblasts, brain synaptosomes and erythrocytes. In all three cell surface membranes, cholesterol is enriched in the inner, cytofacial leaflet. Up to three different cholesterol domains have been identified in the lateral plane of the plasma membrane: a fast exchanging domain comprising less than 10% of cholesterol, a slowly exchanging domain comprising about 30% of cholesterol, and a very slowly or non-exchangeable sterol domain comprising 50-60% of plasma membrane cholesterol. Factors modulating plasma membrane cholesterol domains include polyunsaturated fatty acids, expression of intracellular sterol carrier proteins, drugs such as ethanol, and several membrane pathologies (systemic lupus erythematosus, sickle cell anaemia and aging). Disturbances in plasma membrane cholesterol domains alter transbilayer fluidity gradients in plasma membranes. Such changes are associated with decreased Ca(2+)-ATPase and Na+, K(+)-ATPase activity. Thus, the size, dynamics and distribution of cholesterol domains within membranes not only regulate cholesterol efflux/influx but also modulate plasma membrane protein functions and receptor-effector coupled systems.
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Affiliation(s)
- F Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA
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29
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Goodwin M, Morley JE. Geriatric research, education and clinical centers: their impact in the development of American geriatrics. J Am Geriatr Soc 1994; 42:1012-9. [PMID: 8064090 DOI: 10.1111/j.1532-5415.1994.tb06599.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The GRECC program was established by the VA in 1975 and has been expanded since then to 16 sites. For more than a decade, GRECC staff have made major contributions to advancing the understanding of the aging process and developing approaches that have improved the care of older veterans as well as all frail elderly persons in the United States. Most notably, GRECC staff have been among the leading scientists in the field of aging, have stimulated the growth of some of the highest quality university-based geriatric programs in the country, have provided clinical training in geriatrics to thousands of health professional students and practitioners, and have developed innovative models of geriatric care. The GRECC model of integrating research, education, and clinical activities in a "center of excellence" with specific goals and expectations serves as one of the best examples of how scientific advances can be applied effectively to direct patient care.
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Affiliation(s)
- M Goodwin
- Office of Geriatrics and Extended Care, Veterans Health Administration, US Department of Veterans Affairs, St. Louis, Missouri
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30
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Ho C, Williams BW, Kelly MB, Stubbs CD. Chronic ethanol intoxication induces adaptive changes at the membrane protein/lipid interface. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1189:135-42. [PMID: 8292617 DOI: 10.1016/0005-2736(94)90058-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Modifications were found to occur at the membrane protein/lipid interface of liver microsomes in animals that had been subjected to chronic ethanol ingestion. The effects were revealed by probing this region with 1,6-diphenyl-1,3,5-hexatriene (DPH), trimethylammonium-DPH (TMA-DPH) and DPH attached to the sn-2 chain of phosphatidylcholine (1-palmitoyl-2-[[2-[4-(6-phenyl-trans-1,3,5-hexatrienyl) phenyl]ethyl]carbonyl]-3-sn-phosphatidylcholine, DPH-PC). In intact membranes, it was found that the decay of the excited state was heterogeneous, this being modeled by fitting the data to a fluorescence lifetime distribution. The full-width of the distribution at half-maximum, which relates to the degree of excited state environmental heterogeneity, increased for each fluorophore, as a result of chronic ethanol treatment. For TMA-DPH and DPH the excited state heterogeneity could have arisen from, (i) the protein/lipid interface and (ii) varied degrees of water penetration into the lipid, due to the ability of these fluorophores to sample along the bilayer normal. By contrast, the DPH in DPH-PC, due to its tethering, was only able to sample the heterogeneity at the protein/lipid interface, as confirmed by a homogeneous decay in vesicles of microsomal lipid extracts. The increased degree of DPH-PC fluorescence decay heterogeneity in microsomes from chronic ethanol-treated animals as compared to controls, was found to persist in vesicles of extracted lipids, when apocytochrome C was included in the vesicle preparations as a model protein. This effectively eliminated a protein modification from being responsible and indicated that a chronic-ethanol induced alteration in the lipids was being expressed in the form of a physico-chemical modification at the protein/lipid interface. The degree of DPH-PC environmental heterogeneity was also directly increased by ethanol, however, membranes from chronic ethanol-treated animals were resistant to this effect, showing that the phenomenon of 'membrane tolerance' extends to the membrane protein/lipid interface.
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Affiliation(s)
- C Ho
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
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31
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Geer BW, Heinstra PW, McKechnie SW. The biological basis of ethanol tolerance in Drosophila. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1993; 105:203-29. [PMID: 8359013 DOI: 10.1016/0305-0491(93)90221-p] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- B W Geer
- Department of Biology, Knox College, Galesburg, IL 61401
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32
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Prasad VV. Alterations and recovery of rat brain gangliosides and glycosidases following long-term exposure to alcohol and rehabilitation during development. Brain Res 1993; 610:75-81. [PMID: 8518932 DOI: 10.1016/0006-8993(93)91219-i] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The present study examines effects of continuous exposure to alcohol during gestation, lactation and postweaning periods and rehabilitation on gangliosides and their catabolizing enzymes in whole brain (WB), cerebrum (C), cerebellum (CB) and brain stem (BS) of 63-day-old rats. Continuous exposure to alcohol was found to cause significant deficits in the body and brain weights. On the other hand, the concentration of total ganglioside in whole brain, cerebrum, cerebellum and brain stem showed an increase following exposure to alcohol. In agreement with the increased ganglioside concentration the activities of sialidase, beta-galactosidase, beta-glucosidase and beta-hexosaminidase, which are likely to be involved in the catabolism of gangliosides, showed reductions due to alcohol. Alcohol was also found to alter the proportions of individual gangliosides and the changes were found to be region-specific. However; the alcohol-induced alterations were reversed, at least to some extent, upon abstinence from alcohol. Body weights of control (CT), alcoholic (AC) and rehabilitated (AR) rats were 164 +/- 2, 107 +/- 7 and 139 +/- 3 (mean +/- S.E.M.), respectively. Decrease in tissue weight was significant in whole brain, cerebrum and brain stem but not in cerebellum. In AR rats significant deficits in tissue weights persisted in cerebrum and almost a complete recovery was observed in brain stem. On the other hand, the increase in the concentration of gangliosides in WB, C, CB and BS of AC rats amounted to 23, 19, 19 and 53% of controls, respectively. The corresponding values for the AR rats were 12, 14, 3 and 5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- V V Prasad
- Department of Biochemistry, Faculty of Science, M.S. University of Baroda, India
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33
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Wood WG, Rao AM, Igbavboa U, Semotuk M. Cholesterol exchange and lateral cholesterol pools in synaptosomal membranes of pair-fed control and chronic ethanol-treated mice. Alcohol Clin Exp Res 1993; 17:345-50. [PMID: 8488977 DOI: 10.1111/j.1530-0277.1993.tb00773.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Most studies on effects of ethanol on membrane cholesterol have reported on changes in the total or bulk amount of cholesterol. Membrane cholesterol, however, can be described in terms of its kinetics and domains. The kinetics and size of lateral cholesterol exchangeable and nonexchangeable pools were examined in synaptosomes of pair-fed controls and chronic ethanol-treated mice. Effects of sphingomyelin, an exofacial leaflet phospholipid, that has been shown to affect cholesterol pools, were also examined. Radiolabeled small unilamellar vesicles were used to exchange cholesterol with synaptosomes. The total amounts of membrane cholesterol, phospholipid phosphorus, and the ratio of cholesterol to phospholipid did not differ between the pair-fed control and ethanol groups. In control mice, the rate constant (hr-1) and the t1/2 (hr) of cholesterol exchange were 0.065 +/- 0.001 and 10.7 +/- 0.25 (hr), respectively. The rate constant was significantly slower (0.053 +/- 0.001, p < 0.05) and the t1/2 significantly longer (13.33 +/- 0.58, p < 0.05) in synaptosomes of the ethanol group compared with the control group. The size of the exchangeable pool of cholesterol did not differ significantly between the two groups. Sphingomyelinase-induced hydrolysis of sphingomyelin significantly slowed cholesterol exchange with the largest effect in synaptosomes of the control group as compared with the ethanol group (p < 0.05). Hydrolysis of sphingomyelin had significantly (p < 0.05) less of an effect on cholesterol exchange in synaptosomes of the ethanol group. Membrane cholesterol can be described in terms of total content, transbilayer distribution, kinetics, and size of lateral pools.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W G Wood
- Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center, Minneapolis, MN 55417
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34
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Sun GY, Navidi M, Yoa FG, Wood WG, Sun AY. Effects of chronic ethanol administration on poly-phosphoinositide metabolism in the mouse brain: variance with age. Neurochem Int 1993; 22:11-7. [PMID: 8382982 DOI: 10.1016/0197-0186(93)90063-b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Using a procedure in which poly-phosphoinositides (poly-PI) in C57Bl mouse brain were labeled with [32P]Pi or [32P]ATP, the effects of chronic ethanol administration and age on metabolism of these anionic phospholipids were examined. Within 4 h after intracerebral injection, both labeled precursors were effectively incorporated into membrane phospholipids with high proportions of labeling among phosphatidylcholine, phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate. With few exceptions, the phospholipid labeling patterns in different brain regions, e.g. cortex, hippocampus and hypothalamus, were similar. However, when the brain homogenate was subjected to differential and sucrose-Ficoll gradient centrifugation, different phospholipid labeling patterns were observed in the subcellular membrane fractions. Young adult mice given an ethanol (5% w/v) liquid diet for 2 months showed an increase in the levels of labeled phosphatidylinositol 4-phosphate, phosphatidylinositol 4,5-bisphosphate and phosphatidylserine in the cortex and hippocampus as compared to the pair-fed controls, but these changes were not observed in the hypothalamus. In another study, 12- and 26-month-old mice were administered either an ethanol (8 g/kg in two doses daily) or a control diet by gavage for 3 weeks. The 12-month-old group given the ethanol diet showed an increase in labeled poly-PI which was found largely in the synaptosomal fraction. Surprisingly, the 26-month-old mice given the same ethanol paradigm showed a decrease in labeled poly-PI. Consistent with our previous observations, the 26-month-old mice showed a higher proportion of labeled poly-PI in the synaptosomal fraction as compared to the younger age group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G Y Sun
- Department of Biochemistry, University of Missouri, School of Medicine, Columbia 65212
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Hawthorn MH, Ferrante JN, Kwon YW, Rutledge A, Luchowski E, Bangalore R, Triggle DJ. Effect of an homologous series of aliphatic alcohols on neuronal and smooth muscle voltage-dependent Ca2+ channels. Eur J Pharmacol 1992; 229:143-8. [PMID: 1337043 DOI: 10.1016/0014-2999(92)90548-i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The acute inhibitory actions of alcohol on K(+)-stimulated 45Ca2+ uptake into synaptosomes shows regional variation in sensitivity throughout the brain, suggesting the possibility of a selective action on a specific Ca2+ channel subtype. This was examined by comparing the effects of a homologous series of aliphatic alcohols on synaptosomal Ca2+ channels with their actions on K(+)-stimulated Ca2+ channels in guinea-pig intestinal longitudinal muscle, which have been demonstrated to be of the L-type. K(+)-stimulated contraction of and [3H]nitrendipine binding to smooth muscle were both inhibited by the alcohols at similar concentrations, with the potency increasing with chain length. In synaptosomes, however, K(+)-stimulated 45Ca2+ uptake was 5-30 times more sensitive to the inhibitory actions of alcohol than were [3H]nitrendipine and [125I]omega-conotoxin binding. These observations suggest that K(+)-stimulated 45Ca2+ uptake is mediated by a non-L non-N type channel which is more sensitive to the acute effects of alcohols. This is supported by the observation that K(+)-stimulated 45Ca2+ uptake which is insensitive to L- and N-channel antagonists was inhibited by funnel web spider venom.
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Affiliation(s)
- M H Hawthorn
- Department of Biochemical Pharmacology, School of Pharmacy, SUNY, Buffalo 14260
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Incerpi S, Jefferson JR, Wood WG, Ball WJ, Schroeder F. Na pump and plasma membrane structure in L-cell fibroblasts expressing rat liver fatty acid binding protein. Arch Biochem Biophys 1992; 298:35-42. [PMID: 1326253 DOI: 10.1016/0003-9861(92)90090-j] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Although the intracellular fatty acid binding proteins have been investigated for nearly two decades and purified proteins are now available, little is known regarding the function of these proteins in intact cells. Therefore, L-cell fibroblasts transfected with cDNA encoding for rat liver fatty acid binding protein (L-FABP) were examined as to whether L-FABP expression in intact cells modifies plasma membrane enzyme activities, fluidity, and lipids. Plasma membrane Na/K-ATPase activity was 65.9 +/- 18.7 and 38.6 +/- 22.8 (P less than 0.001) nmol/mg protein x min for control and high-expression transfected cells, respectively. Consistent with this observation, [3H] ouabain binding to whole cells was significantly decreased from 3.7 +/- 0.3 to 2.0 +/- 0.8 pmol ouabain bound/mg cell protein in control and high-expression cells, respectively, whereas the cell's affinity for ouabain was not significantly altered. Unexpectedly, Western blot analysis indicated that transfected cells had higher levels of Na+, K(+)-ATPase protein; in contrast, the activities of 5'-nucleotidase and Mg-ATPase were unaltered. The effects of L-FABP expression on plasma membrane Na/K-ATPase function appeared to be mediated through alterations in plasma membrane lipids and/or structure. The plasma membrane cholesterol/phospholipid ratio decreased and the bulk plasma membrane fluidity increased in the high-expression cells. In conclusion, plasma membrane Na/K-ATPase activity in L cells may be regulated in part through expression of cytosolic L-FABP.
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Affiliation(s)
- S Incerpi
- Department of Biology, University of Rome Tor Vergata, Italy
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Lazar DF, Medzihradsky F. Altered microviscosity at brain membrane surface induces distinct and reversible inhibition of opioid receptor binding. J Neurochem 1992; 59:1233-40. [PMID: 1328516 DOI: 10.1111/j.1471-4159.1992.tb08432.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In synaptosomal membranes from rat and monkey brain cortex, the addition of petroselenic (18:1, cis-delta 6) acid, oleic (18:1, cis-delta 9) acid, and vaccenic (18:1, cis-delta 11) acid or their corresponding methyl esters at 0.5 mumol/mg of membrane protein caused a similar 7-10% decrease in the microviscosity of the membrane core, whereas at the membrane surface the microviscosity was reduced 5-7% by the fatty acids but only 1% by their methyl esters. Concomitantly, the fatty acids, but not the methyl esters, inhibited the specific binding of the tritiated mu-, delta-, and kappa-opioids Tyr-D-Ala-Gly-(Me)Phe-Gly-ol (DAMGO), [D-Pen2,D-Pen5]enkephalin (DPDPE), and U69,593, respectively. As shown with oleic acid, the sensitivity of opioid receptor binding toward inhibition by fatty acids was in the order delta greater than mu much greater than kappa, whereby the binding of [3H]DPDPE was abolished, but significant inhibition of [3H]U69,593 binding, determined in membranes from monkey brain, required membrane modification with a twofold higher fatty acid concentration. Except for the unchanged KD of [3H]U69,593, the inhibition by oleic acid involved both the Bmax and affinity of opioid binding. Cholesteryl hemisuccinate (0.5-3 mumol/mg of protein), added to membranes previously modified by fatty acids, reversed the fluidization caused by the latter compounds and restored inhibited mu-, delta-, and kappa-opioid binding toward control values. In particular, the Bmax of [3H]-DPDPE binding completely recovered after being undetectable.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D F Lazar
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606
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Rottenberg H, Bittman R, Li HL. Resistance to ethanol disordering of membranes from ethanol-fed rats is conferred by all phospholipid classes. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1123:282-90. [PMID: 1536867 DOI: 10.1016/0005-2760(92)90008-j] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Phospholipids extracted from liver microsomes and mitochondria of ethanol-fed rats retained the resistance to membrane disordered by ethanol which is observed in the intact isolated membranes. The lipid extracts were separated into the major phospholipid classes (phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol from microsomes and phosphatidylcholine, phosphatidylethanolamine and cardiolipin from mitochondria) by preparative TLC. The extent of membrane disordering by ethanol of phospholipid vesicles composed of a mixture of phospholipids from ethanol-fed rats and controls was determined from the reduction of the order parameter of the spin-probe 12-doxyl-stearate. In contrast to previous reports, we found that all phospholipid classes from ethanol-fed rats confer resistance to disordering by ethanol. To a first approximation the extent of resistance was proportional to the fraction of lipids from ethanol-fed rats, regardless of the phospholipid head-group. Subtle differences between phospholipid classes may exist but were too small to measure accurately. Except for phosphatidylethanol, incorporation of anionic phospholipids did not have a significant effect on the sensitivity of phospholipid vesicles to the disordering effect of ethanol. Vesicles prepared from mixtures of various dioleoyl phospholipids and natural phospholipids did not indicate a clear effect of fatty acid saturation on the sensitivity to disordering by ethanol. Although the precise molecular changes that occur in phospholipids from ethanol-fed rats have not been fully characterized it appears that subtle changes in all phospholipid classes contribute to the resistance to ethanol disordering of these membranes.
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Affiliation(s)
- H Rottenberg
- Department of Pathology, Hahnemann University, Philadelphia, PA
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Wood WG, Gorka C, Johnson JA, Sun GY, Sun AY, Schroeder F. Chronic ethanol consumption alters transbilayer distribution of phosphatidylcholine in erythrocytes of Sinclair (S-1) miniature swine. Alcohol 1991; 8:395-9. [PMID: 1797035 DOI: 10.1016/0741-8329(91)90648-g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Effects of chronic ethanol consumption on transbilayer distribution of phospholipids in the exofacial and cytofacial leaflets of erythrocytes from chronic ethanol-consuming Sinclair (S-1) miniature swine were examined. Phosphatidylcholine (PC) was predominantly located in the exofacial leaflet and phosphatidylethanolamine (PE) and phosphatidylserine (PS) located primarily in the cytofacial leaflet. Chronic ethanol consumption significantly increased PC content in the exofacial leaflet without changing bulk membrane PC composition. Ethanol-induced changes in PC distribution were specific for PC and not detected in PE or PS. There was also a significant decrease in sphingomyelin in the ethanol group. Sphingomyelin is primarily an exofacial phospholipid. The specific ethanol-induced changes in the exofacial leaflet are consistent with recent studies showing that the exofacial membrane leaflet is more susceptible to effects of ethanol as compared to the cytofacial leaflet. Such specificity of action provides a new way of viewing how ethanol alters membrane structure and function.
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Affiliation(s)
- W G Wood
- Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center, Minneapolis, MN 55417
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Abstract
Cellular responses of neuronal tissue to chronic ethanol exposure are reviewed. Evidence for adaptive responses to the acute actions of ethanol is available for five systems: GABA-activated chloride channels, voltage-sensitive calcium channels, NMDA-activated cation channels, receptors coupled through stimulatory guanine nucleotide binding proteins, and membrane lipid order. We suggest that at least some of these adaptive responses occur because of ethanol actions at the level of gene expression.
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Affiliation(s)
- K J Buck
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262
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Direct action of ethanol on cerebral GABAA receptor complex: Analysis using purified and reconstituted GABAA receptor complex. Neurochem Int 1991. [DOI: 10.1016/0197-0186(91)90015-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Wood WG, Schroeder F, Hogy L, Rao AM, Nemecz G. Asymmetric distribution of a fluorescent sterol in synaptic plasma membranes: effects of chronic ethanol consumption. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1025:243-6. [PMID: 2364080 DOI: 10.1016/0005-2736(90)90103-u] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ethanol-induced structural changes in membranes have in some studies been attributed to an increase in total membrane cholesterol. Consistent changes in cholesterol content, however, have not been observed in membranes of ethanol consuming animals and alcoholic patients. This study examined the hypotheses that cholesterol was asymmetrically distributed in synaptic plasma membranes (SPM) and that chronic ethanol consumption alters the transbilayer distribution of cholesterol. Dehydroergosterol, a fluorescent cholesterol analogue was used to examine sterol distribution and exchange in chronic ethanol-treated and pair-fed control groups. The cytofacial leaflet was found to have significantly more dehydroergosterol as compared to the exofacial leaflet. This asymmetric distribution was significantly reduced by chronic ethanol consumption as was sterol transport. Total cholesterol content did not differ between the two groups. Chronic ethanol consumption appeared to alter transbilayer sterol distribution as determined by the incorporation and distribution of dehydroergosterol in SPM. The changes in transbilayer sterol distribution are consistent with recent reports on the asymmetric effects of ethanol in vitro ((1988) Biochim. Biophys. Acta 946, 85-94) and in vivo ((1989) J. Neurochem. 52, 1925-1930) on membrane leaflet structure. The results of this study also underscore the importance of examining membrane lipid domains in addition to the total content of different lipids.
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Affiliation(s)
- W G Wood
- Geriatric Research, Education and Clinical Center, VA Medical Center, Minneapolis, MN 55417
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Schroeder F, Kier AB, Sweet WD. Role of polyunsaturated fatty acids and lipid peroxidation in LM fibroblast plasma membrane transbilayer structure. Arch Biochem Biophys 1990; 276:55-64. [PMID: 2297230 DOI: 10.1016/0003-9861(90)90009-n] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of polyunsaturated fatty acids and lipid peroxidation on LM fibroblast plasma membrane individual leaflet sterol distribution and structural order were examined. The cytofacial (inner) leaflet was more rigid and contained more sterol than the exofacial (outer) leaflet. The static (limiting anisotropy) and dynamic (rotational relaxation time) structural components of diphenylhexatriene (DPH) motion in each leaflet were determined by phase and modulation fluorometry measurements combined with leaflet-specific quenching by trinitrophenyl groups. Polyunsaturated fatty acids, incorporated into the membrane phospholipids by culture medium supplementation, decreased the limiting anisotrophy of DPH in the cytofacial but not the exofacial leaflet thereby abolishing the transbilayer difference in fluidity. Peroxidation by Fe(II) + H2O2 resulted in a rigidification (increase in limiting anisotropy and rotational relaxation time) of the plasma membrane exofacial leaflet, regardless of whether the membranes contained saturated and monounsaturated fatty acids or were enriched in either linoleate or linolenate. The structure of the cytofacial leaflet reported by DPH was unaffected. Plasma membrane transbilayer sterol distribution, measured by leaflet-specific quenching of dehydroergosterol fluorescence, indicated that 20-28% of the sterol was localized in the exofacial leaflet. Polyunsaturated fatty acid supplementation of LM fibroblasts resulted in a complete reversal of plasma membrane transbilayer sterol distribution (72-76% exofacial leaflet). Sterol transbilayer distribution between the membrane leaflets was completely resistant to alteration by exposure to crosslinking agents and peroxidation in control plasma membranes and by peroxidation in linoleate- or linolenate-supplemented membranes.
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Affiliation(s)
- F Schroeder
- Department of Pharmacology and Medicinal Chemistry, College of Pharmacy, University of Cincinnati Medical Center, Ohio 45267-0004
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