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Sherratt SCR, Mason RP, Libby P, Steg PG, Bhatt DL. Do patients benefit from omega-3 fatty acids? Cardiovasc Res 2024; 119:2884-2901. [PMID: 38252923 PMCID: PMC10874279 DOI: 10.1093/cvr/cvad188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/11/2023] [Accepted: 09/26/2023] [Indexed: 01/24/2024] Open
Abstract
Omega-3 fatty acids (O3FAs) possess beneficial properties for cardiovascular (CV) health and elevated O3FA levels are associated with lower incident risk for CV disease (CVD.) Yet, treatment of at-risk patients with various O3FA formulations has produced disparate results in large, well-controlled and well-conducted clinical trials. Prescription formulations and fish oil supplements containing low-dose mixtures of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have routinely failed to prevent CV events in primary and secondary prevention settings when added to contemporary care, as shown most recently in the STRENGTH and OMEMI trials. However, as observed in JELIS, REDUCE-IT, and RESPECT-EPA, EPA-only formulations significantly reduce CVD events in high-risk patients. The CV mechanism of action of EPA, while certainly multifaceted, does not depend solely on reductions of circulating lipids, including triglycerides (TG) and LDL, and event reduction appears related to achieved EPA levels suggesting that the particular chemical and biological properties of EPA, as compared to DHA and other O3FAs, may contribute to its distinct clinical efficacy. In vitro and in vivo studies have shown different effects of EPA compared with DHA alone or EPA/DHA combination treatments, on atherosclerotic plaque morphology, LDL and membrane oxidation, cholesterol distribution, membrane lipid dynamics, glucose homeostasis, endothelial function, and downstream lipid metabolite function. These findings indicate that prescription-grade, EPA-only formulations provide greater benefit than other O3FAs formulations tested. This review summarizes the clinical findings associated with various O3FA formulations, their efficacy in treating CV disease, and their underlying mechanisms of action.
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Affiliation(s)
- Samuel C R Sherratt
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH, USA
- Elucida Research LLC, Beverly, MA, USA
| | - R Preston Mason
- Elucida Research LLC, Beverly, MA, USA
- Department of Medicine, Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Peter Libby
- Department of Medicine, Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Ph Gabriel Steg
- Université Paris-Cité, INSERM_UMR1148/LVTS, FACT (French Alliance for Cardiovascular Trials), Assistance Publique–Hôpitaux de Paris, Hôpital Bichat, Paris, France
| | - Deepak L Bhatt
- Mount Sinai Fuster Heart Hospital, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, NewYork 10029-5674, NY, USA
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2
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Guo J, Chen S, Zhang Y, Liu J, Jiang L, Hu L, Yao K, Yu Y, Chen X. Cholesterol metabolism: physiological regulation and diseases. MedComm (Beijing) 2024; 5:e476. [PMID: 38405060 PMCID: PMC10893558 DOI: 10.1002/mco2.476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 01/09/2024] [Accepted: 01/12/2024] [Indexed: 02/27/2024] Open
Abstract
Cholesterol homeostasis is crucial for cellular and systemic function. The disorder of cholesterol metabolism not only accelerates the onset of cardiovascular disease (CVD) but is also the fundamental cause of other ailments. The regulation of cholesterol metabolism in the human is an extremely complex process. Due to the dynamic balance between cholesterol synthesis, intake, efflux and storage, cholesterol metabolism generally remains secure. Disruption of any of these links is likely to have adverse effects on the body. At present, increasing evidence suggests that abnormal cholesterol metabolism is closely related to various systemic diseases. However, the exact mechanism by which cholesterol metabolism contributes to disease pathogenesis remains unclear, and there are still unknown factors. In this review, we outline the metabolic process of cholesterol in the human body, especially reverse cholesterol transport (RCT). Then, we discuss separately the impact of abnormal cholesterol metabolism on common diseases and potential therapeutic targets for each disease, including CVD, tumors, neurological diseases, and immune system diseases. At the end of this review, we focus on the effect of cholesterol metabolism on eye diseases. In short, we hope to provide more new ideas for the pathogenesis and treatment of diseases from the perspective of cholesterol.
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Affiliation(s)
- Jiarui Guo
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Silong Chen
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Ying Zhang
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
- Institute of Translational MedicineZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Jinxia Liu
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Luyang Jiang
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Lidan Hu
- National Clinical Research Center for Child HealthThe Children's HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Ke Yao
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Yibo Yu
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
| | - Xiangjun Chen
- Eye Center of the Second Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
- Institute of Translational MedicineZhejiang University School of MedicineHangzhouZhejiang ProvinceChina
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3
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Subczynski WK, Pasenkiewicz-Gierula M, Widomska J. Protecting the Eye Lens from Oxidative Stress through Oxygen Regulation. Antioxidants (Basel) 2023; 12:1783. [PMID: 37760086 PMCID: PMC10525422 DOI: 10.3390/antiox12091783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 09/08/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
Molecular oxygen is a primary oxidant that is involved in the formation of active oxygen species and in the oxidation of lipids and proteins. Thus, controlling oxygen partial pressure (concentration) in the human organism, tissues, and organs can be the first step in protecting them against oxidative stress. However, it is not an easy task because oxygen is necessary for ATP synthesis by mitochondria and in many biochemical reactions taking place in all cells in the human body. Moreover, the blood circulatory system delivers oxygen to all parts of the body. The eye lens seems to be the only organ that is protected from the oxidative stress through the regulation of oxygen partial pressure. The basic mechanism that developed during evolution to protect the eye lens against oxidative damage is based on the maintenance of a very low concentration of oxygen within the lens. This antioxidant mechanism is supported by the resistance of both the lipid components of the lens membrane and cytosolic proteins to oxidation. Any disturbance, continuous or acute, in the working of this mechanism increases the oxygen concentration, in effect causing cataract development. Here, we describe the biophysical basis of the mechanism and its correlation with lens transparency.
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Affiliation(s)
| | - Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, Jagiellonian University, 30-387 Krakow, Poland;
| | - Justyna Widomska
- Department of Biophysics, Medical University of Lublin, 20-090 Lublin, Poland
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Boban Z, Mardešić I, Jozić SP, Šumanovac J, Subczynski WK, Raguz M. Electroformation of Giant Unilamellar Vesicles from Damp Lipid Films Formed by Vesicle Fusion. MEMBRANES 2023; 13:352. [PMID: 36984739 PMCID: PMC10059949 DOI: 10.3390/membranes13030352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/14/2023] [Accepted: 03/16/2023] [Indexed: 06/18/2023]
Abstract
Giant unilamellar vesicles (GUVs) are artificial membrane models which are of special interest to researchers because of their similarity in size to eukaryotic cells. The most commonly used method for GUVs production is electroformation. However, the traditional electroformation protocol involves a step in which the organic solvent is completely evaporated, leaving behind a dry lipid film. This leads to artifactual demixing of cholesterol (Chol) in the form of anhydrous crystals. These crystals do not participate in the formation of the lipid bilayer, resulting in a decrease of Chol concentration in the bilayer compared to the initial lipid solution. We propose a novel electroformation protocol which addresses this issue by combining the rapid solvent exchange, plasma cleaning and spin-coating techniques to produce GUVs from damp lipid films in a fast and reproducible manner. We have tested the protocol efficiency using 1/1 phosphatidylcholine/Chol and 1/1/1 phosphatidylcholine/sphingomyelin/Chol lipid mixtures and managed to produce a GUV population of an average diameter around 40 µm, with many GUVs being larger than 100 µm. Additionally, compared to protocols that include the dry film step, the sizes and quality of vesicles determined from fluorescence microscopy images were similar or better, confirming the benefits of our protocol in that regard as well.
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Affiliation(s)
- Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | - Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | - Sanja Perinović Jozić
- Department of Organic Technology, Faculty of Chemistry and Technology, University of Split, 21000 Split, Croatia
| | - Josipa Šumanovac
- Department of Physics, Faculty of Science, University of Split, 21000 Split, Croatia
| | | | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
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5
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Mardešić I, Boban Z, Subczynski WK, Raguz M. Membrane Models and Experiments Suitable for Studies of the Cholesterol Bilayer Domains. MEMBRANES 2023; 13:320. [PMID: 36984707 PMCID: PMC10057498 DOI: 10.3390/membranes13030320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 06/18/2023]
Abstract
Cholesterol (Chol) is an essential component of animal cell membranes and is most abundant in plasma membranes (PMs) where its concentration typically ranges from 10 to 30 mol%. However, in red blood cells and Schwann cells, PMs Chol content is as high as 50 mol%, and in the PMs of the eye lens fiber cells, it can reach up to 66 mol%. Being amphiphilic, Chol molecules are easily incorporated into the lipid bilayer where they affect the membrane lateral organization and transmembrane physical properties. In the aqueous phase, Chol cannot form free bilayers by itself. However, pure Chol bilayer domains (CBDs) can form in lipid bilayer membranes with the Chol content exceeding 50 mol%. The range of Chol concentrations surpassing 50 mol% is less frequent in biological membranes and is consequently less investigated. Nevertheless, it is significant for the normal functioning of the eye lens and understanding how Chol plaques form in atherosclerosis. The most commonly used membrane models are unilamellar and multilamellar vesicles (MLVs) and supported lipid bilayers (SLBs). CBDs have been observed directly using confocal microscopy, X-ray reflectometry and saturation recovery electron paramagnetic resonance (SR EPR). Indirect evidence of CBDs has also been reported by using atomic force microscopy (AFM) and fluorescence recovery after photobleaching (FRAP) experiments. The overall goal of this review is to demonstrate the advantages and limitations of the various membrane models and experimental techniques suitable for the detection and investigation of the lateral organization, function and physical properties of CBDs.
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Affiliation(s)
- Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | - Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | | | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
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6
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Bach D, Wachtel E. Cholesterol solubility in mixed DMPE/DMPC bilayers as determined by small angle X-ray scattering. Biophys Chem 2023; 297:107014. [PMID: 37027969 DOI: 10.1016/j.bpc.2023.107014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 04/03/2023]
Abstract
Small angle X-ray scattering measurements under ambient conditions (T ≈ 294 K) provide evidence for the formation of separate domains in a ternary, mixed phospholipid ([DMPE]/[DMPC] = 3/1) / cholesterol model bilayer membrane. As we interpret these results, the domains contain cholesterol and DMPC, with which cholesterol is known to preferentially interact in a binary model membrane (solubility limit, mol fraction cholesterol 0.5), as compared to DMPE (solubility limit, mol fraction cholesterol 0.45). The solubility limit for the ternary system is mol fraction cholesterol 0.2-0.3. Although literature EPR spectra find that non-crystalline, cholesterol bilayer domains may be present even prior to the observation of cholesterol crystal diffraction, X-ray scattering cannot detect their presence.
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Affiliation(s)
- Diana Bach
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Ellen Wachtel
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel.
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Mainali L, Raguz M, Subczynski WK. Quantification of Age-Related Changes in the Lateral Organization of the Lipid Portion of the Intact Membranes Isolated from the Left and Right Eye Lenses of the Same Human Donor. MEMBRANES 2023; 13:189. [PMID: 36837692 PMCID: PMC9958954 DOI: 10.3390/membranes13020189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 01/26/2023] [Accepted: 02/01/2023] [Indexed: 06/18/2023]
Abstract
The continuous wave EPR spin-labeling method was used to evaluate age-related changes in the amounts of phospholipids (PLs) and cholesterol (Chol) in domains present in intact, cortical, and nuclear fiber cell plasma membranes isolated separately from the left and right eye lenses of the same human donor. The relative amounts of boundary plus trapped PLs were evaluated with the PL analog 12-doxylstearic acid spin label (12-SASL) and the relative amounts of trapped Chol with the Chol analog androstane spin label (ASL). The donors ranged in age from 15 to 70 years. Both the left and right eye lenses from donors aged 60, 65, and 70 years had nuclear cataracts; additionally, the right eye lens only of the 60-year-old donor had a cortical cataract. In transparent lenses, the relative amounts of boundary plus trapped PLs increase monotonously with donor age, and, at all ages, this amount was greater in nuclear compared with cortical membranes. Moreover, in transparent lenses, the relative amount of trapped Chol increases with age in nuclear membranes. However, the EPR spectrum of ASL from cortical membranes of 15- to 60-year-old donors shows only the weakly immobilized component assigned to ASL in the bulk plus Chol bilayer domain. Only the cortical membranes of 61- to 70-year-old donors contain both weakly and strongly immobilized components. The strongly immobilized component is assigned to ASL in trapped lipids. We speculate that the age of 60 years may be considered as a "threshold" for appearance of trapped lipids in cortical membranes. The relative amounts of boundary plus trapped PLs in lenses with nuclear cataracts is lower than that predicted from the tendency of the age-dependent increase observed for transparent lenses. The differences in amounts of lipids in the indicated left and right eye domains of each donor are smaller than the differences in single donors of a similar age.
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Affiliation(s)
- Laxman Mainali
- Department of Physics, Boise State University, Boise, ID 83725, USA
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID 83725, USA
| | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia
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8
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Cholesterol crystals and atherosclerotic plaque instability: Therapeutic potential of Eicosapentaenoic acid. Pharmacol Ther 2022; 240:108237. [PMID: 35772589 DOI: 10.1016/j.pharmthera.2022.108237] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 12/15/2022]
Abstract
Atherosclerotic plaques associated with acute coronary syndromes (ACS), i.e. culprit lesions, frequently feature a ruptured fibrous cap with thrombotic complications. On imaging, these plaques exhibit a low attenuation, lipid-rich, necrotic core containing cholesterol crystals and are inherently unstable. Indeed, cholesterol crystals are causally associated with plaque vulnerability in vivo; their formation results from spontaneous self-assembly of cholesterol molecules. Cholesterol homeostasis is a central determinant of the physicochemical conditions leading to crystal formation, which are favored by elevated membrane free cholesterol content in plaque endothelial cells, smooth muscle cells, monocyte-derived macrophages, and foam cells, and equally by lipid oxidation. Emerging evidence from imaging trials in patients with coronary heart disease has highlighted the impact of intervention involving the omega-3 fatty acid, eicosapentaenoic acid (EPA), on vulnerable, low attenuation atherosclerotic plaques. Thus, EPA decreased features associated with unstable plaque by increasing fibrous cap thickness in statin-treated patients, by reducing lipid volume and equally attenuating intraplaque inflammation. Importantly, atherosclerotic plaques rapidly incorporate EPA; indeed, a high content of EPA in plaque tissue is associated with decreased plaque inflammation and increased stability. These findings are entirely consistent with the major reduction seen in cardiovascular events in the REDUCE-IT trial, in which high dose EPA was administered as its esterified precursor, icosapent ethyl (IPE); moreover, clinical benefit was proportional to circulating EPA levels. Eicosapentaenoic acid is efficiently incorporated into phospholipids, where it modulates cholesterol-enriched domains in cell membranes through physicochemical lipid interactions and changes in rates of lipid oxidation. Indeed, biophysical analyses indicate that EPA exists in an extended conformation in membranes, thereby enhancing normal cholesterol distribution while reducing propagation of free radicals. Such effects mitigate cholesterol aggregation and crystal formation. In addition to its favorable effect on cholesterol domain structure, EPA/IPE exerts pleiotropic actions, including antithrombotic, antiplatelet, anti-inflammatory, and proresolving effects, whose plaque-stabilizing potential cannot be excluded. Docosahexaenoic acid is distinguished from EPA by a higher degree of unsaturation and longer carbon chain length; DHA is thus predisposed to changes in its conformation with ensuing increase in membrane lipid fluidity and promotion of cholesterol aggregation into discrete domains. Such distinct molecular effects between EPA and DHA are pronounced under conditions of high cellular cholesterol content and oxidative stress. This review will focus on the formation and role of cholesterol monohydrate crystals in destabilizing atherosclerotic plaques, and on the potential of EPA as a therapeutic agent to attenuate the formation of deleterious cholesterol membrane domains and of cholesterol crystals. Such a therapeutic approach may translate to enhanced plaque stability and ultimately to reduction in cardiovascular risk.
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Ruiz-Fernández AR, Campos L, Gutierrez-Maldonado SE, Núñez G, Villanelo F, Perez-Acle T. Nanosecond Pulsed Electric Field (nsPEF): Opening the Biotechnological Pandora’s Box. Int J Mol Sci 2022; 23:ijms23116158. [PMID: 35682837 PMCID: PMC9181413 DOI: 10.3390/ijms23116158] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/23/2022] [Accepted: 05/23/2022] [Indexed: 02/04/2023] Open
Abstract
Nanosecond Pulsed Electric Field (nsPEF) is an electrostimulation technique first developed in 1995; nsPEF requires the delivery of a series of pulses of high electric fields in the order of nanoseconds into biological tissues or cells. They primary effects in cells is the formation of membrane nanopores and the activation of ionic channels, leading to an incremental increase in cytoplasmic Ca2+ concentration, which triggers a signaling cascade producing a variety of effects: from apoptosis up to cell differentiation and proliferation. Further, nsPEF may affect organelles, making nsPEF a unique tool to manipulate and study cells. This technique is exploited in a broad spectrum of applications, such as: sterilization in the food industry, seed germination, anti-parasitic effects, wound healing, increased immune response, activation of neurons and myocites, cell proliferation, cellular phenotype manipulation, modulation of gene expression, and as a novel cancer treatment. This review thoroughly explores both nsPEF’s history and applications, with emphasis on the cellular effects from a biophysics perspective, highlighting the role of ionic channels as a mechanistic driver of the increase in cytoplasmic Ca2+ concentration.
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Affiliation(s)
- Alvaro R. Ruiz-Fernández
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
- Correspondence: (A.R.R.-F.); (T.P.-A.)
| | - Leonardo Campos
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Sebastian E. Gutierrez-Maldonado
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Gonzalo Núñez
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
| | - Felipe Villanelo
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Tomas Perez-Acle
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
- Correspondence: (A.R.R.-F.); (T.P.-A.)
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10
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Boban Z, Mardešić I, Subczynski WK, Jozić D, Raguz M. Optimization of Giant Unilamellar Vesicle Electroformation for Phosphatidylcholine/Sphingomyelin/Cholesterol Ternary Mixtures. MEMBRANES 2022; 12:membranes12050525. [PMID: 35629851 PMCID: PMC9144572 DOI: 10.3390/membranes12050525] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 04/27/2022] [Accepted: 05/13/2022] [Indexed: 11/25/2022]
Abstract
Artificial vesicles are important tools in membrane research because they enable studying membrane properties in controlled conditions. Giant unilamellar vesicles (GUVs) are specially interesting due to their similarity in size to eukaryotic cells. We focus on optimization of GUV production from phosphatidylcholine/sphingomyelin/cholesterol mixtures using the electroformation method. This mixture has been extensively researched lately due to its relevance for the formation of lipid rafts. We measured the effect of voltage, frequency, lipid film thickness, and cholesterol (Chol) concentration on electroformation successfulness using spin-coating for reproducible lipid film deposition. Special attention is given to the effect of Chol concentrations above the phospholipid bilayer saturation threshold. Such high concentrations are of interest to groups studying the role of Chol in the fiber cell plasma membranes of the eye lens or development of atherosclerosis. Utilizing atomic force and fluorescence microscopy, we found the optimal lipid film thickness to be around 30 nm, and the best frequency–voltage combinations in the range of 2–6 V and 10–100 Hz. Increasing the Chol content, we observed a decrease in GUV yield and size. However, the effect was much less pronounced when the optimal lipid film thickness was used. The results underline the need for simultaneous optimization of both electrical parameters and thickness in order to produce high-quality GUVs for experimental research.
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Affiliation(s)
- Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | - Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | | | - Dražan Jozić
- Faculty of Chemistry and Technology, University of Split, 21000 Split, Croatia;
| | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Correspondence: ; Tel.: +385-9876-8819
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11
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Khadka NK, Mortimer MF, Marosvari M, Timsina R, Mainali L. Membrane elasticity modulated by cholesterol in model of porcine eye lens-lipid membrane. Exp Eye Res 2022; 220:109131. [PMID: 35636489 PMCID: PMC10131281 DOI: 10.1016/j.exer.2022.109131] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 05/08/2022] [Accepted: 05/22/2022] [Indexed: 11/29/2022]
Abstract
Experimental evidence shows that the eye lens loses its elasticity dramatically with age. It has also been reported that the cholesterol (Chol) content in the eye lens fiber cell plasma membrane increases significantly with age. High Chol content leads to the formation of cholesterol bilayer domains (CBDs) in the lens membrane. The role of high Chol associated with lens elasticity is unclear. The purpose of this research is to investigate the membrane elasticity of the model of porcine lens-lipid (MPLL) membrane with increasing Chol content to elucidate the role of high Chol in lens membrane elasticity. In this study, we used atomic force microscopy (AFM) to study the mechanical properties (breakthrough force and area compressibility modulus (KA)) of the MPLL membrane with increasing Chol content where KA is the measure of membrane elasticity. We varied Chol concentration in Chol/MPLL membrane from 0 to ∼71 mol%. Supported Chol/MPLL membranes were prepared by fusion of small unilamellar vesicles (SUVs) on top of a flat mica surface. SUVs of the Chol/MPLL lipid mixture were prepared with the rapid solvent exchange method followed by probe-tip sonication. For the Chol/MPLL mixing ratio of 0, AFM image showed the formation of two distinct phases of the membrane, i.e., liquid-disordered phase (ld) and solid-ordered phase (so) membrane. However, with Chol/MPLL mixing ratio of 0.5 and above, only liquid-ordered phase (lo) membrane was formed. Also, two distinct breakthrough forces corresponding to ld and so were observed for Chol/MPLL mixing ratio of 0, whereas only one breakthrough force was observed for membranes with Chol/MPLL mixing ratio of 0.5 and above. No significant difference in the membrane surface roughness was measured with increasing Chol content for these membranes; however, breakthrough force and KA for lo membrane increased when Chol/MPLL mixing ratio was increased from 0.5 to 1. Interestingly above the Chol/MPLL mixing ratio of 1, both breakthrough force and KA decreased, indicating the formation of CBDs. Furthermore, these results showed that membrane elasticity increases at high Chol content, suggesting that high Chol content in lens membrane might be responsible for maintaining lens membrane elasticity.
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Affiliation(s)
- Nawal K Khadka
- Department of Physics, Boise State University, Boise, ID, USA
| | | | - Mason Marosvari
- Department of Physics, Boise State University, Boise, ID, USA
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID, USA
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID, USA; Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA.
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12
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Boban Z, Mardešić I, Subczynski WK, Raguz M. Giant Unilamellar Vesicle Electroformation: What to Use, What to Avoid, and How to Quantify the Results. MEMBRANES 2021; 11:membranes11110860. [PMID: 34832088 PMCID: PMC8622294 DOI: 10.3390/membranes11110860] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/03/2021] [Accepted: 11/05/2021] [Indexed: 12/12/2022]
Abstract
Since its inception more than thirty years ago, electroformation has become the most commonly used method for growing giant unilamellar vesicles (GUVs). Although the method seems quite straightforward at first, researchers must consider the interplay of a large number of parameters, different lipid compositions, and internal solutions in order to avoid artifactual results or reproducibility problems. These issues motivated us to write a short review of the most recent methodological developments and possible pitfalls. Additionally, since traditional manual analysis can lead to biased results, we have included a discussion on methods for automatic analysis of GUVs. Finally, we discuss possible improvements in the preparation of GUVs containing high cholesterol contents in order to avoid the formation of artifactual cholesterol crystals. We intend this review to be a reference for those trying to decide what parameters to use as well as an overview providing insight into problems not yet addressed or solved.
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Affiliation(s)
- Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Doctoral Study of Biophysics, Faculty of Science, University of Split, 21000 Split, Croatia
| | - Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Doctoral Study of Biophysics, Faculty of Science, University of Split, 21000 Split, Croatia
| | | | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (Z.B.); (I.M.)
- Correspondence: ; Tel.: +385-98-768-819
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13
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Khadka NK, Timsina R, Rowe E, O'Dell M, Mainali L. Mechanical properties of the high cholesterol-containing membrane: An AFM study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183625. [PMID: 33891910 DOI: 10.1016/j.bbamem.2021.183625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 04/02/2021] [Accepted: 04/12/2021] [Indexed: 12/11/2022]
Abstract
Cholesterol (Chol) content in most cellular membranes does not exceed 50 mol%, only in the eye lens's fiber cell plasma membrane, its content surpasses 50 mol%. At this high concentration, Chol induces the formation of pure cholesterol bilayer domains (CBDs), which coexist with the surrounding phospholipid-cholesterol domain (PCD). Here, we applied atomic force microscopy to study the mechanical properties of Chol/phosphatidylcholine membranes where the Chol content was increased from 0 to 75 mol%, relevant to eye lens membranes. The surface roughness of the membrane decreases with an increase of Chol content until it reaches 60 mol%, and roughness increases with a further increment in Chol content. We propose that the increased roughness at higher Chol content results from the formation of CBDs. Force spectroscopy on the membrane with Chol content of 50 mol% or lesser exhibited single breakthrough events, whereas two distinct puncture events were observed for membranes with the Chol content greater than 50 mol%. We propose that the first puncture force corresponds to the membranes containing coexisting PCD and CBDs. In contrast, the second puncture force corresponds to the "CBD water pocket" formed due to coexisting CBDs and PCD. Membrane area compressibility modulus (KA) increases with an increase in Chol content until it reaches 60 mol%, and with further increment in Chol content, CBDs are formed, and KA starts to decrease. Our results report the increase in membrane roughness and decrease KA at very high Chol content (>60 mol%) relevant to the eye lens membrane.
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Affiliation(s)
- Nawal K Khadka
- Department of Physics, Boise State University, Boise, ID, USA
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID, USA
| | - Erica Rowe
- Department of Biology, Boise State University, Boise, ID, USA
| | - Matthew O'Dell
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID, USA; Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA.
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14
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Ma GJ, Zhdanov VP, Park S, Sut TN, Cho NJ. Mechanistic Aspects of the Evolution of 3D Cholesterol Crystallites in a Supported Lipid Membrane via a Quartz Crystal Microbalance with Dissipation Monitoring. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:4562-4570. [PMID: 33834785 DOI: 10.1021/acs.langmuir.1c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The irreversible formation of cholesterol monohydrate crystals within biological membranes is the leading cause of various diseases, including atherosclerosis. Understanding the process of cholesterol crystallization is fundamentally important and could also lead to the development of improved therapeutic strategies. This has driven several studies investigating the effect of the environmental parameters on the induction of cholesterol crystallite growth and the structure of the cholesterol crystallites, while the kinetics and mechanistic aspects of the crystallite formation process within lipid membranes remain poorly understood. Herein, we fabricated cholesterol crystallites within a supported lipid bilayer (SLB) by adsorbing a cholesterol-rich bicellar mixture onto a glass and silica surface and investigated the real-time kinetics of cholesterol crystallite nucleation and growth using epifluorescence microscopy and quartz crystal microbalance with dissipation (QCM-D) monitoring. Microscopic imaging showed the evolution of the morphology of cholesterol crystallites from nanorod- and plate-shaped habits during the initial stage to mostly large, micron-sized three-dimensional (3D) plate-shaped crystallites in the end, which was likened to Ostwald ripening. QCM-D kinetics revealed unique signal responses during the later stage of the growth process, characterized by simultaneous positive frequency shifts, nonmonotonous energy dissipation shifts, and significant overtone dependence. Based on the optically observed changes in crystallite morphology, we discussed the physical background of these unique QCM-D signal responses and the mechanistic aspects of Ostwald ripening in this system. Together, our findings revealed mechanistic details of the cholesterol crystallite growth kinetics, which may be useful in biointerfacial sensing and bioanalytical applications.
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Affiliation(s)
- Gamaliel Junren Ma
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
| | - Vladimir P Zhdanov
- Boreskov Institute of Catalysis, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Soohyun Park
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
| | - Tun Naw Sut
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
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15
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Pedroni VI, Sierra MB, Alarcón LM, Verde AR, Appignanesi GA, Morini MA. A certain proportion of docosahexaenoic acid tends to revert structural and dynamical effects of cholesterol on lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183584. [PMID: 33571481 DOI: 10.1016/j.bbamem.2021.183584] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/29/2021] [Accepted: 02/05/2021] [Indexed: 12/19/2022]
Abstract
This work investigates how docosahexaenoic acid (DHA) modifies the effect of Cholesterol (Chol) on the structural and dynamical properties of dipalmitoylphosphatidylcholine (DPPC) membrane. We employ low-cost and non-invasive methods: zeta potential (ZP), conductivity, density, and ultrasound velocity, complemented by molecular dynamics simulations. Our studies reveal that 30% of DHA added to the DPPC-Chol system tends to revert Chol action on a model lipid bilayer. Results obtained in this work shed light on the effect of polyunsaturated fatty acids - particularly DHA - on lipid membranes, with potential preventive applications in many diseases, e.g. neuronal as, Alzheimer's disease, and viral, as Covid-19.
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Affiliation(s)
- V I Pedroni
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina
| | - M B Sierra
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina
| | - L M Alarcón
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina
| | - A R Verde
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina
| | - G A Appignanesi
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina
| | - M A Morini
- Laboratorio de Fisicoquímica, INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Buenos Aires, Argentina.
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16
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Hypothetical Pathway for Formation of Cholesterol Microcrystals Initiating the Atherosclerotic Process. Cell Biochem Biophys 2020; 78:241-247. [PMID: 32602057 PMCID: PMC7403164 DOI: 10.1007/s12013-020-00925-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 06/08/2020] [Indexed: 12/31/2022]
Abstract
Major factors leading to the development of atherosclerosis are a high cholesterol (Chol) level in the blood and oxidative stress. Both promote the formation of Chol microcrystals in blood vessel walls. Deposition of Chol microcrystals in arterial intima causes inflammation, which initiates and accompanies the atherosclerotic process in all its phases. One of the possible sources of Chol in the blood vessel walls is oxidized low-density lipoproteins-this atherosclerotic plaque formation pathway has already been described in the literature. Here, we hypothesize that initiation of the atherosclerotic process may involve Chol domains in the plasma membranes of arterial cells. Increased Chol content and the presence of polyunsaturated phospholipids in these membranes together with oxidative stress (phospholipid peroxidation) may lead to the formation of pure Chol bilayer domains that, with further peroxidation and increased Chol content, may collapse in the form of Chol seed crystals. Independent of their origin, Chol microcrystals activate inflammasomes, thereby stimulate immune responses, and initiate inflammation that may lead to the development of atherosclerosis. This new, hypothetical pathway has not yet been investigated in depth; however, data from the literature and our own results support its feasibility.
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17
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Boban Z, Puljas A, Kovač D, Subczynski WK, Raguz M. Effect of Electrical Parameters and Cholesterol Concentration on Giant Unilamellar Vesicles Electroformation. Cell Biochem Biophys 2020; 78:157-164. [PMID: 32319021 DOI: 10.1007/s12013-020-00910-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 03/30/2020] [Indexed: 10/23/2022]
Abstract
Giant unilamellar vesicles (GUVs) are used extensively as models that mimic cell membranes. The cholesterol (Chol) content in the fiber cell plasma membranes of the eye lens is extremely high, exceeding the solubility threshold in the lenses of old humans. Thus, a methodological paper pertaining to preparations of model lipid bilayer membranes with high Chol content would significantly help the study of properties of these membranes. Lipid solutions containing 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) and Chol were fluorescently labeled with phospholipid analog 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiIC18(3)) and spin-coated to produce thin lipid films. GUVs were formed from these films using the electroformation method and the results were obtained using fluorescent microscopy. Electroformation outcomes were examined for different electrical parameters and different Chol concentrations. A wide range of field frequency-field strength (ff-fs) combinations was explored: 10-10,000 Hz and 0.625-9.375 V/mm peak-to-peak. Optimal values for GUVs preparation were found to be 10-100 Hz and 1.25-6.25 V/mm, with largest vesicles occurring for 10 Hz and 3.75 V/mm. Chol:POPC mixing ratios (expressed as a molar ratio) ranged from 0 to 3.5. We show that increasing the Chol concentration decreases the GUVs size, but this effect can be reduced by choosing the appropriate ff-fs combination.
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Affiliation(s)
- Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, Split, Croatia.,University of Split, Faculty of Science, Doctoral study of Biophysics, Split, Croatia
| | - Ana Puljas
- Department of Medical Physics and Biophysics, University of Split School of Medicine, Split, Croatia
| | - Dubravka Kovač
- Department of Physics, Faculty of Science, University of Split, Split, Croatia
| | | | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, Split, Croatia.
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18
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Sut TN, Park S, Choe Y, Cho NJ. Characterizing the Supported Lipid Membrane Formation from Cholesterol-Rich Bicelles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15063-15070. [PMID: 31670521 DOI: 10.1021/acs.langmuir.9b02851] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Supported lipid bilayers (SLBs) are simplified model membrane systems that mimic the fundamental properties of biological cell membranes and allow the surface-sensitive tools to be used in numerous sensing applications. SLBs can be prepared by various methods including vesicle fusion, solvent-assisted lipid bilayer (SALB), and bicelle adsorption and are generally composed of phospholipids. Incorporating other biologically relevant molecules, such as cholesterol (Chol), into SLBs has been reported with the vesicle fusion and SALB methods, whereas it remains unexplored with the bicelle absorption method. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and fluorescence microscopy techniques, we explored the possibility of forming SLBs from Chol-containing bicelles and discovered that Chol-enriched SLBs can be fabricated with bicelles. We also compared the Chol-enriched SLB formation of the bicelle method to that of vesicle fusion and SALB and discussed how the differences in lipid assembly properties can cause the differences in the adsorption kinetics and final results of SLB formation. Collectively, our findings demonstrate that the vesicle fusion method is least favorable for forming Chol-enriched SLBs, whereas the SALB and bicelle methods are more favorable, highlighting the need to consider the application requirements when choosing a suitable method for the formation of Chol-enriched SLBs.
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Affiliation(s)
- Tun Naw Sut
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Soohyun Park
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Younghwan Choe
- Department of Chemistry , Columbia University , 3000 Broadway , New York 10027 , United States
| | - Nam-Joon Cho
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
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19
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Raguz M, Kumar SN, Zareba M, Ilic N, Mainali L, Subczynski WK. Confocal Microscopy Confirmed that in Phosphatidylcholine Giant Unilamellar Vesicles with very High Cholesterol Content Pure Cholesterol Bilayer Domains Form. Cell Biochem Biophys 2019; 77:309-317. [PMID: 31625023 DOI: 10.1007/s12013-019-00889-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 09/28/2019] [Indexed: 12/14/2022]
Abstract
The cholesterol (Chol) content in the fiber cell plasma membranes of the eye lens is extremely high, exceeding the solubility threshold in the lenses of old humans. This high Chol content forms pure Chol bilayer domains (CBDs) and Chol crystals in model membranes and membranes formed from the total lipid extracts from human lenses. CBDs have been detected using electron paramagnetic resonance (EPR) spin-labeling approaches. Here, we confirm the presence of CBDs in giant unilamellar vesicles prepared using the electroformation method from Chol/1-palmitoyl-2-oleoylphosphocholine and Chol/distearoylphosphatidylcholine mixtures. Confocal microscopy experiments using phospholipid (PL) analog (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-5,5'-disulfonic acid) and cholesterol analog fluorescent probes (23-(dipyrrometheneboron difluoride)-24-norcholesterol) were performed, allowing us to make three major conclusions: (1) In all membranes with a Chol/PL mixing ratio (expressed as a molar ratio) >2, pure CBDs were formed within the bulk PL bilayer saturated with Chol. (2) CBDs were present as the pure Chol bilayer and not as separate patches of Chol monolayers in each leaflet of the PL bilayer. (3) CBDs, presented as single large domains, were always located at the top of giant unilamellar vesicles, independent of the change in sample orientation (right-side-up/upside-down). Results obtained with confocal microscopy and fluorescent Chol and PL analogs, combined with those obtained using EPR and spin-labeled Chol and PL analogs, contribute to the understanding of the organization of lipids in the fiber cell plasma membranes of the human eye lens.
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Affiliation(s)
- Marija Raguz
- Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia. .,Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.
| | - Suresh N Kumar
- Department of Pathology, CRI Imaging Core, Translational and Biomedical Research Center, Medical College of Wisconsin, Wauwatosa, WI, USA
| | - Mariusz Zareba
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Ophthalmology, Medical College of Wisconsin Eye Institute, Milwaukee, WI, USA
| | - Nada Ilic
- Department of Physics, Faculty of Science, University of Split, Split, Croatia
| | - Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Physics, Boise State University, 1910 University Drive, Boise, Idaho, 83725, USA
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20
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Why Is Very High Cholesterol Content Beneficial for the Eye Lens but Negative for Other Organs? Nutrients 2019; 11:nu11051083. [PMID: 31096723 PMCID: PMC6566707 DOI: 10.3390/nu11051083] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 12/13/2022] Open
Abstract
The plasma membranes of the human lens fiber cell are overloaded with cholesterol that not only saturates the phospholipid bilayer of these membranes but also leads to the formation of pure cholesterol bilayer domains. Cholesterol level increases with age, and for older persons, it exceeds the cholesterol solubility threshold, leading to the formation of cholesterol crystals. All these changes occur in the normal lens without too much compromise to lens transparency. If the cholesterol content in the cell membranes of other organs increases to extent where cholesterol crystals forma, a pathological condition begins. In arterial cells, minute cholesterol crystals activate inflammasomes, induce inflammation, and cause atherosclerosis development. In this review, we will indicate possible factors that distinguish between beneficial and negative cholesterol action, limiting cholesterol actions to those performed through cholesterol in cell membranes and by cholesterol crystals.
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21
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Chin H, Gillissen JJJ, Miyako E, Cho NJ. Microfluidic liquid cell chamber for scanning probe microscopy measurement application. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:046105. [PMID: 31043033 DOI: 10.1063/1.5086063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 03/25/2019] [Indexed: 06/09/2023]
Abstract
In this paper, we present a universal microfluidic liquid chamber device platform for atomic force microscopy (AFM), which enables to fabricate the uniform lipid bilayer on the hydrophilic surface using the solvent-assisted lipid bilayer formation method. Using this device enables us to acquire the various properties of delicate soft matter, including morphological data, and mechanical property measurements, using high-resolution AFM systems. The proposed technology is expected to provide an understanding of complicated biological materials.
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Affiliation(s)
- Hokyun Chin
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
| | - Jurriaan J J Gillissen
- Department of Mathematics, University College London, Gower Street, Bloomsbury, London WC1E 6BT, United Kingdom
| | - Eijiro Miyako
- Nanomaterials Research Institute (NMRI), National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
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22
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Sochorová M, Audrlická P, Červená M, Kováčik A, Kopečná M, Opálka L, Pullmannová P, Vávrová K. Permeability and microstructure of cholesterol-depleted skin lipid membranes and human stratum corneum. J Colloid Interface Sci 2019; 535:227-238. [DOI: 10.1016/j.jcis.2018.09.104] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 09/27/2018] [Accepted: 09/30/2018] [Indexed: 10/28/2022]
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23
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Jin X, Dimitriadis EK, Liu Y, Combs CA, Chang J, Varsano N, Stempinski E, Flores R, Jackson SN, Muller L, Woods AS, Addadi L, Kruth HS. Macrophages Shed Excess Cholesterol in Unique Extracellular Structures Containing Cholesterol Microdomains. Arterioscler Thromb Vasc Biol 2018; 38:1504-1518. [PMID: 29853567 PMCID: PMC6023747 DOI: 10.1161/atvbaha.118.311269] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/16/2018] [Indexed: 12/20/2022]
Abstract
Supplemental Digital Content is available in the text. Objective— Cells use various mechanisms to maintain cellular cholesterol homeostasis including efflux of cholesterol from the cellular plasma membrane to cholesterol acceptors such as HDLs (high-density lipoproteins). Little is known about the transfer of cholesterol from cells into the extracellular matrix. Using a unique monoclonal antibody that detects ordered cholesterol arrays (ie, cholesterol micro[or nano]-domains), we previously identified that particles containing these cholesterol domains accumulate in the extracellular matrix during cholesterol enrichment of human monocyte-derived macrophages and are found in atherosclerotic lesions. In this study, we further investigate these deposited particles containing cholesterol microdomains and discover their unexpected morphology. Approach and Results— Although appearing spherical at the resolution of the conventional fluorescence microscope, super-resolution immunofluorescence and atomic force microscopy of in situ cholesterol microdomains, and immunoelectron microscopy of isolated cholesterol microdomains revealed that the microdomains are not vesicles or 3-dimensional crystals but rather appear as branching irregularly shaped deposits of varying size. These cholesterol microdomain-containing deposits are shed from the plasma membrane into the extracellular matrix. Conclusions— To date, research on cellular excretion of excess cholesterol has demonstrated cellular cholesterol efflux in the form of membranous vesicles and discoidal HDL particles released into the fluid-phase medium. Shedding of plasma membrane cholesterol microdomains provides an additional mechanism for cells such as macrophages to maintain plasma membrane cholesterol homeostasis. Furthermore, recognition that macrophages shed cholesterol microdomains into the extracellular matrix is important to our understanding of extracellular buildup of cholesterol in atherosclerosis.
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Affiliation(s)
- Xueting Jin
- From the Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute (X.J., Y.L., J.C., R.F., H.S.K.)
| | - Emilios K Dimitriadis
- Scanning Probe Microscopy Unit, National Institute of Biomedical Imaging and Bioengineering (E.K.D.)
| | - Ying Liu
- From the Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute (X.J., Y.L., J.C., R.F., H.S.K.)
| | - Christian A Combs
- Light Microscopy Core, National Heart, Lung, and Blood Institute (C.A.C.)
| | - Janet Chang
- From the Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute (X.J., Y.L., J.C., R.F., H.S.K.)
| | - Neta Varsano
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (N.V., L.A.)
| | - Erin Stempinski
- Electron Microscopy Core, National Heart, Lung, and Blood Institute (E.S.)
| | - Rhonda Flores
- From the Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute (X.J., Y.L., J.C., R.F., H.S.K.)
| | - Shelley N Jackson
- Structural Biology Core, National Institute of Drug Abuse (S.N.J., L.M., A.S.W.), National Institutes of Health, Baltimore, MD
| | - Ludovic Muller
- Structural Biology Core, National Institute of Drug Abuse (S.N.J., L.M., A.S.W.), National Institutes of Health, Baltimore, MD
| | - Amina S Woods
- Structural Biology Core, National Institute of Drug Abuse (S.N.J., L.M., A.S.W.), National Institutes of Health, Baltimore, MD
| | - Lia Addadi
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (N.V., L.A.)
| | - Howard S Kruth
- From the Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute (X.J., Y.L., J.C., R.F., H.S.K.)
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24
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Local anesthetics induce interdigitation and thermotropic changes in dipalmitoylphosphatidylcholine bilayers. Chem Phys Lipids 2018; 210:22-27. [DOI: 10.1016/j.chemphyslip.2017.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 11/29/2017] [Accepted: 12/19/2017] [Indexed: 01/03/2023]
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25
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Plesnar E, Szczelina R, Subczynski WK, Pasenkiewicz-Gierula M. Is the cholesterol bilayer domain a barrier to oxygen transport into the eye lens? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:434-441. [PMID: 29079282 DOI: 10.1016/j.bbamem.2017.10.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/20/2017] [Accepted: 10/23/2017] [Indexed: 11/16/2022]
Abstract
In the eye lens, the oxygen partial pressure is very low and the cholesterol (Chol) content in cell membranes is very high. Disturbance of these quantities results in cataract development. In human lens membranes, both bulk phospholipid-Chol domains and the pure Chol bilayer domains (CBDs) were experimentally detected. It is hypothesized that the CBD constitutes a significant barrier to oxygen transport into the lens. Transmembrane profiles of the oxygen diffusion-concentration product, obtained with electron paramagnetic resonance spin-labeling methods, allow evaluation of the oxygen permeability (PM) of phospholipid membranes but not the CBD. Molecular dynamics simulation can independently provide components of the product across any bilayer domain, thus allowing evaluation of the PM across the CBD. Therefore, to test the hypothesis, MD simulation was used. Three bilayers containing palmitoyl-oleoyl-phosphorylcholine (POPC) and Chol were built. The pure Chol bilayer modeled the CBD, the 1:1 POPC-Chol bilayer modeled the bulk membrane in which the CBD is embedded, and the POPC bilayer was a reference. To each model, 200 oxygen molecules were added. After equilibration, the oxygen concentration and diffusion profiles were calculated for each model and multiplied by each other. From the respective product profiles, the PM of each bilayer was calculated. Favorable comparison with experimental data available only for the POPC and POPC-Chol bilayers validated these bilayer models and allowed the conclusion that oxygen permeation across the CBD is ~10 smaller than across the bulk membrane, supporting the hypothesis that the CBD is a barrier to oxygen transport into the eye lens.
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Affiliation(s)
- Elzbieta Plesnar
- Department of Computational Biophysics and Bioinformatics, WBBiB, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
| | - Robert Szczelina
- Department of Bioinformatics, MCB, Jagiellonian University, Gronostajowa 7A, 30-387 Krakow, Poland.
| | - Witold K Subczynski
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
| | - Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, WBBiB, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
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Phase separation of the plasma membrane in human red blood cells as a potential tool for diagnosis and progression monitoring of type 1 diabetes mellitus. PLoS One 2017; 12:e0184109. [PMID: 28880900 PMCID: PMC5589169 DOI: 10.1371/journal.pone.0184109] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/17/2017] [Indexed: 12/14/2022] Open
Abstract
Glycosylation, oxidation and other post-translational modifications of membrane and transmembrane proteins can alter lipid density, packing and interactions, and are considered an important factor that affects fluidity variation in membranes. Red blood cells (RBC) membrane physical state, showing pronounced alterations in Type 1 diabetes mellitus (T1DM), could be the ideal candidate for monitoring the disease progression and the effects of therapies. On these grounds, the measurement of RBC membrane fluidity alterations can furnish a more sensitive index in T1DM diagnosis and disease progression than Glycosylated hemoglobin (HbA1c), which reflects only the information related to glycosylation processes. Here, through a functional two-photon microscopy approach we retrieved fluidity maps at submicrometric scale in RBC of T1DM patients with and without complications, detecting an altered membrane equilibrium. We found that a phase separation between fluid and rigid domains occurs, triggered by systemic effects on membranes fluidity of glycation and oxidation. The phase separation patterns are different among healthy, T1DM and T1DM with complications patients. Blood cholesterol and LDL content are positively correlated with the extent of the phase separation patterns. To quantify this extent a machine learning approach is employed to develop a Decision-Support-System (DSS) able to recognize different fluidity patterns in RBC. Preliminary analysis shows significant differences(p<0.001) among healthy, T1DM and T1DM with complications patients. The development of an assay based on Phase separation of the plasma membrane of the Red Blood cells is a potential tool for diagnosis and progression monitoring of type 1 diabetes mellitus, and could allow customization and the selection of medical treatments in T1DM in clinical settings, and enable the early detection of complications.
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Cholesterol Bilayer Domains in the Eye Lens Health: A Review. Cell Biochem Biophys 2017; 75:387-398. [PMID: 28660427 PMCID: PMC5691107 DOI: 10.1007/s12013-017-0812-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 06/15/2017] [Indexed: 11/06/2022]
Abstract
The most unique biochemical characteristic of the eye lens fiber cell plasma membrane is its extremely high cholesterol content, the need for which is still unclear. It is evident, however, that the disturbance of Chol homeostasis may result in damages associated with cataracts. Electron paramagnetic resonance methods allow discrimination of two types of lipid domains in model membranes overloaded with Chol, namely, phospholipid-cholesterol domains and pure Chol bilayer domains. These domains are also detected in human lens lipid membranes prepared from the total lipids extracted from lens cortices and nuclei of donors from different age groups. Independent of the age-related changes in phospholipid composition, the physical properties of phospholipid-Chol domains remain the same for all age groups and are practically identical for cortical and nuclear membranes. The presence of Chol bilayer domains in these membranes provides a buffering capacity for cholesterol concentration in the surrounding phospholipid-Chol domains, keeping it at a constant saturating level and thus keeping the physical properties of the membrane consistent with and independent of changes in phospholipid composition. It seems that the presence of Chol bilayer domains plays an integral role in the regulation of cholesterol-dependent processes in fiber cell plasm membranes and in the maintenance of fiber cell membrane homeostasis.
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28
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Mainali L, Raguz M, O’Brien WJ, Subczynski WK. Changes in the Properties and Organization of Human Lens Lipid Membranes Occurring with Age. Curr Eye Res 2017; 42:721-731. [PMID: 27791387 PMCID: PMC5409882 DOI: 10.1080/02713683.2016.1231325] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/01/2016] [Accepted: 08/28/2016] [Indexed: 10/20/2022]
Abstract
PURPOSE This research was undertaken to document the changes in the organization and properties of human lens lipid membranes that occur with age. METHODS Human lens lipid membranes prepared from the total lipids extracted from clear lens cortices and nuclei of donors from age groups 0-20 and 21-40 years were investigated. An electron paramagnetic resonance technique and nitroxide spin labels (analogues of phospholipids and cholesterol) were used. RESULTS Two distinct lipid domains, the phospholipid-cholesterol domain (PCD) and the pure cholesterol bilayer domain (CBD), were detected in all investigated membranes. Profiles of the acyl chain order, fluidity, hydrophobicity, and oxygen transport parameter across discriminated coexisting lipid domains were assessed. Independent of the age-related changes in phospholipid composition, the physical properties of the PCD remained the same for all age groups and were practically identical for cortical and nuclear membranes. However, the properties of pure CBDs changed significantly with the age of the donor and were related to the size of the CBD, which increased with the age of the donor and was greater in nuclear than in cortical membranes. A more detailed analysis revealed that the size of the CBD was determined mainly by the cholesterol content in the membrane. CONCLUSIONS This paper presents data from four age groups: 0-20, 21-40, 41-60, and 61-70 years. Data from age groups 41-60 and 61-70 years were published previously. Combining the previously published data with those data obtained in the present work allowed us to show the changes in the organization of cortical and nuclear lens lipid membranes as functions of age and cholesterol. It seems that the balance between age-related changes in membrane phospholipid composition and cholesterol content plays an integral role in the regulation of cholesterol-dependent processes in fiber cell membranes and in the maintenance of fiber cell membrane homeostasis.
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Affiliation(s)
- Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Marija Raguz
- Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | - William J. O’Brien
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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29
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High Cholesterol/Low Cholesterol: Effects in Biological Membranes: A Review. Cell Biochem Biophys 2017; 75:369-385. [PMID: 28417231 DOI: 10.1007/s12013-017-0792-7] [Citation(s) in RCA: 173] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/27/2017] [Indexed: 12/11/2022]
Abstract
Lipid composition determines membrane properties, and cholesterol plays a major role in this determination as it regulates membrane fluidity and permeability, as well as induces the formation of coexisting phases and domains in the membrane. Biological membranes display a very diverse lipid composition, the lateral organization of which plays a crucial role in regulating a variety of membrane functions. We hypothesize that, during biological evolution, membranes with a particular cholesterol content were selected to perform certain functions in the cells of eukaryotic organisms. In this review, we discuss the major membrane properties induced by cholesterol, and their relationship to certain membrane functions.
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30
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Litz JP, Thakkar N, Portet T, Keller SL. Depletion with Cyclodextrin Reveals Two Populations of Cholesterol in Model Lipid Membranes. Biophys J 2017; 110:635-645. [PMID: 26840728 DOI: 10.1016/j.bpj.2015.11.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/06/2015] [Accepted: 11/10/2015] [Indexed: 10/22/2022] Open
Abstract
Recent results provide evidence that cholesterol is highly accessible for removal from both cell and model membranes above a threshold concentration that varies with membrane composition. Here we measured the rate at which methyl-β-cyclodextrin depletes cholesterol from a supported lipid bilayer as a function of cholesterol mole fraction. We formed supported bilayers from two-component mixtures of cholesterol and a PC (phosphatidylcholine) lipid, and we directly visualized the rate of decrease in area of the bilayers with fluorescence microscopy. Our technique yields the accessibility of cholesterol over a wide range of concentrations (30-66 mol %) for many individual bilayers, enabling fast acquisition of replicate data. We found that the bilayers contain two populations of cholesterol, one with low surface accessibility and the other with high accessibility. A larger fraction of the total membrane cholesterol appears in the more accessible population when the acyl chains of the PC-lipid tails are more unsaturated. Our findings are most consistent with the predictions of the condensed-complex and cholesterol bilayer domain models of cholesterol-phospholipid interactions in lipid membranes.
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Affiliation(s)
- Jonathan P Litz
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Niket Thakkar
- Department of Chemistry, University of Washington, Seattle, Washington; Department of Applied Mathematics, University of Washington, Seattle, Washington
| | - Thomas Portet
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Sarah L Keller
- Department of Chemistry, University of Washington, Seattle, Washington; Department of Physics, University of Washington, Seattle, Washington.
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31
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Reddy ST, Shrivastava S, Mallesham K, Chattopadhyay A. Cholesterol-dependent thermotropic behavior and organization of neuronal membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2611-2616. [PMID: 27453199 DOI: 10.1016/j.bbamem.2016.07.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 07/15/2016] [Accepted: 07/19/2016] [Indexed: 12/31/2022]
Abstract
The composition of neuronal membranes is unique with diverse lipid composition due to evolutionary requirement. The organization and dynamics of neuronal membranes are crucial for efficient functioning of neuronal receptors. We have previously established hippocampal membranes as a convenient natural source for exploring lipid-protein interactions, and organization of neuronal receptors. Keeping in mind the pathophysiological role of neuronal cholesterol, in this work, we used differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) to explore thermotropic phase behavior and organization (thickness) of hippocampal membranes under conditions of varying cholesterol content. Our results show that the apparent phase transition temperature of hippocampal membranes displays characteristic linear dependence on membrane cholesterol content. These results are in contrast to earlier results with binary lipid mixtures containing cholesterol where phase transition temperature was found to be not significantly dependent on cholesterol concentration. Interestingly, SAXS data showed that hippocampal membrane thickness remained more or less invariant, irrespective of cholesterol content. We believe that these results constitute one of the early reports on the thermotropic phase behavior and organizational characterization of hippocampal membranes under varying cholesterol content. These results could have implications in the functioning of neuronal receptors in healthy and diseased states.
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Affiliation(s)
- S Thirupathi Reddy
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
| | - Sandeep Shrivastava
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
| | - K Mallesham
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
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32
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Subczynski WK, Mainali L, Raguz M, O'Brien WJ. Organization of lipids in fiber-cell plasma membranes of the eye lens. Exp Eye Res 2016; 156:79-86. [PMID: 26988627 DOI: 10.1016/j.exer.2016.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 02/02/2016] [Accepted: 03/07/2016] [Indexed: 11/15/2022]
Abstract
The plasma membrane together with the cytoskeleton forms the only supramolecular structure of the matured fiber cell which accounts for mostly all fiber cell lipids. The purpose of this review is to inform researchers about the importance of the lipid bilayer portion of the lens fiber cell plasma membranes in the maintaining lens homeostasis, and thus protecting against cataract development.
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Affiliation(s)
- Witold K Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
| | - Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Marija Raguz
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA; Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | - William J O'Brien
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Róg T, Pöyry S, Vattulainen I. Building Synthetic Sterols Computationally - Unlocking the Secrets of Evolution? Front Bioeng Biotechnol 2015; 3:121. [PMID: 26347865 PMCID: PMC4543873 DOI: 10.3389/fbioe.2015.00121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/07/2015] [Indexed: 01/28/2023] Open
Abstract
Cholesterol is vital in regulating the physical properties of animal cell membranes. While it remains unclear what renders cholesterol so unique, it is known that other sterols are less capable in modulating membrane properties, and there are membrane proteins whose function is dependent on cholesterol. Practical applications of cholesterol include its use in liposomes in drug delivery and cosmetics, cholesterol-based detergents in membrane protein crystallography, its fluorescent analogs in studies of cholesterol transport in cells and tissues, etc. Clearly, in spite of their difficult synthesis, producing the synthetic analogs of cholesterol is of great commercial and scientific interest. In this article, we discuss how synthetic sterols non-existent in nature can be used to elucidate the roles of cholesterol’s structural elements. To this end, we discuss recent atomistic molecular dynamics simulation studies that have predicted new synthetic sterols with properties comparable to those of cholesterol. We also discuss more recent experimental studies that have vindicated these predictions. The paper highlights the strength of computational simulations in making predictions for synthetic biology, thereby guiding experiments.
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Affiliation(s)
- Tomasz Róg
- Department of Physics, Tampere University of Technology , Tampere , Finland
| | - Sanja Pöyry
- Department of Physics, Tampere University of Technology , Tampere , Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology , Tampere , Finland ; MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark , Odense , Denmark
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34
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Jin X, Freeman SR, Vaisman B, Liu Y, Chang J, Varsano N, Addadi L, Remaley A, Kruth HS. ABCA1 contributes to macrophage deposition of extracellular cholesterol. J Lipid Res 2015. [PMID: 26203076 DOI: 10.1194/jlr.m060053] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We previously reported that cholesterol-enriched macrophages excrete cholesterol into the extracellular matrix. A monoclonal antibody that detects cholesterol microdomains labels the deposited extracellular particles. Macro-phage deposition of extracellular cholesterol depends, in part, on ABCG1, and this cholesterol can be mobilized by HDL components of the reverse cholesterol transport process. The objective of the current study was to determine whether ABCA1 also contributes to macrophage deposition of extracellular cholesterol. ABCA1 functioned in extracellular cholesterol deposition. The liver X receptor agonist, TO901317 (TO9), an ABCA1-inducing factor, restored cholesterol deposition that was absent in cholesterol-enriched ABCG1(-/-) mouse macrophages. In addition, the ABCA1 inhibitor, probucol, blocked the increment in cholesterol deposited by TO9-treated wild-type macrophages, and completely inhibited deposition from TO9-treated ABCG1(-/-) macrophages. Lastly, ABCA1(-/-) macrophages deposited much less extracellular cholesterol than wild-type macrophages. These findings demonstrate a novel function of ABCA1 in contributing to macrophage export of cholesterol into the extracellular matrix.
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Affiliation(s)
- Xueting Jin
- Section of Experimental Atherosclerosis National Institutes of Health, Bethesda, MD 20892
| | - Sebastian R Freeman
- Section of Experimental Atherosclerosis National Institutes of Health, Bethesda, MD 20892
| | - Boris Vaisman
- Lipoprotein Metabolism Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Ying Liu
- Section of Experimental Atherosclerosis National Institutes of Health, Bethesda, MD 20892
| | - Janet Chang
- Section of Experimental Atherosclerosis National Institutes of Health, Bethesda, MD 20892
| | - Neta Varsano
- Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Lia Addadi
- Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Alan Remaley
- Lipoprotein Metabolism Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Howard S Kruth
- Section of Experimental Atherosclerosis National Institutes of Health, Bethesda, MD 20892
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35
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Neutron Scattering at the Intersection of Heart Health Science and Biophysics. J Cardiovasc Dev Dis 2015; 2:125-140. [PMID: 29371515 PMCID: PMC5753099 DOI: 10.3390/jcdd2020125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 05/25/2015] [Indexed: 01/04/2023] Open
Abstract
There is an urgent quest for improved heart health. Here, we review how neutron radiation can provide insight into the molecular basis of heart health. Lower cholesterol, a daily intake of aspirin and supplemental vitamin E are argued to all improve heart health. However, the mechanisms behind these common regimens, and others, are not entirely understood. It is not clear why a daily intake of aspirin can help some people with heart disease, and the benefits of vitamin E in the treatment of reperfusion injury have been heavily debated. The molecular impact of cholesterol in the body is still a hot topic. Neutron scattering experiments present a unique opportunity for biophysicists attempting to address these problems. We review some recently published studies that are advancing our understanding of how cholesterol, vitamin E and aspirin work at the molecular level, by studying the impact of these molecules on the cell membrane. These insights engage the broader health science community with new ways of thinking about these molecules.
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36
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Jurak M, Chibowski E. Characteristics of a phospholipid DOPC/cholesterol bilayer based on surface free energy and its components. RSC Adv 2015. [DOI: 10.1039/c5ra08203j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The effect of the cholesterol (Chol) content (xChol = 0.25; 0.5; 0.75) on the wettability changes of solid supported bilayers of unsaturated 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) was investigated at 20 °C and 37 °C.
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Affiliation(s)
- M. Jurak
- Department of Physical Chemistry
- Faculty of Chemistry
- Maria Curie-Skłodowska University
- 20-031 Lublin
- Poland
| | - E. Chibowski
- Department of Physical Chemistry
- Faculty of Chemistry
- Maria Curie-Skłodowska University
- 20-031 Lublin
- Poland
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37
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Properties of membranes derived from the total lipids extracted from clear and cataractous lenses of 61-70-year-old human donors. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2014; 44:91-102. [PMID: 25502634 DOI: 10.1007/s00249-014-1004-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/18/2014] [Accepted: 11/28/2014] [Indexed: 10/24/2022]
Abstract
Human lens-lipid membranes prepared from the total lipids extracted from clear and cataractous lens cortexes and nuclei of 61-70-year-old donors by use of a rapid solvent-exchange method were investigated. The measured cholesterol-to-phospholipid (Chol/PL) molar ratio in these membranes was 1.8 and 4.4 for cortex and nucleus of clear lenses, respectively, and 1.14 and 1.45 for cataractous lenses. Properties and organization of the lipid bilayer were investigated by use of electron paramagnetic resonance spin-labeling methods. Formation of Chol crystals was confirmed by use of differential scanning calorimetry. Pure cholesterol bilayer domains (CBDs) were formed in all the membranes investigated. It was shown that in clear lens membranes of the nucleus, Chol exists in three different environments: (1) dispersed in phospholipid bilayers (PCDs), (2) in CBDs, and (3) in Chol crystals. In clear lens membranes of the cortex, and in cortical and nuclear cataractous lens membranes, Chol crystals were not detected, because of the lower Chol content. Profiles of membrane properties (alkyl-chain order, fluidity, oxygen transport, and hydrophobicity) across the PCD were very similar for clear and cataractous membranes. Profiles of the oxygen transport parameter across the CBD were, however, different for cortical clear and cataractous membranes-the amount and size of CBDs was less in cataractous membranes. These results suggest that high Chol content, formation of CBDs, and formation of Chol crystals should not be regarded as major predispositions for the development of age-related cataracts.
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38
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Tabaei SR, Jackman JA, Kim SO, Liedberg B, Knoll W, Parikh AN, Cho NJ. Formation of cholesterol-rich supported membranes using solvent-assisted lipid self-assembly. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:13345-52. [PMID: 25286344 DOI: 10.1021/la5034433] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
This paper describes the application of a solvent-exchange method to prepare supported membranes containing high fractions of cholesterol (up to ∼57 mol %) in an apparent equilibrium. The method exploits the phenomenon of reverse-phase evaporation, in which the deposition of lipids in alcohol (e.g., isopropanol) is followed by the slow removal of the organic solvent from the water-alcohol mixture. This in turn induces a series of lyotropic phase transitions successively producing inverse-micelles, monomers, micelles, and vesicles in equilibrium with supported bilayers at the contacting solid surface. By using the standard cholesterol depletion by methyl-β-cyclodextrin treatment, a quartz crystal microbalance with dissipation monitoring assay confirms that the cholesterol concentration in the supported membranes is comparable to that in the surrounding bulk phase. A quantitative characterization of the biophysical properties of the resultant bilayer, including lateral diffusion constants and phase separation, using epifluorescence microscopy and atomic force microscopy establishes the formation of laterally contiguous supported lipid bilayers, which break into a characteristic domain-pattern of coexisting phases in a cholesterol concentration-dependent manner. With increasing cholesterol fraction in the supported bilayer, the size of the domains increases, ultimately yielding two-dimensional cholesterol bilayer domains near the solubility limit. A unique feature of the approach is that it enables preparation of supported membranes containing limiting concentrations of cholesterol near the solubility limit under equilibrium conditions, which cannot be obtained using conventional techniques (i.e., vesicle fusion).
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Affiliation(s)
- Seyed R Tabaei
- School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798, Singapore
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39
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Surface Gibbs energy interaction of phospholipid/cholesterol monolayers deposited on mica with probe liquids. Chem Phys Lipids 2014; 183:60-7. [DOI: 10.1016/j.chemphyslip.2014.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 05/20/2014] [Accepted: 05/21/2014] [Indexed: 12/22/2022]
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40
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Dies H, Toppozini L, Rheinstädter MC. The interaction between amyloid-β peptides and anionic lipid membranes containing cholesterol and melatonin. PLoS One 2014; 9:e99124. [PMID: 24915524 PMCID: PMC4051683 DOI: 10.1371/journal.pone.0099124] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 05/11/2014] [Indexed: 12/21/2022] Open
Abstract
One of the hallmarks of Alzheimer's disease is the formation of senile plaques, primarily consisting of amyloid- (A) peptides. Peptide-membrane and peptide-lipid interactions are thought to be crucial in this process. We studied the interaction of A and A peptides with anionic lipid membranes made of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphoserine (DMPS) using X-ray diffraction. We compare the experimentally determined electron densities in the gel state of the membranes with density calculations from peptide structures reported in the Protein Data Bank in order to determine the position of the peptide in the bilayers. The full length peptide A was found to embed in the hydrocarbon core of the anionic lipid bilayers. Two populations were found for the A peptide: (1) membrane-bound states in the hydrophilic head group region of the bilayers, where the peptides align parallel to the membranes, and (2) an embedded state in the bilayer center. Aging plays an important role in the development of Alzheimer's, in particular with respect to changes in cholesterol and melatonin levels in the brain tissue. Immiscible cholesterol plaques were created by addition of 30 mol% cholesterol to the anionic membranes. The A peptides were found to strongly interact with the lipid bilayers, displacing further cholesterol molecules into the plaques, effectively lowering the cholesterol concentration in the membranes and increasing the total fraction of cholesterol plaques. Addition of 30 mol% melatonin molecules to the anionic membranes drastically reduced the population of the membrane-embedded A state. These results present experimental evidence for an interaction between A peptides, melatonin and cholesterol in lipid membranes.
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Affiliation(s)
- Hannah Dies
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Laura Toppozini
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Maikel C. Rheinstädter
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
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41
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Raguz M, Mainali L, O'Brien WJ, Subczynski WK. Lipid-protein interactions in plasma membranes of fiber cells isolated from the human eye lens. Exp Eye Res 2014; 120:138-51. [PMID: 24486794 DOI: 10.1016/j.exer.2014.01.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 01/20/2014] [Accepted: 01/22/2014] [Indexed: 11/19/2022]
Abstract
The protein content in human lens membranes is extremely high, increases with age, and is higher in the nucleus as compared with the cortex, which should strongly affect the organization and properties of the lipid bilayer portion of intact membranes. To assess these effects, the intact cortical and nuclear fiber cell plasma membranes isolated from human lenses from 41- to 60-year-old donors were studied using electron paramagnetic resonance spin-labeling methods. Results were compared with those obtained for lens lipid membranes prepared from total lipid extracts from human eyes of the same age group [Mainali, L., Raguz, M., O'Brien, W. J., and Subczynski, W. K. (2013) Biochim. Biophys. Acta]. Differences were considered to be mainly due to the effect of membrane proteins. The lipid-bilayer portions of intact membranes were significantly less fluid than lipid bilayers of lens lipid membranes, prepared without proteins. The intact membranes were found to contain three distinct lipid environments termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain. However, the cholesterol bilayer domain, which was detected in cortical and nuclear lens lipid membranes, was not detected in intact membranes. The relative amounts of bulk and trapped lipids were evaluated. The amount of lipids in domains uniquely formed due to the presence of membrane proteins was greater in nuclear membranes than in cortical membranes. Thus, it is evident that the rigidity of nuclear membranes is greater than that of cortical membranes. Also the permeability coefficients for oxygen measured in domains of nuclear membranes were significantly lower than appropriate coefficients measured in cortical membranes. Relationships between the organization of lipids into lipid domains in fiber cells plasma membranes and the organization of membrane proteins are discussed.
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Affiliation(s)
- Marija Raguz
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | - Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - William J O'Brien
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Witold K Subczynski
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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Johnson BB, Heuck AP. Perfringolysin O structure and mechanism of pore formation as a paradigm for cholesterol-dependent cytolysins. Subcell Biochem 2014; 80:63-81. [PMID: 24798008 DOI: 10.1007/978-94-017-8881-6_5] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cholesterol-dependent cytolysins (CDCs) constitute a family of pore forming toxins secreted by Gram-positive bacteria. These toxins form transmembrane pores by inserting a large β-barrel into cholesterol-containing membrane bilayers. Binding of water-soluble CDCs to the membrane triggers the formation of oligomers containing 35-50 monomers. The coordinated insertion of more than seventy β-hairpins into the membrane requires multiple structural conformational changes. Perfringolysin O (PFO), secreted by Clostridium perfringens, has become the prototype for the CDCs. In this chapter, we will describe current knowledge on the mechanism of PFO cytolysis, with special focus on cholesterol recognition, oligomerization, and the conformational changes involved in pore formation.
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Affiliation(s)
- Benjamin B Johnson
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 710 N. Pleasant St., Lederle GRT, Amherst, MA, 01003, USA
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43
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Nakano-Ito K, Fujikawa Y, Hihara T, Shinjo H, Kotani S, Suganuma A, Aoki T, Tsukidate K. E2012-Induced Cataract and Its Predictive Biomarkers. Toxicol Sci 2013; 137:249-58. [DOI: 10.1093/toxsci/kft224] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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44
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Van Ness M, Jensen H, Adamson GN, Kysar PE, Holland P. Neutrophils contain cholesterol crystals in transfusion-related acute lung injury (TRALI). Am J Clin Pathol 2013; 140:170-6. [PMID: 23897251 DOI: 10.1309/ajcpgkojv15avznt] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
OBJECTIVES Intracellular components of transfusion-related acute lung injury (TRALI) were investigated by transmission electron microscopy. METHODS The lungs from 2 fatal TRALI cases and 2 controls, previously studied by scanning electron microscopy, were studied by transmission electron microscopy. Morphologic data by light and phase microscopy, along with scanning and transmission electron microscopic observations, were collated. RESULTS The 2 fatal TRALI cases exhibited dense laminated material within capillaries and postcapillary venules, similar to material identified within their neutrophils when viewed by transmission electron microscopy. This material polarized light and is presumed to be cholesterol crystals. CONCLUSIONS The damage to the pulmonary vascular endothelium in TRALI is related to formation of cholesterol crystals originating within neutrophils.
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Affiliation(s)
- Michael Van Ness
- Department of Pathology and Laboratory Medicine, University of California Davis Health System, Sacramento, CA
| | - Hanne Jensen
- Department of Pathology and Laboratory Medicine, University of California Davis Health System, Sacramento, CA
| | - Grete N. Adamson
- Department of Pathology and Laboratory Medicine, University of California Davis Health System, Sacramento, CA
| | - Patricia E. Kysar
- Department of Pathology and Laboratory Medicine, University of California Davis Health System, Sacramento, CA
| | - Paul Holland
- Department of Pathology and Laboratory Medicine, University of California Davis Health System, Sacramento, CA
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Mainali L, Raguz M, Subczynski WK. Formation of cholesterol bilayer domains precedes formation of cholesterol crystals in cholesterol/dimyristoylphosphatidylcholine membranes: EPR and DSC studies. J Phys Chem B 2013; 117:8994-9003. [PMID: 23834375 DOI: 10.1021/jp402394m] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Saturation-recovery EPR along with DSC were used to determine the cholesterol content at which pure cholesterol bilayer domains (CBDs) and cholesterol crystals begin to form in dimyristoylphosphatidylcholine (DMPC) membranes. To preserve compositional homogeneity throughout the membrane suspension, lipid multilamellar dispersions were prepared using a rapid solvent exchange method. The cholesterol content increased from 0 to 75 mol %. With spin-labeled cholesterol analogues, it was shown that the CBDs begin to form at ~50 mol % cholesterol. It was confirmed by DSC that the cholesterol solubility threshold for DMPC membranes is detected at ~66 mol % cholesterol. At levels above this cholesterol content, monohydrate cholesterol crystals start to form. The major finding is that the formation of CBDs precedes formation of cholesterol crystals. The region of the phase diagram for cholesterol contents between 50 and 66 mol % is described as a structured one-phase region in which CBDs have to be supported by the surrounding DMPC bilayer saturated with cholesterol. Thus, the phase boundary located at 66 mol % cholesterol separates the structured one-phase region (liquid-ordered phase of DMPC with CBDs) from the two-phase region where the structured liquid-ordered phase of DMPC coexists with cholesterol crystals. It is likely that CBDs are precursors of monohydrate cholesterol crystals.
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Affiliation(s)
- Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Plesnar E, Subczynski WK, Pasenkiewicz-Gierula M. Comparative computer simulation study of cholesterol in hydrated unary and binary lipid bilayers and in an anhydrous crystal. J Phys Chem B 2013; 117:8758-69. [PMID: 23848956 DOI: 10.1021/jp402839r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Models created with molecular dynamics simulations are used to compare the organization and dynamics of cholesterol (Chol) molecules in three different environments: (1) a hydrated pure Chol bilayer that models the Chol bilayer domain, which is a pure Chol domain embedded in the bulk membrane; (2) a 2-palmitoyl-3-oleoyl-d-glycerol-1-phosphorylcholine bilayer saturated with cholesterol (POPC-Chol50) that models the bulk membrane; (3) a Chol crystal. The computer model of the hydrated pure Chol bilayer is stable on the microsecond time scale. Some structural characteristics of Chol molecules in the Chol bilayer are similar to those in the POPC-Chol50 bilayer (e.g., tilt of Chol rings and chains), while others are similar to those in Chol crystals (e.g., surface area per Chol, bilayer thickness). The key result of this study is that the Chol bilayer has, unexpectedly, a dynamic structure, with Chol mobility similar to that in the POPC-Chol50 bilayer though slower. This is the major difference compared to Chol crystals, where Chol molecules are immobile. Also, water accessibility to Chol-OH groups in the Chol bilayer is not limited. On average, each Chol molecule makes 2.3 hydrogen bonds with water in the Chol bilayer, compared with 1.7 hydrogen bonds in the POPC-Col50 bilayer.
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Affiliation(s)
- Elzbieta Plesnar
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
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Abstract
BACKGROUND The formation of cholesterol domains in lipoplexes has been associated with enhanced serum stability and transfection rates both in cell culture and in vivo. RESULTS This study utilizes the ability of saturated phosphatidylcholines to promote the formation of cholesterol domains at much lower cholesterol contents than have been utilized in previous work. The results demonstrate that lipoplexes with identical cholesterol and cationic lipid contents exhibit significantly improved transfection efficiencies when a domain is present, consistent with previous work. In addition, studies assessing transfection rates in the absence of serum demonstrate that the ability of domains to enhance transfection is not dependent on interactions with serum proteins. Consistent with this hypothesis, characterization of the adsorbed proteins composing the corona of these lipoplex formulations did not reveal a correlation between transfection and the adsorption of a specific protein. CONCLUSION We have demonstrated that the interaction with serum proteins can promote domain formation in some formulations, and thereby result in enhanced transfection only after serum exposure.
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Mainali L, Raguz M, O'Brien WJ, Subczynski WK. Properties of membranes derived from the total lipids extracted from the human lens cortex and nucleus. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1828:1432-40. [PMID: 23438364 PMCID: PMC3633468 DOI: 10.1016/j.bbamem.2013.02.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 02/08/2013] [Accepted: 02/14/2013] [Indexed: 11/21/2022]
Abstract
Human lens lipid membranes prepared using a rapid solvent exchange method from the total lipids extracted from the clear lens cortex and nucleus of 41- to 60-year-old donors were investigated using electron paramagnetic resonance spin-labeling. Profiles of the phospholipid alkyl-chain order, fluidity, oxygen transport parameter, and hydrophobicity were assessed across coexisting membrane domains. Membranes prepared from the lens cortex and nucleus were found to contain two distinct lipid environments, the bulk phospholipid-cholesterol domain and the cholesterol bilayer domain (CBD). The alkyl chains of phospholipids were strongly ordered at all depths, indicating that the amplitude of the wobbling motion of alkyl chains was small. However, profiles of the membrane fluidity, which explicitly contain time (expressed as the spin-lattice relaxation rate) and depend on the rotational motion of spin labels, show relatively high fluidity of alkyl chains close to the membrane center. Profiles of the oxygen transport parameter and hydrophobicity have a rectangular shape and also indicate a high fluidity and hydrophobicity of the membrane center. The amount of CBD was greater in nuclear membranes than in cortical membranes. The presence of the CBD in lens lipid membranes, which at 37°C showed a permeability coefficient for oxygen about 60% smaller than across a water layer of the same thickness, would be expected to raise the barrier for oxygen transport across the fiber cell membrane. Properties of human membranes are compared with those obtained for membranes made of lipids extracted from cortex and nucleus of porcine and bovine eye lenses.
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Affiliation(s)
- Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Lattermann A, Matthäus C, Bergner N, Beleites C, Romeike BF, Krafft C, Brehm BR, Popp J. Characterization of atherosclerotic plaque depositions by Raman and FTIR imaging. JOURNAL OF BIOPHOTONICS 2013; 6:110-121. [PMID: 23139154 DOI: 10.1002/jbio.201200146] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/28/2012] [Accepted: 09/28/2012] [Indexed: 06/01/2023]
Abstract
Spectroscopy-based imaging techniques can provide useful biochemical information about tissue samples. Here, we employ Raman and Fourier transform infrared (IR) imaging to characterize composition and constitution of atherosclerotic plaques of rabbits, fed with a high cholesterol diet. The results were compared with conventional light microscopy after staining with hematoxylin eosin, and elastica van Gieson. The spectral unmixing algorithm vertex component analysis was applied for data analysis and image reconstruction. IR microscopy allowed for differentiation between lipids and proteins in plaques of full aortic cross sections. Raman microscopy further discriminated cholesterol esters, cholesterol and triglycerides. FTIR and Raman images were recorded at a resolution near 20 micrometer per pixel for a large field of view. High resolution Raman images at 1 micrometer per pixel revealed structural details at selected regions of interest. The intima-media and the lipid-protein ratio were determined in five specimens for quantitation. These results correlate well with histopathology. The described method is a promising tool for easy and fast molecular imaging of atherosclerosis.
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Affiliation(s)
- Annika Lattermann
- University Hospital-Friedrich-Schiller-University of Jena, Clinic for Internal Medicine I, Jena, Germany
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50
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Mainali L, Hyde JS, Subczynski WK. Using spin-label W-band EPR to study membrane fluidity profiles in samples of small volume. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 226:35-44. [PMID: 23207176 PMCID: PMC3529815 DOI: 10.1016/j.jmr.2012.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 10/15/2012] [Accepted: 11/03/2012] [Indexed: 05/18/2023]
Abstract
Conventional and saturation-recovery (SR) EPR at W-band (94GHz) using phosphatidylcholine spin labels (labeled at the alkyl chain [n-PC] and headgroup [T-PC]) to obtain profiles of membrane fluidity has been demonstrated. Dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol have been studied, and the results have been compared with similar studies at X-band (9.4 GHz) (L. Mainali, J.B. Feix, J.S. Hyde, W.K. Subczynski, J. Magn. Reson. 212 (2011) 418-425). Profiles of the spin-lattice relaxation rate (T(1)(-1)) obtained from SR EPR measurements for n-PCs and T-PC were used as a convenient quantitative measure of membrane fluidity. Additionally, spectral analysis using Freed's MOMD (microscopic-order macroscopic-disorder) model (E. Meirovitch, J.H. Freed J. Phys. Chem. 88 (1984) 4995-5004) provided rotational diffusion coefficients (R(perpendicular) and R(||)) and order parameters (S(0)). Spectral analysis at X-band provided one rotational diffusion coefficient, R(perpendicular). T(1)(-1), R(perpendicular), and R(||) profiles reflect local membrane dynamics of the lipid alkyl chain, while the order parameter shows only the amplitude of the wobbling motion of the lipid alkyl chain. Using these dynamic parameters, namely T(1)(-1), R(perpendicular), and R(||), one can discriminate the different effects of cholesterol at different depths, showing that cholesterol has a rigidifying effect on alkyl chains to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. The nondynamic parameter, S(0), shows that cholesterol has an ordering effect on alkyl chains at all depths. Conventional and SR EPR measurements with T-PC indicate that cholesterol has a fluidizing effect on phospholipid headgroups. EPR at W-band provides more detailed information about the depth-dependent dynamic organization of the membrane compared with information obtained at X-band. EPR at W-band has the potential to be a powerful tool for studying membrane fluidity in samples of small volume, ~30 nL, compared with a representative sample volume of ~3 μL at X-band.
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Affiliation(s)
| | | | - Witold K. Subczynski
- Author to whom correspondence should be addressed: Witold Karol Subczynski, Ph.D., D.Sc., Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226-0509, Phone: (414) 456-4038, Fax: (414) 456-6512,
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