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Fernandes E, Lopes CM, Lúcio M. Lipid Biomimetic Models as Simple Yet Complex Tools to Predict Skin Permeation and Drug-Membrane Biophysical Interactions. Pharmaceutics 2024; 16:807. [PMID: 38931927 PMCID: PMC11207520 DOI: 10.3390/pharmaceutics16060807] [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: 05/10/2024] [Revised: 06/07/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
The barrier function of the skin is primarily determined by its outermost layer, the Stratum Corneum (SC). The SC consists of corneocytes embedded in a lipid matrix composed mainly of ceramides, cholesterol, and free fatty acids in equimolar proportions and is organised in a complex lamellar structure with different periodicities and lateral packings. This matrix provides a diffusion pathway across the SC for bioactive compounds that are administered to the skin. In this regard, and as the skin administration route has grown in popularity, there has been an increase in the use of lipid mixtures that closely resemble the SC lipid matrix, either for a deeper biophysical understanding or for pharmaceutical and cosmetic purposes. This review focuses on a systematic analysis of the main outcomes of using lipid mixtures as SC lipid matrix models for pharmaceutical and cosmetic purposes. Thus, a methodical evaluation of the main outcomes based on the SC structure is performed, as well as the main recent developments in finding suitable new in vitro tools for permeation testing based on lipid models.
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Affiliation(s)
- Eduarda Fernandes
- CF-UM-UP—Centro de Física das Universidades do Minho e Porto, Departamento de Física, Universidade do Minho, 4710-057 Braga, Portugal
| | - Carla M. Lopes
- FFP-I3ID—Instituto de Investigação, Inovação e Desenvolvimento, FP-BHS—Biomedical and Health Sciences Research Unit, Faculdade de Ciências da Saúde, Universidade Fernando Pessoa, 4200–150 Porto, Portugal;
- UCIBIO—Applied Molecular Biosciences Unit, MedTech–Laboratory of Pharmaceutical Technology, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal
- Associate Laboratory i4HB, Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal
| | - Marlene Lúcio
- CF-UM-UP—Centro de Física das Universidades do Minho e Porto, Departamento de Física, Universidade do Minho, 4710-057 Braga, Portugal
- CBMA—Centro de Biologia Molecular e Ambiental, Departamento de Biologia, Universidade do Minho, 4710-057 Braga, Portugal
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2
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Bouwstra JA, Nădăban A, Bras W, McCabe C, Bunge A, Gooris GS. The skin barrier: An extraordinary interface with an exceptional lipid organization. Prog Lipid Res 2023; 92:101252. [PMID: 37666282 PMCID: PMC10841493 DOI: 10.1016/j.plipres.2023.101252] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/06/2023]
Abstract
The barrier function of the skin is primarily located in the stratum corneum (SC), the outermost layer of the skin. The SC is composed of dead cells with highly organized lipid lamellae in the intercellular space. As the lipid matrix forms the only continuous pathway, the lipids play an important role in the permeation of compounds through the SC. The main lipid classes are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). Analysis of the SC lipid matrix is of crucial importance in understanding the skin barrier function, not only in healthy skin, but also in inflammatory skin diseases with an impaired skin barrier. In this review we provide i) a historical overview of the steps undertaken to obtain information on the lipid composition and organization in SC of healthy skin and inflammatory skin diseases, ii) information on the role CERs, CHOL and FFAs play in the lipid phase behavior of very complex lipid model systems and how this knowledge can be used to understand the deviation in lipid phase behavior in inflammatory skin diseases, iii) knowledge on the role of both, CER subclasses and chain length distribution, on lipid organization and lipid membrane permeability in complex and simple model systems with synthetic CERs, CHOL and FFAs, iv) similarity in lipid phase behavior in SC of different species and complex model systems, and vi) future directions in modulating lipid composition that is expected to improve the skin barrier in inflammatory skin diseases.
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Affiliation(s)
- Joke A Bouwstra
- Division of Biotherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.
| | - Andreea Nădăban
- Division of Biotherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Wim Bras
- Chemical Sciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - Clare McCabe
- School of Engineering & Physical Science, Heriot-Watt University, Edinburgh, Scotland, UK
| | - Annette Bunge
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO 80401, United States of America
| | - Gerrit S Gooris
- Division of Biotherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
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3
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Badhe Y, Schmitt T, Gupta R, Rai B, Neubert RH. Investigating the nanostructure of a CER[NP]/CER[AP]-based stratum corneum lipid matrix model: A combined neutron diffraction & molecular dynamics simulations approach. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - BIOMEMBRANES 2022; 1864:184007. [PMID: 35863424 DOI: 10.1016/j.bbamem.2022.184007] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 06/29/2022] [Accepted: 07/12/2022] [Indexed: 10/17/2022]
Abstract
The human skin provides a physiochemical and biological protective barrier due to the unique structure of its outermost layer known as the Stratum corneum. This layer consists of corneocytes and a multi-lamellar lipid matrix forming a composite, which is a major determining factor for the barrier function of the Stratum corneum. A substantiated understanding of this barrier is necessary, as controlled breaching or modulation of the same is also essential for various health and personal care applications such as topical drug delivery and cosmetics to a name few. In this study, we discuss the state-of-the-art of neutron diffraction techniques, using specifically deuterated lipids, combined with the information obtained from molecular models using molecular dynamics simulations, to understand the structure and barrier function of the Stratum corneum lipid matrix. As an example, the effect of ceramide concentration on a lipid lamella system consisting of CER[NP]/CER[AP]/Cholesterol/free fatty acid (deprotonated) is studied. This study demonstrates the usefulness of the combined approach of neutron diffraction and molecular dynamics simulations for effective analysis of the model systems created for the Stratum corneum lipid matrix. The optimization of force fields by comparison with experimental data is furthermore an important step in the direction of providing a predictive quality.
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4
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Hermet M, Yanis Espinosa R, Elisa Fait M, Yenisleidy de las Zulueta Díaz M, Morcelle S, Laura Bakás S, Ariel Alvarez H, Laura Fanani M. Arginine-based surfactants alter the rheological and in-plane structural properties of stratum corneum model membranes. J Colloid Interface Sci 2022; 631:224-238. [DOI: 10.1016/j.jcis.2022.10.118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 10/17/2022] [Accepted: 10/22/2022] [Indexed: 11/07/2022]
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5
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Nădăban A, Gooris GS, Beddoes CM, Dalgliesh RM, Bouwstra JA. Phytosphingosine ceramide mainly localizes in the central layer of the unique lamellar phase of skin lipid model systems. J Lipid Res 2022; 63:100258. [PMID: 35931203 PMCID: PMC9421324 DOI: 10.1016/j.jlr.2022.100258] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 07/13/2022] [Accepted: 07/15/2022] [Indexed: 11/17/2022] Open
Abstract
Understanding the lipid arrangement within the skin's outermost layer, the stratum corneum (SC), is important for advancing knowledge on the skin barrier function. The SC lipid matrix consists of ceramides (CERs), cholesterol, and free fatty acids, which form unique crystalline lamellar phases, referred to as the long periodicity phase (LPP) and short periodicity phases. As the SC lipid composition is complex, lipid model systems that mimic the properties of native SC are used to study the SC lipid organization and molecular arrangement. In previous studies, such lipid models were used to determine the molecular organization in the trilayer structure of the LPP unit cell. The aim of this study was to examine the location of CER N-(tetracosanoyl)-phytosphingosine (CER NP) in the unit cell of this lamellar phase and compare its position with CER N-(tetracosanoyl)-sphingosine (CER NS). We selected CER NP as it is the most prevalent CER subclass in the human SC, and its location in the LPP is not known. Our neutron diffraction results demonstrate that the acyl chain of CER NP was positioned in the central part of the trilayer structure, with a fraction also present in the outer layers, the same location as determined for the acyl chain of CER NS. In addition, our Fourier transformed infrared spectroscopy results are in agreement with this molecular arrangement, suggesting a linear arrangement for the CER NS and CER NP. These findings provide more detailed insight into the lipid organization in the SC lipid matrix.
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Affiliation(s)
- Andreea Nădăban
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Gerrit S Gooris
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Charlotte M Beddoes
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Robert M Dalgliesh
- ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, United Kingdom
| | - Joke A Bouwstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.
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6
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Fanani ML, Nocelli NE, Zulueta Díaz YDLM. What can we learn about amphiphile-membrane interaction from model lipid membranes? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2022; 1864:183781. [PMID: 34555419 DOI: 10.1016/j.bbamem.2021.183781] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/30/2021] [Accepted: 09/14/2021] [Indexed: 10/20/2022]
Abstract
Surface-active amphiphiles find applications in a wide range of areas of industry such as agrochemicals, personal care, and pharmaceuticals. In many of these applications, interaction with cell membranes is a key factor for achieving their purpose. How do amphiphiles interact with lipid membranes? What are their bases for membrane specificity? Which biophysical properties of membranes are susceptible to modulation by amphiphilic membrane-effectors? What aspects of this interaction are important for performing their function? In our work on membrane biophysics over the years, questions like these have arisen and we now share some of our findings and discuss them in this review. This topic was approached focusing on the membrane properties and their alterations rather than on the amphiphile structure requirements for their interaction. Here, we do not aim to provide a comprehensive list of the modes of action of amphiphiles of biological interest but to help in understanding them.
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Affiliation(s)
- Maria Laura Fanani
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Córdoba, Argentina.
| | - Natalia E Nocelli
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Córdoba, Argentina
| | - Yenisleidy de Las Mercedes Zulueta Díaz
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Córdoba, Argentina
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7
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Strati F, Mukhina T, Neubert RH, Opalka L, Hause G, Schmelzer CE, Menzel M, Brezesinski G. Cerosomes as skin repairing agent: Mode of action studies with a model stratum corneum layer at liquid/air and liquid/solid interfaces. BBA ADVANCES 2022; 2:100039. [PMID: 37082599 PMCID: PMC10074917 DOI: 10.1016/j.bbadva.2021.100039] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The stratum corneum (SC) is the largest physical barrier of the human body. It protects against physical, chemical and biological damages, and avoids evaporation of water from the deepest skin layers. For its correct functioning, the homeostasis of the SC lipid matrix is fundamental. An alteration of the lipid matrix composition and in particular of its ceramide (CER) fraction can lead to the development of pathologies such as atopic dermatitis and psoriasis. Different studies showed that the direct replenishment of SC lipids on damaged skin had positive effects on the recovery of its barrier properties. In this work, cerosomes, i.e. liposomes composed of SC lipids, have been successfully prepared in order to investigate the mechanism of interaction with a model SC lipid matrix. The cerosomes contain CER[NP], D-CER[AP], stearic acid and cholesterol. In addition, hydrogenated soybean phospholipids have been added to one of the formulations leading to an increased stability at neutral pH. For the mode of action studies, monolayer models at the air-water interface and on solid support have been deployed. The results indicated that a strong interaction occurred between SC monolayers and the cerosomes. Since both systems were negatively charged, the driving force for the interaction must be based on the ability of CERs head groups to establish intermolecular hydrogen bonding networks that energetically prevailed against the electrostatic repulsion. This work proved for the first time the mode of action by which cerosomes exploit their function as skin barrier repairing agents on the SC.
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8
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Strati F, Oliveira JSL, Opalka L, Mukhina T, Dobner B, Neubert RHH, Brezesinski G. Two- and Three-Dimensional Physical-Chemical Characterization of CER[AP]: A Study of Stereochemistry and Chain Symmetry. J Phys Chem B 2021; 125:9960-9969. [PMID: 34463098 DOI: 10.1021/acs.jpcb.1c05572] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The stratum corneum represents the first skin barrier against chemical and physical damage. These unique properties are based on its peculiar lipid composition with ceramides (CERs) as the main protagonists. In this study, the structural and chemical properties of the α-OH phytosphingosine [AP] CER class have been investigated. α-OH CERs are present in the stratum corneum in their d-forms; however, in most model systems the diastereomer mixture with the synthetically produced l-form is used. The d-form is well-known to form a hydrogen bonding network that helps to reduce the permeability of the lipid matrix, while the l-form does not show any hydrogen bonding network formation. In this paper, 2D (monolayers) and 3D (aqueous dispersions) models have been used to thoroughly study the physical-chemical behaviors of CER[AP] diastereomers taking into account how the symmetry of the chain pattern influences the behavior of the molecules. The chains of both diastereomers arrange in an oblique unit cell, but only the d-CER[AP] forms a supramolecular lattice (subgel phase) in both model systems. Interestingly, the chain pattern does not play any role in structure formation since the hydrogen bonding network dictates the packing properties. The 1:1 mixture of the diastereomers phase separates into two domains: one is composed of practically pure d-form and the other one is composed of a mixture of the l-form with a certain amount of d-form molecules.
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Affiliation(s)
- Fabio Strati
- Institute of Applied Dermatopharmacy at Martin Luther University Halle-Wittenberg, Weinbergweg 23, 06120 Halle (Saale), Germany
| | - Joana S L Oliveira
- Max Planck Institute of Colloids and Interfaces, Potsdam Science Park, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Lukas Opalka
- Faculty of Pharmacy in Hradec Kralove, Charles University, Akademika Heyrovskeho 1203, Hradec Kralove, 500 05, Czech Republic
| | - Tetiana Mukhina
- Institute for Condensed Matter Physics, Technical University Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy at Martin Luther University Halle-Wittenberg, Weinbergweg 23, 06120 Halle (Saale), Germany
| | - Gerald Brezesinski
- Institute of Applied Dermatopharmacy at Martin Luther University Halle-Wittenberg, Weinbergweg 23, 06120 Halle (Saale), Germany
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9
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Meeusen JW, Donato LJ, Kopecky SL, Vasile VC, Jaffe AS, Laaksonen R. Ceramides improve atherosclerotic cardiovascular disease risk assessment beyond standard risk factors. Clin Chim Acta 2020; 511:138-142. [PMID: 33058843 DOI: 10.1016/j.cca.2020.10.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 10/01/2020] [Indexed: 12/26/2022]
Abstract
Ceramides are bioactive lipids that act as secondary messengers for both intra- and inter-cellular signaling. Elevated plasma concentrations of ceramides are associated with multiple risk factors of atherosclerotic cardiovascular diseases and comorbidities including obesity, insulin resistance and diabetes mellitus. Furthermore, atherosclerotic plaques have been shown to be highly enriched with ceramides. Increases in ceramide content may accelerate atherosclerosis development by promoting LDL infiltration to the endothelium and aggregation within the intima of artery walls. Thus, ceramides appear to play a key role in the development of cardiometabolic disease due to their central location in major metabolic pathways that intersect lipid and glucose metabolism. Recently published data have shown that ceramides are not only of scientific interest but may also have diagnostic value. Their independent prognostic value for future cardiovascular outcomes over and above LDL cholesterol and other traditional risk factors have consistently been shown in numerous clinical studies. Thus, ceramide testing with a mass spectrometer offers a simple, reproducible and cost-effective blood test for risk stratification in atherosclerotic cardiovascular diseases.
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Affiliation(s)
- Jeffrey W Meeusen
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN, United States.
| | - Leslie J Donato
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN, United States
| | | | - Vlad C Vasile
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN, United States; Department of Cardiology, Mayo Clinic, Rochester, MN, United States
| | - Allan S Jaffe
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN, United States; Department of Cardiology, Mayo Clinic, Rochester, MN, United States
| | - Reijo Laaksonen
- Zora Biosciences Oy, Espoo, Finland; Finnish Cardiovascular Research Center, Tampere University, Tampere, Finland
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10
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Beddoes C, Gooris GS, Foglia F, Ahmadi D, Barlow DJ, Lawrence MJ, Demé B, Bouwstra JA. Arrangement of Ceramides in the Skin: Sphingosine Chains Localize at a Single Position in Stratum Corneum Lipid Matrix Models. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:10270-10278. [PMID: 32816488 PMCID: PMC7498151 DOI: 10.1021/acs.langmuir.0c01992] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Understanding the structure of the stratum corneum (SC) is essential to understand the skin barrier process. The long periodicity phase (LPP) is a unique trilayer lamellar structure located in the SC. Adjustments in the composition of the lipid matrix, as in many skin abnormalities, can have severe effects on the lipid organization and barrier function. Although the location of individual lipid subclasses has been identified, the lipid conformation at these locations remains uncertain. Contrast variation experiments via small-angle neutron diffraction were used to investigate the conformation of ceramide (CER) N-(tetracosanoyl)-sphingosine (NS) within both simplistic and porcine mimicking LPP models. To identify the lipid conformation of the twin chain CER NS, the chains were individually deuterated, and their scattering length profiles were calculated to identify their locations in the LPP unit cell. In the repeating trilayer unit of the LPP, the acyl chain of CER NS was located in the central and outer layers, while the sphingosine chain was located exclusively in the middle of the outer layers. Thus, for the CER NS with the acyl chain in the central layer, this demonstrates an extended conformation. Electron density distribution profiles identified that the lipid structure remains consistent regardless of the lipid's lateral packing phase, this may be partially due to the anchoring of the extended CER NS. The presented results provide a more detailed insight on the internal arrangement of the LPP lipids and how they are expected to be arranged in healthy skin.
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Affiliation(s)
- Charlotte
M. Beddoes
- Division
of BioTherapeutics, Leiden Academic Centre for Drug Research, University of Leiden, Einsteinweg 55, Leiden 2333 CC, The Netherlands
| | - Gert S. Gooris
- Division
of BioTherapeutics, Leiden Academic Centre for Drug Research, University of Leiden, Einsteinweg 55, Leiden 2333 CC, The Netherlands
| | - Fabrizia Foglia
- Chemistry
Department, Christopher Ingold Laboratories, University College London, London WC1H 0AJ, United Kingdom
| | - Delaram Ahmadi
- Pharmaceutical
Science Division, King’s College
London, London WC2R 2LS, United Kingdom
| | - David J. Barlow
- Pharmaceutical
Science Division, King’s College
London, London WC2R 2LS, United Kingdom
| | - M. Jayne Lawrence
- Division
of Pharmacy and Optometry, Manchester University, Manchester M13 9PL, United Kingdom
| | - Bruno Demé
- Institute
Laue-Langevin, Grenoble 38000, France
| | - Joke A. Bouwstra
- Division
of BioTherapeutics, Leiden Academic Centre for Drug Research, University of Leiden, Einsteinweg 55, Leiden 2333 CC, The Netherlands
- . Tel: 00 31 71 527 4208. Fax: 00 31 71 527 4565
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11
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Schmitt T, Neubert RHH. State of the Art in Stratum Corneum Research. Part II: Hypothetical Stratum Corneum Lipid Matrix Models. Skin Pharmacol Physiol 2020; 33:213-230. [PMID: 32683377 DOI: 10.1159/000509019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/05/2020] [Indexed: 12/31/2022]
Abstract
This review is the second part of a series which presents the state of the art in stratum corneum (SC) lipid matrix (LM) research in depth. In this part, the various hypothetical models which were developed to describe the structure and function of the SC LM as the skin's barrier will be discussed. New as well as a cumulative assortment of older results which change the view on the different models are considered to conclude how well the different models are holding up today. As a final conclusion, a model, factoring in as much of the known data as possible, is concluded, unifying the varying different models into one which can be developed further, as new results are found in the future. So far, the model is described with a single crystalline or gel-like phase with a certain amount of nanocrystallites of concentrated ceramides (CERs) and free fatty acids and more fluid nanodomains caused by a fluidizing effect of the cholesterol. These domains are dynamically resolved and reformed and do not impair the barrier function. The chain conformation is not completely clear yet; however, an equilibrium of fully extended and hairpin-folded CERs with ratios depending on the properties of each individual CER species is proposed as most likely. An overlapping middle layer as described for the tri-layer model in part I of this series would be present for both conformations. The macroscopic broad-narrow-broad layering, observed in electron micrographs, is explained by an external templating by the lipid envelope, and an internal templating by short and long lipid chains each preferentially show a homophilic association, forming thicker and thinner bilayers, respectively. The degree of influence of the very long ω-hydroxy-CERs is discussed as well.
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Affiliation(s)
- Thomas Schmitt
- Department I, Institute of Anatomy and Cell Biology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg (IADP), Halle/Saale, Germany, .,Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany,
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12
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Badhe Y, Gupta R, Rai B. Development and application of coarse-grained MARTINI model of skin lipid ceramide [AP]. J Mol Model 2020; 26:182. [PMID: 32583227 DOI: 10.1007/s00894-020-04435-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 06/02/2020] [Indexed: 01/10/2023]
Abstract
Stratum corneum (SC), the outermost layer of the skin, contains large variety of lipids, endowing them with the amphiphilic properties, needed to fulfil their key role in skin's barrier function. The individual role of lipid types in the barrier function is difficult to understand due to the immense heterogeneity and complexity of the lipid's organization within the SC. The lipid organization is being explored using both computational (molecular dynamics simulations) and experimental (neutron diffraction) techniques. Even though atomistic simulations provide unprecedented atomic level details, the major limitation is time and length scale that can be achieved with decent computational facility. Alternatively, coarse-grain (CG) models are currently being used to capture physics at bigger time and length scale without losing essential underlined structural information. In this study, a CG model of α-hydroxy phytosphingosines (CER[AP]) is developed based on philosophy of MARTINI force field. At first, the model is validated with various atomistic simulations and available experimental data. Later on, the model's compatibility with other major skin lipids, cholesterol, and free fatty acid (palmitic acid) is checked by simulating a mixture of lipid multilayer in presence and absence of water. The developed model of CER[AP] is able to predict key structural properties within the acceptable error limits. The phenomena of ceramide conformation transformation, cholesterol flip-flop, and specificity of lipid arrangement within the multilayered systems is observed during the simulation. This signifies the importance of model in capturing higher order structural transformations.
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Affiliation(s)
- Yogesh Badhe
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune, 411013, India
| | - Rakesh Gupta
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune, 411013, India.
| | - Beena Rai
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune, 411013, India
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13
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l-Ascorbic acid alkyl esters action on stratum corneum model membranes: An insight into the mechanism for enhanced skin permeation. Colloids Surf B Biointerfaces 2020; 185:110621. [PMID: 31726308 DOI: 10.1016/j.colsurfb.2019.110621] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 10/17/2019] [Accepted: 10/28/2019] [Indexed: 12/26/2022]
Abstract
L-ascorbic acid alkyl esters (ASCn) are lipophilic forms of vitamin C, which act as skin permeation enhancers. We investigated the physical changes induced by incorporating ASCn into stratum corneum (SC) lipid membranes and correlated this with the mechanism proposed in the literature for skin permeation enhancement phenomena. We used lipid monolayers to explore the 2D structure and elasticity of the lipid-enhancer systems. As a comparison, the classic permeation enhancer, oleic acid (OA) and the non-enhancer analogue stearic acid (SA) were analysed. The incorporation of ASCn or OA into SC membranes resulted in more liquid-like films, with a dose-dependent lowering of the compressibility modulus. Brewster angle microscopy (BAM) evidenced partial miscibility of the enhancer with SC lipid components, stabilising the liquid-expanded phase. At the nanoscale, AFM showed that SC lipids form heterogeneous membranes, which underwent structural alterations after incorporating ASCn and fatty acids, such as SA and OA. The lower, cholesterol-enriched phase appears to concentrate the enhancers, whilst the higher ceramide-enriched phase concentrated the non-enhancer SA. Our results and previously reported pieces of evidence indicate a strong pattern in which the rheological properties of SC lipid films are determinant for skin permeation phenomena.
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Mueller J, Trapp M, Neubert RHH. The effect of hydrophilic penetration/diffusion enhancer on stratum corneum lipid models: Part II*: DMSO. Chem Phys Lipids 2019; 225:104816. [PMID: 31525381 DOI: 10.1016/j.chemphyslip.2019.104816] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 08/28/2019] [Accepted: 09/03/2019] [Indexed: 01/14/2023]
Abstract
To optimize dermal and transdermal administration of drugs, the barrier function of the skin, particularly the stratum corneum (SC), needs to be reduced reversibly. For this purpose, penetration/diffusion enhancers such as DMSO can be applied. However, there is the question whether DMSO is an aggressive penetration/diffusion enhancer in pharmaceutical and cosmetical relevant concentrations? Until now, it is unclear if this penetration/diffusion enhancement is caused by an interaction with the SC lipid matrix or related to effects within the corneocytes. Therefore, the effects of the hydrophilic enhancer DMSO on SC models with different dimensionality ranging from bilayers (liposomes) via oligo-layers to multilayers have been investigated in this study. The effects of DMSO should be compared to that of other relevant hydrophilic enhancers such as urea and taurine. An innovative spectrum of methods was applied to ascertain the mode of action of DMSO in relevant concentrations on a molecular scale. The experiments reveal that there is no specific interaction of 10% and 30% DMSO solutions with the SC model systems. Hence, if DMSO is applied in pharmaceutically and cosmetically relevant concentrations, it has no influence on the SC model systems used. Neither an additional water uptake in the head group region nor a decrease of the lipid chain packing density have been observed. The leakage studies on liposomes show that 10% DMSO is causing just a very slight leakage of 8%, lower than the leakage of 19.4% caused by 10% urea (Müller et al., 2016). Consequently, the interactions of DMSO with the SC model lipids used are very low in concentrations of 10% and 30%, respectively. Since the lipid composition in native SC lipid matrix is far more complex than this model mixture, the results can not be directly transferred to the native SC lipid matrix. However, the outcome of this study, together with various findings in the literature give rise to the assumption that the enhancing effect of DMSO concerning the diffusion of relevant hydrophilic drugs and actives appears to be realized via the corneocytes.
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Affiliation(s)
- J Mueller
- Department of Pharmaceutics and Biopharmaceutics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120, Halle, Germany
| | - M Trapp
- Institute Soft Matter and Functional Materials, Helmholtz-Zentrum-Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109, Berlin, Germany
| | - R H H Neubert
- Institute of Applied Dermatopharmacy, Martin Luther University Halle-Wittenberg, Weinbergweg 23, 06120, Halle, Germany.
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15
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Podewitz M, Wang Y, Gkeka P, von Grafenstein S, Liedl KR, Cournia Z. Phase Diagram of a Stratum Corneum Lipid Mixture. J Phys Chem B 2018; 122:10505-10521. [DOI: 10.1021/acs.jpcb.8b07200] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Maren Podewitz
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Yin Wang
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Paraskevi Gkeka
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527 Athens, Greece
| | - Susanne von Grafenstein
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Zoe Cournia
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527 Athens, Greece
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16
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State of the art in Stratum Corneum research: The biophysical properties of ceramides. Chem Phys Lipids 2018; 216:91-103. [PMID: 30291856 DOI: 10.1016/j.chemphyslip.2018.09.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 09/10/2018] [Accepted: 09/29/2018] [Indexed: 11/20/2022]
Abstract
This review is summarizing an important part of the state of the art in stratum corneum research. A complete overview on discoveries about the general biophysical and physicochemical properties of the known ceramide species' is provided. The ceramides are one of the three major components of the lipid matrix and mainly govern its properties and structure. They are shown to exhibit very little redundancy, despite the minor differences in their chemical structure. The results are discussed, compared to each other as well as the current base of knowledge. New interesting aspects and concepts are concluded or suggested. A novel interpretation of the 3-dimensional structure of the lipid matrix and its influence on the barrier function will be discussed. The most important conclusion is the presentation of a new and up to date theoretical model of the nanostructure of the short periodicity phase. The model suggests three perpendicular layers: The rigid head group region, the rigid chain region and, a liquid-like overlapping middle layer. The general principle of the skin barrier function is highlighted in regard to this structure and the ceramides biophysical and physicochemical properties. As a result of these considerations, the entropy vs. enthalpy principle is introduced, shedding light on the function as well as the effectiveness of the skin barrier. Additionally, general ideas to effectively overcome this barrier principle for dermal and transdermal delivery of actives or how to use it for specific targeting of the stratum corneum are proposed.
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17
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The long periodicity phase (LPP) controversy part I: The influence of a natural-like ratio of the CER[EOS] analogue [EOS]-br in a CER[NP]/[AP] based stratum corneum modelling system: A neutron diffraction study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:306-315. [PMID: 29924985 DOI: 10.1016/j.bbamem.2018.06.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 05/07/2018] [Accepted: 06/11/2018] [Indexed: 01/01/2023]
Abstract
This study used neutron diffraction to investigate a ceramide-[NP] C24/[AP] C24 /[EOS]-br C30/cholesterol/lignoceric acid (0.6: 0.3: 0.1: 0.7: 1) based stratum corneum modelling system. By adding specifically deuterated ceramides-[NP]-D3, [AP]-D3, and [EOS]-br-D3, detailed information on the lamellar and the nanostructure of the system was obtained. For the short periodicity phase a natural-like lamellar repeat distance of 5.47 ± 0.02 nm was observed, similar to the [NP]/[AP] base system without the [EOS]-br. Unlike in this system the ceramides here were slightly tilted, hinting towards a slightly less natural arrangement. Due to the deuteration it was possible to observe that the long ceramide chains were overlapping in the lamellar mid-plane. This is considered to be an important feature for the natural stratum corneum. Despite the presence of a ceramide [EOS] analogue - able to form a long phase arrangement - no distinct long periodicity phase was formed, despite a slightly higher than natural ω-acyl ceramide ratio of 10 mol%. The deuterated variant of this ceramide determined that the very long ceramide was integrated into the short periodicity phase, spanning multiple layers instead. The - compared to the base system - unchanged repeat distance highlights the stability of this structure. Furthermore, the localisation of the very long ceramide in the short periodicity phase indicates the possibility of a crosslinking effect and thus a multilayer stabilizing role for the ceramide [EOS]. It can be concluded, that additionally to the mere presence of ceramide-[EOS] more complex conditions have to be met in order to form this long phase. This has to be further investigated in the future.
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18
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Schmitt T, Gupta R, Lange S, Sonnenberger S, Dobner B, Hauß T, Rai B, Neubert RHH. Impact of the ceramide subspecies on the nanostructure of stratum corneum lipids using neutron scattering and molecular dynamics simulations. Part I: impact of CER[NS]. Chem Phys Lipids 2018; 214:58-68. [PMID: 29859142 DOI: 10.1016/j.chemphyslip.2018.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 05/18/2018] [Accepted: 05/28/2018] [Indexed: 11/19/2022]
Abstract
For this study mixtures based on the ceramides [NS] (NS = non-hydroxy-sphingosine) and [AP] (AP = α-hydroxy-phytosphingosine) in a 2:1 and 1:2 ratio, together with cholesterol and lignoceric acid, were investigated. These mixtures are modelling the uppermost skin layer, the stratum corneum. Neutron diffraction, utilizing specifically deuterated ceramide molecules, was used to obtain a maximum amount of experimental detail. Highly detailed molecular dynamics simulations were used to generate even more information from the experimental data. It was possible to observe a single lamellar phase for both systems. They had a lamellar repeat distance of 5.43 ± 0.05 nm for the [NS]/[AP] 2:1 and a slightly shorter one of 5.34 ± 0.05 nm for the 1:2 system. The structure and water content was uninfluenced by excess humidity. Both the experimental and simulation data indicated slightly tilted ceramides, with their C24 chains overlapping in the lamellar mid-plane. This arrangement is well comparable to systems investigated before. The structure of both systems, except for the differing repeat distance, looks similar at first. However, on a smaller scale there were various distinct differences, demonstrating only low redundancy between the different ceramide species, despite only minor chemical differences. The mainly ceramide [AP] determined 1:2 system has a slightly smaller repeat distance. This is a result of a tighter arrangement of the lipids chain along the bilayer normal and increased overlapping of the long chains in the lamellar middle. For the CER[NS] some novel features could be shown, despite it being the overall most investigated ceramide. These include the low adaptability to changed lateral interactions, leading to an increased chain opening. This effect could explain its low miscibility with other lipids. The investigated model systems allows it to directly compare results from the literature which have used ceramide [NS] to the most recent studies using the phytosphingosine ceramides such as ceramide [AP].
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Affiliation(s)
- Thomas Schmitt
- Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg (IADP), Weinbergweg 23, 06120 Halle/Saale, Germany
| | - Rakesh Gupta
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune, 411013, India
| | - Stefan Lange
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany
| | - Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Thomas Hauß
- Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), Hahn-Meitner-Platz 1, 14109, Berlin, Germany
| | - Beena Rai
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune, 411013, India
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg (IADP), Weinbergweg 23, 06120 Halle/Saale, Germany; Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany.
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19
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Schmitt T, Lange S, Dobner B, Sonnenberger S, Hauß T, Neubert RHH. Investigation of a CER[NP]- and [AP]-Based Stratum Corneum Modeling Membrane System: Using Specifically Deuterated CER Together with a Neutron Diffraction Approach. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1742-1749. [PMID: 28949139 DOI: 10.1021/acs.langmuir.7b01848] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Neutron diffraction was used as a tool to investigate the lamellar as well as molecular nanostructure of ceramide-[NP]/ceramide-[AP]/cholesterol/lignoceric acid model systems with a nativelike 2:1 ratio and a 1:2 ratio to study the influence of the ceramide-[AP]. By using mixtures together with cholesterol and free fatty acids as well as a humidity and temperature chamber while measuring, natural conditions were simulated as closely as possible. Despite its simplicity, the system simulated the native stratum corneum lipid matrix fairly closely, showing a similar lamellar thickness with a repeat distance of 5.45 ± 0.1 nm and a similar arrangement with overlapping long C24 chains. Furthermore, despite the very minor chemical difference between ceramide-[NP] and ceramide-[AP], which is only a single OH group, it was possible to demonstrate substantial differences between the structural influence of the two ceramides. Ceramide-[AP] could be concluded to be arranged in such a way that its C24 chain in both ratios is somehow shorter than that of ceramide-[NP], not overlapping as much with the opposite lamellar leaflet. Furthermore, in the unnatural 1:2 ratio, the higher ceramide-[AP] content causes an increased tilt of the ceramide acyl chains. This leads to even less overlapping within the lamellar midplane, whereas the repeat distance stays the same as for the ceramide-[NP]-rich system. In this nativelike 2:1 ratio, the chains are arranged mostly straight, and the long C24 chains show a broad overlapping region in the lamellar midplane.
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Affiliation(s)
- Thomas Schmitt
- Institute of Applied Dermatopharmacy, Martin Luther University Halle-Wittenberg (IADP) , Weinbergweg 23, 06120 Halle/Saale, Germany
| | - Stefan Lange
- Institute of Medical Physics and Biophysics, University of Leipzig , Härtelstraße 16-18, 04107 Leipzig, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU) , Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU) , Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Thomas Hauß
- Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy, Martin Luther University Halle-Wittenberg (IADP) , Weinbergweg 23, 06120 Halle/Saale, Germany
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20
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Sawama Y, Park K, Yamada T, Sajiki H. New Gateways to the Platinum Group Metal-Catalyzed Direct Deuterium-Labeling Method Utilizing Hydrogen as a Catalyst Activator. Chem Pharm Bull (Tokyo) 2018; 66:21-28. [DOI: 10.1248/cpb.c17-00222] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | - Kwihwan Park
- Laboratory of Organic Chemistry, Gifu Pharmaceutical University
| | - Tsuyoshi Yamada
- Laboratory of Organic Chemistry, Gifu Pharmaceutical University
| | - Hironao Sajiki
- Laboratory of Organic Chemistry, Gifu Pharmaceutical University
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21
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Abstract
PURPOSE OF REVIEW The objective of this review was to summarize evidence gathered for the prognostic value of routine and novel blood lipids and lipoproteins measured in patients with acute coronary syndromes (ACS). RECENT FINDINGS Data supports clear association with risk and actionable value for non-high-density lipoprotein (Non-HDL) cholesterol and plasma ceramides in a setting of ACS. The prognostic value and clinical actionability of apolipoprotein B (apoB) and lipoprotein(a) [Lp(a)] in ACS have not been thoroughly tested, while the data for omega-3 fatty acids and oxidized low-density lipoprotein (Ox-LDL) are either untested or more varied. Measuring basic lipids, which should include Non-HDL cholesterol, at the time of presentation for ACS is guideline mandated. Plasma ceramides also provide useful information to guide both treatment decisions and follow-up. Additional studies targeting ACS patients are necessary for apoB, Lp(a), omega-3 fatty acids, and Ox-LDL.
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Affiliation(s)
- Jeffrey W Meeusen
- Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First St. SW, Rochester, MN, 55905, USA.
| | - Leslie J Donato
- Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First St. SW, Rochester, MN, 55905, USA
| | - Allan S Jaffe
- Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First St. SW, Rochester, MN, 55905, USA.,Department of Cardiology, Mayo Clinic, Rochester, MN, USA
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22
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Schmitt T, Lange S, Sonnenberger S, Dobner B, Demé B, Neubert RHH, Gooris G, Bouwstra JA. Determination of the influence of C24 D/(2R)- and L/(2S)-isomers of the CER[AP] on the lamellar structure of stratum corneum model systems using neutron diffraction. Chem Phys Lipids 2017; 209:29-36. [PMID: 29103906 DOI: 10.1016/j.chemphyslip.2017.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 11/01/2017] [Accepted: 11/01/2017] [Indexed: 10/18/2022]
Abstract
This study was able to investigate the different influence of the d- and l-ceramide [AP] on the lamellar as well as molecular nanostructure of stratum corneum simulating lipid model mixtures. In this case, neutron diffraction together with specifically deuterated ceramide was used as an effective tool to investigate the lamellar and the molecular nanostructure of the mixtures. It could clearly be demonstrated, that both isomers show distinctly different characteristics, even though the variation between both is only a single differently arranged OH-group. The l-ceramide [AP] promotes a crystalline like phase behaviour even if mixed with ceramide [NP], cholesterol and free fatty acids. The d-ceramide [AP] only shows crystalline-like features if mixed only with cholesterol and free fatty acids but adopts a native-like behaviour if additionally mixed with ceramide [NP]. It furthermore demonstrates that the l-ceramide [AP] should not be used for any applications concerning ceramide substitution. It could however possibly serve its own purpose, if this crystalline like behaviour has some kind of positive influence on the SC or can be utilized for any practical applications. The results obtained in this study demonstrate that the diastereomers of ceramide [AP] are an attractive target for further research because their influence on the lamellar as well as the nanostructure is exceptionally strong. Additionally, the results furthermore show a very strong influence on hydration of the model membrane. With these properties, the d-ceramide [AP] could be effectively used to simulate native like behaviour even in very simple mixtures and could also have a strong impact on the native stratum corneum as well as high relevance for dermal ceramide substitution. The unnatural l-ceramide [AP] on the other hand should be investigated further, to assess its applicability.
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Affiliation(s)
- Thomas Schmitt
- Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg (IADP), Weinbergweg 23, 06120 Halle/Saale, Germany
| | - Stefan Lange
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany; Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Wolfgang-Langenbeck-Str. 4, 06120 Halle/Saale, Germany
| | - Bruno Demé
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble CEDEX 9, France
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg (IADP), Weinbergweg 23, 06120 Halle/Saale, Germany.
| | - Gert Gooris
- Leiden Academic Centre for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Max Planckweg 8 2333 CE Leiden, The Netherlands
| | - Joke A Bouwstra
- Leiden Academic Centre for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Max Planckweg 8 2333 CE Leiden, The Netherlands
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23
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Fukagawa S, Haramizu S, Sasaoka S, Yasuda Y, Tsujimura H, Murase T. Coffee polyphenols extracted from green coffee beans improve skin properties and microcirculatory function. Biosci Biotechnol Biochem 2017; 81:1814-1822. [DOI: 10.1080/09168451.2017.1345614] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Abstract
Coffee polyphenols (CPPs), including chlorogenic acid, exert various physiological activities. The purpose of this study was to investigate the effects of CPPs on skin properties and microcirculatory function in humans. In this double-blind, placebo-controlled study, 49 female subjects with mildly xerotic skin received either a test beverage containing CPPs (270 mg/100 mL/day) or a placebo beverage for 8 weeks. The ingestion of CPPs significantly lowered the clinical scores for skin dryness, decreased transepidermal water loss, skin surface pH, and increased stratum corneum hydration and the responsiveness of skin blood flow during local warming. Moreover, the amounts of free fatty acids and lactic acid in the stratum corneum significantly increased after the ingestion of CPPs. These results suggest that an 8-week intake of CPPs improve skin permeability barrier function and hydration, with a concomitant improvement in microcirculatory function, leading to efficacy in the alleviation of mildly xerotic skin.
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Affiliation(s)
- Satoko Fukagawa
- Biological Science Laboratories, Kao Corporation, Tochigi, Japan
| | - Satoshi Haramizu
- Biological Science Laboratories, Kao Corporation, Tochigi, Japan
| | - Shun Sasaoka
- Analytical Science Laboratories, Kao Corporation, Tochigi, Japan
| | - Yuka Yasuda
- Analytical Science Laboratories, Kao Corporation, Tochigi, Japan
| | | | - Takatoshi Murase
- Biological Science Laboratories, Kao Corporation, Tochigi, Japan
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24
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Sonnenberger S, Eichner A, Schmitt T, Hauß T, Lange S, Langner A, Neubert RHH, Dobner B. Synthesis of specific deuterated derivatives of the long chained stratum corneum lipids [EOS] and [EOP] and characterization using neutron scattering. J Labelled Comp Radiopharm 2017; 60:316-330. [PMID: 28370273 DOI: 10.1002/jlcr.3504] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/27/2017] [Indexed: 12/28/2022]
Abstract
The synthesis of specific deuterated derivatives of the long chained ceramides [EOS] and [EOP] is described. The structural differences with respect to the natural compounds are founded in the substitution of the 2 double bonds containing linoleic acid by a palmitic acid branched with a methyl group in 10-position. The specific deuteration is introduced both in the branched and in the terminal methyl group, which was realized by common methods of successive deuteration of carboxylic groups in 3 steps. These modified fatty acids resp. the corresponding ceramides [EOS] and [EOP] were prepared for neutron scattering investigations. First results of these investigations were presented in this manuscript showing that the deuterated compounds could be detected in the stratum corneum lipid model membranes. The deuterated ceramides [EOS] and [EOP] are valuable tools to investigate the influence of these long chained ceramide species on the nanostructure of stratum corneum lipid model membranes.
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Affiliation(s)
- Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany
| | - Adina Eichner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany
| | - Thomas Schmitt
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany.,Institute of Applied Dermatopharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Thomas Hauß
- Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - Stefan Lange
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany.,Institute for Medical Physics and Biophysics, University Leipzig, Leipzig, Germany
| | - Andreas Langner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany
| | - Reinhard H H Neubert
- Institute of Applied Dermatopharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg (MLU), Halle (Saale), Germany
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25
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Influence of the penetration enhancer isopropyl myristate on stratum corneum lipid model membranes revealed by neutron diffraction and 2 H NMR experiments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:745-755. [DOI: 10.1016/j.bbamem.2017.01.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 01/21/2017] [Accepted: 01/25/2017] [Indexed: 12/21/2022]
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26
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Sonnenberger S, Eichner A, Hauß T, Schroeter A, Neubert RH, Dobner B. Synthesis of specifically deuterated ceramide [AP]-C18 and its biophysical characterization using neutron diffraction. Chem Phys Lipids 2017; 204:15-24. [DOI: 10.1016/j.chemphyslip.2017.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 01/13/2017] [Accepted: 02/03/2017] [Indexed: 12/27/2022]
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27
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Schroeter A, Stahlberg S, Školová B, Sonnenberger S, Eichner A, Huster D, Vávrová K, Hauß T, Dobner B, Neubert RHH, Vogel A. Phase separation in ceramide[NP] containing lipid model membranes: neutron diffraction and solid-state NMR. SOFT MATTER 2017; 13:2107-2119. [PMID: 28225091 DOI: 10.1039/c6sm02356h] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The stratum corneum is the outermost layer of the skin and protects the organism against external influences as well as water loss. It consists of corneocytes embedded in a mixture of ceramides, fatty acids, and cholesterol in a molar ratio of roughly 1 : 1 : 1. The unique structural and compositional arrangement of these stratum corneum lipids is responsible for the skin barrier properties. Many studies investigated the organization of these barrier lipids and, in particular, the exact conformation of ceramides. However, so far no consensus has been reached. In this study, we investigate a model system comprised of N-(non-hydroxy-tetracosanoyl)-phytosphingosine/cholesterol/tetracosanoic acid (CER[NP]-C24/CHOL/TA) at a 1 : 1 : 1 molar ratio using neutron diffraction and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Deuterated variants of all three lipid components of the model system were used to enable their separate investigation in the NMR spectra and quantification of the amount of molecules in each phase. Neutron scattering experiments show the coexistence of two lipid phases at low temperatures with repeat spacings of 54.2 Å and 43.0 Å at a physiological skin temperature of 32 °C. They appear to be indistinguishable in the 2H NMR spectra as both phases are crystalline and ceramide molecules do not rotate around their long axis on a microsecond timescale. The evolution of these phases upon heating is followed and with increasing temperature fluid and even isotropically mobile molecules are observed. A model of the organization of the lamellar phases is proposed in which the thicker phase consists of CER[NP]-C24 in a hairpin conformation mixed with CHOL and TA, while the phase with a repeat spacing of 43.0 Å contains CER[NP]-C24 in a V-shape conformation.
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Affiliation(s)
- Annett Schroeter
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Sören Stahlberg
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
| | - Barbora Školová
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany. and Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Adina Eichner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
| | - Kateřina Vávrová
- Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Thomas Hauß
- Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum für Materialien und Energie, Berlin, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Reinhard H H Neubert
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany and Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Alexander Vogel
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
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Eichner A, Sonnenberger S, Dobner B, Hauß T, Schroeter A, Neubert RH. Localization of methyl-branched ceramide [EOS] species within the long-periodicity phase in stratum corneum lipid model membranes: A neutron diffraction study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2911-2922. [DOI: 10.1016/j.bbamem.2016.09.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 08/25/2016] [Accepted: 09/03/2016] [Indexed: 01/03/2023]
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Yamada T, Park K, Yasukawa N, Morita K, Monguchi Y, Sawama Y, Sajiki H. Mild and Direct Multiple Deuterium-Labeling of Saturated Fatty Acids. Adv Synth Catal 2016. [DOI: 10.1002/adsc.201600363] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Tsuyoshi Yamada
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Kwihwan Park
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Naoki Yasukawa
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Kosuke Morita
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Yasunari Monguchi
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Yoshinari Sawama
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Hironao Sajiki
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
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Gupta R, Rai B. Molecular Dynamics Simulation Study of Skin Lipids: Effects of the Molar Ratio of Individual Components over a Wide Temperature Range. J Phys Chem B 2015; 119:11643-55. [DOI: 10.1021/acs.jpcb.5b02093] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rakesh Gupta
- Tata Research Development
and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune - 411013, India
| | - Beena Rai
- Tata Research Development
and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune - 411013, India
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Boncheva M. The physical chemistry of the stratum corneum lipids. Int J Cosmet Sci 2014; 36:505-15. [PMID: 25230344 DOI: 10.1111/ics.12162] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 09/11/2014] [Indexed: 12/20/2022]
Abstract
This article summarizes the current knowledge of the composition, self-assembly, and molecular organization of the stratum corneum (SC) lipids, reviews the evidence connecting these parameters and the barrier properties of human skin, and outlines the immediate issues in the field of SC lipid research.
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Affiliation(s)
- M Boncheva
- Corporate R&D Division, Firmenich SA, PO Box 239, Route des Jeunes 1, Geneva, CH-1211, Switzerland
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Kiselev MA, Ermakova EV, Gruzinov AY, Zabelin AV. Formation of the long-periodicity phase in model membranes of the outermost layer of skin (Stratum corneum). CRYSTALLOGR REP+ 2014. [DOI: 10.1134/s106377451306014x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ryabova NY, Gruzinov AY, Zabelin AV. Synchrotron X-ray diffraction study of the structure of oral stratum corneum model lipid membranes. CRYSTALLOGR REP+ 2014. [DOI: 10.1134/s106377451401012x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Costa A, Siqueira Talarico A, Parra Duarte CDO, Silva Pereira C, de Souza Weimann ET, Sabino de Matos L, Della Coletta LC, Fidelis MC, Tannous TS, Vasconcellos C. Evaluation of the Quantitative and Qualitative Alterations in the Fatty Acid Contents of the Sebum of Patients with Inflammatory Acne during Treatment with Systemic Lymecycline and/or Oral Fatty Acid Supplementation. Dermatol Res Pract 2013; 2013:120475. [PMID: 24191156 PMCID: PMC3803126 DOI: 10.1155/2013/120475] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 08/07/2013] [Indexed: 12/13/2022] Open
Abstract
Background. Acne is a dermatosis that involves an altered sebum pattern. Objectives. (1) To evaluate if a treatment based on antibiotics (lymecycline) can alter fatty acids contents of the sebum of patients with acne; (2) to evaluate if oral supplementation of fatty acids can interfere with fatty acids contents of the sebum of patients with acne; (3) to evaluate if there is any interaction in fatty acids contents of the sebum of patients with acne when they use both antibiotics and oral supplementation of fatty acids. Methods. Forty-five male volunteers with inflammatory acne vulgaris were treated with 300 mg of lymecycline per day, with 540 mg of γ-linolenic acid, 1,200 mg of linoleic acid, and 510 mg of oleic acid per day, or with both regimens for 90 days. Every 30 days, a sample of sebum from the forehead was collected for fatty acids' chromatographic analysis. Results. Twelve fatty acids studied exhibited some kind of pattern changes during the study: C12:0, C14:0, C15:0, C16:1, C18:0, C18:1n9c+C18:1n9t, C18:2n6t, C18:3n6, C18:3n3, C20:1, C22:0, and C24:0. Conclusions. The daily administration of lymecycline and/or specific fatty acids may slightly influence some fatty acids levels present in the sebum of patients with inflammatory acne vulgaris.
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Affiliation(s)
- Adilson Costa
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
- KOLderma Clinical Trials Institute, Campinas, SP, Brazil
| | - Aline Siqueira Talarico
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
| | | | - Caroline Silva Pereira
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
| | | | - Lissa Sabino de Matos
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
| | | | - Maria Carolina Fidelis
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
| | - Thaísa Saddi Tannous
- Service of Dermatology of the Pontifical Catholic University of Campinas, Campinas, SP, Brazil
| | - Cidia Vasconcellos
- Department of Dermatology of the University of Sao Paulo, Sao Paulo, SP, Brazil
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Ryabova NY, Sheverev SG, Hauß T. Neutron diffraction studies of oral stratum corneum model lipid membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2013; 42:621-9. [DOI: 10.1007/s00249-013-0910-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/28/2013] [Accepted: 05/09/2013] [Indexed: 11/29/2022]
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Schroeter A, Engelbrecht T, Neubert RHH. Influence of short chain ceramides and lipophilic penetration enhancers on the nano-structure of stratum corneum model membranes studied using neutron diffraction. Front Chem Sci Eng 2013. [DOI: 10.1007/s11705-013-1302-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Ochalek M, Podhaisky H, Ruettinger HH, Neubert R, Wohlrab J. SC lipid model membranes designed for studying impact of ceramide species on drug diffusion and permeation, Part III: Influence of penetration enhancer on diffusion and permeation of model drugs. Int J Pharm 2012; 436:206-13. [DOI: 10.1016/j.ijpharm.2012.06.044] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/17/2012] [Accepted: 06/20/2012] [Indexed: 11/27/2022]
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38
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SC lipid model membranes designed for studying impact of ceramide species on drug diffusion and permeation – Part II: Diffusion and permeation of model drugs. Eur J Pharm Biopharm 2012; 82:360-6. [DOI: 10.1016/j.ejpb.2012.06.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/20/2012] [Accepted: 06/11/2012] [Indexed: 11/20/2022]
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Ochalek M, Heissler S, Wohlrab J, Neubert R. Characterization of lipid model membranes designed for studying impact of ceramide species on drug diffusion and penetration. Eur J Pharm Biopharm 2012; 81:113-20. [DOI: 10.1016/j.ejpb.2012.02.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 12/16/2011] [Accepted: 02/06/2012] [Indexed: 11/28/2022]
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Engelbrecht TN, Schroeter A, Hauß T, Neubert RH. Lipophilic penetration enhancers and their impact to the bilayer structure of stratum corneum lipid model membranes: Neutron diffraction studies based on the example Oleic Acid. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2798-806. [DOI: 10.1016/j.bbamem.2011.08.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 07/29/2011] [Accepted: 08/09/2011] [Indexed: 10/17/2022]
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