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Kloudová B, Vrkoslav V, Polášek M, Bosáková Z, Cvačka J. Structural characterization of wax esters using ultraviolet photodissociation mass spectrometry. Anal Bioanal Chem 2024; 416:5497-5512. [PMID: 39030399 PMCID: PMC11427557 DOI: 10.1007/s00216-024-05434-2] [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: 04/02/2024] [Revised: 07/01/2024] [Accepted: 07/03/2024] [Indexed: 07/21/2024]
Abstract
Wax esters play critical roles in biological systems, serving functions from energy storage to chemical signaling. Their diversity is attributed to variations in alcohol and acyl chains, including their length, branching, and the stereochemistry of double bonds. Traditional analysis by mass spectrometry with collisional activations (CID, HCD) offers insights into acyl chain lengths and unsaturation level. Still, it falls short in pinpointing more nuanced structural features like the position of double bonds. As a solution, this study explores the application of 213-nm ultraviolet photodissociation (UVPD) for the detailed structural analysis of wax esters. It is shown that lithium adducts provide unique fragments as a result of Norrish and Norrish-Yang reactions at the ester moieties and photoinduced cleavages of double bonds. The product ions are useful for determining chain lengths and localizing double bonds. UVPD spectra of various wax esters are presented systematically, and the effect of activation time is discussed. The applicability of tandem mass spectrometry with UVPD is demonstrated for wax esters from natural sources. The UHPLC analysis of jojoba oil proves the compatibility of MS2 UVPD with the chromatography time scale, and a direct infusion is used to analyze wax esters from vernix caseosa. Data shows the potential of UVPD and its combination with CID or HCD in advancing our understanding of wax ester structures.
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Affiliation(s)
- Barbora Kloudová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo náměstí 542/2, 160 00, Prague 6, Czech Republic
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic
| | - Vladimír Vrkoslav
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo náměstí 542/2, 160 00, Prague 6, Czech Republic
| | - Miroslav Polášek
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 23, Prague 8, Czech Republic
| | - Zuzana Bosáková
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo náměstí 542/2, 160 00, Prague 6, Czech Republic.
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic.
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2
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Ali O, Szabó A. Review of Eukaryote Cellular Membrane Lipid Composition, with Special Attention to the Fatty Acids. Int J Mol Sci 2023; 24:15693. [PMID: 37958678 PMCID: PMC10649022 DOI: 10.3390/ijms242115693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 11/15/2023] Open
Abstract
Biological membranes, primarily composed of lipids, envelop each living cell. The intricate composition and organization of membrane lipids, including the variety of fatty acids they encompass, serve a dynamic role in sustaining cellular structural integrity and functionality. Typically, modifications in lipid composition coincide with consequential alterations in universally significant signaling pathways. Exploring the various fatty acids, which serve as the foundational building blocks of membrane lipids, provides crucial insights into the underlying mechanisms governing a myriad of cellular processes, such as membrane fluidity, protein trafficking, signal transduction, intercellular communication, and the etiology of certain metabolic disorders. Furthermore, comprehending how alterations in the lipid composition, especially concerning the fatty acid profile, either contribute to or prevent the onset of pathological conditions stands as a compelling area of research. Hence, this review aims to meticulously introduce the intricacies of membrane lipids and their constituent fatty acids in a healthy organism, thereby illuminating their remarkable diversity and profound influence on cellular function. Furthermore, this review aspires to highlight some potential therapeutic targets for various pathological conditions that may be ameliorated through dietary fatty acid supplements. The initial section of this review expounds on the eukaryotic biomembranes and their complex lipids. Subsequent sections provide insights into the synthesis, membrane incorporation, and distribution of fatty acids across various fractions of membrane lipids. The last section highlights the functional significance of membrane-associated fatty acids and their innate capacity to shape the various cellular physiological responses.
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Affiliation(s)
- Omeralfaroug Ali
- Agrobiotechnology and Precision Breeding for Food Security National Laboratory, Institute of Physiology and Animal Nutrition, Department of Animal Physiology and Health, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary;
| | - András Szabó
- Agrobiotechnology and Precision Breeding for Food Security National Laboratory, Institute of Physiology and Animal Nutrition, Department of Animal Physiology and Health, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary;
- HUN-REN-MATE Mycotoxins in the Food Chain Research Group, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary
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3
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Butovich IA, Wilkerson A, Yuksel S. Dysregulation of Lipid Metabolism in Aging Meibomian Glands and Its Molecular Markers. Int J Mol Sci 2023; 24:13512. [PMID: 37686319 PMCID: PMC10488057 DOI: 10.3390/ijms241713512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/24/2023] [Accepted: 08/27/2023] [Indexed: 09/10/2023] Open
Abstract
The main function of exocrine Meibomian glands (MGs) is to produce a lipid-rich secretion called meibum which plays a critical role in maintaining the ocular surface homeostasis of humans and most mammals. The chemical composition of meibum, and its quantity produced by MGs, largely determine whether it can fulfill its role successfully. Aging was frequently associated with the onset of various MG-related pathologies. The goal of this study was to determine how aging affects the chemical composition and quantity of meibum in mice, and identify possible molecular markers of aging. Unbiased, untargeted and targeted lipidomic evaluation of mouse MG lipids was conducted using liquid chromatography-high-resolution mass spectrometry, and the results were analyzed using Principal Component, Orthogonal Projections to Latent Structures Discriminant, and Partial Least Square Discriminant Analyses. We found that aging leads to dysregulation of lipid metabolism in MGs, changing the ratios of major classes of MG lipids (such as wax esters, triacylglycerols, and phospholipids) in a progressive manner. Several lipid species that belong to these groups of MG lipids are proposed as clear markers of aging in a mouse model.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
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4
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Walker MK, Bailey LS, Basso KB, Redfern RR. Nonpolar Lipids Contribute to Midday Fogging During Scleral Lens Wear. Invest Ophthalmol Vis Sci 2023; 64:7. [PMID: 36630141 PMCID: PMC9840443 DOI: 10.1167/iovs.64.1.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 12/15/2022] [Indexed: 01/12/2023] Open
Abstract
Purpose To determine correlations between lipids in the fluid reservoir (FR) and the severity of midday fogging (MDF) in scleral lens (SL) wear. Methods SL neophytes were recruited to wear custom SL for 4 days, examined after 8 hours on days 1 and 4. Lens vault and MDF were quantified from anterior segment optical coherence tomography (AS-OCT), and the FR was collected and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Relative abundance of lipids was compared to MDF scores using nonparametric correlation testing (Spearman rank). Ocular surface and SL fitting characteristics (lens vault, fitting curves) were likewise compared to MDF. Results Thirteen participants (26 eyes, 69% female, 28 ± 9 years old) were included in this study. MDF severity after 8 hours of SL wear was 33 ± 29 units on day 1 and 28 ± 24 units on day 4 (r = .94; P < 0.01). Twelve samples were analyzed using LC-MS/MS, and a total of 170 distinct lipid species were detected. The lipid classes with greatest correlation to MDF were the wax esters (r = .73, P = 0.01), cholesteryl esters (r = .59; P = 0.049), and triacylglycerols (r = .64, P = 0.03). Polar lipids were observed abundantly in all samples. None of the measured ocular surface or fitting outcomes were correlated to MDF. Conclusions Nonpolar lipids were the greatest contributors to MDF among these normal participants. Polar lipids may be due to cellular debris, although they do not appear contributory to MDF.
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Affiliation(s)
- Maria K. Walker
- College of Optometry, The Ocular Surface Institute, University of Houston, Houston, Texas, United States
| | - Laura S. Bailey
- Department of Chemistry, University of Florida, Gainesville, Florida, United States
| | - Kari B. Basso
- Department of Chemistry, University of Florida, Gainesville, Florida, United States
| | - Rachel R. Redfern
- College of Optometry, The Ocular Surface Institute, University of Houston, Houston, Texas, United States
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5
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Kyselová L, Vítová M, Řezanka T. Very long chain fatty acids. Prog Lipid Res 2022; 87:101180. [PMID: 35810824 DOI: 10.1016/j.plipres.2022.101180] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 06/21/2022] [Accepted: 07/04/2022] [Indexed: 11/26/2022]
Abstract
Very long chain fatty acids (VLCFAs) are important components of various lipid classes in most organisms, from bacteria to higher plants and mammals, including humans. VLCFAs, or very long chain polyunsaturated fatty acids (VLCPUFAs), can be defined as fatty acids with 23 or more carbon atoms in the molecule. The main emphasis in this review is on the analysis of these acids, including obtaining standards from natural sources or their synthesis. Furthermore, the occurrence and analysis of these compounds in both lower (bacteria, invertebrates) and higher organisms (flowering plants or mammals) are discussed in detail. Attention is paid to their biosynthesis, especially the elongation of very long chain fatty acids protein (ELOVL4). This review deals with papers describing these very interesting compounds, whose chemical, biochemical and biological properties have not been fully explored.
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Affiliation(s)
- Lucie Kyselová
- Research Institute of Brewing and Malting, Lípová 511, 120 44 Prague, Czech Republic.
| | - Milada Vítová
- Institute of Botany, Czech Academy of Sciences, Centre for Phycology, Dukelská 135, 379 01 Třeboň, Czech Republic.
| | - Tomáš Řezanka
- Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
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6
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Viitaja T, Raitanen JE, Hynynen A, Moilanen J, Svedström K, Paananen RO, Ekholm FS. On the importance of chain branching in tear film lipid layer wax and cholesteryl esters. Colloids Surf B Biointerfaces 2022; 214:112429. [PMID: 35278859 DOI: 10.1016/j.colsurfb.2022.112429] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 11/30/2022]
Abstract
The tear film lipid layer (TFLL) is important to the maintenance of ocular surface health. Surprisingly, information on the individual roles of the myriad of unique lipids found therein is limited. The most abundant lipid species are the wax esters (WE) and cholesteryl esters (CE), and, especially their branched analogs. The isolation of these lipid species from the TFLL has proved to be tedious, and as a result, insights on their biophysical profiles and role in the TFLL is currently lacking. Herein, we circumvent these issues by a total synthesis of the most abundant iso-methyl branched WEs and CEs found in the TFLL. Through a detailed characterization of the biophysical properties, by the use of Langmuir monolayer and wide-angle X-ray scattering techniques, we demonstrate that chain branching alters the behavior of these lipid species on multiple levels. Taken together, our results fill an important knowledge gap concerning the structure and function of the TFLL on the whole.
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Affiliation(s)
- Tuomo Viitaja
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland; Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, Helsinki FI-00290, Finland
| | - Jan-Erik Raitanen
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland
| | - Antti Hynynen
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, Helsinki FI-00290, Finland
| | - Kirsi Svedström
- Department of Physics, University of Helsinki, P.O. Box 64, Helsinki FI-00014, Finland
| | - Riku O Paananen
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland; Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, Helsinki FI-00290, Finland.
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland.
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7
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Biochemistry of human tear film: A review. Exp Eye Res 2022; 220:109101. [DOI: 10.1016/j.exer.2022.109101] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 04/18/2022] [Accepted: 04/26/2022] [Indexed: 12/13/2022]
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8
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Widjaja-Adhi MAK, Chao K, Golczak M. Mouse models in studies on the etiology of evaporative dry eye disease. Exp Eye Res 2022; 219:109072. [DOI: 10.1016/j.exer.2022.109072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/28/2022] [Accepted: 04/05/2022] [Indexed: 11/26/2022]
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9
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Mudgil P. Antimicrobial Tear Lipids in the Ocular Surface Defense. Front Cell Infect Microbiol 2022; 12:866900. [PMID: 35433501 PMCID: PMC9008483 DOI: 10.3389/fcimb.2022.866900] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/07/2022] [Indexed: 12/05/2022] Open
Abstract
The concept of antimicrobial lipids as effectors of innate host defense is an emerging field. There is limited knowledge on the antimicrobial role of lipids in the ocular environment. Tears act as first line of defense to protect the ocular surface from infections. Antimicrobial effects of tear lipids have been demonstrated using meibomian lipids that are the source of majority of lipids in tears. This article describes the knowledge available on the antimicrobial role of tear lipids at the ocular surface and the antimicrobial potential of various lipid classes present in tears that can contribute to antimicrobial protection of the eye. Like other mucosal secretions, tears contain many proteins and lipids with known antimicrobial effects. The antimicrobial defense of tears is far stronger than can be demonstrated by the effects of individual compounds many of which are present in low concentrations but synergistic and additive interactions between them provide substantial antimicrobial protection to the ocular surface. It is inferred that antimicrobial lipids play important role in innate defense of tears, and cooperative interactions between various antimicrobial lipids and proteins in tears provide a potent host defense mechanism that is effective against a broad spectrum of pathogens and renders self-sterilizing properties to tears for keeping the microbial load low at the ocular surface.
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10
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Safonova TN, Medvedeva ES. [Modern possibilities of studying the composition of meibomian glands secretion]. Vestn Oftalmol 2022; 138:84-89. [PMID: 35234426 DOI: 10.17116/oftalma202213801184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
As the main source of various lipids, the meibomian glands are involved in the formation of lipid layer of the tear film and the maintenance of homeostasis of the ocular surface. This process is directly dependent on the chemical composition and thickness of the lipid layer. In addition to lipid components, the meibum also contains various proteins that affect the properties of the tear film. The introduction of various modifications of mass spectrometry into clinical practice is a new diagnostic approach that allows obtaining information about the composition of meibomian glands secretion and tears.
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Affiliation(s)
- T N Safonova
- Research Institute of Eye Diseases, Moscow, Russia
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11
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Biophysical properties of tear film lipid layer II. Polymorphism of FAHFA. Biophys J 2022; 121:451-458. [PMID: 34968427 PMCID: PMC8822609 DOI: 10.1016/j.bpj.2021.12.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 12/04/2021] [Accepted: 12/22/2021] [Indexed: 02/03/2023] Open
Abstract
Fatty acid esters of hydroxy fatty acids (FAHFAs) are a newly discovered class of endogenous lipids that consist of two acyl chains connected through a single ester bond. Being a unique species of FAHFAs, (O-acyl)-ω-hydroxy fatty acids (OAHFAs) differ from other FAHFAs in that their hydroxy fatty acid backbones are ultralong and their hydroxy esterification is believed to be solely at the terminal (ω-) position. Only in recent years with technological advances in lipidomics have OAHFAs been identified as an important component of the tear film lipid layer (TFLL). It was found that OAHFAs account for approximately 4 mol% of the total lipids and 20 mol% of the polar lipids in the TFLL. However, their biophysical function and contribution to the TFLL is still poorly understood. Here we studied the molecular biophysical mechanisms of OAHFAs using palmitic-acid-9-hydroxy-stearic-acid (PAHSA) as a model. PAHSA and OAHFAs share key structural similarities that could result in comparable biophysical properties and molecular mechanisms. With combined biophysical experiments, atomic force microscopy observations, and all-atom molecular dynamics simulations, we found that the biophysical properties of a dynamic PAHSA monolayer under physiologically relevant conditions depend on a balance between kinetics and thermal relaxation. PAHSA molecules at the air-water surface demonstrate unique polymorphic behaviors, which can be explained by configurational transitions of the molecules under various lateral pressures. These findings could have novel implications in understanding biophysical functions that FAHFAs, in general, or OAHFAs, specifically, play in the TFLL.
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12
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Butovich IA, Yuksel S, Leonard B, Gadek T, Polans AS, Albert DM. Novel Lipids of the Rabbit Harderian Gland Improve Tear Stability in an Animal Model of Dry Eye Disease. J Ocul Pharmacol Ther 2021; 37:545-555. [PMID: 34590914 PMCID: PMC8713569 DOI: 10.1089/jop.2021.0015] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: Instability of the tear film leads to evaporative dry eye disease (EDED), but the Harderian gland in some terrestrial vertebrates may produce novel lipids that stabilize the tear film and protect against dry eye. Here, the nonpolar lipids in the Harderian gland and tears of the rabbit but absent in human tears were identified and tested in preclinical studies to determine whether they could treat severe EDED. Methods: Lipids were identified primarily by atmospheric pressure chemical ionization mass spectrometry (MS) and fragmentation MS/MS. An identified lipid was synthesized and formulated as an emulsion and as a cyclodextrin (CD) clathrate. Following doses with test agents and controls, tear film breakup time (TBUT), tear production, corneal fluorescein staining, macrophage infiltration, and goblet cell survival were measured using standard tests at 0, 2 and 4 weeks in an animal model of EDED. Results: The lipid emulsion increased TBUT (P < 0.01) and tear production (P < 0.05), while it decreased corneal staining (P < 0.01) compared to controls. The lipid CD formulation increased TBUT (P < 0.05) and tear production (P < 0.05) but had no significant effect on the remaining test parameters. There were no differences in macrophage infiltration and conjunctival impression cytology scores between the formulations and their vehicle controls. Conclusions: Lipids in the rabbit Harderian gland and tears differ from those identified in human meibum and tears. These unique rabbit lipids may confer a protective effect against EDED and, as supplements to human tears, fulfill a similar role.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Brian Leonard
- Department of Surgical & Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Tom Gadek
- MCAL Therapeutics, Inc., Park City, Utah, USA
| | - Arthur S. Polans
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Daniel M. Albert
- Casey Eye Institute, School of Medicine, Oregon Health & Science University, Portland, Oregon, USA
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13
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Phan MAT, Madigan MC, Stapleton F, Willcox M, Golebiowski B. Human meibomian gland epithelial cell culture models: Current progress, challenges, and future directions. Ocul Surf 2021; 23:96-113. [PMID: 34843998 DOI: 10.1016/j.jtos.2021.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/04/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022]
Abstract
The widely used immortalised human meibomian gland epithelia cell (iHMGEC) line has made possible extensive studies of the biology and pathophysiology of meibomian glands (MG). Tissue culture protocols for iHMGEC have been revised and modified to optimise the growth conditions for cell differentiation and lipid accumulation. iHMGEC proliferate in serum-free medium but require serum or other appropriate exogenous factors to differentiate. Several supplements can enhance differentiation and neutral lipid accumulation in iHMGEC grown in serum-containing medium. In serum-free medium, rosiglitazone, a peroxisome proliferator activator receptor-γ (PPARγ) agonist, is reported to induce iHMGEC differentiation, neutral lipid accumulation and expression of key biomarkers of differentiation. iHMGEC cultured in serum-containing medium under hypoxia or with azithromycin increases DNAse 2 activity, a biomarker of terminal differentiation in sebocytes. The production of lipids with composition similar to meibum has not been observed in vitro and this remains a major challenge for iHMGEC culture. Innovative methodologies such as 3D ex vivo culture of MG and generation of MG organoids from stem cells are important for further developing a model that more closely mimics the in vivo biology of human MG and to facilitate the next generation of studies of MG disease and dry eye.
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Affiliation(s)
- Minh Anh Thu Phan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia.
| | - Michele C Madigan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Fiona Stapleton
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Mark Willcox
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Blanka Golebiowski
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
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14
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Tchegnon E, Liao CP, Ghotbi E, Shipman T, Wang Y, McKay RM, Le LQ. Epithelial stem cell homeostasis in Meibomian gland development, dysfunction, and dry eye disease. JCI Insight 2021; 6:e151078. [PMID: 34499624 PMCID: PMC8564894 DOI: 10.1172/jci.insight.151078] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 09/08/2021] [Indexed: 11/17/2022] Open
Abstract
Dry eye disease affects over 16 million adults in the US, and the majority of cases are due to Meibomian gland dysfunction. Unfortunately, the identity of the stem cells involved in Meibomian gland development and homeostasis is not well elucidated. Here, we report that loss of Krox20, a zinc finger transcription factor involved in the development of ectoderm-derived tissues, or deletion of KROX20-expressing epithelial cells disrupted Meibomian gland formation and homeostasis, leading to dry eye disease secondary to Meibomian gland dysfunction. Ablation of Krox20-lineage cells in adult mice also resulted in dry eye disease, implicating Krox20 in homeostasis of the mature Meibomian gland. Lineage-tracing and expression analyses revealed a restricted KROX20 expression pattern in the ductal areas of the Meibomian gland, although Krox20-lineage cells generate the full, mature Meibomian gland. This suggests that KROX20 marks a stem/progenitor cell population that differentiates to generate the entire Meibomian gland. Our Krox20 mouse models provide a powerful system that delineated the identity of stem cells required for Meibomian gland development and homeostasis and can be used to investigate the factors underlying these processes. They are also robust models of Meibomian gland dysfunction-related dry eye disease, with a potential for use in preclinical therapeutic screening.
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Affiliation(s)
- Edem Tchegnon
- Department of Dermatology and.,Genetics, Development and Disease Graduate Program, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Chung-Ping Liao
- Department of Dermatology and.,Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | | | | | | | | | - Lu Q Le
- Department of Dermatology and.,Genetics, Development and Disease Graduate Program, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Hamon Center for Regenerative Science and Medicine.,Simmons Comprehensive Cancer Center, and.,O'Donnell Brain Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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15
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Abstract
Purpose The purpose of this study was to determine if aging affects meibum lipid composition in non-meibomian gland dysfunction (MGD)/non-dry eye (DE) population. Aging has been repeatedly linked to pathological changes in various tissues and organs, including the onset of MGD and DE, in a number of clinical and population-wide surveys. Both conditions have been associated with abnormal meibum secretion and composition, among other factors. However, the chemical basis for such a connection has not been established yet. Methods To identify and characterize possible changes in the meibum and meibogenesis with aging, lipidomic analyses of meibum samples collected from human subjects of two age groups - young (29 ± 5 years, n = 21) and elderly (68 ± 7 years, n = 29) - with similar male to female ratios in each group were conducted. Intact lipid species from major lipid groups of meibum (such as wax esters, cholesteryl esters, free cholesterol, triacylglycerols, etc.) were compared using lipidome-wide untargeted (such as Principal Component Analysis) and targeted (such as Orthogonal Projections to Latent Structures Discriminant Analysis) approaches, along with focused analyses of specific lipid species in liquid-chromatography mass spectrometry (LC-MS) and tandem mass spectrometry (MS-MS) experiments. Results Extremely high similarities of meibum lipids in the two age groups were observed, with only minor changes in the individual lipid species. The magnitude of the intergroup variability for tested lipid species was comparable to the intragroup variability for the same meibum components. No statistically significant differences in the lipid esterification, elongation, and unsaturation patterns were observed. Conclusions Chronological aging itself seems to have only minor effect on meibogenesis in healthy, non-MGD/non-DE subjects.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
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16
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Fineide F, Chen X, Bjellaas T, Vitelli V, Utheim TP, Jensen JL, Galtung HK. Characterization of Lipids in Saliva, Tears and Minor Salivary Glands of Sjögren's Syndrome Patients Using an HPLC/MS-Based Approach. Int J Mol Sci 2021; 22:ijms22168997. [PMID: 34445702 PMCID: PMC8396590 DOI: 10.3390/ijms22168997] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/13/2021] [Accepted: 08/17/2021] [Indexed: 01/11/2023] Open
Abstract
The diagnostic work-up of primary Sjögren’s syndrome (pSS) includes quantifying saliva and tear production, evaluation of autoantibodies in serum and histopathological analysis of minor salivary glands. Thus, the potential for further utilizing these fluids and tissues in the quest to find better diagnostic and therapeutic tools should be fully explored. Ten samples of saliva and tears from female patients diagnosed with pSS and ten samples of saliva and tears from healthy females were included for lipidomic analysis of tears and whole saliva using high-performance liquid chromatography coupled to time-of-flight mass spectrometry. In addition, lipidomic analysis was performed on minor salivary gland biopsies from three pSS and three non-SS females. We found significant differences in the lipidomic profiles of saliva and tears in pSS patients compared to healthy controls. Moreover, there were differences in individual lipid species in stimulated saliva that were comparable to those of glandular biopsies, representing an intriguing avenue for further research. We believe a comprehensive elucidation of the changes in lipid composition in saliva, tears and minor salivary glands in pSS patients may be the key to detecting pSS-related dry mouth and dry eyes at an early stage. The identified differences may illuminate the path towards future innovative diagnostic methodologies and treatment modalities for alleviating pSS-related sicca symptoms.
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Affiliation(s)
- Fredrik Fineide
- Department of Plastic and Reconstructive Surgery, Oslo University Hospital, 1171 Oslo, Norway; (F.F.); (T.P.U.)
- The Norwegian Dry Eye Clinic, Ole Vigs Gate 32 E, 0366 Oslo, Norway
| | - Xiangjun Chen
- Department of Oral Surgery and Oral Medicine, Faculty of Dentistry, University of Oslo, 0317 Oslo, Norway; (X.C.); (J.L.J.)
| | | | - Valeria Vitelli
- Department of Biostatistics, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, 0316 Oslo, Norway;
| | - Tor Paaske Utheim
- Department of Plastic and Reconstructive Surgery, Oslo University Hospital, 1171 Oslo, Norway; (F.F.); (T.P.U.)
- The Norwegian Dry Eye Clinic, Ole Vigs Gate 32 E, 0366 Oslo, Norway
- Department of Medical Biochemistry, Oslo University Hospital, 1171 Oslo, Norway
- Department of Oral Biology, Faculty of Dentistry, University of Oslo, 0316 Oslo, Norway
| | - Janicke Liaaen Jensen
- Department of Oral Surgery and Oral Medicine, Faculty of Dentistry, University of Oslo, 0317 Oslo, Norway; (X.C.); (J.L.J.)
| | - Hilde Kanli Galtung
- Department of Oral Biology, Faculty of Dentistry, University of Oslo, 0316 Oslo, Norway
- Correspondence:
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17
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Abstract
Purpose: The meibomian glands are located in the tarsal plate of the upper and lower eyelid and are responsible for the production of a lipid-rich secretion, the meibum, which forms the outer component of the tear film. Meibomian gland dysfunction results in excessive evaporation of the tear film and is the leading cause of dry eye disease (DED). Despite the high prevalence of DED, the etiology of meibomian gland dysfunction is only basically understood. In addition, the molecular mechanisms of meibomian gland maturation and physiological function are currently the focus of research.Methods: A systematic literature search was performed using the main scientific databases, including all relevant published articles up to September 2020.Results: This article provides an overview of the current state of knowledge about meibomian gland stem cells, cell surface marker expression and PPARγ signaling, as well as the pathological causes of meibomian gland dysfunction.Conclusion: Androgen deficiency, hyperkeratinization, PPARγ signaling and inflammatory reactions including neutrophil extracellular traps (NETs) seem to be key factors within the pathological processes of the meibomian gland.
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Affiliation(s)
- Jana Dietrich
- Institute of Anatomy, Department of Functional and Clinical Anatomy, Friedrich Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Fabian Garreis
- Institute of Anatomy, Department of Functional and Clinical Anatomy, Friedrich Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Friedrich Paulsen
- Institute of Anatomy, Department of Functional and Clinical Anatomy, Friedrich Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.,Department of Topographic Anatomy and Operative Surgery, Sechenov University, Moscow, Russia
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18
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Walther H, Lorentz H, Heynen M, Kay L, Jones LW. The Impact of Incubation Conditions on In Vitro Phosphatidylcholine Deposition on Contact Lens Materials. Optom Vis Sci 2021; 98:341-349. [PMID: 33828039 DOI: 10.1097/opx.0000000000001680] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
SIGNIFICANCE Previous in vitro measurements of contact lenses commonly investigate the impact of nonpolar tear film lipids (i.e., sterols). Polar lipids, however, are equally important stabilizing components of the tear film. This research explores and presents further knowledge about various aspects of polar lipid uptake that may impact contact lens performance. PURPOSE This study evaluated the impact of incubation time, lipid concentration, and replenishment of an artificial tear solution (ATS) on the uptake of phosphatidylcholine (PC) onto conventional hydrogel (CH) and silicone hydrogel (SH) contact lens materials. METHODS Four SHs and two CH lens materials (n = 4) were soaked in a complex ATS containing radioactive 14C-PC as a probe molecule. Phosphatidylcholine uptake was monitored at various incubation time points (1, 3, 7, 14, and 28 days), with different ATS lipid concentrations (0.5×, 1×, 2×) and with and without regular replenishment of the ATS. Phosphatidylcholine was extracted from the lenses, processed, and counted by a β counter, and accumulated PC (μg/lens) was extrapolated from standard lipid calibration curves. RESULTS All materials exhibited increasing PC deposition over time. Conventional hydrogel materials showed significantly lower PC uptake rates (P < .001) than any of the SH materials. Increasing lipid concentration in the ATS resulted in increased PC binding onto the contact lens materials (P < .001). Replenishing the ATS every other day, however, impacted the PC deposition differently, showing increased binding (P < .001) on CHs and reduced PC deposition for SH materials (P < .001). CONCLUSIONS Length of incubation, lipid concentration in the ATS, and renewal of the incubation solution all influenced the amount of PC that sorbed onto various lens materials and therefore need to be considered when conducting future in vitro deposition studies.
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Affiliation(s)
| | | | - Miriam Heynen
- Centre for Ocular Research & Education, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Lise Kay
- Centre for Ocular Research & Education, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
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19
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Borchman D. Lipid conformational order and the etiology of cataract and dry eye. J Lipid Res 2021; 62:100039. [PMID: 32554545 PMCID: PMC7910524 DOI: 10.1194/jlr.tr120000874] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2020] [Indexed: 12/12/2022] Open
Abstract
Lens and tear film lipids are as unique as the systems they reside in. The major lipid of the human lens is dihydrosphingomylein, found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1, more than anywhere else in the body. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins; the lowest amount of oxygen of any tissue; and contains almost no intracellular organelles. The tear film lipid layer (TFLL) is also unique. The TFLL is a thin (100 nm) layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. The major lipids of the TFLL are wax esters and cholesterol esters that are not found in the lens. The hydrocarbon chains associated with the esters are longer than those found anywhere else in the body (as long as 32 carbons), and many are branched. Changes in the composition and structure of the 30,000 different moieties of TFLL contribute to the instability of tears. The focus of the current review is how spectroscopy has been used to elucidate the relationships between lipid composition, conformational order and function, and the etiology of cataract and dry eye.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202.
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20
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Yeboah GK, Lobanova ES, Brush RS, Agbaga MP. Very long chain fatty acid-containing lipids: a decade of novel insights from the study of ELOVL4. J Lipid Res 2021; 62:100030. [PMID: 33556440 PMCID: PMC8042400 DOI: 10.1016/j.jlr.2021.100030] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 01/12/2021] [Accepted: 01/27/2021] [Indexed: 11/18/2022] Open
Abstract
Lipids play essential roles in maintaining cell structure and function by modulating membrane fluidity and cell signaling. The fatty acid elongase-4 (ELOVL4) protein, expressed in retina, brain, Meibomian glands, skin, testes and sperm, is an essential enzyme that mediates tissue-specific biosynthesis of both VLC-PUFA and VLC-saturated fatty acids (VLC-SFA). These fatty acids play critical roles in maintaining retina and brain function, neuroprotection, skin permeability barrier maintenance, and sperm function, among other important cellular processes. Mutations in ELOVL4 that affect biosynthesis of these fatty acids cause several distinct tissue-specific human disorders that include blindness, age-related cerebellar atrophy and ataxia, skin disorders, early-childhood seizures, mental retardation, and mortality, which underscores the essential roles of ELOVL4 products for life. However, the mechanisms by which one tissue makes VLC-PUFA and another makes VLC-SFA, and how these fatty acids exert their important functional roles in each tissue, remain unknown. This review summarizes research over that last decade that has contributed to our current understanding of the role of ELOVL4 and its products in cellular function. In the retina, VLC-PUFA and their bioactive "Elovanoids" are essential for retinal function. In the brain, VLC-SFA are enriched in synaptic vesicles and mediate neuronal signaling by determining the rate of neurotransmitter release essential for normal neuronal function. These findings point to ELOVL4 and its products as being essential for life. Therefore, mutations and/or age-related epigenetic modifications of fatty acid biosynthetic gene activity that affect VLC-SFA and VLC-PUFA biosynthesis contribute to age-related dysfunction of ELOVL4-expressing tissues.
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Affiliation(s)
- Gyening Kofi Yeboah
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Ekaterina S Lobanova
- Department of Ophthalmology Research, University of Florida, Gainesville, FL, USA
| | - Richard S Brush
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK, USA
| | - Martin-Paul Agbaga
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK, USA.
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21
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Wilkerson A, Bhat N, Pham HQH, Yuksel S, Butovich I. Physiological effects of inactivation and the roles of Elovl3/ELOVL3 in maintaining ocular homeostasis. FASEB J 2021; 35:e21327. [PMID: 33455016 PMCID: PMC7891900 DOI: 10.1096/fj.202002323r] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 12/22/2022]
Abstract
Recently, elongase of very long chain fatty acids-3 (ELOVL3) was demonstrated to play a pivotal role in physiology and biochemistry of the ocular surface by maintaining a proper balance in the lipid composition of meibum. The goal of this study was to further investigate the effects of ELOVL3 ablation in homozygous Elovl3-knockout mice (E3hom) in comparison with age and sex matched wild-type controls (E3wt). Slit lamp examination of the ocular surface of mice, and histological examination of their ocular tissues, highlighted a severe negative impact of Elovl3 inactivating mutation on the Meibomian glands (MG) and conjunctiva of mice. MG transcriptomes of the E3hom and E3wt mice were assessed and revealed a range of up- and downregulated genes related to lipid biosynthesis, inflammation, and stress response, compared with E3wt mice. Heat stage polarized light microscopy was used to assess melting characteristics of normal and abnormal meibum. The loss of Elovl3 led to a 8°C drop in the melting temperature of meibum in E3hom mice, and increased its fluidity. Also noted were the excessive accumulation of lipid material and tears around the eye and severe ocular inflammation, among other abnormalities.
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Affiliation(s)
- Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Hoang Quoc Hai Pham
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Igor Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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22
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Abstract
The precorneal tear film keeps the eye surface moist and helps to maintain normal eye function. The outermost lipid layer of the tear film, which attenuates tear film evaporation, contains meibum secreted from the meibomian gland. Most meibum lipids are neutral, including wax esters (WEs), cholesteryl esters (CEs), and diesters (DEs), along with some polar lipids including free fatty acids (FFAs), O-acyl-ω-hydroxy fatty acids (OAHFAs), and trace phospholipids. Detection of neutral lipids by mass spectrometry (MS) is challenging due to interference from impurities, particularly when working with minute-volume meibum samples. Here, we describe procedures for sample preparation and MS analysis of these elusive meibum lipids that can be used to examine dry eye disease mechanisms. Because the method described here minimizes impurity peaks for lipids generally, neutral and otherwise, it may be applied to high-sensitivity analysis of other biological samples.
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Affiliation(s)
- Jianzhong Chen
- Department of Optometry and Vision Science, The University of Alabama at Birmingham, Birmingham, AL, USA.
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23
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Price E, Larrabure D, Gonzales B, McClure P, Espinoza E. Forensic identification of the keratin fibers of South American camelids by ambient ionization mass spectrometry: Vicuña, alpaca and guanaco. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8916. [PMID: 32770752 DOI: 10.1002/rcm.8916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/14/2020] [Accepted: 08/02/2020] [Indexed: 06/11/2023]
Abstract
RATIONALE The keratin fleece of the endangered vicuña (Vicugna vicugna) commands a high value in international markets, and this trade has caused illegal poaching and a substantial decrease in vicuña populations. Morphological analysis of hairs does not have the resolution to determine the species of origin of camelid natural fibers. In addition, commerce in camelid fleece also includes the legal trade of alpaca (Vicugna pacos) and guanaco (Lama guanicoe) wool. METHODS The keratin fiber spectra of vicuña (n = 19), guanaco (n = 20) and alpaca (n = 20) were collected using X-ray fluorescence (XRF) spectrometry, Horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy and direct analysis in real time time-of-flight mass spectrometry (DART-TOFMS). Analysis with each technique evaluated the data to determine if the three taxa could be separated using either descriptive or multivariate statistics. RESULTS XRF analysis showed that the elements detected and their relative concentrations were similar in all three species, whereas HATR-FTIR analysis could identify alpaca fleece but could not differentiate vicuña from guanaco. Ions detected by ambient ionization using DART-TOFMS, in either positive- or negative-ion mode, gave the best results and showed that each taxonomic group is distinctive. Multivariate analysis of the mass spectra created robust models which resolved each species (LOOCV = 99.9%). The analyses of eight validation samples were correctly assigned to the appropriate species and demonstrated the reliability of DART-TOFMS to infer taxonomic source. CONCLUSIONS The DART-TOFMS spectra of unmodified keratin fibers infer that the chemotype of each species is heavily influenced by fatty acids, cholesterol and its analogs, and that these ions are useful in separating the fleece of vicuña, alpaca and guanaco. We posit that the etiological source of these chemotype differences is consistent with genetic modulations and is less influenced by diet. Accurate taxonomic identification of fleece is important to identify violations and assists in the protection of rare species.
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Affiliation(s)
- Erin Price
- National Fish and Wildlife Forensic Laboratory, 1490 E. Main St., Ashland, OR 97520, USA
| | | | - Benito Gonzales
- Faculty of Forest Sciences and Nature Conservation, Universidad de Chile, Chile
| | - Pamela McClure
- National Fish and Wildlife Forensic Laboratory, 1490 E. Main St., Ashland, OR 97520, USA
| | - Edgard Espinoza
- National Fish and Wildlife Forensic Laboratory, 1490 E. Main St., Ashland, OR 97520, USA
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24
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Butovich IA, Suzuki T, Wojtowicz J, Bhat N, Yuksel S. Comprehensive profiling of Asian and Caucasian meibomian gland secretions reveals similar lipidomic signatures regardless of ethnicity. Sci Rep 2020; 10:14510. [PMID: 32883999 PMCID: PMC7471331 DOI: 10.1038/s41598-020-71259-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/10/2020] [Indexed: 01/11/2023] Open
Abstract
Meibum-a lipid secretion that is produced by Meibomian glands (MG) in a process termed meibogenesis-plays a critical role in ocular surface physiology. Abnormalities in the chemical composition of meibum were linked to widespread ocular pathologies-dry eye syndrome (DES) and MG dysfunction (MGD). Importantly, in epidemiologic studies the Asian population was shown to be prone to these pathologies more than the Caucasian one, which was tied to differences in their meibomian lipids. However, biochemical data to support these observations and conclusions are limited. To determine if non-DES/non-MGD Asian meibum was significantly different from that of Caucasians, individual samples of meibum collected from ethnic Asian population living in Japan were compared with those of Caucasians living in the USA. These experiments revealed that composition of major lipid classes, such as wax esters (WE), cholesteryl esters (CE), triacylglycerols, (O)-acylated ω-hydroxy fatty acids (OAHFA), cholesteryl sulfate, cholesteryl esters of OAHFA, and diacylated α,ω-dihydroxy fatty alcohols remained invariable in both races, barring a minor (< 10%; p < 0.01) increase in the Asian CE/WE ratio. Considering the natural variability range for most meibomian lipids (app. ± 15% of the Mean), these differences in meibogenesis were deemed to be minimal and unlikely to have a measurable physiological impact.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA.
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
| | - Jadwiga Wojtowicz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
- Centro Oftalmologico de Valencia, Valencia, Venezuela
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
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25
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Butovich IA, Suzuki T. Delineating a novel metabolic high triglycerides-low waxes syndrome that affects lipid homeostasis in meibomian and sebaceous glands. Exp Eye Res 2020; 199:108189. [PMID: 32805264 DOI: 10.1016/j.exer.2020.108189] [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: 05/26/2020] [Revised: 07/12/2020] [Accepted: 08/07/2020] [Indexed: 10/23/2022]
Abstract
Meibomian glands that are embedded in tarsal plates of human eyelids, and sebaceous glands found in the skin, including that of eyelids, are two related types of holocrine glands that produce lipid-rich secretions called meibum and sebum. Pervasive ocular disorders, such as Meibomian gland dysfunction and dry eye, have been linked to changes in the lipid composition of meibum. However, in most described cases the changes were either small, or random, or insufficiently characterized on the molecular level. Here, we present results of comprehensive lipidomic analyses of meibum, tears and sebum of a patient whose secretions were highly abnormal (abnormal meibum, tears and sebum, or AMTS, patient). The lipidomes were characterized on the level of individual lipid species using ultra-high performance liquid chromatography and high resolution mass spectrometry. The major differences between the AMTS patient and normal age- and gender-matched subjects included, among others, severely diminished pools of normal meibomian lipids such as wax esters and cholesteryl esters in meibum and tears, a 2x increase in total cholesteryl esters to wax esters ratio, their skewed molecular profiles, a ~3x increase in free cholesterol to cholesteryl esters ratio, and, most importantly, a 20x to 30x increase in the triglicerides fraction over the norm. Sebum of the AMTS patient was also highly abnormal lacking major wax esters. Notably, the routine blood lipid panel test of the AMTS patient showed no abnormalities. The data imply that the AMTS patient had a severe, previously unreported, metabolic disorder that affected meibogenesis in Meibomian glands and sebogenesis in sebaceous glands. This is, to the best of our knowledge, a first observation of the condition that we have termed High Triglycerides/Low Waxes (HTLW) syndrome.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan; Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
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26
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Evaluation of Cell Harvesting Techniques to Optimize Lipidomic Analysis from Human Meibomian Gland Epithelial Cells in Culture. Int J Mol Sci 2020; 21:ijms21093277. [PMID: 32384602 PMCID: PMC7247324 DOI: 10.3390/ijms21093277] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/05/2020] [Accepted: 05/05/2020] [Indexed: 12/18/2022] Open
Abstract
The lipidomic analysis of immortalized human meibomian gland epithelial cells (HMGECs) has been proposed as a preclinical model to study meibomian gland dysfunction. An in vitro study was conducted to evaluate neutral lipid recovery following three harvesting techniques and to identify candidate lipid biomarkers of HMGECs. HMGECs were cultured in serum-containing media for two days to promote lipid production. Cells were either harvested by 0.25% trypsin–ethylenediaminetetraacetic acid (EDTA), harvested by 10 mM EDTA, or simultaneously harvested and extracted by 2:1 chloroform–methanol (CM). After extraction by a modified Folch technique, the nonpolar phase was processed and infused into a TripleTOF 5600 mass spectrometer (Sciex, Framingham, MA, USA) with electrospray ionization. MS and MS/MSall spectra were acquired. Nonpolar cholesteryl esters (CEs) were consistently detected in all samples, while wax esters were not. Only small differences in two out of twenty CEs were detected between harvesting methods. CM yielded less CE18:1 than the other methods but greater CE20:4 than the trypsin–EDTA method (p < 0.05 for all). Similar to human meibum, very long-chain CEs with carbon number (nc) ≥ 24 were detected in all samples and may serve as HMGEC lipid biomarkers. Further work is needed to address the absence of wax esters. Overall, the three harvesting methods are reasonably equivalent, though CM promotes much better efficiency and is recommended for higher throughput.
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27
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Hancock SE, Poad BLJ, Willcox MDP, Blanksby SJ, Mitchell TW. Analytical separations for lipids in complex, nonpolar lipidomes using differential mobility spectrometry. J Lipid Res 2019; 60:1968-1978. [PMID: 31511397 PMCID: PMC6824485 DOI: 10.1194/jlr.d094854] [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: 04/22/2019] [Revised: 09/03/2019] [Indexed: 11/20/2022] Open
Abstract
Secretions from meibomian glands located within the eyelid (commonly known as meibum) are rich in nonpolar lipid classes incorporating very-long (22-30 carbons) and ultra-long (>30 carbons) acyl chains. The complex nature of the meibum lipidome and its preponderance of neutral, nonpolar lipid classes presents an analytical challenge, with typically poor chromatographic resolution, even between different lipid classes. To address this challenge, we have deployed differential mobility spectrometry (DMS)-MS to interrogate the human meibum lipidome and demonstrate near-baseline resolution of the two major nonpolar classes contained therein, namely wax esters and cholesteryl esters. Within these two lipid classes, we describe ion mobility behavior that is associated with the length of their acyl chains and location of unsaturation. This capability was exploited to profile the molecular speciation within each class and thus extend meibum lipidome coverage. Intriguingly, structure-mobility relationships in these nonpolar lipids show similar trends and inflections to those previously reported for other physicochemical properties of lipids (e.g., melting point and phase-transition temperatures). Taken together, these data demonstrate that differential ion mobility provides a powerful orthoganol separation technology for the analysis of neutral lipids in complex matrices, such as meibum, and may further provide a means to predict physicochemical properties of lipids that could assist in inferring their biological function(s).
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Affiliation(s)
- Sarah E Hancock
- School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, Australia
- Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Berwyck L J Poad
- Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, Australia
| | - Mark D P Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, Australia
| | - Todd W Mitchell
- School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, Australia
- Illawarra Health and Medical Research Institute, Wollongong, Australia
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28
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Suzuki T, Fujiwara S, Kinoshita S, Butovich IA. Cyclic Change of Fatty Acid Composition in Meibum During the Menstrual Cycle. Invest Ophthalmol Vis Sci 2019; 60:1724-1733. [PMID: 31013345 PMCID: PMC6736406 DOI: 10.1167/iovs.18-26390] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Purpose To evaluate the fatty acid (FA) composition in the meibum of pre- and postmenopausal women and age-matched men. Methods This prospective study involved 24 healthy subjects; six premenopausal women in their 30s with a regular menstrual cycle (young-female [yF] group), six postmenopausal women in their 60s (elderly-female [eF] group), and 12 age-matched men (i.e., young-male [yM] and elderly-male [eM] groups, respectively). The menstrual cycle was divided into six phases (phase I–VI). Meibum was obtained from the meibomian gland orifices via a Daviel spoon, and its FA composition was then analyzed via gas chromatography mass spectrometry (GC-MS). Principal component analysis (PCA) was performed on the GC-MS results. Results The mean FA composition of all subjects was 40% saturated FAs (SFA) and 60% unsaturated FAs (UFAs). The PCA results of all groups indicated two categories (PC1 [77.5%] and PC2 [12.4%]); one consisting of yF-group samples of mainly phase II and III and the other consisting of the yF-group samples of the rest of the cycle, as well as from eF-group, yM-group, and eM-group samples. Each group had a distinctive nature. The FAs that most contributed to PC1 were C14:0, C16:0, and C18:0 in a positive correlation, and C18:1n9 in a negative correlation. Conclusions FA composition noticeably changes during the menstrual cycle and is somewhat affected by sex and age. The ratio of SFAs (C16:0, C18:0) to mono-UFAs (C18:1n9) in the FA composition might have an impact on the lipid quality of meibum, thus suggesting alteration of its melting temperature and viscosity.
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Affiliation(s)
- Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan.,Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
| | | | - Shigeru Kinoshita
- Department of Frontier Medical Science and Technology for Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Igor A Butovich
- Department of Ophthalmology, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
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Butovich IA, Bhat N, Wojtowicz JC. Comparative Transcriptomic and Lipidomic Analyses of Human Male and Female Meibomian Glands Reveal Common Signature Genes of Meibogenesis. Int J Mol Sci 2019; 20:ijms20184539. [PMID: 31540257 PMCID: PMC6769918 DOI: 10.3390/ijms20184539] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 09/09/2019] [Accepted: 09/11/2019] [Indexed: 01/18/2023] Open
Abstract
Meibum is a lipid secretion that is produced by holocrine Meibomian glands (MGs). MGs are a specialized type of sebaceous glands that are embedded in the human eyelids. Chemically, meibum and sebum are different. A detailed characterization of lipidome and transcriptome of MG is required to deconvolute a complex and poorly characterized array of biosynthetic reactions (termed meibogenesis) that lead to formation of meibum. Changes in the composition and quality of meibum have been linked to various ocular disorders, some of which are more prevalent in males, while others in females. To establish the role of gender in meibogenesis in humans, we characterized MG transcriptomes and lipidomes of females and males, and identified signature genes of meibogenesis in both genders. Specimens of MG tissues were subjected to mRNA microarray analyses. Chemical composition of meibum samples was assessed chromatographically and mass spectrometrically. Both targeted and untargeted approaches were used. About 290 signature genes of meibogenesis were identified. The analyses of their expression patterns demonstrated no major differences between the genders. Lipid profiling of major classes of meibomian lipids, such as wax esters, cholesteryl esters, free cholesterol, (O)-acylated omega-hydroxy fatty acids (OAHFA), cholesteryl esters of OAHFA, and triacylglycerols, also demonstrated only minor (and random) differences in these lipids. The results of transcriptomic analyses correlated well with lipidomic data. Taken together, our data imply that in males and females, meibogenesis proceeds in a similar fashion, yielding secretions with similar, highly conserved, compositions. This finding is important for designing novel, gender-independent diagnostic and therapeutic approaches to various MG-related diseases and pathological conditions.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Jadwiga C Wojtowicz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Butovich IA, Wilkerson A, Bhat N, McMahon A, Yuksel S. On the pivotal role of Elovl3/ELOVL3 in meibogenesis and ocular physiology of mice. FASEB J 2019; 33:10034-10048. [PMID: 31208226 DOI: 10.1096/fj.201900725r] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The purpose of this study was to examine the role of Elovl3 gene in meibogenesis and the impact of ELOVL3 protein ablation on the physiology of the mouse ocular surface and Meibomian glands (MGs). Elovl3 knockout, ELOVL3-ablated (E3hom) mice and their wild type littermates (E3wt) were studied side by side. E3hom mice had abnormal ocular phenotypes such as delayed eye opening, weeping eyes, crusty eyelids, eyelid edema, highly vascularized cornea and tarsal plates (TPs), slit eye, and increased tearing that resemble symptoms observed in human subjects with various forms of dry eye, MG dysfunction and blepharitis. Lipid profiling of E3hom TPs was conducted using chromatography and mass spectrometry. The analyses revealed that the lipid composition of E3hom TPs was strikingly different from that of their E3wt littermates. The mutation affected major classes of meibomian lipids - cholesteryl esters, wax esters, and cholesteryl esters of (O)-acylated w-hydroxy fatty acids. The studies illuminated the central role of ELOVL3 in producing C21:0-C29:0 fatty acids, including odd-chain and branched ones. Ablation of ELOVL3 leads to selective changes in the lipid composition of meibum, making E3hom mice instrumental in studying the mechanisms of the biosynthesis of meibum and modeling various pathologies of human ocular surface and adnexa.-Butovich, I. A., Wilkerson, A., Bhat, N., McMahon, A., Yuksel, S. On the pivotal role of Elovl3/ELOVL3 in meibogenesis and ocular physiology of mice.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Anne McMahon
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Butovich IA, McMahon A, Wojtowicz JC, Bhat N, Wilkerson A. Effects of sex (or lack thereof) on meibogenesis in mice (Mus musculus): Comparative evaluation of lipidomes and transcriptomes of male and female tarsal plates. Ocul Surf 2019; 17:793-808. [PMID: 30890458 DOI: 10.1016/j.jtos.2019.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 03/04/2019] [Accepted: 03/12/2019] [Indexed: 01/07/2023]
Abstract
The possible role of sex in the biosynthesis of lipids in the Meibomian glands (termed meibogenesis) remains unclear. To determine if there were any major sex-specific differences in the lipid composition of meibomian gland secretions (meibum) and gene expression patterns (GEP) related to meibogenesis, we conducted a study using healthy, age and diet-matched young adult wild-type C57BL/6J mice (2-2.5 month old). Tarsal plates (TP) were surgically excised from the eyelids of mice and subjected to transcriptomic and lipidomic analyses. The GEP were studied using mRNA microarrays. Lipids were extracted with organic solvents and analyzed using liquid chromatography and mass spectrometry. GEP in the TP of female and male mice demonstrated no statistically significant differences in the expression levels of the main protein-coding genes related to lipid metabolism and storage in general, and meibogenesis specifically (such as Elovl, Scd, Fads, Soat, Far, Awat, Acat, Lss, Dhcr, Hmgcr, Hmgcs, Dgat, Bckdh, Dbt, Fasn, and Plin, among others). The meibomian lipid profiles of female and male mice were virtually indistinguishable: all major lipids such as waxes, cholesteryl esters, cholesterol, (O)-acylated omega-hydroxy fatty acids (OAHFA), cholesteryl esters of OAHFA etc., were present in similar ratios. It seems that the major biosynthetic pathways in the Meibomian glands of male and female mice function in a similar fashion and produce secretions of the same overall chemical composition.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA; Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA.
| | - Anne McMahon
- Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA
| | - Jadwiga C Wojtowicz
- Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA
| | - Nita Bhat
- Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA
| | - Amber Wilkerson
- Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX, 75390-9057, USA
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Untargeted lipidomic analysis of human tears: A new approach for quantification of O-acyl-omega hydroxy fatty acids. Ocul Surf 2019; 17:347-355. [PMID: 30818035 DOI: 10.1016/j.jtos.2019.02.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 02/10/2019] [Accepted: 02/13/2019] [Indexed: 02/06/2023]
Abstract
PURPOSE The purpose of this work was to optimize methodology to analyze the human tear film lipids by using untargeted, direct infusion electrospray ionization-mass spectrometry (ESI-MS) to establish the analytical approach for a large-scale clinical translational study of tear film lipids in ocular surface disease, particularly associated with the O-acyl-omega hydroxy fatty acids (OAHFAs). METHODS Meibum and tear samples were collected from both eyes of five normal subjects without ocular disease using two different microcapillary collection tubes, glass and polytetrafluoroethylene (PTFE). An untargeted lipidomics approach was used to analyze the lipids in human tear and meibum samples using direct infusion ESI-MS in positive and negative ion modes. Direct and indirect quantification methods were evaluated. RESULTS The amount of OAHFAs measured in tears using these techniques was approximately 0.7-0.8% of the total lipids. More phospholipids, including phosphatidylcholine and sphingomyelin, were detected in the tear samples associated with glass microcapillaries compared to PTFE. CONCLUSIONS Reliable assessment of lipids in small volumes of tear film is possible using high resolution, untargeted ESI-MS in positive and negative ion modes. Using this technique, the concentration of OAHFAs can be quantified, as can the presence of other polar lipids.
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Chen J, Panthi S. Lipidomic analysis of meibomian gland secretions from the tree shrew: Identification of candidate tear lipids critical for reducing evaporation. Chem Phys Lipids 2019; 220:36-48. [PMID: 30660743 DOI: 10.1016/j.chemphyslip.2019.01.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/08/2019] [Accepted: 01/14/2019] [Indexed: 02/07/2023]
Abstract
Lipids secreted from the meibomian glands form the outermost layer of the tear film and reduce its evaporation. Abnormal changes in the quantities or compositions of lipids present in meibomian gland secretions (meibum) are known to lead to dry eye disease, although the underlying mechanism is not yet well understood. The tree shrew is the non-primate mammal most closely related to humans. To assess the utility of the tree shrew as a model for the study of dry eye disease, we analyzed the lipid profile of tree shrew meibum using an untargeted ESI-MS and MS/MSall shotgun approach. The resulting lipidome shared many similarities with human meibum, while displaying some interesting differences. For example, several classes of lipids, including wax esters, cholesteryl esters, diesters, and (O-acyl)-ω-hydroxy fatty acids, had relatively longer chain lengths in tree shrew meibum. These increases in length may promote more effective reduction of tear evaporation in the tree shrew, which likely underlies the much longer blinking interval of this mammal. Our results suggest that the tree shrew could be an effective model for the study of dry eye.
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Affiliation(s)
- Jianzhong Chen
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
| | - Shyam Panthi
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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Leger AJ, Caspi RR. Visions of Eye Commensals: The Known and the Unknown About How the Microbiome Affects Eye Disease. Bioessays 2018; 40:e1800046. [PMID: 30289987 PMCID: PMC6354774 DOI: 10.1002/bies.201800046] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 08/13/2018] [Indexed: 12/13/2022]
Abstract
Until recently, the ocular surface is thought by many to be sterile and devoid of living microbes. It is now becoming clear that this may not be the case. Recent and sophisticated PCR analyses have shown that microbial DNA-based "signatures" are present within various ethnic, geographic, and contact lens wearing communities. Furthermore, using a mouse model of ocular surface disease, we have shown that the microbe, Corynebacterium mastitidis (C. mast), can stably colonize the ocular mucosa and that a causal relationship exists between ocular C. mast colonization and beneficial local immunity. While this constitutes proof-of-concept that a bona fide ocular microbiome that tunes immunity can exist at the ocular surface, there remain numerous unanswered questions to be addressed before microbiome-modulating therapies may be successfully developed. Here, the authors will briefly outline what is currently known about the local ocular microbiome as well as microbiomes associated with other sites, and how those sites may play a role in ocular surface immunity. Understanding how commensal microbes affect the ocular surface immune homeostasis has the potential revolutionize how we think about treating ocular surface disease.
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Affiliation(s)
- Anthony J. Leger
- Laboratory of Immunology National Eye Institute, Bethesda, MD 20892, USA; Department of Ophthalmology, University of Pittsburgh School of Medicine Pittsburgh, PA 15213, USA,
| | - Rachel R. Caspi
- Laboratory of Immunology National Eye Institute, Bethesda, MD 20892, USA,
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Chen J, Nichols KK. Comprehensive shotgun lipidomics of human meibomian gland secretions using MS/MS all with successive switching between acquisition polarity modes. J Lipid Res 2018; 59:2223-2236. [PMID: 30279222 PMCID: PMC6210907 DOI: 10.1194/jlr.d088138] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 09/24/2018] [Indexed: 01/11/2023] Open
Abstract
The lipid composition of human meibomian gland secretions (meibum) has been analyzed using both targeted and untargeted mass spectrometric approaches, each of which has its advantages and disadvantages. Herein we report the results of shotgun lipidomic profiling of human meibum using a new approach that combines the advantages of targeted and untargeted analyses to yield highly sensitive and comprehensive profiles. Samples containing an estimated 7-13 µg (8-16 nL) of human meibum lipids were analyzed using MS/MSall, an untargeted approach for MS/MS. Using MS/MSall with ESI and successive polarity switching, we obtained tandem mass spectra in both modes at every 1 Da step for all ions in the m/z 200-1,200 range. In approximately 12 min, a total of 2 MS spectra and 2,000 MS/MS spectra were acquired for each sample, from which targeted analysis information was extracted. This approach allowed for the comprehensive and highly sensitive detection of meibum lipids, including species low in abundance. Altogether, more than 600 unique lipid molecular species were identified in meibum, 3 times more than previously reported in untargeted analyses of meibum samples. This untargeted MS and MS/MSall approach may be extended to other biological systems for the detection of lipids with sensitivity comparable to targeted analysis.
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Affiliation(s)
- Jianzhong Chen
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Kelly K Nichols
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294
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36
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Panthi S, Nichols JJ. An imaging-based analysis of lipid deposits on contact lens surfaces. Cont Lens Anterior Eye 2018; 41:342-350. [DOI: 10.1016/j.clae.2017.12.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 12/06/2017] [Accepted: 12/07/2017] [Indexed: 10/18/2022]
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37
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Hancock SE, Ailuri R, Marshall DL, Brown SHJ, Saville JT, Narreddula VR, Boase NR, Poad BLJ, Trevitt AJ, Willcox MDP, Kelso MJ, Mitchell TW, Blanksby SJ. Mass spectrometry-directed structure elucidation and total synthesis of ultra-long chain ( O-acyl)-ω-hydroxy fatty acids. J Lipid Res 2018; 59:1510-1518. [PMID: 29907595 DOI: 10.1194/jlr.m086702] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 06/13/2018] [Indexed: 01/24/2023] Open
Abstract
The (O-acyl)-ω-hydroxy FAs (OAHFAs) comprise an unusual lipid subclass present in the skin, vernix caseosa, and meibomian gland secretions. Although they are structurally related to the general class of FA esters of hydroxy FAs (FAHFAs), the ultra-long chain (30-34 carbons) and the putative ω-substitution of the backbone hydroxy FA suggest that OAHFAs have unique biochemistry. Complete structural elucidation of OAHFAs has been challenging because of their low abundance within complex lipid matrices. Furthermore, because these compounds occur as a mixture of closely related isomers, insufficient spectroscopic data have been obtained to guide structure confirmation by total synthesis. Here, we describe the full molecular structure of ultra-long chain OAHFAs extracted from human meibum by exploiting the gas-phase purification of lipids through multi-stage MS and novel multidimensional ion activation methods. The analysis elucidated sites of unsaturation, the stereochemical configuration of carbon-carbon double bonds, and ester linkage regiochemistry. Such isomer-resolved MS guided the first total synthesis of an ultra-long chain OAHFA, which, in turn, confirmed the structure of the most abundant OAHFA found in human meibum, OAHFA 50:2. The availability of a synthetic OAHFA opens new territory for future investigations into the unique biophysical and biochemical properties of these lipids.
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Affiliation(s)
- Sarah E Hancock
- School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Ramesh Ailuri
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia.,School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
| | - David L Marshall
- Central Analytical Research Facility, Institute for Future Environments Queensland University of Technology, Brisbane, Queensland, Australia
| | - Simon H J Brown
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia.,School of Biological Sciences, University of Wollongong, Wollongong, New South Wales, Australia
| | - Jennifer T Saville
- School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
| | - Venkateswara R Narreddula
- Central Analytical Research Facility, Institute for Future Environments Queensland University of Technology, Brisbane, Queensland, Australia
| | - Nathan R Boase
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Berwyck L J Poad
- Central Analytical Research Facility, Institute for Future Environments Queensland University of Technology, Brisbane, Queensland, Australia
| | - Adam J Trevitt
- School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
| | - Mark D P Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Michael J Kelso
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia.,School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
| | - Todd W Mitchell
- School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia .,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility, Institute for Future Environments Queensland University of Technology, Brisbane, Queensland, Australia .,School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, Australia
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Tiong SH, Saparin N, Teh HF, Ng TLM, Md Zain MZB, Neoh BK, Md Noor A, Tan CP, Lai OM, Appleton DR. Natural Organochlorines as Precursors of 3-Monochloropropanediol Esters in Vegetable Oils. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:999-1007. [PMID: 29260544 DOI: 10.1021/acs.jafc.7b04995] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
During high-temperature refining of vegetable oils, 3-monochloropropanediol (3-MCPD) esters, possible carcinogens, are formed from acylglycerol in the presence of a chlorine source. To investigate organochlorine compounds in vegetable oils as possible precursors for 3-MCPD esters, we tested crude palm, soybean, rapeseed, sunflower, corn, coconut, and olive oils for the presence of organochlorine compounds. Having found them in all vegetable oils tested, we focused subsequent study on oil palm products. Analysis of the chlorine isotope mass pattern exhibited in high-resolution mass spectrometry enabled organochlorine compound identification in crude palm oils as constituents of wax esters, fatty acid, diacylglycerols, and sphingolipids, which are produced endogenously in oil palm mesocarp throughout ripening. Analysis of thermal decomposition and changes during refining suggested that these naturally present organochlorine compounds in palm oils and perhaps in other vegetable oils are precursors of 3-MCPD esters. Enrichment and dose-response showed a linear relationship to 3-MCPD ester formation and indicated that the sphingolipid-based organochlorine compounds are the most active precursors of 3-MCPD esters.
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Affiliation(s)
- Soon Huat Tiong
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
- Faculty of Food Science and Technology, Universiti Putra Malaysia , 43400 Serdang, Selangor, Malaysia
| | - Norliza Saparin
- Sime Darby Research Sdn. Bhd. , Lot 2664, Jalan Pulau Carey, 42960 Carey Island, Selangor, Malaysia
| | - Huey Fang Teh
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
| | - Theresa Lee Mei Ng
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
| | - Mohd Zairey Bin Md Zain
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
| | - Bee Keat Neoh
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
| | - Ahmadilfitri Md Noor
- Sime Darby Research Sdn. Bhd. , Lot 2664, Jalan Pulau Carey, 42960 Carey Island, Selangor, Malaysia
| | - Chin Ping Tan
- Faculty of Food Science and Technology, Universiti Putra Malaysia , 43400 Serdang, Selangor, Malaysia
| | - Oi Ming Lai
- Faculty of Biotechnology and Biomolecular Science, Universiti Putra Malaysia , 43400 Serdang, Selangor, Malaysia
| | - David Ross Appleton
- Sime Darby Technology Centre Sdn. Bhd. , 1st Floor, Block B, UPM-MTDC Technology Centre III, Lebuh Silikon, 43400 Serdang, Selangor, Malaysia
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Meibomian glands, meibum, and meibogenesis. Exp Eye Res 2017; 163:2-16. [PMID: 28669846 DOI: 10.1016/j.exer.2017.06.020] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 06/14/2017] [Accepted: 06/28/2017] [Indexed: 12/28/2022]
Abstract
Meibum is a lipid-rich secretion that is produced by fully differentiated meibocytes in the holocrine Meibomian glands (MG) of humans and most mammals. The secretion is a part of a defense mechanism that protects the ocular surface from hazardous environmental factors, and from desiccation. Meibomian lipids that have been identified in meibum are very diverse and unique in nature. The lipid composition of meibum is different from virtually any other lipid pool found in the human body. In fact, meibum is quite different from sebum, which is the closest secretion that is produced by anatomically, physiologically, and biochemically related sebaceous glands. However, meibum of mice have been shown to closely resemble that of humans, implying similar biosynthetic mechanisms in MG of both species. By analyzing available genomic, immunohistochemical, and lipidomic data, we have envisioned a unifying network of enzymatic reactions that are responsible for biosynthesis of meibum, which we call meibogenesis. Our current theory is based on an assumption that most of the biosynthetic reactions of meibogenesis are catalyzed by known enzymes. However, the main features that make meibum unique - the ratio of identified classes of lipids, the extreme length of its components, extensive ω-hydroxylation of fatty acids and alcohols, iso- and anteiso-branching of meibomian lipids (e.g. waxes), and the presence of rather unique complex lipids with several ester bonds - make it possible that either the activity of known enzymes is altered in MG, or some unknown enzymes contribute to the processes of meibogenesis, or both. Studies are in progress to elucidate meibogenesis on molecular level.
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Khaksari M, Mazzoleni LR, Ruan C, Kennedy RT, Minerick AR. Determination of water-soluble and fat-soluble vitamins in tears and blood serum of infants and parents by liquid chromatography/mass spectrometry. Exp Eye Res 2017; 155:54-63. [DOI: 10.1016/j.exer.2016.12.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 12/15/2016] [Accepted: 12/16/2016] [Indexed: 11/24/2022]
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41
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Meibomian gland cells display a differentiation-dependent composition of desmosomes. Histochem Cell Biol 2016; 146:685-694. [DOI: 10.1007/s00418-016-1475-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2016] [Indexed: 12/12/2022]
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Zhang T, Chen S, Syed I, Ståhlman M, Kolar MJ, Homan EA, Chu Q, Smith U, Borén J, Kahn BB, Saghatelian A. A LC-MS-based workflow for measurement of branched fatty acid esters of hydroxy fatty acids. Nat Protoc 2016; 11:747-63. [PMID: 26985573 PMCID: PMC4797065 DOI: 10.1038/nprot.2016.040] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are a recently discovered class of endogenous mammalian lipids with antidiabetic and anti-inflammatory effects. We previously identified 16 different FAHFA families, such as branched palmitic acid esters of hydroxy stearic acids (PAHSAs); each family consists of multiple isomers in which the branched ester is at different positions (e.g., 5- and 9-PAHSA). We anticipate increased need for PAHSA measurements as markers of metabolic and inflammatory health. In this protocol, we provide a detailed description of the extraction of FAHFAs from human or mouse tissues, their enrichment by solid-phase extraction and subsequent analysis by LC-MS. For a sample size of 6-12, the time frame is 2-3 d.
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Affiliation(s)
- Tejia Zhang
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Shili Chen
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Ismail Syed
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Marcus Ståhlman
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | | | - Edwin A. Homan
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Qian Chu
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Ulf Smith
- Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Jan Borén
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Barbara B. Kahn
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
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Butovich IA, McMahon A, Wojtowicz JC, Lin F, Mancini R, Itani K. Dissecting lipid metabolism in meibomian glands of humans and mice: An integrative study reveals a network of metabolic reactions not duplicated in other tissues. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:538-53. [PMID: 27032494 DOI: 10.1016/j.bbalip.2016.03.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 03/21/2016] [Accepted: 03/22/2016] [Indexed: 12/18/2022]
Abstract
Lipids comprise the bulk of the meibomian gland secretion (meibum) which is produced by meibocytes. Complex arrays of lipogenic reactions in meibomian glands, which we collectively call meibogenesis, have not been explored on a molecular level yet. Our goals were to elucidate the possible biosynthetic pathways that underlie the generation of meibum, reveal similarities in, and differences between, lipid metabolism in meibomian glands and other organs and tissues, and integrate meibomian gland studies into the field of general metabolomics. Specifically, we have conducted detailed analyses of human and mouse specimens using genomic, immunohistochemical, and lipidomic approaches. Among equally highly expressed genes found in meibomian glands of both species were those related to fatty acid elongation, branching, desaturation, esterification, reduction of fatty acids to alcohols, and cholesterol biosynthesis. Importantly, corresponding lipid products were detected in meibum of both species using lipidomic approaches. For the first time, a cohesive, unifying biosynthetic scheme that connects genomic, lipidomic, and immunohistochemical observations is outlined and discussed.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Anne McMahon
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jadwiga C Wojtowicz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Feng Lin
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ronald Mancini
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kamel Itani
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Influence of Meibomian Gland Expression Methods on Human Lipid Analysis Results. Ocul Surf 2016; 14:49-55. [DOI: 10.1016/j.jtos.2015.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/30/2015] [Accepted: 10/03/2015] [Indexed: 11/17/2022]
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Meibomian Gland Absence Related Dry Eye in Ectodysplasin A Mutant Mice. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:32-42. [DOI: 10.1016/j.ajpath.2015.09.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 09/02/2015] [Accepted: 09/04/2015] [Indexed: 11/19/2022]
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Martínez Díaz Y, Vanegas Laverde G, Reina Gamba L, Mayorga Wandurraga H, Arévalo-Ferro C, Ramos Rodríguez F, Duque Beltrán C, Castellanos Hernández L. Biofilm inhibition activity of compounds isolated from two Eunicea species collected at the Caribbean Sea. REVISTA BRASILEIRA DE FARMACOGNOSIA-BRAZILIAN JOURNAL OF PHARMACOGNOSY 2015. [DOI: 10.1016/j.bjp.2015.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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In vitro effects of docosahexaenoic and eicosapentaenoic acid on human meibomian gland epithelial cells. Exp Eye Res 2015; 140:139-148. [PMID: 26335632 DOI: 10.1016/j.exer.2015.08.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/31/2015] [Accepted: 08/26/2015] [Indexed: 12/31/2022]
Abstract
To investigate the effect of ω-3 fatty acids on human meibomian gland epithelial cells (HMGECs, cell line) in vitro. HMGECs were stimulated with docosahexaenoic acid (DHA) or combinations with eicosapentaenoic acid (EPA) and acetyl sialic acid (ASA). Sudan III fat staining, viability and proliferation assays, electric cell-substrate impedance sensing, real-time PCR for gene expression of cyclooxygenase-2 and 15-lipoxygenase and ELISAs for resolvin D1 (RvD1), IFNγ, TNFα and IL-6 were applied. Lipid droplet accumulation and viability was increased by 100 μM DHA in the presence or absence of EPA in serum cultured HMGECs. In contrast, HMGECs cultured with DHA and EPA under serum-free conditions showed minimal lipid accumulation, decreased proliferation and viability. Normalized impedance was significantly reduced in serum-free cultured HMGECs when stimulated with DHA and EPA. HMGECs cultured in serum containing medium showed increased normalized impedance under DHA and EPA stimulation compared to DHA or EPA alone or controls. IL-6 and IFNγ were downregulated in HMGECs treated for 72 h with DHA and EPA. In general, TNFα, IFNγ and IL-6 levels were decreased after 72 h compared to 24 h in serum containing medium with or without DHA or EPA. The concentration of RvD1 was elevated 2-fold after DHA treatment. Cyclooxygenase-2 gene expression decreased compared to controls during DHA stimulation after 72 h. Treatment with DHA and ASA revealed a decreased 15-lipoxygenase gene expression which was reduced after three days of DHA incubation. DHA and EPA supplementation affected HMGECs in vitro and supported anti-inflammatory effects by influencing cytokine levels, decreasing COX-2 expression and increasing the production of RvD1.
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Chen J, Green KB, Nichols KK. Characterization of Wax Esters by Electrospray Ionization Tandem Mass Spectrometry: Double Bond Effect and Unusual Product Ions. Lipids 2015; 50:821-36. [PMID: 26178197 DOI: 10.1007/s11745-015-4044-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 06/22/2015] [Indexed: 11/26/2022]
Abstract
A series of different types of wax esters (represented by RCOOR') were systematically studied by using electrospray ionization (ESI) collision-induced dissociation tandem mass spectrometry (MS/MS) along with pseudo MS(3) (in-source dissociation combined with MS/MS) on a quadrupole time-of-flight (Q-TOF) mass spectrometer. The tandem mass spectra patterns resulting from dissociation of ammonium/proton adducts of these wax esters were influenced by the wax ester type and the collision energy applied. The product ions [RCOOH2](+), [RCO](+) and [RCO-H2O](+) that have been reported previously were detected; however, different primary product ions were demonstrated for the three wax ester types including: (1) [RCOOH2](+) for saturated wax esters, (2) [RCOOH2](+), [RCO](+) and [RCO-H2O](+) for unsaturated wax esters containing only one double bond in the fatty acid moiety or with one additional double bond in the fatty alcohol moiety, and (3) [RCOOH2](+) and [RCO](+) for unsaturated wax esters containing a double bond in the fatty alcohol moiety alone. Other fragments included [R'](+) and several series of product ions for all types of wax esters. Interestingly, unusual product ions were detected, such as neutral molecule (including water, methanol and ammonia) adducts of [RCOOH2](+) ions for all types of wax esters and [R'-2H](+) ions for unsaturated fatty acyl-containing wax esters. The patterns of tandem mass spectra for different types of wax esters will inform future identification and quantification approaches of wax esters in biological samples as supported by a preliminary study of quantification of isomeric wax esters in human meibomian gland secretions.
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Affiliation(s)
- Jianzhong Chen
- Applied Biotechnology Branch, Air Force Research Laboratory, Dayton, OH, 45433, USA,
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Serum-induced keratinization processes in an immortalized human meibomian gland epithelial cell line. PLoS One 2015; 10:e0128096. [PMID: 26042605 PMCID: PMC4456149 DOI: 10.1371/journal.pone.0128096] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 04/22/2015] [Indexed: 11/19/2022] Open
Abstract
PURPOSE The aim of this study was to evaluate a human meibomian gland epithelial cell line (HMGEC) as a model for meibomian gland (patho)physiology in vitro. METHODS HMGEC were cultured in the absence or presence of serum. Sudan III lipid staining, ultrastructural analysis and lipidomic analyses were performed. Impedance sensing, desmoplakin 1/2 mRNA and cytokeratin (CK) 1, 5, 6, 14 levels were evaluated. Serum containing medium supplemented with higher serum, glucose, an omega-3 lipid cocktail, eicosapentaenoic acid or sebomed medium were investigated for lipid accumulation and ultrastructural morphology. RESULTS Lipid droplet accumulation in HMGEC was induced by serum containing media after 1 day, but decreased over time. Cultivation in serum induced desmosome and cytokeratin filament formation. Desmoplakin 1/2 gene levels were significantly upregulated after 1d of serum treatment. Furthermore, the normalized impedance increased significantly. Lipidome analysis revealed high levels of phospholipids (over 50%), but very low levels of wax ester and cholesteryl esters (under 1%). Stimulation with eicosapentaenoic acid increased lipid accumulation after one day. CONCLUSION Serum treatment of HMGEC caused lipid droplet formation to some extent but also induced keratinization. The cells did not produce typical meibum lipids under these growth conditions. HMGEC are well suited to study (hyper)keratinization processes of meibomian gland epithelial cells in vitro.
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Tanaka H, Harauma A, Takimoto M, Moriguchi T. Association between very long chain fatty acids in the meibomian gland and dry eye resulting from n-3 fatty acid deficiency. Prostaglandins Leukot Essent Fatty Acids 2015; 97:1-6. [PMID: 25795036 DOI: 10.1016/j.plefa.2015.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 10/23/2022]
Abstract
In our previously study, we reported lower tear volume in with an n-3 fatty acid deficient mice and that the docosahexaenoic acid and total n-3 fatty acid levels in these mice are significantly reduced in the meibomian gland, which secretes an oily tear product. Furthermore, we noted very long chain fatty acids (≥25 carbons) in the meibomian gland. To verify the detailed mechanism of the low tear volume in the n-3 fatty acid-deficient mice, we identified the very long chain fatty acids in the meibomian gland, measured the fatty acid composition in the tear product. Very long chain fatty acids were found to exist as monoesters. In particular, very long chain fatty acids with 25-29 carbons existed for the most part as iso or anteiso branched-chain fatty acids. n-3 fatty acid deficiency was decreased the amount of meibum secretion from meibomian gland without change of fatty acid composition. These results suggest that the n-3 fatty acid deficiency causes the enhancement of evaporation of tear film by reducing oily tear secretion along with the decrease of meibomian gland function.
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Affiliation(s)
- Hideko Tanaka
- Laboratory for Functional Analysis of Marine Materials, School of Life and Environmental Science, Azabu University, 1-17-71, Fuchinobe, Chuou, Sagamihara, Kanagawa 252-5201, Japan
| | - Akiko Harauma
- Laboratory for Functional Analysis of Marine Materials, School of Life and Environmental Science, Azabu University, 1-17-71, Fuchinobe, Chuou, Sagamihara, Kanagawa 252-5201, Japan
| | - Mao Takimoto
- Laboratory of Food and Nutritional Science, Department of Food and Life Science, School of Life and Environmental Science, Azabu University, 1-17-71, Fuchinobe, Chuou, Sagamihara, Kanagawa 252-5201, Japan
| | - Toru Moriguchi
- Laboratory for Functional Analysis of Marine Materials, School of Life and Environmental Science, Azabu University, 1-17-71, Fuchinobe, Chuou, Sagamihara, Kanagawa 252-5201, Japan; Laboratory of Food and Nutritional Science, Department of Food and Life Science, School of Life and Environmental Science, Azabu University, 1-17-71, Fuchinobe, Chuou, Sagamihara, Kanagawa 252-5201, Japan.
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