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Nguyen A, Naidoo KK, Ajouz L, Xu X, Zhao C, Robinson MR, Borchman D. Changes in Human Meibum Lipid Composition Related to the Presence and Severity of Meibomian Gland Dysfunction. J Ocul Pharmacol Ther 2024; 40:562-570. [PMID: 39150383 PMCID: PMC11698683 DOI: 10.1089/jop.2024.0063] [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: 04/01/2024] [Accepted: 07/09/2024] [Indexed: 08/17/2024] Open
Abstract
Purpose: Changes in meibum composition and quantity in meibomian gland dysfunction (MGD) result in tear film instability and dry eye. This exploratory study aimed to identify changes in (O-acyl)-ω-hydroxy fatty acid (OAHFA) and hydrocarbon chain (HC) unsaturation levels in meibum related to the presence and severity of MGD. Methods: Meibum samples were collected from 3 cohorts of adults with no MGD, mild-to-moderate MGD, and severe MGD in a noninterventional clinical trial (NCT01979887). OAHFAs, cholesterol esters (CE), HC unsaturation, and HC length in the meibum samples were quantified with 1H-nuclear magnetic resonance spectroscopy using 2 methods of normalization. Results: Meibum samples from 62 subjects were analyzed: 21 non-MGD, 21 mild-to-moderate MGD, and 20 severe MGD. Meibum OAHFA and CE levels and HC unsaturation were reduced with increasing severity of MGD, with most pairwise comparisons significant (P < 0.05, t-tests), following the order non-MGD > mild-to-moderate MGD > severe MGD. Regardless of the resonances used for normalization, each pairwise comparison of OAHFA, CE, and HC unsaturation levels in MGD (combined severities) versus non-MGD samples was significant (P < 0.01, t-test). Analysis using various normalization equations showed reductions of 20%-22% for OAHFAs, 51%-57% for CE, and 36%-66% for HC unsaturation in MGD (combined severities) compared with non-MGD. HC length was not altered in MGD (combined severities) compared with non-MGD samples (t-test). Conclusions: Meibum OAHFA, CE, and HC unsaturation levels were reduced in MGD and were lowest in the severe MGD cohort. These findings may contribute to the understanding of the pathophysiology of MGD.
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Affiliation(s)
- Ashley Nguyen
- Allergan, an AbbVie company, Irvine, California, USA
| | - Kugen K. Naidoo
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, USA
| | - Layla Ajouz
- Allergan, an AbbVie company, Irvine, California, USA
| | - Xiaoming Xu
- Allergan, an AbbVie company, Irvine, California, USA
| | - Cathy Zhao
- Allergan, an AbbVie company, Irvine, California, USA
| | | | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, USA
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2
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Iqbal F, Stapleton F, Masoudi S, Papas EB, Tan J. Meibomian Gland Shortening Is Associated With Altered Meibum Composition. Invest Ophthalmol Vis Sci 2024; 65:49. [PMID: 39083311 PMCID: PMC11290566 DOI: 10.1167/iovs.65.8.49] [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: 05/01/2024] [Accepted: 07/10/2024] [Indexed: 08/02/2024] Open
Abstract
Purpose The purpose of this study was to investigate differences in the composition of meibum extracted from human meibomian glands displaying different morphological characteristics. Methods Adult participants with evidence of meibomian gland shortening were enrolled. Glands were observed using infrared meibography, and meibum was collected from one short and one long gland from the lower eyelid of the same eye. Total protein concentration was evaluated using the detergent compatible (DC) protein assay and lipid analysis was performed using liquid chromatography mass spectrometry. Results Fifteen participants (8 women and 7 men) completed the study (mean age = 34.7 ± 7.7 years). The average volume of meibum collected from the short and long glands was 0.02 ± 0.01 and 0.05 ± 0.03 µL, respectively (P = 0.01). Average protein concentration in the short glands was significantly higher compared to the long glands (0.10 ± 0.03 vs. 0.08 ± 0.02 mg/mL, P = 0.01). Among the non-polar lipids, the mole percent of cholesterol esters (CEs; P = 0.02), triacylglycerols (TAGs; P = 0.04), and ceramide (Cer; P = 0.03) was significantly lower in short glands compared with long glands. Among the polar lipids, the mole percent of (O-acyl)-ω-hydroxy fatty acid (OAHFA; P = 0.01) was significantly lower in short glands, whereas phosphatidylcholine (PC; P = 0.02) and sphingomyelin (SM; P = 0.01) were significantly higher in short glands than long glands. Conclusions Meibum composition differed between short and long glands. The lower mole percent of CE, TAG, OAHFA, and Cer and a higher mole percent of PC and SM among short glands may indicate disease activity. This information may clarify the natural history of meibomian gland dysfunction and future targets for therapy.
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Affiliation(s)
- Fatima Iqbal
- School of Optometry and Vision Science, University of New South Wales, New South Wales, Sydney, Australia
| | - Fiona Stapleton
- School of Optometry and Vision Science, University of New South Wales, New South Wales, Sydney, Australia
| | - Simin Masoudi
- School of Optometry and Vision Science, University of New South Wales, New South Wales, Sydney, Australia
| | - Eric B. Papas
- School of Optometry and Vision Science, University of New South Wales, New South Wales, Sydney, Australia
| | - Jacqueline Tan
- School of Optometry and Vision Science, University of New South Wales, New South Wales, Sydney, Australia
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3
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Wilkerson A, Yuksel S, Acharya R, Butovich IA. Physiological Effects of Soat1 Inactivation on Homeostasis of the Mouse Ocular Surface. Invest Ophthalmol Vis Sci 2024; 65:2. [PMID: 38953847 PMCID: PMC11221616 DOI: 10.1167/iovs.65.8.2] [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: 05/05/2024] [Accepted: 06/10/2024] [Indexed: 07/04/2024] Open
Abstract
Purpose Soat1/SOAT1 have been previously reported to be critical for the biosynthesis of cholesteryl esters (CEs) in the mouse Meibomian glands (MGs) as the loss of function led to an arrest of CE production and a substantial accumulation of nonesterified cholesterol in the meibum, causing an increase in its melting temperature. The purpose of this study was to further investigate the role of Soat1 in meibogenesis and ocular surface physiology. Methods The mouse ocular features of knockout Soat1-/- and wild type (WT) mice were studied using various ophthalmic and histological techniques, mouse lipidomes were monitored using liquid chromatography/mass spectrometry, whereas their transcriptomes were compared to characterize the effects of the mutation on the gene expression profiles in the MG and cornea. Results Soat1-/- mice displayed increased tear production and severe corneal abnormalities, such as corneal thinning, (neo)vascularization, ulceration, and opacification that progressed with aging. Transcriptomic analyses led to identification of a range of significantly disrupted pathways, which included general and specific lipid metabolism-related pathways, keratinization, angiogenesis/(neo)vascularization, muscle contraction, and several other pathways. In addition, histological and histochemical experiments revealed morphological changes in the MG, cornea, and conjunctiva in Soat1-/- mice. Notably, the mRNA microarray expression level of Soat1 in WT MGs (log2 17.5) was 1000 × of that in the mouse cornea (log2 7.5). Conclusions These findings suggest a direct involvement of Soat1/SOAT1 in MGs in maintaining ocular surface homeostasis, in general, and corneal health, specifically.
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Affiliation(s)
- Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Riya Acharya
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
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4
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Chen R, Lu J, Dong J, Zhu Y. Intense pulsed light therapy for ocular surface diseases. Lasers Med Sci 2024; 39:111. [PMID: 38656565 DOI: 10.1007/s10103-024-04060-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024]
Abstract
Intense pulsed light (IPL) is a non-laser, high-intensity light source that has been shown to play a valuable role in dermatology and has been adopted in ophthalmology for treating meibomian gland dysfunction (MGD). In this review, we discuss the mechanism of action of IPL, including its benefits in ophthalmology. IPL therapy has been shown to improve tear film stability, meibomian gland (MG) function, and subjective symptoms of ocular dryness in MGD patients. Moreover, emerging evidence suggests that IPL therapy is beneficial for other ocular surface diseases, such as blepharitis and chalazia. Hence, it can be inferred that IPL has potential as a therapeutic modality in future applications. Large clinical and experimental trials are needed to exploit the full potential of IPL as a treatment for recurrent chalazia, Sjögren's syndrome, and other causes of dry eye disease (DED). This paper reviews the published literature related to the application of IPL for treating ocular surface diseases.
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Affiliation(s)
- Ruida Chen
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, 1 Xihu avenue, Hangzhou, Zhejiang, 310009, China
- Eye Department, Affiliated Dongyang Hospital, Wenzhou Medical University, Dongyang, China
| | - Jiale Lu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, 1 Xihu avenue, Hangzhou, Zhejiang, 310009, China
| | - Jilian Dong
- School of Public Health, Nanjing Medical University, Nanjing, China
| | - Yirui Zhu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, 1 Xihu avenue, Hangzhou, Zhejiang, 310009, China.
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Trevorah RM, Viljanen M, Viitaja T, Stubb H, Sevón J, Konovalov O, Jankowski M, Fontaine P, Hemmerle A, Raitanen JE, Ekholm FS, Svedström KJ. New Insights into the Molecular Structure of Tear Film Lipids Revealed by Surface X-ray Scattering. J Phys Chem Lett 2024; 15:316-322. [PMID: 38170161 PMCID: PMC10788950 DOI: 10.1021/acs.jpclett.3c02958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/12/2023] [Accepted: 12/28/2023] [Indexed: 01/05/2024]
Abstract
The tear film lipid layer (TFLL) is a unique biological membrane that serves a pivotal role in the maintenance of ocular surface health. Reaching an overarching understanding of the functional principle of the TFLL has been hampered by a lack of insights into the structural and functional roles played by individual lipid classes. To bridge this knowledge gap, we herein focus on studying films formed by principal lipid classes by surface scattering methods. Through grazing incidence X-ray diffraction and X-ray reflectivity studies, we reveal quantitative data about the lattice distances, molecular tilt angles, and mono/multilayer thickness and density profiles for central TFLL lipid classes under close to simulated physiological conditions. In addition, we discuss the correlation of the results to those obtained previously with the natural lipid composition of meibum.
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Affiliation(s)
- Ryan M. Trevorah
- Department
of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Mira Viljanen
- Department
of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Tuomo Viitaja
- Department
of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Henrik Stubb
- Department
of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Julia Sevón
- Department
of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Oleg Konovalov
- The
European Synchrotron Radiation Facility - ESRF, 71 Avenue des Martyrs, CS 40220, Grenoble Cedex 9 38043, France
| | - Maciej Jankowski
- The
European Synchrotron Radiation Facility - ESRF, 71 Avenue des Martyrs, CS 40220, Grenoble Cedex 9 38043, France
| | - Philippe Fontaine
- Synchrotron
SOLEIL, L’Orme des Merisiers, Départementale 128, 91190 Saint-Aubin, France
| | - Arnaud Hemmerle
- Synchrotron
SOLEIL, L’Orme des Merisiers, Départementale 128, 91190 Saint-Aubin, France
| | - Jan-Erik Raitanen
- Department
of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Filip S. Ekholm
- Department
of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Kirsi J. Svedström
- Department
of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
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Yazdani M. Tear film lipid layer and corneal oxygenation: a new function? Eye (Lond) 2023; 37:3534-3541. [PMID: 37138094 PMCID: PMC10686381 DOI: 10.1038/s41433-023-02557-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/22/2023] [Accepted: 04/20/2023] [Indexed: 05/05/2023] Open
Abstract
The classic model of tear film is composed of mucin layer, aqueous layer and the outermost tear film lipid layer (TFLL). The complex mixture of different classes of lipids, mainly secreted by meibomian glands, gives the TFLL unique physicochemical properties. Based on these properties, several functions of TFLL have been found and/or proposed such as the resistance to evaporation and facilitating the formation of a thin film. However, the role of TFLL in the oxygenation of the cornea, a transparent avascular tissue, has never been discussed in the literature. The continuous metabolic activity of the corneal surface and the replenishment of atmospheric gas creates an O2 gradient in the tear film. The molecules of O2 must therefore be transferred from the gas phase to the liquid phase through the TFLL. This process is a function of the diffusion and solubility of the lipid layer as well as interface transfer, which is influenced by alterations in the physical state and lipid composition. In the absence of research on TFLL, the present paper aims to bring the topic into the spotlight for the first time based on existing knowledge on O2 permeability of the lipid membranes and evaporation resistance of the lipid layers. The oxidative stress generated in perturbed lipid layers and the consequent adverse effects are also covered. The function of the TFLL proposed here intends to encourage future research in both basic and clinical sciences, e.g., opening new avenues for the diagnosis and treatment of ocular surface conditions.
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Affiliation(s)
- Mazyar Yazdani
- Department of Medical Biochemistry, Oslo University Hospital, Rikshospitalet, 0027, Oslo, Norway.
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7
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Xu X, Wilkerson A, Li G, Butovich IA, Zuo YY. Comparative Biophysical Study of Meibomian Lipids of Wild Type and Soat1-Null Mice: Implications to Meibomian Gland Dysfunction and Dry Eye Disease. Invest Ophthalmol Vis Sci 2023; 64:20. [PMID: 37585190 PMCID: PMC10434715 DOI: 10.1167/iovs.64.11.20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/28/2023] [Indexed: 08/17/2023] Open
Abstract
Purpose The biophysical roles of Meibomian lipids (MLs) played in health and meibomian gland dysfunction (MGD) are still unclear. The purpose of this research is to establish the composition-structure-functional correlations of the ML film (MLF) using Soat1-null mice and comprehensive in vitro biophysical simulations. Methods MLs were extracted from tarsal plates of wild type (WT) and Soat1 knockout (KO) mice. The chemical composition of ML samples was characterized using liquid chromatography - mass spectrometry. Comprehensive biophysical studies of the MLFs, including their dynamic surface activity, interfacial rheology, evaporation resistance, and ultrastructure and topography, were performed with a novel experimental methodology called the constrained drop surfactometry. Results Soat1 inactivation caused multiple alternations in the ML profile. Compared to their WT siblings, the MLs of KO mice were completely devoid of cholesteryl esters (CEs) longer than C18 to C20, but contained 7 times more free cholesterol (Chl). Biophysical assays consistently suggested that the KO-MLF became stiffer than that of WT mice, revealed by reduced film compressibility, increased elastic modulus, and decreased loss tangent, thus causing more energy loss per blinking cycle of the MLF. Moreover, the KO mice showed thinning of their MLF, and reduced evaporation resistance. Conclusions These findings delineated the composition-structure-functional correlations of the MLF and suggested a potential biophysical function of long-chain CEs in optimizing the surface activity, interfacial rheology, and evaporation resistance of the MLF. This study may provide novel implications to pathophysiological and translational understanding of MGD and dry eye disease.
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Affiliation(s)
- Xiaojie Xu
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Amber Wilkerson
- Department of Ophthalmology and Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Guangle Li
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Igor A. Butovich
- Department of Ophthalmology and Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Yi Y. Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States
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8
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Butovich IA, Wilkerson A, Goggans KR, Belyaeva OV, Kedishvili NY, Yuksel S. Sdr16c5 and Sdr16c6 control a dormant pathway at a bifurcation point between meibogenesis and sebogenesis. J Biol Chem 2023; 299:104725. [PMID: 37075844 PMCID: PMC10206187 DOI: 10.1016/j.jbc.2023.104725] [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: 02/21/2023] [Revised: 03/23/2023] [Accepted: 04/13/2023] [Indexed: 04/21/2023] Open
Abstract
Genes Sdr16c5 and Sdr16c6 encode proteins that belong to a superfamily of short-chain dehydrogenases/reductases (SDR16C5 and SDR16C6). Simultaneous inactivation of these genes in double-KO (DKO) mice was previously shown to result in a marked enlargement of the mouse Meibomian glands (MGs) and sebaceous glands, respectively. However, the exact roles of SDRs in physiology and biochemistry of MGs and sebaceous glands have not been established yet. Therefore, we characterized, for the first time, meibum and sebum of Sdr16c5/Sdr16c6-null (DKO) mice using high-resolution MS and LC. In this study, we demonstrated that the mutation upregulated the overall production of MG secretions (also known as meibogenesis) and noticeably altered their lipidomic profile, but had a more subtle effect on sebogenesis. The major changes in meibum of DKO mice included abnormal accumulation of shorter chain, sebaceous-type cholesteryl esters and wax esters (WEs), and a marked increase in the biosynthesis of monounsaturated and diunsaturated Meibomian-type WEs. Importantly, the MGs of DKO mice maintained their ability to produce typical extremely long chain Meibomian-type lipids at seemingly normal levels. These observations indicated preferential activation of a previously dormant biosynthetic pathway that produce shorter chain, and more unsaturated, sebaceous-type WEs in the MGs of DKO mice, without altering the elongation patterns of their extremely long chain Meibomian-type counterparts. We conclude that the Sdr16c5/Sdr16c6 pair may control a point of bifurcation in one of the meibogenesis subpathways at which biosynthesis of lipids can be redirected toward either abnormal sebaceous-type lipidome or normal Meibomian-type lipidome in WT mice.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA; 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
| | - Kelli R Goggans
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Olga V Belyaeva
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Natalia Y Kedishvili
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Viitaja T, Raitanen JE, Moilanen J, Paananen RO, Ekholm FS. Biophysical profiling of synthetic ultra-long tear film lipids. Colloids Surf B Biointerfaces 2023; 223:113145. [PMID: 36701899 DOI: 10.1016/j.colsurfb.2023.113145] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/04/2023] [Accepted: 01/11/2023] [Indexed: 01/15/2023]
Abstract
The tear film lipid layer (TFLL) is a unique biological membrane of importance to the maintenance of ocular surface health. The underlying factors at play, e.g. the ability to retard evaporation and offer protection from the environment, are all closely connected to the properties of individual lipid components and their interplay. The TFLL contains unique ultra-long polar lipid species such as O-acyl-ω-hydroxy fatty acids, type I-St diesters and type II diesters, which are considered important for its proper function. Herein, we have synthesized model compounds from these categories and studied their biophysical and surface rheological properties at the aqueous interface. Altogether, we provide insights on the distinct biophysical profiles of these lipid classes and discuss how their interplay may affect the structure and function of the TFLL.
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Affiliation(s)
- Tuomo Viitaja
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland; Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Jan-Erik Raitanen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Riku O Paananen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland; Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland.
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.
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10
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Tamura Y, Sassa T, Nishizawa T, Kihara A. Incomplete Elongation of Ultra-long-chain Polyunsaturated Acyl-CoAs by the Fatty Acid Elongase ELOVL4 in Spinocerebellar Ataxia Type 34. Mol Cell Biol 2023; 43:1-17. [PMID: 36748939 PMCID: PMC9980445 DOI: 10.1080/10985549.2023.2169563] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/24/2022] [Accepted: 01/11/2023] [Indexed: 02/08/2023] Open
Abstract
Spinocerebellar ataxias (SCAs) are autosomal dominant diseases characterized by cerebellar atrophy and ataxia. The SCA subtype SCA34 is caused by specific mutations in the gene ELOVL4, which encodes a fatty acid (FA) elongase that synthesizes ultra-long-chain (ULC; ≥C26) FAs. However, the pathogenesis and molecular mechanism that confers dominant inheritance remains unknown. Here, a cell-based assay demonstrated that each of the five known SCA34 mutants produced shorter ULC polyunsaturated FA-containing phosphatidylcholines (ULC-PCs) than wild-type protein, in the following order of severity: Q180P and T233M > W246G > I171T and L168F. Next, we generated knock-in mouse embryonic stem cells that contained heterozygous Q180P, heterozygous W246G, or homozygous W246G mutations. Neuronal differentiation-dependent production of ULC-PCs was reduced in heterozygous Q180P and homozygous W246G cells relative to control cells, and we observed shortening of the FA moiety in all mutant cells. This FA shortening was consistent with our prediction that amino acid residues substituted by SCA34 mutations are located in the transmembrane helices that interact with the ω-end region of the FA moiety of the substrate acyl-CoA. Hence, reduced levels and shortening of ULC-PCs in neurons may cause SCA34, and incomplete elongation of ULC polyunsaturated acyl-CoAs by mutated ELOVL4 may induce dominant inheritance.
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Affiliation(s)
- Yuka Tamura
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Takumi Nishizawa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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11
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Image-Based Longitudinal Characterization of Corneal Wound to Understand the Role of Sphingosine-1-Phosphate. Methods Mol Biol 2023; 2625:337-345. [PMID: 36653655 DOI: 10.1007/978-1-0716-2966-6_28] [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: 01/19/2023]
Abstract
Since its discovery, the bioactive sphingolipid sphingosine 1-phosphate (S1P) has been shown to involve in a myriad of cellular and physiological processes. In the process of tissue healing, S1P plays an important role in both normal and pathological healing, leading to fibrosis in multiple tissues including the cornea. Cornea covers the anterior portion of the eye and is responsible for the refraction of light. Corneal transparency is essential to obtain a clear vision, and a proper wound healing process is necessary for a clear cornea. Even though S1P is indicated to be a critical player in corneal fibrosis, we lack a detailed understanding of the role of S1P signaling in corneal wound healing and fibrosis. Herein, we describe a methodology to characterize the in-vivo wound healing process of the cornea using an easy and affordable imaging-based assay. This gives a consistent and easy way to characterize the wound and also the longitudinal healing process.
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12
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Magny R, Regazzetti A, Kessal K, Christin O, Baudouin C, Roulland E, Brignole-Baudouin F, Laprévote O, Auzeil N. Identification of new Omega-3 very long chain poly-unsaturated fatty acids in meibomian gland secretions. Biochimie 2022; 203:3-10. [PMID: 35476941 DOI: 10.1016/j.biochi.2022.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 03/14/2022] [Accepted: 04/19/2022] [Indexed: 12/16/2022]
Abstract
Three new very long chain polyunsaturated fatty acids (VLC PUFA) belonging to the omega-3 family have been identified in meibum samples collected by Schirmer strips. These VLC PUFA, namely FA (32:3), FA (34:3) and FA (36:3), were detected in O-acyl-ω-hydroxy fatty acids using a molecular network approach, and as free fatty acids. Identification was supported by retention time prediction model, exact mass determination and isotopic patterns. Double bond location was determined using cross metathesis reaction associated to tandem mass spectrometry. In meibum, synthesis of these VLC PUFA is likely to be mediated by elongation of very long chain fatty acids 4 enzyme. The biological role of these newly VLC PUFA and their occurrence in other tissues and biological fluids remains to be elucidated.
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Affiliation(s)
- Romain Magny
- Sorbonne Université UM80, INSERM UMR 968, CNRS UMR 7210, Institut de la Vision, IHU ForeSight, 75012, Paris, France; Université Paris Cité, CNRS, CiTCoM, F-75006, Paris, France.
| | | | - Karima Kessal
- Sorbonne Université UM80, INSERM UMR 968, CNRS UMR 7210, Institut de la Vision, IHU ForeSight, 75012, Paris, France; CIC 1423, Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, IHU ForeSight, 75012, Paris, France
| | - Orane Christin
- Université Paris Cité, CNRS, CiTCoM, F-75006, Paris, France
| | - Christophe Baudouin
- Sorbonne Université UM80, INSERM UMR 968, CNRS UMR 7210, Institut de la Vision, IHU ForeSight, 75012, Paris, France; CIC 1423, Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, IHU ForeSight, 75012, Paris, France; Hôpital Ambroise Paré, AP-HP, Université Versailles St Quentin en Yvelines, Paris Saclay, 78180, Montigny-Le-Bretonneux, France
| | | | - Françoise Brignole-Baudouin
- Sorbonne Université UM80, INSERM UMR 968, CNRS UMR 7210, Institut de la Vision, IHU ForeSight, 75012, Paris, France; Université Paris Cité, CNRS, CiTCoM, F-75006, Paris, France; Laboratoire d'ophtalmobiologie, Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, IHU ForeSight, 75012, Paris, France
| | - Olivier Laprévote
- Université Paris Cité, CNRS, CiTCoM, F-75006, Paris, France; Hôpital Européen Georges Pompidou, AP-HP, Service de Biochimie, 75015, Paris, France
| | - Nicolas Auzeil
- Université Paris Cité, CNRS, CiTCoM, F-75006, Paris, France.
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13
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Butovich IA, Wilkerson A. Dynamic Changes in the Gene Expression Patterns and Lipid Profiles in the Developing and Maturing Meibomian Glands. Int J Mol Sci 2022; 23:7884. [PMID: 35887230 PMCID: PMC9321132 DOI: 10.3390/ijms23147884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 11/30/2022] Open
Abstract
Meibomian glands (MGs) and their holocrine secretion-meibum-play crucial roles in the physiology of the eye, providing protection from environmental factors and desiccation, among other functions. Importantly, aging was implicated in the deterioration of the morphology and functions of MGs, and the quantity and quality of meibum they produce, leading to a loss of its protective properties, while the meibum of young individuals and experimental animals provide ample protection to the eye. Currently, the molecular mechanisms of meibum biosynthesis (termed meibogenesis) are not fully understood. To characterize the physiological changes in developing and maturing MGs, we studied the lipidomes and transcriptomes of mouse MGs ranging from newborns to adults. The results revealed a gradual increase in the critical genes of meibogenesis (such as Elovl3, Elovl4, Awat2, and Soat1, among others) that positively correlated with the biosynthesis of their respective lipid products. The MG transcriptomes of young and adult mice were also analyzed using single-cell RNA sequencing. These experiments revealed the existence of multiple unique populations of MG cells (meibocytes, epithelial cells, and others) with specific combinations of genes that encode meibogenesis-related proteins, and identified clusters and subclusters of cells that were tentatively classified as meibocytes at different stages of differentiation/maturation, or their progenitor cells. A hypothesis was formulated that these cells may produce different types of lipids, and contribute differentially to the Meibomian lipidome.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA;
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14
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Association of Serum Lipid Level with Meibum Biosynthesis and Meibomian Gland Dysfunction: A Review. J Clin Med 2022; 11:jcm11144010. [PMID: 35887773 PMCID: PMC9323051 DOI: 10.3390/jcm11144010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/27/2022] [Accepted: 07/05/2022] [Indexed: 11/16/2022] Open
Abstract
The primary role of meibomian glands (MGs) is to actively synthesize and secret lipids and proteins spread onto the tear film, and the glandular lipids promote tear stability, prevent evaporation, and reduce friction. Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease and one of the most common ophthalmic problems worldwide. MGs are densely innervated and regulated by hormones and growth factors. However, since the polar and nonpolar lipids are produced through processes in MGs that are not completely understood, a relevant question has been raised: Would the altered systemic lipids metabolism affect the physiology and structure of MGs? This review introduces the recent update regarding the relationships between serum lipid and MGD in clinical and basic research while providing answers to this question. A causal relationship remains to be established; however, serum lipid level or dyslipidemia may be related to MGD directly or indirectly, or both. Further studies are warranted to establish the role of serum lipid level and meibocyte differentiation/maturation and lipid synthesis.
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Dyall SC, Balas L, Bazan NG, Brenna JT, Chiang N, da Costa Souza F, Dalli J, Durand T, Galano JM, Lein PJ, Serhan CN, Taha AY. Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions. Prog Lipid Res 2022; 86:101165. [PMID: 35508275 PMCID: PMC9346631 DOI: 10.1016/j.plipres.2022.101165] [Citation(s) in RCA: 289] [Impact Index Per Article: 96.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/26/2022] [Accepted: 04/27/2022] [Indexed: 12/21/2022]
Abstract
Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids, and influence cellular function via effects on membrane properties, and also by acting as a precursor pool for lipid mediators. These lipid mediators are formed via activation of pathways involving at least one step of dioxygen-dependent oxidation, and are consequently called oxylipins. Their biosynthesis can be either enzymatically-dependent, utilising the promiscuous cyclooxygenase, lipoxygenase, or cytochrome P450 mixed function oxidase pathways, or nonenzymatic via free radical-catalyzed pathways. The oxylipins include the classical eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes, and also more recently identified lipid mediators. With the advent of new technologies there is growing interest in identifying these different lipid mediators and characterising their roles in health and disease. This review brings together contributions from some of those at the forefront of research into lipid mediators, who provide brief introductions and summaries of current understanding of the structure and functions of the main classes of nonclassical oxylipins. The topics covered include omega-3 and omega-6 PUFA biosynthesis pathways, focusing on the roles of the different fatty acid desaturase enzymes, oxidized linoleic acid metabolites, omega-3 PUFA-derived specialized pro-resolving mediators, elovanoids, nonenzymatically oxidized PUFAs, and fatty acid esters of hydroxy fatty acids.
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16
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Acera A, Abad B, Pereiro X, Rodríguez FD, Ruzafa N, Duran JA, Vecino E. Comparative study of the lipid profile of tears and plasma enriched in growth factors. Exp Eye Res 2022; 219:109061. [DOI: 10.1016/j.exer.2022.109061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/19/2022] [Accepted: 03/30/2022] [Indexed: 01/05/2023]
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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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18
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Otsuka K, Sawai-Ogawa M, Kihara A. Formation of fatty alcohols-components of meibum lipids-by the fatty acyl-CoA reductase FAR2 is essential for dry eye prevention. FASEB J 2022; 36:e22216. [PMID: 35238077 DOI: 10.1096/fj.202101733r] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 12/15/2022]
Abstract
Various lipids (mainly meibum lipids secreted by the meibomian glands) are present in the tear film lipid layer and play important roles in tear stability and the health of the cornea and conjunctiva. Many meibum lipids contain fatty alcohols (FAls) with chain lengths ≥C24, but the fatty acyl-CoA reductases (FARs) that produce them remain unclear. Here, using cell-based assays, we found that the two FAR isozymes (FAR1 and FAR2) show different substrate specificities: FAR1 and FAR2 are involved in the production of C16-C18 and ≥C20 FAls, respectively. Next, we generated Far2 knockout (KO) mice and examined their dry eye phenotype and meibum lipid composition. These mice showed a severe dry eye phenotype, characterized by plugged meibomian gland orifices, corneal damage, and tear film instability. The plugging was attributed to an increase in the melting point of the meibum lipids. Liquid chromatography coupled with tandem mass spectrometry revealed that FAl-containing meibum lipids (wax monoesters and types 1ω, 2α, and 2ω wax diesters) with a hydroxyl group at position 1 were almost completely absent in Far2 KO mice. The levels of di-unsaturated (O-acyl)-ω-hydroxy fatty acids were higher in Far2 KO mice than in wild type mice, but those of tri-unsaturated ones were comparable, suggesting the presence of two synthesis pathways for type 1ω wax diesters. These results indicate the importance of FAl-containing meibum lipids in the formation of a functional tear film lipid layer. In addition, our study provides clues to the molecular mechanism of the biosynthesis of meibum lipids.
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Affiliation(s)
- Kento Otsuka
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Megumi Sawai-Ogawa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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Zhang P, Tian L, Bao J, Li S, Li A, Wen Y, Wang J, Jie Y. Isotretinoin Impairs the Secretory Function of Meibomian Gland Via the PPARγ Signaling Pathway. Invest Ophthalmol Vis Sci 2022; 63:29. [PMID: 35353124 PMCID: PMC8976919 DOI: 10.1167/iovs.63.3.29] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Purpose To investigate the effects of isotretinoin on the ocular surface and to explore the possible mechanisms. Methods Rats were treated with isotretinoin 20 mg/kg/d for five months and tested monthly for tear secretion, fluorescein staining, and infrared photography. After five months of treatment, tissues were harvested for routine staining to evaluate the morphological changes; and real-time polymerase chain reaction, Western blot, and immunohistochemistry to study the expression of associated genes and their products such as forkhead box protein O1 (FoxO1), forkhead box protein O3, peroxisome proliferator–activated receptor γ (PPARγ), adipose differentiation–related protein, elongation of very long chain fatty acids protein 4, fatty acid binding protein 4, matrix metalloproteinase-9, and interleukin-6. Results Systemically, isotretinoin-treated rats have a significantly lower body weight that controls and apparent skin damage. Locally, although there was no alteration in tear secretion, a significant corneal involvement indicated by increased fluorescein staining scores, and also the contrast of meibomian gland was significantly reduced but no significant atrophy of the acinus was found. In addition, isotretinoin causes a decrease in conjunctival goblet cells. Furthermore, isotretinoin treatment did not cause the upregulation of FoxO1 and inflammation related genes but significantly suppressed the expression of PPARγ pathway. Conclusions Isotretinoin does not cause a significant atrophy of the acinus and a significant change of FoxO1 expression in the meibomian gland. Isotretinoin causes meibomian gland dysfunction, affecting meibocyte differentiation and qualitative and quantitative changes in the meibum, through PPARγ pathway.
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Affiliation(s)
- Peng Zhang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Lei Tian
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Jiayu Bao
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Shang Li
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Ao Li
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Ya Wen
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Jingyi Wang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Ying Jie
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
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20
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Zhao H, Wu SN, Shao Y, Xiao D, Tang LY, Cheng Z, Peng J. Lipidomics Profiles Revealed Alterations in Patients With Meibomian Gland Dysfunction After Exposure to Intense Pulsed Light. Front Neurol 2022; 13:827544. [PMID: 35242100 PMCID: PMC8886297 DOI: 10.3389/fneur.2022.827544] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/04/2022] [Indexed: 02/05/2023] Open
Abstract
So far, intense pulsed light (IPL) has been widely used in the treatment of meibomian gland dysfunction (MGD), but there was still a lack of research on its specific mechanism. Determining whether there was a correlation between liposome changes and remission of clinical signs in patients with MGD treated with IPL was of great significance in the clinical evaluation of efficacy in patients with MGD. Our study enrolled the 10 healthy subjects and 26 adult patients, who were diagnosed with MGD and had not received any alternative treatments for at least 3 months. Each patient received a series of three treatments at 3-week intervals. The meibum was collected before the first treatment (T0) and the third treatment (T2). The significant changes in ocular surface parameters before and after IPL treatment were analyzed. The results showed that IPL significantly improved the symptoms of MGD, including ocular surface disease index (OSDI), tear breakup time (TBUT), redness of conjunctival (CR), corneal fluorescein staining (CF), the meibomian gland expressibility (MGE), and meibum quality (all p < 0.05). Lipidomics analysis of the meibum characterized the changes in lipid profiles induced by IPL. A total of 323 lipid species compounds were identified in the spectrum. A total of 41 lipid species were significantly different in patients with MGD (T0) vs. healthy controls. Following IPL treatment (T2), 24 lipid species were significantly different compared with T0: TG (10 lipid species), LPC (6 lipid species), OAHFA (4 lipid species), Cer (2 lipid species), SM (1 lipid species), and PE (1 lipid specie). Among these lipids, 4 of the lipids was a high correlation with TBUT, 5 was TH, 6 was CR, and 11 was meibum quality. In a ward, IPL treatment can achieve the therapeutic effect by changing the alternations of tear film lipids in patients with MGD. The changes in lipid expression profiles are potential indexes to evaluate the therapeutic effectiveness of IPL treatment or other treatments on MGD.
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Affiliation(s)
- Hui Zhao
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shi-Nan Wu
- Department of Ophthalmology, Jiangxi Province Ocular Disease Clinical Research Center, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Yi Shao
- Department of Ophthalmology, Jiangxi Province Ocular Disease Clinical Research Center, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Dong Xiao
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Li-Ying Tang
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Eye Institute of Xiamen University, Xiamen, China
| | - Zhe Cheng
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Eye Institute of Xiamen University, Xiamen, China
| | - Jie Peng
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
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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: 2.0] [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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22
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Human meibum and tear film derived cholesteryl and wax esters in meibomian gland dysfunction and tear film structure. Ocul Surf 2022; 23:12-23. [PMID: 34774809 PMCID: PMC9875797 DOI: 10.1016/j.jtos.2021.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/27/2021] [Accepted: 10/29/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE This study evaluated the presence and roles of cholesteryl esters (CEs) and wax esters (WEs) from human tear film and meibum in meibomian gland dysfunction (MGD). METHODS Out of 195 enrolled subjects, 164 and 179 subjects provided tear and meibum samples, respectively. Subjects were classified into normal, asymptomatic MGD, MGD, and mixed (MGD & aqueous deficient). The precorneal tear film (PCTF) thinning rate (evaporation) was measured using optical coherence tomography. Lipids extracted from tear and meibum samples were infused into a SCIEX 5600 TripleTOF mass spectrometer. CE and WE intensities quantified with Analyst 1.7 TF and LipidView 1.3 were compared across disease groups in MetaboAnalyst 5.0 and correlated with PCTF thinning rates. RESULTS The numbers of unique CEs and WEs identified in the samples were 125 and 86, respectively. Unsupervised Principal Component (PC) analysis and supervised Partial Least Square Discriminant analysis exhibited little separation among groups for both CEs and WEs in tears and meibum. Spearman's correlation analyses showed no association between either the first or second PC scores with PCTF thinning rates. CONCLUSION The abundances of human PCTF and meibum-derived CEs and WEs were independent of MGD disease status and PCTF thinning (evaporation). CEs and WEs alterations do not contribute to alterations in tear film dynamics in MGD, such as has been demonstrated by the (O-acyl) ω-hydroxy fatty acids (OAHFAs).
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Viitaja T, Moilanen J, Svedström KJ, Ekholm FS, Paananen RO. Tear Film Lipid Layer Structure: Self-Assembly of O-Acyl-ω-hydroxy Fatty Acids and Wax Esters into Evaporation-Resistant Monolayers. NANO LETTERS 2021; 21:7676-7683. [PMID: 34468151 DOI: 10.1021/acs.nanolett.1c02475] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In healthy eyes, the tear film lipid layer (TFLL) is considered to act as an evaporation resistant barrier, which prevents eyes from drying. Seeking to understand the mechanisms behind the evaporation resistance of the TFLL, we studied mixtures of lipid layer wax esters and O-acyl-ω-hydroxy fatty acids. Analyzing their self-assembly and biophysical properties led to new discoveries concerning the structure and function of the TFLL. We discovered how these lipids self-assemble at the air-water interface and form an efficient antievaporative barrier, demonstrating for the first time how the interaction of different tear film lipid species can improve the evaporation resistance compared with individual lipid classes on their own. These results provide a potential mechanism for the evaporation resistance of the lipid layer. In addition, the results serve as a base for the future development of improved dry eye treatments and other applications where the evaporation of water represents a significant challenge.
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Affiliation(s)
- Tuomo Viitaja
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | | | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Riku O Paananen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
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Impaired skin barrier function due to reduced ω- O-acylceramide levels in a mouse model of Sjögren-Larsson syndrome. Mol Cell Biol 2021; 41:e0035221. [PMID: 34370553 DOI: 10.1128/mcb.00352-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sjögren-Larsson syndrome (SLS) is an inherited neurocutaneous disorder whose causative gene encodes the fatty aldehyde dehydrogenase ALDH3A2. To date, the detailed molecular mechanism of the skin pathology of SLS has remained largely unclear. We generated double knockout (DKO) mice for Aldh3a2 and its homolog Aldh3b2 (a pseudogene in humans). These mice showed hyperkeratosis and reduced fatty aldehyde dehydrogenase activity and skin barrier function. The levels of ω-O-acylceramides (acylceramides), which are specialized ceramides essential for skin barrier function, in the epidermis of DKO mice were about 60% of those in wild type mice. In the DKO mice, levels of acylceramide precursors (ω-hydroxy ceramides and triglycerides) were increased, suggesting that the final step of acylceramide production was inhibited. A decrease in acylceramide levels was also observed in human immortalized keratinocytes lacking ALDH3A2. Differentiated keratinocytes prepared from the DKO mice exhibited impaired long-chain base metabolism. Based on these results, we propose that the long-chain-base-derived fatty aldehydes that accumulate in DKO mice and SLS patients attack and inhibit the enzyme involved in the final step of acylceramide. Our findings provide insight into the pathogenesis of the skin symptoms of SLS, i.e., decreased acylceramide production, and its molecular mechanism.
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Khanal S, Bai Y, Ngo W, Nichols KK, Wilson L, Barnes S, Nichols JJ. Human Meibum and Tear Film Derived (O-Acyl)-Omega-Hydroxy Fatty Acids as Biomarkers of Tear Film Dynamics in Meibomian Gland Dysfunction and Dry Eye Disease. Invest Ophthalmol Vis Sci 2021; 62:13. [PMID: 34236383 PMCID: PMC8267210 DOI: 10.1167/iovs.62.9.13] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To investigate the association between precorneal tear film (PCTF)- and meibum-derived (O-Acyl)-omega-hydroxy fatty acids (OAHFAs) and PCTF thinning in meibomian gland health and dysfunction. Methods Of 195 eligible subjects (18-84 years, 62.6% female), 178 and 170 subjects provided both PCTF optical coherence tomography (OCT) imaging and mass spectrometry data for tears (n = 178) and meibum (n = 170). The PCTF thinning rate was measured in the right eye using an ultra-high-resolution, custom-built OCT. Tear and meibum samples from the right eye were infused into the SCIEX 5600 TripleTOF mass spectrometer in the negative ion mode. Intensities (m/z) of preidentified OAHFAs were measured with Analyst 1.7TF and LipidView 1.3 (SCIEX). Principal component (PC) analyses and Spearman's correlations (ρ) were performed to evaluate the association between OAHFAs and PCTF thinning rates. Results In meibum and tear samples, 76 and 78 unique OAHFAs were detected, respectively. The first PC scores of the meibum-derived OAHFAs had statistically significant correlations with PCTF thinning rates (ρ = 0.18, P = 0.016). Among 10 OAHFAs with the highest first PC loadings, six OAHFAs had negative correlations with PCTF thinning rate (18:2/16:2, ρ = -0.19, P = 0.01; 18:2/30:1, ρ = -0.21, P = 0.008; 18:1/28:1, ρ = -0.22, P = 0.004; 18:1/30:1, ρ = -0.22, P = 0.005; 18:1/25:0, ρ = 0.22, P = 0 .006; and 18:1/26:1, ρ = -0.22, P = 0.006), while one OAHFA had a positive correlation with PCTF thinning rate (18:2/18:1, ρ = 0.48, P = 0.006). Tear film-derived OAHFAs had no association with the PCTF thinning rate. Conclusions Several human meibum-derived OAHFAs showed significant associations with PCTF thinning, suggesting that these OAHFAs could be implicated in the mechanism underlying the stabilization and thinning of the PCTF. The tear-film derived OAHFAs were, however, independent of the rate of PCTF thinning.
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Affiliation(s)
- Safal Khanal
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Yuqiang Bai
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - William Ngo
- Centre for Ocular Research & Education, School of Optometry & Vision Science, University of Waterloo, Waterloo, Ontario, Canada.,Centre for Eye and Vision Research, 17W Hong Kong Science Park, Hong Kong
| | - Kelly K Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Landon Wilson
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Jason J Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
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Butovich IA, Wilkerson A, Yuksel S. Differential effects of dietary cholesterol and triglycerides on the lipid homeostasis in Meibomian glands. J Steroid Biochem Mol Biol 2021; 211:105894. [PMID: 33819631 PMCID: PMC8217181 DOI: 10.1016/j.jsbmb.2021.105894] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 03/21/2021] [Accepted: 03/31/2021] [Indexed: 12/20/2022]
Abstract
Exocrine Meibomian glands (MG) play a central role in the ocular surface physiology by producing meibum - a lipid secretion composed of cholesteryl esters (CE), cholesterol (Chl), triacylgycerols (TAG), waxes and other types of lipids. MG were previously shown to synthesize Meibomian lipids (ML) in situ via a complex array of reactions termed meibogenesis. However, questions remain about the role of dietary lipids in meibogenesis. To establish if dietary Chl (DC) and TAG (DT) can participate in meibogenesis, we studied mice whose diet was supplemented with trace amounts of deuterated Chl (2H-Chl) and 13C-labeled triolein (13C-TO), and the products of their biosynthetic transformations were analyzed using LC/MS. We demonstrated that 2H-Chl, but not 13C-TO, could be directly incorporated into meibum. Furthermore, 2H-Chl was esterified into MG-specific ultra long 2H-CE, which were vastly different from plasma CE and 2H-CE. The measured 2H-Chl/Chl and 2H-CE/CE ratios in meibum increased in a time-dependent manner reaching ∼5% and ∼1.2 %, respectively. The 2H-Chl/2H-CE ratio was about 3.5x higher than that for endogenous unlabeled Chl and CE, indicating accumulation of 2H-Chl in meibum. The elongation pattern of Meibomian 2H-CE closely replicated that of unlabeled CE. On the other hand, 13C-TO was not detected in any of the ML samples as an intact lipid or its metabolized/hydrolyzed products. We conclude that DC can be directly esterified into MG-specific CE, while DT undergo extensive catabolic transformations before reaching MG. These findings demonstrate that DC can have a direct impact on MG and ocular surface lipid homeostasis and pathophysiology.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA; The 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
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA
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Khanal S, Ngo W, Nichols KK, Wilson L, Barnes S, Nichols JJ. Human meibum and tear film derived (O-acyl)-omega-hydroxy fatty acids in meibomian gland dysfunction. Ocul Surf 2021; 21:118-128. [PMID: 34052415 DOI: 10.1016/j.jtos.2021.05.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 04/22/2021] [Accepted: 05/23/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE The molecular basis of the tear film and lipid layer alterations in meibomian gland dysfunction (MGD) is unknown. This study aimed to identify and compare (O-acyl)-omega-hydroxy fatty acids (OAHFAs) derived from human meibum and tears in MGD. METHODS Of 195 eligible subjects (18-84 years, 62.6% female), 183 and 174 provided samples for tears and meibum, respectively. Subjects were classified into four groups: Normal, Asymptomatic MGD, MGD, and Mixed. Samples from the right eye of each subject were infused into the SCIEX 5600 TripleTOF mass spectrometer in negative ion mode. Lipid intensities identified with Analyst1.7 TF and SCIEX LipidView1.3 were normalized by an internal standard and total ion current, then statistically compared in MetaboAnalyst 4.0. RESULTS In meibum and tears, 76 and 78 unique OAHFAs were identified, respectively. The five most frequent and abundant OAHFAs were 18:2/16:2, 18:1/32:1, 18:1/30:1, 18:2/32:1, and 18:1/34:1. Two OAHFAs, 18:2/20:2 and 18:2/20:1, were identified only in tears. Initial univariate analysis revealed three differently regulated OAHFAs in meibum and eight in tears. Partial Least Square Discriminant Analysis showed 18:1/32:1, 18:2/16:2, 18:1/34:1 and 18:0/32:1 in tears, and 18:2/16:2, 18:1/32:1 and 18:2/32:2 in meibum, had variable importance in projection scores >1.5 and contributed the most to the separation of groups. In both meibum and tears, all OAHFAS except 18:2/16:2 were reduced in MGD compared to the normal group. CONCLUSION MGD is accompanied by differential expression of specific OAHFAs in meibum and tears. These results suggest OAHFAs play a role in the altered biochemical profile of the tear film lipid layer in humans with MGD.
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Affiliation(s)
- Safal Khanal
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - William Ngo
- Centre for Ocular Research & Education, School of Optometry & Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Kelly K Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Landon Wilson
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jason J Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA.
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Sawai M, Watanabe K, Tanaka K, Kinoshita W, Otsuka K, Miyamoto M, Sassa T, Kihara A. Diverse meibum lipids produced by Awat1 and Awat2 are important for stabilizing tear film and protecting the ocular surface. iScience 2021; 24:102478. [PMID: 34113821 PMCID: PMC8169949 DOI: 10.1016/j.isci.2021.102478] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/17/2021] [Accepted: 04/23/2021] [Indexed: 12/16/2022] Open
Abstract
A lipid layer consisting of meibum lipids exists in the tear film and functions in preventing dry eye disease. Although the meibum lipids include diverse lipid classes, the synthesis pathway and role of each class remain largely unknown. Here, we created single and double knockout (KO and DKO, respectively) mice for the two acyl-CoA wax alcohol acyltransferases (Awat1 and Awat2) and investigated their dry eye phenotypes and meibum lipid composition. Awat2 KO and DKO mice exhibited severe dry eye with meibomian gland dysfunction, whereas Awat1 KO mice had mild dry eye. In these mice, specific meibum lipid classes were reduced: (O-acyl)-ω-hydroxy fatty acids and type 1ω wax diesters in Awat1 KO mice, wax monoesters and types 1ω and 2ω wax diesters in Awat2 KO mice, and most of these in DKO mice. Our findings reveal that Awat1 and Awat2 show characteristic substrate specificity and together produce diverse meibum lipids.
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Affiliation(s)
- Megumi Sawai
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Keisuke Watanabe
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Kana Tanaka
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Wataru Kinoshita
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Kento Otsuka
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Masatoshi Miyamoto
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
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Fei T, Leyva-Gutierrez FM, Wan Z, Wang T. Development of a novel soy-wax containing emulsion with enhanced antifungal properties for the postharvest treatment of fresh citrus fruit. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2021.110878] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Watanabe K, Yoshida M, Okumura T, Sassa T, Kihara A, Uchiyama A. Improvement of Evaporative Dry Eye With Meibomian Gland Dysfunction in Model Mice by Treatment With Ophthalmic Solution Containing Mineral Oil. Transl Vis Sci Technol 2021; 10:21. [PMID: 34003999 PMCID: PMC8083063 DOI: 10.1167/tvst.10.4.21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Meibomian gland dysfunction (MGD) is a major cause of evaporative dry eye. The purpose of this study is to assess the efficacy of a mineral oil-containing ophthalmic solution (MO) in mitigating the evaporative dry eye phenotypes in a mouse model in which fatty acid elongase Elovl1 is disrupted. Methods Elovl1-deficient mice were assessed in terms of number of plugged meibomian gland orifices, tear film breakup time (BUT), corneal fluorescein staining (CFS) score, tear quantity, and histology. The effects of the MO on the dry eye phenotypes were compared with those in groups not treated or treated with blank ophthalmic solution (BL). Results Untreated Elovl1-deficient mice exhibited dry eye phenotypes with MGD symptoms such as plugging of meibomian gland orifices (P = 0.002 compared with control mice), high CFS scores (P = 0.002), and shortened BUT (P < 0.001). Among three groups of Elovl1-deficient mice (MO treated, BL treated, and untreated), the MO-treated group exhibited fewer plugged orifices (MO treated, 7.6; BL treated, 10.5 [P = 0.033]; untreated, 13.0 [P < 0.001]), lower CFS scores (MO treated, 1.1; BL treated, 2.7 [P = 0.013]; untreated, 2.5 [P = 0.050]), and improved BUT (MO treated, 19.4 seconds; BL treated, 8.3 seconds [P = 0.098]; untreated, 1.5 seconds [P = 0.008]). Conclusions Elovl1-deficient mice exhibited multiple MGD symptoms, which were improved by MO. Translational Relevance Our findings reveal the usefulness of Elovl1-deficient mice as a model for dry eye with MGD and suggest the potential of mineral oil eye drops as a treatment for this condition.
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Affiliation(s)
- Keisuke Watanabe
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Kanagawa, Japan
| | - Masataka Yoshida
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Kanagawa, Japan
| | - Takashi Okumura
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Kanagawa, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akira Uchiyama
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Kanagawa, Japan
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Nichols JJ, Jones LW, Morgan PB, Efron N. Bibliometric analysis of the meibomian gland literature. Ocul Surf 2021; 20:212-214. [PMID: 33757912 DOI: 10.1016/j.jtos.2021.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/10/2021] [Accepted: 03/16/2021] [Indexed: 11/16/2022]
Affiliation(s)
- Jason J Nichols
- School of Optometry, The University of Alabama at Birmingham, Birmingham, AL, United States.
| | - Lyndon W Jones
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada; Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong
| | - Philip B Morgan
- Eurolens Research, Division of Pharmacy and Optometry, The University of Manchester, Manchester, United Kingdom
| | - Nathan Efron
- School of Optometry and Vision Science, Queensland University of Technology, Kelvin Grove, Queensland, Australia
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Viitaja T, Raitanen JE, Moilanen J, Paananen RO, Ekholm FS. The Properties and Role of O-Acyl-ω-hydroxy Fatty Acids and Type I-St and Type II Diesters in the Tear Film Lipid Layer Revealed by a Combined Chemistry and Biophysics Approach. J Org Chem 2021; 86:4965-4976. [PMID: 33729799 PMCID: PMC8041317 DOI: 10.1021/acs.joc.0c02882] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
The tear film lipid
layer (TFLL) that covers the ocular surface
contains several unique lipid classes, including O-acyl-ω-hydroxy fatty acids, type I-St diesters, and type II
diesters. While the TFLL represents a unique biological barrier that
plays a central role in stabilizing the entire tear film, little is
known about the properties and roles of individual lipid species.
This is because their isolation from tear samples in sufficient quantities
is a tedious task. To provide access to these species in their pure
form, and to shed light on their properties, we here report a general
strategy for the synthesis and structural characterization of these
lipid classes. In addition, we study the organization and behavior
of the lipids at the air–tear interface. Through these studies,
new insights on the relationship between structural features, such
as number of double bonds and the chain length, and film properties,
such as spreading and evaporation resistance, were uncovered.
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Affiliation(s)
- Tuomo Viitaja
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.,Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Jan-Erik Raitanen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Riku O Paananen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.,Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
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Butovich IA, Wilkerson A, Yuksel S. Depletion of Cholesteryl Esters Causes Meibomian Gland Dysfunction-Like Symptoms in a Soat1-Null Mouse Model. Int J Mol Sci 2021; 22:1583. [PMID: 33557318 PMCID: PMC7915537 DOI: 10.3390/ijms22041583] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/01/2021] [Accepted: 02/01/2021] [Indexed: 02/08/2023] Open
Abstract
Previous studies on ablation of several key genes of meibogenesis related to fatty acid elongation, omega oxidation, and esterification into wax esters have demonstrated that inactivation of any of them led to predicted changes in the meibum lipid profiles and caused severe abnormalities in the ocular surface and Meibomian gland (MG) physiology and morphology. In this study, we evaluated the effects of Soat1 ablation that were expected to cause depletion of the second largest class of Meibomian lipids (ML)-cholesteryl esters (CE)-in a mouse model. ML of the Soat1-null mice were examined using liquid chromatography high-resolution mass spectrometry and compared with those of Soat1+/- and wild-type mice. Complete suppression of CE biosynthesis and simultaneous accumulation of free cholesterol (Chl) were observed in Soat1-null mice, while Soat1+/- mutants had normal Chl and CE profiles. The total arrest of the CE biosynthesis in response to Soat1 ablation transformed Chl into the dominant lipid in meibum accounting for at least 30% of all ML. The Soat1-null mice had clear manifestations of dry eye and MG dysfunction. Enrichment of meibum with Chl and depletion of CE caused plugging of MG orifices, increased meibum rigidity and melting temperature, and led to a massive accumulation of lipid deposits around the eyes of Soat1-null mice. These findings illustrate the role of Soat1/SOAT1 in the lipid homeostasis and pathophysiology of MG.
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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.)
- The 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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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: 1.0] [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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35
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Georgiev GA, Gh MS, Romano J, Dias Teixeira KL, Struble C, Ryan DS, Sia RK, Kitt JP, Harris JM, Hsu KL, Libby A, Odrich MG, Suárez T, McKown RL, Laurie GW. Lacritin proteoforms prevent tear film collapse and maintain epithelial homeostasis. J Biol Chem 2020; 296:100070. [PMID: 33187980 PMCID: PMC7948570 DOI: 10.1074/jbc.ra120.015833] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 11/10/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
Lipids in complex, protein-enriched films at air/liquid interfaces reduce surface tension. In the absence of this benefit, the light refracting and immunoprotective tear film on eyes would collapse. Premature collapse, coupled with chronic inflammation compromising visual acuity, is a hallmark of dry eye disease affecting 7 to 10% of individuals worldwide. Although collapse seems independent of mutation (unlike newborn lung alveoli), selective proteome and possible lipidome changes have been noted. These include elevated tissue transglutaminase and consequent inactivation through C-terminal cross-linking of the tear mitogen lacritin, leading to significant loss of lacritin monomer. Lacritin monomer restores homeostasis via autophagy and mitochondrial fusion and promotes basal tearing. Here, we discover that lacritin monomer C-terminal processing, inclusive of cysteine, serine, and metalloproteinase activity, generates cationic amphipathic α-helical proteoforms. Such proteoforms (using synthetic peptide surrogates) act like alveolar surfactant proteins to rapidly bind and stabilize the tear lipid layer. Immunodepletion of C- but not N-terminal proteoforms nor intact lacritin, from normal human tears promotes loss of stability akin to human dry eye tears. Stability of these and dry eye tears is rescuable with C- but not N-terminal proteoforms. Repeated topical application in rabbits reveals a proteoform turnover time of 7 to 33 h with gradual loss from human tear lipid that retains bioactivity without further processing. Thus, the processed C-terminus of lacritin that is deficient or absent in dry eye tears appears to play a key role in preventing tear film collapse and as a natural slow release mechanism that restores epithelial homeostasis.
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Affiliation(s)
- Georgi A Georgiev
- Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | | | - Jeff Romano
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, USA
| | | | - Craig Struble
- Drug Metabolism, Covance Laboratories Inc, Madison, Wisconsin, USA
| | - Denise S Ryan
- Warfighter Refractive Eye Surgery Program and Research Center at Fort Belvoir, Fort Belvoir, Virginia, USA
| | - Rose K Sia
- Warfighter Refractive Eye Surgery Program and Research Center at Fort Belvoir, Fort Belvoir, Virginia, USA
| | - Jay P Kitt
- Department of Chemistry, University of Utah, Salt Lake City, Utah, USA
| | - Joel M Harris
- Department of Chemistry, University of Utah, Salt Lake City, Utah, USA
| | - Ku-Lung Hsu
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Adam Libby
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Marc G Odrich
- Department of Ophthalmology, University of Virginia, Charlottesville, Virginia, USA
| | - Tatiana Suárez
- Department of Research, Development and Innovation, FAES FARMA, Bizkaia, Spain
| | - Robert L McKown
- Department of Integrated Science and Technology, James Madison University, Harrisonburg, Virginia, USA
| | - Gordon W Laurie
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, USA; Department of Ophthalmology, University of Virginia, Charlottesville, Virginia, USA; Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
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Tanno H, Sassa T, Sawai M, Kihara A. Production of branched-chain very-long-chain fatty acids by fatty acid elongases and their tissue distribution in mammals. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1866:158842. [PMID: 33069870 DOI: 10.1016/j.bbalip.2020.158842] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 09/28/2020] [Accepted: 10/09/2020] [Indexed: 01/12/2023]
Abstract
Although most mammalian fatty acids (FAs) are straight-chain, there also exist branched-chain FAs such as iso- and anteiso-FAs, especially in the meibomian glands. Meibum lipids, which are secreted from the meibomian glands and are important for dry eye prevention, contain abundant branched-chain lipids, such as cholesteryl esters and wax esters with chain-lengths of ≥C21 (very-long-chain; VLC). However, the exact tissue distribution of branched-chain lipids or the enzymes involved in the production of branched-chain VLCFAs has remained poorly understood. Here, we revealed that FA elongases ELOVL1, ELOVL3, and ELOVL7, of the seven mammalian ELOVL isozymes, elongated saturated branched-chain acyl-CoAs. ELOVL3 was highly active toward iso-C17:0 and anteiso-C17:0 acyl-CoAs and elongated them up to iso-C23:0 and anteiso-C25:0 acyl-CoAs, respectively. ELOVL1 elongated both iso- and anteiso-C23:0 acyl-CoAs to C25:0 acyl-CoAs. By establishing a liquid chromatography-tandem mass spectrometry method capable of separating branched- and straight-chain lipids, we showed that essentially all of the cholesteryl esters and 88% of the wax esters in the mouse meibomian glands are branched. In Elovl1 mutant mice, the levels of ≥C24:0 branched-chain cholesteryl esters and ≥C25:0 branched-chain wax esters were decreased, indicating that ELOVL1 indeed elongates branched-chain VLC acyl-CoAs in vivo. In addition, substantial amounts of ceramides containing branched-chain FAs were present in the skin, meibomian glands, and liver. Our findings provide new insights into the molecular mechanisms that create FA and lipid diversity.
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Affiliation(s)
- Honoka Tanno
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
| | - Megumi Sawai
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
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Widjaja-Adhi MAK, Silvaroli JA, Chelstowska S, Trischman T, Bederman I, Sayegh R, Golczak M. Deficiency in Acyl-CoA:Wax Alcohol Acyltransferase 2 causes evaporative dry eye disease by abolishing biosynthesis of wax esters. FASEB J 2020; 34:13792-13808. [PMID: 32851726 PMCID: PMC7722226 DOI: 10.1096/fj.202001191r] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/21/2020] [Accepted: 08/05/2020] [Indexed: 01/16/2023]
Abstract
Lipids secreted by the meibomian glands (MGs) of the eyelids are essential to the protection of the eye's surface. An altered meibum composition represents the primary cause of evaporative dry eye disease (DED). Despite the critical importance of the meibum, its biosynthetic pathways and the roles of individual lipid components remain understudied. Here, we report that the genetic deletion of Acyl-CoA:wax alcohol acyltransferase 2 (AWAT2) causes the obstruction of MGs and symptoms of evaporative DED in mice. The lipid composition of the meibum isolated from Awat2-/- mice revealed the absence of wax esters, which was accompanied by a compensatory overproduction of cholesteryl esters. The resulting increased viscosity of meibum led to the dilation of the meibomian ducts, and the progressive degeneration of the MGs. Overall, we provide evidence for the main physiological role of AWAT2 and establish Awat2-/- mice as a model for DED syndrome that can be used in studies on tear film-oriented therapies.
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Affiliation(s)
| | - Josie A. Silvaroli
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Sylwia Chelstowska
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Thomas Trischman
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Ilya Bederman
- Department of Genetics and Genome Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Rony Sayegh
- Department of Ophthalmology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Marcin Golczak
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA,Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Paananen RO, Viitaja T, Olżyńska A, Ekholm FS, Moilanen J, Cwiklik L. Interactions of polar lipids with cholesteryl ester multilayers elucidate tear film lipid layer structure. Ocul Surf 2020; 18:545-553. [PMID: 32562857 DOI: 10.1016/j.jtos.2020.06.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/31/2020] [Accepted: 06/04/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE The tear film lipid layer (TFLL) covers the tear film, stabilizing it and providing a protective barrier against the environment. The TFLL is divided into polar and non-polar sublayers, but the interplay between lipid classes in these sublayers and the structure-function relationship of the TFLL remains poorly characterized. This study aims to provide insight into TFLL function by elucidating the interactions between polar and non-polar TFLL lipids at the molecular level. METHODS Mixed films of polar O-acyl-ω-hydroxy fatty acids (OAHFA) or phospholipids and non-polar cholesteryl esters (CE) were used as a model of the TFLL. The organization of the films was studied by using a combination of Brewster angle and fluorescence microscopy in a Langmuir trough system. In addition, the evaporation resistance of the lipid films was evaluated. RESULTS Phospholipids and OAHFAs induced the formation of a stable multilamellar CE film. The formation of this film was driven by the interdigitation of acyl chains between the monolayer of polar lipids and the CE multilayer lamellae. Surprisingly, the multilayer structure was destabilized by both low and high concentrations of polar lipids. In addition, the CE multilayer was no more effective in resisting the evaporation of water than a polar lipid monolayer. CONCLUSIONS Formation of multilamellar films by major tear film lipids suggest that the TFLL may have a similar structure. Moreover, in contrast to the current understanding, polar TFLL lipids may not mainly act by stabilizing the non-polar TFLL sublayer, but through a direct evaporation resistant effect.
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Affiliation(s)
- Riku O Paananen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland.
| | - Tuomo Viitaja
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland; Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014, Helsinki, Finland
| | - Agnieszka Olżyńska
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 182 23, Prague, Czech Republic
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014, Helsinki, Finland
| | - Jukka Moilanen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 182 23, Prague, Czech Republic
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