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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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2
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Sudjarwo WAA, Toca-Herrera JL. Unraveling Complex Hysteresis Phenomenon in 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine Monolayer: Insight into Factors Influencing Surface Dynamics. Int J Mol Sci 2023; 24:16252. [PMID: 38003442 PMCID: PMC10671618 DOI: 10.3390/ijms242216252] [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: 10/20/2023] [Revised: 11/06/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
This study explores the hysteresis phenomenon in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) monolayers, considering several variables, including temperature, compression and expansion rates, residence time, and subphase content. The investigation focuses on analyzing the influence of these variables on key indicators such as the π-A isotherm curve, loop area, and compression modulus. By employing the Langmuir-Blodgett technique, the findings reveal that all the examined factors significantly affect the aforementioned parameters. Notably, the hysteresis loop, representing dissipated energy, provides valuable insights into the monolayer's viscoelasticity, molecular packing, phase transition changes, and resistance during the isocycle process. These findings contribute to a comprehensive understanding of the structural and dynamic properties of DPPC monolayers, offering insights into their behavior under varying conditions. Moreover, the knowledge gained from this study can aid in the development of precise models and strategies for controlling and manipulating monolayer properties, with potential applications in drug delivery systems, surface coatings, as well as further investigation into air penetration into alveoli and the blinking mechanism.
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Affiliation(s)
- Wisnu Arfian A. Sudjarwo
- Institute of Biophysics, Department of Bionanosciences, University of Natural Resources and Life Sciences Vienna (BOKU), 1190 Vienna, Austria
| | - José L. Toca-Herrera
- Institute of Biophysics, Department of Bionanosciences, University of Natural Resources and Life Sciences Vienna (BOKU), 1190 Vienna, Austria
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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: 2] [Impact Index Per Article: 2.0] [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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4
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Hong M, Tong L, Mehta JS, Ong HS. Impact of Exposomes on Ocular Surface Diseases. Int J Mol Sci 2023; 24:11273. [PMID: 37511032 PMCID: PMC10379833 DOI: 10.3390/ijms241411273] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/04/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.
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Affiliation(s)
- Merrelynn Hong
- Corneal and External Diseases Department, Singapore National Eye Centre, Singapore 168751, Singapore
| | - Louis Tong
- Corneal and External Diseases Department, Singapore National Eye Centre, Singapore 168751, Singapore
- Ocular Surface Group, Singapore Eye Research Institute, Singapore 169856, Singapore
- Department of Ophthalmology and Visual Science, Duke-NUS Medical School, Singapore 169857, Singapore
| | - Jodhbir S Mehta
- Corneal and External Diseases Department, Singapore National Eye Centre, Singapore 168751, Singapore
- Department of Ophthalmology and Visual Science, Duke-NUS Medical School, Singapore 169857, Singapore
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore 169856, Singapore
| | - Hon Shing Ong
- Corneal and External Diseases Department, Singapore National Eye Centre, Singapore 168751, Singapore
- Department of Ophthalmology and Visual Science, Duke-NUS Medical School, Singapore 169857, Singapore
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore 169856, Singapore
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5
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Paranjpe V, Galor A, Grambergs R, Mandal N. The role of sphingolipids in meibomian gland dysfunction and ocular surface inflammation. Ocul Surf 2022; 26:100-110. [PMID: 35973562 PMCID: PMC10259413 DOI: 10.1016/j.jtos.2022.07.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 07/17/2022] [Accepted: 07/22/2022] [Indexed: 11/26/2022]
Abstract
Inflammation occurs in response to tissue injury and invasion of microorganisms and is carried out by the innate and adaptive immune systems, which are regulated by numerous chemokines, cytokines, and lipid mediators. There are four major families of bioactive lipid mediators that play an integral role in inflammation - eicosanoids, sphingolipids (SPL), specialized pro-resolving mediators (SPM), and endocannabinoids. SPL have been historically recognized as important structural components of cellular membranes; their roles as bioactive lipids and inflammatory mediators are recent additions. Major SPL metabolites, including sphingomyelin, ceramide, ceramide 1-phosphate (C1P), sphingosine, sphingosine 1-phosphate (S1P), and their respective enzymes have been studied extensively, primarily in cell-culture and animal models, for their roles in cellular signaling and regulating inflammation and apoptosis. Less focus has been given to the involvement of SPL in eye diseases. As such, the aim of this review was to examine relationships between the SPL family and ocular surface diseases, focusing on their role in disease pathophysiology and discussing the potential of therapeutics that disrupt SPL pathways.
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Affiliation(s)
- Vikram Paranjpe
- Department of Ophthalmology, New York University School of Medicine, 550 First Avenue, New York, NY, 10016, USA
| | - Anat Galor
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL, 33136, USA.
| | - Richard Grambergs
- Departments of Ophthalmology, Anatomy and Neurobiology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN, 38163, USA
| | - Nawajes Mandal
- Departments of Ophthalmology, Anatomy and Neurobiology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN, 38163, USA; Memphis VA Medical Center, Memphis, TN, 38104, USA.
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Park SK, Lee JH, Hwang HS, Kim HS, Han KD, Na KS. Association of Meibomian Gland Dysfunction with Oral Statin Use. J Clin Med 2022; 11:jcm11154632. [PMID: 35956248 PMCID: PMC9369571 DOI: 10.3390/jcm11154632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/29/2022] [Accepted: 08/03/2022] [Indexed: 11/22/2022] Open
Abstract
This retrospective cross-sectional study aimed to determine the association of oral statin use, dry eye disease (DED), and meibomian gland dysfunction (MGD). A total of 93 subjects were included and divided into two groups: statin users (n = 45) and nonstatin users (n = 47). Significant differences were observed in the total cholesterol (p = 0.013), low-density lipoprotein (LDL) (p = 0.005), and meiboscore (p = 0.000) levels between the two groups. For stratified analysis, the statin group was divided into subgroups according to the type or dose of statin and total duration of statin use. However, there were no differences in clinical features between the subgroups. In multiple regression analysis, meiboscore was significantly associated with age (slope = 0.05, p = 0.00) and statin use (slope = −1.19, p = 0.00), with an R2 of 0.44. Thus, older adults and participants who do not use statin appeared to have higher scores. In conclusion, although the mechanism is unclear, statins may exert a protective effect on the meibomian gland. Further lipidomic studies are required to determine the pharmacological effects of statins on the meibomian gland and other meibum components.
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Affiliation(s)
- Sun-Kyoung Park
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Ji-Hye Lee
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Ho-Sik Hwang
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Hyun-Seung Kim
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Kyung-Do Han
- Department of Statistics and Actuarial Science, Soongsil University, Seoul 03080, Korea
| | - Kyung-Sun Na
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Correspondence: ; Tel.: +82-2-2258-1188; Fax: +82-2-590-1693
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Sanchez V, Galor A, Jensen K, Mondal K, Mandal N. Relationships between ocular surface sphingomyelinases, Meibum and Tear Sphingolipids, and clinical parameters of meibomian gland dysfunction. Ocul Surf 2022; 25:101-107. [PMID: 35714913 DOI: 10.1016/j.jtos.2022.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 10/18/2022]
Abstract
PURPOSE Sphingolipids (SPL) are a class of lipid molecules that play important functional and structural roles in our body and are a component of meibum. Sphingomyelinases (SMases) are key enzymes in sphingolipid metabolism that hydrolyze sphingomyelin (SM) and generate ceramide (Cer). The purpose of this study was to examine relationships between ocular surface SMases, SPL composition, and parameters of Meibomian gland dysfunction (MGD). METHODS Individuals were grouped by meibum quality (n = 25 with poor-quality, MGD, and n = 25 with good-quality, control). Meibum and tears were analyzed with LC-MS to quantify SPL classes: Cer, Hexosyl-Ceramide (Hex-Cer), SM, Sphingosine (Sph), and sphingosine 1-phosphate (S1P). SMase activity in tears were quantified using a commercially available 'SMase assay'. Statistical analysis included multiple linear regression analyses to assess the impact of SMase activity on lipid composition, as well as ocular surface symptoms and signs of MGD. RESULTS Demographic characteristics were similar between the two groups. nSMase and aSMase levels were lower in the poor vs good quality group. aSMase activity in tears negatively correlated with SM in meibum and tears and positively with Sph in meibum and S1P in tears. Lower SMase activity were associated with signs of MGD, most notably Meibomian gland dropout. CONCLUSION This study suggests that individuals with MGD have reduced enzymatic activity of SMases in tears. Specifically, individuals with poor vs good meibum quality were noted to have alterations in SMase activity and SPL composition of meibum and tears which may reflect deviations from normal lipid metabolism in individuals with MGD.
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Affiliation(s)
- Victor Sanchez
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Anat Galor
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL, 33136, USA
| | - Katherine Jensen
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA
| | - Koushik Mondal
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN, 38163, USA
| | - Nawajes Mandal
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN, 38163, USA; Departments of Anatomy and Neurobiology, Pharmaceutical Sciences, University of Tennessee Health Sciences Center, 930 Madison Avenue, Memphis, TN, 38163, USA; Memphis VA Medical Center, 1030 Jefferson Avenue, Memphis, TN, 38104, USA.
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8
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Feng KM, Chung CH, Chen YH, Chien WC, Chien KH. Statin Use Is Associated With a Lower Risk of Blepharitis: A Population-Based Study. Front Med (Lausanne) 2022; 9:820119. [PMID: 35372440 PMCID: PMC8965040 DOI: 10.3389/fmed.2022.820119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 02/14/2022] [Indexed: 11/13/2022] Open
Abstract
Background Blepharitis is a common eye disorder that may be overlooked by patients and clinical practitioners. The symptoms of blepharitis often manifest as irritation, a burning sensation, grittiness, and itchiness and may decrease visual acuity if not treated promptly. Meibomian gland dysfunction (MGD), a common cause of blepharitis, is believed to be associated with increased inflammatory marker levels that may disrupt the composition of lipids produced by the sebaceous glands in the eyelids and ultimately cause tear film instability. Methods This is a retrospective, population-based study using National Health Insurance Research Database (NHIRD) data from a 14-year period (2000–2015). Pearson chi-squared and Student's t-tests were used to assess the differences in categorical and continuous variables, respectively, between statin users and non-statin users. Univariate and multivariate Cox regression analyses were performed to calculate the hazard ratios (HRs) after adjusting for confounders. Kaplan-Meier analysis was used to assess the cumulative risk of blepharitis between the two cohorts. Results A total of 67,014 patients who used statins were enrolled as the study cohort, and 268,056 patients who did not use statins were enrolled as the comparison cohort. The incidence of blepharitis was 3.04% with statin treatment and 3.72% without statin treatment (p < 0.001). Patients who used statins had a lower risk of developing blepharitis [adjusted hazard ratio (aHR): 0.746, p < 0.001] than those who did not. In addition, diabetes mellitus (DM), hypertension, coronary heart disease (CHD), stroke, chalazion, rosacea, Sjogren syndrome, psoriasis and atopy were found to be possible risk factors for blepharitis. Conclusion Statin use can decrease the risk of developing blepharitis. However, further prospective studies are needed to evaluate statin treatment for various subtypes of blepharitis and to identify the associated mechanism.
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Affiliation(s)
- Kathy Ming Feng
- Department of Ophthalmology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chi-Hsiang Chung
- Department of Medical Research, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,School of Public Health, National Defense Medical Center, Taipei, Taiwan.,Taiwanese Injury Prevention and Safety Promotion Association, Taipei, Taiwan
| | - Yi-Hao Chen
- Department of Ophthalmology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Wu-Chien Chien
- Department of Medical Research, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,School of Public Health, National Defense Medical Center, Taipei, Taiwan.,Taiwanese Injury Prevention and Safety Promotion Association, Taipei, Taiwan.,Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Ke-Hung Chien
- Department of Ophthalmology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
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Biophysical properties of tear film lipid layer II. Polymorphism of FAHFA. Biophys J 2022; 121:451-458. [PMID: 34968427 PMCID: PMC8822609 DOI: 10.1016/j.bpj.2021.12.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 12/04/2021] [Accepted: 12/22/2021] [Indexed: 02/03/2023] Open
Abstract
Fatty acid esters of hydroxy fatty acids (FAHFAs) are a newly discovered class of endogenous lipids that consist of two acyl chains connected through a single ester bond. Being a unique species of FAHFAs, (O-acyl)-ω-hydroxy fatty acids (OAHFAs) differ from other FAHFAs in that their hydroxy fatty acid backbones are ultralong and their hydroxy esterification is believed to be solely at the terminal (ω-) position. Only in recent years with technological advances in lipidomics have OAHFAs been identified as an important component of the tear film lipid layer (TFLL). It was found that OAHFAs account for approximately 4 mol% of the total lipids and 20 mol% of the polar lipids in the TFLL. However, their biophysical function and contribution to the TFLL is still poorly understood. Here we studied the molecular biophysical mechanisms of OAHFAs using palmitic-acid-9-hydroxy-stearic-acid (PAHSA) as a model. PAHSA and OAHFAs share key structural similarities that could result in comparable biophysical properties and molecular mechanisms. With combined biophysical experiments, atomic force microscopy observations, and all-atom molecular dynamics simulations, we found that the biophysical properties of a dynamic PAHSA monolayer under physiologically relevant conditions depend on a balance between kinetics and thermal relaxation. PAHSA molecules at the air-water surface demonstrate unique polymorphic behaviors, which can be explained by configurational transitions of the molecules under various lateral pressures. These findings could have novel implications in understanding biophysical functions that FAHFAs, in general, or OAHFAs, specifically, play in the TFLL.
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10
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Galor A, Sanchez V, Jensen A, Burton M, Maus K, Stephenson D, Chalfant C, Mandal N. Meibum sphingolipid composition is altered in individuals with meibomian gland dysfunction-a side by side comparison of Meibum and Tear Sphingolipids. Ocul Surf 2022; 23:87-95. [PMID: 34861426 PMCID: PMC8792295 DOI: 10.1016/j.jtos.2021.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 11/23/2021] [Accepted: 11/24/2021] [Indexed: 01/21/2023]
Abstract
PURPOSE Sphingolipids (SPL) play a role in cell signaling, inflammation, and apoptosis. The purpose of this study was to examine meibum and tear SPL composition in individuals with poor versus good meibum quality. METHODS Individuals were grouped by meibum quality (n = 25 with poor quality, case group and n = 25 with good quality, control group). Meibum and tears were analyzed with liquid chromatography-mass spectrometry (LC-MS) to quantify SPL classes. Semiquantitative and relative composition (mole percent) of SPL and major classes, Ceramide (Cer), Hexosyl-Ceramide (Hex-Cer), Sphingomyelin (SM), Sphingosine (Sph), and sphingosine 1-phosphate (S1P) were compared between groups. RESULTS Demographic characteristics were similar between the two groups. Overall, individuals with poor meibum quality had more SPL pmole in meibum and tears than controls. Relative composition analysis revealed that individuals with poor meibum quality had SPL composed of less Cer, Hex-Cer, and Sph and more SM compared to individuals with good quality meibum. This pattern was not reproduced in tears as individuals with poor meibum quality had SPL composed of a similar amount of Cer, but more Hex-Cer, Sph and SM compared to controls. In meibum, SPL pmole and relative composition most strongly correlated with MG metrics while in tears, SPL pmole and relative composition most strongly correlated with tear production. SPL in both compartments, specifically Cer pmole in meibum and S1P% in tears, correlated with DE symptoms. CONCLUSION SPL composition differs in meibum and tears in patients with poor vs good meibum quality. These findings may be translated into therapeutic targets for disease.
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Affiliation(s)
- Anat Galor
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125,Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL 33136
| | - Victor Sanchez
- New York University Grossman School of Medicine, New York, NY 10016
| | - Andrew Jensen
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125
| | - Madeline Burton
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN 38163
| | - Kenneth Maus
- Departments of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620
| | | | - Charles Chalfant
- Departments of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620,The Moffitt Cancer Center, Tampa, FL 33620,Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612
| | - Nawajes Mandal
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN 38163,Departments of Anatomy and Neurobiology, and Pharmaceutical Sciences, University of Tennessee Health Sciences Center, 930 Madison Avenue, Memphis, TN 38163,Memphis VA Medical Center, 1030 Jefferson Avenue, Memphis, TN 38104.,Corresponding Author: Nawajes Mandal, PhD, 930 Madison Avenue, Suite 718, Memphis, TN 38163;
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11
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Butovich IA, Yuksel S, Leonard B, Gadek T, Polans AS, Albert DM. Novel Lipids of the Rabbit Harderian Gland Improve Tear Stability in an Animal Model of Dry Eye Disease. J Ocul Pharmacol Ther 2021; 37:545-555. [PMID: 34590914 PMCID: PMC8713569 DOI: 10.1089/jop.2021.0015] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: Instability of the tear film leads to evaporative dry eye disease (EDED), but the Harderian gland in some terrestrial vertebrates may produce novel lipids that stabilize the tear film and protect against dry eye. Here, the nonpolar lipids in the Harderian gland and tears of the rabbit but absent in human tears were identified and tested in preclinical studies to determine whether they could treat severe EDED. Methods: Lipids were identified primarily by atmospheric pressure chemical ionization mass spectrometry (MS) and fragmentation MS/MS. An identified lipid was synthesized and formulated as an emulsion and as a cyclodextrin (CD) clathrate. Following doses with test agents and controls, tear film breakup time (TBUT), tear production, corneal fluorescein staining, macrophage infiltration, and goblet cell survival were measured using standard tests at 0, 2 and 4 weeks in an animal model of EDED. Results: The lipid emulsion increased TBUT (P < 0.01) and tear production (P < 0.05), while it decreased corneal staining (P < 0.01) compared to controls. The lipid CD formulation increased TBUT (P < 0.05) and tear production (P < 0.05) but had no significant effect on the remaining test parameters. There were no differences in macrophage infiltration and conjunctival impression cytology scores between the formulations and their vehicle controls. Conclusions: Lipids in the rabbit Harderian gland and tears differ from those identified in human meibum and tears. These unique rabbit lipids may confer a protective effect against EDED and, as supplements to human tears, fulfill a similar role.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Brian Leonard
- Department of Surgical & Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Tom Gadek
- MCAL Therapeutics, Inc., Park City, Utah, USA
| | - Arthur S. Polans
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Daniel M. Albert
- Casey Eye Institute, School of Medicine, Oregon Health & Science University, Portland, Oregon, USA
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12
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Phan MAT, Madigan MC, Stapleton F, Willcox M, Golebiowski B. Human meibomian gland epithelial cell culture models: Current progress, challenges, and future directions. Ocul Surf 2021; 23:96-113. [PMID: 34843998 DOI: 10.1016/j.jtos.2021.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/04/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022]
Abstract
The widely used immortalised human meibomian gland epithelia cell (iHMGEC) line has made possible extensive studies of the biology and pathophysiology of meibomian glands (MG). Tissue culture protocols for iHMGEC have been revised and modified to optimise the growth conditions for cell differentiation and lipid accumulation. iHMGEC proliferate in serum-free medium but require serum or other appropriate exogenous factors to differentiate. Several supplements can enhance differentiation and neutral lipid accumulation in iHMGEC grown in serum-containing medium. In serum-free medium, rosiglitazone, a peroxisome proliferator activator receptor-γ (PPARγ) agonist, is reported to induce iHMGEC differentiation, neutral lipid accumulation and expression of key biomarkers of differentiation. iHMGEC cultured in serum-containing medium under hypoxia or with azithromycin increases DNAse 2 activity, a biomarker of terminal differentiation in sebocytes. The production of lipids with composition similar to meibum has not been observed in vitro and this remains a major challenge for iHMGEC culture. Innovative methodologies such as 3D ex vivo culture of MG and generation of MG organoids from stem cells are important for further developing a model that more closely mimics the in vivo biology of human MG and to facilitate the next generation of studies of MG disease and dry eye.
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Affiliation(s)
- Minh Anh Thu Phan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia.
| | - Michele C Madigan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Fiona Stapleton
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Mark Willcox
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Blanka Golebiowski
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
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Ji C, Guo Y, Liu Y, Xu S, Zhao S, Luo X, Qiu F, Huang R, Xu Q, Zheng R, Xia M, Zhao Y, Ren J, Qiu Y. Inhibition of ceramide de novo synthesis ameliorates meibomian gland dysfunction induced by SCD1 deficiency. Ocul Surf 2021; 22:230-241. [PMID: 34474170 DOI: 10.1016/j.jtos.2021.08.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 07/30/2021] [Accepted: 08/26/2021] [Indexed: 11/29/2022]
Abstract
High expression of stearoyl-CoA desaturase-1 (SCD1) in meibomian glands produces monounsaturated fatty acids that allow the biosynthesis of glycerolipids and other wax-esters but only the low production of sphingolipids. Here, we found that SCD1 deficiency in mice induces the spill of free fatty acids into a parallel pathway for ceramide biosynthesis, resulting in severe meibomian gland dysfunction associated with meibum accumulation in duct lumen and orifices and subsequent atrophy and loss of acinar cells. Genetic and pharmacological inhibition of SCD1 in mice resulted in meibomian gland pathological phenotypes, including local lipid microenvironment alterations, reduced normal cellular differentiation, increased keratinization, inflammatory cell infiltration, cell apoptosis, and mitochondrial dysfunction. However, inhibition of serine palmitoyltransferase, the initial enzyme in ceramide biosynthesis, improved meibomian gland metabolism and morphology in SCD1-deficient mice, resulting in normal cell differentiation and reduced inflammation infiltration, cell apoptosis, and keratinization. These results indicate that elevated levels of endogenous ceramides are a sign of MGD and suggest that inhibition of ceramide de novo biosynthesis could be a new clinical approach to treating MGD.
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Affiliation(s)
- Chunyan Ji
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Yuli Guo
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Ying Liu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Sennan Xu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Sichen Zhao
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Xin Luo
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Funan Qiu
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fuzhou, China
| | - Rui Huang
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Qingyan Xu
- Xiamen Hospital of Traditional Chinese Medicine, Xiamen, China
| | - Ruihe Zheng
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Miao Xia
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Yun Zhao
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Jie Ren
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China.
| | - Yan Qiu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China.
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14
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Abstract
Purpose The purpose of this study was to determine if aging affects meibum lipid composition in non-meibomian gland dysfunction (MGD)/non-dry eye (DE) population. Aging has been repeatedly linked to pathological changes in various tissues and organs, including the onset of MGD and DE, in a number of clinical and population-wide surveys. Both conditions have been associated with abnormal meibum secretion and composition, among other factors. However, the chemical basis for such a connection has not been established yet. Methods To identify and characterize possible changes in the meibum and meibogenesis with aging, lipidomic analyses of meibum samples collected from human subjects of two age groups - young (29 ± 5 years, n = 21) and elderly (68 ± 7 years, n = 29) - with similar male to female ratios in each group were conducted. Intact lipid species from major lipid groups of meibum (such as wax esters, cholesteryl esters, free cholesterol, triacylglycerols, etc.) were compared using lipidome-wide untargeted (such as Principal Component Analysis) and targeted (such as Orthogonal Projections to Latent Structures Discriminant Analysis) approaches, along with focused analyses of specific lipid species in liquid-chromatography mass spectrometry (LC-MS) and tandem mass spectrometry (MS-MS) experiments. Results Extremely high similarities of meibum lipids in the two age groups were observed, with only minor changes in the individual lipid species. The magnitude of the intergroup variability for tested lipid species was comparable to the intragroup variability for the same meibum components. No statistically significant differences in the lipid esterification, elongation, and unsaturation patterns were observed. Conclusions Chronological aging itself seems to have only minor effect on meibogenesis in healthy, non-MGD/non-DE subjects.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
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Glasgow BJ. Tear Lipocalin and Lipocalin-Interacting Membrane Receptor. Front Physiol 2021; 12:684211. [PMID: 34489718 PMCID: PMC8417070 DOI: 10.3389/fphys.2021.684211] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/13/2021] [Indexed: 11/24/2022] Open
Abstract
Tear lipocalin is a primate protein that was recognized as a lipocalin from the homology of the primary sequence. The protein is most concentrated in tears and produced by lacrimal glands. Tear lipocalin is also produced in the tongue, pituitary, prostate, and the tracheobronchial tree. Tear lipocalin has been assigned a multitude of functions. The functions of tear lipocalin are inexorably linked to structural characteristics that are often shared by the lipocalin family. These characteristics result in the binding and or transport of a wide range of small hydrophobic molecules. The cavity of tear lipocalin is formed by eight strands (A-H) that are arranged in a β-barrel and are joined by loops between the β-strands. Recently, studies of the solution structure of tear lipocalin have unveiled new structural features such as cation-π interactions, which are extant throughout the lipocalin family. Lipocalin has many unique features that affect ligand specificity. These include a capacious and a flexible cavity with mobile and short overhanging loops. Specific features that confer promiscuity for ligand binding in tear lipocalin will be analyzed. The functions of tear lipocalin include the following: antimicrobial activities, scavenger of toxic and tear disruptive compounds, endonuclease activity, and inhibition of cysteine proteases. In addition, tear lipocalin binds and may modulate lipids in the tears. Such actions support roles as an acceptor for phospholipid transfer protein, heteropolymer formation to alter viscosity, and tear surface interactions. The promiscuous lipid-binding properties of tear lipocalin have created opportunities for its use as a drug carrier. Mutant analogs have been created to bind other molecules such as vascular endothelial growth factor for medicinal use. Tear lipocalin has been touted as a useful biomarker for several diseases including breast cancer, chronic obstructive pulmonary disease, diabetic retinopathy, and keratoconus. The functional possibilities of tear lipocalin dramatically expanded when a putative receptor, lipocalin-interacting membrane receptor was identified. However, opposing studies claim that lipocalin-interacting membrane receptor is not specific for lipocalin. A recent study even suggests a different function for the membrane protein. This controversy will be reviewed in light of gene expression data, which suggest that tear lipocalin has a different tissue distribution than the putative receptor. But the data show lipocalin-interacting membrane receptor is expressed on ocular surface epithelium and that a receptor function here would be rational.
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Affiliation(s)
- Ben J. Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States
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Wang H, Zhou Q, Wan L, Guo M, Chen C, Xue J, Yang L, Xie L. Lipidomic analysis of meibomian glands from type-1 diabetes mouse model and preliminary studies of potential mechanism. Exp Eye Res 2021; 210:108710. [PMID: 34339682 DOI: 10.1016/j.exer.2021.108710] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 04/13/2021] [Accepted: 07/26/2021] [Indexed: 12/25/2022]
Abstract
Diabetes is a significant risk factor for meibomian gland dysfunction (MGD), but its mechanism is poorly understood. The main function of the meibomian glands (MGs) is to synthesize, store, and secrete lipids. In this study, we found that the amount of lipids in the meibomian acini in STZ-induced type 1 diabetic mice decreased, and the lipid droplets became larger and irregular. In all, 31 lipid subclasses were identified in the mouse MGs, which contained 1378 lipid species in total through lipidomics analysis based on LC-MS/MS. Diabetes caused a significant increase in the content of ceramides (Cer) in the MGs but a significant decrease in the ration of sphingomyelin to ceramides (SM/Cer). The quantity of meibocytes in diabetic mice was dramatically decreased, and the proliferation activity was alleviated, which may be associated with cell cycle arrest caused by diabetes-induced abnormal Cer metabolism in MGs. We found an increase in macrophage and neutrophils infiltration in the diabetic MGs, which may be related to the significant reduction of AcCa in diabetic MGs. Taken together, the results of the present study demonstrated that diabetes induced disruption of lipid homeostasis in MGs, which may mediate the decreased cell proliferation and increased inflammation caused by diabetes in MGs.
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Affiliation(s)
- Huifeng Wang
- Department of Medicine, Qingdao University, Qingdao, China; State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China
| | - Qingjun Zhou
- Qingdao Eye Hospital of Shandong First Medical University, Qingdao, China; State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China
| | - Luqin Wan
- Department of Medicine, Qingdao University, Qingdao, China; State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China
| | - Menglong Guo
- Shanghai Applied Protein Technology Co., Ltd., Shanghai, China
| | - Chen Chen
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China
| | - Junfa Xue
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China
| | - Lingling Yang
- Qingdao Eye Hospital of Shandong First Medical University, Qingdao, China; State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China.
| | - Lixin Xie
- Qingdao Eye Hospital of Shandong First Medical University, Qingdao, China; State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Qingdao, China.
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17
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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: 1.7] [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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18
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Meibomian Gland Dysfunction: What Have Animal Models Taught Us? Int J Mol Sci 2020; 21:ijms21228822. [PMID: 33233466 PMCID: PMC7700490 DOI: 10.3390/ijms21228822] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 12/16/2022] Open
Abstract
Studies have estimated that currently 344 million people worldwide and 16.4 million adults in the US have some form of dry eye disease (DED). It is believed that approximately 70% of DED cases are due to some form of evaporative dry eye, for which Meibomian gland dysfunction (MGD) is the major cause. Unfortunately, currently there is no effective treatment for MGD, and solely palliative care is available. Given the importance of MGD in DED, there has been a growing interest in studying Meibomian gland development, homeostasis and pathology, and, also, in developing therapies for treating and/or preventing MGD. For such, animal models have shown to be a vital tool. Much of what is known today about the Meibomian gland and MGD was learnt from these important animal models. In particular, canine and rabbit models have been essential for studying the physiopathology and progression of DED, and the mouse model, which includes different knockout strains, has enabled the identification of specific pathways potentially involved in MGD. Herein, we provide a bibliographic review on the various animal models that have been used to study Meibomian gland development, Meibomian gland homeostasis and MGD, primarily focusing on publications between 2000 and 2020.
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Aldaas KM, Ismail OM, Hakim J, Van Buren ED, Lin FC, Hardin JS, Meyer JJ. Association of Dry Eye Disease With Dyslipidemia and Statin Use. Am J Ophthalmol 2020; 218:54-58. [PMID: 32413410 PMCID: PMC8034500 DOI: 10.1016/j.ajo.2020.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 05/02/2020] [Accepted: 05/04/2020] [Indexed: 11/19/2022]
Abstract
PURPOSE To determine whether an association exists between dry eye disease (DED) and statin use and/or dyslipidemia. DESIGN Retrospective, case-control study. METHODS Setting: University of North Carolina (UNC)-affiliated healthcare facilities. STUDY POPULATION 72,931 patients seen at UNC ophthalmology clinics over a 10-year period. MAIN OUTCOME MEASURES Odds ratios (ORs) calculated between DED and a history of low, moderate, or high-intensity statin use; and ORs calculated between DED and abnormal lipid panel values. RESULTS Total of 39,336 individuals (53.9% female) were analyzed after exclusion of individuals with confounding risk factors for DED. Of these, 3,399 patients (8.6%) carried a diagnosis of DED. Low-, moderate-, and high-intensity statin regimens were used by 751 subjects (1.9%), 2,655 subjects (6.8%), and 1,036 subjects (2.6%). Lipid abnormalities were identified as total cholesterol >200 mg/dL, 4,558 subjects (11.6%); high-density lipoprotein (HDL) <40 mg/dL, 2,078 subjects (5.3%); low-density lipoprotein (LDL) >130 mg/dL, 2,756 subjects (7.0%); and triglycerides (TGs) >150 mg/dL, 2,881 subjects (7.3%). The odds ratios (OR) of carrying a diagnosis of DED given the presence of low-, moderate-, and high-intensity statin use were 1.39 (95% confidence interval [CI]: 1.13-1.72); OR 1.47 (95% CI: 1.30-1.65), and OR 1.46 (95% CI: 1.21-1.75), respectively. The OR of carrying a diagnosis of DED given the presence of total cholesterol >200 mg/dL, HDL <40 mg/dL, LDL >130 mg/dL, and TGs >150 mg/dL were 1.66 (95% CI: 1.52-1.82), 1.45 (95% CI: 1.26-1.67), 1.55 (95% CI: 1.39-1.74), and 1.43 (95% CI: 1.27-1.61), respectively. CONCLUSIONS A history of statin use or dyslipidemia is associated with an increased odds of having a DED diagnosis. Further studies are needed to determine whether statin use and/or dyslipidemia increases the risk of DED.
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Affiliation(s)
- Khalid M Aldaas
- Department of Ophthalmology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA.
| | - Omar M Ismail
- Department of Ophthalmology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA
| | - Judi Hakim
- University of Alabama Birmingham School of Medicine, Birmingham, Alabama, USA
| | - Eric D Van Buren
- Department of Biostatistics, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA
| | - Feng-Chang Lin
- Department of Biostatistics, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA
| | - Joshua S Hardin
- Department of Ophthalmology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jay J Meyer
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
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Butovich IA, Suzuki T, Wojtowicz J, Bhat N, Yuksel S. Comprehensive profiling of Asian and Caucasian meibomian gland secretions reveals similar lipidomic signatures regardless of ethnicity. Sci Rep 2020; 10:14510. [PMID: 32883999 PMCID: PMC7471331 DOI: 10.1038/s41598-020-71259-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/10/2020] [Indexed: 01/11/2023] Open
Abstract
Meibum-a lipid secretion that is produced by Meibomian glands (MG) in a process termed meibogenesis-plays a critical role in ocular surface physiology. Abnormalities in the chemical composition of meibum were linked to widespread ocular pathologies-dry eye syndrome (DES) and MG dysfunction (MGD). Importantly, in epidemiologic studies the Asian population was shown to be prone to these pathologies more than the Caucasian one, which was tied to differences in their meibomian lipids. However, biochemical data to support these observations and conclusions are limited. To determine if non-DES/non-MGD Asian meibum was significantly different from that of Caucasians, individual samples of meibum collected from ethnic Asian population living in Japan were compared with those of Caucasians living in the USA. These experiments revealed that composition of major lipid classes, such as wax esters (WE), cholesteryl esters (CE), triacylglycerols, (O)-acylated ω-hydroxy fatty acids (OAHFA), cholesteryl sulfate, cholesteryl esters of OAHFA, and diacylated α,ω-dihydroxy fatty alcohols remained invariable in both races, barring a minor (< 10%; p < 0.01) increase in the Asian CE/WE ratio. Considering the natural variability range for most meibomian lipids (app. ± 15% of the Mean), these differences in meibogenesis were deemed to be minimal and unlikely to have a measurable physiological impact.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA.
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
| | - Jadwiga Wojtowicz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
- Centro Oftalmologico de Valencia, Valencia, Venezuela
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9057, USA
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21
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Omali NB, Subbaraman LN, Heynen M, Lada M, Canavan K, Fadli Z, Ngo W, Jones L. Lipid deposition on contact lenses in symptomatic and asymptomatic contact lens wearers. Cont Lens Anterior Eye 2020; 44:56-61. [PMID: 32466858 DOI: 10.1016/j.clae.2020.05.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 05/08/2020] [Accepted: 05/11/2020] [Indexed: 11/18/2022]
Abstract
PURPOSE Lipid deposition on contact lenses (CL) has traditionally been believed to reduce comfort during CL wear. The purpose of this study was to quantify lipid deposition on CL in a group of symptomatic and asymptomatic adapted CL wearers. METHODS This was a single-masked, randomized clinical trial. Only confirmed symptomatic (comfortable lens wear time (CWT) < 8 h and a noticeable reduction in comfort over the course of the day) and asymptomatic (CWT > 10 h and minimal reduction in comfort over the course of the day) participants were recruited to participate in the study. Participants wore senofilcon A lenses in combination with a polyquaternium-based care solution (OPTI-FREE Replenish). Worn CL samples were collected on Day 14. Deposited lipid amounts from the lenses (including cholesteryl ester, cholesterol and triolein) were quantified using a liquid chromatography-mass spectrometry technique. RESULTS Lipid deposition was significantly higher in CL extracts of asymptomatic wearers compared to the symptomatic wearers for all lipid types quantified, including cholesteryl ester (2.1 ± 0.6 vs 1.6 ± 0.5 log μg/lens), cholesterol (1.5 ± 0.3 vs 1.1 ± 0.3 log μg/lens) and triolein (0.3 ± 0.2 vs 0.1 ± 0.1 log μg/lens) (all p < 0.002). The amount of cholesteryl ester deposited was greatest (p = 0.0001), followed by cholesterol, then triolein, for both the asymptomatic and symptomatic groups (both p = 0.0001). CONCLUSION This study demonstrated that the asymptomatic group deposited a significantly greater amount of lipid on their CL. Although lipid levels measured are considered low to trigger any observable clinical deposition, they may influence other clinical outcomes, particularly comfort.
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Affiliation(s)
- Negar Babaei Omali
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
| | - Lakshman N Subbaraman
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
| | - Miriam Heynen
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
| | - Mark Lada
- Johnson and Johnson Vision, Jacksonville, USA
| | | | - Zohra Fadli
- Johnson and Johnson Vision, Jacksonville, USA
| | - William Ngo
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
| | - Lyndon Jones
- Centre for Ocular Research & Education (CORE), School of Optometry and Vision Science, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
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Yoshida M, Yamaguchi M, Sato A, Miyake M, Tabuchi N, Kon R, Iimura KI. Effect of Mineral-Oil Addition on Film Stability of Polar Lipid Constituents Derived from Meibum. J Oleo Sci 2020; 69:429-436. [PMID: 32281565 DOI: 10.5650/jos.ess20006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We studied the effects of mineral oil (MO) on the properties and structure of a spread monolayer of polar lipid constituents in meibum, by performing cyclic lateral compression-expansion experiments using a Langmuir trough. A meibum sample without nonpolar lipids (meibumΔnonpolar-lipid) was prepared by removing the nonpolar lipids from biological meibum extruded from rabbit eyelids and spread on a water surface for measuring the cyclic surface pressure (π)-film area (A) isotherms with in situ observation of the film morphology using a Brewster angle microscope. The meibumΔnonpolar-lipid formed a homogeneous fluid monolayer and underwent collapse upon compression. The π-A isotherm shifted to a smaller area upon repeating the compression-expansion cycles. These observations contrasted those obtained for meibum previously, which may have resulted from the absence of nonpolar lipids. The recovery of the film stability against the lateral compression-expansion cycles was analyzed by adding MO as a nonpolar compound to the film system. A spread film of 1:1 mixture (by weight) could recover the high reversibility of the π-A isotherms during the repeated compression and expansion processes.
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Affiliation(s)
- Masataka Yoshida
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation
| | - Masato Yamaguchi
- Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University
| | - Atsushi Sato
- Advanced Analytical Science Laboratories, Research and Development Headquarters, Lion Corporation
| | - Miyuki Miyake
- Advanced Analytical Science Laboratories, Research and Development Headquarters, Lion Corporation
| | - Nobuhito Tabuchi
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation
| | - Ryo Kon
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation
| | - Ken-Ichi Iimura
- Division of Engineering and Agriculture, Graduate School of Regional Development and Creativity, Utsunomiya University
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Hancock SE, Poad BLJ, Willcox MDP, Blanksby SJ, Mitchell TW. Analytical separations for lipids in complex, nonpolar lipidomes using differential mobility spectrometry. J Lipid Res 2019; 60:1968-1978. [PMID: 31511397 PMCID: PMC6824485 DOI: 10.1194/jlr.d094854] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 09/03/2019] [Indexed: 11/20/2022] Open
Abstract
Secretions from meibomian glands located within the eyelid (commonly known as meibum) are rich in nonpolar lipid classes incorporating very-long (22-30 carbons) and ultra-long (>30 carbons) acyl chains. The complex nature of the meibum lipidome and its preponderance of neutral, nonpolar lipid classes presents an analytical challenge, with typically poor chromatographic resolution, even between different lipid classes. To address this challenge, we have deployed differential mobility spectrometry (DMS)-MS to interrogate the human meibum lipidome and demonstrate near-baseline resolution of the two major nonpolar classes contained therein, namely wax esters and cholesteryl esters. Within these two lipid classes, we describe ion mobility behavior that is associated with the length of their acyl chains and location of unsaturation. This capability was exploited to profile the molecular speciation within each class and thus extend meibum lipidome coverage. Intriguingly, structure-mobility relationships in these nonpolar lipids show similar trends and inflections to those previously reported for other physicochemical properties of lipids (e.g., melting point and phase-transition temperatures). Taken together, these data demonstrate that differential ion mobility provides a powerful orthoganol separation technology for the analysis of neutral lipids in complex matrices, such as meibum, and may further provide a means to predict physicochemical properties of lipids that could assist in inferring their biological function(s).
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Affiliation(s)
- Sarah E Hancock
- School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, Australia
- Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Berwyck L J Poad
- Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, Australia
| | - Mark D P Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, Australia
| | - Todd W Mitchell
- School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, Australia
- Illawarra Health and Medical Research Institute, Wollongong, Australia
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Sabeti S, Kheirkhah A, Yin J, Dana R. Management of meibomian gland dysfunction: a review. Surv Ophthalmol 2019; 65:205-217. [PMID: 31494111 DOI: 10.1016/j.survophthal.2019.08.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 08/20/2019] [Accepted: 08/23/2019] [Indexed: 11/15/2022]
Abstract
Meibomian gland dysfunction is the leading cause of evaporative dry eye disease and is one of the most common conditions encountered by eye care providers. The disorder is characterized by obstruction of the meibomian gland terminal ducts and/or changes in their glandular secretion, resulting in changes in tear film stability, inflammation, and symptoms of irritation. There is no gold standard treatment for meibomian gland dysfunction, but rather a diversity of options. Conservative measures include warm compresses and lid hygiene, but there is growing interest and need for medical treatments and procedures. Potential medical treatments include antibiotics, nonsteroidal and steroidal anti-inflammatory agents, essential fatty acid supplementation, hormone therapy, and control of Demodex infestation. Procedures include intraductal meibomian gland probing, the use of electronic heating devices, intense pulsed light therapy, and intranasal neurostimulation. We provide an update on meibomian gland dysfunction treatments based on recent studies.
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Affiliation(s)
- Saama Sabeti
- University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, Ontario, Canada; Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Ahmad Kheirkhah
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA; Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Jia Yin
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
| | - Reza Dana
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA.
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Yoshida M, Yamaguchi M, Sato A, Tabuchi N, Kon R, Iimura KI. Role of Endogenous Ingredients in Meibum and Film Structures on Stability of the Tear Film Lipid Layer against Lateral Compression. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8445-8451. [PMID: 31140811 DOI: 10.1021/acs.langmuir.9b01114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The property and structure of spread films of meibum extruded from rabbit eyelids and its fractions were investigated using the Langmuir film balance technique and Brewster angle microscopy in order to understand the influence of endogenous ingredients in meibum on the structure and stability of the tear film lipid layer against mechanical stimulus. Surface pressure (?)?film area ( A) isotherms for meibum were measured upon repetitive high-speed compression?expansion cycles and were found almost identical to each other with very small hysteresis, indicating the high stability of the meibum film. Brewster angle microcopy observation implied the spontaneous formation of condensed-phase network structures which consist primarily of wax esters and cholesteryl esters as nonpolar ingredients, coexisting with a monolayer phase of polar lipids two-dimensionally confined by the networks, which were spontaneously formed in the meibum film. The networks were gathered densely and deformed when the film was laterally compressed with barriers of Langmuir trough, but returned to the dispersed networks when expanded. The influence of temperature and salts dissolved in an aqueous subphase was also investigated. The results indicated that the temperature change (20 and 35 ?C) induced a difference of surface pressure at the same film areas in rather compressed films, and the presence of salts in the subphase expanded the films. However, the features of isotherm and surface morphology of the film, including their reversibility, were maintained. Phospholipid-removed meibum also formed a stable film, but slight changes were found in the hysteresis and film morphology compared to those in the meibum film. In contrast, in a film of phospholipid- and cholesterol-removed meibum, three-dimensional aggregates grew upon the first compression and not redispersed by the subsequent expansion, giving noticeable hysteresis between the isotherms. It is considered that high deformability upon compression and resilience upon expansion of the networks as well as reversible collapse and spreading property of the confined monolayer phase would hold the stability of the meibum film against repeated compressions.
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Affiliation(s)
- Masataka Yoshida
- Pharmaceutical Research Laboratories, Research and Development Headquarters , Lion Corporation , 100 Tajima , Odawara , Kanagawa 256-0811 , Japan
| | | | - Atsushi Sato
- Advanced Analytical Science Laboratories, Research and Development Headquarters , Lion Corporation , 7-2-1 Hirai , Edogawa-ku, Tokyo 132-0035 , Japan
| | - Nobuhito Tabuchi
- Pharmaceutical Research Laboratories, Research and Development Headquarters , Lion Corporation , 100 Tajima , Odawara , Kanagawa 256-0811 , Japan
| | - Ryo Kon
- Pharmaceutical Research Laboratories, Research and Development Headquarters , Lion Corporation , 100 Tajima , Odawara , Kanagawa 256-0811 , Japan
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Ooi KGJ, Khoo P, Vaclavik V, Watson SL. Statins in ophthalmology. Surv Ophthalmol 2019; 64:401-432. [PMID: 30703407 DOI: 10.1016/j.survophthal.2019.01.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 01/14/2019] [Accepted: 01/17/2019] [Indexed: 01/07/2023]
Abstract
Statins, 3-hydroxy-3-methyl-gutaryl coenzyme A reductase inhibitors, are a class of lipid-lowering drugs with anti-inflammatory, immunomodulatory, and vascular effects. Statins are increasingly being used in the treatment of a variety of medical conditions. We examine the actions of statins on the eye and its associated ophthalmic disorders. Statins can be synthetic or nonsynthetic, and their differentiating derivations may contribute to their varying cholesterol-lowering and pleiotropic effects. There is conflicting evidence on the ocular therapeutic and adverse effects of the statins. Statins may play a role in reducing the burden of dry eye, corneal ulcer scarring, thyroid-associated orbitopathy, glaucoma, uveitis and other associated ocular inflammatory states, cataract, proliferative vitreoretinopathy, diabetic retinopathy, macular degeneration, and choroidal melanoma. Topical preparations of statins can be formulated, thereby extending the range of ocular diseases that may be amenable to treatment. Statins have a relatively safe side effect profile, but rare and serious adverse reactions have been reported with their usage in ophthalmology, including myopathies and rhabdomyolysis with acute renal failure.
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Affiliation(s)
- Kenneth G-J Ooi
- Save Sight Institute, University of Sydney, Sydney, New South Wales, Australia.
| | - Pauline Khoo
- Save Sight Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Veronika Vaclavik
- Jules Gonin Eye Hospital, University of Lausanne, Lausanne, Switzerland
| | - Stephanie L Watson
- Save Sight Institute, University of Sydney, Sydney, New South Wales, Australia
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Role of Bioactive Sphingolipids in Inflammation and Eye Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1161:149-167. [PMID: 31562629 DOI: 10.1007/978-3-030-21735-8_14] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Inflammation is a common underlying factor in a diversity of ocular diseases, ranging from macular degeneration, autoimmune uveitis, glaucoma, diabetic retinopathy and microbial infection. In addition to the variety of known cellular mediators of inflammation, such as cytokines, chemokines and lipid mediators, there is now considerable evidence that sphingolipid metabolites also play a central role in the regulation of inflammatory pathways. Various sphingolipid metabolites, such as ceramide (Cer), ceramide-1-phosphate (C1P), sphingosine-1-phosphate (S1P), and lactosylceramide (LacCer) can contribute to ocular inflammatory diseases through multiple pathways. For example, inflammation generates Cer from sphingomyelins (SM) in the plasma membrane, which induces death receptor ligand formation and leads to apoptosis of retinal pigment epithelial (RPE) and photoreceptor cells. Inflammatory stress by reactive oxygen species leads to LacCer accumulation and S1P secretion and induces proliferation of retinal endothelial cells and eventual formation of new vessels. In sphingolipid/lysosomal storage disorders, sphingolipid metabolites accumulate in lysosomes and can cause ocular disorders that have an inflammatory etiology. Sphingolipid metabolites activate complement factors in the immune-response mediated pathogenesis of macular degeneration. These examples highlight the integral association between sphingolipids and inflammation in ocular diseases.
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Inflammatory Ocular Diseases and Sphingolipid Signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1159:139-152. [DOI: 10.1007/978-3-030-21162-2_8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Paranjpe V, Tan J, Nguyen J, Lee J, Allegood J, Galor A, Mandal N. Clinical signs of meibomian gland dysfunction (MGD) are associated with changes in meibum sphingolipid composition. Ocul Surf 2018; 17:318-326. [PMID: 30553001 DOI: 10.1016/j.jtos.2018.12.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/26/2018] [Accepted: 12/11/2018] [Indexed: 12/16/2022]
Abstract
PURPOSE Sphingolipids (SPL) play roles in cell signaling, inflammation, and apoptosis. Changes in SPL composition have been reported in individuals with MGD, but associations between clinical signs of MGD and compositional changes in meibum SPLs have not been examined. METHODS Forty-three individuals underwent a tear film assessment. Groups were split into those with good or poor quality meibum. Meibum was collected then analyzed with liquid chromatography-mass spectroscopy to quantify SPL classes. Relative composition of SPL and major classes, Ceramide (Cer), Hexosyl-Ceramide (Hex-Cer), Sphingomyelin (SM), Sphingosine (Sph) and Sphingosine 1-phosphate (S1P) was calculated via mole percent. RESULTS 22 and 21 individuals were characterized with good and poor quality meibum, respectively. Individuals with poor quality were older (60 ± 8 vs 51 ± 16 years) and more likely to be male (90% vs 64%). Relative composition analysis revealed that individuals with poor meibum quality had SPL composed of less Cer (33.36% vs 49.49%, p < 0.01), Hex-Cer (4.88% vs 9.15%, p < 0.01), and S1P (0.16% vs 0.31%, p = 0.05), and more SM (58.67% vs 38.18%, p < 0.01) and Sph (2.92% vs 2.87%, p = 0.97) compared to individuals with good quality meibum. Assessment of the ratio of Cer (pro-apoptotic) to S1P (pro-survival) showed that individuals with poor meibum quality had a relative increase in Cer (495.23 vs 282.69, p = 0.07). CONCLUSION Meibum quality, a clinically graded marker of MGD, is associated with compositional changes in meibum sphingolipids. Further investigation of the structural and bioactive roles of sphingolipids in MGD may provide future targets for therapy.
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Affiliation(s)
- Vikram Paranjpe
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL, 33136, USA
| | - Jeremy Tan
- Ophthalmic Surgeons and Consultants of Ohio, Ohio State University, Columbus, OH, 43203, USA
| | - Jason Nguyen
- West Virginia University Eye, Morgantown, WV, 26506, USA
| | - John Lee
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL, 33136, USA
| | - Jeremy Allegood
- Lipidomics Core, Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA, 23249, USA
| | - Anat Galor
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL, 33125, USA; Bascom Palmer Eye Institute, University of Miami, 900 NW 17th Street, Miami, FL, 33136, USA.
| | - Nawajes Mandal
- Department of Ophthalmology, Anatomy and Neurobiology, University of Tennessee Health Sciences Center, Hamilton Eye Institute, 930 Madison Avenue, Memphis, TN, 38163, USA.
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30
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Ooi KG, Lee MH, Burlutsky G, Gopinath B, Mitchell P, Watson S. Association of dyslipidaemia and oral statin use, and dry eye disease symptoms in the Blue Mountains Eye Study. Clin Exp Ophthalmol 2018; 47:187-192. [DOI: 10.1111/ceo.13388] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 09/03/2018] [Accepted: 09/06/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Kenneth G.‐J. Ooi
- Save Sight InstituteUniversity of Sydney Sydney New South Wales Australia
| | - Ming‐Han H. Lee
- Save Sight InstituteUniversity of Sydney Sydney New South Wales Australia
| | - George Burlutsky
- Westmead Millenium Institute, Westmead Hospital CampusUniversity of Sydney Sydney New South Wales Australia
| | - Bamini Gopinath
- Westmead Millenium Institute, Westmead Hospital CampusUniversity of Sydney Sydney New South Wales Australia
| | - Paul Mitchell
- Westmead Millenium Institute, Westmead Hospital CampusUniversity of Sydney Sydney New South Wales Australia
| | - Stephanie Watson
- Save Sight InstituteUniversity of Sydney Sydney New South Wales Australia
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31
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Mudgil P, Borchman D, Ramasubramanian A. Insights into Tear Film Stability from Babies and Young Adults: A Study of Human Meibum Lipid Conformation and Rheology. Int J Mol Sci 2018; 19:ijms19113502. [PMID: 30405031 PMCID: PMC6275043 DOI: 10.3390/ijms19113502] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/31/2018] [Accepted: 11/02/2018] [Indexed: 11/22/2022] Open
Abstract
Babies have the most stable tears and people with dry eye have the least stable tears. Meibum may contribute to tear film stability, so in this study, the hydrocarbon chain conformation and rheology of meibum from babies was studied for the first time. Infrared spectroscopy was used to measure lipid phase transitions. Rheology was measured using Langmuir film technology. Meibum from 25 donors 1 to 13 years old was compared with meibum from 18 donors 13 to 25 years old. The phase transition temperature and lipid order (stiffness) increased with increasing age from 1 to 25 years. The increase in meibum lipid order from 1 to 25 years of age may contribute to the instability of the tear film with age and contribute to films with a higher reciprocal compressibility modulus that are not as compressible and not as viscoelastic. Changes in the lipid phase transition parameters of meibum lipid with dry eye are an exacerbation of the changes observed with age. The lower reciprocal compressibility moduli of meibum films from children and babies compared with meibum from adults reiterates higher stability in their films which spread better, resist deformation, and facilitates their ability to be quickly restored after blinking.
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Affiliation(s)
- Poonam Mudgil
- School of Medicine, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia.
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
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Glasgow BJ, Abduragimov AR. Interaction of ceramides and tear lipocalin. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:399-408. [PMID: 29331331 PMCID: PMC5835416 DOI: 10.1016/j.bbalip.2018.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 12/19/2017] [Accepted: 01/06/2018] [Indexed: 10/18/2022]
Abstract
The distribution of lipids in tears is critical to their function. Lipids in human tears may retard evaporation by forming a surface barrier at the air interface. Lipids complexed with the major lipid binding protein in tears, tear lipocalin, reside in the bulk (aqueous) and may have functions unrelated to the surface. Many new lipids species have been revealed through recent mass spectrometric studies. Their association with lipid binding proteins has not been studied. Squalene, (O-acyl) omega-hydroxy fatty acids (OAHFA) and ceramides are examples. Even well-known lipids such as wax and cholesteryl esters are only presumed to be unbound because extracts of protein fractions of tears were devoid of these lipids. Our purpose was to determine by direct binding assays if the aforementioned lipids can bind tear lipocalin. Lipids were screened for ability to displace DAUDA from tear lipocalin in a fluorescence displacement assay. Di- and tri-glycerides, squalene, OAHFA, wax and cholesterol esters did not displace DAUDA from tear lipocalin. However, ceramides displaced DAUDA. Apparent dissociation constants for ceramide-tear lipocalin complexes using fluorescent analogs were measured consistently in the submicromolar range with 3 methods, linear spectral summation, high speed centrifugal precipitation and standard fluorescence assays. At the relatively small concentrations in tears, all ceramides were complexed to tear lipocalin. The lack of binding of di- and tri-glycerides, squalene, OAHFA, as well as wax and cholesterol esters to tear lipocalin is consonant with residence of these lipids near the air interface.
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Affiliation(s)
- Ben J Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States.
| | - Adil R Abduragimov
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States
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Abstract
Meibum is a lipid-rich secretion that is produced by fully differentiated meibocytes in the holocrine Meibomian glands (MG) of humans and most mammals. The secretion is a part of a defense mechanism that protects the ocular surface from hazardous environmental factors, and from desiccation. Meibomian lipids that have been identified in meibum are very diverse and unique in nature. The lipid composition of meibum is different from virtually any other lipid pool found in the human body. In fact, meibum is quite different from sebum, which is the closest secretion that is produced by anatomically, physiologically, and biochemically related sebaceous glands. However, meibum of mice have been shown to closely resemble that of humans, implying similar biosynthetic mechanisms in MG of both species. By analyzing available genomic, immunohistochemical, and lipidomic data, we have envisioned a unifying network of enzymatic reactions that are responsible for biosynthesis of meibum, which we call meibogenesis. Our current theory is based on an assumption that most of the biosynthetic reactions of meibogenesis are catalyzed by known enzymes. However, the main features that make meibum unique - the ratio of identified classes of lipids, the extreme length of its components, extensive ω-hydroxylation of fatty acids and alcohols, iso- and anteiso-branching of meibomian lipids (e.g. waxes), and the presence of rather unique complex lipids with several ester bonds - make it possible that either the activity of known enzymes is altered in MG, or some unknown enzymes contribute to the processes of meibogenesis, or both. Studies are in progress to elucidate meibogenesis on molecular level.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology and the Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9057, United States.
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Meibomian glands, meibum, and meibogenesis. Exp Eye Res 2017; 163:2-16. [PMID: 28669846 DOI: 10.1016/j.exer.2017.06.020] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 06/14/2017] [Accepted: 06/28/2017] [Indexed: 12/28/2022]
Abstract
Meibum is a lipid-rich secretion that is produced by fully differentiated meibocytes in the holocrine Meibomian glands (MG) of humans and most mammals. The secretion is a part of a defense mechanism that protects the ocular surface from hazardous environmental factors, and from desiccation. Meibomian lipids that have been identified in meibum are very diverse and unique in nature. The lipid composition of meibum is different from virtually any other lipid pool found in the human body. In fact, meibum is quite different from sebum, which is the closest secretion that is produced by anatomically, physiologically, and biochemically related sebaceous glands. However, meibum of mice have been shown to closely resemble that of humans, implying similar biosynthetic mechanisms in MG of both species. By analyzing available genomic, immunohistochemical, and lipidomic data, we have envisioned a unifying network of enzymatic reactions that are responsible for biosynthesis of meibum, which we call meibogenesis. Our current theory is based on an assumption that most of the biosynthetic reactions of meibogenesis are catalyzed by known enzymes. However, the main features that make meibum unique - the ratio of identified classes of lipids, the extreme length of its components, extensive ω-hydroxylation of fatty acids and alcohols, iso- and anteiso-branching of meibomian lipids (e.g. waxes), and the presence of rather unique complex lipids with several ester bonds - make it possible that either the activity of known enzymes is altered in MG, or some unknown enzymes contribute to the processes of meibogenesis, or both. Studies are in progress to elucidate meibogenesis on molecular level.
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Intersubject and Interday Variability in Human Tear and Meibum Lipidomes: A Pilot Study. Ocul Surf 2015; 14:43-8. [PMID: 26416436 DOI: 10.1016/j.jtos.2015.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 08/14/2015] [Accepted: 08/27/2015] [Indexed: 11/21/2022]
Abstract
PURPOSE Our aim was to quantitate day-to-day changes in the tear and meibum lipid profile of individual subjects in a pilot study of healthy humans. METHODS Matched tear and meibum samples were obtained from four subjects on three consecutive days. Quantitative lipid profiles of human basal tears and meibum were compared using multivariate analysis by principal components. RESULTS Substantial differences in the lipid profile between subjects were observed, while lipid profiles were steady across the three consecutive days of sampling. Multivariate principal component analysis demonstrated that lysophosphatidylcholine was the largest variant lipid class between subjects in tears, while wax esters comprised the most variation between subjects in meibum secretions. CONCLUSION Interday variability is shown to be much smaller than interpatient variability, suggesting that tears and meibum subjects both have unique profiles in humans.
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36
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Mori N, Fukano Y, Arita R, Shirakawa R, Kawazu K, Nakamura M, Amano S. Rapid identification of fatty acids and (O-acyl)-ω-hydroxy fatty acids in human meibum by liquid chromatography/high-resolution mass spectrometry. J Chromatogr A 2014; 1347:129-36. [DOI: 10.1016/j.chroma.2014.04.082] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 04/02/2014] [Accepted: 04/22/2014] [Indexed: 11/16/2022]
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Butovich IA, Lu H, McMahon A, Ketelson H, Senchyna M, Meadows D, Campbell E, Molai M, Linsenbardt E. Biophysical and morphological evaluation of human normal and dry eye meibum using hot stage polarized light microscopy. Invest Ophthalmol Vis Sci 2014; 55:87-101. [PMID: 24282231 DOI: 10.1167/iovs.13-13355] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To study melting characteristics and the morphology of human and mouse meibum. METHODS Hot stage cross-polarized light microscopy (HSPM) and immunohistochemical approaches were used. RESULTS Isolated human meibum, and meibum of mice (either isolated or within the meibomian ducts of mice), were found to be in liquid-crystal state at physiological temperatures. Melting of both types of meibum started at approximately 10°C and was completed at approximately 40°C. Melting curves of isolated meibum and meibum inside the meibomian ducts were multiphasic with at least two or three clearly defined phase transition temperatures, typically at approximately 12 ± 2°C (minor transition), 21 ± 3°C, and 32 ± 3°C, regardless the source of meibum. Melting was highly cooperative in nature. Samples of abnormal human meibum collected from dry eye patients with meibomian gland dysfunction often showed an increased presence of nonlipid, nonmelting, nonbirefringent, chloroform-insoluble inclusions of a protein nature. The inclusions were positively stained for cytokeratins. The presence of these inclusions was semiquantitatively characterized using a newly proposed 0 to 4 scale. In the presence of large amounts of these inclusions, melting characteristics of meibum and its structural integrity were altered. CONCLUSIONS HSPM is an effective tool that is suitable for biophysical and morphological evaluation of meibum. Morphological properties and melting characteristics of human meibum were found to be similar to those of mice. Abnormal meibum of many dry eye patients contained large quantities of nonlipid, protein-like inclusions, which were routinely absent in meibum of normal controls.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas
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Mudgil P, Borchman D, Yappert MC, Duran D, Cox GW, Smith RJ, Bhola R, Dennis GR, Whitehall JS. Lipid order, saturation and surface property relationships: A study of human meibum saturation. Exp Eye Res 2013; 116:79-85. [DOI: 10.1016/j.exer.2013.08.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/08/2013] [Accepted: 08/15/2013] [Indexed: 12/01/2022]
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Robciuc A, Hyötyläinen T, Jauhiainen M, Holopainen JM. Ceramides in the pathophysiology of the anterior segment of the eye. Curr Eye Res 2013; 38:1006-16. [PMID: 23885886 DOI: 10.3109/02713683.2013.810273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE Sphingolipid (SL) research reached a peak in the past years. Yet this positive trend was not evident for eye research as the relative number of studies centered on SLs is decreasing. Our aim is to encourage the inclusion of SL metabolites in studies of ocular pathophysiology by summarizing recent findings and current awareness concerning ceramides in the anterior segment of the eye. METHODS Review of literature relating to ceramides as bioactive lipids and the extent to which their particular nature was investigated in ocular pathophysiology. RESULTS Ceramides are rare but indispensable lipids that influence cellular responses through their effects on membrane biophysical properties or direct interaction with target proteins. Their biological significance is increased by variability and adaptability as there are tens of enzymes designed to modulate their function. The eye offers a set of unique environments where ceramides or other SLs have not been extensively studied. Not surprisingly, ceramides were associated with apoptosis in the metabolically active tissues, while little is known about its effects on the biophysical properties of the tears or lens lipids. More so, there are still aspects of the ocular homeostasis control where SLs contribution has not been investigated to date (e.g. pathogen aggression). CONCLUSIONS Ceramides and SL metabolism still receive increasing attention and have proven to be a significant metabolite in many research fields (e.g. cancer, stress response and inflammation) and there are yet many questions that they will aid answer. With the present work, we seek to increase awareness of these lipids also in eye research and to highlight their importance as common regulators of various diseases.
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Affiliation(s)
- Alexandra Robciuc
- Department of Ophthalmology, University of Helsinki, Helsinki Eye Lab, Helsinki, Finland
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Abstract
Human meibomian gland secretions (MGS, or meibum) are formed from a complex mixture of lipids of different classes such as wax esters, cholesteryl esters, (O-acyl)-ω-hydroxy fatty acids (OAHFA) and their esters, acylglycerols, diacylated diols, free fatty acids, cholesterol, and a smaller amount of other polar and nonpolar lipids, whose chemical nature and the very presence in MGS have been a matter of intense debates. The purpose of this review is to discuss recent results that were obtained using different experimental techniques, estimate limitations of their usability, and discuss their biochemical, biophysical, and physiological implications. To create a lipid map of MGS and tears, the results obtained in the author's laboratory were integrated with available information on chemical composition of MGS and tears. The most informative approaches that are available today to researchers, such as HPLC-MS, GC-MS, and proton NMR, are discussed in details. A map of the meibomian lipidome (as it is seen in reverse phase liquid chromatography/mass spectrometry experiments) is presented. Directions of future efforts in the area are outlined.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology and the Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA.
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