1
|
Kleinbeck S, Wolkoff P. Exposure limits for indoor volatile substances concerning the general population: The role of population-based differences in sensory irritation of the eyes and airways for assessment factors. Arch Toxicol 2024; 98:617-662. [PMID: 38243103 PMCID: PMC10861400 DOI: 10.1007/s00204-023-03642-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/16/2023] [Indexed: 01/21/2024]
Abstract
Assessment factors (AFs) are essential in the derivation of occupational exposure limits (OELs) and indoor air quality guidelines. The factors shall accommodate differences in sensitivity between subgroups, i.e., workers, healthy and sick people, and occupational exposure versus life-long exposure for the general population. Derivation of AFs itself is based on empirical knowledge from human and animal exposure studies with immanent uncertainty in the empirical evidence due to knowledge gaps and experimental reliability. Sensory irritation in the eyes and airways constitute about 30-40% of OELs and is an abundant symptom in non-industrial buildings characterizing the indoor air quality and general health. Intraspecies differences between subgroups of the general population should be quantified for the proposal of more 'empirical' based AFs. In this review, we focus on sensitivity differences in sensory irritation about gender, age, health status, and vulnerability in people, based solely on human exposure studies. Females are more sensitive to sensory irritation than males for few volatile substances. Older people appear less sensitive than younger ones. However, impaired defense mechanisms may increase vulnerability in the long term. Empirical evidence of sensory irritation in children is rare and limited to children down to the age of six years. Studies of the nervous system in children compared to adults suggest a higher sensitivity in children; however, some defense mechanisms are more efficient in children than in adults. Usually, exposure studies are performed with healthy subjects. Exposure studies with sick people are not representative due to the deselection of subjects with moderate or severe eye or airway diseases, which likely underestimates the sensitivity of the group of people with diseases. Psychological characterization like personality factors shows that concentrations of volatile substances far below their sensory irritation thresholds may influence the sensitivity, in part biased by odor perception. Thus, the protection of people with extreme personality traits is not feasible by an AF and other mitigation strategies are required. The available empirical evidence comprising age, lifestyle, and health supports an AF of not greater than up to 2 for sensory irritation. Further, general AFs are discouraged for derivation, rather substance-specific derivation of AFs is recommended based on the risk assessment of empirical data, deposition in the airways depending on the substance's water solubility and compensating for knowledge and experimental gaps. Modeling of sensory irritation would be a better 'empirical' starting point for derivation of AFs for children, older, and sick people, as human exposure studies are not possible (due to ethical reasons) or not generalizable (due to self-selection). Dedicated AFs may be derived for environments where dry air, high room temperature, and visually demanding tasks aggravate the eyes or airways than for places in which the workload is balanced, while indoor playgrounds might need other AFs due to physical workload and affected groups of the general population.
Collapse
Affiliation(s)
- Stefan Kleinbeck
- Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.
| | - Peder Wolkoff
- National Research Centre for the Working Environment, Copenhagen, Denmark
| |
Collapse
|
2
|
Moreno I, Verma S, Gesteira TF, Coulson-Thomas VJ. Recent advances in age-related meibomian gland dysfunction (ARMGD). Ocul Surf 2023; 30:298-306. [PMID: 37979775 PMCID: PMC11092925 DOI: 10.1016/j.jtos.2023.11.003] [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: 08/01/2023] [Revised: 11/02/2023] [Accepted: 11/13/2023] [Indexed: 11/20/2023]
Abstract
Meibomian glands (MGs), located within the tarsal plate of the eyelid, secrete meibum which is the lipid-rich secretion necessary for stabilizing the tear film and preventing tear evaporation. Changes in the quality and quantity of meibum produced causes MG dysfunction (MGD), the leading cause of evaporative dry eye disease (EDED). MGD is an underdiagnosed disease and it is estimated that, in the US, approximately 70 % of the population over 60 have MGD. Three forms of MGD occur based on their meibum secretion: hyposecretory, obstructive, and hypersecretory MGD. The pathophysiology of MGD remains poorly understood, however aging is the primary risk factor. With age, MGs undergo various age-related changes, including decreased acinar basal cell proliferation, hyperkeratinization, MG atrophy, and eventual MG drop-out, leading to age-related MGD (ARMGD). Additionally, studies have suggested that MGs can suffer inflammatory cell infiltration and changes innervation patterns with aging, which could also contribute towards ARMGD. This review focuses on how the aging process affects the MG, and more importantly, how age-related changes to the MG can lead to MG atrophy and MG drop-out, ultimately leading to ARMGD. This review also highlights the most recent developments in potential therapeutic interventions for ARMGD.
Collapse
Affiliation(s)
| | - Sudhir Verma
- College of Optometry, University of Houston, USA; Department of Zoology, Deen Dayal Upadhyaya College, University of Delhi, Delhi, India.
| | | | | |
Collapse
|
3
|
Butovich IA, Wilkerson A, Yuksel S. Dysregulation of Lipid Metabolism in Aging Meibomian Glands and Its Molecular Markers. Int J Mol Sci 2023; 24:13512. [PMID: 37686319 PMCID: PMC10488057 DOI: 10.3390/ijms241713512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/24/2023] [Accepted: 08/27/2023] [Indexed: 09/10/2023] Open
Abstract
The main function of exocrine Meibomian glands (MGs) is to produce a lipid-rich secretion called meibum which plays a critical role in maintaining the ocular surface homeostasis of humans and most mammals. The chemical composition of meibum, and its quantity produced by MGs, largely determine whether it can fulfill its role successfully. Aging was frequently associated with the onset of various MG-related pathologies. The goal of this study was to determine how aging affects the chemical composition and quantity of meibum in mice, and identify possible molecular markers of aging. Unbiased, untargeted and targeted lipidomic evaluation of mouse MG lipids was conducted using liquid chromatography-high-resolution mass spectrometry, and the results were analyzed using Principal Component, Orthogonal Projections to Latent Structures Discriminant, and Partial Least Square Discriminant Analyses. We found that aging leads to dysregulation of lipid metabolism in MGs, changing the ratios of major classes of MG lipids (such as wax esters, triacylglycerols, and phospholipids) in a progressive manner. Several lipid species that belong to these groups of MG lipids are proposed as clear markers of aging in a mouse model.
Collapse
Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
| |
Collapse
|
4
|
Nagar S, Ajouz L, Nichols KK, Kumar S, Zhao C, Naidoo KK, Robinson MR, Borchman D. Relationship Between Human Meibum Lipid Composition and the Severity of Meibomian Gland Dysfunction: A Spectroscopic Analysis. Invest Ophthalmol Vis Sci 2023; 64:22. [PMID: 37466951 PMCID: PMC10362926 DOI: 10.1167/iovs.64.10.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Abstract
Purpose Information on the relationship between meibum lipid composition and severity of meibomian gland dysfunction (MGD) is limited. The purpose of this study was to analyze the molecular components of meibum collected from individuals with no MGD, mild-to-moderate MGD, and severe MGD. Methods Adults with and without MGD were enrolled in a prospective, multicenter, exploratory clinical trial (ClinicalTrials.gov Identifier: NCT01979887). Molar ratios of cholesteryl ester to wax ester (RCE/WE) and aldehyde to wax ester (Rald/WE) in meibum samples were measured with 1H-NMR spectroscopy. Results were evaluated for participants grouped by MGD disease status and severity (non-MGD, mild-to-moderate MGD, and severe MGD), as defined by maximum meibum quality scores, Schirmer test results, and Subject Ocular Symptom Questionnaire responses. Results Sixty-nine meibum samples from 69 individuals were included in the analysis: 24 non-MGD, 24 mild-to-moderate MGD, and 21 severe MGD. Mean RCE/WE was 0.29 in non-MGD, 0.14 in mild-to-moderate MGD (P = 0.038 vs. non-MGD, 51% lower), and 0.07 in severe MGD (P = 0.16 vs. mild-to-moderate MGD, 52% lower; P = 0.002 vs. non-MGD, 76% lower). Mean Rald/WE was 0.00022 in non-MGD, 0.00083 in mild-to-moderate MGD (P = 0.07 vs. non-MGD, 277% higher), and 0.0024 in severe MGD (P = 0.003 vs. mild-to-moderate MGD, 190% higher; P < 0.001 vs. non-MGD, 992% higher). Conclusions RCE/WE was lowest and Rald/WE was highest in the severe MGD cohort, suggesting that these meibum constituent molar ratios may result from the pathophysiology associated with MGD and can impact ocular surface lipid and tear film homeostasis. These findings may potentially help identify targets for MGD treatment.
Collapse
Affiliation(s)
- Saumya Nagar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Layla Ajouz
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kelly K Nichols
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Sandeep Kumar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Cathy Zhao
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kugen K Naidoo
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
| | | | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
| |
Collapse
|
5
|
Verma S, Moreno IY, Trapp ME, Ramirez L, Gesteira TF, Coulson-Thomas VJ. Meibomian gland development: Where, when and how? Differentiation 2023; 132:41-50. [PMID: 37202278 DOI: 10.1016/j.diff.2023.04.005] [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: 10/31/2022] [Revised: 04/10/2023] [Accepted: 04/30/2023] [Indexed: 05/20/2023]
Abstract
The Meibomian gland (MG) is an indispensable adnexal structure of eye that produces meibum, an important defensive component for maintaining ocular homeostasis. Normal development and maintenance of the MGs is required for ocular health since atrophic MGs and disturbances in composition and/or secretion of meibum result in major ocular pathologies, collectively termed as Meibomian gland dysfunction (MGD). Currently available therapies for MGD merely provide symptomatic relief and do not treat the underlying deficiency of the MGs. Hence, a thorough understanding of the timeline of MG development, maturation and aging is required for regenerative purposes along with signaling molecules & pathways controlling proper differentiation of MG lineage in mammalian eye. Understanding the factors that contribute to the development of MGs, developmental abnormalities of MGs, and changes in the quality & quantity of meibum with developing phases of MGs are essential for developing potential treatments for MGD. In this review, we compiled a timeline of events and the factors involved in the structural and functional development of MGs and the associated developmental defects of MGs during development, maturation and aging.
Collapse
Affiliation(s)
- Sudhir Verma
- College of Optometry, University of Houston, Houston, TX, USA; Department of Zoology, Deen Dayal Upadhyaya College, University of Delhi, New Delhi, India
| | - Isabel Y Moreno
- College of Optometry, University of Houston, Houston, TX, USA
| | - Morgan E Trapp
- College of Optometry, University of Houston, Houston, TX, USA
| | - Luis Ramirez
- College of Optometry, University of Houston, Houston, TX, USA
| | | | | |
Collapse
|
6
|
Qin G, Chao C, Lattery LJ, Lin H, Fu W, Richdale K, Cai C. Tear proteomic analysis of young glasses, orthokeratology, and soft contact lens wearers. J Proteomics 2023; 270:104738. [PMID: 36191803 DOI: 10.1016/j.jprot.2022.104738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 09/01/2022] [Accepted: 09/06/2022] [Indexed: 02/01/2023]
Abstract
Contact lens-related ocular surface complications occur more often in teenagers and young adults. The purpose of this study was to determine changes in tear proteome of young patients wearing glasses (GL), orthokeratology lenses (OK), and soft contact lenses (SCL). Twenty-two young subjects (10-26 years of age) who were established GL, OK, and SCL wearers were recruited. Proteomic data were collected using a data-independent acquisition-parallel accumulation serial fragmentation workflow. In total, 3406 protein groups were identified, the highest number of proteins identified in Schirmer strip tears to date. Eight protein groups showed higher abundance, and 11 protein groups showed lower abundance in the SCL group compared to the OK group. In addition, the abundance of 82 proteins significantly differed in children compared to young adult GL wearers, among which 67 proteins were higher, and 15 proteins were lower in children. These 82 proteins were involved in inflammation, immune, and glycoprotein metabolic biological processes. In summary, this work identified over 3000 proteins in Schirmer Strip tears. The results indicated that tear proteomes were altered by orthokeratology and soft contact wear and age, which warrants further larger-scale study on the ocular surface responses of teenagers and young adults separately to contact lens wear. SIGNIFICANCE: In this work, we examined the tear proteomes of young patients wearing glasses, orthokeratology lenses, and soft contact lenses using a data-independent acquisition-parallel accumulation serial fragmentation (diaPASEF) workflow and identified 3406 protein groups in Schirmer strip tears. Nineteen protein groups showed significant abundance changes between orthokeratology and soft contact lens wearers. Moreover, eighty-two protein groups significantly differed in abundance in children and young adult glasses wearers. As a pilot study, this work provides a deep coverage of tear proteome and suggests the need to investigate ocular responses to contact lens wear separately for children and young adults.
Collapse
Affiliation(s)
- Guoting Qin
- College of Optometry, University of Houston, Houston, TX 77204, United States of America; Mass Spectrometry Laboratory, Department of Chemistry, University of Houston, Houston, TX 77204, United States of America.
| | - Cecilia Chao
- College of Optometry, University of Houston, Houston, TX 77204, United States of America; School of Optometry and Vision Science, University of New South Wales, Sydney, NSW 2023, Australia
| | - Lauren J Lattery
- College of Optometry, University of Houston, Houston, TX 77204, United States of America
| | - Hong Lin
- Department of Computer Science & Engineering Technology, University of Houston - Downtown, Houston, TX 77002, United States of America
| | - Wenjiang Fu
- Department of Mathematics, University of Houston, Houston, TX 77204, United States of America
| | - Kathryn Richdale
- College of Optometry, University of Houston, Houston, TX 77204, United States of America
| | - Chengzhi Cai
- Mass Spectrometry Laboratory, Department of Chemistry, University of Houston, Houston, TX 77204, United States of America.
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
Khanal S, Bai Y, Ngo W, Nichols KK, Wilson L, Barnes S, Nichols JJ. Human Meibum and Tear Film Derived (O-Acyl)-Omega-Hydroxy Fatty Acids as Biomarkers of Tear Film Dynamics in Meibomian Gland Dysfunction and Dry Eye Disease. Invest Ophthalmol Vis Sci 2021; 62:13. [PMID: 34236383 PMCID: PMC8267210 DOI: 10.1167/iovs.62.9.13] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To investigate the association between precorneal tear film (PCTF)- and meibum-derived (O-Acyl)-omega-hydroxy fatty acids (OAHFAs) and PCTF thinning in meibomian gland health and dysfunction. Methods Of 195 eligible subjects (18-84 years, 62.6% female), 178 and 170 subjects provided both PCTF optical coherence tomography (OCT) imaging and mass spectrometry data for tears (n = 178) and meibum (n = 170). The PCTF thinning rate was measured in the right eye using an ultra-high-resolution, custom-built OCT. Tear and meibum samples from the right eye were infused into the SCIEX 5600 TripleTOF mass spectrometer in the negative ion mode. Intensities (m/z) of preidentified OAHFAs were measured with Analyst 1.7TF and LipidView 1.3 (SCIEX). Principal component (PC) analyses and Spearman's correlations (ρ) were performed to evaluate the association between OAHFAs and PCTF thinning rates. Results In meibum and tear samples, 76 and 78 unique OAHFAs were detected, respectively. The first PC scores of the meibum-derived OAHFAs had statistically significant correlations with PCTF thinning rates (ρ = 0.18, P = 0.016). Among 10 OAHFAs with the highest first PC loadings, six OAHFAs had negative correlations with PCTF thinning rate (18:2/16:2, ρ = -0.19, P = 0.01; 18:2/30:1, ρ = -0.21, P = 0.008; 18:1/28:1, ρ = -0.22, P = 0.004; 18:1/30:1, ρ = -0.22, P = 0.005; 18:1/25:0, ρ = 0.22, P = 0 .006; and 18:1/26:1, ρ = -0.22, P = 0.006), while one OAHFA had a positive correlation with PCTF thinning rate (18:2/18:1, ρ = 0.48, P = 0.006). Tear film-derived OAHFAs had no association with the PCTF thinning rate. Conclusions Several human meibum-derived OAHFAs showed significant associations with PCTF thinning, suggesting that these OAHFAs could be implicated in the mechanism underlying the stabilization and thinning of the PCTF. The tear-film derived OAHFAs were, however, independent of the rate of PCTF thinning.
Collapse
Affiliation(s)
- Safal Khanal
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Yuqiang Bai
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - William Ngo
- Centre for Ocular Research & Education, School of Optometry & Vision Science, University of Waterloo, Waterloo, Ontario, Canada.,Centre for Eye and Vision Research, 17W Hong Kong Science Park, Hong Kong
| | - Kelly K Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Landon Wilson
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Jason J Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| |
Collapse
|
9
|
Viitaja T, Raitanen JE, Moilanen J, Paananen RO, Ekholm FS. The Properties and Role of O-Acyl-ω-hydroxy Fatty Acids and Type I-St and Type II Diesters in the Tear Film Lipid Layer Revealed by a Combined Chemistry and Biophysics Approach. J Org Chem 2021; 86:4965-4976. [PMID: 33729799 PMCID: PMC8041317 DOI: 10.1021/acs.joc.0c02882] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
The tear film lipid
layer (TFLL) that covers the ocular surface
contains several unique lipid classes, including O-acyl-ω-hydroxy fatty acids, type I-St diesters, and type II
diesters. While the TFLL represents a unique biological barrier that
plays a central role in stabilizing the entire tear film, little is
known about the properties and roles of individual lipid species.
This is because their isolation from tear samples in sufficient quantities
is a tedious task. To provide access to these species in their pure
form, and to shed light on their properties, we here report a general
strategy for the synthesis and structural characterization of these
lipid classes. In addition, we study the organization and behavior
of the lipids at the air–tear interface. Through these studies,
new insights on the relationship between structural features, such
as number of double bonds and the chain length, and film properties,
such as spreading and evaporation resistance, were uncovered.
Collapse
Affiliation(s)
- Tuomo Viitaja
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.,Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Jan-Erik Raitanen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Riku O Paananen
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.,Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| |
Collapse
|
10
|
Ravandeh M, Coliva G, Kahlert H, Azinfar A, Helm CA, Fedorova M, Wende K. Protective Role of Sphingomyelin in Eye Lens Cell Membrane Model against Oxidative Stress. Biomolecules 2021; 11:biom11020276. [PMID: 33668553 PMCID: PMC7918908 DOI: 10.3390/biom11020276] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 02/09/2021] [Accepted: 02/11/2021] [Indexed: 12/20/2022] Open
Abstract
In the eye lens cell membrane, the lipid composition changes during the aging process: the proportion of sphingomyelins (SM) increases, that of phosphatidylcholines decreases. To investigate the protective role of the SMs in the lens cell membrane against oxidative damage, analytical techniques such as electrochemistry, high-resolution mass spectrometry (HR-MS), and atomic force microscopy (AFM) were applied. Supported lipid bilayers (SLB) were prepared to mimic the lens cell membrane with different fractions of PLPC/SM (PLPC: 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine). The SLBs were treated with cold physical plasma. A protective effect of 30% and 44% in the presence of 25%, and 75% SM in the bilayer was observed, respectively. PLPC and SM oxidation products were determined via HR-MS for SLBs after plasma treatment. The yield of fragments gradually decreased as the SM ratio increased. Topographic images obtained by AFM of PLPC-bilayers showed SLB degradation and pore formation after plasma treatment, no degradation was observed in PLPC/SM bilayers. The results of all techniques confirm the protective role of SM in the membrane against oxidative damage and support the idea that the SM content in lens cell membrane is increased during aging in the absence of effective antioxidant systems to protect the eye from oxidative damage and to prolong lens transparency.
Collapse
Affiliation(s)
- Mehdi Ravandeh
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Str. 4, 17489 Greifswald, Germany;
- Leibniz-Institute for Plasma Science and Technology, ZIK Plasmatis, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
- Correspondence: (M.R.); (K.W.)
| | - Giulia Coliva
- Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany; (G.C.); (M.F.)
- Center for Biotechnology and Biomedicine, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany
| | - Heike Kahlert
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Str. 4, 17489 Greifswald, Germany;
| | - Amir Azinfar
- Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany; (A.A.); (C.A.H.)
| | - Christiane A. Helm
- Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany; (A.A.); (C.A.H.)
| | - Maria Fedorova
- Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany; (G.C.); (M.F.)
- Center for Biotechnology and Biomedicine, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany
| | - Kristian Wende
- Leibniz-Institute for Plasma Science and Technology, ZIK Plasmatis, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
- Correspondence: (M.R.); (K.W.)
| |
Collapse
|
11
|
Borchman D. Lipid conformational order and the etiology of cataract and dry eye. J Lipid Res 2021; 62:100039. [PMID: 32554545 PMCID: PMC7910524 DOI: 10.1194/jlr.tr120000874] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2020] [Indexed: 12/12/2022] Open
Abstract
Lens and tear film lipids are as unique as the systems they reside in. The major lipid of the human lens is dihydrosphingomylein, found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1, more than anywhere else in the body. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins; the lowest amount of oxygen of any tissue; and contains almost no intracellular organelles. The tear film lipid layer (TFLL) is also unique. The TFLL is a thin (100 nm) layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. The major lipids of the TFLL are wax esters and cholesterol esters that are not found in the lens. The hydrocarbon chains associated with the esters are longer than those found anywhere else in the body (as long as 32 carbons), and many are branched. Changes in the composition and structure of the 30,000 different moieties of TFLL contribute to the instability of tears. The focus of the current review is how spectroscopy has been used to elucidate the relationships between lipid composition, conformational order and function, and the etiology of cataract and dry eye.
Collapse
Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202.
| |
Collapse
|
12
|
Kuklinski EJ, Hom MM, Ying GS, Lin MC, Chapkin RS, Jones R, Moser A, Kim KY, Maguire MG, Asbell PA. Associations Between Systemic Omega-3 Fatty Acid Levels With Moderate-to-Severe Dry Eye Disease Signs and Symptoms at Baseline in the Dry Eye Assessment and Management Study. Eye Contact Lens 2021; 47:2-7. [PMID: 32097181 PMCID: PMC7483206 DOI: 10.1097/icl.0000000000000687] [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] [Accepted: 11/24/2019] [Indexed: 11/26/2022]
Abstract
PURPOSE Omega-3 (n-3) fatty acid supplementation is used to treat systemic inflammatory diseases, but the role of n-3 in the pathophysiology and therapy of dry eye disease (DED) is not definitive. We evaluated the relationship of systemic n-3 levels with signs and symptoms at baseline in the Dry Eye Assessment and Management (DREAM) Study. METHODS Blood samples from participants at baseline were analyzed for n-3 and n-6, measured as relative percentage by weight among all fatty acids in erythrocytes. Symptoms were evaluated using the Ocular Surface Disease Index. Signs including conjunctival staining, corneal staining, tear breakup time (TBUT), and Schirmer's test with anesthesia were also evaluated. RESULTS There was no correlation between the systemic n-3 levels and DED symptoms. When the associations with signs of DED were assessed, lower DHA levels were associated with higher conjunctival staining, with mean scores of 3.31, 2.96, and 2.82 for low, medium, and high levels of DHA, respectively (linear trend P=0.007). None of the other signs were associated with DHA or the other measures of n-3. CONCLUSION Previous studies have found varying results on the role of n-3 supplementation with the signs and symptoms of DED. Among patients with DED enrolled in the DREAM Study, lower systemic n-3 levels were not associated with worse symptoms and most signs of DED.
Collapse
Affiliation(s)
- Eric J. Kuklinski
- Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Gui-Shuang Ying
- Ophthalmology, University of Pennsylvania, Philadelphia, PA, United States
| | - Meng C. Lin
- Clinical Research Center, University of California, Berkeley, CA, United States
| | - Robert S. Chapkin
- Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, TX, United States
| | - Richard Jones
- Kennedy Krieger Institute, Baltimore, MD, United States
| | - Ann Moser
- Kennedy Krieger Institute, Baltimore, MD, United States
| | - Ka Yeun Kim
- Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Maureen G. Maguire
- Ophthalmology, University of Pennsylvania, Philadelphia, PA, United States
| | - Penny A. Asbell
- Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Ophthalmology, University of Tennessee, Memphis, TN, United States
| | | |
Collapse
|
13
|
Ramasubramanian A, Ahmed SF, Borchman D. Changes in meibum composition following plaque bachytherapy for choroidal melanoma. BMJ Open Ophthalmol 2020; 5:e000614. [PMID: 33294624 PMCID: PMC7689590 DOI: 10.1136/bmjophth-2020-000614] [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: 09/08/2020] [Revised: 10/27/2020] [Accepted: 11/12/2020] [Indexed: 11/03/2022] Open
Abstract
Objectives Dry eye is common when external beam radiation is used for the treatment of choroidal melanoma (CM). As meibum structure and composition have been related to dry eye, we determined if plaque bachytherapy for CM alters meibum composition. Design 1H-NMR spectroscopy was used to measure the lipid composition of meibum. Setting The University of Louisville, Kentucky, USA. Participants All 13 participants had CM and one participant had iris melanoma. Main outcome measures Cholesteryl ester (CE) to wax ester (WE) ratio, amount of meibum esters (ME) and meibum lipid saturation were measured. Results ME decreased by 80%±18% (±99% CI) in 11 eyes that were treated compared with the contralateral untreated eye. ME increased by 181% in two eyes that were treated compared with the contralateral untreated eye. The mole % CE/WE for meibum was significantly (p<0.0001) 67% lower in eyes that were irradiated compared with control eyes from donors without CM and were not treated. Plaque brachytherapy induced the de-esterification of CE. The intensity of the meibum cis double bond resonances did not change significantly (p>0.05). Conclusion Eyes that had plaque brachytherapy had a lower amount of expressible meibum and a lower CE/WE ratio compared with meibum from the contralateral eye that received no treatment and eyes that did not have uveal melanoma. Both the quality and quantity of meibum should be considered in designing a therapy for dry eye after plaque brachytherapy.
Collapse
Affiliation(s)
| | - Simra Fatima Ahmed
- Department of Ophthtalmology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Douglas Borchman
- Department of Ophthtalmology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| |
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
Borchman D, Ramasubramanian A, Foulks GN. Human Meibum Cholesteryl and Wax Ester Variability With Age, Sex, and Meibomian Gland Dysfunction. Invest Ophthalmol Vis Sci 2019; 60:2286-2293. [PMID: 31112994 PMCID: PMC6530518 DOI: 10.1167/iovs.19-26812] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Purpose Relationships between tear film lipid (TFL) layer composition, structure, and function could provide insight into the etiology of dry eye. The molar ratio of cholesteryl ester (CE)/wax ester (WE) was measured in meibum from normal donors (Mn) and compared with meibum from donors with meibomian gland dysfunction (MMGD). Methods CE/WE was measured using nuclear magnetic resonance spectroscopy. Results CE/WE was distributed into two populations with 81% distributed near 0.55 and 19% near 0.3. CE/WE were higher in donors 13 to 19 years old compared with donors 1 to 12 years old and 20 to 88 years old. CE/WE for MMGD was 30% lower, 0.34 ± 0.04, compared with Mn, 0.49 ± 0.04. There were no sex differences in CE/WE. There were no significant racial differences between the CE/WE ratios for Asians and Caucasians. The CE/WE ratio was higher for blacks and lower for Hispanics compared to Caucasians. Due to the small number sampled, confirmation of the later racial results is needed. The packing of CE and WE in the TFL layer was proposed. Conclusions Although MMGD contains much less CE than Mn, factors other than the CE content, such as the levels of saturation and/or proteins, may be responsible for the higher order of MMGD. In addition to saturation, CE could contribute to the increase in order of Mn between 0 and 20 years of age. Observed changes in the meibum content of CE alone is not likely to influence tear film stability.
Collapse
Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Gary N Foulks
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| |
Collapse
|
16
|
Osae EA, Steven P, Redfern R, Hanlon S, Smith CW, Rumbaut RE, Burns AR. Dyslipidemia and Meibomian Gland Dysfunction: Utility of Lipidomics and Experimental Prospects with a Diet-Induced Obesity Mouse Model. Int J Mol Sci 2019; 20:ijms20143505. [PMID: 31319467 PMCID: PMC6678820 DOI: 10.3390/ijms20143505] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 07/12/2019] [Accepted: 07/16/2019] [Indexed: 12/16/2022] Open
Abstract
Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease and loss of ocular surface homeostasis. Increasingly, several observational clinical studies suggest that dyslipidemia (elevated blood cholesterol, triglyceride or lipoprotein levels) can initiate the development of MGD. However, conclusive evidence is lacking, and an experimental approach using a suitable model is necessary to interrogate the relationship between dyslipidemia and MGD. This systematic review discusses current knowledge on the associations between dyslipidemia and MGD. We briefly introduce a diet-induced obesity model where mice develop dyslipidemia, which can serve as a potential tool for investigating the effects of dyslipidemia on the meibomian gland. Finally, the utility of lipidomics to examine the link between dyslipidemia and MGD is considered.
Collapse
Affiliation(s)
- Eugene A Osae
- University of Houston, College of Optometry, Houston, TX 77204, USA.
| | - Philipp Steven
- Department of Ophthalmology, Division for Dry-Eye and Ocular GvHD, Medical Faculty, University of Cologne, 50937 Cologne, Germany
| | - Rachel Redfern
- University of Houston, College of Optometry, Houston, TX 77204, USA
| | - Samuel Hanlon
- University of Houston, College of Optometry, Houston, TX 77204, USA
| | - C Wayne Smith
- Baylor College of Medicine, Children's Nutrition Center, Houston, TX 77030, USA
| | - Rolando E Rumbaut
- Baylor College of Medicine, Children's Nutrition Center, Houston, TX 77030, USA
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA
| | - Alan R Burns
- University of Houston, College of Optometry, Houston, TX 77204, USA
| |
Collapse
|
17
|
Lipid Saturation and the Rheology of Human Tear Lipids. Int J Mol Sci 2019; 20:ijms20143431. [PMID: 31336861 PMCID: PMC6678947 DOI: 10.3390/ijms20143431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/24/2019] [Accepted: 07/04/2019] [Indexed: 02/03/2023] Open
Abstract
Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid-lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both.
Collapse
|
18
|
Alanazi SA, Badawood YS, Aldawood MA, El-Hiti GA, Masmali AM. Effect of Refresh Plus ® preservative-free lubricant eyedrops on tear ferning patterns in dry eye and normal eye subjects. Clin Ophthalmol 2019; 13:1011-1017. [PMID: 31354235 PMCID: PMC6582768 DOI: 10.2147/opth.s213365] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 05/29/2019] [Indexed: 12/14/2022] Open
Abstract
Purpose To evaluate the tear ferning patterns in dry eye and normal eye subjects in the 3 hours following application of Refresh Plus® preservative-free lubricant eyedrops. Methods Thirty men with dry eye (mean age 22.14±2.34 years) and 30 age-matched men with normal eyes (mean age 23.91±3.24 years) were enrolled. Eyes were classified as normal or dry based on their Ocular Surface Disease Index score, tear meniscus height, and noninvasive tear breakup time. The tear ferning test was performed before and 30, 60, 120, and 180 minutes after application of a Refresh Plus eyedrop into the right eye in each subject. Results There was a significant change in tear ferning grade after application of Refresh Plus eyedrops (P=0.02, Wilcoxon test) in the group with dry eye, but not in the normal eye group (P=0.19, Wilcoxon test). The correlation of tear ferning grade was moderate (r=0.484, P=0.049) at 60 minutes after application of the eyedrops and strong at 120 minutes (r=0.560, P=0.019) and 180 minutes (r=0.726, P=0.001). There was also a strong correlation (r=0.865, P=0.001) between tear ferning grades obtained 120 and 180 minutes after application. In the normal eye group, there was a moderate (r=0.407, P=0.029) correlation between tear ferning grades obtained before and 60 minutes after application of the eyedrops. There was also a strong correlation (r=0.532, P=0.003) between tear ferning grades obtained 120 and 180 minutes after application. Conclusion Tear ferning patterns improved significantly after application of Refresh Plus preservative-free lubricant eyedrops in subjects with dry eye. Artificial tears containing sodium carboxymethylcellulose, such as Refresh Plus, can be used to improve tear ferning patterns in dry eye for at least 3 hours.
Collapse
Affiliation(s)
- Saud A Alanazi
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, 11433, Saudi Arabia
| | - Yousef S Badawood
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, 11433, Saudi Arabia
| | - Mohammed A Aldawood
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, 11433, Saudi Arabia
| | - Gamal A El-Hiti
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, 11433, Saudi Arabia
| | - Ali M Masmali
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, 11433, Saudi Arabia
| |
Collapse
|
19
|
Nättinen J, Jylhä A, Aapola U, Mäkinen P, Beuerman R, Pietilä J, Vaajanen A, Uusitalo H. Age-associated changes in human tear proteome. Clin Proteomics 2019; 16:11. [PMID: 30976209 PMCID: PMC6441198 DOI: 10.1186/s12014-019-9233-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/25/2019] [Indexed: 12/22/2022] Open
Abstract
Background Prevalence of many eye and ocular surface diseases increases with age. While the clinical characteristics and pathophysiologic mechanisms of these conditions are often either known or extensively studied, the effects of normal aging on tear film and ocular surface have not been as widely researched. Methods In order to examine the effects of aging on tear fluid proteomics, tear fluid samples were collected preoperatively from 115 subjects undergoing strabismus or refractive surgery using glass microcapillary tubes. In addition to their refractive error or strabismus, the subjects did not have any other current, known eye diseases. The non-pooled samples were analysed using NanoLC-TripleTOF implementing a sequential window acquisition of all theoretical fragment ion spectra mass spectrometry, resulting in quantified data of 849 proteins. Results According to correlation results, 17 tear proteins correlated significantly with increased age and many of these proteins were connected to inflammation, immune response and cell death. According to enrichment analysis, growth and survival of cells decreased while immune response and inflammation increased with aging. We also discovered several well-known, activated and inhibited upstream regulators, e.g. NF-κB, which has been previously connected to aging in numerous previous studies. Conclusions Overall, the results show the common age-dependent alterations in tear fluid protein profile, which demonstrate similar age-associated alterations of biological functions previously shown in other tissue and sample types. Electronic supplementary material The online version of this article (10.1186/s12014-019-9233-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Janika Nättinen
- 1SILK, Department of Ophthalmology, Faculty of Medicine and Health Technology, Tampere University, PL 100, 33014 Tampere, Finland
| | - Antti Jylhä
- 1SILK, Department of Ophthalmology, Faculty of Medicine and Health Technology, Tampere University, PL 100, 33014 Tampere, Finland
| | - Ulla Aapola
- 1SILK, Department of Ophthalmology, Faculty of Medicine and Health Technology, Tampere University, PL 100, 33014 Tampere, Finland
| | | | - Roger Beuerman
- 1SILK, Department of Ophthalmology, Faculty of Medicine and Health Technology, Tampere University, PL 100, 33014 Tampere, Finland.,3Singapore Eye Research Institute, Singapore, Singapore.,4Duke-NUS Medical School Ophthalmology and Visual Sciences Academic Clinical Program, Singapore, Singapore
| | | | - Anu Vaajanen
- 5Tays Eye Centre, Tampere University Hospital, Tampere, Finland
| | - Hannu Uusitalo
- 1SILK, Department of Ophthalmology, Faculty of Medicine and Health Technology, Tampere University, PL 100, 33014 Tampere, Finland.,5Tays Eye Centre, Tampere University Hospital, Tampere, Finland
| |
Collapse
|
20
|
Human meibum chain branching variability with age, gender and meibomian gland dysfunction. Ocul Surf 2018; 17:327-335. [PMID: 30553000 DOI: 10.1016/j.jtos.2018.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/07/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022]
Abstract
NMR spectroscopy was used to measure hydrocarbon chain branching variability in meibum with age, gender and Meibomian gland dysfuction (MGD). A cohort of 65 meibum donors without dry eye and 31 donors with MGD was studied. Heteronuclear 2D NMR was used to confirm CH3 resonance assignments allowing us to positively identify 23 of the 27 proton resonances of cholesteryl ester and 1H resonances due to straight chain, iso-branched and anteiso-branched hydrocarbons. Meibum from donors without dry eye contained 57 ± 1% straight-chains, 23 ± 1% iso-branched chains and 20 ± 1% anteiso-branched hydrocarbon chains. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less, 50 ± 2% straight-chains, more, 32 ± 2% iso-branched chains and the same amount, 18.0 ± 0.07%, of anteiso-branched hydrocarbon chains. Meibum hydrocarbon chain branching did not change with age between 22 and 68 years of age, nor was it influenced by gender. Based on previous studies, one would expect anteiso-branched chains would contribute to lowering the phase transition temperature of meibum, decrease the elasticity of the tear film lipid layer and increase the molecular area and spreading of meibum on the surface of the eye. Although we speculate that the observed differences in iso-chain branching do not influence tear film stability or rheology, the speculation has yet to be tested.
Collapse
|
21
|
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.
Collapse
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.
| |
Collapse
|
22
|
Fagehi R. Impact of environmental adaptation on tear film assessments. J Fr Ophtalmol 2018; 41:231-237. [PMID: 29602450 DOI: 10.1016/j.jfo.2017.08.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 06/18/2017] [Accepted: 08/10/2017] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose of this study was to investigate the effect of ocular environmental adaptation on clinical tear film assessment. METHOD Thirty subjects (male, mean age 23±2.5) participated in this study. A number of clinical tear film tests were applied, including: fluorescein tear break-up time (FTBUT), Schirmer test and tear prism height test (TPH). The tear physiology of each subject was evaluated twice, once immediately when they arrived from the external environment, and then after 30minutes adaptation in the exam room environment. RESULTS The mean values were: Schirmer test A (22.1±2.99), Schirmer test B (24.2±2.63), FTBUT A (8.00±1.94), FTBUT B (9.13±2.04), TPH A (0.179±0.026) and TPH B* (0.187±0.023). Statistical testing using Wilcoxon-signed rank test showed a significant difference between the Schirmer test results measured at the different times (P=0.008). Also, the FTBUT and tear prism height test results showed significant differences between the two evaluation times, (P=0.001, 0.011, respectively) (A: tear assessed when the subject comes from the outside environment, B: tear film assessed after 30min adaptation in the clinical environment). CONCLUSION This study showed a significant difference between the tear film test results evaluated when the subjects were assessed immediately from the outside environment and after an adaptation time in the clinic environment. Practitioners must consider the effect of differences between external and clinical environment adaptation on clinical tear film physiology.
Collapse
Affiliation(s)
- R Fagehi
- College of Applied Medical Sciences, King Saud university, Riyadh, Saudi Arabia.
| |
Collapse
|
23
|
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.
Collapse
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
| |
Collapse
|
24
|
Comparison of treatment effect across varying severities of meibomian gland dropout. Cont Lens Anterior Eye 2018; 41:88-92. [DOI: 10.1016/j.clae.2017.09.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 08/23/2017] [Accepted: 09/08/2017] [Indexed: 11/18/2022]
|
25
|
Sledge S, Henry C, Borchman D, Yappert MC, Bhola R, Ramasubramanian A, Blackburn R, Austin J, Massey K, Sayied S, Williams A, Georgiev G, Schikler KN. Human Meibum Age, Lipid-Lipid Interactions and Lipid Saturation in Meibum from Infants. Int J Mol Sci 2017; 18:ijms18091862. [PMID: 28846660 PMCID: PMC5618511 DOI: 10.3390/ijms18091862] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/25/2017] [Accepted: 08/17/2017] [Indexed: 01/21/2023] Open
Abstract
Tear stability decreases with increasing age and the same signs of instability are exacerbated with dry eye. Meibum lipid compositional changes with age provide insights into the biomolecules responsible for tear film instability. Meibum was collected from 69 normal donors ranging in age from 0.6 to 68 years of age. Infrared spectroscopy was used to measure meibum lipid phase transition parameters. Nuclear magnetic resonance spectroscopy was used to measure lipid saturation. Increasing human meibum lipid hydrocarbon chain unsaturation with age was related to a decrease in hydrocarbon chain order, cooperativity, and in the phase transition temperature. The change in these parameters was most dramatic between 1 and 20 years of age. Meibum was catalytically saturated to determine the effect of saturation on meibum lipid phase transition parameters. Hydrocarbon chain saturation was directly related to lipid order, phase transition temperature, cooperativity, changes in enthalpy and entropy, and could account for the changes in the lipid phase transition parameters observed with age. Unsaturation could contribute to decreased tear film stability with age.
Collapse
Affiliation(s)
- Samiyyah Sledge
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Collin Henry
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
| | - Rahul Bhola
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
- Division of Ophthalmology, Children's Hospital of Orange County, Orange, CA 92868, USA.
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Ryan Blackburn
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Jonathan Austin
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Kayla Massey
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Shanzeh Sayied
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Aliza Williams
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Georgi Georgiev
- Model Membranes Lab, Department of Biochemistry, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria.
| | - Kenneth N Schikler
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA.
| |
Collapse
|
26
|
Abstract
The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.
Collapse
|
27
|
Asymptomatic Meibomian Gland Dysfunction and Cardiovascular Disease Risk Factors in a Middle-Aged Population in Taiwan - A Cross-sectional Analysis. Sci Rep 2017; 7:4935. [PMID: 28694455 PMCID: PMC5504032 DOI: 10.1038/s41598-017-05368-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 05/26/2017] [Indexed: 02/08/2023] Open
Abstract
Managing cardiovascular disease (CVD) risk factors is the key to prevent CVD. This study aimed to prevent CVD by introducing asymptomatic meibomian gland dysfunction (MGD), a condition associated with various CVD risk factors, as an early indicator for CVD in middle-aged population. Participants with and without asymptomatic MGD underwent standardized questionnaires, physical examinations, and laboratory investigations. One ophthalmologist completed the identification and grading of MGD by using slit-lamp biomicroscopy examination on the eyelid margins, meibomian gland orifices, and meibomian gland secretions. Standardized techniques were used to measure the CVD risk factor parameters. After adjusted for age and gender, CVD risk factors including elevated uric acid (P = 0.01), total cholesterol (Total-C, P < 0.001), low-density lipoprotein cholesterol (LDL-C, P < 0.001), fasting triglyceride (Fasting TG, P < 0.001), decreased high-density lipoprotein cholesterol (HDL-C, P = 0.04), and presence of hepatic steatosis (P = 0.008) were significantly associated with asymptomatic MGD. Stepwise logistic regression analysis revealed that LDL-C (OR: 1.03, 95% CI: 1.02–1.04) and Fasting TG (OR: 1.01; 95% CI: 1.00–1.01) levels were risk factors for having asymptomatic MGD (P < 0.001). Together, the results suggest that asymptomatic MGD may serve as an indicator for CVD.
Collapse
|
28
|
Mudgil P, Borchman D, Gerlach D, Yappert MC. Sebum/Meibum Surface Film Interactions and Phase Transitional Differences. Invest Ophthalmol Vis Sci 2017; 57:2401-11. [PMID: 27145473 PMCID: PMC5113983 DOI: 10.1167/iovs.16-19117] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Purpose Sebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection. The aims of this study were to determine: if sebum changes the rheology of meibum surface films; if the resonance near 5.2 ppm in the 1H-NMR spectra of sebum is due to squalene (SQ); and if sebum or SQ, a major component of sebum, interacts with human meibum. Methods Human meibum was collected from the lid margin with a platinum spatula. Human sebum was collected using lipid absorbent tape. Langmuir trough technology was used to measure the rheology of surface films. Infrared spectroscopy was used to measure lipid conformation and phase transitions. We used 1H-NMR to measure composition and confirm the primary structure of SQ. Results The NMR resonance near 5.2 ppm in the spectra of human sebum was from SQ which composed 28 mole percent of sebum. Both sebum and SQ lowered the lipid order of meibum. Sebum expanded meibum films at lower concentrations and condensed meibum films at higher concentrations. Sebum caused meibum to be more stable at higher pressures (greater maximum surface pressure). Conclusions Physiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active (qualities beneficial for tear film stability). Sebum would also be expected to stabilize the tear film lipid layer, which may allow it to withstand the high shear pressure of a blink.
Collapse
Affiliation(s)
- Poonam Mudgil
- School of Medicine Western Sydney University, Penrith, New South Wales, Australia
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Dylan Gerlach
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, Kentucky, United States
| |
Collapse
|
29
|
Abstract
PURPOSE To study the epidemiology of meibomian gland (MG) dysfunction in an elderly, predominantly male population. METHODS Prospective study of 233 subjects seen in the Miami Veterans Affairs eye clinic. Patients underwent a complete ocular surface examination, including dry eye questionnaires and tear assessments (osmolarity, tear breakup time, corneal staining, Schirmer test). The main outcome measures were correlations between MG parameters and demographics, dry eye symptoms, and tear parameters. The studied MG parameters were eyelid vascularity and meibum quality; a score ≥2 for either parameter was considered abnormal. RESULTS Mean age of the 233 subjects was 63 years (SD = 11); 91% were male and 59% had at least 1 abnormal MG parameter (abnormal quality 55%; vascularity 17%). Demographically, patients with abnormal MG parameters were significantly older than their counterparts without these findings. Whites were more likely to have abnormal eyelid vascularity compared with blacks [n = 36 (31%) vs. n = 1 (1%), P < 0.0005] but no differences were noted between races with respect to meibum quality. Abnormal meibum quality, but not abnormal vascularity, was significantly associated with more severe dry eye symptoms. Similarly, abnormal meibum quality, but not eyelid vascularity, was significantly associated with worse dry eye signs, including decreased tear breakup time and increased corneal staining (P < 0.05 for all). CONCLUSIONS MG dysfunction is a frequent finding in an elderly, predominantly male population with racial differences noted in the frequency of abnormal eyelid vascularity but not in MG quality. Abnormal meibum quality was significantly associated with more severe dry eye symptoms and signs.
Collapse
|
30
|
Wolkoff P. External eye symptoms in indoor environments. INDOOR AIR 2017; 27:246-260. [PMID: 27444579 DOI: 10.1111/ina.12322] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/19/2016] [Indexed: 05/22/2023]
Abstract
Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.
Collapse
Affiliation(s)
- P Wolkoff
- National Research Centre for the Working Environment, Copenhagen, Denmark
| |
Collapse
|
31
|
Abstract
Dry eye (DE) is a prevalent ocular disease that primarily affects the elderly. Affecting up to 30% of adults aged 50 years and older, DE affects both visual function and quality of life. Symptoms of DE, including ocular pain (aching, burning), visual disturbances, and tearing, can be addressed with therapeutic agents that target dysfunction of the meibomian glands, lacrimal glands, goblet cells, ocular surface, and/or neural network. This review provides an overview of the efficacy, use, and limitations of current therapeutic interventions being used to treat DE.
Collapse
|
32
|
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: 19] [Impact Index Per Article: 2.1] [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.
Collapse
|
33
|
Millar TJ, Schuett BS. The real reason for having a meibomian lipid layer covering the outer surface of the tear film - A review. Exp Eye Res 2015; 137:125-38. [PMID: 25981748 DOI: 10.1016/j.exer.2015.05.002] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 05/05/2015] [Accepted: 05/08/2015] [Indexed: 12/27/2022]
Abstract
This review critically evaluates a broad range of literature in order to show the relationship between meibum, tear lipids and the tear film lipid layer (TFLL). The relationship of meibum composition to dry eye syndrome is briefly discussed. The review also explores the interactions between aqueous and the TFLL by examining the correlations between meibomian lipids and lipids extracted from whole tears, and by considering protein adsorption to the TFLL from the aqueous. Although it is clear to the authors that a normal tear film resists evaporation, an emerging idea from the literature is that the main purpose of the TFLL is to allow the spread of the tear film and to prevent its collapse onto the ocular surface, rather than to be an evaporative blanket. Current models on the possible structure of the TFLL are also examined.
Collapse
Affiliation(s)
- Thomas J Millar
- University of Western Sydney, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
| | - Burkhardt S Schuett
- University of Western Sydney, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
| |
Collapse
|
34
|
Suhalim JL, Parfitt GJ, Xie Y, De Paiva CS, De Pavia CS, Pflugfelder SC, Shah TN, Potma EO, Brown DJ, Jester JV. Effect of desiccating stress on mouse meibomian gland function. Ocul Surf 2014; 12:59-68. [PMID: 24439047 PMCID: PMC3896889 DOI: 10.1016/j.jtos.2013.08.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/30/2013] [Accepted: 08/13/2013] [Indexed: 11/25/2022]
Abstract
PURPOSE Mice exposed to standardized desiccating environmental stress to induce dry eye-like symptoms have been used as a model to study the underlying mechanisms of evaporative dry eye. While studies have shown marked inflammatory and immune changes, the effect of such stress on meibomian gland function remains largely unknown. We sought to evaluate the effects of desiccating stress on meibocyte proliferation and meibum quality. METHODS Ten mice were treated with scopolamine and subjected to a drafty low humidity environment (30-35%). Five and ten days after treatment, eyelids were harvested and cryosections stained with Ki67 antibody to identify cycling cells. Sections were also imaged using stimulated Raman scattering (SRS) microscopy to characterize the gland compositional changes by detecting the vibrational signatures of methylene (lipid) and amide-I (protein). RESULTS Desiccating stress caused a 3-fold increase in basal acinar cell proliferation from 18.3 ± 11.1% in untreated mice to 64.4 ± 19.9% and 66.6 ± 13.4% after 5 and 10 days exposure, respectively (P < .001). In addition, SRS analysis showed a wider variation in the protein-to-lipid ratio throughout the gland, suggesting alterations in meibocyte differentiation and lipid synthesis. CONCLUSIONS These data are consistent with a model that a desiccating environment may have a direct effect on meibomian gland function, leading to a significant increase in basal acinar cell proliferation, abnormal meibocyte differentiation, and altered lipid production.
Collapse
Affiliation(s)
- Jeffrey L Suhalim
- Gavin Herbert Eye Institute, Irvine, CA, USA; Beckman Laser Institute and Medical Clinic, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA
| | | | - Yilu Xie
- Gavin Herbert Eye Institute, Irvine, CA, USA
| | | | - Cintia S De Pavia
- Ocular Surface Center, Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| | - Stephen C Pflugfelder
- Ocular Surface Center, Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| | | | - Eric O Potma
- Beckman Laser Institute and Medical Clinic, Irvine, CA, USA
| | | | - James V Jester
- Gavin Herbert Eye Institute, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA.
| |
Collapse
|
35
|
Lam SM, Tong L, Reux B, Duan X, Petznick A, Yong SS, Khee CBS, Lear MJ, Wenk MR, Shui G. Lipidomic analysis of human tear fluid reveals structure-specific lipid alterations in dry eye syndrome. J Lipid Res 2013; 55:299-306. [PMID: 24287121 DOI: 10.1194/jlr.p041780] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
As current diagnostic markers for dry eye syndrome (DES) are lacking in both sensitivity and specificity, a pressing concern exists to develop activity markers that closely align with the principal axes of disease progression. In this study, a comprehensive lipidomic platform designated for analysis of the human tear lipidome was employed to characterize changes in tear lipid compositions from a cohort of 93 subjects of different clinical subgroups classified based on the presence of dry eye symptoms and signs. Positive correlations were observed between the tear levels of cholesteryl sulfates and glycosphingolipids with physiological secretion of tears, which indicated the possible lacrimal (instead of meibomian) origin of these lipids. Notably, we found wax esters of low molecular masses and those containing saturated fatty acyl moieties were specifically reduced with disease and significantly correlated with various DES clinical parameters such as ocular surface disease index, tear breakup time, and Schirmer's I test (i.e., both symptoms and signs). These structure-specific changes in tear components with DES could potentially serve as unifying indicators of disease symptoms and signs. In addition, the structurally-specific aberrations in tear lipids reported here were found in patients with or without aqueous deficiency, suggesting a common pathology for both DES subtypes.
Collapse
Affiliation(s)
- Sin Man Lam
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
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]
|
37
|
Borchman D, Yappert MC, Milliner SE, Smith RJ, Bhola R. Confirmation of the Presence of Squalene in Human Eyelid Lipid by Heteronuclear Single Quantum Correlation Spectroscopy. Lipids 2013; 48:1269-77. [DOI: 10.1007/s11745-013-3844-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 07/25/2013] [Indexed: 10/26/2022]
|
38
|
Benlloch-Navarro S, Franco I, Sánchez-Vallejo V, Silvestre D, Romero FJ, Miranda M. Lipid peroxidation is increased in tears from the elderly. Exp Eye Res 2013; 115:199-205. [DOI: 10.1016/j.exer.2013.07.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 06/22/2013] [Accepted: 07/12/2013] [Indexed: 10/26/2022]
|
39
|
Sweeney DF, Millar TJ, Raju SR. Tear film stability: a review. Exp Eye Res 2013; 117:28-38. [PMID: 23973716 DOI: 10.1016/j.exer.2013.08.010] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 08/09/2013] [Accepted: 08/13/2013] [Indexed: 02/08/2023]
Abstract
Tear film stability can be assessed via a number of tools designed for clinical as well as research purposes. These techniques can give us insights into the tear film, and allow assessment of conditions that can lead to dry eye symptoms, and in severe cases, to significant ocular surface damage and deterioration of vision. Understanding what drives tear film instability and its assessment is also crucial for evaluating existing and new therapies. This review examines various techniques that are used to assess tear film instability: evaluation of tear break-up time and non-invasive break-time; topographic and interferometric techniques; confocal microscopic methods; aberrometry; and visual function tests. It also describes possible contributions of different tear film components; namely meibomian lipids, ocular mucins and proteins, and factors such as age, contact lens wear, ocular surgery and environmental stimuli, that may influence tear film instability.
Collapse
Affiliation(s)
- Deborah F Sweeney
- Office of the Pro-Vice Chancellor, University of Western Sydney, Locked Bag 1797, Sydney, Penrith, 2751 NSW, Australia.
| | | | | |
Collapse
|
40
|
Borchman D, Yappert MC, Milliner SE, Duran D, Cox GW, Smith RJ, Bhola R. 13C and 1H NMR ester region resonance assignments and the composition of human infant and child meibum. Exp Eye Res 2013; 112:151-9. [DOI: 10.1016/j.exer.2013.04.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/17/2013] [Accepted: 04/20/2013] [Indexed: 11/29/2022]
|
41
|
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.
Collapse
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.
| |
Collapse
|
42
|
Topical azithromycin and oral doxycycline therapy of meibomian gland dysfunction: a comparative clinical and spectroscopic pilot study. Cornea 2013; 32:44-53. [PMID: 22668581 DOI: 10.1097/ico.0b013e318254205f] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE Meibomian gland dysfunction (MGD) is a common clinical problem that is often associated with evaporative dry eye disease. Alterations of the lipids of the meibomian glands have been identified in several studies of MGD. This prospective, observational, open-label clinical trial documents the improvement in both clinical signs and symptoms of disease as well as spectroscopic characteristics of the meibomian gland lipids after therapy with topical azithromycin ophthalmic solution and oral doxycycline treatment. METHODS Subjects with symptomatic MGD were recruited. Signs of MGD were evaluated with a slit lamp. Symptoms of MGD were measured by the response of subjects to a questionnaire. Meibum lipid-lipid interaction strength, conformation, and phase transition parameters, and meibum protein content were measured using Fourier transform infrared spectroscopy and principal component analysis. Terpenoids, short-chain CH3 moieties, lipid oxidation, wax, cholesterylesters and glycerides were measured with a proton nuclear magnetic resonance (H-NMR) spectrometer. RESULTS Topical therapy with azithromycin and oral therapy with doxycycline relieved signs and symptoms and restored the lipid properties of the meibomian gland secretion toward normal. Compared with 4 weeks of azithromycin treatment reported in our previous study, oral doxycycline treatment was slightly less effective in improving foreign body sensation and the signs of plugging and secretion. In subjects with clinical evidence of MGD, changes in ordering of the lipids and phase transition temperature were brought closer to normal with azithromycin treatment than doxycycline treatment. Treatment with doxycycline but not azithromycin restored the Fourier transform infrared spectroscopy-principal component analysis scores and relative area of the H-NMR resonance at 1.26 ppm. Both doxycycline and azithromycin treatment restored the levels of the relative areas of the H-NMR resonance at 5.2 and 7.9 ppm to normal levels. The levels of meibum protein and meibum lipid oxidation were not influenced by azithromycin or doxycycline treatment. CONCLUSIONS The mechanism of action of doxycycline may be different from that of azithromycin in therapy of MGD. It is notable that when carotenoids in meibum are low, as in MGD, the tear film is unstable and patients have the signs and symptoms of dry eyes. When carotenoids are restored with azithromycin and doxycycline treatment, tear film stability is restored and patients no longer have the signs and symptoms of dry eyes.
Collapse
|
43
|
Analysis of Meibum and Tear Lipids. Ocul Surf 2012; 10:230-50. [DOI: 10.1016/j.jtos.2012.07.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/16/2012] [Accepted: 07/01/2012] [Indexed: 11/19/2022]
|
44
|
Faheem S, Kim SH, Nguyen J, Neravetla S, Ball M, Foulks GN, Yappert MC, Borchman D. Wax-tear and meibum protein, wax-β-carotene interactions in vitro using infrared spectroscopy. Exp Eye Res 2012; 100:32-9. [PMID: 22564968 DOI: 10.1016/j.exer.2012.04.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 04/03/2012] [Accepted: 04/10/2012] [Indexed: 10/28/2022]
Abstract
Protein-meibum and terpenoids-meibum lipid interactions could be important in the etiology of meibomian gland dysfunction (MGD) and dry eye symptoms. In the current model studies, attenuated total reflectance (ATR) infrared (IR) spectroscopy was used to determine if the terpenoid β-carotene and the major proteins in tears and meibum affect the hydrocarbon chain conformation and carbonyl environment of wax, an abundant component of meibum. The main finding of these studies is that mucin binding to wax disordered slightly the conformation of the hydrocarbon chains of wax and caused the wax carbonyls to become hydrogen bonded or experience a more hydrophilic environment. Lysozyme and lactoglobulin, two proteins shown to bind to monolayers of meibum, did not have such an effect. Keratin and β-carotene did not affect the fluidity (viscosity) or environment of the carbonyl moieties of wax. Based on these results, tetraterpenoids are not likely to influence the structure of meibum in the meibomian glands. In addition, these findings suggest that it is unlikely that keratin blocks meibomian glands by causing the meibum to become more viscous. Among the tear fluid proteins studied, mucin is the most likely to influence the conformation and carbonyl environment of meibum at the tear film surface.
Collapse
Affiliation(s)
- Samad Faheem
- Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Center, University of Louisville, 301 E. Muhammad Ali Blvd., Louisville, KY 40202, USA
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Borchman D, Foulks GN, Yappert MC, Milliner SE. Differences in human meibum lipid composition with meibomian gland dysfunction using NMR and principal component analysis. Invest Ophthalmol Vis Sci 2012; 53:337-47. [PMID: 22131391 DOI: 10.1167/iovs.11-8551] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Nuclear magnetic resonance (NMR) spectroscopy has been used to quantify lipid wax, cholesterol ester terpenoid and glyceride composition, saturation, oxidation, and CH₂ and CH₃ moiety distribution. This tool was used to measure changes in human meibum composition with meibomian gland dysfunction (MGD). METHODS (1)H-NMR spectra of meibum from 39 donors with meibomian gland dysfunction (Md) were compared to meibum from 33 normal donors (Mn). RESULTS Principal component analysis (PCA) was applied to the CH₂/CH₃ regions of a set of training NMR spectra of human meibum. PCA discriminated between Mn and Md with an accuracy of 86%. There was a bias toward more accurately predicting normal samples (92%) compared with predicting MGD samples (78%). When the NMR spectra of Md were compared with those of Mn, three statistically significant decreases were observed in the relative amounts of CH₃ moieties at 1.26 ppm, the products of lipid oxidation above 7 ppm, and the =CH moieties at 5.2 ppm associated with terpenoids. CONCLUSIONS Loss of the terpenoids could be deleterious to meibum since they exhibit a plethora of mostly positive biological functions and could account for the lower level of cholesterol esters observed in Md compared with Mn. All three changes could account for the higher degree of lipid order of Md compared with age-matched Mn. In addition to the power of NMR spectroscopy to detect differences in the composition of meibum, it is promising that NMR can be used as a diagnostic tool.
Collapse
Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, USA.
| | | | | | | |
Collapse
|