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Dong S, Zhang N, Yi M, Zhang J, Di D, Deng J, Li L, Hu B. Slug-Flow Microextraction Mass Spectrometry for Enhanced Detection of Analytes in Human Tear Fluids using Noninvasive Microsampling and Nanoelectrospray Ionization via a Capillary. Anal Chem 2023; 95:16054-16058. [PMID: 37852267 DOI: 10.1021/acs.analchem.3c03683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
In vivo noninvasive sampling and sensitive analysis of human tear fluids at the microliter level is an important but challenging task in investigating eye health. In this work, capillary microsampling coupled with slug-flow microextraction mass spectrometry (SFME-MS) was developed for enhanced detection of analytes in human tear fluids. As low as 1.0 μL of human tear fluid could be directly sampled using a capillary, and extraction/spray solvent was then loaded into the capillary to perform slug-flow microextraction and direct nanoelectrospray ionization (nESI) of analytes. All analytical procedures, including tear microsampling, microextraction, and ionization of analytes, were performed using a capillary. Enhanced detection of therapeutic drugs and disease biomarkers in human tear fluids was successfully demonstrated. Acceptable analytical performances including sensitivity, reproducibility, and quantitation were obtained. It is found that the use of SFME could improve the nESI-MS detection of trace analytes over 100-fold that depends on the chemical properties of analytes. Overall, this study showed that SFME-nESI-MS is a highly effective method for enhanced detection of trace analytes in tear fluids and is expected to be a potentially powerful tool in significant biological and clinical applications.
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Affiliation(s)
- Songbin Dong
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
| | - Ning Zhang
- Ophthalmology Department, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710064, China
| | - Man Yi
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
| | - Jianfeng Zhang
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
| | - Dandan Di
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
| | - Jiewei Deng
- School of Biomedical and Pharmaceutical Sciences, Smart Medical Innovation Technology Center, Guangdong University of Technology, Guangzhou 510006, China
| | - Lei Li
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
| | - Bin Hu
- Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangdong Provincial Key Laboratory of Speed Capability Research, Jinan University, Guangzhou 510632, China
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Xu X, Li G, Zuo YY. Effect of Model Tear Film Lipid Layer on Water Evaporation. Invest Ophthalmol Vis Sci 2023; 64:13. [PMID: 36656568 PMCID: PMC9872843 DOI: 10.1167/iovs.64.1.13] [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] [Indexed: 01/20/2023] Open
Abstract
Purpose A majority of in vitro models were incapable of reproducing the evaporation resistance of tear film lipid layer (TFLL) in vivo. The purpose of this research is to develop a novel in vitro model to study the effect of TFLL on water evaporation. Methods A ventilated, closed-chamber, droplet evaporimeter with a constant surface area has been invented to study the evaporation resistance of TFLL. This evaporimeter ensures a rigorous control of environmental conditions, including the temperature, relative humidity, airflow rate, surface area, and surface pressure, thus allowing for reproducible water evaporation measurements over a time period of only 5 minutes. The volumetric evaporation rate of this droplet evaporimeter is less than 2.7 µL/min, comparable to the basal tear production of healthy adults. Together with direct film imaging using atomic force microscopy (AFM), we have studied the effect of a model TFLL on water evaporation, as a function of the lipid composition and surface pressure. Results A model TFLL composed of 40% wax esters, 40% cholesteryl esters, and 20% polar lipids was capable of reducing the water evaporation rate by 11% at surface pressure 47 mN/m. AFM revealed that the model TFLL at high surface pressures consists of discrete droplets/aggregates of the nonpolar lipids residing atop a polar lipid monolayer with phase separation. Conclusions The TFLL may resist water evaporation with a combined mechanism by increasing film compactness of the polar lipid film at the air-water surface, and, to a lesser extent, by increasing film thickness of the nonpolar lipid film.
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Affiliation(s)
- Xiaojie Xu
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Guangle Li
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
| | - Yi Y. Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States,Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States
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3
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Walker MK, Bailey LS, Basso KB, Redfern RR. Nonpolar Lipids Contribute to Midday Fogging During Scleral Lens Wear. Invest Ophthalmol Vis Sci 2023; 64:7. [PMID: 36630141 PMCID: PMC9840443 DOI: 10.1167/iovs.64.1.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Purpose To determine correlations between lipids in the fluid reservoir (FR) and the severity of midday fogging (MDF) in scleral lens (SL) wear. Methods SL neophytes were recruited to wear custom SL for 4 days, examined after 8 hours on days 1 and 4. Lens vault and MDF were quantified from anterior segment optical coherence tomography (AS-OCT), and the FR was collected and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Relative abundance of lipids was compared to MDF scores using nonparametric correlation testing (Spearman rank). Ocular surface and SL fitting characteristics (lens vault, fitting curves) were likewise compared to MDF. Results Thirteen participants (26 eyes, 69% female, 28 ± 9 years old) were included in this study. MDF severity after 8 hours of SL wear was 33 ± 29 units on day 1 and 28 ± 24 units on day 4 (r = .94; P < 0.01). Twelve samples were analyzed using LC-MS/MS, and a total of 170 distinct lipid species were detected. The lipid classes with greatest correlation to MDF were the wax esters (r = .73, P = 0.01), cholesteryl esters (r = .59; P = 0.049), and triacylglycerols (r = .64, P = 0.03). Polar lipids were observed abundantly in all samples. None of the measured ocular surface or fitting outcomes were correlated to MDF. Conclusions Nonpolar lipids were the greatest contributors to MDF among these normal participants. Polar lipids may be due to cellular debris, although they do not appear contributory to MDF.
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Affiliation(s)
- Maria K. Walker
- College of Optometry, The Ocular Surface Institute, University of Houston, Houston, Texas, United States
| | - Laura S. Bailey
- Department of Chemistry, University of Florida, Gainesville, Florida, United States
| | - Kari B. Basso
- Department of Chemistry, University of Florida, Gainesville, Florida, United States
| | - Rachel R. Redfern
- College of Optometry, The Ocular Surface Institute, University of Houston, Houston, Texas, United States
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4
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Biochemistry of human tear film: A review. Exp Eye Res 2022; 220:109101. [DOI: 10.1016/j.exer.2022.109101] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 04/18/2022] [Accepted: 04/26/2022] [Indexed: 12/13/2022]
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5
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Mudgil P. Antimicrobial Tear Lipids in the Ocular Surface Defense. Front Cell Infect Microbiol 2022; 12:866900. [PMID: 35433501 PMCID: PMC9008483 DOI: 10.3389/fcimb.2022.866900] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/07/2022] [Indexed: 12/05/2022] Open
Abstract
The concept of antimicrobial lipids as effectors of innate host defense is an emerging field. There is limited knowledge on the antimicrobial role of lipids in the ocular environment. Tears act as first line of defense to protect the ocular surface from infections. Antimicrobial effects of tear lipids have been demonstrated using meibomian lipids that are the source of majority of lipids in tears. This article describes the knowledge available on the antimicrobial role of tear lipids at the ocular surface and the antimicrobial potential of various lipid classes present in tears that can contribute to antimicrobial protection of the eye. Like other mucosal secretions, tears contain many proteins and lipids with known antimicrobial effects. The antimicrobial defense of tears is far stronger than can be demonstrated by the effects of individual compounds many of which are present in low concentrations but synergistic and additive interactions between them provide substantial antimicrobial protection to the ocular surface. It is inferred that antimicrobial lipids play important role in innate defense of tears, and cooperative interactions between various antimicrobial lipids and proteins in tears provide a potent host defense mechanism that is effective against a broad spectrum of pathogens and renders self-sterilizing properties to tears for keeping the microbial load low at the ocular surface.
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Li Q, Jiao SJ, Wang YQ, Xie HT, Zhang MC. Development of a Novel Tear Lipid Test Strip. Cornea 2022; 41:232-237. [PMID: 34743093 DOI: 10.1097/ico.0000000000002869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 07/21/2021] [Indexed: 11/25/2022]
Abstract
PURPOSE The unifying characteristic of dry eye is the loss of tear film homeostasis, and the tear lipid layer is a key component for maintaining film stability. The detection of tear lipid is of great significance for the diagnosis of dry eye. In this study, we explored a new test strip for the detection of tear lipid. METHODS The tear lipid test strip was prepared by coating the strip material with hydrophobic nano-silica. We tested its physical properties with iodine vapor chromogenic and cobalt chloride test methods. Its biosafety was evaluated by an ocular irritation test in rabbits. Finally, we established a rabbit meibomian gland dysfunction model and measured both eyes with the tear lipid test strip at the first, third, seventh, 14th, 16th, and 21st day after surgery. RESULTS The tear lipid test strip had fine lipophilicity and hydrophobicity. It can extract lipid from tear, and the tear lipid can be quantified by measuring the length of lipid infiltration. In the ocular irritation test, the test strip had no obvious eye irritation. The length of lipid infiltration between experimental and control rabbit eyes began to show statistical difference since the third day after surgery. CONCLUSIONS The novel tear lipid test strip has great lipophilicity, hydrophobicity, and biological safety. It might be effectively applied in diagnosis of dry eye.
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Affiliation(s)
- Qian Li
- Department of Ophthalmology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China ; and
| | - Shu-Jie Jiao
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Yue-Qi Wang
- Department of Ophthalmology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China ; and
| | - Hua-Tao Xie
- Department of Ophthalmology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China ; and
| | - Ming-Chang Zhang
- Department of Ophthalmology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China ; and
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Sahu DK, Pradhan D, Biswasroy P, Kar B, Ghosh G, Rath G. Recent trends in nanocarrier based approach in the management of dry eye disease. J Drug Deliv Sci Technol 2021. [DOI: 10.1016/j.jddst.2021.102868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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8
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Masoudi S, Willcox M. A method for studying lipid adsorption to silicone hydrogel contact lenses. BIOFOULING 2021; 37:862-878. [PMID: 34615411 DOI: 10.1080/08927014.2021.1978433] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 08/30/2021] [Accepted: 09/02/2021] [Indexed: 06/13/2023]
Abstract
The aim of this study was to develop an experimental methodology to measure lipid deposition with contact lenses. Contact lenses were incubated in a lipid solution. The amount and types of adsorbed lipids were assessed using mass spectrometry and confocal microscopy. The recovery of lipids from lenses varied with lipid and lens type. Most non-polar and polar lipids were desorbed from lenses during the first 5 min of extraction. Fluorescently labelled phosphatidylcholine bound within the matrix of Senofilcon A lenses but to the surface of Lotrafilcon B lenses, whereas fluorescently labelled cholesteryl ester was found throughout both lenses. The efficacy of extraction of lipids from contact lenses varies for different lipid classes and different lens materials. Differences in the amount and time of lipid desorption probably resulted from the strength of the bond between lipid and lens polymer and the depth of adsorption of lipid in the polymer.
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Affiliation(s)
- Simin Masoudi
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
| | - Mark Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
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9
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Glasgow BJ. Tear Lipocalin and Lipocalin-Interacting Membrane Receptor. Front Physiol 2021; 12:684211. [PMID: 34489718 PMCID: PMC8417070 DOI: 10.3389/fphys.2021.684211] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/13/2021] [Indexed: 11/24/2022] Open
Abstract
Tear lipocalin is a primate protein that was recognized as a lipocalin from the homology of the primary sequence. The protein is most concentrated in tears and produced by lacrimal glands. Tear lipocalin is also produced in the tongue, pituitary, prostate, and the tracheobronchial tree. Tear lipocalin has been assigned a multitude of functions. The functions of tear lipocalin are inexorably linked to structural characteristics that are often shared by the lipocalin family. These characteristics result in the binding and or transport of a wide range of small hydrophobic molecules. The cavity of tear lipocalin is formed by eight strands (A-H) that are arranged in a β-barrel and are joined by loops between the β-strands. Recently, studies of the solution structure of tear lipocalin have unveiled new structural features such as cation-π interactions, which are extant throughout the lipocalin family. Lipocalin has many unique features that affect ligand specificity. These include a capacious and a flexible cavity with mobile and short overhanging loops. Specific features that confer promiscuity for ligand binding in tear lipocalin will be analyzed. The functions of tear lipocalin include the following: antimicrobial activities, scavenger of toxic and tear disruptive compounds, endonuclease activity, and inhibition of cysteine proteases. In addition, tear lipocalin binds and may modulate lipids in the tears. Such actions support roles as an acceptor for phospholipid transfer protein, heteropolymer formation to alter viscosity, and tear surface interactions. The promiscuous lipid-binding properties of tear lipocalin have created opportunities for its use as a drug carrier. Mutant analogs have been created to bind other molecules such as vascular endothelial growth factor for medicinal use. Tear lipocalin has been touted as a useful biomarker for several diseases including breast cancer, chronic obstructive pulmonary disease, diabetic retinopathy, and keratoconus. The functional possibilities of tear lipocalin dramatically expanded when a putative receptor, lipocalin-interacting membrane receptor was identified. However, opposing studies claim that lipocalin-interacting membrane receptor is not specific for lipocalin. A recent study even suggests a different function for the membrane protein. This controversy will be reviewed in light of gene expression data, which suggest that tear lipocalin has a different tissue distribution than the putative receptor. But the data show lipocalin-interacting membrane receptor is expressed on ocular surface epithelium and that a receptor function here would be rational.
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Affiliation(s)
- Ben J. Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States
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10
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Adigal SS, Rizvi A, Rayaroth NV, John RV, Barik A, Bhandari S, George SD, Lukose J, Kartha VB, Chidangil S. Human tear fluid analysis for clinical applications: progress and prospects. Expert Rev Mol Diagn 2021; 21:767-787. [PMID: 34115952 DOI: 10.1080/14737159.2021.1941879] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Introduction: Human blood and saliva are increasingly under investigation for the detection of biomarkers for early diagnosis of non-communicable (e.g.cancers) and communicable diseases like COVID-19. Exploring the potential application of human tears, an easily accessible body fluid, for the diagnosis of various diseases is the need of the hour.Areas covered: This review deals with a comprehensive account of applications of tear analysis using different techniques, their comparison and overall progress achieved till now. The techniques used for tear fluid analysis are HPLC/UPLC/SDS-PAGE, CE, etc., together with ELISA, Mass Spectrometry, etc. But, with advances in instrumentation and data processing methods, it has become easy to couple the various separation methods with highly sensitive optical techniques for the analysis of body fluids.Expert opinion: Tear analysis can provide valuable information about the health condition of the eyes since it contains several molecular constituents, and their relative concentrations may alter under abnormal conditions. Tear analysis has the advantage that it is totally non-invasive. This study recommends tear fluid as a reliable clinical sample to be probed by highly sensitive optical techniques to diagnose different health conditions, with special emphasis on eye diseases.
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Affiliation(s)
- Sphurti S Adigal
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Alisha Rizvi
- Department of Ophthalmology, Kasthurba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Nidheesh V Rayaroth
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Reena V John
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Ajayakumar Barik
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sulatha Bhandari
- Department of Ophthalmology, Kasthurba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sajan D George
- Centre for Applied Nanotechnology, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Jijo Lukose
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Vasudevan B Kartha
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Santhosh Chidangil
- Centre of Excellence for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, Karnataka, India
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Abstract
Purpose The structure of tears has been theoretically considered three tiers with lipids at the air interface, aqueous and proteins in the subphase, and anchored mucins on the corneal epithelial surface. While many lipid and protein species have been identified in tears by mass spectrometry, the localization of the major components within the tear film structure remains speculative. The most controversial components are phospholipids. Although surface active, phospholipids have been presumed to be bound entirely to protein in the aqueous portion of tears or reside at the aqueous-lipid interface. Herein, the possibility that phospholipids are adsorbed at the air-surface interface of tears is interrogated. Methods Polarization-modulated Fourier transform infrared reflective absorption spectroscopy (PM-IRRAS) was used to study the presence of phosphate signals at the tear surface. In order to constrain the depth of signal detection to the surface, an extreme grazing angle of incident radiation was employed. Nulling ellipsometry was used to confirm the presence of monolayers and surface thicknesses when surface active reagents were added to solutions. Results Surface selection of PM-IRRAS was demonstrated by suppression of water and phosphate signals in buffers with monolayers of oleic acid. Phosphate signals were shown to reflect relative concentrations. Absorption peaks attributable to phospholipids were detected by PM-IRRAS on the human tear film surface and were augmented by the addition of phospholipid. Conclusions The data provide strong evidence that phospholipids are present at the surface of tears.
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Affiliation(s)
- Ben J Glasgow
- Departments of Pathology and Ophthalmology, UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, California, United States
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12
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Masoudi S, Mitchell TW, Willcox MD. Profiling of non-polar lipids in tears of contact lens wearers during the day. Exp Eye Res 2021; 207:108567. [PMID: 33848523 DOI: 10.1016/j.exer.2021.108567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 03/23/2021] [Accepted: 04/01/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE This study explored whether the non-polar lipids in the human tear fluid lipidome show diurnal variation with and without contact lens wear. It also addressed the relationship between changes in ocular comfort during the day with the level of non-polar lipids. METHODS Tear samples were collected in the morning and evening with and without contact lenses using fine glass capillary tubes and were analysed by chip-based nano-electrospray ionization tandem mass spectrometric techniques. Tear levels of cholesteryl esters (CE), wax esters (WE) and triacylglycerides (TAG) were quantified. RESULTS TAG 48:0, 52:0 and WE 26:0/16:0, and 27:0/17:0 increased from morning to evening. TAG 52:2, WE 21:0/16:0, 21:0/18:1 and 28:0/18:1 decreased during the day when no lenses were worn. CE 21:0 was the only non-polar lipid that increased from morning to evening in contact lens wear. WE 21:0/16:0 and 27:0/17:0 were lower in the morning in contact lens wear compared to no lens wear (p ≤ 0.05). The level of non-polar lipids did not correlate with ocular comfort at the end of the day. CONCLUSION Even though the level of some of non-polar lipid species changed from morning to evening the total level of major tear non-polar lipids remained unchanged during the day with and without contact lens wear. The effect of change in the quantity and structure of lipid species on tear stability and ocular comfort warrants more investigation.
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Affiliation(s)
- Simin Masoudi
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
| | - Todd W Mitchell
- School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, New South Wales, Australia; Illawara Health and Medical Research Institute, Wollongong, New South Wales, Australia.
| | - Mark D Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
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Glasgow BJ, Abduragimov AR. Lipocalin-1 is the acceptor protein for phospholipid transfer protein in tears. Biochem Biophys Res Commun 2021; 548:35-38. [PMID: 33631671 DOI: 10.1016/j.bbrc.2021.02.054] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/12/2021] [Indexed: 12/12/2022]
Abstract
Phospholipid transfer protein, ∼80 kDa, transfers phospholipids from micelles to lipid binding proteins. The acceptor protein in plasma is apolipoprotein-A1, 28 kDa. Previously, phospholipid transfer protein was found in tears but an acceptor protein was not identified. To search for the acceptor protein(s) in tears a fluorescent phospholipid transfer assay was altered to omit the extrinsic acceptor. Human tears were incubated with fluorescent micelles and showed marked transfer activity verifying a native acceptor protein must be present. Reconstituted tears without tear lipocalin (lipocalin-1) eliminated the transfer of phospholipids. To determine if phospholipid transfer protein is involved in carrying phospholipid to the surface of tears from tear lipocalin, a fraction enriched in phospholipid transfer protein was injected into the subphase of a tear mimicking buffer in which tear lipocalin was present. The addition of phospholipid transfer protein did not increase the thickness of the surface layer regardless of the presence of lipid bearing tear lipocalin. The data show that phospholipid transfer protein transfers phospholipid from micelles to tear lipocalin. Phospholipid transfer protein does not transport the phospholipid. While tear lipocalin has no intrinsic transfer activity from micelles, it is the acceptor protein for phospholipid transfer protein in tears.
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Affiliation(s)
- Ben J Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, 100 Stein Plaza, University of California, Los Angeles, CA, 90095, USA.
| | - Adil R Abduragimov
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, 100 Stein Plaza, University of California, Los Angeles, CA, 90095, USA.
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14
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Borchman D. Lipid conformational order and the etiology of cataract and dry eye. J Lipid Res 2021; 62:100039. [PMID: 32554545 PMCID: PMC7910524 DOI: 10.1194/jlr.tr120000874] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2020] [Indexed: 12/12/2022] Open
Abstract
Lens and tear film lipids are as unique as the systems they reside in. The major lipid of the human lens is dihydrosphingomylein, found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1, more than anywhere else in the body. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins; the lowest amount of oxygen of any tissue; and contains almost no intracellular organelles. The tear film lipid layer (TFLL) is also unique. The TFLL is a thin (100 nm) layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. The major lipids of the TFLL are wax esters and cholesterol esters that are not found in the lens. The hydrocarbon chains associated with the esters are longer than those found anywhere else in the body (as long as 32 carbons), and many are branched. Changes in the composition and structure of the 30,000 different moieties of TFLL contribute to the instability of tears. The focus of the current review is how spectroscopy has been used to elucidate the relationships between lipid composition, conformational order and function, and the etiology of cataract and dry eye.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202.
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15
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López-Cano JJ, González-Cela-Casamayor MA, Andrés-Guerrero V, Herrero-Vanrell R, Molina-Martínez IT. Liposomes as vehicles for topical ophthalmic drug delivery and ocular surface protection. Expert Opin Drug Deliv 2021; 18:819-847. [PMID: 33412914 DOI: 10.1080/17425247.2021.1872542] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Introduction: The development of ophthalmic formulations able to deliver hydrophilic and hydrophobic drugs to the inner structures of the eye and restore the preocular tear film has been a leading topic of discussion over the last few years. In this sense, liposomes represent a suitable strategy to achieve these objectives in ocular drug delivery.Areas covered: Knowledge of the different physiological and anatomical eye structures, and specially the ocular surface are critical to better understanding and comprehending the characteristics required for the development of topical ophthalmic liposomal formulations. In this review, several features of liposomes are discussed such as the main materials used for their fabrication, basic structure and preparation methods, from already established to novel techniques, allowing the control and design of special characteristics. Besides, physicochemical properties, purification processes and strategies to overcome delivery or encapsulation challenges are also presented. Expert opinion: Regarding ocular drug delivery of liposomes, there are some features that can be redesigned. Specific biocompatible and biodegradable materials presenting therapeutic properties, such as lipidic compounds or polymers significantly change the way of tackling ophthalmic diseases. Besides, liposomes entail an effective, safe and versatile strategy for the treatment of diseases in the clinical practice.
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Affiliation(s)
- José Javier López-Cano
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Miriam Ana González-Cela-Casamayor
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Vanessa Andrés-Guerrero
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Rocío Herrero-Vanrell
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Irene Teresa Molina-Martínez
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
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16
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Svitova TF, Lin MC. Evaporation retardation by model tear-lipid films: The roles of film aging, compositions and interfacial rheological properties. Colloids Surf B Biointerfaces 2021; 197:111392. [DOI: 10.1016/j.colsurfb.2020.111392] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/22/2020] [Accepted: 09/28/2020] [Indexed: 01/07/2023]
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17
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Ahmed E, Xiao D, Kabir KMM, Fletcher J, Donald WA. Ambient Pressure Ion Funnel: Concepts, Simulations, and Analytical Performance. Anal Chem 2020; 92:15811-15817. [DOI: 10.1021/acs.analchem.0c02938] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ezaz Ahmed
- School of Chemistry, University of New South Wales, Sydney, NSW 2052 Australia
| | - Dan Xiao
- School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW 2052 Australia
| | - K. M. Mohibul Kabir
- School of Chemistry, University of New South Wales, Sydney, NSW 2052 Australia
| | - John Fletcher
- School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW 2052 Australia
| | - William A. Donald
- School of Chemistry, University of New South Wales, Sydney, NSW 2052 Australia
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18
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Enhanced In Vitro Antimicrobial Activity of Polymyxin B–Coated Nanostructured Lipid Carrier Containing Dexamethasone Acetate. J Pharm Innov 2020. [DOI: 10.1007/s12247-020-09427-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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19
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Borchman D, Ramakrishnan V, Henry C, Ramasubramanian A. Differences in Meibum and Tear Lipid Composition and Conformation. Cornea 2020; 39:122-128. [PMID: 31369460 PMCID: PMC8454188 DOI: 10.1097/ico.0000000000002095] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE The compositional, structural, and functional relationships of meibum may provide insights into the loss of tear film stability. Although the conformation of meibum lipids has been studied rigorously, that of tear lipids has not. METHODS Tear lipids (TLHSCT) and meibum (MHSCT) from patients who had hematopoietic stem cell transplantation were pooled prospectively. The infrared spectra of meibum from donors with (MMGD) and without (Mn) meibomian gland dysfunction were retrospectively analyzed to measure the lipid composition and structure. The infrared CH stretching region was used to measure the relative content of CH3 and CH2 moieties in the meibum. RESULTS The 3 major findings of the current study are as follows: 1) compared with Mn, MHSCT and MMGD had 18% fewer CH3 moieties; 2) compared with MHSCT, the phase transition temperature, cooperativity, and order were approximately 20% greater for TLHSCT; and 3) compared with Mn and MMGD, MHSCT and TLHSCT contained fewer double bonds. CONCLUSIONS Tear lipids are more ordered than meibum lipids, which could have functional consequences. The human meibum peak height ratio of the CH3/CH2 bands is not a factor related to tear film stability with age or sex. The amount of CH3 moieties relative to CH2 moieties and saturation could contribute to a higher meibum lipid order associated with a younger age, meibomian gland dysfunction, and dry eye from hematopoietic stem cell transplantation. Therefore, the hydrocarbon order may be a marker of or contribute to an unstable tear film layer.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY
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20
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Jurišić Dukovski B, Juretić M, Bračko D, Randjelović D, Savić S, Crespo Moral M, Diebold Y, Filipović-Grčić J, Pepić I, Lovrić J. Functional ibuprofen-loaded cationic nanoemulsion: Development and optimization for dry eye disease treatment. Int J Pharm 2019; 576:118979. [PMID: 31870964 DOI: 10.1016/j.ijpharm.2019.118979] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/16/2019] [Accepted: 12/17/2019] [Indexed: 12/31/2022]
Abstract
Inflammation plays a key role in dry eye disease (DED) affecting millions of people worldwide. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used topically to act on the inflammatory component of DED, but their limited aqueous solubility raises formulation issues. The aim of this study was development and optimization of functional cationic nanoemulsions (NEs) for DED treatment, as a formulation approach to circumvent solubility problems, prolong drug residence at the ocular surface and stabilize the tear film. Ibuprofen was employed as the model NSAID, chitosan as the cationic agent, and lecithin as the anionic surfactant enabling chitosan incorporation. Moreover, lecithin is a mixture of phospholipids including phosphatidylcholine and phosphatidylethanolamine, two constituents of the natural tear film important for its stability. NEs were characterized in terms of droplet size, polydispersity index, zeta-potential, pH, viscosity, osmolarity, surface tension, entrapment efficiency, stability, sterilizability and in vitro release. NEs mucoadhesive properties were tested rheologically after mixing with mucin dispersion. Biocompatibility was assessed employing 3D HCE-T cell-based model and ex vivo model using porcine corneas. The results of our study pointed out the NE formulation with 0.05% (w/w) chitosan as the lead formulation with physicochemical properties adequate for ophthalmic application, mucoadhesive character and excellent biocompatibility.
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Affiliation(s)
- Bisera Jurišić Dukovski
- University of Zagreb, Faculty of Pharmacy and Biochemistry, Department of Pharmaceutical Technology, Zagreb, Croatia
| | - Marina Juretić
- R&D, PLIVA Croatia Ltd, TEVA Group Member, Zagreb, Croatia
| | - Danka Bračko
- R&D, PLIVA Croatia Ltd, TEVA Group Member, Zagreb, Croatia
| | - Danijela Randjelović
- University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Microelectronic Technologies, Belgrade, Serbia
| | - Snežana Savić
- University of Belgrade, Faculty of Pharmacy, Department of Pharmaceutical Technology and Cosmetology, Belgrade, Serbia
| | - Mario Crespo Moral
- University of Valladolid, Institute of Applied Ophthalmo-Biology (IOBA), Valladolid, Spain
| | - Yolanda Diebold
- University of Valladolid, Institute of Applied Ophthalmo-Biology (IOBA), Valladolid, Spain; Biomedical Research Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Valladolid, Spain
| | - Jelena Filipović-Grčić
- University of Zagreb, Faculty of Pharmacy and Biochemistry, Department of Pharmaceutical Technology, Zagreb, Croatia
| | - Ivan Pepić
- University of Zagreb, Faculty of Pharmacy and Biochemistry, Department of Pharmaceutical Technology, Zagreb, Croatia
| | - Jasmina Lovrić
- University of Zagreb, Faculty of Pharmacy and Biochemistry, Department of Pharmaceutical Technology, Zagreb, Croatia.
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21
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Ellipsometry of human tears. Ocul Surf 2019; 17:341-346. [PMID: 30818036 DOI: 10.1016/j.jtos.2019.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/12/2019] [Accepted: 02/20/2019] [Indexed: 12/17/2022]
Abstract
PURPOSE The outer surface layer of tears is presumably composed of lipid. The thickness of this layer is considered critical to retard evaporation. Prior thickness measurements differ widely. Advances in ellipsometry have availed more precise and accurate measurements for thin films. The range in thickness of the surface layer of tears was studied by ellipsometry to uncover the source of prior discrepancies. METHODS Tear surface layers of normal and dry eye subjects were measured by in-vitro ellipsometry. Lateral and Z resolutions of ∼1 μm and 0.1 nm, were achieved respectively. Thicknesses were derived from matrices and a Levenberg-Marquardt multivariate regression algorithm to Fresnel equations for multi-layered films. RESULTS Ellipsometric measurements of pooled and individual human tears in-vitro revealed a larger overall range (0-500 nm) of surface film thicknesses than previously reported by any one study. Each sample showed thin areas (0-2.6 nm) with interspersed thicker regions (∼200-500 nm). Repeat measurements of a single donor collected at weekly intervals showed a broad range of surface thicknesses within and between samples. Thickness measurements from a dry eye subject overlapped that of normal subjects. CONCLUSION The data show that published disparity in surface film thickness may be attributable to limitations of prior methodologies. The range and overlap of surface film thicknesses challenge less rigorous methodologies that claim to segregate normal and dry eye.
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22
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Brown CN, Green BD, Thompson RB, den Hollander AI, Lengyel I. Metabolomics and Age-Related Macular Degeneration. Metabolites 2018; 9:metabo9010004. [PMID: 30591665 PMCID: PMC6358913 DOI: 10.3390/metabo9010004] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 12/11/2022] Open
Abstract
Age-related macular degeneration (AMD) leads to irreversible visual loss, therefore, early intervention is desirable, but due to its multifactorial nature, diagnosis of early disease might be challenging. Identification of early markers for disease development and progression is key for disease diagnosis. Suitable biomarkers can potentially provide opportunities for clinical intervention at a stage of the disease when irreversible changes are yet to take place. One of the most metabolically active tissues in the human body is the retina, making the use of hypothesis-free techniques, like metabolomics, to measure molecular changes in AMD appealing. Indeed, there is increasing evidence that metabolic dysfunction has an important role in the development and progression of AMD. Therefore, metabolomics appears to be an appropriate platform to investigate disease-associated biomarkers. In this review, we explored what is known about metabolic changes in the retina, in conjunction with the emerging literature in AMD metabolomics research. Methods for metabolic biomarker identification in the eye have also been discussed, including the use of tears, vitreous, and aqueous humor, as well as imaging methods, like fluorescence lifetime imaging, that could be translated into a clinical diagnostic tool with molecular level resolution.
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Affiliation(s)
- Connor N Brown
- Wellcome-Wolfson Institute for Experimental Medicine (WWIEM), Queen's University Belfast, Belfast BT9 7BL, UK.
| | - Brian D Green
- Institute for Global Food Security (IGFS), Queen's University Belfast, Belfast BT9 6AG, UK.
| | - Richard B Thompson
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
| | - Anneke I den Hollander
- Department of Ophthalmology, Radboud University Nijmegen Medical Centre, Nijmegen 6525 EX, The Netherlands.
| | - Imre Lengyel
- Wellcome-Wolfson Institute for Experimental Medicine (WWIEM), Queen's University Belfast, Belfast BT9 7BL, UK.
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23
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Glasgow BJ, Abduragimov AR. Ligand binding complexes in lipocalins: Underestimation of the stoichiometry parameter (n). BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2018; 1866:1001-1007. [PMID: 30037780 PMCID: PMC6481938 DOI: 10.1016/j.bbapap.2018.07.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 06/15/2018] [Accepted: 07/03/2018] [Indexed: 11/18/2022]
Abstract
The stoichiometry of a ligand binding reaction to a protein is given by a parameter (n). The value of this parameter may indicate the presence of protein monomer or dimers in the binding complex. Members of the lipocalin superfamily show variation in the stoichiometry of binding to ligands. In some cases the stoichiometry parameter (n) has been variously reported for the same protein as mono- and multimerization of the complex. Prime examples include retinol binding protein, β lactoglobulin and tear lipocalin, also called lipocalin-1(LCN1). Recent work demonstrated the stoichiometric ratio for ceramide:tear lipocalin varied (range n = 0.3-0.75) by several different methods. The structure of ceramide raises the intriguing possibility of a lipocalin dimer complex with each lipocalin molecule attached to one of the two alkyl chains of ceramide. The stoichiometry of the ceramide-tear lipocalin binding complex was explored in detail using size exclusion chromatography and time resolved fluorescence anisotropy. Both methods showed consistent results that tear lipocalin remains monomeric when bound to ceramide. Delipidation experiments suggest the most likely explanation is that the low 'n' values result from prior occupancy of the binding sites by native ligands. Lipocalins such as tear lipocalin that have numerous binding partners are particularly prone to an underestimated apparent stoichiometry parameter.
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Affiliation(s)
- Ben J Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States.
| | - Adil R Abduragimov
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States
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24
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Vicario-de-la-Torre M, Caballo-González M, Vico E, Morales-Fernández L, Arriola-Villalobos P, De Las Heras B, Benítez-Del-Castillo JM, Guzmán M, Millar T, Herrero-Vanrell R, Molina-Martínez IT. Novel Nano-Liposome Formulation for Dry Eyes with Components Similar to the Preocular Tear Film. Polymers (Basel) 2018; 10:E425. [PMID: 30966460 PMCID: PMC6415276 DOI: 10.3390/polym10040425] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 04/04/2018] [Accepted: 04/06/2018] [Indexed: 11/16/2022] Open
Abstract
Dry eye is commonly treated with artificial tears; however, developing artificial tears similar to natural tears is difficult due to the complex nature of tears. We characterized and evaluated a novel artificial tear formulation with components similar to the lipid and aqueous constituents of natural tears. Nano-liposomes, composed in part of phosphatidylcholine, were dispersed in an aqueous solution of bioadhesive sodium hyaluronate. Liposome size, zeta potential, and physicochemical properties of the fresh and stored (4 °C) liposomal formulation were analyzed. In vitro tolerance was tested using human corneal and conjunctival cell lines by exposures of 15 min to 4 h. The tolerance of the liposomal formulation was evaluated in animals (rabbits). The average liposome size was 186.3 ± 7.0 nm, and the zeta potential was negative. The osmolarity of the formulation was 198.6 ± 1.7 mOsm, with a surface tension of 36.5 ± 0.4 mN/m and viscosity of 3.05 ± 0.02 mPa·s. Viability values in the human corneal and conjunctival cell lines were always >80%, even after liposomal formulation storage for 8 weeks. Discomfort and clinical signs after instillation in rabbit eyes were absent. The new formulation, based on phosphatidylcholine-liposomes dispersed in sodium hyaluronate has suitable components and characteristics, including high in vitro cell viability and good in vivo tolerance, to serve as a tear substitute.
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Affiliation(s)
- Marta Vicario-de-la-Torre
- Pharmaceutical Innovation in Ophthalmology Research Group, UCM 920415, Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, Plaza Ramón y Cajal, s/n, 28040 Madrid, Spain.
| | - María Caballo-González
- Pharmaceutical Innovation in Ophthalmology Research Group, UCM 920415, Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, Plaza Ramón y Cajal, s/n, 28040 Madrid, Spain.
| | - Eva Vico
- Ocular Surface and Inflammation, Ophthalmology Department, San Carlos Clinical Hospital, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
| | - Laura Morales-Fernández
- Ocular Surface and Inflammation, Ophthalmology Department, San Carlos Clinical Hospital, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
| | - Pedro Arriola-Villalobos
- Ocular Surface and Inflammation, Ophthalmology Department, San Carlos Clinical Hospital, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
| | - Beatriz De Las Heras
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Department of Pharmacology, Faculty of Pharmacy, Complutense University of Madrid, Plaza Ramón y Cajal, s/n, 28040 Madrid, Spain.
| | - José Manuel Benítez-Del-Castillo
- Ocular Surface and Inflammation, Ophthalmology Department, San Carlos Clinical Hospital, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
| | - Manuel Guzmán
- Department of Biomedical Sciences, Faculty of Pharmacy, University of Alcalá, Ctra Madrid-Barcelona, Km 33.6, 28801 Alcalá de Henares, Madrid, Spain.
| | - Thomas Millar
- School of Science and Health, Western Sydney University, Rydalmere Sydney, New South Wales 2116, Australia.
| | - Rocío Herrero-Vanrell
- Pharmaceutical Innovation in Ophthalmology Research Group, UCM 920415, Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, Plaza Ramón y Cajal, s/n, 28040 Madrid, Spain.
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Instituto Universitario de Farmacia Industrial (IUFI), Faculty of Pharmacy, Complutense University, 28040 Madrid, Spain.
| | - Irene T Molina-Martínez
- Pharmaceutical Innovation in Ophthalmology Research Group, UCM 920415, Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, Plaza Ramón y Cajal, s/n, 28040 Madrid, Spain.
- Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC) and the Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Calle Profesor Martín Lagos, s/n, 28040 Madrid, Spain.
- Instituto Universitario de Farmacia Industrial (IUFI), Faculty of Pharmacy, Complutense University, 28040 Madrid, Spain.
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25
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Glasgow BJ, Abduragimov AR. Interaction of ceramides and tear lipocalin. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:399-408. [PMID: 29331331 PMCID: PMC5835416 DOI: 10.1016/j.bbalip.2018.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 12/19/2017] [Accepted: 01/06/2018] [Indexed: 10/18/2022]
Abstract
The distribution of lipids in tears is critical to their function. Lipids in human tears may retard evaporation by forming a surface barrier at the air interface. Lipids complexed with the major lipid binding protein in tears, tear lipocalin, reside in the bulk (aqueous) and may have functions unrelated to the surface. Many new lipids species have been revealed through recent mass spectrometric studies. Their association with lipid binding proteins has not been studied. Squalene, (O-acyl) omega-hydroxy fatty acids (OAHFA) and ceramides are examples. Even well-known lipids such as wax and cholesteryl esters are only presumed to be unbound because extracts of protein fractions of tears were devoid of these lipids. Our purpose was to determine by direct binding assays if the aforementioned lipids can bind tear lipocalin. Lipids were screened for ability to displace DAUDA from tear lipocalin in a fluorescence displacement assay. Di- and tri-glycerides, squalene, OAHFA, wax and cholesterol esters did not displace DAUDA from tear lipocalin. However, ceramides displaced DAUDA. Apparent dissociation constants for ceramide-tear lipocalin complexes using fluorescent analogs were measured consistently in the submicromolar range with 3 methods, linear spectral summation, high speed centrifugal precipitation and standard fluorescence assays. At the relatively small concentrations in tears, all ceramides were complexed to tear lipocalin. The lack of binding of di- and tri-glycerides, squalene, OAHFA, as well as wax and cholesterol esters to tear lipocalin is consonant with residence of these lipids near the air interface.
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Affiliation(s)
- Ben J Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States.
| | - Adil R Abduragimov
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States
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26
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Abstract
Dry eye (DE) is a chronic ocular condition with high prevalence and morbidity. It has a complex pathophysiology and is multifactorial in nature. Chronic ocular surface inflammation has emerged as a key component of DE that is capable of perpetuating ocular surface damage and leading to symptoms of ocular pain, discomfort, and visual phenomena. It begins with stress to the ocular surface leading to the production of proinflammatory mediators that induce maturation of resident antigen-presenting cells which then migrate to the lymph nodes to activate CD4 T cells. The specific antigen(s) targeted by these pathogenic CD4+ T cells remains unknown. Two emerging theories include self-antigens by autoreactive CD4 T cells or harmless exogenous antigens in the setting of mucosal immunotolerance loss. These CD4 T cells migrate to the ocular surface causing additional inflammation and damage. Lifitegrast is the second topical anti-inflammatory agent to be approved by the US Food and Drug Administration for the treatment of DE and the first to show improvement in DE symptoms. Lifitegrast works by blocking the interaction between intercellular adhesion molecule-1 and lymphocyte functional associated antigen-1, which has been shown to be critical for the migration of antigen-presenting cells to the lymph nodes as well as CD4+ T cell activation and migration to the ocular surface. In four large multicenter, randomized controlled trials, lifitegrast has proven to be effective in controlling both the signs and symptoms of DE with minimal side effects. Further research should include comparative and combination studies with other anti-inflammatory therapies used for DE.
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Affiliation(s)
| | - Anat Galor
- Ophthalmology Department, Miami Veterans Administration Medical Center, Miami, FL.,Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, FL, USA
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27
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Garrigue JS, Amrane M, Faure MO, Holopainen JM, Tong L. Relevance of Lipid-Based Products in the Management of Dry Eye Disease. J Ocul Pharmacol Ther 2017; 33:647-661. [PMID: 28956698 PMCID: PMC5655476 DOI: 10.1089/jop.2017.0052] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 08/15/2017] [Indexed: 12/23/2022] Open
Abstract
Components of the ocular surface synergistically contribute to maintaining and protecting a smooth refractive layer to facilitate the optimal transmission of light. At the air-water interface, the tear film lipid layer (TFLL), a mixture of lipids and proteins, plays a key role in tear surface tension and is important for the physiological hydration of the ocular surface and for ocular homeostasis. Alterations in tear fluid rheology, differences in lipid composition, or downregulation of specific tear proteins are found in most types of ocular surface disease, including dry eye disease (DED). Artificial tears have long been a first line of treatment in DED and aim to replace or supplement tears. More recently, lipid-containing eye drops have been developed to more closely mimic the combination of aqueous and lipid layers of the TFLL. Over the last 2 decades, our understanding of the nature and importance of lipids in the tear film in health and disease has increased substantially. The aim of this article is to provide a brief overview of our current understanding of tear film properties and review the effectiveness of lipid-based products in the treatment of DED. Liposome lid sprays, emulsion eye drops, and other lipid-containing formulations are discussed.
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Affiliation(s)
| | | | | | - Juha M. Holopainen
- Helsinki Eye Lab, Ophthalmology, Helsinki University Hospital, University of Helsinki, Helsinki, Finland
| | - Louis Tong
- Singapore Eye Research Institute, Singapore
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Duke-NUS Medical School, Singapore
- Singapore National Eye Center, Singapore
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28
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Georgiev GA, Eftimov P, Yokoi N. Structure-function relationship of tear film lipid layer: A contemporary perspective. Exp Eye Res 2017; 163:17-28. [PMID: 28950936 DOI: 10.1016/j.exer.2017.03.013] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/27/2017] [Accepted: 03/31/2017] [Indexed: 01/29/2023]
Abstract
Tear film lipid layer (TFLL) stabilizes the air/tear surface of the human eye. Meibomian gland dysfunction (MGD) resulting in quantitative and qualitative modifications of TFLL major (>93%) component, the oily secretion of meibomian lipids (MGS), is the world leading cause of dry eye syndrome (DES) with up to 86% of all DES patients showing signs of MGD. Caused by intrinsic factors (aging, ocular and general diseases) and by extrinsic everyday influences like contact lens wear and extended periods in front of a computer screen, DES (resulting in TF instability, visual disturbances and chronic ocular discomfort) is the major ophthalmic public health disease of the present time affecting the quality of life of 10-30% of the human population worldwide. Therefore there is a pressing need to summarize the present knowledge, contradictions and open questions to be resolved in the field of TFLL composition/structure/functions relationship. The following major aspects are covered by the review: (i) Do we have a reliable mimic for TFLL: MGS vs contact lens lipid extracts (CLLE) vs lipid extracts from whole tears. Does TFLL truly consist of lipids only or it is important to keep in mind the TF proteins as well?; (ii) Structural properties of TFLL and of its mimics in health and disease in vitro and in vivo. How the TFLL uniformity and thickness ensures the functionality of the lipid layer (barrier to evaporation, surface properties, TF stability etc.); (iii) What are the main functions of the TFLL? In this aspect an effort is done to emphasize that there is no single main function of TFLL but instead it simultaneously fulfills plethora of functions: suppresses the evaporation (alone or probably in cooperation with other TF constituents) of the aqueous tears; stabilizes (due to its surface properties) the air/tear surface at eye opening and during the interblink interval; and even acts as a first line of defense against bacterial invasion due to its detergency action on the bacterial membranes. An effort is done to highlight how the concept on the importance of TFLL and TF viscoelasticity transpires from old and new studies and what are its clinical implications. An attempt is made to outline the future hot directions of research into the field ranging from quest for molecules that can significantly alter TFLL properties to addressing open questions on the contribution of TFLL to the overall performance of the TF.
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Affiliation(s)
- Georgi As Georgiev
- St. Kliment Ohridski University of Sofia, Department of Optics and Spectroscopy, Faculty of Physics, 5 James Bourchier Blvd., 1164 Sofia, Bulgaria.
| | - Petar Eftimov
- Department of Cytology, Histology and Embryology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia, Bulgaria
| | - Norihiko Yokoi
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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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.
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Jones L, Downie LE, Korb D, Benitez-del-Castillo JM, Dana R, Deng SX, Dong PN, Geerling G, Hida RY, Liu Y, Seo KY, Tauber J, Wakamatsu TH, Xu J, Wolffsohn JS, Craig JP. TFOS DEWS II Management and Therapy Report. Ocul Surf 2017; 15:575-628. [DOI: 10.1016/j.jtos.2017.05.006] [Citation(s) in RCA: 578] [Impact Index Per Article: 82.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 05/03/2017] [Indexed: 02/06/2023]
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Svitova TF, Lin MC. Dynamic interfacial properties of human tear-lipid films and their interactions with model-tear proteins in vitro. Adv Colloid Interface Sci 2016; 233:4-24. [PMID: 26830077 DOI: 10.1016/j.cis.2015.12.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 12/15/2015] [Accepted: 12/15/2015] [Indexed: 11/16/2022]
Abstract
This review summarizes the current state of knowledge regarding interfacial properties of very complex biological colloids, specifically, human meibum and tear lipids, and their interactions with proteins similar to the proteins found in aqueous part of human tears. Tear lipids spread as thin films over the surface of tear-film aqueous and play crucial roles in tear-film stability and overall ocular-surface health. The vast majority of papers published to date report interfacial properties of meibum-lipid monolayers spread on various aqueous sub-phases, often containing model proteins, in Langmuir trough. However, it is well established that natural human ocular tear lipids exist as multilayered films with a thickness between 30 and 100nm, that is very much disparate from 1 to 2nm thick meibum monolayers. We employed sessile-bubble tensiometry to study the dynamic interfacial and rheological properties of reconstituted multilayered human tear-lipid films. Small amounts (0.5-1μg) of human tear lipids were deposited on an air-bubble surface to produce tear-lipid films in thickness range 30-100nm corresponding to ocular lipid films. Thus, we were able to overcome major Langmuir-trough method limitations because ocular tear lipids can be safely harvested only in minute, sub-milligram quantities, insufficient for Langmuir through studies. Sessile-bubble method is demonstrated to be a versatile tool for assessing conventional synthetic surfactants adsorption/desorption dynamics at an air-aqueous solution interface. (Svitova T., Weatherbee M., Radke C.J. Dynamics of surfactant sorption at the air/water interface: continuous-flow tensiometry. J. Colloid Interf. Sci. 2003;261:1170-179). The augmented flow-sessile-bubble setup, with step-strain relaxation module for dynamic interfacial rheological properties and high-precision syringe pump to generate larger and slow interfacial area expansions-contractions, was developed and employed in our studies. We established that this method is uniquely suitable for examination of multilayered lipid-film interfacial properties. Recently it was compellingly proven that chemical composition of human tear lipids extracted from whole tears is substantially different from that of meibum lipids. To be exact, healthy human tear lipids contain 8-16% of polar lipids, similar to lung lipids, and they are mostly double-tailed phospholipids, with C16 and longer alkyl chains. Rationally, one would assume that the results obtained for meibum lipids, devoid of surface-active components such as phospholipids, and, above all, in a form of monolayers, are not pertinent or useful for elucidating behavior and stability of an averaged 60-nm thick ocular tear-lipid films in vivo. The advantage of sessile-bubble technique, specifically, using a small amount of lipids required to attain multilayered films, unlocks the prospect of evaluating and comparing the interfacial properties of human tear lipids collected from a single individual, typically 100-150μg. This is in sharp contrast with several milligrams of lipids that would be required to build equally thick films for Langmuir-trough experiments. The results of our studies provided in-depth understanding of the mechanisms responsible for properties and stability of human tear-lipid films in vivo. Here we summarize recent publications and our latest findings regarding human tear-lipid interfacial properties, their chemical composition, and their interaction with model proteins mimicking the proteins found in human tear-aqueous phase.
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Affiliation(s)
- Tatyana F Svitova
- University of California, Berkeley, School of Optometry, Clinical Research Center, United States
| | - Meng C Lin
- University of California, Berkeley, School of Optometry, Clinical Research Center, United States; University of California, Vision Science Program, United States
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Influence of Meibomian Gland Expression Methods on Human Lipid Analysis Results. Ocul Surf 2016; 14:49-55. [DOI: 10.1016/j.jtos.2015.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/30/2015] [Accepted: 10/03/2015] [Indexed: 11/17/2022]
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Surface Properties of Squalene/Meibum Films and NMR Confirmation of Squalene in Tears. Int J Mol Sci 2015; 16:21813-31. [PMID: 26370992 PMCID: PMC4613282 DOI: 10.3390/ijms160921813] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 08/28/2015] [Accepted: 08/31/2015] [Indexed: 12/16/2022] Open
Abstract
Squalene (SQ) possesses a wide range of pharmacological activities (antioxidant, drug carrier, detoxifier, hydrating, emollient) that can be of benefit to the ocular surface. It can come in contact with human meibum (hMGS; the most abundant component of the tear film lipid layer) as an endogenous tear lipid or from exogenous sources as eyelid sebum or pharmaceuticals. The aims of this study were to determine (i) if SQ is in tear lipids and (ii) its influence on the surface properties of hMGS films. Heteronuclear single quantum correlation NMR confirmed 7 mol % SQ in Schirmer’s strips extracts. The properties of SQ/hMGS pseudo-binary films at the air/water interface were studied with Langmuir surface balance, stress-relaxation dilatational rheology and Brewster angle microscopy. SQ does not possess surfactant properties. When mixed with hMGS squalene (i) localized over the layers’ thinner regions and (ii) did not affect the film pressure at high compression. Therefore, tear SQ is unlikely to instigate dry eye, and SQ can be used as a safe and “inert” ingredient in formulations to protect against dry eye. The layering of SQ over the thinner film regions in addition to its pharmacological properties could contribute to the protection of the ocular surface.
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Controversies Regarding the Role of Polar Lipids in Human and Animal Tear Film Lipid Layer. Ocul Surf 2015; 13:176-8. [DOI: 10.1016/j.jtos.2015.04.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 04/24/2015] [Accepted: 04/24/2015] [Indexed: 11/20/2022]
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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.
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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.
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Abstract
PURPOSE To determine whether tear collection by flushing the ocular surface with saline (flush tears) or collection by stimulation (reflex tears) can be used as an alternative to basal tear collection for the identification and quantification of lipids in the tear film. METHODS Tear samples were collected from 10 participants with no history of ocular surface disease or contact lens wear. Up to 10 μl of basal, reflex, and flush tear samples were collected from each eye using a microcapillary tube on three occasions with the order of methods randomized and allowing at least 24 hours between each collection method. Lipids were quantified from each tear sample using nano-electrospray ionization tandem mass spectrometry. RESULTS Total lipids significantly differed in their concentration (pmol/μl) and mole % with each collection technique. Cholesterol esters [mean % (SE)] formed the major component of the total lipidome in basal [54.8% (3.1)], reflex [35.7% (6.4)], and flush [33.0% (3.1)] tear samples. However, the mole % of each lipid class substantially varied with each tear collection method. Nonpolar lipids, including cholesterol, wax esters, and triacylglycerols, dominated the tear lipidome in basal [92.8% (1.9)], reflex [71.8% (7.9)], and flush [83.6% (3.8)] tear samples. However, the mole % of phospholipids in reflex [27.5% (8.1)] and flush [15.8% (3.8)] tear samples was higher (p = 0.005) than that in basal tears [5.4% (2.0)]. CONCLUSIONS Flush or reflex tears did not have similar lipid profiles in either concentration or in mole % to basal tears. It is recommended that basal tears are used for tear lipid analysis as the reflex or flush tears contain very low levels of most lipid components.
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Pieragostino D, D'Alessandro M, di Ioia M, Di Ilio C, Sacchetta P, Del Boccio P. Unraveling the molecular repertoire of tears as a source of biomarkers: beyond ocular diseases. Proteomics Clin Appl 2015; 9:169-86. [PMID: 25488355 DOI: 10.1002/prca.201400084] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 10/23/2014] [Accepted: 11/24/2014] [Indexed: 01/06/2023]
Abstract
Proteomics and metabolomics investigations of body fluids present several challenges for biomarker discovery of several diseases. The search for biomarkers is actually conducted in different body fluids, even if the ideal biomarker can be found in an easily accessible biological fluid, because, if validated, the biomarker could be sought in the healthy population. In this regard, tears could be considered an optimum material obtained by noninvasive procedures. In the past years, the scientific community has become more interested in the study of tears for the research of new biomarkers not only for ocular diseases. In this review, we provide a discussion on the current state of biomarkers research in tears and their relevance for clinical practice, and report the main results of clinical proteomics studies on systemic and eye diseases. We summarize the main methods for tear samples analyses and report recent advances in "omics" platforms for tears investigations. Moreover, we want to take stock of the emerging field of metabolomics and lipidomics as a new and integrated approach to study protein-metabolites interplay for biomarkers research, where tears represent a still unexplored and attractive field.
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Affiliation(s)
- Damiana Pieragostino
- Department of Experimental and Clinical Sciences, University "G. d'Annunzio" of Chieti- Pescara, Chieti, Italy; Analytical Biochemistry and Proteomics Unit, Research Centre on Aging (Ce.S.I.), University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
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Pucker AD, Haworth KM. The Presence and Significance of Polar Meibum and Tear Lipids. Ocul Surf 2015; 13:26-42. [DOI: 10.1016/j.jtos.2014.06.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 05/27/2014] [Accepted: 06/01/2014] [Indexed: 01/13/2023]
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Abstract
As investigations into the innate immune responses that lead to allergic sensitization become better defined, there is a need to determine how allergens could interact with pattern recognition receptors that bind non-proteinaceous moieties. Many important allergens are not covalently bound to lipid or carbohydrate, but have structures belonging to lipid, glycan and glycolipid-binding families. These include ML-domain proteins, lipopolysaccharide-binding/cell permeability-increasing proteins, von Ebner gland lipocalins, salivary lipocalins/major urinary proteins, plant pathogenesis-related proteins PR-5 and -10, uteroglobins, non-specific lipid transfer proteins, large lipid transfer proteins and proteins with chitin and other carbohydrate-binding modules. The binding expected is overviewed with regard to importance of the allergens and their ability to elicit responses proposed from experimental models. The evidence compiled showing that allergens from the same source sensitize for different types of adaptive immune responses supports the concept that individual allergens within these sources have their own distinctive interactions with innate immunity.
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Racial variations in interfacial behavior of lipids extracted from worn soft contact lenses. Optom Vis Sci 2014; 90:1361-9. [PMID: 24270592 DOI: 10.1097/opx.0000000000000098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To explore interfacial behaviors and effects of temperature and dilatation on dynamic properties of multilayered human tear lipids extracted from silicone hydrogel (SiH) lenses worn by asymptomatic Asian and white subjects. METHODS Interfacial properties of lipids extracted from Focus N&D lenses worn by 14 subjects continuously for 1 month were studied. The lipids were deposited on an air bubble immersed in a model tear electrolyte (MTE) solution to form 100 ± 20-nm-thick films. Surface pressure was recorded during slow expansion/contraction cycles to evaluate compressibility and hysteresis of lipid films. Films were also subjected to fast step-strain dilatations at temperatures of 22 to 45°C for their viscoelastic property assessment. RESULTS Isocycles for Asian and white lipids were similar at low surface pressures but had distinctly different compressibility and hysteresis at dynamic pressures exceeding 30 mN/m. Rheological parameters of reconstituted lipids were also dissimilar between Asian and white. The elastic modulus E∞ for white lipids was 1.5 times higher than that for Asian lipids, whereas relaxation time (t) was on average 1.3 times higher for Asian. No significant changes were observed in rheological properties of both Asian and white lipids when temperature increased from 22.0 to 36.5°C. However, for white lipids, E∞ reduced considerably at temperatures higher than 42.0°C, whereas t remained unchanged. For Asian lipids, both E∞ and t started to decline as temperature increased to 38°C and higher. CONCLUSIONS Higher elastic modulus of white lipids and elasticity threshold at certain deformations indicate stronger structure and intermolecular interactions as compared with more viscous Asian lipids. The differences in interfacial behaviors between Asian and white lipids may be associated with the differences in their chemical compositions.
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Lam SM, Tong L, Duan X, Petznick A, Wenk MR, Shui G. Extensive characterization of human tear fluid collected using different techniques unravels the presence of novel lipid amphiphiles. J Lipid Res 2013; 55:289-98. [PMID: 24287120 DOI: 10.1194/jlr.m044826] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The tear film covers the anterior eye and the precise balance of its various constituting components is critical for maintaining ocular health. The composition of the tear film amphiphilic lipid sublayer, in particular, has largely remained a matter of contention due to the limiting concentrations of these lipid amphiphiles in tears that render their detection and accurate quantitation tedious. Using systematic and sensitive lipidomic approaches, we validated different tear collection techniques and report the most comprehensive human tear lipidome to date; comprising more than 600 lipid species from 17 major lipid classes. Our study confers novel insights to the compositional details of the existent tear film model, in particular the disputable amphiphilic lipid sublayer constituents, by demonstrating the presence of cholesteryl sulfate, O-acyl-ω-hydroxyfatty acids, and various sphingolipids and phospholipids in tears. The discovery and quantitation of the relative abundance of various tear lipid amphiphiles reported herein are expected to have a profound impact on the current understanding of the existent human tear film model.
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Affiliation(s)
- Sin Man Lam
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
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42
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Gasymov OK, Abduragimov AR, Glasgow BJ. Effect of short- and long-range interactions on trp rotamer populations determined by site-directed tryptophan fluorescence of tear lipocalin. PLoS One 2013; 8:e78754. [PMID: 24205305 PMCID: PMC3810256 DOI: 10.1371/journal.pone.0078754] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/20/2013] [Indexed: 11/25/2022] Open
Abstract
In the lipocalin family, the conserved interaction between the main α-helix and the β-strand H is an ideal model to study protein side chain dynamics. Site-directed tryptophan fluorescence (SDTF) has successfully elucidated tryptophan rotamers at positions along the main alpha helical segment of tear lipocalin (TL). The rotamers assigned by fluorescent lifetimes of Trp residues corroborate the restriction expected based on secondary structure. Steric conflict constrains Trp residues to two (t, g−) of three possible χ1 (t, g−, g+) canonical rotamers. In this study, investigation focused on the interplay between rotamers for a single amino acid position, Trp 130 on the α-helix and amino acids Val 113 and Leu 115 on the H strand, i.e. long range interactions. Trp130 was substituted for Phe by point mutation (F130W). Mutations at positions 113 and 115 with combinations of Gly, Ala, Phe residues alter the rotamer distribution of Trp130. Mutations, which do not distort local structure, retain two rotamers (two lifetimes) populated in varying proportions. Replacement of either long range partner with a small amino acid, V113A or L115A, eliminates the dominance of the t rotamer. However, a mutation that distorts local structure around Trp130 adds a third fluorescence lifetime component. The results indicate that the energetics of long-range interactions with Trp 130 further tune rotamer populations. Diminished interactions, evident in W130G113A115, result in about a 22% increase of α-helix content. The data support a hierarchic model of protein folding. Initially the secondary structure is formed by short-range interactions. TL has non-native α-helix intermediates at this stage. Then, the long-range interactions produce the native fold, in which TL shows α-helix to β-sheet transitions. The SDTF method is a valuable tool to assess long-range interaction energies through rotamer distribution as well as the characterization of low-populated rotameric states of functionally important excited protein states.
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Affiliation(s)
- Oktay K. Gasymov
- Departments of Pathology and Laboratory Medicine and Ophthalmology and Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (OG); (BG)
| | - Adil R. Abduragimov
- Departments of Pathology and Laboratory Medicine and Ophthalmology and Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Ben J. Glasgow
- Departments of Pathology and Laboratory Medicine and Ophthalmology and Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (OG); (BG)
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Schuett BS, Millar TJ. An investigation of the likely role of (O-acyl) ω-hydroxy fatty acids in meibomian lipid films using (O-oleyl) ω-hydroxy palmitic acid as a model. Exp Eye Res 2013; 115:57-64. [PMID: 23792170 DOI: 10.1016/j.exer.2013.06.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/23/2013] [Accepted: 06/10/2013] [Indexed: 10/26/2022]
Abstract
(O-acyl) ω-hydroxy fatty acids (OAHFAs) are a recently found group of polar lipids in meibum. Since these lipids can potentially serve as a surfactant in the tear film lipid layer, the surface properties of a molecule of this lipid class was investigated and compared with a structurally related wax ester and a fatty acid. (O-oleyl) ω-hydroxy palmitic acid was synthesized and used as the model OAHFA. It was spread either alone or mixed with human meibum on an artificial tear buffer in a Langmuir trough, and pressure-area isocycle profiles were recorded at different temperatures and compared with those of palmityl oleate and oleic acid. These measurements were accompanied by fluorescence microscopy of meibum mixed films during pressure-area isocycles. The pressure area curves indicated that pure films of the model OAHFA are as surface active as oleic acid films, cover a much larger surface area than either palmityl oleate or oleic acid and show a distinct biphasic pressure-area isocycle profile. The OAHFAs appeared to remain on the aqueous surface and show only a minor re-arrangement into multi-layered structures during repetitive pressure area isocycles. All these properties can be explained by OAHFAs binding weakly to the aqueous surface via an ester group and strongly via a carboxyl group. By contrast, the pressure area profiles of palmityl oleate films indicate that they form multi-layers and oleic acid presumably forms micelles and desorbs into the subphase. When mixed with meibum, similar features as for pure films were observed. In addition, meibum-OAHFA films appeared very homogeneous; a feature not seen with other mixtures. In conclusion these data support the notion that the tested OAHFA is a very potent surfactant which is important in spreading and stabilising meibomian lipid films.
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Affiliation(s)
- Burkhardt S Schuett
- School of Science and Health, University of Western Sydney, Penrith, NSW 2751, Australia
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Abstract
Human meibomian gland secretions (MGS, or meibum) are formed from a complex mixture of lipids of different classes such as wax esters, cholesteryl esters, (O-acyl)-ω-hydroxy fatty acids (OAHFA) and their esters, acylglycerols, diacylated diols, free fatty acids, cholesterol, and a smaller amount of other polar and nonpolar lipids, whose chemical nature and the very presence in MGS have been a matter of intense debates. The purpose of this review is to discuss recent results that were obtained using different experimental techniques, estimate limitations of their usability, and discuss their biochemical, biophysical, and physiological implications. To create a lipid map of MGS and tears, the results obtained in the author's laboratory were integrated with available information on chemical composition of MGS and tears. The most informative approaches that are available today to researchers, such as HPLC-MS, GC-MS, and proton NMR, are discussed in details. A map of the meibomian lipidome (as it is seen in reverse phase liquid chromatography/mass spectrometry experiments) is presented. Directions of future efforts in the area are outlined.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology and the Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA.
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45
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Murphy SA, Nicolaou A. Lipidomics applications in health, disease and nutrition research. Mol Nutr Food Res 2013; 57:1336-46. [PMID: 23729171 DOI: 10.1002/mnfr.201200863] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 02/21/2013] [Accepted: 03/14/2013] [Indexed: 01/14/2023]
Abstract
The structural and functional diversity of lipids accounts for their involvement into a wide range of homeostatic processes and disease states, including lifestyle-related diseases as well as genetic conditions. Challenges presented by this diversity have been addressed to a great extent by the development of lipidomics, a platform that makes possible the detailed profiling and characterisation of lipid species present in any cell, organelle, tissue or body fluid, and allows for a wider appreciation of the biological role of lipid networks. Progress in the field of lipidomics has been greatly facilitated by recent advances in MS and includes a range of analytical platforms supporting applications spanning from qualitative and quantitative assessment of multiple species to lipid imaging. Here we review these MS techniques currently in routine use in lipidomics, alongside with new ones that have started making an impact in the field. Recent applications in health, disease and nutrition-related questions will also be discussed with a view to convey the importance of lipidomics contributions to biosciences and food technology.
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Affiliation(s)
- Sharon A Murphy
- School of Pharmacy and Centre for Skin Sciences, School of Life Sciences, University of Bradford, Bradford, UK
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Yeh PT, Casey R, Glasgow BJ. A novel fluorescent lipid probe for dry eye: retrieval by tear lipocalin in humans. Invest Ophthalmol Vis Sci 2013; 54:1398-410. [PMID: 23361507 DOI: 10.1167/iovs.12-10817] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE A fluorescent probe was used to identify mucin-depleted areas on the ocular surface and to test the hypothesis that tear lipocalin retrieves lipids from the eyes of normal and dry eye subjects. METHODS Fluorescein-labeled octadecyl ester, FODE, was characterized by mass spectrometry and absorbance spectrophotometry. The use of FODE to define mucin defects was studied with impression membranes under conditions that selectively deplete mucin. The kinetics of FODE removal from the ocular surface were analyzed by sampling tears from control and dry eye patients at various times. The tear protein-FODE complexes were isolated by gel filtration and ion exchange chromatographies, monitored with absorption and fluorescent spectroscopies, and analyzed by gel electrophoresis. Immunoprecipitation verified FODE complexed to tear lipocalin in tears. RESULTS FODE exhibits an isosbestic point at 473 nm, pKa of 7.5, and red shift relative to fluorescein. The low solubility of FODE in buffer is enhanced with 1% Tween 80 and ethanol. FODE adheres to the ocular surface of dry eye patients. FODE produces visible staining at the contact sites of membranes, which correlates with removal of mucin. Despite the fact that tear lipocalin is reduced in dry eye patients, FODE removal follows similar rapid exponential decay functions for all subjects. FODE is bound to tear lipocalin in tears. CONCLUSIONS Tear lipocalin retrieves lipid rapidly from the human ocular surface in mild to moderate dry eye disease and controls. With improvements in solubility, FODE may have potential as a fluorescent probe to identify mucin-depleted areas.
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Affiliation(s)
- Po-Ting Yeh
- Departments of Ophthalmology and Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California-Los Angeles, Jules Stein Eye Institute, Los Angeles, California 90095, USA
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Gasymov OK, Abduragimov AR, Glasgow BJ. Tryptophan rotamer distribution revealed for the α-helix in tear lipocalin by site-directed tryptophan fluorescence. J Phys Chem B 2012; 116:13381-8. [PMID: 23088798 DOI: 10.1021/jp309318r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rotamer libraries are a valuable tool for protein structure determination, modeling, and design. Site-directed tryptophan fluorescence (SDTF) was used in combination with the rotamer model for the fluorescence intensity decays to solve α-helical conformations of proteins in solution. Single Trp mutations located in an α-helical segment of human tear lipocalin were explored for structure assignment. Along with fluorescence λ(max) values, the rotamer model assignment of fluorescence lifetimes fits the backbone conformation. Typically, Trp fluorescence in proteins shows three lifetimes. However, for the α-helix, two lifetimes assigned to t and g(-) rotamers were satisfactory to describe Trp fluorescence intensity decays. The g(+) rotamer is not feasible in the α-helix due to steric restriction. Trp rotamer distributions obtained by fluorescence were compared with the rotamer library derived from X-ray crystallography data of proteins. The Trp rotamer distributions vary for solvent exposed and buried (tertiary interaction) sites. A new strategy using the rotamer distribution with SDTF (RD-SDTF) removes the limitation of regular SDTF and other labeling techniques, in which site-specific differences, e.g., accessibility, are presumed. The RD-SDTF technique does not rely on environmental differences of side chains and is able to detect α-helical structure where all side chains are exposed to solvent. Potentially, this technique is applicable to various proteins including membrane proteins, which are rich in α-helix motif.
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Affiliation(s)
- Oktay K Gasymov
- Department of Pathology and Jules Stein Eye Institute, University California at Los Angeles, Los Angeles, California 90095, USA.
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Butovich IA, Lu H, McMahon A, Eule JC. Toward an animal model of the human tear film: biochemical comparison of the mouse, canine, rabbit, and human meibomian lipidomes. Invest Ophthalmol Vis Sci 2012; 53:6881-96. [PMID: 22918629 DOI: 10.1167/iovs.12-10516] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Secretions that are produced by meibomian glands (also known as meibum) are a major source of lipids for the ocular surface of humans and animals alike. Many animal species have been evaluated for their meibomian lipidomes. However, there have been a very small number of studies in which the animals were compared with humans side by side. Therefore, the purpose of this study was to compare meibum collected from humans and three typical laboratory animals, canines, mice, and rabbits, for their meibomian lipid composition in order to determine which animal species most resembles humans. METHODS High pressure liquid chromatography (HPLC) and gas-liquid chromatography (GLC) in combination with mass spectrometry were used to evaluate lipidomes of all tested species. RESULTS Among three tested animal species, mice were found to be the closest match to humans in terms of their meibomian lipidomes, while canines were the second closest species. The lipids of these three species were close to each other structurally and, for most lipid classes, quantitatively. The rabbit meibomian lipidome, on the other hand, was vastly different from lipidomes of all other tested species. Interestingly, a previously described class of lipids, acylated omega-hydroxy fatty acids (OAHFA), was found to be present in every tested species as the major amphiphilic component of meibum. CONCLUSIONS Our side by side comparison of the rabbit and the human meibum demonstrated their vast differences. Thus, the rabbit seems to be a poor animal model of the human tear film, at least when studying its biochemistry and biophysics.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Gasymov OK, Abduragimov AR, Glasgow BJ. Cation-π interactions in lipocalins: structural and functional implications. Biochemistry 2012; 51:2991-3002. [PMID: 22439821 DOI: 10.1021/bi3002902] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cation-π interaction impacts protein folding, structural stability, specificity, and molecular recognition. Cation-π interactions have been overlooked in the lipocalin family. To fill this gap, these interactions were analyzed in the 113 crystal and solution structures from the lipocalin family. The cation-π interactions link previously identified structurally conserved regions and reveal new motifs, which are beyond the reach of a sequence alignment algorithm. Functional and structural significance of the interactions were tested experimentally in human tear lipocalin (TL). TL, a prominent and promiscuous lipocalin, has a key role in lipid binding at the ocular surface. Ligand binding modulation through the loop AB at the "open" end of the barrel has been erroneously attributed solely to electrostatic interactions. Data revealed that the interloop cation-π interaction in the pair Phe28-Lys108 contributes significantly to stabilize the holo-conformation of the loop AB. Numerous energetically significant and conserved cation-π interactions were uncovered in TL and throughout the lipocalin family. Cation-π interactions, such as the highly conserved Trp17-Arg118 pair in TL, were educed in low temperature experiments of mutants with Trp to Tyr substitutions.
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Affiliation(s)
- Oktay K Gasymov
- Department of Pathology and Jules Stein Eye Institute, University California at Los Angeles, California 90095, USA.
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