1
|
Nagar S, Ajouz L, Nichols KK, Kumar S, Zhao C, Naidoo KK, Robinson MR, Borchman D. Relationship Between Human Meibum Lipid Composition and the Severity of Meibomian Gland Dysfunction: A Spectroscopic Analysis. Invest Ophthalmol Vis Sci 2023; 64:22. [PMID: 37466951 PMCID: PMC10362926 DOI: 10.1167/iovs.64.10.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Abstract
Purpose Information on the relationship between meibum lipid composition and severity of meibomian gland dysfunction (MGD) is limited. The purpose of this study was to analyze the molecular components of meibum collected from individuals with no MGD, mild-to-moderate MGD, and severe MGD. Methods Adults with and without MGD were enrolled in a prospective, multicenter, exploratory clinical trial (ClinicalTrials.gov Identifier: NCT01979887). Molar ratios of cholesteryl ester to wax ester (RCE/WE) and aldehyde to wax ester (Rald/WE) in meibum samples were measured with 1H-NMR spectroscopy. Results were evaluated for participants grouped by MGD disease status and severity (non-MGD, mild-to-moderate MGD, and severe MGD), as defined by maximum meibum quality scores, Schirmer test results, and Subject Ocular Symptom Questionnaire responses. Results Sixty-nine meibum samples from 69 individuals were included in the analysis: 24 non-MGD, 24 mild-to-moderate MGD, and 21 severe MGD. Mean RCE/WE was 0.29 in non-MGD, 0.14 in mild-to-moderate MGD (P = 0.038 vs. non-MGD, 51% lower), and 0.07 in severe MGD (P = 0.16 vs. mild-to-moderate MGD, 52% lower; P = 0.002 vs. non-MGD, 76% lower). Mean Rald/WE was 0.00022 in non-MGD, 0.00083 in mild-to-moderate MGD (P = 0.07 vs. non-MGD, 277% higher), and 0.0024 in severe MGD (P = 0.003 vs. mild-to-moderate MGD, 190% higher; P < 0.001 vs. non-MGD, 992% higher). Conclusions RCE/WE was lowest and Rald/WE was highest in the severe MGD cohort, suggesting that these meibum constituent molar ratios may result from the pathophysiology associated with MGD and can impact ocular surface lipid and tear film homeostasis. These findings may potentially help identify targets for MGD treatment.
Collapse
Affiliation(s)
- Saumya Nagar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Layla Ajouz
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kelly K Nichols
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Sandeep Kumar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Cathy Zhao
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kugen K Naidoo
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
| | | | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
| |
Collapse
|
2
|
Agarwal P, Rupenthal ID. Non-aqueous formulations in topical ocular drug delivery - a paradigm shift? Adv Drug Deliv Rev 2023; 198:114867. [PMID: 37178927 DOI: 10.1016/j.addr.2023.114867] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 04/03/2023] [Accepted: 05/07/2023] [Indexed: 05/15/2023]
Abstract
Topical eyedrop application is the preferred route for drug delivery to anterior segment tissues; however, the challenge of overcoming the eye's anatomical and physiological barriers while minimising tissue toxicity has restricted developments in this field. Aqueous vehicles have traditionally been used, which typically require several additives and preservatives to achieve physiologically compatible and sterile eyedrops, elevating their toxicity potential. Non-aqueous vehicles have been suggested as efficient alternatives for topical drug delivery as they can address many of the limitations associated with conventional aqueous eyedrops. However, despite their obvious advantages, non-aqueous eyedrops remain poorly researched and few non-aqueous formulations are currently available in the market. This review challenges the conventional hypothesis that aqueous solubility is a prerequisite to ocular drug absorption and establishes a rationale for using non-aqueous vehicles for ocular drug delivery. Recent advances in the field have been detailed and future research prospects have been explored, pointing towards a paradigm shift in eyedrop formulation in the near future.
Collapse
Affiliation(s)
- Priyanka Agarwal
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, Auckland 1142, New Zealand.
| | - Ilva D Rupenthal
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, Auckland 1142, New Zealand
| |
Collapse
|
3
|
Ewurum A, Veligandla SR, Swindle JS, Clark JD, Borchman D. A spectroscopic approach to measuring meibum lipid composition and conformation in donors with Sjӧgren's syndrome. Exp Eye Res 2021; 210:108713. [PMID: 34363797 PMCID: PMC8429180 DOI: 10.1016/j.exer.2021.108713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 06/22/2021] [Accepted: 07/29/2021] [Indexed: 01/15/2023]
Abstract
Patients with Sjӧgren's syndrome (SS) have dry eye associated with meibomian gland dysfunction (MGD). The meibum from donors with dry eye due to MGD but without SS (MMGD) presents with lower levels of cholesteryl ester, less straight chains, and more ordered hydrocarbon chains compared with meibum from donors without MGD (Mn). The aim of the current study was to compare the composition and hydrocarbon chain conformation of meibum from donors with Sjögren's syndrome (Mss) to Mn and MMGD. Meibum was expressed from patients with SS using an ILUX instrument (Alcon Inc., Fort Worth TX). All of the nine meibum donors with SS were female. Meibum composition was characterized using 1H-NMR and meibum hydrocarbon chain conformation was measured using fourier transform infrared spectroscopy. Meibum from every donor with SS measured contained a significantly (P < 0.01) higher cholesteryl ester/wax ester ratio and more straight chains compared with donors without SS or dry eye. None of the nine phase transitional parameters were significantly different, P > 0.05, for Mss compared with Mn. Nor was the CH3/CH2 band height ratio used to estimate the number of hydrocarbon CH3 and CH2 moieties different, P = 0.22, for Mss compared with Mn. In conclusion, the compositional differences between Mss compared with Mn did not result in differences in any of the nine meibum lipid phase transitional parameters measured. The compositional differences observed between Mss and Mn could be markers for or contribute to SS as the differences could lead to tear film lipid packing differences other than conformational differences.
Collapse
Affiliation(s)
- Anthony Ewurum
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA
| | - Sravya R Veligandla
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA
| | - Jordan S Swindle
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA
| | - Jeremy D Clark
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA.
| |
Collapse
|
4
|
Ewurum A, Ankem A, Georgiev G, Borchman D. A spectroscopic study of the composition and conformation of cholesteryl and wax esters purified from meibum. Chem Phys Lipids 2021; 238:105088. [PMID: 33965419 DOI: 10.1016/j.chemphyslip.2021.105088] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/20/2021] [Accepted: 05/02/2021] [Indexed: 10/21/2022]
Abstract
Elucidating wax ester (WE) and cholesteryl ester (CE) compositional, structural and functional relationships is key to our understanding of how these lipids are involved in natural and pathological processes. Little is known about how CE and WE interact with one another. The focus of the present study is to bridge this gap of knowledge. CE and WE were collected from human meibum as a source of esters with complex hydrocarbon chains. MgO column chromatography was used to separate WE and CE. The esters were characterized using 1H-NMR and Fourier transform infrared spectroscopy. The complexity of the hydrocarbon chains of native WE and CE influenced how changes in the ratio of WE and CE ester influenced some lipid phase transitional parameters but not others. Changes in CE content of WE/CE mixtures undoubtedly modifies the hydrocarbon chain conformation and packing of the mixture. The nature of the change depends on the conformation of the WE and CE. Differences in the complexity of the hydrocarbon chains are likely not to be a major influence on alterations in the order or phase transition temperature when more ordered WE is added to less ordered CE.
Collapse
Affiliation(s)
- Anthony Ewurum
- Department of Chemistry, University of Louisville, Louisville, KY, USA
| | - Akhila Ankem
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Georgi Georgiev
- iBB - Institute for Bioengineering and Biosciences, Interdisciplinary Complex, IST, University of Lisbon, 1649-004, Lisbon, Portugal
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA.
| |
Collapse
|
5
|
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.
Collapse
Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202.
| |
Collapse
|
6
|
Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation. Biochem Biophys Rep 2020; 23:100786. [PMID: 32715105 PMCID: PMC7374597 DOI: 10.1016/j.bbrep.2020.100786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 12/16/2022] Open
Abstract
Purpose Meibum from donors who have had hematological stem cell transplantations (MHSCT) are susceptible to severe dry eye symptoms and exhibit very high lipid order (stiffness) compared with meibum from donors without dry eye (Mn). Since lipid order could have functional consequences, we compared the rheology and composition of Mn and MHSCT to measure meibum compositional, structural and functional relationships. Methods The rheology and composition was measured using Langmuir trough and 1H NMR spectroscopy, respectively. Results MHSCT and Mn was studied from 16 to 43 donors, respectively, using NMR spectroscopy. MHSCT contained significantly 16% more straight chain and 24% less iso-chain hydrocarbons compared with Mn. The cholesteryl ester to wax ester molar ratio, and hydrocarbon chain unsaturation were not significantly different, for MHSCT compared with Mn. Surface pressure-area isotherms of meibum from 30 donors without dry-eye were grouped into 4 pools (PC) and meibum from 32 donors with dry eye who had hematopoietic stem cell transplantation (PT) were grouped into 3 pools. Above 15 years of age the Пmax and (Cs−1)max increased with age for both the PC and the PT cohorts. (Cs−1)max values were higher for PT samples compared with age matched PC samples, indicating they had higher elasticity and stiffness. A more ordered lipid could contribute to the formation of a discontinuous patchy tear film lipid layer, which in turn results in deteriorated spreading, and decreased surface elasticity. Conclusions The composition and rheology of meibum from donors with dry eye and who have had HSCT support the idea from other studies that more ordered meibum may contribute to or be a marker of dry eye. More straight chain and less iso-chain hydrocarbons could contribute to HSCT dry eye. Meibum elasticity and stiffness increased with age. Meibum elasticity and stiffness increased with HSCT dry eye. Differences could contribute to a discontinuous patchy tear film lipid layer. Differences could result in deteriorated spreading, and decreased surface elasticity.
Collapse
|
7
|
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.
Collapse
Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY
| | | | | | | |
Collapse
|
8
|
Abstract
PURPOSE Meibum is considered to be a key component of tears that serve to protect the eye, and conformational changes in meibum have not been studied extensively within the population of patients who had hematopoietic stem cell transplantation (HSCT). The aim of this study was to determine possible lipid conformational changes in the meibum of patients who had HSCT. METHODS Participants who had HSCT were randomly sampled for this prospective comparative study. Control participants did not have dry eye or had not undergone allogeneic or autologous stem cell transplantation. Fourier-transform infrared spectroscopy was used to measure meibum phase transition. RESULTS Meibum was collected from both eyes of 36 donors without dry eye (Mc) and from 22 patients who had undergone HSCT (MHSCT). There were no significant differences between the phase transition parameters based on gender or race. The following were the significant differences (P < 0.0001) between the parameters for Mc compared with MHSCT : lipid order (% trans) at 33.4°C increased from 40 (1) to 54 (2), cooperativity decreased from 7.9 (0.4) to 5.4 (0.3), the phase transition temperature (C) increased from 30.3 (0.4) to 34.2 (0.9), and the magnitude of the phase transition (cm) increased from 4.0 (0.1) to 4.7 (0.5) (standard error of the mean). CONCLUSIONS Conformational and thermodynamic differences were observed between Mc and MHSCT. The changes observed in the lipid conformation of meibum from patients receiving HSCTs suggest that meibum composition changes after stem cell transplantation, and clinicians should consider treating the meibomian glands to improve the ocular surface.
Collapse
|
9
|
Iglesias MJ, Soengas R, Probert I, Guilloud E, Gourvil P, Mehiri M, López Y, Cepas V, Gutiérrez-Del-Río I, Redondo-Blanco S, Villar CJ, Lombó F, Soto S, Ortiz FL. NMR characterization and evaluation of antibacterial and antiobiofilm activity of organic extracts from stationary phase batch cultures of five marine microalgae (Dunaliella sp., D. salina, Chaetoceros calcitrans, C. gracilis and Tisochrysis lutea). PHYTOCHEMISTRY 2019; 164:192-205. [PMID: 31174083 DOI: 10.1016/j.phytochem.2019.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 04/11/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
The chemical composition of five marine microalgae (Dunaliella sp., Dunaliella salina, Chaetoceros calcitrans, Chaetoceros gracilis and Tisochrysis lutea) was investigated through nuclear magnetic resonance (NMR) spectroscopic study of the soluble material obtained by sequential extraction with hexane, ethyl acetate (AcOEt) and methanol of biomass from stationary phase cultures. Hexane extracted the major lipids present in the microalgae during the stationary phase of growth, which correspond to storage lipids. Triacylglycerols (TGs) were the only storage lipids produced by Dunaliella and Chaetoceros. In contrast, T. lutea predominantly stored polyunsaturated long-chain alkenones, with sterols also detected as minor components of the hexane extract. The molecular structure of brassicasterol was determined in T. lutea and the presence of squalene in this sample was also unequivocally detected. Monogalactosyldiacylglycerols (MGDGs) and pigments were concentrated in the AcOEt extracts. C. calcitrans and D. salina constituted an exception due to the high amount of TGs and glycerol produced, respectively, by these two strains. Chlorophylls a and b and β-carotene were the major pigments synthesized by Dunaliella and chlorophyll a and fucoxanthin were the only pigments detected in Chaetoceros and T. lutea. Information concerning the acyl chains present in TGs and MGDGs as well as the positional distribution of acyl chains on the glycerol moiety was obtained by NMR analysis of hexane and AcOEt extracts, with results consistent with those expected for the genera studied. Fatty acid composition of TGs in the two Dunaliella strains was different, with polyunsaturated acyl chains almost absent in the storage lipids produced by D. salina. Except in C. calcitrans, the polar nature of soluble compounds was inferred through the relative extraction yield using methanol as the extraction solvent. Glycerol was the major component of this fraction for the Dunaliella strains. In T. lutea 1,4/2,5-cyclohexanetetrol (CHT) and dimethylsulfoniopropionate (DMSP) preponderated. CHT was also the major polyol present in the Chaetoceros strains in which DMSP was not detected, but prominent signals of 2,3-dihydroxypropane-1-sulfonate (DHSP) were observed in the 1H NMR spectra of methanolic extracts. The presence of DHSP confirms the production of this metabolite by diatoms. In addition, several other minor compounds (digalactosyldiacyglycerols (DGDGs), sulphoquinovosyldiacylglycerols (SQDGs), amino acids, carbohydrates, scyllo-inositol, mannitol, lactic acid and homarine) were also identified in the methanolic extracts. The antibacterial and antibiofilm activities of the extracts were tested. The AcOEt extract from C. gracilis showed a moderate antibiofilm activity.
Collapse
Affiliation(s)
- Ma José Iglesias
- Área de Química Orgánica, Research Centre CIAIMBITAL, Universidad de Almería, Carretera de Sacramento s/n, Almería, 04120, Spain.
| | - Raquel Soengas
- Área de Química Orgánica, Research Centre CIAIMBITAL, Universidad de Almería, Carretera de Sacramento s/n, Almería, 04120, Spain
| | - Ian Probert
- Roscoff Culture Collection, FR2424 Station Biologique de Roscoff (Sorbonne Université / CNRS), 29680, Roscoff, France
| | - Emilie Guilloud
- Roscoff Culture Collection, FR2424 Station Biologique de Roscoff (Sorbonne Université / CNRS), 29680, Roscoff, France
| | - Priscillia Gourvil
- Roscoff Culture Collection, FR2424 Station Biologique de Roscoff (Sorbonne Université / CNRS), 29680, Roscoff, France
| | - Mohamed Mehiri
- Institut de Chimie de Nice, UMR CNRS 7272, Université Nice Sofia Antopolis, 06103, Nice, France
| | - Yuly López
- Barcelona Institute for Global Health (ISGlobal)-Hospital Clinic-Universitat de Barcelona, Carrer Rosselló 132, 08036, Barcelona, Spain
| | - Virginio Cepas
- Barcelona Institute for Global Health (ISGlobal)-Hospital Clinic-Universitat de Barcelona, Carrer Rosselló 132, 08036, Barcelona, Spain
| | - Ignacio Gutiérrez-Del-Río
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain. IUOPA (Instituto Universitario de Oncología del Principado de Asturias), ISPA (Instituto de Investigación Sanitaria del Principado de Asturias), Spain
| | - Saúl Redondo-Blanco
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain. IUOPA (Instituto Universitario de Oncología del Principado de Asturias), ISPA (Instituto de Investigación Sanitaria del Principado de Asturias), Spain
| | - Claudio J Villar
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain. IUOPA (Instituto Universitario de Oncología del Principado de Asturias), ISPA (Instituto de Investigación Sanitaria del Principado de Asturias), Spain
| | - Felipe Lombó
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain. IUOPA (Instituto Universitario de Oncología del Principado de Asturias), ISPA (Instituto de Investigación Sanitaria del Principado de Asturias), Spain
| | - Sara Soto
- Barcelona Institute for Global Health (ISGlobal)-Hospital Clinic-Universitat de Barcelona, Carrer Rosselló 132, 08036, Barcelona, Spain
| | - Fernando López Ortiz
- Área de Química Orgánica, Research Centre CIAIMBITAL, Universidad de Almería, Carretera de Sacramento s/n, Almería, 04120, Spain.
| |
Collapse
|
10
|
Lipid Saturation and the Rheology of Human Tear Lipids. Int J Mol Sci 2019; 20:ijms20143431. [PMID: 31336861 PMCID: PMC6678947 DOI: 10.3390/ijms20143431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/24/2019] [Accepted: 07/04/2019] [Indexed: 02/03/2023] Open
Abstract
Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid-lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both.
Collapse
|
11
|
Xu W, Xiao CJ, Sun JZ, Zhang PP, Wang JW, Dong X, Jiang B. A New Totarane Diterpenoid from the Rhizomes of Isodon lophanthoides. Chem Nat Compd 2019. [DOI: 10.1007/s10600-019-02778-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
12
|
Human meibum chain branching variability with age, gender and meibomian gland dysfunction. Ocul Surf 2018; 17:327-335. [PMID: 30553000 DOI: 10.1016/j.jtos.2018.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/07/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022]
Abstract
NMR spectroscopy was used to measure hydrocarbon chain branching variability in meibum with age, gender and Meibomian gland dysfuction (MGD). A cohort of 65 meibum donors without dry eye and 31 donors with MGD was studied. Heteronuclear 2D NMR was used to confirm CH3 resonance assignments allowing us to positively identify 23 of the 27 proton resonances of cholesteryl ester and 1H resonances due to straight chain, iso-branched and anteiso-branched hydrocarbons. Meibum from donors without dry eye contained 57 ± 1% straight-chains, 23 ± 1% iso-branched chains and 20 ± 1% anteiso-branched hydrocarbon chains. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less, 50 ± 2% straight-chains, more, 32 ± 2% iso-branched chains and the same amount, 18.0 ± 0.07%, of anteiso-branched hydrocarbon chains. Meibum hydrocarbon chain branching did not change with age between 22 and 68 years of age, nor was it influenced by gender. Based on previous studies, one would expect anteiso-branched chains would contribute to lowering the phase transition temperature of meibum, decrease the elasticity of the tear film lipid layer and increase the molecular area and spreading of meibum on the surface of the eye. Although we speculate that the observed differences in iso-chain branching do not influence tear film stability or rheology, the speculation has yet to be tested.
Collapse
|
13
|
de Bengy AF, Forraz N, Danoux L, Berthelemy N, Cadau S, Degoul O, Andre V, Pain S, McGuckin C. Development of new 3D human ex vivo models to study sebaceous gland lipid metabolism and modulations. Cell Prolif 2018; 52:e12524. [PMID: 30402911 PMCID: PMC6430446 DOI: 10.1111/cpr.12524] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 07/26/2018] [Accepted: 07/27/2018] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVES Sebaceous glands maintain skin homeostasis by producing sebum. Low production can induce hair loss and fragile skin. Overproduction provokes seborrhoea and may lead to acne and inflammatory events. To better study sebaceous gland maintenance, sebocyte maturation, lipid production and ageing or inflammatory processes, we developed innovative 3D ex vivo models for human sebaceous glands. MATERIALS AND METHODS Culture conditions and analytical methods optimized on sebocyte monolayers were validated on extracted sebaceous glands and allowed the development of two 3D models: (a) "air-liquid" interface and (b) human fibronectin-coated "sandwich" method. Lipid production was assessed with microscopy, fluorometry or flow cytometry analysis after Nile Red staining. Specific lipids (particularly squalene and peroxidized squalene) were measured by Gas or liquid Chromatography and Mass spectrometry. RESULTS This study allowed us to select appropriate conditions and design Seb4Gln culture medium inducing sebocyte proliferation and neutral lipid production. The "air-liquid" model was appropriate to induce sebocyte isolation. The "sandwich" model enabled sebaceous gland maintenance up to 42 days. A treatment with Insulin Growth Factor-1 allowed validation of the model as we succeeded in mimicking dynamic lipid overproduction. CONCLUSION Functional sebocyte maturation and physiological maintenance were preserved up to 6 weeks in our models. Associated with functional assays, they provide a powerful platform to mimic physiological skin lipid metabolism and to screen for active ingredients modulating sebum production.
Collapse
|
14
|
Lou-Bonafonte JM, Martínez-Beamonte R, Sanclemente T, Surra JC, Herrera-Marcos LV, Sanchez-Marco J, Arnal C, Osada J. Current Insights into the Biological Action of Squalene. Mol Nutr Food Res 2018; 62:e1800136. [PMID: 29883523 DOI: 10.1002/mnfr.201800136] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 05/08/2018] [Indexed: 01/24/2023]
Abstract
Squalene is a triterpenic compound found in a large number of plants and other sources with a long tradition of research since it was first reported in 1926. Herein a systematic review of studies concerning squalene published in the last 8 years is presented. These studies have provided further support for its antioxidant, anti-inflammatory, and anti-atherosclerotic properties in vivo and in vitro. Moreover, an antineoplastic effect in nutrigenetic-type treatments, which depends on the failing metabolic pathway of tumors, has also been reported. The bioavailability of squalene in cell cultures, animal models, and in humans has been well established, and further progress has been made in regard to the intracellular transport of this lipophilic molecule. Squalene accumulates in the liver and decreases hepatic cholesterol and triglycerides, with these actions being exerted via a complex network of changes in gene expression at both transcriptional and post-transcriptional levels. Its presence in different biological fluids has also been studied. The combination of squalene with other bioactive compounds has been shown to enhance its pleiotropic properties and might lead to the formulation of functional foods and nutraceuticals to control oxidative stress and, therefore, numerous age-related diseases in human and veterinary medicine.
Collapse
Affiliation(s)
- José M Lou-Bonafonte
- Departamento de Farmacología y Fisiología, Facultad de Ciencias de la Salud y del Deporte, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, E-22002, Spain.,Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, E-28029, Spain
| | - Roberto Martínez-Beamonte
- Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, E-28029, Spain.,Departamento de Producción Animal y Ciencia de los Alimentos, Escuela Politécnica Superior de Huesca, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Huesca, E-22071, Spain
| | - Teresa Sanclemente
- Departamento de Producción Animal y Ciencia de los Alimentos, Escuela Politécnica Superior de Huesca, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Huesca, E-22071, Spain
| | - Joaquín C Surra
- Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, E-28029, Spain.,Departamento de Producción Animal y Ciencia de los Alimentos, Escuela Politécnica Superior de Huesca, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Huesca, E-22071, Spain
| | - Luis V Herrera-Marcos
- Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Zaragoza, E-50013, Spain
| | - Javier Sanchez-Marco
- Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Zaragoza, E-50013, Spain
| | - Carmen Arnal
- Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, E-28029, Spain.,Departamento de Patología Animal, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Zaragoza, E-50013, Spain
| | - Jesús Osada
- Instituto Agroalimentario de Aragón, CITA-Universidad de Zaragoza, E-50013, Spain.,CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, E-28029, Spain.,Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón-Universidad de Zaragoza, Zaragoza, E-50013, Spain
| |
Collapse
|
15
|
Glasgow BJ, Abduragimov AR. Interaction of ceramides and tear lipocalin. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:399-408. [PMID: 29331331 PMCID: PMC5835416 DOI: 10.1016/j.bbalip.2018.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 12/19/2017] [Accepted: 01/06/2018] [Indexed: 10/18/2022]
Abstract
The distribution of lipids in tears is critical to their function. Lipids in human tears may retard evaporation by forming a surface barrier at the air interface. Lipids complexed with the major lipid binding protein in tears, tear lipocalin, reside in the bulk (aqueous) and may have functions unrelated to the surface. Many new lipids species have been revealed through recent mass spectrometric studies. Their association with lipid binding proteins has not been studied. Squalene, (O-acyl) omega-hydroxy fatty acids (OAHFA) and ceramides are examples. Even well-known lipids such as wax and cholesteryl esters are only presumed to be unbound because extracts of protein fractions of tears were devoid of these lipids. Our purpose was to determine by direct binding assays if the aforementioned lipids can bind tear lipocalin. Lipids were screened for ability to displace DAUDA from tear lipocalin in a fluorescence displacement assay. Di- and tri-glycerides, squalene, OAHFA, wax and cholesterol esters did not displace DAUDA from tear lipocalin. However, ceramides displaced DAUDA. Apparent dissociation constants for ceramide-tear lipocalin complexes using fluorescent analogs were measured consistently in the submicromolar range with 3 methods, linear spectral summation, high speed centrifugal precipitation and standard fluorescence assays. At the relatively small concentrations in tears, all ceramides were complexed to tear lipocalin. The lack of binding of di- and tri-glycerides, squalene, OAHFA, as well as wax and cholesterol esters to tear lipocalin is consonant with residence of these lipids near the air interface.
Collapse
Affiliation(s)
- Ben J Glasgow
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States.
| | - Adil R Abduragimov
- Departments of Ophthalmology, Pathology and Laboratory Medicine, Jules Stein Eye Institute, University of California, Los Angeles, 100 Stein Plaza Rm. BH 623, Los Angeles, CA 90095, United States
| |
Collapse
|
16
|
|
17
|
Sledge S, Henry C, Borchman D, Yappert MC, Bhola R, Ramasubramanian A, Blackburn R, Austin J, Massey K, Sayied S, Williams A, Georgiev G, Schikler KN. Human Meibum Age, Lipid-Lipid Interactions and Lipid Saturation in Meibum from Infants. Int J Mol Sci 2017; 18:ijms18091862. [PMID: 28846660 PMCID: PMC5618511 DOI: 10.3390/ijms18091862] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/25/2017] [Accepted: 08/17/2017] [Indexed: 01/21/2023] Open
Abstract
Tear stability decreases with increasing age and the same signs of instability are exacerbated with dry eye. Meibum lipid compositional changes with age provide insights into the biomolecules responsible for tear film instability. Meibum was collected from 69 normal donors ranging in age from 0.6 to 68 years of age. Infrared spectroscopy was used to measure meibum lipid phase transition parameters. Nuclear magnetic resonance spectroscopy was used to measure lipid saturation. Increasing human meibum lipid hydrocarbon chain unsaturation with age was related to a decrease in hydrocarbon chain order, cooperativity, and in the phase transition temperature. The change in these parameters was most dramatic between 1 and 20 years of age. Meibum was catalytically saturated to determine the effect of saturation on meibum lipid phase transition parameters. Hydrocarbon chain saturation was directly related to lipid order, phase transition temperature, cooperativity, changes in enthalpy and entropy, and could account for the changes in the lipid phase transition parameters observed with age. Unsaturation could contribute to decreased tear film stability with age.
Collapse
Affiliation(s)
- Samiyyah Sledge
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Collin Henry
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
| | - Rahul Bhola
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
- Division of Ophthalmology, Children's Hospital of Orange County, Orange, CA 92868, USA.
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Ryan Blackburn
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Jonathan Austin
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Kayla Massey
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Shanzeh Sayied
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Aliza Williams
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Georgi Georgiev
- Model Membranes Lab, Department of Biochemistry, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria.
| | - Kenneth N Schikler
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA.
| |
Collapse
|
18
|
Rotondo A, Salvo A, Gallo V, Rastrelli L, Dugo G. Quick unreferenced NMR quantification of Squalene in vegetable oils. EUR J LIPID SCI TECH 2017. [DOI: 10.1002/ejlt.201700151] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Archimede Rotondo
- Dipartimento di BIOMORF- Università di Messina; Viale Annunziata Ex Veterinaria; Messina Italy
| | - Andrea Salvo
- Dipartimento di BIOMORF- Università di Messina; Viale Annunziata Ex Veterinaria; Messina Italy
| | - Vito Gallo
- Dipartimento di Ingegneria Civile, Ambientale, del Territorio; Edile e di Chimica−Politecnico di Bari; Bari Italy
| | - Luca Rastrelli
- Dipartimento di Farmacia DIFARMA; Università di Salerno; Fisciano (SA) Italy
| | - Giacomo Dugo
- Dipartimento di BIOMORF- Università di Messina; Viale Annunziata Ex Veterinaria; Messina Italy
| |
Collapse
|
19
|
Abstract
The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.
Collapse
|
20
|
Mudgil P, Borchman D, Gerlach D, Yappert MC. Sebum/Meibum Surface Film Interactions and Phase Transitional Differences. Invest Ophthalmol Vis Sci 2017; 57:2401-11. [PMID: 27145473 PMCID: PMC5113983 DOI: 10.1167/iovs.16-19117] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Purpose Sebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection. The aims of this study were to determine: if sebum changes the rheology of meibum surface films; if the resonance near 5.2 ppm in the 1H-NMR spectra of sebum is due to squalene (SQ); and if sebum or SQ, a major component of sebum, interacts with human meibum. Methods Human meibum was collected from the lid margin with a platinum spatula. Human sebum was collected using lipid absorbent tape. Langmuir trough technology was used to measure the rheology of surface films. Infrared spectroscopy was used to measure lipid conformation and phase transitions. We used 1H-NMR to measure composition and confirm the primary structure of SQ. Results The NMR resonance near 5.2 ppm in the spectra of human sebum was from SQ which composed 28 mole percent of sebum. Both sebum and SQ lowered the lipid order of meibum. Sebum expanded meibum films at lower concentrations and condensed meibum films at higher concentrations. Sebum caused meibum to be more stable at higher pressures (greater maximum surface pressure). Conclusions Physiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active (qualities beneficial for tear film stability). Sebum would also be expected to stabilize the tear film lipid layer, which may allow it to withstand the high shear pressure of a blink.
Collapse
Affiliation(s)
- Poonam Mudgil
- School of Medicine Western Sydney University, Penrith, New South Wales, Australia
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Dylan Gerlach
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, Kentucky, United States
| |
Collapse
|
21
|
Wolkoff P. External eye symptoms in indoor environments. INDOOR AIR 2017; 27:246-260. [PMID: 27444579 DOI: 10.1111/ina.12322] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/19/2016] [Indexed: 05/22/2023]
Abstract
Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.
Collapse
Affiliation(s)
- P Wolkoff
- National Research Centre for the Working Environment, Copenhagen, Denmark
| |
Collapse
|
22
|
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.
Collapse
|
23
|
Millar TJ, Schuett BS. The real reason for having a meibomian lipid layer covering the outer surface of the tear film - A review. Exp Eye Res 2015; 137:125-38. [PMID: 25981748 DOI: 10.1016/j.exer.2015.05.002] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 05/05/2015] [Accepted: 05/08/2015] [Indexed: 12/27/2022]
Abstract
This review critically evaluates a broad range of literature in order to show the relationship between meibum, tear lipids and the tear film lipid layer (TFLL). The relationship of meibum composition to dry eye syndrome is briefly discussed. The review also explores the interactions between aqueous and the TFLL by examining the correlations between meibomian lipids and lipids extracted from whole tears, and by considering protein adsorption to the TFLL from the aqueous. Although it is clear to the authors that a normal tear film resists evaporation, an emerging idea from the literature is that the main purpose of the TFLL is to allow the spread of the tear film and to prevent its collapse onto the ocular surface, rather than to be an evaporative blanket. Current models on the possible structure of the TFLL are also examined.
Collapse
Affiliation(s)
- Thomas J Millar
- University of Western Sydney, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
| | - Burkhardt S Schuett
- University of Western Sydney, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
| |
Collapse
|
24
|
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]
|
25
|
Wizert A, Iskander DR, Cwiklik L. Organization of lipids in the tear film: a molecular-level view. PLoS One 2014; 9:e92461. [PMID: 24651175 PMCID: PMC3961367 DOI: 10.1371/journal.pone.0092461] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 02/21/2014] [Indexed: 01/03/2023] Open
Abstract
Biophysical properties of the tear film lipid layer are studied at the molecular level employing coarse grain molecular dynamics (MD) simulations with a realistic model of the human tear film. In this model, polar lipids are chosen to reflect the current knowledge on the lipidome of the tear film whereas typical Meibomian-origin lipids are included in the thick non-polar lipids subphase. Simulation conditions mimic those experienced by the real human tear film during blinks. Namely, thermodynamic equilibrium simulations at different lateral compressions are performed to model varying surface pressure, and the dynamics of the system during a blink is studied by non-equilibrium MD simulations. Polar lipids separate their non-polar counterparts from water by forming a monomolecular layer whereas the non-polar molecules establish a thick outermost lipid layer. Under lateral compression, the polar layer undulates and a sorting of polar lipids occurs. Moreover, formation of three-dimensional aggregates of polar lipids in both non-polar and water subphases is observed. We suggest that these three-dimensional structures are abundant under dynamic conditions caused by the action of eye lids and that they act as reservoirs of polar lipids, thus increasing stability of the tear film.
Collapse
Affiliation(s)
- Alicja Wizert
- Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland
| | - D. Robert Iskander
- Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, Czech Republic
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, Czech Republic
- Department of Physics, Tampere University of Technology, Tampere, Finland
| |
Collapse
|