title: Wax-tear and meibum protein, wax-β-carotene interactions in vitro using infrared spectroscopy.
abstract: Protein-meibum and terpenoids-meibum lipid interactions could be important in the etiology of meibomian gland dysfunction (MGD) and dry eye symptoms. In the current model studies, attenuated total reflectance (ATR) infrared (IR) spectroscopy was used to determine if the terpenoid β-carotene and the major proteins in tears and meibum affect the hydrocarbon chain conformation and carbonyl environment of wax, an abundant component of meibum. The main finding of these studies is that mucin binding to wax disordered slightly the conformation of the hydrocarbon chains of wax and caused the wax carbonyls to become hydrogen bonded or experience a more hydrophilic environment. Lysozyme and lactoglobulin, two proteins shown to bind to monolayers of meibum, did not have such an effect. Keratin and β-carotene did not affect the fluidity (viscosity) or environment of the carbonyl moieties of wax. Based on these results, tetraterpenoids are not likely to influence the structure of meibum in the meibomian glands. In addition, these findings suggest that it is unlikely that keratin blocks meibomian glands by causing the meibum to become more viscous. Among the tear fluid proteins studied, mucin is the most likely to influence the conformation and carbonyl environment of meibum at the tear film surface.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Center, University of Louisville, 301 E. Muhammad Ali Blvd., Louisville, KY 40202, USA.
authors.forename: Samad
authors.initials: S
authors.lastname: Faheem
authors.forename: Sung-Hye
authors.initials: SH
authors.lastname: Kim
authors.forename: Jonathan
authors.initials: J
authors.lastname: Nguyen
authors.forename: Shantanu
authors.initials: S
authors.lastname: Neravetla
authors.forename: Matthew
authors.initials: M
authors.lastname: Ball
authors.forename: Gary N
authors.initials: GN
authors.lastname: Foulks
authors.forename: Marta C
authors.initials: MC
authors.lastname: Yappert
authors.forename: Douglas
authors.initials: D
authors.lastname: Borchman
mesh_terms: D015352:Dry Eye Syndromes / Q000378:metabolism; D005136:Eye Proteins / Q000737:chemistry*; D005141:Eyelid Diseases / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000737:chemistry*; D006801:Humans; D007633:Keratins / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry; D008537:Meibomian Glands / Q000737:chemistry; D009077:Mucins / Q000737:chemistry*; D009113:Muramidase / Q000737:chemistry; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D014783:Viscosity; D019207:beta Carotene / Q000737:chemistry*
chemical_list: D005136:Eye Proteins; D005231:Fatty Acids, Unsaturated; D007782:Lactoglobulins; D009077:Mucins; C042434:tear proteins; D019207:beta Carotene; D007633:Keratins; C402677:palmityl oleate; D009113:Muramidase