title: Disruption and destabilization of meibomian lipid films caused by increasing amounts of ceramides and cholesterol.
abstract: OBJECTIVE
  We evaluated quantitatively direct effects of ceramide (Cer) and free cholesterol (FC) on meibomian lipid films (MLF) using a Langmuir trough (LT) and a Brewster angle microscope (BAM).
  
  
  METHODS
  Meibum was obtained from healthy volunteers. A series of mixtures of meibum with Cer or FC (mixed MLF) taken in different ratios were tested. Standard rheologic parameters, such as elasticity and hysteresis of MLF, were computed. BAM was used to study the morphology of MLF.
  
  
  RESULTS
  Pure MLF were capable of withstanding multiple compression/expansion cycles with little hysteresis observed (1.9 J/G meibum). The films made of either pure CER or pure FC were clearly collapsible, and had much higher rigidity and hysteresis than pure meibum. Adding progressively higher amounts of CER or FC to meibum had a strong impact on the rigidity, stability, and morphology of the mixed MLF: their hysteresis increased many fold compared to pure meibum. A concomitant increase in the rigidity and collapsibility of the mixed MLF was observed.
  
  
  CONCLUSIONS
  Cer and FC changed the surface properties of mixed MLF in a way that implied their destabilization and/or disruption. One of the mechanisms that might lead to these effects is strong aggregation of meibum lipids with FC or Cer that leads to the formation of smaller particles of meibum surrounded by a thinner layer of FC or Cer. As Cer and FC can be elevated in meibum and the tear film because of certain pathologic processes, or can be of exogenous nature, our results can explain (partially) a less stable tear film in those subjects.
authors: Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9057, USA.
authors: Juan C
authors: JC
authors: Arciniega
authors: Eduardo
authors: E
authors: Uchiyama
authors: Igor A
authors: IA
authors: Butovich
mesh_terms: D000328:Adult; D002518:Ceramides / Q000494:pharmacology*; D002784:Cholesterol / Q000494:pharmacology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008297:Male; D008537:Meibomian Glands / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D012016:Reference Values; D012212:Rheology; D013499:Surface Properties; D013666:Tears / Q000737:chemistry*
chemical_list: D002518:Ceramides; D008055:Lipids; D002784:Cholesterol