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Poonam Mudgil; Biophysical interactions of gamma-linolenic acid with tear lipids at an air-tear interface. Invest. Ophthalmol. Vis. Sci. 2018;59(9):146.
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© ARVO (1962-2015); The Authors (2016-present)
Dietary supplementation of essential fatty acids relieves symptoms of dry eye. Their topical application has also been shown to reduce inflammation at the ocular surface leading to prospects of their commercial use in eye drops for treating dry eye. Being lipid in nature and added topically to the ocular surface, they can interact with the lipid layer of the tear film and affect its integrity. Our previous research has shown that linoleic acid and alpha-linolenic acid affect biophysical properties of tear lipids. The aim of this study was to investigate biophysical interactions of gamma-linolenic acid (GLA), a derivative of linoleic acid having anti-inflammatory effects, with the tear lipids at an air-tear interface.
Human meibomian lipids, GLA, cholesterol oleate (CO) and dipalmitoyl phosphatidylcholine (DPPC) were spread separately on an artificial tear solution in a Langmuir trough at 35°C. The lipid films were compressed and expanded to record pressure-area isocycles. GLA was mixed with meibomian lipids in different mole fraction ratios and their interactions were studied by recording pressure-area isocycles of the mixed films. Interactions of GLA with CO and DPPC were studied from isocylces of their mixed films in equimolar fractions.
Isotherms of mebomian lipids showed lift-off area at ~30Å2 and a Πmax of ~14mN/m. Addition of GLA did not much affect the lift-off area of meibomian lipids film but its increasing amount added as 0.2, 0.4, 0.6 and 0.8 mole fractions increased the Πmax to 16, 19, 22 and 25mN/m, respectively. Equimolar fraction of GLA added to CO decreased its molecular area by ~14Å2 and Πmax by ~14mN/m. Equimolar fraction of GLA added to DPPC decreased its molecular area by ~14Å2 but did not much affect Πmax. The plateau (at ~45mN/m) corresponded to a bilayer that was highly compressible without further increase in pressure in the mixed films and DPPC film but with further increase in pressure in the CO film.
GLA increases surface pressure of meibomian lipids and condenses non-polar and polar lipids of the tear film. These interactions can affect biophysical properties of the tear film and alter its stability. It is recommended that use of essential fatty acids in eye drops for treating eye conditions should be carefully examined using the Langmuir film model to ensure topically added lipids provide beneficial effects without disrupting tear stability.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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