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Yang Liu, Wendy Kam, Juan Ding, David Sullivan; Impact of azithromycin on lipid accumulation in immortalized human meibomian gland epithelial cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4317.
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Meibomian gland dysfunction(MGD) is believed to be the leading cause of dry eye disease(DED) in the world, and afflicts tens of millions Americans. Perhaps the most common MGD treatment in the USA is the off-label use of topical azithromycin.The efficacy of this macrolide antibiotic has been ascribed to its anti-inflammatory and antibacterial actions. However, the mechanism by which azithromycin acts on the meibomian gland is unknown. We hypothesize that azithromycin promotes lipid accumulation in human meibomian gland epithelial cells (HMGEC), given that macrolides are known to stimulate lipid dynamics in other cell types. Our goal was to test this hypothesis.
Immortalized (i) HMGEC (5x104/well) were incubated overnight on 4-well chamber slides in keratinocyte serum-free medium containing epidermal growth factor (EGF; 5 ng/ml) and bovine pituitary extract (50 µg/ml). Following this period cells were cultured in DMEM/F12 medium containing 10% fetal bovine serum (with or without charcoal-stripping) and EGF (10 ng/ml), in the presence or absence of 10µg/ml azithromycin. Cellular morphological appearance was recorded, and cells were stained with LipidTox for neutral lipid assessment, on culture days 1, 3, 5 and 7.
Our results show that azithromycin induces a striking, time-dependent accumulation of lipid in iHMGEC. Within 3 days of azithromycin exposure, the number, size and staining intensity of intracellular lipid-containing vesicles had markedly increased, as compared to those of vehicle-treated control cells. This azithromycin effect on lipids appeared to become maximal at days 5 to 7 of the study. Evaluation of cellular morphology indicated that azithromycin may promote terminal maturation of iHMGEC, given that vesicle accumulation was often followed by a cell break-up and vesicle release.
Our findings support our hypothesis that azithromycin stimulates the accrual of lipid-containing vesicles in iHMGEC. This azithromycin effect may be paralleled by a cellular maturation and a holocrine-like secretion.
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