One man's poison is another man's meat: Using azithromycin-induced phospholipidosis to promote ocular surface health

Abstract

Drug-induced phospholipidosis (PLD) is a common adverse effect which has led to the termination of clinical trials for many candidate pharmaceuticals. However, this lipid-inducing effect may be beneficial in the treatment of meibomian gland dysfunction (MGD). MGD is the major cause of dry eye disease (DED), which affects 40 million people in the USA and has no cure. Azithromycin (AZM) is a PLD-inducing antibiotic that is used off-label to treat MGD, and is presumably effective because it suppresses the MGD-associated conjunctival inflammation (i.e. posterior blepharitis) and growth of lid bacteria. We hypothesize that AZM can act directly to promote the function of human meibomian gland epithelial cells by inducing PLD in these cells, characterized by the accumulation of lipids and lysosomes. We cultured immortalized human meibomian gland epithelial cells (HMGEC) were cultured with or without azithromycin for 5 days. Cells were evaluated for cholesterol (Filipin) and neutral lipid (LipidTox) staining, as well as the appearance of lysosomes (LysoTracker) and lamellar bodies (transmission electron microscopy, TEM). The lipid composition of cellular lysates was analyzed by high performance thin-layer chromatography. Our findings demonstrate that AZM stimulates the accumulation of free cholesterol, neutral lipids and lysosomes in HMGEC. This AZM-induced increase of neutral lipid content occurred predominantly within lysosomes. Many of these vesicles appeared to be lamellar bodies by TEM, which is the characteristic of PLD. Our findings also show that AZM promotes an accumulation of free and esterified cholesterol, as well as phospholipids in HMGEC. Our results support our hypothesis and confirm the beneficial effect of PLD induced by AZM on HMGEC. Our discovery reveals a new potential use of PLD-inducing drugs, and makes this adverse effect a beneficial effect.

Limited Azithromycin Localization to Rabbit Meibomian Glands Revealed by LC-MS-Based Bioanalysis and DESI Imaging

“…19,20) Indeed, topical azithromycin therapy relieved the signs and symptoms of MGD and restored the biophysical properties of meibomian lipids to normal. 5,21) Furthermore, azithromycin topical treatment significantly reduced the number of plugged orifices and ameliorated acinar atrophy in a special diet-induced MGD mouse model.…”

The Combined Effect of Azithromycin and Insulin-Like Growth Factor-1 on Cultured Human Meibomian Gland Epithelial Cells

“…10 The lipid extractions from samples containing equivalent amount of cells were developed on a high-performance thin-layer chromatography (HPTLC) plate (Silica Gel 60; Merck, Darmstadt, Germany). For nonpolar lipid analysis, the plate was developed in benzene:hexane (65:35, vol/vol) alone.…”

“…9 This effect is accompanied by an increased lysosome formation, a decreased cell proliferation, and a holocrine-like lipid secretion, which are the major characteristics of HMGEC differentiation. [9][10][11] In addition, we have discovered that insulin-like growth factor-1 (IGF-1) is essential for meibomian gland health and promotes both cell proliferation and lipid accumulation. 12 Given these findings, we hypothesize that the combination of AZM and IGF-1 will promote cell differentiation and lipid accumulation while preserving the normal cell proliferation in HMGECs.…”

Current and Emerging Therapeutic Strategies for the Treatment of Meibomian Gland Dysfunction (MGD)

“…The study demonstrated that azithromycin stimulates the accumulation of free cholesterol, neutral lipids and lysosomes-a phenomenon termed 'drug-induced phospholipidosis'. While phospholipidosis is a common adverse effect in many candidate pharmaceuticals, which may even lead to the termination of a clinical trial, other medications that undergo similar phospholipidosis could be potential treatment options for MGD [24].…”