The Effect of Solithromycin, a Cationic Amphiphilic Drug, on the Proliferation and Differentiation of Human Meibomian Gland Epithelial Cells

Purpose: We previously discovered that azithromycin (AZM) acts directly on immortalized human meibomian gland epithelial cells (IHMGECs) to stimulate their lipid and lysosome accumulation and overall differentiation. We hypothesize that this phospholipidosis-like effect is due to AZM's cationic amphiphilic drug (CAD) nature. If our hypothesis is correct, then other CADs (e.g., solithromycin [SOL]) should be able to duplicate AZM's action on IHMGECs. Our purpose was to test this hypothesis.Materials and Methods: IHMGECs were cultured in the presence of vehicle or SOL (2, 10, or 20 mu g/ml) for up to 7days under proliferating or differentiating conditions. Positive (epidermal growth factor and bovine pituitary extract for proliferation; AZM for differentiation) and negative (vehicle) controls were included with the experiments. IHMGECs were evaluated for cell number, neutral lipid content, and lysosome accumulation.Results: Our results demonstrate that SOL induces a rapid and dose-dependent increase in the accumulation of neutral lipids and lysosomes in HMGECs. The lysosomal effects were most prominent with the 10 and 20 mu g/ml doses, and occurred earlier (i.e., 1 day) with SOL than with the AZM (10 mu g/ml) control. The effects of SOL and AZM on IHMGEC differentiation were essentially the same after 3days of culture. SOL did not influence the proliferation of HMGECs during a 7-day time period.Conclusions: Our results support our hypothesis that SOL, a CAD, is able to reproduce AZM's impact on lysosome and lipid accumulation, as well as the differentiation, of HMGECs. The effect of SOL on lysosome appearance was faster than that of AZM.