Functionality of a liposome-based anti-inflammatory formulation in an in vitro corneal inflammation model

Abstract

Purpose : Unpreserved liposomal topical formulation used as artificial tears was loaded with the anti-inflammatory agent medroxyprogesterone acetate (MPA). Our aim was to characterize MPA-loaded liposomes (MPA-LP), study its uptake by corneal epithelial cells, and determine its functionality in an in vitro corneal inflammation model.

Methods : Liposomes (LP) composed of phosphatidylcholine, cholesterol, vitamin E, and MPA at a molar ratio 13:3:0.2:0.3 were prepared by solvent evaporation technique and labeled with coumarin-6 (C6-LP) for uptake experiments. LP characterization included diameter size, pH, osmolarity, and viscosity. Drug encapsulation efficiency was also calculated. Human corneal epithelial (HCE) cells were used to in vitro study MPA-LP-induced effects after 60 min of exposure. Blank LP and a MPA reference formulation (Colicursi Medrivas, Alcon Cusi S.A.) were used as controls. LP cytotoxicity was analyzed by the XTT assay. C6-LP uptake by HCE cells was analyzed immediately, 24, 48, and 72h after the exposure period. Changes in protein expression and nuclear translocation of MPA glucocorticoid and progesterone receptors were determined by Western blotting and immunofluorescence. Changes in cell proliferation were measured by the AlamarBlue assay. Also, TNFα-stimulated cells (inflamed) were exposed to MPA-LP and changes in IL-6 and IL-8 production were analyzed by ELISA.

Results : LP showed adequate physicochemical properties for topical ophthalmic formulations and MPA encapsulation efficiency was close to 94%. HCE cells showed LP-associated fluorescence at 24, 48, and 72h after the exposure period without any cytotoxic effect. The protein expression and nuclear translocation of progesterone receptor increased in MPA-LP-exposed cells compared to blank LP-exposed cells, indicating MPA-LP uptake by HCE cells. Moreover, MPA-LP showed anti-proliferative and anti-inflammatory effect by reducing cell proliferation rate and IL-6 and IL-8 production 48h after the exposure period. None of these effects were shown in blank LP-exposed cells, and the reference formulation only reduced IL-6 production.

Conclusions : The LP-based formulation used to replenish the lipids of the tear film may also be used as an anti-inflammatory drug delivery system for the treatment of inflammatory processes associated to ocular surface diseases.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.