Interactions Between Conjunctival Epithelial Cells And Antigen Presenting Cells Exposed To Benzalkonium Chloride

Abstract

Purpose: : To characterize the interactions between antigen presenting cells (APC) and epithelial conjunctival cells (EPC) when exposed to the most common preservative in eye drops, benzalkonium chloride (BAK).

Methods: : APC were obtained from a human monocytic leukemia cell line THP-1 and EPC from Wong Kilbourne-derived human conjunctival cells. APC and EPC were separately exposed to subtoxic concentrations of BAK (10-5% for APC and 10-3% for EPC) and PBS for 24 hours. The cytokine production at 24h was measured in supernatants using a human cytokine array (Proteome Profiler, R&D Systems). Then, APC were cultured with the filtered supernatants obtained after stimulation of EPC with BAK. Similarly, EPC were cultured with the filtered supernatant obtained after stimulation of APC. Phenotype modifications were evaluated using flow cytometry and a panel of clusters of differentiation: CD11b, CD11c, CD33 and CD54 for APC; and CD63, CD95 and CD54 for EPC.

Results: : Exposure to BAK modified the phenotype of APC increasing expression of CD11b and CD11c and decreasing expression of CD33. No change in EPC cell markers was observed after BAK exposure. Supernatants of APC exposed to BAK revealed increased levels of Macrophage Inflammatory Protein-1β (MIP-1β/CCL4), TNF-α, soluble CD54 and IL-1β. Supernatants of EPC exposed to BAK revealed increased levels of Macrophage Migration Inhibitory Factor (MIF) and CXCL8/IL-8. An increased expression of CD54 was observed after stimulation of APC with the supernatant of EPC exposed to BAK.

Conclusions: : Interactions between APC and EPC are involved in iatrogenic ocular surface diseases. BAK could have a direct stimulating effect on APC and also through conjunctival epithelial cells interactions.

Keywords: conjunctiva • cell-cell communication • drug toxicity/drug effects