NC-1059: A Channel-Forming Peptide That Modulates Drug Delivery across In Vitro Corneal Epithelium

PURPOSE: The goal of this study was to determine whether a synthetic peptide, NC-1059, can modulate the corneal epithelium to increase the permeation of therapeutic agents across this barrier. METHODS: An in vitro system employing transformed human corneal epithelial (THCE) cells was optimized for this study. Culture conditions were identified to promote formation of a confluent monolayer that rapidly develops a substantial transepithelial electrical resistance. Electrical parameters were measured with a modified Ussing flux chamber, and solute flux was quantified with fluorescently labeled compounds. RESULTS: NC-1059 causes a concentration-dependent increase in short-circuit current and an increase in transepithelial electrical conductance when assessed in modified Ussing chambers. The effect of NC-1059 on transepithelial electrical resistance was reversible. To test for paracellular permeability and size exclusion, FITC-labeled dextran ranging in size from 10 to 70 kDa was used. Dextran permeated the corneal cell monolayer in the presence, but not the absence, of NC-1059. Fluorescein sodium and carboxyfluorescein were then used as low molecular weight markers with similar NC-1059-modulated kinetics being observed. Maximum permeation for the fluorescein derivatives occurred 30 to 90 minutes after a 5-minute NC-1059 exposure. A prototypical drug, methotrexate, also exhibited increased permeation in the presence of NC-1059. CONCLUSIONS: NC-1059 enhances drug permeation across cultured corneal epithelial cell monolayers by transiently affecting the paracellular pathway. Thus, NC-1059 is a lead compound for development of cotherapeutic agents to enhance access and effectiveness of ophthalmic compounds.