NC-1059: a channel-forming peptide that modulates drug delivery across in vitro corneal epithelium.
OBJECTIVE
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.
Martin
Jesica
J
Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas 66506, USA.
Malreddy
Pradeep
P
Iwamoto
Takeo
T
Freeman
Lisa C
LC
Davidson
Harriet J
HJ
Tomich
John M
JM
Schultz
Bruce D
BD
D002461:Cell Line, Transformed; D002463:Cell Membrane Permeability / Q000187:drug effects; D003911:Dextrans / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D019573:Epithelium, Corneal / Q000378:metabolism* / Q000648:ultrastructure; D019793:Fluorescein / Q000493:pharmacokinetics*; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D006801:Humans; D007473:Ion Channels / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials; D008727:Methotrexate / Q000493:pharmacokinetics*; D010455:Peptides / Q000494:pharmacology; D019108:Tight Junctions / Q000187:drug effects; D013997:Time Factors; D054457:Tissue Scaffolds
D003911:Dextrans; D007473:Ion Channels; C487308:NC-1059; D010455:Peptides; C015219:fluorescein isothiocyanate dextran; D016650:Fluorescein-5-isothiocyanate; D019793:Fluorescein; D008727:Methotrexate