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K.–S. Vellonen, E. Mannermaa, H. Turner, E. Toropainen, P. Honkakoski, A. Urtti; Gene Expression and Activity of Efflux Proteins in Human Corneal Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1597. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Role of MDR1 in cornea has been recently evaluated, but the importance of other efflux proteins remains to be clarified. The aim of this study is to characterize gene expression and activity of efflux transporters in the human corneal epithelium and in a human corneal epithelial (HCE) cell model.
Transcript levels of MDR1, MRP1–MRP6 and BCRP were determined by quantitative RT–PCR. Functionality of efflux proteins in non–differentiated HCE cells was assessed with calcein–AM efflux assay using cyclosporine A, progesterone, MK–571 and verapamil as efflux inhibitors. Furthermore, active transport by MDR1 in differentiated HCE cells was studied by measuring bidirectional permeability of rhodamine 123.
MRP5 transcript was present in isolated human corneal epithelial cells and in the HCE model. In HCE cells, MRP1, MRP3 and BCRP showed the highest expression of mRNA, but these genes were minimally expressed in normal corneal epithelium. Retention of calcein in HCE cells was increased in the presence of efflux inhibitors. Also, directionality of rhodamine 123 permeability was diminished in the presence of verapamil. These results demonstrated functionality of efflux proteins.
MRP5 may be an important transporter in the surface of cornea and importance of MRP5 for drug permeation through cornea needs to be elucidated. In addition, efflux protein activity was shown in the HCE cell model, but it may differ from the corneal epithelium in vivo.
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