Triplex-forming oligonucleotides can modulate aquaporin-5 gene expression in epithelial cells

Triplex-forming oligonucleotides (TFOs) may provide a useful approach to decrease gene transcription in vivo. We have identified two sequences in the rat aquaporin 5 (rAQP5) cDNA that are capable of forming a DNA triple helix. We designed four TFOs based on these sequences (a purine and a pyrimidine TFO per sequence). All four TFOs were able to bind to the rAQP5 cDNA at varying efficiencies in vitro as measured by using gel mobility shift assays. The TFOs were delivered to intact MDCK epithelial cells via adenovirus-polylysine complexes. Experiments with fluorescein-isothiocyanate-labeled oligonucleotides delivered in this way showed primarily a nuclear localization. Three of the four TFOs internalized by adenovirus-polylysine complexes were capable of decreasing rAQP5 expression in intact MDCK cells infected with a recombinant adenovirus encoding rAQP5. These data show that adenovirus-polylysine-TFO complexes can result in TFO delivery to the nucleus in intact epithelial cells and that TFOs may provide a useful way to selectively modulate rAQP5 gene expression.