Intraluminal Water Increases Expression of Plasmid DNA in Rat Lung

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Abstract
Effective gene delivery to specific organs is a major goal for human gene therapy. The lung's structure allows instillation of agents into the airspaces, directly adjacent to the lung epithelium. We hypothesized that the air-space instillation of hypotonic solutions would increase the permeability of the lung epithelium and increase DNA uptake. This hypothesis was tested by instilling plasmid DNA (p4241) encoding the luciferase gene in isotonic and hypotonic solutions. The highest luciferase expression in the lung was achieved after the instillation of this plasmid DNA in distilled water. Aerosolization of water just before the instillation of the plasmid DNA also enhanced the expression level of luciferase in the lung. In addition, an intralobar instillation of the plasmid DNA in water significantly increased the luciferase expression, suggesting that the instillation of the plasmid over a smaller surface area increased expression. Levels of expression could be measured for 3 days. Water increases the permeability of lung epithelial cells transiently and/or enhances gene expression and can be used to achieve gene expression in the lung airspaces for short intervals without toxicity. In vitro studies have found that water transiently increases the apical and basal permeability of human tracheal cells (Widdicombe, et al., 1996). Therefore, water was utilized in vivo to increase the lung epithelial permeability and, thereby, to increase the internalization of plasmids encoding the luciferase gene. Used as the vehicle for the plasmid, or as an aerosol pretreatment to increase the permeability of a greater fraction of the epithelial cells in the lung, water was found to increase luciferase gene expression in the lung, when compared to a variety of other vehicles that included various buffered salt solutions and an adenoviral complex.