1. ¹Department of Anatomy and Cell Biology, University of Iowa College of Medicine, Iowa City, IA 52242, USA
2. ²Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242, USA
3. ³Targeted Genetics, Seattle, WA, USA
4. ⁴Department of Pathology and Anatomical Sciences, Ellis Fischel Cancer Center, University of Missouri School of Medicine, Columbia, MO, USA
5. ⁵Center for Gene Therapy of Cystic Fibrosis and Other Genetic Diseases, University of Iowa College of Medicine, Iowa City, IA 52242, USA

Correspondence: John F. Engelhardt, Department of Anatomy and Cell Biology, University of Iowa, Room 1-111 Bowen Science Building, 51 Newton Road, Iowa City, IA 52242-1109, USA. Fax: (319) 335-6581. E-mail: john-engelhardt@uiowa.edu

Received 27 April 2004; Accepted 17 August 2004.

Abstract

Pharmacologic- and gene-based therapies have historically been developed as two independent therapeutic platforms for cystic fibrosis (CF) lung disease. Inhibition of the dysregulated epithelial Na channel (ENaC) is one pharmacologic approach to enhance airway clearance in CF. We investigated pharmacologic approaches to enhance CFTR gene delivery with recombinant adeno-associated virus (rAAV) and identified compounds that significantly improved viral transduction while simultaneously inhibiting ENaC activity through an unrelated mechanism. Treatment of human CF airway epithelia with proteasome modulating agents (LLnL and doxorubicin) at the time of rAAV2 or rAAV2/5 infection dramatically enhanced CFTR gene delivery and correction of CFTR-mediated short-circuit currents. Surprisingly, these agents also facilitated long-term (15-day) functional inhibition of ENaC currents independent of CFTR vector administration. Inhibition of ENaC activity was predominantly attributed to a doxorubicin-dependent decrease in -ENaC subunit mRNA expression and an increase in -ENaC promoter methylation. This is the first report to describe the identification of compounds with dual therapeutic action that are able to enhance the efficacy of CFTR gene therapy to the airway while simultaneously ameliorating primary aspects of CF disease pathophysiology. The identification of such compounds mark a new area for drug development, not only for CF, but also for other gene therapy disease targets.