Adenovirus-Mediated Atrial Natriuretic Protein Expression in the Lung Protects Rats from Hypoxia-Induced Pulmonary Hypertension

Endogenous as well as exogenous atrial natriuretic peptide (ANP) attenuates the development of chronic hypoxic pulmonary hypertension (CHPH) in rats. We built a recombinant adenovirus type 5 containing ANP cDNA under the control of the Rous sarcoma virus long terminal repeat (Ad.ANP). The efficiency of this vector in delivering the ANP gene was first examined in rat primary cultures of pulmonary vessel smooth muscle cells (SMCs) in comparison with Ad.βGAL. Conditioned medium collected from Ad.ANP-infected cells (1000 TCID₅₀/cell) contained 5 × 10⁹ M immunoreactive ANP and elicited relaxation of isolated rat pulmonary arteries preconstricted with phenylepinephrine. To examine the effects of adenovirus-mediated ANP expression in the CHPH rat lung, Ad.ANP or Ad.βGAL was administered via the tracheal route. Immunoreactive ANP was detected in bronchoalveolar fluid as early as 4 days and until 10-17 days after Ad.ANP administration (5 × 10⁸ TCID₅₀). Lung ANP immunostaining was mainly localized in bronchial and alveolar epithelial cells. As compared with Ad.βGAL-treated controls, rats given Ad.ANP (5 × 10⁸ TCID₅₀) on the day before a 2-week exposure to hypoxia (10% O₂) had lower values for pulmonary artery pressure (32.1 ± 1.93 vs. 35.5 ± 2 mmHg, p < 0.01) and Fulton's index (0.52± 0.089 vs. 0.67 ± 0.12, p < 0.001) and less severe right ventricular hypertrophy and distal vessel muscularization. These results suggest that induction of ANP expression in the lung may hold promise in the treatment of pulmonary hypertension.