AAV Delivery of Tumor Necrosis Factor-α Short Hairpin RNA Attenuates Cold-Induced Pulmonary Hypertension and Pulmonary Arterial Remodeling

Cold temperatures are associated with increased mortality and morbidity of cardiovascular and pulmonary disease. Cold exposure causes lung inflammation, pulmonary hypertension (PH), and right ventricle hypertrophy, but there is no effective therapy because of unknown mechanism. Here, we investigated whether RNA interference silencing of tumor necrosis factor (TNF)-alpha decreases cold-induced macrophage infiltration, PH, and pulmonary arterial (PA) remodeling. We found for the first time that continuous cold exposure (5.0 degrees C) increased TNF-alpha expression and macrophage infiltration in the lungs and PAs right before elevation of right ventricle systolic pressure.The in vivo RNA interference silencing of TNF-alpha was achieved by intravenous delivery of recombinant AAV-2 carrying TNF-alpha short hairpin small-interfering RNA 24 hours before cold exposure. Cold exposure for 8 weeks significantly increased right ventricle pressure compared with the warm controls (40.19 +/- 4.9 versus 22.9 +/- 1.1 mm Hg), indicating that cold exposure caused PH. Cold exposure increased TNF-alpha, interleukin-6, and phosphodiesterase-1C protein expression in the lungs and PAs and increased lung macrophage infiltration. Notably, TNF-alpha short hairpin small-interfering RNA prevented the cold-induced increases in TNF-alpha, interleukin-6, and phosphodiesterase-1C protein expression, abolished lung macrophage infiltration, and attenuated PH (26.28 +/- 1.6 mm Hg), PA remodeling, and right ventricle hypertrophy. PA smooth muscle cells isolated from cold-exposed animals showed increased intracellular superoxide levels and cell proliferation along with decreased intracellular cGMP. These cold-induced changes were prevented by TNF-alpha short hairpin small-interfering RNA. In conclusions, upregulation of TNF-alpha played a critical role in the pathogenesis of cold-induced PH by promoting pulmonary macrophage infiltration and inflammation. AAV delivery of TNF-alpha short hairpin small-interfering RNA may be an effective therapeutic approach for cold-induced PH and PA remodeling.