Targeted Delivery of Sildenafil for Inhibiting Pulmonary Vascular Remodeling

Pulmonary arterial hypertension is a fatal lung disease caused by the progressive remodeling of small pulmonary arteries (PAs). Sildenafil can prevent the remodeling of PAs, but conventional sildenafil formulations have shown limited treatment efficacy for their poor accumulation in PAs. Here, glucuronic acid (GlcA)-modified liposomes (GlcA-Lips) were developed to improve the delivery of sildenafil to aberrant over-proliferative PA smooth muscle cells via targeting the GLUT-1 (glucose transport-1), and, therefore, inhibiting the remodeling of PAs in a monocrotaline-induced PA hypertension model. GlcA-Lips encapsulating sildenafil (GlcA-sildenafil-Lips) had a size of 90 nm and a pH-sensitive drug release pattern. Immunostaining assay indicated the overexpression of GLUT-1 in PA smooth muscle cells. Cellular uptake studies showed a 1-fold increase of GlcA-Lips uptake by PA smooth muscle cells and pharmacokinetics and biodistribution experiments indicated longer blood circulation time of GlcA-Lips and increased ability to target PAs by 1-fold after 8 hours administration. Two-week treatment indicated GlcA-sildenafil-Lips significantly inhibited the remodeling of PAs, with a 32% reduction in the PA pressure, a 41% decrease in the medial thickening, and a 44% reduction of the right ventricle cardiomyocyte hypertrophy, and improved survival rate. Immunohistochemical analysis showed enhanced expression of caspase-3, after administration of GlcA-sildenafil-Lips, and reduced expression of P-ERK1/2 (phosphorylated ERK1/2) and HK-2 (hexokinase-2), and increased level of eNOS (endothelial nitric oxide synthase) and cyclic GMP (cGMP). In conclusion, targeted delivery of sildenafil to PA smooth muscle cells with GlcA-Lips could effectively inhibit the remodeling of PAs in the monocrotaline-induced PA hypertension.