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Background: Excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells (PASMCs) are key mechanisms of pulmonary arterial hypertension (PAH). Despite the multiple combination therapy, a considerable number of patients develop severe pulmonary hypertension (PH) because of the lack of diagnostic biomarker and antiproliferative therapies for PASMCs. Methods: Microarray analyses were used to identify a novel therapeutic target for PAH. In vitro experiments, including lung and serum samples from patients with PAH, cultured PAH-PASMCs, and high-throughput screening of 3336 low-molecular-weight compounds, were used for mechanistic study and exploring a novel therapeutic agent. Five genetically modified mouse strains, including PASMC-specific selenoprotein P (SeP) knockout mice and PH model rats, were used to study the role of SeP and therapeutic capacity of the compounds for the development of PH in vivo. Results: Microarray analysis revealed a 32-fold increase in SeP in PAH-PASMCs compared with control PASMCs. SeP is a widely expressed extracellular protein maintaining cellular metabolism. Immunoreactivity of SeP was enhanced in the thickened media of pulmonary arteries in PAH. Serum SeP levels were also elevated in patients with PH compared with controls, and high serum SeP predicted poor outcome. SeP-knockout mice ( SeP –/– ) exposed to chronic hypoxia showed significantly reduced right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary artery remodeling compared with controls. In contrast, systemic SeP-overexpressing mice showed exacerbation of hypoxia-induced PH. Furthermore, PASMC-specific SeP –/– mice showed reduced hypoxia-induced PH compared with controls, whereas neither liver-specific SeP knockout nor liver-specific SeP-overexpressing mice showed significant differences with controls. Altogether, protein levels of SeP in the lungs were associated with the development of PH. Mechanistic experiments demonstrated that SeP promotes PASMC proliferation and resistance to apoptosis through increased oxidative stress and mitochondrial dysfunction, which were associated with activated hypoxia-inducible factor-1α and dysregulated glutathione metabolism. It is important to note that the high-throughput screening of 3336 compounds identified that sanguinarine, a plant alkaloid with antiproliferative effects, reduced SeP expression and proliferation in PASMCs and ameliorated PH in mice and rats. Conclusions: These results indicate that SeP promotes the development of PH, suggesting that it is a novel biomarker and therapeutic target of the disorder.

Background: Thoracic aortic aneurysm (TAA) and dissection are fatal diseases that cause aortic rupture and sudden death. The small GTP-binding protein GDP dissociation stimulator (SmgGDS) is a crucial mediator of the pleiotropic effects of statins. Previous studies revealed that reduced force generation in aortic smooth muscle cells (AoSMCs) causes TAA and thoracic aortic dissection. Methods: To examine the role of SmgGDS in TAA formation, we used an angiotensin II (1000 ng·min −1 ·kg −1 , 4 weeks)–induced TAA model. Results: We found that 33% of Apoe −/− SmgGDS +/− mice died suddenly as a result of TAA rupture, whereas there was no TAA rupture in Apoe −/− control mice. In contrast, there was no significant difference in the ratio of abdominal aortic aneurysm rupture between the 2 genotypes. We performed ultrasound imaging every week to follow up the serial changes in aortic diameters. The diameter of the ascending aorta progressively increased in Apoe −/− SmgGDS +/− mice compared with Apoe −/− mice, whereas that of the abdominal aorta remained comparable between the 2 genotypes. Histological analysis of Apoe −/− SmgGDS +/− mice showed dissections of major thoracic aorta in the early phase of angiotensin II infusion (day 3 to 5) and more severe elastin degradation compared with Apoe −/− mice. Mechanistically, Apoe −/− SmgGDS +/− mice showed significantly higher levels of oxidative stress, matrix metalloproteinases, and inflammatory cell migration in the ascending aorta compared with Apoe −/− mice. For mechanistic analyses, we primary cultured AoSMCs from the 2 genotypes. After angiotensin II (100 nmol/L) treatment for 24 hours, Apoe −/− SmgGDS +/− AoSMCs showed significantly increased matrix metalloproteinase activity and oxidative stress levels compared with Apoe −/− AoSMCs. In addition, SmgGDS deficiency increased cytokines/chemokines and growth factors in AoSMCs. Moreover, expressions of fibrillin-1 ( FBN1 ), α-smooth muscle actin ( ACTA2 ), myosin-11 ( MYH11 ), MYLLK , and PRKG1 , which are force generation genes, were significantly reduced in Apoe −/− SmgGDS +/− AoSMCs compared with Apoe −/− AoSMCs. A similar tendency was noted in AoSMCs from patients with TAA compared with those from control subjects. Finally, local delivery of the SmgGDS gene construct reversed the dilation of the ascending aorta in Apoe −/− SmgGDS +/− mice. Conclusions: These results suggest that SmgGDS is a novel therapeutic target for the prevention and treatment of TAA.

Introduction: We have previously demonstrated that small GTP-binding protein dissociation stimulator (SmgGDS) plays a crucial role in the pleiotropic effects of HMG-CoA reductase inhibitors (statins) in mice and humans. In the present study, we tested our hypothesis that SmgGDS plays a crucial role in the inhibitory effects of statins on the development of cardiac hypertrophy and fibrosis. Methods & Results: We administered angiotensin II (AngII, 2 mg/kg/day, 2 weeks) to SmgGDS-deficient ( SmgGDS +/- ) mice and littermate controls ( SmgGDS +/+ ), which were orally treated with either statins (atorvastatin 10 mg/kg/day or pravastatin 50 mg/kg/day, n=10 each group) or vehicle. AngII equally elevated systolic blood pressure and promoted cardiac hypertrophy and fibrosis in SmgGDS +/+ and SmgGDS +/- . Both statins significantly reduced LV wall thickness, cardiac myocyte cross-sectional area, and fibrotic area in AngII-infused SmgGDS +/+ mice (all PSmgGDS +/- mice. Additionally, statins significantly improved LV diastolic function (E/A) in SmgGDS +/+ mice (PSmgGDS +/- mice. Interestingly, immunostaining revealed that SmgGDS was highly expressed in cardiac fibroblasts (CFs) in the heart of AngII-infused SmgGDS +/+ mice. Then, we harvested CFs from SmgGDS +/+ and SmgGDS +/- mice and stimulated them with AngII with or without statins. At baseline, SmgGDS +/- CFs showed significant increase in Rac1 expression (1.8-fold), ERK1/2 activity (4.0-fold), Rho-kinase activity (phospho-MYPT/total-MYPT, 1.4-fold) compared to SmgGDS +/+ CFs, whereas Akt activity was significantly less in SmgGDS +/- CFs compared to SmgGDS +/+ CFs (n=4, all PSmgGDS +/+ CFs (-30%, n=4, PSmgGDS +/- CFs, suggesting that SmgGDS mediates the inhibitory effects of statins on Rac1 signaling. Conclusions: These results indicate that SmgGDS plays a crucial role in the inhibitory effects of statins on cardiac hypertrophy and fibrosis, partly through inhibition of Rac1, Rho-kinase, and ERK1/2 pathways.