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Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by a sustained elevation of pulmonary artery (PA) pressure, right ventricular failure, and premature death. Enhanced proliferation and resistance to apoptosis (as seen in cancer cells) of PA smooth muscle cells (PASMCs) is a major pathological hallmark contributing to pulmonary vascular remodeling in PAH, for which current therapies have only limited effects. Emerging evidence points toward a critical role for Enhancer of Zeste Homolog 2 (EZH2) in cancer cell proliferation and survival. However, its role in PAH remains largely unknown. The aim of this study was to determine whether EZH2 represents a new factor critically involved in the abnormal phenotype of PAH-PASMCs. We found that EZH2 is overexpressed in human lung tissues and isolated PASMCs from PAH patients compared to controls as well as in two animal models mimicking the disease. Through loss- and gain-of-function approaches, we showed that EZH2 promotes PAH-PASMC proliferation and survival. By combining quantitative transcriptomic and proteomic approaches in PAH-PASMCs subjected or not to EZH2 knockdown, we found that inhibition of EZH2 downregulates many factors involved in cell-cycle progression, including E2F targets, and contributes to maintain energy production. Notably, we found that EZH2 promotes expression of several nuclear-encoded components of the mitochondrial translation machinery and tricarboxylic acid cycle genes. Overall, this study provides evidence that, by overexpressing EZH2, PAH-PASMCs remove the physiological breaks that normally restrain their proliferation and susceptibility to apoptosis and suggests that EZH2 or downstream factors may serve as therapeutic targets to combat pulmonary vascular remodeling. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is available in the text. 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. [ABSTRACT FROM AUTHOR]

Introduction: Pulmonary arterial hypertension (PAH) is characterized by enhanced proliferation and reduced apoptosis of pulmonary artery smooth muscle cells (PASMCs). Hypothesis: To discover a novel compound for PAH patients from the original 5,562 compounds of Tohoku University. Methods: We performed high-throughput screening using PASMCs from PAH patients (PAH-PASMCs). Next, we performed functional tests for emetine in vivo. Results: We found that emetine inhibits PAH-PASMC proliferation. Interestingly, emetine significantly reduced activities of HIF-1α and -2α in PAH-PASMCs (n=3 each, P <0.05). Consistently, emetine reduced secretion of inflammatory cytokines/chemokines and growth factors, and oxidative stress-augmenting proteins such as cyclophilin A and its receptor basigin in PAH-PASMCs (n=3 each, P <0.05). Moreover, emetine significantly suppressed Rho-kinase activity in PAH-PASMCs (n=3 each, P <0.05). Additionally, emetine increased apoptosis, detected by TUNEL assay and reduced the expression of the anti-apoptotic protein Bcl2 in PAH-PASMCs (n=3 each, P <0.05). Next, we performed functional tests for emetine in vivo. Six-week-old male SD rats were used for the two experimental PH models; monocrotaline-induced PH and Sugen/hypoxia-induced PH. In the prevention protocol, after subcutaneous injection of monocrotaline (60 mg/kg), the animals were assigned to the simultaneous oral administration with emetine (0.05 mg/kg/day) or vehicle for 3 weeks. Emetine significantly reduced right ventricular (RV) systolic pressure (57±3 vs. 77±4 mmHg), RV hypertrophy (0.40±0.02 vs. 0.50±0.02), and PA remodeling compared with controls (all P <0.01, n=10~15). In the treatment protocol, after establishment of PH with Sugen (20 mg/kg) and hypoxia (10% O2) for 3 weeks followed by normoxia for 6 weeks, the animals were assigned to the oral administration of emetine (0.05 mg/kg/day) or vehicle for additional 4 weeks. Emetine significantly reduced RV systolic pressure (93±5 vs. 59±5 mmHg), RV hypertrophy (0.52±0.04 vs. 0.35±0.02), and PA remodeling compared with controls (all P <0.01, n=10~12). Importantly, emetine significantly reduced TNF-α and MCP-1 in serum compared with vehicle controls, suggesting its potent anti-inflammatory effects in vivo. Finally, emetine significantly reduced protein levels of cyclophilin A, basigin, and Rho-kinase activities in both models in vivo. Conclusions: We identified emetine as a novel promising drug for the treatment of PAH. [ABSTRACT FROM AUTHOR]

Background: Thoracic aortic aneurysm (TAA) and dissection (TAD) are fatal diseases, which 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 AoSMCs causes TAA and TAD. Methods and Results: To examine the role of SmgGDS in TAA formation, we employed an angiotensin II (AngII, 1,000 ng/min/kg, 4weeks)-induced TAA model in Apoe-/-SmgGDS+/- (DKO)mice, in which 33% died suddenly due to TAA rupture, whereas there was no TAA rupture in Apoe-/- control mice. In contrast, there was no significant difference in the ratio of AAA rupture between the two genotypes. We performed ultrasound imaging every week to follow the serial changes in aortic diameters. The diameter of the ascending aorta progressively increased in DKO mice compared with Apoe-/- mice, whereas that of the abdominal aorta remained comparable between the two genotypes. Histological analysis of DKO mice showed dissections of major thoracic aorta in the early phase of AngII infusion (day 3~5) and more severe elastin degradation compared with Apoe -/- mice. Mechanistically, DKO 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 AngII (100 nM) treatment for 24 hours, DKO AoSMCs showed significantly increased MMP activity and oxidative stress levels compared with Apoe-/- AoSMCs. In addition, SmgGDS deficiency increased cytokines/chemokines and growth factors in AoSMCs. Moreover, force generation genes were significantly reduced in DKO AoSMCs compared with Apoe-/- AoSMCs. Importantly, RhoA and RhoC activities were significantly decreased in DKO AoSMCs compared with Apoe-/- AoSMCs. Similar tendency was noted in AoSMCs from TAA patients compared with those from controls. Finally, local delivery of the SmgGDS gene construct reversed the dilation of the ascending aorta and prevented TAA rupture in DKO mice. Conclusions: These results suggest that SmgGDS is a novel therapeutic target for the prevention and treatment of TAA. [ABSTRACT FROM AUTHOR]