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The proliferation of pulmonary artery smooth muscle cells (PASMCs) is an important cause of pulmonary vascular remodeling in pulmonary hypertension (PH). It has been reported that miR-137 inhibits the proliferation of tumor cells. However, whether miR-137 is involved in PH remains unclear. In this study, male Sprague-Dawley rats were subjected to 10% O2 for 3 weeks to establish PH, and rat primary PASMCs were treated with hypoxia (3% O2) for 48 h to induce cell proliferation. The effect of miR-137 on PASMC proliferation and calpain-2 expression was assessed by transfecting miR-137 mimic and inhibitor. The effect of calpain-2 on PASMC proliferation was assessed by transfecting calpain-2 siRNA. The present study found for the first time that miR-137 was downregulated in pulmonary arteries of hypoxic PH rats and in hypoxia-treated PASMCs. miR-137 mimic inhibited hypoxia-induced PASMC proliferation and upregulation of calpain-2 expression in PASMCs. Furthermore, miR-137 inhibitor induced the proliferation of PASMCs under normoxia, and knockdown of calpain-2 mRNA by siRNA significantly inhibited hypoxia-induced proliferation of PASMCs. Our study demonstrated that hypoxia-induced downregulation of miR-137 expression promoted the proliferation of PASMCs by targeting calpain-2, thereby potentially resulting in pulmonary vascular remodeling in hypoxic PH. [ABSTRACT FROM AUTHOR]

Background: Pulmonary arterial hypertension (PAH) is characterized by the apoptosis resistance and hyperproliferation of pulmonary artery smooth muscle cells (PASMCs). Its pathogenesis has not been revealed. Here, we carried out experiments to investigate the functions of miR‐140‐5p and tumor necrosis factor‐α (TNF‐α). Methods: We selected GSE703 from Gene Expression Omnibus (GEO) Database to conduct microarray analysis using R software and Gene Set Enrichment Analysis (GSEA). Combing bioinformatics results, the upregulation of miR‐140‐5p inhibited PAH progression through targeting TNF‐α. RNA expression was measured by quantitative real‐time polymerase chain reaction (RT‐qPCR) and protein level was measured by western blot analysis and enzyme‐linked immunosorbent assays (ELISA). We conducted monocrotaline (MCT) injection to rats to form PAH animal models. The lung tissues were observed by hematoxylin–eosin (HE) staining and Sirius red‐picric acid staining. Right ventricular systolic pressure (RVSP) and the ratio of right ventricle (RV)‐to‐left ventricle (LV) plus septum (S) weight (RV/[LV + S]) were measured in MCT‐induced animal models. Overexpression of miR‐140‐5p and TNF‐α were utilized to research the proliferation, migration, and phenotypic variation of hypoxia‐mediated PASMCs. The binding between miR‐140‐5p and TNF‐α 3′‐untranslated region (3′‐UTR) was confirmed via luciferase reporter assay. Results: Downregulation of miR‐140‐5p and upregulation of TNF‐α were observed in PAH rat model and hypoxia‐mediated PASMCs. And we proved that overexpression of miR‐140‐5p could suppress the proliferation, migration, and phenotypic variation of PASMCs, therefore inhibiting PAH pathogenesis. Luciferase assay verified that miR‐140‐5p targeted TNF‐α directly. A converse correlation was also shown between miR‐140‐5p and TNF‐α in PASMCs. Conclusions: miR‐140‐5p and TNF‐α are important regulators in PAH pathology and may serve as a therapeutic target for PAH. miR‐140‐5p might inhibit the occurrence and development of pulmonary arterial hypertension (PAH) by repressing tumor necrosis factor‐α (TNF‐α) expression via the TNF signaling pathway. These findings may help in the search of promising strategies for achieving better treatment outcome in patients diagnosed with PAH. [ABSTRACT FROM AUTHOR]

Aim Chronic hypoxia leads to right ventricular hypertrophy (RVH). RVH is believed to result from hypoxia-induced pulmonary hypertension. However, if hypoxia impacts RVH directly awaits clarification. Hypoxia triggers oxidative stress, and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) mediates reactive oxygen species (ROS) generation in different cells. Therefore, this study aims to explore whether LOX-1-mediated oxidative stress accounts for hypoxia-induced RVH. Main methods Rats developed RVH after 3 weeks of hypoxia (10% O 2 ). Immunofluorescence staining was performed to evaluate H9C2 cell hypertrophy induced by hypoxia (3% O 2 ). Real-time PCR and Western-blot were performed to assess LOX-1, NADPH oxidases (NOX), collagen I/III, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) expression. DCFH-DA staining was performed to measure ROS generation. Key findings Hypoxia induced RVH and cardiac fibrosis in rats, as indicated by enlarged cardiomyocytes and deposition of extracellular matrix. Interestingly, hypoxia treatment directly induced H9C2 cardiomyocyte hypertrophy, implying direct effects of hypoxia on cell hypertrophy. Rat and H9C2 hypertrophy model revealed that cell hypertrophy was accompanied by marked increase in LOX-1 expression. Knockdown of LOX-1 significantly ameliorated H9C2 cell hypertrophy. Mechanistically, hypoxia induced prominent oxidative stress in rat right ventricles and H9C2 cells, most likely as a result from increased expression of NOX2/4, contributing to RVH. Knockdown of LOX-1 significantly attenuated H9C2 cell oxidative stress, with a concomitant decrease in NOX2/4 expression. Significance LOX-1/NOX/ROS pathway could represent a novel mechanism underlying hypoxia-induced RVH. Therapeutic targeting of LOX-1 would be exploited to treat RVH owing to chronic hypoxia exposure. [ABSTRACT FROM AUTHOR]

Aims Pulmonary hypertension (PH) is a proliferative disorder characterized by enhanced proliferation and suppressed apoptosis of intrapulmonary vascular smooth muscle cells. Recently, network-based bioinformatics have identified let-7 family, a tumor suppressive microRNA, regulate multiple interacting targets relevant to PH. However, the role of let-7 in vascular homeostasis in PH remains unknown. Thus, we wanted to investigate the role of let-7 in hypoxia-induced PASMCs proliferation and the underlying mechanism in hypoxic pulmonary hypertension (HPH). Main methods The male Sprague–Dawley (SD) rats were exposed to hypoxia (10% O 2 ) for 21 days to induce HPH. The expression of let-7 was determined by quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization. Primary rat PASMCs were exposed to hypoxia (3% O 2 ). MTS and EDU were performed to evaluate PASMCs proliferation. The mRNA and protein expression of c-myc, Bmi-1 and p16 were determined by qRT-PCR and Western blotting, respectively. The functions of let-7g on PASMCs proliferation, c-myc, Bmi-1 and p16 expression were assessed by let-7g mimic and inhibitor transfection. Key findings Among let-7 family members, only let-7b and let-7g were significantly down-regulated in remodeled pulmonary artery in HPH rats. Furthermore, only let-7g level was decreased in hypoxic PASMCs. Either hypoxia or let-7g inhibitor stimulated proliferation of PASMCs, let-7g mimic inhibited hypoxia-induced PASMCs proliferation. C-myc was the target of let-7g in PASMCs. Transfect of let-7g mimic inhibited hypoxia-induced c-myc, Bmi-1 up-regulation and p16 down-regulation, which ultimately controls cell cycle progression. Significance Loss of inhibition on c-myc-Bmi-1-p16 signaling pathway by let-7g may lead to PASMCs proliferation and vascular remodeling in HPH. [ABSTRACT FROM AUTHOR]