title: MicroRNA let-7g inhibited hypoxia-induced proliferation of PASMCs via G0/G1cell cycle arrest by targeting c-myc.
abstract: OBJECTIVE
  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).
  
  
  METHODS
  The male Sprague-Dawley (SD) rats were exposed to hypoxia (10% O2) for 21days 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% O2). 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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Loss of inhibition on c-myc-Bmi-1-p16 signaling pathway by let-7g may lead to PASMCs proliferation and vascular remodeling in HPH.
authors.affiliation: Department of Pharmacy/Cardiovascular medicine, The Second Affiliated Hospital of Nanchang University, Nanchang 330006, China.
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Zhang
authors.affiliation: Jiangxi Supervision and Inspection Center for Medical Devices, Nanchang 330029, China.
authors.forename: You-Wen
authors.initials: YW
authors.lastname: Xiong
authors.affiliation: Department of Pharmacology, School of Pharmaceutical Science, Central South University, Changsha 410078, China.
authors.forename: Tian-Tian
authors.initials: TT
authors.lastname: Zhu
authors.affiliation: Department of Pharmacy/Cardiovascular medicine, The Second Affiliated Hospital of Nanchang University, Nanchang 330006, China.
authors.forename: Ai-Zhen
authors.initials: AZ
authors.lastname: Xiong
authors.affiliation: Department of Pharmacy/Cardiovascular medicine, The Second Affiliated Hospital of Nanchang University, Nanchang 330006, China.
authors.forename: Hui-Hui
authors.initials: HH
authors.lastname: Bao
authors.affiliation: Department of Pharmacy/Cardiovascular medicine, The Second Affiliated Hospital of Nanchang University, Nanchang 330006, China. Electronic address: xiaoshumenfan@126.com.
authors.forename: Xiao-Shu
authors.initials: XS
authors.lastname: Cheng
mesh_terms: D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints; D006706:Homeostasis; D006976:Hypertension, Pulmonary / Q000378:metabolism* / Q000473:pathology; D000860:Hypoxia; D017403:In Situ Hybridization; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D032389:Myocytes, Smooth Muscle / Q000166:cytology; D063150:Polycomb Repressive Complex 1 / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016192:Resting Phase, Cell Cycle; D015398:Signal Transduction; D066253:Vascular Remodeling / Q000502:physiology
chemical_list: C489420:Bmi1 protein, rat; D019941:Cyclin-Dependent Kinase Inhibitor p16; C548145:MIRNLET7 microRNA, rat; D035683:MicroRNAs; D016271:Proto-Oncogene Proteins c-myc; D063150:Polycomb Repressive Complex 1
keywords: Cell cycle; Cell proliferation; HPH; Vascular remodeling; let-7; microRNA