title: HIF-1 alpha-induced up-regulation of miR-9 contributes to phenotypic modulation in pulmonary artery smooth muscle cells during hypoxia.
abstract: Pulmonary artery smooth muscle cells (PASMCs) are associated with the development of hypoxic pulmonary hypertension (HPH). Recent studies have implicated a critical role for microRNAs (miRNAs) in HPH; however, their expression and regulation in hypoxia-mediated phenotypic modulation of PASMCs remains largely unclear. Here, we report that miR-9 was induced in hypoxia and involved in a hypoxia-induced phenotypic switch in rat primary PASMCs. Knockdown of miR-9 followed by hypoxia exposure attenuated PASMCs proliferation and enhanced the expression of contractile genes in vascular smooth muscle cells (VSMCs), while overexpression of miR-9 in normoxia promoted a proliferative phenotype in PASMCs. The primary transcripts of miR-9-1 and miR-9-3, but not miR-9-2, increased dramatically after hypoxia, whereas silencing of the hypoxia-associated transcription factor HIF-1α following hypoxia exposure abolished the enhancement of both primary transcripts in PASMCs. Using in silico analysis, we found three putative HIF-1α binding motifs on miR-9-1 and one motif on miR-9-3 located within the 5-kb region upstream of the transcriptional start sites. Chromatin immunoprecipitation assay revealed that hypoxia enhanced the direct interaction between HIF-1α and the regulatory elements of miR-9-1 and miR-9-3. Reporter assays showed that the regulatory regions of miR-9-1 and miR-9-3 behaved as enhancers in a HIF-1α-dependent manner during hypoxia. Taken together, our data uncover a regulatory mechanism involving HIF-1α-mediated up-regulation of miR-9, which plays a role in the hypoxia-induced phenotypic switch of PASMCs.
authors.affiliation: Department of Pathophysiology and High Altitude Physiology, College of High Altitude Military Medicine, Chongqing, China; Key Laboratory of High Altitude Medicine, Ministry of Education, Chongqing, China; Key Laboratory of High Altitude Medicine, PLA, Third Military Medical University, Chongqing, China.
authors.forename: Fabo
authors.initials: F
authors.lastname: Shan
authors.forename: Junxia
authors.initials: J
authors.lastname: Li
authors.forename: Qing-Yuan
authors.initials: QY
authors.lastname: Huang
mesh_terms: D000818:Animals; D001665:Binding Sites; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D010641:Phenotype; D011651:Pulmonary Artery / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D013997:Time Factors; D024363:Transcription Initiation Site; D014162:Transfection; D015854:Up-Regulation
chemical_list: C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C582333:MIRN9 microRNA, rat; D035683:MicroRNAs