HIF-1 alpha-induced up-regulation of miR-9 contributes to phenotypic modulation in pulmonary artery smooth muscle cells during hypoxia.

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.

Shan F ，Li J ，Huang QY 《-》

MicroRNA-103/107 is involved in hypoxia-induced proliferation of pulmonary arterial smooth muscle cells by targeting HIF-1β.

Activation of hypoxia inducible factor-1 (HIF) is a hallmark in hypoxia-induced pulmonary hypertension (HPH). microRNAs play a significant role in regulating proliferation of pulmonary arterial smooth muscle cells (PASMCs) in pulmonary hypertension. Previous studies have shown that HIF-1β is a target of miR-103/107. In this present study, we aimed to investigate whether miR-103/107 regulate vascular remodeling in HPH via HIF-1β. The HPH model was built by hypoxia exposure in rats. Real-time PCR and Western blotting were used to determine the expression of miR-103/107 and HIF-1β. Proliferation of PASMCs was examined by 5-bromo-2'-deoxyuridine (BrdU) incorporation method. The functions of miR-103/107 on PASMCs proliferation, HIF-1α and HIF-1β expression were assessed by transfecting miR-103/107 mimics and inhibitors. Significant down-regulation of miR-103/107 was observed in remodeled intrapulmonary vascular in HPH rats and hypoxia-exposured PASMCs, whereas HIF-1α and HIF-1β expression were up-regulated. Hypoxia exposure induced significant proliferation of PASMCs, overexpression of miR-103/107 inhibited but miR-103/107 inhibitors exacerbated PASMCs proliferation. Gain-of-function and loss-of-function experiments showed that miR-103/107 expression was inversely correlated with HIF-1β level. No significant changes of HIF-1α expression were observed under miR-103/107 mimic treatment. Loss of suppression on HIF-1β by miR-103/107 may contribute to excess proliferation of PASMCs and vascular remodeling in hypoxic pulmonary hypertension.

Deng B ，Du J ，Hu R ，Wang AP ，Wu WH ，Hu CP ，Li YJ ，Li XH ... -  《-》

[Effect of opening of mitochondrial ATP-sensitive K(+) channels on the expression of hypoxia inducible factor-1alpha and cell proliferation in pulmonary arterial smooth muscle cells of rats].

Zhao JP ，Guo Z ，Zhou ZG ，Chen J ，Hu HL ，Wang T ，Zhang ZX ... -  《-》

[Effects of RNAi on hypoxia inducible factor-1alpha activity and proliferation of hypoxic pulmonary artery smooth muscle cells in rat].

Zhang W ，Cao Y ，Zhang Y ，Ma QS ，Ma L ，Ge RL ... -  《-》

Hypoxia inducible factor-1 mediates expression of miR-322: potential role in proliferation and migration of pulmonary arterial smooth muscle cells.

Zeng Y ，Liu H ，Kang K ，Wang Z ，Hui G ，Zhang X ，Zhong J ，Peng W ，Ramchandran R ，Raj JU ，Gou D ... -  《Scientific Reports》