RESUMEN
The discovery and replacement of lung surfactant have helped increase survival rates for neonatal respiratory distress syndrome in extremely premature infants.
Asunto(s)
Recien Nacido Prematuro , Surfactantes Pulmonares , Síndrome de Dificultad Respiratoria del Recién Nacido , Humanos , Recién Nacido , Recien Nacido Extremadamente Prematuro , Surfactantes Pulmonares/metabolismo , Historia del Siglo XXRESUMEN
We have reported previously that during hypoxia exposure, the expression of mature miR-17â¼92 was first upregulated and then downregulated in pulmonary artery smooth muscle cells (PASMC) and in mouse lungs in vitro and in vivo. Here, we investigated the mechanisms regulating this biphasic expression of miR-17â¼92 in PASMC in hypoxia. We measured the level of primary miR-17â¼92 in PASMC during hypoxia exposure and found that short-term hypoxia exposure (3% O2, 6 h) induced the level of primary miR-17â¼92, whereas long-term hypoxia exposure (3% O2, 24 h) decreased its level, suggesting a biphasic regulation of miR-17â¼92 expression at the transcriptional level. We found that short-term hypoxia-induced upregulation of miR-17â¼92 was hypoxia-inducible factor 1α (HIF1α) and E2F1 dependent. Two HIF1α binding sites on miR-17â¼92 promoter were identified. We also found that long-term hypoxia-induced suppression of miR-17â¼92 expression could be restored by silencing of p53. Mutation of the p53-binding sites in the miR-17â¼92 promoter increased miR-17â¼92 promoter activity in both normoxia and hypoxia. Our findings suggest that the biphasic transcriptional regulation of miR-17â¼92 during hypoxia is controlled by HIF1/E2F1 and p53 in PASMC: during short-term hypoxia exposure, stabilization of HIF1 and induction of E2F1 induce the transcription of miR-17â¼92, whereas during long-term hypoxia exposure, hyperphosphorylation of p53 suppresses the expression of miR-17â¼92.NEW & NOTEWORTHY We showed that the biphasic transcriptional regulation of miR-17â¼92 during hypoxia is controlled by two distinct mechanisms: during short-term hypoxia exposure, induction of HIF1 and E2F1 upregulates miR-17â¼92. Longer hypoxia exposure induces hyperphosphorylation of p53 at ser15, which leads to its binding to miR-17â¼92 promoter and inhibition of its expression. Our findings provide novel insights into the spatiotemporal regulation of miR-17â¼92 that may play a role in the development of human lung diseases including pulmonary hypertension (PH).