Abstract 11386: Nitric Oxide Up-regulates MicroRNA-210 to Repress Iron-Sulfur Cluster-dependent Mitochondrial Metabolism in Vascular Endothelial Cells
Background: Exposure of vascular endothelium to nitric oxide (NO) induces pleiotropic responses such as repression of mitochondrial metabolism. In the short term, this is adaptive but chronically results in vascular and organ dysfunction. Hypoxia induces a similar metabolic switch — it is regulated by a master transcription factor, HIF-1α; and as we recently reported, HIF-1α up-regulates microRNA-210 (miR-210) to repress iron-sulfur cluster (ISC) assembly and ISC-dependent mitochondrial function. Since NO also up-regulates HIF-1α, we propose miR-210 as a novel regulatory factor that modulates NO-dependent repression of mitochondrial function in vascular endothelium.
Methods and Results: In human pulmonary arterial endothelial cells (HPAECs), miR-210 is upregulated by hypoxia (30.4 fold change±4.15619, mean± SEM) or the nitric oxide donor DETA-NONOate (4.6 fold change±0.25, mean± SEM) in a HIF-1α-dependent manner, as assessed by quantitative PCR. Using bioinformatics algorithms and reporter/gene expression assays, we identify the iron-sulfur cluster assembly proteins (ISCU1/2) as direct targets for repression by miR-210, and correspondingly, we show that hypoxia or NO downregulates ISCU1/2 expression. ISCU1/2 direct the assembly of iron-sulfur clusters, prosthetic groups essential for electron transport and redox reactions. Through upregulating miR-210 and repressing ISCU1/2, the in vivo integrity of iron-sulfur clusters is disrupted, as assessed by >45% reduction of spectroscopic signal by electron paramagnetic resonance. In turn, by using miRNA oligonucleotide duplex mimics and antisense inhibitors, we find that miR-210 controls, at least in part, NO-dependent repression of iron-sulfur enzyme activities such as Complex I (2.3 fold upregulation±0.28 of Complex I specific activity by inhibition of miR-210 in the presence of NO).
Conclusions: During hypoxia or NO exposure, miR-210 downregulates ISCU1/2 to repress iron-sulfur dependent metabolic processes. These results identify a novel shared connection between hypoxia and NO signaling, and they suggest overlapping mechanisms by which iron-sulfur cluster moieties are maintained in vascular health and dysregulated in disease.
- © 2010 by American Heart Association, Inc.