Forced expression of microRNA-146b reduces TRAF6-dependent inflammation and improves ischemia-induced neovascularization in hypercholesterolemic conditions.
BACKGROUND AND AIMS
MicroRNA (miR)-146 is a key regulator of inflammation, endothelial activation and atherosclerosis. This study sought to define its potential role for the modulation of ischemia-induced neovascularization in atherosclerotic conditions.


METHODS
Next generation sequencing and qRT-PCR analyses were used to compare microRNA expression in the ischemic muscles of hypercholesterolemic ApoE-deficient (ApoE-/-) mice vs. wild type mice, and in HUVECs exposed or not to oxLDL. Neovascularization was investigated in a mouse model of hindlimb ischemia and the functional activities of HUVECs and pro-angiogenic cells (PACs) were assessed in vitro.


RESULTS
We found that miR-146b (but not miR-146a) is significantly reduced in the ischemic muscles of ApoE-/- mice, and in HUVECs exposed to oxLDL. Inhibition of miR-146b reduces angiogenesis in vitro, whereas forced expression of miR-146b rescues oxLDL-mediated impairment of endothelial cell proliferation and tube formation. Mechanistically, miR146b directly targets tumor necrosis factor-alpha (TNFa) Receptor Associated Factor 6 (TRAF6) to inhibit inflammation. We found that hypercholesterolemia and oxLDL exposure are associated with higher levels of TRAF6, and increased expression of TNFa. However, forced expression of miR-146b in high cholesterol conditions reduces the expression of these inflammatory factors. In vivo, intramuscular injection of miR-146b mimic reduces ischemic damages and restores blood flow recuperation and capillary density in the ischemic muscles of ApoE-/- mice. Treatment with miR-146b also increases the number and functional activities of pro-angiogenic cells (PACs).


CONCLUSIONS
Hypercholesterolemia is associated with reduced expression of miR-146b, which increases TRAF6-dependent inflammation and is associated with poor neovascularization in response to ischemia. Forced expression of miR-146b using a miR mimic could constitute a novel therapeutic strategy to improve ischemia-induced neovascularization in atherosclerotic conditions.
['Desjarlais|Michel|M|', 'Dussault|Sylvie|S|', 'Rivard|François|F|', 'Harel|Sharon|S|', 'Sanchez|Veronica|V|', 'Hussain|Sabah N A|SNA|', 'Rivard|Alain|A|']
D000818:Animals D001783:Blood Flow Velocity D002465:Cell Movement D049109:Cell Proliferation D006614:Hindlimb D061307:Human Umbilical Vein Endothelial Cells D006801:Humans D006937:Hypercholesterolemia D007249:Inflammation D047908:Intracellular Signaling Peptides and Proteins D007511:Ischemia D008077:Lipoproteins, LDL D051379:Mice D000074085:Mice, Knockout, ApoE D035683:MicroRNAs D009389:Neovascularization, Pathologic D017382:Reactive Oxygen Species D017423:Sequence Analysis, RNA D000074084:THP-1 Cells D048029:TNF Receptor-Associated Factor 6
Inflammation Neovascularization microRNA Angiogenesis Hypercholesterolemia