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Circ Res. 2015 Jun 19;117(1):e1-e11. doi: 10.1161/CIRCRESAHA.117.305844. Epub 2015 Apr 22.

Apolipoprotein E enhances microRNA-146a in monocytes and macrophages to suppress nuclear factor-κB-driven inflammation and atherosclerosis.

Author information

1
From the Division of Vascular and Endovascular Surgery, Department of Surgery, University of California San Francisco and Veterans Affairs Medical Center.
2
From the Division of Vascular and Endovascular Surgery, Department of Surgery, University of California San Francisco and Veterans Affairs Medical Center. robert.raffai@ucsf.edu.

Abstract

RATIONALE:

Apolipoprotein E (apoE) exerts anti-inflammatory properties that protect against atherosclerosis and other inflammatory diseases. However, mechanisms by which apoE suppresses the cellular activation of leukocytes commonly associated with atherosclerosis remain incompletely understood.

OBJECTIVE:

To test the hypothesis that apoE suppresses inflammation and atherosclerosis by regulating cellular microRNA levels in these leukocytes.

METHODS AND RESULTS:

An assessment of apoE expression among such leukocyte subsets in wild-type mice revealed that only macrophages and monocytes express apoE abundantly. An absence of apoE expression in macrophages and monocytes resulted in enhanced nuclear factor-κB signaling and an exaggerated inflammatory response on stimulation with lipopolysaccharide. This correlated with reduced levels of microRNA-146a, a critical negative regulator of nuclear factor-κB signaling. Ectopic apoE expression in Apoe(-/-) macrophages and monocytes raised miR-146a levels, whereas its silencing in wild-type cells had an opposite effect. Mechanistically, apoE increased the expression of transcription factor purine-rich PU-box-binding protein 1, which raised levels of pri-miR-146 transcripts, demonstrating that apoE exerts transcriptional control over miR-146a. In vivo, even a small amount of apoE expression in macrophages and monocytes of hypomorphic apoE mice led to increased miR-146a levels, and inhibited macrophage proinflammatory responses, Ly-6C(high) monocytosis, and atherosclerosis in the settings of hyperlipidemia. Accordingly, cellular enrichment of miR-146a through the systemic delivery of miR-146a mimetics in Apoe(-/-)Ldlr(-/-) and Ldlr(-/-) mice attenuated monocyte/macrophage activation and atherosclerosis in the absence of plasma lipid reduction.

CONCLUSIONS:

Our data demonstrate that cellular apoE expression suppresses nuclear factor-κB-mediated inflammation and atherosclerosis by enhancing miR-146a levels in monocytes and macrophages.

KEYWORDS:

apolipoproteins E; atherosclerosis; macrophages; microRNAs

PMID:
25904598
PMCID:
PMC4475484
DOI:
10.1161/CIRCRESAHA.117.305844
[Indexed for MEDLINE]
Free PMC Article

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