MicroRNA-155 promotes atherosclerosis by repressing Bcl6 in macrophages
Maliheh Nazari-Jahantigh, … , Christian Weber, Andreas Schober
Maliheh Nazari-Jahantigh, … , Christian Weber, Andreas Schober
Published November 1, 2012; First published October 8, 2012
Citation Information: J Clin Invest. 2012;122(11):4190-4202. https://doi.org/10.1172/JCI61716.
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Categories: Research Article Cardiology

MicroRNA-155 promotes atherosclerosis by repressing Bcl6 in macrophages

Abstract

Macrophages in atherosclerotic plaques drive inflammatory responses, degrade lipoproteins, and phagocytose dead cells. MicroRNAs (miRs) control the differentiation and activity of macrophages by regulating the signaling of key transcription factors. However, the functional role of macrophage-related miRs in the immune response during atherogenesis is unknown. Here, we report that miR-155 is specifically expressed in atherosclerotic plaques and proinflammatory macrophages, where it was induced by treatment with mildly oxidized LDL (moxLDL) and IFN-γ. Leukocyte-specific Mir155 deficiency reduced plaque size and number of lesional macrophages after partial carotid ligation in atherosclerotic (Apoe–/–) mice. In macrophages stimulated with moxLDL/IFN-γ in vitro, and in lesional macrophages, loss of Mir155 reduced the expression of the chemokine CCL2, which promotes the recruitment of monocytes to atherosclerotic plaques. Additionally, we found that miR-155 directly repressed expression of BCL6, a transcription factor that attenuates proinflammatory NF-κB signaling. Silencing of Bcl6 in mice harboring Mir155–/– macrophages enhanced plaque formation and CCL2 expression. Taken together, these data demonstrated that miR-155 plays a key role in atherogenic programming of macrophages to sustain and enhance vascular inflammation.

Authors

Maliheh Nazari-Jahantigh, Yuanyuan Wei, Heidi Noels, Shamima Akhtar, Zhe Zhou, Rory R. Koenen, Kathrin Heyll, Felix Gremse, Fabian Kiessling, Jochen Grommes, Christian Weber, Andreas Schober

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Figure 6

Identification of miR-155 targets in BMDMs.

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Identification of miR-155 targets in BMDMs. (A and B) Effect of Mir155 d...
(A and B) Effect of Mir155 deficiency on expression of potential miR-155 targets Hif1a (n = 4) and Rela, Socs1, Tcf7l2, Bcl6, Pparg, and Sfpi1 (n = 3 for each) in unstimulated (A) and moxLDL- and IFN-γ–stimulated (B) BMDMs. *P < 0.05 vs. Mir155+/+. (C) Quantitative RT-PCR of miR-155 in immunoprecipitates from moxLDL- and IFN-γ–stimulated Mir155+/+ and Mir155–/– BMDMs. Precipitates were obtained after incubation of cell lysates with an anti-EIF2C2 or nonspecific IgG control antibody (n = 4 independent experiments per group). *P < 0.05 vs. IgG. (D) Enrichment of potential miR-155 targets in EIF2C2-IP from moxLDL/IFN-γ–stimulated Mir155+/+ and Mir155–/– BMDMs by quantitative RT-PCR (n = 3–4 independent experiments per group). Results are expressed as target enrichment in Mir155–/– BMDMs normalized to that in Mir155+/+ BMDMs. *P < 0.05 vs. Mir155+/+. (E) Potential target sites for miR-155 in the 3′UTR of murine Bcl6 mRNA, as predicted by the miRanda prediction algorithm (sites A and B; blue). Target site A (sequence highlighted in green) was mutated in the binding region. The same sites in the human Bcl6 3′UTR are also predicted binding sites for human miR-155, differing from mouse miR-155 by 1 nucleotide. (F) Luciferase reporter assays in HEK293 cells treated with miR-155 mimics or nontargeting control mimics using the pEZX-MT01 vector containing the Bcl6 3′UTR or the Bcl6 3′UTR with mutations in predicted miR-155 binding site A (n = 3 independent experiments per group). *P < 0.05 vs. control. Data are mean ± SEM.