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miR-125a-5p regulates differential activation of macrophages and inflammation
Sami Banerjee1, Huachun Cui, Na Xie
1From the Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294 and.
Abstract:
Macrophage activation is a central event in immune responses. Macrophages undergoing classical activation (M1 macrophages) are proinflammatory, whereas alternatively activated macrophages (M2 macrophages) are generally anti-inflammatory. miRNAs play important regulatory roles in inflammatory response. However, the manner in which miRNAs regulate macrophage activation in response to different environmental cues has not been well defined. In this study, we found that M-BMM macrophages (M2) express greater levels of miR-125a-5p than do GM-BMM macrophages (M1). Stimulation of macrophages through TLR2 and TLR4 but not through TLR3 enhanced miR-125a-5p expression. Up-regulation of miR-125a-5p after TLR2/4 activation requires the adaptor MYD88 but not TRIF. Overexpression of miR-125a-5p diminished M1 phenotype expression induced by LPS but promoted M2 marker expression induced by IL-4. In contrast, knockdown of miR-125a-5p promoted M1 polarization and diminished IL-4-induced M2 marker expression. We found that miR-125a-5p targets KLF13, a transcriptional factor that has an important role in T lymphocyte activation and inflammation. KLF13 knockdown had similar effects on M1 activation as did miR-125a-5p overexpression. In addition, miR-125a-5p regulates phagocytic and bactericidal activities of macrophages. Our data suggest that miR-125a-5p has an important role in suppressing classical activation of macrophages while promoting alternative activation.
Insights
MicroRNAs regulate macrophage activation. miR-125a-5p suppresses proinflammatory M1 macrophage activation and promotes anti-inflammatory M2 activation by targeting KLF13.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Macrophage activation is crucial for immune responses, with M1 (proinflammatory) and M2 (anti-inflammatory) phenotypes.
- MicroRNAs (miRNAs) are key regulators of inflammation, but their specific roles in macrophage polarization remain unclear.
Purpose of the Study:
- To investigate the role of miR-125a-5p in regulating macrophage activation phenotypes.
- To identify the molecular mechanisms by which miR-125a-5p influences M1 and M2 polarization.
Main Methods:
- Comparing miR-125a-5p levels in M1 and M2 macrophages.
- Stimulating macrophages via Toll-like receptors (TLR2, TLR4, TLR3) and assessing miR-125a-5p expression.
- Overexpressing and knocking down miR-125a-5p to observe effects on macrophage polarization markers.
- Identifying miR-125a-5p targets using molecular assays.
- Evaluating macrophage phagocytic and bactericidal activities.
Main Results:
- M2 macrophages express higher miR-125a-5p than M1 macrophages.
- TLR2 and TLR4 stimulation upregulate miR-125a-5p via MYD88.
- miR-125a-5p overexpression inhibits M1 polarization and enhances M2 polarization.
- miR-125a-5p knockdown promotes M1 polarization and reduces M2 polarization.
- KLF13 is identified as a direct target of miR-125a-5p, and its knockdown mimics miR-125a-5p overexpression effects.
- miR-125a-5p influences macrophage phagocytic and bactericidal functions.
Conclusions:
- miR-125a-5p acts as a negative regulator of classical (M1) macrophage activation.
- miR-125a-5p promotes alternative (M2) macrophage activation.
- The miR-125a-5p/KLF13 axis is a novel mechanism controlling macrophage polarization and function.
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