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Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
MicroRNA-223 is a crucial mediator of PPARγ-regulated alternative macrophage activation
Abstract:
Polarized activation of adipose tissue macrophages (ATMs) is crucial for maintaining adipose tissue function and mediating obesity-associated cardiovascular risk and metabolic abnormalities; however, the regulatory network of this key process is not well defined. Here, we identified a PPARγ/microRNA-223 (miR-223) regulatory axis that controls macrophage polarization by targeting distinct downstream genes to shift the cellular response to various stimuli. In BM-derived macrophages, PPARγ directly enhanced miR-223 expression upon exposure to Th2 stimuli. ChIP analysis, followed by enhancer reporter assays, revealed that this effect was mediated by PPARγ binding 3 PPARγ regulatory elements (PPREs) upstream of the pre-miR-223 coding region. Moreover, deletion of miR-223 impaired PPARγ-dependent macrophage alternative activation in cells cultured ex vivo and in mice fed a high-fat diet. We identified Rasa1 and Nfat5 as genuine miR-223 targets that are critical for PPARγ-dependent macrophage alternative activation, whereas the proinflammatory regulator Pknox1, which we reported previously, mediated miR-223-regulated macrophage classical activation. In summary, this study provides evidence to support the crucial role of a PPARγ/miR-223 regulatory axis in controlling macrophage polarization via distinct downstream target genes.
Insights
This study reveals how PPARγ and microRNA-223 (miR-223) control macrophage polarization, impacting obesity-related health risks. This regulatory axis influences adipose tissue macrophages (ATMs) and metabolic functions.
Area of Science:
- Immunology
- Metabolic Disease Research
- Molecular Biology
Background:
- Adipose tissue macrophage (ATM) polarization is vital for metabolic health and obesity-associated cardiovascular risks.
- The precise regulatory mechanisms governing ATM polarization remain incompletely understood.
Purpose of the Study:
- To elucidate the regulatory network controlling macrophage polarization.
- To identify key molecular players in PPARγ-mediated macrophage activation.
Main Methods:
- Investigated the PPARγ/microRNA-223 (miR-223) axis in bone marrow-derived macrophages.
- Utilized Chromatin Immunoprecipitation (ChIP) and enhancer reporter assays.
- Assessed macrophage polarization in ex vivo cultures and high-fat diet-fed mice with miR-223 deletion.
Main Results:
- Identified a PPARγ/miR-223 regulatory axis controlling macrophage polarization.
- Demonstrated PPARγ directly enhances miR-223 expression via binding to upstream regulatory elements.
- Showed that miR-223 is critical for PPARγ-dependent alternative macrophage activation, targeting Rasa1 and Nfat5.
- Confirmed miR-223 regulates classical macrophage activation through Pknox1.
Conclusions:
- The PPARγ/miR-223 axis plays a crucial role in regulating macrophage polarization.
- Distinct downstream targets of miR-223 mediate its effects on alternative and classical macrophage activation.
- This axis is a key regulator of adipose tissue macrophage function and metabolic homeostasis.
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