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Updated: Jun 22, 2026
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
Dynamics of macrophage polarization reveal new mechanism to inhibit IL-1beta release through pyrophosphates
Pablo Pelegrin1, Annmarie Surprenant
1Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK. pablo.pelegrin@ffis.es
Abstract:
In acute inflammation, extracellular ATP activates P2X(7) ion channel receptors (P2X(7)R) on M1 polarized macrophages to release pro-inflammatory IL-1beta through activation of the caspase-1/nucleotide-binding domain and leucine-rich repeat receptor containing pyrin domain 3 (NLRP3) inflammasome. In contrast, M2 polarized macrophages are critical to the resolution of inflammation but neither actions of P2X(7)R on these macrophages nor mechanisms by which macrophages switch from pro-inflammatory to anti-inflammatory phenotypes are known. Here, we investigated extracellular ATP signalling over a dynamic macrophage polarity gradient from M1 through M2 phenotypes. In macrophages polarized towards, but not at, M2 phenotype, in which intracellular IL-1beta remains high and the inflammasome is intact, P2X(7)R activation selectively uncouples to the NLRP3-inflammasome activation but not to upstream ion channel activation. In these intermediate M1/M2 polarized macrophages, extracellular ATP now acts through its pyrophosphate chains, independently of other purine receptors, to inhibit IL-1beta release by other stimuli through two independent mechanisms: inhibition of ROS production and trapping of the inflammasome complex through intracellular clustering of actin filaments.
Insights
Extracellular ATP binding to P2X7 receptors (P2X7R) on M1 macrophages releases IL-1beta. On intermediate M1/M2 macrophages, P2X7R activation inhibits IL-1beta release by blocking ROS and trapping the inflammasome.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Extracellular ATP (eATP) and P2X7 receptors (P2X7R) mediate pro-inflammatory IL-1beta release from M1 macrophages via the NLRP3 inflammasome.
- M2 macrophages resolve inflammation, but P2X7R roles and M1-to-M2 phenotype switching mechanisms remain unclear.
Purpose of the Study:
- Investigate eATP signaling in macrophages transitioning from M1 to M2 phenotypes.
- Elucidate P2X7R function during macrophage polarization and its impact on IL-1beta release.
Main Methods:
- Macrophage polarization induction.
- Extracellular ATP stimulation.
- P2X7R activation assays.
- IL-1beta release measurements.
- Reactive Oxygen Species (ROS) production assessment.
- Inflammasome complex and actin filament dynamics imaging.
Main Results:
- In M1/M2 intermediate macrophages, P2X7R activation uncouples from NLRP3 inflammasome activation.
- eATP, via pyrophosphate chains, inhibits IL-1beta release from other stimuli.
- This inhibition occurs through ROS production suppression and inflammasome complex trapping via actin filament clustering.
Conclusions:
- P2X7R signaling in intermediate M1/M2 macrophages shifts from pro-inflammatory to anti-inflammatory roles.
- eATP acts as a regulator of macrophage phenotype and inflammatory response, distinct from its role in M1 cells.
- These findings reveal novel mechanisms for controlling IL-1beta release and macrophage polarization.
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