Dynamics of macrophage polarization reveal new mechanism to inhibit IL‐1β release through pyrophosphates

P Pelegrin, A Surprenant - The EMBO journal, 2009 - embopress.org
P Pelegrin, A Surprenant
The EMBO journal, 2009embopress.org
In acute inflammation, extracellular ATP activates P2X7 ion channel receptors (P2X7R) on
M1 polarized macrophages to release pro‐inflammatory IL‐1β 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 P2X7R on these macrophages nor
mechanisms by which macrophages switch from pro‐inflammatory to anti‐inflammatory …
In acute inflammation, extracellular ATP activates P2X7 ion channel receptors (P2X7R) on M1 polarized macrophages to release pro‐inflammatory IL‐1β 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 P2X7R 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‐1β remains high and the inflammasome is intact, P2X7R 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‐1β release by other stimuli through two independent mechanisms: inhibition of ROS production and trapping of the inflammasome complex through intracellular clustering of actin filaments.
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