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

Abstract

In acute inflammation, extracellular ATP activates P2X 7 ion channel receptors (P2X 7 R) on M1 polarized macrophages to release pro-inflammatory IL-1b 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-1b 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-1b release by other stimuli through two independent mechanisms: inhibition of ROS production and trapping of the inflammasome complex through intracellular clustering of actin filaments.

Selective Impairment of P2Y Signaling by Prostaglandin E2 in Macrophages: Implications for Ca2+-Dependent Responses

“…In addition to this, during macrophage transition from M1 to M2 phenotype, it has been described the uncoupling of P2X7 receptor signaling to reactive oxygen species production, NLRP-3 inflammasome/caspase-1 cascade activation, and IL-b release. The effect of extracellular ATP on antiinflammatory phenotype progression does not involve P2Y/P2X receptor-mediated processes but is dependent on pyrophosphate ATP chains, which induce actin cytoskeletal rearrangements/actin filaments clustering that trap inflammasome complex (54). In agreement with this, ectonucleotidases seem to play a role in the FIGURE 5.…”

“…LPS-treated macrophages (M1) show a rapid and sustained suppression of phospholipase C b1 and b2 expression that could affect P2 receptor signaling (65). It is well established that in M1 macrophages P2X7 receptor induce the release of IL-1b (52,54). In addition to this, during macrophage transition from M1 to M2 phenotype, it has been described the uncoupling of P2X7 receptor signaling to reactive oxygen species production, NLRP-3 inflammasome/caspase-1 cascade activation, and IL-b release.…”

CLEC5A is critical for dengue virus–induced inflammasome activation in human macrophages

“…In addition, Pelegrin and Surprenant found that exogenous ATP activated NLRP3 inflammasome to produce IL-1␤ via induction of ROS in LPS/IFN-␥ polarized murine BMM , whereas exogenous ATP inhibited ROS and was unable to activate NLRP3 inflammasome in IL-4-polarized murine BMM . 47 This indicated that distinct BMM subset responds oppositely to ATP simulation. Therefore, the local environment of inflammatory sites has strong influences on macrophage differentiation and affect their response to same stimuli.…”

P2X7 Receptor-Dependent Intestinal Afferent Hypersensitivity in a Mouse Model of Postinfectious Irritable Bowel Syndrome

“…Sections were blocked for 20 min with 3% BSA (Dako Diagnostics) supplemented with 1% swine serum (Dako Diagnostics) or rabbit serum (Vector Labs) for T-CD3 or IL-1b immunostaining, respectively. Three well-validated primary Abs were used for immunostaining: a polyclonal rabbit anti-CD3 Ab (1:50; Dako Diagnostics), a monoclonal rat anti-IL-1b Ab (1:100; R&D Systems), and a polyclonal anti-P2X 7 C terminus Ab (1:100; Sigma) (25)(26)(27). Sections were incubated with the Abs overnight at 4˚C.…”