The role of microglial P2X7: modulation of cell death and cytokine release

Abstract

BackgroundATP-gated P2X7 is a non-selective cation channel, which participates in a wide range of cellular functions as well as pathophysiological processes including neuropathic pain, immune response, and neuroinflammation. Despite its abundant expression in microglia, the role of P2X7 in neuroinflammation still remains unclear.MethodsPrimary microglia were isolated from cortices of P0-2 C57BL/6 wild-type or P2X7 knockout (P2X7−/−) mouse pups. Lipopolysaccharide, lipopolysaccharide plus IFNγ, or IL4 plus IL13 were used to polarize microglia to pro-inflammatory or anti-inflammatory states. P2rx7 expression level in resting or activated mouse and human microglia was measured by RNA-sequencing and quantitative real-time PCR. Microglial cell death was measured by cell counting kit-8 and immunocytochemistry, and microglial secretion in wild-type or P2X7−/− microglia was examined by Luminex multiplex assay or ELISA using P2X7 agonist BzATP or P2X7 antagonist A-804598. P2X7 signaling was analyzed by Western blot.ResultsFirst, we confirmed that P2rx7 is constitutively expressed in mouse and human primary microglia. Moreover, P2rx7 mRNA level was downregulated in mouse microglia under both pro- and anti-inflammatory conditions. Second, P2X7 agonist BzATP caused cell death of mouse microglia, while this effect was suppressed either by P2X7 knockout or by A-804598 under both basal and pro-inflammatory conditions, which suggests the mediating role of P2X7 in BzATP-induced microglial cell death. Third, BzATP-induced release of IL1 family cytokines including IL1α, IL1β, and IL18 was blocked in P2X7−/− microglia or by A-804598 in pro-inflammatory microglia, while the release of other cytokines/chemokines was independent of P2X7 activation. These findings support the specific role of P2X7 in IL1 family cytokine release. Finally, P2X7 activation was discovered to be linked to AKT and ERK pathways, which may be the underlying mechanism of P2X7 functions in microglia.ConclusionsThese results reveal that P2X7 mediates BzATP-induced microglial cell death and specific release of IL1 family cytokines, indicating the important role of P2X7 in neuroinflammation and implying the potential of targeting P2X7 for the treatment of neuroinflammatory disorders.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-017-0904-8) contains supplementary material, which is available to authorized users.

Sleep deprivation selectively down-regulates astrocytic 5-HT2B receptors and triggers depressive-like behaviors via stimulating P2X7 receptors

“…Likewise, BzATP induced the dephosphorylation of AKT in primary cultured astrocytes (Fig. 4C), similar effects of BzATP on the dephosphorylation of AKT was also reported in microglia (He, Taylor, Fourgeaud, & Bhattacharya, 2017). At the same time BzATP did not change the activation of AKT in granule neurones (Ortega, Pérez-Sen, Delicado, & Miras-Portugal, 2009).…”

Enhanced ATP release and CD73‐mediated adenosine formation sustain adenosine A2A receptor over‐activation in a rat model of Parkinson's disease

“…It induces neurodegeneration directly through P2X7 receptors and, indirectly, through A 2A receptors after its extracellular conversion into adenosine. Notably, there is a striking parallel between the control operated by P2X7 receptors and by A 2A receptors of different processes contributing tor neurodegeneration: Thus, the antagonism of either P2X7 or A 2A receptors directly prevents the damage of neurons (Ohishi et al, ; Silva, Porciúncula, Canas, Oliveira, & Cunha, ) as well as astrocytosis (Apolloni, Amadio, Montilli, Volonté, & D'Ambrosi, ; Matos et al, ) and microgliosis (Gomes et al, ; He, Taylor, Fourgeaud, & Bhattacharya, ). However, it is currently unknown if there is any interaction between A 2A and P2X7 receptors, apart from their parallel functioning in the control of brain damage (see Rodrigues et al, ; see also Ye et al, ).…”

Modulation of three key innate immune pathways for the most common retinal degenerative diseases

“…Growing evidence suggests that dysregulated purinergic signaling contributes to gliosis in the diseased retina (Sanderson et al, ). Degenerating cells or elevated glucose levels increase the extracellular ATP concentration, which activates the P2X7 receptor (P2X7R) on MPs and induces a chemokine release through PKC/MAP kinase pathway activation (Fig ; Potucek et al, ; Costa et al, ; Shiratori et al, ; He et al, ). ATP stimulation evokes the release of pro‐inflammatory cytokines IL‐6, TNF‐α, and CCL2 in primary microglia, which was absent when P2X7 was deleted (Morigiwa et al, ; Shieh et al, ).…”