title: ADP and AMP induce interleukin-1beta release from microglial cells through activation of ATP-primed P2X7 receptor channels.
abstract: P2X(7) is a subtype of ATP-gated channels that is highly expressed in astrocytes, microglia, and other immune cells. Activation of P2X(7) purinoceptors by ATP or 3'-O-(4-benzoyl)-benzoyl ATP (BzATP) induces the formation of cytolytic pores and provokes release of interleukin-1beta from immune cells. We investigated the actions of other endogenous nucleotides on recombinant and microglial P2X(7) receptors using electrophysiology, fluorescence imaging, and interleukin-1beta release measurement. We found that initial application of ADP or AMP to Xenopus oocytes expressing P2X(7) receptors was ineffective. However, when ADP and AMP, but not UTP or adenosine, were applied after a brief exposure to ATP or BzATP, they activated P2X(7) receptors in a dose-dependent manner. Moreover, responses to ADP and AMP were also elicited after exposure to low concentrations of ATP and were recorded several minutes after removal of ATP from the extracellular medium. Whole-cell recordings from mouse microglial cells showed that significant responses to ADP and AMP were elicited only after ATP application. YO-PRO-1 dye uptake imaging revealed that, unlike ATP, prolonged application of ADP or AMP did not cause an opening of large cytolytic pores in mouse microglial cells. Finally, ADP and AMP stimulated the release of interleukin-1beta from ATP-primed mouse and human microglial cells. We conclude that selective sensitization of P2X(7) receptors to ADP and AMP requires priming with ATP. This novel property of P2X(7) leads to activation by ATP metabolites and proinflammatory cytokine release from microglia without cytotoxicity.
authors.affiliation: Cell Biology of Excitable Tissue Group and Neuroimmunology Unit, Montreal Neurological Institute, Montreal, Quebec, Canada.
authors.forename: Yassar
authors.initials: Y
authors.lastname: Chakfe
authors.forename: Rosanne
authors.initials: R
authors.lastname: Seguin
authors.forename: Jack P
authors.initials: JP
authors.lastname: Antel
authors.forename: Céline
authors.initials: C
authors.lastname: Morissette
authors.forename: Danielle
authors.initials: D
authors.lastname: Malo
authors.forename: Duncan
authors.initials: D
authors.lastname: Henderson
authors.forename: Philippe
authors.initials: P
authors.lastname: Séguéla
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000249:Adenosine Monophosphate / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D019898:Autocrine Communication / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis*; D015640:Ion Channel Gating / Q000187:drug effects; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D007375:Interleukin-1; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006593:Hexokinase