title: TLR agonists stimulate Nlrp3-dependent IL-1β production independently of the purinergic P2X7 receptor in dendritic cells and in vivo.
abstract: On the basis of studies in mouse macrophages, activation of the nucleotide-binding oligomerization domain-like receptor (NLR) pyrin domain-containing 3 (Nlrp3) inflammasome is thought to require two signals. The first signal is provided by TLR stimulation and triggers the synthesis of the IL-1β precursor and Nlrp3. The second signal can be mediated by stimulation of the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) by millimolar concentrations of ATP. However, these high concentrations of ATP are not found normally in the in vivo extracellular milieu, raising concern about the physiological relevance of the ATP-P2X7 pathway of inflammasome activation. In this article, we show that unlike macrophages, murine bone marrow-derived and splenic dendritic cells (DCs) can secrete substantial amounts of mature IL-1β upon stimulation with TLR ligands in the absence of ATP stimulation. The differential ability of DCs to release IL-1β and activate caspase-1 was associated with increased expression of Nlrp3 under steady-state conditions and of pro-IL-1β and Nlrp3 after stimulation with TLR agonists. IL-1β secretion from stimulated DCs was largely dependent on the Nlrp3 inflammasome, but independent of P2X7 and unaffected by incubation with apyrase. More importantly, i.p. administration of LPS induced IL-1β production in serum, which was abrogated in Nlrp3-null mice but was unaffected in P2X7-deficient mice. These results demonstrate differential regulation of the Nlrp3 inflammasome in macrophages and DCs. Furthermore, they challenge the idea that the ATP-P2X7 axis is critical for TLR-induced IL-1β production via the Nlrp3 inflammasome in vivo.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: He
authors.forename: Luigi
authors.initials: L
authors.lastname: Franchi
authors.forename: Gabriel
authors.initials: G
authors.lastname: Núñez
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D058847:Inflammasomes / Q000378:metabolism / Q000502:physiology; D053583:Interleukin-1beta / Q000096:biosynthesis* / Q000378:metabolism / Q000502:physiology; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D011498:Protein Precursors / Q000096:biosynthesis / Q000378:metabolism; D058486:Receptors, Purinergic P2X7 / Q000172:deficiency / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D051193:Toll-Like Receptors / Q000819:agonists* / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D008024:Ligands; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D011498:Protein Precursors; D058486:Receptors, Purinergic P2X7; D051193:Toll-Like Receptors; D000255:Adenosine Triphosphate