title: Alarmin HNP-1 promotes pyroptosis and IL-1β release through different roles of NLRP3 inflammasome via P2X7 in LPS-primed macrophages.
abstract: Defensins are the first endogenous mediators to be characterized as alarmins and play multifunctional roles in immune response. Previous studies reported that human neutrophil peptide (HNP)-1, a member of the α-defensin subfamily, could regulate the IL-1β post-translational process; however, the underlying mechanism remained unknown. Using an LPS-primed THP-1 macrophage model, we found that inhibition of P2X purinoceptor 7 (P2X7) suppressed HNP-1-initiated mature IL-1β release. Confocal microscopy and glutathione S-transferase (GST) pull-down assay demonstrated that HNP-1 bound to P2X7 directly. HNP-1 treatment increased the activated level of caspase-1, and inhibition of caspase-1 abolished IL-1β release. Incubation of LPS-primed macrophages with potassium chloride also prevented HNP-1-induced export of mature IL-1β. Likewise, an ethidium bromide uptake test showed that the P2X7-K(+) efflux-caspase-1 signaling pathway triggered by HNP-1 contributed to pyroptotic pore formation. Furthermore, knock down of inflammasome adaptor Nod-like receptor family pyrin domain containing 3 (NLRP3) decreased activated caspase-1 level and reduced pore formation in macrophages, whereas IL-1β release was not significantly impaired. These findings not only illustrated the mechanism for alarmin HNP-1 in enhancing inflammatory response, but also provided therapeutic targets for certain inflammatory diseases in which defensins play important roles.
authors.affiliation: 1Department of Anesthesiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: Qixing
authors.initials: Q
authors.lastname: Chen
authors.forename: Yue
authors.initials: Y
authors.lastname: Jin
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Guangxun
authors.initials: G
authors.lastname: Meng
authors.forename: Xiangming
authors.initials: X
authors.lastname: Fang
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020170:Caspase 1 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects*; D002460:Cell Line; D004789:Enzyme Activation; D055785:Gene Knockdown Techniques; D005822:Genetic Vectors; D057809:HEK293 Cells; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects*; D053583:Interleukin-1beta / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D018272:Porins / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics; D023084:alpha-Defensins / Q000494:pharmacology*
chemical_list: D002352:Carrier Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D018272:Porins; D058486:Receptors, Purinergic P2X7; D023084:alpha-Defensins; C406413:human neutrophil peptide 1; D020170:Caspase 1; D011188:Potassium
keywords: Defensin; cytokine; immunomodulation; pyroptosis; signal transduction