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P58(IPK) suppresses NLRP3 inflammasome activation and IL-1? production via inhibition of PKR in macrophages.

ABSTRACT: The NLRP3 inflammasome activation is a key signaling event for activation and secretion of pro-inflammatory cytokines such as IL-1? from macrophages. p58(IPK) is a molecular chaperone that regulates protein homeostasis through inhibiting eIF-2? kinases including double-stranded RNA-dependent protein kinase (PKR), which has been recently implicated in inflammasome activation. Herein we investigate the role of p58(IPK) in TLR4 signaling and inflammasome activation in macrophages. Primary bone marrow-derived macrophages (BMDM) was isolated from p58(IPK) knockout (KO) and wildtype (WT) mice and treated with lipopolysaccharide (LPS) and ATP to activate TLR4 signaling and stimulate inflammasome activation. Compared to WT macrophages, p58(IPK) deficient cells demonstrated significantly stronger activation of PKR, NF-?B, and JNK and higher expression of pro-inflammatory genes TNF-? and IL-1?. Coincidently, p58(IPK) deletion intensified NLRP3-inflammasome activation indicated by enhanced caspase 1 cleavage and increased IL-1? maturation and secretion. Pretreatment with specific PKR inhibitor or overexpression of p58(IPK) largely abolished the changes in inflammasome activation and IL-1? secretion in p58(IPK) null macrophages. Furthermore, immunoprecipitation assay confirmed the binding of p58(IPK) with PKR, but not other TLR4 downstream signaling molecules. Collectively, these results suggest a novel and crucial role of p58(IPK) in regulation of inflammasome activation and IL-1? secretion in macrophages.

SUBMITTER: Boriushkin E

PROVIDER: S-EPMC4845006 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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p58(IPK) suppresses NLRP3 inflammasome activation and IL-1β production via inhibition of PKR in macrophages.

Boriushkin Evgenii E Wang Joshua J JJ Li Junhua J Bhatta Maulasri M Zhang Sarah X SX

Scientific reports 20160426

The NLRP3 inflammasome activation is a key signaling event for activation and secretion of pro-inflammatory cytokines such as IL-1β from macrophages. p58(IPK) is a molecular chaperone that regulates protein homeostasis through inhibiting eIF-2α kinases including double-stranded RNA-dependent protein kinase (PKR), which has been recently implicated in inflammasome activation. Herein we investigate the role of p58(IPK) in TLR4 signaling and inflammasome activation in macrophages. Primary bone marr ...[more]

PMID: 27113095

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Project description:ObjectiveProtein kinase-like endoplasmic reticulum kinase (PERK) and protein kinase R (PKR) are implicated in endoplasmic reticulum stress-induced arthritis and pro-inflammatory cytokine-mediated cartilage degradation in vitro, respectively. We determined whether knockout of the cellular inhibitor of PERK and PKR, P58(IPK) causes joint degeneration in vivo and whether these molecules are activated in human osteoarthritis (OA).Materials and methodsSections of knee joints from P58(IPK)-null and wild-type mice aged 12-13 and 23-25 months were stained with toluidine blue and scored for degeneration using the osteoarthritis research society international (OARSI) system. Bone changes were assessed by radiology and high-resolution micro-computed tomography of hind limbs. Sections from the medial tibial plateaus of two human knees, removed in total knee replacement surgery for OA, were immunolabelled for phosphorylated PERK and PKR and P58(IPK).ResultsKnockout mice exhibited narrower tibiae (p = 0.0031) and smaller epiphyses in tibiae (p = 0.0004) and femora (p = 0.0214). Older knockout mice had reduced total volume inside the femoral periosteal envelope (p = 0.023), reduced tibial (p = 0.03), and femoral (p = 0.0012) bone volumes (BV) and reduced femoral BV fraction (p = 0.025). Compared with wild-types, younger P58(IPK)-null mice had increased OARSI scores in medial femoral condyles (p = 0.035). Thirty four percent of null mice displayed severe joint degeneration with complete articular cartilage loss from the medial compartment and heterotopic chondro-osseous tissue in the medial joint capsule. Phosphorylated PERK and PKR were localized throughout human osteoarthritic tibial plateaus but, in particular, in areas exhibiting the most degeneration. There was limited expression of P58(IPK).ConclusionThis study is the first to reveal a critical role for P58(IPK) in maintaining joint integrity in vivo, implicating the PKR and PERK stress signaling pathways in bony changes underlying the pathogenesis of joint degeneration.

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Dataset Information

P58(IPK) suppresses NLRP3 inflammasome activation and IL-1? production via inhibition of PKR in macrophages.

Publications

p58(IPK) suppresses NLRP3 inflammasome activation and IL-1β production via inhibition of PKR in macrophages.

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