Activating the NLRP3 Inflammasome Using the Amyloidogenic Peptide IAPP

Westwell‐Roper, Clara; Dunne, Aisling; Kim, Man Lyang; Verchere, C. Bruce; Masters, Seth L.

doi:10.1007/978-1-62703-523-1_2

Cited by 19 publications

(15 citation statements)

References 15 publications

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“…In support of this, hIAPP aggregates have been shown to promote maturation of proIL-1β to IL-1β via activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome [46,47]. In addition, we recently showed that the inhibition of amyloid formation reduces islet IL-1β levels and Fas upregulation [7].…”

Section: Discussionmentioning

confidence: 80%

The role of caspase-8 in amyloid-induced beta cell death in human and mouse islets

et al. 2014

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Aims/hypothesis Reduced beta cell mass due to increased beta cell apoptosis is a key defect in type 2 diabetes. Islet amyloid, formed by the aggregation of human islet amyloid polypeptide (hIAPP), contributes to beta cell death in type 2 diabetes and in islet grafts in patients with type 1 diabetes. In this study, we used human islets and hIAPP-expressing mouse islets with beta cell Casp8 deletion to (1) investigate the role of caspase-8 in amyloid-induced beta cell apoptosis and (2) test whether caspase-8 inhibition protects beta cells from amyloid toxicity. Methods Human islet cells were cultured with hIAPP alone, or with caspase-8, Fas or amyloid inhibitors. Human islets and wild-type or hIAPP-expressing mouse islets with or without caspase-8 expression (generated using a Cre/loxP system) were cultured to form amyloid. Caspase-8 and -3 activation, Fas and FLICE inhibitory protein (FLIP) expression, islet beta cell and amyloid area, IL-1β levels, and the beta:alpha cell ratio were assessed. Results hIAPP treatment induced activation of caspase-8 and -3 in islet beta cells (via Fas upregulation), resulting in apoptosis, which was markedly reduced by blocking caspase-8, Fas or amyloid. Amyloid formation in cultured human and hIAPP-expressing mouse islets induced caspase-8 activation, which was associated with Fas upregulation and elevated islet IL-1β levels. hIAPP-expressing mouse islets with Casp8 deletion had comparable amyloid, IL-1β and Fas levels with those expressing hIAPP and Casp8, but markedly lower beta cell apoptosis, higher beta:alpha cell ratio, greater beta cell area, and enhanced beta cell function. Conclusions/interpretation Beta cell Fas upregulation by endogenously produced and exogenously applied hIAPP aggregates promotes caspase-8 activation, resulting in beta cell apoptosis. The prevention of amyloid-induced caspase-8 activation enhances beta cell survival and function in islets.

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Section: Discussionmentioning

confidence: 80%

The role of caspase-8 in amyloid-induced beta cell death in human and mouse islets

et al. 2014

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“…Immediately prior to each experiment, IAPP was dissolved in 0.1 M acetic acid and diluted in culture medium. To assess amyloid fibril formation, IAPP aggregation was monitored by thioflavin T fluorescence (21). For examination of fibril formation by transmission electron microscopy (TEM), 3-l aliquots of IAPP prepared by dissolution at 100 M in distilled water and incubation at room temperature for 0 -16 h were adsorbed to glow-discharged carboncoated collodion film on copper grids.…”

Section: Methodsmentioning

confidence: 99%

Differential Activation of Innate Immune Pathways by Distinct Islet Amyloid Polypeptide (IAPP) Aggregates

Westwell‐Roper¹,

Denroche

Ehses

et al. 2016

Journal of Biological Chemistry

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Aggregation of islet amyloid polypeptide (IAPP) contributes to beta cell dysfunction in type 2 diabetes and islet transplantation. Like other amyloidogenic peptides, human IAPP induces macrophage IL-1␤ secretion by stimulating both the synthesis and processing of proIL-1␤, a pro-inflammatory cytokine that (when chronically elevated) impairs beta cell insulin secretion. We sought to determine the specific mechanism of IAPP-induced proIL-1␤ synthesis. Soluble IAPP species produced early during IAPP aggregation provided a Toll-like-receptor-2-(TLR2-) dependent stimulus for NF-B activation in HEK 293 cells and bone marrow-derived macrophages (BMDMs). Nonamyloidogenic rodent IAPP and thioflavin-T-positive fibrillar amyloid produced by human IAPP aggregation failed to activate TLR2. Blockade of TLR6 but not TLR1 prevented hIAPP-induced TLR2 activation, consistent with stimulation of a TLR2/6 heterodimer. TLR2 and its downstream adaptor protein MyD88 were required for IAPP-induced cytokine production by BMDMs, a process that is partially dependent on autoinduction by IL-1. BMDMs treated with soluble but not fibrillar IAPP provided a TLR2-dependent priming stimulus for ATP-induced IL-1␤ secretion, whereas late IAPP aggregates induced NLRP3-dependent IL-1␤ secretion by LPS-primed macrophages. Moreover, inhibition of TLR2 and depletion of islet macrophages prevented up-regulation of Il1b and Tnf expression in human IAPP-expressing transgenic mouse islets. These data suggest participation by both soluble and fibrillar aggregates in IAPPinduced islet inflammation. IAPP-induced activation of TLR2 and secretion of IL-1 may be important therapeutic targets to prevent amyloid-associated beta cell dysfunction.

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“…Moreover, islet macrophages are the major source of hIAPPinduced IL-1β in islets, and islet macrophage depletion can improve hIAPP-induced islet dysfunction (7). Given that IAPP can deliver the two signals required for IL-1β secretion [9,10,23] and that anti-IL-1 therapy can improve beta cell function in patients with type 2 diabetes [12], here we asked whether IL-1 mediates hIAPP-induced islet dysfunction in vivo. We found that IL-1Ra markedly improved glycaemia and islet inflammation in a mouse model of islet amyloid formation and type 2 diabetes.…”

Section: Il-1ra Limits Islet Amyloid Formation In Lean A-hiappmentioning

confidence: 99%

“…While in vitro evidence suggests that interaction of hIAPP with macrophages induces release of cytokines such as IL-1β that at high local concentrations are known to cause beta cell dysfunction [10,23], it is likely that IL-1 also plays an important physiological role in regulating islet homeostasis. For example, low concentrations of IL-1β promote beta cell proliferation, and IL-1β knockout mice have impaired glucose tolerance and decreased islet Pdx1 expression [43].…”

Section: Il-1ra Limits Islet Amyloid Formation In Lean A-hiappmentioning

confidence: 99%

IL-1 mediates amyloid-associated islet dysfunction and inflammation in human islet amyloid polypeptide transgenic mice

et al. 2014

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Aims/hypothesis Aggregation of islet amyloid polypeptide (IAPP) to form amyloid contributes to beta cell dysfunction in type 2 diabetes. Human but not non-amyloidogenic rodent IAPP induces islet macrophage proIL-1β synthesis. We evaluated the effect of IL-1 receptor antagonist (IL-1Ra) on islet inflammation and dysfunction in a mouse model of type 2 diabetes with amyloid formation. Methods Lean and obese male mice (A/a or A vy /A at the agouti locus, respectively) with or without beta cell human IAPP expression (hIAPP Tg/0 ) were treated with PBS or IL-1Ra (50 mg kg) from 16 weeks of age. Intraperitoneal glucose and insulin tolerance tests were performed after 8 weeks. Pancreases were harvested for histology and gene expression analysis. Results Aggregation of human IAPP was associated with marked upregulation of proinflammatory gene expression in islets of obese hIAPP Tg/0 mice, together with amyloid deposition and fasting hyperglycaemia. IL-1Ra improved glucose tolerance and reduced plasma proinsulin:insulin in both lean and obese hIAPP Tg/0 mice with no effect on insulin sensitivity. The severity and prevalence of islet amyloid was reduced by IL-1Ra in lean hIAPP Tg/0 mice, suggesting a feed-forward mechanism by which islet inflammation promotes islet amyloid at the early stages of disease. IL-1Ra limited Il1a, Il1b, Tnf and Ccl2 expression in islets from obese hIAPP Tg/0 mice, suggesting an altered islet inflammatory milieu. Conclusions/interpretation These data provide the first in vivo evidence-using a transgenic mouse model with amyloid deposits resembling those found in human islets-that IAPP-induced beta cell dysfunction in type 2 diabetes may be mediated by IL-1. Anti-IL-1 therapies may limit islet inflammation and dysfunction associated with amyloid formation.

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Activating the NLRP3 Inflammasome Using the Amyloidogenic Peptide IAPP

Cited by 19 publications

References 15 publications

The role of caspase-8 in amyloid-induced beta cell death in human and mouse islets

The role of caspase-8 in amyloid-induced beta cell death in human and mouse islets

Differential Activation of Innate Immune Pathways by Distinct Islet Amyloid Polypeptide (IAPP) Aggregates

IL-1 mediates amyloid-associated islet dysfunction and inflammation in human islet amyloid polypeptide transgenic mice

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