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  • Low concentration IL-1β promotes islet amyloid formation by increasing hIAPP release from humanised mouse islets in vitro.

Low concentration IL-1β promotes islet amyloid formation by increasing hIAPP release from humanised mouse islets in vitro.

Diabetologia (2020-07-31)
Andrew T Templin, Mahnaz Mellati, Daniel T Meier, Nathalie Esser, Meghan F Hogan, Joseph J Castillo, Rehana Akter, Daniel P Raleigh, Sakeneh Zraika, Rebecca L Hull, Steven E Kahn, Andrew T Templin, Mahnaz Mellati, Daniel T Meier, Nathalie Esser, Meghan F Hogan, Joseph J Castillo, Rehana Akter, Daniel P Raleigh, Sakeneh Zraika, Rebecca L Hull, Steven E Kahn
ABSTRACT

Aggregation of the beta cell secretory product human islet amyloid polypeptide (hIAPP) results in islet amyloid deposition, a pathological feature of type 2 diabetes. Amyloid formation is associated with increased levels of islet IL-1β as well as beta cell dysfunction and death, but the mechanisms that promote amyloid deposition in situ remain unclear. We hypothesised that physiologically relevant concentrations of IL-1β stimulate beta cell islet amyloid polypeptide (IAPP) release and promote amyloid formation. We used a humanised mouse model of endogenous beta cell hIAPP expression to examine whether low (pg/ml) concentrations of IL-1β promote islet amyloid formation in vitro. Amyloid-forming islets were cultured for 48 h in the presence or absence of IL-1β with or without an IL-1β neutralising antibody. Islet morphology was assessed by immunohistochemistry and islet mRNA expression, hormone content and release were also quantified. Cell-free thioflavin T assays were used to monitor hIAPP aggregation kinetics in the presence and absence of IL-1β. Treatment with a low concentration of IL-1β (4 pg/ml) for 48 h increased islet amyloid prevalence (93.52 ± 3.89% vs 43.83 ± 9.67% amyloid-containing islets) and amyloid severity (4.45 ± 0.82% vs 2.16 ± 0.50% amyloid area/islet area) in hIAPP-expressing mouse islets in vitro. This effect of IL-1β was reduced when hIAPP-expressing islets were co-treated with an IL-1β neutralising antibody. Cell-free hIAPP aggregation assays showed no effect of IL-1β on hIAPP aggregation in vitro. Low concentration IL-1β did not increase markers of the unfolded protein response (Atf4, Ddit3) or alter proIAPP processing enzyme gene expression (Pcsk1, Pcsk2, Cpe) in hIAPP-expressing islets. However, release of IAPP and insulin were increased over 48 h in IL-1β-treated vs control islets (IAPP 0.409 ± 0.082 vs 0.165 ± 0.051 pmol/5 islets; insulin 87.5 ± 8.81 vs 48.3 ± 17.3 pmol/5 islets), and this effect was blocked by co-treatment with IL-1β neutralising antibody. Under amyloidogenic conditions, physiologically relevant levels of IL-1β promote islet amyloid formation by increasing beta cell release of IAPP. Neutralisation of this effect of IL-1β may decrease the deleterious effects of islet amyloid formation on beta cell function and survival.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ribonuclease A from bovine pancreas, (Solution of 50% glycerol, 10mM Tris-HCL pH 8.0)
Sigma-Aldrich
Monoclonal Anti-Insulin antibody produced in mouse, clone K36AC10, ascites fluid
Sigma-Aldrich
Thioflavin T, used as stain for amyloid
Sigma-Aldrich
Bovine Serum Albumin, lyophilized powder, essentially fatty acid free and essentially globulin free, ≥99% (agarose gel electrophoresis)
Sigma-Aldrich
L-(−)-Glucose, ≥99%