Amyloid formation disrupts the balance between interleukin-1ß and interleukin-1 receptor antagonist in human islets.

OBJECTIVES: ß-cell dysfunction and apoptosis associated with islet inflammation play a key role in the pathogenesis of type 2 diabetes (T2D). Growing evidence suggests that islet amyloid, formed by aggregation of human islet amyloid polypeptide (hIAPP), contributes to islet inflammation and ß-cell death in T2D. We recently showed the role of interleukin-1ß (IL-1ß)/Fas/caspase-8 apoptotic pathway in amyloid-induced ß-cell death. In this study, we used human islets in culture as an ex vivo model of amyloid formation to: (1) investigate the effects of amyloid on islet levels of the natural IL-1 receptor antagonist (IL-1Ra); (2) examine if modulating the IL-1ß/IL-1Ra balance can prevent amyloid-induced ß-cell Fas upregulation and apoptosis. METHODS: Isolated human islets (n = 10 donors) were cultured in elevated glucose (to form amyloid) with or without a neutralizing human IL-1ß antibody for up to 7 days. Parallel studies were performed with human islets in which amyloid formation was prevented by adeno-siRNA-mediated suppression of hIAPP expression (as control). ß-cell levels of IL-1Ra, Fas, apoptosis as well as islet function, insulin- and amyloid-positive areas, and IL-1Ra release were assessed. RESULTS: Progressive amyloid formation in human islets during culture was associated with alterations in IL-1Ra. Islet IL-1Ra levels were higher at early stages but were markedly reduced at later stages of amyloid formation. Furthermore, IL-1Ra release from human islets was reduced during 7-day culture in a time-dependent manner. These changes in IL-1Ra production and release from human islets during amyloid formation adversely correlated with islet IL-1ß levels, ß-cell Fas expression and apoptosis. Treatment with IL-1ß neutralizing antibody markedly reduced amyloid-induced ß-cell Fas expression and apoptosis, thereby improving islet ß-cell survival and function during culture. CONCLUSIONS: These data suggest that amyloid formation impairs the balance between IL-1ß and IL-1Ra in islets by increasing IL-1ß production and reducing IL-1Ra levels thereby promoting ß-cell dysfunction and death. Restoring the IL-1ß/IL-1Ra ratio may provide an effective strategy to protect islet ß-cells from amyloid toxicity in T2D.

Low E-prostanoid 2 receptor levels and deficient induction of the IL-1ß/IL-1 type I receptor/COX-2 pathway: Vicious circle in patients with aspirin-exacerbated respiratory disease.

BACKGROUND: We hypothesized that the 2 reported alterations in aspirin-exacerbated respiratory disease (AERD), reduced expression/production of COX-2/prostaglandin (PG) E2 and diminished expression of E-prostanoid (EP) 2 receptor, are closely linked. OBJECTIVE: We sought to determine the mechanisms involved in the altered regulation of the COX pathway in patients with AERD. METHODS: Fibroblasts were obtained from nasal mucosa; samples of control subjects (NM-C, n = 8) and from nasal polyps from patients with aspirin-exacerbated respiratory disease (NP-AERD, n = 8). Expression of the autocrine loop components regulating PGE2 production and signaling, namely IL-1 type I receptor (IL-1RI), COX-2, microsomal prostaglandin E synthase 1 (mPGES-1), and EP receptors, was assessed at baseline and after stimulation with IL-1ß, PGE2, and specific EP receptor agonists. RESULTS: Compared with NM-C fibroblasts, basal expression levels of IL-1RI and EP2 receptor were lower in NP-AERD fibroblasts. IL-1ß-induced IL-1RI, COX-2, and mPGES-1 expression levels were also lower in these cells. Levels of IL-1RI positively correlated with COX-2 and mPGES-1 expression in both NM-C and NP-AERD fibroblasts. Incubation with either exogenous PGE2 or selective EP2 agonist significantly increased expression of IL-1RI in NM-C fibroblasts and had hardly any effect on NP-AERD fibroblasts. Alterations in IL-1RI, COX-2, and mPGES-1 expression that were found in NP-AERD fibroblasts were corrected when EP2 receptor expression was normalized by transfection of NP-AERD fibroblasts. CONCLUSION: Altered expression of EP2 in patients with AERD contributes to deficient induction of IL-1RI, reducing the capacity of IL-1ß to increase COX-2 and mPGES-1 expression, which results in low PGE2 production. This impairment in the generation of PGE2 subsequently reduces its ability to induce IL-1RI.