Abstract

Objective: Aggregation of human amylin (hA) into β-sheet-containing oligomers is linked to islet β-cell dysfunction and the pathogenesis of type-2 diabetes. Here we investigated possible contributions of Fas-associated death-receptor signaling to the mechanism of hA-evoked β-cell apoptosis.

Research Design and Methods: We measured responses to hA in isolated mouse islets and two insulinoma cell lines, wherein we measured Fas/FasL and FADD expression by qRT-PCR, western-blotting and immunofluorescence staining. We employed two anti-Fas/FasL blocking antibodies and the Fas/FasL antagonist, Kp7-6, to probe roles of Fas interactions in the regulation of apoptosis in hA-treated β-cells and measured Kp7-6-mediated effects on β-sheet formation and aggregation using circular dichroism and thioflavin-T binding.

Results: Human amylin treatment stimulated Fas and FADD expression in β-cells. Both blocking antibodies suppressed hA-evoked apoptosis but did not modify its aggregation. Therefore, Fas receptor interactions played a critical role in induction of this pathway. Interestingly, hA-evoked β-cell apoptosis was suppressed and rescued by Kp7-6, which also impaired hA β-sheet formation.

Conclusions: This is the first report linking hA-evoked induction and activation of Fas and FADD to β-cell apoptosis. We have identified a Fas/FasL antagonist, Kp7-6, as a potent inhibitor of hA aggregation and related β-cell death. These results also support an interaction between hA and Fas on the surface of apoptotic β-cells. Increased expression and activation of Fas in β-cells could constitute a molecular event common to the pathogenesis of both type-1 and type-2 diabetes, although the mode of pathway activation may differ between these common forms of diabetes.