Human Amylin Stimulates Inflammatory Cytokine Secretion from Human Glioma Cells

Abstract

Chronic neurodegeneration in the brains of Alzheimer’s disease (AD) patients may be mediated, at least in part, by the ability of amyloid beta (Aβ) to exacerbate inflammatory pathways in a conformation-dependent manner. In this regard, we previously reported that the Aβ-peptide-mediated potentiation of inflammatory cytokine secretion from interleukin-1β (IL-1β)-stimulated human astrocytoma cells was conformation dependent. Other amyloidogenic peptides, such as human amylin, which display similar conformation-dependent neurotoxic effects, may also elicit inflammatory cytokine secretion from glial cells. To test this hypothesis, we compared human and rat amylin for the effects on cytokine production in U-373 MG human astrocytoma cells. Human amylin alone stimulated U-373 MG cells to secrete IL-6 and IL-8 in a concentration-dependent manner with maximum effects seen at 10–25 μM peptide. In addition, human amylin markedly potentiated IL-1β-stimulated cytokine production with a similar concentration dependence. In contrast, nonamyloidogenic rat amylin modestly stimulated cytokine secretion, either alone or combined with IL-1β. Aging human amylin resulted in diminished cytokine secretion, probably due to the formation of large, less active aggregates. In agreement with our previous studies using Aβ, extracellular Ca²⁺ was necessary for human amylin stimulation of cytokine secretion. Our data suggest that amyloidogenic peptides promote cytokine secretion through similar β-sheeted secondary-structure- and extracellular-Ca²⁺-dependent mechanisms.