title: Amyloid beta peptide potentiates cytokine secretion by interleukin-1 beta-activated human astrocytoma cells.
abstract: Neurodegenerative processes in Alzheimer disease (AD) are thought to be driven in part by the deposition of amyloid beta (A beta), a 39- to 43-amino acid peptide product resulting from an alternative cleavage of amyloid precursor protein. Recent descriptions of in vitro neurotoxic effects of A beta support this hypothesis and suggest toxicity might be mediated by A beta-induced neuronal calcium disregulation. In addition, it has been reported that "aging" A beta results in increased toxic potency due to peptide aggregation and formation of a beta-sheet secondary structure. In addition, A beta might also promote neuropathology indirectly by activating immune/inflammatory pathways in affected areas of the brain (e.g., cortex and hippocampus). Here we report that A beta can modulate cytokine secretion [interleukins 6 and 8 (IL-6 and IL-8)] from human astrocytoma cells (U-373 MG). Freshly prepared and aged A beta modestly stimulated IL-6 and IL-8 secretion from U-373 MG cells. However, in the presence of interleukin-1 beta (IL-1 beta), aged, but not fresh, A beta markedly potentiated (3- to 8-fold) cytokine release. In contrast, aged A beta did not potentiate substance P (NK-1)- or histamine (H1)-stimulated cytokine production. Further studies showed that IL-1 beta-induced cytokine release was potentiated by A beta-(25-35), while A beta-(1-16) was inactive. Calcium disregulation may be responsible for the effects of A beta on cytokine production, since the calcium ionophore A23187 similarly potentiated IL-1 beta-induced cytokine secretion and EGTA treatment blocked either A beta or A23187 activity. Thus, chronic neurodegeneration in AD-affected brain regions may be mediated in part by the ability of A beta to exacerbate inflammatory pathways in a conformation-dependent manner.
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology; D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001254:Astrocytoma; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004660:Encephalitis / Q000209:etiology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007378:Interleukins / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D011487:Protein Conformation; D014407:Tumor Cells, Cultured
chemical_list: D016229:Amyloid beta-Peptides; D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D007378:Interleukins; D010446:Peptide Fragments; D002118:Calcium