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Alzheimer's disease ( AD) is the most common form of dementia and displays the characteristics of chronic neurodegenerative disorders; amyloid plaques ( AP) that contain amyloid β-protein (Aβ) accumulate in AD, which is also characterized by tau phosphorylation. Epidemiological evidence has demonstrated that long-term treatment with nonsteroidal anti-inflammatory drugs ( NSAIDs) markedly reduces the risk of AD by inhibiting the expression of cyclooxygenase 2 ( COX-2). Although the levels of COX-2 and its metabolic product prostaglandin ( PG) E2 are elevated in the brain of AD patients, the mechanisms for the development of AD remain unknown. Using human- or mouse-derived glioblastoma and neuroblastoma cell lines as model systems, we delineated the signaling pathways by which COX-2 mediates the reciprocal regulation of interleukin-1β ( IL-1β) and Aβ between glial and neuron cells. In glioblastoma cells, COX-2 regulates the synthesis of IL-1β in a PGE2-dependent manner. Moreover, COX-2-derived PGE2 signals the activation of the PI3- K/ AKT and PKA/ CREB pathways via cyclic AMP; these pathways transactivate the NF-κB p65 subunit via phosphorylation at Ser 536 and Ser 276, leading to IL-1β synthesis. The secretion of IL-1β from glioblastoma cells in turn stimulates the expression of COX-2 in human or mouse neuroblastoma cells. Similar regulatory mechanisms were found for the COX-2 regulation of BACE-1 expression in neuroblastoma cells. More importantly, Aβ deposition mediated the inflammatory response of glial cells via inducing the expression of COX-2 in glioblastoma cells. These findings not only provide new insights into the mechanisms of COX-2-induced AD but also initially define the therapeutic targets of AD. [ABSTRACT FROM AUTHOR]