摘要
Aim: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline, deposits of amyloid beta and neurofibrillary tangles. Inflammation facilitated by microglia, the resident immune cells of the brain, contribute to the pathogenesis of AD. Epidemiological data indicate that nonsteroidal anti-inflammatory drugs (NSAIDs), which are cyclooxygenase (COX) inhibitors, reduce the risk of developing AD when administered over the course of two or more years. The mechanisms underlying this protective effect are unknown. Acetaminophen (paracetamol), which is not effective as an inhibitor of COX in peripheral tissues, may provide similar protection without the adverse effects of chronic NSAID use. The beneficial effects of acetaminophen have been proposed to stem from its metabolites p-aminophenol and N-arachidonoylaminophenol (AM404), of which, AM404 possesses analgesic and antipyretic properties. The goal of this study was to compare the effects of acetaminophen and its metabolites on microglial immune function and to elucidate the molecular mechanisms engaged by these compounds. Methods: Lipopolysaccharide-stimulated BV-2 murine microglia were used as models. Microglial activation was monitored by their secretion of nitric oxide. Results: P-aminophenol and AM404 suppressed nitric oxide secretion from stimulated microglia more effectively than acetaminophen through pathways that were independent of COX inhibition, cannabinoid receptor type two (CB2) inhibition, and activation of transient receptor potential cation channel subfamily V member 1 (TRPV1). Conclusion: Since AM404 has been previously demonstrated to attenuate NF-kB activation, it is likely that the protective effects of acetaminophen against adverse microglia activation are mediated by its metabolites p-aminophenol and AM404 inhibiting this transcription factor.
