Anti-inflammatory drugs: a hope for Alzheimer's disease?

Human brain cells are capable of initiating and amplifying a brain specific inflammatory response involving the synthesis of cytokines, acute-phase proteins, complement proteins, prostaglandins and oxygen radicals. In Alzheimer's disease (AD), all signs of an inflammatory microglial and astroglial activation are present inside and outside amyloid depositions and along axons of neurones with neurofibrillary tangles. Cell culture and animal models suggest a bidirectional relationship between inflammatory activation of glial cells and the deposition of amyloid. Although it remains unclear which of the different pathophysiological processes in AD may be the driving force in an individual case, the inflammatory activation may increase the speed of cognitive decline. Epidemiological studies point to a reduced risk of AD among users of anti-inflammatory drugs. Therefore, anti-inflammatory drugs have become the focus of several new treatment strategies. A clinical trial with the non-steroidal anti-inflammatory drug (NSAID) indomethacin showed promising results, while a clinical trial with steroids did not show a beneficial effect. Further trials with NSAIDs such as unselective cyclooxygenase (COX) and selective cyclooxygenase-2 (COX-2) inhibitors are on their way. COX inhibitors may not only act on microglial and astroglial cells but also reduce neuronal prostaglandin production. New data suggest that prostaglandins enhance neurotoxicity or induce pro-inflammatory cytokine synthesis in astroglial cells. Amongst these promising new strategies to reduce microglial or monocyte activation, interfering with intracellular pathways has been shown to be effective in various cell culture and animal models but clinical studies have not yet been performed.