The enigma of cell death in neurodegenerative disorders
Progressive cell loss in specific neuronal populations is the pathological hallmark of neurodegenerative diseases, but its mechanisms remain unresolved. Apoptotic cell death has been implicated as a major mechanism in Alzheimer disease (AD), Parkinson disease (PD) and other neurodegenerative disorders. However, DNA fragmentation in human brain as a sign of neuronal cell injury is too frequent to account for the continuous loss in these slowly progressive diseases. In a series of autopsy confirmed cases of AD, PD, related disorders, and age-matched controls, DNA fragmentation using the TUNEL method, an array of apoptosis-related proteins (ARP), proto-oncogenes, and activated caspase-3, the key enzyme of late-stage apoptosis, were examined. In AD, a considerable number of hippocampal neurons and glial cells showed DNA fragmentation with a 3- to 6-fold increase related to neurofibrillary tangles and amyloid deposits, but only 1 in 2.600 to 5.600 neurons displayed apoptotic morphology and cytoplasmic immunoreactivity for activated caspase-3, whereas no neurons were labeled in age-matched controls. caspase-3 immunoreactivity was seen in granules of cells with granulovacuolar degeneration, in around 25% co-localized with early cytoplasmic deposition of tau-protein. In progressive supranuclear palsy, only single neurons and several oligodendrocytes in brainstem, some with tau-deposits, were TUNEL-positive and expressed both ARPs and activated caspase-3. In PD, dementia with Lewy bodies, multisystem atrophy (MSA), and corticobasal degeneration.
KeywordsAmyotrophic Lateral Sclerosis Alzheimer Disease Parkinson Disease Multiple System Atrophy Dementia With Lewy Body
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