The role of phospholipase A2 in neuronal homeostasis and memory formation: implications for the pathogenesis of Alzheimer's disease

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Phospholipase A2 (PLA2) is a key enzyme in cerebral phospholipid metabolism. Preliminary post-mortem studies have shown that PLA2 activity is decreased in frontal and parietal areas of the AD brain, which is in accordance with recent 31P-Magnetic Resonance Spectroscopy evidence of reduced phospholipid turnover in the pre-frontal cortex of moderately demented AD patients. Such abnormality may also be observed in peripheral cells, and reduced PLA2 activity in platelet membranes of AD patients, and correlates with the severity of dementia. In rat hippocampal slices, PLA2 has been implicated in mechanisms of synaptic plasticity. In adult rats, the stereotaxic injection of PLA2 inhibitors in the CA1 area of hippocampus impaired, in a dose-dependent manner, the formation of short- and long-term memory. Additionally, such inhibition resulted in a reduction of the fluidity of hippocampal membranes. In primary cultures of cortical and hippocampal neurons, the inhibition of PLA2 precluded neurite outgrowth, and the sustained inhibition of the enzyme in mature cultures lead to loss of viability. Taken together, these findings reinforce the involvement of PLA2 enzymes in neurodevelopment and neurodegeneration processes, and further suggest that reduced PLA2 activity, probably reducing membrane phospholipids breakdown, may contribute to the memory impairment in AD.

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