Elevated Activities of Lipases and Lysophospholipase in Alzheimer's Disease

Abstract

Two plasma membrane fractions were obtained from different regions of brains from patients with Alzheimer''s disease (AD) and normal aged individuals. One fraction was from synaptosomes (synaptosomal plasma membrane; SPM) and the other from glial cells and neuronal cell bodies (plasma membrane; PM). Among various regions analyzed, PM and SPM from the nucleus basalis of AD brains displayed 6- to 8-fold higher activities of mono- and diacylglycerol lipases than membranes from age-matched normal individuals. Membranes from the hippocampus region of AD brains also showed consistently higher activities of lipases than those from control brains. Similarly, the lysophospholipase activity in the cytosolic fraction of these regions also showed higher activity (4- to 6-fold) in AD than in corresponding fractions from normal human brains. The cause of increased activities of lipases and lysophospholipases in the nucleus basalis and hippocampus regions is not understood. However, marked elevations of acylhydrolases in the above regions may be due to overexpression, changes in levels of neuropeptides, intracellular calcium ions and/or lipid peroxides. All these are known to stimulate acylhydrolases. Autolytic changes which occur in the brain after death may markedly affect the activities of mono- and diacylglycerol lipases.