Amyloid beta protein (25–35) stimulation of phospholipases A, C and D activities of LA‐N‐2 cells

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Abstract
[3H]Myristic acid prelabeled LA‐N‐2 cells were exposed to varying concentrations of amyloid beta protein (25–35), from 20 to 250 μg/ml, and the activation of phospholipases A and D estimated. A progressive increase in phosphatidylethanol formation, a measure of phospholipase D activity, and of free fatty acid release, a measure of phospholipase A activity, was observed over a time‐course of 60 min. [3H]Inositol prelabeled LA‐N‐2 cells were exposed to varying concentrations of AβP, from 20 to 125 μg/ml, and phospholipase C activation was measured. There was an increased release of inositol phosphates in the presence of amyloid beta protein as a function of incubation time. The effects of adrenergic, metabotropic amino acid and bombesin antagonists on the AβP mediated stimulation of phospholipase C activity was investigated. Propranolol, a β adrenergic antagonist, 7‐chlorokynurenic acid, a metabotropic amino acid antagonist, and [Tyr4‐d‐Phe12]bombesin, a bombesin antagonist, blunted the AβP stimulation of phospholipase C activity in [3H]inositol prelabeled L‐AN‐2 cells. This suggests that amyloid beta protein activation of phospholipase C may be receptor mediated. The phospholipase C inhibitor U 71322 prevented the activation of phospholipase C by AβP. However, this activation was not effected by tocopherol, propylgallate, or vitamin C.