Amyloid beta but not bradykinin induces phosphatidylcholine hydrolysis in immortalized rat brain endothelial cells

We describe the inhibitory effect of A beta (25-35) fragment of amyloid-bet a peptide and bradykinin (BK) on phosphatidylcholine (PtdCho) metabolism in immortalized rat brain GP8.39 endothelial cells (EC). Cultures were incuba ted either with A beta for 24-48 h, or with BK for 30 min-4 h. The peroxida tion indices (malondialdehyde, conjugated dienes) and lactate dehydrogenase (LDH) release significantly increased after A beta peptide (10-50 mu M) tr eatment. The BK (10 mu M) stimulation of cells brought about an increase in conjugated dienes and LDH release only after 4 h. Following 24 h treatment with 50 mu M A beta peptide, the [Me-H-3]choline incorporation into PtdCho strongly decreased while the [H-3]choline release increased, indicating Pt dCho hydrolysis. The effect was most likely due to peptide prooxidant effec t. After 4 h preincubation with BK, the [Me-H-3]choline incorporation into PtdCho strongly decreased, but no significant [H-3]choline release was foun d. Following long-term treatment, the action of 50 mu M A beta on [H-3]chol ine release was not enhanced by 10 mu M BK. Cell exposure to alpha-tocopher ol (1 mM) prior to the addition of both agents did not abolish stimulated P tdCho breakdown. The data suggest that: (a) A beta peptide and BK may modul ate phospholipid turnover in microvessel cells; (b) they could not synergis tically interact in vascular EC damage during processes involving amyloid a ccumulation and inflammatory response. (C) 1999 Elsevier Science Ireland Lt d. All rights reserved.