Elsevier

Biochemical Pharmacology

Volume 34, Issue 9, 1 May 1985, Pages 1571-1575
Biochemical Pharmacology

Inhibition of platelet and neutrophil phospholipase A2 by hydroxyeicosatetraenoic acids (HETEs) A novel pharmacological mechanism for regulating free fatty acid release

https://doi.org/10.1016/0006-2952(85)90701-4Get rights and content

Abstract

The present study demonstrated that acid-extracted platelet phospholipase A2 (PLA2) exhibited marked hydrolytic activity against both [1-14C]oleic acid- and [1-14C]arachidonic acid-labeled Escherichia coli. The rate of hydrolysis was linear up to 30 min and was directly proportional to the amount of enzyme added to the reaction mixture. The data further indicated that 5-hydroxy-6,8,11,15- eicosatetraenoic acid (5-HETE) inhibited platelet PLA2 in a dose-dependent manner (ic50 = 42 μM), whereas 5-lactone HETE had no inhibitory effect up to 100 μM. The degree of inhibition of PLA2 activity was unaffected by Ca2+ concentrations but was reduced in the presence of increasing amounts of E. coli substrate. Both 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) and 15-hydroxy- 5,8,11,13-eicosatetraenoic acid (15-HETE) also inhibited platelet PLA2 activity (IC = 26 and 72 μM respectively). Furthermore, the inhibitory effects of these monoHETEs were confirmed with a PLA2 preparation derived from rat neutrophils. Thus, these data suggest a novel pharmacological action of HETEs on PLA2 which may have potential ramifications in the regulation of arachidonic acid metabolism.

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